JP2020044129A - Sweat detection device - Google Patents

Abstract

To provide a sweat detection device capable of accurately detecting sweat of a living body.SOLUTION: A sweat detection device SD is a device for detecting sweat of a living body using a detection circuit including first and second electrodes 1 and 2 that insulation-coat principal surfaces 1sf and 2sf, and a guide element 3, and includes: a resistance-variable member 4 that varies a resistance value according to a liquid absorption amount; a resonance resistance measuring unit 5 for measuring a resonance resistance value of the detection circuit; and a sweat determination unit 62 for determining a sweat rate on the basis of the resonance resistance value measured by the resonance resistance measuring unit 5. The first and second electrodes 1 and 2 are juxtaposed through the resistance-variable member 4 while coming into contact with the resistance-variable member 4 on the surfaces other than the principal surfaces.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sweat detection device for detecting sweat in a living body, for example, sweat in a vehicle occupant.

  2. Description of the Related Art In recent years, attention has been paid to sweat in order to detect a mental state of a person, such as presence or absence of nervousness, and a physical state, such as physical condition. As one of the methods for detecting the sweat, there is a measurement of skin resistance, which is disclosed in Patent Document 1, for example.

  The skin resistance measuring device disclosed in Patent Literature 1 is a device for measuring skin resistance of a human body, has first and second electrodes, and a surface of a contact surface with which the human body contacts is made of an insulator. A driving circuit that has a covered electrode portion and a high-frequency power supply configured to be capable of changing a frequency, and that supplies an AC voltage generated by the high-frequency power supply to the first electrode; and a connection to the second electrode. A detection circuit that detects a current of the second electrode and outputs a detection signal indicating the detected current value; and an electric path from the high-frequency power supply to the first electrode, or the second electrode to the second electrode. An inductive element provided in any one of the electric paths to the detection circuit, and a control unit that changes and controls the frequency of the high-frequency power supply and receives the detection signal from the detection circuit; Power supply Using the force voltage and the current value indicated by the detection signal, the impedance of the human body in contact with the electrode unit is obtained, and in the relationship between this impedance and the frequency of the high-frequency power supply, the value of the impedance at a frequency at which the impedance is minimal. Is used to determine the skin resistance of the human body.

JP-A-2006-220961

  Meanwhile, the skin resistance measuring device disclosed in Patent Document 1 seeks skin resistance from impedance at the time of resonance, and attempts to detect sweat based on electrodermal activity (EDA). In addition, the resonance resistance value may fluctuate due to the movement of the finger in contact with the second electrode, and it is difficult to accurately detect sweat.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sweat detection device that can detect sweat of a living body with higher accuracy.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the sweat detection device according to one aspect of the present invention is a sweat detection device that detects sweat of a living body using a detection circuit including first and second electrodes whose main surfaces are insulated and coated and an inductive element, A resistance variable member that changes a resistance value in accordance with a liquid absorption amount, a resonance resistance measurement unit that measures a resonance resistance value of the detection circuit, and a sweat amount based on a resonance resistance value measured by the resonance resistance measurement unit. A sweat determination unit for determining, wherein the first and second electrodes are juxtaposed via the variable resistance member while being in contact with the variable resistance member on another surface other than the main surface.

  When the resistance variable member in such a sweat detection device absorbs sweat, its resistance value changes. Since the sweat detection device includes the resistance variable member that changes the resistance value by absorbing the sweat between the first and second electrodes, the movement of the finger in contact with the first and second electrodes The resonance resistance value of the detection circuit changes due to a change in the resistance value of the resistance variable member according to the presence or absence of perspiration, which is not significantly affected by the perspiration. Therefore, the sweat detection device can more accurately detect the amount of perspiration, for example, the presence or absence of perspiration such as perspiration amount 0 (no perspiration) and perspiration amount, by measuring the resonance resistance value of the detection circuit.

  In another aspect, in the sweat detection device described above, the detection circuit includes a first and a second circuit that change a characteristic curve representing a change in resonance resistance with respect to a change in resonance frequency according to the resistance value of the variable resistance member. The characteristic curve includes two characteristic curves, and the sweat determination unit further determines the characteristic curve in which the detection circuit is operating based on the resonance resistance value measured by the resonance resistance measurement unit, thereby determining the amount of perspiration. Is determined.

  The resistance variable member in such a sweat detection device includes a resistance value when a predetermined first sweat amount (a relatively small amount of sweat) is absorbed, and a predetermined second sweat amount (relative amount) larger than the first sweat amount. Resistance when a large amount of perspiration is absorbed. Since the sweat detection device includes the resistance variable member that changes the resistance value according to the amount of sweat absorbed between the first and second electrodes, the characteristic curve of the detection circuit changes according to the amount of sweat. For this reason, the sweat detection device determines the characteristic curve in which the detection circuit is operating based on the resonance resistance value measured by the resonance resistance measurement unit. The amount of perspiration can be determined based on the second amount of perspiration.

  In another aspect, in the above-described sweat detection device, the sweat determination unit further includes a transition time between the first and second characteristic curves based on a resonance resistance value measured by the resonance resistance measurement unit. The amount of perspiration is determined by determining a time change rate of the resonance resistance value at a predetermined time.

  Such a sweat detection device further considers the transition time between the first and second characteristic curves or the time change rate of the resonance resistance value at a predetermined time, so that the sweating amount can be determined with higher accuracy.

  In another aspect, in the above-described sweat detection device, the resistance variable member is a porous resin member.

  In such a sweat detection device, a resistance variable member can be easily realized with a porous resin member.

  In another aspect, in the above-described sweat detection device, the living body is a occupant riding in a vehicle for a vehicle.

  Such a sweat detection device can detect the occupant's sweat.

  In another aspect, in the above-described sweat detection device, the first and second electrodes are arranged in a vehicle part touched by the occupant's hand.

  In such a sweat detection device, since the first and second electrodes are disposed in a vehicle part touched by the occupant, the occupant can naturally detect the occupant's sweat without being conscious of the occupant.

  The sweat detection device according to the present invention can detect sweat of a living body with higher accuracy.

It is a figure showing composition of a sweat detecting device in an embodiment. It is a figure for explaining the case where an electrode part is arranged in a steering handle as an example. FIG. 4 is a diagram for explaining a current path flowing through a detection circuit. FIG. 4 is a diagram illustrating a characteristic curve representing a change in resonance resistance with respect to a change in resonance frequency. It is a figure which shows the resonance resistance change before and after the timing which made the resistance variable member absorb tap water. It is a flowchart which shows operation | movement of the sweat detection apparatus in embodiment.

  Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In each of the drawings, components denoted by the same reference numerals indicate the same components, and the description thereof will be omitted as appropriate. In this specification, a generic name is denoted by a reference numeral with a suffix omitted, and an individual configuration is denoted by a reference numeral with a suffix.

  FIG. 1 is a diagram illustrating a configuration of a sweat detection device according to the embodiment. FIG. 1A is a circuit diagram mainly showing a portion around the electrode portion, and FIG. 1B is a block diagram mainly showing another portion excluding the portion around the electrode portion. FIG. 2 is a diagram for explaining, as an example, a case where an electrode portion is provided on a steering handle. 2A is a front view, and FIG. 2B is a cross-sectional view taken along a line II in FIG. 2A. FIG. 3 is a diagram for explaining a current path flowing through the detection circuit. FIG. 3A shows a current path α1 (α1-1, α1-2) flowing through the detection circuit when there is no perspiration, and FIG. 3B shows a relatively small amount of perspiration, and the small amount of perspiration is applied to the resistance variable member. FIG. 3C shows a current path α2 flowing through the detection circuit when the absorption is performed, and FIG. 3C illustrates a current path α3 flowing through the detection circuit when the relatively large amount of sweat is absorbed by the resistance variable member. Show. FIG. 4 is a diagram illustrating a characteristic curve representing a change in resonance resistance with respect to a change in resonance frequency. In FIG. 4, the dashed line represents the first characteristic curve β1 when a relatively small amount of sweat is absorbed by the variable resistance member (normal time, small amount of sweating), and the solid line is relatively relative to the variable resistance member. FIG. 9 shows a second characteristic curve β2 when a large amount of sweat is absorbed (at the time of absorption and at the time of heavy sweating). The horizontal axis in FIG. 4 is the resonance frequency fr represented by HMz, and the vertical axis is the resonance resistance (minimum impedance) Zmin represented by kΩ. FIG. 5 is a diagram illustrating a change in resonance resistance before and after the timing when the tap water is absorbed by the variable resistance member. The horizontal axis in FIG. 5 is the elapsed time, and the vertical axis is the resonance resistance value Zmin represented by Ω.

  The sweat detection device SD in the embodiment includes, for example, as shown in FIGS. 1 and 2, first and second electrodes 1 and 2, an inductive element 3, a variable resistance member 4, a resonance resistance measuring unit 5, A control processing unit 6 and an output unit 7 are provided.

  The first electrode 1 is a relatively thin plate-shaped (layered, film-shaped) member made of a conductive material, and its main surface 1sf is made of an electrically insulating material. It is covered with a first insulating layer (first insulating film) 1a formed as thin as possible.

  The second electrode 2 is a relatively thin plate-shaped (layered, film-shaped) member formed of a conductive material, and the main surface 2sf is made of an electrically insulating material. It is covered with a second insulating layer (first insulating film) 2a formed as thin as possible.

  The thickness of each of the first electrode 1 covered with the first insulating layer 1a and the second electrode 2 covered with the second insulating layer 2a is about 1 mm or less, but in FIG. 1 and FIG. For convenience of drawing, it is emphasized. Further, the one “main surface” 1sf of the first electrode 1 and the one “main surface” 2sf of the second electrode 2 each correspond to an example of a “main surface” in the claims.

  The resistance variable member 4 is a member that changes a resistance value according to the amount of liquid absorbed. The resistance variable member 4 is, for example, a porous resin member (a porous body made of resin), and more specifically, is, for example, a sponge or the like because it gives a relatively good tactile sensation. In a state in which the porous resin member does not absorb liquid, the pores are filled with a gas such as air, and have a relatively high resistance value as they are substantially electrically insulated. When the liquid containing the electrolyte adheres to the surface, the gas in the pores is replaced with the liquid to absorb the liquid, and the resistance value decreases as the absorption amount of the liquid increases. Since the sweat is a liquid containing an electrolyte, the resistance variable member 4 changes its resistance value to a value corresponding to the amount of sweat absorbed.

  The first and second electrodes 1 and 2 are arranged so that the first and second insulating layers 1a and 2a face the outside, and are juxtaposed via a variable resistance member 4. The first electrode 1 contacts the variable resistance member 4 on the other surface except the main surface 1sf covered with the first insulating layer 1a, and in the example shown in FIGS. ing. More specifically, when the resistance variable member 4 has a resistance value at which current can flow, the first electrode 1 can electrically conduct between the first electrode 1 and the resistance variable member 4 on the right side surface. Connected to. The second electrode 2 contacts the variable resistance member 4 on the other surface except the main surface 2sf covered with the second insulating layer 2a, and in the example shown in FIGS. ing. More specifically, when the resistance variable member 4 has a resistance value that allows current to flow, the second electrode 2 can electrically conduct between the second electrode 2 and the resistance variable member 4 on the left side surface. Connected to.

  The electrode portion D is configured by the first electrode 1, the first insulating layer 1a, the variable resistance member 4, the second electrode 2, and the second insulating layer 2a. When detecting the sweat of a living body, the electrode portion D having such a configuration is brought into contact with the living body over the surfaces of the first insulating layer 1a, the variable resistance member 4, and the second insulating layer 2a. When the sweat detection device SD is for a vehicle, the electrode portion D is a vehicle part that is touched by an arm or a hand of a driver (an example of a living body) such as a driver or a fellow passenger who gets on the vehicle, preferably, From the viewpoint that the sweat glands are relatively developed, the vehicle parts touched by the occupant's hands (for example, palms and fingers), such as steering handles (steering wheels) and door trims (for example, grip handles for door trims and armrests for door trims) Placed in FIG. 2 shows an example in which the electrode portion D is provided on the steering handle SH. As shown in FIG. 2A, for example, the steering handle SH has a columnar member having an annular shape. FIG. 2A shows a state in which the steering handle SH is in the neutral position, and a part of the annular portion of the steering handle SH which is to be gripped by the rider (here, the driver) in the first circumferential direction includes: As shown in FIG. 2B, an electrode portion D is provided so that the first and second electrodes 1 and 2 are juxtaposed via a resistance variable member 4 in the second circumferential direction of the columnar shape. The electrode portion D of the steering handle HS is arranged so that the surface of the electrode portion D (the respective surfaces of the first insulating layer 1a, the variable resistance member 4 and the second insulating layer 2a) and the surface of the steering handle HS are flush. The electrode portion D is disposed in the recess by, for example, being adhered with an adhesive AD. The electrode portion D may be arranged over the entire circumference of the ring. In the example shown in FIG. 2, since the first and second electrodes 1 and 2 and the variable resistance member 4 are each in the shape of a curved plate because they are arranged in the circumferential direction of the columnar shape, May be in the form of a flat plate.

  The space in the space formed by the first and second electrodes 1 and 2 (the space in the gap between the first electrode 1 and the second electrode 2 juxtaposed to each other) for arranging the resistance variable member 4 is Since the living body, for example, a finger, does not enter between the first and second electrodes 1 and 2, it is preferably 3 mm to 5 mm because it can sufficiently absorb sweat and change the resistance value.

  The inductive element 3 is an element for forming a resonance circuit with respect to the electrode section D, and is, for example, a coil having a predetermined inductance L.

  The resonance resistance measurement unit 5 is a device that measures the resonance resistance of the detection circuit including the above-described electrode unit D and the inductive element 3. More specifically, the resonance resistance measuring unit 5 includes an AC power supply 51 and an ammeter 52. The AC power supply 51 is configured to be able to change the frequency within a predetermined frequency range, for example, in a range of 500 kHz to 4 MHz, is connected to the control processing unit 6, and controls the electrode unit D at a predetermined voltage value according to the control of the control processing unit 6. It is a device that supplies power, for example, a high-frequency power supply that supplies high-frequency power with variable frequency. The ammeter 52 is a device that is connected to the control processing unit 6 and measures the current value of the electrode unit D. The ammeter 52 outputs the measured current value to the control processing unit 6.

  The connection between the resonance resistance measuring unit 5 and the control processing unit 6 may be wired or wireless. In the case of wireless connection, for example, short-range wireless communication such as the Bluetooth (registered trademark) standard or the IrDA (Infrared Data Association) standard may be used.

  The inductive element 3 may be connected to any of the first and second electrodes 1 and 2 in the electrode section D, but in the example shown in FIG. 1, one terminal is connected to the first electrode 1 and the other terminal is connected. Are grounded via the AC power supply 51 of the resonance resistance measuring unit 5. The ammeter 52 of the resonance resistance measuring unit 5 has one terminal connected to the second electrode 2 and the other terminal grounded.

  The output unit 7 is a device that is connected to the control processing unit 6 and outputs the presence or absence of perspiration and the amount of perspiration determined by the control processing unit 6 as described later according to the control of the control processing unit 6, and includes, for example, a CRT display. , A display unit (display device) such as an LCD (liquid crystal display device) and an organic EL display, and a printing device such as a printer.

  The control processing unit 6 controls each of the units 5 and 7 of the sweat detection device SD in accordance with the function, for example, the amount of perspiration (for example, the presence or absence of perspiration such as perspiration 0 (no perspiration) and perspiration, and the relative This is a circuit for detecting perspiration of a living body (e.g., the amount of perspiration such as a small amount of perspiration and a relatively large amount of perspiration). The control processing unit 6 includes, for example, a microcomputer including a CPU (Central Processing Unit), a storage element, a peripheral circuit thereof, and the like. The storage element is, for example, a non-volatile storage element such as a ROM (Read Only Memory), a rewritable non-volatile storage element such as an EEPROM (Electrically Erasable Programmable Read Only Memory), or a volatile storage element. A random access memory (RAM) serving as a so-called working memory of the CPU, and stores various predetermined programs and various predetermined data. The various predetermined programs include, for example, a control program for controlling each of the units 5 and 7 of the sweat detection device SD according to the function or a sweat program based on the resonance resistance value measured by the resonance resistance measurement unit 5. A control processing program such as a sweat determination program for performing a predetermined determination process related to detection is included. The various types of predetermined data include, for example, data necessary for executing each program, such as thresholds Thn described below. The control processing unit 6 includes a control unit 61 and a sweat determination unit 62 in the CPU functionally by executing the control processing program.

  The control unit 61 controls each unit 5, 7 of the sweat detection device SD according to the function, and controls the entire sweat detection device SD.

  The sweat determination unit 62 performs a predetermined determination process regarding sweat detection based on the resonance resistance value measured by the resonance resistance measurement unit 5. In the present embodiment, the sweat determination unit 62 determines the amount of perspiration based on the resonance resistance value measured by the resonance resistance measurement unit.

  More specifically, the sweat determination unit 62 determines the presence or absence of perspiration and the amount of perspiration as follows. As described above, the resistance variable member 4 changes the resistance value according to the liquid absorption amount. More specifically, when there is no liquid absorption, the resistance variable member 4 has a relatively high resistance value as it is substantially electrically insulated, and its resistance value decreases as the liquid absorption amount increases. Let it. In the case where the resistance variable member 4 is a porous resin member, when there is no liquid absorption, the hole is filled with a gas such as air, and the resistance variable member 4 is substantially electrically insulated. Is relatively high resistance value (predetermined first resistance value), and when the liquid containing the electrolyte adheres to the surface thereof, the gas in the pores is replaced by the liquid to absorb the liquid, The resistance value is decreased in accordance with the increase in the absorption amount of the liquid, and when the entire hole is filled with the liquid, the resistance value is relatively low (a predetermined second resistance value lower than the first resistance value) so that current can flow. Value). Conversely, the variable resistance member 4 having the second resistance value, which can be energized, increases the resistance value when the absorbed liquid comes off due to drying, and completely drys, and becomes substantially electrically insulated. The first resistance value.

  For this reason, when the living body LB, for example, the finger LB contacts the electrode portion D across the first and second electrodes 1 and 2 via the first and second insulating layers 1a and 2a, the resistance is variable when there is no perspiration. Since the resistance is relatively high as the member 4 is substantially electrically insulated, the current supplied from the AC power supply 51 is, as shown in FIG. One electrode 1, first insulating layer 1a, finger LB, second insulating layer 2a, second electrode 2 and first A path α1-1 of ammeter 52 and AC power supply 51, inductive element 3, first electrode 1, first electrode It flows through the insulating layer 1a and the first B path α1-2 of the living body LB (for example, a path grounded via the living body LB). In FIG. 3A, Cs_TX is the capacitance between the first electrode 1 and the finger LB via the first insulating layer 1a, and Cs_RX is the capacitance between the second electrode 2 and the finger LB via the second insulating layer 2a. , Rs is the resistance value of the finger LB, Cb is the capacitance of the living body LB, and Rb is the resistance value of the living body LB.

  On the other hand, when the living body LB sweats and the sweat adheres to the variable resistance member 4 and is absorbed, the resistance value of the variable resistance member 4 decreases as compared with the case where there is no perspiration. That is, when the resistance variable member 4 absorbs the predetermined first amount of perspiration, as shown in FIG. 3B, the current supplied from the AC power supply 51 is the AC power supply 51, the inductive element 3, the first electrode 1, The first insulating layer 1a, the finger LB, the second insulating layer 2a, the second electrode 2 and the second A path α2-1 of the ammeter 52 and the AC power supply 51, the first electrode 1, the resistance variable member 4, the second electrode 2, The current flows through the second B path α2-2 of the ammeter 52. 3B, Cm is the capacitance of the variable resistance member 4, and Rm is the resistance value of the variable resistance member 4.

  As described above, the resistance variable member 4 changes from the insulated state to the energizable state depending on the presence or absence of perspiration, and the current path changes from the first path α1 (α1-1, α1-2) to the second path α2 (α2-) as described above. 1, α2-2), the presence or absence of perspiration can be determined by determining the resonance resistance value using a threshold value. More specifically, the sweat determination unit 62 compares the resonance resistance value measured by the resonance resistance measurement unit 5 with a predetermined first threshold value Th1, and as a result of the comparison, the resonance resistance measurement unit If the resonance resistance value measured at 5 is equal to or greater than the predetermined first threshold value Th1, it is determined that there is no perspiration, and if the resonance resistance value measured at the resonance resistance measurement unit 5 is less than the predetermined first threshold value Th1, In some cases, it is determined that sweating is present. The resonance resistance value is a current value measured by the ammeter 52 while changing (scanning, sweeping) the frequency of the AC power supply 51, and is a current value when the ammeter 52 detects an extreme value. It is given by the value obtained by dividing the value (resonance resistance value = (voltage value of AC power supply 51) / (measured current value of ammeter 52 at extreme value)).

  When the first insulating layer 1a and the second insulating layer 2a are connected to each other with the same material as the first and second insulating layers 1a and 2a instead of the variable resistance member 4, when the finger LB sweats, the sweat of the finger LB is generated due to the sweating. The resistance value Rs decreases, and the resonance frequency fr changes so as to decrease in a state where the resonance frequency fr hardly changes. However, the change is small, so that the detection is difficult. Further, since the resonance resistance value fluctuates even by a slight movement of the finger LB, it is difficult to determine whether the change in the resonance resistance value is caused by sweating or the movement of the finger LB. On the other hand, in the present embodiment, since the resistance variable member 4 is used, the resonance resistance value can be clearly changed as compared with the change in the resistance value Rs of the finger LB due to perspiration, and the presence or absence of perspiration is more accurately determined. It becomes detectable.

  In the case where the resistance variable member 4 absorbs a predetermined second sweat amount (for example, the upper limit amount of the resistance variable member 4) larger than the first sweat amount, such as when the living body LB sweats a relatively large amount, for example, the resistance is reduced. As shown in FIG. 3C, the current supplied from the AC power supply 51 mainly includes the AC power supply 51, the inductive element 3, the first electrode 1, and the resistance variable member. 4, flows through the second electrode 2 and the third path α3 of the ammeter 52.

In the case of relatively small amount of absorption shown in FIG. 3B (normal time, small amount of absorption) and in the case of relatively large amount of absorption shown in FIG. A circuit in which a parallel circuit including a capacitor having a capacitance Cm and a resistor having a resistance value Rm is connected in parallel to a series circuit including a capacitor having a capacitance Cs_TX, a resistance having a resistance value Rs, and a capacitor having a capacitance value Cs_RX. Although formed, at the time of large-volume absorption shown in FIG. 3C, as described above, the conduction in the variable resistance member 4 becomes dominant, and at the time of large-volume absorption shown in FIG. The capacitance Cc increases, and the combined resistance value Rc decreases. The resonance resistance value (minimum impedance value in frequency scanning) Zmin is given by the following equation 1.
Formula 1; Zmin = Rc · L / (L + Cc · Rc ² )

  As an example, the combined capacitance Cc and the combined resistance value Rc at the time of small absorption shown in FIG. 3B are 10.5 pF and 14 kΩ, respectively (Cc = 10.5 pF, Rc = 14 kΩ), and the combination at the time of large absorption shown in FIG. 3C. When the capacitance Cc and the combined resistance value Rc are set to 22 pF and 2.4 kΩ, respectively (Cc = 22 pF, Rc = 2.4 kΩ), the simulation shown in FIG. 4 yields the results shown in FIG. In FIG. 4, a first characteristic curve β1 indicated by a broken line and representing a change in resonance resistance with respect to a change in resonance frequency is a simulation result at the time of absorption of a small amount shown in FIG. 3B. The two characteristic curves β2 are simulation results at the time of large-volume absorption shown in FIG. 3C. As can be seen from FIG. 4, in each of the first and second characteristic curves β1, β2, the resonance resistance value Zmin also increases as the resonance frequency fr increases. The first and second characteristic curves β1 and β2 have a relationship that the resonance resistance value Zmin of the second characteristic curve β2 is larger than the resonance resistance value Zmin of the first characteristic curve β1 when the resonance frequency fr is the same. .

  As described above, the characteristic curve β representing the resonance resistance change with respect to the resonance frequency change indicates whether the resistance variable member 4 has absorbed a relatively small amount of sweat or a relatively large amount of sweat (that is, the resistance variable member 4 (Change in resistance). Therefore, the amount of perspiration can be determined by determining the characteristic curve based on the resonance resistance value. More specifically, the detection circuit including the electrode unit D and the inductive element 3 mutually changes the characteristic curve β representing the resonance resistance change with respect to the resonance frequency change according to the resistance value of the resistance variable member 4 as described above. The first and second characteristic curves β1 and β2 include two differently, and the sweat determination unit 62 determines the characteristic in which the detection circuit operates based on the resonance resistance value measured by the resonance resistance measurement unit 5. The amount of perspiration is determined by determining the curve. More specifically, the sweat determination unit 62 determines that the detection circuit is operating with the first characteristic curve β1 when the resonance resistance value measured by the resonance resistance measurement unit 5 is less than the second threshold value Th2. If the resonance resistance value measured by the resonance resistance measuring unit 5 is equal to or greater than the second threshold Th2, the detection circuit determines that the first perspiration amount is a perspiration (a relatively small amount of perspiration). It is determined that the operation is performed by the characteristic curve β2, and it is determined that the second sweat amount is larger than the first sweat amount (relatively large amount of sweat).

  In the above description, the amount of perspiration can be determined if the living LB sweats in a small amount or in a large amount. On the other hand, as a result of continuing a small amount of perspiration, the variable resistance member 4 may be filled with sweat, and the variable resistance member 4 may absorb a large amount of sweat. As described above, only by comparing the resonance resistance value with the second threshold value Th2, when the resonance resistance value measured by the resonance resistance measurement unit 5 is equal to or more than the second threshold value Th2, a small amount of sweating continues, This includes the case where the detection circuit operates during the transition from the first characteristic curve β1 to the second characteristic curve β2. In the above description, when the resonance resistance value measured by the resonance resistance measuring unit 5 is equal to or more than the second threshold value Th2, the sweat determination unit 62 determines whether the detection circuit has the second characteristic curve β2 or the first characteristic curve β1 It is determined that the operation is being performed during the transition to the two characteristic curves β2, and it is determined that the second amount of sweating is a perspiration (relatively large amount of perspiration). For this reason, in order to determine a large amount of sweat more accurately, the transition time between the first and second characteristic curves or the time change rate of the resonance resistance value at a predetermined time is used. FIG. 5 shows the results of one experimental example. In this experiment, the passage of the resonance resistance value (minimum impedance) when power was supplied from the AC power supply 51 to the detection circuit at a predetermined resonance frequency was observed, and at about 30 seconds after the start of the experiment, a large amount of sweating was observed. Instead, sufficient tap water (tap water usually contains an electrolyte) was attached to the resistance variable member 4. As can be seen from FIG. 5, when sufficient tap water is attached to the resistance variable member 4, the detection circuit operates on the second characteristic curve β2 in a relatively short time. Therefore, by determining the transition time between the first and second characteristic curves with the threshold value, it is possible to determine whether or not a large amount of sweating occurs. Alternatively, it is possible to determine whether or not it is a large amount of sweating by determining a time change rate (slope) of the resonance resistance value at a predetermined time by a threshold value. More specifically, the sweat determination unit 62 further determines a transition time between the first and second characteristic curves β1 and β2 or a predetermined time based on the resonance resistance value measured by the resonance resistance measurement unit 5. The amount of perspiration is determined by determining the time change rate of the resonance resistance value. More specifically, the sweat determination unit 62 further determines, based on the resonance resistance value measured by the resonance resistance measurement unit 5, that the resonance resistance value is larger than the predetermined first sub-threshold Ths <b> 1 than the first sub-threshold. The time required to reach the second sub-threshold Ths2 is determined. If the determined time is equal to or less than the predetermined third threshold Th3, it is determined that the second amount of perspiration is a perspiration (relatively large amount of perspiration). When the obtained time exceeds the third threshold Th3, it is determined that the perspiration is not the second amount of perspiration. Alternatively, the sweat determination unit 62 further obtains a time change rate of the resonance resistance value for a predetermined time based on the resonance resistance value measured by the resonance resistance measurement unit 5, and determines the time change of the obtained resonance resistance value. When the rate is equal to or greater than a predetermined fourth threshold Th4, it is determined that the second amount of sweating is perspiration (relatively large amount of perspiration), and the time change rate of the obtained resonance resistance value is less than the fourth threshold Th4. In some cases, it is determined that the perspiration is not the second amount of perspiration.

  The above-described first to fourth threshold values Th1 to Th4, the first and second sub-threshold values Ths1, Ths2, and the predetermined time are appropriately set in advance from a plurality of samples. Alternatively, the predetermined first to fourth thresholds Th1 to Th4, the predetermined first and second sub-thresholds Ths1, Ths2, and the predetermined time are the first electrodes covered with the first insulating layer 1a. 1. Design values (simulations) obtained by considering the materials and shapes of the second electrode 2 and the variable resistance member 4 covered with the second insulating layer 2a and the inductance L of the inductive element 3 and the like. Values (including values).

  When the transition time between the first and second characteristic curves or the time change rate of the resonance resistance value at a predetermined time is used, the first threshold value Th1 and the second threshold value Th2 are equal. (Th1 = Th2). In such a case, if the resonance resistance value is equal to or greater than the first threshold value Th1 (second threshold value Th2), the sweat determination unit 62 determines that there is no perspiration, and the resonance resistance value is reduced to the first threshold value Th1 (second threshold value Th2). Th2), if the time change rate of the resonance resistance value at a predetermined time is less than the fourth threshold Th4 (or if the time exceeds the third threshold Th3), the sweat determination unit 62 Is determined when there is a small amount of perspiration, the resonance resistance value is less than the first threshold value Th1 (second threshold value Th2), and the time change rate of the resonance resistance value in a predetermined time is equal to or greater than the fourth threshold value Th4. (Or the time is equal to or less than the third threshold Th3), the sweat determination unit 62 determines that there is a large amount of perspiration. In other words, the sweat determination unit 62 determines that the resonance resistance value measured by the resonance resistance measurement unit 5 has a tendency to decrease and falls below the first threshold Th1 (second threshold Th2) (in FIG. (To T1), when it shows an increasing tendency and increases at a time rate of change equal to or greater than the fourth threshold value Th4 (in FIG. 5, from point T1 to point T2, further to point T3), it is determined that there is a large amount of sweating.

  Next, the operation of the present embodiment will be described. FIG. 6 is a flowchart illustrating the operation of the sweat detection device according to the embodiment. Here, since the first and second sub-thresholds Ths1 and Ths2 are not required, the case where the time change rate of the resonance resistance value is used will be described. However, the case where the transition time between the first and second characteristic curves is used is also described. The same can be said. Further, the vehicle is provided with a thermometer for measuring the temperature in the passenger compartment. The thermometer is connected to the control processing unit 6, and measures the temperature in the passenger compartment according to the control of the control processing unit 6, and the measurement result is obtained. Is output to the control processing unit 6.

  When the power of the sweat detection device SD is turned on, the necessary components are initialized, and the sweat detection device SD starts operating. By executing the control processing program, the control processing unit 6 has a control unit 61 and a sweat determination unit 62 functionally configured. The sweat detection device SD detects sweat in the living body LB by operating as follows at predetermined sampling intervals set in advance.

  In FIG. 6, the control processing unit 6 determines whether or not the temperature change ΔT in the cabin measured by the thermometer is less than a preset temperature threshold value T0 (S1). It is said that it is possible to determine whether the sweat is due to the mental condition or the sweat due to the physical condition based on the amount of sweat. However, since the sweat is caused also by the ambient temperature (environmental temperature) of the living body LB, this process S1 is performed. Is a process for determining whether or not sweating is caused by the ambient temperature of the living body LB. If the result of this determination is that the temperature change ΔT in the vehicle compartment is equal to or greater than the temperature threshold value T0 (No), the control processing unit 6 ends the process at the current sampling timing. When the temperature change ΔT in the room is less than the temperature threshold value T0 (Yes), the control processing unit 6 next executes a process S2.

  In this process S2, the control processing unit 6 measures the resonance resistance value using the resonance resistance measurement unit 5 (S2). More specifically, the control processing unit 6 measures the current value with the ammeter 52 while changing the frequency of the AC power supply 51, thereby obtaining the current value at the time when the ammeter 52 detects the extreme value. By dividing the voltage value of the AC power supply 51 by the obtained current value, the result of the division is obtained as a resonance resistance value.

  Subsequently, the control processing unit 6 causes the sweat determination unit 62 to determine whether or not the obtained resonance resistance value is equal to or more than the first threshold Th1 (S3). If the result of this determination is that the resonance resistance value is equal to or greater than the first threshold value Th1 (Yes), the sweat determination unit 62 determines that sweating has not occurred and ends the processing at the current sampling timing. Note that the sweat determination unit 62 may end the processing at the current sampling timing after outputting to the output unit 7 that there is no perspiration. On the other hand, if the result of the determination is that the resonance resistance value is less than the first threshold value Th1 (No), then the sweat determination unit 62 executes the process S4. In this embodiment, as an example, the first threshold value Th1 (= second threshold value Th2) is approximately 255Ω to 275Ω, and is set to, for example, 260Ω.

  In this process S4, the sweat determination unit 62 obtains the time change rate of the resonance resistance value at a predetermined time, and determines whether the obtained time change rate of the resonance resistance value is equal to or more than the fourth threshold Th4. . As a result of this determination, if the time rate of change of the resonance resistance value is less than the fourth threshold Th4 (No), the sweat determination unit 62 determines that the perspiration is a relatively small amount, and then this small amount of perspiration is detected. Is output to the output unit 7 (S5), and the process at the current sampling timing ends. On the other hand, as a result of the determination, if the time rate of change of the resonance resistance value is equal to or greater than the fourth threshold value Th4 (Yes), the sweat determination unit 62 determines that the perspiration is a relatively large amount. The fact that sweating is present is output to the output unit 7 (S6), and the processing at the current sampling timing is terminated. In this embodiment, as an example, the fourth threshold value Th4 is approximately 30Ω / sec to 60Ω / sec, and is set to, for example, 30Ω / sec. Although not shown, in another experiment, the minimum value of the resonance resistance value at the time of a small amount of sweating was 194.53Ω, and the minimum value of the resonance resistance value at the time of a large amount of sweating was 336.86Ω. The transition time from the time of heavy sweating to the time of heavy sweating was 2.5 seconds. According to this, the time change rate of the resonance resistance value was 56.932Ω, which was about 60Ω.

  As described above, the sweat detection device SD according to the present embodiment includes the resistance variable member 4 that changes the resistance value by absorbing sweat between the first and second electrodes 1 and 2 as described above. The resonance resistance value of the detection circuit changes due to a change in the resistance value of the resistance variable member 4 according to the presence or absence of perspiration, which is hardly affected by the movement of the finger in contact with the second electrodes 1 and 2. Therefore, the sweat detection device SD can more accurately detect the presence or absence of perspiration by measuring the resonance resistance value of the detection circuit.

  Since the sweat detection device SD includes the resistance variable member 4 that changes the resistance value according to the amount of sweat absorbed as described above, between the first and second electrodes 1 and 2, the characteristics of the detection circuit according to the amount of sweat are determined. The curve β (the first and second characteristic curves β1, β2 in the example shown in FIG. 4) changes. Therefore, the sweat detection device SD determines, for example, a characteristic curve in which the detection circuit is operating based on the resonance resistance value measured by the resonance resistance measurement unit 5, and thereby, for example, a relatively small amount of sweat ( The amount of perspiration can be determined based on whether the perspiration is a first amount of perspiration or a relatively large amount of perspiration (a second amount of perspiration).

  By the way, it is said that it is possible to determine whether the sweat is caused by a mental condition or a sweat caused by a physical condition based on the amount of sweat. However, in the skin resistance measuring device disclosed in Patent Document 1, the amount of sweat is determined. Is difficult to detect, and it is difficult to detect the cause of perspiration. Also, by examining the correlation between the skin resistance value and the amount of perspiration, it was considered to convert the skin resistance value into the amount of perspiration. However, the first insulating layer 1a and the second insulating layer 1 without the variable resistance member 4 were provided. In the configuration of the first and second electrodes 1 and 2 connected to each other, the first and second electrodes 1 and 2 are connected to each other via the first and second insulating layers 1a and 2a connected to each other. The resonance resistance value fluctuates due to the slight movement of the finger LB, and it is difficult to examine the correlation between the skin resistance value and the amount of perspiration, and it has been difficult to convert the skin resistance value into the amount of perspiration. However, since the sweat detection device SD according to the present embodiment is configured to include the resistance variable member 4 as described above, the sweat amount can be determined.

  The sweat detection device SD only needs to bring the living body LB into contact between the first and second electrodes 1 and 2, and thus can detect the presence or absence of sweat and the amount of sweat in a non-invasive manner.

  The sweat detection device SD further considers the transition time between the first and second characteristic curves β1 and β2 or the time change rate of the resonance resistance value at a predetermined time, so that the sweating amount can be determined with higher accuracy. .

  When mounted on a vehicle, the sweat detection device SD can detect a passenger's sweat. In such a case, since the first and second electrodes 1 and 2 are arranged in the vehicle part touched by the occupant, the sweat detection device SD naturally occupies the occupant without making the occupant aware. Sweat can be detected.

  Although the present invention has been described above appropriately and sufficiently through the embodiments with reference to the drawings in order to express the present invention, it is easy for those skilled in the art to modify and / or improve the above-described embodiments. It should be recognized that it is possible. Therefore, unless a modification or improvement performed by those skilled in the art is at a level that departs from the scope of the claims set forth in the claims, the modification or the improvement will not be included in the scope of the claims. Is interpreted as being included in

SD Sweat detector 1 First electrode 1a First insulating layer 2 Second electrode 2a Second insulating layer 3 Inductive element 4 Variable resistance member 5 Resonance resistance measuring unit 6 Control processing unit 7 Output unit 51 AC power supply (high frequency power supply)
52 ammeter 61 control unit 62 sweat determination unit

Claims (6)

A sweat detection device for detecting sweat of a living body using a detection circuit including first and second electrodes having a main surface insulated and an inductive element,
A resistance variable member that changes a resistance value according to a liquid absorption amount,
A resonance resistance measurement unit that measures a resonance resistance value of the detection circuit,
A sweat determination unit that determines the amount of perspiration based on the resonance resistance value measured by the resonance resistance measurement unit,
The first and second electrodes are juxtaposed via the variable resistance member while being in contact with the variable resistance member on another surface other than the main surface,
Sweat detection device. The detection circuit includes two characteristic curves representing a resonance resistance change with respect to a resonance frequency change as first and second characteristic curves so as to be different from each other according to a resistance value of the resistance variable member,
The sweat determination unit further determines the amount of perspiration by determining a characteristic curve on which the detection circuit is operating, based on the resonance resistance value measured by the resonance resistance measurement unit.
The sweat detection device according to claim 1. The sweat determination unit may further determine a time change rate of the resonance resistance value at a transition time between the first and second characteristic curves or a predetermined time based on the resonance resistance value measured by the resonance resistance measurement unit. By determining, the amount of perspiration is determined,
The sweat detection device according to claim 2. The variable resistance member is a porous resin member,
The sweat detection device according to any one of claims 1 to 3. For vehicles,
The living body is a passenger riding a vehicle,
The sweat detection device according to any one of claims 1 to 4. The first and second electrodes are disposed in a vehicle part touched by the occupant's hand,
The sweat detection device according to claim 5.

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