JP4956481B2 - FUEL CELL SYSTEM AND CONTROL METHOD FOR FUEL CELL SYSTEM - Google Patents

Description

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

  In recent years, a polymer electrolyte fuel cell (Polymer Electrolyte Fuel Cell) that generates electricity by supplying hydrogen (fuel gas, reactive gas) to the anode and oxygen-containing air (oxidant gas, reactive gas) to the cathode, respectively. The development of fuel cells such as PEFC is active.

  When such a fuel cell generates power, if the reaction gas becomes insufficient, the power generation efficiency of the fuel cell decreases and the electrolyte membrane (solid polymer membrane) constituting the MEA (Membrane Electrode Assembly) of the fuel cell ) And the like are decomposed and the fuel cell is deteriorated.

  Thus, a technique is known that limits the generated current of the fuel cell and copes with the shortage of reaction gas when the fuel cell generates power (see Patent Document 1).

JP-A-5-151983

  However, if the command value (command current) of the current taken out from the fuel cell is limited based on the target current corresponding to the required power generation amount or the target reaction gas flow rate, for example, when the required power generation amount rises rapidly (acceleration of the fuel cell vehicle In some cases, the flow rate of the reaction gas actually supplied to the fuel cell did not increase with this, but the command current was increased to generate power. That is, the flow rate of the reaction gas actually supplied to the fuel cell is smaller than the flow rate of the reaction gas corresponding to the large command current (the flow rate of the reaction gas consumed in the fuel cell). This is because the fuel cell and the reaction gas supply means are usually separated from each other, and even if the number of revolutions of the reaction gas supply means (compressor when the reaction gas is air) is increased as the required power generation amount increases, the reaction gas Since the reaction gas is compressed between the supply unit and the fuel cell, the reaction gas is delayed until it reaches the fuel cell from the reaction gas supply unit. As a result, when the fuel cell generates power, there is a risk of insufficient stoichiometry (reaction gas shortage).

  Therefore, an object of the present invention is to provide a fuel cell system and a control method for the fuel cell system that prevent the stoichiometric shortage when the fuel cell generates power.

  As means for solving the above-mentioned problems, the present invention provides a fuel cell that generates power when a reaction gas is supplied, a reaction gas supply unit that supplies the reaction gas to the fuel cell, and a reaction gas that supplies the reaction gas. Based on the delay time calculating means for calculating the delay time from the means to the fuel cell, the volume flow rate of the reactive gas toward the fuel cell, and the delay time calculated by the delay time calculating means Based on a function indicating a volume flow rate of the reaction gas in the fuel cell calculated by the reaction gas volume flow rate function calculation means, A reaction gas volume flow rate calculating means for calculating a volume flow rate of the reaction gas in the actual fuel cell; and a reaction gas in the actual fuel cell calculated by the reaction gas volume flow rate calculating means. A power generation current calculating means for calculating a power generation current corresponding to the volume flow rate; and a power generation current limiting means for limiting the power generation current of the fuel cell, wherein the power generation current limiting means is the power generation calculated by the power generation current calculation means. The fuel cell system is characterized in that the actual power generation current of the fuel cell is limited so as to be a current.

  According to such a fuel cell system, the delay time calculation means calculates the reaction gas delay time from the reaction gas supply means to the fuel cell. Further, the reaction gas volume flow rate function calculating means calculates a function indicating the volume flow rate of the reaction gas in the fuel cell based on the volume flow rate of the reaction gas toward the fuel cell and the delay time. In addition, the reactive gas volume flow rate calculation means calculates the actual reactive gas volume flow rate in the fuel cell based on a function indicating the reactive gas volume flow rate in the fuel cell. Further, the generated current calculation means calculates the generated current corresponding to the volume flow rate of the reaction gas in the actual fuel cell. Then, the generated current limiting means limits the actual generated current of the fuel cell so that the calculated generated current is obtained.

  In this way, the generated current limiting means limits the generated current of the fuel cell so that the calculated generated current is obtained, so that the volume flow rate of the reaction gas supplied to the fuel cell and the fuel cell are consumed. Since the volume flow rate of the reaction gas corresponds, it is possible to prevent the stoichiometric shortage (reaction gas shortage) when the fuel cell generates power. Thereby, deterioration of the fuel cell can be prevented without reducing the power generation efficiency of the fuel cell.

  Further, the delay time calculating means calculates the delay time based on a volume flow rate of the reaction gas toward the fuel cell.

  According to such a fuel cell system, the delay time calculation means appropriately calculates the delay time based on the volume flow rate of the reaction gas toward the fuel cell, that is, varies the delay time according to the volume flow rate. be able to. Therefore, appropriate current limiting can be performed. Thereby, it is possible to prevent the stoichiometric shortage when the fuel cell generates power.

  A flow rate sensor for detecting a mass flow rate of the reaction gas upstream of the reaction gas supply unit; and a volume flow rate calculation unit for calculating a volume flow rate of the reaction gas based on the mass flow rate of the reaction gas detected by the flow rate sensor. And the delay time calculation means uses the delay time as a time until the reaction gas reaches the fuel cell from the flow rate sensor.

  According to such a fuel cell system, the volume flow rate calculation means calculates the volume flow rate of the reaction gas based on the mass flow rate of the reaction gas detected by the flow rate sensor. Further, the delay time calculating means calculates the reaction gas delay time from the flow rate sensor to the fuel cell. Further, the reaction gas volume flow rate function calculating means calculates a function indicating the volume flow rate of the reaction gas in the fuel cell based on the volume flow rate of the reaction gas toward the fuel cell and the delay time. In addition, the reactive gas volume flow rate calculation means calculates the actual reactive gas volume flow rate in the fuel cell based on a function indicating the reactive gas volume flow rate in the fuel cell. Further, the generated current calculation means calculates the generated current corresponding to the volume flow rate of the reaction gas in the actual fuel cell. Then, the generated current limiting means limits the actual generated current of the fuel cell so that the calculated generated current is obtained.

In this way, the generated current limiting means limits the generated current of the fuel cell so that the calculated generated current is obtained, so that the volume flow rate of the reaction gas supplied to the fuel cell and the fuel cell are consumed. Since the volume flow rate of the reaction gas corresponds, it is possible to prevent the stoichiometric shortage when the fuel cell generates power. Thereby, deterioration of the fuel cell can be prevented without reducing the power generation efficiency of the fuel cell.
Further, by providing the flow rate sensor on the upstream side of the reaction gas supply means, the reaction gas supply is actually performed in comparison with the case where the flow sensor is provided in an environment other than the upstream side of the reaction gas supply means, for example, in a humidified reaction gas environment. The mass flow rate of the reaction gas taken into the means can be accurately detected. Furthermore, by providing the flow sensor in a non-humidified environment that is not in a humidified reaction gas environment, the flow sensor can safely detect the flow rate of the reaction gas toward the fuel cell.

  The fuel cell system further comprises a temperature sensor for detecting an outside air temperature, wherein the volume flow rate calculation unit corrects the volume flow rate of the reaction gas based on the outside temperature detected by the temperature sensor. .

  According to such a fuel cell system, the volume flow rate calculation means corrects the volume flow rate of the reaction gas based on the outside temperature detected by the temperature sensor, compared with a case where the volume flow rate calculation means is not corrected based on the outside temperature. A more accurate volume flow rate is calculated. Thereby, the accurate delay time and the volume flow rate of the reaction gas in the fuel cell are calculated. Therefore, appropriate current limiting is performed. By appropriately limiting the current in this way, it is possible to prevent the stoichiometric shortage when the fuel cell generates power.

  The fuel cell system further comprises an external air pressure sensor for detecting an external air pressure, and the volume flow rate calculating unit corrects the volume flow rate of the reaction gas based on the external air pressure detected by the external air pressure sensor. It is.

  According to such a fuel cell system, the volume flow rate calculation means corrects the volume flow rate of the reaction gas based on the external air pressure detected by the external air pressure sensor, so that it is not corrected based on the external air pressure. A more accurate volume flow rate is calculated. Thereby, the accurate delay time and the volume flow rate of the reaction gas in the fuel cell are calculated. Therefore, appropriate current limiting is performed. By appropriately limiting the current in this way, it is possible to prevent the stoichiometric shortage when the fuel cell generates power.

  A fuel cell that generates power by supplying a reaction gas, a reaction gas supply unit that supplies the reaction gas to the fuel cell, and a delay time until the reaction gas reaches the fuel cell from the reaction gas supply unit A reaction time calculating means, a reaction for calculating a function indicating a volume flow rate of the reaction gas in the fuel cell based on a volume flow rate of the reaction gas toward the fuel cell and a delay time calculated by the delay time calculation means. Based on the gas volume flow rate function calculating means and the function indicating the volume flow rate of the reaction gas in the fuel cell calculated by the reaction gas volume flow rate function calculating means, the actual volume flow rate of the reaction gas in the fuel cell is calculated. Reactive gas volume flow rate calculating means, and a generated current for calculating a generated current corresponding to the actual volume flow rate of the reaction gas in the fuel cell calculated by the reactive gas volume flow rate calculating means A fuel cell system control method comprising: an output means; and a generated current limiting means for limiting the generated current of the fuel cell, wherein a delay time until the reaction gas reaches the fuel cell from the reaction gas supply means Calculating a function indicating the volume flow rate of the reaction gas in the fuel cell based on the volume flow rate of the reaction gas toward the fuel cell and the calculated delay time, and calculating the fuel cell A step of calculating a volume flow rate of the reaction gas in the actual fuel cell based on a function indicating a volume flow rate of the reaction gas in the fuel cell, and a generated current corresponding to the calculated volume flow rate of the reaction gas in the fuel cell. And a step of limiting the actual power generation current of the fuel cell so as to obtain the calculated power generation current. It is a control method.

  According to such a control method of the fuel cell system, the delay time calculation means calculates the reaction gas delay time from the reaction gas supply means to the fuel cell. Further, the reaction gas volume flow rate function calculating means calculates a function indicating the volume flow rate of the reaction gas in the fuel cell based on the volume flow rate of the reaction gas toward the fuel cell and the delay time. In addition, the reactive gas volume flow rate calculation means calculates the actual reactive gas volume flow rate in the fuel cell based on a function indicating the reactive gas volume flow rate in the fuel cell. Further, the generated current calculation means calculates the generated current corresponding to the volume flow rate of the reaction gas in the actual fuel cell. Then, the generated current limiting means limits the actual generated current of the fuel cell so that the calculated generated current is obtained.

  In this way, the generated current limiting means limits the generated current of the fuel cell so that the calculated generated current is obtained, so that the volume flow rate of the reaction gas supplied to the fuel cell and the fuel cell are consumed. Since the volume flow rate of the reaction gas corresponds, it is possible to prevent the stoichiometric shortage (reaction gas shortage) when the fuel cell generates power. Thereby, deterioration of the fuel cell can be prevented without reducing the power generation efficiency of the fuel cell.

  According to the present invention, it is possible to provide a fuel cell system and a control method for the fuel cell system that prevent a stoichiometric shortage when the fuel cell generates power.

  An embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to this embodiment shown in FIG. 1 is mounted on a fuel cell vehicle (moving body) (not shown). The fuel cell system 1 includes a fuel cell 10, an anode system that supplies and discharges hydrogen (fuel gas and reaction gas) to and from the anode of the fuel cell 10, and air that contains oxygen to the cathode of the fuel cell 10 (oxidant) Gas, reactive gas), a power consumption system connected to an output terminal (not shown) of the fuel cell 10 and consuming power generated by the fuel cell 10, an accelerator pedal 51, and a temperature sensor 52 And an external air pressure sensor 53 and an ECU (Electronic Control Unit) 60 for electronically controlling them. The fuel cell 10 generates electric power according to the amount of depression of the accelerator pedal 51 by the driver, and the driving motor 41 is driven by the generated electric power, so that the fuel cell vehicle is driven.

<Fuel cell>
The fuel cell (fuel cell stack) 10 is configured by stacking (stacking) a plurality of (for example, 200 to 400) solid polymer type single cells, and the plurality of single cells are electrically connected in series. ing. The single cell includes an MEA (Membrane Electrode Assembly) and two conductive anode separators and cathode separators sandwiching the MEA.

  The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane (for example, perfluorosulfonic acid type), and an anode and a cathode sandwiching the electrolyte membrane. The anode and cathode are mainly composed of a conductive porous material such as carbon paper, and contain a catalyst (Pt, Ru, etc.) for causing an electrode reaction in the anode and cathode.

The anode separator is formed with a through-hole (called an internal manifold) extending in the stacking direction of the single cells and a groove extending in the surface direction of the single cells in order to supply and discharge hydrogen to the anode of each MEA. These through holes and grooves function as the anode flow path 11 (fuel gas flow path).
The cathode separator is formed with a through-hole (referred to as an internal manifold) extending in the stacking direction of the single cells and a groove extending in the surface direction of the single cells in order to supply and discharge air to and from the cathode of each MEA. These through holes and grooves function as the cathode channel 12 (oxidant gas channel).

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

  When power is generated in this way, part of the water (water vapor) generated at the cathode permeates the electrolyte membrane and moves to the anode. Therefore, the cathode off-gas discharged from the cathode and the anode off-gas discharged from the anode are humid.

<Anode system>
The anode system includes a hydrogen tank (fuel gas (reactive gas) supply means) 21, a shutoff valve 22, a pressure reducing valve 23, an ejector 24, and a purge valve 25.
The hydrogen tank 21 is connected to the inlet of the anode channel 11 through a pipe 21a, a shutoff valve 22, a pipe 22a, a pressure reducing valve 23, a pipe 23a, an ejector 24, and a pipe 24a in this order. When the shutoff valve 22 is opened by the ECU 60, hydrogen is supplied to the anode flow path 11 through the pipe 21a and the like. Further, the pressure of the air flowing toward the cathode flow path 12 is input as a signal pressure (pilot pressure) to the pressure reducing valve 23 for reducing the hydrogen pressure to a predetermined pressure, and the pressure of the air and the pressure of hydrogen in the anode flow path 11 are Are controlled to be equal to each other. The signal pressure is controlled by an exhaust valve 34 described later.

The outlet of the anode channel 11 is connected to a pipe 25a, a purge valve 25, and a pipe 25b in this order. The middle of the pipe 25a is connected to the ejector 24 via the pipe 25c. A check valve (not shown) that prevents backflow is provided in the middle of the pipe 25c.
The purge valve 25 is an on-off valve such as a gate valve, and is normally closed. When the purge valve 25 is closed in this way, the anode offgas (exhaust fuel gas) containing unreacted hydrogen discharged from the anode flow path 11 is returned to the ejector 24 via the pipe 25c, and again. The fuel cell 10 is supplied, that is, hydrogen is circulated.
On the other hand, when impurities such as moisture in the anode off gas increase, that is, when impurities accompanying the circulating hydrogen increase, the purge valve 25 is opened by the ECU 60, and the anode off gas passes through the pipe 25b to the diluter. It is discharged (not shown).

<Cathode system>
The cathode system includes a compressor (oxidant gas (reactive gas) supply means) 31, a back pressure valve 32, an orifice 33, an exhaust valve 34, and a flow sensor 35.
The compressor 31 is connected to the inlet of the cathode channel 12 via a pipe 31a. When the compressor 31 is operated in accordance with a command from the ECU 60, oxygen-containing air is supplied to the cathode channel 12. The pipe 31a is provided with a humidifier (not shown) so that the air sent to the fuel cell 10 is appropriately humidified.
Such a compressor 31 operates using a fuel cell 10 and / or a high-voltage battery (not shown) that charges and discharges power generated by the fuel cell 10 as a power source.

The outlet of the cathode channel 12 is connected to a diluter (not shown) via a pipe 32a, a back pressure valve 32, and a pipe 32b. Then, the cathode off gas discharged from the cathode channel 12 (cathode) is discharged to the diluter via the pipe 32a and the like.
The back pressure valve 32 is a butterfly valve or the like, and its opening degree is controlled by the ECU 60 in accordance with a required power generation amount such as a depression amount of the accelerator pedal 51.

The middle of the pipe 31a is connected to the pressure reducing valve 23 through the pipe 31b, an orifice 33 for reducing the flow rate of air, and the pipe 33a. The middle of the pipe 31a is also connected to the exhaust valve 34 via the pipe 31b, the orifice 33, and the pipe 33b.
The exhaust valve 34 is an air discharge valve that discharges air, and is normally closed, whereby the air from the compressor 31 flows to the pressure reducing valve 23 via the pipe 31b and the like.
On the other hand, when the amount of air flowing through the pressure reducing valve 23 is too large (the air pressure is too high), the exhaust valve 34 is opened by the ECU 60 so that the air is discharged to the outside through the pipe 34a. It has become.
As described above, the signal pressure (pilot pressure) of the air flowing through the pressure reducing valve 23 is controlled by opening and closing the exhaust valve 34, whereby the hydrogen pressure in the anode flow path 11 is controlled. .

  The flow sensor 35 is a sensor that detects a mass flow rate (g / s) of air taken into the compressor 31, and is provided in a pipe 35 a upstream of the compressor 31. The flow sensor 35 is configured to output the detected mass flow rate to the ECU 60.

<Power consumption system>
The power consuming system includes an electric traveling motor 41 that causes the fuel cell vehicle to travel, a VCU (Voltage Control Unit) 42, and an output detector 43. The traveling motor 41 includes an inverter (not shown), It is connected to the output terminal (not shown) of the fuel cell 10 through the VCU 42 and the output detector 43 in this order.

The traveling motor 41 is an electric motor that causes the fuel cell vehicle to travel.
The VCU 42 is a unit that controls the generated power (output) of the fuel cell 10 in accordance with a command from the ECU 60, and includes a DC-DC chopper and the like. That is, if the ECU 60 appropriately controls the VCU 42 in response to the power generation request, current is extracted from the fuel cell 10 in response to the power generation request, and the fuel cell 10 generates power.

  That is, in this embodiment, the generated current limiting means for limiting the generated current of the fuel cell is configured to include the VCU 42 and the ECU 60.

  The output detector 43 is a device that detects a generated current (output current) and a generated voltage (output voltage) of the fuel cell 10, and includes an ammeter and a voltmeter, and the ammeter and the voltmeter are disposed at appropriate positions. ing. The output detector 43 is connected to the ECU 60, and the ECU 60 detects the current generated current and generated voltage of the fuel cell 10.

<Accelerator pedal>
The accelerator pedal 51 is a pedal that the driver steps on to accelerate the fuel cell vehicle, and is disposed at the foot of the driver's seat. The accelerator pedal 51 is connected to the ECU 60, and the ECU 60 detects the amount of depression of the accelerator pedal 51 (accelerator opening).

<Temperature sensor>
The temperature sensor 52 is a sensor for detecting the outside air temperature, and is provided at an appropriate position of the fuel cell vehicle. The temperature sensor 52 is connected to the ECU 60, and the ECU 60 detects the outside air temperature where the fuel cell vehicle is traveling (traveling location).

<External air pressure sensor>
The external air pressure sensor 53 is a sensor that detects the external air pressure, and is provided at an appropriate position of the fuel cell vehicle. The external air pressure sensor 53 is connected to the ECU 60, and the ECU 60 detects the external air pressure where the fuel cell vehicle is traveling (traveling location).

<ECU>
The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like.
When the ECU 60 detects an IG (ignition) ON signal (not shown), the ECU 60 opens the shutoff valve 22, operates the compressor 31, and appropriately controls the opening degree of the back pressure valve 32 and the VCU 42 to generate power from the fuel cell 10. Configured to start.

  Further, the ECU 60 has a function of calculating the volume flow rate (L / s) of air taken into (discharged from) the compressor 31 based on the mass flow rate of air detected by the flow sensor 35. Furthermore, a function of calculating a delay time until the air reaches the fuel cell 10 from the flow rate sensor 35 based on the volume flow rate of the air is also provided.

  Further, the ECU 60 has a function of calculating a function indicating the volume flow rate of air in the fuel cell 10 based on the volume flow rate of air and the delay time. Further, the ECU 60 has a function of calculating the actual volume flow of air in the fuel cell 10 based on a function indicating the volume flow of air in the fuel cell. Furthermore, it has a function of calculating a generated current corresponding to the volume flow rate of air in the fuel cell 10.

  Next, the ECU 60 has a function of limiting the generated current of the fuel cell 10 so that the calculated generated current is obtained. Specifically, the ECU 60 is set to appropriately control the VCU 42 corresponding to the calculated generated current.

  That is, in the present embodiment, the volume flow rate calculation means, the delay time calculation means, the reaction gas volume flow rate function calculation means, the reaction gas volume flow rate calculation means, and the generated current calculation means are configured to include the ECU 60.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 will be described with reference mainly to FIG. This operation is repeated every predetermined time (for example, 10 ms).

  In step S <b> 11, the ECU 60 detects the mass flow rate of air taken into the compressor 31 via the flow rate sensor 35.

  In step S12, the ECU 60 (volume flow rate calculation means) calculates the volume flow rate (sensor value) of air taken into the compressor 31 based on the mass flow rate of air and FIG. As shown in FIG. 3, as the mass flow rate of air increases, the volume flow rate also increases. Note that the map shown in FIG. 3 is obtained by a preliminary test or a simulation and stored in advance in the ECU 60.

  The ECU 60 may be configured to correct the volume flow rate of the air based on the outside air temperature detected by the temperature sensor 52 when calculating the volume flow rate of the air based on the mass flow rate of the air. In addition, the volume flow rate of air may be further corrected based on the external air pressure detected by the external air pressure sensor 53. As shown in FIG. 3, when the outside air temperature becomes high and the outside air pressure becomes low, the air expands, so that the volume flow rate of the air is corrected.

In step S13, the ECU 60 (delay time calculation means) calculates the delay time of air until it reaches the fuel cell 10 from the flow sensor 35, based on the volume flow rate (sensor value) of this air and FIG. As shown in FIG. 4, when the volume flow rate of the air taken into the compressor 31 increases, the pressure loss increases. Therefore, the delay time of the air from the flow sensor 35 to the fuel cell 10 becomes longer. Yes. Note that the map shown in FIG. 4 is obtained by a preliminary test or the like and stored in the ECU 60 in advance.
In addition, for example, immediately after the rotation speed of the compressor 31 increases, the rise of the air is further delayed, so that the delay time becomes longer than the delay time calculated from this map, and this delay time is also obtained by a preliminary test or the like. And stored in the ECU 60 in advance. In addition, when the rotation speed of the compressor 31 is not increasing, that is, when the volume flow rate (sensor value) of air is small, there is almost no delay time.

In step S <b> 14, the ECU 60 (reactive gas volume flow function calculation means) determines whether the fuel cell 10 contains the volume flow rate (sensor value) of air and the delay time of air until the flow rate sensor 35 reaches the fuel cell 10. A function indicating the volume flow rate of the air is calculated.
In step S15, the ECU 60 (reactive gas volume flow rate calculation means) calculates the actual volume flow rate (stack value) of the air in the fuel cell 10 based on the function indicating the volume flow rate of the air in the fuel cell 10. calculate.
Here, a specific function of calculating the volumetric flow rate of air in the fuel cell 10 and the actual calculation process of the volumetric flow rate of air in the fuel cell are as follows. At time t1, the volumetric flow rate (sensor value) a Is calculated with reference mainly to FIG. 5A.

First, the ECU 60 (reactive gas volume flow rate function calculating means) is based on the volume flow rate (sensor value) a of air calculated in step S12 this time (time t1) and the air delay time calculated in step S13. Thus, the coordinate a1 at which the volume flow rate of air in the fuel cell 10 becomes a is predicted, that is, the above-described coordinate a1 is calculated by shifting the volume flow rate (sensor value) a of this time by the delay time.
Next, the ECU 60 (reactive gas volume flow function calculating means) connects the coordinate a1 predicted this time and the coordinate s predicted in the previous step S14 (time t0), and calculates the volume flow rate of air in the fuel cell 10. The function shown (line connecting the coordinate s and the coordinate a1 in FIG. 5A) is calculated.
Then, the ECU 60 (reactive gas volume flow rate calculation means) calculates a coordinate a2 on the function at the time t1 when the volume flow rate (sensor value) a of air is calculated. This coordinate a2 becomes the actual volumetric flow rate (stack value) of the air in the fuel cell 10.

Further, the ECU 60 (reactive gas volume flow function calculating means) repeats the same calculation process as described above even when the volume flow rates (sensor values) b, c, d of air calculated in step S12 are calculated. , A function indicating the volume flow rate of the air in the fuel cell 10 (a line connecting the coordinates a1 and b1 in FIG. 5B, a line connecting the coordinates b1 and c1 in FIG. 5C, and a coordinate in (d) a line connecting c1 and the coordinate d1).
Further, the ECU 60 (reactive gas volume flow rate calculation means) calculates the coordinates on the function at the time when the volume flow rates (sensor values) b, c, and d of the air are calculated, so that the actual air flow in the fuel cell 10 is calculated. Volume flow rates (stack values) b2, c2, and d2 are calculated (see FIGS. 5B, 5C, and 5D).
Thereby, the ECU 60 can calculate a function indicating the volumetric flow rate of air in the fuel cell 10 and an actual volumetric flow rate (stack value) of air in the fuel cell 10 (see FIG. 5E).
By performing such steps S11 to S15, it is possible to calculate the actual volumetric flow rate (stack value) of air in the fuel cell 10 that cannot be directly detected.

In step S16, the ECU 60 (generated current calculation means) converts the actual volume flow (stack value) of air in the fuel cell 10 into the actual mass flow of air in the fuel cell 10, and this actual fuel. Based on the mass flow rate of the air in the battery 10 and FIG. 6, the generated current (command current) corresponding to the actual volume flow (stack value) of the air in the fuel cell 10 is calculated. As shown in FIG. 6, when the mass flow rate of the air in the fuel cell 10 increases, the generated current (command current) also increases. Note that the map shown in FIG. 6 is obtained by a preliminary test or the like and stored in the ECU 60 in advance.
The ECU 60 determines the generated current (command current) corresponding to the actual volume flow (stack value) of the air in the fuel cell 10 based on the actual volume flow (stack value) of the air in the fuel cell 10. It may be calculated.

In step S17, the ECU 60 limits the actual generated current of the fuel cell 10 so that the calculated generated current (command current) is obtained, that is, appropriately controls the VCU 42.
Thereafter, the processing of the ECU 60 returns to the start via return.

≪Effect of fuel cell system≫
Since the fuel cell system 1 is configured as described above, the following operational effects can be obtained.
The ECU 60 calculates the volume flow rate (sensor value) of air based on the mass flow rate of air detected by the flow rate sensor 35. Further, the ECU 60 calculates an air delay time from the flow rate sensor 35 to the fuel cell 10 based on the volume flow rate (sensor value) of the air. Further, the ECU 60 calculates a function indicating the volume flow rate of the air in the fuel cell 10 based on the volume flow rate (sensor value) of the air and the delay time. Further, the ECU 60 calculates the actual volume flow rate (stack value) of air in the fuel cell 10 based on this function. Further, the ECU 60 calculates a generated current (command current) corresponding to the volume flow rate (stack value) of the air. Then, the generated current limiting means limits the actual generated current of the fuel cell so as to be the calculated generated current (command current).

Thus, the volume flow rate of the air supplied to the fuel cell 10 by the generated current limiting means limiting the actual generated current of the fuel cell 10 so that the calculated generated current (command current) is obtained. And the volume flow rate of air consumed in the fuel cell 10 correspond to each other, it is possible to prevent the stoichiometric shortage (air shortage) when the fuel cell 10 generates power. Thereby, deterioration of the fuel cell 10 can be prevented without lowering the power generation efficiency of the fuel cell 10.
Further, by providing the flow rate sensor 35 on the upstream side of the compressor 31, the air actually taken into the compressor 31 is compared with the case other than the upstream side of the compressor 31, for example, in the case of being provided in an environment of humidified air. The mass flow rate can be accurately detected. Furthermore, by providing the flow sensor 35 in a non-humidified environment that is not in a humidified air environment, the flow sensor 35 can safely detect the flow rate of air toward the fuel cell 10.

  Further, the ECU 60 can appropriately calculate the delay time based on the volume flow rate of the air toward the fuel cell 10, that is, the delay time can be varied according to the volume flow rate. Therefore, appropriate current limiting can be performed. Thereby, when the fuel cell 10 generates electric power, it is possible to prevent a shortage of stoichiometry.

  Further, the ECU 60 corrects the volume flow rate of the air based on the outside air temperature and / or the outside air pressure by correcting the air volume flow rate based on the outside air temperature and / or the outside air pressure detected by the temperature sensor 52 and / or the outside air pressure sensor 53. Compared to the case where it is not performed, a more accurate volume flow rate of air is calculated. Thereby, the accurate delay time and the volume flow rate (stack value) of the air in the fuel cell 10 are calculated. Therefore, appropriate current limiting is performed. By appropriately limiting the current in this way, it is possible to prevent the stoichiometric shortage when the fuel cell 10 generates power.

≪Example of fuel cell system operation≫
With reference to FIG. 7, an example of operation of the fuel cell system 1 will be described by taking acceleration as an example.
When the accelerator pedal 51 is depressed, the depression amount (accelerator opening), that is, the command generated current value commanded to the fuel cell 10 increases.
When the accelerator pedal 51 is depressed, the compressor 31 operates at a higher speed and the back pressure valve 32 is controlled in the closing direction. The flow rate of air taken into the compressor 31, that is, the mass flow rate of air detected by the flow sensor 35. Will increase.
As the mass flow rate of air detected by the flow sensor 35 increases in this way, the volume flow rate (sensor value) of air calculated by the volume flow rate calculation means also increases accordingly.
On the other hand, the volume flow rate (stack value) of the air in the fuel cell 10 is compared with the volume flow rate (sensor value) of the air calculated by the volume flow rate calculation means until the air reaches the fuel cell 10 from the flow rate sensor 35. Due to the time delay, a shift occurs.
In spite of such deviation, when the actual generated current of the fuel cell 10 is limited based on the command generated current value (command current), the volume flow rate (consumption amount) of air consumed by the fuel cell 10 ) Is the volume flow rate (sensor value) of air corresponding to the command generated current value (command current), but the volume flow rate (supply amount) of air actually supplied to the fuel cell 10 is Because of the volume flow rate (stack value) of the air inside, the consumption amount and the supply amount do not correspond, that is, the supply amount is smaller than the consumption amount. As a result, the stoichiometric ratio (supply amount / consumption amount) of air decreases, that is, when the fuel cell 10 generates power, the stoichiometry is insufficient (air shortage) (comparative example).

Therefore, the volume flow rate calculation means calculates the volume flow rate (sensor value) of air based on the mass flow rate of air detected by the flow rate sensor 35 (S12). Further, the delay time calculating means calculates an air delay time from the flow sensor 35 to the fuel cell 10 based on the volume flow rate (sensor value) of the air (S13). Further, the reactive gas volume flow rate function calculating means calculates a function indicating the volume flow rate of the air in the fuel cell 10 based on the volume flow rate (sensor value) of the air and the delay time (S14). Further, the reactive gas volume flow rate calculation means calculates the actual volume flow rate (stack value) of the air in the fuel cell 10 based on this function (S15). Further, the generated current calculation means calculates a generated current (command current) corresponding to the volume flow rate (stack value) of the air in the fuel cell 10 (S16). Then, the generated current limiting means limits the actual generated current of the fuel cell 10 so as to be the calculated generated current (command current) (S17).
In this way, the generated current limiting means limits the actual generated current of the fuel cell 10 so that the calculated generated current (command current) is obtained, so that the air actually supplied to the fuel cell 10 is reduced. Volume flow (stack value) (supply amount) corresponds to the volume flow rate (consumption) of air consumed by the fuel cell 10, so that when the fuel cell generates power without reducing the air stoichiometric ratio It is possible to prevent the stoichiometric shortage (Example).

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be modified, for example, as follows without departing from the spirit of the present invention. You may combine a structure suitably.

  In the above-described embodiment, the fuel cell system 1 includes the flow rate sensor 35 and the volume flow rate calculation unit calculates the volume flow rate (sensor value) of the air based on the mass flow rate of the air detected by the flow rate sensor 35. Although the present invention is applied, the present invention may be applied to a fuel cell system that does not include the flow sensor 35. In this case, by controlling the rotation speed of the compressor 31 by the ECU 60, the mass flow rate of the air taken into the compressor 31 is calculated from the rotation speed, and the volume flow rate of the air is calculated based on the mass flow rate of the air. (See FIGS. 3 and 8).

  In the above-described embodiment, the delay time calculation means calculates the delay time based on the volume flow rate (sensor value) of air, but is not limited to this, for example, the depression amount of the accelerator pedal 51 It may be calculated based on (accelerator opening), that is, a command generated current value commanded to the fuel cell 10.

In the above-described embodiment, the power generation current of the fuel cell 10 is limited based on the delay time of the air from the flow rate sensor 35 to the fuel cell 10, but the present invention is not limited to this. Based on the delay time of hydrogen until the fuel cell 10 is reached, the power generation current of the fuel cell 10 may be limited to prevent the shortage of stoichiometry (hydrogen shortage).
In this case, the anode system includes a hydrogen tank (fuel gas (reactive gas) supply means) 21, a shutoff valve 22, and a flow rate sensor 35, and the flow rate sensor 35 is disposed on the downstream side of the shutoff valve 22. The configuration.

  In the above-described embodiment, the actual generated current of the fuel cell 10 is limited to cope with the shortage of stoichiometry (reaction gas shortage). However, for example, the flow rate of the reaction gas supplied to the fuel cell 10 increases. By doing so (increasing the flow rate of the reaction gas from the reaction gas supply means), it is possible to prevent a shortage of stoichiometry.

  In the above-described embodiment, the case where hydrogen is used as the fuel gas is exemplified, but the present invention is not limited to this. For example, what can be used as fuel gas, such as methane, should just be used.

In the above-described embodiment, the present invention is applied to the fuel cell system 1 in which the anode off-gas containing unreacted hydrogen is circulated to the ejector 24 as it is, but the present invention is not limited to this.
For example, in order to remove impurities such as moisture in the anode off-gas, the anode off-gas containing unreacted hydrogen is returned to the ejector 24 through a gas-liquid separator (not shown) and re-supplied to the anode channel 11. The present invention may be applied to a fuel cell system.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been illustrated. However, for example, a fuel cell system mounted on a motorcycle, a train, or a ship may be used. Further, it may be a stationary fuel cell system for home use or business use, or a fuel cell system incorporated in a hot water supply system.

It is a figure which shows the structure of the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment. It is a map which shows the relationship between the mass flow rate of air, and the volume flow rate (sensor value) of air. It is a map which shows the relationship between the volume flow rate (sensor value) of air, and delay time. It is a figure which shows the relationship between time and the volume flow volume of air. It is a map which shows the relationship between the mass flow rate of the air in a fuel cell, and a generated electric current (command current). It is a time chart which shows one operation example of the fuel cell system concerning this embodiment. It is a map which shows the relationship between the rotation speed of a compressor, and the mass flow rate of air.

Explanation of symbols

1 Fuel Cell System 10 Fuel Cell 31 Compressor 42 VCU
60 ECU

Claims (6)

A fuel cell that generates electricity by supplying reactive gas;
Reactive gas supply means for supplying a reactive gas to the fuel cell;
A delay time calculating means for calculating a delay time until the reaction gas reaches the fuel cell from the reaction gas supply means;
Reactive gas volume flow rate function calculating means for calculating a function indicating the volume flow rate of the reactive gas in the fuel cell based on the volume flow rate of the reactive gas toward the fuel cell and the delay time calculated by the delay time calculating means; ,
A reaction gas volume flow rate calculating means for calculating an actual volume flow rate of the reaction gas in the fuel cell based on a function indicating a volume flow rate of the reaction gas in the fuel cell calculated by the reaction gas volume flow rate function calculating means; ,
A generated current calculating means for calculating a generated current corresponding to the actual volume flow of the reaction gas in the fuel cell calculated by the reactive gas volume flow calculating means;
Power generation current limiting means for limiting the power generation current of the fuel cell,
The fuel cell system characterized in that the generated current limiting means limits the actual generated current of the fuel cell so as to be the generated current calculated by the generated current calculating means. 2. The fuel cell system according to claim 1, wherein the delay time calculating unit calculates the delay time based on a volume flow rate of a reactive gas toward the fuel cell. A flow rate sensor for detecting a mass flow rate of the reaction gas upstream of the reaction gas supply means;
Volume flow rate calculating means for calculating a volume flow rate of the reaction gas based on a mass flow rate of the reaction gas detected by the flow sensor, and
3. The fuel cell system according to claim 1, wherein the delay time calculation unit sets the delay time as a time until the reaction gas reaches the fuel cell from the flow rate sensor. 4. A temperature sensor for detecting the outside air temperature;
The fuel cell system according to claim 3, wherein the volume flow rate calculation unit corrects the volume flow rate of the reaction gas based on an outside air temperature detected by the temperature sensor. An external air pressure sensor for detecting the external air pressure is further provided,
5. The fuel cell system according to claim 3, wherein the volume flow rate calculation unit corrects the volume flow rate of the reaction gas based on an external air pressure detected by the external air pressure sensor. A fuel cell that generates power by supplying a reaction gas, a reaction gas supply unit that supplies the reaction gas to the fuel cell, and a delay time until the reaction gas reaches the fuel cell from the reaction gas supply unit A reaction time calculating means, a reaction for calculating a function indicating a volume flow rate of the reaction gas in the fuel cell based on a volume flow rate of the reaction gas toward the fuel cell and a delay time calculated by the delay time calculation means. Based on the gas volume flow rate function calculating means and the function indicating the volume flow rate of the reaction gas in the fuel cell calculated by the reaction gas volume flow rate function calculating means, the actual volume flow rate of the reaction gas in the fuel cell is calculated. Reactive gas volume flow rate calculating means, and a generated current for calculating a generated current corresponding to the actual volume flow rate of the reaction gas in the fuel cell calculated by the reactive gas volume flow rate calculating means Means out a control method of a fuel cell system and a power generation current limiting means for limiting the generated current of the fuel cell,
Calculating a delay time until the reaction gas reaches the fuel cell from the reaction gas supply means;
Calculating a function indicating the volume flow rate of the reaction gas in the fuel cell based on the volume flow rate of the reaction gas toward the fuel cell and the calculated delay time; and
Calculating a volume flow rate of the actual reaction gas in the fuel cell based on a function indicating the calculated reaction gas volume flow rate in the fuel cell;
Calculating the generated current corresponding to the calculated volume flow rate of the reaction gas in the fuel cell;
Limiting the actual generated current of the fuel cell so that the calculated generated current is obtained. A control method for a fuel cell system, comprising:

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