JP2013239250A - Fuel battery system and operating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system capable of continuously supplying fuel gas to a fuel battery even when a requested power generation amount is small.SOLUTION: The fuel battery system comprises: a fuel battery stack 10; a fuel gas supply flow passage in which hydrogen is circulated; a fuel gas circulation flow passage for circulating the hydrogen; a first injector 24 provided on the fuel gas supply flow passage on an upper stream side than a connection point of the fuel gas circulation flow passage, and emitting the hydrogen; a bypass flow passage connecting the fuel gas supply flow passage on an upstream side of the first injector 24 to the fuel gas supply flow passage on a downstream side of the first injector 24, and bypassing the hydrogen to the first injector 24; small flow rate supply means provided on the bypass flow passage and constituted so that the hydrogen can be continuously supplied at a small flow rate; region determination means for determining whether the requested power generation amount is in a low load region or not; and control means for controlling the first injector 24. When the region determination means determines the requested power generation amount as the low load region, the control means stops the first injector 24, and the small flow rate supply means continuously supplies fuel gas at a small flow rate.

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  As a power source for a fuel cell vehicle or the like, a fuel cell that generates electric power by supplying hydrogen (fuel gas) and oxygen-containing air (oxidant gas) has attracted attention. Then, a method has been proposed in which an injector is provided upstream of the anode, hydrogen is injected by PWM control of the injector corresponding to the required power generation amount, and the flow rate of hydrogen to the fuel cell is controlled (see Patent Document 1). ).

JP 2007-165237 A

  However, when the fuel cell vehicle stops, for example, waiting for a signal or waiting for a person, and enters an idle state (no load state), the required power generation amount becomes small and the closing time of the injector becomes long, and hydrogen is not supplied to the fuel cell. There is a risk that a period will be formed.

  Therefore, an object of the present invention is to provide a fuel cell system capable of continuously supplying fuel gas to the fuel cell even when the required power generation amount is small, and an operation method thereof.

  As means for solving the above-mentioned problems, the present invention provides a fuel cell having a fuel gas flow path, which generates power when fuel gas is supplied to the fuel gas flow path, and an inlet of the fuel gas flow path. A fuel gas supply channel through which fuel gas directed to the fuel gas channel flows, and an outlet of the fuel gas channel and the fuel gas supply channel are connected, and fuel from the fuel gas channel is connected The off-gas is returned to the fuel gas supply flow path, and the fuel gas circulation flow path for circulating the fuel gas and the fuel gas supply flow path upstream from the connection point of the fuel gas circulation flow path are provided to inject the fuel gas Connecting the injector, the fuel gas supply channel upstream of the injector, and the fuel gas supply channel downstream of the injector, and bypassing the fuel gas bypassing the injector, the bypass flow A small flow rate supply means configured to be capable of continuously supplying fuel gas at a low flow rate, an area determination means for determining whether the required power generation amount is in a low load area, and a control means for controlling the injector The control means stops the injector and the small flow rate supply means continuously supplies fuel gas at a low flow rate when the region determination means determines that the region is a low load region. It is a battery system.

According to such a configuration, when the region determination unit determines that the region is a low load region, the control unit stops the injector (stopped state, OFF state), so that the fuel gas is not injected by the injector, and the fuel Gas pressure and flow do not pulsate.
Here, the stopped state (OFF state) of the injector means a state in which the injector is continuously closed and fuel gas is not continuously injected. On the other hand, the injector operating state (ON state) means a state in which the injector is intermittently or intermittently opened and closed, fuel gas is injected intermittently or intermittently, and the pressure and flow of the fuel gas pulsate. If the secondary pressure of the injector exceeds the target pressure and overshoots due to pulsation, fuel gas is not injected even if an open command is input to the injector.

  Since the small flow rate supply means continuously supplies the fuel gas at a small flow rate, the fuel gas bypasses the injector through the bypass channel and is continuously supplied to the fuel gas channel of the fuel cell. Accordingly, the fuel cell is unlikely to be short of fuel gas, that is, the fuel gas is unlikely to be short of the stoichiometric ratio, and the power generation of the fuel cell is stabilized. The stoichiometric ratio here means the surplus rate of the fuel gas, and it is actually compared with the fuel gas (hydrogen etc.) necessary to react with the oxidant gas (oxygen) supplied to the cathode without excess or deficiency. It is a ratio indicating how much excess fuel gas is present.

  In the fuel cell system, a regulator that is provided in the fuel gas supply channel upstream of a connection point on the upstream side of the bypass channel and adjusts the pressure of the fuel gas to a pressure corresponding to a required power generation amount, and the fuel Based on the pressure of the gas between the purge valve that connects to the gas circulation flow path and opens the gas in the fuel gas circulation flow path to the outside, and the gas between the regulator and the purge valve, the gas leaks Gas leakage determining means for determining whether or not the fuel gas leakage is determined, the area determining means determines that the load is low, the injector is stopped, and the small flow rate supplying means continuously supplies fuel gas at a small flow rate. When the valve closing command is input to the purge valve, the gas leak determination means preferably determines whether or not gas is leaking.

  According to such a configuration, when the region determination unit determines that the region is a low load region, the injector is stopped, and the small flow rate supply unit continuously supplies fuel gas at a low flow rate, the purge valve is closed. When the command is input, the fuel gas pressure is not pulsating.

  Here, when gas is not leaking, the pressure of the gas between the regulator and the purge valve is adjusted to be approximately constant by the regulator, or extremely slowly decreases as the fuel gas is consumed by the fuel cell. On the other hand, when the gas is leaking, the pressure of the gas between the regulator and the purge valve is greatly reduced compared to when the gas is not leaking.

  As described above, when the pressure of the fuel gas is not pulsating and the valve closing command is input to the purge valve, the gas leakage determination means determines whether or not the gas is leaking. Leakage can be judged.

  The fuel cell system includes flooding determination means for determining whether flooding has occurred in the fuel cell, the area determination means determines that the area is a low load area, the injector stops, and the small flow rate In the case where the supply means continuously supplies fuel gas at a small flow rate, the control means preferably operates the injector when the flood determination means determines that flooding has occurred.

  According to such a configuration, when the flooding determination unit determines that flooding has occurred when the injector is stopped and the fuel gas is continuously supplied at a low flow rate in the low load region, the control unit Activates the injector.

  Thereby, since fuel gas is injected intermittently or intermittently by an injector, the flow of fuel gas pulsates. Then, when the pulsating fuel gas flows through the fuel gas flow path of the fuel cell, water staying in the fuel gas flow path and water adhering to the MEA are quickly discharged from the fuel gas flow path. The power generation stability is restored.

  In the fuel cell system, the small flow rate supply means supplies a fuel gas at a flow rate corresponding to a lower limit value of the required power generation amount, and a fuel gas bypass valve that supplies / shuts off the fuel gas and the fuel cell can generate power. It is preferable to provide an orifice set in a flow path cross-sectional area.

  According to such a configuration, the fuel gas can be continuously supplied at a low flow rate by simply opening the fuel gas bypass valve while simplifying the configuration of the low flow rate supply means.

  According to the present invention, it is possible to provide a fuel cell system capable of continuously supplying fuel gas to the fuel cell even when the required power generation amount is small, and an operation method thereof.

1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 1st Embodiment. It is a map which shows the relationship between request | requirement electric power (request | requirement electric power generation amount) and instruction | command electric current (hydrogen flow rate). (A) is a time chart which shows the operation example of the fuel cell system which concerns on 1st Embodiment, (b) is a comparative example. It is a time chart which shows the change of the anode pressure at the time of normal time (no gas leak) and anode leak occurrence. It is a graph which shows the relationship between the target hydrogen pressure (secondary pressure of the regulator) and the hydrogen flow rate (bypass amount) flowing through the bypass channel. It is a block diagram of the fuel cell system which concerns on 2nd Embodiment. It is a block diagram of the fuel cell system which concerns on 3rd Embodiment.

<< First Embodiment >>
A first embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
A fuel cell system 1 shown in FIG. 1 is mounted on a fuel cell vehicle (vehicle, moving body) (not shown). The fuel cell vehicle is, for example, an automobile, a tricycle, a motorcycle, a unicycle, a train, or the like. However, the structure mounted in the other mobile body, for example, a ship, an aircraft, may be sufficient.

  The fuel cell system 1 includes a fuel cell stack 10, a cell voltage monitor 15, an anode system that supplies and discharges hydrogen (fuel gas and reactive gas) to and from the anode of the fuel cell stack 10, and a cathode of the fuel cell stack 10. In contrast, a cathode system that supplies and discharges air containing oxygen (oxidant gas and reaction gas), a power control system that controls power generation of the fuel cell stack 10, and an ECU 70 (Electronic Control Unit, electronic control device) that electronically controls these systems ) And.

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (for example, 200 to 400) solid polymer type single cells 11, and the plurality of single cells 11 are electrically connected in series. The single cell 11 includes an MEA (Membrane Electrode Assembly) and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane or the like, and an anode and a cathode (electrode) that sandwich the membrane.

  The anode and the cathode include a porous body having conductivity such as carbon paper, and a catalyst (Pt, Ru, etc.) supported on the anode and causing an electrode reaction in the anode and the cathode.

  Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA, and through holes for supplying and discharging hydrogen or air to all single cells. It functions as a passage 12 (fuel gas passage) and a cathode passage 13 (oxidant gas passage).

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

2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

<Cell voltage monitor>
The cell voltage monitor 15 is a device that detects a cell voltage for each of the plurality of single cells 11 constituting the fuel cell stack 10, and includes a monitor main body and a wire harness that connects the monitor main body and each single cell. .

  The monitor body scans all the single cells 11 at a predetermined period, detects the cell voltage of each single cell 11, and calculates the average cell voltage and the lowest cell voltage. The monitor main body (cell voltage monitor 15) outputs an average cell voltage and a minimum cell voltage to the ECU 70.

<Anode system>
The anode system includes a hydrogen tank 21 (fuel gas supply source), a normally closed shut-off valve 22, a regulator 23, a first injector 24 (first flow rate adjusting means), and a second injector 25 (second flow rate adjustment). Means), a normally closed hydrogen bypass valve 26, an ejector 27, and a purge valve 28.

  The hydrogen tank 21 is connected to the inlet of the anode channel 12 via a pipe 21a, a shutoff valve 22, a pipe 22a, a regulator 23, a first injector 24, a pipe 24a, an ejector 27, and a pipe 27a. The pipe 23a is connected to the pipe 27a via the pipe 25a, the second injector 25, and the pipe 25b. The pipe 23a is connected to the pipe 24a via the pipe 26a, the hydrogen bypass valve 26, and the pipe 26b.

  When the first injector 24 and / or the second injector 25 injects hydrogen with the shut-off valve 22 open, or when the hydrogen bypass valve 26 opens, the hydrogen in the hydrogen tank 21 passes through the pipe 21a and the like. The anode channel 12 is supplied.

  Here, the fuel gas supply channel that is connected to the inlet of the anode channel 12 and through which hydrogen supplied to the anode channel 12 flows is a pipe 21a, a pipe 22a, a pipe 23a, a pipe 24a, and a pipe. 27a. The first injector 24 is provided in a fuel gas supply channel upstream of a connection point of a pipe 29b (fuel gas circulation channel) described later. The ejector 27 is provided at a connection point between the fuel gas supply channel and the pipe 29b (fuel gas circulation channel).

  A fuel gas supply flow path (pipe 24a) upstream of the first injector 24 and a connection point between the downstream of the first injector 24 and the pipe 29b (fuel gas circulation flow path). The bypass flow path in which hydrogen bypasses the first injector 24 includes a pipe 26a and a pipe 26b. A hydrogen bypass valve 26 is provided in the bypass flow path, and an orifice 26 c is provided in a pipe 26 b downstream of the hydrogen bypass valve 26.

  That is, the small flow rate supply means provided in the bypass channel and configured to be able to continuously supply hydrogen at a small flow rate includes a hydrogen bypass valve 26 for supplying / blocking hydrogen and an orifice 26c (throttle means). Has been. The flow path cross-sectional area in the portion where the orifice 26c is provided is the idle state (no load state) in which the accelerator opening is 0, that is, the fuel cell stack 10 is capable of generating power and has a lower limit value of the required power generation amount. The area where hydrogen is continuously supplied at a corresponding flow rate and stoichiometric ratio is set.

  In addition, a second bypass flow path that includes the pipe 25a and the pipe 25b and in which hydrogen bypasses the first injector 24 and the ejector 27 is configured, and the second injector 25 is provided in the second bypass flow path. .

  The hydrogen tank 21 is a container in which hydrogen is stored at a high pressure.

  The shutoff valve 22 is a normally closed electromagnetic valve, and is a valve that supplies / shuts off hydrogen by opening / closing in accordance with a command from the ECU 70.

  The regulator 23 includes a valve body and a valve seat having a port that is opened and closed by the valve body. The valve body opens and closes the port to depressurize hydrogen, and the secondary pressure is set to a required power (required power generation). It is a device that adjusts the pressure corresponding to the amount. The regulator 23 is provided in the fuel gas supply channel upstream of the connection point on the upstream side of the bypass channel.

  Specifically, the pressure of the air toward the cathode flow path 13 is input to the regulator 23 as a pilot pressure through a pipe 23b provided with an orifice 23c, and the valve body controls the port based on the pilot pressure. It opens and closes. The regulator 23 increases the secondary pressure as the pilot pressure increases, and balances the pressure in the anode channel 12 and the pressure in the cathode channel 13.

When the required power increases, the rotational speed of the compressor 41 increases, the discharge pressure increases, and the pilot pressure also increases. Based on this, the regulator 23 adjusts the secondary pressure.
However, the specific configuration of the regulator 23 is not limited to this, and for example, an electromagnetic actuator may be provided, and the valve body may be opened and closed by this actuator to control the secondary side pressure corresponding to the required power. .

  The first injector 24 and the second injector 25 are injection devices that inject hydrogen intermittently (intermittently) by being electronically controlled by the ECU 70. The first injector 24, the second injector 25, the shutoff valve 22, the compressor 41 described later, and the like use the fuel cell stack 10 and / or the battery 54 described later as a power source. The first injector 24 operates mainly when the required power is in a low load region to a medium load region, and the second injector 25 operates mainly in a high load region.

  The first injector 24 is configured to be capable of small flow injection, and the second injector 25 is configured to be capable of large flow injection. Such a difference in the injection flow rate is configured by changing the injection area of the nozzle that injects hydrogen and the stroke amount of the valve body that reciprocates in the first injector 24 and the second injector 25. Further, since the second bypass flow path provided with the second injector 25 bypasses the first injector 24 and the ejector 27, the fuel cell stack 10 is short of hydrogen even during high load power generation in which the second injector 25 operates. Not.

  The first injector 24 also has a function as a pressure adjusting means (regulator) for adjusting the secondary side pressure by repeatedly injecting / stopping hydrogen. Therefore, the regulator 23 can be omitted.

  The ejector 27 includes a nozzle 27b that generates a negative pressure by injecting new hydrogen from the first injector 24 and / or the hydrogen bypass valve 26, and a pipe 29b (fuel off-gas circulation flow that is sucked with the new hydrogen and the negative pressure. And a diffuser 27c that mixes with the anode off-gas of the channel and feeds it toward the pipe 27a (anode channel 12).

  The outlet of the anode flow path 12 is connected to the intake port of the ejector 27 via a pipe 29a, a check valve 29, and a pipe 29b. The anode off gas (fuel off gas) containing unconsumed hydrogen discharged from the anode flow path 12 is returned to the ejector 27 (fuel gas supply flow path). Therefore, the fuel gas circulation channel that circulates hydrogen by returning the anode off-gas discharged from the anode channel 12 to the ejector 27 includes a pipe 29a and a pipe 29b.

  The check valve 29 is a valve that prevents the backflow of the anode off gas. The pipe 29a is provided with a gas-liquid separator (not shown) for separating liquid water accompanying the anode off gas.

  The middle of the pipe 29a is connected to a diluter 43 described later via a pipe 28a, a purge valve 28, and a pipe 28b. The purge valve 28 discharges (purifies) impurities (water vapor, nitrogen, etc.) contained in the anode off-gas circulating through the pipe 29a during power generation of the fuel cell stack 10, or replaces the anode flow path 12 with hydrogen when the system is started. When it does, it is opened by ECU70. The ECU 70 opens the purge valve 28 when, for example, the lowest cell voltage detected via the cell voltage monitor 15 is equal to or lower than a predetermined voltage at which impurities are to be discharged.

  The middle of the pipe 29a is connected to the pipe 27a via the pipe 31a, the circulation pump 31, and the pipe 31b. For example, the circulation pump 31 is configured to operate according to a command from the ECU 70 when it is determined that flooding has occurred in the fuel cell stack 10. Then, when the circulation pump 31 is activated, the flow rate of the gas flowing through the anode flow path 12 is increased, and water staying in the anode flow path 12 and water adhering to the surface of the anode are discharged from the anode flow path 12, The flooding in the fuel cell stack 10 is eliminated.

  The pressure sensor 32 is attached to the pipe 27a. The pressure sensor 32 detects the pressure in the pipe 27 a (substantially equal to the pressure in the anode flow path 12) and outputs it to the ECU 70. Note that the pressure sensor 32 is not limited to the upstream side of the anode channel 12, and may be configured to be attached to, for example, a pipe 29 a, a pipe 28 a, or the like downstream of the anode channel 12. In the first embodiment, when the required power is in the low load region and the valve closing command is input to the purge valve 28, the purge valve 28 is normally closed based on the pressure value detected by the pressure sensor 32. Therefore, it is preferable that the pressure sensor 32 is attached to the pipe 28a immediately upstream of the purge valve 28.

<Cathode system>
The cathode system includes a compressor 41, a humidifier 42, a diluter 43, and a normally closed air bypass valve 44.
The discharge port of the compressor 41 is connected to the inlet of the cathode channel 13 via a pipe 41a, a humidifier 42, and a pipe 42a. When the compressor 41 operates in accordance with a command from the ECU 70, it takes in oxygen-containing air and supplies it to the cathode flow path 13 through the piping 41a and the like.

  The humidifier 42 includes a hollow fiber membrane 42d that is permeable to moisture. Then, the humidifier 42 exchanges moisture between the new air heading toward the cathode flow path 13 and the humid cathode offgas via the hollow fiber membrane 42d to humidify the new air.

A pipe 42b, a humidifier 42, a pipe 43a, a diluter 43, and a pipe 43b are sequentially connected to the outlet of the cathode flow path 13. And the cathode off gas from the cathode flow path 13 is discharged | emitted out of a vehicle through piping 42b etc. As shown in FIG.
The pipe 43a is provided with a back pressure valve (not shown) for controlling the back pressure (the pressure of the cathode channel 13) in accordance with a command from the ECU 70.

  The diluter 43 is a container that mixes the anode off-gas and the cathode off-gas and dilutes the hydrogen in the anode off-gas with the cathode off-gas (dilution gas), and has a dilution space therein.

  The middle of the pipe 41a is connected to the pipe 43a via the pipe 44a, the air bypass valve 44, and the pipe 44b. When the air bypass valve 44 is opened by the ECU 70, the air from the compressor 41 passes through the pipe 44a or the like, that is, bypasses the humidifier 42 and the fuel cell stack 10, and flows into the pipe 43a. Yes.

<Power control system>
The power control system includes a motor 51, a PDU 52 (Power Drive Unit), a power controller 53, and a battery 54. The motor 51 is connected to an output terminal (not shown) of the fuel cell stack 10 via the PDU 52 and the power controller 53, and the battery 54 is connected to the power controller 53. That is, the motor 51 and the battery 54 are connected in parallel to the power controller 53 (fuel cell stack 10).

  The motor 51 is an electric motor that generates a driving force for running the fuel cell vehicle.

  The PDU 52 is an inverter that converts DC power from the power controller 53 into three-phase AC power and supplies it to the motor 51 in accordance with a command from the ECU 70.

  The power controller 53 is configured to (1) control the output (generated power, current value, voltage value) of the fuel cell stack 10 according to a command from the ECU 70, and (2) control the charge / discharge of the battery 54, It has. Such a power controller 53 includes various electronic circuits such as a DC-DC chopper circuit.

  The battery 54 is a power storage device that charges / discharges electric power, and includes, for example, an assembled battery formed by combining a plurality of lithium ion type cells.

<Other equipment>
The IG 61 is a start switch of the fuel cell system 1 (fuel cell vehicle), and is provided around the driver's seat. The IG 61 is connected to the ECU 70, and the ECU 70 detects an ON signal (system start signal) and an OFF signal (system stop signal) of the IG 61.

  The accelerator opening sensor 62 is a sensor that detects an accelerator opening that is a depression amount of an accelerator pedal (not shown). The accelerator opening sensor 62 outputs the accelerator opening to the ECU 70.

  The warning lamp 63 is a lamp for informing the driver of gas leakage, and is provided around the driver's seat.

<ECU>
The ECU 70 is a control device that electronically controls the fuel cell system 1 and includes a CPU, ROM, RAM, various interfaces, electronic circuits, and the like, and controls various devices according to programs stored therein. However, various processes are executed.

<ECU-Injector control function>
The ECU 70 (control means) has a function of controlling the opening and closing (PWM control) of the first injector 24 and the second injector 25 independently. That is, the ECU 70 has a function of changing the ratio of the opening time to the closing time (duty ratio) of the first injector 24 and changing the amount of hydrogen injected by the first injector 24 including zero. . The ECU 70 has a function of controlling the second injector 25 in the same manner.

  In addition, the ECU 70 has a function of controlling the opening and closing of the hydrogen bypass valve 26, allowing the first injector 24 to bypass, and appropriately allowing hydrogen to flow into the pipe 24a.

<ECU-region determination function>
The ECU 70 (region determination means) determines whether the required power (required power generation amount) required for the fuel cell stack 10 is a low load region, a medium load region, or a high load region (see FIG. 3). It has a function. A specific determination method will be described later.

<ECU-Gas leak judgment function>
The ECU 70 (gas leakage determination means) has a function of determining whether or not anode leakage has occurred. That is, the ECU 70 determines whether or not the purge valve 28 to which the valve closing command is input is normally closed based on the change amount (measured ΔP) of the pressure value detected via the pressure sensor 32 in a predetermined time. In other words, the purge valve 28 is not normally closed but has an open failure, and the gas containing hydrogen that should remain in the flow path between the regulator 23 and the purge valve 28 (in the pipe 28a or the like) is downstream of the purge valve 28 ( It has a function to determine whether it has leaked out to the outside. A specific determination method will be described later.

<ECU-Flooding determination function>
The ECU 70 (flooding determination means) is based on the lowest cell voltage detected via the cell voltage monitor 15, whether or not flooding has occurred in the fuel cell stack 10, that is, stays in the anode flow path 12 or the like. It has a function to determine whether or not moisture (condensed water, etc.) should be discharged.

≪Operation and effect of fuel cell system≫
Next, the operation and effect of the fuel cell system 1 will be described with reference mainly to FIG.
Here, in the operation method of the fuel cell system 1 according to the first embodiment, the determination step (S101) for determining whether or not the required power is in the low load region, and the determination that the required power is in the low load region. In this case, a stop step (S102) for stopping the first injector 24 and a small flow continuous supply step (S102) for continuously supplying hydrogen at a small flow rate by the small flow rate supply means are included.
As an initial state, the IG 61 is turned on, hydrogen and air are supplied to the fuel cell stack 10, and the fuel cell stack 10 is generating electric power.

  In step S101, the ECU 70 determines whether the required power (required power generation amount, load request) is in a low load region. The required power is the power required from the fuel cell stack 10 by an external load such as an auxiliary device such as the motor 51 and the compressor 41, and an air conditioner. Here, when the command current is less than the first predetermined current, it is determined that the required power is in the low load region.

  Specifically, the ECU 70 calculates the current required power based on the accelerator opening input from the accelerator opening sensor 62 and the required power map. In the required power map, the required power increases as the accelerator opening increases.

  Then, the ECU 70 calculates a command current based on the required power and the map of FIG. The command current is a current value that the fuel cell stack 10 should output, and is a command value that the ECU 70 outputs to the power controller 53. The map of FIG. 3 is obtained by a preliminary test, simulation, or the like, and stored in the ECU 70 in advance.

  Further, as the command current increases, the rotational speed of the compressor 41 increases because the flow rate and pressure of the air flowing through the cathode flow path 13 are increased. When the rotational speed of the compressor 41 increases, the pilot pressure input to the regulator 23 increases, the secondary pressure of the regulator 23 increases, and the flow rate of hydrogen toward the anode flow path 12 also increases. (See FIG. 3).

  As shown in FIG. 3, the load is divided into a low load region, a medium load region, and a high load region according to the magnitude of the command current. The low load region is a region where the command current is less than the first predetermined current (command current <first predetermined current), and the medium load region is the region where the command current is greater than the first predetermined current and less than the second predetermined current (first predetermined current). Current ≦ command current ≦ second predetermined current), and the high load region is a region where the command current exceeds the second predetermined current (second predetermined current <command current). The first predetermined current and the second predetermined current are obtained by a preliminary test or the like and stored in the ECU 70 in advance.

  As shown in FIG. 3, in the low load region, the hydrogen bypass valve 26 is set in an open state, and the first injector 24 and the second injector 25 are set in a stopped state (OFF state, control stopped state). However, the first injector 24 for small flow rate injection is switched to the operating state (ON state, controllable state) as necessary, for example, when the required power from the air conditioner becomes large, and injects hydrogen. Is set to

In the middle load region, the hydrogen bypass valve 26 is set in an open state, the first injector 24 is in an operating state (ON state), and the second injector 25 is in a stopped state.
In the high load region, the hydrogen bypass valve 26 is set in an open state, the first injector 24 is in an operating state (ON state), and the second injector 25 is in an operating state (ON state).

  When it is determined that the required power is in the low load region (S101 / Yes), the process of the ECU 70 proceeds to step S102. When it determines with request | requirement electric power not being a low load area | region (S101 * No), the process of ECU70 progresses to step S121.

  In step S102, the ECU 70 opens the hydrogen bypass valve 26 and puts the first injector 24 and the second injector 25 into a stopped state (OFF state). As a result, the hydrogen injection stops, and the hydrogen pressure does not pulsate.

Then, hydrogen is continuously supplied to the anode flow path 12 at a small flow rate through the pipe 26a, the hydrogen bypass valve 26, the pipe 26b provided with the orifice 26c, the ejector 27, and the pipe 27a (FIG. )reference). The flow path cross-sectional area in the portion where the orifice 26c is provided is set to an area where hydrogen can be continuously supplied at a flow rate and stoichiometric ratio corresponding to the lower limit value of the required power, where the fuel cell stack 10 can generate power. Therefore, it becomes difficult for the fuel cell stack 10 to be short of hydrogen, and as a result, the power generation of the fuel cell stack 10 is stabilized.
Therefore, after that, the accelerator pedal is depressed to increase the required power. For example, even when shifting to a high load region, it becomes difficult for the fuel cell stack 10 to become short of the hydrogen stoichiometric ratio, and the fuel cell vehicle accelerates smoothly.

  When the ECU 70 determines that the required power is in the low load area, the required power has increased within the low load area due to, for example, an increase in the output of the air conditioner by the driver. When the required power increases, the first injector 24 is operated (ON state), that is, is controlled to be opened and closed, and hydrogen is injected (see FIG. 4A).

  In this case, since hydrogen is continuously supplied at a small flow rate, the opening time (driving time, energization time) of the first injector 24 is shortened compared to the comparative example of FIG. And power consumption by the first injector 24 can be suppressed. In addition, since the opening time of the 1st injector 24 becomes short, the fluctuation range and maximum value of the amount of hydrogen supplied to the anode flow path 12 become small.

  In step S103, the ECU 70 keeps the first injector 24 in a stopped state (OFF state) for a predetermined time (for example, 5 seconds to 60 seconds) immediately before it, and continues to close the purge valve 28. It is determined whether or not a command is input. The predetermined time is the shortest time during which hydrogen leakage can be determined in step S104, which will be described later, is obtained by a preliminary test or the like, and is stored in the ECU 70 in advance.

  When it is determined that the first injector 24 is in a stopped state (OFF state) and a valve closing command is input to the purge valve 28 (S103 / Yes), the process of the ECU 70 proceeds to step S104. If it is determined that the first injector 24 is not continuously stopped (OFF state) or that the valve closing command is not input to the purge valve 28 (S103, No), the process of the ECU 70 proceeds to step S111.

  In step S104, the ECU 70 determines whether or not the actually measured change amount ΔP of the anode pressure detected via the pressure sensor 32 is equal to or less than the predetermined change amount ΔP during the predetermined time immediately before (for example, 5 seconds to 60 seconds). judge. The predetermined change amount ΔP is a pressure change amount that is a criterion for determining whether hydrogen is leaking between the regulator 23 and the purge valve 28 (whether there is an anode leak), and is obtained by a preliminary test or the like. Pre-stored in the ECU 70.

  When it is determined that the actually measured change amount ΔP is equal to or less than the predetermined change amount ΔP (S104 / Yes), the process of the ECU 70 proceeds to step S111. When it is determined that the actually measured change amount ΔP is not less than or equal to the predetermined change amount ΔP (S104 · No), the process of the ECU 70 proceeds to step S105.

  When the process proceeds to step S105 as described above, it is determined that there is a possibility that hydrogen leaks between the regulator 23 and the purge valve 28 (there is an anode leak). That is, the purge valve 28 to which the valve closing command is input is not completely closed. For example, an O-ring (seal member) provided in the gap between the valve body and the valve seat is hardened with use, It is determined that there is a risk of hydrogen leaking downstream of the purge valve 28.

  Here, the leakage of hydrogen is generally detected by a hydrogen sensor such as a catalytic combustion type, and the hydrogen sensor is attached to a hydrogen passage location or a location where it tends to stay. However, the catalyst that constitutes the hydrogen sensor and burns hydrogen deteriorates with use, and the hydrogen sensor is also exposed to water vapor generated by power generation, and if this water vapor adheres to the catalyst, it becomes difficult for hydrogen to burn. , Hydrogen detection sensitivity decreases.

  Therefore, according to the present embodiment, based on the pressure value detected by the pressure sensor 32, it can be determined whether there is an anode leak, that is, whether the purge valve 28 is normally closed. Therefore, it is not necessary to attach a hydrogen sensor downstream of the purge valve 28, and the number of parts and cost can be reduced, and the labor required for maintenance and replacement of the hydrogen sensor can be omitted.

  Further, the fluctuation range of the target hydrogen pressure is a low load region (S101 / Yes), and the first injector 24 is continuously stopped (OFF state) and continues to the purge valve 28 immediately before the predetermined time. When the valve closing command is input (S103 / Yes), the hydrogen leakage determination is executed (S104). Therefore, if hydrogen leakage occurs, the pressure value (anode pressure) detected by the pressure sensor 32 greatly decreases with time, and the actual measurement ΔP at a predetermined time increases, so that hydrogen leakage can be detected with high accuracy. , False detection can be prevented (see FIG. 5).

  In FIG. 5, the pressure value (anode pressure) detected by the pressure sensor 32 gradually decreases even in a normal case where there is no hydrogen leakage. This is because an amount less than the amount consumed is supplied.

  In step S105, the ECU 70 turns on the warning lamp 63 to notify the driver that hydrogen is leaking (there is an anode leak).

  In step S106, the ECU 70 opens the air bypass valve 44. Thereby, the air from the compressor 41 passes through the piping 44a and the piping 44b, bypasses the humidifier 42 and the cathode flow path 13 (fuel cell stack 10), and flows into the piping 43a.

  Here, since the humidifier 42 and the cathode channel 13 have a small channel cross-sectional area and a large pressure loss, the air flows into the diluter 43 by bypassing the humidifier 42 and the cathode channel 13. To increase. Therefore, even if the purge valve 28 is not completely closed and hydrogen flows into the diluter 43 through the pipe 28b, the hydrogen is well diluted by the air having an increased flow rate. It will not be discharged outside the vehicle.

  Here, since the amount of hydrogen leakage is expected to increase as the actually measured change amount ΔP in step S104 increases, the amount of air that bypasses and flows into the diluter 43 is increased. Therefore, as the actually measured change amount ΔP increases. Alternatively, the rotation speed of the compressor 41 may be increased.

Thereafter, the process of the ECU 70 proceeds to END, and the series of processes is terminated.
When there is a possibility of hydrogen leakage in this way, the amount of air (cathode off-gas) is increased and diluted reliably, so that power generation in the fuel cell stack 10 can be continued, and the fuel cell vehicle is a fuel cell vehicle. Since the vehicle can be self-propelled by the electric power output from the battery stack 10 and can be self-propelled by the electric power of the battery 54 (battery can be driven), the driver can bring the fuel cell vehicle to a repair shop or the like. In this case, the shutoff valve 22 is closed when the predetermined time has elapsed from the determination that there is a risk of hydrogen leakage (Yes in S104) or when switching to battery running so as to stop hydrogen leakage reliably. Also good.

  In step S111, the ECU 70 determines whether or not the lowest cell voltage input from the cell voltage monitor 15 is equal to or lower than a predetermined cell voltage. When the minimum cell voltage is equal to or lower than the predetermined cell voltage, it is determined that flooding (water clogging or the like) has occurred in the fuel cell stack 10. The predetermined cell voltage is a voltage that is a criterion for determining whether flooding has occurred, is determined by a preliminary test or the like, and is stored in the ECU 70 in advance.

  When it is determined that the minimum cell voltage is equal to or lower than the predetermined cell voltage (S111 / Yes), the process of the ECU 70 proceeds to step S112. When it is determined that the minimum cell voltage is not equal to or lower than the predetermined cell voltage (S111 · No), the process of the ECU 70 proceeds to step S101.

  In step S112, the ECU 70 activates the first injector 24 (ON state) at a predetermined time, for example, that is, outputs a valve opening command / valve command to the first injector 24, and causes the first injector 24 to Open and close and inject hydrogen intermittently.

  Then, hydrogen that pulsates due to intermittent (intermittent) injection flows through the anode flow path 12, and water staying in the anode flow path 12 and water adhering to the anode are pushed out from the anode flow path 12. . Thereby, hydrogen is easily supplied to the anode, the minimum cell voltage is increased, and the power generation stability of the fuel cell stack 10 is restored. In addition to this, the purge valve 28 may be opened intermittently (intermittently).

  Thereafter, the processing of the ECU 70 proceeds to step S101.

  Next, step S121 that proceeds when the determination result of step S101 is “No” will be described. Note that the process proceeds to step S121 in this way when the required power (command current) is in the middle load region or the high load region (see FIG. 3).

  In step S121, the ECU 70 sets the first injector 24 and the second injector 25 to the operating state (ON state) while the hydrogen bypass valve 26 is open. The hydrogen bypass valve 26 may be closed.

  Specifically, when the command current (required power) is in the middle load region, the ECU 70 keeps the second injector 25 in the stopped state (OFF state) and corresponds to the magnitude of the command current. Only open / close control (PWM control) is performed. When the command current (required power) is in a high load region, the first injector 24 and the second injector 25 are controlled to open and close (PWM control) in accordance with the magnitude of the command current.

  And the target total injection amount Q (L / min) in the unit time by the 1st injector 24 and the 2nd injector 25 is given by Formula (3), for example.

  Target total injection amount Q = consumption amount Q1 + pressure feedback amount Q2-bypass amount Q3 (3)

  The consumption amount Q1 (L / min) is the amount of hydrogen consumed in the fuel cell stack 10, and is calculated based on the command current value. Note that the consumption Q1 increases as the command current value increases.

  The pressure feedback amount Q2 is the hydrogen amount to be corrected in the PID control, and is calculated based on the difference between the target hydrogen pressure and the actually measured pressure value detected by the pressure sensor 32. For example, when the measured pressure value is lower than the target hydrogen pressure, the pressure feedback amount Q2 is calculated on the plus side (increase side), and when the measured pressure value is higher than the target hydrogen pressure, the pressure feedback amount Q2 is minus side (decrease). Side). The target hydrogen pressure is calculated based on the required power (required power generation amount), and the target hydrogen pressure increases as the required power increases.

  The bypass amount Q3 is the amount of hydrogen from the bypass channel (pipe 26a, pipe 26b). As shown in FIG. 6, the bypass amount Q3 has a relationship that increases as the target hydrogen pressure (secondary pressure of the regulator 23) increases.

  Thereafter, the processing of the ECU 70 proceeds to step S101.

≪Modification≫
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, For example, it can change as follows. Moreover, it can also combine suitably with embodiment mentioned later.

In the above-described embodiment, in the step S112, the first injector 24 is operated and hydrogen is intermittently (intermittently) injected. However, in addition to this, the hydrogen bypass valve 26 is closed. The flow rate change width (pulsation width) of hydrogen accompanying opening and closing of the first injector 24 increases, and water and the like are easily discharged from the anode flow path 12.
Further, if the circulation pump 31 is operated intermittently (intermittently) in response to such hydrogen injection, the flow rate change width (pulsation width) of hydrogen is further increased.

  In the above-described embodiment, the fuel cell system 1 mounted on the fuel cell vehicle is exemplified, but the application location is not limited to this, and for example, a configuration incorporated in a stationary fuel cell system may be used.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, a different part from 1st Embodiment is demonstrated.

  The ejector 27 according to the second embodiment includes a nozzle 27d (small flow supply means) for injecting hydrogen from the hydrogen bypass valve 26 in addition to the nozzle 27b for injecting hydrogen from the first injector 24. That is, the downstream end of the pipe 26b is connected to the nozzle 27d.

The nozzle 27b and the nozzle 27d are arranged obliquely with respect to the central axis of the diffuser 27c (ejector 27). In addition, the center of the throat portion that is the throttle portion of the ejector 27 is disposed on the central axis of the nozzle 27b or the nozzle 27d, and hydrogen injected from the nozzle 27b or the nozzle 27d passes through the throat portion and passes through the diffuser. It is going to 27c.
In the second embodiment, the orifice 26c (see FIG. 1) is not provided in the pipe 26b.

  The nozzle 27d has the same function as the orifice 26c. That is, the nozzle 27d has an injection port area that is the same as the cross-sectional area of the flow path in the portion where the orifice 26c is provided and is in an idle state (no load state) in which the accelerator opening is 0, that is, a fuel cell stack. 10 is set to an area where hydrogen can be generated and hydrogen is continuously supplied at a flow rate and stoichiometric ratio corresponding to the lower limit value of the required power generation amount. In other words, the area of the nozzle 27d is smaller than the area of the nozzle 27b that injects hydrogen when the required power is in the middle load region or the high load region.

  According to such a configuration, when the required power is in a low load region and the hydrogen bypass valve 26 is opened, hydrogen from the hydrogen bypass valve 26 is injected by the nozzle 27d. In this case, the area of the nozzle 27d is smaller than that of the nozzle 27b. Therefore, even if the flow rate is small, the flow rate of hydrogen is greatly increased, and a large negative pressure is likely to be generated.

  Thereby, it becomes easy to suck the anode off-gas in the pipe 29b by a large negative pressure, and as a result, the flow rate of the gas (hydrogen) in the anode channel 12 also increases. Therefore, water does not easily stay in the anode flow path 12, and the power generation stability of the fuel cell stack 10 that generates power in the low load region is improved.

«Third embodiment»
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, a different part from 1st Embodiment is demonstrated.

  In the third embodiment, the hydrogen bypass valve 26 is not provided, the downstream end of the pipe 26a is connected to the pipe 24a, and the orifice 26c is provided in the pipe 26a.

  According to such a configuration, hydrogen flows into the pipe 24a through the pipe 26a regardless of the required power in any of the low load area, the medium load area, and the high load area. Thereby, the opening / closing control processing of the hydrogen bypass valve 26 between the low load region and the middle load region / high load region can be omitted and simplified. Further, since the hydrogen bypass valve 26 is not provided, the number of parts can be reduced and the fuel cell system 1 can be configured at low cost.

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
11 Single cell (fuel cell)
12 Anode channel (fuel gas channel)
13 Cathode channel (oxidant gas channel)
21a, 22a, 23a, 27a Piping (fuel gas supply flow path)
23 Regulator 24 First injector 25 Second injector 26 Hydrogen bypass valve (small flow rate supply means, fuel gas bypass valve)
26a, 26b Piping (bypass flow path)
26c Orifice (small flow rate supply means)
27 Ejector 27d Nozzle (small flow rate supply means)
28 Purge valve 29a, 29b Piping (fuel gas circulation flow path)
70 ECU (control means, area determination means, gas leak determination means, flooding determination means)

Claims (5)

A fuel cell having a fuel gas channel, and generating power by supplying fuel gas to the fuel gas channel;
A fuel gas supply channel connected to an inlet of the fuel gas channel and through which a fuel gas directed to the fuel gas channel flows;
A fuel gas circulation channel for connecting the outlet of the fuel gas channel and the fuel gas supply channel, returning the fuel off-gas from the fuel gas channel to the fuel gas supply channel, and circulating the fuel gas;
An injector for injecting fuel gas, provided in the fuel gas supply channel upstream of the connection point of the fuel gas circulation channel;
A bypass flow path connecting the fuel gas supply flow path upstream of the injector and the fuel gas supply flow path downstream of the injector, wherein the fuel gas bypasses the injector;
A small flow rate supply means provided in the bypass channel and configured to continuously supply fuel gas at a small flow rate;
Region determination means for determining whether the required power generation amount is a low load region;
Control means for controlling the injector;
With
The fuel cell system, wherein when the region determination unit determines that the region is a low load region, the control unit stops the injector, and the small flow rate supply unit continuously supplies fuel gas at a low flow rate. A regulator that is provided in the fuel gas supply channel upstream of a connection point on the upstream side of the bypass channel, and that adjusts the pressure of the fuel gas to a pressure corresponding to the required power generation amount;
A purge valve connected to the fuel gas circulation passage and opened to discharge the gas in the fuel gas circulation passage to the outside;
Gas leakage determination means for determining whether or not gas is leaking based on the pressure of the gas between the regulator and the purge valve;
With
When the region determination unit determines that the region is a low load region, the injector is stopped, and the small flow rate supply unit continuously supplies fuel gas at a small flow rate, a valve closing command is input to the purge valve. When
The fuel cell system according to claim 1, wherein the gas leak determination unit determines whether or not gas is leaking. A flooding determining means for determining whether flooding has occurred in the fuel cell;
When the region determination unit determines that the region is a low load region, the injector is stopped, and the small flow rate supply unit continuously supplies fuel gas at a low flow rate, the flooding determination unit generates flooding. When it is determined that
The fuel cell system according to claim 1, wherein the control unit operates the injector. The small flow rate supply means includes a fuel gas bypass valve that supplies / shuts off fuel gas, and a flow path cross-sectional area in which the fuel cell can generate power and is supplied at a flow rate corresponding to a lower limit value of the required power generation amount. The fuel cell system according to any one of claims 1 to 3, further comprising: an orifice set to the following. A fuel cell having a fuel gas channel, and generating power by supplying fuel gas to the fuel gas channel;
A fuel gas supply channel connected to an inlet of the fuel gas channel and through which a fuel gas directed to the fuel gas channel flows;
A fuel gas circulation channel for connecting the outlet of the fuel gas channel and the fuel gas supply channel, returning the fuel off-gas from the fuel gas channel to the fuel gas supply channel, and circulating the fuel gas;
An injector for injecting fuel gas, provided in the fuel gas supply channel upstream of the connection point of the fuel gas circulation channel;
A bypass flow path connecting the fuel gas supply flow path upstream of the injector and the fuel gas supply flow path downstream of the injector, wherein the fuel gas bypasses the injector;
A small flow rate supply means provided in the bypass channel and configured to continuously supply fuel gas at a small flow rate;
A method for operating a fuel cell system comprising:
A determination step for determining whether the required power generation amount is in a low load region; and
When it is determined that the required power amount is in the low load region, a stop step of stopping the injector;
A small flow continuous supply step of continuously supplying fuel gas at a small flow rate by the small flow rate supply means;
A method for operating a fuel cell system, comprising:

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