JP6155795B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As a conventional fuel cell system, there is one in which an anode gas supply passage connecting a hydrogen tank and a fuel cell is provided with a shut-off valve and a pressure regulating valve in order from the upstream. In this conventional fuel cell system, after a stop request for the fuel cell system is issued, a valve closing command is issued to the shutoff valve and the fuel cell is continuously generated with a constant load, and when a predetermined time has elapsed from the valve closing command. On the basis of the pressure change amount ΔP upstream of the pressure regulating valve, the shut-off valve open adhesion diagnosis has been performed. Specifically, if the pressure change amount ΔP is equal to or greater than the reference pressure change amount, it is diagnosed that the shut-off valve is normally closed, and if it is less than the reference pressure change amount, the valve closing command is issued. It was diagnosed that the shut-off valve was in an open stuck state where it was not normally closed (see Patent Document 1).

JP 2005-123076 A

  When performing an open adhesion diagnosis of the shut-off valve by such a method, it is desirable to increase the reference pressure change amount in order to ensure the diagnosis accuracy.

  However, the above-described conventional fuel cell system uses a mechanical pressure reducing valve as a pressure regulating valve. Since the mechanical pressure reducing valve maintains the pressure on the secondary side (downstream side of the pressure regulating valve) at a constant pressure, if the anode gas in the fuel cell is consumed by continuing power generation in the fuel cell, the amount of consumption is reduced. The anode gas flows from the primary side (upstream side of the pressure regulating valve) to the secondary side. Therefore, if the shut-off valve is closed based on the valve closing command, the pressure upstream of the pressure regulating valve decreases in proportion to the consumption rate of the anode gas in the fuel cell.

  Here, the consumption rate of the anode gas in the fuel cell becomes faster as the load of the fuel cell becomes higher. However, after the fuel cell system is requested to stop, the electric parts that can consume the electric power generated by the fuel cell (that is, the electric parts that can be driven) are limited. Therefore, the load of the fuel cell cannot be a certain load.

  For this reason, when a mechanical pressure reducing valve is used as the pressure regulating valve, the pressure drop rate upstream of the pressure regulating valve cannot be increased to a certain level, and if the reference pressure change amount is increased to ensure diagnosis accuracy, There is a problem that the diagnosis time of the open fixation diagnosis becomes longer.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide a fuel cell system capable of shortening the diagnosis time of the open-fixation diagnosis of the shut-off valve.

According to an aspect of the present invention, a fuel supply passage connecting a fuel supply source and a fuel cell, a cutoff valve provided in the fuel supply passage, a fuel supply passage downstream of the cutoff valve, and supplied to the fuel cell There is provided a fuel cell system including a pressure regulating valve that adjusts the pressure of the fuel to be controlled, an upstream pressure detecting means that detects an upstream pressure of the pressure regulating valve, and a downstream pressure detecting means that detects a downstream pressure of the pressure regulating valve. Then, the fuel cell system includes a pressure regulating valve control means for controlling the opening degree of the pressure regulating valve according to the load of the fuel cell, and a cutoff so that the downstream pressure of the pressure regulating valve becomes a predetermined pressure corresponding to the load of the fuel cell A diagnostic means for issuing a valve closing command to the valve, consuming fuel by setting a load of the fuel cell to a predetermined load, and performing an open sticking diagnosis of the shut-off valve based on a change in upstream pressure after issuing the valve closing command; In the open sticking diagnosis , the shutoff valve is diagnosed so that the downstream pressure of the pressure regulating valve becomes higher than a predetermined pressure corresponding to the load of the fuel cell after issuing a valve closing command to the shutoff valve. And a pressure regulating valve control means for diagnosis for controlling the opening degree.

  According to this aspect, at the time of open adhesion diagnosis, the downstream pressure of the pressure regulating valve is set to be higher than the pressure set according to the load of the fuel cell at the normal time. Thereby, compared with the case where the downstream pressure of a pressure regulation valve is made into the pressure set according to the load of the fuel cell, the fall rate of the upstream pressure of a pressure regulation valve can be made quick. Therefore, the diagnosis time for the open sticking diagnosis of the shut-off valve can be shortened.

1 is a schematic view of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining control of the cutoff valve and anode pressure regulation valve by one Embodiment of this invention. It is a flowchart explaining the normal process of a cutoff valve and an anode pressure regulation valve. It is a table which calculates target control anode pressure tP2 based on the target generated electric power of a fuel cell stack. It is a flowchart explaining the open sticking diagnosis process of a shut-off valve. It is a time chart explaining operation | movement of the open adhesion diagnostic process by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In a fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), an anode gas containing hydrogen in the anode electrode (fuel gas), and a cathode gas containing oxygen in the cathode electrode (oxidant) Electricity is generated by supplying gas. The electrode reaction that proceeds in both the anode electrode and the cathode electrode is as follows.

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)

  The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

  When a fuel cell is used as a power source for automobiles, a large amount of electric power is required. Therefore, the fuel cell is used as a fuel cell stack in which several hundred fuel cells are stacked. Then, a fuel cell system that supplies anode gas and cathode gas to the fuel cell stack is configured, and electric power for driving the vehicle is taken out.

  FIG. 1 is a schematic diagram of a fuel cell system 100 according to an embodiment of the present invention.

  The fuel cell system 100 includes a fuel cell stack 1, a cathode gas supply / discharge device 2, an anode gas supply / discharge device 3, and a controller 4. Note that the cooling device for cooling the fuel cell stack 1 is not a main part of the present invention, and is not shown for easy understanding.

  The fuel cell stack 1 is formed by stacking several hundred fuel cells, and is supplied with anode gas and cathode gas to drive motors (not shown) and auxiliary equipment (batteries, various compressors, heaters, etc.) Electric power to be supplied to various electric parts necessary for driving the vehicle is generated.

  The cathode gas supply / discharge device 2 supplies the cathode gas to the fuel cell stack 1 and discharges the cathode off-gas discharged from the fuel cell stack 1 to the outside air. The cathode gas supply / discharge device 2 includes a cathode gas supply passage 21, a cathode gas discharge passage 22, a filter 23, a cathode compressor 24, an intercooler 25, and a water recovery device (hereinafter referred to as “WRD”). 26 and a cathode pressure regulating valve 27.

  The cathode gas supply passage 21 is a passage through which the cathode gas supplied to the fuel cell stack 1 flows. The cathode gas supply passage 21 has one end connected to the filter 23 and the other end connected to the cathode gas inlet hole of the fuel cell stack 1.

  The cathode gas discharge passage 22 is a passage through which the cathode off gas discharged from the fuel cell stack 1 flows. One end of the cathode gas discharge passage 22 is connected to the cathode gas outlet hole of the fuel cell stack 1, and the other end is an open end. The cathode off gas is a mixed gas of the cathode gas and water vapor generated by the electrode reaction.

  The filter 23 removes foreign matters in the cathode gas taken into the cathode gas supply passage 21.

  The cathode compressor 24 is provided in the cathode gas supply passage 21. The cathode compressor 24 takes air (outside air) as cathode gas through the filter 23 into the cathode gas supply passage 21 and supplies it to the fuel cell stack 1.

  The intercooler 25 is provided in the cathode gas supply passage 21 downstream of the cathode compressor 24. The intercooler 25 cools the cathode gas discharged from the cathode compressor 24.

  The WRD 26 is connected to each of the cathode gas supply passage 21 and the cathode gas discharge passage 22, collects moisture in the cathode off-gas flowing through the cathode gas discharge passage 22, and cathode that flows through the cathode gas supply passage 21 with the collected moisture. Humidify the gas.

  The cathode pressure regulating valve 27 is provided in the cathode gas discharge passage 22 downstream of the WRD 26. The opening of the cathode pressure regulating valve 27 is controlled to an arbitrary opening by the controller 4 to adjust the pressure of the cathode gas supplied to the fuel cell stack 1 to a desired pressure.

  The anode gas supply / discharge device 3 supplies anode gas to the fuel cell stack 1 and discharges anode off-gas discharged from the fuel cell stack 1 to the cathode gas discharge passage 22. The anode gas supply / discharge device 3 includes a high-pressure tank 31, an anode gas supply passage 32, a shutoff valve 33, an anode pressure regulating valve 34, an anode gas discharge passage 35, a purge valve 36, a diagnostic pressure sensor 37, A control pressure sensor 38.

  The high pressure tank 31 stores the anode gas supplied to the fuel cell stack 1 in a high pressure state.

  The anode gas supply passage 32 is a passage for supplying the anode gas discharged from the high-pressure tank 31 to the fuel cell stack 1. The anode gas supply passage 32 has one end connected to the high pressure tank 31 and the other end connected to the anode gas inlet hole of the fuel cell stack 1.

  The shut-off valve 33 is an electromagnetic valve that is controlled to be opened and closed by the controller 4 and is provided on the most upstream side of the anode gas supply passage 32. When the shutoff valve 33 is opened based on the valve opening command from the controller 4, supply of anode gas from the high pressure tank 31 to the fuel cell stack 1 is started. On the other hand, when the shutoff valve 33 is closed based on the valve closing command from the controller 4, the supply of the anode gas from the high pressure tank 31 to the fuel cell stack 1 is stopped.

  The anode pressure regulating valve 34 is provided in the anode gas supply passage 32 downstream of the shutoff valve 33. The anode pressure regulating valve 34 is an electromagnetic valve whose opening degree is controlled by the controller 4 to an arbitrary opening degree, and adjusts the pressure of the anode gas supplied to the fuel cell stack 1 to a desired pressure.

  The anode gas discharge passage 35 is a passage through which the anode off gas discharged from the fuel cell stack 1 flows. The anode gas discharge passage 35 has one end connected to the anode gas outlet hole of the fuel cell stack 1 and the other end connected to the cathode gas discharge passage 22. The anode off gas is a mixed gas of excess anode gas that has not been used in the electrode reaction and an inert gas such as nitrogen that has leaked from the cathode side.

  The anode off gas discharged to the cathode gas discharge passage 22 via the anode gas discharge passage 35 is mixed with the cathode off gas in the cathode gas discharge passage 22 and discharged to the outside of the fuel cell system 100. Since the anode off gas contains surplus anode gas (hydrogen) that has not been used for the electrode reaction, the anode off gas is mixed with the cathode off gas and discharged outside the fuel cell system 100, whereby hydrogen in the exhaust gas is discharged. The density is set to be equal to or lower than a predetermined density.

  The purge valve 36 is provided in the anode gas discharge passage 35. The purge valve 36 is controlled to be opened and closed by the controller 44 and controls the flow rate of the anode off gas discharged from the anode gas discharge passage 35 to the cathode gas discharge passage 22.

  The diagnostic pressure sensor 37 is a pressure used for diagnosing open adhesion of the shutoff valve 33, specifically, an anode gas pressure in the anode gas supply passage 32 between the shutoff valve 33 and the anode pressure regulating valve 34 (hereinafter referred to as “diagnostic anode”). It is called “pressure”.) P1 is detected.

  The control pressure sensor 38 is a pressure used for opening control of the anode pressure regulating valve 34, specifically, an anode gas pressure in the anode gas supply passage 32 downstream from the anode pressure regulating valve 34 (hereinafter “control anode pressure”). ) P2 is detected. In the present embodiment, this control anode pressure is used as the pressure of the anode gas flow path 11 inside the fuel cell stack 1.

  The controller 4 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  In addition to the diagnostic pressure sensor 37 and the control pressure sensor 38 described above, the controller 4 includes a current sensor 41 that detects the output current of the fuel cell stack 1 and a voltage sensor that detects the output voltage of the fuel cell stack 1. 42, an accelerator stroke sensor 43 for detecting the amount of depression of the accelerator pedal (hereinafter referred to as “accelerator operation amount”), a flow rate sensor 44 for detecting the flow rate of the cathode gas supplied to the fuel cell stack 1, and the fuel cell stack 1 Signals from various sensors such as a pressure sensor 45 that detects the pressure of the cathode gas are input.

  If there is no request to stop the fuel cell system 100, the controller 4 opens the shut-off valve 33, calculates the load of the fuel cell stack 1 based on the detection signals of these various sensors, the operating states of the auxiliary machines, etc. The opening degree of the anode pressure regulating valve 34 is controlled according to the load (normal processing) so that the anode pressure P2 becomes an appropriate pressure according to the load.

  On the other hand, when the controller 4 is requested to stop the fuel cell system 100, the controller 4 closes the shut-off valve 33 and performs normal processing in order to diagnose whether the shut-off valve 33 is normally closed. The opening degree of the anode pressure regulating valve 34 is controlled by a method different from that (open sticking diagnosis processing).

  Hereinafter, control of the shutoff valve 33 and the anode pressure regulating valve 34 according to this embodiment will be described.

  FIG. 2 is a flowchart for explaining the control of the shutoff valve 33 and the anode pressure regulating valve 34 according to this embodiment. The controller 4 repeatedly executes this routine at a predetermined calculation cycle.

  In step S <b> 1, the controller 4 determines whether or not there is a request to stop the fuel cell system 100. If there is no stop request for the fuel cell system 100, the controller 4 proceeds to the process of step S2, and if there is a stop request, the controller 4 proceeds to the process of step S3.

  In step S <b> 2, the controller 4 performs normal processing of the cutoff valve 33 and the anode pressure regulating valve 34. Details of the normal processing will be described later with reference to FIG.

  In step S <b> 3, the controller 4 performs an open sticking diagnosis process for the shutoff valve 33. Details of the open adhesion diagnosis process of the shutoff valve 33 will be described later with reference to FIG.

  FIG. 3 is a flowchart for explaining normal processing of the shutoff valve 33 and the anode pressure regulating valve 34.

  In step S <b> 21, the controller 4 issues a valve opening command to the cutoff valve 33 and opens the cutoff valve 33.

  In step S <b> 22, the controller 4 calculates the target generated power of the fuel cell stack 1 based on the load of the fuel cell stack 1. Specifically, the required power of the drive motor is calculated based on the accelerator operation amount, the power consumption of the auxiliary machinery is calculated according to the operating state of the auxiliary machinery, and the required power of the drive motor and the auxiliary machinery power are calculated. The total value with the power consumption is calculated as the target generated power of the fuel cell stack 1.

  In step S23, the controller 4 refers to the table of FIG. 4 and calculates the target control anode pressure tP2 based on the target generated power of the fuel cell stack 1. As shown in FIG. 4, the target control anode pressure tP2 increases as the target generated power of the fuel cell stack 1 increases.

  In step S24, the controller 4 feedback-controls the opening degree of the anode pressure regulating valve 34 so that the control anode pressure P2 becomes the target control anode pressure tP2.

  FIG. 5 is a flowchart for explaining the open sticking diagnosis process of the shut-off valve 33.

  In step S <b> 31, the controller 4 issues a valve closing command to the cutoff valve 33 to close the cutoff valve 33. However, since it is not known whether the shutoff valve 33 has been normally closed simply by issuing a valve closing command, it is diagnosed whether the shutoff valve 33 has been normally closed in the following steps.

  In step S32, the controller 4 continues the power generation of the fuel cell stack 1 with a predetermined load for a predetermined open adhesion diagnosis. Specifically, since the electric parts that can be driven after the stop request of the fuel cell system 100 are limited, only the auxiliary machines (for example, the cathode compressor) necessary for continuing the power generation in the fuel cell are set in an operating state. The power generation of the fuel cell stack 1 is continued using the power consumption of the auxiliary equipment as the target power generation at the time of open fixation diagnosis.

  In step S33, the controller 4 feedback-controls the opening degree of the anode pressure regulating valve 34 so that the control anode pressure P2 becomes the predetermined open adhesion diagnosis anode pressure Px.

  The anode pressure Px for open adhesion diagnosis is set in consideration of the pressure resistance of each component such as the anode gas supply passage 32 and the fuel cell stack 1 downstream from the anode pressure regulating valve 34. It is set to a value higher than the target control anode pressure tP2 obtained by referring to the table of FIG. In this embodiment, a value obtained by subtracting a predetermined margin from the maximum allowable withstand pressure Pmax determined from the specifications of the components downstream from the anode pressure regulating valve 34 is set as the anode pressure Px for open adhesion diagnosis.

  As described above, the open adhesion diagnosis anode pressure Px is set to a value higher than the target control anode pressure tP2 set when the fuel cell stack 1 is generated with a load for open adhesion diagnosis during normal processing. The Thereby, the diagnosis time Tdiag of the open fixation diagnosis can be shortened, and the reason will be described later with reference to FIG.

  In step S <b> 34, the controller 4 determines whether or not the pressure change amount ΔP of the diagnostic anode pressure P <b> 1 since the start of the open adhesion diagnosis process is equal to or greater than a predetermined reference pressure change amount Pb. If the pressure change amount ΔP of the diagnostic anode pressure P1 is greater than or equal to the reference pressure change amount Pb, the controller 4 proceeds to the process of step S35. On the other hand, if the pressure change amount ΔP of the diagnostic anode pressure P1 is less than the reference pressure change amount Pb, the process proceeds to step S37.

  In step S35, the controller 4 determines that the shutoff valve 33 is normally closed.

  In step S36, the controller 4 stops power generation in the fuel cell stack 1 and fully closes the anode pressure regulating valve 34.

  In step S37, the controller 4 determines whether or not the elapsed time T from the start of the open adhesion diagnostic process has exceeded a predetermined diagnostic time Tdiag. If the elapsed time T exceeds the diagnosis time Tdiag, the controller 4 proceeds to the process of step S38, and if not, the current process is terminated.

  In step S <b> 38, the controller 4 determines that the shutoff valve 33 is in an open fixing state where it is not normally closed.

  FIG. 6 is a time chart for explaining the operation of the open adhesion diagnosis processing according to the present embodiment. In order to facilitate understanding of the invention, the operation when the control anode pressure P2 is controlled to the target control anode pressure tP2 calculated according to the load at the time of the open fixation diagnosis is shown as a comparative example.

  When a stop request for the fuel cell system 100 is issued at time t1, a valve closing command is issued to the shutoff valve 33, and the shutoff valve 33 is closed.

  At this time, in the case of the present embodiment, the anode pressure regulating valve 34 is set so that the control anode pressure P2 becomes the open fixing diagnosis anode pressure Px higher than the target control anode pressure tP2 calculated according to the load. The opening is controlled.

  Therefore, if the shutoff valve 33 is normally closed, the diagnostic anode pressure P1 can be reduced more quickly than in the comparative example. As a result, in the comparative example, the time taken until time t3 until the pressure change amount ΔP of the diagnostic anode pressure P1 is equal to or larger than the reference pressure change amount Pb can be shortened to time t2 in the present embodiment. .

  Therefore, the diagnostic time Tdiag necessary for determining whether the shutoff valve 33 is in the open fixing state can be shortened compared to the comparative example.

  According to this embodiment described above, at the time of open adhesion diagnosis, the control anode pressure P2 is set when the fuel cell stack 1 is generated with a load for open adhesion diagnosis during normal processing. The opening degree of the anode pressure regulating valve 34 is controlled so that the anode pressure Px for open adhesion diagnosis is higher than the pressure tP2.

  As a result, the diagnostic anode pressure P1 upstream of the anode pressure regulating valve 34 can be quickly reduced, and the diagnostic time Tdiag of the open adhesion diagnosis can be shortened. In addition, since the diagnosis time Tdiag of the open adhesion diagnosis can be shortened, the reference pressure change amount Pb can also be increased, and the diagnosis accuracy of the open adhesion diagnosis can be improved.

  In addition, according to the present embodiment, the anode pressure Px for open adhesion diagnosis is set in consideration of the pressure resistance of each component downstream from the anode pressure regulating valve 34, so that the durability and reliability of each component are ensured. Can do.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in order to prevent freezing of residual water in the anode electrode while the fuel cell system 100 is stopped, after the open fixation diagnosis according to the present embodiment, the shutoff valve 33 and the anode pressure regulating valve 34 are opened again to supply high-pressure hydrogen to the anode electrode. The fuel cell system 100 may be completely stopped after the residual water is discharged to the outside of the fuel cell stack.

  By performing such residual water discharge control after the open adhesion diagnosis, the generated water generated by the power generation during the open adhesion diagnosis can be reliably discharged out of the fuel cell stack. Therefore, freezing of residual water in the anode electrode can be prevented while the fuel cell system 100 is stopped.

1 Fuel cell stack (fuel cell)
4 Controller (pressure regulating valve control means, diagnostic means, pressure regulating valve control means during diagnosis, residual water discharge means)
31 High-pressure tank (fuel supply source)
32 Anode gas supply passage (fuel supply passage)
33 Shutoff valve 34 Anode pressure regulating valve (pressure regulating valve)
37 Pressure sensor for diagnosis (upstream pressure detection means)
38 Pressure sensor for control (downstream pressure detection means)

Claims (3)

A fuel supply passage connecting the fuel supply source and the fuel cell;
A shutoff valve provided in the fuel supply passage;
A pressure regulating valve that is provided in the fuel supply passage downstream of the shutoff valve and adjusts the pressure of the fuel supplied to the fuel cell;
Upstream pressure detecting means for detecting the upstream pressure of the pressure regulating valve;
Downstream pressure detecting means for detecting the downstream pressure of the pressure regulating valve;
A fuel cell system comprising:
Pressure regulating valve control means for controlling the opening of the pressure regulating valve according to the load of the fuel cell, so that the downstream pressure of the pressure regulating valve becomes a predetermined pressure according to the load of the fuel cell;
A shut-off command is issued to the shut-off valve, the fuel cell load is set to a predetermined load, fuel is consumed, and the shut-off valve is stuck open based on a change in the upstream pressure after the shut-off command is issued. Diagnostic means for making a diagnosis;
At the time of open adhesion diagnosis for performing the open adhesion diagnosis of the shutoff valve, after issuing the valve closing command to the shutoff valve, the downstream pressure of the pressure regulating valve is made higher than a predetermined pressure corresponding to the load of the fuel cell. And a pressure regulating valve control means for diagnosis for controlling the opening of the pressure regulating valve,
A fuel cell system comprising: The diagnostic pressure control valve control means includes:
Increasing the opening of the pressure regulating valve until the downstream pressure of the pressure regulating valve rises to a pressure set in consideration of the pressure resistance of downstream components of the pressure regulating valve,
The fuel cell system according to claim 1. After there is a stop request said fuel cell system comprises a residual water discharging means for discharging the residual water in the fuel cell by opening the shut-off valve and the front Sulfur butterfly valve outside the fuel cell,
The diagnostic means includes
After the request to stop the fuel cell system, before carrying out the residual water discharge means, perform an open adhesion diagnosis of the shut-off valve,
The fuel cell system according to claim 1 or 2, wherein

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