JP5541802B2 - MEASUREMENT DEVICE, CAPACITANCE SENSOR, AND MEASUREMENT METHOD - Google Patents

Description

  The present invention relates to a measurement device, a capacitance sensor, and a measurement method, and more particularly to a measurement device, a capacitance sensor, and a measurement method that improve the measurement accuracy of capacitance.

  Conventionally, a predetermined voltage is applied to the detection electrode, electric charge is accumulated according to the capacitance generated between the detection electrode and the space around the detection electrode, and the accumulated electric charge is stored in a capacitor having a known capacitance. A capacitance measuring device that measures the capacitance between the detection electrode and the surroundings of the detection electrode by transferring and measuring the voltage of the capacitor has been proposed (for example, see Patent Document 1).

  In addition, conventionally, an electrostatic charge is first accumulated in a capacitor, transferred to a capacitance generated between the detection electrode and a detection target, and the capacitance of the capacitance measured by measuring the voltage of the detection electrode. A capacity measuring device has been proposed (see, for example, Patent Document 2).

  Further, the capacitance of the detection electrode differs depending on whether or not an object is present around the detection electrode. Further, when an object existing around the detection electrode moves, the capacitance of the detection electrode changes. Therefore, using this, for example, an object detection sensor that detects the presence or absence of an object based on a change in capacitance of a detection electrode measured by a capacitance measuring device, or an object movement detection that detects the movement of an object A sensor is realized.

  By the way, when measuring the capacitance using the capacitance measuring device, the object near the detection electrode has a potential with respect to the ground to which the capacitance measuring device is electrically connected, A potential difference may occur between the detection electrode and the object. For example, when an object having a positive potential exists around the detection electrode, electrons having a negative charge are attracted by the influence of the potential difference, and the number of electrons accumulated in the detection electrode increases. This makes it impossible to accurately measure the capacitance.

  Further, for example, consider a case where a detection electrode of a capacitance measuring device is incorporated in a door handle of an automobile and an approach of an object such as a human hand to the door handle is detected. In this case, if a power line supplying power to a motor of an automobile is near the detection electrode, it is accumulated on the detection electrode even though the capacitance is not changed due to the potential of the power line. In some cases, the amount of charge to be changed changes and erroneous capacitance is measured. Therefore, when power supply to the motor is turned on / off, there is a possibility that it is erroneously determined that an object has approached even though an object such as a hand is not approaching near the door handle.

Japanese translation of PCT publication No. 2002-530680 JP 2006-78292 A

  However, in the inventions described in Patent Documents 1 and 2, when an object having a potential exists around the detection electrode, it affects the amount of charge accumulated in the detection electrode during the measurement, so that an error occurs in the measurement result. Occurs.

  The present invention has been made in view of such a situation, and makes it possible to improve the measurement accuracy of capacitance.

  A measuring apparatus according to a first aspect of the present invention is a measuring apparatus that measures the capacitance between a first electrode and a space around the first electrode. The ground that can be connected to the reference voltage point, the first connecting means that can connect the first electrode, the first resistor, and the capacitance are sufficiently larger than the first electrode, and the first end is the first. A first capacitor connected to a first end of the resistor, a capacitance sufficiently larger than the first electrode, a first end connected to the second end of the first resistor, and a second A first capacitor having one end connected to the first connection means, a first end connected to the second end of the first capacitor, and a second end connected to the ground. The first opening is connected to the second end of the second battery, and the second end is connected to the ground. A second opening / closing means, a first opening connected to the charge supply means, a third opening / closing means connected to the first end of the first battery, and a first end The fourth opening / closing means connected to the second end of the third opening / closing means, the second end connected to the ground, and the input unit connected to the second end of the third opening / closing means. A first voltage measuring unit; and a capacitance measuring unit that controls the first to fourth opening / closing units and that measures a capacitance based on the voltage measured by the first voltage measuring unit. .

  In the first aspect of the present invention, the first to fourth opening / closing means are controlled, and the space around the first electrode and the first electrode is based on the voltage measured by the first voltage measuring means. Is measured.

  Therefore, the capacitance measurement accuracy is improved.

  This 1st electrode is comprised by the electrode which consists of stainless steel etc., for example. The charge supply means includes, for example, a DC power supply, a constant voltage circuit, a constant current circuit, a predetermined charge supply circuit, an intermittent operation charge supply circuit, and the like. This reference voltage point is set to, for example, ground or body ground. The first connection means is constituted by, for example, a connection terminal. This 1st electrical storage device and the 2nd electrical storage device are constituted by a capacitor, for example. The first to fourth opening / closing means are composed of, for example, various switches, relays, microcomputers and the like. This first voltage measuring means is constituted by, for example, an A / D converter, a voltmeter or the like. This capacitance measuring means is constituted by, for example, a microcomputer.

  A second resistor can be connected between the first end of the first capacitor and the second end of the third opening / closing means.

  Accordingly, the first voltage measuring means can be configured by a comparator or the like that outputs a result of comparing the input voltage with a predetermined threshold voltage.

  The capacitance measuring means controls the first opening / closing means, the second opening / closing means, and the fourth opening / closing means to connect to the first capacitor, the second capacitor, and the first connecting means. After discharging the charge of the first electrode, the second opening / closing means and the third opening / closing means are controlled to charge the second capacitor until the voltage of the second capacitor reaches a predetermined threshold value. Thereafter, the third opening / closing means is controlled to charge the second capacitor and the first electrode, and then the first opening / closing means and the second opening / closing means are controlled so that the voltage of the second capacitor is The charge of the second capacitor is transferred to the first capacitor until the threshold is reached, and the charge transfer process for discharging the charge of the first electrode is executed at least once, and the charge is stored in the first capacitor by the charge transfer process. The electrostatic capacity can be measured based on the amount of charge to be obtained.

  Thereby, the measurement precision of an electrostatic capacitance can be improved more.

  A second resistor having a first end connected to the first end of the second capacitor, a first end connected to the charge supply means, and a second end connected to the second resistor A fifth opening / closing means connected to one end; a sixth opening / closing means having a first end connected to a second end of the fifth opening / closing means and a second end connected to the ground; A second voltage measuring means having an input portion connected to the second end of the fifth opening / closing means; a third opening / closing means; a fourth opening / closing means; and a first voltage measuring means. The capacitance measuring means controls the first opening / closing means, the second opening / closing means, the fifth opening / closing means, and the sixth opening / closing means, and is measured by the second voltage measuring means. The capacitance can be measured based on the voltage to be measured.

  Thereby, the measurement accuracy of electrostatic capacitance can be improved with a different circuit configuration.

  The fifth opening / closing means and the sixth opening / closing means are constituted by various switches, relays, microcomputers and the like, for example. This second voltage measuring means is constituted by, for example, a comparator, an A / D converter, a voltmeter, a microcomputer and the like.

  The capacitance measuring means controls the first opening / closing means, the second opening / closing means, and the sixth opening / closing means to connect to the first capacitor, the second capacitor, and the first connecting means. After the electric charge of the first electrode is discharged, the second opening / closing means and the fifth opening / closing means are controlled to charge the second capacitor until the voltage of the second capacitor reaches a predetermined threshold value. Then, the fifth opening / closing means is controlled to charge the second capacitor and the first electrode, and then the first opening / closing means and the second opening / closing means are controlled so that the voltage of the second capacitor is The charge of the second capacitor is transferred to the first capacitor until the threshold is reached, and the charge transfer process for discharging the charge of the first electrode is executed at least once, and the charge is stored in the first capacitor by the charge transfer process. The electrostatic capacity can be measured based on the amount of charge to be obtained.

  Thereby, the measurement precision of an electrostatic capacitance can be improved more.

The first end is connected to the charge supply means, the second end is connected to the first end of the second battery, and the first end is the fifth opening / closing means. And a second voltage measuring means whose input section is connected to a second end of the fifth opening / closing means. The capacitance measuring means controls the first to sixth opening / closing means, the voltage measured by the first voltage measuring means, and the voltage measured by the second voltage measuring means. Based on the above, the capacitance can be measured.

  As a result, the measurement speed can be increased without reducing the capacitance measurement accuracy.

  The fifth opening / closing means and the sixth opening / closing means are constituted by various switches, relays, microcomputers and the like, for example. This second voltage measuring means is constituted by, for example, a comparator, an A / D converter, a voltmeter, a microcomputer and the like.

  The capacitance measuring means controls the first opening / closing means, the second opening / closing means, the fourth opening / closing means, and the sixth opening / closing means, so that the first capacitor, the second capacitor, and the second After discharging the charge of the first electrode connected to the first connecting means, the second opening / closing means and the third opening / closing means are controlled until the voltage of the second capacitor reaches a predetermined threshold value. After charging the second capacitor, the fifth opening / closing means is controlled to charge the second capacitor and the first electrode, the first opening / closing means and the second opening / closing means are controlled, and the second The charge of the second capacitor is transferred to the first capacitor until the voltage of the capacitor reaches the threshold value, and the charge transfer process for discharging the charge of the first electrode is executed one or more times. Capacitance can be measured based on the amount of charge stored in the capacitor .

  Thereby, the measurement precision of an electrostatic capacitance can be improved more.

  Threshold setting means for setting the threshold value used for measuring the electrostatic capacitance that minimizes the electrostatic capacitance among the electrostatic capacitances measured by the electrostatic capacitance measuring means using a plurality of different threshold values as a formal threshold value. Can be provided.

  Thereby, a threshold value can be set appropriately and capacitance measurement accuracy can be further improved. Moreover, the trouble of setting the threshold can be saved.

  This threshold value setting means is constituted by a microcomputer, for example.

  A second connection means connected to the ground and capable of connecting the second electrode can be further provided.

  Thus, by using the second electrode to shield, it is possible to give directionality to the capacitance measurement by the first electrode.

  The second connecting means capable of connecting the second electrode, the third resistor, the capacitance is sufficiently larger than the second electrode, and the first end is connected to the first end of the third resistor. A third capacitor having a second end connected to the second connection means, a first end connected to a second end of the third capacitor, and a second end connected to ground. A seventh opening / closing means, an eighth opening / closing means having a first end connected to the charge supply means and a second end connected to the second end of the third resistor, and a first end. Is connected to the second end of the eighth opening / closing means, the ninth opening / closing means is connected to the second end, and the input is connected to the second end of the eighth opening / closing means. The third voltage measuring means and the seventh to ninth opening / closing means are controlled so that the second capacitor and the third capacitor have the same voltage. The same potential control means can be further provided that.

  Thereby, even if the shape, relative dielectric constant, temperature, etc. of the first electrode and the second electrode change, the measurement accuracy of the capacitance can be further improved with almost no influence.

  This 2nd electrode is comprised by the electrode which consists of stainless steel etc., for example. The second connection means is constituted by, for example, a connection terminal. This third battery is composed of, for example, a capacitor. The seventh to ninth opening / closing means are constituted by, for example, various switches, relays, microcomputers and the like. This third voltage measuring means is constituted by, for example, a comparator, an A / D converter, a voltmeter, a microcomputer, and the like. This equipotential control means is constituted by, for example, a microcomputer.

  A tenth opening / closing means having a first end connected to the charge supply means, a second end connected to the first end of the third battery, and a first end connected to the first opening of the tenth opening / closing means. And an eleventh opening / closing means connected to one end of the second terminal and the second end connected to the ground, and the third voltage measuring means is not the eighth opening / closing means but the tenth opening / closing means. The same potential control means is connected to the second end and controls the seventh to eleventh opening / closing means so that the second capacitor and the third capacitor are controlled to have the same voltage. Can do.

  As a result, even if the shape, relative dielectric constant, temperature, etc. of the first electrode and the second electrode change, the measurement accuracy of the capacitance can be further improved and the measurement speed can be increased with little influence. Can be fast.

  The tenth and eleventh opening / closing means are constituted by, for example, various switches, relays, microcomputers and the like.

  The measuring device according to the second aspect of the present invention can be connected to a charge supply means for supplying charges and an external reference voltage point in the measuring device for measuring the capacitance between the electrodes and the space around the electrodes. A plurality of units, a connection means capable of connecting an electrode, a first resistor, and a capacitance sufficiently larger than that of the electrode, wherein the first end is a first end of the first resistor. A first capacitor connected, a capacitance sufficiently larger than that of the electrode, a first end connected to the second end of the first resistor, and a second end connected to the connection means; Two capacitors, a first opening / closing means having a first end connected to a second end of the first capacitor, a second end connected to the ground, and a first capacitor being a second capacitor. A second opening / closing means connected to the second end of the second opening and the second end connected to the ground; The first end is connected to the charge supply means, the second end is connected to the first end of the first battery, and the first end is the third opening / closing means of the third opening / closing means. A fourth open / close means connected to one end of the second open end and a second end connected to the ground; a first voltage measuring means connected to the second end of the third open / close means; A plurality of units each having a capacitance measuring means for controlling the first to fourth opening / closing means and measuring a capacitance based on the voltage measured by the first voltage measuring means; Role setting means for setting a plurality of electrodes respectively connected to the connection means of the unit as either a detection electrode used for detecting capacitance or a shield electrode used for shielding an electric field, and the plurality of electrodes having the same voltage Same potential control means for controlling to be Equipped with a.

  In the measuring apparatus according to the second aspect of the present invention, the plurality of electrodes respectively connected to the connecting means of the plurality of units are either detection electrodes used for detecting capacitance or shield electrodes used for shielding electric fields. The plurality of electrodes are controlled to have the same voltage, and in each unit, the first to fourth opening / closing means are controlled, and based on the voltage measured by the first voltage measuring means, the electrodes and The capacitance between the electrode and the surrounding space is measured.

  Therefore, the capacitance measurement accuracy is improved. Further, even after the electrode is installed at a predetermined position, the position and direction in which the capacitance is measured can be flexibly changed.

  This electrode is constituted by an electrode made of, for example, stainless steel. The charge supply means includes, for example, a DC power supply, a constant voltage circuit, a constant current circuit, a predetermined charge supply circuit, an intermittent operation charge supply circuit, and the like. This reference voltage point is set to, for example, ground or body ground. This 1st electrical storage device and the 2nd electrical storage device are constituted by a capacitor, for example. The first to fourth opening / closing means are composed of, for example, various switches, relays, microcomputers and the like. This first voltage measuring means is constituted by, for example, an A / D converter, a voltmeter or the like. The capacitance measuring means, role setting means, and potential setting means are constituted by, for example, a microcomputer.

  A capacitance sensor according to a third aspect of the present invention is a capacitance sensor that detects an object based on a capacitance between an electrode and a space around the electrode. A supply means, a ground connectable to an external reference voltage point, a first resistor, a capacitance is sufficiently larger than that of the electrode, and a first end is connected to a first end of the first resistor. A first capacitor, a second capacitor having a sufficiently larger capacitance than the electrode, a first end connected to the second end of the first resistor, and a second end connected to the electrode; A first opening / closing means having a first end connected to a second end of the first capacitor, a second end connected to the ground, and a first end a second end of the second capacitor. And a second opening / closing means having a second end connected to the ground, and a first end having a charge supply. And a third opening / closing means connected to the first end of the first battery, and a first end connected to the second end of the third opening / closing means. A fourth opening / closing means having a second end connected to the ground; a first voltage measuring means having an input connected to the second end of the third opening / closing means; The opening / closing means is controlled, and the capacitance measuring means for measuring the capacitance based on the voltage measured by the first voltage measuring means, and the detection of the object around the electrode based on the capacitance. And an object detection means for performing.

  In the third aspect of the present invention, the first to fourth opening / closing means are controlled, and based on the voltage measured by the first voltage measuring means, the electrostatic capacitance between the electrode and the space around the electrode is determined. The capacitance is measured, and an object around the electrode is detected based on the capacitance.

  Therefore, the capacitance measurement accuracy is improved. As a result, the object detection accuracy is improved.

  This electrode is constituted by an electrode made of, for example, stainless steel. The charge supply means includes, for example, a DC power supply, a constant voltage circuit, a constant current circuit, a predetermined charge supply circuit, an intermittent operation charge supply circuit, and the like. This reference voltage point is set to, for example, ground or body ground. This 1st electrical storage device and the 2nd electrical storage device are constituted by a capacitor, for example. The first to fourth opening / closing means are composed of, for example, various switches, relays, microcomputers and the like. This first voltage measuring means is constituted by, for example, an A / D converter, a voltmeter or the like. The capacitance measuring means and the object detecting means are constituted by, for example, a microcomputer.

  A measurement method according to a fourth aspect of the present invention is a measurement method of a measurement device that measures the capacitance between an electrode and a space around the electrode. A second capacitor that is sufficiently larger than the electrode and connected in series with the electrode, a discharge step that discharges the electrode, and only the second capacitor until the voltage of the second capacitor reaches a predetermined threshold. A first charging step of charging, a second charging step of charging the second capacitor and the electrode by applying a predetermined voltage higher than a threshold value to both ends of the series circuit including the second capacitor and the electrode, The charge is transferred from the second capacitor to the first capacitor until the voltage of the capacitor reaches the threshold, and the charge transfer step for discharging the electrode charge, the second charge step, and the charge transfer step are performed once. Real Based on the amount of charge accumulated in the first capacitor by including a step of measuring a capacitance.

  In the fourth aspect of the present invention, a first capacitor having a sufficiently larger capacitance than the electrode, a second capacitor having a sufficiently larger capacitance than the electrode and connected in series to the electrode, and the electrode being discharged After only the second capacitor is charged until the voltage of the second capacitor reaches a predetermined threshold, a predetermined voltage greater than the threshold is applied to both ends of the series circuit composed of the second capacitor and the electrode, Charging the second capacitor and the electrode, transferring the charge from the second capacitor to the first capacitor until the voltage of the second capacitor reaches a threshold, and discharging the electrode charge one or more times, The capacitance is measured based on the amount of charge accumulated in the first capacitor.

  Therefore, the capacitance measurement accuracy is improved.

  This electrode is constituted by an electrode made of, for example, stainless steel. The first capacitor and the second capacitor are composed of capacitors, for example. The discharging step, the first charging step, the second charging step, the charge transfer step, and the measuring step are executed by a microcomputer, for example.

  According to the first to fourth aspects of the present invention, the capacitance between the electrode and the space around the electrode can be measured. In particular, according to the first to fourth aspects of the present invention, capacitance measurement accuracy is improved.

It is a figure which shows the structural example of 1st Embodiment of an electrostatic capacitance measuring device. It is a figure which shows the structural example of a microcomputer. It is a figure which shows the structural example of a voltage measurement part. It is a flowchart for demonstrating a measurement process. It is a figure which shows transition of the accumulation charge amount of the capacitor | condenser and detection electrode during a measurement process. It is a graph which shows transition of the voltage of A thru | or C point of the electrostatic capacitance measuring device in measurement processing. It is a flowchart for demonstrating the detail of a total charge discharge process. It is a figure which shows the flow of the positive charge during a total charge discharge process. It is a flowchart for demonstrating the detail of a C2 charge process. It is a figure which shows the flow of the positive charge during C2 charge process. It is a flowchart for demonstrating the detail of a detection electrode charge process. It is a figure which shows the flow of the positive charge during a detection electrode charge process. It is a flowchart for demonstrating the detail of a charge transfer process. It is a figure which shows the flow of the positive charge during a charge transfer process. It is a flowchart for demonstrating the detail of a parameter measurement process. It is a figure which shows the flow of the positive charge during a parameter measurement process. It is a flowchart for demonstrating the modification of a measurement process. It is a flowchart for demonstrating the modification of a parameter measurement process. It is a figure which shows the structural example of 2nd Embodiment of an electrostatic capacitance measuring device. It is a flowchart for demonstrating a measurement process. It is a flowchart for demonstrating the detail of a total charge discharge process. It is a figure which shows the flow of the positive charge during a total charge discharge process. It is a flowchart for demonstrating the detail of a C2 charge process. It is a figure which shows the flow of the positive charge during C2 charge process. It is a flowchart for demonstrating the detail of a detection electrode charge process. It is a figure which shows the flow of the positive charge during a detection electrode charge process. It is a flowchart for demonstrating the detail of a charge transfer process. It is a figure which shows the flow of the positive charge during a charge transfer process. It is a flowchart for demonstrating the detail of a parameter measurement process. It is a figure which shows the flow of the positive charge during a parameter measurement process. It is a figure which shows the modification of 2nd Embodiment of an electrostatic capacitance measuring apparatus. It is a figure which shows the structural example of 3rd Embodiment of an electrostatic capacitance measuring device. It is a flowchart for demonstrating a measurement process. It is a flowchart for demonstrating the detail of a total charge discharge process. It is a figure which shows the flow of the positive charge during a total charge discharge process. It is a flowchart for demonstrating the detail of a C2 charge process. It is a figure which shows the flow of the positive charge during C2 charge process. It is a flowchart for demonstrating the detail of a detection electrode charge process. It is a figure which shows the flow of the positive charge during a detection electrode charge process. It is a flowchart for demonstrating the detail of a charge transfer process. It is a figure which shows the flow of the positive charge during a charge transfer process. It is a flowchart for demonstrating the detail of a parameter measurement process. It is a figure which shows the flow of the positive charge during a parameter measurement process. It is a figure which shows the structural example of 4th Embodiment of an electrostatic capacitance measuring device. It is sectional drawing which shows the structural example of a shield electrode. It is a figure which shows the structural example of 5th Embodiment of an electrostatic capacitance measuring device. It is a flowchart for demonstrating a measurement process. It is a flowchart for demonstrating the detail of a total charge discharge process. It is a figure which shows the flow of the positive charge during a total charge discharge process. It is a flowchart for demonstrating the detail of C2, C3 charge process. It is a figure which shows the flow of the positive charge during C2 and C3 charge processing. It is a flowchart for demonstrating the detail of a detection electrode and a shield electrode charge process. It is a figure which shows the flow of the positive charge during a detection electrode and a shield electrode charge process. It is a flowchart for demonstrating the detail of a charge transfer process. It is a figure which shows the flow of the positive charge during a charge transfer process. It is a figure which shows the modification of 6th Embodiment of an electrostatic capacitance measuring device. It is a flowchart for demonstrating a measurement process. It is a flowchart for demonstrating the detail of a total charge discharge process. It is a figure which shows the flow of the positive charge during a total charge discharge process. It is a flowchart for demonstrating the detail of a detection electrode and a shield electrode charge process. It is a figure which shows the flow of the positive charge during a detection electrode and a shield electrode charge process. It is a figure which shows the structural example of 7th Embodiment of an electrostatic capacitance measuring apparatus. It is a figure which shows the structural example of a microcomputer. It is a flowchart for demonstrating a measurement process. It is a figure which shows the structural example of 8th Embodiment of an electrostatic capacitance measuring apparatus. It is a figure which shows the structural example of an electrostatic capacitance sensor. It is a flowchart for demonstrating an object detection process. It is a figure which shows the structural example of 9th Embodiment of an electrostatic capacitance measuring apparatus. It is a flowchart for demonstrating a threshold voltage setting process.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. First embodiment (basic configuration example of capacitance measuring device)
2. Second embodiment (first example enabling measurement time to be shortened)
3. Third embodiment (second example enabling measurement time to be shortened)
4). Fourth Embodiment (Example in which directionality is given to capacitance measurement)
5. Fifth Embodiment (Example in which detection electrode and shield electrode are controlled to have the same voltage)
6). Sixth embodiment (an example in which the measurement time of the fifth embodiment can be shortened)
7). Seventh Embodiment (Example in which a plurality of electrodes can be used for both detection electrodes and shield electrodes)
8). Eighth embodiment (example of measuring the capacitance between two electrodes)
9. Ninth embodiment (example applied to a capacitance sensor)
10. Tenth Embodiment (Example in which threshold voltage can be automatically set)
11. Modified example

<1. First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS.

[Configuration Example of Capacitance Measuring Device 101]
FIG. 1 is a diagram illustrating a configuration example of a capacitance measuring device 101 according to the first embodiment of the present invention.

  The capacitance measuring device 101 is a device that measures the capacitance between the detection electrode 112 and the space around the detection electrode 112.

  Instead of measuring the capacitance itself, it is also possible to measure a capacitance parameter corresponding to the capacitance. The electrostatic capacity parameter is a physical quantity that can be converted into an electrostatic capacity by a calculation formula, and includes, for example, a voltage, an amount of charge, the number of repetitions of an operation until reaching a predetermined voltage, a time until reaching a predetermined voltage, and the like.

  The capacitance measured by the capacitance measuring device of the present invention includes a capacitance parameter that is a physical quantity that can be converted into a capacitance by a calculation formula. Therefore, hereinafter, the process of measuring the capacitance may be described as “measuring the capacitance parameter”.

  As will be described later, the capacitance measuring device 101 has, for example, a predetermined potential with respect to a predetermined reference voltage point by the power source 104 in a state where the detection electrode 112 is installed at a predetermined position. When there is no object 103 near the detection electrode 112, the potential of the detection electrode 112 with respect to the reference voltage point is changed by accumulating charges in the detection electrode 112, so that the potential of the detection electrode 112 and the object 103 becomes equal. The capacitance is measured when Thereby, the influence of the potential of the object 103 can be removed, and the capacitance between the object 102 to be detected and the detection electrode 112 can be accurately measured.

  The reference voltage point can be arbitrarily set according to the usage application of the capacitance measuring device 101, and is set to, for example, ground, vehicle body ground, or the like.

  The capacitance measuring device 101 is configured to include a microcomputer 111, a detection electrode 112, a resistor R1, capacitors C1 and C2, and a connection terminal T1. Further, the microcomputer 111 includes ports P1 to P4.

  The capacitor C1 is connected between the port P1 and the port P2. The resistor R1 is connected between the port P2 and the port P3. The capacitor C2 is connected between the port P3 and the port P4. The connection terminal T1 is connected to the port P4. The detection electrode 112 is detachable from the connection terminal T1. Note that the detection electrode 112 may be directly connected to the port P4 instead of the connection terminal T1.

  Further, the capacitances of the capacitor C1 and the capacitor C2 are set to be sufficiently larger than the capacitance between the detection electrode 112 and the surrounding space.

  FIG. 2 is a diagram showing a detailed configuration example of the microcomputer 111. The microcomputer 111 includes voltage measuring units 121 and 122, a parameter measuring unit 123, an arithmetic processing unit 124, an output unit 125, charge supply units 126-1 and 126-2, and SW (switches) 1 to 6. Composed.

  One end of SW1 is connected to port P1, and the other end of SW1 is connected to ground. One end of SW2 is connected to port P4, and the other end of SW2 is connected to ground. One end of SW3 is connected to the charge supply unit 126-1, and the other end of SW3 is connected to port P2. One end of SW4 is connected to port P2, and the other end of SW4 is connected to ground. One end of SW5 is connected to the charge supply unit 126-2, and the other end of SW5 is connected to one end of ports P3 and SW6. The other end of SW6 is connected to the ground. The ground is connected to an external reference voltage point, and as a result, the reference voltage for the operation of the microcomputer 111 is set as the reference voltage point.

  The voltage measurement unit 121 has an input terminal connected to the port P <b> 2 and supplies a measurement result of the voltage input to the input terminal to the parameter measurement unit 123.

  The voltage measurement unit 122 has an input terminal connected to the port P <b> 3, and supplies the measurement result of the voltage input to the input terminal to the parameter measurement unit 123.

  For example, the voltage measuring units 121 and 122 include a comparator 141 as shown in FIG. The comparator 141 measures the voltage input to the input terminal, compares the measured voltage with a predetermined threshold voltage Vref, and outputs the result.

  Note that the digital signal input terminal of the microcomputer 111 can be used as the comparator 141. That is, since the digital signal input terminal identifies whether the input signal is high level or low level based on whether or not the voltage of the input signal is equal to or higher than a predetermined threshold, the function can be used. It is. In addition, for example, the threshold voltage Vref can be set to an arbitrary value by using a 2-bit terminal of the microcomputer 111 for input and output and inputting a voltage by resistance division.

  The parameter measurement unit 123 controls the opening and closing of SW1 to SW6 and measures the capacitance parameter based on the measurement results of the voltage measurement unit 121 and the voltage measurement unit 122. The parameter measurement unit 123 supplies the measured capacitance parameter to the arithmetic processing unit 124.

  Based on the capacitance parameter measured by the parameter measurement unit 123, the calculation processing unit 124 calculates another capacitance parameter, for example, a capacitance. The arithmetic processing unit 124 supplies the capacitance parameter measured by the parameter measurement unit 123 and the calculated capacitance parameter to the output unit 125.

  The output unit 125 outputs the capacitance parameter to the outside.

  Hereinafter, the capacitance of the capacitor C1 is represented by C1, the voltage is represented by Vc1, and the accumulated charge amount is represented by Qc1. The capacitance of the capacitor C2 is represented by C2, the voltage is represented by Vc2, and the accumulated charge amount is represented by Qc2. Furthermore, the capacitance between the detection electrode 112 and the surrounding space is represented by Cx, the voltage of the detection electrode 112 is represented by Vx, and the accumulated charge amount is represented by Qx. The resistance value of the resistor R1 is represented by R1. Further, hereinafter, the electrode on the port P2 side of the capacitor C1 is referred to as a positive electrode, and the electrode on the port P1 side is referred to as a negative electrode. Hereinafter, the electrode on the port P3 side of the capacitor C2 is referred to as a positive electrode, and the electrode on the port P4 side is referred to as a negative electrode.

  Hereinafter, an example in which the charge supply units 126-1 and 126-2 are configured by a power supply Vcc that is a constant voltage power supply will be described. Accordingly, in the specification and drawings, the power supply Vcc is shown instead of the charge supply units 126-1 and 126-2. Hereinafter, the voltage of the power supply Vcc is represented by Vcc.

  Further, hereinafter, the voltage at point A (potential at point A with reference to the reference voltage point) among the resistor R1, the capacitor C1, and the port P2 is represented by Va. The voltage Va is substantially equal to the voltage input to the voltage measuring unit 121. A voltage at point B (potential at point B with reference to the reference voltage point) among the resistor R1, capacitor C2, and port P3 is represented by Vb. The voltage Vb is substantially equal to the voltage input to the voltage measuring unit 122. Further, a voltage at a point C between the capacitor C2, the connection terminal T1, and the port P4 (a potential at a point C with respect to the reference voltage point) is represented by Vc.

[Processing of Capacitance Measuring Device 101]
Next, processing of the capacitance measuring apparatus 101 will be described with reference to FIGS.

  First, a measurement process executed by the capacitance measuring device 101 will be described with reference to FIGS. FIG. 4 is a flowchart for explaining the measurement process. FIG. 5 is a diagram showing transitions of the accumulated charge amount Qc1 of the capacitor C1, the accumulated charge amount Qc2 of the capacitor C2, and the accumulated charge amount Qx of the detection electrode 112 during the measurement process. FIG. 6 is a graph showing changes in voltage Va at point A, voltage Vb at point B, and voltage Vc at point C. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates voltage (potential with respect to the reference voltage point).

  In step S <b> 1, the capacitance measuring device 101 performs a total charge discharge process.

  Here, with reference to FIG. 7 and FIG. 8, the detail of the all-charge discharge process of step S1 is demonstrated. FIG. 7 is a flowchart for explaining the all charge discharge process, and FIG. 8 is a diagram showing the flow of positive charges during the all charge discharge process.

  In step S21, the parameter measurement unit 123 turns on SW1, SW2, SW4, and SW6. As a result, a positive charge moves in the direction of arrow A1 from the positive electrode of the capacitor C1 to the ground via SW4, and discharging of the capacitor C1 is started. Further, the positive charge moves from the positive electrode of the capacitor C2 to the ground via the SW6 in the direction of the arrow A2, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A3, and the discharge of the detection electrode 112 is started.

  In step S <b> 22, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for all the charges of the capacitor C <b> 1, the capacitor C <b> 2, and the detection electrode 112 to be discharged.

  In step S23, the parameter measurement unit 123 turns off SW1, SW2, SW4, and SW6. Thereafter, the total charge discharge process ends.

  As a result, as shown in FIG. 5A, the accumulated charge amount Qc1 of the capacitor C1, the accumulated charge amount Qc2 of the capacitor C2, and the accumulated charge amount Qx of the detection electrode 112 become substantially zero. If the time at the end of the total charge discharge is t0, the voltage Va at point A, the voltage Vb at point B, and the voltage Vc at point C at time t0 are as shown in FIG. Is almost equal to

  Returning to FIG. 4, in step S <b> 2, the capacitance measuring device 101 executes a C2 charging process.

  Here, with reference to FIG. 9 and FIG. 10, the detail of the C2 charge process of step S2 is demonstrated. FIG. 9 is a flowchart for explaining the C2 charging process, and FIG. 10 is a diagram showing the flow of positive charges during the C2 charging process.

  In step S41, the parameter measurement unit 123 turns on SW2 and SW3. As a result, a positive charge moves from the power source Vcc to the positive electrode of the capacitor C2 through SW3 and the resistor R1 in the direction of arrow A4, and a positive charge moves from the negative electrode of the capacitor C2 to the ground through SW2 in the direction of arrow A5. The charging of the capacitor C2 is started.

  Assuming that the start time of the process of step S41 is t1, as shown in FIG. 6, at time t1, the voltage Va at point A is substantially equal to the voltage Vcc, and the voltage Vb at point B is the capacitor C2 after time t1. As the battery charges, it gradually rises.

  In step S42, the voltage measurement unit 122 measures the voltage Vc2 of the capacitor C2 (more precisely, the voltage between the positive electrode of the capacitor C2 and the reference voltage point). The voltage measurement unit 122 compares the measured voltage Vc2 with a predetermined threshold, that is, the threshold voltage Vref, and supplies the result to the parameter measurement unit 123.

  In step S43, the parameter measurement unit 123 determines whether or not the voltage Vc2 of the capacitor C2 is equal to or higher than a threshold value (= threshold voltage Vref) based on the measurement result by the voltage measurement unit 122. When it is determined that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process returns to step S42. Thereafter, the processes in steps S42 and S43 are repeatedly executed until it is determined in step S43 that the voltage Vc2 of the capacitor C2 is equal to or higher than the threshold value. As a result, the capacitor C2 is charged until the voltage Vc2 of the capacitor C2 reaches a threshold value or more.

  On the other hand, if it is determined in step S43 that the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold value, the process proceeds to step S44.

  In step S44, the parameter measurement unit 123 turns off SW2 and SW3. Thereby, charging of the capacitor C2 is stopped. Thereafter, the C2 charging process ends.

  As a result, as shown in FIG. 5B, the accumulated charge amount Qc2 of the capacitor C2 becomes approximately Qref (= C2 × Vref), and the accumulated charge amounts of the capacitor C1 and the detection electrode 112 remain almost zero. If the time when the C2 charging process is completed is t2, as shown in FIG. 6, at time t2, the voltage Va at the point A and the voltage Vc at the point C are substantially equal to the voltage at the reference voltage point, and the point B The voltage Vb is substantially equal to the threshold voltage Vref.

  Returning to FIG. 4, in step S <b> 3, the capacitance measuring device 101 executes the detection electrode charging process.

  Here, with reference to FIG. 11 and FIG. 12, the detail of the detection electrode charge process of step S3 is demonstrated. FIG. 11 is a flowchart for explaining the detection electrode charging process, and FIG. 12 is a diagram showing the flow of positive charges during the detection electrode charging process.

  In step S61, the parameter measurement unit 123 turns on SW5. As a result, the voltage Vb at the point B becomes substantially equal to the voltage Vcc, and a voltage substantially equal to the voltage Vcc is applied to both ends of the series circuit composed of the capacitor C2 and the detection electrode 112. Then, a positive charge moves in the direction of arrow A6 from the power source Vcc to the positive electrode of the capacitor C2 via SW5, and charging of the capacitor C2 is started. Further, since positive charges are accumulated on the positive electrode of the capacitor C2, the same amount of positive charges moves from the negative electrode of the capacitor C2 to the detection electrode 112 in the direction of the arrow A7, and charging of the detection electrode 112 is started. At this time, since the amount of charge moving in the direction of arrow A6 and the amount of charge moving in the direction of arrow A7 are substantially equal, the amount of increase in the charge of capacitor C2 and detection electrode 112 is substantially equal.

  In step S62, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for the detection electrode 112 to be fully charged.

  In step S63, the parameter measurement unit 123 turns off SW5. Thereby, charging of the capacitor C2 and the detection electrode 112 is stopped. Thereafter, the detection electrode charging process ends.

  The voltage Vc2 of the capacitor C2 and the voltage Vx of the detection electrode 112 at the time when the detection electrode charging process is completed are stored in advance in the capacitor C2 with a charge amount Qref (= C2 × Vref) before the detection electrode charging process. Therefore, the following equations (1) and (2) are obtained.

  Here, since the capacitance C2 of the capacitor C2 is set to the capacitance Cx of the detection electrode 112, Cx / (C2 + Cx) ≈0 and C2 / (C2 + Cx) ≈1. When this is applied to the equations (1) and (2), the voltage Vc2≈Vref of the capacitor C2 and the voltage Vx≈Vcc−Vref of the detection electrode 112 are obtained. Then, by setting the threshold voltage Vref to an appropriate value, the voltage Vx when the detection electrode 112 is charged can be set to a value substantially equal to the voltage of the object 103. Therefore, the threshold voltage Vref is set to a value obtained by subtracting the voltage (= the voltage of the power supply 104) with respect to the reference voltage point of the object 103 from the voltage Vcc of the power supply Vcc.

  Then, by setting the voltage Vx during charging of the detection electrode 112 to a value substantially equal to the voltage of the object 103, the charge accumulated by the capacitance between the detection electrode 112 and the object 103 is substantially zero. Charge is accumulated in the detection electrode 112. In other words, a charge corresponding to the capacitance excluding the capacitance between the detection electrode 112 and the object 103 out of the capacitance between the detection electrode 112 and its surroundings is accumulated in the detection electrode 112. The In other words, charges are accumulated in the detection electrode 112 with little influence from the potential of the object 103.

  Further, if the increase amount of the charge of the capacitor C2 due to the detection electrode charging process is ΔQ, ΔQ is substantially equal to the accumulated charge amount of the detection electrode 112 at the end of the detection electrode charging process. Therefore, the charge increase amount ΔQ of the capacitor C2 is also a value that is hardly affected by the object 103.

  As shown in FIG. 5C, when the detection electrode charging process is completed, the accumulated charge amount Qc2 of the capacitor C2 = Qref + ΔQ, and the accumulated charge amount Qx = ΔQ of the detection electrode 112 is obtained. The charge increase amount ΔQ is expressed by the following equation (3).

  Returning to FIG. 4, in step S <b> 4, the capacitance measuring device 101 executes a charge transfer process.

  Here, with reference to FIG. 13 and FIG. 14, the details of the charge transfer processing in step S4 will be described. FIG. 13 is a flowchart for explaining the charge transfer process, and FIG. 14 is a diagram showing the flow of positive charges during the charge transfer process.

  In step S81, the parameter measurement unit 123 turns on SW1 and SW2. As a result, the positive charge moves from the capacitor C2 to the capacitor C1 via the resistor R1 in the direction of the arrow A8, and the transfer of the charge from the capacitor C2 to the capacitor C1 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A9, and the discharge of the detection electrode 112 is started.

  In step S82, the voltage Vc2 of the capacitor C2 is measured as in the process of step S42 of FIG. 9, and in step S83, it is determined whether or not the voltage Vc2 of the capacitor C2 is equal to or lower than a threshold value (= threshold voltage Vref). The If it is determined that the voltage Vc2 of the capacitor C2 is greater than the threshold value, the process returns to step S82. Thereafter, in step S83, steps S82 and S83 are repeatedly executed until it is determined that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value. As a result, charges are transferred from the capacitor C2 to the capacitor C1 until the voltage Vc2 of the capacitor C2 becomes equal to or lower than the threshold value.

  On the other hand, when it is determined in step S83 that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, the process proceeds to step S84.

  In step S84, the parameter measurement unit 123 turns off SW1 and SW2. Thereby, the transfer of charge from the capacitor C2 to the capacitor C1 is stopped. Thereafter, the charge transfer process ends.

  As a result of this charge transfer process, as shown in FIG. 5D, an amount of charge approximately equal to the increase amount ΔQ of the charge of the capacitor C2 due to the detection electrode charging process in step S3 is transferred from the capacitor C2 to the capacitor C1. Therefore, the voltage Vc1 of the capacitor C1 at this time is obtained by the following equation (4).

  As described above, since the increase amount ΔQ of the charge of the capacitor C2 is hardly affected by the object 103, the accumulated charge amount Qc1 of the capacitor C1 is hardly affected by the object 103.

  Returning to FIG. 4, in step S <b> 5, the parameter measurement unit 123 determines whether the processes of steps S <b> 3 to S <b> 5 have been repeated a predetermined number of times. If it is determined that the predetermined number of times has not been repeated, the process returns to step S3, and the processes in steps S3 to S5 are repeatedly executed until it is determined in step S5 that the predetermined number of times has been repeated.

  On the other hand, if it is determined in step S5 that the processes in steps S3 to S5 have been repeated a predetermined number of times, the process proceeds to step S6.

  If the processes in steps S3 to S5 are repeated n times, as shown in FIG. 5E, the capacitor C1 stores an amount of charge of n × ΔQ. Further, the voltage Vc1 (n) of the capacitor C1 after the processes of steps S3 to S5 are repeated n times is a value represented by the following equation (5).

  Accordingly, as shown in FIG. 6, the voltage Va at the point A increases as the charging of the capacitor C1 proceeds during the period in which the processing of steps S3 to S5 is repeated (the period between time t2 and time t3 in the figure). Will gradually rise. In the period between time t2 and time t3, the voltage Va at point A is substantially equal to the value of equation (5) when the detection electrode 112 is discharged, and is substantially equal to the voltage Vcc when the detection electrode 112 is charged. Become. Further, the voltage Va at the point A does not exceed the voltage Vcc.

  The voltage Vb at point B is substantially equal to the reference voltage Vref when the detection electrode 112 is discharged, and is substantially equal to the voltage Vcc when the detection electrode 112 is charged.

  Further, the voltage Vc at the point C is substantially equal to the voltage at the reference voltage point when the detection electrode 112 is discharged, and is substantially equal to Vcc−Vref when the detection electrode 112 is charged.

  In step S <b> 6, the capacitance measuring device 101 executes parameter measurement processing.

  Here, with reference to FIG. 15 and FIG. 16, the details of the parameter measurement processing in step S6 will be described. FIG. 15 is a flowchart for explaining the parameter measurement process, and FIG. 16 is a diagram showing the flow of positive charges during the parameter measurement process.

  In step S101, the parameter measurement unit 123 turns on SW1 and SW5. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C1 via SW5 and the resistor R1 in the direction of arrow A10, and the positive charge moves from the negative electrode of the capacitor C1 to the ground via SW1 in the direction of arrow A11. The charging of the capacitor C1 is started.

  Therefore, if the start time of the parameter measurement process is t3, as shown in FIG. 6, the voltage Vb at the point B becomes substantially equal to the voltage Vcc at the time t3, and the voltage Va at the point A gradually increases after the time t3. To rise.

  In step S102, the parameter measurement unit 123 starts time measurement.

  In step S103, the voltage measurement unit 121 measures the voltage Vc1 of the capacitor C1 (more precisely, the voltage between the positive electrode of the capacitor C1 and the reference voltage point). The voltage measurement unit 121 compares the measured voltage Vc1 with a predetermined threshold, that is, the threshold voltage Vref, and supplies the result to the parameter measurement unit 123.

  In step S <b> 104, the parameter measurement unit 123 determines whether or not the voltage Vc <b> 1 of the capacitor C <b> 1 is greater than or equal to the threshold based on the measurement result by the voltage measurement unit 121. If it is determined that the voltage Vc1 of the capacitor C1 is less than the threshold value, the process returns to step S103. Thereafter, the processes in steps S103 and S104 are repeatedly executed until it is determined in step S104 that the voltage Vc1 of the capacitor C1 is equal to or higher than the threshold value.

  On the other hand, if it is determined in step S104 that the voltage Vc1 of the capacitor C1 is greater than or equal to the threshold value, the process proceeds to step S105.

  In step S105, the parameter measurement unit 123 ends the time measurement. As a result, the charging time t until the voltage Vc1 of the capacitor C1 reaches the threshold voltage Vref from the voltage shown in the above equation (5) is measured. The parameter measuring unit 123 supplies the measured charging time t to the arithmetic processing unit 124.

  Note that the relationship between the voltage Vc1 (n) of the capacitor C1 and the charging time t after the charge transfer process of step S4 is performed n times is expressed by the following equation (6).

  As the electrostatic capacitance Cx of the detection electrode 112 is larger and the value of the accumulated charge amount ΔQ is larger, the accumulated charge amount Qc1 and the voltage Vc1 of the capacitor C1 at the start of the parameter measurement process are larger, so the charging time t is shorter. . Conversely, as the electrostatic capacitance Cx of the detection electrode 112 decreases, the accumulated charge amount Qc1 and the voltage Vc1 of the capacitor C1 at the start of the parameter measurement process decrease, so the charging time t increases.

  Further, as described above, the accumulated charge amount Qc1 of the capacitor C1 is hardly affected by the object 103, and therefore the charging time t is hardly affected by the object 103. That is, the charging time t is a value reflecting the capacitance Cx of the detection electrode 112 excluding the influence of the object 103.

  In step S106, the parameter measurement unit 123 turns off SW1 and SW5. Thereby, the charging of the capacitor C1 is stopped. Thereafter, the parameter measurement process ends.

  If the time at the end of the parameter measurement process is t4, as shown in FIG. 6, the voltage Va at the point A becomes substantially equal to the threshold voltage Vref at the time t4, and the voltage Vb at the point B is equal to the voltage Vcc. Almost equal. Further, when the capacitance C1 of the capacitor C1 and the capacitance C2 of the capacitor C2 are equal, as shown in FIG. 5F, the accumulated charge amounts of the capacitor C1 and the capacitor C2 are both about Qref.

  Note that the capacitances of the capacitors C1 and C2 are not necessarily matched.

  Returning to FIG. 4, in step S7, the arithmetic processing unit 124 performs arithmetic processing. For example, the arithmetic processing unit 124 calculates the capacitance Cx of the detection electrode 112 using the charging time t. Specifically, the following equation (7) is obtained by substituting equation (5) into equation (6) described above and solving for the capacitance Cx.

  The arithmetic processing unit 124 calculates the capacitance Cx of the detection electrode 112 based on Expression (7). Thereby, the capacitance Cx of the detection electrode 112 excluding the influence of the object 103 can be obtained. The arithmetic processing unit 124 supplies the calculated capacitance Cx and the charging time t measured by the parameter measuring unit 123 to the output unit 125.

  In step S8, the output unit 125 outputs the measurement result. At this time, both the capacitance Cx and the charging time t may be output, or one of them may be output. Thereafter, the measurement process ends.

  Although the case where the capacitance measurement process is performed once has been described above, it is also possible to repeatedly perform the measurement process. When the measurement process is repeatedly performed, as indicated by a broken line in FIG. 4, the process returns to step S1 after the process of step S8 is completed. In this case, it is necessary to turn off only SW5 in step S105 of FIG.

  Thereby, after the process of step S8 is completed, in step S1, the all-charge discharge process of FIG. 7 is executed, and the charges accumulated in the capacitors C1 and C2 and the detection electrode 112 are discharged. If the time at this time is t5, as shown in FIG. 6, at time t5, the voltage Va at point A and the voltage Vb at point B are substantially equal to the voltage at the reference voltage point. Subsequently, by performing the processing from step S2 onward in FIG. 4, it is possible to repeatedly measure the capacitance parameter.

  As described above, the influence of the object 103 having a voltage different from the reference voltage point can be removed, and the electrostatic capacitance between the detection electrode 112 and the surrounding space can be measured.

  For example, when measuring the capacitance of the surrounding space in an automobile, an object having a potential difference from the reference body ground, such as another electronic circuit or a detection unit of another sensor, exists around the detection electrode. There are many cases. However, if the capacitance measuring device 101 is used, even when an object having a potential difference with respect to the body ground exists around the detection electrode 112, the capacitance can be measured without being affected by the object. .

  Further, as shown in FIG. 6, the voltage Vc at the point C (≈the voltage Vx of the detection electrode 112) has dropped to the reference voltage point in most of the time. It can be made difficult to receive.

  Further, as shown in FIG. 6, the voltage Va at the point A and the voltage Vb at the point B do not exceed the voltage of the power source Vcc, and the voltage exceeding the voltage of the power source Vcc is present in the voltage measuring unit 121 and the voltage measuring unit 122. It is not applied. Therefore, it is possible to suppress the occurrence of failure and deterioration of the elements constituting the voltage measuring unit 121.

  The capacitance parameter is not limited to the above example, and changes according to the capacitance Cx of the detection electrode 112 (accumulated charge amount ΔQ of the detection electrode 112 accumulated by one charge). Other types of parameters may be measured. Here, another example of the capacitance parameter will be described with reference to FIGS. 17 and 18.

[First Modification of Capacitance Parameter]
First, a first modification of the capacitance parameter will be described with reference to FIG. FIG. 17 is a flowchart for explaining a measurement process corresponding to the first modification of the capacitance parameter.

  In step S121, as in the process of step S1 of FIG. 4, the all charge discharge process is executed.

  In step S122, the C2 charging process is executed in the same manner as in step S2 of FIG.

  In step S123, the detection electrode charging process is executed in the same manner as in step S3 of FIG.

  In step S124, the charge transfer process is executed in the same manner as the process in step S4 of FIG.

  In step S125, the voltage Vc1 of the capacitor C1 is measured as in the process of step S103 in FIG.

  In step S126, the parameter measurement unit 123 increments the number of times the capacitor C1 is charged.

  In step S127, it is determined whether or not the voltage Vc1 of the capacitor C1 is equal to or higher than the threshold, as in the process of step S104 of FIG. When it is determined that the voltage Vc1 of the capacitor C1 is less than the threshold value, the process returns to step S123. Thereafter, the processes in steps S123 to S127 are repeatedly executed until it is determined in step S127 that the voltage Vc1 of the capacitor C1 is equal to or higher than the threshold value.

  On the other hand, if it is determined in step S127 that the voltage Vc1 of the capacitor C1 is greater than or equal to the threshold value, the process proceeds to step S128.

  In step S128, the arithmetic processing unit 124 performs arithmetic processing. Specifically, the parameter measuring unit 123 supplies the counted number of times of charging n to the arithmetic processing unit 124. The arithmetic processing unit 124 calculates the capacitance Cx of the detection electrode 112 based on the number of times of charging n. If the number of times of charging when the capacitor Vc1 is equal to or higher than the threshold voltage Vref is n, the capacitance Cx of the detection electrode 112 is substituted by substituting Vc1 (n) = Vref into the left side of the above-described equation (5). Can be calculated. The arithmetic processing unit 124 supplies the calculated capacitance Cx and the number of times of charging n measured by the parameter measuring unit 123 to the output unit 125.

  In step S129, the output unit 125 outputs the measurement result. At this time, both the capacitance Cx and the number of times of charging n may be output, or one of them may be output. Thereafter, the measurement process ends.

  Instead of the number of times of charging n, the charging time until the voltage Vc1 of the capacitor C1 becomes equal to or greater than a threshold value may be measured as a capacitance parameter.

[Second Modification of Capacitance Parameter]
Next, a second modification of the capacitance parameter will be described with reference to FIG.

  In the case of the second modification, the voltage measuring units 121 and 122 are configured by, for example, A / D converters. That is, the voltage measuring units 121 and 122 convert the input analog voltage value into a digital voltage value and output the digital voltage value.

  In this case, the parameter measurement process in step S6 in FIG. 4 is executed according to the flowchart in FIG.

  That is, in step S161, the parameter measurement unit 123 turns on SW1.

  In step S <b> 162, the voltage measurement unit 122 measures the voltage Vc <b> 1 of the capacitor C <b> 1 and supplies the measurement result to the parameter measurement unit 123. In this case, not the comparison result of the voltage Vc1 of the capacitor C1 and the threshold voltage Vref but the actual measurement value of the voltage Vc1 is supplied to the parameter measurement unit 123. The parameter measurement unit 123 sets the obtained actual measurement value of the voltage Vc1 as a capacitance parameter.

  And if voltage Vc1 is known, the electrostatic capacitance Cx of the detection electrode 112 can be calculated | required based on Formula (5) mentioned above.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the cost can be reduced as compared with the first embodiment.

[Configuration Example of Capacitance Measuring Device 201]
FIG. 19 is a diagram illustrating a configuration example of the capacitance measuring device 201 according to the second embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance measuring device 201 is different from the capacitance measuring device 101 of FIG. 2 in that a resistor R 2 is added and a microcomputer 211 is provided instead of the microcomputer 111. The microcomputer 211 is different from the microcomputer 111 in that a parameter measurement unit 221 is provided instead of the parameter measurement unit 123, and the voltage measurement units 122, SW5, SW6, and the port P3 are deleted.

  Furthermore, in the capacitance measuring device 201, the connection of each component is partially different compared to the capacitance measuring device 101. Specifically, one end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R1 is connected to one end of the capacitor C2. The other end of the resistor R2 is connected to the port P2. One end of the capacitor C1 is connected between the resistors R1 and R2, and the other end of the capacitor C1 is connected to the port P1. One end different from the one connected to the resistor R1 of the capacitor C2 is connected to the port P4 and the connection terminal T1. The connection of other components is the same as that of the capacitance measuring apparatus 101.

  The parameter measuring unit 221 controls the opening and closing of SW1 to SW4, and measures the capacitance parameter based on the measurement result of the voltage measuring unit 121. The parameter measurement unit 221 supplies the measured capacitance parameter to the arithmetic processing unit 124.

[Processing of Capacitance Measuring Device 201]
Next, processing of the capacitance measuring device 201 will be described with reference to FIGS.

  First, the measurement process executed by the capacitance measuring device 201 will be described with reference to the flowchart of FIG.

  In step S201, the capacitance measuring device 201 performs a total charge discharge process.

  Here, with reference to FIG. 21 and FIG. 22, the details of the all charge discharge process in step S201 will be described. FIG. 21 is a flowchart for explaining the all charge discharge process, and FIG. 22 is a diagram showing the flow of positive charges during the all charge discharge process.

  In step S221, the parameter measurement unit 221 turns on SW1, SW2, and SW4. As a result, a positive charge moves in the direction of arrow A21 from the positive electrode of the capacitor C1 to the ground via the resistors R2 and SW4, and discharging of the capacitor C1 is started. Further, the positive charge moves from the positive electrode of the capacitor C2 to the ground via the resistors R1, R2 and SW4 in the directions of the arrows A22 and A21, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A23, and the discharge of the detection electrode 112 is started.

  In step S222, the parameter measurement unit 221 waits for a predetermined time, that is, a time sufficient for all the charges of the capacitor C1, the capacitor C2, and the detection electrode 112 to be discharged.

  In step S223, the parameter measurement unit 221 turns off SW1, SW2, and SW4. Thereafter, the total charge discharge process ends.

  Returning to FIG. 20, in step S <b> 202, the capacitance measuring device 201 executes a C2 charging process.

  Here, with reference to FIG. 23 and FIG. 24, the detail of the C2 charge process of step S202 is demonstrated. FIG. 23 is a flowchart for explaining the C2 charging process, and FIG. 24 is a diagram showing the flow of positive charges during the C2 charging process.

  In step S241, the parameter measurement unit 221 turns on SW2 and SW3. As a result, a positive charge moves from the power source Vcc to the positive electrode of the capacitor C2 via SW3, the resistor R2 and the resistor R1 in the direction of arrow A24, and from the negative electrode of the capacitor C2 to the ground via SW2 to the positive direction of the arrow A25 Moves, and charging of the capacitor C2 is started.

  In step S242, the parameter measurement unit 221 turns off SW3 after a predetermined time has elapsed. Thereby, charging of the capacitor C2 is stopped.

  In step S243, the voltage measurement unit 121 measures the voltage Vc2 of the capacitor C2. The voltage measurement unit 121 compares the measured voltage Vc2 with the threshold voltage Vref and supplies the result to the parameter measurement unit 221.

  In step S244, it is determined whether or not the voltage Vc2 of the capacitor C2 is equal to or higher than the threshold, as in the process of step S43 of FIG. If it is determined that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process proceeds to step S245.

  In step S245, the parameter measurement unit 221 turns on SW3. As a result, charging of the capacitor C2 resumes.

  Thereafter, the process returns to step S242, and the processes of steps S242 to S245 are repeatedly executed until it is determined in step S244 that the voltage Vc2 of the capacitor C2 is equal to or higher than the threshold value. As a result, the capacitor C2 is charged until the voltage Vc2 of the capacitor C2 reaches a threshold value or more.

  On the other hand, if it is determined in step S244 that the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold value, the process proceeds to step S246.

  In step S246, the parameter measurement unit 221 turns off SW2. Thereafter, the C2 charging process ends.

  Returning to FIG. 20, in step S <b> 203, the capacitance measuring device 201 executes detection electrode charging processing.

  Here, with reference to FIG. 25 and FIG. 26, the detail of the detection electrode charge process of step S203 is demonstrated. FIG. 25 is a flowchart for explaining the detection electrode charging process, and FIG. 26 is a diagram showing a flow of positive charges during the detection electrode charging process.

  In step S261, the parameter measurement unit 221 turns on SW3. As a result, a positive charge moves in the direction of arrow A26 from the power supply Vcc to the positive electrode of the capacitor C2 via SW3, the resistor R2, and the resistor R1, and charging of the capacitor C2 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C2, the positive charge moves from the negative electrode of the capacitor C2 to the detection electrode 112 in the direction of arrow A27, and charging of the detection electrode 112 is started.

  In step S262, the parameter measurement unit 221 waits for a predetermined time, that is, a time sufficient for the detection electrode 112 to be fully charged.

  In step S263, the parameter measurement unit 221 turns off SW3. Thereby, charging of the capacitor C2 and the detection electrode 112 is stopped. Thereafter, the detection electrode charging process ends.

  Returning to FIG. 20, in step S <b> 204, the capacitance measuring device 201 executes charge transfer processing.

  Here, with reference to FIG. 27 and FIG. 28, the details of the charge transfer processing in step S204 will be described. FIG. 27 is a flowchart for explaining the charge transfer process, and FIG. 28 is a diagram showing the flow of positive charges during the charge transfer process.

  In step S281, the parameter measurement unit 221 turns on SW1 and SW2. As a result, the positive charge moves from the capacitor C2 to the capacitor C2 via the resistor R2 in the direction of the arrow A28, and the transfer of the charge from the capacitor C2 to the capacitor C1 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A29, and the discharge of the detection electrode 112 is started.

  In step S282, the voltage Vc2 of the capacitor C2 is measured as in the process of step S243 of FIG.

  In step S283, it is determined whether or not the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, similarly to the process in step S83 of FIG. If it is determined that the voltage Vc2 of the capacitor C2 is greater than the threshold value, the process returns to step S282. Thereafter, the processes of steps S282 and S283 are repeatedly executed until it is determined in step S283 that the voltage Vc2 of the capacitor C2 is equal to or less than the threshold value. As a result, charges are transferred from the capacitor C2 to the capacitor C1 until the voltage Vc2 of the capacitor C2 becomes equal to or lower than the threshold value.

  On the other hand, when it is determined in step S283 that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, the process proceeds to step S284.

  In step S284, the parameter measurement unit 221 turns off SW1 and SW2. Thereby, the transfer of charge from the capacitor C2 to the capacitor C1 is completed. Thereafter, the charge transfer process ends.

  Returning to FIG. 20, in step S205, the parameter measurement unit 221 determines whether or not the processing in steps S203 to S205 has been repeated a predetermined number of times. If it is determined that the process has not been repeated a predetermined number of times, the process returns to step S203, and the processes of steps S203 to S205 are repeatedly executed until it is determined in step S205 that the process has been repeated a predetermined number of times.

  On the other hand, if it is determined in step S205 that the processes in steps S203 to S205 have been repeated a predetermined number of times, the process proceeds to step S206.

  In step S206, the capacitance measuring device 201 executes parameter measurement processing.

  Here, with reference to FIG. 29 and FIG. 30, the details of the parameter measurement processing in step S206 will be described. FIG. 29 is a flowchart for explaining the parameter measurement process, and FIG. 30 is a diagram showing the flow of positive charges during the parameter measurement process.

  In step S301, the parameter measurement unit 221 turns on SW1, SW2, and SW3. As a result, a positive charge moves in the direction of arrow A30 from the power source Vcc to the positive electrode of the capacitor C1 via SW3 and the resistor R2, and charging of the capacitor C1 is started.

  In step S302, the parameter measurement unit 221 starts time measurement.

  In step S303, the parameter measurement unit 221 turns off SW3 after a predetermined time has elapsed. Thereby, the charging of the capacitor C1 is stopped.

  In step S304, the voltage Vc1 of the capacitor C1 is measured as in the process of step S103 in FIG.

  In step S305, it is determined whether or not the voltage Vc1 of the capacitor C1 is equal to or higher than the threshold, as in the process of step S104 of FIG. When it is determined that the voltage Vc1 of the capacitor C1 is less than the threshold value, the process proceeds to step S306.

  In step S306, the parameter measurement unit 221 turns on SW3. Thereby, charging of the capacitor C1 is resumed.

  Thereafter, the process returns to step S303, and the processes of steps S303 to S306 are repeatedly executed until it is determined in step S305 that the voltage Vc1 of the capacitor C1 is equal to or higher than the threshold value.

  On the other hand, if it is determined in step S305 that the voltage Vc1 of the capacitor C1 is greater than or equal to the threshold value, the process proceeds to step S307.

  In step S307, the time measurement is completed in the same manner as in step S105 of FIG.

  As a result of the processes in steps S302 to S307, the charging time until the voltage Vc1 of the capacitor C1 reaches the threshold voltage Vref from the voltage shown in the above equation (5), as in the processes in steps S102 to S105 in FIG. t is measured.

  In step S306, the parameter measurement unit 221 turns off SW1 and SW2. Thereafter, the parameter measurement process ends.

  Returning to FIG. 20, in step S207, calculation processing is performed in the same manner as in step S7 in FIG. 4, and in step S208, measurement results are output in the same manner as in step S8 in FIG. Thereafter, the measurement process ends.

  As described above, the capacitance measuring device 201 removes the influence of the object 103 having a voltage different from the reference voltage point in the same manner as the capacitance measuring device 101, and the detection electrode 112 and the surrounding space are removed. The capacitance between the two can be measured. In addition, the capacitance measuring device 201 can reduce the voltage measuring units 122, SW5, and SW6 as compared with the capacitance measuring device 101, and can realize cost reduction.

  Regarding the measurement time, since the flow of electric charges is delayed by the addition of the resistor R2, the capacitance measuring device 201 is slower than the capacitance measuring device 101.

[Modification of Second Embodiment]
FIG. 31 is a diagram illustrating a configuration example of a capacitance measuring device 251 which is a modified example of the second embodiment of the present invention. The capacitance measuring device 251 is obtained by deleting the resistor R2 from the capacitance measuring device 201 of FIG.

  When this configuration is adopted, a voltage measuring unit 121 that can measure an actual measured value of the input voltage, such as an A / D converter, or the method described above with reference to FIG. It is necessary to perform processing.

<3. Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, as in the second embodiment, the cost can be reduced as compared with the first embodiment.

[Configuration Example of Capacitance Measuring Device 301]
FIG. 32 is a diagram illustrating a configuration example of a capacitance measuring device 301 according to the third embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance measuring device 301 is different from the capacitance measuring device 101 of FIG. 1 in that a resistor R2 is added and a microcomputer 311 is provided instead of the microcomputer 111. The microcomputer 311 is different from the microcomputer 111 in that a parameter measurement unit 321 is provided instead of the parameter measurement unit 123, and the voltage measurement units 121, SW3, SW4, and the port P2 are deleted.

  Furthermore, in the capacitance measuring device 301, the connection of each component is partially different compared to the capacitance measuring device 101. Specifically, one end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R1 is connected to one end of the capacitor C1. The other end of the resistor R2 is connected to the port P3. One end of the capacitor C1 that is different from the one connected to the resistor R1 is connected to the port P1. One end of the capacitor C2 is connected between the resistors R1 and R2, and the other end of the capacitor C2 is connected to the port P4 and the connection terminal T1. The connection of other components is the same as that of the capacitance measuring apparatus 101.

  The parameter measurement unit 321 controls the opening / closing of SW1, SW2, SW5, and SW6, and measures the capacitance parameter based on the measurement result of the voltage measurement unit 122. The parameter measurement unit 321 supplies the measured capacitance parameter to the arithmetic processing unit 124.

[Processing of Capacitance Measuring Device 301]
Next, processing of the capacitance measuring device 301 will be described with reference to FIGS.

  First, a measurement process executed by the capacitance measuring device 301 will be described with reference to a flowchart of FIG.

  In step S401, the capacitance measuring device 301 performs a total charge discharge process.

  Here, with reference to FIG. 34 and FIG. 35, the detail of the all-charge discharge process of step S401 is demonstrated. FIG. 34 is a flowchart for explaining the all-charge discharge process, and FIG. 35 is a diagram showing the flow of positive charges during the all-charge discharge process.

  In step S421, the parameter measurement unit 321 turns on SW1, SW2, and SW6. As a result, positive charge moves from the positive electrode of the capacitor C2 to the ground via the resistors R2 and SW6 in the direction of the arrow A41, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the positive electrode of the capacitor C1 to the ground through the resistors R1, R2 and SW6 in the directions of arrows A42 and A41, and the discharge of the capacitor C1 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A43, and the discharge of the detection electrode 112 is started.

  In step S422, the parameter measurement unit 321 waits for a predetermined time, that is, a time sufficient for all the charges of the capacitor C1, the capacitor C2, and the detection electrode 112 to be discharged.

  In step S423, the parameter measurement unit 321 turns off SW1, SW2, and SW6. Thereafter, the total charge discharge process ends.

  Returning to FIG. 33, in step S402, the capacitance measuring device 301 executes the C2 charging process.

  Here, with reference to FIG. 36 and FIG. 37, the detail of the C2 charge process of step S402 is demonstrated. 36 is a flowchart for explaining the C2 charging process, and FIG. 37 is a diagram showing the flow of positive charges during the C2 charging process.

  In step S441, the parameter measurement unit 321 turns on SW2 and SW5. As a result, positive charge moves from the power source Vcc to the positive electrode of the capacitor C2 via SW5 and resistor R2 in the direction of arrow A44, and positive charge moves from the negative electrode of the capacitor C2 to ground via SW2 in the direction of arrow A45. The charging of the capacitor C2 is started.

  In step S442, the voltage Vc2 of the capacitor C2 is measured as in the process of step S42 of FIG.

  In step S443, it is determined whether or not the voltage Vc2 of the capacitor C2 is greater than or equal to the threshold value, as in the process of step S43 of FIG. When it is determined that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process returns to step S442. Thereafter, the processes of steps S442 and S443 are repeatedly executed until it is determined in step S443 that the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold value. As a result, the capacitor C2 is charged until the voltage Vc2 of the capacitor C2 reaches a threshold value or more.

  On the other hand, if it is determined in step S443 that the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold value, the process proceeds to step S444.

  In step S444, the parameter measurement unit 321 turns off SW2 and SW5. Thereby, charging of the capacitor C2 is stopped. Thereafter, the C2 charging process ends.

  Returning to FIG. 33, in step S403, the capacitance measuring device 301 executes the detection electrode charging process.

  Here, with reference to FIG. 38 and FIG. 39, the detail of the detection electrode charge process of step S403 is demonstrated. FIG. 38 is a flowchart for explaining the detection electrode charging process, and FIG. 39 is a diagram showing the flow of positive charges during the detection electrode charging process.

  In step S461, the parameter measurement unit 321 turns on SW5. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C2 through SW5 and the resistor R2 in the direction of arrow A46, and charging of the capacitor C2 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C2, the positive charge moves from the negative electrode of the capacitor C2 to the detection electrode 112 in the direction of arrow A47, and charging of the detection electrode 112 is started.

  In step S462, the parameter measurement unit 321 waits for a predetermined time, that is, a time sufficient for the detection electrode 112 to be fully charged.

  In step S463, the parameter measurement unit 321 turns off SW5. Thereby, charging of the capacitor C2 and the detection electrode 112 is stopped. Thereafter, the detection electrode charging process ends.

  Returning to FIG. 33, in step S404, the capacitance measuring device 301 executes a charge transfer process.

  Here, with reference to FIG. 40 and FIG. 41, the details of the charge transfer processing in step S404 will be described. 40 is a flowchart for explaining the charge transfer process, and FIG. 41 is a diagram showing the flow of positive charges during the charge transfer process.

  In step S481, the parameter measurement unit 321 turns on SW1 and SW2. As a result, the positive charge moves from the capacitor C2 to the capacitor C1 via the resistor R1 in the direction of the arrow A48, and the transfer of the charge from the capacitor C2 to the capacitor C1 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A49, and the discharge of the detection electrode 112 is started.

  In step S482, the voltage Vc2 of the capacitor C2 is measured as in the process of step S82 of FIG.

  In step S483, it is determined whether or not the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, similarly to the process in step S83 of FIG. If it is determined that the voltage Vc2 of the capacitor C2 is greater than the threshold value, the process returns to step S482. Thereafter, the processes of steps S482 and S483 are repeatedly executed until it is determined in step S483 that the voltage Vc2 of the capacitor C2 is equal to or less than the threshold value. As a result, charges are transferred from the capacitor C2 to the capacitor C1 until the voltage Vc2 of the capacitor C2 reaches a threshold value or less.

  On the other hand, when it is determined in step S483 that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, the process proceeds to step S484.

  In step S484, the parameter measurement unit 321 turns off SW1 and SW2. Thereby, the transfer of charge from the capacitor C2 to the capacitor C1 is completed. Thereafter, the charge transfer process ends.

  Returning to FIG. 33, in step S405, the parameter measurement unit 321 determines whether or not the processing in steps S403 to S405 has been repeated a predetermined number of times. If it is determined that the process has not been repeated a predetermined number of times, the process returns to step S403, and the processes of steps S403 to S405 are repeatedly executed until it is determined in step S405 that the process has been repeated a predetermined number of times.

  On the other hand, if it is determined in step S405 that the processes in steps S403 to S405 have been repeated a predetermined number of times, the process proceeds to step S406.

  In step S406, the capacitance measuring device 301 executes parameter measurement processing.

  Here, with reference to FIG. 42 and FIG. 43, the details of the parameter measurement processing in step S406 will be described. 42 is a flowchart for explaining the parameter measurement process, and FIG. 43 is a diagram showing the flow of positive charges during the parameter measurement process.

  In step S501, the parameter measurement unit 321 turns on SW1 and SW5. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C1 through SW5, the resistor R2, and the resistor R1 in the direction of arrow A50, and from the negative electrode of the capacitor C1 to the ground through SW1 to the ground in the direction of arrow A51 Moves, and charging of the capacitor C1 is started.

  In steps S502 to S505, the same processing as in steps S102 to S105 in FIG. 15 is executed, and the charging time t until the voltage Vc1 of the capacitor C1 reaches the threshold voltage Vref from the voltage shown in the above equation (5) is reached. It is measured.

  In step S506, the parameter measurement unit 321 turns off SW1 and SW5. Thereby, the charging of the capacitor C1 is stopped. Thereafter, the parameter measurement process ends.

  Returning to FIG. 33, in step S407, calculation processing is performed in the same manner as in step S7 in FIG. 4, and in step S408, measurement results are output in the same manner as in step S8 in FIG. Thereafter, the measurement process ends.

  As described above, the capacitance measuring device 301 removes the influence of the object 103 having a voltage different from that of the reference voltage point in the same manner as the capacitance measuring device 101, and the detection electrode 112 and the surrounding space are removed. The capacitance between the two can be measured. In addition, the capacitance measuring device 301 can reduce the voltage measuring units 121, SW3, and SW4 as compared with the capacitance measuring device 101, and can realize cost reduction.

  Regarding the measurement time, since the flow of electric charges is delayed by the addition of the resistor R2, the capacitance measuring device 301 is slower than the capacitance measuring device 101.

<4. Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the fourth embodiment, the direction of detection of the capacitance Cx of the detection electrode 112 is made directional.

[Configuration example of capacitance measuring device]
FIG. 44 is a diagram illustrating a configuration example of a capacitance measuring device 401 according to the fourth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance measuring device 401 is different from the capacitance measuring device 101 of FIG. 2 in that a microcomputer 411 is provided instead of the microcomputer 111, and a shield electrode 412 and a connection terminal T2 are added. . The microcomputer 411 is different from the microcomputer 111 in that a port P5 is added.

  The port P5 is connected to the ground and connected to the connection terminal T2.

  The shield electrode 412 is an electrode used for shielding an electric field, and is detachable from the connection terminal T2. In addition, the shield electrode 412 is connected to the ground of the microcomputer 411 via the connection terminal T2 and the port P5 while being connected to the connection terminal T2, and is held at the voltage at the reference voltage point. The shield electrode 412 may be directly connected to the port P5 instead of the connection terminal T2.

  Hereinafter, the capacitance between the shield electrode 412 and the surrounding space is represented by Cs, the voltage of the shield electrode 412 is represented by Vs, and the accumulated charge amount is represented by Qs.

  FIG. 45 is a cross-sectional view schematically showing an example of the shape of the shield electrode 412. In this example, the shield electrode 412 has a box shape that covers the detection electrode 112.

  As described above, since the shield electrode 412 is held at the voltage of the reference voltage point, even if an object approaches from the shield electrode 412 side, the electric field around the detection electrode 112 hardly changes. Therefore, it is possible to limit the measurement direction of capacitance. For example, in the case of the example of FIG. 45, it is possible to limit the measurement direction of the capacitance to the upward direction on the paper surface. Also, for example, as shown in FIG. 44, by arranging a shield electrode 412 between the detection electrode 112 and the object 103, the influence of the object 103 can be reduced and the capacitance can be measured. Become.

  In the above description, the shield electrode 412 is connected to the ground. However, the shield electrode 412 may be connected to a voltage holding means other than the ground so that the voltage of the shield electrode 412 becomes substantially constant. .

<5. Fifth embodiment>
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In the fifth embodiment, the detection electrode 112 and the shield electrode 412 are controlled so as to have the same voltage as in the fourth embodiment.

[Configuration Example of Capacitance Measuring Device 401]
FIG. 46 is a diagram illustrating a configuration example of a capacitance measuring device 501 according to the fifth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 44 are denoted by the same reference numerals, and description of portions having the same processing will be omitted as appropriate since description thereof will be repeated.

  The capacitance measuring device 501 is different from the capacitance measuring device 401 of FIG. 44 in that a microcomputer 511 is provided instead of the microcomputer 411, and a capacitor C3 and a resistor R3 are added. The microcomputer 511 is different from the microcomputer 411 in that a voltage measuring unit 521, the same potential control unit 522, SW7 to SW9, and a port P6 are added.

  One end of the resistor R3 is connected to the port P5, and the other end of the resistor R3 is connected to one end of the capacitor C3. The other end of the capacitor C3 is connected to the connection terminal T2 and the port P6. One end of SW7 is connected to port P6, and the other end is connected to the ground. One end of SW8 is connected to the power supply Vcc, and the other end of SW8 is connected to port P5. One end of SW9 is connected to port P5, and the other end of SW9 is connected to ground.

  Further, the capacitance of the capacitor C3 is set to be sufficiently larger than the capacitance Cs between the shield electrode 412 and the surrounding space.

  Hereinafter, the capacitance of the capacitor C3 is represented by C3, the voltage is represented by Vc3, and the accumulated charge amount is represented by Qc3.

  Hereinafter, the electrode on the resistor R3 side of the capacitor C3 is referred to as a positive electrode, and the electrode on the connection terminal T2 side is referred to as a negative electrode.

  The voltage measuring unit 521 has an input terminal connected to the port P5. Similarly to the voltage measuring units 121 and 122, the voltage measuring unit 521 measures the voltage input to the input terminal, compares the measured voltage with a predetermined threshold (threshold voltage Vref), and controls the comparison result to the same potential. To the unit 522.

  The same potential control unit 522 controls the opening and closing of SW7 to SW9 based on the measurement result of the voltage measurement unit 521, and adjusts the voltage of the detection electrode 112 and the shield electrode 412 to be the same.

[Processing of Capacitance Measuring Device 501]
Next, processing of the capacitance measuring device 501 will be described with reference to FIGS.

  First, the measurement process executed by the capacitance measuring device 501 will be described with reference to the flowchart of FIG.

  In step S601, the capacitance measuring device 501 executes a total charge discharge process.

  Here, with reference to FIG. 48 and FIG. 49, the details of the all charge discharge process in step S601 will be described. FIG. 48 is a flowchart for explaining the all charge discharge process, and FIG. 49 is a diagram showing the flow of positive charges during the all charge discharge process.

  In step S621, the parameter measurement unit 123 turns on SW1, SW2, SW4, and SW6, and the same potential control unit 522 turns on SW7 and SW9. As a result, the positive charge moves from the capacitor C1 to the ground via the SW4 in the direction of the arrow A61, and the discharge of the capacitor C1 is started. Further, the positive charge moves in the direction of arrow A62 from the positive electrode of the capacitor C2 to the ground via SW6, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A63, and the discharge of the capacitor C2 is started.

  Further, positive charge moves from the positive electrode of the capacitor C3 to the ground via the resistors R3 and SW9 in the direction of the arrow A64, and the discharge of the capacitor C3 is started. Further, the positive charge moves from the shield electrode 412 to the ground via SW7 in the direction of arrow A65, and the discharge of the shield electrode 412 is started.

  In step S622, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for discharging the capacitors C1 to C3, the detection electrode 112, and the shield electrode 412 all.

  In step S623, the parameter measurement unit 123 turns off SW1, SW2, SW4, and SW6, and the same potential control unit 522 turns off SW7 and SW9. Thereafter, the total charge discharge process ends.

  Returning to FIG. 47, in step S602, the capacitance measuring device 501 performs C2 and C3 charging processing.

  Here, with reference to FIG. 50 and FIG. 51, the details of the C2 and C3 charging processing in step S602 will be described. FIG. 50 is a flowchart for explaining the C2, C3 charging process, and FIG. 51 is a diagram showing the flow of positive charges during the C2, C3 charging process.

  In step S641, the parameter measurement unit 123 turns on SW2 and SW3, and the same potential control unit 522 turns on SW7 and SW8. As a result, a positive charge moves from the power source Vcc to the positive electrode of the capacitor C2 via SW3 and the resistor R1 in the direction of arrow A66, and a positive charge moves from the negative electrode of the capacitor C2 to the ground via SW2 in the direction of arrow A67. The charging of the capacitor C2 is started. Further, a positive charge moves from the power source Vcc to the positive electrode of the capacitor C3 via SW8 and the resistor R3 in the direction of arrow A68, and a positive charge moves from the negative electrode of the capacitor C3 to the ground via SW7 in the direction of arrow A69. Charging of the capacitor C3 is started.

  In step S642, the parameter measurement unit 123 determines whether or not SW3 is on. If it is determined that SW3 is on, the process proceeds to step S643.

  In step S643, the voltage measuring unit 122 and the voltage measuring unit 521 measure the voltages of the capacitor C2 and the capacitor C3. Specifically, the voltage measurement unit 122 measures the voltage Vc2 of the capacitor C2, compares the measured voltage Vc2 with a threshold value (threshold voltage Vref), and supplies the result to the parameter measurement unit 123.

  In step S644, the parameter measurement unit 123 determines whether or not the voltage Vc2 of the capacitor C2 is greater than or equal to the threshold based on the measurement result by the voltage measurement unit 122. If it is determined that the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold, the process proceeds to step S645.

  In step S645, the parameter measurement unit 123 turns off SW2 and SW3. Thereby, charging of the capacitor C2 is stopped. Thereafter, the process proceeds to step S646.

  On the other hand, if it is determined in step S644 that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process of step S645 is skipped, and the process proceeds to step S646.

  If it is determined in step S642 that SW3 is off, steps S643 to S645 are skipped, and the process proceeds to step S646.

  In step S646, the same potential control unit 522 determines whether the SW8 is on. If it is determined that SW8 is on, the process proceeds to step S647.

  In step S647, the voltage measurement unit 521 measures the voltage of the capacitor C3. Specifically, the voltage measurement unit 521 measures the voltage Vc3 of the capacitor C3, compares the measured voltage Vc3 with a threshold value (threshold voltage Vref), and supplies the result to the same potential control unit 522.

  In step S648, the same potential control unit 522 determines whether or not the voltage Vc3 of the capacitor C3 is equal to or higher than a threshold based on the measurement result by the voltage measurement unit 521. If it is determined that the voltage Vc3 of the capacitor C3 is equal to or higher than the threshold, the process proceeds to step S649.

  In step S649, the same potential control unit 522 turns off SW7 and SW8. Thereby, charging of the capacitor C3 is stopped. Thereafter, the process proceeds to step S650.

  On the other hand, if it is determined in step S648 that the voltage Vc3 of the capacitor C3 is less than the threshold value, the process of step S649 is skipped, and the process proceeds to step S650.

  If it is determined in step S646 that SW8 is off, steps S647 to S649 are skipped, and the process proceeds to step S650.

  In step S650, parameter measurement unit 123 determines whether both SW3 and SW8 are off. If it is determined that at least one of SW3 and SW8 is on, the process returns to step S642. Thereafter, the processes in steps S642 to S650 are repeatedly executed until it is determined in step S650 that both SW3 and SW8 are off.

  On the other hand, if it is determined in step S650 that both SW3 and SW8 are off, the C2 and C3 charging processing ends.

  In this way, the capacitors C2 and C3 are charged until they have substantially the same voltage (threshold voltage Vref).

  Returning to FIG. 47, in step S603, the capacitance measuring device 501 executes the detection electrode and shield electrode charging process.

  Here, with reference to FIG. 52 and FIG. 53, the details of the detection electrode and shield electrode charging process in step S603 will be described. 52 is a flowchart for explaining the detection electrode / shield electrode charging process, and FIG. 53 is a diagram showing the flow of positive charges during the detection electrode / shield electrode charging process.

  In step S661, the parameter measurement unit 123 turns on SW5, and the same potential control unit 522 turns on SW8. As a result, a positive charge moves in the direction of arrow A70 from the power supply Vcc to the positive electrode of the capacitor C2 via SW5, and charging of the capacitor C2 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C2, the positive charge moves from the negative electrode of the capacitor C2 to the detection electrode 112 in the direction of arrow A71, and charging of the detection electrode 112 is started. Further, a positive charge moves in the direction of arrow A72 from the power source Vcc to the positive electrode of the capacitor C3 via SW8 and the resistor R3, and charging of the capacitor C3 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C3, the positive charge moves from the negative electrode of the capacitor C3 to the shield electrode 412 in the direction of arrow A73, and charging of the shield electrode 412 is started.

  In step S662, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for the detection electrode 112 and the shield electrode 412 to be fully charged.

  In step S663, the parameter measurement unit 123 and the same potential control unit 522 turn off SW5, and the same potential control unit 522 turns off SW8. Thereby, charging of the capacitor C2, the capacitor C3, the detection electrode 112, and the shield electrode 412 is stopped. Thereafter, the detection electrode and shield electrode charging process ends.

  Here, since the capacitance C3 of the capacitor C3 >> the capacitance Cs of the shield electrode 412, the voltage of the shield electrode 412 after charging is approximately equal to the voltage Vcc of the power supply Vcc−the reference voltage Vref. Therefore, the voltage of the shield electrode 412 after charging is substantially equal to the voltage of the detection electrode 112 after charging.

  Accordingly, the detection electrode 112, the shield electrode 412 and the object 103 are almost equal in voltage, and the charge accumulated by the electrostatic capacitance between the detection electrode 112, the object 103 and the shield electrode 412 is almost zero, and the detection electrode 112 The charge is accumulated in the. In other words, the charge corresponding to the capacitance excluding the capacitance between the detection electrode 112 and the object 103 and the shield electrode 412 out of the capacitance between the detection electrode 112 and its surroundings is detected by the detection electrode. 112 is accumulated.

  Therefore, the charge amount ΔQ of the detection electrode 112 per time (= charge amount of the capacitor C1 per time) is a value substantially excluding the influence of the object 103 and the shield electrode 412. Therefore, even if the shape, relative dielectric constant, temperature, and the like of the detection electrode 112 and the shield electrode 412 change, the capacitance can be measured with almost no influence.

  Returning to FIG. 47, in step S604, the capacitance measuring device 501 executes a charge transfer process.

  Here, with reference to FIG. 54 and FIG. 55, the details of the charge transfer processing in step S604 will be described. FIG. 54 is a flowchart for explaining the charge transfer process, and FIG. 55 is a diagram showing the flow of positive charges during the charge transfer process.

  In step S681, the parameter measurement unit 123 turns on SW1 and SW2, and the same potential control unit 522 turns on SW7 and SW9. As a result, the positive charge moves from the capacitor C2 to the capacitor C1 via the resistor R1 in the direction of the arrow A74, and the transfer of the charge from the capacitor C2 to the capacitor C1 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW2 in the direction of the arrow A75, and the discharge of the detection electrode 112 is started. Further, a positive charge moves in the direction of arrow A76 from the positive electrode of the capacitor C3 to the ground via the resistors R3 and SW9, and discharging of the capacitor C3 is started. Further, the positive charge moves from the shield electrode 412 to the ground via SW7 in the direction of arrow A77, and the discharge of the shield electrode 412 is started.

  In step S682, the voltages of the capacitors C2 and C3 are measured in the same manner as in step S642 of FIG.

  In step S683, the parameter measurement unit 123 determines whether or not the voltage Vc2 of the capacitor C2 is equal to or less than a threshold based on the measurement result by the voltage measurement unit 122. If it is determined that the voltage Vc2 of the capacitor C2 is greater than the threshold value, the process returns to step S682. Thereafter, the processes of steps S682 and S683 are repeatedly executed until it is determined in step S683 that the voltage Vc2 of the capacitor C2 is equal to or less than the threshold value. As a result, charges are transferred from the capacitor C2 to the capacitor C1 until the voltage Vc2 of the capacitor C2 reaches a threshold value or less.

  On the other hand, when it is determined in step S683 that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold value, the process proceeds to step S684.

  In step S684, the parameter measurement unit 123 turns off SW1 and SW2. Thereby, the transfer of charge from the capacitor C2 to the capacitor C1 is stopped.

  In step S <b> 685, the equipotential control unit 522 determines whether the voltage of the capacitor C <b> 3 is equal to or less than the threshold based on the measurement result of the voltage measurement unit 521. If it is determined that the voltage of the capacitor C3 is greater than the threshold, the process returns to step S682. Thereafter, the processes in steps S682 to S685 are repeatedly executed until it is determined in step S685 that the voltage of the capacitor C3 is equal to or lower than the threshold value.

  On the other hand, if it is determined in step S685 that the voltage of the capacitor C3 is equal to or lower than the threshold value, the process proceeds to step S686.

  In step S686, the same potential control unit 522 turns off SW7 and SW9. Thereby, the discharge of the shield electrode 412 is stopped. Thereafter, the charge transfer process ends.

  Returning to FIG. 47, in step S605, the parameter measurement unit 123 determines whether or not the processing in steps S603 to S605 has been repeated a predetermined number of times. If it is determined that the processes in steps S603 to S605 have not been repeated a predetermined number of times, the process returns to step S603. Thereafter, the processes in steps S603 to S605 are repeatedly executed until it is determined in step S605 that the process has been repeated a predetermined number of times.

  On the other hand, if it is determined in step S605 that the processes in steps S603 to S605 have been repeated a predetermined number of times, the process proceeds to step S606.

  The processing in steps S606 to S608 is the same as the processing in steps S6 to S8 in FIG. Thereafter, the measurement process ends.

  As described above, the measurement accuracy of the capacitance can be further improved as compared with the fourth embodiment.

<6. Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described with reference to FIGS. In the sixth embodiment, the measurement time can be shortened as compared with the fifth embodiment.

[Configuration Example of Capacitance Measuring Device 601]
FIG. 56 is a diagram illustrating a configuration example of a capacitance measuring device 601 according to the sixth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 46 are denoted by the same reference numerals, and description of portions having the same processing will be omitted as appropriate since description thereof will be repeated.

  The capacitance measuring device 601 is different from the capacitance measuring device 501 in FIG. 46 in that a microcomputer 611 is provided instead of the microcomputer 511. Also, the microcomputer 611 is different from the microcomputer 511 in that SW10, SW11, and a port P7 are added, and the same potential control unit 621 is provided instead of the same potential control unit 522.

  Further, in the capacitance measuring device 601, the connection of each component is partially different compared to the capacitance measuring device 501. Specifically, one end of the resistor R3 is connected to the port P5, and the other end of the resistor R3 is connected to the port P7 and one end of the capacitor C3. The other end of the capacitor C3 is connected to the connection terminal T2 and the port P6. One end of SW10 is connected to power supply Vcc, and the other end of SW10 is connected to port P7. One end of SW11 is connected to port P7, and the other end of SW11 is connected to ground. The input unit of the voltage measurement unit 521 is connected to the port P7.

  The equipotential control unit 621 controls the opening and closing of SW7 to SW11 based on the measurement result of the voltage measurement unit 521, and adjusts the voltage of the detection electrode 112 and the shield electrode 412 to be the same.

[Processing of Capacitance Measuring Device 601]
Next, processing of the capacitance measuring device 601 will be described with reference to FIGS.

  First, measurement processing executed by the capacitance measuring device 601 will be described with reference to the flowchart of FIG.

  In step S701, the capacitance measuring device 601 performs a total charge discharge process.

  Here, with reference to FIG. 58 and FIG. 59, the details of the all-charge discharging process in step S701 will be described. 58 is a flowchart for explaining the all-charge discharge process, and FIG. 59 is a diagram showing the flow of positive charges during the all-charge discharge process.

  In step S721, the parameter measurement unit 123 turns on SW1, SW2, SW4, and SW6, and the same potential control unit 621 turns on SW7 and SW11. As a result, the positive charge moves from the capacitor C1 to the ground via the SW4 in the direction of the arrow A81, and the discharge of the capacitor C1 is started. Further, the positive charge moves in the direction of arrow A82 from the positive electrode of the capacitor C2 to the ground via SW6, and the discharge of the capacitor C2 is started. Further, positive charges move from the detection electrode 112 to the ground via SW2 in the direction of the arrow A83, and discharging of the capacitor C2 is started.

  Further, the positive charge moves from the positive electrode of the capacitor C3 to the ground via the SW11 in the direction of the arrow A84, and the discharge of the capacitor C3 is started. At this time, unlike the case of the capacitance measuring device 501 (FIG. 49), the electric charge of the capacitor C3 is discharged without going through the resistor R3, so that the discharge time can be shortened. Further, the positive charge moves from the shield electrode 412 to the ground via SW7 in the direction of arrow A85, and the discharge of the shield electrode 412 is started.

  In step S722, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for discharging the capacitors C1 to C3, the detection electrode 112, and the shield electrode 412 all.

  In step S723, the parameter measurement unit 123 turns off SW1, SW2, SW4, and SW6, and the same potential control unit 621 turns off SW7 and SW11. Thereafter, the total charge discharge process ends.

  Returning to FIG. 57, in step S702, the C2 and C3 charging processes are executed in the same manner as in step S602 of FIG.

  In step S703, the capacitance measuring device 601 performs detection electrode and shield electrode charging processing.

  Here, with reference to FIG. 60 and FIG. 61, the details of the detection electrode and shield electrode charging process in step S703 will be described. 60 is a flowchart for explaining the detection electrode and shield electrode charging process, and FIG. 61 is a diagram showing the flow of positive charges during the detection electrode and shield electrode charging process.

  In step S761, the parameter measurement unit 123 turns on SW5, and the same potential control unit 621 turns on SW10. As a result, the positive charge moves in the direction of arrow A86 from the power source Vcc to the positive electrode of the capacitor C2 via SW5, and charging of the capacitor C2 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C2, the positive charge moves from the negative electrode of the capacitor C2 to the detection electrode 112 in the direction of arrow A87, and charging of the detection electrode 112 is started.

  Further, the positive charge moves in the direction of arrow A88 from the power source Vcc to the positive electrode of the capacitor C3 via SW10, and charging of the capacitor C3 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C3, the positive charge moves from the negative electrode of the capacitor C3 to the shield electrode 412 in the direction of arrow A89, and charging of the shield electrode 412 is started. At this time, unlike the case of the capacitance measuring device 501 (FIG. 49), the charge flows from the power source Vcc to the capacitor C3 without passing through the resistor R3, so that the charging time can be shortened.

  In step S762, the parameter measurement unit 123 waits for a predetermined time, that is, a time sufficient for the detection electrode 112 and the shield electrode 412 to be fully charged.

  In step S763, the parameter measurement unit 123 turns off SW5, and the same potential control unit 621 turns off SW10. Thereby, charging of the capacitor C2, the capacitor C3, the detection electrode 112, and the shield electrode 412 is stopped. Thereafter, the detection electrode and shield electrode charging process ends.

  Returning to FIG. 57, the processing in steps S704 to S708 is the same as the processing in steps S604 to S608 in FIG. Thereafter, the measurement process ends.

  As described above, the capacitance measuring device 601 can shorten the charging time of the capacitor C3 and the shield electrode 412 and the discharging time of the capacitor C3 as compared with the capacitance measuring device 501, The measurement time of the entire result can be shortened.

<7. Seventh embodiment>
Next, a seventh embodiment of the present invention will be described with reference to FIGS. In the seventh embodiment, a plurality of electrodes are provided so that each electrode can be used as either a detection electrode or a shield electrode.

[Configuration Example of Capacitance Measuring Device 701]
FIG. 62 is a diagram illustrating a configuration example of a capacitance measuring device 701 according to the seventh embodiment of the present invention.

  The capacitance measuring device 701 includes a microcomputer 711, resistors R1-1 to R1-n, capacitors C1-1 to C1-n, capacitors C2-1 to C2-n, connection terminals T1-1 to T1-n, and , Electrodes 712-1 to 712-n. The microcomputer 711 includes ports P1-1 to P1-n, P2-1 to P2-n, P3-1 to P3-n, and P4-1 to P4-n.

  The capacitor C1-i (i = 1 to n) is connected between the port P1-i and the port P2-i. The resistor R1-i is connected between the port P2-i and the port P3-i. The capacitor C2-i is connected between the port P3-i and the port P4-i. The connection terminal T1-i is connected to the port P4-i. The electrode 712-i is detachable from the connection terminal T1-i. The electrode 712-i may be directly connected to the port P4-i instead of the connection terminal T1-i.

  Hereinafter, resistors R1-1 to R1-n, capacitors C1-1 to C1-n, capacitors C2-1 to C2-n, connection terminals T1-1 to T1-n, electrodes 712-1 to 712-n, When it is not necessary to individually distinguish the ports P1-1 to P1-n, P2-1 to P2-n, P3-1 to P3-n, and P4-1 to P4-n, simply the resistor R1 and the capacitor C1, capacitor C2, connection terminal T1, electrode 712, port P1, port P2, port P3, and port P4 will be referred to.

[Configuration Example of Microcomputer 711]
FIG. 63 is a diagram illustrating a configuration example of the microcomputer 711. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The microcomputer 711 is configured to include measurement units 731-1 to 731-n, a role setting unit 732, and the same potential control unit 733.

  Each of the measurement units 731-1 to 731-n has the same configuration as the microcomputer 111 of FIG. Therefore, the measurement unit 731-i (i = 1 to n), the resistor R1-i, the capacitor C1-i, the capacitor C2-i, and the electrode 712-i have the same configuration as the capacitance measuring device 101. One unit is configured, and a total of n units are provided in the capacitance measuring device 701.

  Hereinafter, when it is not necessary to individually distinguish the measurement units 731-1 to 731-n, they are simply referred to as measurement units 731.

  The role setting unit 732 sets the role of the electrode 712 connected to each measurement unit 731. That is, the role setting unit 732 sets whether each electrode 712 is used as a detection electrode or a shield electrode.

  The same potential control unit 733 has a function similar to that of the same potential control unit 522 in FIG. 46 and controls each electrode 712 to have the same voltage.

[Processing of Capacitance Measuring Device 701]
Next, measurement processing executed by the capacitance measuring device 701 will be described with reference to the flowchart in FIG.

  In step S901, the role setting unit 732 sets the role of each electrode 712. That is, the role setting unit 732 sets which electrode of each electrode 712 is used as a detection electrode or a shield electrode based on a user setting or the like.

  The processing in steps S902 to S909 is the same as the processing in steps S1 to S8 in FIG.

[Usage example of capacitance measuring device 701]
In the capacitance measuring device 701, the position and direction in which the capacitance is measured can be changed by switching the role of each electrode.

  For example, by setting one electrode 712 on each of the front and back of the door of the vehicle, setting the electrode 712 on the front side of the door as a detection electrode, and setting the electrode 712 on the back side as a shield electrode, Capacitance on the front side of the door can be measured without being affected by the back side. Conversely, by setting the electrode 712 on the front side of the door as a shield electrode and the electrode 712 on the back side as a detection electrode, the capacitance on the back side of the door is measured without being affected by the front side of the door. Can do.

<8. Eighth Embodiment>
Next, an eighth embodiment of the present invention will be described with reference to FIG. In the eighth embodiment, the capacitance between two electrodes can be measured.

[Configuration Example of Capacitance Measuring Device 801]
FIG. 65 is a diagram showing a configuration example of a capacitance measuring device 801 according to the eighth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and description of portions having the same processing will be omitted because it is repeated.

  The capacitance measuring device 801 is different from the capacitance measuring device 101 of FIG. 2 in that a connection terminal T2 and a reference voltage electrode 811 are added.

  The connection terminal T2 is connected to a reference voltage point, and the reference voltage electrode 811 is connected to the connection terminal T2. Therefore, the voltage of the reference voltage electrode 811 is held at the voltage at the reference voltage point.

  Thereby, the electrostatic capacitance generated between the detection electrode 112 and the reference voltage electrode 811 can be measured. If a conductive band or a dielectric exists in the vicinity of the space formed by the detection electrode 112 and the reference voltage electrode 811, the measured value of the capacitance changes.

<9. Ninth Embodiment>
Next, with reference to FIGS. 66 and 67, a ninth embodiment of the present invention will be described. In the ninth embodiment, the present invention is applied to a capacitance sensor that detects surrounding objects (for example, detection of the presence or absence of an object or movement) based on the capacitance. is there.

[Configuration Example of Capacitance Sensor 901]
FIG. 66 is a diagram showing a configuration example of a capacitance sensor 901 according to the ninth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance sensor 901 is different from the capacitance measuring device 101 in FIG. 2 in that a microcomputer 911 is provided instead of the microcomputer 111. Further, the microcomputer 911 is different from the microcomputer 111 in that the object detection unit 921 is provided and the arithmetic processing unit 124 and the output unit 125 are not provided.

  The object detection unit 921 detects the presence / absence of an object around the detection electrode 112 based on the capacitance parameter measured by the parameter measurement unit 123.

[Processing of Measurement Capacitance Sensor 901]
Next, an object detection process executed by the capacitance sensor 901 will be described with reference to the flowchart of FIG.

  In steps S1001 to S1006, processing similar to that in steps S1 to S6 in FIG. 4 is performed, and the charging time t of the capacitor C1, which is a capacitance parameter based on the capacitance Cx of the detection electrode 112, is measured. As described above, the charging time t is shortened as the capacitance Cx of the detection electrode 112 is increased, and the charging time t is increased as the capacitance Cx is decreased.

  In step S1007, the object detection unit 921 determines whether or not the charging time t is greater than or equal to a predetermined threshold value. If it is determined that the charging time t is less than the threshold value, that is, if the capacitance Cx of the detection electrode 112 is greater than or equal to a predetermined value, the process proceeds to step S1008.

  In step S <b> 1008, the object detection unit 921 determines that an object exists around the detection electrode 112. The object detection unit 921 outputs the determination result to the outside, and the object detection process ends.

  On the other hand, if it is determined in step S1007 that the charging time t is greater than or equal to the threshold value, that is, if the capacitance Cx of the detection electrode 112 is less than a predetermined value, the process proceeds to step S1009.

  In step S <b> 1009, the object detection unit 921 determines that no object exists around the detection electrode 112. The object detection unit 921 outputs the determination result to the outside, and the object detection process ends.

  As described above, since the measured value of the capacitance parameter is hardly affected by the object 103, the object around the detection electrode 112 (for example, the object 102) is surely affected without being affected by the object 103. Can be detected.

  Note that the object may be detected using other capacitance parameters, for example, the number n of times of charging described above, the voltage Vc1 of the capacitor C1, the capacitance Cx of the detection electrode 112, and the like.

  It is also possible to detect a movement of an object such as approaching or moving away based on a change in capacitance parameter.

<10. Tenth Embodiment>
Next, a tenth embodiment of the present invention will be described with reference to FIGS. In the tenth embodiment, the threshold voltage Vref can be automatically set according to the voltage of the object 103.

[Configuration Example of Capacitance Measuring Device 1001]
FIG. 68 is a diagram showing a configuration example of a capacitance measuring device 1001 according to the tenth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance measuring device 1001 is different from the capacitance measuring device 101 in FIG. 2 in that a microcomputer 1011 is provided instead of the microcomputer 111. The microcomputer 1011 is different from the microcomputer 111 in that a threshold voltage setting unit 1021 is provided.

  The threshold voltage setting unit 1021 obtains the threshold voltage Vref based on the capacitance parameter measured by the parameter measuring unit 123 and sets it in the voltage measuring units 121 and 122.

[Processing of Capacitance Measuring Device 1001]
Next, a threshold voltage setting process executed by the capacitance measuring device 1001 will be described with reference to the flowchart of FIG. Note that this processing is performed in a state where, for example, the detection electrode 112 is installed at a position where the detection electrode 112 is actually used and no object other than the object 103 to be excluded from the detection target exists around the detection electrode 112.

  In step S1101, the threshold voltage setting unit 1021 temporarily sets the threshold voltage Vref. For example, the threshold voltage setting unit 1021 sets the threshold voltage Vref of the voltage measurement units 121 and 122 to the voltage at the reference voltage point.

  In step S1102, the measurement process described above with reference to FIG. 4 is executed. That is, the capacitance is measured using the threshold voltage Vref temporarily set in step S1101, and the measurement result is supplied from the output unit 125 to the threshold voltage setting unit 1021.

  In step S1103, the threshold voltage setting unit 1021 changes the threshold voltage Vref. For example, the threshold voltage setting unit 1021 increases the threshold voltage Vref of the voltage measurement units 121 and 122 by a predetermined value.

  In step S1104, the measurement process described above with reference to FIG. 4 is executed. That is, the capacitance is measured using the threshold voltage Vref changed in step S1103, and the measurement result is supplied from the output unit 125 to the threshold voltage setting unit 1021.

  In step S1105, the threshold voltage setting unit 1021 determines whether or not the current capacitance has increased from the previous time and the previous capacitance has decreased from the previous time. In this case, since the measurement process has only been performed twice, this process is not performed, and the process returns to step S1103.

  Thereafter, in step S1105, the processes of steps S1103 to S1105 are repeatedly executed until it is determined that the current capacitance has increased from the previous time and the previous capacitance has decreased from the previous time. Thereby, the threshold voltage Vref that minimizes the measured capacitance value is searched.

  On the other hand, if it is determined in step S1105 that the current capacitance has increased from the previous time and the previous capacitance has decreased from the previous time, the process proceeds to step S1106.

  In step S1106, the threshold voltage setting unit 1021 sets the previous threshold voltage Vref to an official value. That is, the previous threshold voltage Vref is the threshold voltage Vref that minimizes the measured capacitance value, and the voltage (voltage Vcc−threshold voltage Vref) at the time of charging the detection electrode 112 is closest to the voltage of the object 103. is expected. Therefore, the threshold voltage setting unit 1021 sets the previous threshold voltage Vref as a formal value in the voltage measurement units 121 and 122.

  Thereafter, the threshold voltage setting process ends.

  In this way, the threshold voltage Vref can be automatically set according to the voltage of the object 103 to be excluded from the detection target.

  In the above description, the threshold voltage Vref is set based on the capacitance. However, the threshold voltage Vref may be set using a capacitance parameter other than the capacitance.

<11. Modification>
In the above description, the example in which the capacitance Cx of the detection electrode 112 is calculated by the arithmetic processing unit 124 after measuring the capacitance parameter has been shown. However, when the value of the capacitance Cx is not particularly required, This calculation process may be omitted.

  Moreover, you may make it combine each embodiment in the possible range. For example, the configuration of the capacitance measuring device 201 according to the second embodiment or the capacitance measuring device 301 according to the third embodiment can be applied to the fourth to tenth embodiments. .

  Furthermore, in the above description, the example in which the power supply Vcc is used for the charge supply units 126-1 and 126-2 that supply charges to the capacitors C1 to C3, the detection electrode 112, and the shield electrode 412, has been described. May be used. In the above description, the capacitance is calculated by calculating the amount of charge based on the power supply voltage Vcc. However, if the amount of charge supplied to each capacitor, the detection electrode 112, and the shield electrode 412 is known, it is supplied. Capacitance can be calculated based on the amount of charge.

  For example, a constant current circuit may be used as the charge supply means. In this case, since the constant current circuit continues to supply charges with a constant current, the amount of charge supplied during a predetermined time is constant. Therefore, the capacitance can be obtained based on the amount of charge supplied during a predetermined time. In this case, the resistance value of the resistor R1 of each capacitance measuring device can be set to a small value.

  Further, for example, a predetermined charge supply circuit that supplies charges satisfying a predetermined condition every unit time may be used. In this case, for example, by supplying a predetermined amount of charge per unit time, the capacitance can be obtained based on the supplied amount of charge. In this case, the amount of charge supplied by program control of the microcomputer may be changed.

  Further, for example, an intermittent charge supply circuit that repeatedly supplies charges with a time interval may be used. In this case, if a predetermined charge is intermittently supplied, the capacitance can be obtained based on the supplied charge amount.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, in addition to the above-described microcomputer, a computer incorporated in dedicated hardware or various types of programs can be executed by installing various programs. For example, a general-purpose personal computer Includes computers.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  Furthermore, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 101 Capacitance measuring device 102,103 Object 111 Microcomputer 112 Detection electrode 121,122 Voltage measuring part 123 Parameter measuring part 124 Operation processing part 141 Comparator 201 Capacitance measuring apparatus 211 Microcomputer 251 Capacitance measuring apparatus 301 Static Capacitance measuring device 311 Microcomputer 401 Capacitance measuring device 411 Microcomputer 412 Shield electrode 501 Capacitance measuring device 511 Microcomputer 521 Voltage measuring unit 522 Same potential control unit 601 Capacitance measuring device 611 Microcomputer 621 Same potential control Unit 701 Capacitance measuring device 711 Microcomputer 712-1 to 712-n Electrode 731-1 to 731-n Measuring unit 732 Role setting unit 733 Equipotential control unit 8 01 Capacitance Measuring Device 811 Reference Voltage Electrode 901 Capacitance Sensor 911 Microcomputer 921 Object Detection Unit 1001 Capacitance Measuring Device 1011 Microcomputer 1021 Threshold Voltage Setting Units C1 to C3, C1-1 to C1-n, C2- 1 to C2-n capacitors R1 to R3, R1-1 to R1-n, R2-1 to R2-n resistors SW1 to SW11 switches T1, T2, T1-1 to T1-n connection terminals P1 to P7, P1-1 To P1-n, P2-1 to P2-n, P3-1 to P3-n, P4-1 to P4-n ports

Claims (14)

In the measuring device for measuring the capacitance between the first electrode and the space around the first electrode,
Charge supply means for supplying charge;
A ground that can be connected to an external reference voltage point;
First connection means capable of connecting the first electrode;
A first resistor;
A first capacitor having a sufficiently larger capacitance than the first electrode and having a first end connected to a first end of the first resistor;
A second capacitor having a sufficiently larger capacitance than the first electrode, a first end connected to the second end of the first resistor, and a second end connected to the first connecting means; With a battery of
A first opening / closing means having a first end connected to a second end of the first capacitor and a second end connected to the ground;
A second opening / closing means having a first end connected to a second end of the second battery, and a second end connected to the ground;
A third opening / closing means having a first end connected to the charge supply means and a second end connected to the first end of the first capacitor;
A fourth opening / closing means having a first end connected to a second end of the third opening / closing means and a second end connected to the ground;
A first voltage measuring means having an input connected to a second end of the third opening / closing means;
And a capacitance measuring means for controlling the first to fourth opening / closing means and measuring the capacitance based on a voltage measured by the first voltage measuring means. Measuring device. The measuring device according to claim 1, wherein a second resistor is connected between a first end of the first capacitor and a second end of the third opening / closing means. The capacitance measuring means is
The first opening / closing means, the second opening / closing means, and the fourth opening / closing means are controlled to be connected to the first capacitor, the second capacitor, and the first connecting means. The second opening and closing means and the third opening and closing means are controlled after discharging the electric charge of the first electrode, and the second capacitor until the voltage of the second capacitor reaches a predetermined threshold value. After charging the battery,
Controlling the third opening / closing means to charge the second capacitor and the first electrode, and then controlling the first opening / closing means and the second opening / closing means to The charge of the second capacitor is transferred to the first capacitor until the voltage reaches the threshold, and the charge transfer process for discharging the charge of the first electrode is performed once or more,
The measurement device according to claim 1, wherein the capacitance is measured based on an amount of charge accumulated in the first battery by the charge transfer process. A second resistor having a first end connected to the first end of the second capacitor;
A fifth opening / closing means having a first end connected to the charge supply means and a second end connected to a second end of the second resistor;
A sixth opening / closing means having a first end connected to a second end of the fifth opening / closing means and a second end connected to the ground;
A second voltage measuring means connected to a second end of the fifth opening / closing means;
The third opening / closing means, the fourth opening / closing means, and the first voltage measuring means are not provided,
The capacitance measuring means controls the first opening / closing means, the second opening / closing means, the fifth opening / closing means, and the sixth opening / closing means, and the second voltage measuring means The measurement device according to claim 1, wherein the capacitance is measured based on a measured voltage. The capacitance measuring means is
The first opening / closing means, the second opening / closing means, and the sixth opening / closing means are controlled to be connected to the first capacitor, the second capacitor, and the first connecting means. The second opening and closing means and the fifth opening and closing means are controlled after discharging the charge of the first electrode, and the second capacitor is controlled until the voltage of the second capacitor reaches a predetermined threshold value. After charging the battery,
Controlling the fifth opening / closing means to charge the second capacitor and the first electrode, and then controlling the first opening / closing means and the second opening / closing means to control the second capacitor. The charge of the second capacitor is transferred to the first capacitor until the voltage reaches the threshold, and the charge transfer process for discharging the charge of the first electrode is performed once or more,
The measurement device according to claim 4, wherein the capacitance is measured based on an amount of charge accumulated in the first capacitor by the charge transfer process. A fifth opening / closing means having a first end connected to the charge supply means and a second end connected to the first end of the second battery;
A sixth opening / closing means having a first end connected to a second end of the fifth opening / closing means and a second end connected to the ground;
A second voltage measuring means connected to a second end of the fifth opening / closing means;
The capacitance measuring means controls the first to sixth opening / closing means, the voltage measured by the first voltage measuring means, and the voltage measured by the second voltage measuring means. The measurement device according to claim 1, wherein the capacitance is measured based on the measurement. The capacitance measuring means is
Controlling the first opening / closing means, the second opening / closing means, the fourth opening / closing means, and the sixth opening / closing means to control the first capacitor, the second capacitor, and the first connection After the electric charge of the first electrode connected to the discharge means is discharged, the second open / close means and the third open / close means are controlled so that the voltage of the second capacitor reaches a predetermined threshold value. After charging the second battery until
Controlling the fifth opening and closing means to charge the second capacitor and the first electrode; controlling the first opening and closing means and the second opening and closing means; and controlling the voltage of the second capacitor Transferring the charge of the second capacitor to the first capacitor until the threshold value reaches the threshold, and performing charge transfer processing for discharging the charge of the first electrode one or more times,
The measurement device according to claim 6, wherein the capacitance is measured based on an amount of charge accumulated in the first battery by the charge transfer process. The threshold value setting means which sets the said threshold value with which the said electrostatic capacitance measured by the said electrostatic capacitance measurement means among several different said threshold values becomes the said formal threshold value further, It is characterized by the above-mentioned. 8. The measuring device according to either 5 or 7. A second connection means connected to the ground and capable of connecting a second electrode ;
Measurement apparatus according to any one of claims 1, 4 or 6, characterized in that it comprises the of et. A second connecting means capable of connecting the second electrode;
A third resistor;
A third capacitor having a sufficiently larger capacitance than the second electrode, a first end connected to the first end of the third resistor, and a second end connected to the second connecting means. With a battery of
A seventh opening / closing means having a first end connected to a second end of the third capacitor and a second end connected to the ground;
An eighth opening / closing means having a first end connected to the charge supply means and a second end connected to a second end of the third resistor;
A ninth opening / closing means having a first end connected to a second end of the eighth opening / closing means and a second end connected to the ground;
A third voltage measuring means having an input portion connected to a second end of the eighth opening / closing means;
2. The same potential control means for controlling the seventh to ninth opening / closing means to control the second capacitor and the third capacitor to have the same voltage. 4. The measuring device according to any one of 4 and 6. A tenth opening / closing means having a first end connected to the charge supply means and a second end connected to a first end of the third battery;
An eleventh opening / closing means having a first end connected to a second end of the tenth opening / closing means and a second end connected to the ground;
The third voltage measuring means is connected to the second end of the tenth opening / closing means, not the eighth opening / closing means,
The said same electric potential control means controls the said 7th thru | or 11th opening-and-closing means, and controls so that a said 2nd electrical storage device and a said 3rd electrical storage device may become the same voltage. The measuring device described. In a measuring device for measuring the capacitance between the electrode and the space around the electrode,
Charge supply means for supplying charge;
A ground that can be connected to an external reference voltage point;
Multiple units,
Connection means capable of connecting the electrodes;
A first resistor;
A first capacitor having a sufficiently larger capacitance than the electrode and having a first end connected to a first end of the first resistor;
A second capacitor having a sufficiently larger capacitance than the electrode, a first end connected to a second end of the first resistor, and a second end connected to the connection means;
A first opening / closing means having a first end connected to a second end of the first capacitor and a second end connected to the ground;
A second opening / closing means having a first end connected to a second end of the second battery, and a second end connected to the ground;
A third opening / closing means having a first end connected to the charge supply means and a second end connected to the first end of the first capacitor;
A fourth opening / closing means having a first end connected to a second end of the third opening / closing means and a second end connected to the ground;
A first voltage measuring means having an input connected to a second end of the third opening / closing means;
A plurality of units each controlling the first to fourth opening / closing means and each including a capacitance measuring means for measuring the capacitance based on a voltage measured by the first voltage measuring means; ,
Role setting means for setting a plurality of the electrodes respectively connected to the connection means of the plurality of units as either a detection electrode used for detecting the capacitance or a shield electrode used for shielding an electric field;
And a same potential control means for controlling the plurality of electrodes to have the same voltage. In a capacitance sensor that detects an object based on capacitance between an electrode and a space around the electrode,
The electrode;
Charge supply means for supplying charge;
A ground that can be connected to an external reference voltage point;
A first resistor;
A first capacitor having a sufficiently larger capacitance than the electrode and having a first end connected to a first end of the first resistor;
A second capacitor having a sufficiently larger capacitance than the electrode, a first end connected to the second end of the first resistor, and a second end connected to the electrode;
A first opening / closing means having a first end connected to a second end of the first capacitor and a second end connected to the ground;
A second opening / closing means having a first end connected to a second end of the second battery, and a second end connected to the ground;
A third opening / closing means having a first end connected to the charge supply means and a second end connected to the first end of the first capacitor;
A fourth opening / closing means having a first end connected to a second end of the third opening / closing means and a second end connected to the ground;
A first voltage measuring means having an input connected to a second end of the third opening / closing means;
A capacitance measuring means for controlling the first to fourth opening / closing means and measuring the capacitance based on a voltage measured by the first voltage measuring means;
An electrostatic capacity sensor comprising: an object detection unit configured to detect an object around the electrode based on the electrostatic capacity. In the measuring method of the measuring device that measures the capacitance between the electrode and the space around the electrode,
A first capacitor having a capacitance sufficiently larger than the electrode, a second capacitor having a capacitance sufficiently larger than the electrode and connected in series to the electrode, and a discharging step of discharging the electrode;
A first charging step of charging only the second capacitor until the voltage of the second capacitor reaches a predetermined threshold;
A second charging step of applying a predetermined voltage larger than the threshold value to both ends of a series circuit including the second capacitor and the electrode, and charging the second capacitor and the electrode;
A charge transfer step of transferring charge from the second capacitor to the first capacitor until the voltage of the second capacitor reaches the threshold; and discharging the charge of the electrode;
A measurement method comprising: measuring the capacitance based on an amount of charge accumulated in the first capacitor by executing the processes of the second charging step and the charge transfer step one or more times. .

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