JP2011075529A - Liquid leakage detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect surely and quickly the leakage of a specific liquid having a high ion concentration distinctively from a liquid having a low ion concentration. <P>SOLUTION: This device includes: a first electrode D1; a second electrode D2 provided at an interval of a prescribed distance from the first electrode D1; a voltage generation part 12 which is a voltage application means for applying a voltage having a step waveform through a current restriction resistor between the first electrode D1 and the second electrode D2; a detection part 13 which is a potential detection means for detecting potential between the first electrode D1 and the second electrode D2 with the passage of time; and a determination means 21 for determining the leakage of a specific liquid based on the potential detected by the detection part 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid leak detection apparatus that detects a leak of a specific liquid having a high ion concentration separately from a liquid having a low ion concentration, and particularly a liquid having a high ion concentration used in the medical field, such as blood and physiological saline. In addition, the present invention relates to a liquid leak detection apparatus for performing leak detection on a liquid such as various infusion drug solutions while distinguishing it from water having a low ion concentration.

  As a conventional liquid leak detection device, as shown in FIG. 10A, two electrodes D1 and D2 are arranged at a fixed distance, and a DC voltage V is applied between the electrodes D1 and D2 by a DC power source E. And what measures the impedance between electrodes D1 and D2 is known (refer to patent documents 1). Instead of the DC voltage V from the DC power source E, there is also known one that performs measurement by giving a waveform voltage (see Patent Document 2).

  In the above apparatus, as shown in FIG. 10 (b), the impedance when the blood B to be detected is slightly adhered between the electrodes D1 and D2, and the electrode D1 as shown in FIG. 10 (c). , D2 cannot be distinguished from the impedance when a large amount of water droplets W that are not detected are attached. Therefore, erroneous detection may occur in an environment where the portions of the electrodes D1 and D2 are condensed.

  On the other hand, as shown in FIG. 11 (a), when blood leakage is detected, the red light source R and the light sensor S, which are best absorbed by blood, are arranged to face each other, and the red light source R There is known an apparatus in which an optical path between the sensor and the optical sensor S is arranged at a place where blood leakage is expected. As shown in FIG. 11B, when the blood B to be detected exists in the optical path, the occurrence of leakage is notified. According to this apparatus, it is possible to distinguish between blood and condensed water droplets.

  The apparatus using the above optical sensor S has a problem that the monitoring range is narrow because the optical path between the red light source R and the optical sensor S is monitored. In order to solve this, it is possible to provide a liquid flow path that leads from the wide range of areas where leakage is expected to the optical path, but there is a time lag before the liquid flows to the optical path through the liquid flow path, and quick detection is possible. There is a possibility of not being able to. Further, when the amount of leakage is small, there is a possibility that the optical path may not be reached.

Japanese Utility Model Publication No. 63-26302 Japanese Unexamined Patent Publication No. 03-2652

  The present invention has been made as a solution to the problems of the conventional liquid leak detection apparatus as described above, and its purpose is to distinguish the leakage of a specific liquid having a high ion concentration from a liquid having a low ion concentration. Another object of the present invention is to provide a liquid leak detection device that can detect reliably and quickly. The present invention is an improvement of the devices described in Patent Documents 1 and 2 described above. In these devices, only the total impedance is taken into account, and thus the above-described erroneous detection occurs. However, the present invention achieves the above object by individually considering the individual impedances of the resistance of the liquid itself (solution resistance) and the resistance of the contact portion between the electrode and the liquid (charge transfer resistance). Is.

  A liquid leak detection apparatus according to the present invention is a liquid leak detection apparatus that detects a leak of a specific liquid having a high ion concentration by distinguishing it from a liquid having a low ion concentration, and includes a first electrode, the first electrode, A second electrode provided with a gap of a predetermined distance; a voltage applying means for applying a step waveform voltage between the first electrode and the second electrode via a current limiting resistor; A potential detecting means for detecting the potential between the first electrode and the second electrode over time; and a judging means for judging leakage of the specific liquid based on the potential detected by the potential detecting means. It is characterized by comprising.

  In the liquid leak detection apparatus according to the present invention, the voltage of the step waveform is applied to the determination unit when the liquid having a low ion concentration adheres over the first electrode and the second electrode. The initial potential is registered in advance as a reference initial potential, and the initial potential detected by the potential detecting means at the initial stage when the voltage of the step waveform is applied is greater than the previously registered reference initial potential. When the value is lower, the determination means determines that the specific liquid is leaking.

  In the liquid leakage detection device according to the present invention, when the initial potential is higher than the pre-registered reference initial potential, the determination unit applies the initial potential and the voltage of the step waveform to a steady state. The presence or absence of leakage of the specific liquid is determined based on the steady potential detected by the potential detection means at that time.

  The liquid leak detection device according to the present invention applies a step waveform voltage between the first electrode and the second electrode, detects the potential between the two electrodes over time, and detects this over time. Since the leakage of a specific liquid is determined based on the potential, by detecting the potential over time, the resistance of the liquid itself (solution resistance) and the resistance of the contact portion between the electrode and the liquid (charge transfer resistance) Impedance can be detected, and the type of liquid can be determined by taking into account each detected impedance individually, so that leaks of specific liquids with high ion concentration can be detected quickly and reliably from liquids with low ion concentration can do.

  In the liquid leak detection device according to the present invention, when the initial potential is lower than the reference initial potential, the determination unit determines that a specific liquid having a high ion concentration is leaking. A liquid leakage of a liquid having a high ion concentration, such as blood, which is different from the adhesion of a low liquid, can be detected quickly and reliably.

  In the liquid leak detection apparatus according to the present invention, when the initial potential is higher than the reference initial potential registered in advance, the determination unit determines whether or not a specific liquid leaks based on the initial potential and the steady potential. Therefore, it is possible to detect the inherent resistance (solution resistance) of the liquid with the initial potential, detect the charge transfer resistance with the steady potential, and determine the type of the liquid based on the value of those resistances. The liquid leakage can be detected quickly and reliably.

The block diagram which shows the structure of embodiment of the liquid leak detection apparatus which concerns on this invention. The figure which shows schematic structure of the principal part in the embodiment of the liquid leak detection apparatus which concerns on this invention, and the equivalent circuit of a liquid. The figure which shows the equivalent circuit containing the change of the response potential at the time of applying the voltage of a step waveform by embodiment of the liquid leak detection apparatus based on this invention, and a voltage generation part and a liquid. The figure which shows the state which the blood adhered between two electrodes in embodiment of the liquid leak detection apparatus which concerns on this invention, and the figure which shows the change of the response potential at the time of applying the voltage of a step waveform in this case. The figure which shows the state which the water droplet adhered between two electrodes in embodiment of the liquid leak detection apparatus which concerns on this invention, and the figure which shows the change of the response potential at the time of applying the voltage of a step waveform in this case. The figure which shows the two-dimensional map showing whether the liquid adhering in embodiment of the liquid leak detection apparatus which concerns on this invention is blood or water. The block diagram which shows the structural example of the blood temperature control apparatus to which embodiment of the liquid leak detection apparatus which concerns on this invention is applied. AA sectional drawing in FIG. BB sectional drawing in FIG. The block diagram which shows the structure of the conventional liquid leak detection apparatus by a direct current application. The block diagram which shows the structure of the conventional liquid leak detection apparatus by red light.

  Hereinafter, a liquid leak detection apparatus according to the present invention will be described with reference to the accompanying drawings. In the present embodiment, the detection target is blood and is detected separately from water droplets. As shown in FIG. 1, the liquid leakage detection apparatus according to the present invention includes a liquid leakage sensor unit 11, a voltage generation unit 12, a detection unit 13, and a processing unit 14 as main components. The processing unit 14 includes an arithmetic processing unit 15, a display unit 16, and an alarm generation unit 17. As shown in FIG. 2A, the liquid leakage sensor unit 11 includes a first electrode D1 composed of a printed wiring printed on a printed circuit board, and a gap d of a predetermined distance from the first electrode D1. The second electrode D2 provided in the first electrode D2 is provided to detect a specific liquid F (blood) to be detected that adheres integrally between the two electrodes D1 and D2. As an example, the first electrode D1 and the second electrode D2 can be set such that the gap d is 1 mm, the electrode length is 130 mm, and the width is 1 mm when blood is a liquid to be detected.

  The voltage generator 12 forms a voltage Vin having a step waveform as shown in FIG. 3 (a) and applied between the first electrode D1 and the second electrode D2. It is. Here, the step waveform voltage Vin applies a rectangular pulse repeatedly, and the pulse width of the step waveform is a terminal after the voltage Vin is applied between a first electrode D1 and a second electrode D2, which will be described later. More than the time until the potential V of T becomes constant (steady state) (the electric double layer capacitance Cw is sufficiently charged), and the time between the adjacent rectangular pulses is the charge of the electric double layer capacitance Cw. More than the time when the battery is sufficiently discharged and the potential V of the terminal T becomes constant. In this embodiment, in order to use blood as a liquid to be detected, for example, a rectangular wave having a magnitude of 5 V, a pulse width of 500 msec, and a time between adjacent rectangular pulses of 500 msec, that is, a frequency of 1 Hz is generated. Thus, the voltage generator 12 can be set.

  Further, it may be set so as to generate a rectangular wave (duty ratio 50%) having a pulse width much shorter than the time until the steady state is reached, for example, a magnitude of 5 V and a frequency of 10 kHz. In this case, the magnitude (pp value) of the AC component of the voltage observed at the terminal T reflects the solution resistance, and the magnitude of the DC component reflects the charge transfer resistance.

  The detection unit 13 detects a potential generated between the first electrode D1 and the second electrode D2. In this embodiment, the detection unit 13 is provided with an A / D converter, and a voltage value sampled at a predetermined sampling rate is sent to the arithmetic processing unit 15.

  As shown in FIG. 2 (b), an equivalent circuit in the case where the electrolytic solution F adheres between the first electrode D1 and the second electrode D2 is shown in FIG. 2 (b). Rl and the charge transfer resistor Rt are connected in series, and the electric double layer capacitance Cw is connected in parallel to the charge transfer resistor Rt. Further, the voltage generator 12 is a circuit in which a power source of the voltage Vin and a current limiting resistor Rr are connected in series as shown in FIG.

  The detection unit 13 detects the potential V of the terminal T in the equivalent circuit shown in FIG. In this manner, the detection unit 13 constitutes a potential detection unit that detects the potential between the first electrode D1 and the second electrode D2 over time. The arithmetic processing unit 15 includes determination means 21 that determines liquid leakage based on the potential sent from the detection unit 13.

  The determination means 21 applies the potential detected by the detection unit 13 and the potential V of the terminal T when the voltage of the terminal T becomes constant (steady state) at the initial stage of applying the voltage of the step waveform. Liquid leakage is determined based on the potential detected by the detection unit 13.

  The process regarding the determination means 21 is demonstrated in detail. When the electrolytic solution F adheres between the first electrode D1 and the second electrode D2 as shown in FIG. 2A, the terminal T of the equivalent circuit shown in FIG. The potential V changes as shown in FIG. Here, the potential V of the terminal T at the initial stage when the step waveform voltage Vin is applied is ΔV1 (ΔV1 = Vin × Rl / (Rr + Rl)), which represents a voltage drop in the solution resistance Rl.

  Further, the potential V of the terminal T gradually increases as shown in FIG. 3A, and the potential V of the terminal T when the step waveform voltage Vin is applied and becomes a steady state becomes the above ΔV1. A potential obtained by adding ΔV2 (ΔV2 = Vin × Rt / (Rr + Rl + Rt)). Here, the potential ΔV2 represents a voltage drop in the charge transfer resistance Rt. The potential ΔV3 related to the difference of the step waveform up to the voltage Vin represents a voltage drop in the current limiting resistor Rr, and ΔV3 = Vin × Rr / (Rr + Rl + Rt).

  When a small amount of blood B adheres between the first electrode D1 and the second electrode D2 as shown in FIG. 4A, the potential V of the terminal T with respect to the voltage Vin of the step waveform over time. 4B, and a large amount of water droplets W are formed between the first electrode D1 and the second electrode D2 due to condensation as shown in FIG. 5A. The change with time of the potential V of the terminal T with respect to the voltage Vin of the step waveform when adhering to is as shown in FIG. 5B. As can be seen from FIGS. 4B and 5B, when a small amount of blood and a large amount of water droplets adhere to the electrode, the difference in potential when the potential of the terminal T becomes constant is notable. Not appearing. Accordingly, it is difficult to distinguish and detect a small amount of blood and a large amount of water droplets in a conventional apparatus that detects leakage only by detecting the potential when the potential at the terminal T becomes constant.

  In the present embodiment, when the water droplet W adheres to the entire first electrode D1 and the second electrode D2, the initial potential when the step waveform voltage Vin is applied is determined as the reference initial value. It is registered in advance as a potential. The solution resistance of the blood B and the water droplet W is smaller than that of the water droplet W when the amount is the same. The solution resistance of the water droplet W is the smallest when the water droplet W adheres over the first electrode D1 and the second electrode D2 as described above. In this case, the solution resistance of the water droplet W is the solution of the blood B. May be less than resistance. Therefore, the reference initial potential is set to a value corresponding to the minimum value of the voltage drop in the solution resistance of the water droplet W attached between the first electrode D1 and the second electrode D2.

  It is assumed that the potential V of the terminal T when the voltage Vin having the step waveform is applied changes as shown in FIG. The determination unit 21 compares the potential ΔV1 with the reference initial potential, and determines that the attached liquid is blood if the potential ΔV1 is lower than the reference initial potential. If the potential ΔV1 is equal to or higher than the reference initial potential, whether the attached liquid is blood or water droplets is determined in consideration of ΔV2 as follows.

The determination means 21 also registers a two-dimensional map shown in FIG. FIG. 6 is a map representing whether the attached liquid is blood or water using the potentials ΔV1 and ΔV2 as parameters. When the potential ΔV1 is lower than the reference initial potential, the adhering liquid is blood. When the potential ΔV1 is low and the potential ΔV2 is high, the map is created. When the potential ΔV1 is high and the potential ΔV2 is low. It is water. The unclear area is set on the safe side, in this case blood.

  For example, if the point determined by the potential ΔV1 and the potential ΔV2 is the point A, it is determined that the detected liquid is water. This is because the potential ΔV1 is relatively low (solution resistance is relatively small) and the potential ΔV2 is also low (charge transfer resistance is small), so it is determined that a large amount of water is attached to the sensor. If the point determined by the potential ΔV1 and the potential ΔV2 is point B, the potential ΔV1 is relatively low (solution resistance is relatively small) and the potential ΔV2 is high (charge transfer resistance is large). It is determined that the applied liquid is blood.

  In this embodiment, whether the blood is water or water is determined based on the potential ΔV1 and the potential ΔV2, but the potential V of the terminal T with respect to the step waveform when blood is attached (FIG. 4B, FIG. 5B, etc.) ) May be stored and the presence or absence of blood adhesion may be determined based on the similarity compared to the actually measured waveform. If the liquid to be detected is different, it is necessary to set the reference initial potential and the two-dimensional map according to the liquid to be detected.

  The display unit 16 shown in FIG. 1 is configured to display messages such as “blood leakage occurrence” and “condensation occurrence” by the arithmetic processing unit 15 based on the determination result by the determination unit 21. The alarm generation unit 17 includes a speaker and generates an alarm sound. When the determination result by the determination unit 21 is “blood leak occurrence”, the arithmetic processing unit 15 is configured to generate the alarm sound. To generate an alarm sound.

  FIG. 7 shows a configuration example of a blood temperature control apparatus to which the liquid leak detection apparatus according to the present invention is applied. The blood temperature adjusting device is shown in FIG. 8 or the like in a housing 30 made of a material that is difficult to transfer heat, such as plastic, except for a place where a cooling / heating means 51 to be described later is attached. The heat medium 31 is enclosed. As the heat medium 31, water, antifreeze, or the like can be used.

  A laterally long opening 32 is formed on one wall surface of the housing 30 so that an infusion circuit 41 for transfusing blood can be inserted and removed. The bottom wall of the casing 30 erected as shown in FIG. 7 is made of a metal such as copper or stainless steel, which is a good heat conducting material, and has a cooling / heating means 51 made up of Peltier elements attached thereto. The heat medium 31 in the housing 30 is cooled / warmed by the cooling / warming means 51.

  FIG. 8 is a cross-sectional view taken along the line AA of FIG. 7, and FIG. FIGS. 8 and 9 both show the storage state in which the infusion circuit 41 is inserted into the storage chamber 33 from the opening 32. The storage chamber 33 connected to the opening 32 is made of a metal or metal alloy that is a good heat conductive material, and is watertight from the heat medium 31.

  The storage chamber 33 is provided at a substantially middle position of the height of the housing 30 and has a size capable of storing a required portion of the infusion circuit 41. Here, the required part is a part in which the tube 42 constituting the infusion circuit 41 is folded or a bag body in which a meandering blood passage is formed as disclosed in JP-A-9-602. Point to. Preferably, the infusion circuit 41 is in contact with all the walls of the storage chamber 33 so that heat exchange between the heat medium 31 surrounding the storage chamber 33 and the liquid in the infusion circuit 41 is performed.

  In the housing 30, an agitation unit 34 configured by, for example, a pump for agitating the heat medium 31 is provided. In this embodiment, the arrangement position of the stirring means 34 is the bottom bottom surface of the wall surface facing the wall surface in which the opening 32 is formed, and everything including the heat medium 31 above and below the storage chamber 33 can receive good stirring. Is arranged.

  The liquid in the infusion circuit 41 is sent out by an infusion pump or the like (not shown) and flows in the directions of arrows S1 and S2 in FIG. A temperature sensor 52 is provided in the tube 42 near the opening 32 for temperature adjustment by the cooling / warming means 51. Here, the temperature sensor 52 is provided in each of the tube 42 on the side where the liquid flows into the storage chamber 33 and the tube 42 on the side where the liquid flows out of the storage chamber 33.

  The signal detected by the temperature sensor 52 is taken into the control unit 60 and used as temperature data. The control unit 60 is provided with set temperature information, and the control unit 60 performs power control on the cooling / heating unit 51 according to the difference between the set temperature information and the temperature data obtained as described above. Make adjustments.

  The first electrode D1 and the second electrode D2 are embedded in the lower surface position of the portion surrounding the opening 32 in the storage chamber 33 of the housing 30 in an insulated state and the housing 30 in an insulated state. . A device case 70 is disposed on the top plate of the housing 30 via a heat insulating member (not shown).

  In the apparatus case 70, each component shown in FIG. 1 other than the first electrode D1 and the second electrode D2 is provided. In this example, the display unit 16 and the alarm generation unit 17 are provided on the surface of the device case 70.

  A voltage having a step waveform is supplied from a voltage generator 12 (not shown) in the device case 70 to the first electrode D1 and the second electrode D2 via the cord 71. Further, a signal line 72 extends from the first electrode D 1 and the second electrode D 2 to a detection unit 13 (not shown) in the apparatus case 70, and the detection unit 13 detects a potential via the signal line 72.

  According to such a configuration, when an infusion part such as the tube 42 stored in the storage chamber 33 is damaged and blood leaks, the blood flowing out from the opening 32 adheres between the first electrode D1 and the second electrode D2. To do. In the liquid leak detection device in the device case 70, the voltage generation unit 12 supplies the voltage Vin having a step waveform, the detection unit 13 detects a potential, and the determination means 21 in the arithmetic processing unit 15 of the processing unit 14 is described above. Judgment is made as follows.

  Therefore, the case where water droplets due to condensation adhere between the first electrode D1 and the second electrode D2 is properly distinguished from the case where blood adheres between the first electrode D1 and the second electrode D2. You will be informed of a blood leak.

  In the example described above, the detection target of leakage is blood and is detected separately from water droplets. However, the present invention is not limited to this, and leakage of a specific liquid having a high ion concentration is regarded as a liquid having a low ion concentration. It can be applied to distinguish and detect.

DESCRIPTION OF SYMBOLS 11 Liquid leak sensor part 12 Voltage generation part 13 Detection part 14 Processing part 15 Operation processing part 16 Display part 17 Alarm generation part 21 Determination means 30 Case 31 Heat medium 32 Opening 33 Storage chamber 34 Stirring means 41 Infusion circuit 42 Tube 51 Addition Temperature means 52 Temperature sensor 60 Control unit 70 Device case

Claims (3)

A liquid leak detection device that detects a leak of a specific liquid having a high ion concentration separately from a liquid having a low ion concentration,
A first electrode;
A second electrode provided at a predetermined distance from the first electrode;
A voltage applying means for applying a step waveform voltage between the first electrode and the second electrode via a current limiting resistor;
A potential detecting means for detecting a potential between the first electrode and the second electrode over time;
A liquid leakage detection apparatus comprising: determination means for determining leakage of the specific liquid based on a potential detected by the potential detection means. When the liquid having a low ion concentration adheres over the first electrode and the second electrode, the determination unit uses the initial potential applied with the step waveform voltage as a reference initial potential. When the initial potential that is registered in advance and detected by the potential detection means at the initial stage of applying the voltage of the step waveform is lower than the pre-registered reference initial potential, the determination means 2. The liquid leak detection apparatus according to claim 1, wherein it is determined that a specific liquid is leaking. When the initial potential is higher than the pre-registered reference initial potential, the determination means is the potential detection means when the initial potential and the voltage of the step waveform are applied to reach a steady state. The liquid leakage detection device according to claim 2, wherein presence or absence of leakage of the specific liquid is determined based on the detected steady potential.