Fuel cell system

Abstract

To provide a technique for accurately determining hydrogen gas leakage from a hydrogen gas flow passage.SOLUTION: The fuel cell system includes a fuel cell, a hydrogen gas tank, a hydrogen gas flow path, a pressure gauge, and a control device. The controller is configured to execute a learning operation of calculating a first pressure decrease speed that is a pressure decrease speed in the hydrogen gas flow path after supply of hydrogen gas from the hydrogen gas tank to the fuel cell is stopped, and a determination operation of calculating a second pressure decrease speed that is a pressure decrease speed in the hydrogen gas flow path after supply of hydrogen gas from the hydrogen gas tank to the fuel cell is stopped after the learning operation, and determining whether or not the second pressure decrease speed is larger than a pressure decrease speed threshold determined based on the first pressure decrease speed. The control device executes the determination operation based on the pressure decrease speed threshold. Therefore, a hydrogen gas leak from the hydrogen gas flow path can be determined more accurately than in the case where the threshold is fixed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell system. [Background technology]

[0002] The fuel cell system disclosed in Patent Document 1 includes a fuel cell, a hydrogen gas tank, a hydrogen gas flow path that supplies hydrogen gas to the fuel cell, and a control device. A pressure gauge is provided in the hydrogen gas flow path. The pressure gauge detects the pressure in the hydrogen gas flow path. After stopping the supply of hydrogen gas from the hydrogen gas tank to the fuel cell, the control device determines whether the rate of pressure decrease in the hydrogen gas flow path is equal to or greater than a threshold value. The control device determines whether a hydrogen gas leak has occurred, using the rate of pressure decrease being equal to or greater than the threshold value as one of the conditions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-95973 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem with Patent Document 1 is that the accuracy of determining whether or not a hydrogen gas leak has occurred is low. This specification proposes a technology for accurately determining whether or not a hydrogen gas leak has occurred from a hydrogen gas flow path. [Means for solving the problem]

[0005] (Aspect 1) The fuel cell system disclosed in this specification comprises a fuel cell, a hydrogen gas tank, a hydrogen gas flow path that passes through the fuel cell and through which hydrogen gas supplied from the hydrogen gas tank flows, a pressure gauge that detects the pressure in the hydrogen gas flow path, and a control device, wherein the control device performs a learning operation to calculate a first pressure decrease rate, which is the pressure decrease rate in the hydrogen gas flow path, after the supply of hydrogen gas from the hydrogen gas tank to the fuel cell is stopped, and a determination operation to calculate a second pressure decrease rate, which is the pressure decrease rate in the hydrogen gas flow path, after the supply of hydrogen gas from the hydrogen gas tank to the fuel cell is stopped after the learning operation, and determine whether the second pressure decrease rate is greater than a pressure decrease rate threshold determined based on the first pressure decrease rate.

[0006] In the above fuel cell system, the control device determines a pressure decrease rate threshold based on the first pressure decrease rate calculated in the learning operation, and performs a determination operation based on the pressure decrease rate threshold. Therefore, the determination operation can be performed more accurately than when the threshold is fixed. As a result, it is possible to accurately determine whether hydrogen gas is leaking from the hydrogen gas flow path. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell system. [Figure 2] FIG. 2 is an explanatory diagram showing the state of a fuel cell system and changes in parameters over time. [Figure 3] 4 is a flowchart of a determination operation of the fuel cell system. [Figure 4] FIG. 4 is an explanatory diagram of hydrogen gas pressure values ​​in a closed flow path. DETAILED DESCRIPTION OF THE INVENTION

[0008] Following the above-mentioned first embodiment, additional configurations of the fuel cell system disclosed in this specification will be described below. (Aspect 2) 2. The fuel cell system of claim 1, wherein the control device performs the learning operation when the pressure in the hydrogen gas flow path is higher than atmospheric pressure. (Aspect 3) A fuel cell system as described in aspect 1 or 2, wherein the control device calculates multiple first pressure decrease rates by performing the learning operation multiple times, and in the judgment operation, the control device calculates the pressure decrease rate threshold based on the multiple first pressure decrease rates. (Aspect 4) A fuel cell system according to any one of aspects 1 to 3, wherein the control device corrects the first pressure decrease rate so that the corrected first pressure decrease rate becomes larger the higher the temperature of the hydrogen gas during the learning operation, and corrects the second pressure decrease rate so that the corrected second pressure decrease rate becomes larger the higher the temperature of the hydrogen gas during the determination operation. (Aspect 5) 5. The fuel cell system according to any one of aspects 1 to 4, wherein the fuel cell system is mounted on a vehicle, and the control device executes the determination operation when the pressure in the hydrogen gas flow path is equal to or higher than atmospheric pressure when the vehicle is started.

[0009] According to the second aspect, the pressure decrease rate threshold can be set appropriately.

[0010] According to the third aspect, the learning operation is performed multiple times. Therefore, the pressure decrease rate threshold can be calculated with high accuracy. As a result, the determination operation can be performed with high accuracy, and therefore, it is possible to accurately determine whether or not hydrogen gas is leaking from the hydrogen gas flow path.

[0011] According to the fourth aspect, the influence of fluctuations in the pressure of hydrogen gas caused by temperature can be suppressed and the determination operation can be performed.

[0012] The fuel cell system 100 shown in FIG. 1 is mounted on a fuel cell vehicle. However, the fuel cell system 100 may also be mounted on devices other than fuel cell vehicles that use a fuel cell as a power source. The fuel cell system 100 has a fuel cell 10, a hydrogen gas tank 12, and a hydrogen gas flow path 20. The hydrogen gas tank 12 stores high-pressure hydrogen gas. Compressed air is supplied to the fuel cell 10 from an air compressor (not shown), and hydrogen gas is supplied from the hydrogen gas tank 12. The fuel cell 10 generates electricity by reacting oxygen and hydrogen, and supplies the electricity to a motor (not shown).

[0013] The hydrogen gas flow path 20 includes an internal flow path 22 provided inside the fuel cell 10, a hydrogen gas supply path 24, a hydrogen gas discharge path 26, and a circulation path .

[0014] The hydrogen gas supply channel 24 is connected to the upstream end of the internal flow path 22 and the hydrogen gas tank 12. Hydrogen gas is supplied from the hydrogen gas tank 12 to the fuel cell 10 through the hydrogen gas supply channel 24. The hydrogen gas supply channel 24 is provided with valves 14a, 14b, and 14c, and pressure gauges 16a, 16b, and 16c. The valve 14a is provided at the outlet of the hydrogen gas tank 12. The valve 14b is located on the hydrogen gas supply channel 24, downstream of the valve 14a. The valve 14c is located on the hydrogen gas supply channel 24, downstream of the valve 14b. The valves 14a, 14b, and 14c open and close the hydrogen gas supply channel 24. The flow rate of hydrogen gas flowing through the hydrogen gas supply channel 24 is adjusted by the opening degrees of the valves 14a, 14b, and 14c.

[0015] Pressure gauge 16a is disposed in hydrogen gas supply channel 24, between valve 14a and valve 14b. Pressure gauge 16b is disposed in hydrogen gas supply channel 24, between valve 14b and valve 14c. Pressure gauge 16c is disposed in hydrogen gas supply channel 24, between valve 14c and the downstream end of hydrogen gas supply channel 24. Pressure gauges 16a, 16b, and 16c detect the pressure inside hydrogen gas supply channel 24.

[0016] The hydrogen gas discharge channel 26 is connected to the downstream end of the internal flow channel 22. The hydrogen gas that has passed through the internal flow channel 22 is discharged to the outside via the hydrogen gas discharge channel 26. The hydrogen gas discharge channel 26 is provided with a gas-liquid separator 30 and a valve 32. The gas-liquid separator 30 removes moisture from the hydrogen gas that has passed through the internal flow channel 22. The removed moisture is discharged to the outside via the hydrogen gas discharge channel 26.

[0017] The valve 32 is disposed in the hydrogen gas discharge channel 26 downstream of the gas-liquid separator 30. The valve 32 opens and closes the hydrogen gas discharge channel 26. By adjusting the opening degree of the valve 32, the flow rate of hydrogen gas flowing from the gas-liquid separator 30 to the downstream side of the hydrogen gas discharge channel 26 is adjusted.

[0018] The upstream end of the circulation flow path 28 is connected to the gas-liquid separator 30. The downstream end of the circulation flow path 28 is connected to the hydrogen gas supply path 24, which is located downstream of the valve 14c. The hydrogen gas from which moisture has been removed by the gas-liquid separator 30 branches off and flows into the circulation flow path 28 and the hydrogen gas discharge path 26. The hydrogen gas that has passed through the circulation flow path 28 is supplied to the fuel cell 10 via the hydrogen gas supply path 24.

[0019] The fuel cell system 100 has a cooling device 40, a cooling flow path 42, and a temperature sensor 44. The cooling flow path 42 is provided so as to pass through the fuel cell 10. A refrigerant flows through the cooling flow path 42. The cooling device 40 is provided in the cooling flow path 42 upstream of the fuel cell 10. The cooling device 40 cools the refrigerant flowing through the cooling flow path 42. The fuel cell 10 is cooled by the refrigerant flowing through the cooling flow path 42. The temperature sensor 44 detects the temperature of the refrigerant flowing through the cooling flow path 42.

[0020] The fuel cell system 100 includes a control device 50. The control device 50 controls the fuel cell 10, the valves 14a, 14b, 14c, and the like.

[0021] At time t0 (see FIG. 2 ) during the period when power generation in the fuel cell 10 is stopped, the control device 50 closes the valves 14a to 14c to stop the supply of hydrogen gas from the hydrogen gas tank 12 to the fuel cell 10. At the same time, the control device 50 closes the valve 32. As a result, the flow path formed by the internal flow path 22, the hydrogen gas supply path 24 downstream of the valve 14c, the circulation flow path 28, and the hydrogen gas discharge path 26 upstream of the gas-liquid separator 30 is blocked from the hydrogen gas tank 12 and the hydrogen gas discharge path 26 and sealed. Hereinafter, this sealed flow path may be referred to as the “sealed flow path.” In this state, the pressure gauge 16c detects the pressure of hydrogen gas in the sealed flow path. The control device 50 can perform the learning operation described below after time t0, when the supply of hydrogen gas from the hydrogen gas tank 12 to the fuel cell 10 is stopped, and when the pressure of hydrogen gas in the sealed flow path is higher than atmospheric pressure.

[0022] In the learning operation, at time ta after time t0, the hydrogen gas pressure value Pa detected by the pressure gauge 16c is obtained. Next, the control device 50 obtains the hydrogen gas pressure value Pb at time tb. The hydrogen gas remaining in the sealed flow path reacts with oxygen in the fuel cell 10 and is consumed between time ta and time tb. As a result, the pressure of the hydrogen gas in the sealed flow path decreases between time ta and time tb. Therefore, the hydrogen gas pressure value Pb is lower than the hydrogen gas pressure value Pa. The control device 50 calculates a first pressure decrease rate ΔP1, which is the pressure decrease rate, from the following relational expression. ΔP1=-(Pb-Pa) / (tb-ta)

[0023] In addition, the control device 50 detects the temperature of the hydrogen gas in the sealed flow path using a temperature sensor (not shown) between times ta and tb, calculates a temperature coefficient T1 that has a positive correlation with the detected temperature, and calculates a corrected first pressure decrease rate ΔP1a using the following formula. ΔP1a=ΔP1·T1

[0024] The control device 50 executes the above-described learning operation multiple times, and calculates an average value ΔP1ave of the corrected first pressure decrease rate ΔP1a obtained in each learning operation.

[0025] The average value ΔP1ave corresponds to the pressure decrease rate of hydrogen gas under normal circumstances (i.e., when no hydrogen gas leak occurs). The control device 50 calculates the average value ΔP1ave based on multiple first pressure decrease rates ΔP1 calculated by performing the learning operation multiple times, and therefore can accurately calculate the pressure decrease rate of hydrogen gas under normal circumstances.

[0026] The control device 50 executes a determination operation after the learning operation. The determination operation is executed when the fuel cell vehicle is stopped and then started (i.e., when the ignition is turned off and then on). The determination operation will be described in detail below.

[0027] When the ignition is turned off, the control device 50 acquires the hydrogen gas pressure value Px (i.e., the pressure of the hydrogen gas in the sealed flow path) detected by the pressure gauge 16c, and also acquires the time tx (see FIG. 2) at that time. At this time, the control device 50 also acquires the hydrogen gas temperature in the sealed gas flow path using a temperature sensor (not shown).

[0028] Furthermore, when the ignition is turned on after time tx (time ty in FIG. 2), the control device 50 executes the process shown in FIG.

[0029] In step S2, the control device 50 acquires the hydrogen gas pressure value Py (i.e., the pressure of the hydrogen gas in the sealed flow path) detected by the pressure gauge 16c, and also acquires the current time ty (see FIG. 2). Also in step S2, the control device 50 detects the temperature of the hydrogen gas in the sealed flow path using a temperature sensor (not shown), and calculates a temperature coefficient T2 that has a positive correlation with the detected temperature.

[0030] In step S4, the control device 50 determines whether the hydrogen gas pressure value Py is between a first reference value A1 and a second reference value A2. The first reference value A1 is higher than atmospheric pressure, and the second reference value A2 is lower than atmospheric pressure. If the determination in step S4 is NO, the control device 50 ends the processing of FIG. 3.

[0031] If the answer is YES in step S4, the control device 50 determines in step S6 whether the hydrogen gas pressure value Py is lower than atmospheric pressure. If the hydrogen gas pressure value Py is equal to or higher than atmospheric pressure (if the answer is NO in step S6), the control device 50 executes a first abnormality detection operation in step S8. In the first abnormality detection operation, the control device 50 calculates a second pressure decrease rate ΔP2, which is the pressure decrease rate in the sealed flow path, from the following relational expression: ΔP2=-(Py-Px) / (ty-tx) Furthermore, the control device 50 calculates the corrected second pressure decrease rate ΔP2a using the following formula. ΔP2a=ΔP2·T2 Furthermore, the control device 50 determines whether the value obtained by subtracting the average value ΔP1ave from the corrected second pressure decrease rate ΔP2a is greater than a reference value A3. That is, the control device 50 determines whether ΔP2a>ΔP1ave+A3. In this way, ΔP1ave+A3 is an example of a pressure decrease rate threshold.

[0032] ΔP2a-ΔP1ave>A3 means that the corrected second pressure decrease rate ΔP2a deviates significantly from the average value ΔP1ave, which is the pressure decrease rate under normal conditions. If the corrected second pressure decrease rate ΔP2a does not deviate significantly from the average value ΔP1ave, the control device 50 determines NO in step S8. In this case, the control device 50 determines that no hydrogen gas leak has occurred and ends the processing of FIG. 3. On the other hand, if the corrected second pressure decrease rate ΔP2a deviates significantly from the average value ΔP1ave (YES in step S8), step S10 is executed.

[0033] If the answer is YES in step S6 or YES in step S8, the control device 50 executes a second abnormality detection operation in step S10. In the second abnormality detection operation, the control device 50 executes a determination as to whether or not a hydrogen gas leak has occurred using a method with higher accuracy than that in step S8. The second abnormality detection operation is a detection operation that takes a longer time than the first abnormality detection operation. After executing the second abnormality detection operation, the control device 50 ends the processing of FIG. 3.

[0034] Normally, when the supply of hydrogen gas from the hydrogen gas tank 12 to the fuel cell 10 is stopped, the hydrogen gas remaining in the sealed flow path reacts with oxygen within the fuel cell 10 and is consumed. Therefore, as shown in FIG. 4, under normal circumstances, the pressure of the hydrogen gas in the sealed flow path drops below atmospheric pressure. However, if a hydrogen gas leak occurs in the sealed flow path, the pressure of the hydrogen gas in the sealed flow path drops to near atmospheric pressure at a faster rate than normal. Therefore, during the period from when the supply of hydrogen gas is stopped until the pressure of the hydrogen gas in the sealed flow path drops to atmospheric pressure, if a hydrogen gas leak occurs, the pressure of the hydrogen gas in the sealed flow path drops faster than normal. Therefore, in step S8, if the corrected second pressure decrease rate ΔP2a of the hydrogen gas in the sealed flow path is faster than the normal pressure decrease rate (i.e., ΔP1ave), the determination in step S8 shown in FIG. 3 is YES. This allows a hydrogen gas leak to be detected. In this embodiment, the normal pressure decrease rate is learned, making it possible to accurately determine whether a hydrogen gas leak is occurring in the sealed flow path. In particular, since the corrected second pressure decrease rate ΔP2a is compared with an average value of multiple pressure decrease rates obtained by performing the learning operation multiple times, hydrogen gas leaks can be detected more accurately.

[0035] Furthermore, as shown in FIG. 4, under normal circumstances, the pressure of hydrogen gas in the sealed flow path drops below atmospheric pressure and then rises to near atmospheric pressure. However, if a hydrogen gas leak occurs in the sealed flow path, the pressure of hydrogen gas in the sealed flow path drops to atmospheric pressure and then remains approximately constant. Therefore, after the pressure of hydrogen gas in the sealed flow path drops below atmospheric pressure, the first anomaly detection operation cannot properly detect a hydrogen gas leak. Therefore, in this embodiment, when the hydrogen gas pressure value Py is lower than atmospheric pressure (YES in step S6), the control device 50 does not perform the first anomaly detection operation, but performs the second anomaly detection operation.

[0036] The control device 50 corrects the first pressure decrease rate ΔP1 and the second pressure decrease rate ΔP2 based on the hydrogen gas temperature in the sealed flow path during each operation. This makes it possible to suppress the influence of fluctuations in hydrogen gas pressure caused by temperature, and more accurately determine whether hydrogen gas is leaking from the sealed flow path.

[0037] In the above-described embodiment, the control device 50 executes the learning operation multiple times. However, the control device 50 may execute the learning operation one or more times.

[0038] In the above-described embodiment, the control device 50 corrects the first pressure decrease rate ΔP1 and the second pressure decrease rate ΔP2 based on the hydrogen gas temperature in the closed flow path during each operation. However, the control device 50 does not have to correct the first pressure decrease rate ΔP1 and the second pressure decrease rate ΔP2 based on the hydrogen gas temperature in the closed flow path.

[0039] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0040] 10: fuel cell, 12: hydrogen gas tank, 14a, 14b, 14c, 32: valves, 16a, 16b, 16c: pressure gauges, 20: hydrogen gas flow path, 22: internal flow path, 24: hydrogen gas supply path, 26: hydrogen gas discharge path, 28: circulation flow path, 30: gas-liquid separator, 50: control device, 100: fuel cell system, A1: first reference value, A2: second reference value, A3: reference value, Pa, Pb, Px, Py: hydrogen gas pressure values, T1, T2: temperature coefficient, ΔP1: first pressure decrease rate, ΔP1a: corrected first pressure decrease rate, ΔP1ave: average value, ΔP2: second pressure decrease rate, ΔP2a: corrected second pressure decrease rate

Claims

1. 1. A fuel cell system, comprising: A fuel cell; A hydrogen gas tank, a hydrogen gas flow path passing through the fuel cell and through which hydrogen gas supplied from the hydrogen gas tank flows; a pressure gauge for detecting the pressure in the hydrogen gas flow path; a control device; Equipped with The control device a learning operation of calculating a first pressure decrease rate, which is a pressure decrease rate in the hydrogen gas flow path, after the supply of the hydrogen gas from the hydrogen gas tank to the fuel cell is stopped; a determination operation of calculating a second pressure decrease rate, which is a pressure decrease rate in the hydrogen gas flow path, after the supply of hydrogen gas from the hydrogen gas tank to the fuel cell has stopped after the learning operation, and determining whether the second pressure decrease rate is greater than a pressure decrease rate threshold determined based on the first pressure decrease rate; To execute Fuel cell system.

2. 2. The fuel cell system according to claim 1, wherein the control device executes the learning operation when the pressure in the hydrogen gas flow path is higher than atmospheric pressure.

3. the control device calculates a plurality of the first pressure decrease rates by executing the learning operation a plurality of times; 3. The fuel cell system according to claim 1, wherein in the determining operation, the control device calculates the pressure decrease rate threshold based on a plurality of the first pressure decrease rates.

4. The control device correcting the first pressure decrease rate so that the corrected first pressure decrease rate becomes larger as the temperature of the hydrogen gas during the learning operation increases; correcting the second pressure decrease rate so that the corrected second pressure decrease rate becomes larger as the temperature of the hydrogen gas in the determining operation increases; 3. The fuel cell system according to claim 1 or 2.

5. The fuel cell system is mounted on a vehicle, 3. The fuel cell system according to claim 1, wherein the control device executes the determination operation when the pressure in the hydrogen gas flow path is equal to or higher than atmospheric pressure at the time of starting the vehicle.

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