WO2006048983A1

WO2006048983A1 - Fuel cell system

Info

Publication number: WO2006048983A1
Application number: PCT/JP2005/017679
Authority: WO
Inventors: Kenichi Goto
Original assignee: Nissan Motor Co., Ltd.
Priority date: 2004-11-04
Filing date: 2005-09-27
Publication date: 2006-05-11
Also published as: JP2006134647A

Abstract

An upstream purge valve (16) and a downstream purge valve (17) are provided in series on a hydrogen discharge passage (13) for discharging hydrogen gas from the anode (2a) or the hydrogen circulation passage (11a) of a fuel cell to the outside of the system. Furthermore, a pressure sensor (15) is provided for detecting the pressure of the hydrogen discharge passage (13b) between the upstream purge valve (16) and the downstream purge valve (17). A system control section (18) encloses the hydrogen discharge passage (13b) by closing the upstream purge valve (16) and the downstream purge valve (17) and monitors time variation in detection value of the pressure sensor (15). When the detection value of the pressure sensor (15) lowers toward the atmospheric pressure, the system control section (18) judges open lock failure of the downstream purge valve (17) has occurred and when the detection value lowers toward the pressure of the anode (2a) that it judges that open lock failure of the upstream purge valve (16) has occurred.

Description

Fuel cell system

Technical field

TECHNICAL FIELD [0001] The present invention relates to a fuel cell system, and more particularly to a fuel cell system with improved purge valve failure detection.

Background art

[0002] A fuel cell is one in which a fuel gas such as hydrogen and an oxidant gas having oxygen are electrochemically reacted via an electrolyte, and electric energy is directly taken out between electrodes provided on both sides of the electrolyte. It is. In particular, solid polymer fuel cells using solid polymer electrolytes are attracting attention as power sources for electric vehicles because of their low operating temperature and easy handling. Fuel cell vehicles are equipped with hydrogen storage devices such as high-pressure hydrogen tanks, liquid hydrogen tanks, hydrogen storage alloy tanks, etc., and hydrogen supplied from them and air containing oxygen are sent to the fuel cells for reaction. The motor connected to the drive wheels is driven by the electric energy extracted from the fuel cell power. Therefore, the only material discharged from the fuel cell vehicle is water.

[0003] Many polymer electrolytes used in polymer electrolyte fuel cells do not exhibit good cation conductivity unless they are in a wet state. Oxidant gas (hereinafter, both are collectively referred to as reaction gas) is humidified. In addition, in order to increase power generation efficiency, more gas than the amount of reaction gas required from the output current of the fuel cell is supplied, and surplus hydrogen gas is recirculated to the anode inlet through the hydrogen circulation path.

[0004] In such a fuel cell system, the inert gas (nitrogen, argon, etc.) in the air that leaks the electrolyte membrane from the power sword to the anode accumulates in the hydrogen circulation path, lowers the hydrogen partial pressure, As a result, power generation efficiency is reduced. In addition, the generated water generated by the electrochemical reaction of power generation becomes liquid water and accumulates in the gas passage, which may interfere with gas distribution and gas diffusion, leading to a decrease in power generation efficiency and power generation stoppage. In order to sweep out such impurity gas and liquid water from the gas passage, the wafer-off gas discharged from the anode is discharged out of the circulation path. A purge valve is provided.

[0005] Normally, a diluting device and a catalytic combustion device are provided downstream of the purge valve as a waste hydrogen treatment device. The dilution device dilutes the purge gas concentration below the limit concentration with air and releases it to the outside of the system. The catalytic combustion device burns hydrogen in the purge gas by the combustion catalyst and releases it as water vapor.

[0006] Conventionally, as a failure diagnosis of the purge valve, a comparison is made between the target anode pressure and the actual anode pressure when the purge valve is opened and closed during a constant operation in which the fluctuation of the power generation output of the fuel cell is within a predetermined range. (See JP 2003-092125, page 5 and FIG. 2).

Disclosure of the invention

[0007] However, in the above prior art, the diagnosis of the purge valve can be diagnosed only when the power generation output of the fuel cell is within a predetermined range, and thus the diagnosis frequency is limited. Further, when the purge line system is extremely small, a pressure change due to the purge appears in the anode pressure, and it may be difficult to make a precise diagnosis.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell system capable of diagnosing a purge valve failure regardless of the operating state of the fuel cell system.

[0009] A fuel supply system according to a first aspect of the present invention includes a fuel cell that generates power using a fuel gas supplied to a fuel electrode and an oxidant gas supplied to an oxidant electrode, A fuel circulation path for returning excess fuel gas discharged to the fuel electrode, a fuel discharge path for releasing a part of the gas in the fuel circulation path to the outside, and a plurality of fuel circulation paths arranged in series in the fuel discharge path A purge valve, at least one pressure sensor for measuring the pressure in the space between the plurality of purge valves, and at least one gas of the purge valve force based on the change over time of the pressure value detected by the pressure sensor And a failure detector for detecting a failure of the purge valve by detecting a leak.

[0010] A fuel supply system according to a second aspect of the present invention includes a fuel cell that generates power using a fuel gas supplied to a fuel electrode and an oxidant gas supplied to an oxidant electrode, and A fuel circulation path for recirculating surplus fuel gas discharged to the fuel electrode, and the fuel circulation path At least one pressure for measuring a pressure of a space between the plurality of purge valves, a plurality of purge valves arranged in series in the fuel discharge path, A failure detection means for detecting a failure of the purge valve by detecting a gas leak of at least one purge valve force based on a time change of a pressure value detected by the pressure sensor. It is characterized by that.

[0011] A failure diagnosis method for a fuel supply system according to a third aspect of the present invention includes: a fuel cell that generates power using a fuel gas supplied to a fuel electrode and an oxidant gas supplied to an oxidant electrode; A fuel circulation path for returning surplus fuel gas discharged as much as possible to the fuel electrode, a fuel discharge path for releasing a part of the gas in the fuel circulation path to the outside, and the fuel discharge path in series A plurality of disposed purge valves, a step of measuring a pressure in a space between the plurality of purge valves, and a gas having at least one purge valve force based on a change over time of the measured pressure value. And detecting a failure of the purge valve by detecting leakage.

Brief Description of Drawings

FIG. 1 is a configuration diagram illustrating the configuration of Example 1 of a fuel cell system according to the present invention.

FIG. 2 is a timing chart for diagnosing a purge valve failure during operation of the fuel cell system in the first embodiment.

FIG. 3 is a flowchart for diagnosing a purge valve failure when idling is stopped in the first embodiment.

[FIG. 4] FIG. 4 is a timing chart for identifying a failure site in Example 1.

FIG. 5 is a timing chart for diagnosing a purge valve failure when the fuel cell system is stopped in the first embodiment.

FIG. 6 is a flowchart for diagnosing a purge valve failure when the fuel cell system is stopped in the first embodiment.

[Fig. 7] Fig. 7 is a configuration diagram for explaining a main configuration of Example 2 of the fuel cell system according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail with reference to the drawings. Each embodiment described below is a fuel cell system suitable for a fuel cell vehicle, although not particularly limited.

[0014] (Example 1)

FIG. 1 shows the configuration of Example 1 of the fuel cell system according to the present invention. In the first embodiment, two purge valves are provided in a hydrogen discharge passage that is a fuel discharge passage.

In FIG. 1, a fuel cell system 1 includes hydrogen as a fuel gas supplied to an anode (fuel electrode) 2a and air as an oxidant gas supplied to a force sword (oxidant electrode) 2b. It has a fuel cell 2 that generates electricity through an electrochemical reaction. The air as the oxidant gas is compressed by the air compressor 3 and supplied to the power sword 2 b of the fuel cell 2 through the air supply path 4. Part of the oxygen in the air is used for the power generation reaction, and the remaining oxygen and nitrogen are discharged outside the system through the air discharge path 5a, the air pressure regulating valve 6, the air discharge path 5b, and the collective discharge path 14. The air pressure regulating valve 6 adjusts the air pressure of the force sword 2b by controlling the opening degree.

[0016] Hydrogen as a fuel gas is stored in a high-pressure hydrogen tank 7. The hydrogen in the high-pressure hydrogen tank 7 is depressurized to a certain pressure, for example, IMPa, by the pressure reducing valve 8, and then depressurized to a desired pressure by the hydrogen pressure regulating valve 9, and is supplied to the fuel cell 2 via the hydrogen supply path 10. Supplied to anode 2a. Hydrogen that has not reacted at the anode 2a joins the hydrogen supply path 10 via the hydrogen circulation path l la, the hydrogen circulation pump 12, and the hydrogen circulation path l ib, and is supplied to the anode 2a again.

[0017] In this fuel cell system 1, the inert gas (nitrogen, argon, etc.) in the air that leaks the electrolyte membrane from the force sword 2b to the anode 2a accumulates in the hydrogen circulation path and lowers the hydrogen partial pressure. To reduce power generation efficiency. In addition, the water generated by the electrochemical reaction of power generation becomes liquid water and accumulates in the gas passage, which may hinder gas flow and gas diffusion, leading to a decrease in power generation efficiency and power generation stoppage. In order to sweep out such impurity gas and liquid water from the gas passage, a hydrogen discharge passage 13 is provided in order to discharge the anode-off gas from which the anode force is also discharged out of the circulation passage. Further, an upstream purge valve 16 and a downstream purge valve 17 are provided in series on the hydrogen discharge path 13. Here, the branching point A force with the hydrogen circulation path 11a is 13a in the hydrogen discharge path to the upstream purge valve 16 and the upstream purge valve 16 to the downstream purge valve. The hydrogen discharge path up to 17 is designated as 13b, and the hydrogen purge path 13c from the downstream purge valve 17 to the point B where the hydrogen discharge path joins the air discharge path 5b. In addition, downstream from the junction B of the air discharge path 5b and the hydrogen discharge path 13c is a collective discharge path 14 through which hydrogen is diluted with air and discharged. The upstream purge valve 16 is a purge valve capable of controlling the opening degree.

[0018] The downstream purge valve 17 and the pressure sensor 15 are characteristic components of the present invention. The downstream purge valve 17 may be a valve whose opening degree can be controlled in the same manner as the upstream purge valve 16, but in this embodiment, it is a simple open / close valve. During normal operation, the downstream purge valve 17 is opened, and the amount of purge of the Hanoff gas is adjusted by controlling the opening of the upstream purge valve 16.

The pressure sensor 15 is a sensor that detects the pressure in the hydrogen discharge path 13b that is sealed by the upstream purge valve 16 and the downstream purge valve 17, and the detected value is input to the system control unit 18. Yes. The system control unit 18 controls the entire fuel cell system 1 and detects the pressure change of the anode off-gas sealed between the upstream purge valve 16 and the downstream purge valve 17 with the pressure sensor 15, thereby detecting both purge valves. Purge valve that detects 16 and 17 faults Also serves as a fault detector. In the present specification, the pressure in the hydrogen discharge passage 13b sealed by the upstream purge valve 16 and the downstream purge valve 17 is also referred to as a purge line pressure.

Although not particularly limited! In the present embodiment, the system control unit 18 is configured by a microprocessor having a CPU, a program ROM, a working RAM, and an input / output interface. When the CPU executes the control program stored in the program ROM, control of the entire system and failure diagnosis of the purge valve are achieved. The system control unit 18 also has a function as a power generation stop determination device that determines whether or not to stop power generation of a fuel cell, which will be described later.

[0021] In addition, the volume of the hydrogen discharge passage 13b, which is a space sealed by the upstream purge valve 16 and the downstream purge valve 17, is minimized, in other words, the upstream purge valve 16 and the downstream purge valve 17 are arranged close to each other. By doing so, the pressure fluctuation sensitivity of the pressure sensor 15 due to leakage of the purge valves 16 and 17 can be increased. By increasing the sensitivity of the pressure sensor 15 in this way, failure of the purge valves 16 and 17 can be diagnosed with high accuracy.

Hereinafter, a failure diagnosis method for the purge valves 16 and 17 will be described. First, referring to FIG. 2, the purge valve failure diagnosis during normal operation of the fuel cell system will be described. In Figure 2 The timing chart for diagnosing the leakage of the purge valves 16 and 17 is shown. 2 (a) shows the hydrogen pressure in the hydrogen discharge passage 13b, FIG. 2 (b) shows the hydrogen pressure in the anode 2a, and FIG. 2 (c) shows the open / close state of the downstream purge valve 17. In FIG. 2, (d) shows the open / close state of the upstream purge valve 16.

[0023] First, in the state 1 which is a normal operation state, the downstream purge valve 17 is closed at a timing tl at which diagnosis is started. Then, the state 1 is changed to the state 2, and the hydrogen discharge path 13b, which is the space between the upstream purge valve 16 and the downstream purge valve 17, is equivalent to the hydrogen pressure in the anode 2a and the hydrogen circulation paths 11a and 1 lb. Pressure is maintained. When a certain amount of time has passed in state 2 and the detected value of pressure sensor 15 has stabilized, the detected value is stored as pressure P1 in system control unit 18, and upstream purge valve 16 is closed at timing t2. This transitions from state 2 to state ₃ . Subsequently, in state 3, the pressure sensor 15 monitors the change over time in the pressure of the blocked hydrogen discharge passage 13b. If there is a gas leak in either the upstream purge valve 16 or the downstream purge valve 17, the pressure in the hydrogen discharge passage 13 b is relatively quickly adjusted to the outside of the purge valve as shown by curve D in (a) in FIG. It changes toward pressure. That is, for example, when there is a gas leak in the downstream purge valve 17, it converges to the atmospheric pressure, and when there is a leak in the upstream purge valve 16, it converges to the pressure in the anode 2a. That is, it is possible to determine the presence or absence of gas leakage from the purge valves 16 and 17 based on the variation width of the pressure in the hydrogen discharge passage 13b at a predetermined time.

[0024] On the other hand, when the pressure in the anode 2a and the hydrogen circulation paths 11a, ib and the pressure in the hydrogen discharge path 13b indicate relatively close pressures, the upstream purge valve 16 in which the change appearing in the detected value of the pressure sensor 15 is small. It is difficult to detect leakage. Therefore, in state 3, the electric power is taken out from the fuel cell 2 to consume the hydrogen of the anode 2a, and the pressure of the anode 2a is reduced within the range allowed by the power generation requirement of the fuel cell. By doing so, when there is a leak in the upstream purge valve 16, the pressure of the hydrogen discharge passage 13b decreases with the lower pressure of the anode 2a, so that a highly accurate diagnosis can be made. And even if the pressure of the anode 2a is decreased as shown by the curve E in (b) in FIG. 2, the hydrogen pressure in the hydrogen discharge passage 13b remains as shown by the curve C in (a) in FIG. If there is almost no drop, it can be determined that there is no leakage from the purge valves 16 and 17.

[0025] Next, referring to FIG. 3 and FIG. 4, the failure diagnosis of the purge valve when idling is stopped. I will explain this. Fig. 4 shows the timing chart of the leak diagnosis of the purge valve when idling stop of the fuel cell system. 4 (a) shows the hydrogen pressure in the hydrogen discharge passage 13b, FIG. 4 (b) shows the hydrogen pressure in the anode 2a, and FIG. 4 (c) shows the open / close state of the downstream purge valve 17. In FIG. 4, (d) shows the open / close state of the upstream purge valve 16.

[0026] First, in step SO, the system control unit 18 identifies whether or not the current fuel cell is in an idling stop state. If it is not in the idling stop state, in step S2, it is determined whether or not the idling stop permission condition for determining whether or not the fuel cell power generation may be temporarily stopped is satisfied. As an idling stop condition, for example, in the case of a fuel cell vehicle equipped with a secondary battery, the required power amount based on the accelerator depression amount is sufficiently covered by the discharge amount of the secondary battery.

If it is determined in step S2 that the idling stop permission condition is satisfied, the upstream purge valve 16 is opened and the downstream purge valve 17 is closed in step S4. Thereafter, in step S6, whether the pressure between the upstream purge valve 16 and the downstream purge valve 17 rises within a predetermined time is checked based on the detection value of the pressure sensor 15. Here, if the pressure does not increase even after a predetermined time has elapsed, the downstream purge valve 17 remains open, that is, the downstream purge valve is in an open / fixed failure state, or the upstream purge valve 16 remains closed. That is, the upstream purge valve is closed. In this case, the process proceeds from step S6 to step S14, and it is determined that the purge valve has failed, and the system control is performed by setting the purge valve failure experience flag (flag = 1) to indicate that the purge valve has failed. Store in part 18.

[0028] On the other hand, if the pressure between the upstream purge valve 16 and the downstream purge valve 17 increases in step S6, the process proceeds to step S8, the upstream purge valve 16 is closed, and both the purge valves 16, 17 While maintaining the pressure of the hydrogen discharge passage 13b, the pressure P1 between the purge valves 16, 17 detected by the pressure sensor 15 is stored in the system control unit 18 (pressure Pl = purge line pressure). Further, immediately after the upstream purge valve 16 is closed, measurement of the time during which the upstream purge valve 16 is closed is started. Further, immediately after closing both purge valves 16 and 17, the supply of hydrogen and air is stopped to stop the power generation of the fuel cell temporarily. The pressure of the anode 2a is controlled to be lower than the pressure of the hydrogen discharge passage 13b sealed by the purge valves 16, 17 (step S10). As a result, a pressure difference occurs before and after the upstream purge valve 16, so that leakage of the upstream purge valve 16 can also be detected.

Step S 12 is a purge valve diagnosis step. In step S12, the time measured immediately after the pressure between the purge valves 16 and 17 drops by more than a predetermined pressure with respect to the pressure value stored in step S8 (pressure P1) and immediately after the upstream purge valve 16 is closed. Check if the force is less than or equal to the predetermined time T1. If a pressure drop equal to or higher than the predetermined pressure P is detected within the predetermined time T1 in step S12, the process proceeds to step S14 because there is a leak in the upstream purge valve 16 or the downstream purge valve 17, and it is determined that the purge valve has failed. In addition, the fact that the purge valve is faulty is stored in the system control unit 18 by setting a purge valve fault experience flag. On the other hand, if it is determined in step S12 that there is no pressure drop, the idling stop state is continued.

[0030] As described above, in the fuel cell having the idling stop function, the function of processing the exhaust hydrogen from the fuel discharge path during the idling stop to stop the auxiliary device of the fuel cell during the idling stop. Will be damaged or restricted. Therefore, it is necessary to accurately diagnose the leakage of the purge valve during the idling stop. According to this embodiment, since the leak diagnosis of the purge valve can be performed when the idling stop is being performed, the hydrogen leak from the purge valve in the idling stop state can be detected in real time.

[0031] On the other hand, when the idling stop state is identified in step SO, it is determined in step S16 whether or not there is a force that needs to cancel the idling stop, that is, the condition for canceling the idling stop. If it is determined in step S16 that the conditions for releasing the idling stop are satisfied, hydrogen supply is started in step S18 and air supply is started.In step S20, the normal opening of the upstream purge valve 16 is started. At the same time as starting the control, the downstream purge valve 17 is opened to shift to the normal power generation state. If it is determined in step S16 that the conditions for releasing the idling stop are not satisfied, the process proceeds to step S12, and the idling stop is continued while continuing the diagnosis of the purge valve.

[0032] Here, whether or not the purge valve is determined to be in the open fixed state may be added to the idling stop cancellation condition of step S16. Step during idling stop If it is determined in S14 that the purge valve is in an open stuck state, that is, a failure state, the idling stop return condition is satisfied in step S16, and the normal power generation state is shifted in accordance with steps S18 and S20. . Further, in the idling stop permission condition of step S2, the purge valve is not determined to be in the open stuck state, that is, the purge valve failure experience flag is set (plug ≠ 1). You can add it. If it is determined in step S14 that the purge valve is in the open stuck state during the idling stop, the idling stop return condition is satisfied in step S16, and the normal power generation state is set in accordance with steps S18 and S20. However, after that, the idling stop permission condition is not satisfied. As a result, if a leak of the purge valve is detected during idling stop, the idling stop can be immediately released and the function of treating the purged hydrogen of the purge valve force can be restored. Hydrogen can be prevented from being discharged. In addition, if a purge valve leak is detected, it is possible to prevent the idling stop from being performed thereafter.As a result, the idling stop force returns to the operating state as soon as the purge valve malfunctions. Can be prevented. Furthermore, in the present invention, when the system control unit 18 determines in step S2 that it is possible to stop the power generation of the fuel cell, before shifting to the state where the power generation of the fuel cell 2 is temporarily stopped, In steps S4 and S6, failure of purge valves 16, 17 is detected. Therefore, if a failure of the purge valves 16 and 17 is detected in steps S4 and S6, the function of processing the exhaust hydrogen from the purge valve is maintained because the process does not proceed to step S8 and the idling stop is not performed. As a result, hydrogen above the specified concentration can be prevented from being discharged outside the vehicle.

Next, a method for diagnosing which of purge valves 16 and 17 has failed in the idling stop state will be described. As shown in FIG. 4, first, in the state 4 in the idling stop state, the downstream purge valve 17 is closed at the timing t4. Then, the state 4 changes to the state 5, and a pressure corresponding to the hydrogen pressure in the anode 2a is held in the hydrogen discharge path 13b. When a certain amount of time elapses in state 5 and the detected value of pressure sensor 15 becomes stable, the detected value is stored as pressure P1 in system control unit 18, and upstream purge valve 16 is closed at timing t5. This transitions from state 5 to state 6. Subsequently, in state 6, the blocked water The pressure sensor 15 monitors the time change of the pressure in the element discharge passage 13b. If it is determined in state 6 that the purge valve is stuck open, at time t6, the pressure at this time is stored as pressure P2 in the system control unit 18, and at the same time, the upstream purge valve 16 is controlled to open. . Here, if the upstream purge valve 16 is originally open and fixed, even if the upstream purge valve 16 is controlled to open, the state of the upstream purge valve 16 and the hydrogen discharge passage 13b from state 6 to state 7 will be described. Therefore, as shown by the curve F in FIG. 4, the way in which the pressure between the purge valves 16 and 17 is released does not change significantly. However, if the downstream purge valve 17 is stuck open, the upstream purge valve 16 is opened, and as shown by the curve G in FIG. This means that the area where the pressure can be released has increased, and the pressure can be released more quickly. That is, in the state 7, since both the purge valves 16 and 17 are opened, the hydrogen between the purge valves 16 and 17 quickly flows out to the anode 2a side and the collecting discharge path 14 side. Therefore, by comparing the pressure drop rate until the pressure P1 is changed to the pressure P2 and the pressure drop rate after the upstream purge valve 16 is opened and the pressure P2 is changed to the pressure P3, which purge valve is It is possible to determine whether the purge valve has failed or not. Thereby, subsequent repairs can be performed quickly. In addition, optimal fail-safe control can be performed according to the fault location.

[0034] Here, as shown in FIG. 1, when the gas discharged from the purge valves 16 and 17 is diluted with the off-gas of the power sword, the purge valves 16 and 17 It is sufficient to supply enough air to dilute the hydrogen to be discharged, but if the purge valve 16 or 17 is stuck open and more hydrogen than usual is expected, it will be It is necessary to supply air. Here, if the upstream purge valve 16 is out of order, the normal purge control function is impaired, so that the diluted hydrogen air can be diluted to a safe concentration in order to ensure that the discharged hydrogen of the purge valve force is diluted to a safe concentration. Perform fail-safe treatment to increase the capacity of the hydrogen treatment function, such as increasing the amount. As a result, the hydrogen concentration discharged outside the fuel cell system can be suppressed to a low level. Even if the downstream purge valve 17 has an open stuck failure as a result of identifying the failure location of the purge valve, the normal purge control can be performed by the upstream purge valve 16, so that the normal power generation control can be continued. .

Next, referring to FIG. 5, the purge valve malfunctions when the fuel cell system is shut down. Explain the diagnosis.

[0036] Normal operating state force of fuel cell system After the system is stopped and transitioned to stop state 8, downstream purge valve 17 is closed at timing t8. Then, in the state 9, a pressure corresponding to the hydrogen pressure of the anode 2a is held in the hydrogen discharge path 13b. At this time, the pressure detected by the pressure sensor 15 is stored in the system control unit 18 as the pressure P1, and the upstream purge valve 16 is closed at timing t9. Subsequently, in state 10, the pressure sensor 15 monitors the change over time in the pressure of the blocked hydrogen discharge passage 13b. If there is no leakage in the upstream purge valve 16 or the downstream purge valve 17, the pressure in the hydrogen discharge passage 13b hardly decreases as shown by curve H in FIG. If the upstream purge valve 16 or the downstream purge valve 17 leaks, the pressure in the hydrogen discharge passage 13b changes toward the pressure outside the purge valve relatively quickly as shown by curve I in FIG. . For example, if there is a leak in the downstream purge valve 17, it converges to atmospheric pressure, and if there is a leak in the upstream purge valve 16, it converges to the pressure of the anode 2 a. In other words, whether or not the purge valves 16 and 17 are leaking can also be determined by the pressure variation width within the hydrogen discharge passage 13b at a predetermined time.

FIG. 6 shows a flowchart of the purge valve diagnosis when the operation of the fuel cell system is stopped.

First, in step S40, it is determined whether or not the fuel cell system is activated. When the fuel cell system is not activated, it is determined in step S42 whether or not the fuel cell system is stopped.

If it is determined in step S42 that the system stop condition is satisfied, the upstream purge valve 16 is opened and the downstream purge valve 17 is closed in step S44. Thereafter, in step S46, it is checked whether the pressure between the upstream purge valve 16 and the downstream purge valve 17 rises within a predetermined time based on the detection value of the pressure sensor 15. Here, if the pressure does not increase even after a predetermined time has elapsed, the downstream purge valve 17 remains open, that is, the downstream purge valve is stuck open, or the upstream purge valve 16 remains closed, that is, the upstream purge. The valve is closed. In this case, the process proceeds from step S46 to step S54, and it is determined that the purge valve has failed, and the purge valve failure experience flag is set (flag = 1) to indicate that the purge valve has failed. To remember.

[0039] On the other hand, in step S46, the pressure between the upstream purge valve 16 and the downstream purge valve 17 increases. If this is the case, the process proceeds to step S48, the upstream purge valve 16 is closed, the pressure in the hydrogen discharge passage 13b between the purge valves 16 and 17 is maintained, and the pressure between the purge valves 16 and 17 detected by the pressure sensor 15 Is stored in the system control unit 18 (pressure Pl = purge line pressure). Also, immediately after the upstream purge valve 16 is closed, measurement of the time during which the upstream purge valve 16 is closed is started. Further, immediately after closing both purge valves 16 and 17, supply of hydrogen and air is stopped. In step S50, the electric power is taken out from the fuel cell 2 and the pressure of the anode 2a is controlled to be lower than the pressure of the hydrogen discharge passage 13b sealed by the purge valves 16 and 17.

Step S52 is a purge valve diagnosis step. In step S52, the time measured immediately after closing the upstream purge valve 16 when the pressure between the purge valves 16 and 17 drops by more than a predetermined pressure with respect to the pressure value (pressure P1) stored in step S48. Confirm whether or not is less than T1 for a predetermined time. If a pressure drop equal to or greater than the predetermined pressure P1 within the predetermined time T1 at step S52, it is determined that there is a leak in the upstream purge valve 16 or the downstream purge valve 17 and the process proceeds to step S54, where it is determined that the purge valve has failed. The fact that the purge valve is faulty is stored in the system controller 18 by setting the purge valve fault experience flag. On the other hand, if it is determined in step S52 that there is no pressure drop, stop operation and return.

[0041] When the fuel cell system is activated next time, it is first recognized as activated in step S40. If it is recognized at step S40 that the engine has been started, it is determined in step S56 that the purge valve has failed due to the diagnosis at the previous stop and whether it has been detected. If it is not determined that the purge valve has failed in the previous diagnosis, the purge valve is recognized as normal and is started without increasing the air in step S60. On the other hand, if the previous diagnosis is determined to be NG in step S56, the purge valve is recognized to be abnormal, and the purge valve force is increased in step S58 to sufficiently dilute the hydrogen estimated to be discharged. In step S62, hydrogen supply is started and the fuel cell is started.

[0042] In this way, by determining the failure of the purge valve when the fuel cell system is stopped and storing the result, and adjusting the amount of air supplied to the fuel cell according to the failure determination result stored at the time of startup, It is not necessary to determine the failure at startup, and the startup time of the fuel cell system can be shortened. If the failure is not judged at the stop, the possibility that the purge valve is stuck As a matter of fact, it is necessary to increase the amount of air at startup. However, if failure diagnosis is performed at the time of stoppage, it is not necessary to increase the amount of air even when the purge valve is not fixed open. Noise can be reduced.

[0043] (Example 2)

FIG. 7 shows a part of the configuration of Example 2 of the fuel cell system according to the present invention, and shows an example in which three purge valves are provided in series with the hydrogen discharge path. In FIG. 7, in the hydrogen discharge passage 13, three purge valves, an upstream purge valve 16, a middle purge valve 20, and a downstream purge valve 17, are arranged in series. The pressure sensor 21 detects the pressure of the hydrogen discharge path sandwiched between the upstream purge valve 16 and the intermediate purge valve 20, and the pressure sensor detects the pressure of the hydrogen discharge path sandwiched between the intermediate purge valve 20 and the downstream purge valve 17. 15 is provided. Other configurations are the same as those of the first embodiment shown in FIG.

[0044] In the present embodiment, the failure test of the three purge valves is divided into two tests. In the first test, a failure test of the intermediate purge valve 20 and the downstream purge valve 17 is performed using the detection value of the pressure sensor 15 with the upstream purge valve 16 opened. This can be done by replacing the upstream purge valve 16 with the middle purge valve 20 in the tests of the upstream purge valve 16 and the downstream purge valve 17 in the failure test of the first embodiment.

In the second test, a failure test of the upstream purge valve 16 and the intermediate purge valve 20 is performed using the detection value of the pressure sensor 21 with the downstream purge valve 17 opened. This can be done by replacing the intermediate purge valve 20 with the downstream purge valve 17 and the pressure sensor 15 with the pressure sensor 21 in the tests of the upstream purge valve 16 and the downstream purge valve 17 in the failure test of the first embodiment.

As described above, in a configuration including three or more purge valves, a failure test is performed so that a failure test of two adjacent purge valves is performed in a state where the purge valves other than the adjacent purge valves to be tested are opened. When the test is divided, the divided failure tests can be performed in the same manner as in Example 1.

[0047] The entire contents of Japanese Patent Application No. 2004-320659 (filing date: November 4, 2004) are incorporated herein by reference.

[0048] The contents of the present invention have been described above according to the embodiments and examples. However, the present invention is not limited to these descriptions, and various modifications and improvements can be made. Work It is self-evident to the person.

Industrial applicability

According to the present invention, a plurality of purge valves and a pressure sensor for detecting the pressure in the space sandwiched between the purge valves are provided in the fuel discharge path for releasing a part of the gas in the fuel circulation path to the outside. The fuel gas is sealed in the space between the two purge valves, and the failure of the purge valve can be diagnosed by detecting the pressure change in the space with a pressure sensor. Since the space for sealing the fuel gas between the purge valves is not affected by the normal operation state of the fuel cell, the failure diagnosis of the purge valve can be performed in any operation state.

Claims

The scope of the claims

[1] A fuel cell that generates electricity using the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode;

A fuel circulation path for returning excess fuel gas discharged from the fuel as much as possible to the fuel electrode; a fuel discharge path for releasing a part of the gas in the fuel circulation path to the outside;

A plurality of purge valves arranged in series in the fuel discharge passage;

At least one pressure sensor for measuring a pressure in a space between the plurality of purge valves, and detecting a gas leak of at least one of the purge valve forces based on a temporal change in a pressure value detected by the pressure sensor. A failure detector for detecting a failure of the purge valve;

A fuel cell system comprising:

[2] The pressure of the fuel circulation path is adjusted to a pressure lower than the pressure at the time of detecting the failure when the failure detector detects the failure of the purge valve. The fuel cell system according to 1.

[3] A determination device for determining whether or not to stop the power generation of the fuel cell is provided,

When the determination device determines that it is possible to stop the power generation of the fuel cell, the power generation of the fuel cell is temporarily stopped, while when the determination device cancels the power generation stop of the fuel cell, 2. The fuel cell system according to claim 1, wherein power generation of the fuel cell is resumed.

[4] When the determination device determines that it is possible to stop the power generation of the fuel cell, the failure detector detects a failure before shifting to a state where the power generation of the fuel cell is temporarily stopped. The fuel cell system according to claim 3, wherein detection is performed.

[5] The fuel according to claim 4, wherein when the failure detector detects a gas leak with at least one purge valve force, the fuel cell is temporarily stopped from generating power. Battery system.

[6] The determination device includes a storage device that stores failure information of the purge valve, When the failure detector detects a gas leak with at least one purge valve force, the failure information is stored in the storage device, and then the determination device limits the determination of stoppage of power generation. The fuel cell system according to claim 4.

[7] When the failure detector detects gas leakage with at least one purge valve force, the fuel gas pressure value detected by the pressure sensor is stored in the storage device, and the pressure sensor is sandwiched between them. Of the two purge valves, the purge valve closer to the fuel circulation path is opened, and the time change in the detected value of the pressure sensor is monitored. 5. The fuel cell system according to claim 4, wherein it is determined whether or not it exists.

[8] When the failure detector detects gas leakage from the purge valve on the downstream side, the state of temporarily stopping the power generation of the fuel cell is canceled and the power generation of the fuel cell is restarted. 8. The fuel cell system according to claim 7, wherein

[9] When the failure detector determines that there is a gas leak from the purge valve on the upstream side, the state where the fuel cell power generation is temporarily stopped is released, and the exhaust gas concentration of the purge valve force is reduced. The fuel cell system according to claim 7, wherein a process for reducing is performed.

[10] When the fuel cell system is stopped, if the failure detector detects a failure of the purge valve, the air supply amount to the fuel cell is increased from the normal time at the next start of the fuel cell system. The fuel cell system according to claim 1.

[11] The failure test of two adjacent purge valves is performed in a state where three or more purge valves are provided and a purge valve other than the two adjacent purge valves to be tested is opened. The fuel cell system according to any one of claims 10 to 11.

[12] A fuel cell that generates electricity using the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode;

A plurality of purge valves arranged in series in the fuel discharge passage; At least one pressure sensor for measuring a pressure in a space between the plurality of purge valves, and detecting a gas leak of at least one of the purge valve forces based on a temporal change in a pressure value detected by the pressure sensor. Failure detection means for detecting a failure of the purge valve;

A fuel cell system comprising:

A fuel cell that generates electricity using the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode, and a fuel circulation that recirculates the excess fuel gas discharged as much as possible to the fuel electrode Providing a passage, a fuel discharge passage for releasing a part of the gas in the fuel circulation passage to the outside, and a plurality of purge valves arranged in series in the fuel discharge passage;

Measuring the pressure in the space between the plurality of purge valves;

Detecting a failure of the purge valve by detecting gas leakage from at least one of the purge valves based on a time change of the measured pressure value;

A failure diagnosis method for a fuel cell system, comprising: