JP4696643B2 - Fuel cell system, control method thereof, and vehicle equipped with the same - Google Patents

Description

  The present invention relates to a fuel cell system, a control method thereof, and a vehicle equipped with the same.

Conventionally, as a fuel cell system, one that stops and restarts the power generation operation of the fuel cell when a predetermined condition is satisfied has been proposed (for example, see Patent Document 1). In the system described in Patent Document 1, the power generation operation of the fuel cell is stopped when the power generation efficiency is low, and then the amount of condensed water inside the fuel cell generated by the temperature drop during the power generation stoppage is reduced. When the predetermined value is exceeded, the power generation operation is resumed. Thus, the fuel efficiency is improved by stopping the power generation operation. Further, since the power generation operation is resumed before the amount of condensed water increases too much, the power generation operation of the fuel cell after restart can be performed in a stable state.
JP 2004-22464 A

  However, in the fuel cell system described in Patent Document 1, since the power generation operation is resumed based on the temperature obtained after the fuel cell power generation operation is stopped, the state of the fuel cell before the power generation operation is stopped is sufficiently considered. However, by continuing to stop the power generation operation of the fuel cell, the power generation capability of the fuel cell may be lower than expected. In other words, it was not always possible to stop the power generation operation or restart the power generation operation under conditions suitable for the state of the fuel cell.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a fuel cell system capable of stopping and restarting a power generation operation under conditions suitable for the state of the fuel cell, and a control method thereof. One of them. Another object is to provide a vehicle equipped with such a fuel cell system.

  The present invention employs the following means in order to achieve at least a part of the above-described object.

The fuel cell system of the present invention comprises:
A fuel cell that generates electricity through an electrochemical reaction;
State detecting means for detecting the state of the fuel cell;
When the start condition of the stop / restart operation in which the power generation operation of the fuel cell is stopped and the power generation operation is resumed after the stop is satisfied, the state of the fuel cell detected by the state detection means during the power generation operation of the fuel cell is established. Control means for setting an execution condition for the stop / restart operation of the fuel cell based on the control and controlling the power generation operation of the fuel cell under the set execution condition;
It is equipped with.

  In this fuel cell system, when the start condition for the stop / restart operation of the fuel cell is satisfied, the stop / restart operation of the fuel cell is performed based on the state of the fuel cell detected by the state detection means during the power generation operation of the fuel cell. An execution condition is set, and the power generation operation of the fuel cell is controlled under the set execution condition. In this way, the state of the fuel cell before stopping the power generation operation is grasped, and the execution conditions for the subsequent stop and restart of the power generation operation are set. Therefore, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell.

  In the fuel cell system of the present invention, the control means may set a stop time of the power generation operation of the fuel cell as the execution condition. Here, the “power generation operation stop time” may be set to a time that does not hinder the power generation operation after restarting the power generation operation even if the power generation capacity is reduced due to the stop of the power generation operation, The time may be set such that the improvement in fuel consumption obtained in the entire operation of stopping and restarting power generation is optimal.

Alternatively, the fuel cell system of the present invention includes:
A fuel cell that generates electricity through an electrochemical reaction;
State detecting means for detecting the state of the fuel cell;
When the start condition of the stop / restart operation in which the power generation operation of the fuel cell is stopped and the power generation operation is resumed after the stop is satisfied, the state of the fuel cell detected by the state detection means during the power generation operation of the fuel cell is established. Control means for setting a stop time of the power generation operation of the fuel cell in the stop / restart operation based on the stop time and controlling the stop of the power generation operation of the fuel cell with the set stop time as a limit;
It is good also as a thing provided.

  In this fuel cell system, the state of the fuel cell before stopping the power generation operation is grasped, a subsequent stop time of the power generation operation is set, and the stop of the power generation operation of the fuel cell is continued up to the set stop time. Therefore, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell.

    In the fuel cell system of the present invention, the control means may set the execution condition so that the stop time is shortened when the power generation capacity of the fuel cell is low. By so doing, it is possible to suppress further reduction in the power generation capacity of the fuel cell.

  In the fuel cell system of the present invention that adopts a mode in which the stop time of the power generation operation of the fuel cell is set as the execution condition, the control means again after restarting the power generation operation of the fuel cell as the execution condition. A re-stop prohibition time until the power generation operation is stopped may be set. In this way, frequent repetition of stop and restart of the power generation operation can be suppressed by the re-stop prohibition time set according to the state of the fuel cell. Here, the “re-stop prohibition time” may be set as a time sufficient to recover the state of the fuel cell that has become difficult to generate power by stopping the power generation operation, for example. At this time, the control means resumes the power generation operation of the fuel cell after continuing the stop of the power generation operation of the fuel cell with the set stop time as a limit until the set re-stop prohibition time elapses. The power generation operation of the fuel cell may be continued. At this time, the execution condition may be set so that the stop time is shortened and the re-stop prohibition time is lengthened when the power generation capability of the fuel cell is low. By so doing, it is possible to reliably suppress a decrease in the power generation capacity of the fuel cell in order to suppress the restart of the power generation operation.

  In the fuel cell system of the present invention, the state detection unit may detect a parameter relating to a current-voltage characteristic of the fuel cell. In this way, since the execution conditions for stopping and restarting the power generation operation are set based on the parameter relating to the current-voltage characteristic, which is one of the important indexes indicating the power generation capability of the fuel cell, the power generation operation is stopped more appropriately. And a restart can be performed. The parameter relating to the current-voltage characteristics of the fuel cell is a parameter that cannot be obtained while the fuel cell power generation is stopped.

  In the fuel cell system of the present invention, the fuel cell may include an electrolyte membrane sandwiched between an anode and a cathode, and the state detection unit may detect a parameter relating to a wet state of the electrolyte membrane. In this way, the state of the fuel cell can be detected based on the parameter relating to the wet state of the electrolyte membrane. At this time, the state detection means may detect the impedance of the fuel cell as a parameter relating to a wet state of the electrolyte membrane. In this way, since the conditions for stopping and restarting the power generation operation are set based on the impedance of the fuel cell, which is one of the important indicators of the wet state of the electrolyte membrane, the wet state of the electrolyte membrane is relatively easy. Can be detected, and the power generation operation can be stopped and restarted more appropriately. The impedance of the fuel cell is a parameter that cannot be obtained while the operation is stopped.

  The vehicle of the present invention is equipped with the fuel cell system according to any of the various aspects described above. Since the fuel cell system of the present invention can stop and restart the power generation operation under conditions suitable for the state of the fuel cell, a vehicle equipped with the same will also have the same effect.

The control method of the fuel cell system of the present invention includes:
A control method of a fuel cell system in which a fuel cell generates electricity by an electrochemical reaction,
When the start condition of the stop / restart operation in which the power generation operation of the fuel cell is stopped and the power generation operation is resumed after the stop is satisfied, the fuel cell is based on the state of the fuel cell detected during the power generation operation of the fuel cell. This includes setting the execution condition of the stop / restart operation and controlling the power generation operation of the fuel cell with the set execution condition.

  In this fuel cell system control method, when the start condition of the fuel cell stop / restart operation is satisfied, the fuel cell stop / restart operation is executed based on the state of the fuel cell detected during the power generation operation of the fuel cell. Conditions are set, and the power generation operation of the fuel cell is controlled under the set execution conditions. In this way, the state of the fuel cell before stopping the power generation operation is grasped, and the execution conditions for the subsequent stop and restart of the power generation operation are set. Therefore, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell. In the control method of the fuel cell system, various aspects of the above-described fuel cell system may be adopted, and steps for realizing the functions of the above-described fuel cell system may be added.

  Next, the best mode for carrying out the present invention will be described using examples.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an outline of the configuration of the fuel cell vehicle 20, and FIG. 2 is an explanatory diagram showing a schematic configuration of the fuel cell 31. The fuel cell vehicle 20 is a vehicle on which the fuel cell system 12 is mounted. As shown in FIG. 1, a plurality of fuel cells 31 that generate electricity by an electrochemical reaction between hydrogen as a fuel gas and oxygen in the air as an oxidizing gas. The voltage of the stacked fuel cell stack 30, the power storage device 46 capable of storing or discharging power, the inverter 41 connected to the power line 48, and the power line 48 connected to the output terminal of the fuel cell stack 30 are adjusted. In addition, the DC / DC converter 42 that charges and discharges the power storage device 46, the drive motor 43 that is driven and controlled by switching of the switching elements of the inverter 41, and exchanges power with the drive shaft 64, and the entire fuel cell system 12 are controlled. And an electronic control unit (ECU) 70. The drive shaft 64 is connected to the drive wheels 63 and 63 via the differential gear 62 so that the power output from the drive motor 43 is finally output to the drive wheels 63 and 63. It has become.

  The fuel cell stack 30 has a stack structure in which a plurality of fuel cells 31 that are solid polymer electrolyte type single cells are stacked, and functions as a high-voltage power supply (several hundred volts). As shown in FIG. 2, the fuel cell 31 is configured by sandwiching a membrane electrode assembly (MEA) 35 in which an electrolyte membrane 32 is sandwiched between an anode 33 and a cathode 34 between a pair of separators 36 and 36. The electrolyte membrane 32 is an ion exchange membrane that exhibits good proton conductivity in a wet state. Each of the anode 33 and the cathode 34 is composed of catalyst electrodes 33a and 34a carrying platinum or an alloy made of platinum and another metal, and gas diffusion electrodes 33b and 34b formed of carbon cloth. The separators 36 and 36 form a fuel gas passage 37 and an oxidizing gas passage 38 between the anode 33 and the cathode 34. In this fuel cell 31, hydrogen gas is supplied to the anode 33 from the hydrogen tank 22 and the gas circulation pump 24, and compressed air whose pressure is adjusted is supplied to the cathode 34 from the air supplier 28, and a predetermined electrochemical reaction proceeds. By doing so, an electromotive force is generated with the generation of water. The surplus hydrogen that has not reacted is sent to the gas circulation pump 24 and reused as fuel gas (see FIG. 1).

  As shown in FIG. 1, the fuel cell stack 30 includes a voltmeter 54 that detects a voltage V output from each fuel cell 31, an ammeter 56 that detects a current I output from the fuel cell 31, and the fuel cell stack 30. An impedance detector 58 for detecting the impedance is attached. These sensors are connected to the ECU 70 by signal lines. The impedance detector 58 is an AC milliohm sensor that obtains an impedance from an alternating voltage when a minute alternating current is applied to the output terminal of the fuel cell stack 30. In the configuration of the fuel cell 31, the impedance of the fuel cell stack 30 is roughly divided into a resistance based on the anode 33, the cathode 34, and the separator 36 and a resistance based on the proton conductivity of the electrolyte membrane 32. Since the anode 33, the cathode 34, and the separator 36 are made of a conductive material, their impedances hardly change depending on whether or not they are wet. On the other hand, the electrolyte membrane 32 exhibits good proton conductivity when wet, but the proton conductivity deteriorates when dry up. Therefore, the impedance of the fuel cell stack 30 reflects the wet state of the electrolyte membrane 32. The voltmeter 54, the ammeter 56, and the impedance detector 58 correspond to the state detection means of the present invention.

  The ECU 70 is configured as a microprocessor centered on the CPU 72, and includes a ROM 74 that stores a processing program, a RAM 76 that temporarily stores data, a timer 78 that measures time, and an input / output port (not shown). With. The ECU 70 includes an output voltage Vfc from a voltmeter 54 attached between output terminals of the fuel cell stack 30, an output current Ifc from an ammeter 56 attached to an output terminal of the fuel cell stack 30, and an impedance detector 58. From the impedance Z of the fuel cell stack 30, the current of each phase applied to the drive motor 43 from the current sensor (not shown) attached in the inverter 34, and the angle sensor (not shown) attached to the drive motor 43 The rotation angle of the rotor of the driving motor 43, the vehicle speed v from the vehicle speed sensor 88, the shift position SP from the shift position sensor 82 that detects the position of the shift lever 81, and the accelerator pedal position that detects the depression amount of the accelerator pedal 83 Accelerator pedal position AP, sensor from sensor 84 A brake pedal position BP from a brake pedal position sensor 86 that detects the depression amount of Kipedaru 85 is input via the input port. Further, the ECU 70 outputs a drive signal to the gas circulation pump 24, a control signal to the valve 26, a drive signal to the air supply device 28, a control signal to the DC / DC converter 42, a control signal to the inverter 41, and the like. It is output through the port. The ECU 70 corresponds to the control means of the present invention.

  Next, the operation of the fuel cell system of this embodiment will be described. FIG. 3 is a flowchart showing an example of a fuel cell control routine executed by the CPU 72 of the ECU 70 of the fuel cell system. This routine is stored in the ROM 74, and is repeatedly executed at predetermined timings (for example, every several milliseconds) after the system is started by the CPU 72.

  When this control routine is started, the CPU 72 first determines whether or not the re-stop prohibition flag Fp is set to 1 (step S100). This re-stop prohibition flag Fp is a flag that is set to 1 during the prohibition of re-stop until the power generation operation is stopped again after stopping the power generation operation of the fuel cell stack 30 and restarting the power generation operation after the stop. Yes, the initial value is set to zero. When the re-stop prohibition flag Fp is not set to 1, it is determined whether or not the operation stop execution flag Fs is set to 1 (step S110). The operation stop execution Fs is a flag that is set to 1 during the power generation stop of the stop / restart operation of the fuel cell stack 30, and the initial value is set to zero. When the operation stop execution flag Fs is not set to 1, the CPU 72 determines whether or not the start condition of the stop / restart operation of the power generation operation of the fuel cell stack 30 is satisfied (step S120). Here, the stop / restart operation condition is, for example, when the fuel cell vehicle 20 is in a predetermined low speed range (for example, 20 km / h or less), the required power generation amount is low, and the power storage amount of the power storage device 46 is sufficient. This is established when the power generation efficiency of the stack 30 falls below a predetermined range and the fuel cell stack 30 can be stopped.

  When the start condition for the stop / restart operation is not satisfied, the CPU 72 executes the normal operation control (step S130) and ends this routine. In this normal operation control, various information such as the shift position SP, the accelerator opening Acc, the brake pedal position BP, and the vehicle speed V is input, and the required power required for the vehicle is calculated based on the various information. Auxiliaries (such as the gas circulation pump 24, the air supply device 28, the inverter 41, and the DC / DC converter 42) of the fuel cell stack 30 are driven and controlled so that the required power is output. For example, the auxiliary devices of the fuel cell stack 30 are driven and controlled so that all the electric power corresponding to the required power is output from the fuel cell stack 30, or the electric power corresponding to the required power is supplied from the fuel cell stack 30 and the power storage device 46. The fuel cell stack 30 is driven and controlled so that it is output, and the fuel cell stack 30 outputs power that matches the required power and the power required for charging the power storage device 46. It drives and controls auxiliary equipment of the battery stack 30.

  On the other hand, when the start condition for the stop / restart operation is satisfied in step S120, the CPU 72 inputs the impedance Z, the output voltage Vfc, and the output current Ifc of the fuel cell stack 30 (step S140), and inputs the various information. Based on the above, an operation stop time ts for stopping the power generation operation of the fuel cell stack 30 and a re-stop prohibition time tp for prohibiting the restart after restarting from the operation stop are set.

  Here, the setting of the operation stop time ts and the re-stop prohibition time tp will be described. In this embodiment, these values are set based on the current-voltage characteristics (IV characteristics) and the impedance Z. FIG. 4 is an explanatory diagram of IV characteristics of the fuel cell stack 30. The solid line indicates the IV characteristics of the normal power generation capacity, and the dotted line indicates the IV characteristics when the power generation capacity is reduced. Hereinafter, setting of the operation stop time tsiv and the re-stop prohibition time tpiv based on the IV characteristics will be described. First, the relationship between the IV characteristics before stopping the power generation operation, the time during which the power generation operation is stopped, and the IV characteristics of the fuel cell after restarting after this time has been empirically obtained. Next, based on the obtained results, a stop time that does not hinder the subsequent power generation operation even if the power generation capacity is reduced by stopping the power generation operation is obtained, and this time is set as the operation stop time tsiv. Further, based on the obtained result, the operation time after restart sufficient to recover the power generation capacity that has been reduced by executing the operation stop time tsiv is obtained, and this time is calculated as the re-stop prohibition time. Let tpiv. Then, the relationship between the IV characteristic before stopping the power generation operation, the operation stop time tsiv and the re-stop prohibition time tpiv is stored in the ROM 74 as an IV characteristic-time relationship map, and the operation stop by the IV characteristic is performed using this map. The time tsiv and the re-stop prohibition time tpiv are obtained. This IV characteristic-time relationship map is determined by, for example, using the internal resistance R of the fuel cell stack 30 obtained from the output voltage Vfc and the output current Ifc as the IV characteristic, and by determining the relationship between the internal resistance R and the operation stop time tsiv. it can. The internal resistance R is obtained from R = ΔV / Ifc from the voltage difference ΔV between the so-called open-circuit voltage (OCV) and the output voltage Vfc and the output current Ifc. FIG. 5 is an explanatory diagram illustrating an example of an IV characteristic-time relationship map. This map is set so that when the internal resistance R of the fuel cell stack 30 before stopping the power generation operation is high (when the power generation capacity is low), the operation stop time tsiv is shortened and the re-stop prohibition time tpiv is lengthened. Yes. In addition, this map is set so that when the internal resistance R of the fuel cell stack 30 before the power generation operation stop is low (when the power generation capacity is high), the operation stop time tsiv becomes longer and the re-stop prohibition time tpiv becomes shorter. Has been. Note that the IV characteristic-time relationship map may define a relationship among the output voltage Vfc, the output current Ifc, the operation stop time tsiv, and the re-stop prohibition time tpiv without using the internal resistance R as the IV characteristic.

  Next, the setting of the operation stop time tsz and the re-stop prohibition time tpz based on the impedance Z of the fuel cell stack 30 will be described. First, the relationship between the impedance Z before stopping the power generation operation of the fuel cell stack 30, the time during which the power generation operation is stopped, and the impedance Z of the fuel cell after restarting after this time is obtained empirically. Next, based on the obtained result, even if the wet state of the electrolyte membrane 32 changes due to the stop of the power generation operation, a stop time is determined so that the subsequent power generation operation is not hindered, and this time is stopped. Let time tsz. Further, based on the obtained result, the operation time after restarting sufficient to bring the wet state of the electrolyte membrane 32 changed by executing the operation stop time tsz to the appropriate range is obtained by performing the operation stop time tsz. The time is defined as a re-stop prohibition time tpz. Then, the relationship between the impedance Z before stopping the power generation operation, the operation stop time tsz and the re-stop prohibition time tpz is stored in the ROM 74 as an impedance-time relationship map, and the operation stop time tsz due to the impedance using this map. And the re-stop prohibition time tpz is obtained. FIG. 6 is an explanatory diagram showing an example of an impedance-time relationship map when the fuel cell stack 30 shows a dry state. In this map, when the impedance Z is large (in the dry state), the electrolyte membrane 32 is wetted by water generated by the power generation operation. The time tpz is set to be long.

  Then, after obtaining the operation stop time tsiv based on the IV characteristic and the operation stop time tsz based on the impedance, the CPU 72 compares these times and sets the shorter one as the operation stop time ts. At this time, the re-stop prohibition time tp is set to correspond to the adopted operation stop time ts. As described above, the execution conditions that do not lower the power generation capability of the fuel cell system 12 among the operation stop times tsiv and tsz obtained based on two or more parameters are preferentially set. In addition, the state of the fuel cell stack 30 before stopping the power generation operation is grasped, and the execution conditions for the subsequent power generation operation stop and restart operation are set.

  Now, after setting the operation stop time ts and the re-stop prohibition time tp in step S150, the CPU 72 sets the operation stop execution flag Fs to 1, and starts the timer 78 that measures the operation stop time ts and the re-stop prohibition time tp. At the same time, the stop / restart operation of the fuel cell stack 30 is started (step S160). Here, in the stop / restart operation, the fuel gas supply valve 26 is closed to stop the supply of the fuel gas from the hydrogen tank 22, and the driving / control of the auxiliary devices of the fuel cell stack 30 is stopped to stop the fuel cell. This is started by stopping the power generation operation of the stack 30.

  Subsequently, when the operation stop execution flag Fs is set to 1 in step S110, the CPU 72 determines whether or not an end condition for stopping the power generation operation is satisfied (step S170). Here, the stop condition for stopping the power generation operation is satisfied when the operation stop time ts ends and when the stop / restart operation condition described above is canceled. That is, the power generation operation is stopped with the operation stop time ts as a limit. The stop / restart operation condition is canceled when, for example, the required power generation amount is increased by depressing the accelerator pedal 83 while the power generation operation is stopped, or when the power storage amount of the power storage device 46 is decreased. Whether or not the operation stop time ts has ended is determined based on the count value of the timer 78. When the termination condition for stopping the power generation operation is not satisfied in step S170, the CPU 72 ends this routine as it is. That is, the power generation operation is stopped. On the other hand, when the stop condition for stopping the power generation operation is satisfied, the CPU 72 resets the operation stop execution flag Fs to zero and sets the re-stop prohibition flag Fp to 1 (step S180), and the normal operation control described above. Is executed (step S130), and this routine is terminated. That is, the power generation operation of the fuel cell stack 30 is resumed by driving and controlling the auxiliary devices of the fuel cell stack 30. When the stop / restart operation condition is canceled while the power generation operation is stopped (step S170), the stop / restart operation is terminated and the normal operation control is executed even before the operation stop time ts has elapsed. (Step S130).

  When the re-stop prohibition flag Fp is set to 1 in step S100, the CPU 72 determines whether or not the re-stop prohibition time tp has ended based on the count value of the timer 78 (step S190). When the stop prohibition time tp has not ended, normal operation control is executed (step S130), and this routine is ended. That is, after the power generation operation of the fuel cell stack 30 is resumed, the power generation operation is continued until the re-stop prohibition time tp elapses. On the other hand, when the re-stop prohibition time tp ends, the CPU 72 resets the re-stop prohibition flag Fp to zero, resets the timer 78 (step S200), executes normal operation control (step S130), and executes this routine. finish. Thus, even if the execution of the stop / restart operation is terminated before the operation stop time ts has elapsed in step S170, the normal operation control is continued until the re-stop prohibition time tp ends. Thus, stable power generation operation is ensured (steps S100, S130, S190, S200).

  According to the fuel cell vehicle 20 of the present embodiment described in detail above, when the start condition for the stop / restart operation of the fuel cell stack 30 is satisfied, the fuel cell stack 30 is stopped / restarted based on the state of the fuel cell stack 30. An operation execution condition is set, and the power generation operation is controlled under the set execution condition. Thus, in order to grasp the state of the fuel cell stack 30 before stopping the power generation operation and set the execution conditions for the subsequent stop and restart of the power generation operation, power generation is performed under conditions suitable for the state of the fuel cell stack 30. Operation can be stopped and restarted.

  Further, since the operation stop time ts is set to be short when the power generation capacity of the fuel cell stack 30 before the power generation operation stop is low, it is possible to suppress the power generation capacity of the fuel cell stack 30 from further decreasing. it can. Alternatively, when the power generation capacity of the fuel cell stack 30 before the power generation operation is stopped is high, the operation stop time ts is set to be long, so that the fuel consumption can be improved. Furthermore, since the re-stop prohibition time tp is set, frequent repetition of stop and restart of the power generation operation can be suppressed. Furthermore, since the execution condition is set so that the re-stop prohibition time tp becomes longer when the power generation capacity of the fuel cell stack 30 before the stop of the power generation operation is low, the power generation capacity is suppressed by suppressing the stop of the power generation operation. It can suppress reliably that it falls. Alternatively, since the execution condition is set so that the re-stop prohibition time tp is shortened when the power generation capacity before the power generation operation is stopped, the fuel consumption can be improved by increasing the frequency of the stop / restart operation. Accordingly, it is possible to maintain the decrease in the power generation capacity of the fuel cell stack 30 within an allowable range and improve the fuel efficiency.

  Further, since the execution condition is set before the power generation operation is stopped, the execution condition for the stop / restart operation using the IV characteristic which is one of the parameters relating to the power generation capacity which cannot be obtained while the fuel cell stack 30 is stopped. Can be set. For this reason, it is possible to appropriately stop and restart the power generation operation.

  Furthermore, since the execution condition is set before the stop of the power generation operation, the execution condition of the stop / restart operation using the impedance that is one of the parameters relating to the power generation capacity that cannot be obtained while the fuel cell stack 30 is stopped. Can be set. For this reason, the wet state of the electrolyte membrane 32 can be detected relatively easily using the impedance of the fuel cell stack 30, and appropriate power generation operation can be stopped and restarted.

  Then, a short restart time among the operation stop times tsiv and tsz obtained based on a plurality of parameters (IV characteristics and impedance) representing the state of the fuel cell stack 30 is preferentially adopted as an execution condition, and the stop / restart operation is performed. Therefore, the power generation operation of the fuel cell system 12 can be performed while maintaining a stable state.

  In addition, this invention is not limited to the Example mentioned above at all, and as long as it belongs to the technical scope of this invention, it cannot be overemphasized that it can implement with a various aspect.

  For example, in the above-described embodiment, the execution condition of the stop / restart operation is set using the IV characteristic and the impedance as representing the state of the fuel cell stack 30, but only one of them may be set. Even in this case, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell stack 30. In addition, as an indication of the state of the fuel cell stack 30, a stop / restart operation execution condition may be set using a parameter related to the temperature of the fuel cell stack 30. For example, when the temperature of the fuel cell stack 30 before stopping the power generation operation is low, the moisture in the stack increases, so that the operation stop time ts is set to be short and the re-stop prohibition time tp is set to be long. . On the other hand, when the temperature of the fuel cell stack 30 before stopping the power generation operation is high, the temperature of the stack can be lowered by stopping the operation, so that the operation stop time ts is set to be long and the re-stop prohibition time tp is shortened. Set as follows. The parameters relating to the temperature of the fuel cell stack 30 include the actual temperature of the stack and the cooling water temperature of the stack. Even in this case, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell stack 30.

  Alternatively, as an indication of the state of the fuel cell stack 30, for example, a stop / restart operation execution condition may be set using parameters relating to the fuel gas of the fuel cell stack 30. For example, when the nitrogen concentration of the anode 33 of the fuel cell stack 30 before the power generation operation stop is high (hydrogen concentration is low), it becomes more difficult to generate power at the time of restart. Since it is necessary to suppress the cross leak, the operation stop time ts is set to be short and the re-stop prohibition time tp is set to be long. On the other hand, when the nitrogen concentration of the anode 33 of the fuel cell stack 30 before the stop of the power generation operation is low (hydrogen concentration is high), the cross-leakage of nitrogen from the cathode 34 during the stop of the power generation operation is allowed to some extent. The ts is set to be long and the re-stop prohibition time tp is set to be short. The parameters relating to the fuel gas of the fuel cell stack 30 include the hydrogen concentration, nitrogen concentration, oxygen concentration, etc. of the fuel gas flow path 37. Even in this case, the power generation operation can be stopped and restarted under conditions suitable for the state of the fuel cell stack 30.

  In the above-described embodiment, the execution condition is set by detecting the output voltage Vfc and output current Ifc of the entire fuel cell stack 30. However, each voltage Vc and current Ic of the fuel cell 31 that is each single cell is detected. The execution condition may be set, or the execution condition may be set by detecting the voltage of one or more fuel cells 31 selected from the plurality of stacked fuel cells 31. The execution condition may be set by detecting the voltage of the unit cell module in which the fuel cells 31 are combined. At this time, the execution condition may be set based on the detected one having the lowest power generation capability. By so doing, it is possible to stop and restart the power generation operation under conditions more suitable for the state of the fuel cell stack 30.

  Furthermore, in the above-described embodiment, the execution condition is set by detecting the impedance Z of the entire fuel cell stack 30, but the execution condition may be set by detecting the impedance of the fuel cell 31 of each single cell. The execution condition may be set by detecting the impedance of one or more fuel cells 31 selected from a plurality of stacked fuel cells 31, or the impedance of a single cell module in which several fuel cells 31 are combined. May be detected and the execution condition may be set. At this time, the execution condition may be set based on the detected one having the lowest power generation capability. By so doing, it is possible to stop and restart the power generation operation under conditions more suitable for the state of the fuel cell stack 30.

  Furthermore, in the above-described embodiment, the IV characteristics are obtained based on the output current Ifc and the output voltage Vfc of the fuel cell. The IV characteristics are the hydrogen gas concentration, the fuel cell temperature Tfc, the cooling water temperature of the fuel cell, the oxidizing gas. Since it changes depending on the flow rate or the like, the IV characteristics may be obtained instead of or in addition to these parameters.

  In the above-described embodiment, the stop time that does not hinder the subsequent power generation operation even if the power generation capacity is reduced due to the stop of the power generation operation is set as the operation stop time tsiv based on the IV characteristic. The stop time at which the improvement in fuel consumption obtained in the entire subsequent drive is optimal may be set as the drive stop time tsiv. If the operation stop time tsiv is lengthened, the fuel consumption is improved by the operation stop. However, since the power generation capacity is reduced correspondingly, the fuel consumption may be deteriorated in the subsequent power generation operation. Therefore, the operation stop time tsiv that improves the fuel consumption in the entire stop / restart operation may be obtained.

  In the above-described embodiments, the fuel cell system 12 mounted on an automobile has been described. However, the same fuel cell system may be mounted on another vehicle such as a train or a moving body such as a ship or an aircraft. You may incorporate in a stationary system (for example, cogeneration system etc.).

It is a block diagram which shows the outline of a structure of the fuel cell vehicle 20 of a present Example. It is explanatory drawing which shows schematic structure of the fuel cell 31 of a present Example. It is a flowchart of the fuel cell control routine of a present Example. It is explanatory drawing of the IV characteristic of the fuel cell stack 30 of a present Example. It is explanatory drawing of the IV characteristic-time relationship map of a present Example. It is explanatory drawing of the impedance-time relationship map of a present Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 Fuel cell system, 20 Fuel cell vehicle, 22 Hydrogen tank, 24 Gas circulation pump, 26 Valve, 28 Air supply device, 30 Fuel cell stack, 31 Fuel cell, 32 Electrolyte membrane, 33 Anode, 34 Cathode, 33a, 34a Catalyst Electrode, 33b, 34b Gas diffusion electrode, 35 MEA, 36 Separator, 37 Fuel gas flow path, 38 Oxidation gas flow path, 41 Inverter, 42 DC / DC converter, 43 Drive motor, 46 Power storage device, 48 Power line, 54 Voltmeter, 56 Ammeter, 58 Impedance detector, 62 Differential gear, 63 Drive wheel, 64 Drive shaft, 70 ECU, 72 CPU, 74 ROM, 76 RAM, 78 Timer, 81 Shift lever, 82 Shift position sensor, 83 Accelerator pedal, 4 accelerator pedal position sensor, 85 brake pedal, 86 a brake pedal position sensor, 88 vehicle speed sensor.

Claims (9)

A fuel cell that generates electricity through an electrochemical reaction;
State detecting means for detecting the state of the fuel cell;
When the start condition of the stop / restart operation in which the power generation operation of the fuel cell is stopped and the power generation operation is resumed after the stop is satisfied, the state of the fuel cell detected by the state detection means during the power generation operation of the fuel cell is established. Control means for setting an execution condition for the stop / restart operation of the fuel cell based on and controlling the power generation operation of the fuel cell under the set execution condition ,
The control means sets the stop time of the power generation operation of the fuel cell as the execution condition, and sets the stop time to be shorter when the power generation capability of the fuel cell is low, with the set stop time as a limit. Control to continue the stop of the power generation operation of the fuel cell,
Fuel cell system. It said control means sets a re-stop prohibition time to further stopping the power generation operation again after resumed power generation operation of the fuel cell as the execution condition, the fuel cell system according to 請 Motomeko 1. The control means resumes the power generation operation of the fuel cell after continuing the stop of the power generation operation of the fuel cell with the set stop time as a limit until the set re-stop prohibition time elapses. continuing the power generation operation, the fuel cell system according to 請 Motomeko 2. Wherein, according to the when the fuel cell power generation capacity is lower state sets the execution condition as the stop time becomes longer is and the re-stop prohibition time short,請 Motomeko 2 or 3 Fuel cell system. It said state detecting means, the fuel cell current - detecting a parameter related to voltage characteristics, the fuel cell system according to item 1 either 請 Motomeko 1-4. The fuel cell includes an electrolyte membrane sandwiched between an anode and a cathode,
It said state detecting means detects a parameter relating to the wet state of the electrolyte membrane, a fuel cell system according to any one of 請 Motomeko 1-4. It said state detecting means detects an impedance of the fuel cell as a parameter related to the wet state of the electrolyte membrane, a fuel cell system according to 請 Motomeko 6. Vehicle equipped with a fuel cell system according to any one of claims 1-7. A control method of a fuel cell system in which a fuel cell generates electricity by an electrochemical reaction,
When the start condition of the stop / restart operation in which the power generation operation of the fuel cell is stopped and the power generation operation is resumed after the stop is satisfied, the fuel cell is based on the state of the fuel cell detected during the power generation operation of the fuel cell. Setting the execution condition of the stop and restart operation, and controlling the power generation operation of the fuel cell under the set execution condition ,
In the step, the stop time of the power generation operation of the fuel cell is set as the execution condition, and the stop time is set to be short when the power generation capability of the fuel cell is low, and the stop time set as the limit is the limit. Control to stop the fuel cell power generation operation,
Control method of fuel cell system.

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