JP2005134230A - Liquid level detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily-maintainable liquid level detection device simply detecting highly-accurate liquid level. <P>SOLUTION: This liquid level detection device 1 for detecting the water level in a water storage tank 2 for storing water 3 is equipped with small-sized heaters 5A, 5B for generating the heat in the water storage tank 2, thermocouples 6A, 6B arranged near the small-sized heaters 5A, 5B, for detecting the temperature, and a water level detection part 7C for detecting the water level based on the temperature difference between the non-heating state and the heating state of the small-sized heaters 5A, 5B from the temperature detected by the thermocouples 6A, 6B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid level detection device that is easy to maintain and can easily detect a high-accuracy liquid level.

  Conventionally, a float type, a capacitance type, a self-power generation type thermistor type, and the like are known as methods for detecting a specific water level in a water tank. In the float type, the float is floated on the water surface, and the reed switch is activated by the vertical movement of the magnet in the float accompanying the vertical movement of the water surface, thereby detecting the water level. In the capacitance type, two electrodes are inserted into water, and the water level is detected by measuring the dielectric constant difference between the dielectric constant of water and the dielectric constant of air. The self-power generation type thermistor type uses a self-heating type thermistor and detects the water level by a resistance difference (see Patent Document 1).

JP 2001-159556 A

  However, the float type described above has a problem in that, due to long-term use, scales or the like adhere to the movable part of the reed switch, and the reed switch does not operate normally and the water level cannot be detected accurately. . In addition, since the capacitance type requires an electrode having a predetermined length, there is a problem in that it cannot be used for a water tank that does not satisfy the predetermined size due to the limitation of the size of the water tank. It was. Further, the self-heating type thermistor type requires calibration in accordance with the use environment of the thermistor, and the calibration is performed each time according to the change of the use environment, so that there is a problem that it takes time and labor for that.

  In view of the above circumstances, an object of the present invention is to provide a liquid level detection device that is easy to maintain and can easily detect a highly accurate liquid level.

  In order to achieve the above object, a liquid level detection device according to claim 1 is a liquid level detection device that detects a liquid level of a liquid tank that stores liquid, and a heating means that generates heat in the liquid tank. A temperature detecting means for detecting a temperature, and a liquid level detecting means for detecting the liquid level based on the temperature detected by the temperature detecting means. To do.

  According to a second aspect of the present invention, there is provided the liquid level detection device according to the above invention, wherein the liquid level detection means detects the liquid level based on a temperature difference between a non-heat generation state and a heat generation state of the heat generation means. Features.

  According to a third aspect of the present invention, there is provided the liquid level detection device according to the above invention, wherein the liquid level detection means detects the liquid level based on a temperature change after the heat generation means starts to generate heat.

  According to a fourth aspect of the present invention, there is provided a liquid level detection device for detecting a liquid level of a liquid tank for storing a liquid, wherein the liquid level detection device is disposed in the liquid tank and detects temperature, and the temperature And a liquid level detecting means for detecting the liquid level based on the temperature detected by the detecting means.

  According to the fourth aspect of the invention, the liquid level is detected by discriminating the temperature detected by the temperature detecting means.

  According to a fifth aspect of the present invention, in the liquid level detection device according to the first aspect, the liquid level detection means detects the liquid level based on a temperature difference between the temperature of the liquid and the temperature of the gas in the liquid tank. It is characterized by that.

  According to a sixth aspect of the present invention, there is provided the liquid level detection device according to the above invention, wherein a combination of the heat generation means and the temperature detection means or a plurality of the temperature detection means are arranged in the depth direction of the liquid tank. .

  According to a seventh aspect of the present invention, there is provided the liquid level detection apparatus according to the above invention, wherein the temperature detection means is disposed above and below the depth of the liquid tank with respect to the heat generation means.

  The liquid level detection device according to claim 8 is the liquid level control according to the above aspect, wherein the liquid level in the liquid tank is controlled to be a predetermined liquid level based on the liquid level detected by the liquid level detection means. Means are provided.

  According to a ninth aspect of the present invention, there is provided the liquid level detection device according to the above invention, further comprising temperature control means for performing control for maintaining the temperature of the liquid in the liquid tank at a predetermined temperature.

  According to the present invention, there is an effect that maintenance is easy and a highly accurate liquid level can be easily detected.

  Exemplary embodiments of a liquid level detection device according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a liquid level detection device according to Embodiment 1 of the present invention. The liquid level detection device 1 includes a water tank 2 for storing water 3, temperature detectors 4A, 4B, 4C installed in the water tank 2, a water supply pump 12 for supplying water to the water tank 2, and a water tank 2 An input for inputting signals from a solenoid valve 13 for discharging water 3 from the heater, a heater 11 for heating water 3 in the water tank 2, and thermocouples 6A, 6B, 6C attached to the temperature detectors 4A, 4B, 4C. An output unit 9 that outputs control signals to the unit 8, the heater 11, the water supply pump 12, and the solenoid valve 13, and detects and outputs the water level of the water tank 2 based on the signal input through the input unit 8. 9 includes a control unit 7 that controls the water level via 9 and a display unit 10 that displays various types of information.

  The control unit 7 includes a small heater control unit 7A that controls the small heaters 5A and 5B attached to the temperature detectors 4A and 4B, and thermocouples 6A and 6B that are attached to the temperature detectors 4A, 4B, and 4C. A temperature measurement unit 7B that inputs a voltage signal from 6C and measures the temperature corresponding to the voltage detected by thermocouples 6A, 6B, and 6C, and a water level detection that detects the water level based on the temperature measured by temperature measurement unit 7B The temperature of the water 3 in the water tank 2 based on the temperature of the water 3 detected by the temperature detector 4C and the water level controller 7D that controls the water level based on the water level detected by the unit 7C, the water level detector 7C. It has the water temperature control part 7E to control.

  In the temperature detectors 4A and 4B, small heaters 5A and 5B and thermocouples 6A and 6B are arranged in the vicinity so that the thermocouples 6A and 6B can efficiently detect the heat from the small heaters 5A and 5B. . On the other hand, only the thermocouple 6C is attached to the temperature detector 4C, and the thermocouple 6C detects the temperature of the water 3. The temperature detector 4C is provided in the vicinity of the bottom of the water storage tank 2 so that the temperature can be detected even when the water level is low. The temperature detectors 4 </ b> A and 4 </ b> B are arranged above and below across a “predetermined water level” that maintains the water level.

  The small heater control unit 7A energizes the small heaters 5A and 5B through the output unit 9 at predetermined intervals for a predetermined time, and the temperature measurement unit 7B transmits the temperature from the thermocouples 6A, 6B, and 6C through the input unit 8. Measure.

  FIG. 2 shows the time change of the temperature measured by the temperature measuring unit 7B when the temperature detectors 4A and 4B are in the air. When the small heaters 5A and 5B are energized for a predetermined time Δt (t0 to t1), the small heaters 5A and 5B generate heat, and the generated heat conducts air and is transferred to the thermocouples 6A and 6B disposed in the vicinity. The thermocouples 6A and 6B detect a temperature rise as a voltage by the heat transferred, and the temperature measurement unit 7B outputs a temperature rise corresponding to the voltage. The temperature measurement unit 7B measures the temperature rise detected by the thermocouples 6A and 6B as a temperature difference ΔT (T1-T0) at a predetermined time Δt. On the other hand, FIG. 3 shows the time change of the temperature measured by the temperature measuring unit 7B when the temperature detectors 4A and 4B are in water. In this case, the small heaters 5A and 5B generate heat, and the generated heat is conducted to the thermocouples 6A and 6B, but the medium is different. Therefore, the temperature measurement unit 7B is heated by energizing the heaters 5A and 5B for a predetermined time Δt. The difference ΔTT (T3−T2) is measured.

  When the heat medium is air, the heat conductivity of air is 0.59 W / (m · K), and when the heat medium is water, the heat conductivity of water is 0.022 W / (m · K), Air is more likely to transfer heat than water. For this reason, the heat transferred to the thermocouples 6A and 6B during the predetermined time Δt is more often when the heat medium is air than when the heat medium is water. As a result, the temperature difference detected by the thermocouples 6A and 6B and measured by the temperature measurement unit 7B via the input unit 8 is the temperature difference ΔT (T1-T0) in the air, and the temperature difference in the water. It is a difference ΔTT (T3−T2), and the relationship ΔT> ΔTT (T1−T0)> (T3−T2)) in which the temperature difference in air exceeds the temperature difference in water.

  Therefore, the water level detection unit 7C is provided with a threshold value Th ((T1-T0)> Th> (T3-T2)) between the temperature difference ΔT in the air and the temperature difference ΔTT in the water in advance. It is determined whether 4A and 4B are in the air or the water, and the water level is detected based on the determined result. It should be noted that a predetermined width may be provided for the threshold Th to obtain the threshold width ΔTh to eliminate the water level detection error.

  As shown in FIG. 4, even when the temperature detectors 4A and 4B are in warm water and the water temperatures are different, the water level can be detected by energizing the small heaters 5A and 5B for a predetermined time Δt. Here, the temperature difference ΔTT ′ (T3′−T2 ′) is the same as the temperature difference ΔTT (T3−T2), and it can be determined that the temperature detectors 4A and 4B are in water.

  The liquid level detection device 1 has the temperature detector 4B installed at the “low water level” position, the temperature detector 4A installed at the “full water level” position, and the gap between the “low water level” and the “full water level”. The “predetermined water level” is set so that the water level of the water 3 in the water tank 2 is maintained at the “predetermined water level”. In the initial state, when there is no water 3 in the water storage tank 2, the water level detection unit 7C determines that the water level is “low water level” or less, and outputs the determination result to the water level control unit 7D. Based on the determination result, the water level control unit 7D closes the electromagnetic valve 13 via the output unit 9 and operates the water supply pump 12 to start water supply. If the water supply is continued, water 3 is stored in the water tank 2 and the water level increases, and the water level eventually exceeds the “low water level”. When the water level is “low water level” or less, the temperature measurement unit 7B measures the temperature difference ΔT (T1−T0) based on the temperature detected by the thermocouple 6B, and the water level detection unit 7C Recognizing that it is greater than or equal to Th (ΔT> Th), the water level is determined to be “low water level” or less. When the water level exceeds the “low water level”, the temperature measurement unit 7B measures the temperature difference ΔTT (T3−T2) based on the temperature detected by the thermocouple 6B, and the water level detection unit 7C Recognizing the threshold value Th or less (ΔTT <Th), the water level is determined to be “low water level” or more.

  When the water level is not less than “low water level” and not more than “full water level”, the water level detection unit 7C determines that the water level is “predetermined water level” and notifies the water level control unit 7D that the water level is “predetermined water level”. Output. When the water level is “predetermined water level”, the water level control unit 7D stops the water supply pump 12 via the output unit 9 and stops water supply to the water storage tank 2.

  However, a time lag occurs after the water level detection unit 7C detects the “predetermined water level” until the water supply pump 12 stops water supply, or the interval between the “predetermined water level” is set narrow and the water level is stopped before the water supply stops. When the water level exceeds the “full water level”, the water level detection unit 7C detects that the water level is equal to or higher than the “full water level” and outputs to the water level control unit 7D that the water level is equal to or higher than the “full water level”. When the water level control unit 7D inputs that the water level is “full water level” or higher, the electromagnetic valve 13 is operated via the output unit 9 to discharge the water 3 so that the water level is restored to the “predetermined water level”. Adjust.

  In this way, when the water level of the water 3 in the water storage tank 2 is maintained at the “predetermined water level”, the water level detection unit 7C outputs that the water level is the “predetermined water level” to the water temperature control unit 7E to control the water temperature. The unit 7E starts control using the heater 11 and the temperature detector 4C so as to keep the temperature of the water 3 at the predetermined temperature TW. The heater 11 is inserted into the water 3 of the water tank 2 and is energized through the output unit 9 to generate heat. The temperature of the water 3 rises due to heat conduction from the heater 11 that has generated heat. A thermocouple 6C is attached to the temperature detector 4C, and the thermocouple 6C detects the temperature of the water 3, and the temperature measuring unit 7B via the input unit 8 measures the measured temperature TC.

  The temperature measurement unit 7B outputs the measured measurement temperature TC to the water temperature control unit 7E. The water temperature control unit 7E compares the input measurement temperature TC with the predetermined temperature TW, and the measurement temperature TC is equal to or lower than the predetermined temperature TW. The heater 11 is energized via the output unit 9. Further, the water temperature control unit 7E stops energization to the heater 11 via the output unit 9 when the measured temperature TC is equal to or higher than the predetermined temperature TW. In this way, the water temperature control unit 7E keeps the temperature of the water 3 at the predetermined temperature TW. Further, when the water temperature control unit 7E determines that the temperature detector 4C is in the air based on the temperature detected by the temperature detector 4C in order to stop the heater 11 from being blown and prevent the heater 11 from being damaged. The energization to the heater 11 is stopped. In this case, since the temperature of the water 3 is kept higher than the temperature of the air, when the set temperature TU is provided for the temperature of the water 3 and the measured temperature TC is lower than the set temperature TU, the water level is a temperature detector. It is assumed that the temperature becomes 4C or less, and energization to the heater 11 is stopped.

  Next, in a state where the water level of the water 3 in the water tank 2 is maintained at the “predetermined water level” and the predetermined temperature TW, the control unit 7 receives a discharge instruction of the water 3 from the host system. When the control unit 7 receives the water 3 discharge instruction, the water level control unit 7D opens the electromagnetic valve 13 via the output unit 9, and continues to discharge the water 3 until receiving a water 3 discharge stop instruction from the host system. . Next, when the control unit 7 receives an instruction to stop the discharge of water 3 from the host system, the water level control unit 7D closes the electromagnetic valve 13 via the output unit 9 and stops the discharge of water 3.

  When the water level falls below the “low water level” due to the discharge of the water 3, the water level detection unit 7C detects that the water level falls below the “low water level” via the temperature detector 4B. ”Is output to the water level control unit 7D. When the water level is equal to or lower than the “low water level”, the water level control unit 7D operates the water supply pump 12 via the output unit 9, starts water supply to the water storage tank 2 again, and restores the “predetermined water level” to the water level. To do.

  FIG. 5 is a flowchart showing a control procedure by the controller 7 that maintains the “predetermined water level” of the water 3 in the water storage tank 2 and the predetermined temperature TW. First, the small heater control unit 7A and the temperature measurement unit 7B are activated (step S101). When the small heater control unit 7A and the temperature measurement unit 7B start to operate, the small heater control unit 7A energizes the small heaters 5A and 5B through the output unit 8 at predetermined time intervals for a predetermined time, and the temperature measurement unit. 7B measures the temperature difference corresponding to the voltage detected by the thermocouples 6A and 6B via the input unit 8. The temperature measurement unit 7B outputs the measured temperature difference to the water level detection unit 7C, and the water level detection unit 7C determines that the water level is “low water level” or less by the temperature difference, and the water level is “low water level” or less. Is output to the water level control unit 7D. The water level control unit 7D activates the water supply pump 12 via the output unit 9 and starts water supply (step S102).

  When the water supply is continued, the water level rises, and when the water level exceeds the “low water level”, the water level detection unit 7C determines that the water level has reached the “predetermined water level” (Yes in step S103). The water level detection unit 7C notifies the water level control unit 7D that the water level has reached the “predetermined water level”. When the water level is “predetermined water level”, the water level control unit 7D stops the operation of the water supply pump 12 via the output unit 9, and the water supply stops (step S104). There is a time lag while the water supply pump 12 stops operating after the water level detection unit 7C detects the “predetermined water level”. When the water level stabilizes, the water level exceeds the “full water level” and the water level detection unit 7C Is determined to be at or above the “full water level” (step S105, Yes), the water level detection unit 7C notifies the water level control unit 7D that the water level is at or above the “full water level”. When the water level is equal to or higher than the “full water level”, the water level control unit 7D opens the electromagnetic valve 13 via the output unit 9 (step S107), discharges the water 3, and the water level detection unit 7C determines that “the predetermined water level”. Lower the water level until

  On the other hand, even if the water supply is stopped (step S104), there is no overshoot of the water level (step S105, No), and when the water level is maintained at the “predetermined water level”, the water temperature control unit 7E is connected via the output unit 9. The heater 11 is energized, and the temperature measurement unit 7B measures the temperature of the water 3 detected by the temperature detector 4C via the input unit 8 (step S106). The temperature measurement unit 7B outputs the measured measurement temperature TC to the water temperature control unit 7E, and the water temperature control unit 7E determines whether the measurement temperature TC is equal to or higher than the predetermined temperature TW (step S108). When it is determined that the temperature is equal to or higher than the predetermined temperature TW (step S108, Yes), the power supply to the heater 11 is stopped (step S109).

  The water temperature control unit 7E compares the measured temperature TC with the predetermined temperature TW, repeats energization of the heater 11 and stops energization, and keeps the temperature of the water 3 at the predetermined temperature TW. In this way, the water level is kept at the “predetermined water level”, and the temperature of the water 3 is kept at the predetermined temperature TW. When the control unit 7 receives a water discharge instruction from the host system (step S110, Yes), the water level control unit 7D opens the potential valve 13 via the output unit 9 and starts discharging the water 3 (step S111). ).

  Next, if the control part 7 receives discharge stop of the water 3 from a high-order system (step S112, Yes), the water level control part 7D will close the solenoid valve 13 via the output part 9, and will stop discharge of the water 3 (Step S113). When the amount of water 3 discharged is large and the water level falls below the “low water level”, the water level detection unit 7C determines that the water level is below the “low water level” (step 114, Yes), and the water level detection unit 7C It outputs to the water level control part 7D that it is below "low water level". When the water level is equal to or lower than the “low water level”, the water level control unit 7D operates the feed water pump 12 via the output unit 9, starts water supply, and performs control to restore the water level to the “predetermined water level”. When the water level is further below the “low water level” and is below the depth of the temperature detector 4C, the water temperature control unit 7E stops energization of the heater 11 (step S115) and prevents the heater 11 from being blown. . If the discharge of the water 3 is small and the water level does not fall below the “low water level” (No at step S114), the water level control unit 7D maintains the current state.

  FIG. 6 shows the temperature detected by the thermocouples 6A and 6B in the time Δt ′ (t0 to t1 ′) shorter than the predetermined time Δt (t0 to t1) in which the water level detector 7C energizes the small heaters 5A and 5B. It shows that the water level can be detected by the difference in the degree of increase (T5-T0) / (t1'-t0), (T4-T2) / (t1'-t0). In this way, the water level can be quickly controlled.

  FIG. 7 shows a block diagram in which small heaters 5A and 5B are arranged in parallel. With the arrangement shown in FIG. 7, the small heaters 5A and 5B can be uniformly energized, and the temperature can be measured more accurately. Further, as shown in FIG. 8, by arranging a large number of temperature detectors 4A, 4B, 4C, 4D, and 4E in the water storage tank 2 in the direction of change of the water level, a more accurate water level can be detected, Can be varied.

  FIG. 9 shows a temperature detector 40 in which thermocouples 60A and 60B are arranged symmetrically with respect to one small heater 50 in the vertical direction. If this temperature detector 40 is arranged at the “predetermined water level”, it can be detected that the water level is between the thermocouples 60A and 60B only by measuring that the temperatures detected by the thermocouples 60A and 60B are different. Furthermore, if the temperature detector 40 is moved in the direction of change of the water level in the water storage tank 2, the “predetermined water level” can be varied.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, a small heater and a thermocouple in the vicinity thereof are attached to the temperature detector, the small heater is heated, the temperature difference of the generated heat is detected by the thermocouple, and the detected temperature difference is based on the detected temperature difference. In the second embodiment, thermocouples are installed in a pair of temperature detectors, and the water level is detected based on the temperature difference detected by each thermocouple. ing.

  FIG. 10 is a block diagram showing a schematic configuration of the liquid level detection device 20 according to the embodiment of the present invention. 10, the same components as those in the liquid level detection device 1 shown in FIG.

  In FIG. 10, the liquid level detection device 20 includes temperature detectors 4F, 4G, and 4H to which thermocouples 6F, 6G, and 6H are attached, and the temperature detector 4G is at the “low water level” position of the water tank 2. The temperature detector 4F is attached at the “full water level” position of the water tank 2 so as to keep the water level at a “predetermined water level” between the “low water level” and the “full water level”.

  The liquid level detection device 20 includes a heater 11 and a temperature detector 4H so that the water 3 in the water storage tank 2 is maintained at a predetermined temperature. Further, the water level detection device 20 has a preheating heater 14 between the water storage tank 2 and the water supply pump 12, and the preheating heater 14 is energized when water is supplied to the water storage tank 2, so that the temperature of the water 3 does not change rapidly. I am doing so.

  It is empirically known that when the temperature of the water 3 is 40 ° C. or higher, the temperature in the water is measured 5 ° C. or more higher than the temperature in the air above the water. Accordingly, the water temperature control unit 7E controls the temperature of the water 3 to be kept at 40 ° C. or more, measures the temperature input from the temperature detectors 4F and 4G by the temperature measurement unit 7B via the input unit 8, and If the temperature difference is 5 ° C. or more, the water level detection unit 7C can determine that the water level is at the “predetermined water level”. Thus, if the temperature of the water 3 is kept at a predetermined temperature and the temperature is detected by the temperature detectors 4F and 4G, the water level can be detected. Further, if the water level can be detected, as described in the first embodiment, the “predetermined water level” can be maintained by the water level control unit 7D controlling the water level. Of course, in the second embodiment, the temperature of the water 3 is set to 40 ° C. or higher. However, by knowing the temperature of air corresponding to the case where the temperature is set to 40 ° C. or lower, the water level is not dependent on the temperature of the water 3. May be detected.

  In the first and second embodiments described above, the water level detected by the water level detection unit 7C is output to the water level control unit 7D to automatically control the water level, but the water level is displayed on the display unit 10. The operator may control the water level based on the displayed water level. In this case, the contents of the display unit 10 are output to the host system. Thereby, when the water supply status and the discharge status change, control corresponding to the change can be performed. In addition, a new input unit may be provided to control locally. Further, in the first and second embodiments, the temperature is detected using the thermocouples 6A, 6B, 6C, 6F, and 6H. However, other temperature detection means such as a thermistor may be used.

  In the first and second embodiments described above, the thermocouples 6C and 6H provided in the temperature detectors 4C and 4H are used to detect the temperature of the water 3, but the thermocouples 6B and 6G are used instead. Also good.

  In the first and second embodiments described above, the liquid is water and the gas in the liquid tank is air. However, for example, the liquid may be used for beverages, or the gas in the liquid tank may be used. It is good also as gas added to drinks, such as a carbon dioxide gas.

It is a block diagram which shows schematic structure of the liquid level detection apparatus which is Embodiment 1 of this invention. It is a graph which shows the temperature which a temperature measurement part measures. It is a graph which shows the temperature which a temperature measurement part measures. It is a graph which shows the temperature which a temperature measurement part measures. It is a flowchart in which a control part shows control of a water level and water temperature. It is a graph which shows the temperature which a temperature measurement part measures. It is a block diagram which shows the small heater wiring which is a modification of Embodiment 1 of this invention. It is a block diagram which shows arrangement | positioning of the several temperature detector which is a modification of Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the temperature detector which is a modification of Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the liquid level detection apparatus which is Embodiment 2 of this invention.

Explanation of symbols

1,20 Liquid level detector 2 Water tank 3 Water 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 40 Temperature detector 5A, 5B, 50 Small heater 6A, 6B, 6G, 6H, 60A, 60B Thermocouple 7 Control unit 7A Small heater control unit 7B Temperature measurement unit 7C Water level detection unit 7D Water level control unit 7E Water temperature control unit 8 Input unit 9 Output unit 10 Display unit 11 Heater 12 Water supply pump 13 Electromagnetic valve 14 Preheating heater

Claims (9)

In the liquid level detection device that detects the liquid level of the liquid tank that stores the liquid,
Heating means for generating heat in the liquid tank;
A temperature detecting means arranged in the vicinity of the heat generating means for detecting the temperature;
Based on the temperature detected by the temperature detecting means, a liquid level detecting means for detecting the liquid level;
A liquid level detection device comprising:   The liquid level detection device according to claim 1, wherein the liquid level detection unit detects the liquid level based on a temperature difference between a non-heat generation state and a heat generation state of the heat generation unit.   The liquid level detection device according to claim 1, wherein the liquid level detection unit detects the liquid level based on a temperature change after the heat generation unit starts to generate heat. In the liquid level detection device that detects the liquid level of the liquid tank that stores the liquid,
A temperature detecting means arranged in the liquid tank for detecting the temperature;
Based on the temperature detected by the temperature detecting means, a liquid level detecting means for detecting the liquid level;
A liquid level detection device comprising:   The liquid level detection device according to claim 4, wherein the liquid level detection unit detects a liquid level based on a temperature difference between a temperature of the liquid and a temperature of a gas in the liquid tank.   The liquid level detection device according to any one of claims 1 to 5, wherein a combination of the heat generation unit and the temperature detection unit or a plurality of the temperature detection units are arranged in the depth direction of the liquid tank. .   The liquid level detection device according to claim 1, wherein the temperature detection unit is disposed above and below the heat generation unit in a depth direction of the liquid tank. .   The liquid level control means which performs control which maintains the liquid level of the said liquid tank at a predetermined liquid level based on the liquid level which the said liquid level detection means detected is provided. Liquid level detection device as described in one.   The liquid level detection device according to any one of claims 1 to 8, further comprising a temperature control unit that performs control to maintain a temperature of the liquid in the liquid tank at a predetermined temperature.

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