JP5061453B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system with improved idle stop performance suitable for a power source of a moving body.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for electric vehicles because of its low operating temperature and easy handling. That is, a fuel cell vehicle is equipped with a hydrogen storage device such as a high-pressure hydrogen tank, a liquid hydrogen tank, or a hydrogen storage alloy tank in the vehicle, and reacts by supplying hydrogen supplied therefrom and air containing oxygen to the fuel cell. This is the ultimate clean vehicle that drives the motor connected to the drive wheels with the electric energy extracted from the fuel cell, and the only exhaust material is water.

  By the way, in the operation region where the output of the fuel cell is small, there is a system in which power generation is stopped because power generation efficiency is low and power is supplied from a power storage device such as a secondary battery or a capacitor. In this system, it is possible to avoid an operation region where the power generation efficiency of the fuel cell is low and to improve the fuel efficiency of the fuel cell system.

For example, the fuel cell vehicle disclosed in Patent Document 1 performs idle stop when the required pressure for power generation is not more than a predetermined value and the differential pressure between the hydrogen pressure at the anode inlet and the atmospheric pressure is not less than the predetermined value. It has a prohibition condition.
JP 2004-173450 A (page 6, FIG. 3)

  However, in the above conventional example, the accelerator is released from the power generation state with a high load and a high operating pressure, and the vehicle speed is reduced by the brake operation, and even if the required power generation amount becomes a predetermined value or less, the hydrogen pressure at the anode does not decrease. Slowly, since the differential pressure condition between the anode pressure and the atmospheric pressure is not satisfied, idle stop cannot be performed, and there is a problem that fuel consumption performance is lowered and acoustic vibration characteristics are lowered.

In order to solve the above problems, the present invention provides a fuel supply device that supplies fuel gas, an oxidant supply device that supplies oxidant gas, and the fuel gas and oxidant electrode supplied to the fuel electrode. A fuel cell that generates electricity by electrochemically reacting the oxidant gas, and the fuel gas and the oxidant when the fuel cell is at a low load and the fuel gas pressure at the fuel electrode is equal to or lower than a predetermined pressure. A fuel cell system comprising: an idle stop control means for temporarily stopping supply of gas; and a fuel circulation path and a circulation pump for circulating fuel gas that has not been consumed at the fuel electrode from the outlet to the inlet of the fuel electrode. When the stop control means temporarily stops the supply of the fuel gas and the oxidant gas, a pressure reducing operation is performed to reduce the fuel gas pressure at the fuel electrode below the predetermined pressure, Serial decompression operations are current extraction operation from the fuel cell, by increasing than the rotational speed of the said depressurization immediately before the rotational speed of the circulating pump in the pressure reducing operation, because of the current extraction in the depressurization The gist of the present invention is to make the electrical load larger than the electrical load immediately before the start of the pressure reducing operation.
The present invention also provides an electrochemical reaction between a fuel supply device that supplies fuel gas, a compressor that supplies oxidant gas, and the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode. A fuel cell for generating power, and an idle stop control means for temporarily stopping the supply of the fuel gas and the oxidant gas when the fuel gas pressure at the fuel electrode is equal to or lower than a predetermined pressure at a low load of the fuel cell And when the idle stop control means temporarily stops the supply of the fuel gas and the oxidant gas, a pressure reducing operation for reducing the fuel gas pressure at the fuel electrode to be equal to or lower than the predetermined pressure is performed. The depressurization operation is a current extraction operation from the fuel cell, and the rotation speed of the compressor during the depressurization operation is increased from the rotation speed immediately before the start of the depressurization operation. Ri, it is summarized in that to increase the pressure reducing electrical load for current extraction in operation than the pressure reduction operation immediately before the start of the electrical load.

  According to the present invention, it is possible to idle stop even when the pressure of at least one of the fuel gas pressure at the fuel electrode and the oxidant gas pressure at the oxidant electrode is high, improving the fuel efficiency of the fuel cell system, There is an effect that the acoustic vibration performance can be improved.

Next, embodiments of the present invention will be described in detail with reference to the drawings. Although not particularly limited, the following reference examples and examples are examples in which the present invention is applied to a fuel cell vehicle.

[Reference Example 1]
FIG. 1 is a system configuration diagram illustrating an outline of a reference example 1 of a fuel cell system according to the present invention. In the figure, the fuel cell system includes a solid polymer fuel cell body 1, for example. The fuel cell main body 1 has a structure in which a plurality of single cells (cells) sandwiching an electrolyte membrane (not shown) between an oxidant electrode (cathode) 1a and a fuel electrode (anode) 1b are stacked, but only a single cell is shown.

  Hydrogen gas is supplied as fuel to the fuel electrode 1b, and air is supplied as oxidant gas to the oxidant electrode 1a. The electrode reaction shown below proceeds to generate electric power.

Fuel electrode (anode): H ₂ → 2H ⁺ + 2e ⁻ (1)
Oxidant electrode (cathode): 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
The air as the oxidant is supplied to the oxidant electrode 1a through the air supply path 12 as the air compressed by the air compressor 11 as the oxidant supply means. An air-type humidifier 13 and an air pressure gauge 16 are provided on the air supply path 12 to humidify the air supplied to the oxidizer electrode 1a, while detecting the air pressure and transmitting it to the controller 45. An air exhaust path 14 and an air pressure regulating valve 15 are provided at the oxidant electrode outlet, and the controller 45 controls the opening degree of the air pressure regulating valve 15 to control the oxidant electrode pressure.

  Hydrogen as a fuel gas is supplied from the high-pressure hydrogen tank 21 to the fuel electrode 1b via the hydrogen supply path 22. The high-pressure hydrogen supplied from the high-pressure hydrogen tank 21 is depressurized to a desired pressure by the hydrogen pressure regulating valve 23, further humidified by the hydrogen-based humidifier 25, and supplied to the fuel electrode 1b. The pressure at the fuel electrode inlet is detected by the hydrogen pressure gauge 29 and transmitted to the controller 45.

  A hydrogen circulation path 26 that circulates hydrogen gas that has not been consumed at the fuel electrode from the outlet to the inlet of the fuel electrode 1b and a hydrogen circulation pump 24 are provided.

  The generated voltage of the fuel cell body 1 is detected by the voltmeter 41 and transmitted to the controller 45. In addition, a load device 40 is connected to the fuel cell main body 1 via an ammeter 42, and the generated power of the fuel cell is supplied to the load device 40. The fuel cell system includes a battery 44 as a power storage device and a battery controller 43 that controls charging and discharging thereof. The battery controller 43 discharges the battery 44 from the battery 44 to the load device 40 when the generated power of the fuel cell main body 1 is insufficient, and from the fuel cell main body 1 to the battery 44 when there is surplus in the generated power of the fuel cell main body 1. Control the charging.

  Further, the battery controller 43 detects the voltage and charge / discharge current of the battery 44, and further, if necessary, the battery temperature, etc., and detects or estimates the amount of electricity stored in the battery 44 based on these detection results, and sends it to the controller 45. Send.

  In order to maintain the operating temperature of the fuel cell main body 1 at an appropriate value, a cooling system for circulating the cooling water is provided. The cooling system connects a cooling water pump 31 that circulates and drives the cooling water, a cooling water path in the fuel cell main body 1, a cooling water thermometer 34, and a heat exchanger 33 that releases heat of the cooling water to the outside of the system. A cooling water circulation path 32 is provided.

  The controller 45 controls each actuator in the system using each sensor signal at the time of starting, stopping, and generating power of the fuel cell system.

  In order to supply air as an oxidant to the oxidant electrode 1a, nitrogen that does not react chemically passes through the electrolyte membrane and accumulates in the hydrogen circulation system including the fuel electrode 1b, the hydrogen circulation path 26, and the hydrogen circulation pump 24. . If the amount of nitrogen accumulated in the hydrogen circulation system becomes too large, the mass density of the gas in the hydrogen circulation system increases and the gas circulation amount by the hydrogen circulation pump 24 cannot be maintained, so the amount of nitrogen in the hydrogen circulation system is managed. There is a need. Therefore, the gas containing nitrogen in the hydrogen circulation system is discharged to the outside by the hydrogen discharge valve 28 so that the circulation performance can be maintained for the amount of nitrogen present in the hydrogen circulation system.

  Although not shown in FIG. 1, the controller 45 includes a vehicle speed sensor for detecting the vehicle speed, an accelerator sensor for detecting the accelerator operation amount, a brake switch for detecting whether or not the brake is in operation (the same as the brake lamp lighting signal). Signal) is connected. Then, a vehicle speed signal, an accelerator operation amount signal, and a brake operation state signal are input to the controller 45 from these sensors.

Controller 45, CPU, ROM, a working RAM, and is constituted by a microprocessor with input and output interface. The controller 45 controls the entire fuel cell system by executing a control program stored in the ROM, and idle stop control means for temporarily stopping the supply of fuel gas and oxidant gas when the fuel cell is under a low load. It is.

  Further, when detecting a low load on the fuel cell, the controller 45 closes the hydrogen pressure regulating valve 23 to stop the supply of hydrogen gas, and instructs the current extraction from the fuel cell body 1 or opens the hydrogen discharge valve 28. Then, a pressure reducing operation for reducing the pressure of the fuel electrode 1b to a predetermined pressure or less is performed.

  FIG. 2 is a schematic cross-sectional view of a single cell constituting the fuel cell main body 1 of FIG. The fuel cell single cell 100 includes a membrane electrode assembly (MEA) 101 and separators 107 and 108. The MEA 101 includes an electrolyte membrane 102 that conducts hydrogen ions and does not conduct electrons, a fuel electrode catalyst layer 103 and an oxidant electrode catalyst layer 104 that are formed on both surfaces of the electrolyte membrane 102 and each support catalyst fine particles such as platinum on carbon. The fuel electrode gas diffusion layer 105 and the oxidant electrode gas diffusion layer 106, each of which is formed of a conductive porous material, are provided.

  A fuel gas channel 109 is formed in the separator 107 on the fuel electrode side, and hydrogen as a fuel gas is supplied. An oxidant gas flow path 110 is formed in the separator 108 on the oxidant electrode side, and air as an oxidant gas is supplied. Hydrogen and oxygen in the air generate electricity by causing an electrochemical reaction of the above formulas (1) and (2).

Next, the operation of the controller 45 in Reference Example 1 will be described with reference to the control flowchart of FIG. This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

  First, in step (hereinafter, step is abbreviated as S) 01, the controller 45 reads the vehicle state and the state of the fuel cell system. These states include the vehicle speed detected by the vehicle speed sensor, the accelerator operation amount (accelerator opening) detected by the accelerator sensor, the brake switch indicating whether or not the brake is in operation, the required output to the fuel cell, and the hydrogen pressure gauge 29 The hydrogen pressure of the fuel electrode 1b, the air pressure of the oxidant electrode 1a detected by the air pressure gauge 16, and the amount of charge of the battery 44 detected by the battery controller 43 are included.

Next, in S02, the controller 45 determines whether or not idle stop is permitted. As an idle stop determination condition, for example, the vehicle speed is a predetermined speed or less, the accelerator opening is 0, the brake operation is being performed, the required output is a predetermined value or less, and the battery charge amount is a predetermined value or more are all satisfied. When it is determined that the idle stop is permitted. (Of course, all combinations of these conditions are not essential, and any condition determination may be performed.)
When it is determined in S02 that the idle stop is permitted, the process proceeds to S03. When it is determined that the idle stop is not permitted, the process returns to the main routine without doing anything.

  In S03, the controller 45 closes the hydrogen pressure regulating valve 23 to stop new hydrogen supply to the fuel electrode 1b. Next, in S04, the controller 45 determines whether or not the hydrogen pressure of the fuel electrode 1b detected by the hydrogen pressure gauge 29 exceeds a predetermined pressure value. If the hydrogen pressure exceeds the predetermined pressure value, the process proceeds to S05, and if the hydrogen pressure does not exceed the predetermined pressure value, the process proceeds to S06.

  In S05, the controller 45 instructs the load device 40 to take out the current from the fuel cell main body 1 and consume it, and then returns to the main routine. As a result, the hydrogen in the fuel electrode 1b and the hydrogen circulation path 26 is consumed, and the fuel electrode pressure is lowered, thereby enabling an idle stop.

  In S06, the controller 45 instructs the load device 40 to stop current extraction from the fuel cell main body 1, and returns to the main routine. Thereafter, an idle stop stop processing routine (not shown) called from the main routine performs measures such as stopping the air compressor and stopping the hydrogen circulation pump.

  In S05, when the battery 44 has a sufficient free capacity, the battery 44 may be charged via the battery controller 43 without consuming the current extracted from the fuel cell body 1 by the load device 40. Thus, there is an effect that the fuel consumption in the decompression operation can be used without waste and the fuel efficiency of the fuel cell system can be further improved.

[Example]
Next, examples of the fuel cell system according to the present invention will be described. The system configuration of the embodiment is the same as that of the reference example 1 shown in FIG. In this embodiment, when idling stop is permitted, current consumption is performed by increasing the rotational speed of at least one of the hydrogen circulation pump 24 and the air compressor 11, and the hydrogen pressure of the fuel electrode is reduced to a predetermined pressure value or less. It is characterized in that it is lowered. According to the present embodiment, even when the load device cannot consume current, the decompression operation by current consumption can be performed, the frequency of idle stop can be improved, and the fuel efficiency of the fuel cell can be improved. is there.

Figure 4 is a control flowchart for explaining the operation of definitive controller 45 in the examples. This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

The processing contents from S01 to S04 in FIG. 4 are the same as those in Reference Example 1 shown in FIG. In S04, the controller 45 determines whether or not the hydrogen pressure of the fuel electrode 1b detected by the hydrogen pressure gauge 29 exceeds a predetermined pressure value. If the hydrogen pressure exceeds the predetermined pressure value, the process proceeds to S05, and if the hydrogen pressure does not exceed the predetermined pressure value, the process proceeds to S06.

  In S05, the controller 45 instructs to take out the current from the fuel cell body 1 for consumption by increasing the rotational speed of at least one of the hydrogen circulation pump 24 and the air compressor 11, and returns to the main routine. . As a result, the fuel electrode 1b and the hydrogen in the hydrogen circulation path are consumed, and the fuel electrode pressure decreases. In S06, the controller 45 instructs stop of the current extraction from the fuel cell main body 1, and returns to the main routine.

[Reference Example 2]
Next, Reference Example 2 of the fuel cell system according to the present invention will be described. The system configuration of Reference Example 2 is the same as that of Reference Example 1 shown in FIG. In this reference example, when the depressurization operation for reducing the hydrogen pressure of the fuel electrode to a predetermined pressure value or less is performed by taking out the current from the fuel cell when the idle stop is permitted, the oxidant electrode that is not depressurized is used. It is characterized in that the target gas supply amount is set to be equal to or greater than the supply amount corresponding to the extraction current. According to this reference example, it is possible to sufficiently supply the reaction gas to the electrode that is not operated under reduced pressure, and it is possible to prevent the deterioration of the fuel cell main body due to the lack of the reaction gas.

FIG. 5 is a control flowchart for explaining the operation of the controller 45 in Reference Example 2 . This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

The processing contents from S01 to S04 in FIG. 5 are the same as those in Reference Example 1 shown in FIG. In S04, the controller 45 determines whether or not the hydrogen pressure of the fuel electrode 1b detected by the hydrogen pressure gauge 29 exceeds a predetermined pressure value. If the hydrogen pressure exceeds the predetermined pressure value, the process proceeds to S05, and if the hydrogen pressure does not exceed the predetermined pressure value, the process proceeds to S06. In S06, the current extraction from the fuel cell is terminated, and the process returns to the main routine.

  In S05, the controller 45 instructs the load device 40 to take out current from the fuel cell main body 1 and consume it. As a result, the fuel electrode 1b and the hydrogen in the hydrogen circulation path are consumed, and the fuel electrode pressure decreases. Next, in S07, it is determined whether or not the rotational speed of the air compressor 11 is less than a predetermined rotational speed. The predetermined number of revolutions is the number of revolutions that can supply the air flow rate corresponding to the current value instructed to extract current from the fuel cell in S05.

  If it is determined in S07 that the rotation speed of the air compressor 11 is not less than the predetermined rotation speed (if it is equal to or higher than the predetermined rotation speed), it is determined that the air flow rate corresponding to the extraction current is supplied, and the process proceeds to S10. If it is determined in S07 that the rotational speed of the air compressor 11 is less than the predetermined rotational speed, the process proceeds to S08. In S08, it is determined whether or not the rotational speed of the hydrogen circulation pump 24 is less than a predetermined rotational speed. The predetermined number of revolutions is the number of revolutions that can supply the hydrogen circulation flow rate corresponding to the current value instructed to extract current from the fuel cell in S05.

  If it is determined in S08 that the rotation speed of the hydrogen circulation pump 24 is less than the predetermined rotation speed, the process proceeds to S09. If it is determined in S08 that the rotation speed of the hydrogen circulation pump 24 is not less than the predetermined rotation speed (if it is equal to or higher than the predetermined rotation speed), the process proceeds to S10.

  In S09, the extraction current from the fuel cell main body 1 is increased, the rotation speed of the hydrogen circulation pump 24 is increased, the rotation speed of the air compressor 11 is increased, and the process returns to the main routine. As a result, the amount of air supplied to the fuel cell main body 1 is increased, and sufficient gas is supplied to the electrode that does not perform the depressurization operation, so that deterioration due to a shortage of supply gas during the depressurization operation does not occur.

  In S10, the extraction current from the fuel cell main body 1 is maintained (fixed), the rotation speed of the hydrogen circulation pump 24 and the rotation speed of the air compressor 11 are maintained (fixed), and the process returns to the main routine.

[Reference Example 3]
Next, Reference Example 3 of the fuel cell system according to the present invention will be described. The system configuration of the reference example 3 is substantially the same as that of the reference example 1 shown in FIG. 1, but a nitrogen concentration detection means (not shown in FIG. 1) is provided in the fuel electrode 1 b or the hydrogen circulation path 26. In this reference example, when idling stop is permitted, when the depressurization operation for reducing the hydrogen pressure of the fuel electrode to a predetermined pressure value or less is performed by taking out the current from the fuel cell, the fuel electrode or the hydrogen circulation path (fuel circulation) The characteristic is that the current extraction is limited when the nitrogen concentration in the road) is detected and the detected nitrogen concentration is a predetermined value or more. According to this reference example, when the nitrogen concentration of the fuel electrode is high, current extraction is not performed, so there is no idle stop when the nitrogen concentration is high, and the hydrogen partial pressure increases when returning from idle stop. It becomes difficult to deteriorate the fuel cell stack.

FIG. 6 is a control flowchart for explaining the operation of the controller 45 in Reference Example 3 . This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

  First, in S01, the controller 45 reads the vehicle state and the state of the fuel cell system. These states include the vehicle speed detected by the vehicle speed sensor, the accelerator operation amount (accelerator opening) detected by the accelerator sensor, the brake switch indicating whether or not the brake is in operation, the required output to the fuel cell, and the hydrogen pressure gauge 29 The hydrogen pressure of the fuel electrode 1b, the air pressure of the oxidant electrode 1a detected by the air pressure gauge 16, and the nitrogen concentration detected by the nitrogen concentration detecting means are included.

  Next, in S02, the controller 45 determines whether or not idle stop is permitted. As an idle stop determination condition, for example, when the vehicle speed is equal to or lower than a predetermined speed, the accelerator opening is 0, the brake operation is performed, and the required output is equal to or lower than a predetermined value, the idle stop is permitted. judge.

  When it is determined in S02 that the idle stop is permitted, the process proceeds to S03. When it is determined that the idle stop is not permitted, the process returns to the main routine without doing anything.

  In S03, the controller 45 closes the hydrogen pressure regulating valve 23 to stop new hydrogen supply to the fuel electrode 1b. Next, in S04, the controller 45 determines whether or not the hydrogen pressure of the fuel electrode 1b detected by the hydrogen pressure gauge 29 exceeds a predetermined pressure value. If the hydrogen pressure exceeds the predetermined pressure value, the process proceeds to S05, and if the hydrogen pressure does not exceed the predetermined pressure value, the process proceeds to S06.

  In S05, the controller 45 determines whether or not the nitrogen concentration in the fuel electrode 1b or the hydrogen circulation path 24 detected by the nitrogen concentration detecting means is less than a predetermined concentration. If the nitrogen concentration is less than the predetermined concentration, the process proceeds to S07. If the nitrogen concentration is not less than the predetermined concentration (if it is equal to or higher than the predetermined concentration), the process proceeds to S06.

  In S07, the controller 45 instructs the load device 40 to take out the current from the fuel cell main body 1 and consume it, and then returns to the main routine. As a result, the fuel electrode 1b and the hydrogen in the hydrogen circulation path are consumed, and the fuel electrode pressure decreases. In S06, the controller 45 instructs the load device 40 to stop current extraction from the fuel cell main body 1, and returns to the main routine.

[Reference Example 4]
Next, reference example 4 of the fuel cell system according to the present invention will be described. The system configuration of Reference Example 4 is the same as that of Reference Example 1 shown in FIG. This reference example is characterized in that, when idling stop is permitted, a depressurization operation for reducing the hydrogen pressure of the fuel electrode to a predetermined pressure value or less is performed by opening a hydrogen discharge valve (purge valve).

FIG. 7 is a control flowchart for explaining the operation of the controller 45 in Reference Example 4 . This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

  First, in S01, the controller 45 reads the vehicle state and the state of the fuel cell system. These states include the vehicle speed detected by the vehicle speed sensor, the accelerator operation amount (accelerator opening) detected by the accelerator sensor, the brake switch indicating whether or not the brake is in operation, the required output to the fuel cell, and the hydrogen pressure gauge 29 The hydrogen pressure of the fuel electrode 1b and the air pressure of the oxidant electrode 1a detected by the air pressure gauge 16 are included.

  Next, in S02, the controller 45 determines whether or not idle stop is permitted. As an idle stop determination condition, for example, when the vehicle speed is equal to or lower than a predetermined speed, the accelerator opening is 0, the brake operation is performed, and the required output is equal to or lower than a predetermined value, the idle stop is permitted. judge.

  When it is determined in S02 that the idle stop is permitted, the process proceeds to S03. When it is determined that the idle stop is not permitted, the process returns to the main routine without doing anything.

  In S03, the controller 45 closes the hydrogen pressure regulating valve 23 to stop new hydrogen supply to the fuel electrode 1b. Next, in S04, the controller 45 determines whether or not the hydrogen pressure of the fuel electrode 1b detected by the hydrogen pressure gauge 29 exceeds a predetermined pressure value. If the hydrogen pressure exceeds the predetermined pressure value, the process proceeds to S05, and if the hydrogen pressure does not exceed the predetermined pressure value, the process proceeds to S06.

  In S05, the controller 45 opens the hydrogen discharge valve 28 and executes a purge for discharging the hydrogen in the fuel electrode 1b and the hydrogen circulation path 26 from the hydrogen exhaust path 27 to the outside of the system, thereby reducing the hydrogen pressure. Return to the main routine. As a result, the hydrogen pressure in the fuel electrode 1b and the hydrogen circulation path decreases. In S06, the controller 45 gives an instruction to close the hydrogen discharge valve 28 and returns to the main routine in order to end the purge.

[Reference Example 5]
Next, Reference Example 5 of the fuel cell system according to the present invention will be described. The system configuration of the reference example 5 is substantially the same as that of the reference example 1 shown in FIG. 1, but includes a fuel gas diluting means for diluting the discharged hydrogen at the air flow rate supplied by the air compressor 11 downstream of the hydrogen discharge valve 28. ing. In this reference example, when idling stop is permitted, when the hydrogen discharge valve (purge valve) is opened to reduce the hydrogen pressure of the fuel electrode below a predetermined pressure value, the hydrogen discharge valve is discharged. It is characterized in that the hydrogen flow rate is limited and the dilution air flow rate is diluted so as to be less than a predetermined concentration (hydrogen combustion lower limit concentration).

FIG. 8 is a control flowchart for explaining the operation of the controller 45 in Reference Example 5 . This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

The processing contents from S01 to S06 in FIG. 8 are the same as those in Reference Example 4 shown in FIG. In this reference example, steps S07 to S10 are added after the step S05 in FIG. In S05, the controller 45 opens the hydrogen discharge valve 28 and executes a purge for discharging the hydrogen in the fuel electrode 1b and the hydrogen circulation path 26 from the hydrogen exhaust path 27 to the outside of the system, thereby reducing the hydrogen pressure. , Go to S07.

  In S07, it is determined whether or not the flow rate of dilution air for diluting the hydrogen discharged by the purge execution exceeds a predetermined flow rate. For detection of the air flow rate, a flow rate sensor may be provided downstream of the air compressor 11, or the air flow rate may be estimated from the rotation speed of the air compressor 11. The predetermined flow rate used in the determination of S07 is an air flow rate for diluting the hydrogen flow rate discharged from the hydrogen discharge valve 28 to less than the lower limit concentration of hydrogen combustion.

  If it is determined in S07 that the dilution air flow rate exceeds the predetermined flow rate, the process proceeds to S08, and if not, the process proceeds to S10. In S08, it is determined whether the rotation speed of the air compressor 11 is less than a predetermined rotation speed. If the rotation speed of the air compressor is less than the predetermined rotation speed, the process proceeds to S09, and if not, the process proceeds to S10.

  In S09, the purge flow rate, which is the discharge flow rate from the hydrogen discharge valve 28, is increased, and the process returns to the main routine. In S09, the purge flow rate is reduced and the process returns to the main routine. Thereby, sufficient safety can be ensured during the decompression operation of the fuel electrode.

For example, there are the following three methods for changing the purge flow rate of the hydrogen discharge valve 28 in this reference example.

(1) The purge flow rate is changed by periodically opening the hydrogen discharge valve 28 and changing the time rate during which the hydrogen discharge valve 28 is open.

(2) As the hydrogen discharge valve 28, a plurality of hydrogen discharge valves having different orifice diameters are provided, and the purge flow rate is changed by switching the hydrogen discharge valve to be opened.

(3) The hydrogen discharge valve 28 is provided with a valve whose opening degree can be changed, and the purge flow rate is changed by controlling the opening degree.

  By these three kinds of purge flow rate adjustments, hydrogen more than a necessary amount is not released when the fuel electrode pressure is reduced, and fuel is not consumed wastefully.

[Reference Example 6]
Next, Reference Example 6 of the fuel cell system according to the present invention will be described. The system configuration of Reference Example 6 is the same as that of Reference Example 1 shown in FIG. In this reference example, when idle stop is permitted, the depressurization operation to reduce the hydrogen pressure of the fuel electrode to a predetermined pressure value or less is performed by extracting current from the fuel cell, and the hydrogen discharge valve (purge valve) is opened. It is characterized in that it is used together. According to this reference example , since the pressure reducing operation can be performed by using both the current extraction operation and the purge operation, there is an effect that the pressure can be reduced to a desired pressure in a short time.

FIG. 9 is a control flowchart for explaining the operation of the controller 45 in Reference Example 6 . This control flowchart is called and executed from the main routine of the controller every fixed control cycle, for example, every 100 [ms].

The processing contents from S01 to S04 in FIG. 9 are the same as those in Reference Example 1 shown in FIG. In this reference example, if it is determined in S04 that the hydrogen pressure exceeds the predetermined pressure, the process proceeds to S05, and if not, the process returns to the main routine without doing anything.

  In S05, it is determined whether or not current extraction (current consumption) from the fuel cell is permitted. For example, when the load device 40 can consume current, or when the battery 44 can be charged, it is determined that current extraction from the fuel cell body 1 is permitted, and the load device 40 cannot consume current, and the battery If 44 is not chargeable, it is determined that current consumption is not permitted. When it is determined in S05 that current consumption is permitted, the process proceeds to S06, current is consumed, and the process proceeds to S08. If it is determined in S05 that current consumption is not permitted, the process proceeds to S07, where the current consumption is terminated, and the process proceeds to S08.

  In S08, it is determined whether the purge operation is permitted. For example, when the hydrogen discharged from the hydrogen discharge valve 28 cannot be diluted to below the lower combustion limit concentration at the air flow rate delivered by the air compressor 11, it is determined that the purge operation is not permitted.

  When it is determined in S08 that the purge operation is permitted, the process proceeds to S09, the hydrogen discharge valve 28 is opened, the purge operation is executed, and the process returns to the main routine. When it is determined in S08 that the purge operation is not permitted, the process proceeds to S10, the hydrogen discharge valve 28 is closed, the purge is terminated, and the process returns to the main routine.

  While the preferred embodiments have been described above, they are not intended to limit the invention. For example, when an idle stop permission condition other than the air pressure is satisfied, it is conceivable to perform the pressure reducing operation of the oxidizer electrode while stopping the air supply from the air compressor and continuing the hydrogen supply. Further, as the depressurization operation, a configuration in which the fuel electrode pressure and the oxidant electrode pressure are simultaneously reduced is possible.

1 is a system configuration diagram showing an overall configuration of a fuel cell system according to the present invention. It is a schematic cross section explaining the structure of a fuel cell single cell. 5 is a control flowchart of Reference Example 1. It is a control flowchart of an Example . 10 is a control flowchart of Reference Example 2 . 10 is a control flowchart of Reference Example 3 . 10 is a control flowchart of Reference Example 4 . 10 is a control flowchart of Reference Example 5 . 10 is a control flowchart of Reference Example 6 .

DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 1a ... Oxidizer electrode 1b ... Fuel electrode 11 ... Air compressor 13 ... Air-type humidifier 15 ... Air pressure regulator 21 ... High-pressure hydrogen tank 23 ... Hydrogen pressure regulator 24 ... Hydrogen circulation pump 25 ... Hydrogen-type humidifier 26 ... Hydrogen circulation path 28 ... Hydrogen discharge valve 40 ... Load device 43 ... Battery controller 44 ... Battery 45 ... Controller

Claims (2)

A fuel supply device for supplying fuel gas;
An oxidant supply device for supplying an oxidant gas;
A fuel cell that generates electricity through an electrochemical reaction between the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode;
An idle stop control means for temporarily stopping the supply of the fuel gas and the oxidant gas when the fuel cell is at a low load and the fuel gas pressure of the fuel electrode is equal to or lower than a predetermined pressure;
A fuel circulation path and a circulation pump for circulating the fuel gas that has not been consumed at the fuel electrode from an outlet to an inlet of the fuel electrode;
In a fuel cell system comprising:
When the idle stop control means temporarily stops the supply of the fuel gas and the oxidant gas, a pressure reducing operation for reducing the fuel gas pressure at the fuel electrode to be equal to or lower than the predetermined pressure is performed, and the pressure reducing operation is a fuel cell. An electric load for extracting current during the decompression operation by increasing the number of revolutions of the circulating pump during the decompression operation from the number of revolutions immediately before the start of the decompression operation. A fuel cell system characterized in that it is larger than the electric load immediately before the start of operation. A fuel supply device for supplying fuel gas;
A compressor for supplying oxidant gas;
A fuel cell that generates electricity through an electrochemical reaction between the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode;
An idle stop control means for temporarily stopping the supply of the fuel gas and the oxidant gas when the fuel cell is at a low load and the fuel gas pressure of the fuel electrode is equal to or lower than a predetermined pressure;
In a fuel cell system comprising:
When the idle stop control means temporarily stops the supply of the fuel gas and the oxidant gas, a pressure reducing operation for reducing the fuel gas pressure at the fuel electrode to be equal to or lower than the predetermined pressure is performed, and the pressure reducing operation is a fuel cell. a current extraction operation from, by increasing than the rotational speed of the depressurization immediately before the rotational speed of the compressor in the depressurization, the pressure reducing operation of the electric load for the current extraction during the depressurization fuel cell system that is characterized in that larger than the electric load immediately before the start.

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