JP5441182B2 - 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 a second end of the first capacitor, and a second One end of which is connected to the first connection means, the first end is connected to the charge supply means, and the second end is connected to the second end of the first resistor. The first opening / closing means and the first end are connected to the second end of the first opening / closing means, and the second end is connected to the ground. Second opening / closing means, a first end connected to the charge supply means, a third opening / closing means connected to the second end of the first battery, and a first end Is connected to the second end of the third opening / closing means, the fourth opening / closing means having the second end connected to the ground, and the first end connected to the second end of the second capacitor. A fifth opening / closing means having a second end connected to the ground, a first voltage measuring means having an input portion connected to the second end of the first opening / closing means, and a third input portion. The second voltage measuring means connected to the second end of the opening / closing means and the first to fifth opening / closing means are controlled and measured by the first voltage measuring means and the second voltage measuring means. And a capacitance measuring means for measuring the capacitance based on the voltage.

  In the first aspect of the present invention, the first to fifth opening / closing means are controlled, and based on the voltages measured by the first voltage measuring means and the second voltage measuring means, The capacitance between the space around one electrode 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 fifth opening / closing means are constituted by, for example, various switches, relays, microcomputers and the like. The first voltage measuring means and the second voltage measuring means are constituted by, for example, an A / D converter, a voltmeter, and the like. This capacitance measuring means is constituted by, for example, a microcomputer.

  The capacitance measuring means controls the second opening / closing means, the fourth opening / closing means, and the fifth 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 first opening and closing means and the fifth opening and closing means are controlled, and the first and second capacitors are controlled until the voltage of the second capacitor reaches a predetermined threshold value. After charging the second capacitor, the third opening / closing means is controlled to charge the second capacitor and the first electrode, and then the second opening / closing means and the fifth opening / closing means are controlled, The charge of the first capacitor and the second capacitor is discharged until the voltage of the first capacitor reaches the threshold value, and the charge / discharge process for discharging the charge of the first electrode is executed one or more times. To measure the capacitance based on the amount of charge released from the battery Door can be.

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

  Sixth opening / closing means having a first end connected to the first end of the first battery and a second end connected to the ground is further provided, and the input of the first voltage measuring means is The first opening / closing means is connected to the first end of the sixth opening / closing means instead of the second end of the first opening / closing means. The capacitance measuring means controls the first to sixth opening / closing means and The capacitance can be measured based on the voltage measured by the voltage measuring means and the second voltage measuring means.

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

  The sixth opening / closing means is composed of, for example, various switches, relays, microcomputers and the like.

  The capacitance measuring means controls the fourth opening / closing means, the fifth opening / closing means, and the sixth opening / closing means, and is connected to the first capacitor, the second capacitor, and the first connecting means. After discharging the charge of the first electrode, the first opening and closing means and the fifth opening and closing means are controlled, and the first and second capacitors are controlled until the voltage of the second capacitor reaches a predetermined threshold value. After charging the second capacitor, the third opening / closing means is controlled to charge the second capacitor and the first electrode, and then the second opening / closing means and the fifth opening / closing means are controlled, The charge of the first capacitor and the second capacitor is discharged until the voltage of the first capacitor reaches the threshold value, and the charge / discharge process for discharging the charge of the first electrode is executed one or more times. To measure the capacitance based on the amount of charge released from the battery Door can be.

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

  Threshold setting means can be further provided for setting a threshold value that minimizes the capacitance measured by the capacitance measurement means among a plurality of different threshold values as a formal threshold value.

  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 connection means is constituted by, for example, a connection terminal.

  The second connecting means capable of connecting the second electrode, the second resistor, the capacitance is sufficiently larger than that of the second electrode, and the first end is connected to the first end of the second resistor. A third battery having a second end connected to the second connection means, a first end connected to the charge supply means, and a second end connected to the second end of the second resistor. A seventh opening / closing means, an eighth opening / closing means having a first end connected to the second end of the seventh opening / closing means and a second end connected to the ground, A ninth opening / closing means having one end connected to the second end of the third capacitor, a second end connected to the ground, and an input unit connected to the second end of the seventh 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 open / close means connected to one end of the second open end and a second end connected to the ground, and the third voltage measuring means is not the second end of the seventh open / close means but the second open end. 10 is connected to the second end of the switching means, and the same potential control means controls the seventh to eleventh opening / closing means so that the second and third capacitors have the same voltage. You can make it.

  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 ground, a plurality of units, a connection means capable of connecting electrodes, a resistance, a capacitance sufficiently larger than that of the electrodes, and a first end connected to a first end of the resistance And a second capacitor in which the first end is connected to the second end of the first capacitor and the second end is connected to the first connection means. A first opening / closing means having a first end connected to the charge supply means, a second end connected to the second end of the resistor, and a first end connected to the second opening of the first opening / closing means. A second opening / closing means connected to one end of the first opening and the second end connected to the ground; A third opening / closing means having an end connected to the charge supply means and a second end connected to the second end of the first battery; and a first end being the second end of the third opening / closing means. A fourth opening / closing means having a second end connected to the ground, a first end connected to the second end of the second battery, and a second end connected to the ground. The fifth opening / closing means, the first voltage measuring means having the input section connected to the second end of the first opening / closing means, and the input section being connected to the second end of the third opening / closing means. The second voltage measuring means and the first to fifth opening / closing means are controlled, and the capacitance is measured based on the voltages measured by the first voltage measuring means and the second voltage measuring means. A plurality of units each having a capacitance measuring means for connecting, and a connecting means for the plurality of units. Role setting means for setting each of a plurality of electrodes connected to either a detection electrode used for detecting capacitance or a shield electrode used for shielding an electric field, so that the plurality of electrodes have the same voltage. And equipotential control means for controlling.

  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. And the plurality of electrodes are controlled to have the same voltage. In each unit, the first to fifth opening / closing means are controlled and measured by the first voltage measuring means and the second voltage measuring means. Based on the voltage, the capacitance between the first electrode and the space around the first electrode 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 fifth opening / closing means are constituted by, for example, various switches, relays, microcomputers and the like. The first voltage measuring means and the second voltage measuring means are constituted by, for example, an A / D converter, a voltmeter, and 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 first accumulator having a supply means, a ground connectable to an external reference voltage point, a resistance, a capacitance sufficiently larger than that of the electrode, and a first end connected to the first end of the resistance; A second capacitor in which the capacitance is sufficiently larger than the electrode, the first end is connected to the second end of the first capacitor, the second end is connected to the electrode, and the first end is charged. A first opening / closing means connected to the supply means and having a second end connected to the second end of the resistor; a first end connected to the second end of the first opening / closing means; One end of which is connected to the ground, and the first end is connected to the charge supply means. A third opening / closing means having a second end connected to a second end of the first battery, a first end connected to a second end of the third opening / closing means, and a second end A fourth opening / closing means connected to the ground, a fifth opening / closing means having a first end connected to the second end of the second battery, and a second end connected to the ground; The first voltage measuring means whose input section is connected to the second end of the first opening / closing means, and the second voltage measuring means whose input section is connected to the second end of the third opening / closing means And a capacitance measuring means for controlling the first to fifth opening / closing means and measuring a capacitance based on the voltage measured by the first voltage measuring means and the second voltage measuring means, Object detection means for detecting an object around the electrode based on the capacitance.

  In the third aspect of the present invention, the first to fifth opening / closing means are controlled, and based on the voltages measured by the first voltage measuring means and the second voltage measuring means, the electrodes The capacitance between the space and the space 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 fifth opening / closing means are constituted by, for example, various switches, relays, microcomputers and the like. The first voltage measuring means and the second voltage measuring means are constituted by, for example, an A / D converter, a voltmeter, and the like. The parameter 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 having a capacitance sufficiently larger than that of the electrode and connected in series to the electrode; a discharging step for discharging the electrode; and the first capacitor and the second capacitor until the voltage of the second capacitor reaches a predetermined threshold value. A first charging step for supplying and charging the same amount of charge to two capacitors, a predetermined voltage greater than a threshold value is applied to both ends of a series circuit comprising the second capacitor and an electrode, and the second capacitor and the electrode are A second charging step for charging, a discharging step for discharging the same amount of charge from the first capacitor and the second capacitor until the voltage of the second capacitor reaches a threshold value, and a second charging step and a discharging step. Processing 1 Based on the amount of charge released from the first capacitor by running more, and a step of measuring the 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 The same amount of charge is supplied and charged to the first capacitor and the second capacitor until the voltage of the second capacitor reaches a predetermined threshold, and both ends of the series circuit composed of the second capacitor and the electrode are A large predetermined voltage is applied, the second capacitor and the electrode are charged, the same amount of charge is discharged from the first capacitor and the second capacitor until the voltage of the second capacitor reaches a threshold, The capacitance is measured based on the amount of charge released from the 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 discharging step, and the measuring step are executed by, for example, a microcomputer.

  According to the first to fourth aspects of the present invention, capacitance measurement accuracy can be 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 during a measurement process, and a detection electrode. 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 C1, C2 charge processing. It is a figure which shows the flow of the positive charge during C1 and C2 charge processing. 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 C2 voltage adjustment process. It is a figure which shows the flow of the positive charge during a C2 voltage adjustment 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 detection electrode charging process. It is a flowchart for demonstrating the modification of a C2 voltage adjustment process. It is a figure which shows the flow of the positive charge during the process of the modification of a detection electrode charge process and a C2 voltage adjustment 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 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 3rd 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 4th 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 C1, C2, C3 charge processing. It is a figure which shows the flow of the positive charge during a C1, C2, C3 charge 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 flowchart for demonstrating the detail of a C2, C3 voltage adjustment process. It is a figure which shows the flow of the positive charge during C2 and C3 voltage adjustment processing. It is a figure which shows the modification of 4th Embodiment of an electrostatic capacitance measuring apparatus. It is a figure which shows the modification 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 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 6th 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 7th 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 8th 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 (example of enabling measurement time to be shortened)
3. Third Embodiment (Example in which directionality is given to capacitance measurement)
4). Fourth embodiment (an example in which the detection electrode and the shield electrode are controlled to have the same voltage)
5. Fifth embodiment (an example in which the measurement time of the fourth embodiment can be shortened)
6). Sixth Embodiment (Example in which a plurality of electrodes can be used for both detection electrodes and shield electrodes)
7). Seventh embodiment (an example of measuring the capacitance between two electrodes)
8). Eighth embodiment (example applied to capacitance sensor)
9. Ninth Embodiment (Example in which threshold voltage can be automatically set)
10. 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 P3.

  One end of the resistor R1 is connected to the port P1, and the other end of the resistor R1 is connected to one end of the capacitor C1. The other end of the capacitor C1 is connected to the port P2. The capacitor C2 is connected between the port P2 and the port P3. The connection terminal T1 is connected to the port P3. The detection electrode 112 is detachable from the connection terminal T1. Note that the detection electrode 112 may be directly connected to the port P3 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 5. Composed.

  One end of SW1 is connected to the charge supply unit 126-1, and the other end of SW1 is connected to the port P1. One end of SW2 is connected to port P1, and the other end of SW2 is connected to ground. One end of SW3 is connected to the charge supply unit 126-2, and the other end of SW3 is connected to the 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 port P3, and the other end of SW5 is connected to 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> 1 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> 2, and supplies a 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 SW5 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 resistor R1 side of the capacitor C1 is referred to as a positive electrode, and the electrode on the port P2 side is referred to as a negative electrode. Hereinafter, the port P2 side electrode of the capacitor C2 is referred to as a positive electrode, and the port P3 side electrode 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 between the resistor R1 and the capacitor C1 (potential at point A with reference to the reference voltage point) is represented by Va. Further, the voltage at point B (capacitance at point B with reference to the reference voltage point) between the capacitors C1, 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, the voltage at point C between the capacitor C2, the connection terminal T1, and the port P3 (the potential at point C with reference 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 SW2, SW4, and SW5. As a result, the positive charge moves from the positive electrode of the capacitor C1 to the ground via the resistors R1 and SW2 in the direction of the arrow A1, and the discharge of the capacitor C1 is started. Further, the positive charge moves from the positive electrode of the capacitor C2 to the ground via SW4 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 SW5 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 SW2, SW4, and SW5. 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 C <b> 1 and C <b> 2 charging processing.

  Here, with reference to FIG. 9 and FIG. 10, the detail of the C1 and C2 charge process of step S2 is demonstrated. 9 is a flowchart for explaining the C1, C2 charging process, and FIG. 10 is a diagram showing the flow of positive charges during the C1, C2 charging process.

  In step S41, the parameter measurement unit 123 turns on SW1 and SW5. As a result, a positive charge moves in the direction of arrow A4 from the power supply Vcc to the positive electrode of the capacitor C2 via SW1 and the resistor R1, and charging of the capacitor C1 is started. Further, by accumulating positive charge on the positive electrode of the capacitor C1, almost the same amount of positive charge moves from the negative electrode of the capacitor C1 to the positive electrode of the capacitor C2 in the direction of the arrow A5, and from the negative electrode of the capacitor C2 via SW5. The positive charge moves to the ground in the direction of arrow A6, and charging of the capacitor C2 is started. At this time, since the amount of charge moving in the directions of the arrows A4 to A6 is substantially equal, the charge amounts of the capacitor C1 and the capacitor C2 are substantially equal.

  Assuming that the start time of the process in step S41 is t1, as shown in FIG. 6, the voltage Va at the point A and the voltage Vb at the point B gradually increase as the charging of the capacitors C1 and C2 progresses after the time t1. To do.

  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. Accordingly, the capacitors C1 and C2 are 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 SW1 and SW5. Thereby, charging of the capacitors C1 and C2 is stopped. Thereafter, the C1 and C2 charging processes are terminated.

  As a result, as shown in FIG. 5B, the accumulated charge amount Qc2 of the capacitor C2 becomes approximately Qref (= C2 × Vref). The accumulated charge amount Qc1 of the capacitor C1 is also about Qref, similarly to the capacitor C2. The accumulated charge amount of the detection electrode 112 remains substantially zero.

  FIG. 5 shows an example in which the capacitances of the capacitor C1 and the capacitor C2 are equal. In this case, in FIG. 5B, the accumulated charge amount (= voltage) of each capacitor is substantially equal. However, the capacitances of the capacitor C1 and the capacitor C2 do not necessarily have to be equal, and when the capacitances are different, the height of the accumulated charge amount of each capacitor in FIG. 5B is different.

  Further, when the time when the C1 and C2 charging processes are finished is t2, as shown in FIG. 6, at time t2, the voltage Va at the point A becomes a voltage between the voltage of the power supply Vcc and the threshold voltage Vref. The voltage Vb at point B is substantially equal to the threshold voltage Vref. The voltage Vc at the point C remains almost zero.

  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 SW3. 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 A7 from the power source Vcc to the positive electrode of the capacitor C2 via SW3, and charging of the capacitor C2 is started. In addition, since positive charges are accumulated on the positive electrode of the capacitor C2, almost 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 A8, and charging of the detection electrode 112 is started. At this time, since the amount of charge moving in the direction of arrow A7 and the amount of charge moving in the direction of arrow A8 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 SW3. 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 at the time of charging the detection electrode 112 to a value substantially equal to the voltage of the object 103, the capacitance between the detection electrode 112 and the object 103 is substantially zero, and the detection electrode 112 is charged. Charge is accumulated. 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 accumulated charge amount Qc1 of the capacitor C1 remains Qref. 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 C2 voltage adjustment process.

  Here, with reference to FIG. 13 and FIG. 14, the detail of the C2 voltage adjustment process of step S4 is demonstrated. FIG. 13 is a flowchart for explaining the C2 voltage adjustment process, and FIG. 14 is a diagram showing the flow of positive charges during the C2 voltage adjustment process.

  In step S81, the parameter measurement unit 123 turns on SW2 and SW5. As a result, the positive charge moves from the positive electrode of the capacitor C1 to the ground via the resistors R1 and SW2 in the direction of the arrow A9, and the discharge of the capacitor C1 is started. Further, when the positive charge is discharged from the positive electrode of the capacitor C1, the positive charge moves in the direction of the arrow A10 from the positive electrode of the capacitor C2 to the negative electrode of the capacitor C1, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW5 in the direction of the arrow A11, 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, the capacitors C1 and C2 are discharged 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 SW2 and SW5. Thereby, the discharge of the capacitors C1 and C2 is stopped. Thereafter, the C2 voltage adjustment process ends.

  By this C2 voltage adjustment process, as shown in FIG. 5D, an amount of charge that is substantially equal to the increase amount ΔQ of the charge of the capacitor C2 by the detection electrode charging process in step S3 is discharged from the capacitors C1 and C2. That is, the accumulated charge amount of the capacitors C1 and C2 also decreases by about ΔQ. Therefore, the voltage Vc1 of the capacitor C1 at this time is obtained by the following equation (4).

  As described above, the increase amount ΔQ of the charge of the capacitor C2 due to the detection electrode charging process in step S3 is hardly affected by the object 103. Therefore, the accumulated charge amount Qc1 of the capacitor C1 after the C2 voltage adjustment process is Little affected.

  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 has a charge of about Qref−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).

  Therefore, as shown in FIG. 6, the voltage Va at the point A increases as the discharge of the capacitor C1 progresses 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). Gradually descends. 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 when the detection electrode 112 is charged, the voltage Va of equation (5) is obtained. It becomes almost equal to the value obtained by adding Vcc-Vref to the value. Further, the voltage Va at the point A may exceed the voltage of the power supply 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 SW4. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C1 via SW1 and the resistor R1 in the direction of arrow A12, and the positive charge moves from the negative electrode of the capacitor C1 to the ground via SW4 to the direction of arrow A13. The charging of the capacitor C1 is started.

  Accordingly, if the start time of the parameter measurement process is t3, as shown in FIG. 6, at time t3, the voltage Va at point A becomes substantially equal to the voltage shown in equation (5) and the voltage Vb at point B. Is substantially equal to the voltage at the reference voltage point. Further, the voltage Va at the point A gradually increases after time t3.

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

  In step S103, the parameter measurement unit 123 turns off SW1. As a result, the charging of the capacitor C1 is temporarily stopped.

  In step S104, 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 S105, the parameter measurement unit 123 turns on SW1. Thereby, charging of the capacitor C1 is resumed.

  In step S <b> 106, 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 to S106 are repeatedly executed until it is determined in step S106 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 S106 that the voltage Vc1 of the capacitor C1 is greater than or equal to the threshold value, the process proceeds to step S107.

  In step S107, 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 smaller, so the charging time t is longer. . On the contrary, 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 increase, and therefore the charging time t decreases.

  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 S108, the parameter measurement unit 123 turns off SW1 and SW4. Thereby, the charging of the capacitor C1 is stopped.

  In step S109, the parameter measurement unit 123 turns on SW5. As a result, positive charges move from the detection electrode 112 to the ground via SW5 in the direction of the arrow A14, and the charge of the detection electrode 112 is discharged.

  Thereafter, the parameter measurement process ends.

  When the time at the end of the parameter measurement process is t4, at time t4, the voltage Va at the point A becomes substantially equal to the threshold voltage Vref, and the voltage Vb at the point B and the voltage Vc at the point C are almost equal to the voltage at the reference voltage point. Will be equal.

  Note that the threshold voltage Vref for the capacitor C1 and the threshold voltage Vref for the capacitor C2 are not necessarily set to the same value. FIG. 5 shows an example in which the capacitance of the capacitor C1 and the capacitor C2 and the threshold voltage Vref are set to the same value. In this case, as shown in FIG. The amount of charge stored in the capacitor C1 is about Qref.

  Returning to FIG. 4, in step S <b> 7, 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.

  As described above, it is possible to remove the influence of the object 103 having a voltage different from the reference voltage point, and measure the capacitance based on the capacitance between the detection electrode 112 and the surrounding space.

  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.

[Modification of Detection Electrode Charging Process and C2 Voltage Adjustment Process]
Here, with reference to FIGS. 17 to 19, a modification of the detection electrode charging process in step S3 and the C2 voltage adjustment process in step S4 in FIG. 4 will be described. 17 is a flowchart for explaining a modification of the detection electrode charging process, FIG. 18 is a flowchart for explaining a modification of the C2 voltage adjustment process, and FIG. 19 is a detection electrode charging process. It is a figure which shows the flow of the positive charge during C2 voltage adjustment processing.

  First, with reference to FIG. 17 and FIG. 19, the modification of the detection electrode charging process of step S3 of FIG. 4 is demonstrated.

  In step S121, the parameter measurement unit 123 turns on SW4. As a result, the voltage Vb at the point B becomes substantially equal to the voltage at the reference voltage point, and a voltage substantially equal to −Vref is applied to both ends of the series circuit including the capacitor C2 and the detection electrode 112. Then, the positive charge moves from the positive electrode of the capacitor C2 in the direction of arrow A21 via SW4, and discharging of the capacitor C2 is started. Further, when the positive charge is discharged from the positive electrode of the capacitor C2, the same amount of positive charge moves from the detection electrode 112 to the negative electrode of the capacitor C2 in the direction of arrow A22, and the discharge of the positive charge of the detection electrode 112 starts. Is done. Note that, since the accumulated charge amount of the detection electrode 112 has become almost zero by the all-charge discharge process in step S1, the detection electrode 112 is substantially charged by the negative charge by releasing the positive charge.

  At this time, since the amount of charge moving in the direction of the arrow A21 and the amount of charge moving in the direction of the arrow A22 are substantially equal, the amount of decrease in the charges of the capacitor C2 and the detection electrode 112 is substantially equal.

  In step S122, 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 S123, the parameter measurement unit 123 turns off SW4. Thereby, discharging of the capacitor C2 and charging of the detection electrode 112 are stopped. Thereafter, the detection electrode charging process ends.

  Next, a modification of the C2 voltage adjustment process in step S4 of FIG. 4 will be described with reference to FIGS.

  In step S141, the parameter measurement unit 123 turns on SW1 and SW5. Thereby, a positive charge moves in the direction of arrow A23 from the power source Vcc to the positive electrode of the capacitor C1 via SW1 and the resistor R1, and charging of the capacitor C1 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C1, the positive charge moves from the negative electrode of the capacitor C1 to the positive electrode of the capacitor C2 in the direction of arrow A24, and from the negative electrode of the capacitor C2 through SW5 to the direction of arrow A25. The positive charge moves to, and charging of the capacitor C2 is started. At this time, the amount of increase in the charges of the capacitor C1 and the capacitor C2 is substantially equal.

  Although not shown in the figure, the positive electrode moves from the ground to the detection electrode 112 via SW5, whereby the discharge of the detection electrode 112 is started.

  In step S142, the voltage Vc2 of the capacitor C2 is measured as in the process of step S42 of FIG. 9, and in step S143, it is determined whether or not the voltage Vc2 of the capacitor C2 is equal to or higher than a threshold value (= threshold voltage Vref). The When it is determined that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process returns to step S142. Thereafter, the processes of steps S142 and S143 are repeatedly executed until it is determined in step S143 that the voltage Vc2 of the capacitor C2 is equal to or higher than the threshold value. Thereby, charging of the capacitor C1 and the capacitor C2 is continued until the voltage Vc2 of the capacitor C2 becomes equal to or higher than the threshold value.

  On the other hand, if it is determined in step S143 that the voltage Vc2 of the capacitor C2 is greater than or equal to the threshold value, the process proceeds to step S144.

  In step S144, the parameter measurement unit 123 turns off SW1 and SW5. Thereby, charging of the capacitor C1 and the capacitor C2 is stopped.

  Therefore, in this modification, the accumulated charge amount Qc1 of the capacitor C1 increases by ΔQ every time the detection electrode charging process and the C2 voltage adjustment process are executed.

  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. 20 and 21. FIG.

[First Modification of Capacitance Parameter]
First, a first modification of the capacitance parameter will be described with reference to FIG. FIG. 20 is a flowchart for explaining a measurement process corresponding to the first modification of the capacitance parameter.

  In step S161, as in the process of step S1 of FIG. 4, the all charge discharge process is executed.

  In step S162, the C1 and C2 charging processes are executed as in the process of step S2 of FIG.

  In step S163, the detection electrode charging process is executed in the same manner as the process in step S3 of FIG.

  In step S164, a charge transfer process is executed in the same manner as in step S4 of FIG.

  In step S165, the voltage Vc1 of the capacitor C1 is measured as in the process of step S104 in FIG.

  In step S166, the parameter measurement unit 123 increments the number of discharges of the capacitor C1.

  In step S167, the parameter measurement unit 123 determines whether or not the voltage Vc1 of the capacitor C1 is equal to or less than a threshold value. If it is determined that the voltage Vc1 of the capacitor C1 is greater than the threshold value, the process returns to step S163. Thereafter, the processes in steps S163 to S167 are repeatedly executed until it is determined in step S167 that the voltage Vc1 of the capacitor C1 is equal to or less than the threshold value.

  On the other hand, when it is determined in step S167 that the voltage Vc1 of the capacitor C1 is equal to or less than the threshold value, the process proceeds to step S168.

  In step S168, the arithmetic processing unit 124 performs arithmetic processing. Specifically, the parameter measurement unit 123 supplies the counted number of discharges 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 discharges n. If the number of discharges when the capacitor Vc1 is equal to or lower 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 equation (5). Can be calculated. However, the threshold voltage Vref at this time needs to be set to a value lower than the voltage Vc1 of the capacitor C1 at the end of the C1 and C2 charging processes.

  The arithmetic processing unit 124 supplies the calculated capacitance Cx and the number of discharges n measured by the parameter measuring unit 123 to the output unit 125.

  In step S169, the output unit 125 outputs the measurement result. At this time, both the capacitance Cx and the number of discharges n may be output, or one of them may be output. Thereafter, the measurement process ends.

  Instead of the number of discharges n, the discharge time until the voltage Vc1 of the capacitor C1 becomes equal to or less than the 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 of FIG. 4 is executed according to the flowchart of FIG.

  That is, in step S181, the parameter measurement unit 123 turns on SW4.

  In step S <b> 182, 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 measurement time can be shortened as compared with the first embodiment.

[Configuration Example of Capacitance Measuring Device 201]
FIG. 22 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 microcomputer 211 is provided instead of the microcomputer 111. Further, the microcomputer 211 is different from the microcomputer 111 in that ports P4 and SW6 are added and a parameter measurement unit 221 is provided instead of the parameter measurement unit 123.

  Furthermore, in the capacitance measuring device 201, the connection of each component is partially different compared to the capacitance measuring device 101. Specifically, the resistor R1 is connected between the port P1 and the port P4, and the capacitor C1 is connected between the port P4 and the port P2. One end of SW6 is connected to port P4, and the other end is connected to the ground. The voltage measuring unit 121 has an input terminal connected to the port P4. The connection of other components is the same as that of the capacitance measuring apparatus 101.

  The parameter measurement unit 221 controls the opening and closing of SW1 to SW6, and measures capacitance parameters based on the measurement results of the voltage measurement unit 121 and the voltage measurement unit 122. 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, a 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. 24 and FIG. 25, the detail of the all-charge discharge process of step S201 is demonstrated. FIG. 24 is a flowchart for explaining the all-charge discharge process, and FIG. 25 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 SW4, SW5, and SW6. As a result, the positive charge moves from the positive electrode of the capacitor C1 to the ground via the SW6 in the direction of the arrow A31, and the discharge of the capacitor C1 is started. Further, the positive charge moves in the direction of arrow A32 from the positive electrode of the capacitor C2 to the ground via SW4, and discharging of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW5 in the direction of the arrow A33, and the discharge of the detection electrode 112 is started.

  At this time, the electric charge of the capacitor C1 can be discharged without going through the resistor R1, and the discharge time can be shortened.

  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 123 turns off SW4, SW5, and SW6. Thereafter, the total charge discharge process ends.

  Returning to FIG. 23, the processing in steps S202 to S205 is the same as the processing in steps S2 to S5 in FIG.

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

  Here, with reference to FIG. 26 and FIG. 27, the details of the parameter measurement processing in step S206 will be described. FIG. 26 is a flowchart for explaining the parameter measurement process, and FIG. 27 is a diagram showing the flow of positive charges during the parameter measurement process.

  In step S241, the parameter measurement unit 221 turns on SW1 and SW4. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C1 via SW1 and the resistor R1 in the direction of arrow A34, and the positive charge moves from the negative electrode of the capacitor C1 to the ground via SW4 to the direction of arrow A35. The charging of the capacitor C1 is started.

  In step S242, the parameter measurement unit 221 starts time measurement.

  In step S243, the voltage Vc1 of the capacitor C1 is measured as in the process of step S104 in FIG. At this time, compared with the parameter measurement process of FIG. 15, the voltage Vc1 of the capacitor C1 can be measured while the capacitor C1 is continuously charged without turning off the SW1, and the measurement time can be shortened.

  In step S244, the parameter measurement unit 221 determines whether or not the voltage Vc1 of the capacitor C1 is equal to or higher than a threshold based on the measurement result by the voltage measurement unit 121. When it is determined that the voltage Vc1 of the capacitor C1 is less than the threshold value, the process returns to step S243. Thereafter, the processes in steps S243 to S244 are repeatedly executed until it is determined in step S244 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 S244 that the voltage Vc1 of the capacitor C1 is equal to or greater than the threshold value, the process proceeds to step S245.

  The processing in steps S245 and S246 is the same as the processing in steps S107 and S108 in FIG. 15, and the description thereof will be omitted because it will be repeated.

  Returning to FIG. 23, the processing in steps S207 and S208 is the same as the processing in steps S7 and S8 in FIG.

  Thus, in the second embodiment, the capacitance measurement time can be shortened as compared with the first embodiment.

<3. Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, the direction of detection of the capacitance Cx of the detection electrode 112 is provided.

[Configuration example of capacitance measuring device]
FIG. 28 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. 2 in that a microcomputer 311 is provided instead of the microcomputer 111, and a shield electrode 312 and a connection terminal T2 are added. . The microcomputer 311 is different from the microcomputer 111 in that a port P4 is added.

  The port P4 is connected to the ground and connected to the connection terminal T2.

  The shield electrode 312 is an electrode used for shielding an electric field, and is detachable from the connection terminal T2. In addition, the shield electrode 312 is connected to the ground of the microcomputer 311 via the connection terminal T2 and the port P3 while being connected to the connection terminal T2, and is held at the voltage at the reference voltage point. The shield electrode 312 may be directly connected to the port P3 instead of the connection terminal T2.

  Hereinafter, the capacitance between the shield electrode 312 and the surrounding space is represented by Cs, the voltage of the shield electrode 312 is represented by Vs, and the accumulated charge amount is represented by Qs.

  FIG. 29 is a cross-sectional view schematically showing an example of the shape of the shield electrode 312. In this example, the shield electrode 312 has a box shape that covers the detection electrode 112.

  As described above, since the shield electrode 312 is held at the voltage at the reference voltage point, the electric field around the detection electrode 112 hardly changes even when an object approaches from the shield electrode 312 side. Therefore, even if an object approaches from the shield electrode 312 side, the capacitance Cx of the detection electrode 112 hardly changes, so that the capacitance measurement direction can be limited. For example, in the case of the example of FIG. 29, the capacitance measurement direction can be limited to the upward direction on the paper. Further, for example, as shown in FIG. 28, by arranging a shield electrode 312 between the detection electrode 112 and the object 103, the influence of the object 103 can be made smaller and the capacitance can be measured. Become.

  In the above description, the shield electrode 312 is connected to the ground. However, the shield electrode 312 may be substantially constant by connecting to a voltage holding unit other than the ground. .

<4. Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the fourth embodiment, as compared with the third embodiment, the detection electrode 112 and the shield electrode 312 are controlled so as to have the same voltage.

[Configuration Example of Capacitance Measuring Device 401]
FIG. 30 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. 28 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 401 is different from the capacitance measuring device 301 of FIG. 28 in that a microcomputer 411 is provided instead of the microcomputer 311 and a resistor R2 and a capacitor C3 are added. Further, the microcomputer 411 is different from the microcomputer 311 in that a voltage measuring unit 421, the same potential control unit 422, SW7 to SW9, and a port P5 are added.

  One end of the resistor R2 is connected to the port P5, and the other end of the resistor R2 is connected to one end of the capacitor C3. The other end of the capacitor C3 is connected to the port P4 and the connection terminal T2. One end of SW7 is connected to the power supply Vcc, and the other end of SW7 is connected to port P5. One end of SW8 is connected to port P5, and the other end of SW8 is connected to ground. One end of SW9 is connected to port P4, and the other end of SW9 is connected to the ground.

  Further, the capacitance of the capacitor C3 is set to be sufficiently larger than the capacitance Cs between the shield electrode 312 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 421 has an input terminal connected to the port P5. Similarly to the voltage measuring units 121 and 122, the voltage measuring unit 421 measures the voltage input to the input terminal, compares the measured voltage with a predetermined threshold value (threshold voltage Vref), and controls the comparison result to the same potential. To the unit 422.

  The equipotential control unit 422 controls the opening and closing of SW7 to SW9 based on the measurement results of the voltage measurement unit 122 and the voltage measurement unit 421 so as to adjust the voltages of the detection electrode 112 and the shield electrode 312 to be the same. .

[Processing of Capacitance Measuring Device 401]
Next, processing of the capacitance measuring device 401 will be described with reference to FIGS.

  First, the measurement process executed by the capacitance measuring device 401 will be described with reference to the flowchart of FIG.

  In step S301, the capacitance measuring device 401 performs a total charge discharge process.

  Here, with reference to FIG. 32 and FIG. 33, the details of the all charge discharge process in step S301 will be described. FIG. 32 is a flowchart for explaining the all charge discharge process, and FIG. 33 is a diagram showing the flow of positive charges during the all charge discharge process.

  In step S321, the parameter measurement unit 123 turns on SW2, SW4, and SW5, and the same potential control unit 422 turns on SW8 and SW9. As a result, positive charge moves from the positive electrode of the capacitor C1 to the ground via the resistors R1 and SW2 in the direction of the arrow A51, and the discharge of the capacitor C1 is started. Further, the positive charge moves from the positive electrode of the capacitor C2 to the ground via SW4 in the direction of the arrow A52, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW5 in the direction of the arrow A53, and the discharge of the detection electrode 112 is started.

  Further, the positive charge moves from the positive electrode of the capacitor C3 to the ground via the resistors R2 and SW8 in the direction of the arrow A54, and the discharge of the capacitor C3 is started. Further, the positive charge moves from the shield electrode 312 to the ground via SW9 in the direction of the arrow A55, and the discharge of the shield electrode 312 is started.

  In step S322, 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 312 all.

  In step S323, the parameter measurement unit 123 turns off SW2, SW3, and SW5, and the same potential control unit 422 turns off SW8 and SW9. Thereafter, the total charge discharge process ends.

  Referring back to FIG. 31, in step S302, the capacitance measuring device 401 performs C1, C2, and C3 charging processing.

  Here, with reference to FIG. 34 and FIG. 35, the details of the C1, C2, and C3 charging processes in step S302 will be described. FIG. 34 is a flowchart for explaining the C1, C2, C3 charging process, and FIG. 35 is a diagram showing the flow of positive charges during the C1, C2, C3 charging process.

  In step S341, the parameter measurement unit 123 turns on SW1 and SW5, and the same potential control unit 422 turns on SW7 and SW9. As a result, the positive charge moves from the power source Vcc to the positive electrode of the capacitor C1 via SW1 and the resistor R1 in the direction of arrow A56, and charging of the capacitor C1 is started. Further, since positive charge is accumulated in the positive electrode of the capacitor C1, the positive charge moves from the negative electrode of the capacitor C1 to the positive electrode of the capacitor C2 in the direction of the arrow A57, and from the negative electrode of the capacitor C2 to the ground via the SW5, the arrow A58. The positive charge moves in the direction of and 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 the SW7 and the resistor R2 in the direction of arrow A59, and a positive charge moves from the negative electrode of the capacitor C3 to the ground via the SW9 in the direction of arrow A60. Charging of the capacitor C3 is started.

  In step S342, the parameter measurement unit 123 determines whether SW1 and SW5 are on. If it is determined that SW1 and SW5 are on, the process proceeds to step S343.

  In step S343, the voltage Vc2 of the capacitor C2 is measured as in the process of step S42 in FIG. 9, and in step S344, whether the voltage Vc2 of the capacitor C2 is equal to or greater than the threshold value, as in the process of step S43 in FIG. It is determined whether or not. If it is determined that the voltage Vc3 of the capacitor C3 is equal to or greater than the threshold, the process proceeds to step S345.

  In step S345, the parameter measurement unit 123 turns off SW1 and SW5. Thereby, charging of the capacitors C1 and C2 is stopped. Thereafter, the process proceeds to step S346.

  On the other hand, when it is determined in step S344 that the voltage Vc2 of the capacitor C2 is less than the threshold value, the process of step S345 is skipped, and the process proceeds to step S346.

  If it is determined in step S342 that SW1 and SW5 are off, the processes in steps S343 to S345 are skipped, and the process proceeds to step S346.

  In step S346, the same potential control unit 422 determines whether SW7 and SW9 are on. If it is determined that SW7 and SW9 are on, the process proceeds to step S347.

  In step S347, the voltage measurement unit 421 measures the voltage Vc3 of the capacitor C3. Specifically, the voltage measuring unit 421 measures the voltage Vc3 of the capacitor C3 (more precisely, the voltage between the positive electrode of the capacitor C3 and the reference voltage point), and uses the measured voltage Vc3 as a threshold value (threshold voltage Vref). And the result is supplied to the same potential controller 422.

  In step S348, the same potential control unit 422 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 421. If it is determined that the voltage Vc3 of the capacitor C3 is equal to or greater than the threshold, the process proceeds to step S349.

  In step S349, the same potential control unit 422 turns off SW7 and SW9. Thereby, charging of the capacitor C3 is stopped. Thereafter, the process proceeds to step S350.

  On the other hand, when it is determined in step S348 that the voltage Vc3 of the capacitor C3 is less than the threshold value, the process of step S349 is skipped, and the process proceeds to step S350.

  If it is determined in step S346 that SW7 and SW9 are off, the processes in steps S347 to S349 are skipped, and the process proceeds to step S350.

  In step S350, the parameter measurement unit 123 determines whether all the switches are off. If it is determined that one or more switches are on, the process returns to step S342. Thereafter, the processes in steps S342 to S350 are repeatedly executed until it is determined in step S350 that all the switches are off.

  On the other hand, if it is determined in step S350 that all the switches are off, the C1, 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. 31, in step S303, the capacitance measuring device 401 executes the detection electrode and shield electrode charging process.

  Here, with reference to FIG. 36 and FIG. 37, the details of the detection electrode and shield electrode charging process in step S303 will be described. 36 is a flowchart for explaining the detection electrode and shield electrode charging process, and FIG. 37 is a diagram showing the flow of positive charges during the detection electrode and shield electrode charging process.

  In step S361, the parameter measurement unit 123 turns on SW3, and the same potential control unit 422 turns on SW7. Thereby, a positive charge moves in the direction of arrow A61 from the power source Vcc to the positive electrode of the capacitor C2 via SW3, 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 A62, and charging of the detection electrode 112 is started. Further, the positive charge moves in the direction of arrow A63 from the power source Vcc to the positive electrode of the capacitor C3 via SW7 and the resistor R2, and charging of the capacitor C3 is started. Further, as 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 312 in the direction of arrow A64, and charging of the shield electrode 312 is started.

  In step S362, the parameter measurement unit 123 and the same potential control unit 422 wait for a predetermined time, that is, a time sufficient for the detection electrode 112 and the shield electrode 312 to be fully charged.

  In step S363, the parameter measurement unit 123 turns off SW3, and the same potential control unit 522 turns off SW7. Thereby, charging of the capacitor C2, the capacitor C3, the detection electrode 112, and the shield electrode 312 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 312, the voltage of the shield electrode 312 after charging is substantially equal to the voltage Vcc of the power supply Vcc−the reference voltage Vref. Therefore, the voltage of the shield electrode 312 after charging is substantially equal to the voltage of the detection electrode 112 after charging.

  Accordingly, charges are accumulated in the detection electrode 112 in a state where the voltages of the detection electrode 112, the shield electrode 312 and the object 103 are substantially equal and the capacitance between the detection electrode 112, the object 103 and the shield electrode 312 is substantially zero. The In other words, the electric charge according to the capacitance excluding the capacitance between the detection electrode 112 and the object 103 and the shield electrode 312 out of the capacitance between the detection electrode 112 and its surroundings is the detection electrode. 112 is accumulated.

  Therefore, the charge amount ΔQ of the detection electrode 112 per time (= the discharge amount of the capacitor C1 per C2, C3 voltage adjustment process described later) is a value substantially excluding the influence of the object 103 and the shield electrode 312. . Therefore, even if the shape, relative dielectric constant, temperature, and the like of the detection electrode 112 and the shield electrode 312 change, the capacitance can be measured with almost no influence.

  Returning to FIG. 31, in step S304, the capacitance measuring device 401 executes C2 and C3 voltage adjustment processing.

  Here, with reference to FIG. 38 and FIG. 39, the detail of the C2 and C3 voltage adjustment process of step S304 is demonstrated. FIG. 38 is a flowchart for explaining the C2, C3 voltage adjustment processing, and FIG. 39 is a diagram showing the flow of positive charges during the C2, C3 voltage adjustment processing.

  In step S381, the parameter measurement unit 123 turns on SW2 and SW5, and the same potential control unit 422 turns on SW8 and SW9. As a result, positive charge moves from the positive electrode of the capacitor C1 to the ground via the resistors R1 and SW2 in the direction of the arrow A65, and discharging of the capacitor C1 is started. Further, when the positive charge is discharged from the positive electrode of the capacitor C1, the positive charge moves from the positive electrode of the capacitor C2 to the negative electrode of the capacitor C1 in the direction of arrow A66, and the discharge of the capacitor C2 is started. Further, the positive charge moves from the detection electrode 112 to the ground via SW5 in the direction of the arrow A67, and the discharge of the detection electrode 112 is started.

  Further, the positive charge moves in the direction of arrow A68 from the positive electrode of the capacitor C3 to the ground via the resistors R2 and SW8, and the discharge of the capacitor C3 is started. Further, the positive charge moves in the direction of arrow A69 from the shield electrode 312 to the ground via SW9, and the discharge of the shield electrode 312 is started.

  In step S382, the parameter measurement unit 123 determines whether SW2 and SW5 are on. If it is determined that SW2 and SW5 are on, the process proceeds to step S383.

  In step S383, the voltage Vc2 of the capacitor C2 is measured in the same manner as in step S42 of FIG. 9, and in step S384, whether the voltage Vc2 of the capacitor C2 is equal to or less than the threshold value, as in step S83 of FIG. It is determined whether or not. If it is determined that the voltage Vc2 of the capacitor C2 is equal to or lower than the threshold, the process proceeds to step S385.

  In step S385, the parameter measurement unit 123 turns off SW2 and SW5. Thereby, the discharge of the capacitors C1 and C2 is stopped.

  On the other hand, if it is determined in step S384 that the voltage Vc2 of the capacitor C2 is greater than the threshold value, the process of step S385 is skipped, and the process proceeds to step S386.

  If it is determined in step S382 that SW2 and SW5 are off, the processes in steps S383 to S385 are skipped, and the process proceeds to step S386.

  In step S386, the same potential controller 422 determines whether SW8 and SW9 are on. If it is determined that SW8 and SW9 are on, the process proceeds to step S387.

  In step S387, the voltage Vc3 of the capacitor C3 is measured by the voltage measuring unit 421 as in the process of step S347 of FIG.

  In step S388, the equipotential control unit 422 determines whether or not the voltage Vc3 of the capacitor C3 is equal to or less than a threshold based on the measurement result by the voltage measurement unit 421. If it is determined that the voltage Vc3 of the capacitor C3 is equal to or lower than the threshold value, the process proceeds to step S389.

  In step S389, the same potential control unit 422 turns off SW8 and SW9. Thereby, the discharge of the capacitor C3 is stopped. Thereafter, the process proceeds to step S390.

  On the other hand, if it is determined in step S388 that the voltage Vc3 of the capacitor C3 is greater than the threshold value, the process of step S389 is skipped, and the process proceeds to step S390.

  If it is determined in step S386 that SW8 and SW9 are on, the processes in steps S387 to S389 are skipped, and the process proceeds to step S390.

  In step S390, the parameter measurement unit 123 determines whether all the switches are off. If it is determined that one or more switches are on, the process returns to step S382. Thereafter, the processes in steps S382 to S390 are repeatedly executed until it is determined in step S390 that all the switches are off.

  On the other hand, if it is determined in step S390 that all the switches are off, the C2 and C3 voltage adjustment processing ends.

  Returning to FIG. 31, in step S305, the parameter measurement unit 123 determines whether the processing in steps S303 to S305 has been repeated a predetermined number of times. If it is determined that the processes in steps S303 to S305 have not been repeated a predetermined number of times, the process returns to step S303. Thereafter, the processes in steps S303 to S305 are repeatedly executed until it is determined in step S305 that the process has been repeated a predetermined number of times.

  On the other hand, if it is determined in step S305 that the processes in steps S303 to S305 have been repeated a predetermined number of times, the process proceeds to step S306.

  The processing in steps S306 to S308 is the same as the processing in steps S6 to S8 in FIG. Thereafter, the measurement process ends.

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

[Modification of Capacitance Measuring Device 401]
FIG. 40 shows a modification of the capacitance measuring device 401. In this example, an offset capacitor 451 having a known capacitance is added to the shield electrode 312, and the shield electrode 312 and the offset capacitor 451 constitute one shield electrode. One end of the offset capacitor 451 is connected to the connection terminal T2, and the other end is connected to the reference voltage point.

  In this way, by adding the offset capacitor 451, even if the capacitance of the shield electrode 312 changes due to factors such as an object approaching the shield electrode 312, the degree of change can be reduced. As a result, fluctuations in the voltage of the shield electrode 312 are reduced, and control for making the detection electrode 112 and the shield electrode 312 the same voltage is facilitated.

  For example, if the electrostatic capacity of the shield electrode 312 is Cs and the electrostatic capacity of the offset capacitor 451 is Coffs, the electrostatic capacity Ct of the entire shield electrode is expressed by the following equation (9).

Ct = Cs + Cofs
= Cofs × (Cs / Cofs + 1) (9)

  Here, when the capacitance Cofs is set so that Cs << Cofs, Cs / Cofs becomes almost zero. Accordingly, even if the capacitance Cs changes, the capacitance Ct hardly changes.

<5. Fifth embodiment>
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In the fifth embodiment, the measurement time can be shortened as compared with the fourth embodiment.

[Configuration Example of Capacitance Measuring Device 501]
FIG. 41 is a circuit diagram showing 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 FIGS. 22 and 30 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 capacitance measuring device 501 is different from the capacitance measuring device 401 in FIG. 30 in that a microcomputer 511 is provided instead of the microcomputer 411. Further, compared with the microcomputer 411, the microcomputer 511 has SW6, SW10, SW11 and ports P6, P7 added, and instead of the parameter measurement unit 123 and the same potential control unit 422, the parameter measurement unit 521 and the same potential are added. The difference is that a control unit 522 is provided.

  Furthermore, in the capacitance measuring device 501, connection of each component is partly different compared to the capacitance measuring device 401. Specifically, the resistor R1 is connected between the port P1 and the port P6, and the capacitor C1 is connected between the port P2 and the port P6. One end of SW6 is connected to port P6, and the other end is connected to the ground. The voltage measuring unit 121 has an input terminal connected to the port P6.

  The resistor R2 is connected between the port P5 and the port P7, and the capacitor C3 is connected between the port P4 and the port P7. 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 the ground. The voltage measuring unit 421 has an input terminal connected to the port P7. The connection of other components is the same as that of the capacitance measuring device 401.

  The parameter measuring unit 521 controls the opening and closing of SW1 to SW6 and measures the capacitance parameter based on the measurement results of the voltage measuring unit 121 and the voltage measuring unit 122. The parameter measurement unit 521 supplies the measured capacitance parameter to the arithmetic processing unit 124.

  The equipotential control unit 522 controls the opening and closing of SW7 to SW11 based on the measurement results of the voltage measuring unit 122 and the voltage measuring unit 421 so as to adjust the voltages of the detection electrode 112 and the shield electrode 312 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 S401, the capacitance measuring device 501 performs a total charge discharge process.

  Here, with reference to FIG. 43 and FIG. 44, the details of the all charge discharge process in step S401 will be described. FIG. 43 is a flowchart for explaining the all-charge discharge process, and FIG. 44 is a diagram showing the flow of positive charges during the all-charge discharge process.

  In step S421, the parameter measurement unit 521 turns on SW4, SW5, and SW6, and the same potential control unit 422 turns on SW9 and SW11. As a result, positive charges move from the positive electrode of the capacitor C1 to the ground via the SW6 in the direction of the arrow A81, and the discharge of the capacitor C1 is started. Further, the positive charge moves from the positive electrode of the capacitor C2 to the ground via SW4 in the direction of the arrow A82, and the discharge of the capacitor C2 is started. Further, positive charges move from the detection electrode 112 to the ground via SW5 in the direction of the arrow A83, and the discharge of the detection electrode 112 is started.

  At this time, the electric charge of the capacitor C1 can be discharged without going through the resistor R1, and the discharge time can be shortened.

  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. Further, the positive charge moves from the shield electrode 312 to the ground via SW9 in the direction of the arrow A85, and the discharge of the shield electrode 312 is started.

  At this time, the electric charge of the capacitor C3 can be discharged without going through the resistor R2, and the discharge time can be shortened.

  In step S422, the parameter measurement unit 521 waits for a predetermined time, that is, a time sufficient for discharging all the capacitors C1 to C3, the detection electrode 112, and the shield electrode 312.

  In step S423, the parameter measurement unit 521 turns off SW4, SW5, and SW6, and the same potential control unit 422 turns off SW9 and SW11. Thereafter, the total charge discharge process ends.

  Returning to FIG. 42, in step S402, the C1, C2, and C3 charging processes are executed in the same manner as in step S302 of FIG.

  In step S403, the capacitance measuring device 501 executes a detection electrode and shield electrode charging process.

  Here, with reference to FIG. 45 and FIG. 46, the details of the detection electrode and shield electrode charging process in step S403 will be described. 45 is a flowchart for explaining the detection electrode and shield electrode charging process, and FIG. 46 is a diagram showing the flow of positive charges during the detection electrode and shield electrode charging process.

  In step S461, the parameter measurement unit 123 turns on SW3, and the same potential control unit 422 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 SW3, 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, as 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 312 in the direction of arrow A89, and charging of the shield electrode 312 is started.

  At this time, the capacitor C3 can be charged without going through the resistor R2, and as a result, the charging time of the capacitor C3 and the shield electrode 312 can be shortened.

  In step S462, the parameter measurement unit 521 and the same potential control unit 522 wait for a predetermined time, that is, a time sufficient for the detection electrode 112 and the shield electrode 312 to be fully charged.

  In step S463, the parameter measurement unit 123 turns off SW3, and the same potential control unit 522 turns off SW10. Thereby, charging of the capacitor C2, the capacitor C3, the detection electrode 112, and the shield electrode 312 is stopped. Thereafter, the detection electrode and shield electrode charging process ends.

  Returning to FIG. 42, the processing of steps S404 to S408 is the same as the processing of steps S303 to S308 of FIG. 31, and the description thereof will be omitted because it will be repeated.

  As described above, the capacitance measurement time can be shortened 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, 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 601]
FIG. 47 is a diagram illustrating a configuration example of a capacitance measuring device 601 according to the sixth embodiment of the present invention.

  The capacitance measuring device 601 includes a microcomputer 611, 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 612-1 to 612-n. The microcomputer 611 includes ports P1-1 to P1-n, P2-1 to P2-n, and P3-1 to P3-n.

  One end of the resistor R1-i (i = 1 to n) is connected to the port P1-i, and the other end of the resistor R1-i is connected to one end of the capacitor C1-i. The other end of the capacitor C1-i is connected to the port P2-i. The capacitor C2-i is connected between the port P2-i and the port P3-i. The connection terminal T1-i is connected to the port P3-i. The electrode 612-i is detachable from the connection terminal T1-i. The electrode 612-i may be directly connected to the port P3-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 612-1 to 612-n, When it is not necessary to individually distinguish the ports P1-1 to P1-n, P2-1 to P2-n, and P3-1 to P3-n, the resistor R1, the capacitor C1, the capacitor C2, and the connection terminal T1 are simply used. , Electrode 612, port P1, port P2, and port P3.

[Configuration Example of Microcomputer 611]
FIG. 48 is a diagram illustrating a configuration example of the microcomputer 611. 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 611 is configured to include measurement units 631-1 to 631-n, a role setting unit 632, and the same potential control unit 633.

  Each of the measurement units 631-1 to 631-n has the same configuration as the microcomputer 111 of FIG. Therefore, the measurement unit 631-i (i = 1 to n), the resistor R1-i, the capacitor C1-i, the capacitor C2-i, and the electrode 612-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 601.

  Hereinafter, when it is not necessary to individually distinguish the measurement units 631-1 to 631-n, they are simply referred to as measurement units 631.

  The role setting unit 632 sets the role of the electrode 612 connected to each measurement unit 631. That is, the role setting unit 632 sets whether each electrode 612 is used as a detection electrode or a shield electrode.

  The same potential control unit 633 has a function similar to that of the same potential control unit 422 in FIG. 30 and controls the electrodes 612 to have the same voltage.

[Processing of Capacitance Measuring Device 601]
Next, measurement processing executed by the capacitance measuring device 601 will be described with reference to the flowchart in FIG.

  In step S601, the role setting unit 632 sets the role of each electrode 612. That is, the role setting unit 632 sets whether to use each electrode 612 as a detection electrode or a shield electrode based on a user setting or the like.

  The processing in steps S602 to S609 is the same as the processing in steps S1 to S8 in FIG.

[Usage example of capacitance measuring device 601]
The capacitance measuring device 601 can change the position and direction in which the capacitance is measured by switching the role of each electrode.

  For example, by setting one electrode 612 on each of the front and back of a vehicle door, setting the electrode 612 on the front side of the door as a detection electrode, and setting the electrode 612 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 612 on the front side of the door as a shield electrode and the electrode 612 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.

<7. Seventh Embodiment>
Next, a seventh embodiment of the present invention will be described with reference to FIG. In the seventh embodiment, the capacitance between two electrodes can be measured.

[Configuration Example of Capacitance Measuring Device 701]
FIG. 50 is a diagram illustrating a configuration example of a capacitance measuring device 701 according to the seventh 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 701 is different from the capacitance measuring device 101 of FIG. 2 in that a connection terminal T2 and a reference voltage electrode 711 are added.

  The connection terminal T2 is connected to a reference voltage point, and the reference voltage electrode 711 is connected to the connection terminal T2. Accordingly, the voltage of the reference voltage electrode 711 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 711 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 711, the measured value of the capacitance changes.

<8. Eighth Embodiment>
Next, with reference to FIG. 51 and FIG. 52, an eighth embodiment of the present invention will be described. In the eighth 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 801]
FIG. 51 is a diagram illustrating a configuration example of a capacitance sensor 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 the description of portions having the same processing will be omitted as appropriate because the description will be repeated.

  The capacitance sensor 801 is different from the capacitance measuring apparatus 101 in FIG. 2 in that a microcomputer 811 is provided instead of the microcomputer 111. Further, the microcomputer 811 is different from the microcomputer 111 in that the object detection unit 821 is provided and the arithmetic processing unit 124 and the output unit 125 are not provided.

  The object detection unit 821 detects the presence or 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 801]
Next, the object detection process executed by the capacitance sensor 801 will be described with reference to the flowchart of FIG.

  In steps S701 to S706, 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 becomes longer as the capacitance Cx of the detection electrode 112 becomes larger, and the charging time t becomes shorter as the capacitance Cx becomes smaller.

  In step S707, the object detection unit 821 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 greater than or equal to 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 S708.

  In step S <b> 708, the object detection unit 821 determines that an object exists around the detection electrode 112. The object detection unit 821 outputs the determination result to the outside, and the object detection process ends.

  On the other hand, if it is determined in step S707 that the charging time t is less than 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 S709.

  In step S <b> 709, the object detection unit 821 determines that no object exists around the detection electrode 112. The object detection unit 821 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.

  The object may be detected using other capacitance parameters, for example, the number of discharges n 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.

<9. Ninth Embodiment>
Next, with reference to FIGS. 53 and 54, a ninth embodiment of the present invention will be described. In the ninth embodiment, the threshold voltage Vref can be automatically set according to the voltage of the object 103.

[Configuration Example of Capacitance Measuring Device 901]
FIG. 53 is a diagram showing a configuration example of a capacitance measuring device 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 measuring device 901 is different from the capacitance measuring device 101 in FIG. 2 in that a microcomputer 911 is provided instead of the microcomputer 111. The microcomputer 911 is different from the microcomputer 111 in that a threshold voltage setting unit 921 is provided.

  The threshold voltage setting unit 921 obtains the threshold voltage Vref based on the capacitance parameter measured by the parameter measurement unit 123 and sets it in the voltage measurement units 121 and 122.

[Processing of Capacitance Measuring Device 901]
Next, the threshold voltage setting process executed by the capacitance measuring device 901 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 S801, the threshold voltage setting unit 921 temporarily sets the threshold voltage Vref. For example, the threshold voltage setting unit 921 sets the threshold voltage Vref of the voltage measuring units 121 and 122 to the voltage at the reference voltage point.

  In step S802, 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 S901, and the measurement result is supplied from the output unit 125 to the threshold voltage setting unit 921.

  In step S803, the threshold voltage setting unit 921 changes the threshold voltage Vref. For example, the threshold voltage setting unit 921 increases the threshold voltage Vref of the voltage measurement units 121 and 122 by a predetermined value.

  In step S804, 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 S803, and the measurement result is supplied from the output unit 125 to the threshold voltage setting unit 921.

  In step S805, the threshold voltage setting unit 921 determines whether 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 been performed only twice, this process is not performed and the process returns to step S803.

  Thereafter, in step S805, the processes of steps S803 to S805 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 S805 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 S806.

  In step S806, the threshold voltage setting unit 921 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 921 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.

<10. 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 of the second embodiment can be applied to the third embodiment and the sixth to ninth 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 312 has been shown. 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 312 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 apparatus 102,103 Object 111 Microcomputer 112 Detection electrode 121,122 Voltage measuring part 123 Parameter measuring part 124 Arithmetic processing part 141 Comparator 201 Capacitance measuring apparatus 211 Microcomputer 221 Parameter measuring part 301 Capacitance Measurement device 311 Microcomputer 312 Shield electrode 401 Capacitance measurement device 411 Microcomputer 421 Voltage measurement unit 422 Equipotential control unit 451 Offset capacitor 501 Capacitance measurement device 511 Microcomputer 521 Parameter measurement unit 522 Equipotential control unit 601 Electrostatic Capacitance measuring device 611 Microcomputer 612-1 to 612-n Electrode 631-1 to 631-n Measuring unit 632 Role setting unit 633 Equipotential control unit 7 01 Capacitance Measuring Device 711 Reference Voltage Electrode 801 Capacitance Sensor 811 Microcomputer 821 Object Detection Unit 901 Capacitance Measuring Device 911 Microcomputer 921 Threshold Voltage Setting Unit C1 to C3, C1-1 to C1-n, C2- 1 to C2-n capacitors R1, R2, R1-1 to R1-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 ports

Claims (11)

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 capacitance in which the capacitance is sufficiently larger than the first electrode, the first end is connected to the second end of the first capacitor, and the second end is connected to the first connection means. With a battery of
A first opening / closing means having a first end connected to the charge supply means and a second end connected to a second end of the first resistor;
A second opening / closing means having a first end connected to a second end of the first opening / closing means 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 a second end of the first battery;
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 fifth opening / closing means having a first end connected to a second end of the second capacitor and a second end connected to the ground;
First voltage measuring means having an input connected to a second end of the first opening and closing means;
A second voltage measuring means having an input portion connected to a second end of the third opening / closing means;
Capacitance measuring means for controlling the first to fifth opening / closing means and for measuring the capacitance based on voltages measured by the first voltage measuring means and the second voltage measuring means. A measuring device comprising: and. The capacitance measuring means is
The second opening / closing means, the fourth opening / closing means, and the fifth opening / closing means are controlled to be connected to the first capacitor, the second capacitor, and the first connecting means. The first opening / closing means and the fifth opening / closing means are controlled after discharging the electric charge of the first electrode, and the first capacitor is controlled until the voltage of the second capacitor reaches a predetermined threshold value. And charging the second capacitor and the second capacitor,
The second capacitor is controlled by controlling the third switch and charging the second capacitor and the first electrode, and then controlling the second switch and the fifth switch. The charge of the first capacitor and the second capacitor is discharged until the voltage reaches the threshold, and the charge / discharge process for discharging the charge of the first electrode is performed once or more,
The measurement apparatus according to claim 1, wherein the capacitance is measured based on an amount of electric charge released from the first battery by the charge / discharge process. A sixth opening / closing means having a first end connected to a first end of the first capacitor and a second end connected to the ground;
The input part of the first voltage measuring means is connected to the first end of the sixth opening means instead of the second end of the first opening means,
The capacitance measuring means controls the first to sixth opening / closing means, and based on the voltages measured by the first voltage measuring means and the second voltage measuring means, The measuring device according to claim 1, wherein: The capacitance measuring means is
The fourth opening / closing means, the fifth 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 first opening / closing means and the fifth opening / closing means are controlled after discharging the electric charge of the first electrode, and the first capacitor is controlled until the voltage of the second capacitor reaches a predetermined threshold value. And charging the second capacitor and the second capacitor,
The second capacitor is controlled by controlling the third switch and charging the second capacitor and the first electrode, and then controlling the second switch and the fifth switch. The charge of the first capacitor and the second capacitor is discharged until the voltage reaches the threshold, and the charge / discharge process for discharging the charge of the first electrode is performed once or more,
The measurement device according to claim 3, wherein the capacitance is measured based on an amount of charge released from the first capacitor by the charge / discharge 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 becomes the minimum among several different said threshold values is further provided. 4. The measuring device according to 4. The measuring apparatus according to claim 1, further comprising: second connection means connected to the ground and capable of connecting a second electrode. A second connecting means capable of connecting the second electrode;
A second resistor;
A third capacitor having a sufficiently larger capacitance than the second electrode, a first end connected to the first end of the second resistor, and a second end connected to the second connection means; With a battery of
A seventh 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;
An eighth opening / closing means having a first end connected to a second end of the seventh opening / closing means and a second end connected to the ground;
A ninth opening / closing means having a first end connected to a second end of the third capacitor and a second end connected to the ground;
A third voltage measuring means having an input portion connected to a second end of the seventh 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. Or the measuring apparatus of 3. 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 instead of the second end of the seventh opening / closing means,
The said same electric potential control means controls the said 7th thru | or 11th opening-and-closing means, It 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;
Resistance,
A first capacitor having a sufficiently larger capacitance than the electrode and having a first end connected to a first end of the resistor;
A second capacitor having a sufficiently larger capacitance than the electrode, a first end connected to a second end of the first capacitor, and a second end connected to the first connection means; ,
A first opening / closing means having a first end connected to the charge supply means and a second end connected to a second end of the resistor;
A second opening / closing means having a first end connected to a second end of the first opening / closing means 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 a second end of the first battery;
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 fifth opening / closing means having a first end connected to a second end of the second capacitor and a second end connected to the ground;
First voltage measuring means having an input connected to a second end of the first opening and closing means;
A second voltage measuring means having an input portion connected to a second end of the third opening / closing means;
Capacitance measuring means for controlling the first to fifth opening / closing means and for measuring the capacitance based on voltages measured by the first voltage measuring means and the second voltage measuring means. A plurality of units each comprising and
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;
Resistance,
A first capacitor having a sufficiently larger capacitance than the electrode and having a first end connected to a first end of the resistor;
A second capacitor having a capacitance sufficiently larger than the electrode, a first end connected to a second end of the first capacitor, and a second end connected to the electrode;
A first opening / closing means having a first end connected to the charge supply means and a second end connected to a second end of the resistor;
A second opening / closing means having a first end connected to a second end of the first opening / closing means 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 a second end of the first battery;
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 fifth opening / closing means having a first end connected to a second end of the second capacitor and a second end connected to the ground;
First voltage measuring means having an input connected to a second end of the first opening and closing means;
A second voltage measuring means having an input portion connected to a second end of the third opening / closing means;
Capacitance measuring means for controlling the first to fifth opening / closing means and for measuring the capacitance based on voltages measured by the first voltage measuring means and the second voltage measuring means. When,
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 supplying and charging the same amount of charge to the first capacitor and 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 discharging step of discharging the same amount of charge from the first capacitor and the second capacitor until the voltage of the second capacitor reaches the threshold;
A measurement method comprising: measuring the capacitance based on an amount of charge released from the first battery by executing the processes of the second charging step and the discharging step one or more times.

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