JP7606675B2 - Toilet seat device - Google Patents

Description

Aspects of the present invention generally relate to toilet seat devices.

There is a capacitance type human body detection sensor that detects a human body by the change in capacitance depending on the presence or absence of a human body. It has been proposed to use such a capacitance type human body detection sensor in a toilet seat device. For example, in the toilet seat seat detection device of Patent Document 1, a heat conductive conductor (aluminum foil) attached to a heater wire provided on the toilet seat is used as an electrode, and a change in capacitance is detected to detect the presence of a human body on the toilet seat.
In a toilet seat device equipped with a capacitance sensor, noise may cause false detection of a human body. For example, noise from the power line of the toilet seat device may reduce the accuracy of human body detection.

Japanese Patent Application Publication No. 6-138247

The present invention was made based on the recognition of such problems, and aims to provide a toilet seat device that can suppress false detection of the human body caused by noise.

The first invention is a toilet seat device comprising: a toilet seat; a detection electrode whose capacitance changes depending on whether a human body is seated on the toilet seat; a capacitance detection means having an input terminal electrically connected to the detection electrode and detecting the capacitance of the detection electrode; a control unit which determines whether or not the human body is seated based on the detection result of the capacitance detection means; and an overvoltage detection means which detects an overvoltage at the input terminal, wherein when the overvoltage detection means detects the overvoltage, the capacitance detection means temporarily suspends and then resumes detection of the capacitance.

With this toilet seat device, even if an overvoltage occurs at the input terminal due to noise from the power supply or the like, the capacitance detection means temporarily suspends capacitance detection, thereby preventing false detections caused by noise.

The second invention is a toilet seat device according to the first invention, characterized in that the capacitance detection means includes an integrating means for storing the charge discharged from the detection electrode, a first switch connected to a predetermined voltage, and a second switch connected to the input terminal and the integrating means, and executes a switching operation that alternates between a first state in which the first switch is on and the second switch is off and the detection electrode is charged to the predetermined voltage, and a second state in which the first switch is off and the second switch is on and the detection electrode is discharged, the integrating means stores the charge discharged from the detection electrode in the second state that is repeated by the switching operation, the control unit determines whether or not the human body is seated according to the charge stored in the integrating means, and when the overvoltage detection means detects the overvoltage, the capacitance detection means temporarily suspends the switching operation, sets the first switch and the second switch to the first state, and then resumes the switching operation.

According to this toilet seat device, when an overvoltage occurs at the input terminal due to, for example, noise from a power supply, the capacitance detection means temporarily suspends the switching operation and enters the first state. This stops the integration (accumulation of charge) of the integrating means, making it possible to prevent large errors in the integral value caused by noise. This makes it possible to prevent false detections caused by noise.

The third invention is the toilet seat device according to the second invention, further comprising an off-delay means for causing the first state to continue for a predetermined time when the overvoltage detection means detects the overvoltage.

According to this toilet seat device, the first state continues, so that the integration by the integrating means continues to be suspended, and therefore, false detection caused by noise can be further suppressed.
For example, the toilet seat device circuit may contain capacitive or inductive components, which may cause noise to continue to be present at the input terminal. In other words, because the toilet seat device circuit contains capacitive and inductive components, even if the applied overvoltage is instantaneous, the potential fluctuation due to the noise does not immediately become zero, but takes a certain amount of time to converge. Even in such a case, the off-delay means continues the first state for a predetermined period of time, so that the integration by the integrating means is interrupted, and time is secured until the potential fluctuation due to the noise converges, thereby preventing a large error due to noise from occurring in the integrated value. Therefore, false detection due to noise can be further prevented.

The fourth invention is a toilet seat device according to any one of the first to third inventions, characterized in that the detection electrode is provided on the underside of the toilet seat, has an area larger than that of a heater that warms the toilet seat, and diffuses heat from the heater to the toilet seat.

According to this toilet seat device, the large area of the detection electrode widens the seating detection range, making it possible to suppress false detections due to seating position. On the other hand, when the detection electrode is large, the capacitance of the detection electrode is large, so the charging and discharging time is long, and the time required to detect the capacitance is also long. This increases the frequency with which overvoltage occurs at the input terminal due to noise (such as short-period noise on the power line) during capacitance detection. Even in such cases, false detections due to noise can be suppressed by having the capacitance detection means temporarily suspend capacitance detection. Therefore, it is possible to suppress false detections due to noise while widening the seating detection range.

The fifth invention is a toilet seat device according to the second or third invention, characterized in that the capacitance detection means is capable of changing the frequency of the switching operation that repeats the first state and the second state to a plurality of mutually different frequencies, and when changing the frequency of the switching operation, the time of one of the first state and the second state is made variable, and the time of the other of the first state and the second state is made fixed.

According to this toilet seat device, by changing the frequency of the switching operation, it is possible to reduce errors in the capacitance detection results caused by noise of a specific frequency. On the other hand, when the switching operation is switched between the first state and the second state, this switching operation may trigger a phenomenon in which the potential of the detection electrode oscillates. Here, if the frequency of the switching operation is changed, the effect of the vibration of the potential of the detection electrode on the capacitance detection result changes, which may result in erroneous detection of the presence or absence of a human body. In response to this, by fixing the time of the other of the first state and the second state when changing the frequency of the switching operation, it is possible to reduce the change in the effect of the vibration of the potential of the detection electrode caused by the change in frequency. This makes it possible to suppress erroneous detection.

The sixth invention is the toilet seat device of the fifth invention, characterized in that the one is in the first state and the other is in the second state.

In the first state, the voltage of the detection electrode at the end of the first state affects the detection result of the capacitance detection means. For example, even if noise occurs in the detection electrode during the first state, there is no substantial effect on the detection result. Therefore, with this toilet seat device, even if the time of the first state is extended and the possibility of noise entering the detection electrode during the first state increases, it is possible to suppress a decrease in noise resistance.

According to an aspect of the present invention, a toilet seat device is provided that can prevent false detection of a human body due to noise.

FIG. 1 is a perspective view illustrating a toilet apparatus provided with a toilet seat apparatus according to an embodiment. FIG. 2 is a block diagram illustrating an example of a human body detection sensor included in the toilet seat apparatus according to the embodiment. FIG. 3 is a cross-sectional view that diagrammatically illustrates a portion of the toilet seat according to the embodiment. FIG. 4 is a plan view that illustrates the toilet seat according to the embodiment. FIG. 5 is a partial cross-sectional view that diagrammatically illustrates a portion of the toilet seat according to the embodiment. FIG. 6 is a block diagram that illustrates a toilet seat device according to an embodiment. 7A to 7D are graphs each showing a schematic example of the operation of the detection circuit according to the embodiment. 8A to 8C are graphs that diagrammatically show an example of the operation of the detection circuit according to the embodiment. FIG. 9 is a schematic block diagram showing a human body detection sensor according to a reference example. 10A to 10D are graphs each showing a schematic example of the operation of the detection circuit according to the reference example. 11A to 11C are graphs each showing a schematic example of the operation of the detection circuit according to the reference example. FIG. 12 is a block diagram illustrating a specific example of a human body detection sensor according to the embodiment. 13A to 13G are graphs that diagrammatically show an example of the operation of the detection circuit according to the embodiment. 14A to 14F are graphs that diagrammatically show an example of the operation of the detection circuit according to the embodiment. FIG. 11 is a block diagram illustrating a toilet seat device according to another embodiment of the present invention. 16A and 16B are graphs that diagrammatically show the switching operation according to the embodiment. 17A and 17B are graphs that diagrammatically show the switching operation according to the embodiment. 18A and 18B are graphs that diagrammatically show an example of the operation of the detection circuit. 19A and 19B are graphs illustrating an example of the operation of the detection circuit. 20A and 20B are graphs illustrating another example of the operation of the detection circuit. 21(a) and 21(b) are graphs illustrating the timing at which the discharge time ends.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals and detailed description thereof will be omitted as appropriate.
FIG. 1 is a perspective view illustrating a toilet apparatus provided with a toilet seat apparatus according to an embodiment.
1, the toilet device 100 includes a toilet seat device 110 according to an embodiment, and a Western-style seated toilet bowl (hereinafter, for convenience of explanation, simply referred to as a "toilet bowl") 104. The toilet seat device 110 is provided on top of the toilet bowl 104. The toilet seat device 110 includes a main body 112, a toilet seat 114, and a toilet lid 116.

The toilet 104 has a bowl portion 104a that is recessed downward. The toilet 104 receives waste such as urine and feces from the user in the bowl portion 104a. The main body portion 112 of the toilet seat device 110 is provided at the rear and above the bowl portion 104a of the toilet 104. The main body portion 112 supports the toilet seat 114 and the toilet lid 116 so that they can be opened and closed.

The toilet seat 114 has an opening 114a. The toilet seat 114 is provided on the toilet bowl 104 so as to surround the outer edge of the bowl portion 104a, exposing the bowl portion 104a through the opening 114a. This allows a user to defecate into the bowl portion 104a while sitting on the toilet seat 114. In this example, a so-called O-shaped toilet seat 114 is shown, in which a through-hole-like opening 114a is formed. The toilet seat 114 is not limited to an O-shape, and may be U-shaped, etc.

The toilet seat device 110 has a heating function that warms the seating surface of the toilet seat 114. The toilet seat device 110 also has a sanitary washing function that washes private parts such as the buttocks of a user sitting on the toilet seat 114. In other words, the toilet seat device 110 is a sanitary washing device. However, the toilet seat device 110 does not necessarily have to have the sanitary washing function or the heating function. The toilet seat device 110 may be, for example, a heated toilet seat device that only has a heating function.

The toilet seat device 110 has a nozzle 120 for washing the private parts of the human body. The nozzle 120 is provided in the main body 112, and moves back and forth between a position stored in the main body 112 and a position advanced from the main body 112 into the bowl portion 104a. Note that FIG. 1 shows the nozzle 120 advanced into the bowl portion 104a.

The main body 112 is configured to be able to communicate with an operation unit 106 such as a remote control. The communication between the main body 112 and the operation unit 106 may be wired communication or wireless communication. The main body 112 advances the nozzle 120 into the bowl portion 104a in response to, for example, an operation instruction input from the operation unit 106.

The nozzle 120 ejects water toward the human body parts to cleanse the human body parts. A bidet cleansing water outlet 120a and a buttocks cleansing water outlet 120b are provided at the tip of the nozzle 120. The nozzle 120 can eject water from the bidet cleansing water outlet 120a provided at its tip to clean the female parts of a woman sitting on the toilet seat 114. Alternatively, the nozzle 120 can eject water from the buttocks cleansing water outlet 120b provided at its tip to clean the buttocks of a user sitting on the toilet seat 114.

FIG. 2 is a block diagram illustrating an example of a human body detection sensor included in the toilet seat apparatus according to the embodiment.
The toilet seat device 110 has a human body detection sensor 10. The human body detection sensor 10 has a detection electrode 12, a detection circuit 14, and a control unit 16.

The human body detection sensor 10 determines whether or not a human body is present. The human body detection sensor 10 is, for example, a seating detection sensor that can detect whether or not a user is sitting on the toilet seat 114. The toilet seat device 110 can control the functions of the toilet seat device 110 based on the result of the human body detection sensor 10's determination of the presence or absence of a human body (seated). For example, the control unit 16 can control the cleaning function (moving the nozzle 120 forward and backward and stopping the nozzle 120 from spouting water) and turn the heating function on and off based on the result of the human body detection sensor 10's determination.

The capacitance of the detection electrode 12 changes depending on whether or not a human body is present. For example, the detection electrode 12 is attached to the toilet seat 114, and the capacitance changes depending on whether or not a human body is seated on the toilet seat 114. The detection electrode 12 is electrostatically coupled to the human body when the human body is seated. As a result, the capacitance of the detection electrode 12 is larger when the human body is seated than when the human body is not seated. That is, as shown in FIG. 2, the detection electrode 12 is connected to a common potential GND via the human body, for example, and forms a capacitance C1 (capacitor) that changes depending on whether or not a human body is present. The capacitance C1 changes depending on whether or not a human body is in proximity (seated state) and not in proximity (not seated state). For example, when a pulse signal is transmitted to the detection electrode 12, the current flowing through the detection electrode 12 is larger when the human body is seated than when the human body is not seated. In this example, the human body detection sensor 10 is a so-called self-capacitance type capacitive human body detection sensor that uses a single electrode to detect changes in capacitance due to the presence or absence of a human body.

The detection circuit 14 has a capacitance detection means 17, an overvoltage detection means 11, and an off-delay means 19.

The capacitance detection means 17 has an input terminal 15 electrically connected to the detection electrode 12 .
The capacitance detection means 17 detects a change in the capacitance of the detection electrode 12 by transmitting a signal to the detection electrode 12 via the input terminal 15. For example, the capacitance detection means 17 transmits a pulse signal of a predetermined number of pulses to the detection electrode 12 via the input terminal 15. The capacitance detection means 17 then detects, via the input terminal 15, the charge accumulated in the detection electrode 12 when each pulse is applied to the detection electrode 12, and integrates the charge for each application of a pulse. The capacitance detection means 17 detects a change in the capacitance of the detection electrode 12 based on the integral value of this charge.

The input terminal 15 is not necessarily limited to a connecting member such as a metal fitting, but may be at least a part of a conductor (e.g., wiring) that electrically connects the detection electrode 12 and the inside of the capacitance detection means 17.

The control unit 16 controls the detection of capacitance by the capacitance detection means 17. The control unit 16 also determines whether or not a human body is seated based on the detection result of the capacitance detection means 17, i.e., the capacitance of the detection electrode 12. In a self-capacitance type sensor, as described above, the capacitance of the detection electrode 12 is larger when a human body is seated than when a human body is not seated. In this case, the control unit 16 determines that a human body is seated when, for example, the integral value of the charge detected by the capacitance detection means 17 exceeds a threshold value, and determines that a human body is not seated when the integral value of the charge detected by the capacitance detection means 17 does not exceed the threshold value. The control unit 16 can be a circuit such as a microcomputer.

The overvoltage detection means 11 is electrically connected to the input terminal 15 of the capacitance detection means 17. The voltage of the input terminal 15 is input to the overvoltage detection means 11. As a result, the overvoltage detection means 11 detects an overvoltage at the input terminal 15. In other words, the overvoltage detection means 11 detects whether the voltage of the input terminal 15 has reached a predetermined voltage. In addition, the overvoltage detection means 11 is electrically connected to the capacitance detection means 17 via the off-delay means 19.

When an overvoltage is detected by the overvoltage detection means 11, a signal corresponding to the detection of the overvoltage is input to the capacitance detection means 17 via the off-delay means 19. Then, the capacitance detection means 17 temporarily suspends the detection of the capacitance of the detection electrode 12, and then resumes the detection of the capacitance of the detection electrode 12.

For example, electrical noise may occur in the detection circuit 14. An overvoltage may occur at the input terminal 15 due to the noise. As described later, such noise may be, for example, noise occurring in the power line of the human body detection sensor 10. However, the noise in the embodiment is not necessarily limited to noise from the power line. If noise (overvoltage) occurs at the input terminal 15 and a current caused by the noise flows from the input terminal 15 to the capacitance detection means 17, a large error may occur in the detection result (i.e., the integral value) of the capacitance detection means 17. Therefore, there is a risk of false detection of the human body due to noise. In other words, an overvoltage means a voltage that is so excessive that it causes false detection of the human body, and not only voltage fluctuations on the positive side but also voltage fluctuations on the negative side are overvoltages. To give a specific numerical value, the overvoltage detection means 11 detects both +50V or more and -50V or less as overvoltage.

In contrast, in the detection circuit 14, as described above, when the overvoltage detection means 11 detects an overvoltage, the capacitance detection means 17 temporarily suspends and then resumes capacitance detection. As a result, even if an overvoltage occurs at the input terminal due to noise from a power supply, for example, the capacitance detection means temporarily suspends capacitance detection, thereby preventing erroneous detection due to noise.

When detecting the capacitance of the detection electrode 12, the charge accumulated in the capacitance C1 is input to a charge amount measuring section (e.g., an integrating means described later) of the capacitance detection means 17 via the input terminal 15. For example, as described later, the capacitance detection means 17 is provided with a switch. By periodically turning the switch on and off, the transmission of a pulse signal to the detection electrode 12 and the integration of the charge for each application of a pulse are periodically repeated. In this case, pausing the detection of the capacitance of the detection electrode 12 corresponds to, for example, pausing the periodic on/off of the switch. Furthermore, resuming the detection of the capacitance of the detection electrode 12 corresponds to resuming the periodic on/off of the switch.

The off-delay means 19 is electrically connected to the overvoltage detection means 11 and the capacitance detection means 17. The off-delay means 19 is a circuit for causing the capacitance detection means 17 to maintain a state in which the capacitance detection is temporarily suspended for a predetermined time. When the off-delay means 19 receives a signal from the overvoltage detection means 11 corresponding to the detection of an overvoltage, it transmits a signal to the capacitance detection means 17. In response to the signal from the off-delay means 19, the capacitance detection means 17 maintains a state in which the capacitance detection is temporarily suspended for a predetermined time. The length of time for which the capacitance detection is temporarily suspended can be adjusted by the output of the off-delay means 19.

For example, noise occurring in the detection circuit 14 may cause noise occurring at the input terminal 15 to continue. Even in such a case, the off-delay means 19 can continue the state in which capacitance detection is temporarily suspended, thereby suppressing the effect of noise on the detection result of the capacitance detection means 17. Note that the off-delay means 19 does not necessarily have to be provided in the embodiment.

Below, a specific example of the toilet seat device 110 and the human body detection sensor 10 will be described using an example in which the detection electrode 12 is a thermal diffusion sheet for diffusing heat from a heater provided on the toilet seat.

FIG. 3 is a cross-sectional view that diagrammatically illustrates a portion of the toilet seat according to the embodiment.
FIG. 3 is a schematic cross-sectional view taken along line A1-A2 in FIG.
As shown in FIG. 3, the toilet seat 114 has an internal space SP. In other words, the toilet seat 114 is hollow. The toilet seat 114 has, for example, an upper plate 130 and a lower plate 132, and the upper plate 130 and the lower plate 132 are joined together to form an internal space SP between the upper plate 130 and the lower plate 132. The upper plate 130 has a seating surface 130a on which a user sits, and an inner surface 130b facing the lower plate 132. In other words, the inner surface 130b is a surface (the back surface of the toilet seat 114) facing the opposite side to the seating surface 130a in the internal space SP. The upper plate 130 and the lower plate 132 may be joined together by adhesion using an adhesive, or by welding using vibration welding or the like. However, the configuration of the toilet seat 114 is not limited to the above, and may be any configuration having at least an internal space SP, a seating surface 130a, and an inner surface 130b.

FIG. 4 is a plan view that illustrates the toilet seat according to the embodiment.
FIG. 5 is a partial cross-sectional view that diagrammatically illustrates a portion of the toilet seat according to the embodiment.
4 and 5, the heater 204 is provided in the internal space SP, and heats the seating surface 130a from the inside via the inner surface 130b by applying an AC voltage from the outside. The heater 204 generates heat by passing an electric current through it. The heater 204 is, for example, an electric heating wire.

The detection electrode 12 is provided on the inner surface 130b. The detection electrode 12 is, for example, sheet-shaped. The heater 204 is, for example, cord-shaped. The area of the detection electrode 12 is larger than the area of the heater 204. As a result, the detection electrode 12 diffuses the heat of the heater 204 to the inner surface 130b. In this way, the detection electrode 12 is provided on the inner surface 130b, changes the electrostatic capacitance depending on whether or not the toilet seat 114 is seated, has an area larger than the heater 204, and diffuses the heat of the heater 204 to the inner surface 130b. In other words, the detection electrode 12 functions as an electrode that detects whether or not the toilet seat 114 is seated, and also functions as a heat diffusion sheet that diffuses the heat of the heater 204 to the inner surface 130b.

A first adhesive 240 is provided between the detection electrode 12 and the heater 204. The first adhesive 240 bonds the detection electrode 12 and the heater 204.

A second adhesive 242 is provided between the detection electrode 12 and the inner surface 130b of the upper plate 130. The second adhesive 242 bonds the detection electrode 12 and the inner surface 130b of the upper plate 130. As a result, the detection electrode 12 is provided on the inner surface 130b of the upper plate 130.

The detection electrode 12 is a conductor. The detection electrode 12 is, for example, a metal foil. The thermal conductivity of the metal foil is higher than the thermal conductivity of the upper plate 130, which is generally made of resin. Examples of the detection electrode 12 include aluminum foil and copper foil.

As shown in FIG. 4, the heater 204 snakes around the detection electrode 12 and is disposed over almost the entire circumference of the detection electrode 12. The detection electrode 12 is also disposed over almost the entire circumference of the inner surface 130b of the upper plate 130. The heater 204 snakes around under the inner surface 130b of the upper plate 130 and is disposed over almost the entire inner surface 130b. In this manner, the cord-shaped heater 204 is disposed on the inner surface 130b while being bent. The heater 204 is not limited to being cord-shaped, and may be sheet-shaped or the like. The heater 204 may be configured in any manner that can heat the seating surface 130a from the inside.

FIG. 6 is a block diagram that illustrates a toilet seat device according to an embodiment.
As shown in FIG. 6, the toilet seat device 110 has a power supply circuit 18 (switching power supply circuit). The power supply circuit 18 is electrically connected to an AC power supply PS via a coil 38 and a power supply terminal 30. The power supply circuit 18 converts AC power supplied from the AC power supply PS into DC power, and supplies the converted DC power to the detection circuit 14 and the control unit 16. The detection circuit 14 and the control unit 16 operate based on the supply of DC power from the power supply circuit 18. The AC power supply PS is, for example, a commercial power supply of AC 100V (effective value). The power supply terminal 30 is, for example, an outlet plug. The power supply circuit 18 is, for example, an insulated AC/DC converter. A varistor 60 is provided between the ground side 30a and the non-ground side 30b of the power supply terminal 30. A varistor 61 is provided between the ground side 30a of the power supply terminal 30 and a common potential GND.

The power supply circuit 18 has, for example, a rectifier circuit 31, a smoothing capacitor 32, and a conversion circuit 33. The rectifier circuit 31 rectifies the AC voltage supplied from the AC power supply PS and converts it into a pulsating rectified voltage. The rectifier circuit 31 is, for example, a full-wave rectifier using a diode bridge, and converts the AC voltage into a full-wave rectified voltage. The rectifier circuit 31 may be, for example, a half-wave rectifier.

The smoothing capacitor 32 smoothes the rectified voltage rectified by the rectifier circuit 31 and converts the rectified voltage into a DC voltage.

The conversion circuit 33 converts the DC voltage converted by the smoothing capacitor 32 into DC power compatible with the detection circuit 14 and the control unit 16. The conversion circuit 33 is a so-called DC-DC converter. The conversion circuit 33 converts, for example, a DC voltage of 100V into a DC voltage of about 5V to 24V. In other words, the conversion circuit 33 is a step-down converter. The conversion circuit 33 supplies the converted DC power to the detection circuit 14 and the control unit 16. This enables the detection circuit 14 and the control unit 16 to operate in response to the supply of DC power from the conversion circuit 33 (power supply circuit 18).

The conversion circuit 33 has a transformer 34 that electrically insulates the primary side (AC power supply PS side) from the secondary side (load side). In other words, the conversion circuit 33 electrically insulates the input side from the output side. The conversion circuit 33 is, for example, an isolated converter. The conversion circuit 33 is, for example, a flyback converter. However, the conversion circuit 33 does not necessarily have to be an isolated converter. The power supply circuit 18 may be configured in any way that can convert AC power into DC power according to the detection circuit 14 and the control unit 16.

The coil 38 is, for example, a common mode choke coil for suppressing common mode noise. The end 38a of the coil 38 is electrically connected to one input terminal of the rectifier circuit 31. The end 38b of the coil 38 is electrically connected to the other input terminal of the rectifier circuit 31. The end 38c of the coil 38 is connected to a common potential GND via the varistor 61. The end 38d of the coil 38 is electrically connected to the non-grounded side 30b of the power supply terminal 30. The common potential GND is, for example, the potential of the earth (so-called earth). The common potential GND may be, for example, the potential of a conductive frame or chassis of the device (so-called frame ground or chassis ground).

The power supply circuit 18 further includes a capacitor 37. The capacitor 37 is provided between the common potential GND on the primary side of the conversion circuit 33 and the common potential GND on the secondary side. The capacitor 37 suppresses noise that is carried to the GND on the secondary side due to the voltage conversion operation of the conversion circuit 33.

The toilet seat device 110 has a heater 204 that heats the toilet seat 114. The heater 204 is connected to the power supply terminal 30. This allows an AC voltage supplied from an AC power supply PS to be applied to the heater 204. A switching element 220 is provided between the heater 204 and the power supply terminal 30 to switch between applying and stopping the AC voltage to the heater 204. For example, a phototriac can be used as the switching element 220. The switching element 220 is connected to the control unit 16. The control unit 16 controls the on/off switching of the switching element 220. In other words, the control unit 16 controls the supply of electricity to the heater 204 (application and stopping of the AC voltage).

The control unit 16 controls the supply of electricity to the heater 204 so that the temperature of the seating surface 130a of the toilet seat 114 becomes a predetermined set temperature set by operating the operation unit 106, for example. In addition, the control unit 16 sets the temperature of the seating surface 130a of the toilet seat 114 lower than the set temperature when the detection circuit 14 does not detect a seated person. Then, the control unit 16 raises the temperature of the seating surface 130a of the toilet seat 114 to the set temperature when the detection circuit 14 detects a seated person. This reduces unnecessary power consumption when not in use, and reduces the power consumption of the toilet seat device 110.

The control unit 16 controls the supply of current to the heater 204, for example, by a pattern control method in which multiple half-waves of AC voltage are treated as one unit. The control unit 16 switches between supplying current to the heater 204 and stopping supplying current, for example, depending on the detection result of the zero-cross point. The control unit 202 increases the number of half-waves to be supplied with current, for example, when the temperature of the seating surface 130a is to be increased, and decreases the number of half-waves to be supplied with current, for example, when the temperature of the seating surface 130a is to be kept warm or decreased. This makes it possible to control the temperature of the seating surface 130a to a desired temperature.

In this example, the detection electrode 12 uses the thermal diffusion sheet described in relation to Figures 4 and 5. A capacitance C1 is formed between the thermal diffusion sheet (detection electrode 12) provided on the toilet seat 114 and the human body HB. The capacitance detection means 17 detects the capacitance C1.

The capacitance detection means 17 includes, for example, a switch unit 20, a charge amount measurement unit 22, a protective resistor 42, and a varistor 44. The switch unit 20 functions, for example, as a pulse output unit. That is, the switch unit 20 transmits a pulse signal to the detection electrode 12 based on an input from the control unit 16. The charge amount measurement unit 22 measures the capacitance of the detection electrode 12 based on the charge amount of the detection electrode 12 when the switch unit 20 transmits a pulse signal to the detection electrode 12. The measured capacitance is input to the control unit 16. For example, the integral value of the charge is input to the control unit 16 as the capacitance of the detection electrode 12.

The switch unit 20 has a first switch 71, a second switch 72, an inverter circuit 73, and an OR circuit 74. One of the inputs of the OR circuit 74 is connected to the control unit 16. The output of the OR circuit is connected to the first switch 71 and to the second switch 72 via the inverter circuit 73. One end of the first switch 71 is connected to a predetermined voltage (power supply voltage VCC), and the other end of the first switch 71 is connected to one end of the second switch 72. The other end of the second switch 72 is connected to the charge amount measurement unit 22 (integration means 52).

The charge amount measuring unit 22 has an integrating means 52 (capacitor), a transistor 54, a resistor 55, and a resistor 56. One end of the integrating means 52 is connected to the second switch 72, and the other end of the integrating means 52 is connected to the common potential GND on the secondary side. The base of the transistor 54 is connected to the control unit 16 via the resistor 55 and to the common potential GND on the secondary side via the resistor 56. The emitter of the transistor 54 is connected to the common potential GND on the secondary side. The collector of the transistor 54 is connected to the control unit 16 and is connected between the second switch 72 and the integrating means 52.

One end of the protective resistor 42 is connected between the first switch 71 and the second switch 72. The other end of the protective resistor 42 is connected to the input terminal 15. In other words, the first switch 71 and the second switch 72 are electrically connected to the input terminal 15 via the protective resistor 42. For the first switch 71 and the second switch 72, for example, an analog switch or the like can be used. However, the first switch 71 and the second switch 72 are not limited to this, and any configuration that can switch between conductive and non-conductive can be used. The protective resistor 42 is a component that protects the capacitance detection means 17, which is composed of electronic components, from electrical stress coming from the outside. The varistor 44 is connected between the common potential GND on the secondary side and the input terminal 15, and protects the capacitance detection means 17 from component destruction due to overvoltage or the like.
A specific example of the overvoltage detection means 11 and the off-delay means 19 will be described later with reference to FIG.

Next, referring to Figures 7 and 8, an example of the operation of the capacitance detection means 17 when no noise is occurring, i.e., when no overvoltage is occurring at the input terminal 15, will be described.

FIGS. 7(a)-7(d) and 8(a)-8(c) are graphs that show a schematic example of the operation of the detection circuit according to the embodiment. In these figures, the vertical axis represents the signal (voltage) and the horizontal axis represents the time. FIGS. 8(a), 8(b), and 8(c) show enlarged portions of FIGS. 7(b), 7(c), and 7(d), respectively.

As shown in FIG. 7(a), when detecting that the human body HB is seated, the control unit 16 first inputs a Hi signal to the base side of the transistor 54. That is, the signal S3 on the base side of the transistor 54 is set to Hi. This turns on the transistor 54, discharges the integrating means 52, and resets the signal S2 of the integrating means 52 to the common potential GND on the secondary side as shown in FIG. 7(d).

After that, as shown in FIG. 7(b), the control unit 16 periodically alternates between inputting a Hi signal and a Lo signal to the switch unit 20. That is, the signal S1 on the input side of the switch unit 20 is periodically alternately set to Hi and Lo. Note that if no overvoltage is detected at the input terminal 15, the output signal S6 of the OR circuit 74 is Hi when the signal S1 is Hi, and is Lo when the signal S1 is Lo.

The first switch 71 and the second switch 72 are turned on when a Hi signal is input, and turned off when a Lo signal is input. That is, the first switch 71 is on when the signal S1 is Hi, and turned off when the signal S1 is Lo. Conversely, the second switch 72 is off when the signal S1 is Hi, and turned on when the signal S1 is Lo. In this way, the capacitance detection means 17 performs a switching operation that periodically alternates between a first state in which the first switch 71 is on and the second switch 72 is off, and a second state in which the first switch 71 is off and the second switch 72 is on, in response to the input from the control unit 16.

In the first state, the detection electrode 12 is conductive with the power supply voltage VCC via the input terminal 15, the protective resistor 42, and the first switch 71. This causes charge to accumulate in the capacitance C1 of the detection electrode 12. In this way, the first state is a state in which charge is accumulated in the capacitance C1 of the detection electrode 12. Figures 7(c) and 8(b) show the signal S100 of the input terminal 15, which corresponds to the potential of the detection electrode 12. For example, as shown in Figure 8(b), the signal S100 is at a predetermined voltage (power supply voltage VCC in this example) immediately before times T1, T3, T5, and T7. In other words, the first state is a state in which the capacitance C1 of the detection electrode 12 is charged to a predetermined voltage.

On the other hand, in the second state, the detection electrode 12 is conductive with the integrating means 52 via the input terminal 15, the protective resistor 42, and the second switch 72. As a result, the charge stored in the capacitance C1 is input to the integrating means 52. In this way, the second state is a state in which the charge stored in the capacitance C1 of the detection electrode 12 is output to the integrating means 52. Therefore, as shown in FIG. 8(b), for example, the signal S100 drops from the predetermined potential between time T1 and time T2, between time T3 and time T4, and between time T5 and time T6. In other words, the second state is a state in which the capacitance C1 of the detection electrode 12 is discharged.

In this way, a pulse signal corresponding to a predetermined voltage is input to the detection electrode 12 by the switching operation of switching the first state and the second state of the switch unit 20 at a predetermined frequency, and the charge accumulated in the capacitance C1 is input to the integrating means 52. The frequency of the pulse signal can be changed according to the frequency of the signal S1. Also, the signal S100 has a dull waveform compared to the signal S1 due to the delay caused by the CR circuit such as the capacitance C1 and the protective resistor 42.

The integrating means 52 stores the charge discharged from the capacitance C1 of the detection electrode 12 in the second state, which is repeated by the above switching operation. Therefore, as shown in FIG. 8(c), for example, the signal S2 output from the integrating means 52 increases in proportion to the number of times the first state and the second state are switched to, i.e., the "number of integrations." For example, like the signal levels at times T1, T3, and T5, the signal S2 increases by a predetermined value each time the capacitance detection means 17 enters the second state.

Electrical circuits generate random noise called white noise, but as the number of integrations increases, the random noise is averaged out and the output of the integration circuit 50 becomes more stable. In other words, as the number of integrations increases, the signal amount increases and the noise decreases, resulting in a high S/N operation for the detection circuit 14.

In this way, the integrating means 52 integrates the charge of the capacitance C1 input at a predetermined frequency in response to the switching operation, and outputs the integrated value to the control unit 16 as the detection result. The control unit 16 A/D converts the integrated value and determines whether or not the human body HB is seated. The capacitance C1 in a state where the human body HB is present (a state where a human body is close to the detection electrode 12) is larger than the capacitance C1 in a state where the human body HB is not present (a state where a human body is not close to the detection electrode 12). Therefore, when switching between the first state and the second state is performed a predetermined number of times at a predetermined cycle, and the charge of the capacitance C1 is integrated as described above, the integrated value (amount of change) in a state where the human body HB is present is larger than the integrated value in a state where the human body HB is not present.

The control unit 16 judges whether or not the human body HB is seated based on the charge accumulated in the integrating means 52 (the result of A/D conversion of the integrated value). More specifically, for example, the control unit 16 sets the signal S2 (in this example, the common potential GND on the secondary side) after resetting the integrating means 52 as a reference value, and treats the amount of change from the reference value of the signal S2 after switching between the first state and the second state a predetermined number of times as an integral value (the result of detection of the electrostatic capacitance). The control unit 16 judges whether or not the human body HB is seated based on this integral value. The number of times (number of pulses) the first state and the second state are switched is, for example, about 1000 times.

The capacitance detection means 17 repeatedly executes the operations shown in Fig. 7(a) to Fig. 7(d) at a predetermined cycle. This causes the control unit 16 to repeatedly determine at a predetermined cycle whether or not the human body HB is seated, and as a result, seating detection can be performed continuously.

Next, an example of noise and false positives will be described.
The inventors of the present application have found that in a conventional capacitance type seating sensor, if the area of the detection electrode is increased, the influence of noise increases, and there is a risk that erroneous detection of the seating state may become more likely.

As mentioned above, there is a method of using a thermal diffusion sheet with a larger area than the heater as the detection electrode 12. The thermal diffusion sheet is strongly thermally coupled to the heater inside the toilet seat. The role of the thermal diffusion sheet is to spread the heat generated by the heater almost evenly over the entire toilet seat. For this reason, the thermal diffusion sheet is provided over a wide area of the toilet seat where a user may sit. Therefore, if the thermal diffusion sheet is used as the detection electrode, it is possible to prevent the user from missing the seat depending on where they sit. In addition, since there is no need to provide a detection electrode separate from the thermal diffusion sheet, it is preferable to use the thermal diffusion sheet as the detection electrode.

However, because the thermal diffusion sheet is strongly thermally coupled to the heater, the electrostatic coupling between the thermal diffusion sheet and the heater is also strong. This means that there is a risk of noise being transmitted from the heater to the thermal diffusion sheet, i.e., from the heater to the detection electrode. One example of this noise is noise from a commercial power supply that is directly connected to the heater.

The area of the thermal diffusion sheet is as large as the seating area of the toilet seat, for example. The large area of the thermal diffusion sheet results in a large detection capacitance. According to experiments conducted by the inventors of the present application, for example, the coupling capacitance between the heater and the thermal diffusion sheet is about 300 pF, which is constantly detected even when the user is not seated. Furthermore, when the user sits down, the human body adds about 100 pF to the detection capacitance, making the total detection capacitance about 400 pF. However, this is only when the user is simply sitting on the toilet seat. If the user places their bare feet on the floor or touches surrounding metal with their hands, the electrical coupling between the human body and the ground will be strengthened, and the detection capacitance will further increase. Therefore, there are cases where the capacitance detection circuit is required to have the performance to detect a capacitance of up to several hundred pF.

And, large-capacity electrostatic detection imposes limitations on the measurement time. An example is given below. First, the detection capacitance is large because the area of the detection electrode is large, and as a result, external noise is easily introduced into the detection electrode. Therefore, as an input protection means for the capacitance detection circuit, a protective resistor can be attached in series with the detection electrode. There are several methods for detecting electrostatic capacitance, and as mentioned above, there is a method in which an AC pulse is applied to the detection electrode and the amount of charge that flows out or in at that time is measured. For example, if the detection electrode has a large area and a large detection capacitance, and a protective resistor is attached to it, the time constant determined by the multiplication of the detection capacitance and the protective resistance becomes large. For example, the pulse width of the AC pulse mentioned above is set to a sufficient time taking this time constant into account.

According to a trial calculation, if the detection capacitance is 400 pF and the protective resistance is 10 kΩ, the time constant is 4 μs. Taking into account the CR transient phenomenon, for example, charging and discharging to about 99% of the final value is possible with 5 times the time constant, so if the Hi/Lo times of the AC pulse are each 20 μs, the AC pulse period will be 40 μs and the frequency will be 25 kHz. It is also possible to improve the accuracy of capacitance measurement by repeatedly outputting AC pulses and measuring the electric charge. For example, if 1000 AC pulses are output for one capacitance measurement, the measurement time will be 40 μs x 1000 times = 40 ms.

A typical capacitance sensor is one that detects touch operations using a fingertip, for example. In this case, the detection capacitance is, for example, about 1 pF, so if calculated in a similar way, the measurement time is 0.1 ms. In this way, with a capacitance-type seating sensor that uses the heat diffusion sheet of the toilet seat as the detection electrode, the measurement time can be orders of magnitude longer than with a typical capacitance sensor.

Here is an example of the "noise from commercial power sources" mentioned above. A typical method of power control is "phase control." This controls the switching element thyristors from off to on and on to off at any phase of the AC power waveform, allowing the load to conduct for any length of time. This control is performed for each half-wave of the AC power supply. During this process, there is a sudden current fluctuation, which generates high-frequency, short-duration clicking noise on the power line. In other words, the noise generated when the thyristors are turned on is superimposed on each half-wave of the power supply waveform. If the frequency of the commercial power supply is 50 Hz, noise occurs every 10 ms.

The capacitance measurement time mentioned above was 40 ms, so if a device that performs phase control is connected to the same power line, noise will be introduced multiple times during one measurement. Noise voltage can be as high as 1 kV, for example, and if such a voltage is introduced into the capacitance detection circuit during measurement, the measurement results will fluctuate significantly, and there is a risk of false detection of the seated state.

For example, one possible method for preventing such false detections is to attach something similar to the aforementioned "capacitive sensor that detects fingertip touch operations" to part of the toilet seat and detect seating over a narrow area, such as the size of a fingertip. In this case, the detection capacitance is small, for example about 1 pF, so the measurement time is short and seating detection can be performed while avoiding noise that occurs in cycles of about 10 ms. For example, it is possible to complete capacitance detection in the time between one noise and the next. However, because the detection area is small, the detection range is limited to a narrow area. Therefore, false detection may occur depending on the user's seated position.

Another method for preventing false positives is to discard the measurement data for a single measurement when noise is detected during measurement. However, if the measurement time is long or noise occurs in short cycles, noise occurs frequently during a single measurement, so most of the measurement data would be discarded, making it impossible to detect seating.

As described above, in a toilet seat having a thermal diffusion sheet, if the thermal diffusion sheet of the toilet seat is used as a detection electrode, the seating detection range can be widened without providing a new detection electrode, and false detection due to seating position can be suppressed. On the other hand, if the detection area (electrode) is increased, the detection capacity increases, the charging and discharging time of the detection electrode becomes longer, and the measurement time becomes longer. If the measurement time becomes longer, the influence of noise on the measurement result may become greater. For example, it becomes difficult to avoid the influence of power supply noise that occurs in a short cycle (for example, noise that occurs at twice the power supply frequency due to phase control). Therefore, it is desirable to suppress false detection due to noise while widening the seating detection area of the toilet seat.

For example, as shown by arrow AR1 in FIG. 6, noise is transmitted from the power supply terminal 30 to the input terminal 15 via the capacitance C2 between the heater 204 and the detection electrode 12. Furthermore, as shown by arrow AR2 in FIG. 6, the noise is transmitted from the input terminal 15 to the common potential GND on the secondary side via the capacitance detection means 17, transmitted to the common potential GND on the primary side via the capacitor 37 of the power supply circuit 18, and then passes through the coil 38 to the earth potential. For example, the capacitor 37 and the coil 38 are on the path of the noise from the detection electrode 12 to the ground, which may affect seating detection.

An example of the effect of noise on seating detection will be described with reference to FIG. 9, FIG. 10(a) to FIG. 10(d), and FIG. 11(a) to FIG. 11(c).
FIG. 9 is a schematic block diagram showing a toilet seat apparatus according to a reference example.
Fig. 9 shows a human body detection sensor 910 provided in a toilet seat device of a reference example. In the human body detection sensor 910 of the reference example, an overvoltage detection means and an off-delay means are not provided. In addition, the OR circuit 74 is not provided. Other than this, the configuration of the toilet seat device of the reference example is the same as that of the toilet seat device described with reference to Fig. 6 etc. In the reference example as well, a thermal diffusion sheet of a heater is used for the detection electrode.

Figures 10(a) to 10(d) and 11(a) to 11(c) are graphs that show a schematic example of the operation of a detection circuit according to a reference example. These figures show the case where an overvoltage occurs at the input terminal during seating detection by the human body detection sensor 910 shown in Figure 9. In these figures, the vertical axis represents the signal (voltage) and the horizontal axis represents time. Figures 11(a), 11(b), and 11(c) show enlarged portions of Figures 10(b), 10(c), and 10(d), respectively.

As shown in FIG. 10(b), a pulse signal is sent to the detection capacitance by alternately turning on and off the two switches. As a result, the detection capacitance is repeatedly charged and discharged, as shown in the input terminal waveform in FIG. 10(c), and the output potential of the integrating means rises, as shown in FIG. 10(d).

During the integral operation, noise may occur, causing the voltage at the input terminal to fluctuate significantly, as shown in FIG. 10(c). For example, as shown between time T15 and time T17 in FIG. 11(b), when the input terminal is in a state (second state) where it is conductive with the integral means via the protective resistor and the second switch, noise that causes large oscillations in the voltage at the input terminal occurs. If the capacitance detection means is in the second state when an overvoltage (noise) occurs at the input terminal, charge caused by the noise is accumulated in the integral means, and this charge causes an error in the detection result (integral value). This may result in erroneous detection of the human body.

For example, the peak value of momentary noise (e.g., one pulse at time T16 in Figure 11 (b)) is about 1 kV, and the pulse width is about 1 μs. The peak value can be suppressed to a certain voltage by the varistor at the input terminal. Even so, depending on the selection of the varistor, the peak value can become several tens of volts or more. The momentary noise enters the heat diffusion sheet from the heater via capacitive coupling. In other words, the noise at the input terminal becomes an AC signal via the capacitor, so the noise enters both positive and negative.

The energy of the momentary noise passes through the circuit of the toilet seat device and escapes to the ground. At that time, the voltage of the input terminal oscillates due to the capacitance component of the capacitor of the power circuit of the toilet seat device and the induction component of the coil. For example, when observing the waveform in detail, such as between time T16 and time T17 in FIG. 11(b), after the momentary noise is introduced, the secondary side where the detection circuit is located fluctuates with a time delay. Since the secondary circuit has a resistive component coupled with the ground due to loads such as valves and nozzles (not shown), the oscillation is attenuated and disappears. Depending on the state of the toilet seat device, the time is, for example, several μs to several tens of μs. This time is longer than the time during which the momentary noise is applied (for example, about 1 μs). Therefore, even if the noise voltage is relatively suppressed by the varistor connected to the input terminal, the error in the detection result (integral value) becomes large because it corresponds to the product of the oscillating voltage and time, as shown in FIG. 10(d) and FIG. 11(c).

As explained above, even if the noise is momentary, if the noise voltage is large, the error in the integrated value will be large. Furthermore, even if the noise voltage is not extremely large, if it takes a long time for the voltage to decay, the integrated error will be large.

In response to this, in the embodiment, as described above, the overvoltage detection means 11 is provided. When the overvoltage detection means 11 detects an overvoltage, the capacitance detection means 17 temporarily stops detecting the capacitance and then resumes it. This makes it possible to suppress false detections caused by noise while widening the seat occupancy detection area of the toilet seat. An example of the overvoltage detection means 11, off-delay means 19, and detection operation will be described with reference to Figures 12, 13(a)-(g), and 14(a)-(f).

FIG. 12 is a block diagram illustrating a specific example of a human body detection sensor according to the embodiment.
The detection circuit 14 shown in Fig. 12 is an example of the detection circuit 14 of the human body detection sensor 10 described with reference to Fig. 6. As shown in Fig. 12, the overvoltage detection means 11 has diodes 80 and 89, Zener diodes 81 and 82, transistors 83 and 84, and resistors 85, 86, 87, and 88.

The anode side of the diode 80 is electrically connected to the input terminal 15, and the cathode side of the diode 80 is electrically connected to the cathode side of the Zener diode 81. The anode side of the Zener diode 81 is electrically connected to the base of the transistor 84 via a resistor 87. In the transistor 84, the emitter is connected to the common potential GND on the secondary side, and a resistor 88 is connected between the emitter and the base. The collector of the transistor 84 is electrically connected to the off-delay means 19.

The cathode side of the diode 89 is electrically connected to the input terminal 15, and the anode side of the diode 89 is electrically connected to the anode side of the Zener diode 82. The cathode side of the Zener diode 82 is electrically connected to the base of the transistor 83 via a resistor 86. In the transistor 83, the emitter is connected to the power supply voltage VCC, and a resistor 85 is connected between the emitter and the base. The collector of the transistor 83 is electrically connected to the base of the transistor 84 via a resistor 87.

The off-delay means 19 has a resistor 91, a capacitor 93, and an inverter circuit 95. One end of the resistor 91 is electrically connected to the power supply voltage VCC, and the other end of the resistor 91 is connected to the secondary common potential GND via the capacitor 93. The collector of the transistor 84 is electrically connected between the resistor 91 and the capacitor 93. As a result, the output signal of the overvoltage detection means 11 is input between the resistor 91 and the capacitor 93. The input side of the inverter circuit 95 is electrically connected between the resistor 91 and the capacitor 93, and the output side of the inverter circuit 95 is electrically connected to the input side of the OR circuit 74.

For example, the Zener voltage Vz1 of the Zener diode 81 and the Zener voltage Vz2 of the Zener diode 82 are each selected to be smaller than the protection voltage Vp of the varistor 44. Note that in this embodiment, the varistor 44 and the protection resistor 42 do not necessarily have to be provided, and are provided as necessary.

Figures 13(a) to 13(g) and 14(a) to 14(f) are graphs that show an example of the operation of the detection circuit according to the embodiment. These figures show the case where an overvoltage (noise) occurs at the input terminal 15 during seating detection by the human body detection sensor 10 shown in Figure 12. In these figures, the vertical axis shows the signal (voltage) and the horizontal axis shows the time. Figures 14(a), 14(b), 14(c), 14(d), 14(e), and 14(f) show enlarged portions of Figures 13(b), 13(c), 13(d), 13(e), 13(f), and 13(g), respectively.

As shown in FIG. 13(a), when detecting that the human body HB is seated, the control unit 16 first sets the signal S3 on the base side of the transistor 54 to Hi. This resets the signal of the integrating means 52. Then, as shown in FIG. 13(b), a switching operation is performed in which the first state and the second state are periodically alternately repeated. Then, the charging and discharging of the capacitance C1 are alternately repeated, and the waveform of the input terminal 15 oscillates, as shown in FIG. 13(c). Accordingly, the charge discharged from the capacitance C1 is integrated in the integrating means, and as shown in FIG. 13(g), the change in the signal S2 from the reference value becomes large.

In such an integral operation, the voltage at the input terminal may fluctuate significantly, as shown in FIG. 13(c). For example, as shown in FIG. 14(b), momentary noise is introduced into input terminal 15 at time T26. Then, between time T26 and time T27, the noise at input terminal 15 oscillates and decays.

For example, when a positive overvoltage occurs at the input terminal 15, as shown in FIG. 13(d) and FIG. 14(c), the signal S4 on the base side of the transistor 84 changes from Lo to Hi. For example, a pulse occurs in the signal S4. In this way, the overvoltage detection means 11 detects an overvoltage at the input terminal 15. The overvoltage detection in the overvoltage detection means 11 operates when the overvoltage exceeds the Zener voltage of the Zener diode. More specifically, in the case of a positive overvoltage, an overvoltage is detected when the voltage of the input terminal 15 exceeds a predetermined value (Vf1+Vz1+Vbe1). Here, Vf1 is the forward voltage of the diode 80, Vz1 is the Zener voltage of the Zener diode 81, and Vbe1 is the base-emitter voltage of the transistor 84. In the case of a negative overvoltage, an overvoltage is detected when the voltage of the input terminal 15 falls below a predetermined value (VCC-Vbe2-Vz2-Vf2). Here, VCC is the power supply voltage, Vbe2 is the base-emitter voltage of transistor 83, Vz2 is the Zener voltage of Zener diode 82, and Vf2 is the forward voltage of diode 89. Note that the predetermined value (overvoltage) detected by overvoltage detection means 11 can be appropriately determined so as to suppress erroneous detection, taking into account the magnitude of error that noise can cause in the detection result.

When the overvoltage detection means 11 detects a positive or negative overvoltage, the capacitor 93 of the off-delay means 19 is discharged. This causes the voltage on the input side of the inverter circuit 95 to fluctuate, and as shown in Figures 13(e) and 14(d), the signal S5 on the output side of the inverter circuit 95 goes from Lo to Hi. For example, a pulse is generated in the signal S5. The width of this pulse corresponds to the CR time constant of the capacitor 93 and resistor 91.

The output of the off-delay means 19, i.e., signal S5, is input to the OR circuit 74. Therefore, when signal S5 is Hi, the output of the OR circuit 74 (signal S6) becomes Hi regardless of the input (signal S1) from the control unit 16. This causes the capacitance detection means 17 to enter the first state in which the first switch 71 is on and the second switch 72 is off. In other words, when an overvoltage is detected, the capacitance detection means 17 is forced to enter the first state.

This first state continues while signal S5 is Hi. In the first state, since second switch 72 is off, no charge is integrated in integrating means 52, and noise at input terminal 15 is not integrated either. Therefore, as shown in FIG. 14(f), for example, signal S2 does not change between time T26 and time T27.

In addition, because the first switch 71 is on, the input terminal 15 is connected to the power supply voltage VCC, so noise is more likely to escape to a power supply with low impedance. In other words, in order to prevent noise from being integrated, it is sufficient to simply forcibly turn off the second switch 72 when an overvoltage is detected. When such control is performed, a state in which both the first switch 71 and the second switch 72 are off (i.e., the third state) may occur, but since the first switch 71 is on in the first state, noise is more likely to attenuate quickly compared to when both are off.

After that, when the signal S5 changes from Hi to Lo again, the output of the OR circuit 74 (signal S6) will again periodically repeat Hi and Lo in response to the signal S1. In other words, the capacitance detection means 17 resumes the switching operation based on the input from the control unit 16.

Thus, in this embodiment, the integration operation is paused at the moment when noise is applied to input terminal 15 and for a predetermined time immediately thereafter. This predetermined time can be adjusted, for example, by the pulse width of signal S5. As shown in Figures 14(c) and 14(d), the pulse of signal S5 is longer than the pulse of signal S4. For example, the pulse width of signal S5 is determined so that signal S5 is Hi from time T26 in Figure 14(b) until the noise at input terminal 15 oscillates and attenuates to a small level. For example, the pulse width of signal S5 is 10 μs or more and 100 μs or less.

Even if the noise oscillates in a damped manner due to the capacitive or inductive components of the power supply circuit, the off-delay means 19 can wait for the integration operation to resume until the noise becomes small. For example, by temporarily suspending the switching operation, the duration of the first state becomes longer than the duration of the periodic first state caused by the switching operation. That is, for example, in the example of FIG. 14(e), the duration of the first state from time T26 to time T28 is longer than the duration of the first state from time T24 to time T25. In the embodiment, the integration is suspended at the moment when the noise is introduced and for the voltage fluctuations thereafter, so that it is possible to prevent the noise from being integrated and causing a large error.

At this time, depending on the timing of the noise and the signal S1, the original signal (the charge on the capacitance C1) may not be integrated. In that case, the integral value for one switching operation (the amount of change in the signal S2 due to one charge/discharge of the capacitance C1) will be an error, but if one measured capacitance is integrated over, for example, 1,000 switching operations, the effect is only 0.1%. In the human body detection sensor of the reference example in FIG. 9, the error due to noise may be several percent, so by interrupting the integration operation and not integrating the noise as in the embodiment, it is possible to prevent large errors from occurring. Therefore, it is possible to prevent false detection of the human body due to noise.

As described above, in the embodiment, when the overvoltage detection means 11 detects an overvoltage at the input terminal 15, the capacitance detection means 17 suspends the switching operation of alternately repeating the first state and the second state, and sets the first switch 71 and the second switch 72 to the first state. After that, the capacitance detection means 17 resumes the switching operation.
According to this configuration, when an overvoltage occurs at the input terminal 15 due to noise from a power supply or the like, the capacitance detection means 17 temporarily suspends the switching operation and enters the first state, which interrupts the integration (accumulation of charge) of the integrating means, thereby making it possible to prevent a large error in the integral value caused by noise. Therefore, it is possible to prevent false detection caused by noise.

Furthermore, when the overvoltage detection means 11 detects an overvoltage, the off-delay means 19 causes the capacitance detection means 17 to continue the first state for a predetermined time.
According to this configuration, the first state continues, and thus the interruption of integration by the integrating means continues, so that erroneous detection caused by noise can be further suppressed.
For example, application of an overvoltage (noise) may cause a potential fluctuation in the reference voltage (secondary GND) of the circuit of the toilet seat device. At this time, for example, due to the inclusion of a capacitive component or an inductive component in the circuit of the toilet seat device, the state in which the potential fluctuation occurs in the input terminal may continue. This potential fluctuation may cause a large error in the capacitance detection. That is, since the circuit of the toilet seat device has a capacitive component and an inductive component, even if the applied overvoltage is instantaneous, the potential fluctuation due to the noise does not immediately become zero, and it takes a certain amount of time to converge. In contrast, according to the embodiment, the off-delay means continues the first state for a predetermined time, so that the interruption of the integration by the integrating means continues, and the time until the potential fluctuation due to the noise converges is secured, and it is possible to suppress the occurrence of a large error due to the noise in the integral value. Therefore, it is possible to further suppress the occurrence of erroneous detection due to noise.

As already mentioned, when a thermal diffusion sheet is used for the detection electrode 12, the area of the detection electrode 12 is large, so that the seating detection range is widened and erroneous detection due to seating position can be suppressed. On the other hand, when the detection electrode 12 is large, the capacitance of the detection electrode 12 is large, so that the charging and discharging time is long and the time required for capacitance detection is long. For this reason, the frequency of overvoltage occurring at the input terminal 15 due to noise (such as short-period noise on the power line) during capacitance detection increases. Even in such a case, erroneous detection due to noise can be suppressed by the capacitance detection means 17 temporarily suspending the detection of capacitance. Therefore, it is possible to suppress erroneous detection due to noise while widening the seating detection range.

In this embodiment, the noise detected by the overvoltage detection means is not necessarily limited to noise caused by the power supply as described above, but may be any noise that generates an overvoltage at the input terminal 15.

The detection electrode 12 is not limited to the heat diffusion sheet of the heater 204, but may be provided separately from the heat diffusion sheet. The heat diffusion sheet is, for example, a metal foil arranged over almost the entire inner surface 130b of the toilet seat 114, and diffuses the heat of the heater 204 to the inner surface 130b. In this case, the detection electrode 12 can be arranged on the inner surface 130b of the toilet seat 114. For example, the detection electrode 12 may be overlapped on the heat diffusion sheet or under the heat diffusion sheet. In either arrangement, the heat diffusion sheet, which is a metal, is electrostatically bonded to the human body and also to the detection electrode 12, so that it is possible to measure the electrostatic capacitance with the human body from the detection electrode 12 via the heat diffusion sheet. Alternatively, only the part of the heat diffusion sheet that overlaps with the detection electrode 12 may be cut out to eliminate the electrostatic effect of the heat diffusion sheet. In this case, the area of the detection electrode 12 may be smaller than the area of the heat diffusion sheet 250. Also, the arrangement of the detection electrode 12 does not necessarily have to be on the inner surface 130b. The detection electrode 12 may be positioned anywhere that can properly detect a human body sitting on the toilet seat 114.

The human body detection sensor according to the embodiment is not limited to the self-capacitance type as described above, but may be a mutual capacitance type. In a mutual capacitance type capacitive sensor, the detection electrode has a transmitting electrode and a receiving electrode. The detection circuit is electrically connected to the transmitting electrode and the receiving electrode. Since the electric field around the detection electrode changes depending on the presence or absence of a human body, the amount of charge received by the receiving electrode changes when a pulse signal of a predetermined frequency is transmitted to the transmitting electrode. The detection circuit measures the amount of charge received by the receiving electrode as the capacitance of the detection electrode. The presence or absence of a human body can be determined from the change in capacitance.

FIG. 15 is a block diagram that illustrates a schematic diagram of another toilet seat device according to an embodiment.
15 has a detection circuit 14b instead of the above-mentioned detection circuit 14. As described below, the toilet seat device 111 differs from the above-mentioned toilet seat device 110 in the switching operation by the capacitance detection means 17b of the detection circuit 14b and the operation of the control unit 16. Other than this, the same explanation as for the toilet seat device 110 can be applied to the explanation of the configuration of the toilet seat device 111.

Detection circuit 14b does not include overvoltage detection means 11 and off-delay means 19. Furthermore, detection circuit 14b includes capacitance detection means 17b instead of capacitance detection means 17. Unlike capacitance detection means 17, capacitance detection means 17b does not include OR circuit 74. In capacitance detection means 17b, signal S1 becomes an input signal to switch 71 and inverter circuit 73. Other than this, the same explanation as for detection circuit 14 can be applied to the explanation of the configuration of detection circuit 14b.

That is, the toilet seat device 111 has a toilet seat 114, a detection electrode 12, a capacitance detection means 17b, and a control unit 16. The detection electrode 12 changes its capacitance C1 in response to a human body sitting on the toilet seat 114. The capacitance detection means 17b is electrically connected to the detection electrode 12, and detects the change in capacitance C1 of the detection electrode 12. The control unit 16 determines whether or not a human body is sitting on the toilet seat based on the detection result (integral value) of the capacitance detection means. Note that, like the detection circuit 14, the detection circuit 14b also has an overvoltage detection means 11, an off-delay means 19, and an OR circuit 74, and the detection of the capacitance may be temporarily stopped or resumed.

The capacitance detection means 17b has a first switch 71, a second switch 72, and an integrating means 52. As described above, the first and second switches 71 and 72 are analog switches including elements such as transistors. The first switch 71 connects a predetermined voltage (power supply voltage VCC) to the detection electrode 12. By turning on the first switch 71, the predetermined voltage is connected to the detection electrode 12, and by turning off the first switch 71, the predetermined voltage is not connected to the detection electrode 12. The second switch 72 connects the integrating means 52 to the detection electrode 12. By turning on the second switch 72, the integrating means 52 is connected to the detection electrode 12, and by turning off the second switch 72, the integrating means 52 is not connected to the detection electrode 12.

The capacitance detection means 17b detects a change in the capacitance C1 of the detection electrode 12 by a switching operation. The switching operation is an operation of alternately repeating a first state (charging) and a second state (discharging) at a predetermined frequency and transmitting a pulse signal of a predetermined frequency to the detection electrode 12. As described above, in the first state, the first switch 71 is on and the second switch 72 is off. In the first state, a pulse signal is transmitted to the detection electrode 12 to set the detection electrode 12 to a predetermined voltage, and the detection capacitance (capacitance C1 and capacitance C2) is charged. In the second state, the first switch 71 is off and the second switch 72 is on. In the second state, the detection capacitance is discharged. The integration means 52 stores the charge discharged from the detection electrode 12.

The capacitance detection means 17b can change the frequency of the switching operation that repeats the first state and the second state to a plurality of different frequencies. In other words, the capacitance detection means 17b can transmit a plurality of pulse signals with different frequencies to the detection electrode 12. The frequency of the switching operation, i.e., the frequency of the pulse signal, is the frequency of the signal S1 and is controlled by the control unit 16.

For example, the capacitance detection means 17b can switch the frequency of the switching operation between a first frequency and a second frequency different from the first frequency. In other words, there are a first switching operation at a first frequency and a second switching operation at a second frequency. The first switching operation repeats the first and second states at the first frequency by the signal S1 at the first frequency, and transmits a pulse signal at the first frequency. The first switching operation repeats the first and second states a predetermined number of times at the first frequency, i.e., transmits a predetermined number of pulse signals at the first frequency, and detects a change in the capacitance C1. Similarly, the second switching operation repeats the first and second states a predetermined number of times at the second frequency, i.e., transmits a predetermined number of pulse signals at the second frequency, and detects a change in the capacitance C1. Note that even if the frequency of the signal S1 is different, the charge accumulated in the integration means 52 will be the same as long as the predetermined number of repetitions is the same. In other words, even if the frequency of the signal S1 is changed, there is no effect on the detection result of the capacitance in principle.

For example, the capacitance detection means 17b changes the frequency of the switching operation at a predetermined timing or at random timing. For example, the capacitance detection means 17b may alternately repeat a first switching operation and a second switching operation. However, this is not limited to this, and the frequency of the switching operation can be changed at an appropriate timing. Furthermore, the frequency of the switching operation may be three or more frequencies, not just two frequencies, the first frequency and the second frequency.

16(a), 16(b), 17(a) and 17(b) are graphs that diagrammatically show the switching operation according to the embodiment.
In these figures, the vertical axis represents the signal (voltage) and the horizontal axis represents time. Figures 16(a) and 16(b) illustrate a first switching operation at a first frequency by the capacitance detection means 17b. Figures 17(a) and 17(b) illustrate a second switching operation at a second frequency by the capacitance detection means 17b.

Figure 16(a) shows signal S1 at the first frequency, and Figure 16(b) shows signal S100 when signal S1 changes as in Figure 16(a). Similarly, Figure 17(a) shows signal S1 at the second frequency, and Figure 17(b) shows signal S100 when signal S1 changes as in Figure 17(a). When signal S1 is Hi, capacitance detection means 17b is in the first state (charging), and when signal S1 is Lo, capacitance detection means 17b is in the second state (discharging).

In Figures 16(b) and 17(b), the solid line waveform is the waveform when damping vibration, which will be described later, occurs, and the dotted line waveform is the waveform when it is assumed that the damping vibration does not occur. In other words, the dotted line waveform is a waveform in which the effects of damping vibration, which will be described later, have been removed from the solid line waveform, and corresponds to, for example, an ideal waveform in terms of design. Note that, for the sake of convenience, this damping vibration has been omitted in the explanations and graphs (e.g., Figures 8(b), 11(b), 14(b), etc.) relating to the toilet seat device 110 according to the embodiment and the toilet seat device according to the reference example described above.

As shown in FIG. 16(a), for example, at time T31, the capacitance detection means 17b switches from the second state to the first state. Then, the first state continues from time T31 to time T32. At time T32, the capacitance detection means 17b switches from the first state to the second state. Then, the second state continues from time T32 to time T33. In the first switching operation, the same operation from time T31 to time T33 is periodically repeated.

As shown in FIG. 17(a), for example, at time T41, the capacitance detection means 17b switches from the second state to the first state. Then, the first state continues from time T41 to time T42. At time T42, the capacitance detection means 17b switches from the first state to the second state. Then, the second state continues from time T42 to time T43. In the second switching operation, the same operation from time T41 to time T43 is periodically repeated.

As described above, the first frequency and the second frequency are different from each other. That is, the period P1 of the first switching operation (e.g., from time T31 to time T33) is different from the period P2 of the second switching operation (e.g., from time T41 to time T43). The period P2 is longer than the period P1.

When changing the frequency of the switching operation, the capacitance detection means 17b makes the time of one of the first and second states variable and fixes the time of the other of the first and second states. That is, the duration of one of the first and second states (hereinafter sometimes referred to as the "variable side") in the first switching operation is different from the duration of the variable side in the second switching operation, and the duration of the other of the first and second states (hereinafter sometimes referred to as the "fixed side") in the first switching operation is the same as the duration of the fixed side in the second switching operation.

For example, in this example, the time of the first state (charging) is variable, and the time of the second state (discharging) is fixed. More specifically, the duration P11 of the first state in the first switching operation shown in FIG. 16(a) (e.g., from time T31 to time T32) is shorter than the duration P21 of the first state in the second switching operation shown in FIG. 17(a) (e.g., from time T41 to time T42). On the other hand, the duration P12 of the second state in the first switching operation shown in FIG. 16(a) (e.g., from time T32 to time T33) is the same as the duration P22 of the second state in the second switching operation shown in FIG. 17(a) (e.g., from time T42 to time T43).

In addition, in an embodiment, when changing the frequency of the switching operation, the time of the first state may be fixed and the time of the second state may be variable. Furthermore, "fixed" time does not only mean that it does not change strictly, but also that it may change slightly within the range of variation (for example, variation due to characteristic changes over time of elements that make up the circuit).

By changing the frequency of the switching operation, it is possible to reduce errors in the capacitance detection result caused by noise of a specific frequency. On the other hand, for example, as shown in FIG. 16(b) and FIG. 17(b), when the first state and the second state are switched in the switching operation, the potential of the detection electrode may oscillate. For example, as described later, the circuit through which the current flows to charge and discharge the detection capacitance in the first state and the second state includes LCRs (inductors, capacitors, and resistors) connected in series with each other. Therefore, when the first state and the second state are switched, the potential of the detection electrode 12 may oscillate with damping according to the LCR. This damping oscillation occurs in the same way in both the first state and the second state. Here, if the frequency of the switching operation is changed, the effect of the vibration of the potential of the detection electrode on the capacitance detection result changes, and as a result, there is a risk of false detection of the presence or absence of a human body. In contrast, when the frequency of the switching operation is changed, the time of the other of the first state and the second state is fixed, so that the change in the effect of the vibration of the potential of the detection electrode due to the change in frequency can be reduced. This makes it possible to suppress the occurrence of false detection. This will be explained below with reference to specific examples.

The detection electrode 12 is affected by noise present in the measurement environment. Typical noise is called white noise, and is random noise that contains many frequency components. If the charge and discharge operation, i.e., the integration operation, is repeated at a constant frequency, the random noise and the timing of the integration operation will vary and will not be limited to a specific pattern, so the effect of the noise will be averaged out by multiple integration operations, and ultimately (if the number of integrations is large) the effect of the noise will be essentially zero.

However, there are cases where noise has a specific frequency. For example, there are things that emit noise of a specific frequency depending on their operation, such as switching power supplies, motors, and wireless devices. When the noise frequency and the charge/discharge frequency are synchronized, in other words, when there is an integer ratio relationship, the effect of the noise on the charge/discharge operation will be the same every time, and the effect of the noise will accumulate with repeated charging and discharging, causing a large error in the detection result (integral value), resulting in a false capacitance detection.

In such cases, one possible measure is to change the charge/discharge frequency (the frequency of the switching operation) so that the charge/discharge operation is not synchronized with the noise. Conditions for changing the charge/discharge frequency include randomly changing the charge/discharge frequency during the normal measurement stage (frequency burst), or measuring at a different charge/discharge frequency when the seated/not seated determination changes and checking the results.

Meanwhile, in this example, the charging and discharging operation of the capacitance detection circuit is performed on the path DL shown by the dashed line in Figure 15. The capacitance detection means 17b is on the secondary side, and the detection electrode 12 is electrostatically coupled to the heater 204, meaning that before the human body sits down, there is already a large capacitance C2 in the non-seated state, and the capacitance detection means 17b charges and discharges this capacitance C2. Since charging and discharging are electrical operations, they form a closed circuit, and the path from the capacitance detection means 17b through the detection electrode 12, heater 204, power line 30a (including 30b when the switching element 220 is on), line filter coil 38, and capacitor 37 between the primary and secondary, and back to the secondary GND, forms the charging and discharging circuit.

In this closed circuit, electrical elements such as a protective resistor 42, a coupling capacitance (capacitance C2) between the detection electrode 12 and the heater 204, a coil 38, and a capacitor 37 between the primary and secondary are connected in series. Here, the capacitor 37 between the primary and secondary is sufficiently larger than the capacitance C2 (for example, 10 times or more), so the capacitance (series capacitance) of the charge/discharge path is approximately equal to the capacitance C2. In other words, the capacitor 37 between the primary and secondary can be considered to be approximately short-circuited and excluded. Then, R of the protective resistor 42, C of the coupling capacitance (capacitance C2), and L of the line filter (coil 38) are in series, forming a circuit in which damped oscillation of LCR series resonance occurs. The charge/discharge operation is an operation in which the power supply voltage is alternately output as a pulse to the detection electrode 12 during charging, and an integrated voltage is alternately output as a pulse to the detection electrode 12 during discharging, so that the potential change causes damped oscillation of LCR resonance in the closed circuit of the charge/discharge operation. This oscillation becomes an error factor in the integral value of the capacitance detection means.

In this way, the circuit that passes current through the detection electrode 12 when charging and discharging includes an LCR series circuit. That is, the circuit through which the current that charges the detection capacitance in the first state and the current that discharges from the detection capacitance in the second state flows includes an inductor, a capacitor, and a resistor connected in series with each other. Therefore, switching from the first state to the second state, or switching from the second state to the first state, may cause damped oscillation in the potential of the detection electrode 12.

In the embodiment, the charge/discharge path of the detection electrode 12 is not necessarily limited to the example in FIG. 15. The LCR connected to the charge/discharge path does not necessarily have to be the coil 38 of the line filter, the coupling capacitance (capacitance C2) of the detection electrode 12, and the protective resistor 42. In addition, the toilet seat device may have not only a toilet seat heating function but also a sanitary cleaning function, etc., and an element of an electrical load (motor, etc.) for this purpose may be added as a new LCR component. Therefore, the charge/discharge path of the detection electrode 12 includes a resistive component, an inductive component, and a capacitive component of the entire toilet seat device, and the potential of the detection electrode 12 undergoes damped oscillation at least during charging and discharging.

A specific example in which such potential oscillation becomes an error factor will be described.
In detecting capacitance, the detection electrode 12 is charged with a constant voltage V, and a charge (Q = C x V) proportional to the capacitance C2 of the detection electrode 12 is accumulated, which is then discharged and integrated to convert into an electrical signal. For this reason, if the charging voltage V is not constant, for example, this method does not work in principle, and fluctuations in the charging voltage V may result in detection errors in the capacitance detection means. The damping oscillation of the LCR changes the V portion of Q = C x V, and therefore causes detection errors in capacitance both during charging and discharging.

18A and 18B are graphs that diagrammatically show an example of the operation of the detection circuit.
Figures 18(a) and 18(b) show waveforms in which damped oscillation due to LCR occurs in the waveforms shown in Figures 8(a) and 8(b), with the time axis further enlarged. In other words, the waveforms during charging and discharging may actually become like this.

As shown in FIG. 18(a), at time T51, the capacitance detection means switches from the second state to the first state. The first state continues from time T51 to time T52. At time T52, the capacitance detection means switches from the first state to the second state. The second state continues from time T52 to time T53.

In FIG. 18(b), if the voltage at the end of charging (e.g., time T52) deviates from the original charging voltage (power supply voltage VCC) due to damped oscillation, this voltage difference ΔV becomes a cause of error. In the case of FIG. 18(b), since the charging end voltage is lower than the power supply voltage VCC, the charging voltage of the detection electrode 12 becomes lower, the charge charged decreases, and the charge integrated during discharge also decreases, resulting in a smaller capacitance detection result. In other words, the oscillation component at the end of charging becomes a detection error.

Similarly, the vibration component is integrated during discharge. This is affected by the area IS during integration (voltage difference from the ideal waveform x time). If the sum of the areas IS is not zero for the ideal waveform as designed, an error will occur. As described above, the vibration component during integration becomes the detection error from the ideal value (when there is no vibration). Note that the ideal waveform and ideal value are the waveform and voltage value when there is no damped vibration due to the LCR. The area IS is the integral value obtained by integrating over time the difference between the waveform when there is no damped vibration (dashed line) and the waveform when there is damped vibration (solid line). During integration during discharge, the area IS becomes a factor of error. In other words, the integral value of the vibration component during the discharge period becomes the detection error.

The seating sensor (control unit 16) determines that a person is seated when the capacitance C1 between the detection electrode 12 and the human body HB is added to the capacitance C2 between the detection electrode 12 and the heater 204, and the integral value changes. In other words, it is sufficient to determine that the detection capacitance increases relatively based on the capacitance C2, so even if there is a detection error, as long as it is constant, the effect on seating detection (seating determination) can be suppressed. In the first place, from the perspective of the purpose of detecting a human body being seated, the capacitance C2 itself is a fixed detection error.

Therefore, if the charge/discharge time is fixed, the effect of damping vibration due to the LCR is fixed, and by treating this as a fixed offset component of the detection capacitance, seating determination can be performed.

If the charge/discharge time is constant, the effect of the damping vibration caused by the LCR can be fixed, but in order to avoid the effect of noise at the specific frequency mentioned above, the charge/discharge time, i.e., the charge/discharge frequency, may be changed. This changes the effect of the damping vibration caused by the LCR, causing a difference in the capacitance detection results, which may result in an erroneous detection of the seating state.

19A and 19B are graphs illustrating an example of the operation of the detection circuit.
Figures 19(a) and 19(b) show the case where the charge/discharge time is shortened in Figures 18(a) and 18(b). That is, Figures 19(a) and 19(b) show the case where the charge/discharge frequency (frequency of switching operation) is increased for the purpose of, for example, noise reduction.

As shown in FIG. 19(a), at time T54, the capacitance detection means switches from the second state to the first state. The first state continues from time T54 to time T55. At time T55, the capacitance detection means switches from the first state to the second state. The second state continues from time T55 to time T56.

In the examples of Figures 18 and 19, when the charge/discharge frequency changes, both the time in the first state (charging time) and the time in the second state (discharging time) are variable. That is, the charging time in Figure 19(a) (from time T54 to time T55) is shorter than the charging time in Figure 18(a) (from time T51 to time T52). Also, the discharging time in Figure 19(a) (from time T55 to time T56) is shorter than the discharging time in Figure 18(a) (from time T52 to time T53).

As shown in FIG. 19(b), charging and discharging are switched in the middle of the damped oscillation by the LCR, so the voltage at the end of charging and the integral amount during discharging change depending on the timing. In other words, the voltage difference ΔV at the end of charging in FIG. 19(b) is different from the voltage difference ΔV at the end of charging in FIG. 18(b), and the sum of the areas IS during discharging in FIG. 19(b) is different from the sum of the areas IS during discharging in FIG. 18(b). Therefore, simply changing the charging and discharging frequency causes differences in the capacitance detection results. As a result, there is a risk of erroneous detection of the seated state.

Since it is the damping oscillation that is affected, a method of waiting until the damping oscillation converges before carrying out the charge/discharge operation may be considered.
20A and 20B are graphs illustrating another example of the operation of the detection circuit.
20(a) and 20(b) show the case where the charge/discharge time is extended in comparison with FIGS. 18(a) and 18(b).

As shown in FIG. 20(a), at time T57, the capacitance detection means switches from the second state to the first state. The first state continues from time T57 to time T58. At time T58, the capacitance detection means switches from the first state to the second state. The second state continues from time T58 to time T59.

The charging time in Fig. 20(a) (from time T57 to time T58) is longer than the charging time in Fig. 18(a). Therefore, the voltage difference ΔV at the end of charging in Fig. 20(b) is smaller than the voltage difference ΔV at the end of charging in Fig. 18(b). For example, the voltage difference ΔV at the end of charging in Fig. 20(b) is sufficiently attenuated, and can be considered to be substantially zero.
Also, the discharge time in Fig. 20(a) (from time T58 to time T59) is longer than the discharge time in Fig. 18(a). Therefore, the vibration is sufficiently attenuated at the timing when the discharge time ends (time T59), and the sum of the areas IS during discharge in Fig. 20(b) is not easily affected by the discharge time and is stable. On the other hand, the sum of the areas IS during discharge in Fig. 18(b) is easily affected by the integration time and is not stable. Therefore, for example, the sum of the areas IS during discharge in Fig. 20(b) can be regarded as a substantially fixed value, and the error can be regarded as zero.

In this way, by lengthening the charge/discharge time and converging the damping vibration, it is possible to suppress errors caused by damping vibration. However, in this example, in order to change the charge/discharge frequency, the charge/discharge time must be made even longer. In this case, the detection time becomes longer, and there is a risk that the seating determination will be delayed.

In contrast, in the embodiment, as described above with reference to Figs. 16(a) and 17(a), when changing the charge/discharge frequency, one of the charge time and the discharge time is made variable and the other is fixed. In other words, when changing the frequency of the switching operation, one of the time of the first state and the second state is made variable and the other time of the first state and the second state is made fixed. As a result, the only operation affected by the change in damping oscillation is either charging or discharging, so the effect of damping oscillation can be reduced. Therefore, false detection of the human body can be further suppressed.

In the embodiment, as shown in FIG. 16(a) and FIG. 17(a), the variable side of the first state and the second state is longer than the fixed side of the first state and the second state. For example, in FIG. 16(a) and FIG. 17(a), the time of the variable side is longer than the time for the oscillation of the potential of the detection electrode 12 to attenuate when the first state and the second state are switched. On the other hand, the time of the fixed side is shorter than the time for the oscillation of the potential of the detection electrode 12 to attenuate when the first state and the second state are switched. Note that the time for the oscillation of the potential of the detection electrode to attenuate is, for example, two or more periods, preferably three or more periods, of the attenuated oscillation when the capacitance detection means 17b is switched from the fixed side to the variable side.

By making the time on the variable side longer than the vibration decay time, the effect of the vibration of the potential of the detection electrode 12 on the variable side on the capacitance detection result can be reduced. Therefore, the change in the effect of the vibration of the potential of the detection electrode 12 caused by changing the charge/discharge frequency can be reduced. For example, in Figures 16(b) and 17(b), the charging time is long, and the vibration has almost converged at the end of charging (e.g., time T32 and time T42), and the charging voltage is stable. The voltage difference ΔV is sufficiently small at the end of charging. In this way, if the vibration component at the end of charging has decayed, the error is small even if the charging time is changed.

On the other hand, since the time on the fixed side is relatively short, the vibration of the potential of the detection electrode 12 on the fixed side is not attenuated, and affects the capacitance detection result. However, since the time on the fixed side is fixed, the effect of the vibration of the potential of the detection electrode 12 does not change with the change in frequency and is a constant value. For example, in Figures 16(b) and 17(b), the discharge time is short and fixed, so the integral value is stable. The integral value (area IS) of the vibration component during the discharge period becomes an error in the capacitance detection result, but since the discharge time is fixed, the integral value (area IS) is suppressed from changing. Therefore, even if there is an error in the capacitance detection result, the error component is kept constant regardless of the charge/discharge frequency, so the effect on the seating determination result can be suppressed.

In addition, by shortening the time on the fixed side, the time for one cycle is prevented from becoming longer, and the overall detection time is prevented from becoming longer. Even if the charging time is lengthened, the overall charging and discharging time can be kept relatively short, so the response of the seat sensor is prevented from becoming slow.

As already mentioned, in the examples of Figures 16(a) and 17(a), the fixed side is in the first state, and the variable side is in the second state. In other words, the time on the variable side is the charging time, and the time on the fixed side is the discharging time.

In the charging operation (first state), the voltage at the end of charging (the final voltage applied to the capacitance) is proportional to the charge stored in the capacitance, so the voltage at the end of charging affects the detection result of the capacitance. Therefore, for example, even if noise is received during charging, there is no substantial effect on the detection result of the capacitance. Therefore, even if the charging time is extended and the possibility of noise entering the detection electrode during charging increases, the noise resistance does not decrease.
On the other hand, the discharge operation (second state) is an operation of discharging and integrating the charge stored in the detection electrode 12, so if noise is introduced during the discharge operation, the noise is also input to the integrating means and integrated, so that the noise remains as an error in the integrated voltage, and the detection result of the capacitance changes. Therefore, if the discharge time is longer, the noise resistance decreases accordingly.
For the above reasons, when the charging and discharging times are the same (the reaction time of the seating detection is the same), noise resistance is improved by selecting a longer charging time and a shorter discharging time. In Fig. 16(a) and Fig. 17(a), the discharging time is shorter than the charging time, so noise is less likely to occur during the discharging time.

21(a) and 21(b) are graphs illustrating the timing at which the discharge time ends.
Figures 21(a) and 21(b) show waveforms during charging and discharging, similar to Figures 18(a) and 18(b). As shown in Figure 21(a), the capacitance detection means is in the first state from time T61 to T62. The capacitance detection means switches from the first state to the second state at time T62. The waveform shown in Figure 21(b) is a waveform when the user is not seated on the toilet seat. In order to explain the waveform of the damped vibration, a waveform in which the second state continues is shown for convenience, rather than a waveform in which the second state switches back to the first state after time T62.

The time of the second state is desirably 1/4 of the period Pd of the damped oscillation of the potential of the detection electrode when switching between the first state and the second state while not seated. That is, as shown in FIG. 21(a), it is desirably that the capacitance detection means switches from the second state to the first state at time T63, which is 1/4 period after time T62.

The resonant frequency of an LCR is determined by L and C, and therefore changes with fluctuations in L and C. Both L and C are subject to individual variation and temperature changes, and there is also variation in the operating frequency of the control unit (e.g., a microcomputer) that generates the charge and discharge time. Therefore, even if the discharge time is controlled to a fixed value, the integration result will contain variation, and it is impossible to completely avoid the effects of vibration, and conditions that are more stable against the effects of vibration are preferable.

The timing of 1/4 of the vibration period Pd is the flat portion where the voltage waveform of the detection electrode 12 changes from descending to ascending, and even if there is a change in the resonant frequency, the impact can be kept small compared to the portion where the slope of the vibration waveform is steep. The timing of 1/2 cycle and 1 cycle has a steep vibration slope and is therefore easily affected by changes in vibration conditions, making the capacitance detection results unstable, so is less suitable than the timing of 1/4 cycle. At the timing of 1/4 of the vibration period Pd, the vibration waveform is flat and is less affected by changes in vibration conditions.

Note that there is a flat portion in the 3/4 cycle portion, but this is where the vibration waveform changes from rising to falling, and the LC resonant circuit has energy that lowers the voltage of the detection electrode 12. If you switch from discharging to charging at this point, the voltage of the detection electrode 12 will increase, so the polarity of both is reversed. Therefore, at the 3/4 cycle timing, it may not be possible to transition to charging smoothly compared to the 1/4 cycle timing. At the 1/4 cycle timing, the opposite is true, and both the LC resonance and charging operation increase the potential of the detection electrode 12, so there is a smooth transition to charging.

However, in the embodiment, the time in the second state (timing of the end of discharge) is not necessarily limited to 1/4 of the period Pd, and may be any timing. In addition, the time in the second state being 1/4 of the period Pd does not necessarily mean 1/4 in the exact sense, but may also include, for example, the range of variation in the elements that make up the circuit.

The above describes the embodiments of the present invention. However, the present invention is not limited to these descriptions. Any design modifications made by a person skilled in the art to the above-described embodiments are also included within the scope of the present invention as long as they include the features of the present invention. For example, the shape, dimensions, materials, arrangement, installation form, etc. of each element of the toilet seat device are not limited to those exemplified, and can be modified as appropriate.
Furthermore, the elements of each of the above-described embodiments can be combined to the extent technically possible, and such combinations are also included within the scope of the present invention as long as they include the features of the present invention.

10 Human body detection sensor, 11 Overvoltage detection means, 12 Detection electrode, 14, 14b Detection circuit, 15 Input terminal, 16 Control unit, 17, 17b Capacitance detection means, 18 Power supply circuit, 19 Off-delay means, 20 Switch unit, 22 Charge amount measurement unit, 30 Power supply terminal, 31 Rectifier circuit, 32 Smoothing capacitor, 33 Conversion circuit, 34 Transformer, 37 Capacitor, 38 Coil, 42 Protection resistor, 44 Varistor, 50 Integration circuit, 52 Integration means, 54 Transistor, 55, 56 Resistor, 60, 61 Varistor, 71 First switch, 72 Second switch, 73 Inverter circuit, 74 OR circuit, 80 Diode, 81, 82 Zener diode, 83, 84 Transistor, 85-88 Resistor, 89 Diode, 91 Resistor, 93 Capacitor, 95 Inverter circuit, 100 Toilet device, 104 Toilet bowl, 104a Bowl portion, 106 Operation portion, 110, 111 Toilet seat device, 112 Main body portion, 114 Toilet seat, 114a Opening, 116 Toilet lid, 120 Nozzle, 120a Bidet cleansing water outlet, 120b Rear cleansing water outlet, 130 Upper plate, 130a Seating surface, 130b Inner surface, 132 Lower plate, 202 Control portion, 204 Heater, 220 Switching element, 240, 242 First and second adhesives, 250 Thermal diffusion sheet, 910 Human body detection sensor, ΔV Voltage difference, C1, C2 Capacitance, DL Path, HB Human body, IS Area, P1, P2 Period, P11, P12, P21, P22 Duration, Pd Period, PS AC power supply, S1-S6, S100 Signal, SP Internal space, T31-T33, T41-T43, T51-T59, T61-T63 Time, VCC Power supply voltage

Claims (5)

The toilet seat,
A detection electrode whose capacitance changes in response to a person sitting on the toilet seat;
a capacitance detection means having an input terminal electrically connected to the detection electrode and detecting the capacitance of the detection electrode;
a control unit that determines whether or not the human body is seated based on a detection result of the capacitance detection means;
an overvoltage detection means for detecting an overvoltage at the input terminal;
Equipped with
When the overvoltage detection means detects the overvoltage, the capacitance detection means temporarily stops detecting the capacitance and then resumes detecting the capacitance ;
The capacitance detection means is
an integrating means for storing the charge discharged from the detection electrode;
a first switch connected to a predetermined voltage;
a second switch connected to the input terminal and the integrating means;
a switching operation that alternately repeats a first state in which the first switch is on and the second switch is off to charge the detection electrode to the predetermined voltage, and a second state in which the first switch is off and the second switch is on to discharge the detection electrode;
the integrating means stores the charge discharged from the detection electrode in the second state that is repeated by the switching operation;
The control unit determines whether or not the human body is seated based on the charge accumulated in the integrating means,
A toilet seat device characterized in that, when the overvoltage detection means detects the overvoltage, the capacitance detection means temporarily suspends the switching operation, sets the first switch and the second switch to the first state, and then resumes the switching operation . 2. The toilet seat apparatus according to claim 1 , further comprising an off-delay means for causing the first state to continue for a predetermined period of time when the overvoltage detection means detects the overvoltage. 3. The toilet seat apparatus according to claim 1, wherein the detection electrode is provided on a rear surface of the toilet seat, has an area larger than that of a heater that warms the toilet seat, and diffuses heat from the heater to the toilet seat. The toilet seat device according to claim 1 or 2, characterized in that the capacitance detection means is capable of changing the frequency of the switching operation that repeats the first state and the second state to a plurality of mutually different frequencies, and when changing the frequency of the switching operation, the time of one of the first state and the second state is made variable, and the time of the other of the first state and the second state is made fixed. the one being the first state,
The toilet seat apparatus according to claim 4 , wherein the other of the two is in the second state.

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