JP5091903B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In recent years, the development of fuel cells that generate electricity by supplying hydrogen (fuel gas) and oxygen-containing air (oxidant gas) has been promoted. For example, it is expected as a power source for fuel cell vehicles (moving bodies). ing. Such a fuel cell has an anode flow path (fuel gas flow path) through which hydrogen flows and a cathode flow path (oxidant gas flow path) through which air flows.

An anode offgas passage (fuel offgas passage) through which anode offgas (fuel offgas) flows is connected to an outlet of the anode passage, and a gas-liquid separator, a purge valve is connected to the anode offgas passage. A scavenging gas discharge valve, a drain valve, etc. (both are discharge devices) are provided (see Patent Documents 1 and 2).
Further, a cathode offgas passage (oxidant offgas passage) through which a cathode offgas (oxidant offgas) flows is connected to the outlet of the cathode passage, and a humidifier and a back pressure valve are connected to the cathode offgas passage. , A diluter, etc. (both are discharge devices) (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2005-267961 JP 2008-282794 A

Here, when the fuel cell generates power, water vapor (generated water) is generated at the cathode, and a part of the generated water passes through the MEA (Membrane Electrode Assembly) and cross leaks into the anode flow path. Accordingly, the anode off-gas and cathode off-gas are humid and contain moisture (water vapor and condensed water).
Therefore, moisture adheres and stays on the discharging device such as the back pressure valve. Therefore, if the system is exposed to a low-temperature environment (for example, 0 ° C. or lower) after the power generation of the fuel cell is stopped, the discharging device such as the back pressure valve may be frozen.

  In view of this, a method is conceivable in which a temperature sensor is attached to each discharging device, and the water that stays is removed based on the temperature detected by each temperature sensor to prevent freezing. However, when a plurality of temperature sensors are attached, the cost required for the system configuration increases and the system weight increases.

  Therefore, an object of the present invention is to provide a fuel cell system that prevents freezing of a discharge device such as a back pressure valve while simplifying the system configuration.

As means for solving the above problems, the present invention has a fuel gas flow path and an oxidant gas flow path, wherein the fuel gas flow path is fuel gas, and the oxidant gas flow path is oxidant gas. A fuel cell that generates electricity by being supplied; a fuel off-gas channel connected to an outlet of the fuel gas channel, through which the fuel off-gas discharged from the fuel gas channel flows; and an oxidant gas channel An oxidant off-gas channel connected to an outlet and through which an oxidant off-gas discharged from the oxidant gas channel flows; and a discharge device provided in the fuel off-gas channel or the oxidant off-gas channel; A staying water removing means for removing the water staying in the discharge device, and a control means for controlling the staying water removing means, wherein the control means controls the flow rate of the oxidant gas supplied to the fuel cell. Integrated value, previous Integrated value of the power generation current of the fuel cell, the integrated value of the generated power of the fuel cell, based on a plurality of the temperature of the discharge device estimates respectively, the average value of the estimated temperature is less than the determination threshold In this case, the retained water removing process for removing the moisture of the discharge device by the retained moisture removing unit is performed after scavenging the oxidant gas flow path .

According to such a fuel cell system, the temperature of the discharge device is estimated based on a plurality of integrated values of the flow rate of the oxidant gas, the integrated value of the generated current, and the integrated value of the generated power . When the average value of the temperatures is less than the determination threshold value , the control unit executes the retained moisture removal process by the retained moisture removing unit, and removes the moisture from the discharge device. Thereby, the discharging device is not frozen thereafter.
Further, since the temperature sensor for detecting the temperature of the discharging device is not provided, the system configuration is simplified.

  The fuel cell system further includes an outside air temperature sensor that detects an outside air temperature, and the control unit corrects the temperature of the discharge device to be low when the outside air temperature detected by the outside air temperature sensor is low. It is characterized by that.

  According to such a fuel cell system, when the outside air temperature becomes low, correction is performed so that the temperature of the discharge device becomes low, so that the temperature of the discharge device is appropriately estimated.

In the fuel cell system, the discharge device includes a valve device, and the control means includes an integrated value of the flow rate of the oxidant gas supplied to the fuel cell, an integrated value of the generated current of the fuel cell, Based on a plurality of integrated values of the generated power of the fuel cell, the temperature of the valve device is estimated, and when the average value of the estimated temperature is less than the predetermined temperature which is the determination threshold, the accumulated moisture removal The residual water removal process by the means is performed after scavenging the oxidant gas flow path .

  According to such a fuel cell system, when the estimated temperature of the valve device is lower than the predetermined temperature, the control means executes the retained water removal process by the stayed water removal means. Thereby, freezing of a valve apparatus can be prevented.

The present invention also includes a fuel gas flow path and an oxidant gas flow path, and generates fuel by supplying fuel gas to the fuel gas flow path and supplying oxidant gas to the oxidant gas flow path. A battery, a fuel off-gas channel connected to an outlet of the fuel gas channel, through which a fuel off-gas discharged from the fuel gas channel flows, and an outlet of the oxidant gas channel; An oxidant off-gas channel through which the oxidant off-gas discharged from the gas channel flows, a discharge device provided in the fuel off-gas channel or the oxidant off-gas channel, and moisture remaining in the discharge device And a control means for controlling the residual water removal means, wherein the control means is an integrated value of the flow rate of the oxidant gas supplied to the fuel cell, and the power generation of the fuel cell. Integrated current, Integrated value of the generated power of the serial fuel cell, a residence moisture removal parameter is a plurality of average value, is less than determination threshold value, the residence moisture removal process for removing water of the discharge device according to the staying water removing means The fuel cell system is executed after scavenging of the oxidant gas flow path .

According to such a fuel cell system, when the stay water removal parameter is less than the determination threshold value, the control unit executes the stay water removal process by the stay water removal unit, and removes the water from the discharge device. Thereby, the discharging device is not frozen thereafter.
Further, since the temperature sensor for detecting the temperature of the discharging device is not provided, the system configuration is simplified.

  The fuel cell system further includes an outside temperature sensor that detects an outside temperature, and the control unit corrects the determination threshold to increase when the outside temperature detected by the outside temperature sensor decreases. And

  According to such a fuel cell system, when the outside air temperature decreases, the determination threshold value is corrected so as to increase. Therefore, it is possible to appropriately determine whether or not to perform the retained water removal process by the retained water removal means.

  Further, in the fuel cell system, the control means executes the determination after stopping the power generation of the fuel cell.

  According to such a fuel cell system, after the power generation of the fuel cell is stopped, the integrated value of the flow rate of the oxidant gas, the integrated value of the generated current of the fuel cell, and the integrated value of the generated power of the fuel cell are not changed (stable In the state), the determination as to whether or not to execute the retained water removal process is executed, so that the determination can be made appropriately.

  Further, in the fuel cell system, the control means performs the determination when monitoring a system state that is executed every predetermined time after the power generation of the fuel cell is stopped.

  According to such a fuel cell system, when the system state is monitored every predetermined time, the determination is performed, that is, repeated. For example, even if the outside air temperature changes after power generation is stopped, It can be determined appropriately by correcting the temperature of the discharge device or the determination threshold corresponding to the outside air temperature.

  Further, in the fuel cell system, the accumulated water removing means is an oxidant gas supply means for supplying an oxidant gas to the oxidant gas flow path of the fuel cell, and the oxidation gas from the oxidant gas supply means. Moisture staying in the discharge device is removed by the agent gas.

  According to such a fuel cell system, the retained water removing means is the oxidant gas supply means, so that the system configuration is simplified.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which prevents freezing of discharge devices, such as a back pressure valve, can be provided, simplifying a system structure.

It is a figure which shows the structure of the fuel cell system which concerns on 1st Embodiment. It is a time chart explaining the outline | summary (temperature change of a fuel cell stack and a back pressure valve) of this invention. It is a map which shows the relationship between the air flow integrated value, the current integrated value, the power integrated value, and the current temperature of the back pressure valve. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 2nd Embodiment.

<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, when the current temperature of the back pressure valve 32 that is a discharge device is estimated and it is determined that the back pressure valve 32 may freeze after power generation of the fuel cell stack 10 is stopped, the back pressure valve The structure which removes the water | moisture content (condensation water, water vapor | steam) which stays in 32 is illustrated.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to the first 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. (Oxidant gas, reactive gas) cathode system, scavenging gas introduction system for guiding the scavenging gas from the cathode system to the anode system when scavenging the fuel cell stack 10, and power consumption for consuming the fuel cell stack 10 power The system and an ECU 70 (Electronic Control Unit) for electronically controlling them are provided.

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (for example, 200 to 400) solid polymer type single cells 11, and the plurality of single cells 11 are connected in series. The single cell 11 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 provided 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 the single cells 11. It functions as an anode channel 12 (fuel gas channel) and a cathode channel 13 (oxidant gas channel).

When hydrogen is supplied to each anode via the anode flow path 12, the electrode reaction of Formula (1) occurs, and when air is supplied to each cathode via the cathode flow path 13, Formula (2) Thus, a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell 11. Next, the fuel cell stack 10 and an external load such as a motor 51 described later are electrically connected, and when the current is taken out, the fuel cell stack 10 generates power.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

  Since moisture (water vapor) is generated at the cathode in this way, the cathode off-gas discharged from the cathode becomes humid and contains moisture (water vapor, condensed water, etc.). Further, a part of the generated moisture permeates the MEA and cross leaks to the anode flow path 12, so that the anode off-gas discharged from the anode is also humid and contains moisture.

<Anode system>
The anode system includes a hydrogen tank 21, a normally closed shut-off valve 22, an ejector 23, a gas-liquid separator 24 (discharge device), a normally closed purge valve 25 (discharge device), and a normally closed valve. A scavenging gas discharge valve 26 (discharge device) and a normally closed drain valve 27 (discharge device) are provided.

  The hydrogen tank 21 is connected to the inlet of the anode flow path 12 via a pipe 21a, a shutoff valve 22, a pipe 22a, an ejector 23, and a pipe 23a. When the shutoff valve 22 is opened by a command from the ECU 70, hydrogen is supplied from the hydrogen tank 21 to the anode flow path 12 through the shutoff valve 22 and the like.

  The outlet of the anode channel 12 is connected to the intake port of the ejector 23 via a pipe 24a, a gas-liquid separator 24, and a pipe 24b. Then, the anode offgas (fuel offgas) containing unconsumed hydrogen discharged from the anode flow path 12 is returned to the ejector 23 through the pipe 24a and the like, and then resupplied to the anode flow path 12. It has become.

<Gas-liquid separator>
The gas-liquid separator 24 separates moisture (condensation water, water vapor) contained in the anode off gas, and temporarily stores the separated moisture in, for example, the bottom (tank portion).
As a gas-liquid separation method in the gas-liquid separator 24, for example, (1) a method of increasing the anode off-gas channel cross-sectional area to decrease the flow rate and separating water by retaining its own weight. And (2) a system in which the water vapor of the anode off-off gas is condensed by a refrigerant pipe through which a low-temperature refrigerant flows, and (3) a system in which the anode off-gas is meandered or swirled and separated by applying centrifugal force to moisture. , Etc. can be adopted.

<Purge valve>
The pipe 24b is connected to a diluter 33 which will be described later via a pipe 25a, a purge valve 25, and a pipe 25b.
The purge valve 25 discharges (purges) impurities (water vapor, nitrogen, etc.) contained in the anode off-gas that is discharged from the anode flow path 12 and circulates through the pipe 24a and the pipe 24b, for example, during power generation of the fuel cell stack 10. In the case, it is opened by the ECU 70.
For example, the ECU 70 determines that the impurities need to be discharged when the voltage (cell voltage) of the single cells constituting the fuel cell stack 10 is equal to or lower than a predetermined cell voltage, and opens the purge valve 25. It has become. The cell voltage is detected, for example, via a voltage sensor (cell voltage monitor) that detects the voltage of a single cell.

<Scavenging gas discharge valve>
Further, the pipe 24b upstream from the connection position of the pipe 25a is connected to a diluter 33 described later via the pipe 26a, the scavenging gas discharge valve 26, and the pipe 26b.
The scavenging gas discharge valve 26 discharges the scavenging gas discharged from the anode flow path 12 and the pushed moisture to the diluter 33 (external) when the anode flow path 12 is scavenged. Open with 27.

<Drain valve>
The bottom of the gas-liquid separator 24 is connected to a diluter 33 described later through a pipe 27a, a drain valve 27, and a pipe 27b.
The drain valve 27 is opened by the ECU 70 when the water stored in the bottom of the gas-liquid separator 24 is discharged to the diluter 33. The amount of stored water in the gas-liquid separator 24 is detected (calculated) based on the water level sensor and the accumulated current value of the fuel cell stack 10.

Therefore, in the first embodiment, the anode offgas passage (fuel offgas passage) through which the anode offgas (fuel offgas) discharged from the anode passage 12 (fuel gas passage) flows is the pipes 24a, 24b, 25a. 25b, 26a, 26b, 27a, 27b.
In the anode off-gas flow path configured as described above, a gas-liquid separator 24, a purge valve 25 (valve device), a scavenging gas discharge valve 26 (valve device), and a drain valve 27 (valve device) are used as discharge devices. Is provided.

<Cathode system>
The cathode system includes a compressor 31 (oxidant gas supply means, scavenging gas supply means, and accumulated water removal means), a normally open back pressure valve 32, a diluter 33, and a mass flow sensor 34.

The compressor 31 is connected to the inlet of the cathode channel 13 via a pipe 31a. When the compressor 31 operates in accordance with a command from the ECU 70, the compressor 31 takes in oxygen-containing air and supplies the air to the cathode channel 13 via the pipe 31a.
Further, the compressor 31 functions as a scavenging gas supply means for supplying a scavenging gas when scavenging the fuel cell stack 10.
Further, the compressor 31 functions as a retained moisture removing unit that supplies scavenging gas for blowing away moisture when removing the moisture remaining in the back pressure valve 32.

  In addition, the humidifier (not shown) is provided so that the piping 31a and the piping 32a may be straddled. This humidifier incorporates a plurality of hollow fiber membranes having moisture permeability, and through this hollow fiber membrane, air directed to the cathode channel 13 and the humid cathode off gas discharged from the cathode channel 13 Moisture exchange is performed between them to humidify the air toward the cathode channel 13.

The outlet of the cathode channel 13 is connected to the diluter 33 via a pipe 32a, a back pressure valve 32, and a pipe 32b. And the cathode off gas discharged | emitted from the cathode flow path 13 (cathode) is guide | induced to the diluter 33 through the piping 32a etc. FIG.
The back pressure valve 32 is configured by, for example, a butterfly valve, and controls the air pressure in the cathode flow path 13 by controlling the opening degree by the ECU 70 based on the accelerator opening degree.

  The diluter 33 is a container that mixes the anode off-gas from the purge valve 25 and the cathode off-gas (dilution gas) from the pipe 32b and dilutes the hydrogen in the anode off-gas with the cathode off-gas. It has space. The diluted gas is discharged out of the vehicle through the pipe 33a.

Therefore, in the first embodiment, the cathode offgas channel (oxidant offgas channel) through which the cathode offgas (oxidant offgas) discharged from the cathode channel 13 (oxidant gas channel) flows is the pipe 32a, 32b and 33a are provided.
A humidifier (not shown), a back pressure valve 32 (valve device), and a diluter 33 are provided in the cathode offgas flow path configured as described above as discharge devices.

The mass flow sensor 34 is attached to the intake side of the compressor 31, detects the mass flow rate (g / s) of air sucked into the compressor 31, and outputs it to the ECU 70. During the power generation of the fuel cell stack 10, the air discharged from the compressor 31 is supplied to the cathode flow path 13, so the mass flow rate detected by the mass flow sensor 34 is the air supplied to the cathode flow path 13. Is approximately equal to the mass flow rate.
Instead of the mass flow sensor 34, a volume flow sensor that detects a volume flow rate (L / s) may be used. Further, the mass flow sensor 34 only needs to be able to detect the flow rate of the air flowing through the cathode flow path 13, and may be configured to be attached to the pipe 31a, for example.

<Scavenging gas introduction system>
The scavenging gas introduction system includes a normally closed scavenging gas introduction valve 41. The upstream side of the scavenging gas introduction valve 41 is connected to the pipe 31a via a pipe 41a, and the downstream side of the scavenging gas introduction valve 41 is connected to the pipe 23a via a pipe 41b.
When the scavenging gas introduction valve 41 is opened by the ECU 70 while the compressor 31 is operating during scavenging of the fuel cell stack 10 (anode passage 12), the scavenging gas from the compressor 31 is introduced into the anode passage 12. It has come to be.

<Power consumption system>
The power consumption system includes a traveling motor 51, a power controller 52, and an output detector 53. The motor 51 is connected to an output terminal (not shown) of the fuel cell stack 10 via a power controller 52 and an output detector 53.

The motor 51 is an external load that generates the driving force of the fuel cell vehicle using electric power.
The power controller 52 is a device that controls the generated power (output current, output voltage) of the fuel cell stack 10 in accordance with a command current value input from the ECU 70, and an electronic circuit such as a DC / DC chopper, a DC / DC converter, or the like. It has.

  The output detector 53 is a device that detects the current output current and output voltage of the fuel cell stack 10, and includes a current sensor and a voltage sensor. The output detector 53 is configured to output the detected output current and output voltage to the ECU 70.

<Other equipment>
The IG 61 is a start switch of the fuel cell system 1 (fuel cell vehicle), and is provided around the driver's seat. Moreover, IG61 is connected with ECU70, ECU70 detects the ON / OFF signal of IG61.

  The outside air temperature sensor 62 is a sensor that detects the outside air temperature, and is attached to an appropriate place of the fuel cell vehicle. The outside air temperature sensor 62 outputs the detected outside air temperature to the ECU 70.

<ECU>
The ECU 70 (control means) 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 according to a program stored therein, It exhibits various functions and controls various devices.

<Outline of the present invention>
Here, the outline | summary of this invention is demonstrated with reference to FIG.

<Fuel cell stack temperature>
As shown in FIG. 2, it is considered that the temperature of the fuel cell stack 10 and the temperature of the back pressure valve 32 during power generation stop (system stop) are substantially equal to the outside air temperature.
When power generation starts, the temperature of the fuel cell stack 10 rises due to self-heating due to power generation, and is maintained at a steady temperature (FC steady temperature, for example, 80 to 90 ° C.) regardless of the outside air temperature. That is, the current temperature of the fuel cell stack 10 is estimated based on the temperature at the start of power generation and the amount of heat generated by the fuel cell stack 10 from the start of power generation to the present.

Here, the calorific value of the fuel cell stack 10 includes the integrated value of the flow rate of air supplied to the fuel cell stack 10 (integrated value of air flow rate), the integrated value of current of the fuel cell stack 10 (current integrated value), and the fuel cell. It is calculated based on at least one of the integrated power values (power integrated value) of the stack 10. That is, as the air flow integrated value, current integrated value, and power integrated value increase, the amount of heat generated by the fuel cell stack 10 from the start of power generation to the present increases.
Therefore, the current temperature of the fuel cell stack 10 is estimated based on at least one of the temperature at the start of power generation (outside air temperature), the air flow integrated value, the current integrated value, and the power integrated value.

<Temperature of back pressure valve>
On the other hand, since the back pressure valve 32 is arranged away from the fuel cell stack 10, the temperature of the back pressure valve 32 rises more gently than the temperature of the fuel cell stack 10 after the start of power generation, and then reaches a steady temperature (back pressure valve steady state). Temperature).

Further, the temperature difference ΔT between the temperature of the back pressure valve 32 and the temperature of the fuel cell stack 10 increases as the distance between the back pressure valve 32 and the fuel cell stack 10 increases, and increases as the outside air temperature decreases. Here, since the distance between the back pressure valve 32 and the fuel cell stack 10 is a fixed value according to the system configuration, the temperature difference ΔT changes based on the outside air temperature.
Accordingly, the current temperature of the back pressure valve 32 is estimated based on the current temperature of the fuel cell stack 10 and the outside air temperature (temperature difference ΔT1).

Then, as described above, the current temperature of the fuel cell stack 10 is estimated based on at least one of the temperature at the start of power generation (outside air temperature), the air flow integrated value, the current integrated value, and the power integrated value. Therefore, the current temperature of the back pressure valve 32 is estimated based on the temperature at the start of power generation (outside air temperature), at least one of the air flow integrated value, the current integrated value, and the power integrated value, and the current outside air temperature. Will be.
Here, the integrated air flow value, the integrated current value, and the integrated power value are parameters related to whether or not to perform the stay water removal process for removing the water staying in the back pressure valve 32, and are therefore collectively referred to as a stay water removal parameter. .
When the fuel cell vehicle does not travel for a long time, that is, when the operation time of the fuel cell system 1 is not a long time, the outside air temperature at the start of power generation and the current outside air temperature can be substantially equal.

<ECU—Back pressure valve temperature estimation function>
Therefore, the ECU 70 (back pressure valve temperature estimation means) has a function of estimating the current temperature of the back pressure valve 32 in consideration of the temperature change characteristics of the fuel cell stack 10 and the back pressure valve 32 described above.
That is, the ECU 70 assumes that the outside air temperature at the start of power generation is substantially equal to the current outside air temperature, and at least one of the outside air temperature at the start of power generation, the air flow integrated value, the current integrated value, and the power integrated value, Based on the map of FIG. 3, the current temperature of the back pressure valve 32 is estimated. That is, when the outside air temperature decreases, the temperature of the back pressure valve 32 is corrected so as to decrease.
3 is obtained by a preliminary test or the like and stored in the ECU 70 in advance.

<ECU-Residual moisture removal determination function>
Based on the current temperature of the back pressure valve 32 and a predetermined temperature (determination threshold), the ECU 70 (residual water removal determination means) should prevent the back pressure valve 32 from freezing when the current temperature is lower than the predetermined temperature. , A function for determining that it is necessary to remove moisture remaining in the back pressure valve 32 is provided.
The predetermined temperature is a temperature at which it is determined that it is necessary to remove moisture, and is slightly higher than the temperature at which moisture freezes (0 ° C.), and is set to 3 to 5 ° C., for example.

<ECU-Residual moisture removal processing execution function>
When the ECU 70 determines that it is necessary to remove the moisture remaining in the back pressure valve 32, the compressor 31 is operated, the scavenging gas is sent to the back pressure valve 32, and the retained moisture that removes the moisture remaining in the back pressure valve 32 is removed. A function for executing the removal process is provided.

<ECU-scavenging judgment / execution function>
The ECU 70 has a function of determining whether or not the fuel cell stack 10 needs to be scavenged after stopping the power generation of the fuel cell stack 10 and executing a scavenging process when it is determined that scavenging is necessary.

Specifically, when the outside air temperature is lower than a predetermined temperature (for example, 5 ° C.) at which the scavenging is set in advance, the fuel cell stack 10 may be frozen as it is, so it is necessary to scavenge. It is set to determine that there is.
Then, when such determination is made, the ECU 70 operates the compressor 31 and then supplies the scavenging gas from the compressor 31 to the anode flow path 12 and the cathode flow path 13. It is set to push out the staying moisture and scavenge the fuel cell stack 10.

Note that the anode channel 12 and the cathode channel 13 may be scavenged simultaneously, for example, the cathode channel 13 and the anode channel 12 may be scavenged in this order.
When scavenging the cathode flow path 13 in this way, the water pushed out from the cathode flow path 13 may stay in the back pressure valve 32. Therefore, although it will not be mentioned in the operation description to be described later, It is desirable to execute after scavenging the cathode flow path 13.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 will be described with reference to FIG.
When the IG 62 is turned on, the process of FIG. 4 starts. Further, the outside air temperature (the temperature of the back pressure valve 32) when the IG 62 is turned on (when power generation is started) is temporarily stored in the ECU 70 in conjunction with the IG 62 being turned on.

In step S <b> 101, the ECU 70 starts power generation of the fuel cell stack 10.
Specifically, the ECU 70 determines that there has been a start request from the driver, opens the shut-off valve 22, supplies hydrogen to the anode flow path 12, operates the compressor 31, and supplies air to the cathode flow path 13. . Then, the ECU 70 starts taking out the current from the fuel cell stack 10 by the power controller 52 and starts the power generation of the fuel cell stack 10.

In step S102, the ECU 70 estimates the current temperature of the back pressure valve 32.
Specifically, the ECU 70 determines the outside air temperature at the start of power generation (the temperature of the back pressure valve 32), at least one of the air flow integrated value, the current integrated value, and the power integrated value from the start of power generation to the present, and the map of FIG. Based on the above, the current temperature of the back pressure valve 32 is estimated.
When the current temperature of the back pressure valve 32 is estimated based on a plurality of integrated air flow values, integrated current values, and integrated power values, for example, the estimated temperatures may be averaged.

In step S103, the ECU 70 determines whether or not the IG 61 is turned off.
When it is determined that the IG 61 has been turned off (S103 / Yes), the processing of the ECU 70 proceeds to step S104. On the other hand, when it is determined that the IG 61 is not turned off (No in S103), the process of the ECU 70 returns to Step S102.

In step S104, the ECU 70 stops the power generation of the fuel cell stack 10.
Specifically, the ECU 70 determines that there has been a stop request from the driver, stops taking out the current from the fuel cell stack 10 by the power controller 52, and stops the power generation of the fuel cell stack 10. Then, the ECU 70 closes the shut-off valve 22 and stops the compressor 31.

In step S105, the ECU 70 determines whether or not the temperature of the back pressure valve 32 estimated in step S102 is less than a predetermined temperature (determination threshold).
When it determines with the temperature of the back pressure valve 32 being less than predetermined temperature (S105 * Yes), the process of ECU70 progresses to step S106. On the other hand, when it determines with the temperature of the back pressure valve 32 not being less than predetermined temperature (S105 * No), the process of ECU70 progresses to step S107.

Note that the determination process in step S105 is performed not only immediately after the power generation of the fuel cell stack 10 is stopped, but also when the system state is monitored every predetermined time (30 minutes to 1 hour) after the power generation is stopped. Good.
When the determination process of step S105 is performed during such system state monitoring, the temperature of the back pressure valve 32 gradually decreases from the temperature at the time of power generation stop (see FIG. 2). It is preferable to correct the temperature of the back pressure valve 32 based on the elapsed time from the stop of power generation and the outside air temperature.

In step S <b> 106, the ECU 70 executes a retained water removal process that removes the water remaining in the back pressure valve 32.
Specifically, the ECU 70 operates the compressor 31 and supplies the scavenging gas from the compressor 31 to the back pressure valve 32. Then, the moisture remaining in the back pressure valve 32 is pushed downstream by the scavenging gas and removed from the back pressure valve 32. Thereby, even if it exposes to a low-temperature environment after that, the back pressure valve 32 does not freeze.

In addition, when the retained water removal process is executed, the rotation speed of the compressor 31 is increased compared to the case where the cathode flow path 13 is scavenged so that the water in the back pressure valve 32 is quickly and reliably removed. It is preferable to increase the flow rate of the scavenging gas to be discharged.
Furthermore, a bypass pipe for connecting the pipe 31a and the pipe 32a is provided, and the scavenging gas bypasses the humidifier (not shown) arranged so as to straddle the cathode flow path 13, the pipe 31a, and the pipe 32a, It is good also as a structure supplied to the back pressure valve 32. FIG.
Furthermore, during the retention water removal process, the valve body built in the back pressure valve 32 (butterfly valve or the like) may be actuated (turned) so that water droplets adhering to the valve body can be quickly blown off.

  Then, for example, after the retained water removal process is executed at a predetermined time obtained by a preliminary test or the like, the process of the ECU 70 proceeds to the end.

In step S107, the ECU 70 determines whether or not a predetermined time (for example, 30 minutes to 1 hour) has elapsed after the determination processing in step S105.
When it is determined that the predetermined time has elapsed (S107: Yes), the process of the ECU 70 proceeds to step S105, and the determination process of step S105 is executed.
In this case, since the temperature of the back pressure valve 32 is gradually decreased (see FIG. 2), the temperature of the back pressure valve 32 is based on the temperature at the time of power generation stop, the elapsed time from the power generation stop, and the outside air temperature. Is preferably corrected.

  On the other hand, when it is determined that the predetermined time has not elapsed (No in S107), the ECU 70 repeats the determination process in step S107.

≪Effect of fuel cell system≫
According to such a fuel cell system 1, the following effects are obtained.
Since the temperature of the back pressure valve 32 can be estimated without providing the back pressure valve 32 and a temperature sensor in the immediate vicinity thereof, the system configuration is simplified. Since the temperature of the back pressure valve 32 is corrected based on the outside air temperature, it is appropriately estimated.
And since the detention water removal process is performed based on the estimated temperature of the back pressure valve 32 and the predetermined temperature, the freezing of the back pressure valve 32 can be prevented appropriately.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, For example, it can change as follows in the range which does not deviate from the meaning of this invention. Moreover, you may combine suitably with the structure of 2nd Embodiment mentioned later.

  In the above-described embodiment, the compressor 31 is an oxidant gas supply unit that supplies air to the cathode flow path 13, and is a stagnant moisture removing unit that supplies scavenging gas that removes the moisture remaining in the back pressure valve 32. In addition, for example, a configuration may be adopted in which a nitrogen tank is provided as the staying water removing means, and the water in the back pressure valve 32 is removed by nitrogen from the nitrogen tank.

  In the above-described embodiment, the case where the moisture of the back pressure valve 32 is removed to prevent freezing is exemplified, but the moisture removal target is not limited to this, and a humidifier provided so as to straddle the piping 31a and the piping 32a ( (Not shown), a diluter 33, a gas-liquid separator 24, a purge valve 25, a scavenging gas discharge valve 26, and a drain valve 27 may be used.

  In addition to the configuration of the above-described embodiment, if the configuration includes a temperature sensor that detects the temperature of the fuel cell stack 10, the temperature detected by this temperature sensor may be the outside air temperature, or the temperature detected by the temperature sensor. Based on this, the temperature of the back pressure valve 32 may be estimated.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been illustrated. However, the fuel cell system may be mounted on other mobile bodies such as motorcycles, trains, and ships. Further, the present invention may be applied to a stationary fuel cell system.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, the contents of the program set in the ECU 70 are partially different, the temperature of the back pressure valve 32 is not estimated, and the accumulated moisture removal parameters (air flow integrated value, current integrated value and power when the power generation is stopped) are not estimated. Based on at least one of the integrated values) and a predetermined value (determination threshold), it is determined whether or not to perform the retained water removal process (see FIG. 2).
Further, the predetermined value serving as a determination criterion is corrected so as to increase as the outside air temperature at the time of determination decreases (see FIG. 2).
Hereinafter, a different part from 1st Embodiment is demonstrated.

In the second embodiment, the process of the ECU 70 proceeds to step S201 after step S101.
In step S201, the ECU 70 calculates a stay water removal parameter (at least one of an air flow integrated value, a current integrated value, and a power integrated value).
Thereafter, the process of the ECU 70 proceeds to step S103, and if the determination result in step S103 is No, the process returns to step S201.

In the second embodiment, the process of the ECU 70 proceeds to step S202 after step S104.
In step S202, the ECU 70 determines whether or not the retained water removal parameter when the fuel cell stack 10 stops generating power is less than a predetermined value.
Predetermined values serving as determination criteria are set for each of the air flow integrated value, current integrated value, and power integrated value adopted as the accumulated moisture removal parameter. If the accumulated moisture removal parameter is less than the predetermined value, the back pressure valve 32 is frozen. In order to prevent this, it is set to a value at which it is determined that the remaining water should be removed.

Further, since the back pressure valve 32 is likely to freeze when the outside air temperature decreases, the ECU 70 corrects the predetermined value to increase when the outside air temperature decreases.
Furthermore, if a plurality of accumulated air flow values, accumulated current values, and accumulated power values are employed as the accumulated moisture removal parameter, erroneous determination is less likely to occur.

  Note that the determination process in step S202 is performed not only immediately after the power generation of the fuel cell stack 10 is stopped, but also when the system state is monitored every predetermined time (30 minutes to 1 hour) after the power generation is stopped. Good.

When it is determined that the retained water removal parameter is less than the predetermined value (S202 / Yes), the process of the ECU 70 proceeds to step S106, and in step S106, the ECU 70 executes the retained water removal process. Thereby, the water | moisture content which retains in the back pressure valve 32 is removed, and the back pressure valve 32 does not freeze after that.
On the other hand, when it is determined that the retained water removal parameter is not less than the predetermined value (S202 / No), the process of the ECU 70 proceeds to the end.

  As described above, according to the second embodiment, since it is determined whether or not the retained water removal process is executed without estimating the temperature of the back pressure valve 32, the control flow can be simplified compared to the first embodiment. .

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
11 Single cell (fuel cell)
12 Anode channel (fuel gas channel)
13 Cathode channel (oxidant gas channel)
24 Gas-liquid separator (discharge device)
25 Purge valve (discharge device, valve device)
26 Scavenging gas discharge valve (discharge device, valve device)
27 Drain valve (discharge device, valve device)
24a, 24b, 25a, 25b, 26a, 26b, 27a, 27b Piping (fuel off-gas flow path)
31 Compressor (Oxidant gas supply means, accumulated water removal means)
32 Back pressure valve (discharge device, valve device)
33 Diluter (discharge device)
32a, 32b, 33a Piping (oxidant off-gas flow path)
34 Mass flow sensor 53 Output detector 62 Outside air temperature sensor 70 ECU (control means)

Claims (8)

A fuel cell having a fuel gas channel and an oxidant gas channel, wherein fuel gas is generated by supplying fuel gas to the fuel gas channel and oxidant gas to the oxidant gas channel;
A fuel off-gas channel connected to an outlet of the fuel gas channel and through which the fuel off-gas discharged from the fuel gas channel flows;
An oxidant off-gas channel connected to an outlet of the oxidant gas channel and through which the oxidant off-gas discharged from the oxidant gas channel flows;
A discharge device provided in the fuel offgas flow path or the oxidant offgas flow path;
Retained water removing means for removing water remaining in the discharge device;
Control means for controlling the staying water removing means;
With
The control means, the flow rate integrated value of the fuel cell to supply oxidant gas, the integrated value of the power generation current of the fuel cell, the integrated value of the generated power of the fuel cell, based on a plurality of said a discharge The temperature of the device is estimated, and when the average value of the estimated temperature is less than the determination threshold, the oxidant gas flow path is used to remove the retained moisture removing process for removing the moisture of the discharging device by the retained moisture removing means. A fuel cell system, which is executed after scavenging . It has an outside temperature sensor that detects the outside temperature,
2. The fuel cell system according to claim 1, wherein when the outside temperature detected by the outside temperature sensor is low, the control unit corrects the temperature of the discharge device to be low. The discharge device comprises a valve device;
The control means includes
The temperature of the valve device is estimated based on a plurality of integrated values of the flow rate of the oxidant gas supplied to the fuel cell, integrated values of the generated current of the fuel cell, and integrated values of the generated power of the fuel cell , respectively. And
The retained water removing process by the retained water removing unit is executed after scavenging the oxidant gas flow path when the estimated average value of the temperatures is less than a predetermined temperature which is the determination threshold value. The fuel cell system according to claim 1 or 2. A fuel cell having a fuel gas channel and an oxidant gas channel, wherein fuel gas is generated by supplying fuel gas to the fuel gas channel and oxidant gas to the oxidant gas channel;
A fuel off-gas channel connected to an outlet of the fuel gas channel and through which the fuel off-gas discharged from the fuel gas channel flows;
An oxidant off-gas channel connected to an outlet of the oxidant gas channel and through which the oxidant off-gas discharged from the oxidant gas channel flows;
A discharge device provided in the fuel offgas flow path or the oxidant offgas flow path;
Retained water removing means for removing water remaining in the discharge device;
Control means for controlling the staying water removing means;
With
The control means, the flow rate integrated value of the fuel cell to supply oxidant gas, the integrated value of the power generation current of the fuel cell, the integrated value of the generated power of the fuel cell, a plurality of average values in a residence moisture When the removal parameter is less than the determination threshold, the retained water removing process for removing the moisture of the discharge device by the retained water removing unit is executed after scavenging the oxidant gas flow path. . It has an outside temperature sensor that detects the outside temperature,
5. The fuel cell system according to claim 4, wherein the control unit corrects the determination threshold value so as to increase when an outside air temperature detected by the outside air temperature sensor decreases. The fuel cell system according to any one of claims 1 to 5, wherein the control unit performs the determination after power generation of the fuel cell is stopped. The said control means performs the said determination in the case of the monitoring of the system state performed every predetermined time progress after the power generation stop of the said fuel cell. The one of the Claims 1-6 characterized by the above-mentioned. The fuel cell system described in 1. The stagnant moisture removing means is an oxidant gas supply means for supplying an oxidant gas to the oxidant gas flow path of the fuel cell,
The fuel cell system according to any one of claims 1 to 7, wherein water remaining in the discharge device is removed by an oxidant gas from the oxidant gas supply means.

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