JP5515111B2 - Moisture detector - Google Patents

Description

  The present invention relates to a moisture detection device, and more particularly to a moisture detection device that can detect wetness of diapers and the like in a non-contact manner.

  In recent years, with the aging, the number of people who need nursing care tends to increase, and the number of people wearing diapers also tends to increase. A person wearing a diaper is uncomfortable if the diaper becomes wet with excrement (urine or stool) due to incontinence, etc., and may cause hygiene problems such as diaper rash if not removed promptly. Since it is necessary to detect this as soon as possible, various diaper wetness sensors have been developed.

  A resonance circuit consisting of a coil pattern and a capacitor pattern is provided on the insulator as a moisture detection device that can detect moisture without burdening the person or caregiver wearing a moisture detection target such as a diaper, and transmitting a radio wave with a resonance frequency. Resonator that generates reflected radio waves when it is present in a dry field where it is transmitted, transmits the radio wave to the field, performs reception operation in synchronization with transmission, and receives after the transmission of the transceiver stops There has been proposed a moisture detection device including a transmitter / receiver that detects moisture based on the received intensity of residual radio waves (see Patent Document 1).

JP 2000-241366 A

  However, the moisture detection device has a configuration in which moisture adheres to the resonance circuit itself composed of the coil pattern and the capacitor pattern, and the change in the Q value is large, and the presence or absence of moisture is determined based on the presence or absence of the reflected radio wave. For this reason, there is a problem that it is difficult to determine the degree of wetting. Whether the diaper is wet, the distance between the resonant circuit and the receiving circuit exceeds the detectable range, or the diaper is not worn, etc. There is a problem that it cannot be determined only by the presence or absence of radio waves.

  The present invention has been made based on the above-described circumstances, and can detect moisture without being affected by the distance between the transceiver and the resonance circuit, and can detect the degree of moisture adhesion without contact. An object of the present invention is to provide a moisture detecting device capable of performing the above.

The moisture detection device of the present invention includes a resonance circuit unit composed of a coil and a capacitor, a sensor unit connected to the resonance circuit unit and configured to cause electrical conduction and / or resistance value change by moisture, and an oscillation circuit The resonance circuit unit generates a reflected radio wave by a transmission radio wave from the unit, and includes a reception circuit unit that receives the reflected radio wave, and an analysis circuit that analyzes the reflected radio wave received by the reception circuit unit, the analysis circuit Analyzes the damped oscillation waveform of the reflected radio wave and compares at least two timing voltages to detect moisture in the sensor unit and to detect the absence of a resonant circuit unit. .

  According to the present invention, a current path is generated in the sensor unit due to moisture, and the resistance value of the sensor unit changes according to the degree of wetting. The waveform of the reflected radio wave generated from the resonance circuit unit is affected by the electrical resistance of the sensor unit due to moisture. This waveform is captured by the attenuation constant α in the waveform of the reflected radio wave when it is wet and when it is not wet, and by analyzing the change, it is possible to determine whether it is wet or not. Presence / absence can be determined without contact. The attenuation constant α can be analyzed by comparing the voltages of at least two timings of the damped oscillation waveform in the reflected radio wave, so that it is possible to detect moisture stably without being affected by the distance between the transceiver and the resonance circuit. .

It is a perspective view of the diaper wetness detection apparatus of one Example of this invention. It is a perspective view which shows typically the weaving state of the warp and the weft of an anisotropic conductive fabric. (A) is a top view of the state which connected the two electroconductive thread | yarns of the sensor part to the resonance circuit part, (b) is the equivalent circuit schematic. It is a figure which shows the structural example of the transmitter / receiver of one Example of this invention. It is a wave form diagram which shows the transmission waveform (a) of an oscillation part, and the damped oscillation waveform (b) of a resonance circuit part. Note that (b) shows the waveform of the resonance part, but the waveform induced in the receiving antenna is similar. It is a wave form diagram which shows a damping vibration waveform when the sensor part is dry and when it is wet. It is a wave form diagram which shows the simulation result of the example of a transmission waveform used as the base of analysis of attenuation constant (alpha), and various examples of a received waveform.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 7. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated to the same or equivalent member or element.

  FIG. 1 shows an outline of a detection device such as a diaper wetting of the present invention. The diaper main body 11 made of a paper diaper or the like is provided with an absorbent material 12 and absorbs excrement (urine or stool) when the wearer incontinence or the like. And in this detection apparatus, the inside of the diaper main body 11 is equipped with the moisture sensor part 13 which consists of an anisotropic conductive woven fabric which has arrange | positioned two electroconductive thread | yarns to a longitudinal direction as an example. The transmission / reception device 15 is a device for detecting wetness of the diaper, and has a size that can be carried by a caregiver or the like.

  A configuration example of the anisotropic conductive woven fabric is shown in FIG. The anisotropic conductive woven fabric includes at least two conductive yarns Z and Z between the insulating yarns as the warp yarn x, and woven the insulating yarn as the weft yarn y. In this example, electroless copper-plated yarns made of polyester fibers are used as the conductive yarns Z and Z, and yarns made of polyester fibers are used as the insulating yarns x and y. The woven conductive yarns Z and Z are arranged in parallel in the longitudinal direction of the woven fabric so that the conductive yarns Z and Z do not cross each other, and have electric conductivity in the direction and at the same time, the same flexibility as a normal yarn. The woven fabric is gentle to the wearer's skin. Moreover, it has higher retainability with respect to excrement by using a polyester fiber with high water absorption for the insulating yarn.

  3A shows a state in which the sensor unit 13 and the resonance circuit unit 14 are connected. The resonance circuit unit 14 including the coil L and the capacitor C is connected to the resonance circuit unit 14 including the anisotropic conductive fabric constituting the sensor unit 13. Two conductive yarns Z, Z are connected. In this example, one end of the two conductive yarns Z and Z of the sensor unit 13 is connected to either end of either the coil L or the capacitor C of the resonance circuit unit 14 and the other end is opened. The distance between the conductive yarns Z and Z can be set as appropriate within a range of about 1 mm to 20 mm. The sensor unit 13 itself is inexpensive because it is composed of an anisotropic conductive woven fabric in which two conductive yarns are arranged in the longitudinal direction, and the sensing part is simplified by connecting it to the resonance circuit unit 14. it can.

  It is preferable that terminals 20a and 20b are provided at one ends of the two conductive yarns Z and Z so that they can be connected to and disconnected from the terminals of the resonance circuit unit 14. At this time, except for the terminals 20a and 20b, the entire resonance circuit 14 is installed in a waterproof case or bag so that moisture does not adhere to the resonance circuit section 14, and the sensor section 13 and the resonance circuit section 14 are also configured. Are preferably connectable to each other. Thereby, it is also possible to make only the sensor part 13 disposable and to use the resonance circuit part 14 repeatedly.

  FIG. 3B is an equivalent circuit of the resonance circuit unit 14 including such a wetness sensor. The function as a wetness sensor is shown as a variable resistor R in the figure. When the sensor unit 13 is dry, no current is generated between the conductive yarns Z and Z. When the sensor unit 13 is wet and contains moisture between the conductive yarns Z and Z, the conductive yarns Z and Z are electrically connected to generate a current. When a large amount of moisture is included, the resistance value generated between the conductive yarns Z and Z is smaller than when the moisture is small.

  FIG. 4 is a configuration example of the transmission / reception device 15 of the present invention. The transceiver 15 includes an oscillator 21 and a transmission antenna 22 (oscillation circuit unit) that intermittently generate high-frequency alternating magnetic flux, and a reception antenna 23 and a reception circuit 24 (reception circuit) that detect the alternating magnetic flux generated by the resonance circuit unit 14. Part) and an analysis circuit 26 for damped vibration. The timing circuit 25 generates signals related to transmission and reception, start timing of waveform analysis, and the like. The transmission antenna 22 and the reception antenna 23 are a coil made of a metal wire or a coil made of a spiral conductive film formed on a base (not shown). A core such as ferrite may be provided for the purpose of improving transmission sensitivity.

  Although not shown, the transmission / reception device 15 includes a notification means using a liquid crystal display panel, an LED, and the like and an output circuit. Based on the analysis of the analysis circuit 26, whether or not the diaper is wet, whether the diaper is changed or not. Information such as necessity, presence / absence of the resonance circuit unit 14 and detection error can be notified. Such notification can also be performed by voice. The transmission / reception device 15 also includes a switch for executing moisture detection, a necessary power source, and the like. The oscillator 21 and the transmission antenna 22, the reception antenna 23, the reception circuit 24, and the analysis circuit 26 may be separate devices. In this case, the analysis circuit 26 needs to include a synchronization circuit that cuts out only the attenuated portion of the received waveform.

  The resonance circuit unit 14 is mounted on the diaper side as shown in FIG. 1 and is connected to the sensor unit 13 described above. An apparatus for detecting the influence of the resistance value of the sensor unit 13 on the Q of the resonance circuit unit 14 as a change in the damping constant α of the damped vibration waveform by the receiving circuit 24 and the analysis circuit 26 and detecting the presence or absence of moisture in the sensor unit 13 is there. In order to use the inductive coupling of the coil, the coil portion of the resonance circuit unit 14, the transmission antenna coil 22, and the reception antenna coil 23 are coupled by inductive coupling.

  By analyzing the damped vibration waveform of the resonance circuit composed of the sensor unit 13 and the resonance circuit unit 14, this apparatus can detect wetting with high accuracy without worrying about the distance between the transmission / reception unit and the resonance circuit unit. In addition, since an induction electromagnetic field that attenuates in inverse proportion to the cube of the distance is used, the system does not operate unless the entire system is within an appropriate distance of about 1 m. Therefore, even if there are a plurality of diaper wearers in the same room, it is possible to examine only the wetness of a nearby diaper.

  In this circuit, when the sensor unit 13 is dry, that is, when the conductive yarns Z and Z are in an insulated state, the resonance circuit unit 14 resonates at a predetermined frequency, but is wet and conducts between the conductive yarns Z and Z. Then the amplitude becomes smaller. However, since the amplitude is also strongly influenced by the distance between the transmission / reception unit and the resonance circuit unit, whether the sensor unit 13 is wet or whether the transmission / reception unit and the resonance circuit are separated from each other cannot be determined only by the magnitude of the amplitude. . If wetting is to be measured with the magnitude of the amplitude, the distance between the transmission / reception unit and the resonance circuit unit must always be kept constant, which is problematic in practicality.

  Therefore, in the present invention, the damping constant of the damping vibration of the magnetic flux re-radiated from the resonance circuit unit 14 immediately after turning off the oscillation by the oscillator 21 is analyzed. By doing so, a decrease in the Q value is detected, and wetting is detected without being affected by the distance between the transmission / reception unit and the resonance circuit unit. As shown in FIG. 5A, the oscillator 21 oscillates a predetermined high frequency (for example, frequency f = 125 kHz), but transmits a burst waveform that repeats ON-OFF at an arbitrary time (for example, 1.6 ms). .

  The resonance circuit section 14 is induced to resonate in response to a change in the magnetic flux of the oscillator 21, but when the oscillation is turned off, the resistance in the resonance circuit inhibits the vibration, and the vibration gradually weakens and attenuates, and no current flows. When the oscillator 21 starts to oscillate, resonance starts again (see FIG. 5B).

  The receiving circuit 24 captures the damped vibration waveform of the resonance circuit unit 14 after the oscillation is turned off. The resonance circuit unit 14 re-radiates the magnetic flux H proportional to the oscillating current i that attenuates. The receiving circuit 24 includes a receiving antenna 23 and is induced by the magnetic flux H to output a voltage pulse. This voltage change is similar to the decay wave. A method for analyzing the waveform of the reflected radio wave received by the receiving circuit 24 by the analyzing circuit 26 will be described below.

但し、ｉｏ：ｔ＝０（発振ＯＦＦ時）におけるコイル電流、α：減衰定数、ｆ：周波数、θ：初期位相角、ｔ：時間 The damped oscillation waveform of the coil current of the resonance circuit unit 14 immediately after the burst is stopped is generally expressed by Expression (1). FIG. 6 shows a schematic diagram of the damped vibration waveform.

However, io: coil current at t = 0 (when oscillation is OFF), α: attenuation constant, f: frequency, θ: initial phase angle, t: time

  Equation (1) indicates that a small α indicates that the vibration is gradually attenuated in time, and a large α indicates that the α is rapidly attenuated. If the sensor unit 13 is incorporated in parallel with the resonance circuit 14, when the resistance value of the resistor R is infinite (not wet), the attenuation constant α is small and the resistance value of the resistor R is generated (wetting). The damping constant α is large.

Well, it is provided with a circuit for sampling the voltage V ₂ after a lapse of a predetermined time and voltage V ₁ of the immediately oscillation OFF held in the analyzing circuit 26. Further, for example, an analog divider that outputs V ₂ / V ₁ is incorporated in the analysis circuit 26. That is, when the sampled V ₂ / V ₁ is large, α is large (dry), and when V ₂ / V ₁ is small, α is small (wet). Can be determined.

When the distance between the transmission / reception unit and the resonance circuit unit increases, the coupling between the two decreases and the wave height decreases, but the ratio between V ₁ and V ₂ does not change, and the overall wave height decreases with a similar shape. Therefore, by detecting the attenuation constant α, it is possible to detect the degree of wetting without contact within a fixed distance without being affected by the distance.

  In addition, the switch which can switch oscillation and reception is provided, and the transmission antenna 22 and the reception antenna 23 can be shared by a single transmission / reception antenna by controlling the switch switching by the timing circuit 25. . The sensor unit 13 may be connected in series with the resonance circuit. In this case, the resistance value of the sensor unit 13 decreases ⇒ Q increases ⇒ Check for the presence or absence of damped vibration immediately after burst oscillation. If there is attenuation (if α is small), it is wet (if α is large). It becomes a way of distinguishing that there is no.

  In the above method, if the transmitter / receiver is brought close to the diaper and there is a response, it will be wet, so it will not be related to the distance (it will not respond if it is too far), but it will not react even if you do not see α It can be detected only by the presence or absence. This is a method similar to a dip meter, but has the advantage that it is not necessary to oscillate the frequency unlike a dip meter.

  The conventional moisture detection device is a method for detecting the presence or absence of moisture by utilizing the fact that a reflected radio wave is not emitted when the coil pattern of the resonance circuit or the capacitor pattern is short-circuited (column 0012 in Patent Document 1). reference). In this method, even a small amount of moisture causes the resonant circuit to be short-circuited, and it is difficult to determine the degree of wetting. However, the moisture detection device of the present invention includes the sensor unit 13 separately from the resonance circuit unit 14 so that moisture does not enter the resonance circuit unit 14 but only moisture enters the sensor unit 13 and the resistance value changes. It has become.

  For this reason, in the moisture detection device of the present invention, the resistance value of the sensor unit 13 varies widely depending on the degree of wetting, and the control of the change width of the Q value is easy. Therefore, the resistance value changes according to the degree of wetting, the Q value changes, and the attenuation constant α changes, so that the degree of wetting can be determined from the attenuation constant α.

  In addition, in the conventional moisture detection device, since the wetting is directly detected by the resonance circuit portion, it is necessary to arrange the resonance circuit portion composed of a coil pattern and a capacitor pattern of a certain size in the crotch of the diaper that is easily twisted. However, when the resonance circuit portion is twisted, there is a problem that the L value or the C value changes, the resonance frequency changes, and a deviation from the resonance frequency of the transmission / reception circuit tends to occur. In order to obtain a predetermined L value for resonating, some design ingenuity is essential. However, if a strong structure is used, the wearing site is a delicate place, and the wearer feels uncomfortable. On the other hand, in the moisture detection device of the present invention, the coil pattern and the capacitor pattern can be separately attached to a position that does not get in the way like a card, and they are arranged on the abdomen and buttocks that are difficult to twist even when incorporated in a diaper. Therefore, the above-mentioned problems do not occur and highly stable moisture detection can be performed.

  Moreover, in the conventional water | moisture content detection apparatus, when a diaper gets wet and the response when a sensor does not exist becomes the same, both cannot be discriminate | determined (refer the 0024 column of patent document 1). However, in the moisture detection device of the present invention, when the diaper gets wet, the response is V2 / V1 = small, and both V1 and V2 are only noise components, and when V2 / V1 = 1, it can be treated as no diaper. Both can be discriminated. This also contributes to the fact that the rate of change of the Q value corresponding to the amount of water adhesion is moderate.

FIG. 7 shows simulation results of various waveforms. (A) shows an example of a transmission waveform in the transmission coil 22. The waveform oscillates at a frequency 125kHz sent between 0.4 ms, oscillates OFF at time _{t 0.} (B) shows an example of a received waveform in the receiving coil 23, in which the sensor unit 13 is open (resistance value is infinite) and there is no moisture. Also in this case, the vibration waveform attenuates after time t _{0 when the} oscillation is turned off due to the resistance of the coil and the capacitor itself.

This attenuation is expressed by i = i ₀ e ^−αt , and when converted into an expression for ^obtaining the attenuation constant α,
α = −ln (i / i0) / t For example, from the oscillation OFF (t ₀ ), when the value after 0.01 ms is calculated as i ₀ , the value after 0.04 ms is set as i, and 0.04−0.01 = 0.03 ms is calculated as t, the attenuation in this case The constant α is about 14000 [s ⁻¹ ].

(C) shows an example of a received waveform in the receiving coil 23 when the sensor unit 13 is wet and the resistance between the terminals of the sensor unit 13 is 2 kΩ. In this case, the attenuation constant α calculated on the same basis as above is about 79000 [s ⁻¹ ].

(D) is a case where the resonance circuit part 14 and the sensor part 13 do not exist. For example, there is no diaper wearer. The received waveform of the reception coil 23 is only the direct reception amount of the transmission waveform of the transmission coil 22 in the case, amplitude after t ₀ is approximately zero. Since the received waveform after 0.01 ms from t ₀ is not observed, it is determined that there is no diaper wearer in this case. At this time, since the received waveforms after 0.01 ms and 0.03 ms from t ₀ are only equal to both noise components, the attenuation constant α is about 0 [s ⁻¹ ]. Even if the sensor unit 13 is considerably wet, there is a possibility that V1 and V2 become substantially the same as a result of rapid attenuation. However, it is possible to set the resistance between the terminals of the sensor unit 13 to 1 kΩ or more, for example. Is possible. That is, the received waveform after 0.01 ms from t ₀ can be prevented from becoming zero. In this way, by setting the minimum resistance value between the terminals, α becomes extremely large in the case of excessive wetting, and α becomes 0 in the absence of the wearer, so that discrimination is possible.

  Therefore, by detecting the attenuation constant α, it is possible to reliably detect the degree of diaper wetting and the absence of the resonance circuit unit 14 itself regardless of the distance between the transmission / reception coils 22 and 23 and the resonance circuit unit 14.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

  The present invention can reliably detect the degree of diaper wetting and the absence of the resonance circuit unit itself regardless of the distance between the transmission / reception coil and the resonance circuit unit by detecting the attenuation constant α of the damped vibration waveform. Therefore, it can be suitably used for detecting diaper wetting in the field of nursing care and the like.

Claims (4)

A resonant circuit unit comprising a coil and a capacitor;
A sensor unit connected to the resonant circuit unit and configured to cause electrical conduction and / or a change in resistance value due to moisture;
The resonance circuit unit generates a reflected radio wave by a transmission radio wave from the oscillation circuit unit, and receives the reflected radio wave;
An analysis circuit for analyzing the reflected radio wave received by the receiving circuit unit;
The analysis circuit analyzes a damped oscillation waveform of the reflected radio wave and compares at least two timing voltages to detect moisture in the sensor unit and to detect the absence of a resonant circuit unit. apparatus.   The moisture detection device according to claim 1, wherein the analysis of the damped oscillation waveform of the reflected radio wave is performed by comparing a voltage immediately after the oscillation is turned off with a voltage after a certain period of time thereafter.   The moisture detection apparatus according to claim 1, wherein moisture is not attached to the resonance circuit unit.   The moisture detection device according to claim 1, wherein the sensor unit is made of an anisotropic conductive woven fabric in which at least two conductive yarns are arranged in the longitudinal direction.

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