JP5483130B2 - Fuel cell system and gas leak detection method - Google Patents

Description

  The present invention relates to a fuel cell system and a gas leak detection method thereof, and relates to an improved technique for accurately performing a gas leak judgment of a reaction gas system, particularly a fuel leak judgment of a fuel system.

  In a fuel cell system, it is very important to accurately detect leakage of fuel gas. In order to meet such demands, a plurality of closed spaces are formed by shutoff valves arranged in a fuel gas circulation supply system (hereinafter referred to as fuel system) including a fuel cell, and the pressure drop speed in each closed space and the front and rear of each shutoff valve etc. A technique for detecting a fuel gas leak by detecting a differential pressure has been proposed (see, for example, Patent Document 1). Moreover, in this patent document 1, the technique which specifies a leak location is also proposed.

JP 2003-308866 A

  By the way, due to cross-leakage during shutdown, residual air on the cathode side passes through the electrolyte membrane in the fuel cell and flows into the anode side. When a combustion reaction occurs in the anode catalyst due to the hydrogen gas supplied to the anode side, the hydrogen gas is consumed by the combustion reaction. Then, since a pressure drop is detected even though no hydrogen gas leak has occurred, this may be erroneously determined as a gas leak.

Therefore, an object of the present invention is to solve the above problem by increasing the accuracy of gas leak determination .

In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that generates power upon receiving a reaction gas, a reaction gas system that supplies and discharges the reaction gas to the fuel cell, and a reaction gas system that is provided in the reaction gas system. A plurality of pressure regulating valves, a test target section set between adjacent pressure control valves, a test target section set upstream of the pressure control valve positioned upstream, and a pressure control valve positioned downstream In the fuel cell system comprising: a pressure sensor provided in each inspection target section including the fuel cell set on the downstream side; and a gas leakage determination unit that determines gas leakage in the inspection target section. After the downstream side pressure reaches the specified pressure, the downstream side pressure does not operate in a closed state unless the pressure falls below a certain level. the amount of change If the gas change amount of the inspection target section is calculated using the volume of fine the inspection target section is above a predetermined threshold value, the gas change when delaying the final determination of gas leakage was the delayed When the amount is equal to or greater than a predetermined threshold, it is determined that there is a gas leak.

  In the fuel cell system having the above-described configuration, the gas leakage determination unit determines the determination when the amount of change in gas when a specified time elapses as a determination time for the gas leakage determination is equal to or greater than a predetermined threshold. The final determination may be delayed by extending the time by a predetermined time.

  In the fuel cell system having the above-described configuration, the gas leakage determination unit is configured to perform the gas leakage when the gas change amount when a specified time elapses as a determination time for the gas leakage determination is equal to or greater than a predetermined threshold. The final determination may be delayed by repeating the leak determination again.

In addition, a gas leak detection method for a fuel cell system according to the present invention includes a fuel cell that generates power upon receiving a reaction gas, a reaction gas system that supplies and discharges the reaction gas to the fuel cell, and a reaction gas system that is provided in the reaction gas system. A plurality of pressure regulating valves, a test target section set between adjacent pressure control valves, a test target section set upstream of the pressure control valve positioned upstream, and a pressure control valve positioned downstream A pressure sensor provided in each inspection target section including the fuel cell set on the downstream side, and a gas leak determination unit for determining a gas leak in the inspection target section, and the pressure regulating valve on the downstream side In the gas leak detection method for a fuel cell system, after the pressure reaches a specified pressure, if the downstream pressure does not drop more than a certain level, it does not operate in a closed state. If the gas change amount of the inspection target section is calculated using the volume of al of the pressure variation and the inspection target section is greater than a predetermined threshold value, delays the final decision of the gas leak, was the delayed When the gas change amount at the time is equal to or greater than a predetermined threshold, it is determined that the gas leaks.

In the gas leak detection method having the above configuration, when the gas leak is determined, the determination is performed when the amount of gas change when a predetermined time elapses as a determination time for the gas leak determination is equal to or greater than a predetermined threshold. The final determination is delayed by extending the time by a predetermined time .

In the gas leak detection method of the above configuration, when the gas leak is determined, the gas change amount when a specified time elapses as a determination time for the gas leak determination is equal to or greater than a predetermined threshold, the gas The final determination is delayed by repeating the leak determination again .

According to the present invention, just because the amount of gas change is equal to or greater than the predetermined threshold value does not immediately determine that a gas leak has occurred, the gas leak detection accuracy is improved.

1 is a block diagram showing a system configuration of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining one reference example of the gas leak detection process using the fuel cell system . It is a flowchart explaining the gas leak detection process which concerns on one Embodiment of this invention. It is explanatory drawing which shows that the pressure drop by factors other than gas leakage can be distinguished by the embodiment. It is a flowchart explaining the gas leak detection process which concerns on other embodiment of this invention . It is explanatory drawing which shows that the pressure drop by factors other than gas leakage can be distinguished by the embodiment.

  Next, preferred embodiments for carrying out the present invention will be described with reference to the drawings. The embodiment described below is a fuel cell system mounted on a moving body such as an electric vehicle, but is only one embodiment of the present invention and can be applied to other fuel cell systems. Moreover, the case of hydrogen gas is illustrated as a reaction gas which is a target of leakage determination according to the present invention.

  FIG. 1 shows a system configuration diagram of the fuel cell system. As shown in this figure, the fuel cell system includes a system for supplying hydrogen gas (reactive gas) as a fuel to the fuel cell stack 10 (hereinafter referred to as fuel system (reactive gas system) 1), air (reactive gas). ) And a system (not shown) for cooling the fuel cell stack 10.

  The fuel cell stack 10 includes a stack structure in which a plurality of cells including a separator having a flow path of hydrogen gas, air, and cooling water and a MEA (Membrane Electrode Assembly) sandwiched between a pair of separators are stacked. Yes. The separator is, for example, a conductive body having a metal as a base material, and plays a role of blocking mixing of different fluids supplied to adjacent cells.

  The fuel system 1 for supplying hydrogen gas to the fuel cell stack 10 includes, in order from the hydrogen gas supply source, a hydrogen tank 11, a main stop valve SV1, a pressure sensor P1, a pressure regulating valve RG1, a pressure sensor P2, a pressure regulating valve RG2, A hydrogen pump 13 is provided via the pressure sensor P3, the pressure regulating valve RG3, the pressure sensor P4, and the fuel cell stack 10.

  The pressure sensor P1 is between the main stop valve SV1 and the pressure regulating valve RG1 (hereinafter referred to as the inspection target section C1), the pressure sensor P2 is between the pressure regulating valve RG1 and the pressure regulating valve RG2 (hereinafter referred to as the inspection target section C2), and the pressure sensor P3 is the pressure regulating valve RG2. The pressure sensor P4 detects the pressure between the pressure regulating valve RG3, the fuel cell stack 10, the hydrogen pump 13 and the junction 15 (hereinafter referred to as the inspection target section C4), between the pressure regulating valves RG3 (hereinafter referred to as the inspection target section C3).

  The hydrogen tank 11 is a high-pressure hydrogen tank. Instead of the high-pressure hydrogen tank, a hydrogen tank using a hydrogen storage alloy, a hydrogen supply mechanism using a reformed gas, a tank for supplying hydrogen from a liquid hydrogen tank, a liquefied gas fuel A storage tank or the like is applicable.

  The main stop valve SV1 controls whether hydrogen gas is supplied from the hydrogen tank 11. The pressure regulating valve RG1 is a pressure reducing valve for reducing the hydrogen gas compressed to a high pressure to a medium pressure, the pressure adjusting valve RG2 is a pressure reducing valve for reducing the hydrogen gas reduced to a medium pressure to a low pressure, and the pressure adjusting valve RG3 is a hydrogen pressure reduced to a low pressure. This is a pressure reducing valve that further reduces the gas to a predetermined pressure. The hydrogen pump 13 forcibly circulates hydrogen gas in a hydrogen gas circulation path that reaches the junction 15 via the fuel cell stack 10 and the hydrogen pump 13.

  The system 2 for supplying air to the fuel cell stack 10 is not shown in FIG. 1, but is an air cleaner that purifies the outside air and takes it into the fuel cell system, and compresses and supplies the taken-in air according to the control of the control unit 20. A compressor that changes the amount of air and air pressure, a humidifier that adds air to the compressed air by exchanging air off-gas and moisture, and the cooling system of the fuel cell stack 10 includes a radiator, A fan and a cooling pump are provided.

  The control unit 20 is a known computer system such as an ECU, and may be configured by mutual communication of a plurality of computers. These computers are capable of performing hydrogen gas leak detection processing in this fuel cell system by sequentially executing software programs stored in a built-in ROM or the like.

  That is, the control unit 20 outputs a control signal for controlling the opening and closing of the valves SV1 and RG1 to RG4 and a control signal for determining the driving amount of the hydrogen pump 13 and the compressor according to the procedure described later (FIG. 2). Gas leak detection is executed based on detection signals from the sensors P1 to P4.

<Reference example>
Next, a reference example of a gas leak detection process performed using this fuel cell system will be described with reference to the flowchart of FIG. The gas leak detection process in this flowchart is merely an example, and is executed, for example, when the fuel cell system is started.

  First, for example, when the driver turns on the ignition key, the control unit 20 outputs a valve opening control signal to the main stop valve SV1, and opens the main stop valve SV1 (step S1). Until the predetermined time elapses after the main stop valve SV1 is opened, the open state of the main stop valve SV1 is maintained (step S3: NO), and when the predetermined time elapses (step S3: YES), the control unit 20 A valve closing control signal is output to the main stop valve SV1, and the main stop valve SV1 is closed (step S5). The predetermined time here is set in advance for each fuel cell system, and timed by a timer or the like.

  When the main stop valve SV1 is closed, the gas supply from the hydrogen tank 11 to the fuel cell stack 10 is gradually reduced according to the response characteristics of the pressure regulating valves RG1 to RG3 located downstream thereof, and the pressure regulating valves RG1 to RG1 While the pressure on the primary (upstream) side of RG3 starts to decrease, the pressure on the secondary (downstream) side increases. When the secondary pressure reaches the specified pressure, the pressure regulating valves RG1 to RG3 are closed, between the main stop valve SV1 and the pressure regulating valve RG1 (inspection target section C1), and between the pressure regulating valve RG1 and the pressure regulating valve RG2. (Inspection target section C2), between the pressure regulating valve RG2 and the pressure regulating valve RG3 (inspection target section C3), and from the pressure regulating valve RG3 to the junction 15 through the fuel cell stack 10 and the hydrogen pump 13 (inspection target section) A closed section is formed at C4).

  At this time, depending on the response characteristics of the pressure regulating valves RG1 to RG3, the closed state may not be reached. The closed state does not mean a complete shut-off state, but means a state where pressure adjustment on the secondary side of the valve has been completed, and a state where the closed state has not been reached means that pressure is still being adjusted.

  Next, the control unit 20 refers to the detection signals from the pressure sensors P1 to P4 and applies pressures p1 to p4 in the inspection target sections C1 to C4, in other words, upstream and downstream of the pressure regulating valves RG1 to RG4. The pressures p1 to p4 in the closed space to be formed are detected at a predetermined sampling interval (step S7). Then, the difference between the pressures p1 ′ to p4 ′ detected last time and the pressures p1 to p4 detected this time is calculated to calculate the pressure drop amounts Δp1 to Δp4 for a predetermined time. A total sum Q of hydrogen gas change amounts (fuel change amounts) in the inspection target sections C1 to C4 is calculated (step S9).

  Q = (Δp1 × v1 + Δp2 × v2 + Δp3 × v3 + Δp4 × v4) ÷ t × N

  Here, v1 to v4 are piping volumes of the inspection target sections C1 to C4, t is a measurement interval of the pressure p, and N is a unit conversion coefficient. When the pressure drop amount within a predetermined time t in a pipe having a volume v is Δp, this calculation formula indicates that the hydrogen gas change amount ΔQ in this pipe is “ΔQ = Δp × v ÷ t × N”. Based on what is required.

  According to the above arithmetic expression, if hydrogen gas leakage occurs in any of the inspection target sections C1 to C4, the sum Q of the hydrogen gas change amounts in these inspection target sections C1 to C4 is calculated as a negative number ( Therefore, the occurrence of hydrogen gas leakage can be detected.

  That is, if no hydrogen gas leak occurs, even if there is a hydrogen gas outflow from the inspection target section C1 to the inspection target section C2 because the pressure regulating valve RG1 is still adjusting the pressure, the inspection target section C1 If the sum of the hydrogen gas outflow and the hydrogen gas inflow in the section C2 to be inspected is taken, the outflow and inflow will be offset, and the total amount of hydrogen gas change should be zero in the calculation. is there.

  Therefore, if the sum Q of the amount of change in the hydrogen gas in all the inspection target sections C1 to C4 is taken, regardless of the pressure adjustment state of all the pressure regulating valves RG1 to RG4, when it becomes a negative number, all the inspection target sections This means that the balance between the total outflow and the total inflow at C1 to C4 does not match, and it can be determined that hydrogen gas leakage has occurred.

  In determining whether or not hydrogen gas leaks based on the total amount Q of hydrogen gas change, pressure sensors P1 to P4 are determined based on whether the total amount Q of hydrogen gas change is zero or a negative number. There is a risk of false detection due to the measurement ability or measurement error.

Therefore, in this reference example , the threshold value for determining the presence or absence of hydrogen gas leakage has a certain width, and the absolute value of the total amount Q of hydrogen gas variation (hereinafter simply referred to as the total sum Q) is a predetermined threshold value Qth. When it is below, it is determined that there is no hydrogen gas leakage, and when this threshold value Qth is exceeded, it is determined that there is fuel leakage.

  As a result of the calculation in step S9, when the sum Q of the hydrogen gas change amounts exceeds the threshold value Qth (step S11: YES), as described above, hydrogen gas leaks in any of the inspection target sections C1 to C4. It means that it has occurred.

  Therefore, the control unit 20 sets “1” indicating that hydrogen gas leak has been detected in the leak detection flag (step S13), and the gas leak detection process ends. This threshold value Qth is set to a value that does not cause erroneous detection even if the gas leak determination is performed.

  On the other hand, as a result of the calculation in step S9, when the sum Q of the hydrogen gas change amounts is equal to or less than the predetermined threshold value Qth (step S11: NO), hydrogen gas leakage occurs in any of the inspection target sections C1 to C4. Means not.

  Therefore, the control unit 20 sets “0” indicating that no hydrogen gas leak has been detected in the leak detection flag (step S15), and the gas leak detection process ends.

  As described above, according to the present reference example, using all the pressure change amounts Δp1 to Δp4 from the pressure sensors P1 to P4 disposed in the adjacent inspection target sections C1 to C4, all the inspection target sections C1 to C4 are used. Since the sum Q of the hydrogen gas fuel change amount in the engine is calculated and the presence or absence of hydrogen gas leakage is determined based on the calculation result, regardless of the pressure adjustment state of the pressure regulating valves RG1 to RG3, that is, Whether or not any or all of the pressure regulating valves RG1 to RG3 are already closed and in the closed state, whether or not the pressure adjustment is still in progress and the closed state can be detected accurately.

  Therefore, there is a possibility that hydrogen gas leakage may not be detected depending on the characteristics / operations of the pressure control valves RG1 to RG3, or the possibility of erroneous detection that hydrogen gas leakage has not occurred may be reduced. Thus, the accuracy of leak detection can be improved.

Next, a gas leak detection process according to an embodiment of the present invention will be described with reference to the flowchart of FIG.

  Further, in the present embodiment, it is assumed that processing corresponding to the processing in steps S1 to S5 in FIG. 2 is executed in advance prior to the processing shown in the flowchart in FIG. When the same processing is performed, the reference step numbers shown in the flowchart of FIG. 2 are appropriately used.

  The control unit (gas leakage determination unit) 20 refers to the detection signals from the pressure sensors P1 to P4, detects the upstream and downstream pressures of the pressure regulating valves RG1 to RG3 as reference pressures P1 to P4, and monitors the time described later. The timing of t is started (step S21). Then, when a predetermined time has elapsed from the start of the monitoring time t, the detection signals from the pressure sensors P1 to P4 are referred to again to detect the current pressures p1 to p4 in the inspection target sections C1 to C4 (step S23).

  Next, it is determined whether or not the current pressures p1 to p3 are larger than a predetermined specified pressure (set pressure of the pressure regulating valves RG1 to RG3) (step S25). If the determination result is “NO”, that is, When the current pressures p1 to p3 are equal to or less than the specified pressures, an abnormal process is performed (step S43). In this abnormal process, for example, “1” indicating that a hydrogen gas leak has been detected is set in the leak detection flag. Thereafter, the gas leak detection process of FIG. 3 ends.

  When the upstream pressure of the pressure regulating valves RG1 to RG3 becomes equal to or lower than the predetermined specified pressure, the amount of pressure drop per unit time due to gas leakage becomes small. However, in the present embodiment, when the determination result in step S25 is “NO”, the process at the time of abnormality (step S43) is performed, so that such erroneous determination can be avoided. Become.

  On the other hand, if the determination result in step S25 is “YES”, that is, if the current pressures p1 to p3 are greater than the predetermined specified pressure, the reference pressures P1 to P4 are subtracted from the current pressures p1 to p4. Then, the pressure drop amounts Δp1 to Δp4 in a predetermined time are obtained (step S27), and based on the pressure drop amounts Δp1 to Δp4, the hydrogen gas leakage amounts Q1 to Q1 in the inspection target sections C1 to C4 are calculated using the following arithmetic expressions. Q4 is calculated (step S29).

Qn = (Δp _n × v _n ) ÷ t × N

Here, v _n: pipe volume of the inspection target section C _n, t: measurement interval of the current pressure p _n, N: unit conversion coefficient, n: natural number of 1 to 4, which is.

  Next, it is determined whether or not the monitoring time t has reached a predetermined specified time (step S31). If the determination result is “NO”, that is, the monitoring time t is still below the specified time. In the case, the process returns to step S23. On the other hand, if the determination result in step S31 is “YES”, that is, if the monitoring time t has already exceeded the specified time, the hydrogen gas leakage amounts Q1 to Q4 calculated in step S29 are less than a predetermined leakage threshold. (Step S33).

  If the determination result in step S33 is “YES”, that is, if the hydrogen gas leakage amounts Q1 to Q4 are less than the leakage threshold, normal processing is performed. In this normal processing, for example, “0” indicating that no hydrogen gas leak has been detected is set in the leak detection flag. Thereby, the gas leak detection process of FIG. 3 is complete | finished.

  On the other hand, if the determination result in step S33 is “NO”, that is, if the hydrogen gas leakage amounts Q1 to Q4 are greater than or equal to the leakage threshold value, the specified time is extended by a predetermined time (step S41), and then the process is step. Return to S23.

  As described above, in the present embodiment, it is not determined that hydrogen gas leakage has occurred immediately because “hydrogen gas leakage amount ≧ predetermined leakage threshold” at the time of determination in step S33. After extending the monitoring time t in S41, the process after step S23 is repeated again to delay the final determination of gas leak detection.

  Therefore, for example, the combustion reaction in the anode catalyst is caused by oxygen in the air that has permeated the electrolyte membrane due to cross leakage during shutdown and flowed into the anode side, and hydrogen gas supplied to the anode side for gas leak detection processing. Even if no hydrogen gas leaks from the fuel system 1 as a result of the occurrence and consumption of hydrogen gas due to the combustion reaction, such a hydrogen gas is produced according to this embodiment. It is possible to detect a gas leak with higher accuracy by distinguishing between a pressure drop due to factors other than gas leak and a pressure drop due to hydrogen gas leak.

  FIG. 4 shows that a pressure drop (solid line) due to a combustion reaction (a factor other than hydrogen gas leak) in the anode catalyst caused by cross leak during shutdown and a pressure drop (broken line) due to hydrogen gas leak are shown in FIG. It is explanatory drawing which shows that it can distinguish with embodiment. In this figure, p1 and P1 are measured pressure and reference pressure when the gas leak detection process is started, p2 and P2 are measured pressure and reference pressure when a predetermined monitoring time t has elapsed from that time, and p3 and P3 are at that time. The measured pressure and the reference pressure when it is further extended for a predetermined time.

  The measured pressures p1 to p3 here are the pressures acquired in the process of step S23. Of the reference pressures P1 to P3 here, the reference pressure P1 is the pressure obtained in the process of step S21, and the reference pressures P2 and P3 are the reference values when it is assumed that hydrogen gas leaks. The pressure is expected to gradually decrease with the passage of time from the pressure P1.

As shown in the figure, when the monitoring time t elapses, the measured pressure drop Δp ₁₂ (Δp ₁₂ = p1 to p2) and the pressure drop ΔP ₁₂ (ΔP ₁₂ = P1 due to hydrogen gas leak) Assuming that the case where P2) is equal occurs, even if the cause of the drop in the measured pressure is actually the combustion reaction, the pressure drop due to the combustion reaction may be erroneously determined as a pressure drop due to hydrogen gas leakage. There is sex.

  However, when the monitoring time t is further extended by t ′, if the cause of the pressure drop is a hydrogen gas leak, the pressure is maintained at the same gradient as during the monitoring time t as shown by the broken line in FIG. In contrast, when the cause of the pressure drop is the combustion reaction, as shown by the solid line in FIG. 4, the hydrogen gas consumption decreases as the combustion reaction progresses. The pressure drops with a gentler slope, and eventually the pressure drop stops as shown after time extension t ′.

That is, as apparent from FIG. 4, when the cause of the pressure drop is the combustion reaction, the pressure drop amount Δp ₁₃ from the start of the monitoring time t to the time extension t ′ indicates that the cause of the pressure drop is a hydrogen gas leak It becomes smaller than the pressure drop amount ΔP ₁₃ in the case of. Therefore, even when the pressure drop amount Δp ₁₂ when the monitoring time t elapses is equal to the pressure drop amount ΔP ₁₂ due to hydrogen gas leak, by delaying the gas leak detection determination by the time extension t ′, Differentiating from the pressure drop due to the combustion reaction, the pressure drop due to hydrogen gas leakage can be determined.

Next, a gas leak detection process according to another embodiment of the present invention will be described with reference to the flowchart of FIG.

  Further, in the present embodiment, it is assumed that processing corresponding to the processing in steps S1 to S5 in FIG. 2 is executed in advance prior to the processing shown in the flowchart in FIG. When the same processing is performed, the reference step numbers shown in the flowchart of FIG. 2 are appropriately used.

  The control unit (gas leakage determination unit) 20 refers to the detection signals from the pressure sensors P1 to P4, detects the upstream and downstream pressures of the pressure regulating valves RG1 to RG3 as reference pressures P1 to P4, and monitors the time described later. The timing of t is started (step S21). Then, when a predetermined time has elapsed from the start of the monitoring time t, the detection signals from the pressure sensors P1 to P4 are referred to again to detect the current pressures p1 to p4 in the inspection target sections C1 to C4 (step S23).

  Next, it is determined whether or not the current pressures p1 to p3 are larger than a predetermined specified pressure (set pressure of the pressure regulating valves RG1 to RG3) (step S25). If the determination result is “NO”, that is, When the current pressures p1 to p3 are equal to or less than the specified pressures, an abnormal process is performed (step S43). In this abnormal process, for example, “1” indicating that a hydrogen gas leak has been detected is set in the leak detection flag. Thereafter, the gas leak detection process in FIG. 5 ends.

  On the other hand, if the determination result in step S25 is “YES”, that is, if the current pressures p1 to p3 are greater than the predetermined specified pressure, the reference pressures P1 to P4 are subtracted from the current pressures p1 to p4. Then, the pressure drop amounts Δp1 to Δp4 in a predetermined time are obtained (step S27), and based on the pressure drop amounts Δp1 to Δp4, the hydrogen gas leakage amounts Q1 to Q1 in the inspection target sections C1 to C4 are calculated using the following arithmetic expressions. Q4 is calculated (step S29).

Qn = (Δp _n × v _n ) ÷ t × N

Here, v _n: pipe volume of the inspection target section C _n, t: measurement interval of the current pressure p _n, N: unit conversion coefficient, n: natural number of 1 to 4, which is.

  Next, it is determined whether or not the monitoring time t has reached a predetermined specified time (step S31). If the determination result is “NO”, that is, the monitoring time t is still below the specified time. In the case, the process returns to step S23. On the other hand, if the determination result in step S31 is “YES”, that is, if the monitoring time t has already exceeded the specified time, the hydrogen gas leakage amounts Q1 to Q4 calculated in step S29 are less than a predetermined leakage threshold. (Step S33).

  If the determination result in step S33 is “YES”, that is, if the hydrogen gas leakage amounts Q1 to Q4 are less than the leakage threshold, normal processing is performed. In this normal processing, for example, “0” indicating that no hydrogen gas leak has been detected is set in the leak detection flag. Thereby, the gas leak detection process of FIG. 5 is complete | finished.

  On the other hand, if the determination result in step S33 is “NO”, that is, if the hydrogen gas leak amounts Q1 to Q4 are equal to or greater than the leak threshold, the time is measured at the start of the gas leak detection process shown in the flowchart of FIG. After the started monitoring time t is reset (step S51), the process returns to step S21.

  As described above, in the present embodiment, it is not determined that hydrogen gas leakage has occurred immediately because “hydrogen gas leakage amount ≧ predetermined leakage threshold” at the time of determination in step S33. After resetting the monitoring time t that has been counted until step S51, the process after step S21 is repeated again to delay the final determination of gas leak detection.

That is, the pressure drop due to factors other than hydrogen gas leak and the pressure drop due to hydrogen gas leak are distinguished based on the total pressure drop after the start of the gas leak detection process in the embodiment according to FIG. On the other hand, in the present embodiment, it is different in that it is based on the pressure drop after the monitoring time t is reset, but even with such a configuration, the pressure drop due to factors other than hydrogen gas leak and the pressure drop due to hydrogen gas leak are different. It is possible to distinguish and detect a gas leak with higher accuracy.

  FIG. 6 shows a pressure drop (solid line) due to a combustion reaction (a factor other than hydrogen gas leak) in the anode catalyst caused by cross leak during shutdown, and a pressure drop (broken line) due to hydrogen gas leak. It is explanatory drawing which shows that it can distinguish with embodiment. In this figure, p1 and P1 are measured pressure and reference pressure when the gas leak detection process is started, p2 and P2 are measured pressure and reference pressure when a predetermined monitoring time t has elapsed from that time, and p3 and P3 are at that time. Measured pressure and reference pressure when the same monitoring time t elapses.

As in the case of the embodiment according to FIG. 3 , the measured pressures p1 to p3 here are the pressures acquired in the process of step S23. Of the reference pressures P1 to P3 here, the reference pressure P1 is the pressure obtained in the process of step S21, and the reference pressures P2 and P3 are the reference values when it is assumed that hydrogen gas leaks. The pressure is expected to gradually decrease with the passage of time from the pressure P1.

  Also in the present embodiment, the gas leak determination is repeated after waiting for the same monitoring time t again after the lapse of the monitoring time t. Therefore, when the cause of the pressure drop is hydrogen gas leakage, it is indicated by a broken line in FIG. Thus, the pressure drops during the re-monitoring time t with the same gradient as during the monitoring time t, whereas when the cause of the pressure drop is the combustion reaction, as shown by the solid line in FIG. In addition, since the consumption of hydrogen gas decreases as the combustion reaction proceeds, the pressure drops with a gentler slope during the remonitoring time t than during the monitoring time t.

That is, as apparent from FIG. 6, the pressure drop amount Δp ₂₃ (Δp ₂₃ = Δp2−Δp3) during the remonitoring time t when the cause of the pressure drop is the combustion reaction is that the cause of the pressure drop is hydrogen. It becomes smaller than the pressure drop amount ΔP ₂₃ (ΔP ₂₃ = ΔP2−ΔP3) in the case of gas leakage. Therefore, even when the pressure drop amount Δp ₁₂ when the monitoring time t has elapsed is equal to the pressure drop amount ΔP ₁₂ due to hydrogen gas leak, by delaying the determination of gas leak detection by the re-monitoring time t, Differentiating from the pressure drop due to the combustion reaction, the pressure drop due to hydrogen gas leakage can be determined.

  The present invention can be applied with various modifications other than the above embodiment. For example, a fuel cell inlet shut-off valve is provided on the upstream side of the inlet of the fuel cell stack 10 of the fuel system 1, or the fuel cell outlet shut-off valve is provided on the downstream side of the outlet of the fuel cell stack 10 of the fuel system 1. A gas-liquid separator and shutoff valve for removing moisture and other impurities generated by the reaction from the hydrogen offgas, a check valve for preventing the backflow of hydrogen gas, and a branch from between the hydrogen pump 13 and the check valve to discharge the hydrogen offgas. And a purge shut-off valve that is disposed in the purge flow path and is opened at the time of purging may be provided.

  DESCRIPTION OF SYMBOLS 1 ... Fuel system, 10 ... Fuel cell stack, 20 ... Control part (gas leak determination part), C1-C4 ... Test object area (closed area), P1-P4 ... Pressure sensor, RG1-RG4 ... Pressure regulating valve

Claims (6)

A fuel cell that generates power upon receiving the supply of a reaction gas, a reaction gas system that supplies and discharges the reaction gas to and from the fuel cell, a plurality of pressure regulating valves provided in the reaction gas system, and a setting between adjacent pressure regulating valves An inspection target section set on the upstream side of the pressure regulating valve located upstream and an inspection target section including the fuel cell set on the downstream side of the pressure regulating valve located downstream. In a fuel cell system comprising: a pressure sensor provided; and a gas leakage determination unit that determines gas leakage in the inspection target section.
After the pressure on the downstream side reaches the specified pressure, the pressure regulating valve does not operate in a closed state unless the pressure on the downstream side falls below a certain level.
The gas leak determination unit is configured to detect a gas leak when a gas change amount in the inspection target section calculated using a pressure change amount from the pressure sensor and a volume of the inspection target section is equal to or greater than a predetermined threshold. the final decision is delayed, the
A fuel cell system that determines a gas leak when the amount of gas change at the time of delay is equal to or greater than a predetermined threshold .   The gas leak determination unit extends the determination time by a predetermined time when the gas change amount when a specified time elapses as a determination time for the gas leak determination is equal to or greater than a predetermined threshold. The fuel cell system according to claim 1, wherein the final determination is delayed.   The gas leak determination unit repeats the gas leak determination again when the gas change amount at the elapse of a specified time set as a determination time of the gas leak determination is equal to or greater than a predetermined threshold value, thereby repeating the final determination. The fuel cell system according to claim 1, wherein the determination is delayed. A fuel cell that generates power upon receiving the supply of a reaction gas, a reaction gas system that supplies and discharges the reaction gas to and from the fuel cell, a plurality of pressure regulating valves provided in the reaction gas system, and a setting between adjacent pressure regulating valves An inspection target section set on the upstream side of the pressure regulating valve located upstream and an inspection target section including the fuel cell set on the downstream side of the pressure regulating valve located downstream. A pressure sensor provided, and a gas leakage determination unit for determining gas leakage in the inspection target section, and after the pressure regulating valve reaches a specified pressure on the downstream side, the downstream pressure is constant. In a gas leak detection method for a fuel cell system that does not operate in a closed state unless it is lowered further,
When determining the gas leakage, if the amount of gas change in the inspection target section calculated using the amount of change in pressure from the pressure sensor and the volume of the inspection target section is equal to or greater than a predetermined threshold, A gas leak detection method for a fuel cell system, in which a final determination is delayed and a gas leak is determined when the gas change amount at the time of the delay is equal to or greater than a predetermined threshold .   In determining the gas leakage, when the gas change amount at the time when a predetermined time that is set in advance as the determination time of the gas leakage determination is equal to or greater than a predetermined threshold, the determination time is extended by a predetermined time. The gas leak detection method for a fuel cell system according to claim 4, wherein the final determination is delayed.   When determining the gas leak, when the gas change amount at the elapse of a specified time that is set in advance as a determination time of the gas leak determination is equal to or greater than a predetermined threshold, the gas leak determination is repeated again to determine the final value. The gas leak detection method for a fuel cell system according to claim 4, wherein the determination is delayed.

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