JP2006302836A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which time required for restarting power generation can be shortened, in which noises and vibrations in idling stopping are suppressed, and in which a user's feeling of discomfort can be reduced. <P>SOLUTION: A controller 30 of the fuel cell system 1 maintains a voltage of the fuel cell 2 high in idling stopping by carrying out any one operation of raising an air pressure of a cathode 4 by reducing the opening of an air pressure regulator 22 immediately before idling stopping, of increasing an air pressure of the cathode 4 by increasing a rotation speed of a compressor 16, or of reducing a cathode hydrogen pressure by extracting an electric power from the fuel cell 2 by closing a hydrogen pressure regulating valve 7, or an operation of combining these. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system that performs idle stop at no load or low load.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for electric vehicles because of its low operating temperature and easy handling. That is, a fuel cell vehicle has a hydrogen storage device and a hydrogen generator mounted on the vehicle, and hydrogen supplied from the vehicle and oxygen-containing air are sent to the fuel cell to react with each other, and electric energy extracted from the fuel cell is used. It drives the motor connected to the drive wheels, and is the ultimate clean vehicle that only emits water.

  In such a fuel cell vehicle, an idle stop similar to that of the internal combustion engine vehicle can be considered. In the low load region or no load region where the power generation efficiency of the fuel cell is low, the power generation of the fuel cell is temporarily stopped and the required power is supplied from the secondary battery. Then, when the fuel cell has power generation capacity, charging the secondary battery improves the overall fuel efficiency.

As a conventional technique of idle stop in such a fuel cell vehicle, a technique described in Patent Document 1 is known. According to this technology, in order to quickly return from the idle stop state to the power generation state, during the idle stop, the compressor is intermittently driven to supply air to the cathode of the fuel cell, or from the hydrogen supply system. Hydrogen was supplied to the anode to maintain the remaining amount of oxygen and hydrogen in the fuel cell.
JP 2004-172028 A (page 8, FIG. 3)

  However, according to the above prior art, during the idle stop of the fuel cell, the compressor is temporarily driven to supply air or hydrogen, so that, for example, even when the driver releases the accelerator pedal or the brake is depressed. Regardless, there is a problem in that the sound and vibration are intermittently increased and the user feels uncomfortable.

  In order to solve the above problems, the present invention provides a fuel cell system that performs idle stop for stopping power generation of a fuel cell when a required output becomes a predetermined value or less. The gist is provided with a control means for performing an operation to increase the fuel cell voltage during idling stop at the time of transition.

Referring to FIG. 11, the relationship between the voltage value E of the fuel cell, each cell voltage value Vi (i = 1, 2, 3,..., N, n = number of cells) and the average value Vav of the cell voltages. Is
E = Σ (Vi) = n × Vav
It is. The solid line in FIG. 11 shows a state where the variation (dispersion) of the cell voltage is small, and the broken line shows a case where the variation of the cell voltage is large. For example, in a polymer electrolyte fuel cell, the average cell voltage value Vav increases as the cell voltage variation decreases. In a polymer electrolyte fuel cell, in order to increase the average cell voltage during idle stop in a cell voltage range (for example, 0.9 V or less) in which the electrode catalyst does not deteriorate, variation in cell voltage may be suppressed.

  According to the present invention, since the fuel cell voltage during idling stop is increased by operating the control means, the time required for restarting power generation is shortened, and the frequency of air supply during idling stop is reduced, and noise and vibration are reduced. This has the effect of suppressing the user's discomfort.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. In addition, although each Example described below is not specifically limited, it is an Example which applied this invention to the fuel cell vehicle.

  FIG. 1 is a schematic diagram showing the overall configuration of a first embodiment of a fuel cell system according to the present invention. The fuel cell system 1 includes, for example, a fuel cell 2 in which a solid polymer electrolyte is sandwiched between an anode 3 and a cathode 4, a hydrogen supply device 5 that supplies hydrogen to the anode 3 by a fuel reformer, a hydrogen storage device, and the like, Shut-off valve 6, hydrogen pressure regulating valve 7, hydrogen supply pipe 8, anode pressure sensor 9, hydrogen circulation passage 10, hydrogen circulation pump 11, purge valve 12, hydrogen discharge pipe 13, filter 14, air flow meter 15, air Compressor 16 to be compressed, cooler 17, humidifier 18 to humidify the air supplied to cathode 4 with moisture from exhaust from cathode 4, air supply pipe 19, cathode pressure sensor 20, air discharge pipe 21, air pressure adjustment valve 22 The DC / DC converter 23 that converts the output voltage of the fuel cell 2 into the voltage of the battery 24 is charged from the DC / DC converter 23. The battery 24 that discharges when the output of the fuel cell 2 is insufficient, the SOC detector 25 that detects the state of charge (SOC) of the battery 24, the DC / DC converter 23, and / or the inverter 26 that converts direct current from the battery 24 into alternating current , A vehicle drive motor 27 that is operated by an AC of the inverter 26, a voltage sensor 28 that detects the output voltage of the fuel cell 2, each cell voltage of the fuel cell 2, or a voltage of each cell group in which a predetermined number of cells are connected in series A cell voltage sensor 29 to be detected and a controller (ECU) 30 that also functions as a control means for controlling the entire fuel cell system 1 and increasing the fuel cell voltage during idling stop.

  Hydrogen supplied from the hydrogen supply device 5 is supplied to the anode 3 via the hydrogen pressure regulating valve 7. The pressure of hydrogen at the anode inlet of the fuel cell 2 is measured by an anode pressure sensor 9. The hydrogen pressure regulating valve 7 is controlled by the controller 30 so that the pressure measured by the anode pressure sensor 9 becomes a pressure corresponding to the required output of the fuel cell 2. Normally, the purge valve 12 is closed, and hydrogen discharged from the anode outlet of the fuel cell 2 is circulated to the inlet of the anode 3 by the hydrogen circulation pipe 10 and the hydrogen circulation pump 11.

  When water overflow occurs in the fuel cell 2, impurities accumulate in the hydrogen circulation path, or when the operating pressure of the fuel cell 2 is reduced, the purge valve 12 is opened and the hydrogen discharge pipe 13 is not shown. Discharge hydrogen to a hydrogen diluter.

  The air that becomes the oxidant gas removes dust and harmful chemical substances by the filter 14 and is compressed by the compressor 9. The air compressed by the compressor 9 is cooled by the cooler 17 and supplied to the humidifier 18. The humidifier 18 is, for example, a humidity exchanging device using a polymer hollow fiber membrane, and humidifies by supplying the water vapor contained in the exhaust of the cathode 4 to the air from the cooler 17. The humidified air is supplied to the cathode 4 through the air supply pipe 19. The air pressure at the inlet of the cathode 4 is measured by the cathode pressure sensor 20.

  The anode pressure sensor 9, the air flow sensor 15, the cathode pressure sensor 20, the voltage sensor 28, and the cell voltage sensor 29 are each connected to an input terminal of the controller 30, and input each detection signal to the controller 30.

  The hydrogen cutoff valve 6, the hydrogen pressure adjustment valve 7, the hydrogen circulation pump 11, the purge valve 12, the compressor 16, and the air pressure adjustment valve 22 are connected to the output terminals of the controller 30, respectively, and control signals output from the controller 30. Controlled by

  The controller 30 determines the operating state of the fuel cell 2 from the input signals of the sensors, and controls the entire fuel cell system 1. Further, the controller 30 controls the idle stop of the fuel cell 2 based on the required load for the fuel cell system 1 input from a vehicle travel control device (not shown).

  The controller 30 is not particularly limited. In the present embodiment, the controller 30 is composed of a CPU, a ROM that stores control parameters such as a control program and a control map in advance, a working RAM, and a microprocessor that includes an input / output interface. Has been.

  Further, the electric power extracted from the fuel cell 2 is controlled by the DC / DC converter 23. The DC / DC converter 23 is, for example, a step-up / step-down DC / DC converter capable of stepping up and stepping down an input voltage, charging the battery 24 with electric power generated by the fuel cell 2, and a vehicle driving motor via an inverter 26. 27 is supplied.

  FIG. 2 is a flowchart for explaining the idle stop control of the controller 30 in the first embodiment, and is executed at regular intervals. Embodiment 1 is an embodiment that realizes increasing the cathode oxygen partial pressure during idle stop by increasing the air pressure supplied to the cathode 4 immediately before the idle stop, and consequently increasing the fuel cell voltage during the idle stop. is there.

  In FIG. 2, first, in step (hereinafter, step is abbreviated as S) 10, it is determined whether or not the idle stop condition is satisfied. The idle stop condition determination in S10 may use the idle stop condition in the conventional fuel cell system. An example of the idle stop condition determination in this embodiment will be described later with reference to FIG. Next, at S20, the value of the idle stop condition flag is determined. If the idle stop condition flag = 1, the condition is established and the process proceeds to S21. If the idle stop condition flag = 0, the idle stop condition is not established and the process returns.

  In S21, the opening degree of the air pressure adjusting valve 22 is decreased to increase the cathode air pressure. At this time, the difference between the respective pressures detected by the cathode pressure sensor 20 and the anode pressure sensor 9 is equal to or lower than the withstand pressure between the anode and the cathode, or the difference between the cathode pressure and the cooling channel pressure in the fuel cell 2 (not shown) is the cathode / cooling channel. The air pressure adjusting valve 22 is controlled within a range that is equal to or lower than the inter-pressure resistance. Next, the process proceeds to S30 to execute idle stop. Details of S30 will be described later with reference to FIG.

  FIG. 3A is a flowchart for explaining an example of the idle stop condition determination subroutine. When the idle stop condition determination is started, first, the required output Prq [W] for the fuel cell system is detected or calculated in S11. In the case of a fuel cell vehicle, for example, the required output Prq is calculated from the vehicle speed and the accelerator pedal operation amount (required torque). Next, the SOC of the battery 24 is read from the SOC detector 25 in S12, and an output Pbt [W] that can be taken out from the battery 24 is calculated based on the SOC by referring to the control table in S13. The SOC detector 25 detects SOC [%] as the ratio of the charge amount to the maximum capacity of the battery 24, for example. The output Pbt that can be taken out from the battery 24 is limited by the characteristics of the battery to be used. For example, if the SOC exceeds 30 [%], the maximum takeable electric power is used. It is preferable to reduce it according to.

  Next, in S14, it is determined whether or not the required output Prq is less than a predetermined value P1. If the requested output is less than P1, it is determined in S15 whether the requested output Prq is less than the battery extractable output Pbt. If Prq is smaller than Pbt, the required output can be taken out from the battery 24 even if the fuel cell system 1 is idle stopped, so that the process proceeds to S16, the idle stop condition flag is set to “1”, and the process returns.

  If the determination in S14 or S15 is negative, the process proceeds to S17, the idle stop condition flag is reset to “0”, and the process returns.

  FIG. 3B is a flowchart for explaining an example of the idle stop execution subroutine. When the idle stop execution is started, first, the hydrogen pressure adjustment valve 7 is closed in S31 to stop the new hydrogen supply to the anode 3, and if the purge valve 12 is open, it is closed. In S32, the compressor 16 is stopped to stop supplying air to the cathode 4, and the air pressure adjusting valve 22 is closed. Next, the power extraction by the DC / DC converter 23 is stopped in S33, and the hydrogen circulation pump 11 is stopped in S34. Next, in S35, the cooling water pump and the radiator fan not shown in FIG. 1 are stopped.

  4A and 4B are diagrams for explaining the effect of the first embodiment. FIG. 4A shows the change over time in the fuel cell voltage, and FIG. 4B shows the change over time in the cathode air pressure. In both the diagrams (a) and (b), the conventional example is indicated by a solid line, and the present embodiment is indicated by a broken line. Time 101 is an idle stop start time, and time 102 is an idle stop end time. In the conventional example, the cathode air pressure before idling stop (before time 101) is 132, and the air pressure decreases as indicated by 114 during idling stop (from time 101 to time 102). In the present embodiment, as shown at 113, the cathode air pressure is increased from 132 immediately before idling stop (time 101), so the cathode air pressure during idling stop (time 101 to time 102) is the conventional example. A higher value than 114 can be maintained. Correspondingly, the fuel cell voltage shown in (a) can be maintained at a higher value in Example 111 than in Conventional Example 112.

  When the compressor is restarted at the idle stop end time 102, the air supply to the cathode is restarted, and the hydrogen supply to the anode is started, the fuel cell voltage example 111 is before the idle stop at time 103 (before time 101). The voltage 131 is recovered. At this time, hydrogen is supplied by adjusting the opening of the hydrogen pressure regulating valve 7, but since air is supplied by the work of the compressor 16, the speed of gas supply is higher for hydrogen. The air supply speed is dominant with respect to the rising speed of the fuel cell voltage. The voltage of the conventional example 112 recovers to 131 at time 104, which is later than the example.

  Next, a second embodiment of the fuel cell system according to the present invention will be described. The configuration of the second embodiment is the same as that of the first embodiment shown in FIG. In the second embodiment, the operation of increasing the flow rate of air supplied to the cathode immediately before the idle stop (time 101) suppresses the cell voltage variation during the idle stop (time 101 to time 102). It is an Example which raises the fuel cell voltage inside.

  FIG. 5 is a flowchart for explaining the idle stop control of the controller 30 in the second embodiment, and is executed at regular intervals. First, in S10, it is determined whether or not the idle stop condition is satisfied. An example of the idle stop condition determination in S10 is the same as that in the first embodiment of FIG. Next, in S20, the value of the idle stop condition flag is determined. If the idle stop condition flag = 1, the condition is established and the process proceeds to S41. If the idle stop condition flag = 0, the idle stop condition is not established and the process returns.

  In S41, the rotation speed of the compressor 16 is increased to increase the cathode air flow rate. At this time, the difference between the respective pressures detected by the cathode pressure sensor 20 and the anode pressure sensor 9 is equal to or lower than the withstand pressure between the anode and the cathode, or the difference between the cathode pressure and the cooling channel pressure in the fuel cell 2 (not shown) is the cathode / cooling channel. The air pressure adjusting valve 22 is controlled within a range that is equal to or lower than the inter-pressure resistance. Next, the process proceeds to S30, executes an idle stop, and returns.

  The details of the determination of the idle stop condition in S10 of FIG. 5 and the execution of the idle stop in S30 are the same as those in the first embodiment shown in FIGS. 3 (a) and 3 (b).

  FIGS. 6A and 6B are diagrams for explaining the effect of the second embodiment. FIG. 6A shows the change over time in the fuel cell voltage, and FIG. 6B shows the change over time in the cathode air flow rate. In both the diagrams (a) and (b), the conventional example is indicated by a solid line, and the present embodiment is indicated by a broken line. Time 101 is an idle stop start time, and time 102 is an idle stop end time. The cathode air flow rate 118 in the conventional example is 132 before the idle stop (before time 101), and the air flow rate decreases as shown by 118 during the idle stop (time 101 to time 102) due to the rotational moment and resistance of the compressor. To do. In this embodiment, immediately before the idling stop (time 101), the compressor rotation speed is increased and the cathode air flow rate 117 is increased from 132, so that the number of water droplets etc. hindering the air flow in the cell is reduced and the idling stop is performed. The variation in the cell voltage in the middle (from time 101 to time 102) is reduced. For this reason, as described in FIG. 11, the average cell voltage also rises from the conventional example. For this reason, the fuel cell voltage 115 during the idle stop (time 101 to time 102) of the embodiment is maintained at a value higher than the fuel cell voltage 116 of the conventional example.

  When the compressor driving is restarted at the idle stop end time 102, the air supply to the cathode is restarted and the hydrogen supply to the anode is started, the fuel cell voltage example 115 is the time 105 before the idle stop (before time 101). Although the voltage recovers to the voltage 131, the voltage of the conventional example 116 recovers to 131 at time 104, which is later than the example.

  Next, a third embodiment of the fuel cell system according to the present invention will be described. The configuration of the third embodiment is the same as that of the first embodiment shown in FIG. In Example 3, the amount of hydrogen leaking from the anode to the cathode during the idle stop is reduced by performing an operation for reducing the anode pressure immediately before the idle stop (time 101), and this leaked hydrogen is reduced to oxygen in the cathode air. This is an example in which the reduction of the cathode oxygen partial pressure due to the reaction is suppressed, and as a result, the fuel cell voltage during idle stop is increased.

  FIG. 7 is a flowchart for explaining the idle stop control of the controller 30 in the third embodiment, and is executed at regular time intervals. First, in S10, it is determined whether or not the idle stop condition is satisfied. An example of the idle stop condition determination in S10 is the same as that in the first embodiment of FIG. Next, in S20, the value of the idle stop condition flag is determined. If the idle stop condition flag = 1, the condition is established and the process proceeds to S51. If the idle stop condition flag = 0, the idle stop condition is not established and the process returns.

  In S51, the hydrogen pressure regulating valve 7 is closed and electric power is taken out from the fuel cell 2, thereby reducing the anode hydrogen pressure. At this time, the difference between the pressures detected by the cathode pressure sensor 20 and the anode pressure sensor 9 is equal to or less than the withstand pressure between the anode and the cathode, or the difference between the anode pressure and the cooling channel pressure in the fuel cell 2 (not shown) is the anode / cooling channel. The hydrogen pressure regulating valve 7 is controlled within a range that is equal to or lower than the inter-pressure resistance. Next, the process proceeds to S30, executes an idle stop, and returns.

  The details of the determination of the idle stop condition in S10 of FIG. 7 and the execution of the idle stop in S30 are the same as those in the first embodiment shown in FIGS. 3 (a) and 3 (b).

  FIGS. 8A and 8B are diagrams for explaining the effect of the third embodiment, where FIG. 8A shows the change over time in the fuel cell voltage, and FIG. 8B shows the change over time in the anode pressure. In both the diagrams (a) and (b), the conventional example is indicated by a solid line, and the present embodiment is indicated by a broken line. Time 101 is an idle stop start time, and time 102 is an idle stop end time. In the conventional example, the anode hydrogen pressure before idling stop is 132, and the hydrogen pressure decreases like 122 after idling stop. In this embodiment, the anode hydrogen pressure is reduced from 132 by closing the hydrogen pressure adjusting valve 7 and taking out electric power from the fuel cell 2 immediately before idling stop. Therefore, the anode hydrogen pressure after the idle stop is also lower in the example 121 than in the conventional example 122, and the leakage of hydrogen from the anode to the cathode after the idle stop is also reduced. As a result, the decrease in cathode oxygen partial pressure during idle stop is less in the embodiment than in the conventional example, and the decrease in the fuel cell voltage shown in FIG.

  When the driving of the compressor is resumed at the idle stop end time 102, the supply of air to the cathode is resumed and the supply of hydrogen to the anode is started, the fuel cell voltage 119 of the embodiment is restored to the voltage 131 before the idle stop at the time 106. However, the fuel cell voltage 120 of the conventional example recovers to 131 at time 104, which is later than the embodiment.

  Next, a fourth embodiment of the fuel cell system according to the present invention will be described. The configuration of the fourth embodiment is the same as the configuration of the first embodiment shown in FIG. Example 4 is an example in which Example 1 and Example 3 are combined. That is, in Example 4, by increasing the air pressure supplied to the cathode 4 immediately before the idle stop, the cathode oxygen partial pressure during the idle stop is increased, and as a result, the fuel cell voltage during the idle stop is increased. By reducing the anode pressure immediately before the idle stop, the amount of hydrogen leaking from the anode to the cathode during the idle stop is reduced, and the leaked hydrogen reacts with oxygen in the cathode air to reduce the cathode oxygen partial pressure. This is an embodiment that suppresses the lowering and, as a result, increases the fuel cell voltage during idling stop.

  FIG. 9 is a flowchart for explaining the idle stop control of the controller 30 in the fourth embodiment, and is executed at regular time intervals. First, in S10, it is determined whether or not the idle stop condition is satisfied. An example of the idle stop condition determination in S10 is the same as that in the first embodiment of FIG. Next, in S20, the value of the idle stop condition flag is determined. If the idle stop condition flag = 1, the condition is established and the process proceeds to S61. If the idle stop condition flag = 0, the idle stop condition is not established and the process returns.

  In S61, the hydrogen pressure regulating valve 7 is closed and electric power is taken out from the fuel cell 2, thereby reducing the anode hydrogen pressure. In S61, the opening of the air pressure adjustment valve 22 is decreased to increase the cathode air pressure. At this time, the difference between the pressures detected by the cathode pressure sensor 20 and the anode pressure sensor 9 is equal to or less than the withstand pressure between the anode and the cathode, or the difference between the anode pressure or the cathode pressure and the cooling channel pressure in the fuel cell 2 (not shown) is a gas. The hydrogen pressure regulating valve 7 and the air pressure regulating valve 22 are controlled within a range that is equal to or lower than the pressure resistance between the flow path and the cooling water path. Next, the process proceeds to S30, executes an idle stop, and returns.

  The details of the determination of the idle stop condition in S10 of FIG. 9 and the execution of the idle stop in S30 are the same as those in the first embodiment shown in FIGS. 3 (a) and 3 (b).

  FIG. 10 is a graph for explaining the effect of Example 4, wherein (a) shows the fuel cell voltage, (b) shows the cathode air pressure, and (c) shows the changes over time in the anode hydrogen pressure. In any of the drawings (a) to (c), the conventional example is indicated by a solid line, and the present embodiment is indicated by a broken line. Time 101 is an idle stop start time, and time 102 is an idle stop end time. In the conventional example, the anode hydrogen pressure and the cathode air pressure before idling stop are 132, and the air and hydrogen pressures are reduced like 126 and 128 after idling stop.

  As shown in FIG. 10B, the cathode air pressure 125 in this embodiment is increased from 132 just before the idling stop, so that the cathode air pressure after the idling stop is higher than that in the conventional example 126. can do.

  In this embodiment, the anode hydrogen pressure is reduced from 132 by closing the hydrogen pressure adjusting valve 7 and taking out electric power from the fuel cell 2 immediately before the idling stop. For this reason, the anode hydrogen pressure after the idle stop is also lower in the embodiment 127 than the conventional example 128, and the leakage of hydrogen from the anode to the cathode after the idle stop is also reduced. As a result, the decrease in the cathode oxygen partial pressure during the idling stop is less in the embodiment than in the conventional example, and the decrease in the fuel cell voltage shown in FIG.

  When the compressor is restarted at the idle stop end time 102, the air supply to the cathode is restarted, and the hydrogen supply to the anode is started, the fuel cell voltage 123 of the embodiment recovers to the voltage 131 before the idle stop at the time 107. However, the fuel cell voltage 124 of the conventional example recovers to 131 at time 104, which is later than the embodiment.

  In the fourth embodiment, the first embodiment and the third embodiment are combined. However, the present invention is not limited to this, and any combination of the first to third embodiments can be realized.

1 is a system configuration diagram illustrating an embodiment of a fuel cell system according to the present invention. 3 is a flowchart illustrating idle stop control according to the first embodiment. It is a flowchart explaining the determination process of (a) idle stop conditions, and the execution process of (b) idle stop, respectively. It is a figure explaining time passage of (a) fuel cell voltage and (b) air pressure. 6 is a flowchart illustrating idle stop control according to the second embodiment. It is a figure explaining time passage of (a) fuel cell voltage and (b) air flow rate. 10 is a flowchart illustrating idle stop control according to a third embodiment. It is a figure explaining the time passage of (a) fuel cell voltage and (b) hydrogen pressure. 10 is a flowchart illustrating idle stop control according to a fourth embodiment. It is a figure explaining time passage of (a) fuel cell voltage, (b) air pressure, and (c) hydrogen pressure. It is a figure explaining the correspondence of cell voltage distribution and average cell voltage.

Explanation of symbols

1: Fuel cell system 2: Fuel cell 3: Anode 4: Cathode 5: Hydrogen supply device 7: Hydrogen pressure adjustment valve 8: Hydrogen supply pipe 9: Anode pressure sensor 10: Hydrogen circulation pipe 11: Hydrogen circulation pump 12: Purge valve 13: Hydrogen discharge pipe 14: Filter 15: Air flow sensor 16: Compressor 17: Cooler 18: Humidifier 19: Air supply pipe 20: Cathode pressure sensor 21: Air discharge pipe 22: Air pressure adjustment valve 23: DC / DC Converter 24: Battery 25: SOC detector 26: Inverter 27: Vehicle drive motor 28: Voltage sensor 29: Cell voltage sensor 30: Controller

Claims (10)

In the fuel cell system that performs idle stop to stop the power generation of the fuel cell when the required output becomes a predetermined value or less,
A fuel cell system comprising control means for performing an operation of increasing a fuel cell voltage during idle stop when the fuel cell shifts from a power generation state to an idle stop state.   The operation for increasing the fuel cell voltage during idle stop by the control means is an operation for suppressing variation in cell voltage while suppressing each cell voltage during idle stop to a predetermined voltage or less. The fuel cell system described.   The fuel cell system according to claim 2, wherein the control means performs an operation of increasing a cathode oxygen partial pressure during idle stop.   4. The fuel cell system according to claim 3, wherein the control means increases the cathode oxygen partial pressure during the idle stop by increasing the air pressure supplied to the cathode immediately before the idle stop.   The fuel cell system according to claim 4, wherein the air pressure is increased to a predetermined pressure less than a withstand pressure between the anode and the cathode.   The fuel cell system according to claim 4, wherein the air pressure is increased to a predetermined pressure less than a withstand pressure between the cathode and the cooling water channel.   The fuel cell system according to claim 2, wherein the control means performs an operation of increasing a flow rate of air supplied to the cathode immediately before idling stop.   2. The fuel cell system according to claim 1, wherein the control unit performs an operation of delaying a decrease in the fuel cell voltage during idle stop. 3.   9. The fuel cell system according to claim 8, wherein the control means lowers the anode pressure immediately before idling stop to reduce hydrogen cross leak from the anode to the cathode during idling stop.   10. The fuel cell system according to claim 9, wherein the decrease in the anode pressure is performed within a range that does not exceed a breakdown voltage between the anode and the cathode and / or a breakdown voltage between the cathode and the cooling water channel.

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