JP2018060688A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of more reliably removing impurity adhered to an electrode of a fuel cell.SOLUTION: A fuel cell system comprises: a fuel cell 10, provided with a cathode and an anode, which supplies power to a secondary battery 102; a blower 20; a fuel gas tank 30; a first inlet-side valve 51; a second inlet-side valve 52; a first outlet-side valve 61; a second outlet-side valve 62; and an ECU 100. The ECU 100 carries out charge control, discharge control, and purge control one or more times. In the charge control, the ECU 100 opens the first inlet-side valve 51, the second inlet-side valve 52, the first outlet-side valve 61, and the second outlet-side valve 62 so as to electrically connect the fuel cell 10 to the secondary battery 102. In the discharge control, the ECU 100 closes the first inlet-side valve 51, the second inlet-side valve 52, the first outlet-side valve 61, and the second outlet-side valve 62 so as to electrically cut off the fuel cell 10 from the secondary battery 102. In the purge control, the ECU 100 opens the first inlet-side valve 51, the second inlet-side valve 52, the first outlet-side valve 61, and the second outlet-side valve 62.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  A fuel cell of a fuel cell system is configured by forming a joined body in which a solid polymer electrolyte membrane is sandwiched between an anode and a cathode, and stacking a plurality of cells formed by sandwiching the outside of the joined body with a pair of separators. Some of them have a stack. Then, the fuel cell is caused to generate power by supplying hydrogen as a fuel gas to the anode and air as an oxidizing gas to the cathode.

  In a fuel cell, since air is taken in from the outside, impurities such as sulfur compounds in the air may enter the fuel cell. Moreover, there is a possibility that impurities are generated with the deterioration of the anode and the cathode. Such impurities cause corrosion of the anode and cathode electrodes and separators.

  For such a problem, the amount of water discharged from the electrode of the fuel cell is increased by means such as increasing the secondary battery of the fuel cell, lowering the temperature of the fuel cell, or humidifying the oxidizing gas, A fuel cell system that prevents deterioration of the electrode catalyst by removing impurities with water has been proposed (see, for example, Patent Document 1).

  However, in the fuel cell system according to Patent Document 1, when water remains in the fuel cell, only water is evaporated and discharged to the outside of the fuel cell, and impurities dissolved in the water adhere to the electrode catalyst. .

JP 2008-77911 A

  The present invention has been made in view of such circumstances, and an object thereof is to provide a fuel cell system that can more reliably remove impurities adhering to the electrode of the fuel cell.

  A first aspect of the present invention that solves the above problems includes a fuel cell that includes a cathode and an anode, supplies power to a secondary battery, oxidizing gas supply means that supplies an oxidizing gas to the cathode, and fuel to the anode. A fuel gas supply means for supplying gas, a pipe connecting the oxidizing gas supply means and the inlet of the cathode, and a pipe connecting the fuel gas supply means and the inlet of the anode, respectively. A first outlet side valve and a second outlet provided in each of an inlet side valve and a second inlet side valve, a pipe connecting the cathode outlet and the outside, and a pipe connecting the anode outlet and the outside A side valve, and a control means for controlling opening and closing of the first inlet side valve, the second inlet side valve, the first outlet side valve and the second outlet side valve, the control means comprising the fuel cell Stop command to When the activation command is issued, the first inlet side valve, the second inlet side valve, the first outlet side valve, and the second outlet side valve are opened, and the fuel cell is electrically connected to the secondary battery. Charging control to be connected to the fuel cell, and closing the first inlet side valve, the second inlet side valve, the first outlet side valve and the second outlet side valve, and electrically connecting the fuel cell from the secondary battery The discharge control for cutting and the purge control for opening the first inlet side valve, the second inlet side valve, the first outlet side valve, and the second outlet side valve are executed at least once. In the fuel cell system.

  In the first aspect, the charge control is executed to cause the oxidizing gas and the fuel gas to undergo an electrochemical reaction, thereby increasing the amount of water in the fuel cell. And by performing discharge control, a cell voltage is reduced, the impurities adhering to an electrode or a separator are reduced and removed, and it dissolves in water. Thereafter, by performing purge control, water in which impurities are dissolved can be discharged to the outside of the fuel cell. Thus, impurities adhering to the electrode and separator of the fuel cell can be dissolved in water and removed more reliably to the outside. Thereby, it can suppress that the electrode and separator of a fuel cell corrode, and can recover electric power generation performance.

  According to a second aspect of the present invention, in the fuel cell system according to the first aspect, the control means executes the charge control, the discharge control, and the purge control a plurality of times. In the system.

  In the second aspect, the fuel cell impurities can be more reliably removed.

  According to a third aspect of the present invention, in the fuel cell system according to the first or second aspect, the control means includes the cell voltage of the fuel cell when the charge control is being executed, and the previous time. A fuel characterized in that execution of the charge control, the discharge control, and the purge control is stopped on condition that a difference from a cell voltage of the fuel cell when the charge control is executed is equal to or less than a predetermined threshold value. In the battery system.

  In the third aspect, impurities generated in the fuel cell can be more reliably removed.

  According to a fourth aspect of the present invention, in the fuel cell system according to any one of the first to third aspects, in the purge control, the first inlet side valve and the second inlet side valve are opened. In the fuel cell system, the first outlet side valve and the second outlet side valve are opened.

  In the fourth aspect, water in which impurities are dissolved can be more reliably discharged from the fuel cell to the outside by the oxidizing gas and the fuel gas energized using the negative pressure.

  According to a fifth aspect of the present invention, there is provided the fuel cell system according to any one of the first to fourth aspects, further comprising humidifying means for humidifying the fuel gas.

  In the fifth aspect, the fuel gas is humidified to become a fuel gas containing a large amount of moisture. Thereby, the amount of water generated when performing charge control and discharge control in the fuel cell can be increased. Since the amount of water generated in the fuel cell is increased in this way, more impurities can be dissolved in water and removed from the fuel cell.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can remove the impurity adhering to the electrode of a fuel cell more reliably is provided.

1 is a schematic diagram of a fuel cell system according to Embodiment 1. FIG. It is the schematic which shows a fuel cell system when performing discharge control. It is the schematic which shows a fuel cell system when performing purge control. 6 is a graph showing the cell voltage of the fuel cell and the amount of water generated in the fuel cell when charge control, discharge control, and purge control are executed. It is a flowchart which shows the operation | movement at the time of a stop of a fuel cell system. It is a flowchart which shows the operation | movement of the removal process of the impurity of a fuel cell system. 4 is a schematic diagram of a fuel cell system according to Embodiment 2. FIG.

  Hereinafter, modes for carrying out the present invention will be described. In addition, description of embodiment is an illustration and this invention is not limited to the following description.

<Embodiment 1>
FIG. 1 is a schematic diagram showing the configuration of the fuel cell system according to the present embodiment. The fuel cell system 1 of this embodiment is mounted on an electric vehicle (not shown), and outputs electric power mainly used as a driving force of the electric vehicle in response to a driver's request.

  The fuel cell system 1 includes a fuel cell 10 (abbreviated as FC in the figure), a blower 20, a fuel gas tank 30, a first inlet side valve 51, a second inlet side valve 52, and a first outlet side. The valve 61, the 2nd exit side valve 62, and ECU100 which is an example of a control means are provided. Furthermore, the fuel cell system 1 of this embodiment includes a drive motor 101, a secondary battery 102, and a discharge device 103.

  The fuel cell 10 is a polymer electrolyte fuel cell that is supplied with hydrogen as a fuel gas and air as an oxidizing gas, and generates power by an electrochemical reaction between oxygen and hydrogen. Although the specific configuration of the fuel cell 10 is not particularly limited, the fuel cell 10 has a stack structure in which a plurality of cells (not shown) are stacked. Each cell includes a membrane electrode assembly in which an anode and a cathode are arranged on both surfaces of a solid polymer electrolyte membrane, and a gas diffusion layer provided outside the membrane electrode assembly. Moreover, the anode and cathode of each cell contain platinum as a catalyst.

  The cathode separator is provided with a flow path for supplying an oxidizing gas to the cathode. An oxidizing gas pipe 21 is connected to the inlet of the flow path of the cathode side separator, and a first exhaust pipe 80 is connected to the outlet of the flow path. The oxidant gas pipe 21 is an example of a pipe that connects the oxidant gas supply means described in the claims to the inlet of the cathode. The 1st exhaust pipe 80 is an example of piping which connects the exit and the exterior of the cathode which are described in a claim.

  The anode-side separator is provided with a flow path for supplying fuel gas to the anode. A fuel gas pipe 31 is connected to the inlet of the flow path of the anode-side separator, and a second exhaust pipe 90 is connected to the outlet of the flow path. The fuel gas pipe 31 is an example of a pipe connecting the fuel gas supply means described in the claims and the inlet of the anode. The 2nd exhaust pipe 90 is an example of piping which connects the exit of the anode described in a claim, and the exterior.

  A plurality of such cells are stacked via a separator to form a fuel cell 10 having a stack structure. Although not particularly illustrated, one oxidizing gas pipe 21 branches into a plurality according to the number of cells, and the oxidizing gas is supplied to the separator of each cell. The same applies to the fuel gas pipe 31. One first exhaust pipe 80 branches into a plurality according to the number of cells, and guides exhaust gas and water discharged from the separator of each cell to the first reservoir 41. Similarly, with respect to the second exhaust pipe 90, the exhaust gas and water discharged from the separator of each cell are guided to the second reservoir 42.

  The blower 20 is an example of an oxidizing gas supply unit, and is an apparatus that supplies compressed air by taking outside air as an oxidizing gas to the cathode of the fuel cell 10. A first inlet side valve 51 is provided in the oxidizing gas pipe 21 that connects the blower 20 and the cathode.

  The first inlet side valve 51 is normally in a closed state and opens when air having a predetermined pressure is supplied from the blower 20 to the oxidizing gas pipe 21. With such a configuration, the oxidizing gas is supplied from the blower 20 to the cathode of the fuel cell 10 at a constant pressure. The first inlet side valve 51 can be controlled to open and close by the ECU 100.

  The fuel gas tank 30 is an example of a fuel gas supply unit, and is a device that supplies hydrogen stored at high pressure as fuel gas to the anode of the fuel cell 10. The fuel gas pipe 31 connecting the fuel gas tank 30 and the anode is provided with a second inlet side valve 52.

  The second inlet side valve 52 is a valve for reducing the hydrogen stored in the fuel gas tank 30 at a high pressure to a predetermined pressure to obtain a constant pressure. With such a configuration, the fuel gas is supplied from the fuel gas tank 30 to the anode of the fuel cell 10 at a constant pressure. Of course, it is also possible to stop the supply of hydrogen by closing the fuel gas pipe 31. The second inlet side valve 52 can be controlled to open and close by the ECU 100.

  A first outlet side valve 61 is provided in the first exhaust pipe 80. The first outlet side valve 61 can be controlled to open and close by the ECU 100. A first circulation pipe 81 branched from the first exhaust pipe 80 is connected to a part on the upstream side of the blower 20. Further, the first exhaust pipe 80 is provided with a first reservoir 41 on the downstream side (the side opposite to the fuel cell 10) from the first outlet side valve 61.

  The first storage unit 41 is a container that stores moisture in the exhaust gas discharged from the cathode of the fuel cell 10. The cathode of the fuel cell 10 is connected to the outside via the first exhaust pipe 80. That the cathode is connected to the outside means that exhaust gas and water discharged from the cathode can be discharged to the outside. As in the present embodiment, the water discharged from the cathode may be stored once in the first storage portion 41 and discharged from the first storage portion 41 to the outside.

  Exhaust gas and water discharged from the cathode of the fuel cell 10 are gas-liquid separated by a gas-liquid separator (not shown), moisture in the exhaust gas is stored in the first storage unit 41 as water, and the exhaust gas is the first circulation pipe 81. To the upstream side of the blower 20.

  A second outlet side valve 62 is provided in the second exhaust pipe 90. The second outlet side valve 62 can be opened and closed by the ECU 100. A second circulation pipe 91 branched from the second exhaust pipe 90 is connected to a part of the downstream side of the fuel gas tank 30. Furthermore, the second exhaust pipe 90 is provided with a second reservoir 42 on the downstream side (opposite to the fuel cell 10) of the second outlet side valve 62.

  The second reservoir 42 is a container that stores moisture in the exhaust gas discharged from the anode of the fuel cell 10. The anode of the fuel cell 10 is connected to the outside through the second exhaust pipe 90. The fact that the anode is connected to the outside means that exhaust gas and water discharged from the anode can be discharged to the outside. As in the present embodiment, the configuration may be such that the water discharged from the anode is once stored in the second storage part 42 and discharged from the second storage part 42 to the outside.

  The exhaust gas and water discharged from the anode of the fuel cell 10 are gas-liquid separated by a gas-liquid separator (not shown), the water in the exhaust gas is stored in the second storage unit 42 as water, and the exhaust gas (unburned hydrogen) is The pressure is boosted by the circulation pump 95 to the downstream side of the fuel gas tank 30 via the second circulation pipe 91.

  The drive motor 101 generates a positive drive force (torque) for driving drive wheels (not shown) of the electric vehicle by the electric power from the fuel cell 10 and the secondary battery 102. Further, the drive motor 101 operates as a generator during deceleration or the like, and generates a negative regenerative force (torque). The drive motor 101 is connected to the fuel cell 10 and the secondary battery 102 via an inverter (not shown). The inverter converts DC power generated by the fuel cell 10 or DC power charged in the secondary battery 102 into AC power and supplies the AC power to the drive motor 101. Further, the regenerative power generated by the drive motor 101 is converted into DC power by an inverter and charged in the secondary battery 102.

  The secondary battery 102 is, for example, a lithium ion battery, and charges the electric power generated by the fuel cell 10 or the regenerative electric power generated by the drive motor 101. The electric power charged by the secondary battery 102 is mainly used for driving the drive motor 101. The secondary battery 102 is electrically connected to the fuel cell 10 or disconnected from the fuel cell 10 by the ECU 100.

  The discharge device 103 is a device that discharges the electric power generated by the fuel cell 10, and is, for example, a discharge resistor that is electrically connected to an anode and a cathode. The discharge device 103 is electrically connected to the fuel cell 10 or disconnected from the fuel cell 10 by the ECU 100.

  ECU100 is comprised by the microcomputer provided with a central processing unit and a main memory. The ECU 100 controls opening / closing of the first inlet side valve 51 and the second inlet side valve 52 based on detection signals read from various sensors, output requests, and programs on the main storage device, and is supplied from the blower 20. The power generation by the fuel cell 10 is controlled by adjusting the flow rate of air.

  The control when the fuel cell 10 is normally operated will be described. The fuel cell system 1 of FIG. 1 represents a state during normal operation, and the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve, which are represented in white, are shown in white. 62 shows an open state. In the subsequent drawings, when these valves are expressed in white, they are in an open state, and when they are expressed in black, they are in a closed state.

  During normal operation, the ECU 100 supplies fuel gas and oxidizing gas to the fuel cell 10 and performs control to connect the fuel cell 10 to the drive motor 101 and the secondary battery 102. Specifically, the ECU 100 causes the secondary battery 102 to supply power to the drive motor 101 in accordance with the amount of accelerator depression, and drives the drive motor 101.

  In response to the output request, the ECU 100 opens the first inlet side valve 51 and the second inlet side valve 52 and controls the flow rate of air supplied from the blower 20 when the power of the secondary battery 102 is insufficient. Thus, the fuel cell 10 is brought into an operating state to generate power. Further, the first outlet side valve 61 and the second outlet side valve 62 are also opened, and the exhaust gas and water from the fuel cell 10 are circulated or discharged to the first reservoir 41 and the second reservoir 42.

  Then, the ECU 100 causes the drive motor 101 to supply the power generated by the fuel cell 10. When the ECU 100 detects that the SOC of the secondary battery 102 is equal to or less than a predetermined value, the power generated by the fuel cell 10 is supplied to the secondary battery 102.

  Further, the ECU 100 executes a series of controls including charge control, discharge control, and purge control one or more times when a stop command or start command for the fuel cell 10 is given. Hereinafter, this series of control is referred to as removal processing. An example of the stop command for the fuel cell 10 is that an ignition switch of an electric vehicle is turned off. Moreover, as a starting command of the fuel cell 10, for example, an ignition switch of an electric vehicle is turned on.

  In the charge control, the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve 62 are opened, and the fuel cell 10 is electrically connected to the secondary battery 102. It is. The ECU 100 performs control to open the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve 62 as shown in FIG. The difference from the normal operation is that the power generated by the fuel cell 10 is not supplied to the drive motor 101 but supplied to the secondary battery 102 for charging.

  During normal operation, since the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61 and the second outlet side valve 62 are opened, the ignition switch is turned off. In some cases, the control of supplying the power of the fuel cell 10 only to the secondary battery 102 is practically performed.

  When the fuel cell 10 is stopped, the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve 62 are closed. Therefore, when the ignition switch is turned on, these valves are opened, and control is performed so that the power of the fuel cell 10 is supplied only to the secondary battery 102.

FIG. 2 is a schematic diagram showing the fuel cell system when the discharge control is executed.
In the discharge control, the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61 and the second outlet side valve 62 are closed, and the fuel cell 10 is driven by the drive motor 101, the secondary battery 102, and the discharge device. This is a control for electrically disconnecting from 103.

  The flow path from the first inlet side valve 51 to the cathode of the fuel cell 10 and from the cathode to the first outlet side valve 61 is a closed space (hereinafter referred to as a cathode side closed space). The cathode-side closed space becomes a sealed space that is blocked from the outside, and the oxidizing gas remains after the valves are closed.

  Similarly, the flow path from the second inlet side valve 52 to the anode of the fuel cell 10 and from the anode to the second outlet side valve 62 is a closed space (hereinafter referred to as an anode side closed space). This anode side closed space becomes a sealed space blocked from the outside, and the fuel gas remains after these valves are closed.

  Although the fuel cell 10 is not electrically connected to the secondary battery 102, the oxidizing gas and the fuel gas remaining in the cathode side closed space and the anode side closed space undergo an electrochemical reaction. For this reason, the oxidizing gas and the fuel gas gradually decrease, and the cell voltage also decreases accordingly.

  When such discharge control is performed, the cathode side closed space and the anode side closed space have negative pressure because the oxidizing gas and the fuel gas are reduced. Furthermore, since the temperature in the closed space is lowered, the water vapor existing in the closed space is condensed into water. Since this condensed water fills the flow paths and electrodes provided in the separator of the cell, impurities adhering to those flow paths and electrodes are dissolved in the condensed water.

FIG. 3 is a schematic diagram showing the fuel cell system when the purge control is executed.
The purge control is control for opening the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve 62. The fuel cell 10 is electrically disconnected from the secondary battery 102 by the discharge control, but the valve is opened as it is.

  Specifically, as shown in FIG. 3A, the ECU 100 first opens the first inlet side valve 51 and the second inlet side valve 52. Since the cathode side closed space and the anode side closed space have negative pressure, the air from the blower 20 and the fuel gas from the fuel gas tank 30 that have been operated in advance flow into the cathode and the anode.

  Next, as shown in FIG. 3 (b), the ECU 100 opens the first outlet side valve 61 and the second outlet side valve 62. Thus, in FIG. 3A, the oxidizing gas and the fuel gas that are energized by the negative pressure and flow into the cathode and the anode easily flow out to the first outlet side valve 61 and the second outlet side valve 62 by that momentum. It has become. For this reason, the force which pushes out the condensed water which these oxidizing gas and fuel gas in a cathode and an anode becomes strong, and condensed water is discharged | emitted from a cathode and an anode, and is guide | induced to the 1st storage part 41 and the 2nd storage part 42 side. .

  According to such purge control, the condensed water accumulated in the cathode and the anode can be discharged to the outside by the oxidizing gas and the fuel gas energized using the negative pressure. As described above, since the impurities in the fuel cell 10 are dissolved in the condensed water, the impurities attached to the flow paths and electrodes of the fuel cell 10 can be discharged to the outside of the fuel cell 10.

  The time from opening the first inlet side valve 51 and the second inlet side valve 52 to opening the first outlet side valve 61 and the second outlet side valve 62 is the same as that of the first inlet side valve 51 and the second outlet valve 52. The time required for the oxidizing gas and fuel gas flowing into the two inlet side valve 52 to reach the first outlet side valve 61 and the second outlet side valve 62 is preferably set. Such a time can be determined based on the flow rates of the oxidizing gas and the fuel gas, the shape and length of the flow path provided in the fuel cell 10, and the like.

  Next, when performing the charge control, the first inlet side valve 51, the second inlet side valve 52, the first outlet side valve 61, and the second outlet side valve 62 are opened in the purge control. May be controlled to electrically connect the fuel cell 10 to the secondary battery 102.

  The ECU 100 executes a series of controls including the above-described charging control, discharging control, and purge control one or more times.

  FIG. 4 is a graph showing the cell voltage of the fuel cell and the amount of water generated in the fuel cell when charge control, discharge control, and purge control are executed. The horizontal axis represents time, and the vertical axis represents the cell voltage of the fuel cell 10 and the amount of water generated in the fuel cell 10, respectively.

  As shown in the figure, it is assumed that the ignition switch is turned off at time A before the first charge control (indicated as charge in the figure). While the charge control is being performed, the amount of water is increasing because the oxidizing gas and the fuel gas are supplied to the fuel cell 10 to generate power. Further, since the fuel cell 10 charges the secondary battery 102, the cell voltage is lower than the open circuit voltage (eg, 1.0V) (eg, 0.8V).

  Next, after the first charge control, discharge control (shown as discharge in the figure) is performed. The timing for performing the discharge control is not particularly limited. For example, when the charge control is performed for a predetermined time, the charge control may be switched to the discharge control. In addition, the charging control may be switched to the discharging control when the fluctuation of the cell voltage during the charging control becomes a predetermined value or less. The fluctuation of the cell voltage can be obtained as a difference between the maximum value and the minimum value of the cell voltage within a predetermined time in the past.

  During the discharge control, the oxidizing gas and fuel gas remaining in the cathode closed space and the anode closed space are consumed, so that the cell voltage decreases and the amount of water increases. In the discharge control, the amount of water is increased only for the remaining oxidizing gas and fuel gas. However, the amount of water is increased by the oxidizing gas and the fuel gas supplied from the blower 20 and the fuel gas tank 30 by performing the charge control before the discharge control. Thereby, in addition to the amount of water generated at the time of discharge control, impurities attached to the electrodes and separator of the fuel cell 10 can be dissolved by the amount of water generated at the time of charge control. That is, the fuel cell system 1 of the present embodiment that performs charge control before discharge control can dissolve more impurities in water than performing only discharge control to dissolve impurities in water.

  Next, after the discharge control, purge control (denoted as purge in the figure) is performed. There is no particular limitation on the timing for performing the purge control. For example, the discharge control may be switched to the purge control when the cell voltage drops due to the discharge control and falls below a threshold (for example, 0.6 V or less). When the cell voltage is low, impurities and oxides adhering to the electrode catalyst (platinum) are reduced and removed. Therefore, it is preferable to set a voltage that causes such reduction and removal as a threshold value.

  By purging control, water in which impurities and the like are dissolved can be discharged from the fuel cell 10 to the outside.

  Note that, when the ignition switch is turned off during normal operation, the discharge control may be started. Assume that the ignition switch is turned off at time B shown in FIG. In such a case, since the fuel cell 10 is charging the secondary battery 102 in the normal operation before the ignition switch is turned off, this is regarded as charge control. Therefore, even if the ignition control is started when the ignition switch is turned off, the discharge control is performed from the charge control before and after the ignition switch is turned off.

  The ECU 100 executes the series of charge control, discharge control, and purge control described above once or more. In the example shown in the figure, the operation is performed three times, and after the fourth discharge, these controls are not performed and the fuel cell 10 is completely stopped. The complete stop is a state in which the supply of the oxidizing gas and the fuel gas is stopped. By executing such control a plurality of times, impurities in the fuel cell 10 can be more reliably removed.

  Moreover, you may complete | finish charge control, discharge control, and purge control based on the cell voltage at the time of charge. For example, the cell voltage during the first charge control is 0.8V. And the cell voltage at the time of performing charge control of the 2nd time is 0.85V higher than it. This is because the power generation performance of the fuel cell has been restored because a considerable amount of impurities have been removed from the electrodes and separator by charge control, discharge control and purge control.

  As described above, when the difference between the second time and the previous cell voltage is not the same or when a difference of a certain level or more is opened, the removal process is not finished and the process is executed once again.

  Next, the cell voltage during the third charge control is 0.85 V, which is the same as the second cell voltage. The fact that the cell voltage does not change despite the removal process for removing the impurities can be said that the impurities have been almost completely removed from the fuel cell 10.

  As described above, when the difference between the third (current) and second (previous) cell voltages is the same or when the difference is equal to or less than the predetermined threshold, the removal process is terminated. That is, the fourth removal process is not executed, and after the discharge control is executed, the fuel cell 10 is completely stopped.

  As described above, as the condition for terminating the removal process, the fact that the change in the cell voltage during the charge control is applied is applied, so that impurities and the like generated in the fuel cell 10 can be more reliably removed.

FIG. 5 is a flowchart showing the operation of the fuel cell system 1 according to this embodiment when stopped. The following processing is executed by the ECU 100.
First, it is determined whether or not there has been an instruction to stop the fuel cell (abbreviated as FC in the figure) (step S1). When there is no stop instruction (step S1: No), RETURN is performed (for example, execution is performed from START after a predetermined time elapses).

  When there is a stop instruction (step S1: Yes), SOC detection of the secondary battery 102 is performed (step S2). Next, it is determined whether the operation time is equal to or greater than the threshold value a (step S3). The operation time is, for example, an accumulated time from when impurities are removed from the fuel cell 10 by executing a series of controls including charge control, discharge control, and purge control last time. Although there is no particular limitation on the threshold value a, for example, several hundred hours are set. When the operation time is less than the threshold value a (step S3: No), RETURN is performed. That is, it has been determined that it is not necessary to remove impurities since the time has not passed since the last time impurities were removed.

  Next, if the operation time is equal to or greater than the threshold value a (step S3: Yes), it is determined whether the SOC is equal to or less than the threshold value b (step S4). The threshold value b is a threshold value for determining whether or not there is enough free space to accept the power charged at this time when the secondary battery 102 is charged by the charge control. For example, the threshold value b is set to 50%.

  When the SOC is larger than the threshold value b (step S4: No), that is, when the secondary battery 102 cannot sufficiently accept the power, RETURN is performed. When the SOC is equal to or less than the threshold value b (step S4: Yes), the impurity removal process is executed by a series of controls including the above-described charge control, discharge control, and purge control (step S5).

  The operating time may be the frequency at which impurities are removed. For example, the threshold value a is set as appropriate, such as once every six months, and if the frequency is higher than that, the impurity removal process is not executed. Further, not only the operation time but also the impurity removal process may be executed on the condition that the cell voltage at a predetermined current density has decreased below a predetermined value. In addition, impurity removal processing may be performed periodically.

  Although not particularly illustrated, the flow when the start instruction of the fuel cell 10 is given by turning on the ignition switch or the like can be performed as follows, for example.

First, the ECU 100 starts the fuel cell 10 when an instruction to start the fuel cell is given. Specifically, as shown in FIG. 1, each valve is opened, and oxidizing gas and fuel gas are supplied to the fuel cell 10.
Thereafter, the same processing as in steps S2 to S4 shown in FIG. 5 is executed. Then, it is determined whether a certain time (for example, 10 minutes) elapses when there is no output request for the fuel cell 10. If a certain time has elapsed, it can be estimated that the vehicle will not start for a while. Then, a screen for confirming whether or not to perform the removal process is displayed on the display device in the vehicle of the electric vehicle, and when the driver inputs that the removal process may be performed, the impurity removal process may be executed. Good.

  FIG. 6 is a flowchart showing an operation of removing impurities in the fuel cell system 1 of the present embodiment. The following processing is executed by the ECU 100.

  ECU 100 detects the cell voltage of fuel cell 10 (step S10). Next, the ECU 100 performs charge control (step S11) and performs discharge control (step S12). As described above, the condition for switching from the charge control to the discharge control may be after a certain period of time has elapsed, or a condition such that the cell voltage fluctuation is equal to or less than a threshold value may be employed.

  Next, it is determined whether the cell voltage of the fuel cell 10 is equal to or less than the threshold value e (step S13). The threshold value e is set to a sufficiently low voltage so that impurities and oxides attached to the electrode catalyst (platinum) are reduced and removed. For example, it is 0.6V.

  If the cell voltage is larger than the threshold value e (step S13: No), it is estimated that the impurities have not been sufficiently reduced and removed, and thus the discharge control is continued (step S12).

  If the cell voltage is equal to or lower than the threshold value e (step S13: Yes), it is estimated that the impurities have been sufficiently reduced and removed, so the discharge control is terminated and the purge control is executed (step S14).

  Next, the ECU 100 determines an end condition. Here, it is assumed that the cell voltage when the charge control is performed in the previous removal process is f, and the cell voltage when the charge control is performed in the current removal process is g. Then, the end condition is that the cell voltage f and the cell voltage g are equal or the number of times of performing the negative pressure purge is equal to or greater than the threshold value h.

  For example, the cell voltages when the first and second charge control in FIG. 4 are performed are different. That is, since the cell voltage f and the cell voltage g are different (step S15: No), the removal process is not terminated, and the process returns to step S10 to execute the next removal process.

  The cell voltage is the same when the second and third charge control of FIG. 4 is performed. That is, since the cell voltage f and the cell voltage g are equal (step S15: Yes), the removal process is terminated. Alternatively, even if the cell voltage f and the cell voltage g are different, if the number of times purge control is executed is equal to or greater than the threshold value h (step S15: Yes), the removal process is terminated.

  According to the fuel cell system 1 according to this embodiment described above, the charge control is executed to cause the oxidizing gas and the fuel gas to undergo an electrochemical reaction, thereby increasing the amount of water in the fuel cell 10. And by performing discharge control, a cell voltage is reduced, the impurities adhering to an electrode or a separator are reduced and removed, and it dissolves in water. Thereafter, by performing purge control, water in which impurities are dissolved can be discharged to the outside of the fuel cell 10. In this way, impurities attached to the electrode and separator of the fuel cell 10 can be more reliably removed to the outside. Thereby, it can suppress that the electrode and separator of the fuel cell 10 corrode, and can recover electric power generation performance.

  In addition to the amount of water generated during discharge control, the amount of water generated during charge control can dissolve impurities adhering to the electrodes and separator of the fuel cell 10. That is, the fuel cell system 1 of the present embodiment that performs charge control before discharge control can dissolve more impurities in water than performing only discharge control to dissolve impurities in water. Thereby, more impurities can be removed to the outside of the fuel cell 10.

  The fuel cell system 1 according to the present embodiment executes a removal process including charge control, discharge control, and purge control a plurality of times. Thereby, the impurities of the fuel cell 10 can be more reliably removed.

  The fuel cell system 1 according to the present embodiment ends the removal process on condition that the difference between the cell voltage at the time of charge control in the previous and current removal processes is within a predetermined threshold. When such a condition is satisfied, the impurities are almost completely removed from the fuel cell 10. Therefore, since the removal process is terminated under such conditions, impurities and the like generated in the fuel cell 10 can be more reliably removed.

  When performing the purge control, the fuel cell system 1 according to the present embodiment first opens the first inlet side valve 51 and the second inlet side valve 52, and then the first outlet side valve 61 and the second outlet side. The valve 62 is opened. According to such purge control, the condensed water accumulated in the cathode and the anode can be more reliably discharged to the outside by the oxidizing gas and the fuel gas energized using the negative pressure.

<Embodiment 2>
In the present embodiment, a fuel cell system 1A provided with humidifying means will be described. FIG. 7 is a schematic diagram of the fuel cell system according to the present embodiment. In addition, the same code | symbol is attached | subjected to the same thing as Embodiment 1, and the overlapping description is abbreviate | omitted.

  The fuel cell system 1 </ b> A of the present embodiment includes a humidifier 110. The humidifier 110 is an example of a humidifier and is a device that humidifies the fuel gas. Specifically, the humidifier 110 is provided with a film 111 that partitions an internal space into two. The membrane 111 does not transmit gas but allows water to pass therethrough.

  Water contained in the exhaust gas flows into the one space 112 partitioned by such a film from the second exhaust pipe 90. The water that has flowed into the space 112 is sent to the second reservoir 42. Further, a humidifying pipe 114 a and a humidifying pipe 114 b branched from the fuel gas pipe 31 are connected to the other space 113 partitioned by the membrane 111.

  The fuel gas flowing through the fuel gas pipe 31 flows into the space 113 through the humidifying pipe 114a. Then, the fuel gas comes into contact with the water that has permeated through the membrane 111, becomes a fuel gas containing moisture, and returns to the fuel gas pipe 31 through the humidifying pipe 114b.

  According to such a humidifier 110, the fuel gas is humidified to become a fuel gas containing a large amount of moisture. Thereby, the amount of water generated when performing charge control and discharge control in the fuel cell 10 can be increased. According to the fuel cell system 1A provided with the humidifier 110 as described above, the amount of water generated in the fuel cell 10 is increased, so that more impurities can be dissolved in water and removed from the fuel cell 10.

  In addition, a humidification means is not limited to such an aspect, What is necessary is just a structure which can humidify fuel gas.

<Other embodiments>
As mentioned above, although one embodiment of the present invention has been described, of course, the present invention is not limited to the above-described embodiment, and addition, omission, replacement, etc., of a configuration is possible without departing from the spirit of the present invention. And other changes are possible.

  For example, the outlet of the fuel gas tank 30 and the inlet of the blower 20 may have a valve that prevents inflow of gas when the negative pressure generation control is executed.

  In the fuel cell system 1 according to Embodiment 1, the example in which the removal process is executed three times has been described, but the number of times is not limited to this, and may be any number of times as long as it is one or more times.

  In the fuel cell system 1 according to Embodiment 1, the first storage unit 41 and the second storage unit 42 are connected to both the cathode and the anode, but the present invention is not limited to such a mode. For example, a common reservoir may be provided for both the cathode and the anode.

  In the fuel cell system 1 according to Embodiment 1, during the purge control, the first inlet side valve 51 and the second inlet side valve 52 are first opened, and then the first outlet side valve 61 and the second outlet side valve are opened. Although 62 is opened, the present invention is not limited to such an embodiment, and the order may be reversed, or the valves may be opened almost simultaneously.

  Although the fuel cell system 1 according to Embodiment 1 is mounted on an electric vehicle, the present invention is not limited to such an embodiment, and can be applied to any application as a power source.

1, 1A Fuel cell system 10 Fuel cell 20 Blower (oxidizing gas supply means)
30 Fuel gas tank (fuel gas supply means)
51 First inlet side valve 52 Second inlet side valve 61 First outlet side valve 62 Second outlet side valve 101 Drive motor 102 Secondary battery 103 Discharge device 110 Humidifier (humidifier)

Claims (5)

A fuel cell comprising a cathode and an anode and supplying power to the secondary battery;
An oxidizing gas supply means for supplying an oxidizing gas to the cathode;
Fuel gas supply means for supplying fuel gas to the anode;
A first inlet side valve and a second inlet side valve provided in each of a pipe connecting the oxidizing gas supply means and the cathode inlet, and a pipe connecting the fuel gas supply means and the anode inlet; ,
A first outlet side valve and a second outlet side valve provided in each of a pipe connecting the cathode outlet and the outside, and a pipe connecting the anode outlet and the outside;
Control means for controlling opening and closing of the first inlet side valve, the second inlet side valve, the first outlet side valve, and the second outlet side valve;
The control means, when there is a stop command or start command to the fuel cell,
Charging control for opening the first inlet side valve, the second inlet side valve, the first outlet side valve, and the second outlet side valve and electrically connecting the fuel cell to the secondary battery;
A discharge control for closing the first inlet side valve, the second inlet side valve, the first outlet side valve and the second outlet side valve, and electrically disconnecting the fuel cell from the secondary battery;
The fuel cell system, wherein the first inlet side valve, the second inlet side valve, the first outlet side valve, and the purge control for opening the second outlet side valve are executed at least once. The fuel cell system according to claim 1, wherein
The control means includes
The fuel cell system, wherein the charge control, the discharge control, and the purge control are executed a plurality of times. In the fuel cell system according to claim 1 or 2,
The control means includes
On the condition that the difference between the cell voltage of the fuel cell when executing the charge control and the cell voltage of the fuel cell when executing the previous charge control is equal to or less than a predetermined threshold. The fuel cell system, wherein execution of charge control, discharge control, and purge control is stopped. In the fuel cell system according to any one of claims 1 to 3,
In the purge control, after opening the first inlet side valve and the second inlet side valve, the first outlet side valve and the second outlet side valve are opened. In the fuel cell system according to any one of claims 1 to 4,
A fuel cell system comprising humidifying means for humidifying the fuel gas.

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