JP5110415B2 - 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

However , in the technique proposed in Patent Document 1, since leakage detection is performed only at one place where the pressure drop speed is the fastest, depending on the characteristics / operations of the pressure regulating valve disposed in the fuel system, fuel gas leakage may occur. Although it cannot be detected or there is no fuel gas leak, there is a risk of erroneous detection that it has occurred.

Accordingly, the present invention is that it enables inspection without being affected by the pressure adjustment state of the pressure regulating valve, and an object thereof is to solve the above Symbol challenges.

In order to solve the above-described problems, the present invention provides a fuel cell that generates power upon receiving a supply of a reaction gas, a reaction gas system that supplies and discharges the reaction gas to and from the fuel cell, and a plurality of reaction gas systems. Set to the downstream side of the pressure regulating valve, the inspection target section set between the adjacent pressure regulating valves, the inspection target section set upstream of the pressure regulating valve located upstream, and the downstream side of the pressure regulating valve in a fuel cell system including a pressure sensor provided respectively on the inspection target section is a front dangerous査determines the gas leakage determination unit gas leakage target section, and

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 judgment unit is calculated using the amount of change in pressure from the pressure sensor, based on the total sum of the gas change amount before Symbol inspected section performs gas leakage judgment of those inspected section.

  Due to its hysteresis characteristics, the pressure regulator with a general structure operates in a closed state if the secondary side pressure does not drop more than a certain level after the secondary (downstream) pressure reaches the specified pressure. do not do. Therefore, if the pressure drop speed is monitored only at one location upstream (primary side) from the pressure regulating valve, the following problem occurs when performing a gas (for example, fuel) leak inspection at the time of system startup, for example.

  First, when the gas leak inspection is started, if the pressure adjustment by the pressure regulating valve has already been completed, that is, if the secondary pressure has reached the specified pressure, the downstream side (secondary side) of the pressure regulating valve Even if a gas leak occurs, the closed state is maintained until the pressure on the secondary side of the pressure regulating valve drops more than a certain level, so that the pressure drop cannot be detected at the pressure monitoring point upstream of the pressure regulating valve. For this reason, gas leakage may not be detected.

  On the other hand, according to the above configuration of the present invention, if there is a gas leak on the downstream side of the pressure regulating valve, the sum of the gas change amounts on the upstream side and downstream side of the pressure regulating valve becomes a negative number (minus). The occurrence of leakage can be detected. In other words, if there is no gas leakage, the outflow to the downstream on the upstream side of the pressure regulating valve and the inflow from the upstream side on the downstream side of the pressure regulating valve cancel each other, and the total amount of gas change is zero in the calculation. However, the negative value means that the outflow from the upstream side of the pressure regulating valve to the downstream side is not directly the inflow from the downstream side of the pressure regulating valve. Means that has occurred.

  Note that when determining whether there is a gas leak based on the total amount of gas change, based on whether the total amount of gas change is zero or negative, the pressure sensor's measurement performance, measurement error, etc. This may cause false detection.

  Therefore, a certain range is given to the threshold value for determining the presence or absence of gas leakage, and it is determined that there is no gas leakage when the absolute value of the total amount of gas change is less than or equal to the predetermined threshold value. It is preferable to judge that there is a gas leak.

  Next, when the pressure regulating valve is under pressure adjustment when the gas leak inspection is started, that is, when the secondary side pressure has not yet reached the specified pressure, the pressure regulating valve is not closed. There is a flow of gas from the upstream side of the pressure regulating valve to the downstream side, whereby a pressure drop is detected at the pressure monitoring point upstream of the pressure regulating valve. For this reason, it may be erroneously detected that a gas leak has occurred even though no gas leak has occurred.

  On the other hand, according to the above configuration of the present invention, even if a pressure drop on the upstream side of the pressure regulating valve due to the gas flow from the upstream side of the pressure regulating valve to the downstream side is detected, no gas leakage occurs. Because the outflow to the downstream side on the upstream side of the pressure regulating valve and the inflow from the upstream side on the downstream side of the pressure regulating valve are offset, the total amount of gas change becomes zero in the calculation. There is no false detection. Note that when a gas leak occurs during the pressure adjustment of the pressure regulating valve, as described, the sum of the gas change amounts exceeds a negative number (minus) or a predetermined threshold value, so that the gas leak can be detected.

  In the above configuration, the gas leak determination unit may end the gas leak determination when the pressure upstream of the pressure regulating valve becomes equal to or lower than the set pressure of the pressure regulating valve during the gas leak determination. .

The present invention relates to a fuel cell that generates power upon receiving a supply of a reaction gas, a reaction gas system that supplies and discharges the reaction gas to the fuel cell, and a pressure regulating valve that is provided in the reaction gas system. After the pressure reaches the specified pressure, it is set between the pressure regulating valves adjacent to each other with respect to the fuel cell system including a plurality of pressure regulating valves that do not operate in a closed state unless the pressure on the downstream side drops below a certain level. A fuel cell for determining a gas leak in an inspection target section set on the upstream side of the pressure regulating valve located upstream from the inspection target section and an inspection target section set on the downstream side of the pressure regulating valve positioned downstream. In the system gas leak detection method,
Based on the total sum of the gas change amount before Symbol inspected section judges gas leakage thereof inspection target section.

  In the above configuration, when the pressure upstream of the pressure regulating valve becomes equal to or lower than the set pressure of the pressure regulating valve during the gas leakage judgment, the gas leakage judgment may be terminated.

  According to the present invention, the total amount of gas change in the fully closed section is calculated using the amount of change in pressure from each pressure sensor disposed in the adjacent closed section, and the presence or absence of gas leakage is determined based on the calculation result. Since the determination is made, it is possible to perform an inspection that is not affected by the pressure adjustment state of the pressure regulating valve, and 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 the gas leak detection process which concerns on the same embodiment. It is a flowchart explaining the gas leak detection process which concerns on a 1st reference example . It is explanatory drawing which shows that it is possible to distinguish the pressure drop by factors other than gas leak by the reference example . It is a flowchart explaining the gas leak detection process which concerns on a 2nd reference example . It is explanatory drawing which shows that it is possible to distinguish the pressure drop by factors other than gas leak by the reference example .

  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.

<First Embodiment>
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.

  Next, a gas leak detection process performed in 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 embodiment, the threshold for determining the presence or absence of hydrogen gas leakage has a certain width, and the absolute value of the sum Q of hydrogen gas change amounts (hereinafter simply referred to as sum Q) is a predetermined threshold 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 embodiment, all the inspection target sections C1 to C4 are used by using the pressure change amounts Δp1 to Δp4 from the pressure sensors P1 to P4 arranged in the adjacent inspection target sections C1 to C4. 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.

<First Reference Example >
Next, the gas leak detection process according to the first reference example will be described with reference to the flowchart of FIG. The fuel cell system according to this reference example can be applied to the same system as the fuel cell system according to the first embodiment.

Further, in this reference example, it is assumed that the 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 this reference example , when the determination result of 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 = (Δpn × vn) ÷ t × N
Here, vn: the piping volume of the section Cn to be inspected, t: the measurement interval of the current pressure pn, N: the unit conversion coefficient, n: a natural number of 1 to 4.

  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 this reference example , just because “hydrogen gas leak amount ≧ predetermined leak threshold” at the time of determination in step S33, it is not determined that hydrogen gas leak has occurred immediately. 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. occurs as a result of hydrogen gas by the combustion reaction is consumed, even from the fuel system 1 has occurred despite the pressure drop of hydrogen gas leakage has not occurred, according to the present embodiment, such hydrogen 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 an explanatory view showing that are distinguishable by the reference example. 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 has elapsed, the pressure drop amount Δp12 (Δp12 = p1 to p2) of the measured pressure and the pressure drop amount ΔP12 (ΔP12 = P1 to P2) due to hydrogen gas leakage are measured. If the equal cases occur, 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.

  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 is apparent from FIG. 4, when the cause of the pressure drop is the combustion reaction, the pressure drop Δp13 from the start of the monitoring time t to the time extension t ′ is the cause of the pressure drop due to hydrogen gas leakage. It becomes smaller than the pressure drop amount ΔP13 in some cases. Therefore, even if the pressure drop amount Δp12 when the monitoring time t elapses is equal to the pressure drop amount ΔP12 due to hydrogen gas leak, the determination of gas leak detection is delayed by the time extension t ′, whereby the combustion Differentiating from the pressure drop due to the reaction, the pressure drop due to hydrogen gas leakage can be determined.

< Second Reference Example >
Next, the gas leak detection process according to the second reference example will be described with reference to the flowchart of FIG. The fuel cell system according to this reference example can be applied to the same system as the fuel cell system according to the first embodiment.

Further, in this reference example, it is assumed that the processing corresponding to the processing of step S1 to step S5 of FIG. 2 is executed in advance prior to the processing shown in the flowchart of 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 = (Δpn × vn) ÷ t × N
Here, vn: the piping volume of the section Cn to be inspected, t: the measurement interval of the current pressure pn, N: the unit conversion coefficient, n: a natural number of 1 to 4.

  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 this reference example , just because “hydrogen gas leakage amount ≧ predetermined leakage threshold” is determined in step S33, it is not determined immediately that hydrogen gas leakage has occurred. 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.

In other words, 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 starting the gas leak detection process in the first reference example. The reference example is different in that it is based on the amount of pressure drop after resetting the monitoring time t, but even with such a configuration, the pressure drop due to factors other than hydrogen gas leak is distinguished from the pressure drop due to hydrogen gas leak, It is possible to 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 an explanatory view showing that are distinguishable by the reference example. 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 first reference example , 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 this reference example , the gas leak determination is repeated after waiting for the same monitoring time t again after the monitoring time t elapses. 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 Δp23 (Δp23 = 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 gas leakage. Is smaller than the pressure drop amount ΔP23 (ΔP23 = ΔP2−ΔP3). Therefore, even if the pressure drop Δp12 when the monitoring time t elapses is equal to the pressure drop ΔP12 due to hydrogen gas leak, the combustion detection is delayed by delaying the determination of the gas leak by the remonitoring time t. Differentiating from the pressure drop due to the reaction, the pressure drop due to hydrogen gas leakage can be determined.

<Other embodiments>
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.

  In such a configuration, it is possible to form a closed space between the valves. Therefore, a pressure sensor is provided for each of these closed spaces, and based on the total amount of fuel change in the fully closed space formed during the actual inspection. Perform leak detection. In actual inspection, it is not always necessary to form a closed section between all the valves. By setting the shut-off valve to the open or closed state corresponding to the section to be inspected, the selective section of the inspection target section can be selected. Adjustment is possible.

  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 (4)

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 Pressure sensors provided respectively in the inspection target section set on the upstream side of the pressure regulating valve located upstream and the inspection target section set on the downstream side of the pressure regulating valve positioned downstream. If, before and determines the gas leakage determination unit gas leakage dangerous査target section, the fuel cell system equipped with,
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 judgment unit is configured is calculated using the amount of change in pressure from the pressure sensor, based on the total sum of the gas change amount before Symbol inspection target section, fuel perform the gas leakage judgment of those inspected section Battery system.   2. The fuel cell according to claim 1, wherein the gas leak determination unit terminates the gas leak determination when a pressure upstream of the pressure regulating valve becomes equal to or lower than a set pressure of the pressure regulating valve during the gas leak determination. system. A fuel cell that generates power upon receiving supply of a reaction gas, a reaction gas system that supplies and discharges the reaction gas to and from the fuel cell, and a pressure regulating valve provided in the reaction gas system, the pressure on the downstream side of which is a specified pressure After the pressure reaches, a fuel cell system including a plurality of pressure regulating valves that do not operate in a closed state unless the pressure on the downstream side drops more than a certain level, an inspection target section set between adjacent pressure regulating valves, Gas leakage of the fuel cell system for determining gas leakage in an inspection target section set on the upstream side of the pressure regulating valve located upstream and an inspection target section set on the downstream side of the pressure regulating valve positioned downstream In the detection method,
Based on the total sum of the gas change amount before Symbol inspection target section, a gas leak detection method of a fuel cell system for determining gas leakage thereof inspection target section.   The gas leak detection method for a fuel cell system according to claim 3, wherein when the pressure upstream of the pressure regulating valve becomes equal to or lower than the set pressure of the pressure regulating valve during the gas leak judgment, the gas leak judgment is terminated.

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