Electrostatic capacitance sensor

Abstract

The purpose of the present invention, when a capacitance sensor is used in, e.g., an automatic faucet device or other product that detects an operation involving a human body approaching, is to suppress any incidence of erroneous action by suppressing an installation portion, which is where a sensor electrode of a product is installed, from becoming the sensor electrode. The present invention is a capacitance sensor 1 for detecting an operation in which a user approaches a sensor electrode 2 on the basis of the capacitance change of the sensor electrode 2, the capacitance sensor 1 comprising: the sensor electrode 2, which is positively charged; and voltage application means 4 that, in an automatic faucet device 100 (product) in which the electrostatic capacitance sensor 1 is used, applies a voltage to a water-introducing portion 12 (sensor installation portion) of a faucet fixture 10 that is installed in a state where the sensor electrode 2 has been insulated, so that the water-introducing portion will be in-phase with the sensor electrode 2.

Description

Capacitive Sensor

[0001] The present disclosure relates to a capacitance sensor that detects a user's proximity operation to a sensor electrode based on a change in the capacitance of the sensor electrode. Note that in the present disclosure, the proximity operation refers to an operation of bringing a part of the user's body, such as a hand or finger (hereinafter referred to as a "detectable object") close to the sensor electrode, and includes cases where the detected object is brought close enough to come into contact with the sensor electrode, as well as cases where the detected object is brought close enough to come into contact with the sensor electrode.

[0002] For example, automatic faucet devices that use a human body detection sensor to detect when a user approaches a faucet fitting and automatically switch the water on and off are widely used 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 system, the sensor window installed in the faucet to send and receive infrared light is black, which can create a sense of incongruity with the design of the space the faucet is located in. Furthermore, the infrared sensor's detection distance can vary depending on the intensity of the light reflected from the human body, and it can also malfunction due to the influence of setting sun.

[0004] Japanese Patent Application Laid-Open No. 2005-227146

[0005] Therefore, the inventors investigated 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 so 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 changes in the capacitance of the sensor electrode. The sensor electrode is positively charged. When a user's hand or other body part (hereinafter referred to as the "detected object") approaches the sensor electrode and interferes with the electric field generated by the sensor electrode, the positive charge on the sensor electrode causes electrostatic induction in the detected object, 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 proximity to the sensor electrode, which in turn switches the faucet device between discharging and stopping water.

[0006] After extensive research, the inventors have found that installing a sensor electrode on a faucet fitting causes the following problem. Specifically, as shown in Figure 9, the positive charge on sensor electrode 2 causes electrostatic induction in the area surrounding sensor electrode 2 on faucet fitting 10. Negative charges within the conductor are attracted by the positive charge on sensor electrode 2 to the area of ​​the surrounding area of ​​faucet fitting 10 closest to sensor electrode 2, and positive charges of an equal magnitude to the negative charges move to the area farther from sensor electrode 2. An electric field is then formed between sensor electrode 2 and the area of ​​faucet fitting 10 to which the negative charges have moved. Electric field lines emerge from the area of ​​faucet fitting 10 to which the positive charges have moved, and the same number of electric field lines emerge as between sensor electrode 2 and the negative charges. As a result, the area surrounding sensor electrode 2 on faucet fitting 10 becomes a sensor electrode, and the capacitance of sensor electrode 2 changes not only when a detected object 101 approaches sensor electrode 2, but also when a detected object 101 approaches the area surrounding 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 the user's proximity operation being mistakenly detected, resulting in a malfunction in which the water flow is switched on and off erroneously.

[0007] One possible measure to prevent the faucet fittings from becoming sensor electrodes is to make them out of resin. Making the faucet fittings out of resin insulates them from the sensor electrode, preventing electrostatic induction and preventing the faucet fittings from becoming sensor electrodes. However, making the faucet fittings out of resin reduces the faucet fittings' durability, making them more susceptible to scratches and reducing their weather resistance to hot and cold water. Another problem is that resin faucet fittings lack the beautiful luster and shine seen in metal faucet fittings, compromising their design.

[0008] Another possible measure to prevent the faucet fitting from becoming a sensor electrode is to ground the faucet fitting. Grounding the faucet fitting prevents electrostatic induction from occurring in the faucet fitting, preventing it from becoming a sensor electrode. However, the inventors' research revealed that if the faucet fitting is grounded, the electric field generated from the sensor electrode 2 couples with the grounded faucet fitting 10, as shown in Figure 10, impairing the electric field generated from the sensor electrode 2 in the direction of detecting the object to be detected. Therefore, if the faucet fitting 10 is grounded, the electric field emitted from the sensor electrode 2 into the surrounding space is weakened by the grounding of the faucet fitting 10, reducing the detection distance (detection sensitivity) of the object to be detected from the sensor electrode 2. This creates the problem that the proximity operation of the object to be detected cannot be detected unless the object to be detected is brought close enough to the sensor electrode 2 to make contact with it.

[0009] The present disclosure focuses on solving the above-mentioned 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.

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

[0011] Item 1. A capacitance sensor that detects a user's proximity operation to a sensor electrode based on a change in capacitance of the sensor electrode, comprising: a sensor electrode that is charged with a positive electric charge; a detection device that detects a user's proximity operation to the sensor electrode based on a change in capacitance of the sensor electrode; and voltage application means that applies a voltage to a conductive sensor installation section that is installed in an insulated state with the sensor electrode and surrounds the sensor electrode in a product in which the capacitance sensor is used, so that the voltage is in phase and at the same potential as the sensor electrode, and the detection device is a capacitance sensor in the form of a module into which the sensor electrode is incorporated.

[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 sensors 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 in the sensor installation portion.

[0016] The capacitance sensor of the present disclosure can prevent the sensor installation section, where the sensor electrode is installed in an insulated state in a product using the capacitance sensor, from becoming a sensor electrode, thereby preventing malfunctions and ensuring a large detection distance for the object to be detected from the sensor electrode.

[0017] FIG. 1 is a perspective view showing the exterior of an automatic faucet device using a capacitance sensor of this embodiment. FIG. 2 is a diagram showing the functional configuration of the capacitance sensor of this embodiment. 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 portion (the portion where the sensor electrode is installed) of the faucet fitting. FIG. 4 is a diagram explaining the operating principle of the capacitance sensor of this embodiment. FIG. 5(A) is a model diagram of FIG. 9, and FIG. 5(B) is a model diagram of FIG. 4. FIG. 6(A) shows the functional configuration of the capacitance sensor of this embodiment when an LCR component occurs in the power supply line, and FIG. 6(B) is a model diagram explaining the operating principle of the capacitance sensor of FIG. 6(A). FIG. 7 is a model diagram explaining the operating principle of the capacitance sensor of this embodiment. FIG. 8 is a model diagram explaining the operating principle of the capacitance sensor of this embodiment. FIG. 9 is a diagram explaining the issues that arise when a conventional capacitance sensor is used in an automatic faucet device. FIG. 10 is a diagram explaining the issues that arise when a conventional capacitance sensor is used in an automatic faucet device and the faucet fitting is grounded.

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

[0019] 1 and 2, the automatic faucet device 100 comprises a capacitance sensor 1, a faucet fitting 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 their body (detectable object), such as a hand, close to a predetermined part (part) of the faucet fitting 10, automatically switching the faucet fitting 10 between discharging and stopping water. The automatic faucet device 100 uses the capacitance sensor 1 as a human body detection sensor that detects user operation.

[0020] First, each component of the automatic faucet device 100 will be described below.

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

[0022] As shown in Figures 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 approach, and is a detection area that detects the user's proximity 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 area.

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

[0024] The capacitance sensor 1 comprises a sensor electrode 2 that is charged with a positive electric charge, a detection device 3 that detects a user's proximity 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; metal such as aluminum, copper, silver, and gold; conductive resin such as thiophene-based conductive polymer and polystyrene sulfonate (PSS); or a composite material of these.

[0026] The sensor electrode 2 is in the form of a sheet, for example, and has an outer shape such as a rectangular shape (e.g., 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] 3A, a positive pulse voltage with respect to 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 considered 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 sensed object approaches the sensor electrode 2, the parasitic capacitance generated between the sensor electrode 2 and the sensed object is added to the reference capacitance, increasing the capacitance of the sensor electrode 2. This change in the capacitance of the sensor electrode 2 is detected by the detection device 3.

[0029] Detector The detector 3 determines whether or not a user has performed a proximity operation on the sensor electrode 2 based on a change in capacitance of the sensor electrode 2. As shown in Fig. 2 , the detector 3 includes a detector 8 that detects a change in capacitance of the sensor electrode 2, and a controller 9 that determines that a touch operation has been performed on the sensor electrode 2 based on a detection signal output from the detector 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 a change in capacitance of the sensor electrode 2. To detect the change in capacitance of the sensor electrode 2, the detection unit 8 is preferably configured to include, for example, a CV amplifier that converts the change in capacitance into a change in voltage, and a detection circuit having a CV amplifier gain adjustment function to adjust sensitivity. When the user does not approach the sensor electrode 2, there is no change in capacitance of the sensor electrode 2, and there is no change in voltage from the CV amplifier. On the other hand, when the user approaches 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 for detecting the change in capacitance 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 based on a change in the oscillation state of an oscillation circuit. The detection unit 8 can be configured with electric / electronic circuits, switches, etc. that are used in conventionally known capacitance sensors and are suitable for methods (1) and (2).

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

[0033] The receiving unit 90 is configured as an interface that receives the detection signal. If the detection signal is in the form of analog data, the receiving 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 a user has performed a proximity operation on the sensor electrode 2 based on the detection signal. For example, the processing unit 91 determines that a user has performed a proximity operation on the sensor electrode 2 when it determines that a change in capacitance of the sensor electrode 2 exceeds a predetermined threshold stored in memory. 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 upon determining that a user has performed a proximity operation on the sensor electrode 2. The control signal may be in the form of analog data or digital data. If 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 portion 12, which is part of the faucet fitting 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. That is, 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 portion 12. As a result, as shown in FIG. 5(B), the water conducting portion 12 has no potential difference with the sensor electrode 2, and no electric field is generated between the water conducting portion 12 and the sensor electrode 2, resulting in zero capacitance. In this way, because the water conducting portion 12 has no potential difference with the sensor electrode 2, the water conducting portion 12 is not subject to electrostatic induction and does not become a sensor electrode. Instead, it becomes an electrode (shield electrode) with the same phase and potential as the sensor electrode 2. As a result, the faucet fitting 10 suppresses electrostatic induction between the sensor electrode 2 and surrounding conductors due to various factors.

[0036] In other words, when the sensor electrode 2 is simply installed in the water conducting portion 12 of the faucet 10, as shown in the model diagram of FIG. 5(A), electrostatic induction occurs in the water conducting portion 12 due to the influence of the positive charge on the sensor electrode 2, and negative charges in the conductor are attracted to the positive charge on the sensor electrode 2 and move to the portion of the water conducting portion 12 closest to the sensor electrode 2, while positive charges of an equal amount to the negative charges move to the portion farther from the sensor electrode 2. An electric field is then formed between the sensor electrode 2 and the portion of the water conducting portion 12 to which the negative charges have moved, and electric field lines emerge from the portion of the water conducting portion 12 to which the positive charges have moved, in the same number as the electric field lines between the sensor electrode 2 and the negative charges. As a result, the water conducting portion 12 functions as a sensor electrode. When the water conducting portion 12 functions as a sensor electrode, the parasitic capacitance generated between the water conducting portion 12 and the detected object 101 when the detected object 101 approaches the water conducting portion 12 is added to the reference capacitance of the sensor electrode 2, causing a change in the electrostatic capacitance of the sensor electrode 2. 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 the water flow and water stop are erroneously switched on and off.

[0037] In contrast, when the water conducting section 12 is configured as a shield electrode, as shown in the model diagrams of Figures 4 and 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 has been independently charged in the water conducting section 12, but electrostatic induction does not occur in the sensor electrode 2. Therefore, the positive charge possessed by the sensor electrode 2 is not affected by the approach of the detected object 101, and it is possible to prevent 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 rather than the sensor electrode 2 (sensor window 14), detection of a user's proximity operation is prevented, and as a result, it is possible to prevent a malfunction in which water discharge and water stop are erroneously switched on and off.

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

[0039] The voltage application means 4 can be configured, 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 portion 12 of the faucet fitting 10. As shown in FIG. 2 , the voltage application means 4 includes a pulse voltage generation unit 5, a buffer circuit 6, a capacitance device 7, and a power supply line 16. The power supply line 16 connects the detection unit 8 of the detection device 3 to the water conducting portion 12 of the faucet fitting 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 unit 8 to the sensor electrode 2 is applied to the water conducting portion 12. The power supply line 16 is fixed to the water conducting portion 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 secure the power supply line 16 to the water conducting portion 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 detecting unit 8 of the detecting device 3 or an electrical signal synchronized therewith, and sends the generated pulse voltage to the water conducting unit 12 of the faucet fitting 10. The pulse voltage generating unit 5 can be configured using, for example, a coupling capacitor and an amplifier (e.g., an operational amplifier). The coupling capacitor blocks the DC component from the sensor drive pulse signal sent from the detecting unit 8 of the detecting 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. To correct the input offset voltage of the operational amplifier, it is preferable to use a known method, such as applying an external voltage opposite to the input offset voltage.

[0041] The buffer circuit 6 is located downstream (at the water conducting section 12) of the pulse voltage generating section 5 on the power supply line 16. In an actual environment, as shown in FIG. 6A , invisible LCR components such as parasitic capacitance, parasitic inductance, and parasitic resistance occur on the power supply line 16. This causes a drop in the voltage applied to the water conducting section 12 by the pulse voltage generating section 5. As shown in the model diagram of FIG. 6B , if the positive charge stored in the water conducting section 12 becomes insufficient, a potential difference occurs between the sensor electrode 2 and the water conducting section 12, causing electrostatic induction between the sensor electrode 2 and the water conducting section 12. Therefore, the water conducting section 12 functions as a sensor electrode. As shown in the model diagram of FIG. 6B , when a 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 stored in the water conducting section 12 but also the positive charge stored in the sensor electrode 2, which may change the capacitance of the sensor electrode 2.

[0042] In contrast, the buffer circuit 6 has the function of correcting the voltage input from the pulse voltage generating unit 5. Therefore, if the buffer circuit 6 is connected to the power supply line 16, even if the voltage drop described above occurs, the buffer circuit 6 corrects the voltage drop and applies the corrected voltage to the water conducting portion 12, as shown in the model diagram of FIG. 7 . This ensures that the water conducting portion 12 is sufficiently positively charged, maintaining a state in which there is no potential difference between the water conducting portion 12 and the sensor electrode 2. This zeroes the capacitance between the water conducting portion 12 and the sensor electrode 2, preventing the water conducting portion 12 from being subjected to electrostatic induction and thereby preventing it from becoming a sensor electrode. Therefore, even if the object to be detected 101 approaches the water conducting portion 12, electrostatic induction occurs in the object to be detected 101 due to the influence of the positive charge independently stored in the water conducting portion 12, and the positive charge on the sensor electrode 2 is not affected by the approach of the object to be detected 101. This effectively prevents the electrostatic capacitance of the sensor electrode 2 from changing when the object to be detected 101 approaches the water conducting portion 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), the detection of the user's proximity operation is effectively suppressed, thereby effectively suppressing malfunctions such as switching between water discharge and water stop.

[0043] The capacitance device 7 is located downstream of the buffer circuit 6 on the power supply line 16 and is connected in parallel with the pulse voltage generating unit 5. The capacitance 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 fitting 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 occurs 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 function as a sensor electrode.

[0045] In contrast, if the capacitance device 7 is located 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 is suddenly generated due to contact of the detected object 101 with the water conducting section 12, the charge stored in the capacitance device 7 is released from the capacitance device 7 and replenished in the water conducting section 12, increasing the voltage applied to the water conducting section 12 and returning the water conducting section 12 to a state where there is no potential difference with the sensor electrode 2. As a result, the capacitance between the water conducting section 12 and the sensor electrode 2 becomes zero, and the water conducting section 12 is not affected by electrostatic induction and does not become a sensor electrode. Therefore, even if the detected object 101 contacts the water conducting section 12, the positive charge on 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 prevented from changing. As a result, when the detected object 101 contacts the water conducting section 12, the user's proximity operation is not detected, thereby preventing a malfunction that erroneously switches between water discharge and water stop.

[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 a user brings a detectable object 101, such as a hand, close to the sensor window 14 of the faucet fitting 10, the capacitance of the sensor electrode 2 changes, causing the capacitance sensor 1 to detect the user's proximity action. This detection information is then transmitted as a control signal from the capacitance sensor 1 to the control device 15 via wire or wirelessly. This causes the control device 15 to open the solenoid valve and automatically cause water to be discharged from the water discharger 13. After water has been discharged for a predetermined period of time, the control device 15 closes the solenoid valve to automatically stop water from being discharged from the water discharger 13. Alternatively, when the capacitance sensor 1 detects a proximity action in which the user brings the detectable object 101, such as a hand, close to the sensor window 14 again, the control device 15 closes the solenoid valve to automatically stop the water flow.

[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 open and close the solenoid valve to switch between water discharge and water stop when it detects a user's proximity operation.

[0049] Function and effects of the capacitance sensor 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 potential with 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, preventing the water conducting section 12 from becoming a sensor electrode. Therefore, when a detectable object 101 such as a user's hand approaches the water conducting section 12 of the faucet fitting 10, a change in capacitance of the sensor electrode 2 is suppressed, so that the user's proximity operation is not detected when the detectable object 101 approaches the water conducting section 12. Therefore, the capacitance sensor 1 of this embodiment can prevent the automatic faucet device 100 in which the capacitance sensor 1 is used from malfunctioning, such as accidentally 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 guide portion 12 of the faucet fitting 10 .

[0052] As a result, in the capacitance sensor 1 of this embodiment, as described above, 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, 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] The capacitance sensor 1 of this embodiment is also 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, as described above, even if an extremely large parasitic capacitance is suddenly generated when the water conducting section 12 is brought into contact with the detected object 101, such as a user's hand, the charge stored in the capacitance device 7 is released from the capacitance device 7 and replenished in the water conducting section 12 (sensor installation section), thereby maintaining the voltage applied to the water conducting section 12. Therefore, according to the capacitance sensor 1 of this embodiment, even if an extremely large parasitic capacitance is suddenly generated when the detected object comes into contact with the water conducting section 12, 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.

[0055] While the embodiments of the capacitance sensor of the present disclosure have been described above, the above-described embodiments are merely examples and are not limiting. Therefore, the capacitance sensor of the present disclosure is not limited to the above-described embodiments, 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 fitting 10, from becoming a sensor electrode and to turn the water conducting section 12 into a shield electrode, but the voltage application means 4 may also 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 is the sensor installation portion, may also be made into a shielded electrode.

[0058] For example, in the above embodiment, the capacitance sensor of the present disclosure is applied to an automatic faucet device 100 in a kitchen, but the capacitance sensor 1 of the present disclosure may also be applied to an 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, such as products that use a human body detection sensor to detect a user's proximity and perform various functions (e.g., opening and closing a door, turning a switch or button on and off, etc.), 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.

[0060] REFERENCE SIGNS LIST 1 Capacitance sensor 2 Sensor electrode 3 Detector 4 Voltage application means 5 Pulse voltage generator 6 Buffer circuit 7 Capacitor 10 Faucet fitting 12 Water conveyance part (part of faucet fitting) 100 Automatic faucet device

Claims

1. A capacitance sensor that detects a user's approach to a sensor electrode based on a change in capacitance of the sensor electrode, comprising: a sensor electrode that is charged with a positive electric charge; a detection device that detects a user's approach to the sensor electrode based on a change in capacitance of the sensor electrode; and a voltage application means that applies a voltage to a conductive sensor installation section that surrounds the sensor electrode and is installed in an insulated state in a product in which the capacitance sensor is used, so that the voltage is in phase and at the same potential as the sensor electrode, and the detection device is a capacitance sensor in the form of a module in which the sensor electrode is incorporated.

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. The capacitance sensor according to claim 1 or 2, wherein the voltage application means further comprises a capacitance device for replenishing charge in the sensor installation portion.

Images