Liquid hydrogen storage system

Abstract

A liquid hydrogen storage system (10) includes a hydrogen tank (12) that stores liquid hydrogen; a first flow path (24) that communicates the hydrogen tank (12) with the outside of a vehicle; a reaction section (25) that reacts hydrogen gas flowing in the first flow path (24) with oxygen to convert the hydrogen gas into water and then discharges the water to the outside of the vehicle through the first flow path (24); and a first safety valve (20) that is provided between the hydrogen tank (12) and the reaction section (25), opens if an internal pressure of the hydrogen tank (12), i.e., a tank internal pressure (Pt), exceeds a first opening reference value (Po1), and discharges the hydrogen gas in the hydrogen tank (12) to the reaction section (25).

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Japanese Patent Application No. 2022-107581 filed on August 4, 2022, and incorporates by reference herein its entirety, including specification, claims, drawings, and abstract. Technical Field

[0003] This specification discloses a system for storing liquid hydrogen in a vehicle. Background Art

[0004] In the past, it has been proposed to store hydrogen in a liquid state inside vehicles that use hydrogen as one of their energy sources (e.g., fuel cell vehicles and hydrogen engine vehicles). For example, Patent Document 1 discloses a liquid hydrogen storage device that includes a liquid hydrogen storage tank inside a vacuum tank.

[0005] In a liquid hydrogen storage tank, if the liquid hydrogen vaporizes and produces a large amount of hydrogen gas, the internal pressure of the tank will increase excessively. To suppress this pressure increase, Patent Document 1 provides a discharge pipe for discharging hydrogen gas to the outside of the hydrogen storage tank, and an open valve and a safety valve are installed in parallel with the discharge pipe. The open valve opens at a predetermined first differential pressure, and the safety valve opens at a second operating pressure higher than the first operating pressure. This structure can prevent the internal pressure of the tank from increasing excessively to a certain extent.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-106794

[0009] However, Patent Document 1 does not fully examine the handling of hydrogen gas released from the release valve or the safety valve. Therefore, Patent Document 1 leaves room for improvement in ensuring safety when storing liquid hydrogen in a vehicle.

[0010] Therefore, this specification discloses a liquid hydrogen storage system capable of storing liquid hydrogen more safely in a vehicle. Summary of the Invention

[0011] The liquid hydrogen storage system disclosed in this specification is characterized in that it comprises: a hydrogen tank for storing liquid hydrogen in a vehicle; a first flow path for connecting the hydrogen tank with the outside of the vehicle; a reaction unit for reacting the hydrogen gas flowing in the first flow path with oxygen to convert it into water and then releasing it to the outside of the vehicle through the first flow path; and a first safety valve provided between the hydrogen tank and the reaction unit, which opens if the internal pressure of the hydrogen tank, i.e., the tank internal pressure, exceeds a first opening reference value, and releases the hydrogen gas in the hydrogen tank to the reaction unit.

[0012] This structure can suppress the increase in the internal pressure of the tank and safely release the hydrogen gas to the outside of the vehicle. As a result, liquid hydrogen can be stored more safely in the vehicle.

[0013] In this case, the first safety valve may be closed when the tank internal pressure becomes equal to or lower than a first closing reference value, and the first closing reference value may be equal to or lower than the first opening reference value.

[0014] This structure can prevent the hydrogen gas in the tank from being excessively released to the outside.

[0015] In this case, it may be that the device further comprises: a second flow path connecting the hydrogen tank and the outside of the vehicle; and a second safety valve, which is arranged in the middle of the second flow path and opens when the pressure in the tank exceeds a second opening reference value to release the hydrogen gas in the hydrogen tank to the outside of the vehicle via the second flow path. The second flow path guides the hydrogen gas to the upper part or rear part of the vehicle in a path that avoids the high-temperature parts in the vehicle and releases it to the outside of the vehicle in a gaseous state. The second opening reference value is higher than the first opening reference value.

[0016] This structure can more reliably prevent the internal pressure of the tank from increasing excessively. In addition, since the hydrogen gas is released to the outside of the vehicle along a path that avoids high-temperature areas, the safety of the passengers can be more reliably ensured.

[0017] In this case, the second safety valve may be closed when the tank internal pressure is equal to or lower than the second closing reference value, and the second closing reference value may be equal to or lower than the second opening reference value.

[0018] This structure can prevent the hydrogen gas in the tank from being excessively released to the outside.

[0019] In this case, an alarm may be further provided for outputting a warning when the second safety valve is opened.

[0020] With this configuration, the occupants can recognize that an abnormality has occurred in the hydrogen tank and can retreat outside the vehicle as needed. As a result, the safety of the occupants can be more reliably ensured.

[0021] In this case, the feature is that it further comprises: a third flow path connecting the hydrogen tank with the outside of the vehicle; and a closing member, which is provided in the middle of the third flow path, prohibits the passage of the hydrogen gas, and is destroyed to allow the passage of the hydrogen gas when the internal pressure of the hydrogen tank exceeds a third reference value which is higher than the second opening reference value. The third flow path guides the hydrogen gas to the upper part or rear part of the vehicle in a path that avoids the high-temperature parts inside the vehicle, and is released to the outside of the vehicle in a gaseous state.

[0022] By providing the closing member that is broken at a pressure exceeding a third reference value, even in the case where an electric failure occurs, if the pressure in the tank exceeds the third reference value and becomes significantly high, the hydrogen can be released to the outside of the tank. As a result, it is possible to prevent the pressure in the tank from becoming excessively high, and it is possible to more reliably ensure the safety of the occupant.

[0023] In this case, it can be that the first flow path, the second flow path, and the third flow path each extend from a vicinity of a gravity direction upper end of the hydrogen tank toward the outside of the vehicle.

[0024] By providing this structure, even in the case where the liquid surface in the vehicle and further in the hydrogen tank is tilted, the inlets of the first flow path, the second flow path, and the third flow path can be prevented from being blocked by the liquid hydrogen. Thus, depending on the pressure in the tank, the hydrogen can be appropriately released from the first flow path, the second flow path, and the third flow path.

[0025] In addition, it can be that a pump that pressurizes the liquid hydrogen accumulated in the hydrogen tank and outputs it to the outside of the hydrogen tank is further provided.

[0026] By providing this structure in which the liquid hydrogen is pressurized when it is taken out, it is possible to suppress the pressure of the liquid hydrogen accumulated in the hydrogen tank to be low. Also, as a result, it is possible to suppress the allowable maximum pressure of the hydrogen tank itself to be low, and it is possible to reduce the cost related to the hydrogen tank.

[0027] According to the liquid hydrogen storage system disclosed in this specification, it is possible to more safely accumulate liquid hydrogen in a vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic view showing the structure of the liquid hydrogen storage system.

[0029] Figure 2 is a perspective view of the hydrogen tank.

[0030] Figure 3 is a flowchart showing a process of managing the pressure in the tank. DETAILED DESCRIPTION

[0031] Hereinafter, the structure of the liquid hydrogen storage system 10 will be described with reference to the drawings. Figure 1 is a schematic view showing the structure of the liquid hydrogen storage system 10. In addition, Figure 2 is a perspective view of the hydrogen tank 12.

[0032] The liquid hydrogen storage system 10 is mounted on a vehicle 100 and stores hydrogen in a liquid state. In this case, the vehicle 100 is a vehicle that uses hydrogen as one of energy sources, and is, for example, a fuel cell vehicle or a hydrogen engine vehicle. Hereinafter, the liquid hydrogen storage system 10 will be described taking a hydrogen engine vehicle that mounts a direct injection type hydrogen engine (not shown) that directly injects hydrogen gas into an engine cylinder as an example.

[0033] The liquid hydrogen storage system 10 includes a hydrogen tank 12 for storing liquid hydrogen. The hydrogen tank 12 stores liquid hydrogen while isolating it. For example, a double-tube structure container can be used, in which a vacuum insulation layer is provided between an inner tank made of SUS and an outer tank covering the inner tank. In addition, the hydrogen tank 12 is spherical or shaped in order to maintain uniform pressure on the inner wall. Figure 2 The sandbag type shown.

[0034] In the hydrogen tank 12, liquid hydrogen is kept at a low temperature. In addition, in the hydrogen tank 12, the pressure of the liquid hydrogen is approximately the same as or slightly higher than the atmospheric pressure, for example, below 1 MPa. The hydrogen tank 12 is provided with a pump 16 that pumps up the accumulated liquid hydrogen and sends it to the hydrogen engine side. In this example, the pump 16 is a booster pump that pressurizes the liquid hydrogen while pumping it up. The pump 16 is driven by a pump motor 18. By providing a pump 16 with such a boosting function, the pressure resistance required for the hydrogen tank 12 can be reduced, and the cost associated with the hydrogen tank 12 can be reduced.

[0035] That is, as mentioned above, in this example, the hydrogen engine is a direct injection type that directly injects hydrogen into the engine cylinder. The directly injected hydrogen is required to be very high pressure compared to the atmospheric pressure (for example, 5 MPa to tens of MPa, etc.). In order to obtain this high-pressure hydrogen, it is required to be sufficiently high pressure before gasification, that is, in the liquid state. Therefore, it is also possible to consider storing high-pressure (for example, tens of MPa) liquid hydrogen in the hydrogen tank 12. However, in this case, it is necessary to improve the pressure resistance of the hydrogen tank 12, which will lead to an increase in the cost and weight associated with the hydrogen tank 12.

[0036] On the other hand, in this example, the pressure of the liquid hydrogen in the hydrogen tank 12 is maintained at a pressure substantially equal to or slightly higher than atmospheric pressure. When the liquid hydrogen is vaporized, the pressure is sufficiently increased to the level required for vaporization by the pump 16 before being withdrawn. This configuration allows for the production of sufficiently high-pressure hydrogen while suppressing the pressure resistance of the hydrogen tank 12.

[0037] A collector 14 that is recessed relative to the surrounding area is provided on the bottom surface of the hydrogen tank 12. A pump 16 is disposed in the collector 14. This structure allows the pump 16 to be positioned in the liquid even when the remaining amount of liquid hydrogen decreases, allowing the liquid hydrogen to be pumped to the end.

[0038] like Figure 2As shown, a liquid hydrogen filling port 60 and a hydrogen return port 62 are formed on the side of the hydrogen tank 12. The liquid hydrogen filling port 60 is an orifice for receiving a supply of liquid hydrogen from the outside. In addition, the hydrogen return port 62 is an orifice for attracting hydrogen gas (so-called boil-off gas) that is vaporized due to natural heat input from the outside and releasing it to the outside when the liquid hydrogen is filled. In order to properly attract boil-off gas, the liquid level of liquid hydrogen when fully filled is lower than the hydrogen return port 62. In other words, in this example, the internal volume of the hydrogen tank 12 is larger than the capacity of liquid hydrogen when fully filled. Therefore, there is always a space larger than a specified volume (hereinafter referred to as the "upper space") on the upper part of the hydrogen tank 12. The hydrogen gas generated by the vaporization of the liquid hydrogen accumulated in the tank is retained in the upper space. The hydrogen tank 12 is provided with a pressure sensor 50 that detects the pressure of the upper space as the tank internal pressure Pt. The detection value of the pressure sensor 50 is sent to the controller 54.

[0039] In addition, if Figure 2 As shown, a pump orifice 64, a first orifice 22, a second orifice 32 and a third orifice 42 are formed near the top of the hydrogen tank 12, that is, near the upper end in the direction of gravity of the hydrogen tank 12. By arranging the first orifice 22, the second orifice 32 and the third orifice 42 near the upper end in the direction of weight, even when the liquid level of the liquid hydrogen in the vehicle 100 and the tank is tilted relative to the horizontal plane, these orifices 22, 32, 42 are not easily blocked by the liquid. Moreover, thereby, the hydrogen gas in the hydrogen tank 12 can be reliably guided to the first flow path 24, the second flow path 34 and the third flow path 44 described later. It should be noted that other orifices are also formed near the top of the hydrogen tank 12, but the illustration of the other orifices is omitted here. The pump orifice 64 is the orifice through which the cylinder of the pump 16 is inserted.

[0040] The first orifice 22 is connected to the first flow path 24 (see Figure 1) is connected to an orifice. The first flow path 24 is a flow path that connects the hydrogen tank 12 to the outside of the vehicle. A first safety valve 20 is provided in the middle of the first flow path 24. The first safety valve 20 is a valve that opens if the tank internal pressure Pt exceeds the specified first open reference value Po1, and closes if the tank internal pressure Pt becomes less than the specified first closed reference value Pc1. The first open reference value Po1 is a value that is sufficiently smaller than the maximum allowable pressure Pmax of the hydrogen tank 12, for example, a value of about 1 / 5 to 1 / 2 of the maximum allowable pressure Pmax of the hydrogen tank 12. The first open reference value Po1 can be a fixed value that is always constant, or a variable value that changes according to conditions (such as the outside temperature, the driving state of the vehicle 100, etc.). In addition, the first closed reference value Pc1 is a value less than the first open reference value Po1. Therefore, the first closed reference value Pc1 can be the same value as the first open reference value Po1. By setting Pc1=Po1, the opening and closing control of the first safety valve 20 can be simplified. In addition, the first closing reference value Pc1 may be a value smaller than the first opening reference value Po1. <Po1而使第一封闭基准值Pc1与第一开放基准值Po1之间具有规定的幅度,能够防止第一安全阀20在短时间内反复开闭。

[0041] The first safety valve 20 may be an electric valve that opens and closes in response to an electrical signal, or a mechanical valve that opens by mechanical deformation when subjected to a pressure exceeding a predetermined value. In this example, the first safety valve 20 is a solenoid valve that opens and closes in response to a control signal from the controller 54 .

[0042] A reaction unit 25 is provided on the downstream side of the first safety valve 20. The reaction unit 25 causes the hydrogen flowing in the first flow path 24 to react with the air (more precisely, the oxygen contained in the air) to be converted into water and then released outside the vehicle. In order to cause the reaction of the hydrogen, a catalyst 26 and a fan 28 for supplying air to the catalyst 26 are provided in the reaction unit 25. The catalyst 26 induces a reaction to generate water from hydrogen and oxygen (hereinafter referred to as "water generation reaction"), and is, for example, copper. When the first safety valve 20 is opened, the fan 28 rotates according to the instructions of the controller 54 to supply air to the catalyst 26. In addition, Figure 1 Although not shown, the reaction unit 25 may also include a heat source for heating at least one of the hydrogen and oxygen. The heat source may be, for example, a self-heating heater or a heat transfer member that transfers heat from another heat source to the reaction unit 25. "Other heat sources" may include, for example, at least one of a hydrogen engine and a fuel cell. Furthermore, the reaction unit 25 may also include a hydrogen sensor upstream or downstream of the catalyst 26, or both, for detecting the concentration of hydrogen. The controller 54 may adjust the air flow rate supplied to the catalyst 26 and the amount of heating for the hydrogen or oxygen based on the detection results of the hydrogen sensor.

[0043] The water generated by the reaction unit 25 is discharged outside the vehicle through the first flow path 24. It should be noted that the first flow path 24 can be a dedicated flow path that is independent of the other flow paths until its end, or it can merge with other drainage flow paths midway. For example, a hydrogen engine or fuel cell outputs water during its operation. Therefore, the vehicle equipped with such a hydrogen engine or fuel cell is provided with a drainage flow path for discharging water from the hydrogen engine or fuel cell. The first flow path 24 can merge with this drainage flow path downstream of the reaction unit 25.

[0044] The second orifice 32 is connected to the second flow path 34 (see Figure 1 ) is connected to the orifice. A second safety valve 30 is provided in the middle of the second flow path 34. The second safety valve 30 is a valve that opens if the tank internal pressure Pt exceeds the specified second open reference value Po2, and closes if the tank internal pressure Pt becomes less than the second closed reference value Pc2. The second open reference value Po2 is a value that is higher than the first open reference value Po1 and is sufficiently smaller than the maximum allowable pressure Pmax of the hydrogen tank 12. For example, the second open reference value Po2 is a value of about 1.05 to 1.2 times the first open reference value Po1. The second open reference value Po2 can be a fixed value that is always constant, or it can be a variable value that changes according to conditions (such as the outside temperature, the driving state of the vehicle 100, etc.). In addition, the second closed reference value Pc2 is a value below the second open reference value Po2. Therefore, it can be Pc2=Po2, or it can be Pc2 <Po2。

[0045] The second safety valve 30 can be an electric valve that opens and closes in response to an electrical signal, or a mechanical valve that opens due to mechanical deformation when subjected to a pressure exceeding a specified value. However, as described later, when the second safety valve 30 is opened, the controller 54 activates the alarm 52. Therefore, if the second safety valve 30 is a mechanical valve, a sensor is provided to detect the open or closed state of the second safety valve 30. For example, a hydrogen sensor that detects the concentration of hydrogen gas downstream of the second safety valve 30 can be used as this sensor.

[0046] When the second safety valve 30 is opened, the second flow path 34 guides the hydrogen gas to the upper or rear portion of the vehicle 100, avoiding high-temperature areas within the vehicle, and releases it to the outside of the vehicle in a gaseous state. A high-temperature area is, for example, the area surrounding the hydrogen engine. Thus, for example, the second flow path 34 extends from the hydrogen tank 12 in a direction opposite to the hydrogen engine. Alternatively, if the hydrogen gas is released from the upper portion of the vehicle 100, the second flow path 34 can also reach the roof. In this case, the second flow path 34 can pass through the interior of the pillars.

[0047] The third orifice 42 is connected to the third flow path 44 (see Figure 1) is connected to an orifice. A closure member 40 is provided midway through the third flow path 44. The closure member 40 closes the third flow path 44, preventing hydrogen gas from passing through. The closure member 40 mechanically and irreversibly destroys when the tank internal pressure Pt exceeds a predetermined third reference value P3. The destruction of the closure member 40 allows hydrogen gas to escape from the vehicle through the third flow path 44.

[0048] The third reference value P3 is a value higher than the second opening reference value Po2 and lower than the maximum allowable pressure Pmax of the hydrogen tank 12. For example, the third reference value P3 is a value of approximately 1.3 to 2 times the first opening reference value Po1 or a value of 0.4 to 0.6 times the maximum allowable pressure Pmax of the hydrogen tank 12.

[0049] When the closing member 40 is destroyed, the third flow path 44 guides the hydrogen to the upper part or rear part of the vehicle 100 in a path that avoids the high-temperature parts in the vehicle, and releases it to the outside of the vehicle in a gaseous state. The third flow path 44 can be a flow path completely separated from the second flow path 34, or it can be a flow path that merges with the second flow path 34 midway. The confluence point in the case of confluence is on the downstream side of the second safety valve 30 and on the downstream side of the closing member 40. In addition, the third flow path 44 can advance from the hydrogen tank 12 to the direction opposite to the hydrogen engine in the same way as the second flow path 34. In addition, the third flow path 44 can reach the roof and pass through the inside of the pillar.

[0050] The alarm 52 outputs a warning to urge the occupants to evacuate the vehicle when the second safety valve 30 is opened. The alarm 52 outputs at least one of sound and light, and includes, for example, at least one of a speaker, a buzzer, a lamp, and a display.

[0051] The controller 54 controls the driving of the pump motor 18, the safety valves 20, 30, and the alarm 52. The controller 54 is a computer that physically has a processor 56 and a memory 58. Figure 1 , the controller 54 is shown as a single computer, but the controller 54 may be composed of a combination of two or more mechanically separate computers. Furthermore, the controller 54 may be provided exclusively for the liquid hydrogen storage system 10 or may be utilized as a computer used for other control functions of the vehicle 100.

[0052] The controller 54 drives the pump motor 18 to supply a required amount of hydrogen to the hydrogen engine side in accordance with a request from a higher-level vehicle control device. In addition, the controller 54 monitors the detected value of the pressure sensor 50, i.e., the tank pressure Pt. Also, the controller 54 controls the opening and closing of the first safety valve 20 and the second safety valve 30 in accordance with the tank pressure Pt. Furthermore, the controller 54 causes the alarm 52 to actuate to notify the occupant of the vehicle 100 of a warning in the case where the second safety valve 30 is open. The output of this warning continues until the second safety valve 30 is closed, and stops if the second safety valve 30 is closed.

[0053] Next, the management of the tank pressure Pt in the liquid hydrogen storage system 10 will be described. Figure 3 is a flowchart showing the flow of management of the tank pressure Pt of the hydrogen tank 12. In the initial state, the first safety valve 20 and the second safety valve 30 are closed, and the closing member 40 cuts off the third flow path 44. In addition, liquid hydrogen is stored in the hydrogen tank 12 at a pressure that is substantially the same as or slightly higher than atmospheric pressure. Although the hydrogen tank 12 has high thermal insulation performance, it cannot completely cut off the input of heat to the internal space. Thus, as time passes, the stored liquid hydrogen gradually vaporizes. Also, as the liquid hydrogen vaporizes, the tank pressure Pt gradually rises.

[0054] The controller 54 compares the tank pressure Pt detected by the pressure sensor 50 with the first opening reference value Po1 (S10). In the case where the result of the comparison is Pt≤Po1 (NO in S10), the controller 54 maintains the state in which the first safety valve 20 is closed.

[0055] On the other hand, in the case where it becomes Pt>Po1 (YES in S10), the controller 54 opens the first safety valve 20 (S12). By opening the first safety valve 20, the hydrogen gas remaining in the hydrogen tank 12 is released to the outside of the hydrogen tank 12 through the first safety valve 20, and the tank pressure Pt falls. In addition, if the first safety valve 20 is opened, the controller 54 drives the fan 28 of the reaction section 25 to supply air to the catalyst 26 (S12). The hydrogen gas released from the hydrogen tank 12 and the oxygen gas contained in the air generate a chemical reaction, and the hydrogen gas is converted to water. The water generated by the water generation reaction at the reaction section 25 is released to the outside of the vehicle from the end of the first flow path 24. That is, according to this example, the boil-off gas generated in the hydrogen tank 12 is released to the outside of the vehicle in a safe and environmentally friendly stable molecular structure, i.e., as water molecules.

[0056] After the first safety valve 20 is opened, the controller 54 compares the tank pressure Pt with the first closing reference value Pc1 (S14). If the result of the comparison becomes Pt≤Pc1 (YES in S14), the controller 54 closes the first safety valve 20 and stops the drive of the reaction section 25 (S16).

[0057] If Pt>Pc1 in step S14, the controller 54 further compares the tank internal pressure Pt with the second opening reference value Po2 (S18). If the comparison result is Pt≤Po2 (No in S18), the controller 54 returns to step S14.

[0058] On the other hand, when Pt>Po2 (yes in S18), the controller 54 further opens the second safety valve 30 (S20). By opening the second safety valve 30 in addition to the first safety valve 20, more hydrogen is released from the hydrogen tank 12. As a result, it is possible to more reliably prevent the tank internal pressure Pt from exceeding the maximum allowable pressure Pmax of the hydrogen tank 12. In addition, when the second safety valve 30 is opened, the controller 54 further activates the alarm 52 to notify the occupants of a warning and urge them to retreat from the vehicle 100 (S20). By urging the occupants to retreat in this way, the occupants accept the warning and retreat from the vehicle 100, thereby more reliably ensuring the safety of the occupants. When the second safety valve 30 is opened, hydrogen is released to the outside of the vehicle through the second flow path 34. At this time, since the second flow path 34 avoids the high-temperature parts inside the vehicle, the hydrogen can be safely released to the outside of the vehicle.

[0059] The controller 54 then compares the tank internal pressure Pt with the second closing reference value Pc2 ( S22 ). If the comparison result satisfies Pt ≤ Pc2 (YES in S22 ), the controller 54 closes the second safety valve 30 and deactivates the alarm 52 ( S24 ). The controller 54 then returns to step S14 .

[0060] On the other hand, it is assumed that: after the second safety valve 30 is opened, the rise in the tank pressure Pt continues, and the tank pressure Pt exceeds the third reference value P3 (yes in S26). In this case, the closing member 40 is destroyed (S28). As a result, the hydrogen in the hydrogen tank 12 flows not only to the first flow path 24 and the second flow path 34 but also to the third flow path 44. And, thereby, the rise in the tank pressure Pt is more effectively suppressed. It should be noted that since the destruction of the closing member 40 is an irreversible change, at the time point when the closing member 40 is destroyed, the use of the liquid hydrogen storage system and the boarding of people on the vehicle 100 are prohibited.

[0061] Thus, by providing the sealing member 40 that is automatically mechanically broken when the predetermined third reference value P3 is reached, even in the event of an electrical failure, such as a failure of the pressure sensor 50, if the internal tank pressure Pt becomes excessively high, hydrogen gas can be reliably released to the outside of the hydrogen tank 12. As a result, the safety of the occupants can be more reliably ensured.

[0062] It should be noted that in Figure 3 In the example, the presence or absence of damage to the closing member 40 is determined based on the tank internal pressure Pt (i.e., the detection value of the pressure sensor 50). However, the controller 54 can also determine the state of the closing member 40 without relying on the detection value of the pressure sensor 50. For example, a hydrogen sensor for detecting hydrogen concentration can be provided on the downstream side of the closing member 40 in the third flow path 44, and when the hydrogen concentration above the threshold is detected by the hydrogen sensor, it is determined that the closing member 40 is damaged. Moreover, in the case where the closing member 40 is damaged, a warning can be output from the alarm 52 regardless of the detection value of the pressure sensor 50. By setting it as this structure, even if the pressure sensor 50 fails for some reason, the state in which the tank internal pressure Pt becomes too large can be grasped, and the safety of the occupants can be ensured more reliably.

[0063] It is obvious from the above description that according to this example, the evaporated gas generated in the hydrogen tank 12 is converted into water and then released outside the vehicle. By setting it as this structure, it is possible to prevent the internal pressure Pt of the tank from becoming excessively high, and in addition, the evaporated gas can be safely released outside the vehicle. It should be noted that the structure described so far is an example. As long as there is a first flow path 24 that connects the hydrogen tank 12 to the outside of the vehicle, a first safety valve 20 that is opened when the internal pressure Pt of the tank becomes above the first opening reference value Po1, and a reaction part 25 that converts the hydrogen released from the first safety valve 20 into water, other structures can also be changed. Therefore, for example, the second safety valve 30 and the second flow path 34 may also be absent. Similarly, the closing member 40 and the third flow path 44 may also be absent.

[0064] Description of Reference Numerals

[0065] 10 liquid hydrogen storage system, 12 hydrogen tank, 14 collector, 16 pump, 18 pump motor, 20 first safety valve, 22 first orifice, 24 first flow path, 25 reaction unit, 26 catalyst, 28 fan, 30 second safety valve, 32 second orifice, 34 second flow path, 40 closing member, 42 third orifice, 44 third flow path, 50 pressure sensor, 52 alarm, 54 controller, 56 processor, 58 memory, 60 liquid hydrogen filling port, 62 hydrogen return port, 64 pump orifice, 100 vehicle.

Claims

1. A liquid hydrogen storage system, characterized in that: have: Hydrogen tanks, which store liquid hydrogen in the vehicle; A first flow path connects the hydrogen tank to the outside of the vehicle; a reaction unit that reacts the hydrogen gas flowing in the first flow path with oxygen to convert the hydrogen gas into water, and then releases the water to the outside of the vehicle through the first flow path; a first safety valve disposed between the hydrogen tank and the reaction unit, and opening when the internal pressure of the hydrogen tank, i.e., the tank internal pressure, exceeds a first opening reference value to release the hydrogen gas in the hydrogen tank to the reaction unit; a second flow path connecting the hydrogen tank to the outside of the vehicle; a second safety valve provided midway in the second flow path, which opens when the tank internal pressure exceeds a second opening reference value to release the hydrogen gas in the hydrogen tank to the outside of the vehicle through the second flow path; as well as The second flow path guides the hydrogen gas to the upper part or the rear part of the vehicle along a path that avoids the high-temperature part in the vehicle, and releases the hydrogen gas to the outside of the vehicle in a gaseous state. The second opening reference value is higher than the first opening reference value, The liquid hydrogen storage system further comprises: A third flow path connects the hydrogen tank to the outside of the vehicle; and a sealing member disposed midway in the third flow path, prohibiting passage of the hydrogen gas, and being destroyed to permit passage of the hydrogen gas when the internal pressure of the hydrogen tank exceeds a third reference value higher than the second opening reference value; The third flow path guides the hydrogen gas toward the upper portion or rear portion of the vehicle along a path that avoids high-temperature areas inside the vehicle, and releases the hydrogen gas to the outside of the vehicle in a gaseous state.

2. The liquid hydrogen storage system according to claim 1, characterized in that: If the tank internal pressure becomes lower than a first closing reference value, the first safety valve closes. The first closing reference value is equal to or less than the first opening reference value.

3. The liquid hydrogen storage system according to claim 1, characterized in that: The first flow path, the second flow path, and the third flow path all extend from near the upper end of the hydrogen tank in the direction of gravity toward the outside of the vehicle.

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