JP5443776B2 - FUEL CELL SYSTEM AND METHOD FOR OPERATING FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system.

  In recent years, the development of fuel cells that generate electricity by supplying hydrogen (fuel gas, reactive gas) and oxygen-containing air (oxidant gas, reactive gas) has been promoted rapidly. Expected as a source.

  When such a fuel cell generates power, it self-heats and generates water (water vapor) by an electrode reaction at its cathode. And some of the produced | generated moisture permeate | transmits (cross-leaks) MEA (Membrane Electrode Assembly: membrane electrode assembly), and goes to an anode. Therefore, the anode off-gas and cathode off-gas discharged from the fuel cell are humid and contain condensed water formed by condensation of moisture.

  Further, in such a fuel cell vehicle, when the vehicle is in an unloaded state due to waiting for a signal or waiting for a person, the fuel cell vehicle is in an idle state (idling state). However, since hydrogen is consumed in the fuel cell even during the idling, when the predetermined idle stop condition is satisfied, the consumption of hydrogen is stopped by stopping the power generation of the fuel cell at the predetermined idle stop time. An idle stop technique for improving fuel consumption is known (Patent Document 1).

JP 2007-250429 A

  However, if the vehicle outside temperature (outside air temperature) is low and the engine stops idling, the fuel cell heat generation also stops, so the temperature of the offgas piping through which the anode offgas and cathode offgas flow decreases, and the offgas piping is turned off during idling. There is a risk of freezing.

  Therefore, an object of the present invention is to provide a fuel cell system and an operation method of the fuel cell system that can appropriately stop idling while preventing freezing of off-gas piping.

As means for solving the above-mentioned problems, the present invention controls a fuel cell that generates electric power when a reaction gas is supplied, an off-gas pipe through which off-gas discharged from the fuel cell flows, and idle stop of the system If the idle stop control means, the freeze determination means for determining whether or not the off-gas piping is frozen during the idle stop, and the freeze determination means are determined to freeze, the idle stop is prohibited. A prohibiting means, and a canceling means for canceling the prohibition of the idle stop by the prohibiting means when the canceling condition of the prohibition of the idle stop is satisfied while the prohibition of the idling stop by the prohibiting means is established. when the current temperature of the off-gas piping became then when idle stop off pipes releasing temperature or higher which does not freeze, Standing city, when the outside air temperature is lower, the release temperature is changed to be higher, and, when the idle stop time is prolonged to an idle stop, the fuel cell, characterized in that it is modified to the release temperature is high System.

  According to such a fuel cell system, if the freezing determination means temporarily stops idling, the prohibiting means prohibits idling stop when it is determined that the offgas pipe is frozen during the idling stop. Thereby, freezing of off-gas piping during idle stop is prevented.

When the prohibition means prohibits the idling stop, the current temperature of the offgas pipe is equal to or higher than a release temperature at which the offgas pipe is not frozen when the idling stop is subsequently performed, and when the release condition is satisfied, the release means is prohibited. The prohibition of idling stop by is canceled, and idling can be stopped, that is, permitted. Thus, the off-gas piping can be prevented from freezing during the subsequent idle stop while the idle stop control means starts the idle stop at an appropriate timing.
Further, since the release temperature is changed so as to increase as the outside air temperature decreases, the release temperature can be set appropriately and the prohibition of idling stop can be canceled at an appropriate timing.
Further, when the idle stop time becomes longer, the release temperature is changed so as to increase. Therefore, it is possible to appropriately set the release temperature and release the prohibition of idle stop at an appropriate timing.

  In the fuel cell system, the current temperature of the offgas pipe is calculated based on an integrated value of the heat balance of the offgas pipe.

According to such a fuel cell system, it is possible to appropriately calculate the current temperature of the offgas pipe based on the integrated value (cal etc.) of the heat balance (cal / s etc.) of the offgas pipe.
Note that the heat balance of the off-gas piping is given by, for example, the difference between the heat absorption amount and the heat dissipation amount of the off-gas piping as in an embodiment described later.

  In the fuel cell system, the heat balance of the off-gas piping (in the embodiment described later, the heat absorption amount) is calculated based on the output of the fuel cell that self-heats with power generation.

According to such a fuel cell system, the heat balance of the off-gas piping can be calculated appropriately based on the output of the fuel cell that self-heats with power generation. As the output of the fuel cell stack increases, the amount of self-heating generated during power generation increases, and the heat balance (heat absorption amount) of the off-gas piping increases.
In addition, since a temperature sensor for detecting the temperature of the off-gas piping is not required, the system configuration can be simplified.

Further, in the fuel cell system, the freezing determination means predicts the temperature of the off-gas pipe during idling stop when the idling stop is temporarily performed based on the current temperature of the off-gas pipe and the outside air temperature. Whether or not the off-gas piping is frozen is determined based on the temperature and freezing temperature of the off-gas piping.

The present invention also includes a fuel cell that generates electric power when supplied with a reaction gas, an offgas pipe through which offgas discharged from the fuel cell flows, and an idle stop control means that controls idle stop of the system. In the fuel cell system operation method provided, if it is determined that the off-gas piping is frozen during the idle stop, if it is determined that the off-gas piping is frozen during the idle stop, A prohibiting step for prohibiting idling stop, and a canceling step for canceling prohibition of idling stop when a canceling condition for prohibiting idling stop is satisfied during the prohibition of idling stop, and the canceling condition includes the off-gas piping When the current temperature of the gas is higher than the release temperature at which the off-gas piping will not freeze when the engine is subsequently idled Enacted, if the outside air temperature is lower, the release temperature is changed to be higher, and, when the idle stop time is prolonged to an idle stop, the fuel cell, characterized in that it is modified to the release temperature is high This is a system operation method.
Further, in the operation method of the fuel cell system, based on the current temperature of the off-gas pipe and the outside air temperature, the temperature of the off-gas pipe during the idle stop when the idle stop is temporarily predicted is predicted. Whether or not the off-gas piping is frozen is determined based on the temperature and the freezing temperature of the off-gas piping.

  According to such an operation method of the fuel cell system, if idling is stopped, if it is determined that the offgas pipe is frozen during the idling stop (freezing determination step), idling stop is prohibited (prohibition step). Thereby, freezing of off-gas piping during idle stop is prevented.

  Then, when the idle stop is prohibited, the current temperature of the off-gas piping is equal to or higher than the release temperature at which the off-gas piping does not freeze when the idle stop is subsequently performed. Step), idle stop is possible, that is, allowed. Thus, the off-gas piping can be prevented from freezing during the subsequent idle stop while the idle stop control means starts the idle stop at an appropriate timing.

  According to the present invention, it is possible to provide a fuel cell system and an operation method of the fuel cell system that can appropriately stop idling while preventing the off-gas piping from freezing.

It is a figure which shows the structure of the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the fuel cell system concerning this embodiment. FIG. 5 is a map showing a relationship between an idle stop prohibition release temperature (an integrated value of heat balance of off-gas piping, an integrated value of fuel cell stack output), an idle stop time, and an outside air temperature; It is a time chart which shows one operation example of the fuel cell system concerning this embodiment. It is a time chart which shows one operation example of the fuel cell system concerning this embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to this embodiment shown in FIG. 1 is mounted on a fuel cell vehicle (moving body) (not shown). The fuel cell system 1 includes a fuel cell stack 10, an anode system that supplies and discharges hydrogen (fuel gas and reaction gas) to and from the anode of the fuel cell stack 10, and air that contains oxygen with respect to the cathode of the fuel cell stack 10. A cathode system for supplying and discharging (oxidant gas, reaction gas), a power consumption system for consuming the generated power of the fuel cell stack 10, a brake device 51, and the like, and an ECU 60 (Electronic Control Unit) for electronically controlling them. Control device).

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (eg, 200 to 400) solid polymer type single cells, and the plurality of single cells are connected in series. The single cell includes an MEA (Membrane Electrode Assembly) and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane or the like, and an anode and a cathode (electrode) that sandwich the membrane.

The anode and the cathode include a porous body having conductivity such as carbon paper, and a catalyst (Pt, Ru, etc.) supported on the anode and causing an electrode reaction in the anode and the cathode.
Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA, and through holes for supplying and discharging hydrogen or air to all single cells. It functions as a channel 11 (fuel gas channel) and a cathode channel 12 (oxidant gas channel).

When hydrogen is supplied to each anode via the anode flow path 11, the electrode reaction of Formula (1) occurs, and when air is supplied to each cathode via the cathode flow path 12, Formula (2) Thus, a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell. Next, when the fuel cell stack 10 and the motor 41 (external load) are electrically connected and a current is taken out, the fuel cell stack 10 generates power.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

<Anode system>
The anode system includes a hydrogen tank 21 and a normally closed shut-off valve 22.
The hydrogen tank 21 is connected to the inlet of the anode flow path 11 via a pipe 21a, a shutoff valve 22, and a pipe 22a. When the shutoff valve 22 is opened by a command from the ECU 60, hydrogen is supplied from the hydrogen tank 21 to the anode flow path 11 via the shutoff valve 22 and the like.

  A pipe 22 b is connected to the outlet of the anode channel 11. The anode off gas containing unconsumed hydrogen discharged from the anode channel 11 is discharged outside the vehicle through the pipe 22b.

<Cathode system>
The cathode system includes a compressor 31, an intercooler 32, and a three-way valve 33.

The compressor 31 is connected to the inlet of the cathode channel 12 through a pipe 31a, an intercooler 32, and a pipe 32a. When the compressor 31 operates according to a command from the ECU 60, the compressor 31 takes in oxygen-containing air and supplies it to the cathode channel 12.
The compressor 31 operates using the fuel cell stack 10 and / or a battery (not shown) as a power source. The pipe 32a is provided with a humidifier (not shown) that humidifies the air toward the cathode channel 12.

  The intercooler 32 appropriately cools the air that has been heated to a high temperature by being compressed by the compressor 31, and is configured by, for example, an air cooling system.

A pipe 33a, a three-way valve 33, and a pipe 33b are sequentially connected to the outlet of the cathode channel 12. The three-way valve 33 is normally set to a position where the pipe 33a and the pipe 33b communicate with each other. And the humid cathode off gas discharged | emitted from the cathode flow path 12 is discharged | emitted out of a vehicle through piping 33a, 33b.
Therefore, in the present embodiment, the “off-gas piping through which the cathode off-gas flows” includes the piping 33a and the piping 33b.

  A pipe 33c is connected to the three-way valve 33. The pipe 33c is disposed near the intercooler 32 and then opens to the outside of the vehicle. When the three-way valve 33 controlled by the ECU 60 connects the pipe 33a and the pipe 33c, the cathode off-gas is discharged outside the vehicle through the pipes 33a and 33c.

  Here, the cathode off-gas is heated by the fuel cell stack 10 that self-heats with power generation. The warm cathode off-gas flows through the intercooler 32 via the intercooler 32 and warms the air toward the cathode flow path 12 when flowing through the pipe 33 c in the vicinity of the intercooler 32. ing.

  Thereby, for example, when the outside air temperature is extremely low at the time of starting the system, the waste heat of the fuel cell stack 10 is effectively used by warming the air toward the cathode flow path 12 with the cathode off gas in this way. The warm-up of the fuel cell stack 10 is promoted.

When the three-way valve 33 communicates the pipe 33a and the pipe 33b and the cathode off gas does not flow through the pipe 33c, the intercooler 32 is not warmed and the intercooler 32 does not lose its function.
The position where the cathode off gas warms the air toward the cathode flow path 12, that is, the position where heat exchange is performed is not limited to this. For example, the air sucked into the compressor 31 or the air flowing through the pipe 32a and the heat An exchange configuration may be used.

<Power consumption system>
The power consumption system includes a motor 41, a power controller 42, and an output detector 43. The motor 41 is connected to the output terminal of the fuel cell stack 10 via the power controller 42.

The motor 41 is an electric motor serving as a power source for the fuel cell vehicle.
The power controller 42 controls the generated power (current, voltage) of the fuel cell stack 10 in accordance with a command from the ECU 60, and incorporates electronic circuits such as a DC / DC chopper and a DC / DC converter.

  The output detector 43 detects an output current value and an output voltage value of the fuel cell stack 10, and includes a current sensor and a voltage sensor. The output detector 43 is configured to output the detected current value and voltage value to the ECU 60.

Note that a PDU (Power Drive Unit) (not shown) is provided between the motor 41 and the power controller 42 to convert DC power from the power controller 42 into a three-phase AC current and supply the three-phase AC current to the motor 41. .
Further, the power controller 42 is connected to a battery (not shown) that stores surplus generated power of the fuel cell stack 10 and regenerative power from the motor 41. The power controller 42 controls charging / discharging of the battery in accordance with a command from the ECU 60.

<Brake device, etc.>
The brake device 51 is a device that brakes the fuel cell vehicle, and includes a brake pedal, a hydraulic circuit, and the like. When the brake device 51 is activated and brakes the fuel cell vehicle, the brake device 51 outputs an operation signal (such as an ON signal of a brake pedal) to the ECU 60.

  The vehicle speed sensor 52 is a sensor that detects the vehicle speed of the fuel cell vehicle. The vehicle speed sensor 52 outputs the detected vehicle speed to the ECU 60.

  The temperature sensor 53 is a sensor that detects the outside air temperature, and is provided at an appropriate position of the fuel cell vehicle. The temperature sensor 53 is configured to output the detected outside air temperature to the ECU 60.

<ECU>
The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and exhibits various functions according to programs stored therein. In addition, various devices are controlled.

<ECU-Idle stop control function>
The ECU 60 (idle stop control means) has an idle stop control function that idles the fuel cell system 1 (fuel cell vehicle) when a predetermined idle stop condition is satisfied.
The case where the predetermined idle stop condition is satisfied is, for example, a case where the brake device 51 is operated and the vehicle speed input from the vehicle speed sensor 52 is continuously zero for a predetermined time.
When the idle stop condition is satisfied and the idle stop is started, the ECU 60 closes the shut-off valve 22, stops the compressor 31, and stops the power generation of the fuel cell stack 10 by the power controller 42.

<ECU-Freezing judgment function>
The ECU 60 (freezing determination means) is configured to turn off-gas piping (piping) during idle stop that is executed at a predetermined idle stop time (for example, 1 minute) after the idle stop when the idle stop condition is satisfied. 33a, 33b) has a function of determining whether or not to freeze.

  Specifically, the ECU 60 determines that the temperature of the offgas pipe is less than the freezing temperature (for example, 0 ° C.) within the idle stop time when the idling is stopped based on the current temperature of the offgas pipe and the outside air temperature. When it is predicted that the off-gas piping will be frozen, it is determined that the off-gas piping is frozen (see case B in FIG. 4 and cases C and D in FIG. 5). In this case, as the outside air temperature becomes lower, the temperature of the off-gas piping tends to decrease greatly during the temporary idle stop.

Here, the current temperature of the off-gas pipe may be, for example, a structure in which a temperature sensor is attached to the pipe 33a or the like and directly detected by this temperature sensor. In this embodiment, the ECU 60 operates after the system is started (the fuel cell stack 10 The calculation is based on the heat balance (cal / s) of the off-gas piping from the start of power generation to the present, that is, the integrated value (cal) of the heat flow into and out of the off-gas piping (cal / s).
Note that the temperature of the off-gas pipe becomes lower as it goes away from the fuel cell stack 10 and is likely to freeze. Therefore, the temperature of the downstream end of the off-gas pipe may be the temperature of the off-gas pipe.

  That is, the ECU 60 assumes that the temperature of the off-gas piping at the time of system startup is equal to the outside air temperature, and calculates the temperature of the off-gas piping at the time of system startup and the heat balance of the off-gas piping up to the present (heat absorption amount−heat dissipation) The current temperature of the offgas pipe is calculated based on the integrated value integrated over time.

  The heat balance (cal / s) of the off-gas piping is given by the difference (heat absorption amount−heat radiation amount) between the heat absorption amount (cal / s) and the heat release amount (cal / s). Here, as will be described later, the amount of heat absorbed by the off-gas piping depends on the output of the fuel cell stack 10 that self-heats with power generation, the material of the off-gas piping, and the like. Further, the heat release amount of the off-gas piping depends on the outside air temperature, the material of the off-gas piping, and the like.

  In the present embodiment, the ECU 60 outputs the accumulated value (cal) of the heat absorption amount (heat balance) of the off-gas piping to the output (current value and / or voltage value) of the fuel cell stack 10 input from the output detector 43. It is calculated based on the integrated value.

  That is, if the integrated value of the output of the fuel cell stack 10 from the system startup to the present increases, the integrated calorific value of the fuel cell stack 10 that self-heats due to power generation increases. ) Is large and is calculated so that the current temperature of the off-gas piping becomes high. On the contrary, if the integrated value of the output of the fuel cell stack 10 is small, the current temperature of the off-gas piping is calculated to be low.

  In addition, when the temperature of the off-gas piping and the device temperature detected by the temperature sensor attached to the other device have a predetermined correlation, the temperature of the off-gas piping is calculated based on the device temperature and the predetermined correlation. You can also

<ECU-Idle stop prohibition function>
The ECU 60 (prohibiting means) has a function of prohibiting the idling stop when it is determined that the off-gas piping is frozen during the idling stop if the idling stop condition is satisfied.

<ECU-Idle stop prohibition release function>
The ECU 60 (release means) has a function of releasing the prohibition of idling stop, that is, permitting the idling stop and enabling the idling stop when a predetermined release condition is satisfied while the idling stop is prohibited. The case where the predetermined release condition is satisfied is that idling stop is prohibited, and even in the idling fuel cell system 1, even if the current temperature of the off-gas piping is subsequently idle-stopped, the off-gas piping does not freeze. This is the case when the release temperature is exceeded.

  In this case, the lower the outside air temperature (and the easier the off-gas piping dissipates heat), the more the temperature of the off-gas piping drops when the engine is subsequently idled (see FIGS. 4 and 5). As shown, the lower the outside air temperature, the higher the release temperature (the integrated value of the off-gas piping heat balance, the integrated value of the output of the fuel cell stack 10) is set (changed).

  Note that the map of FIG. 3 is obtained by a preliminary test or the like and is stored in the ECU 60 in advance. In the case of a system in which the idle stop time is variable, as shown in FIG. 3, the release temperature is set (changed) so that the release temperature becomes higher as the idle stop time becomes longer.

  Further, when the fuel cell stack travels on a battery (not shown) while the fuel cell stack 10 is idling, the off-gas piping is cooled by the traveling wind, so that the vehicle speed of the fuel cell vehicle running on the battery increases. It is preferable to correct so that the temperature of the off-gas piping is lowered.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 and the operation method thereof will be described with reference to the flowchart of FIG.
Here, in the operation method of the fuel cell system 1 according to the present embodiment, if the idling stop is performed, the freezing determination step for determining whether or not the off-gas piping is frozen during the idling stop and the freezing determination step are performed. If it is determined, it includes a prohibiting step for prohibiting idling stop, and a canceling step for canceling prohibition of idling when the canceling condition is satisfied while the idling stop is prohibited.
In the initial state, the fuel cell stack 10 generates power. Further, the ECU 60 grasps the current temperature of the offgas piping based on the outside air temperature at the time of system startup and the integrated value of the output of the fuel cell stack 10 from the system startup to the present time.

In step S101, the ECU 60 determines whether or not the fuel cell system 1 (fuel cell vehicle) is currently idling (no load state).
If it is determined that there is no power generation request from the accelerator or the air conditioner and the vehicle is currently idle (S101 / Yes), the process of the ECU 60 proceeds to step S102. On the other hand, when it determines with not being idle now (S101 * No), the process of ECU60 progresses to step S113.

In step S102, the ECU 60 determines whether or not a predetermined idle stop condition is satisfied.
When it is determined that the idle stop condition is satisfied (S102 / Yes), the process of the ECU 60 proceeds to step S103. On the other hand, when it is determined that the idle stop condition is not satisfied (S102, No), the process of the ECU 60 proceeds to step S113.

  In step S <b> 103, the ECU 60 detects the outside air temperature via the temperature sensor 53. Further, the ECU 60 calculates the current temperature of the offgas pipe based on the integrated value of the output of the fuel cell stack 10.

  In step S105 (freezing determination step, prohibition step), the ECU 60 thereafter temporarily stops idling based on the outside air temperature and the current temperature of the off-gas piping, and a predetermined idle stop time (for example, 1 minute). If the idle stop is continued at, it is determined whether or not the off-gas piping is frozen during the idle stop.

  When it is determined that the off-gas piping is frozen (S104 / Yes), the process of the ECU 60 proceeds to step S105. Thus, when progressing to step S105, idle stop is prohibited and the idle state of the fuel cell system 1 continues. On the other hand, when it is determined that the off-gas piping is not frozen (S104, No), the process of the ECU 60 proceeds to step S108.

In step S105, the ECU 60 sets a release temperature at which the prohibition of the idle stop can be canceled based on a predetermined idle stop time, the outside air temperature, and the map of FIG.
When the outside air temperature is extremely low while the idling stop is prohibited, the three-way valve 33 causes the pipe 33a and the pipe 33c to communicate with each other in order to effectively use the waste heat of the fuel cell stack 10. The air toward the cathode channel 12 may be heated.

  In step S106, the ECU 60 detects the output (current value, voltage value) of the fuel cell stack 10 via the output detector 43.

In step S107 (release step), the ECU 60 determines whether or not the current temperature of the off-gas piping calculated based on the integrated value of the output of the fuel cell stack 10 is equal to or higher than the release temperature.
When it is determined that the current temperature of the off-gas piping is equal to or higher than the release temperature (Yes in S107), the process of the ECU 60 proceeds to step S108. In this way, when the process proceeds to step S108, the prohibition of idle stop is released. On the other hand, when it determines with the present temperature of off-gas piping not being more than a cancellation | release temperature (S107 * No), the process of ECU60 progresses to step S109.

In step S108, the ECU 60 starts idling stop.
Specifically, the ECU 60 stops the compressor 31 and stops power consumption by the compressor 31. In addition, the ECU 60 closes the shut-off valve 22 and stops the supply of hydrogen to the anode flow path 11, and stops the power generation of the fuel cell stack 10 by the power controller 42. Thereby, the hydrogen consumption by the fuel cell stack 10 is stopped, the remaining amount of hydrogen in the hydrogen tank 21 is secured, and the fuel consumption of the fuel cell vehicle is increased.
Thereafter, the processing of the ECU 60 proceeds to step S110.

In step S109, the ECU 60 determines whether or not the idle stop condition is continuously established.
When it is determined that the idle stop condition is satisfied (S109 / Yes), the process of the ECU 60 proceeds to step S106. On the other hand, when it is determined that the idle stop condition is not satisfied (No in S109), the process of the ECU 60 proceeds to Step S113. For example, when the brake is released or the accelerator is depressed, it is determined that the idle stop condition is not satisfied.

In step S110, the ECU 60 uses the built-in clock to determine whether or not a predetermined idle stop time has elapsed after starting the idle stop in step S108.
When it is determined that the idle stop time has elapsed (S110 / Yes), the process of the ECU 60 proceeds to step S111. On the other hand, when it determines with the idle stop time not having passed (S110 * No), the process of ECU60 progresses to step S112.

In step S111, the ECU 60 ends (cancels) the idle stop.
Specifically, the ECU 60 opens the shut-off valve 22 and supplies hydrogen to the anode channel 11, operates the compressor 31, and supplies air to the cathode channel 12. Then, the ECU 60 controls the power controller 42 to generate power again in the fuel cell stack 10.
Thereafter, the processing of the ECU 60 proceeds to step S113.

In step S112, the ECU 60 determines whether or not the idle stop condition is continuously established.
When it is determined that the idle stop condition is satisfied (S112 / Yes), the process of the ECU 60 proceeds to step S110. On the other hand, when it is determined that the idle stop condition is not satisfied (S112 / No), the process of the ECU 60 proceeds to step S111.

In step S113, the ECU 60 normally generates power in the fuel cell stack 10. That is, the ECU 60 causes the fuel cell stack 10 to generate power in response to the power generation request amount based on the accelerator opening.
Thereafter, the process of the ECU 60 returns to the start through a return.

≪Effect of fuel cell system≫
According to such a fuel cell system 1, the following effects are obtained.
Even if the idle stop condition is satisfied (S102 / Yes), if it is determined that the offgas pipe is frozen during the idle stop (S104 / Yes), the idle stop is prohibited, so the offgas pipe is frozen. Can be prevented.

In addition, when the current temperature of the off-gas piping is equal to or higher than the release temperature while the idle stop is prohibited (Yes at S107), the prohibition of the idle stop is canceled and the off-gas piping is frozen during the subsequent idle stop. While being prevented, the idle stop can be started at an appropriate timing (S108).
≪Example of fuel cell system operation≫
Next, an operation example of the fuel cell system 1 will be described with reference to FIGS.
As shown in case A of FIG. 4, when the idle stop condition is satisfied (S102 / Yes), when it is determined that the off-gas piping is not frozen if the idle stop is temporarily performed (S104 / No), the idle stop is started. (S108).

  On the other hand, as shown in case A of FIG. 4 and cases C and D of FIG. 5, when the idle stop condition is satisfied (Yes in S102), when it is determined that the offgas piping is frozen when the idle stop is temporarily performed ( S104 / Yes), idle stop is prohibited. In each case, after an appropriate release temperature is set (S105), when the current temperature of the off-gas piping reaches the unlocking temperature (Yes in S107), the prohibition of idle stop is canceled and the idle stop is started. (S108).

As mentioned above, although one Embodiment of this invention was described, it is not limited to this, For example, it can deform | transform as follows.
In the above-described embodiment, the purpose is to prevent freezing of the pipe 33a through which the cathode off-gas flows, but instead of or in addition to this, it is possible to prevent freezing of the pipe 22b through which the anode off-gas flows. It may be aimed at.
In the above-described embodiment, the configuration in which the fuel cell system 1 is mounted on a fuel cell vehicle (four-wheeled vehicle) is exemplified, but other configurations such as a motorcycle, a train, and a ship may be used. The fuel cell system 1 may be a stationary type.

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
60 ECU (idle stop control means, freeze determination means, prohibition means, release means)

Claims (6)

A fuel cell that generates electricity by supplying reactive gas;
Off-gas piping through which off-gas discharged from the fuel cell flows;
Idle stop control means for controlling idle stop of the system;
If it is idle stopped, a freezing determination means for determining whether or not the off-gas piping is frozen during the idle stop,
When the freezing determining means determines that it is frozen, a prohibiting means for prohibiting idle stop;
A release means for releasing the prohibition of the idle stop by the prohibit means when the release condition for the prohibition of the idle stop is satisfied while the idle stop is prohibited by the prohibit means;
With
The release condition is satisfied when the current temperature of the off-gas pipe is equal to or higher than a release temperature at which the off-gas pipe is not frozen when idling is stopped thereafter .
The fuel cell system , wherein the release temperature is changed to be higher when the outside air temperature is lower, and the release temperature is changed to be higher when the idle stop time for idling is longer . The fuel cell system according to claim 1, wherein the current temperature of the off-gas pipe is calculated based on an integrated value of a heat balance of the off-gas pipe. The fuel cell system according to claim 2, wherein the heat balance of the off-gas piping is calculated based on an output of the fuel cell that self-heats with power generation. The freezing determination means predicts the temperature of the offgas pipe during the idle stop when the idle stop is temporarily performed based on the current temperature of the offgas pipe and the outside air temperature, and the predicted temperature of the offgas pipe Based on the freezing temperature, it is determined whether or not the off-gas piping is frozen.
The fuel cell system according to any one of claims 1 to 3, wherein A fuel cell that generates electricity by supplying reactive gas;
Off-gas piping through which off-gas discharged from the fuel cell flows;
Idle stop control means for controlling idle stop of the system;
A method for operating a fuel cell system comprising:
If the idle stop is performed, a freezing determination step for determining whether or not the offgas pipe is frozen during the idle stop,
A prohibiting step for prohibiting idle stop when it is determined that the freezing determination step is frozen;
A release step for releasing the prohibition of idling stop when the canceling condition of prohibiting the idling stop is satisfied while prohibiting the idling stop;
Including
The release condition is satisfied when the current temperature of the off-gas pipe is equal to or higher than a release temperature at which the off-gas pipe is not frozen when idling is stopped thereafter .
The operation of the fuel cell system is characterized in that when the outside air temperature is lowered, the release temperature is changed so as to be increased, and when the idle stop time for idling is prolonged, the release temperature is changed so as to be increased. Method. In the freezing determination step, based on the current temperature of the off-gas piping and the outside air temperature, the temperature of the off-gas piping during the idling stop when the idling is stopped is predicted, and the predicted temperature of the off-gas piping Based on the freezing temperature, it is determined whether or not the off-gas piping is frozen.
The operation method of the fuel cell system according to claim 5.

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