JP4929937B2 - Capacitance detection device - Google Patents

Description

  The present invention relates to a capacitance detection device.

Examples of conventional capacitance detection devices include those described in Patent Documents 1 to 3.
US Pat. No. 6,466,036 JP 2005-106665 A JP 2002-221402 A

  The capacitance detection device is incorporated in a system that controls opening and closing of a vehicle door such as an automobile, for example, and a detection signal of the capacitance detection device is used as a trigger when unlocking. Specifically, when the user approaches the vehicle and the ID code is collated between the vehicle side and the user, when the vehicle side transitions to the unlock permission mode, the user handles the outside handle of the vehicle door. When an unlock sensor (electrode) arranged inside is touched, the capacitance detection device detects a change in capacitance of the electrode and outputs it as a trigger. In other words, the capacitance detection device detects and outputs the intention of unlocking by the user based on a change in capacitance.

  In addition, the electrostatic capacity detection device is built into a safety device that controls the distance between the head and the headrest in order to reduce lashing at the time of rear impact, and the electrostatic capacity changes according to the distance between the electrode and the human body. There is also a need to be used as a distance sensor that detects the distance between the head and the headrest by utilizing this.

  In the capacitance detection device disclosed in Patent Document 1, a DC voltage source is connected to one end of a reference capacitor Cs via an open / close switch S1, and one end is grounded to the other end of the reference capacitor Cs via a sensor electrode. Alternatively, a measured capacitor Cx connected to the free space is connected, an open / close switch S2 is connected between the other end of the reference capacitor Cs and the ground, and an open / close switch S3 is connected to both ends of the reference capacitor Cs. One end of the reference capacitor Cs is connected to a potential measuring unit that measures the potential of the one end.

  In this capacitance detection device, first, the switches S2 and S3 are closed to discharge the charges of the direct reference capacitance Cs and the measured capacitance Cx. Next, the switch S1 is closed to charge the reference capacitor Cs and the measured capacitor Cx with a DC voltage source, and the potential of the reference capacitor is increased to a voltage determined by the capacitance ratio between the reference capacitor and the measured capacitor. The operation of opening S1, closing the switch S2 and grounding the other end of the reference capacitor to discharge the charge of the specific measurement capacitor, and repeatedly measuring the potential of the reference capacitor by the potential measuring unit, the potential of the reference capacitor is repeated. The number of times until the voltage rises to the set potential is counted. The presence or absence of a change in the capacitance value of the measured capacitance is detected by increasing or decreasing the number of times until the potential of the reference capacitor rises to the set potential.

  Patent Document 1 also describes a capacitance detection device that detects the presence or absence of changes in two measured capacitances. In this capacitance detection device, sensor electrodes are connected to both ends of a reference capacitor Cs, and two measured capacitors Cx1 and Cx2 having one side connected to ground or free space are connected to each sensor electrode. One end of the reference capacitor Cs is connected to a DC voltage source via an open / close switch S1 and grounded via an open / close switch S2. The other end of the reference capacitor Cs is connected to a DC voltage source via an open / close switch S3 and grounded via an open / close switch S4. In the capacitance detection device, the open / close switches S1 to S4 are operated, and the potentials at both ends of the reference capacitor Cs are measured by the two potential measuring units to determine whether there are changes in the two measured capacitances Cx1 and Cx2. Detected.

In the capacitance detection device disclosed in Patent Document 2, one end of a reference capacitor Cs having an open / close switch S1 connected between both ends thereof is connected to a DC voltage source, and the other end of the reference capacitor Cs is connected to a measured capacitor Cx. Connected to one end, the other end of the measured capacitor Cx is grounded, and an open / close switch S3 is connected between both ends of the measured capacitor Cx. In this capacitance detection device, after performing the first switch operation for closing the open / close switch S1, the second switch operation for opening the open / close switch S2 and then opening the open / close switch S2 and closing the open / close switch S3 are performed. The third switch operation for returning from the open state to the open state is alternately repeated, and the capacitance value of the measured capacitance Cx is determined based on the number of times of the second switch operation until the potential at the other end of the reference capacitance Cs changes to a predetermined potential. Changes are detected.
In the capacitance detection device disclosed in Patent Document 3, the areas of two electrodes facing the object to be measured are equalized, and the alternating current is fed back to the two capacitors formed between each electrode and the object to be measured. A signal is sent and the distance to the object to be measured is obtained from the impedance of the two capacitors.

However, in the electrostatic capacitance detection devices described in Patent Documents 1 and 2, since the potential of the sensor electrode greatly fluctuates, a large radio noise is generated and the electromagnetic detection is synchronized with the open / close switch S2 or the open / close switch S4. If there is a disturbance, there is a risk that the detection accuracy will deteriorate and the normal operation will not be performed.
An object of the present invention is to realize a capacitance detection device that suppresses generation of radio noise and has high detection accuracy.

In order to achieve the above object, a capacitance detection device according to a first aspect of the present invention includes:
A first open / close switch having one end connected to the first power supply potential and the other end connected to the first node;
A first reference capacitor having one end connected to the first node and the other end connected to a second power supply potential;
A second open / close switch having one end connected to the first node and the other end connected to a second node;
A third open / close switch having one end connected to the second node and the other end connected to a third power supply potential;
A first sensor electrode that is connected to the second node and forms a capacitor that faces the object to be measured and exhibits a capacitance according to a distance from the object to be measured;
A fourth open / close switch having one end connected to the third power supply potential and the other end connected to a third node;
A second reference capacitor having one end connected to the third node and the other end connected to a fourth power supply potential;
A fifth open / close switch having one end connected to the third node and the other end connected to a fourth node;
A sixth open / close switch having one end connected to the fourth node and the other end connected to the first power supply potential;
A capacitor connected to the fourth node, facing the object to be measured and having a capacitance corresponding to a distance from the object to be measured is formed, and in proximity to the first sensor electrode A second sensor electrode having a capacitance between the first sensor electrode and the first sensor electrode;
A comparator in which the first node is connected to one input terminal and the third node is connected to the other input terminal;
After performing the first switch operation for opening the first open / close switch and the fourth open / close switch after closing them, the second open / close switch and the fifth open / close switch are closed. Switch control means for alternately repeating a second switch operation for returning the switch from the open state to the open state, and a third switch operation for returning the open state to the open state after closing the third open / close switch and the sixth open / close switch;
Counting means for counting the number of times the second switch operation is repeated;
Based on the number of times of the second switch operation counted by the counting means until the level of the input voltage at both input terminals of the comparator is reversed, a change in capacitance with the object to be measured is determined. A determination means;
It is characterized by providing.

The ratio between the area of the first sensor electrode and the capacity of the first reference capacitor and the ratio of the area of the second sensor electrode and the capacity of the second reference capacitor are substantially equal. But you can.
The areas of the first sensor electrode and the second sensor electrode may be equal.

In order to achieve the above object, a capacitance detection device according to a second aspect of the present invention includes:
A first sensor electrode that constitutes one electrode of a capacitor that opposes the object to be measured and whose capacitance changes in accordance with the distance between the object to be measured;
A second sensor electrode that constitutes one electrode of a capacitor that opposes the object to be measured and whose capacitance changes according to the distance between the object to be measured;
The fluctuation of the electric charge stored in the capacitor in which the first sensor electrode and the second sensor electrode become one electrode accompanying the change in the potential of the first sensor electrode and the second sensor electrode, Accumulating in a reference capacity corresponding to each of the first sensor electrode and the second sensor electrode,
A capacitance detection device that detects a capacitance of a capacitor in which the first sensor electrode and the second sensor electrode are one electrode by a potential difference between both terminals of the reference capacitance,
The fluctuations of the potentials of the first sensor electrode and the second sensor electrode have substantially the same fluctuation width, and the fluctuation directions are opposite directions.

  The areas of the first sensor electrode and the second sensor electrode may be equal.

The first sensor electrode is composed of an arbitrary number of conductors,
The second sensor electrode is composed of an arbitrary number of conductors,
The center of gravity of the first sensor electrode and the center of gravity of the second sensor electrode may substantially coincide.

  The first sensor electrode and the second sensor electrode may be arranged symmetrically with respect to two or more planes passing through the center of gravity.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of radio noise is suppressed and the electrostatic capacitance detection apparatus with high detection accuracy is realizable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a configuration diagram illustrating a capacitance detection device according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of part A of FIG.

  The capacitance detection device includes a first opening / closing switch S11, a second opening / closing switch S21, a third opening / closing switch S31, a fourth opening / closing switch S12, a fifth opening / closing switch S22, and a sixth opening / closing switch S21. Open / close switch S32, first reference capacitor Cs1, second reference capacitor Cs2, first sensor electrode E1, second sensor electrode E2, comparator CMP1, switch control unit (not shown), count The control part 10 which comprises a means is provided.

  One end of the open / close switch S11 is connected to the power supply potential V1 (first power supply voltage), and the other end of the open / close switch S11 is connected to the first node N1. One end of the reference capacitor Cs1, one end of the open / close switch S21, and one input terminal Vin− of the comparator CMP1 are connected to the node N1.

  The other end of the open / close switch S21 is connected to the second node N2. The sensor electrode E1 is connected to the node N2, and one end of the open / close switch S31 is connected to the node N2. The other end of the open / close switch S31 is connected to the power supply potential V2 (second power supply voltage). The other end of the reference capacitor Cs1 is connected to the power supply potential V3 (third power supply voltage). The power supply potential V3 may be equal to the power supply potential V1.

  Further, one end of the open / close switch S12 is connected to the power supply potential V2, and the other end of the open / close switch S12 is connected to the third node N3. One end of the reference capacitor Cs2, one end of the open / close switch S21, and the other input terminal Vin + of the comparator CMP1 are connected to the node N3.

  The other end of the open / close switch S22 is connected to the fourth node N4. The sensor electrode E2 is connected to the node N4, and one end of the open / close switch S32 is connected to the node N4. The other end of the open / close switch S32 is connected to the power supply potential V1. The other end of the reference capacitor Cs2 is connected to the power supply potential V4 (fourth power supply voltage). The power supply potential V4 may be equal to the power supply potential V2.

  The output terminal of the comparator CMP1 is connected to the control circuit 10. The open / close operation of each open / close switch S11, S21, S31, S12, S22, S32 is controlled by a switch control unit (not shown).

  As shown in FIG. 2, the sensor electrodes E1 and E2 respectively form measured capacitors Cx11 and Cx21 facing the conductor E0 to be detected, and the sensor electrodes E1 and E2 are measured capacitors Cx11. , Cx21. The sensor electrodes E1 and E2 are arranged close to each other, and a capacitance Cx0 is also formed between the sensor electrodes E1 and E2.

Next, the operation of the capacitance detection device of FIG. 1 will be described with reference to FIG.
FIGS. 3A to 3G are timing charts for explaining the operation of FIG. 1, in which the power supply potential V1 is higher than the power supply potential V2, and in the initial state, the reference capacitors Cs1, Cs2 and the capacitance to be measured Cx11, Cx21 and capacitance Cx0 are shown as being discharged.

  The switch control unit performs the first switch operation for opening and closing the open / close switches S11 and S12 from the open state to the closed state for a predetermined period (FIG. 3A), and after performing the first switch operation, A second switch operation (FIG. 3 (b)) for switching the open / close switches S21, 22 from the closed state to the open state for a predetermined period and closing the open / close switches S31, S32 from the closed state to the open state for a predetermined period again. The third switch operation (FIG. 3C) to be closed is repeated alternately.

  By the first switch operation, the reference capacitors Cs1 and Cs2 are charged, for example, the voltage of the input terminal Vin− of the comparator CMP1 increases, for example, and the voltage of the input terminal Vin + decreases (FIG. 3 (f)). Then, the voltage Vout output from the output terminal of the comparator CMP1 becomes low level (FIG. 3 (g)).

  By the second switch operation, the reference capacitor Cs1 is connected to the measured capacitor Cx11, the reference capacitor Cs2 is connected to the measured capacitor Cx21, the reference capacitors Cs1 and Cs2 are discharged, and the measured capacitors Cx11 and Cx21 are charged. Is done. When the measured capacitors Cx11 and Cx21 are charged, the potential VE1 of the sensor electrode E1 rises and the potential VE2 of the sensor electrode E2 falls (FIGS. 3D and 3E). That is, the potential VE1 of the sensor electrode E1 and the potential VE2 of the sensor electrode E2 change in opposite directions.

  Here, since the capacitance Cx0 is formed between the sensor electrode E1 and the sensor electrode E2, the change timings of the potential VE1 of the sensor electrode E1 and the potential VE2 of the sensor electrode E2 are substantially equal. Thereby, generation | occurrence | production of radio noise is suppressed.

  When the reference capacitor Cs1 is discharged, the voltage of the input terminal Vin− of the comparator CMP1 is decreased, and when the reference capacitor Cs2 is discharged, the voltage of the input terminal Vin + of the comparator CMP1 is increased.

  By repeating the second switch operation and the third switch operation, the voltage of the input terminal Vin− decreases, and the reference capacitor Cs2 is discharged, so that the voltage of the input terminal Vin + and the input terminal Vin− of the comparator CMP1 is decreased. The output signal Vout of the comparator CMP1 changes from the low level to the high level.

  The control circuit 10 counts the number of second switch operations repeatedly performed until the output signal Vout of the comparator CMP1 transitions, and changes in the capacitances of the measured capacitors Cx11 and Cx21 based on the counted number. Determine.

As described above, this embodiment has the following advantages.
(1) Since the sensor electrodes E1 and E2 are arranged close to each other to perform the first switch operation, the second switch operation, and the third switch operation, the potentials VE1 and VE2 of the sensor electrodes E1 and E2 are shown in FIG. As shown in (d) and (e), the change occurs at the same timing and the change direction is reversed, so that the generation of radio noise can be reduced.

  (2) The direction of changes in the potentials VE1 and VE2 when the open / close switches S21 and S22 are closed is opposite. As a result, the change in the potentials of the input terminals Vin− and Vin + is also opposite. On the other hand, when there is an electromagnetic disturbance, the electromagnetic disturbance affects the potentials of the input terminals Vin− and Vin + in the same direction, so that the output signal of the comparator CMP1 is affected by the electromagnetic disturbance. Can be suppressed.

  (3) By making the ratio of the area of the sensor electrode E1 and the capacity of the reference capacity Cs1 and the ratio of the area of the sensor electrode E2 and the capacity of the reference capacity Cs2 substantially equal, the charge induced by the electromagnetic disturbance is reduced. In proportion to the area of the sensor electrodes E1, E2, the potential fluctuations of the reference capacitors Cs1, Cs2, that is, the potential fluctuations of the input terminals Vin− and Vin + are inversely proportional to the capacitances of the reference capacitors Cs1, Cs2, and are proportional to the amount of change in charge. Therefore, the fluctuation range of the potentials of the input terminals Vin− and Vin + due to electromagnetic disturbance becomes equal, and the influence on the timing at which the potentials of the input terminals Vin− and Vin + are reversed can be suppressed.

  (4) By making the areas of the sensor electrodes E1, E2 equal, radio noise can be further suppressed. Furthermore, by making the ratio of the area of the sensor electrode E1 and the capacity of the reference capacity Cs1 and the ratio of the area of the sensor electrode E2 and the capacity of the reference capacity Cs2 substantially equal, the potentials VE1, VE2 of the sensor electrodes E1, E2 As a result, the radio noise can be further reduced.

[Second Embodiment]
FIG. 4 is a configuration diagram showing a capacitance detection device according to the second embodiment of the present invention.

  This capacitance detection device includes open / close switches S51, S61, S71, S52, S62, S72, sensor electrodes E11, E12, reference capacitors Cs11, Cs12, operational amplifiers (hereinafter referred to as operational amplifiers) OP1, OP2, The comparator CMP2, the control circuit 20, and a switching control unit (not shown) for controlling the opening / closing of the open / close switches S51, S61, S71, S52, S62, and S72 are provided.

  One end of the reference capacitor Cs11 and the open / close switch S51 is connected to the output terminal of the operational amplifier OP1, and the other end of the reference capacitor Cs11 and the open / close switch 51 and one end of the open / close switch 61 are connected to the inverting input terminal of the operational amplifier OP1. The other end of the open / close switch 61 is connected to the other end of the open / close switch 71 whose one end is connected to the power supply potential V1 and the sensor electrode E11. The non-inverting input terminal of the operational amplifier OP1 is connected to the power supply potential V3. The output terminal of the operational amplifier OP1 is connected to one input terminal Vin− of the comparator CMP2.

  One end of the reference capacitor Cs12 and the open / close switch S52 is connected to the output terminal of the operational amplifier OP2, and the other end of the reference capacitor Cs12 and the open / close switch 52 and one end of the open / close switch 62 are connected to the inverting input terminal of the operational amplifier OP2. The other end of the open / close switch 62 is connected to the other end of the open / close switch 72 whose one end is connected to the power supply potential V2 and the sensor electrode E12. The non-inverting input terminal of the operational amplifier OP2 is connected to the power supply potential V4. The output terminal of the operational amplifier OP2 is connected to the other input terminal Vin + of the comparator CMP2. The output terminal of the comparator CMP2 is connected to the control circuit 20.

  As shown in FIG. 5, the sensor electrodes E11 and E12 form the measured capacitors Cx11 and Cx21, respectively, facing the conductor E0 to be detected, and the sensor electrodes E11 and E12 are respectively measured capacitors Cx11. , Cx21. The sensor electrodes E11 and E12 are arranged close to each other, and a capacitance Cx0 is also formed between the sensor electrodes E11 and E12. By forming this capacitance Cx0, the timing at which the potential VE11 of the sensor electrode E11 and the potential VE12 of the sensor electrode E12 change is the same.

  For example, the power supply potential V1 is higher than the power supply potential V2, the power supply potential V2 is higher than the power supply potential V3, and the power supply potential V3 is higher than the power supply potential V4.

Next, the operation of this capacitance detection device will be described with reference to FIG.
6A to 6G are timing charts for explaining the operation of FIG. As an initial state, the potential VE11 is shown as being charged to the power supply potential V1, and the potential VE12 is shown as being charged to the power supply potential V4.

  The switch control unit performs the first switch operation for returning the open / close switches S51 and S52 from the open state to the open state for a predetermined period, and then changing the open / close switches S61 and S62 from the closed state to the open state for a predetermined period again. The second switch operation to return to the closed state and the third switch operation to return the open / close switches S71 and S72 from the open state to the closed state for a predetermined period are repeated.

  By the first switch operation, the reference capacitors Cs11 and Cs12 are discharged, the potential of the input terminal Vin− increases, the potential of the input terminal Vin + decreases, and the output signal Vout of the comparator CMP2 becomes low level. As a result of the second switch operation, the reference capacitors Cs11 and Cs12 are charged by the charges charged in the potentials VE11 and VE12 of the sensor electrodes E11 and E12, and the potential of the input terminal Vin− is lowered. The potential increases. By the third switch operation, the potential VE11 of the sensor electrode E11 becomes the power supply potential V1 again, and the potential VE12 of the sensor electrode E12 becomes the power supply potential V2 again.

  By repeating the second switch operation and the third switch operation, the level of the input terminal Vin− and the level of the input terminal Vin + are inverted, the level of the output signal Vout of the comparator CMP2 changes, and becomes high again.

  The control circuit 20 counts the number of second switch operations repeatedly performed until the output signal Vout of the comparator CMP2 transitions, and changes in the capacitances of the measured capacitors Cx11 and Cx21 based on the counted number. Determine.

  As described above, in the present embodiment, charges corresponding to the capacitances of the measured capacitors Cx11 and Cx21 are accumulated in the reference capacitors Cs11 and Cs12, and a signal based on the potential difference between both ends of the reference capacitors Cs11 and Cs12 is stored in the comparator CMP. The capacitances of the measured capacitances Cx11 and Cx21 are detected, for example. For example, V1-V3 = V4-V2, and the sensor electrodes E11, E12 are made equal by setting the areas of the sensor electrodes E11, E12 equal. The fluctuation ranges of the potentials VE11 and VE12 can be made equal and can be changed equally at the same timing in the opposite direction. Thereby, the influence of electromagnetic disturbance can be suppressed. Moreover, generation of radio noise can be suppressed.

[Third Embodiment]
Various forms are conceivable for the sensor electrodes E1 and E2 of the capacitance detection device of the first embodiment and the sensor electrodes E11 and E12 of the capacitance detection device of the second embodiment. In the present embodiment, these will be described.

FIG. 7 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
The sensor electrodes E1 and E11 and the sensor electrodes E2 and E12 are opposed to each other and have convex portions that protrude to the other side. It arrange | positions so that the convex part of sensor electrode E1, E11 and the convex part of sensor electrode E2, E12 may not overlap. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The centroids of the sensor electrodes E1, E11 and the centroids of the sensor electrodes E2, 12 are substantially coincident.

  By equalizing the area, the total sum of charges accumulated in the sensor electrodes E1, E11 and the sensor electrodes E2, E12 becomes equal. Considering that the electric charges accumulated in the sensor electrodes E1 and E11 and the sensor electrodes E2 and E12 are concentrated near the center of gravity by matching the centers of gravity, a change in electric moment when viewed from the outside is reduced, and radio noise Is suppressed. Further, the charges induced by the disturbance are also equal in the sensor electrodes E1, E11 and the sensor electrodes E2, E12, and the influence of the disturbance can be reduced.

FIG. 8 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
The sensor electrodes E1 and E11 and the sensor electrodes E2 and E12 are arranged concentrically. The sensor electrodes E1 and E11 surround the outside of the sensor electrodes E2 and E12. The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E11 and E2, E12 have a symmetrical shape with two or more symmetry planes passing through the center of gravity.

  In this way, the sensor electrodes E1, E11, E2, and E12 are symmetrically shaped on two or more symmetry planes that pass through the center of gravity, thereby reducing changes in electrical moment when viewed from the outside and further suppressing radio noise. it can. Further, the charges induced by the disturbance can be made more uniform by the sensor electrodes E1, E11 and the sensor electrodes E2, E12, and the influence of the disturbance can be further reduced.

FIG. 9 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
The sensor electrodes E2 and E12 are square, and the sensor electrodes E1 and E11 are formed so as to surround the sensor electrodes E2 and E12.
The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E1 and E2, E12 have a symmetrical shape with two or more symmetry planes passing through the center of gravity.

FIG. 10 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
The sensor electrodes E2 and E12 are rectangular, and the sensor electrodes E1 and E11 are formed so as to surround the sensor electrodes E2 and E12.
The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E11 and E2, E12 have a symmetrical shape with two or more symmetry planes passing through the center of gravity.

FIG. 11 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
Each of the sensor electrodes E1 and E11 and the sensor electrodes E2 and E12 can be composed of an arbitrary number of conductors. In FIG. 11, the sensor electrodes E1 and E11 are constituted by two square conductors, the sensor electrodes E2 and E12 are constituted by two square conductors, the conductors of the sensor electrodes E1 and E11, and the conductors of the sensor electrodes E2 and E12. Are arranged diagonally.

  The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E1 and E2, E12 are symmetric with respect to two or more planes of symmetry passing through the center of gravity.

FIG. 12 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
In FIG. 12, the sensor electrodes E1 and E11 are composed of two square conductors, the sensor electrodes E2 and E12 are composed of one rectangular conductor, and the sensor electrodes E1 and E11 are the conductors of the sensor electrodes E2 and E12. The arrangement is sandwiched between.
The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E11 and E2, E12 are symmetric with respect to two or more planes of symmetry passing through the center of gravity.

FIG. 13 is a diagram illustrating an example of the sensor electrodes E1, E2 and E11, E12.
In FIG. 13, the sensor electrodes E1 and E11 are composed of three triangular conductors, the sensor electrodes E2 and E12 are composed of three triangular conductors, and these are alternately arranged so as to form a hexagon as a whole. Yes.

  The center of gravity of the sensor electrodes E1 and E11 and the center of gravity of the sensor electrodes E2 and E12 substantially coincide. Moreover, the area of sensor electrode E1, E11 and the area of sensor electrode E2, E12 are equal. The sensor electrodes E1, E1 and E2, E12 are symmetric with respect to two or more planes of symmetry passing through the center of gravity.

It is a block diagram which shows the electrostatic capacitance detection apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing of the A section of FIG. 3 is a timing chart for explaining the operation of the capacitance detection device of FIG. 1. It is a block diagram which shows the electrostatic capacitance detection apparatus which concerns on the 2nd Embodiment of this invention. It is explanatory drawing of the A section of FIG. . It is a timing chart for demonstrating operation | movement of the electrostatic capacitance detection apparatus of FIG. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode. It is a figure which shows an example of a sensor electrode.

Explanation of symbols

S11, S12, S21, S22, S31, S32, S51, S52, S61, S62, S71, S72... Open / close switch Cs1, Cs2, Cs11, Cs12... Reference capacity E1, E2, E11, E12. Sensor electrodes CMP1, CMP2 ... Comparator V1 ... First power supply voltage V2 ... Second power supply voltage V3 ... Third power supply voltage V4 ... Fourth power supply voltage N1 ... First 1 node N2 ... 2nd node N3 ... 3rd node N4 ... 4th node 10 ... control circuit (counting means, judging means)

Claims (7)

A first open / close switch having one end connected to the first power supply potential and the other end connected to the first node;
A first reference capacitor having one end connected to the first node and the other end connected to a second power supply potential;
A second open / close switch having one end connected to the first node and the other end connected to a second node;
A third open / close switch having one end connected to the second node and the other end connected to a third power supply potential;
A first sensor electrode that is connected to the second node and forms a capacitor that faces the object to be measured and exhibits a capacitance according to a distance from the object to be measured;
A fourth open / close switch having one end connected to the third power supply potential and the other end connected to a third node;
A second reference capacitor having one end connected to the third node and the other end connected to a fourth power supply potential;
A fifth open / close switch having one end connected to the third node and the other end connected to a fourth node;
A sixth open / close switch having one end connected to the fourth node and the other end connected to the first power supply potential;
A capacitor connected to the fourth node, facing the object to be measured and having a capacitance corresponding to a distance from the object to be measured is formed, and in proximity to the first sensor electrode A second sensor electrode having a capacitance between the first sensor electrode and the first sensor electrode;
A comparator in which the first node is connected to one input terminal and the third node is connected to the other input terminal;
After performing the first switch operation for opening the first open / close switch and the fourth open / close switch after closing them, the second open / close switch and the fifth open / close switch are closed. Switch control means for alternately repeating a second switch operation for returning the switch from the open state to the open state, and a third switch operation for returning the open state to the open state after closing the third open / close switch and the sixth open / close switch;
Counting means for counting the number of times the second switch operation is repeated;
Based on the number of times of the second switch operation counted by the counting means until the level of the input voltage at both input terminals of the comparator is reversed, a change in capacitance with the object to be measured is determined. A determination means;
An electrostatic capacity detection device comprising:   The ratio between the area of the first sensor electrode and the capacity of the first reference capacitor and the ratio of the area of the second sensor electrode and the capacity of the second reference capacitor are substantially equal. The capacitance detection device according to claim 1.   The capacitance detection device according to claim 1, wherein areas of the first sensor electrode and the second sensor electrode are equal. A first sensor electrode that constitutes one electrode of a capacitor that opposes the object to be measured and whose capacitance changes in accordance with the distance between the object to be measured;
A second sensor electrode that constitutes one electrode of a capacitor that opposes the object to be measured and whose capacitance changes according to the distance between the object to be measured;
The fluctuation of the electric charge stored in the capacitor in which the first sensor electrode and the second sensor electrode become one electrode accompanying the change in the potential of the first sensor electrode and the second sensor electrode, Accumulating in a reference capacity corresponding to each first sensor electrode and second sensor electrode,
A capacitance detection device that detects a capacitance of a capacitor in which the first sensor electrode and the second sensor electrode are one electrode by a potential difference between both terminals of the reference capacitance,
The capacitance detection device according to claim 1, wherein the fluctuations of the potentials of the first sensor electrode and the second sensor electrode have substantially the same fluctuation width and opposite fluctuation directions.   The capacitance detection device according to claim 4, wherein areas of the first sensor electrode and the second sensor electrode are equal. The first sensor electrode is composed of an arbitrary number of conductors,
The second sensor electrode is composed of an arbitrary number of conductors,
6. The capacitance detection device according to claim 5, wherein the center of gravity of the first sensor electrode and the center of gravity of the second sensor electrode substantially coincide with each other.   The capacitance detection apparatus according to claim 6, wherein the first sensor electrode and the second sensor electrode are arranged symmetrically with respect to two or more planes passing through the center of gravity.

Images