JP5772682B2 - Fuel cell system and control method thereof - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a technique for improving the startability of a fuel cell at a low temperature.

  A polymer electrolyte fuel cell (hereinafter, also simply referred to as “fuel cell”) generates electric power by utilizing proton movement in an electrolyte membrane that exhibits good proton conductivity in a wet state. Therefore, during operation of the fuel cell, it is preferable that the inside of the fuel cell be maintained in a wet state so that the electrolyte membrane is in an appropriate wet state. However, if a large amount of water remains inside the fuel cell after the fuel cell is stopped, the water freezes when the fuel cell is started under a low temperature environment such as below freezing point. In some cases, the start-up performance deteriorates. In order to solve such a problem, a technique for reducing the amount of water in the fuel cell by scavenging the inside of the fuel cell (also referred to as “purge”) at the end of the operation of the fuel cell has been proposed so far (see below). Patent Document 1).

JP 2010-113827 A JP 2011-204447 A JP 2010-153067 A Japanese Patent Laid-Open No. 2004-22198

  However, the scavenging treatment so far has not been able to sufficiently drain the water inside the fuel cell. Moreover, the dark current by temperature measurement was not fully considered. Note that a current that flows during a period in which the ignition key of the vehicle is turned off is generally called “dark current” (also referred to as “dark current”).

  The present invention suppresses freezing by efficiently discharging the amount of water remaining inside the fuel cell while suppressing an increase in dark current due to frequent measurement of the temperature of the fuel cell after the operation is completed. It aims at improving the startability of the fuel cell at the time of start-up.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples. According to one aspect of the present invention, a fuel cell system is provided. The fuel cell system includes a fuel cell, a gas supply unit capable of supplying a purge gas to a gas flow path inside the fuel cell after receiving an instruction to stop the operation of the fuel cell system, and a first representing an outside air temperature. A first temperature measuring unit for measuring the temperature of the fuel cell, a second temperature measuring unit for measuring a second temperature representing a temperature of the fuel cell or a temperature of a portion through which the purge gas flows, and the gas supply unit. And a control unit that performs a scavenging process using the purge gas, and the control unit receives the first and second measurement cycles in a first measurement period after receiving an instruction to stop the operation of the fuel cell. When the second temperature when measured at the first measurement timing is lower than the determination threshold value, the scavenging process with the purge gas is executed, and the second temperature is equal to or higher than the determination threshold value. In the case of 1 and the second temperature are used to predict the second temperature at the next measurement timing, and when the temperature predicted by the control unit is lower than the determination threshold, the next measurement timing is The period until the next measurement timing is made shorter than the first measurement period so that the second temperature becomes the determination threshold. According to this aspect, when the second temperature is likely to be lower than the determination threshold in the next measurement, the second measurement is performed until the next measurement so that the second temperature at the next measurement timing becomes the determination threshold. Since the cycle is shorter than the first measurement cycle, icing of water can be suppressed. Further, since the number of temperature measurements can be suppressed as a whole, an increase in dark current can be suppressed.

[Application Example 1]
A fuel cell system comprising: a fuel cell; a gas supply unit capable of supplying purge gas to a gas flow path inside the fuel cell after receiving an instruction to stop the operation of the fuel cell system; A first temperature measuring unit that measures the temperature of the first temperature, a second temperature measuring unit that measures a temperature of the fuel cell, or a second temperature that represents a temperature of a portion through which the purge gas flows, and the gas supply unit And a control unit that executes a scavenging process using the purge gas, and the control unit receives the first and second measurement cycles in a first measurement period after receiving an instruction to stop the operation of the fuel cell. When the second temperature measured at the first measurement timing is lower than the determination threshold value, the scavenging process using the purge gas is executed, and the second temperature is determined to be the determination threshold value. In the above case, before The first temperature and the second temperature are used to predict the second temperature at the next measurement timing, and when the temperature predicted by the control unit is lower than the determination threshold, the next measurement timing is reached. The fuel cell system is configured such that the period is shorter than the first measurement period.
According to this application example, when the second temperature is likely to be lower than the determination threshold value in the next measurement, the period until the next measurement is made shorter than the first measurement period, so that water freezing is suppressed. can do. Further, since the scavenging process can be performed at a temperature at which the second temperature is lower than the determination threshold value, most of the moisture inside the fuel cell can be condensed, and the moisture inside the fuel cell can be efficiently blown away. Can be improved. Furthermore, since the number of temperature measurements can be suppressed as a whole, an increase in dark current can be suppressed.

[Application Example 2]
In the fuel cell system according to Application Example 1, the control unit calculates a period until the second temperature becomes the determination threshold, sets the period as a second measurement period, and sets the first measurement timing. When the first and second temperatures are measured at the second measurement timing after the second measurement cycle, and the second temperature measured at the second measurement timing is lower than the determination threshold value A fuel cell system that performs a scavenging process with the purge gas.
According to this application example, the first and second temperatures are measured by calculating the period during which the second temperature becomes the determination threshold, so that the measurement timing of the first and second temperatures is appropriate, and the number of times of measurement is determined. By reducing, the increase in the dark current of the fuel cell can be suppressed.

[Application Example 3]
In the fuel cell system according to Application Example 2, when the second measurement period is shorter than the third measurement period shorter than the first measurement period, the control unit sets the third measurement period. A fuel cell system that defines the second measurement timing as the second measurement cycle.
According to this application example, when the second period is shorter than the third period, it is assumed that the temperature of the fuel cell hardly decreases, so that the number of measurements increases and the dark current may increase. Therefore, in this application example, when the second period from which the next measurement timing is calculated is shorter than the predetermined third period, the next measurement period is set as the third period, and the number of measurements is increased. It suppresses the increase in dark current.

[Application Example 4]
In the fuel cell system according to Application Example 2 or 3, when the second temperature measured at the second measurement timing is equal to or higher than the determination threshold, the control unit follows the second measurement timing. The fuel cell system, wherein the first and second temperatures are measured after a lapse of the first measurement period from a measurement timing immediately before the second measurement timing.
If the next measurement after the measurement in the second measurement cycle is after the second measurement cycle, the measurement cycle is shortened, the number of measurements is increased, and the dark current may be increased. On the other hand, if the measurement timing in the second measurement cycle is the starting point and the measurement timing is after the first cycle, the second temperature may fall below freezing point during that time. Therefore, in this application example, the next measurement after the measurement in the second measurement cycle is performed after the first measurement cycle elapses from the measurement performed immediately before the second measurement cycle.

[Application Example 5]
In the fuel cell system according to any one of the application examples 1 to 4, when the first temperature measured at an arbitrary measurement timing is equal to or higher than the determination threshold, the control unit The fuel cell system, wherein the first and second temperatures are measured after the first measurement period has elapsed from the measurement timing.
It is unlikely that the second temperature is lower than the determination threshold when the first temperature is equal to or higher than the determination threshold. Therefore, in this application example, the measurement cycle is set to the first measurement cycle, thereby reducing the number of measurements and suppressing the increase in dark current.

[Application Example 6]
A control method for a fuel cell system, wherein (1) after receiving an instruction to stop the operation of the fuel cell system, a first temperature representing an outside air temperature is measured at a first measurement cycle, and the fuel cell system A step of measuring a second temperature representing the temperature; and (2) if the second temperature measured at the first measurement timing is lower than the determination threshold value, a scavenging process using a purge gas is executed. And (3) predicting the second temperature at the next measurement timing using the first and second temperatures when the second temperature is equal to or higher than a determination threshold; 4) A step of controlling the fuel cell system, comprising: a step of shortening a cycle until the next measurement timing to be shorter than the first measurement cycle when the temperature predicted by the control unit is lower than the determination threshold. Method.
According to this application example, when the second temperature is likely to be lower than the determination threshold value in the next measurement, the period until the next measurement is made shorter than the first measurement period, so that water freezing is suppressed. can do. Further, since the scavenging process can be performed at a temperature at which the second temperature is lower than the determination threshold value, most of the moisture inside the fuel cell can be condensed, and the moisture inside the fuel cell can be efficiently blown away. Can be improved. Furthermore, since the number of temperature measurements can be suppressed as a whole, an increase in dark current can be suppressed.

  The present invention can be realized in various forms, for example, a fuel cell system and a vehicle equipped with the fuel cell system, a system and a vehicle control method, a control device, the system and a vehicle The present invention can be realized in the form of a control method, a computer program for realizing the functions of the control device, a recording medium on which the computer program is recorded, and the like.

It is the schematic which shows the structure of the fuel cell system as one Example of this invention. It is an operation | movement flowchart from a vehicle stop to a purge process. It is explanatory drawing explaining the reason for performing step S120,130. It is explanatory drawing which shows an example of an application example. It is explanatory drawing which shows the case where the temperature of a fuel cell when it measures with a 2nd period is higher than a determination threshold value. It is a graph which shows the temperature change of 0 degreeC vicinity of a fuel cell when outside temperature is -30 degreeC.

A. Example:
FIG. 1 is a schematic diagram showing the configuration of a fuel cell system as an embodiment of the present invention. This fuel cell system 100 is mounted on a fuel cell vehicle and outputs electric power used as driving force in response to a request from a driver. The fuel cell system 100 includes a fuel cell 10, a control unit 20, a cathode gas supply unit 30, a cathode gas discharge unit 40, an anode gas supply unit 50, an anode gas circulation discharge unit 60, and a refrigerant supply unit 70. Is provided.

  The fuel cell 10 is a polymer electrolyte fuel cell that generates power by receiving supply of hydrogen (anode gas) and air (cathode gas) as reaction gases. The fuel cell 10 has a stack structure in which a plurality of single cells 11 that are power generators are stacked. Each single cell 11 has a membrane electrode assembly (not shown) that is a power generator in which electrodes are arranged on both surfaces of the electrolyte membrane, and two separators (not shown) that sandwich the membrane electrode assembly. .

  The electrolyte membrane of the fuel cell 10 can be composed of a solid polymer thin film that exhibits good proton conductivity in a wet state including moisture inside. The electrode can be composed of conductive particles carrying a catalyst for promoting a power generation reaction. As the catalyst, for example, platinum (Pt) can be adopted, and as the conductive particles, for example, carbon (C) particles can be adopted.

  The control unit 20 can be configured by a microcomputer including a central processing unit and a main storage device. The control unit 20 has a function as a power generation control unit that controls each component described below to generate power corresponding to the output request in the fuel cell 10. Further, the control unit 20 has a function as the purge process execution unit 21.

  The purge processing execution unit 21 controls each component of the fuel cell system 100 after the operation of the fuel cell 10 is stopped, and adheres to moisture remaining in the fuel cell 10 and piping / valves of the fuel cell system 100. A scavenging process (purge process) is performed to reduce the water content. The execution procedure of the purge process by the purge process execution unit 21 will be described later.

  The cathode gas supply unit 30 includes a cathode gas pipe 31, an air compressor 32, an air flow meter 33, and an on-off valve 34. The cathode gas pipe 31 is a pipe connected to the cathode side of the fuel cell 10. The air compressor 32 is connected to the fuel cell 10 via the cathode gas pipe 31 and supplies air compressed by taking in outside air to the fuel cell 10 as cathode gas.

  The air flow meter 33 measures the amount of outside air taken in by the air compressor 32 on the upstream side of the air compressor 32, and transmits it to the control unit 20. The control unit 20 controls the amount of air supplied to the fuel cell 10 by driving the air compressor 32 based on the measured value. The on-off valve 34 is provided between the air compressor 32 and the fuel cell 10. The on-off valve 34 is normally closed, and opens when air having a predetermined pressure is supplied from the air compressor 32 to the cathode gas pipe 31.

  The cathode gas discharge unit 40 includes a cathode exhaust gas pipe 41, a pressure regulating valve 43, and a pressure measurement unit 44. The cathode exhaust gas pipe 41 is a pipe connected to the cathode side of the fuel cell 10, and discharges the cathode exhaust gas to the outside of the fuel cell system 100. The pressure regulating valve 43 adjusts the pressure of the cathode exhaust gas in the cathode exhaust gas pipe 41 (back pressure on the cathode side of the fuel cell 10). The pressure measurement unit 44 is provided on the upstream side of the pressure regulating valve 43, measures the pressure of the cathode exhaust gas, and transmits the measured value to the control unit 20. The control unit 20 adjusts the opening degree of the pressure regulating valve 43 based on the measurement value of the pressure measurement unit 44.

  The anode gas supply unit 50 includes an anode gas pipe 51, a hydrogen tank 52, an on-off valve 53, a regulator 54, a hydrogen supply device 55, and a pressure measurement unit 56. The hydrogen tank 52 is connected to the anode of the fuel cell 10 through the anode gas pipe 51, and supplies hydrogen filled in the tank to the fuel cell 10.

  The on-off valve 53, the regulator 54, the hydrogen supply device 55, and the pressure measuring unit 56 are provided in the anode gas pipe 51 in this order from the upstream side (hydrogen tank 52 side). The on-off valve 53 opens and closes according to a command from the control unit 20 and controls the inflow of hydrogen from the hydrogen tank 52 to the upstream side of the hydrogen supply device 55. The regulator 54 is a pressure reducing valve for adjusting the pressure of hydrogen on the upstream side of the hydrogen supply device 55, and its opening degree is controlled by the control unit 20.

  The hydrogen supply device 55 can be configured by, for example, an injector that is an electromagnetically driven on-off valve. The pressure measurement unit 56 measures the pressure of hydrogen on the downstream side of the hydrogen supply device 55 and transmits it to the control unit 20. The control unit 20 controls the amount of hydrogen supplied to the fuel cell 10 by controlling the hydrogen supply device 55 based on the measurement value of the pressure measurement unit 56.

  The anode gas circulation discharge unit 60 includes an anode exhaust gas pipe 61, a gas-liquid separation unit 62, an anode gas circulation pipe 63, a hydrogen circulation pump 64, an anode drain pipe 65, a drain valve 66, and a pressure measurement unit 67. With. The anode exhaust gas pipe 61 is a pipe that connects the outlet of the anode of the fuel cell 10 and the gas-liquid separator 62, and anode exhaust gas containing unreacted gas (such as hydrogen and nitrogen) that has not been used for power generation reaction. Guide to the gas-liquid separator 62.

  The gas-liquid separator 62 is connected to the anode gas circulation pipe 63 and the anode drain pipe 65. The gas-liquid separator 62 separates the gas component and moisture contained in the anode exhaust gas, guides the gas component to the anode gas circulation pipe 63, and guides the moisture to the anode drain pipe 65.

  The anode gas circulation pipe 63 is connected downstream of the hydrogen supply device 55 of the anode gas pipe 51. The anode gas circulation pipe 63 is provided with a hydrogen circulation pump 64, and hydrogen contained in the gas component separated in the gas-liquid separation unit 62 by the hydrogen circulation pump 64 is supplied to the anode gas pipe 51. Sent out.

  As described above, in this fuel cell system 100, during operation of the fuel cell 10, hydrogen contained in the anode exhaust gas is circulated and supplied to the fuel cell 10 again, thereby improving the utilization efficiency of hydrogen. . In the fuel cell system 100 of the present embodiment, the hydrogen circulation pump 64 is used as a driving power source for supplying purge gas to the fuel cell 10 during the purge process, and details thereof will be described later.

  The anode drain pipe 65 is a pipe for discharging the water separated in the gas-liquid separator 62 to the outside of the fuel cell system 100. The drain valve 66 is provided in the anode drain pipe 65 and opens and closes according to a command from the control unit 20. During operation of the fuel cell system 100, the control unit 20 normally closes the drain valve 66 and opens the drain valve 66 at a predetermined drain timing set in advance or at a discharge timing of the inert gas in the anode exhaust gas. open.

  The pressure measuring unit 67 of the anode gas circulation discharge unit 60 is provided in the anode exhaust gas pipe 61. The pressure measuring unit 67 measures the pressure of the anode exhaust gas (back pressure on the anode side of the fuel cell 10) in the vicinity of the outlet of the hydrogen manifold of the fuel cell 10, and the control unit 20 transmits the pressure.

  The refrigerant supply unit 70 includes a refrigerant pipe 71, a radiator 72, a three-way valve 73, a refrigerant circulation pump 75, and two refrigerant temperature measuring units 76a and 76b. The refrigerant pipe 71 is a pipe for circulating a refrigerant for cooling the fuel cell 10, and includes an upstream pipe 71a, a downstream pipe 71b, and a bypass pipe 71c.

  The upstream side pipe 71 a connects the refrigerant outlet manifold provided in the fuel cell 10 and the inlet of the radiator 72. The downstream pipe 71 b connects the refrigerant inlet manifold provided in the fuel cell 10 and the outlet of the radiator 72. One end of the bypass pipe 71c is connected to the upstream pipe 71a via the three-way valve 73, and the other end is connected to the downstream pipe 71b. The control unit 20 controls the opening and closing of the three-way valve 73, thereby adjusting the amount of refrigerant flowing into the bypass pipe 71c and controlling the amount of refrigerant flowing into the radiator 72.

  The radiator 72 is provided in the refrigerant pipe 71 and cools the refrigerant by exchanging heat between the refrigerant flowing through the refrigerant pipe 71 and the outside air. The refrigerant circulation pump 75 is provided on the downstream side pipe 71b on the downstream side (the refrigerant inlet side of the fuel cell 10) from the connection point of the bypass pipe 71c, and is driven based on a command from the control unit 20.

  The two refrigerant temperature measuring units 76 a and 76 b are provided in the upstream pipe 71 a and the downstream pipe 71 b, respectively, and transmit the measured values to the control unit 20. Hereinafter, the refrigerant temperature measurement unit 76a of the upstream pipe 71a is also referred to as “exit side temperature measurement unit 76a”, and the refrigerant temperature measurement unit 76b of the downstream side pipe 71b is also referred to as “inlet side temperature measurement unit 76b”.

  The control unit 20 detects the operating temperature of the fuel cell 10 from the difference between the measured values of the refrigerant temperature measuring units 76a and 76b, and controls the rotational speed of the refrigerant circulation pump 75 based on the operating temperature. The operating temperature of the fuel cell 10 is adjusted. Further, the purge process execution unit 21 uses the measured value of the outlet side temperature measurement unit 76a for determining whether or not the purge process can be performed.

  The fuel cell system 100 further includes an outside air temperature sensor 80 that can measure the outside air temperature (outside air temperature) outside the fuel cell vehicle. The outside air temperature sensor 80 transmits the measurement result to the control unit 20. The purge process execution unit 21 uses the temperature measured by the outside air temperature sensor 80 to determine whether or not the purge process can be performed.

  The fuel cell system 100 includes a secondary battery and a DC / DC converter, although illustration and detailed description are omitted. The secondary battery stores electric power and regenerative power output from the fuel cell 10 and functions as a power source together with the fuel cell 10. The DC / DC converter can control the charge / discharge of the secondary battery and the output voltage of the fuel cell 10. Each component of the fuel cell system 100 described above can be driven even after the fuel cell 10 is stopped by using the power of the secondary battery.

  By the way, as described above, each single cell 11 of the fuel cell 10 includes an electrolyte membrane that exhibits good proton conductivity in a wet state. Therefore, it is desirable to keep the inside of the fuel cell 10 in a wet state during operation of the fuel cell 10. However, after the operation of the fuel cell 10 is finished, if a large amount of moisture remains in the fuel cell 10 or in the connection piping, the moisture will freeze in a low temperature environment such as below freezing point. Such freezing of residual moisture causes problems such as blocking of the flow path of the reaction gas in the fuel cell 10 and its connecting pipe, and causes the startability of the fuel cell 10 to be reduced.

  Therefore, in the fuel cell system 100 of the present embodiment, after the operation of the fuel cell 10 is completed, the purge process execution unit 21 performs a purge process for scavenging the inside of the fuel cell 10 and the flow path of the reaction gas in the connection pipe. . In the present specification, “after completion of operation of the fuel cell 10” means a state after the driver stops the operation of the vehicle (a state in which the so-called ignition key is off), and the fuel cell 10 represents a state in which output of electric power according to a request from the driver is stopped. The purge process and the temperature measurement of the fuel cell 10 are performed by the power of the secondary battery (not shown) after the operation of the fuel cell 10 is finished, and therefore a dark current (also referred to as “dark current”) flows. . Here, a current that flows during a period in which an ignition key (not shown) is turned off is generally called “dark current”. It is preferable to perform the purge process efficiently without increasing the dark current.

  FIG. 2 is an operation flowchart from the vehicle stop to the purge process. In step S100, an ignition key (not shown) of a vehicle (not shown) on which the fuel cell system 100 is mounted is turned off, the fuel cell 10 (FIG. 1) is stopped, and the vehicle is stopped.

  In step S110, the control unit 20 estimates and calculates the temperature of the fuel cell 10 after the basic measurement cycle. Specifically, the control unit 20 acquires the outside air temperature (first temperature) when the fuel cell 10 is stopped from the outside air temperature sensor 80, and the refrigerant that comes out of the fuel cell 10 when the fuel cell 10 is stopped. The temperature (second temperature) is acquired from the refrigerant temperature measurement unit 76a. Here, the temperature of the refrigerant coming out of the fuel cell 10 is estimated to be approximately equal to the temperature of the fuel cell 10. Therefore, hereinafter, the temperature of the refrigerant coming out of the fuel cell 10 is used as the temperature of the fuel cell 10 when calculating the temperature of the fuel cell 10 after the basic measurement cycle.

式（１）で、Ｒは放熱係数（Ｗ／Ｋ）、Ｔは外気温（Ｋ）、Ｔ_Sは燃料電池１０の温度（Ｋ）、ｃは燃料電池の熱容量（Ｊ／Ｋ）、Δｔは基本計測周期の長さ、Ｔ_calは算出した次の基本計測周期後の燃料電池１０の温度（Ｋ）である。なお、外気温Ｔ、燃料電池１０の温度Ｔ_S、次の基本計測周期後の燃料電池１０の温度Ｔ_cal、燃料電池の熱容量ｃは、の温度単位は、絶対温度ではなく、摂氏で表しても良い。 Next, the control unit 20 calculates the temperature of the fuel cell 10 after the basic measurement cycle by the following equation (1).

In Equation (1), R is the heat dissipation coefficient (W / K), T is the outside air temperature (K), T _S is the temperature (K) of the fuel cell 10, c is the heat capacity (J / K) of the fuel cell, and Δt is The length of the basic measurement cycle, T _cal, is the calculated temperature (K) of the fuel cell 10 after the next basic measurement cycle. The temperature unit of the outside air temperature T, the temperature T _S of the fuel cell 10, the temperature T _cal of the fuel cell 10 after the next basic measurement cycle, and the heat capacity c of the fuel cell is expressed in degrees Celsius, not in absolute temperature. Also good.

In step S120, the control unit 20 determines whether or not the estimated temperature of the fuel cell 10 after the next basic measurement cycle is smaller than the determination threshold value _Tth . The determination threshold T _th is preferably set to a temperature in the vicinity of the freezing point that is, for example, about 2 to 5 ° C. higher than the freezing point. If it is in the vicinity of the freezing point, the saturated water vapor pressure at the determination threshold value T _th is low, so that most of the water vapor is condensed into liquid water. The condensed water can be efficiently blown out of the fuel cell 10 by a purge process.

When the estimated temperature of the fuel cell 10 is smaller than the determination threshold value T _th , the control unit 20 proceeds to step S130, and when the estimated temperature of the fuel cell 10 is not smaller than the determination threshold value T _th , The process proceeds to step S140. In step S130, the control unit 20 calculates a time when the temperature of the fuel cell 10 becomes the determination threshold value _Tth, and sets the time as the second period.

FIG. 3 is an explanatory diagram for explaining the reason for performing steps S120 and S130. The horizontal axis in FIG. 3 is the time since the vehicle stopped. The vertical axis represents the temperature. When the control unit 20 measures the temperature of the fuel cell 10 in the basic measurement cycle, the temperature of the fuel cell 10 is greater than the determination threshold T _{th at} timings t1 and t2, but at the timing t3, the temperature of the fuel cell 10 (second 2) is below freezing. When the temperature of the fuel cell 10 (second temperature) falls below freezing point, the water inside the fuel cell 10 may freeze, which may reduce the startability of the fuel cell. Moreover, it is difficult to blow off the frozen water (ice) by the purge process. Therefore, it is preferable that the control unit 20 causes the purge processing execution unit 21 to perform a purge process before the moisture freezes to remove the moisture. In such a case, if the control unit 20 waits for measurement until the next timing t3 in the basic measurement cycle, the water inside the fuel cell 10 may be frozen. Therefore, as shown in the lower diagram of FIG. 3, the control unit 20 advances the next measurement cycle from the basic measurement cycle, and measures the second temperature at the timing t3 ′. At the timing t3 ′, the temperature of the fuel cell 10 is lower than the determination threshold T _th but higher than the freezing point, so that the moisture inside the fuel cell 10 does not freeze. Further, at a temperature lower than the determination threshold T _{th and} higher than the freezing point, the saturated vapor pressure is small, so that water hardly exists as water vapor. That is, most of the water vapor is condensed and becomes liquid water. If the purge process is performed in this state, the water in the fuel cell 10 can be efficiently blown out of the fuel cell 10.

ここでΔＴ_thは、燃料電池１０の温度が判定閾値Ｔ_thとなるまでの推定時間である。なお、他のパラメータの意味は式（１）と同じである。制御部２０は推定時間ΔＴ_thを次回の計測周期（第２の測定周期）とする。第２の測定周期は、計算上、燃料電池１０の温度が判定閾値Ｔ_thとなる時間である。 The control unit 20 calculates the second cycle by the following equation (2).

Here, ΔT _th is an estimated time until the temperature of the fuel cell 10 reaches the determination threshold T _th . The meanings of the other parameters are the same as in equation (1). The control unit 20 sets the estimated time ΔT _th as the next measurement cycle (second measurement cycle). The second measurement cycle is a time during which the temperature of the fuel cell 10 becomes the determination threshold T _th in calculation.

Returning to FIG. If the estimated temperature of the fuel cell 10 after the next basic measurement cycle is not smaller than the determination threshold value _Tth in step S120, in step S140, the control unit sets the next measurement cycle without changing the measurement cycle. Maintain the basic measurement period.

In step S150, the control unit 20 measures the outside air temperature and the temperature of the fuel cell 10 after the elapse of the period determined in step S130 or 140. In step S160, the control unit 20 determines whether or not the outside air temperature is lower than the determination threshold value _Tth . When the outside air temperature is lower than the determination threshold T _th , the control unit 20 proceeds to step S170, and when the outside air temperature is not lower than the determination threshold T _th , the processing proceeds to step S110. Since the fuel cell 10 is cooled by the refrigerant cooled by the outside air temperature, it is unlikely that the temperature of the fuel cell 10 will be lower than the outside air temperature if the outside air temperature is not lower than the determination threshold T _th .

If the outside air temperature is not lower than the determination threshold value _{Tth in} step S160, the process proceeds to step S110. In this case, the measurement cycle is the original basic measurement cycle as defined in step S110. However, the starting point of the period measurement is not the timing at which the measurement at step S160 is performed, but the timing before the measurement at step S160. The reason for setting the measurement cycle as the original basic measurement cycle is as follows. That is, if the measurement is performed in the second measurement cycle, the basic measurement cycle is short, so that the number of measurements increases and the dark current may increase. In the present embodiment, by returning the measurement cycle to the basic measurement cycle, frequent measurement of the outside air temperature and the temperature of the fuel cell 10 in the second measurement cycle is suppressed, and an increase in dark current is suppressed. Further, the reason why the starting point of the period measurement is not the timing at which the measurement at step S160 is performed, but the timing before the measurement at step S160 is as follows. That is, if the next measurement is the basic measurement period with the cycle measurement starting point as the measurement timing of step S160, the moisture in the fuel cell 10 may freeze before the next measurement.

In step S170, the control unit 20 measures the temperature of the fuel cell 10 and determines whether it is lower than the determination threshold value _Tth . When the temperature of the fuel cell 10 is lower than the determination threshold value T _th , the control unit 20 proceeds to step S180, and when the temperature of the fuel cell 10 is not lower than the determination threshold value T _th , at step S160. Similarly to, the process proceeds to step S110.

  In step S180, the control unit causes the purge process execution unit 21 to execute the purge process. Specifically, the purge process execution unit 21 executes the following process. The purge processing execution unit 21 drives the hydrogen circulation pump 64 of the anode gas circulation discharge unit 60 (FIG. 1) to circulate the gas containing hydrogen remaining in the fuel cell 10 as the purge gas. Then, the drain valve 66 is opened at a predetermined timing, and the liquid water separated in the gas-liquid separator 62 is drained. In this way, by performing the purge process for circulating the gas on the anode side of the fuel cell 10, the amount of water remaining in the fuel cell 10 and its connecting piping, the fuel cell 10 and the hydrogen piping 51, The amount of hydrogen remaining in 61 and 63 can be reduced.

FIG. 4 is an explanatory diagram illustrating an example of an application example. FIG. 4 is a graph showing the fuel cell, the outside air temperature, and the measurement timing, in which the horizontal axis and the vertical axis are the same as those in FIG. The temperature measurement timing in FIG. 4 is t1, t2,... T5 (t5 ′). At timing t1, the control unit 20 (FIG. 1) measures the outside air temperature and the temperature of the fuel cell 10. Since the temperature of the fuel cell 10 is higher than the determination threshold value T _th , the control unit 20 does not cause the purge process execution unit 21 to perform the purge process at this timing. The fuel cell estimates the temperature of the fuel cell 10 after the basic measurement period (timing t2) according to step S110 of FIG. Since the estimated temperature is higher than the determination threshold value T _th , the control unit 20 performs the process of step S140 and sets the next measurement cycle as the basic measurement cycle, that is, the timing t2. In step S150, the control unit 20 measures the outside air temperature and the temperature of the fuel cell 10. Since the outside air temperature is equal to or lower than 0 ° C., the answer is Yes in Step S160, and the temperature of the fuel cell 10 is higher than the determination threshold value _Tth at the timing t2, so No in Step S170 and the process returns to Step S110. Thereafter, the processing continues at timings t2, t3,.

In FIG. 4, at timing t4, the following processing is performed. Similarly, at the timing t4, the temperature of the fuel cell at the timing 5 after the next basic measurement cycle is estimated from the measured outside air temperature and the temperature of the fuel cell 10 (step S110 in FIG. 2). However, since this estimated temperature is lower than the determination threshold value _Tth , the determination in step S120 is Yes, and the process proceeds to step S130. In step S130, the control unit 20 calculates the estimated time ΔT _th until the temperature of the fuel cell 10 reaches the determination threshold value T _th , sets the estimated time ΔT _th as the next measurement cycle (second cycle), and the measurement timing. Is not a timing t5 but a timing t5 ′. In step S150, the outside air temperature and the temperature of the fuel cell 10 are measured at timing t5 ′. Since the outside air temperature at the timing t5 ′ is below freezing point and the temperature of the fuel cell 10 is lower than the determination threshold value _Tth , both Steps S160 and S170 are Yes, and the control unit 20 performs the purge process to the purge process execution unit 21 in Step S180. Is executed.

FIG. 5 is an explanatory diagram showing a case where the temperature of the fuel cell when measured in the second period is higher than the determination threshold. In FIG. 5, the outside air temperature and the temperature of the fuel cell 10 are measured in the basic measurement cycle until the timing tn, and the length from the timing tn to the next timing tn + 1 is the second cycle. Since the temperature of the fuel cell 10 measured at the timing tn + 1 is higher than the determination threshold value _Tth , the result in Step S170 is No, and the process proceeds to Step S110. At this time, in step S110, the measurement cycle is set to the basic measurement cycle. In this case, if the outside air temperature and the temperature of the fuel cell 10 are measured after the basic measurement period from the timing tn + 1, the temperature of the fuel cell 10 becomes lower than the determination threshold T _th at the measurement timing, and the internal temperature of the fuel cell 10 is increased. Water may freeze. Therefore, the control unit 20 sets the measurement cycle as the basic measurement cycle, but sets the starting point as the previous timing tn instead of the timing tn + 1. Thereby, the freezing of the water | moisture content inside the fuel cell 10 can be suppressed.

FIG. 6 is a graph showing a temperature change in the vicinity of 0 ° C. of the fuel cell 10 when the outside air temperature is −30 ° C. As can be seen from this figure, it takes about 4 minutes for the temperature of the fuel cell to change by 1 ° C. 1 ° C. is a temperature larger than the difference between the determination threshold T _th and 0 ° C. Accordingly, assuming that the basic measurement cycle is 4 minutes, if the temperature of the fuel cell 10 is higher than the determination threshold value T _th at a certain measurement timing, it will be below the freezing point (below 0 ° C.) at the measurement timing of the next basic measurement cycle. Is hard to think. That is, at a certain outside air temperature (for example, −30 ° C.), if the temperature of the fuel cell 10 is not lower than the determination threshold T _th , the basic measurement is performed so that the temperature of the fuel cell 10 after the basic measurement cycle does not fall below freezing point. A period may be determined in advance.

As described above, according to the present embodiment, the control unit 20 acquires the outside air temperature and the temperature of the fuel cell 10 in the basic measurement cycle after stopping the operation of the fuel cell 10. When the temperature of the fuel cell 10 is lower than the determination threshold value T _th , a purge process with purge gas is executed. When the temperature of the fuel cell 10 is equal to or higher than the determination threshold value T _th , the outside air temperature and the fuel cell 10 The temperature of the fuel cell 10 at the next measurement timing is predicted using the temperature. The temperature at which this control unit 20 predicts is lower than by the determination threshold T _th, the temperature of the fuel cell 10 calculates the period [Delta] T _th until a determination threshold T _th, the period [Delta] T _th second The measurement period is set, and after the second measurement period, the outside air temperature and the temperature of the fuel cell 10 are measured. If the temperature of the fuel cell 10 is lower than the determination threshold value T _th , the purge process using the purge gas is executed. Therefore, the increase in the dark current of the fuel cell 10 can be suppressed by optimizing the measurement timing of the outside air temperature and the temperature of the fuel cell 10 and reducing the number of measurements. In addition, since the temperature of the fuel cell 10 is purged at a temperature lower than the determination threshold value T _{th and} higher than the freezing point, freezing of moisture inside the fuel cell 10 is suppressed, and the inside of the fuel cell 10 is efficiently processed. Water can be blown away, and the startability of the fuel cell at low temperatures can be improved.
B. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

In the above embodiment, the second period is shorter than the basic measurement period, but may be longer than the third period shorter than the predetermined basic measurement period. In this case, in step S130 of FIG. When the calculated period ΔT _th is shorter than the third period, the next measurement period may be set as the third period. When the period ΔT _th is short, it is assumed that the temperature of the fuel cell after ΔT _th hardly decreases, so the next measurement timing is a third period longer than ΔT _th and shorter than the basic measurement period. It is.

Further, when the outside air temperature is not below freezing, it is unlikely that the temperature of the fuel cell 10 will be below freezing. Therefore, the control unit 20 may measure only the outside air temperature in the basic measurement cycle, and measure the temperature of the fuel cell 10 after the outside air temperature becomes lower than the determination threshold value _Tth . When the outside air temperature and the temperature of the fuel cell 10 decrease at substantially the same temperature, when 0 ° C. is used as a reference, when the outside air temperature becomes lower than 0 ° C., the temperature of the fuel cell 10 simultaneously becomes lower than 0 ° C. The case is considered. Therefore, in this case, the timing for measuring the temperature of the fuel cell 10 may be after the outside air temperature becomes lower than the determination threshold value T _th .

  The length of the basic measurement cycle may be changed depending on the outside air temperature. When the outside air temperature is low, the temperature of the fuel cell 10 decreases quickly, so the length of the basic measurement cycle is shortened. Conversely, when the outside air temperature is high, the temperature of the fuel cell 10 decreases slowly. You may lengthen the length of a basic measurement period.

In the above embodiment, the temperature of the fuel cell 10 in the next measurement cycle, if it becomes lower than the determination threshold T _th, the temperature of the fuel cell 10 is to calculate the time [Delta] T _th used as a determination threshold T _th, the following However, instead of calculating the time ΔT _th , the next measurement cycle may be shorter than the basic measurement cycle. That is, during a period in which the temperature of the fuel cell 10 is assumed to be higher than the determination threshold value T _th , the control unit 20 measures the outside air temperature and the temperature of the fuel cell 10 with a relatively long basic measurement cycle, and the next measurement cycle. When the temperature of the fuel cell 10 is likely to be lower than the determination threshold _Tth , the next measurement cycle is set to a cycle shorter than the basic measurement cycle, thereby reducing the overall number of times of temperature measurement and performing the purge process. Timing can be determined with high accuracy.

  The embodiments of the present invention have been described above based on some examples. However, the above-described embodiments of the present invention are for facilitating the understanding of the present invention and limit the present invention. It is not a thing. The present invention can be changed and improved without departing from the spirit and scope of the claims, and it is needless to say that the present invention includes equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 11 ... Single cell 20 ... Control part 21 ... Purge process execution part 30 ... Cathode gas supply part 31 ... Cathode gas piping 32 ... Air compressor 33 ... Air flow meter 34 ... On-off valve 40 ... Cathode gas discharge part 41 ... Cathode Exhaust gas piping 43 ... Pressure regulating valve 44 ... Pressure measurement unit 50 ... Anode gas supply unit 51 ... Anode gas piping 52 ... Hydrogen tank 53 ... On-off valve 54 ... Regulator 55 ... Hydrogen supply device 56 ... Pressure measurement unit 60 ... Anode gas circulation discharge unit 61 ... Anode exhaust gas pipe 62 ... Gas-liquid separation part 63 ... Anode gas circulation pipe 64 ... Hydrogen circulation pump 65 ... Anode drain pipe 66 ... Drain valve 67 ... Pressure measuring part 70 ... Refrigerant supply part 71 ... Refrigerant pipe 71a ... Upstream Side piping 71b ... Downstream piping 71c ... Bypass piping 72 ... Radiator 73 ... Three-way valve 75 ... Refrigerant circulation pump 76a ... Refrigerant temperature measuring unit (outlet side temperature measuring unit)
76b ... Refrigerant temperature measuring unit (inlet side temperature measuring unit)
80 ... ambient temperature sensor 100: fuel cell system T _th ... determination threshold [Delta] T _th ... estimated time (period)

Claims (5)

A fuel cell system,
A fuel cell;
A gas supply unit capable of supplying a purge gas to a gas flow path inside the fuel cell after receiving an instruction to stop the operation of the fuel cell system;
A first temperature measuring unit for measuring a first temperature representing the outside air temperature;
A second temperature measuring unit for measuring a second temperature representing a temperature of the fuel cell or a temperature of a portion through which the purge gas flows;
A control unit that controls the gas supply unit to execute a scavenging process using the purge gas,
The controller is
After the fuel cell receives an instruction to stop operation, the first and second temperatures are measured in a first measurement cycle;
When the second temperature measured at the first measurement timing is lower than the determination threshold, the scavenging process with the purge gas is executed,
When the second temperature is equal to or higher than the determination threshold, the second temperature at the next measurement timing is predicted using the first and second temperatures, and the temperature predicted by the control unit is When lower than the determination threshold, the period until the next measurement timing is made shorter than the first measurement period so that the second temperature at the next measurement timing becomes the determination threshold . Fuel cell system. The fuel cell system according to claim 1, wherein
The controller is
Calculating a period until the second temperature reaches the determination threshold, and setting the period as a second measurement cycle;
The second measurement timing which is the next measurement timing is set as a timing after the second measurement cycle from the first measurement timing ,
In the second measurement timing, and measuring the first and second temperature,
The fuel cell system, wherein when the second temperature measured at the second measurement timing is lower than the determination threshold, a scavenging process using the purge gas is executed. The fuel cell system according to claim 2 , wherein
When the second temperature measured at the second measurement timing is equal to or higher than the determination threshold, the control unit measures the first and second temperatures next to the second measurement timing. A fuel cell system, which is performed after elapse of the first measurement period from a measurement timing immediately before the second measurement timing. The fuel cell system according to any one of claims 1 to 3 ,
When the first temperature measured at an arbitrary measurement timing is equal to or higher than the determination threshold, the control unit performs the first and second temperature measurements from the measurement timing. A fuel cell system that is performed after the elapse of the measurement cycle. A control method for a fuel cell system, comprising:
(1) After receiving an instruction to stop the operation of the fuel cell system, a first temperature representing an outside air temperature is measured in a first measurement cycle, and a second temperature representing the temperature of the fuel cell is Measuring process;
(2) When the second temperature when measured at the first measurement timing is lower than a determination threshold, a step of performing a scavenging process with a purge gas;
(3) predicting the second temperature at the next measurement timing using the first and second temperatures when the second temperature is equal to or higher than a determination threshold;
(4) When the temperature predicted by the control unit is lower than the determination threshold, the period until the next measurement timing is set so that the second temperature at the next measurement timing becomes the determination threshold. The step of making it shorter than the first measurement period;
A control method for a fuel cell system.

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