Capacitive sensor

Abstract

To prevent an installation part where a sensor electrode of a product is installed from becoming a sensor electrode to suppress the occurrence of malfunction when a capacitive sensor is used in the product that detects proximity operation of a human body, such as an automatic faucet device.SOLUTION: A capacitive sensor 1 that detects proximity operation of a user to a sensor electrode 2 on the basis of the change in capacitance of the sensor electrode 2 includes the sensor electrode 2 that is charged with a positive charge and voltage application means 4 that applies a voltage to a water supply part 12 (sensor installation part) of a faucet fitting 10 that is installed in a state where the sensor electrode 2 is insulated on an automatic faucet device 100 (product) in which the capacitive sensor 1 is used so as to be the same phase and same electrical potential as the sensor electrode 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a capacitance sensor that detects a user's approach operation to a sensor electrode based on a change in capacitance of the sensor electrode. In this disclosure, the approach operation refers to an operation of bringing a part of the user's body such as a hand or a finger (hereinafter referred to as a "detectable object") close to the sensor electrode, and includes a case where the detected object is brought close to the vicinity of the sensor electrode (a close position that does not contact the sensor electrode) as well as a case where the detected object is brought close enough to contact the sensor electrode. [Background technology]

[0002] For example, automatic faucet devices that use a human body detection sensor to detect when a user brings their hand or other object close to a faucet fitting and automatically switch water on and off are widespread in water supply facilities in kitchens, washrooms, toilets, bathrooms, etc. Infrared sensors are widely used as the human body detection sensors used in this type of automatic faucet device (see, for example, Patent Document 1).

[0003] However, when an infrared sensor is used as a human body detection sensor in an automatic faucet device, the sensor window installed in the faucet to send and receive infrared rays is black, which can cause a sense of incongruity with the design of the space the faucet is located in, resulting in design problems.In addition, infrared sensors can have different detection distances depending on the intensity of the light reflected from the human body, or can malfunction due to a reaction to the influence of the setting sun. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-227146 A Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the present inventors have studied the use of a capacitance sensor instead of an infrared sensor as a human body detection sensor for an automatic faucet device. The capacitance sensor is configured such that a sensor electrode is installed on the faucet while being insulated from the faucet, and a detection device connected to the sensor electrode detects the change in capacitance of the sensor electrode. The sensor electrode is positively charged, and when a part of the body such as a user's hand (hereinafter referred to as the "detected object") approaches the sensor electrode and interferes with the electric field generated by the sensor electrode, electrostatic induction occurs in the detected object due to the influence of the positive charge charged in the sensor electrode, and the capacitance of the sensor electrode increases as the detected object approaches the sensor electrode. By detecting this change in capacitance of the sensor electrode, it is possible to detect the user's approach to the sensor electrode, and as a result, the faucet in the automatic faucet device switches between discharging and stopping water.

[0006] As a result of intensive research by the inventor, it was found that the following problem occurs when a sensor electrode is installed on a faucet. That is, as shown in FIG. 9, electrostatic induction occurs in the surrounding area of ​​the sensor electrode 2 of the faucet 10 due to the influence of the positive charge charged on the sensor electrode 2, and the negative charge in the conductor moves to the part of the surrounding area of ​​the faucet 10 close to the sensor electrode 2 due to the attraction of the positive charge of the sensor electrode 2, and the positive charge of an amount equal to the negative charge moves to the part far from the sensor electrode 2. Then, an electric field is formed between the sensor electrode 2 and the part of the faucet 10 to which the negative charge has moved, and the part of the faucet 10 to which the positive charge has moved emits electric field lines in the same number as the electric field lines between the sensor electrode 2 and the negative charge. As a result, the part of the faucet 10 surrounding the sensor electrode 2 becomes a sensor electrode, and the capacitance of the sensor electrode 2 changes not only when the detected object 101 approaches the sensor electrode 2, but also when the detected object 101 approaches the part surrounding the sensor electrode 2. Therefore, even if the object to be detected approaches the area surrounding the sensor electrode 2 rather than the sensor electrode 2, a change in the capacitance of the sensor electrode 2 will be detected, resulting in an erroneous detection of the user's approach operation, resulting in a malfunction in which water is erroneously switched on and off.

[0007] One possible measure to prevent the above-mentioned faucet fittings from becoming sensor electrodes is to make the faucet fittings out of resin. If the faucet fittings are made out of resin, they will be insulated from the sensor electrodes, so electrostatic induction will not occur in the faucet fittings and it will be possible to prevent the faucet fittings from becoming sensor electrodes. However, if the faucet fittings are made out of resin, there are problems in that the durability of the faucet fittings will be impaired, they will be prone to scratches, and their weather resistance to hot and cold water will also be impaired. In addition, there is a problem in that resin faucet fittings do not have the beautiful luster and shine seen in metal faucet fittings, and the design will also be impaired.

[0008] Another possible measure to prevent the above-mentioned faucet fitting from becoming a sensor electrode is to ground the faucet fitting. If the faucet fitting is grounded, electrostatic induction will not occur in the faucet fitting, and the faucet fitting can be prevented from becoming a sensor electrode. However, as a result of the inventor's investigation, it was found that if the faucet fitting is grounded, as shown in FIG. 10, the electric field generated from the sensor electrode 2 will be coupled with the grounded faucet fitting 10, and the electric field generated from the sensor electrode 2 in the direction of detecting the detected object will be impaired. Therefore, if the faucet fitting 10 is grounded, the electric field emitted from the sensor electrode 2 to the surrounding space will be weakened by the grounding of the faucet fitting 10, and the detection distance (detection sensitivity) of the detected object relative to the sensor electrode 2 will decrease, resulting in a problem that the proximity operation of the detected object cannot be detected unless the detected object is brought close enough to contact the sensor electrode 2.

[0009] The present disclosure focuses on solving the above problems, and aims to prevent malfunctions by preventing the sensor installation section where the sensor electrode of a product is installed from becoming a sensor electrode when a capacitance sensor is used in a product that detects proximity operation of a human body, such as an automatic faucet device, and to prevent a decrease in the detection distance (detection sensitivity) of the sensor electrode. [Means for solving the problem]

[0010] In order to solve the above problems, the subject of the capacitance sensor of the present disclosure is the capacitance sensor described in item 1 below.

[0011] Item 1. A capacitance sensor that detects a user's approach to a sensor electrode based on a change in capacitance of the sensor electrode, a sensor electrode that is positively charged; a voltage application means for applying a voltage to a conductive sensor installation portion in which the sensor electrode is installed in an insulated state in a product in which the capacitance sensor is used, so that the voltage has the same phase and potential as the sensor electrode; A capacitive sensor comprising:

[0012] Furthermore, the capacitance sensor of the present disclosure encompasses the capacitance sensor described in the following item 2 as a preferred embodiment of the capacitance sensor described in item 1 above.

[0013] Item 2. The capacitance sensor according to item 1, wherein the voltage application means further includes a buffer circuit for correcting the voltage applied to the sensor installation portion.

[0014] Furthermore, the capacitance sensor of the present disclosure encompasses the capacitance sensor described in the following item 3 as a preferred embodiment of the capacitance sensor described in items 1 and 2 above.

[0015] Item 3. The capacitance sensor according to item 1 or 2, wherein the voltage application means further includes a capacitance device for replenishing charge to the sensor installation portion. Effect of the Invention

[0016] According to the capacitance sensor of the present disclosure, in a product in which the capacitance sensor is used, the sensor installation section, which is installed in a state in which the sensor electrode is insulated, can be prevented from becoming a sensor electrode, thereby preventing malfunctions and ensuring a large detection distance for an object to be detected from the sensor electrode. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing the appearance of an automatic faucet device in which the capacitance sensor of this embodiment is used. [Diagram 2]FIG. 2 is a diagram showing the functional configuration of the capacitance sensor of this embodiment. [Diagram 3] FIG. 3(A) shows a chart of the voltage applied to the sensor electrode, and FIG. 3(B) shows a chart of the voltage applied to the water conducting part of the faucet (the part where the sensor electrode is installed). [Figure 4] FIG. 4 is a diagram illustrating the operation principle of the capacitance sensor of this embodiment. [Diagram 5] 5(A) is a model diagram of FIG. 9, and FIG. 5(B) is a model diagram of FIG. [Figure 6] FIG. 6(A) is a diagram showing the functional configuration when an LCR component occurs in the power supply line in the capacitance sensor of this embodiment, and FIG. 6(B) is a model diagram explaining the operating principle of the capacitance sensor of FIG. 6(A). [Figure 7] FIG. 7 is a model diagram illustrating the operating principle of the capacitance sensor of this embodiment. [Figure 8] FIG. 8 is a model diagram illustrating the operation principle of the capacitance sensor of this embodiment. [Figure 9] FIG. 9 is a diagram for explaining the problems that arise when a conventional capacitance sensor is used in an automatic faucet device. [Figure 10] FIG. 10 is a diagram for explaining a problem that occurs when a conventional capacitance sensor is used in an automatic faucet device and the faucet fitting is grounded. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the capacitance sensor of the present disclosure will be described with reference to the accompanying drawings. In the following embodiment, the capacitance sensor of the present disclosure is used in an automatic faucet device configured to detect a user's approach operation to a sensor electrode and switch between water discharge and water stop by a faucet fitting. Note that the capacitance sensor of the present disclosure is not limited to the following embodiment.

[0019] Explanation of automatic faucet device 1 and 2, the automatic faucet device 100 comprises a capacitance sensor 1, a plumbing fixture 10, and a control device 15. The automatic faucet device 100 is used in water supply facilities such as kitchens, washrooms, toilets, and bathrooms, and detects when a user brings a part of the body (detectable object) such as a hand close to a specific part (part) of the plumbing fixture 10, and automatically switches the plumbing fixture 10 between discharging and stopping water. The automatic faucet device 100 uses the capacitance sensor 1 as a human body detection sensor that detects the user's operation.

[0020] In the following, first, each component of the automatic faucet device 100 will be described.

[0021] Explanation of faucet fittings As shown in Fig. 1, the faucet 10 includes a base 11, a water conducting section 12, and a water discharge section 13. The base 11, the water conducting section 12, and the water discharge section 13 are made of a conductive material such as metal, for example an alloy such as brass. The base 11, the water conducting section 12, and the water discharge section 13 are insulated from each other, for example, by a resin ring interposed between them. The faucet 10 has a built-in water supply hose, and the water supply hose is provided with a solenoid valve. The solenoid valve is electrically connected to a control device 15 (shown in Fig. 2), and the opening and closing of the solenoid valve is controlled by the control device 15.

[0022] As shown in Figs. 1 and 2, a sensor window 14 is opened in a cylindrical water conducting section 12 that is a part of the faucet fitting 10. The sensor window 14 is an area to which a detected object 101, such as a user's hand, can be brought close, and is a detection area that detects the user's approach operation. A sensor electrode 2 of the capacitance sensor 1 is arranged in the water conducting section 12 so as to face the sensor window 14. The sensor electrode 2 is surrounded by the water conducting section 12 of the faucet fitting 10. The sensor electrode 2 is arranged with a gap between it and the faucet fitting 10, and is insulated from the faucet fitting 10. The sensor window 14 may be covered with a cover or the like. In this embodiment, the water conducting section 12 of the faucet fitting 10 is the sensor installation section.

[0023] Capacitive Sensor Description The capacitance sensor 1 detects a change in capacitance of the sensor electrode 2 that occurs when a detected object approaches the sensor electrode 2, thereby determining whether or not a proximity operation by the user has been performed on the sensor electrode 2.

[0024] The capacitance sensor 1 includes a sensor electrode 2 that is positively charged, a detection device 3 that detects a user's approach operation to the sensor electrode 2 based on a change in capacitance of the sensor electrode 2, and a voltage application means 4.

[0025] Sensor Electrode The sensor electrode 2 is conventionally known and can be formed from a material that has conventionally been used for sensor electrodes of capacitance sensors, for example, carbon such as graphite and carbon black; metals such as aluminum, copper, silver and gold; conductive resins such as thiophene-based conductive polymers and polystyrene sulfonate (PSS); or composite materials of these.

[0026] The sensor electrode 2 is in the form of a planar body, for example, in the form of a plate or sheet, and its outer shape is, for example, a rectangle such as a rectangle, a circle, etc. The size of the sensor electrode 2 is not particularly limited, but is preferably 30 mm to 100 mm in length and 10 mm to 40 mm in width (in the case of a circle, the diameter is 6 mm to 50 mm).

[0027] As shown in Fig. 3(A), a positive pulse voltage with respect to the ground is applied to the sensor electrode 2 via the detection unit 8 (shown in Fig. 2) of the detection device 3. As a result, a positive charge is charged to the sensor electrode 2. The detection unit 8 of the detection device 3 includes a power supply circuit (not shown), and applies a pulse voltage to the sensor electrode 2 by, for example, amplifying or pulse modulating the power supply voltage based on the sensor drive pulse signal.

[0028] A parasitic capacitance occurs between the sensor electrode 2 and an object (conductor) that can be regarded as ground and is located near the sensor electrode 2. This parasitic capacitance is used as the reference capacitance for the capacitance of the sensor electrode 2. When a detected object approaches the sensor electrode 2, the parasitic capacitance occurring between the sensor electrode 2 and the detected object is added to the reference capacitance, so that the capacitance of the sensor electrode 2 increases. This change in the capacitance of the sensor electrode 2 is detected by the detection device 3.

[0029] Detection Equipment The detection device 3 determines whether or not a user has performed a proximity operation on the sensor electrode 2 based on a capacitance change of the sensor electrode 2. As shown in Fig. 2, the detection device 3 includes a detection unit 8 that detects a capacitance change of the sensor electrode 2, and a control unit 9 that determines that a touch operation has been performed on the sensor electrode 2 based on a detection signal output from the detection unit 8.

[0030] The detection unit 8 is electrically connected to the sensor electrode 2. The detection unit 8 has an electric / electronic circuit for detecting the capacitance change of the sensor electrode 2. In order to detect the capacitance change of the sensor electrode 2, the detection unit 8 is preferably configured to include, for example, a CV amplifier that converts the capacitance change into a voltage change, and a detection circuit having a gain adjustment function of the CV amplifier to adjust the sensitivity. When there is no approach operation by the user to the sensor electrode 2, there is no change in the capacitance of the sensor electrode 2 and no voltage change from the CV amplifier. On the other hand, when there is a approach operation by the user to the sensor electrode 2, the capacitance of the sensor electrode 2 increases, and a voltage change obtained by multiplying the voltage change corresponding to the increase in capacitance from the CV amplifier by a gain is output from the detection circuit. The detection signal may be in the form of analog data or digital data.

[0031] The method of detecting the capacitance change of the sensor electrode 2 by the detection unit 8 is not limited to the above-mentioned example, and various conventionally known methods can be used, such as (1) a method of measuring the time difference required for discharging the sensor electrode 2 after charging it with a certain charge, and (2) a method of detecting the change in capacitance of the sensor electrode 2 by a change in the oscillation state of an oscillation circuit. The detection unit 8 can be composed of electric / electronic circuits, switches, etc., which are used in conventionally known capacitance sensors and are suitable for the methods (1) and (2).

[0032] The control unit 9 may be configured by, for example, a microcomputer, and includes a reception unit 90, a processing unit 91, an output unit 92, and the like.

[0033] The reception unit 90 is configured as an interface that receives the detection signal. When the detection signal is in the form of analog data, the reception unit is configured to include an appropriate conversion circuit including an A / D converter. The processing unit 91 is configured to determine whether or not the user has performed a proximity operation on the sensor electrode 2 based on the detection signal. For example, when the processing unit 91 determines that the amount of change in capacitance of the sensor electrode 2 exceeds a predetermined threshold value stored in the memory, it determines that the user has performed a proximity operation on the sensor electrode 2. The output unit 92 is configured as an interface that outputs a control signal to the control device 15. The processing unit 91 is configured to output a control signal from the output unit 92 by determining that the user has performed a proximity operation on the sensor electrode 2. The control signal may be in the form of analog data or in the form of digital data. When the control signal is in the form of analog data, the output unit is configured to include an appropriate conversion circuit including a D / A converter.

[0034] The detection device 3 may be in the form of a module in which the sensor electrode 2 is incorporated, or may be in a form separate from the sensor electrode 2.

[0035] Voltage Application Means The voltage application means 4 applies a voltage to the water conducting section 12, which is a part of the faucet 10 and on which the sensor electrode 2 is installed, so that the voltage is in phase and at the same potential as the sensor electrode 2. In other words, as shown in FIG. 3(B), a positive pulse voltage having the same frequency and amplitude as the pulse voltage applied to the sensor electrode 2 is synchronously applied to the water conducting section 12. As a result, as shown in FIG. 5(B), the water conducting section 12 is in a state where there is no potential difference with the sensor electrode 2, and no electric field is generated between the water conducting section 12 and the sensor electrode 2, and the capacitance is zero. In this way, since there is no potential difference between the water conducting section 12 and the sensor electrode 2, the water conducting section 12 is not subjected to electrostatic induction and does not become a sensor electrode, but becomes an electrode (shield electrode) with the same potential as the sensor electrode 2. As a result, the faucet 10 suppresses electrostatic induction of the sensor electrode 2 with the surrounding conductors due to various factors.

[0036] That is, when the sensor electrode 2 is simply installed in the water conducting part 12 of the faucet 10, as explained in FIG. 9, electrostatic induction occurs in the water conducting part 12 due to the influence of the positive charge charged in the sensor electrode 2, as shown in the model diagram of FIG. 5(A), and the negative charge in the conductor moves to the part of the water conducting part 12 close to the sensor electrode 2 due to the attraction of the positive charge of the sensor electrode 2, and the positive charge of an amount equal to the negative charge moves to the part far from the sensor electrode 2. Then, an electric field is formed between the sensor electrode 2 and the part of the water conducting part 12 to which the negative charge has moved, and the part of the water conducting part 12 to which the positive charge has moved produces electric field lines in the same number as the electric field lines between the sensor electrode 2 and the negative charge. As a result, the water conducting part 12 becomes a sensor electrode. When the water conducting part 12 becomes a sensor electrode, the parasitic capacitance generated between the water conducting part 12 and the detected object 101 when the detected object 101 approaches the water conducting part 12 is added to the reference capacitance of the sensor electrode 2, and the electrostatic capacitance of the sensor electrode 2 changes. Therefore, even if the object to be detected 101 approaches the water-conducting section 12 rather than the sensor electrode 2 (sensor window 14), a change in capacitance of the sensor electrode 2 is detected, resulting in the user's approach operation being detected, resulting in a malfunction in which water discharge is erroneously switched on and off.

[0037] In contrast, when the water conducting section 12 is made into a shield electrode, as shown in the model diagrams of Fig. 4 and Fig. 5(B), no electric field is formed between the water conducting section 12 and the sensor electrode 2, and when the detected object 101 approaches the water conducting section 12, electrostatic induction occurs in the detected object 101 due to the influence of the positive charge that is uniquely charged in the water conducting section 12, and electrostatic induction to the sensor electrode 2 is not performed. Therefore, the positive charge of the sensor electrode 2 is not affected by the approach of the detected object 101, and it is possible to suppress a change in the capacitance of the sensor electrode 2 when the detected object 101 approaches the water conducting section 12. Therefore, when the detected object 101 approaches the water conducting section 12 instead of the sensor electrode 2 (sensor window 14), detection of the user's approach operation is suppressed, and as a result, it is possible to suppress the occurrence of a malfunction in which water discharge and water stop are erroneously switched.

[0038] If the faucet fitting 10 is one in which the base 11 and the water conducting portion 12, or the water conducting portion 12 and the water discharge portion 13 are not insulated from each other and the base 11 and the water conducting portion 12, or the water conducting portion 12 and the water discharge portion 13 are integrated, the base 11 and the water conducting portion 12, or the water conducting portion 12 and the water discharge portion 13, become the sensor installation portion, and the base 11 and the water conducting portion 12, or the water conducting portion 12 and the water discharge portion 13, become the shield electrode. If the faucet fitting 10 is one in which the base 11, the water conducting portion 12, and the water discharge portion 13 are not insulated from each other and the base 11, the water conducting portion 12, and the water discharge portion 13 are integrated, the entire faucet fitting 10 becomes the sensor installation portion, and the entire faucet fitting 10 becomes the shield electrode.

[0039] The voltage application means 4 can be formed, for example, by a substrate equipped with an electric / electronic circuit for applying a voltage of the same phase and potential as the sensor electrode 2 to the water conducting part 12 of the faucet 10. As shown in FIG. 2, the voltage application means 4 includes a pulse voltage generating part 5, a buffer circuit 6, a capacitance device 7, and a power supply line 16. The power supply line 16 connects the detection part 8 of the detection device 3 to the water conducting part 12 of the faucet 10 via the voltage application means 4, so that a pulse voltage of the same phase and potential as the pulse voltage applied from the detection part 8 to the sensor electrode 2 is applied to the water conducting part 12. The power supply line 16 is fixed to the water conducting part 12 via a conductive material 17, for example, a terminal. The conductive material 17 is not particularly limited, and may be a metal member, a metal foil tape such as copper foil tape, a conductive adhesive, or the like, as long as it can fix the power supply line 16 to the water conducting part 12 in a conductive manner.

[0040] The pulse voltage generating unit 5 generates a pulse voltage having the same phase and potential as the pulse voltage applied to the sensor electrode 2 based on the sensor drive pulse signal sent from the detection unit 8 of the detection device 3 or an electrical signal synchronized therewith, and sends it to the water conducting unit 12 of the faucet 10. The pulse voltage generating unit 5 can be configured using, for example, a coupling capacitor and an amplifier (for example, an operational amplifier). The coupling capacitor blocks the DC component from the sensor drive pulse signal sent from the detection unit 8 of the detection device 3 or an electrical signal synchronized therewith, extracting only the AC component, and the operational amplifier applies an appropriate bias to the AC component, thereby generating a pulse voltage having the same frequency and amplitude as the pulse voltage applied to the sensor electrode 2. It is preferable that the operational amplifier uses a known method, such as applying a voltage opposite to the input offset voltage from the outside, to correct the input offset voltage.

[0041] The buffer circuit 6 is disposed on the power supply line 16 downstream (at the water conducting section 12) of the pulse voltage generating section 5. In an actual environment, as shown in FIG. 6(A), invisible LCR components such as parasitic capacitance, parasitic inductance, and parasitic resistance are generated on the power supply line 16. This causes the voltage applied to the water conducting section 12 by the pulse voltage generating section 5 to drop, and as shown in the model diagram of FIG. 6(B), when the positive charge charged to the water conducting section 12 becomes insufficient, a potential difference occurs between the sensor electrode 2 and the water conducting section 12, and electrostatic induction occurs between the sensor electrode 2 and the water conducting section 12. Therefore, when the water conducting section 12 becomes a sensor electrode, and as shown in the model diagram of FIG. 6(B), when the detected object 101 approaches the water conducting section 12, electrostatic induction occurs in the detected object 101 due to the influence of not only the positive charge charged to the water conducting section 12 but also the positive charge possessed by the sensor electrode 2, so that the capacitance of the sensor electrode 2 may change.

[0042] On the other hand, since the buffer circuit 6 has a function of correcting the voltage input from the pulse voltage generating unit 5, if the buffer circuit 6 is arranged on the power supply line 16, even if the above-mentioned voltage drop occurs, the dropped voltage is corrected by the buffer circuit 6 as shown in the model diagram of FIG. 7, and the corrected voltage is applied to the water conducting part 12. As a result, the water conducting part 12 is sufficiently charged with positive charges, so that the water conducting part 12 maintains a state in which there is no potential difference between the water conducting part 12 and the sensor electrode 2, and the electrostatic capacitance between the water conducting part 12 and the sensor electrode 2 becomes zero, so that the water conducting part 12 is not subjected to electrostatic induction and does not become a sensor electrode. Therefore, even if the detected object 101 approaches the water conducting part 12, electrostatic induction occurs in the detected object 101 due to the influence of the positive charge independently charged in the water conducting part 12, and the positive charge of the sensor electrode 2 is not affected by the approach of the detected object 101. Therefore, it is possible to effectively suppress the change in the electrostatic capacitance of the sensor electrode 2 when the detected object 101 approaches the water conducting part 12. As a result, when the object to be detected 101 approaches the water conducting section 12 rather than the sensor electrode 2 (sensor window 14), detection of the user's proximity operation is effectively suppressed, thereby effectively suppressing malfunctions such as erroneous switching between water discharge and water stop.

[0043] Capacitive device 7 is located downstream of buffer circuit 6 on power supply line 16 and is connected in parallel with pulse voltage generating unit 5. Capacitive device 7 is an electronic component that stores and releases electricity (charge).

[0044] When a detected object 101, such as a user's hand, comes into contact with the water conducting part 12 of the faucet 10, a very large parasitic capacitance is suddenly generated between the water conducting part 12 and the detected object 101, causing a drop in the voltage applied to the water conducting part 12 by the pulse voltage generating part 5. When the voltage applied to the water conducting part 12 drops, a potential difference is generated between the sensor electrode 2 and the water conducting part 12, causing electrostatic induction between the sensor electrode 2 and the water conducting part 12, causing the water conducting part 12 to become a sensor electrode.

[0045] On the other hand, if the capacitance device 7 is disposed downstream of the buffer circuit 6 on the power supply line 16, as shown in the model diagram of FIG. 8, when a very large parasitic capacitance occurs suddenly due to the contact of the detected object 101 with the water conducting part 12, the charge stored in the capacitance device 7 is discharged from the capacitance device 7 and replenished to the water conducting part 12, so that the voltage applied to the water conducting part 12 increases and the water conducting part 12 returns to a state where there is no potential difference with the sensor electrode 2. As a result, the capacitance between the water conducting part 12 and the sensor electrode 2 becomes zero, and the water conducting part 12 does not become a sensor electrode because it is not subjected to electrostatic induction. Therefore, even if the detected object 101 contacts the water conducting part 12, the positive charge held by the sensor electrode 2 is not affected by the contact of the detected object 101, and the capacitance of the sensor electrode 2 can be suppressed from changing. As a result, when the detected object 101 contacts the water conducting part 12, the detection of the user's proximity operation is suppressed, so that the occurrence of a malfunction in which the water discharge and the water stop are erroneously switched can be suppressed.

[0046] Although not particularly limited, a bypass capacitor can be preferably used as the capacitance device 7. The bypass capacitor is a capacitor connected between the power supply line 16 and the ground.

[0047] Description of the control device The control device 15 can be configured, for example, by a microcomputer. When the user brings the detected object 101, such as a hand, close to the sensor window 14 of the faucet 10, the capacitance of the sensor electrode 2 changes, and the capacitance sensor 1 detects the user's approach operation, and this detection information is transmitted as a control signal from the capacitance sensor 1 to the control device 15 by wire or wirelessly. As a result, the control device 15 opens the solenoid valve to automatically discharge water from the water discharge unit 13. When water has been discharged for a predetermined time, the control device 15 closes the solenoid valve to automatically stop water discharge from the water discharge unit 13, or when the capacitance sensor 1 detects the user's approach operation of bringing the detected object 101, such as a hand, close to the sensor window 14 again, the control device 15 closes the solenoid valve to automatically stop water.

[0048] In addition, instead of the control device 15, the control unit 9 in the detection device 3 of the capacitance sensor 1 may be configured to automatically switch between water discharge and water stop by opening and closing the solenoid valve when it detects a user's proximity operation.

[0049] Functions and Effects of Capacitive Sensors The capacitance sensor 1 of the above-described embodiment is characterized by comprising a sensor electrode 2 charged with a positive charge, and a voltage application means 4 that applies a voltage to the water-conducting section 12 (sensor installation section) of the faucet fitting 10 in which the sensor electrode 2 is installed in an insulated state, so that the voltage is in phase and at the same potential as the sensor electrode 2.

[0050] As a result, in the capacitance sensor 1 of this embodiment, as described above, the water conducting section 12 on which the sensor electrode 2 is installed is made into a shield electrode, and the water conducting section 12 can be prevented from becoming a sensor electrode. Therefore, when a detected object 101 such as a user's hand approaches the water conducting section 12 of the faucet fitting 10, the change in capacitance of the sensor electrode 2 is suppressed, so that the user's approach operation is not detected when the detected object 101 approaches the water conducting section 12. Therefore, according to the capacitance sensor 1 of this embodiment, it is possible to prevent the automatic faucet device 100 in which the capacitance sensor 1 is used from erroneously switching between water discharge and water stop.

[0051] Furthermore, the capacitance sensor 1 of this embodiment is characterized in that the voltage application means 4 includes a buffer circuit 6 for correcting the voltage applied to the water-conducting portion 12 of the faucet fitting 10.

[0052] As a result, in the capacitance sensor 1 of this embodiment, even if the voltage applied to the water conducting section 12 drops due to the influence of the LCR component generated in the power supply line 16, as described above, the dropped voltage is corrected by the buffer circuit 6, and the corrected voltage is applied to the water conducting section 12 (sensor installation section). Therefore, according to the capacitance sensor 1 of this embodiment, even if a voltage drop occurs due to the influence of the LCR component of the power supply line 16, the water conducting section 12 remains as a shield electrode, and it is possible to prevent the water conducting section 12 from becoming a sensor electrode.

[0053] Further, the capacitance sensor 1 of this embodiment is characterized in that the voltage application means 4 includes a capacitance device 7 for replenishing the water-conducting portion 12 with electric charge.

[0054] As a result, in the capacitance sensor 1 of this embodiment, even if an extremely large parasitic capacitance is suddenly generated when a detectable object 101 such as a user's hand comes into contact with the water conducting section 12, as described above, the charge stored in the capacitance device 7 is discharged from the capacitance device 7 and replenished in the water conducting section 12 (sensor installation section), and the voltage applied to the water conducting section 12 is maintained. Therefore, according to the capacitance sensor 1 of this embodiment, even if an extremely large parasitic capacitance is suddenly generated when a detectable object comes into contact with the water conducting section 12, the water conducting section 12 is maintained as a shield electrode, and it is possible to prevent the water conducting section 12 from becoming a sensor electrode.

[0055] Description of the Variations Although the embodiment of the capacitance sensor of the present disclosure has been described above, the above-mentioned embodiment is merely illustrative and not restrictive. Therefore, the capacitance sensor of the present disclosure is not limited to the above-mentioned embodiment, and various modifications are possible without departing from the spirit of the present disclosure.

[0056] For example, in the above embodiment, the voltage application means 4 is provided with the buffer circuit 6 and the capacitance device 7 in order to prevent the water conducting section 12, which is the sensor installation section in the faucet 10, from becoming a sensor electrode and to make the water conducting section 12 a shield electrode, but the voltage application means 4 may be provided with at least one of the buffer circuit 6 and the capacitance device 7. Alternatively, the voltage application means 4 does not need to be provided with both the buffer circuit 6 and the capacitance device 7 as long as the pulse voltage generation section 5 has a sufficiently high capacity and can apply a pulse voltage of the same phase and potential as the sensor electrode 2 to the water conducting section 12 (sensor installation section).

[0057] For example, in the above embodiment, the sensor electrode 2 is arranged in the water conducting portion 12 of the faucet fitting 10 and the water conducting portion 12 is made into a shielded electrode, but if the sensor electrode 2 is arranged in the base 11 or the water discharge portion 13 of the faucet fitting 10, the base 11 or the water discharge portion 13, which are the sensor installation portions, may be made into a shielded electrode.

[0058] For example, in the above embodiment, the capacitance sensor of the present disclosure is applied to the automatic faucet device 100 in the kitchen, but the capacitance sensor 1 of the present disclosure may also be applied to the automatic faucet device 100 in a washroom, toilet, bathroom, or other water supply facility.

[0059] For example, in the above embodiment, the capacitance sensor of the present disclosure is applied to the automatic faucet device 100, but the capacitance sensor of the present disclosure can also be applied to products other than the automatic faucet device 100 that use a human body detection sensor to detect a user's approaching operation to execute various functions (e.g., opening and closing a door, turning a switch or button on and off, etc.) and in which the sensor electrode 2 is surrounded by a conductive material such as metal. For example, the capacitance sensor can be suitably applied to products such as refrigerators, kitchen appliances, range hoods, elevators, robots, and industrial controllers. [Explanation of symbols]

[0060] 1 Capacitive Sensor 2 Sensor electrodes 3. Detection device 4. Voltage application means 5 Pulse voltage generator 6 Buffer Circuit 7 capacity equipment 10 Faucet fittings 12 Water conveyance section (part of the faucet) 100 Automatic faucet device

Claims

1. A capacitance sensor that detects a user's approach operation to a sensor electrode based on a change in capacitance of the sensor electrode, a sensor electrode that is positively charged; a voltage application means for applying a voltage to a conductive sensor installation portion in which the sensor electrode is installed in an insulated state in a product in which the capacitance sensor is used, so that the voltage has the same phase and potential as the sensor electrode; A capacitive sensor comprising:

2. 2. The capacitance sensor according to claim 1, wherein said voltage application means further comprises a buffer circuit for correcting the voltage applied to said sensor installation portion.

3. 3. The capacitance sensor according to claim 1, wherein the voltage application means further comprises a capacitance device for replenishing charge to the sensor installation portion.

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