JP4515362B2 - Fuel cell vehicle and fuel cell control method - Google Patents

Description

  The present invention relates to a fuel cell vehicle equipped with a fuel cell that generates power by reaction of a reaction gas, and a fuel cell control method.

  In recent years, a fuel cell vehicle equipped with a fuel cell as a driving source of the vehicle has been proposed. As a fuel cell used here, one having a structure in which a predetermined number of unit cells each having a polymer electrolyte chamber membrane interposed between an anode and a cathode is laminated is known. In the case of this fuel cell, hydrogen (fuel gas) is introduced into the anode and air (oxidant gas) is introduced into the cathode, and power is generated by an electrochemical reaction between hydrogen and oxygen.

  Since fuel cells generate water during power generation, moisture tends to remain in the fuel cells when power generation is stopped. And when power generation stops with moisture remaining in the fuel cell, for example, when starting the vehicle in a low temperature environment, the remaining water in the fuel cell freezes and the reaction gas flow path is blocked, Start-up time will be longer. From the viewpoint of preventing such a situation, a technique for removing residual water inside the battery when the fuel cell is stopped has been proposed.

In this technique, for example, when the fuel cell is stopped, a dry reaction gas is allowed to flow at a constant flow rate in the cell (in the reaction gas flow path), and moisture in the cell is scavenged by the reaction gas. (For example, refer to Patent Document 1).
JP 2004-265684 A

  However, since this fuel cell system keeps the reaction gas flowing in the battery at a constant flow rate when power generation is stopped, the flow rate of the reaction gas is set so that the residual water in the reaction gas channel can be discharged reliably. If it is increased, the energy consumption for scavenging will increase, and if the remaining moisture in the electrolyte membrane and the moisture on the surface of the reaction gas channel are completely removed, the scavenging operation time will be longer and the energy consumption will be further increased. Will become bigger.

  In addition, in a fuel cell vehicle equipped with such a fuel cell system, the scavenging operation can be continued for a while after the operation switch is turned off and power generation by the fuel cell is stopped. There is concern about giving a sense of incongruity.

  Therefore, the present invention is capable of improving both startability and energy saving of the fuel cell, and does not give the driver who leaves the vehicle after stopping power generation the uncomfortable feeling caused by continuing the scavenging operation. It is an object of the present invention to provide a method for controlling a fuel cell.

As means for solving the above-mentioned problems, the invention according to claim 1 is an automobile equipped with a fuel cell (for example, a fuel cell 1 in an embodiment described later) that generates electric power by a chemical reaction of a supplied reaction gas. In the above, a reaction gas flow path (for example, a hydrogen supply flow path 3 and an air supply flow path 6 in an embodiment described later) through which the reaction gas flows, and a scavenging means for scavenging the reaction gas passage with a scavenging gas (for example, An air compressor 5) in an embodiment to be described later, a first scavenging process for performing scavenging at a large flow rate to remove liquefied water in the reaction gas channel when power generation of the fuel cell is stopped; Control means for performing a standby process for stopping scavenging for a predetermined time after the first scavenging process and a second scavenging process for scavenging the reaction gas flow path after the standby process (for example, implementation described later) Comprising a, a control unit 12) in the state, the predetermined time, the driver turns off the ignition switch, sets the average sufficiently longer than the time until separated sufficiently from the vehicle off the vehicle, The scavenging means is composed of an air compressor, and the control means is configured to stop the air compressor during the standby process .

  In the case of the present invention, when the power generation of the fuel cell is stopped by the driver, first, a large amount of reaction gas is caused to flow in the reaction gas flow path by the first scavenging process, whereby droplets are formed inside the cell. After the residual water remaining in the form is discharged, a stop process for stopping scavenging for a predetermined time is performed. The driver gets out of the vehicle at this timing, and the second scavenging process is performed after the driver disappears in the fuel cell. Residual moisture in the electrolyte membrane and moisture on the surface of the reaction gas flow path are evaporated and removed by this second scavenging process.

  According to a second aspect of the present invention, in the first aspect of the invention, the second scavenging process is performed at a temperature exceeding a set lower limit temperature at which the dehumidifying performance in the fuel cell decreases.

Invention of Claim 3 is provided with the heating means which heats the said fuel cell in the invention of Claim 2, and the said control means is when the temperature of the said fuel cell becomes below the said setting minimum temperature, After the first scavenging process is performed, the heating process by the heating unit is performed, and then the second scavenging process by the scavenging unit is performed after the temperature of the fuel cell exceeds the set lower limit temperature. I tried to make it.
In this case, when the temperature of the fuel cell becomes equal to or lower than the set lower limit temperature when the power generation of the fuel cell is stopped, after the residual water inside the battery is discharged by the first scavenging process, the temperature of the fuel cell exceeds the set lower limit temperature. Heating by the heating means is performed, and then the second scavenging process is performed. Therefore, the second scavenging process is always performed at a temperature exceeding the set lower limit temperature.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the second scavenging process is performed at a flow rate smaller than a flow rate at the time of the first scavenging process. I made it.

According to a fifth aspect of the present invention, there is provided a control method for a fuel cell that is mounted on a vehicle and generates power by a chemical reaction of a supplied reaction gas. Scavenging at a large flow rate to remove the moisture , and then stopping the air compressor to stop scavenging for a predetermined time, and then scavenging the reaction gas flow path again , The driver turned off the ignition switch, and set it to a time sufficiently longer than the average time from getting off the vehicle and sufficiently leaving the vehicle.

According to the present invention, when the power generation is stopped, the residual water in the battery is first discharged to the outside by the first scavenging process with a large flow rate, and then the scavenging is stopped for a predetermined time by the stop process, and then the second flow with the small flow rate is stopped. Since the scavenging process is performed, it is possible to reliably remove residual water and residual moisture in the battery without prolonging the scavenging operation time, and the driver gets off the vehicle at the timing of the stop process. Thus, the driver does not feel uncomfortable due to the continued scavenging operation.
Therefore, according to the present invention, it is possible to improve the startability of the fuel cell in cold weather and to save energy, and to improve the merchantability by eliminating the uncomfortable feeling when the driver gets out of the vehicle. .

  In particular, according to the second aspect of the present invention, the second scavenging process is performed at a temperature exceeding the set lower limit temperature at which the dehumidifying performance in the fuel cell is reduced. It can be prevented that the temperature becomes lower than the set lower limit temperature and the evaporation of moisture in the fuel cell is inhibited.

  According to the third aspect of the present invention, the temperature of the fuel cell is positively increased by the heating means when the temperature of the fuel cell is equal to or lower than the set lower limit temperature. The remaining water can be removed sufficiently.

  Furthermore, according to the invention described in claim 4, by performing the initial scavenging process at a large flow rate, the residual water in the battery can be efficiently discharged to the outside, and the subsequent scavenging process is performed at a small flow rate. As a result, water vapor can be taken into the scavenging gas more efficiently and energy consumption can be reduced.

Embodiments of a fuel cell vehicle and a fuel cell control method according to the present invention will be described below with reference to the drawings.
First, the first embodiment shown in FIGS. 1 to 4 will be described.

FIG. 1 is a functional block diagram of a fuel cell system used in the fuel cell vehicle of this embodiment.
The fuel cell 1 is configured by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane 1a made of, for example, a solid polymer ion exchange membrane from both sides with an anode 1b and a cathode 1c. FIG. 1 schematically shows a single cell.

  Hydrogen as a fuel is supplied to the anode 1b of the fuel cell 1 configured as described above, and air containing oxygen as an oxidant is supplied to the cathode 1c. As a result, hydrogen ions generated by the catalytic reaction at the anode 1b move through the electrolyte membrane 1a to the cathode 1c and cause an electrochemical reaction with oxygen at the cathode 1c to generate electric power. At this time, water is generated. . At this time, part of the generated water generated on the cathode 1c side is back-diffused to the anode 1b side through the electrolyte membrane 1a, so that the generated water is also present on the anode 1b side.

Hydrogen supplied from the hydrogen tank 2 is supplied to the anode 1 b of the fuel cell 1 through the shutoff valve 4 and the hydrogen supply flow path 3.
On the other hand, air is pumped from the air compressor 5 that operates using the battery 20 as a power source to the air supply passage 6 and supplied to the cathode 1 c of the fuel cell 1.

  Further, the hydrogen supply flow path 3 and the air supply flow path 6 are connected via a merging flow path 9. The merging flow path 9 is provided with a scavenging valve 10. By releasing the scavenging valve 10, the supply air of the air compressor 5 flows into the hydrogen supply path 3 as a scavenging gas.

  Unreacted hydrogen that is supplied to the anode 1b through the hydrogen supply path 3 and not consumed by the fuel cell 1 is discharged from the anode 1b to the circulation passage 13 together with residual water such as produced water on the anode 1b side. The hydrogen supply channel 3 is joined via the ejector 14. That is, the hydrogen discharged from the fuel cell 1 merges with fresh hydrogen supplied from the hydrogen tank 2 and is supplied again to the anode 1 b of the fuel cell 1.

  The hydrogen discharge flow path 7 branched from the circulation flow path 13 is provided with an anode pressure adjustment valve 17. The used hydrogen off-gas is discharged from the hydrogen discharge flow path 7 by opening the anode pressure adjustment valve 17. To do. The hydrogen gas discharged from the hydrogen discharge channel 7 is diluted to a predetermined concentration or less by a dilution box (not shown).

  On the other hand, a cathode pressure adjusting valve 18 is provided in the air discharge channel 8. By opening the cathode pressure regulating valve 18, the reacted air-off gas is discharged from the air discharge channel 8. Further, the air pressure (cathode pressure) supplied to the cathode 1c of the fuel cell 1 can be adjusted by adjusting the opening of the cathode pressure adjusting valve 18. The hydrogen supply flow path 3 and the air supply flow path 6 are provided with pressure sensors (not shown) for measuring the anode pressure and the cathode pressure, respectively, and signals from these pressure sensors are sent to the control unit 12 which is a control means. It is designed to be entered.

  The control unit 12 is connected to an ignition switch 15, and signals for various sensors 21 and 22 on the fuel cell 1 for detecting voltage, gas pressure, temperature, etc., and for cooling and heating the fuel cell 1. The water temperature signal of the thermostat 24 of the temperature adjusting circuit 23 and the remaining capacity signal of the storage battery 20 are input, and the air compressor 5 is controlled together with the shutoff valve 4, the scavenging valve 10 and the pressure adjusting valves 17 and 18 based on these signals. It is like that.

  The temperature adjustment circuit 23 has two passages through which the coolant introduced into the fuel cell 1 circulates, and includes a regular passage 26 that passes through the radiator 25 and a bypass passage 27 that does not pass through the radiator 25. It can be switched by a thermostat 24. The thermostat 24 connects the fuel cell 1 to the regular flow path 26 at room temperature, and switches the flow path connection to the bypass flow path 27 side when the temperature of the cooling water reaches a temperature lower than the set lower limit temperature. Further, the refrigerant pump 28 in the temperature adjustment circuit 23 for circulatingly supplying the cooling water continues to operate during the scavenging process described later.

The operation of the fuel cell system having the above configuration will be described with reference to the flowchart of FIG.
First, in step S10, when the ignition switch 15 is switched from ON to OFF and an operation stop signal is input to the control unit 12, in step S12, the shutoff valve 4 of the hydrogen supply flow path 3 is closed to the anode 1b. The power generation of the fuel cell 1 is stopped by stopping the supply of hydrogen.

  Next, in step S14, the rotational speed of the compressor 5 is increased from that during normal power generation, and large flow scavenging, which is the first scavenging process, is started. At this time, the anode pressure adjusting valve 17 and the cathode pressure adjusting valve 18 are fully opened, and the air pressure supplied to the anode 1b and the cathode 1c is lowered. Also, by supplying a large amount of air at this time, the differential pressure between the residual water accumulation sites in the anode 1b and the cathode 1c of the fuel cell 1 and the discharge passages 7 and 8 is increased, and the droplets remain in the fuel cell 1 as droplets. It is possible to promote the discharge of residual water (condensed water). Note that this large flow scavenging is stopped by a command from the control unit 12 when, for example, the differential pressure at the inlet / outlet of the flow path becomes a set value or less.

  Thereafter, in step S16, the temperature in the fuel cell is detected based on the water temperature signal from the thermostat portion, and in step S18, it is determined whether the temperature in the fuel cell 1 is higher than the set lower limit temperature, If it is determined that the temperature is higher than the set lower limit temperature, the process proceeds to step S22 after waiting for the elapse of a predetermined time in step S20. If it is determined that the temperature in the fuel cell 1 is equal to or lower than the set lower limit temperature, the predetermined time is The process proceeds to step S22 without waiting for elapse of time.

Here, the set lower limit temperature is a temperature at which the dehumidification performance in the fuel cell 1 is lowered and the battery output at the time of restarting is lowered when the next second scavenging process is performed in an environment below that temperature. Say that. The temperature at the start of scavenging and the battery output at the time of restart have a relationship as shown in FIG. 4, and when the temperature at the start of the scavenging is below a certain temperature as shown in FIG. To drop. The temperature at which the battery output starts to drop rapidly is taken as the set lower limit temperature.
The predetermined time in step S20 is sufficiently longer than the average time from when the driver turns off the ignition switch 15 until the driver gets off the vehicle and sufficiently leaves the vehicle, for example, about 20 to 30 minutes. Is set.

  In step S22, the time during which the subsequent small flow scavenging can be continued is determined. This continuable time is obtained by calculating the remaining capacity of the battery 20 and dividing the remaining capacity of the battery 20 by the energy consumption of the compressor 5 necessary for supplying the optimum amount of air with the following small flow rate scavenging.

  Subsequently, in step S24, the small flow rate scavenging that is the second scavenging process is performed by lowering the rotation of the compressor 5. At this time, the rotation speed of the compressor 5 is lower than the rotation speed during normal power generation. Here, by performing the small flow scavenging in this way, it is possible to increase the efficiency of taking in (saturating) the residual moisture into the scavenging gas as water vapor.

  In the next step S26, it is determined whether or not the scavenging time determined in step S22 has elapsed after the start of the small flow scavenging. When it is determined that the scavenging time has elapsed, the process proceeds to step 27 and the system is stopped. .

  If it is determined in step S18 that the temperature in the fuel cell 1 is equal to or lower than the set lower limit temperature, the process proceeds to step S22 and subsequent steps without waiting for the elapse of a predetermined time due to a decrease in outside air temperature or the like. This is to prevent the temperature in the fuel cell 1 from further decreasing with the passage of time. That is, as the temperature in the fuel cell 1 becomes lower than the set lower limit temperature, the moisture is less likely to evaporate in the scavenging gas, and the water removal efficiency in the cell during the second scavenging process is reduced. Therefore, in order to eliminate this problem, standby processing (waiting for a predetermined time) is not performed.

As described above, according to the fuel cell vehicle of this embodiment, immediately after the power generation of the fuel cell 1 is stopped, a large amount of residual water in the fuel cell 1 is discharged in a short time by scavenging the first stage with a large flow rate, and then the fuel If the temperature of the battery 1 is not equal to or lower than the set lower limit temperature, after waiting for a predetermined time sufficient for the driver to leave the vehicle, the remaining moisture and the flow path in the electrolyte membrane 1a are removed by scavenging at a small flow rate in the second stage. Since the water adhering to the surface is removed, the water in the battery can be removed sufficiently and efficiently when the power generation of the fuel cell 1 is stopped, and the fuel cell when the driver leaves the vehicle. By temporarily stopping the one scavenging process, it is possible to eliminate the problem of giving the driver a sense of discomfort due to the scavenging noise.
Therefore, in this fuel cell vehicle, the startability of the fuel cell is improved in cold weather by sufficiently removing moisture inside the battery when power generation is stopped, and a large flow scavenging and a small flow scavenging are performed in stages. Thus, energy saving can be achieved, and the merchantability of the vehicle can be improved by eliminating scavenging noise when the driver leaves the vehicle.

  FIG. 3 is a characteristic diagram showing the change in output when the fuel cell system of this embodiment and the fuel cell system before scavenging without countermeasures are restarted (the characteristic of this embodiment is “after countermeasures” As is clear from this figure, when the fuel cell system of this embodiment is adopted, sufficient output can be obtained immediately after restarting.

Next, the second embodiment shown in FIG. 5 will be described.
The configuration of the fuel cell system of this embodiment is substantially the same as that of the first embodiment, except that another process is performed when the internal temperature of the fuel cell is lower than the set lower limit temperature.
Specifically, in the case of this embodiment, the reaction heat due to the operation of the fuel cell 1 is used as a means for heating the fuel cell 1, and when the temperature of the fuel cell 1 is equal to or lower than the set lower limit temperature, the set lower limit The power generation of the fuel cell 1 is continued again until the temperature is exceeded.

Steps S31 and S32 interposed between steps S18 and S20 in the flowchart of FIG. 5 correspond to the control described here. The same processing parts as those in the flowchart of FIG. 2 are given the same step names.
Hereinafter, the process between step S18 and step 20 will be described.
In step S18, when the temperature in the fuel cell 1 is higher than the set lower limit temperature, the process proceeds to step S20 in the same manner as in the first embodiment, waits for a predetermined time, and the temperature in the battery 1 is set to the set lower limit temperature. In the following cases, the process proceeds to step S31 to start power generation of the fuel cell 1 to increase the temperature in the cell 1. The power generation of the fuel cell 1 for increasing the temperature is continued until it is determined in step S32 that the temperature in the battery 1 has exceeded the set lower limit temperature, and if it is determined in step S32 that the set lower limit temperature has been exceeded, step S32 is performed. It progresses to S20 and it is judged whether predetermined time passed.

  Therefore, in the control of this embodiment, even if the temperature of the fuel cell 1 is lower than the set lower limit temperature in a cold region or the like, the temperature of the fuel cell 1 is actively increased by regenerating the fuel cell 1. As a result, moisture can be efficiently evaporated into the scavenging gas in the subsequent small flow scavenging.

6 and 7 show a third embodiment.
The fuel cell system of this embodiment is almost the same as that of the first embodiment, but an external heater 40 such as a catalytic combustion heater or an electric heater using hydrogen is interposed in the temperature adjustment circuit 23 as shown in FIG. The point is different. Therefore, in FIG. 6, the same parts as those in FIG.

  FIG. 7 is a flowchart showing the control of the fuel cell system of this embodiment, but only the step S131 is different from the flowchart of the second embodiment shown in FIG. Processing is in progress. That is, in this embodiment, in the second embodiment, the re-power generation of the fuel cell in step S31 is heated by the external heater 40 in step S131.

  In the case of this embodiment, the generation of new moisture does not occur because the power generation of the fuel cell 1 is not resumed, so that the remaining moisture can be removed more efficiently.

  In addition, this invention is not limited to the said embodiment, A various design change is possible in the range which does not deviate from the summary. For example, the detection of the internal temperature of the fuel cell is not limited to the water temperature of the temperature adjustment circuit, and a temperature sensor may be provided on the inlet side of the reaction gas flow path, and the temperature may be detected by the sensor.

1 is a block diagram of a fuel cell system according to a first embodiment of the present invention. The flowchart which shows the control of the same embodiment. The output characteristic figure at the time of restart of the embodiment and a comparative example. FIG. 6 is a relationship characteristic diagram between a scavenging start temperature and a restart output for explaining the embodiment. The flowchart which shows the control of 2nd Embodiment of this invention. The block diagram of the fuel cell system in 3rd Embodiment of this invention. The flowchart which shows the control of the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 3 ... Hydrogen supply flow path (reaction gas flow path)
5 ... Air compressor 6 ... Air supply channel (reactive gas channel)
7 ... Hydrogen discharge channel (reaction gas channel)
8 ... Air discharge channel (reactive gas channel)
12 ... Control unit (control means)

Claims (5)

In an automobile equipped with a fuel cell that generates electricity by a chemical reaction of the supplied reaction gas,
A reaction gas flow path through which the reaction gas flows;
Scavenging means for scavenging the reaction gas passage with scavenging gas;
A first scavenging process for performing scavenging at a large flow rate to remove liquefied water in the reaction gas channel when power generation of the fuel cell is stopped, and scavenging is stopped for a predetermined time after the first scavenging process And a control means for performing a second scavenging process for scavenging the reaction gas flow path after the standby process ,
The predetermined time is set to a time sufficiently longer than an average time until the driver turns off the ignition switch, gets off the vehicle and sufficiently leaves the vehicle,
The scavenging means is composed of an air compressor,
The fuel cell vehicle characterized in that the control means stops the air compressor during the standby process .   2. The fuel cell vehicle according to claim 1, wherein the second scavenging process is performed at a temperature that exceeds a set lower limit temperature at which the dehumidifying performance in the fuel cell decreases. A heating means for heating the fuel cell;
When the temperature of the fuel cell is equal to or lower than the set lower limit temperature, the control means causes the heating means to perform heat treatment after the first scavenging process, and then the temperature of the fuel cell. 3. The fuel cell vehicle according to claim 2, wherein after the temperature exceeds the set lower limit temperature, the second scavenging process is performed by the scavenging means.   The fuel cell vehicle according to any one of claims 1 to 3, wherein the second scavenging process is performed at a flow rate that is smaller than a flow rate during the first scavenging process. In a control method of a fuel cell that is mounted on a vehicle and generates power by a chemical reaction of a supplied reactive gas,
At the time of stopping the power generation of the fuel cell, scavenging at a large flow rate for removing liquefied water in the reaction gas flow path is performed by an air compressor, and then the air compressor is stopped and the scavenging is stopped for a predetermined time. The inside of the reaction gas passage is scavenged again, and the predetermined time is set to a time sufficiently longer than the average time until the driver turns off the ignition switch, gets off the vehicle and sufficiently leaves the vehicle. A control method for a fuel cell.

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