Liquid level detection system

Abstract

To provide a technology that makes it possible to downsize and simplify the composition of a liquid level detection system.SOLUTION: A liquid level detection system comprises: a sheath tube extending along the vertical direction; a heater encapsulated in the sheath tube and extending along the vertical direction through the center of the sheath tube; a plurality of temperature sensors located at the surrounding of the header in the sheath tube and arranged at temperature detection points mutually different in the vertical direction; an energization unit for energizing the heater; a temperature information acquisition unit for acquiring temperature information from each of the plurality of temperature sensors in synchronism with energization to the heater; and an identification unit for identifying, on the basis of temperature information, which of a liquid phase and a gaseous phase each of the mutually different temperature detection points is located at, and identifying a liquid level.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a liquid level detection system.

Background Art

[0002] Patent Document 1 discloses a liquid level detection system including: a plurality of sheath tubes extending along the vertical direction; a plurality of heaters enclosed inside each of the plurality of sheath tubes and extending along the vertical direction at the center of each of the plurality of sheath tubes; and a plurality of temperature sensors each having a temperature detection point disposed inside each of the plurality of sheath tubes. The liquid level detection system further includes: a power supply unit for supplying power to the plurality of heaters; a temperature information acquisition unit for acquiring temperature information from each of the plurality of temperature sensors in synchronization with the power supply to the plurality of heaters; and an identification unit for identifying, based on the temperature information, whether each temperature detection point of the plurality of temperature sensors is located in a liquid phase or a gas phase, and identifying the liquid level.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional system, it is necessary to individually provide at least one heater for each temperature sensor, and there is a problem that the configuration of the system becomes large and complex.

[0005] This specification provides a technology capable of miniaturizing and simplifying the configuration of a liquid level detection system.

Means for Solving the Problems

[0006] The liquid level detection system disclosed in this specification includes a sheath tube extending along the vertical direction, a heater enclosed in the sheath tube and extending along the vertical direction through the center of the sheath tube, a plurality of temperature sensors located around the heater in the sheath tube and arranged at temperature detection points that are different from each other in the vertical direction, a power supply unit for energizing the heater, a temperature information acquisition unit for acquiring temperature information from each of the plurality of temperature sensors in synchronization with the energization of the heater, and an identification unit for identifying, based on the temperature information, whether each of the different temperature detection points is located in a liquid phase or a gas phase and identifying the liquid level.

[0007] According to the above configuration, in the liquid level detection system, one heater is shared by a plurality of temperature sensors. Therefore, compared with the conventional configuration, the configuration of the liquid level detection system can be miniaturized and simplified. In addition, since the number of sheath tubes and heaters is reduced, the evaporation of the liquid due to energizing the heater can also be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] (Configuration of the Liquid Level Detection System) Referring to FIGS. 1 and 2, the liquid level detection system 2 will be described. Although it is an example, the liquid level detection system 2 detects the liquid level of liquid hydrogen stored in a hydrogen engine vehicle, a hydrogen engine vehicle. As shown in FIG. 1, the liquid level detection system 2 includes a liquid level detection device 10 and a control device 12. The liquid level detection device 10 and the control device 12 are electrically connected.

[0010] The liquid level detection device 10 includes a sheath tube 20, a heater 22, a first temperature sensor unit 24, a second temperature sensor unit 26, a flange 28, and a relay amplifier 29. The sheath tube 20 extends along the vertical direction. The sheath tube 20 houses (encases) the heater 22, the first temperature sensor unit 24, and the second temperature sensor unit 26. The inside of the sheath tube 20 is filled with an inorganic insulator (for example, MgO).

[0011] The heater 22, the first temperature sensor unit 24, and the second temperature sensor unit 26 extend along the vertical direction within the sheath tube 20. The heater 22, the first temperature sensor unit 24, and the second temperature sensor unit 26 are connected to the relay amplifier 29. As shown in FIG. 2, the heater 22 includes a front heater wire 30 extending along the vertical direction, a lower heater wire 32, and a rear heater wire 34 extending along the vertical direction. The lower heater wire 32 is connected in a substantially U shape between the lower end of the front heater wire 30 and the lower end of the rear heater wire 34. The front heater wire 30 is disposed on the front side of the central axis A of the sheath tube 20, and the rear heater wire 34 is disposed on the rear side of the central axis A. The front heater wire 30 and the rear heater wire 34 are spaced apart from the central axis A by the same distance. The front heater wire 30 includes a first upper resistance portion 30A provided at the upper part of the front heater wire 30 and a first lower resistance portion 30B provided at the lower part of the front heater wire 30. The rear heater wire 34 includes a second upper resistance portion 34A provided at the upper part of the rear heater wire 34 and a second lower resistance portion 34B provided at the lower part of the rear heater wire 34. The upper resistance value, which is the sum of the resistance values of the first upper resistance portion 30A and the second upper resistance portion 34A, is larger than the lower resistance value, which is the sum of the resistance values of the first lower resistance portion 30B and the second lower resistance portion 34B. Also, the upper resistance value is larger than the total resistance value of the portions of the heater 22 that are different from the first upper resistance portion 30A, the first lower resistance portion 30B, the second upper resistance portion 34A, and the second lower resistance portion 34B. According to such a configuration, the calorific value in the vicinity of the first lower resistance portion 30B and the second lower resistance portion 34B can be made smaller than the calorific value in the vicinity of the first upper resistance portion 30A and the second upper resistance portion 34A. Note that, in a modified example, the upper resistance value and the lower resistance value may be the same. Also, in another modified example, the heater 22 may not include the first upper resistance portion 30A, the first lower resistance portion 30B, the second upper resistance portion 34A, and the second lower resistance portion 34B.

[0012] The first temperature sensor unit 24 in FIG. 1 includes a first front thermocouple wire 40 extending along the vertical direction, a first lower thermocouple wire 42 bent rearward from the lower end of the first front thermocouple wire 40, and a first rear thermocouple wire (not shown) bent upward from the rear end of the first lower thermocouple wire 42. A first temperature detection point 42A is provided at a first thermocouple 44 at the central portion of the first lower thermocouple wire 42. As an example, the first thermocouple 44 is a K thermocouple or an E thermocouple. The first lower thermocouple wire 42 is located slightly below the lower end of the flange 28. Specifically, the vertical position of the first lower thermocouple wire 42 is the same as the vertical central position of the first upper resistance portion 30A and the second upper resistance portion 34A.

[0013] The second temperature sensor unit 26 includes a second front thermocouple wire 50 extending along the vertical direction, a second lower thermocouple wire 52 bent rearward from the lower end of the second front thermocouple wire 50, and a second rear thermocouple wire 54 bent upward from the rear end of the second lower thermocouple wire 52. A second temperature detection point 52A is provided at a second thermocouple 56 at the central portion of the second lower thermocouple wire 52. The second lower thermocouple wire 52 is located between the lower end of the sheath tube 20 and the lower end of the heater 22. In a modified example, the lower end of the heater 22 may be located below the second lower thermocouple wire 52. In this case, it is preferable that the vertical positions of the first lower resistance portion 30B and the second lower resistance portion 34B and the vertical position of the second lower thermocouple wire 52 are the same.

[0014] The first temperature sensor unit 24 and the second temperature sensor unit 26 are arranged around the heater 22 such that a first distance, which is the distance between the first thermocouple 44 and the central axis A, and a second distance, which is the distance between the second thermocouple 56 and the central axis A, are the same. Also, the first temperature sensor unit 24 and the second temperature sensor unit 26 are arranged around the heater 22 such that the second thermocouple 56 is located on the opposite side of the first thermocouple 44 with respect to the central axis A.

[0015] The control device 12 is composed of a computer such as a CPU. The control device 12 includes a power supply unit 60, a temperature information acquisition unit 62, and a specifying unit 64. The power supply unit 60 supplies power to the heater 22. When power is supplied to the heater 22, the heater 22 is heated. The temperature information acquisition unit 62 acquires temperature information from the first temperature sensor unit 24 and the second temperature sensor unit 26 in synchronization with the energization of the heater 22. Specifically, the temperature information acquisition unit 62 acquires the electromotive forces of the first temperature sensor unit 24 and the second temperature sensor unit 26. Then, the temperature information acquisition unit 62 converts the acquired electromotive force into a temperature signal and supplies it to the specifying unit 64. The specifying unit 64 specifies the liquid level using the temperature signal acquired from the temperature information acquisition unit 62. In this embodiment, the specifying unit 64 determines whether the liquid level of liquid hydrogen is above the first temperature sensor unit 24, between the first temperature sensor unit 24 and the second temperature sensor unit 26, or below the second temperature sensor unit 26.

[0016] In the memory (not shown) of the control device 12, temperature relationship information indicating the relationship between the temperature change amount when the heater 22 is energized and the liquid level corresponding to the temperature change amount is stored in advance. The temperature relationship information is determined by experiments.

[0017] (Liquid level detection process) The liquid level detection process executed by the control device 12 will be described.

[0018] First, the control device 12 supplies power to the heater 22 via the energization unit 60. When power is supplied to the heater 22, the heater 22 generates heat. In this case, the liquid hydrogen around the sheath tube 20 is heated. Then, the first temperature detected by the first temperature sensor unit 24 and the second temperature detected by the second temperature sensor unit 26 change. The control device 12 acquires a first temperature signal corresponding to the first temperature and a second temperature signal corresponding to the second temperature via the temperature information acquisition unit 62. Then, the control device 12 uses the first temperature signal, the second temperature signal, and the temperature relationship information stored in the memory to detect the liquid level of the liquid hydrogen. Specifically, the control device 12 determines whether the first temperature detection point 42A is located in the liquid phase or the gas phase based on the temperature change amount of the first temperature, and determines whether the second temperature detection point 52A is located in the liquid phase or the gas phase based on the temperature change amount of the second temperature. When the control device 12 determines that the first temperature detection point 42A and the second temperature detection point 52A are located in the liquid phase, it determines that the liquid level is above the first temperature detection point 42A. Further, when the control device 12 determines that the first temperature detection point 42A is located in the gas phase and the second temperature detection point 52A is located in the liquid phase, it determines that the liquid level is between the first temperature detection point 42A and the second temperature detection point 52A. Furthermore, when the control device 12 determines that the first temperature detection point 42A and the second temperature detection point 52A are located in the gas phase, it determines that the liquid level is below the second temperature detection point 52A. In this way, the liquid level is detected.

[0019] (Effect of this embodiment) As described above, the liquid level detection system 2 includes a sheath tube 20 extending along the vertical direction, a heater 22 enclosed in the sheath tube 20 and extending along the vertical direction through the center of the sheath tube 20, a first thermocouple 44 and a second thermocouple 56 (an example of "a plurality of temperature sensors") located around the heater 22 in the sheath tube 20 and arranged at a first temperature detection point 42A and a second temperature detection point 52A that are different from each other in the vertical direction, a power supply unit 60 for energizing the heater 22, a temperature information acquisition unit 62 for acquiring temperature information from each of the first thermocouple 44 and the second thermocouple 56 in synchronization with the energization of the heater 22, and a specifying unit 64 for specifying whether each of the first temperature detection point 42A and the second temperature detection point 52A is located in the liquid phase or the gas phase based on the temperature information and specifying the liquid level.

[0020] According to the above configuration, in the liquid level detection system 2, one heater 22 is shared for the first temperature detection point 42A and the second temperature detection point 52A. Therefore, compared with the conventional configuration, the configuration of the liquid level detection system 2 can be miniaturized and simplified. Further, since the number of sheath tubes and heaters is reduced, evaporation of the liquid due to energization of the heater can also be suppressed.

[0021] In the above embodiment, two thermocouples 44 and 56 are arranged around the heater 22. In a modified example, as shown in FIG. 3(A), three thermocouples 124, 126, and 128 may be arranged around the heater 22, or as shown in FIG. 3(B), four thermocouples 224, 226, 228, and 230 may be arranged around the heater 22. Further, in another modified example, five or more thermocouples may be arranged around the heater 22.

Explanation of Reference Numerals

[0022] 2: Liquid level detection system, 10: Liquid level detection device, 12: Control device, 20: Sheath tube, 22: Heater, 24: First temperature sensor unit, 26: Second temperature sensor unit, 28: Flange, 29: Relay amplifier, 30: Front heater wire, 30A: First upper resistance part, 30B: First lower resistance part, 32: Lower heater wire, 34: Rear heater wire, 34A: Second upper resistance part, 34B: Second lower resistance part, 40: First front thermocouple wire, 42: First lower thermocouple wire, 44: First thermocouple, 50: Second front thermocouple wire, 52: Second lower thermocouple wire, 54: Second rear thermocouple wire, 56: Second thermocouple, 60: Energization part, 62: Temperature information acquisition part, 64: Specifying part

Claims

Claim 1 A liquid level detection system, comprising: a sheath tube extending along the vertical direction; a heater enclosed in the sheath tube and extending along the vertical direction through the center of the sheath tube; a plurality of temperature sensors located around the heater in the sheath tube and arranged at different temperature detection points in the vertical direction; a power supply unit for energizing the heater; a temperature information acquisition unit for acquiring temperature information from each of the plurality of temperature sensors in synchronization with the energization of the heater; a specifying unit for specifying, based on the temperature information, whether each of the different temperature detection points is located in the liquid phase or the gas phase and specifying the liquid level; A liquid level detection system comprising the above components.

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