JP2005228477A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which operates a fuel cell stably and effectively in a low cost structure and gives no excessive load to a separation mechanism of anti-freeze liquid and water. <P>SOLUTION: The fuel cell 10 is provided. Circulation passages 12, 14, 26, 34, 42 for cooling the fuel cell 10 by the cooling water of pure water are provided. A humidifying part 16 for humidifying the reaction gas air supplied to the fuel cell 10 by the cooling water is provided. Only when an operation of the fuel cell 10 is stopped, and further, under a cold temperature environment where freezing of the cooling water is forecast, the cooling water is recovered from the circulation passages and stored in an anti-freeze liquid tank 30. When separation of the cooling water and the anti-freeze liquid is demanded, pure water is separated from the mixed liquid in the anti-freeze liquid tank 30 by a separation film unit 38. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system suitable for mounting in a vehicle.

  Conventionally, as disclosed in JP-A-8-185877, a fuel cell system provided with a cooling mechanism and a humidifying mechanism is known. A fuel cell exhibits good electrical characteristics when the electrolyte disposed therein is in a moderately wet state. According to the above conventional system, the electrolyte can be humidified using the humidification mechanism, so that the fuel cell can be operated efficiently. In addition, since the electrode reaction in the fuel cell is an exothermic reaction, it is essential to cool the inside in order to maintain a stable operation state. According to the conventional system, the requirement can be satisfied by using the cooling mechanism.

  By the way, it is necessary to use pure water to humidify the fuel cell in order to avoid various disadvantages. On the other hand, in order to avoid freezing of the cooling water, it is necessary to mix an antifreeze with the cooling water. Therefore, the above-described conventional system circulates cooling water containing antifreeze liquid in the cooling path of the fuel cell, while using pure water separated from the cooling water containing antifreeze liquid using a device that separates the antifreeze liquid and water. Therefore, the electrolyte is humidified.

  According to such a configuration, the requirement for humidification and the prevention of freezing can be avoided while avoiding separately preparing the supply / circulation mechanism of cooling water containing antifreeze and the supply / circulation mechanism of pure water not containing antifreeze. Both requirements can be met. In this regard, the above-described conventional system has an excellent feature that the fuel cell can be stably and efficiently operated with an inexpensive configuration.

JP-A-8-185877 JP-A-6-223855 JP 2003-36874 A JP-A-5-190193 JP 2003-234113 A

  However, in the conventional system described above, it is necessary to operate a separation mechanism that separates the antifreeze and pure water at all times during operation of the fuel cell. Naturally, the deterioration of the separation mechanism is more likely to proceed as the operating time is longer. For this reason, the conventional system has a characteristic that the separation mechanism is easily deteriorated at an early stage.

  The present invention has been made to solve the above-described problems. The fuel cell can be stably and efficiently operated with an inexpensive configuration, and further, a separation mechanism for separating the antifreeze liquid and water. An object of the present invention is to provide a fuel cell system that does not place an excessive burden on the fuel cell system.

In order to achieve the above object, a first invention is a fuel cell system,
A fuel cell;
A cooling mechanism for cooling the fuel cell with pure water cooling water;
A humidifying mechanism for humidifying the reaction gas supplied to the fuel cell with the cooling water;
An antifreeze mixing mechanism that mixes the cooling water with the antifreeze only under a low temperature environment in which the fuel cell is stopped and the cooling water is expected to freeze;
A cooling water separation mechanism for separating the cooling water mixed by the antifreezing liquid mixing mechanism from the antifreezing liquid under a situation where separation of the cooling water and the antifreezing liquid is required;
It is characterized by providing.

  According to a second aspect, in the first aspect, the cooling water separating mechanism separates the cooling water from the antifreeze when the humidifying mechanism humidifies the reaction gas.

The third invention is the first or second invention, wherein
The cooling mechanism includes a cooling water circulation path including the fuel cell,
The antifreezing liquid mixing mechanism includes an antifreezing liquid tank that collects cooling water in the cooling water circulation path and stores the cooling water in a state of being mixed with the antifreezing liquid.

  According to the first aspect, during operation of the fuel cell, the pure gas can be circulated as the cooling water, and the reaction gas can be humidified by the pure water. Therefore, according to the present invention, the fuel cell can be stably and efficiently operated without separately preparing the cooling water path and the humidifying pure water path. Further, according to the present invention, when the cooling water of pure water is expected to freeze while the fuel cell is stopped, the cooling water can be prevented from freezing by mixing the cooling water with the antifreeze liquid. . In that case, pure water for humidification can be prepared by separating the pure water from the antifreeze by the cooling water separation mechanism. Furthermore, according to the present invention, the cooling water of pure water is mixed with the antifreeze liquid only in a low temperature environment where freezing is expected, so that the burden that the cooling water separation mechanism should bear is reduced, and its deterioration is sufficiently reduced. Can be suppressed.

  According to the second invention, when the humidification mechanism requires the humidification of the reaction gas, the cooling water can be separated from the antifreeze liquid, so that the necessary pure water can be reliably prepared without waste.

  According to the third invention, under a low temperature environment, the cooling water in the cooling water circulation path can be collected in the antifreeze liquid tank, and the mixed liquid of the antifreeze liquid and the cooling water can be stored therein. For this reason, according to the present invention, it is possible to avoid the cooling water from remaining in the cooling water circulation path in a cold environment, and to reliably prevent the components of the antifreeze liquid from entering the cooling water circulation path. it can.

Embodiment 1 FIG.
[Hardware Configuration of System of First Embodiment]
FIG. 1 is a diagram for explaining a configuration of a fuel cell system according to Embodiment 1 of the present invention. The system of this embodiment can be used in a state where it is mounted on a vehicle, for example. This system includes a fuel cell 10. The fuel cell 10 incorporates an electrolyte that generates power using hydrogen gas H ₂ , air Air, or the like as a reaction gas and an electrode (none of which are shown).

  The reaction that occurs inside the fuel cell 10 with the generation of electric power is an exothermic reaction. Therefore, a cooling water passage (not shown) for cooling the periphery of the electrode is provided inside the fuel cell 10. The cooling water passage communicates with pipes 12 and 14 externally attached to the fuel cell 10. As will be described later, pure water cooling water can be circulated through the pipes 12 and 14 and the cooling water channel. For this reason, according to the system of this embodiment, overheating of the fuel cell 10 can be effectively prevented.

  In addition, the fuel cell 10 has a humidifying unit 16 attached to the outside or the inside thereof. The humidifying unit 16 can humidify the reaction gas supplied to the fuel cell 10 using the cooling water flowing through the pipe line 14. The fuel cell 10 exhibits good power generation characteristics when the reaction gas is in a moderately wet state. For this reason, according to the system of this embodiment, the fuel cell 10 can generate electric power efficiently.

  The pipe line 14 communicates with the suction port of the pump 18. The pump 18 includes a motor 20 as its drive source. The discharge port of the pump 18 communicates with the first switching valve 24 via the pipeline 22. The first switching valve 24 communicates with a conduit 28 leading to the reserve tank 26 and a conduit 32 leading to the antifreeze liquid tank 30.

  The first switching valve 24 is an electromagnetic valve that selectively realizes three states according to a command supplied from the outside. That is, the first switching valve 24 specifically includes a first state in which the pipe line 22 is communicated with the reserve tank 26, a second state in which the pipe line 22 is communicated with the antifreeze liquid tank 30, and any tank in which the pipe line 22 is communicated. It is possible to selectively realize any one of the cut-off states that are separated from each other.

  The reserve tank 26 communicates with the second switching valve 36 through a pipe line 34. On the other hand, the antifreeze liquid tank 30 communicates with the second switching valve 36 through the separation membrane unit 38 and the conduit 40. The second switching valve 36 further communicates with the heat exchanger 42 that communicates with the pipe 12 described above.

  Similar to the first switching valve 24, the second switching valve 36 is an electromagnetic valve that selectively realizes one of three states in response to an external command. Specifically, according to the second switching valve 36, a first state in which the reserve tank 26 is electrically connected to the heat exchanger 42, a second state in which the separation membrane unit 38 is electrically connected to the heat exchanger 42, and a heat exchanger Either of the shut-off states that separate 42 from both of them can be selectively realized.

  An antifreeze liquid containing ethylene glycol, glycerin and the like is stored in the antifreeze liquid tank 30 in a mixed state with water. The separation membrane unit 38 has a built-in separation membrane that separates only water from the mixed solution of antifreeze and water, that is, a separation membrane that can separate pure water from the antifreeze containing water. Such a separation membrane can be realized by, for example, an ultrafiltration membrane disclosed in JP-A-8-185877.

  For this reason, the pure water cooling water not containing the antifreeze liquid flows out to the pipe line 40 located downstream of the separation membrane unit 38. In the system shown in FIG. 1, pure water that does not contain antifreeze liquid circulates in all other areas except the antifreeze liquid tank 30 and the separation unit 38, as in the inside of the pipe 40. That is, pure water coolant flows through the heat exchanger 42, the coolant passage in the fuel cell 10, and the pump 18. The reserve tank 26 also stores pure water cooling water that does not contain antifreeze.

  The system shown in FIG. 1 includes a CPU 50. The CPU 50 is a unit for controlling the operation of the fuel cell system of the present embodiment. The CPU 50 is supplied with outputs from two temperature sensors 52 and 54, an output from the internal temperature sensor 56, an output from the outside air temperature sensor 58, and the like. The temperature sensors 52 and 54 are sensors that respectively detect the temperature of the cooling water flowing into the fuel cell 10 and the temperature of the cooling water flowing out of the fuel cell 10. The internal temperature sensor 56 is a sensor that detects the internal temperature of the fuel cell 10. The outside air temperature sensor 58 is a sensor that detects the temperature of the outside air surrounding the fuel cell 10.

  The CPU 50 is further connected to a motor 20, which is a power source of the pump, a first switching valve 24, a second switching valve 36, and the like. The CPU 50 can appropriately drive those actuators based on the outputs of the various sensors described above.

[Operation of System of First Embodiment]
(Operation during normal operation)
Hereinafter, the operation of the system of the present embodiment will be described with reference to FIGS. FIG. 2 shows a “normal operation” state of the system of the present embodiment. When the internal temperature of the fuel cell 10 reaches an appropriate temperature after the operation of the fuel cell 10 is started, the system of the present embodiment starts normal operation thereafter.

  During normal operation, the first switching valve 24 is controlled to be in a state (first state) in which the pump 18 is conducted to the reserve tank 26, and the second switching valve 36 is conducted to the reserve tank 26 to the heat exchanger 42. The state (first state) is controlled. As a result, in the system of the present embodiment, a circulation path is formed that follows the path of the heat exchanger 42 → the fuel cell 10 → the pump 18 → the reserve tank → the heat exchanger 42. That is, a circulation path that does not include the antifreeze liquid tank 30 and the separation membrane unit 38 is formed.

  The normal control is started in a situation where there is sufficient pure water cooling water in the circulation path. Further, the pump 18 is in an operating state during execution of normal control. As a result, according to the normal control, a sufficient amount of pure water can be circulated in the circulation path as shown in FIG.

  The heat exchanger 42 can cool the medium flowing through the inside thereof. According to the above circulation path, the low-temperature cooling water (pure water) after being cooled by the heat exchanger 42 can flow into the fuel cell 10. For this reason, according to the normal control, the fuel cell 10 can be sufficiently cooled.

  At this time, since the medium flowing in the circulation path is pure water, the humidifying unit 16 can appropriately humidify the reaction gas using the pure water. For this reason, according to the normal control, it is possible to efficiently generate power in the fuel cell 10 while cooling the fuel cell 10 sufficiently and appropriately.

  By the way, during the execution of the normal control described above, the separation membrane unit 38 is not required to perform any work for separating water and antifreeze liquid. That is, since the separation membrane unit 38 is disconnected from the circulation path, substantially no work for separating the antifreeze liquid and water is performed during the execution of the normal control. Thus, the system of the present embodiment can keep the fuel cell 10 operating stably and efficiently without imposing any burden on the separation membrane unit 38 during the execution of the normal control.

(Operation at warm stop, warm start)
In a warm environment where the outside air temperature exceeds 5 ° C., the system of the present embodiment stops the circulation of cooling water while maintaining the circulation path shown in FIG. 2 when the operation of the fuel cell 10 is stopped. (Hereinafter, this operation is referred to as “operation during warming stop”). Then, when the fuel cell 10 is subsequently restarted in such a warm environment, the cooling water circulation is started while maintaining the circulation path shown in FIG. 2 (hereinafter, this operation is referred to as “warm start-up time”). ”Behavior).

  While the fuel cell 10 is stopped, no exothermic reaction takes place inside the fuel cell 10, so that the temperature of the cooling water is reduced to an equivalent value to the outside air temperature. More specifically, the CPU 50 determines that the environment in which the pure water does not freeze with such a temperature change is a warm environment. For this reason, the operation | movement at the time of a warm stop and the operation | movement at the time of a warm stop are performed only when freezing does not arise in the cooling water of a pure water.

  If the cooling water of pure water does not freeze, it is not necessary to mix the antifreeze of the cooling water. If the cooling water does not freeze, even if the cooling water exists in the circulation path, no inconvenience occurs. Further, according to the operation at the time of the warm stop and the operation at the warm start described above, since the cooling water does not flow out from the circulation path used during the normal operation, there is sufficient pure water cooling water in the circulation path. The state can be maintained. If this state can be maintained, normal operation can be resumed without causing the antifreeze liquid tank 30 and the separation membrane unit 38 to perform any work. In this respect, the system of the present embodiment also has desirable characteristics for reducing the burden on the separation membrane unit 38.

(Operation at low temperature stop)
FIG. 3A shows a state in which the system of the present embodiment is performing “operation at low temperature stop”. FIG. 3B shows a state of “during cold stop” of the system of the present embodiment. The CPU 50 determines that the environment in which pure water is expected to freeze, specifically, the environment in which the outside air temperature is lower than the determination temperature set to about 0 to 5 ° C. is the “low temperature environment”. When the CPU 50 detects the low-temperature environment when the fuel cell 10 is stopped or during the stop, the CPU 50 performs the operation at the time of low-temperature stop shown in FIG.

  In the operation at the time of low temperature stop, the first switching valve 24 is controlled to be in a state where the pump 18 is conducted to the antifreeze liquid tank 30 (second state), the second switching valve 36 is controlled to be in the shut-off state, and the pump 18 is operated. Controlled by the state. In the system according to the present embodiment, when such control is performed, cooling water (pure water) in the circulation path located downstream from the second switching valve 36 is pumped out by the pump 18, and the antifreeze liquid tank 30. It is comprised so that it may be transferred to. For this reason, according to the operation at the time of low temperature stop, almost all of the pure water existing in the circulation path used in the normal operation can be transferred to the antifreeze liquid tank 30.

(State during cold stop)
When the transfer of the cooling water (pure water) to the antifreeze liquid tank 30 is finished, the operation at the time of low temperature stop is finished at that time. As a result, the low temperature stop state shown in FIG. 3B is formed. Here, both the first switching valve 24 and the second switching valve 36 are shut off, and the pump 18 is stopped.

  During the cold stop, almost no cooling water (pure water) remains in the circulation path. For this reason, even if the temperature of the outside air surrounding the fuel cell system is further lowered, there is no inconvenience due to freezing of the cooling water inside the circulation path. In addition, since antifreeze components such as ethylene glycol and glycerin are stored in advance in the antifreeze tank 30, the pure water transferred to the antifreeze solution 30 mixes with these components and has a sufficiently low freezing point. It becomes. For this reason, the cooling water (mixed liquid) does not freeze even inside the antifreeze liquid tank 30. Thus, according to the system of this embodiment, freezing of the cooling water during the low temperature stop can be reliably avoided.

(Operation at low temperature start)
When the start of the fuel cell 10 is requested after the cooling water is transferred by the operation at the time of low temperature stop, the system of the present embodiment first executes “operation at the time of low temperature start”. FIG. 4A shows a state where the system of the present embodiment is performing “operation during cold start”. Here, the first switching valve 24 is controlled to be in a state (first state) in which the pump 18 is conducted to the reserve tank 26, and the second switching valve 36 is in a state in which the separation membrane unit 38 is conducted to the heat exchanger 42 ( (Second state).

  According to the above control, it is possible to create a state in which the cooling water flowing out from the pump 18 is guided to the reserve tank 26 instead of the antifreeze liquid tank 30. In addition, the separation membrane unit 38 is connected to the circulation path (heat exchanger 42), so that the separation membrane unit 38 separates only water from the mixed solution, and the resulting pure water flows into the circulation path. Can produce. However, at the time of cold start, the pump 18 is stopped. For this reason, the cooling water does not substantially flow into the fuel cell 10 while the operation at the time of cold start is performed.

  The fuel cell 10 exhibits its original power generation capability when its internal temperature reaches an appropriate activation temperature. For this reason, when the start is attempted in a low temperature environment, it is desirable to quickly raise the internal temperature. During the execution of the operation at the low temperature start described above, the cooling water does not flow into the fuel cell 10, so that the heat generated by the exothermic reaction is not lost to the cooling water. For this reason, according to the operation at the low temperature start, the internal temperature of the fuel cell 10 can be quickly increased, and the power generation efficiency of the fuel cell 10 can be sufficiently increased in a short time after the start of the start. it can.

(Operation of low-temperature machine process)
When the system of the present embodiment is started in a low temperature environment, when the internal temperature of the fuel cell 10 reaches a predetermined warm-up temperature, the operation at the low temperature start shown in FIG. B) Start “low warming process operation”. Here, the pump 18 is put into an operating state while maintaining the state of the first switching valve 24 and the second switching valve 36 at the low temperature starting state. As a result, the pure water cooling water starts to flow along the path of the separation membrane unit 38 → the heat exchanger → the fuel cell 10 → the pump 18 → the reserve tank, and the inside of the fuel cell 10 starts to be appropriately cooled.

  The operation of the low warming process is performed when a desired amount of pure water is taken out from the antifreeze liquid tank 30, that is, when pure water necessary for normal operation is stored in the reserve tank 26. Is terminated. Then, following the operation, the above-described normal operation (see FIG. 2) is started. After the start of the normal operation, the separation membrane unit 38 is not burdened as described above. That is, in the system of the present embodiment, the water separation burden is applied to the separation membrane unit 38 substantially only during the period during which the operation of the low warmer process is performed. For this reason, according to the system of the present embodiment, the fuel cell 10 can be stably and efficiently operated while sufficiently suppressing the deterioration of the separation membrane unit 38.

[Specific Processing in Embodiment 1]
FIG. 5 is a flowchart of a routine executed by the CPU 50 in order to realize the above function. Note that this routine is repeatedly executed at predetermined time intervals even after the fuel cell 10 is stopped, at least when the operation at the time of low temperature stop is not being executed.

  In the routine shown in FIG. 5, it is first determined whether or not the operation of the fuel cell 10 is stopped (step 100). The CPU 50 can make the above determination based on, for example, the state of the ON / OFF switch of the fuel cell 10 or the state of the ignition switch of the vehicle when the fuel cell 10 is mounted on the vehicle. .

  As a result, if it is determined that the fuel cell 10 is stopped, it is next determined whether or not a low temperature environment is formed (step 102). The CPU 50 determines the establishment of the low temperature environment when freezing of pure water is predicted. Specifically, it is determined that the low temperature environment is established when the outside air temperature sensor 58 detects an outside air temperature that is lower than the determination temperature set to about 0 to 5 ° C. However, the determination method is not limited to this. For example, the determination may be performed based on the internal temperature of the fuel cell 10 or the coolant temperature detected by the temperature sensors 52 and 54. Good.

  If formation of a low temperature environment is not recognized as a result of the above processing, it can be determined that freezing does not occur even if the cooling water remains pure water under the current environment. In this case, the pump 18 is turned off while the state of the first switching valve 24 and the second switching valve 36 is maintained in the state before stopping, that is, the state during normal operation (step 104). As a result, the circulation of the cooling water is stopped while the circulation path is formed as shown in FIG.

  If a low temperature environment is formed around the fuel cell 10 when it is stopped or stopped, it is determined in step 102 that the low temperature environment is established. If such a determination is made, it is next determined whether or not the transferred flag is ON (step 106). As will be described later, the transferred flag is a flag that is turned on when cooling water (pure water) in the circulation path is transferred to the antifreeze liquid tank 30 by performing an operation at a low temperature stop.

  If it is determined in step 106 that the transfer flag is ON, it can be determined that the operation during the low-temperature stop has already been performed. In this case, the current routine is immediately terminated without any further processing. On the other hand, if it is determined that the transferred flag is not ON, the pump 18 is turned ON and the first switching valve 24 is in the second state (conducting between the pump 18 and the antifreeze liquid tank 30 to start the operation at the time of low temperature stop. And the second switching valve 36 is shut off (step 108). When the above processing is executed, the operation at the time of low temperature stop shown in FIG. 3A is started, and the cooling water (pure water) existing in the circulation path starts to be transferred to the antifreeze liquid tank 30.

  Thereafter, when the transfer completion condition (for example, elapse of a predetermined time) is recognized (step 110), the pump 18 is turned off and the first switching valve 24 and the second switching valve 24 are turned off to finish the operation at the low temperature stop. Both switching valves 36 are shut off (step 112). When the above processing is executed, the state during the low-temperature stop shown in FIG. 3B, that is, the state where the cooling water cannot be frozen is realized. Thereafter, the transferred flag is turned on (step 114), and then the current routine is terminated.

  During operation of the fuel cell 10, the determination of operation stop is denied in step 100. In this case, it is next determined whether or not the starting flag is ON (step 116). As will be described later, the start time flag is a flag that is turned ON when an operation during normal operation is started. Therefore, if it is determined that this flag is ON, it can be determined that the processing to be executed by this routine has already been completed. In this case, the current routine is immediately terminated thereafter.

  On the other hand, if it is determined in step 116 that the start flag is not ON, it is next determined whether or not the transferred flag is ON (step 118). As described above, the transferred flag is a flag that is turned ON only when the cooling water in the circulation path is transferred to the antifreeze liquid tank 30 while the fuel cell 10 is stopped. Therefore, if the flag is not ON, it can be determined that the cooling water remains in the circulation path without being transferred to the antifreeze liquid tank 30. Further, in this case, it can be determined that the first switching valve 24 and the second switching valve 36 are maintained in the state during normal operation.

  In this case, to start the warm start operation (see FIG. 2), first, it is determined whether the internal temperature of the fuel cell 10 has increased to the activation temperature (step 120). If the internal temperature of the fuel cell 10 has not reached the activation temperature, it can be determined that the temperature should still be raised and cooling of the fuel cell 10 should not be started. For this reason, when the activation temperature is not reached, the arrival of the pump 18 is awaited with the pump 18 kept in the OFF state, that is, without starting the circulation of the cooling water.

  When it is determined that the internal temperature of the fuel cell 10 has reached the activation temperature, the pump 18 is turned on to prevent overheating of the internal temperature (step 122). As a result, thereafter, the operation during normal operation (see FIG. 2) is started so that the internal temperature of the fuel cell 10 is maintained at an appropriate temperature. When the above processing is completed, the starting flag is turned off (step 124), and then the current routine is terminated.

  If the operation at the time of low temperature stop is performed when the fuel cell 10 is stopped, it is determined that the transferred flag is ON in step 118 after the fuel cell 10 is restarted (step 118). In this case, after the transferred flag is turned OFF (step 126), the first switching valve 24 is set to the first state and the second state is started in order to start the operation at the low temperature start shown in FIG. The switching valve 36 is controlled to the second state (step 128). As a result, a state is formed in which the pump 18 is conducted to the reserve tank 26 and the separation membrane unit 38 is conducted to the heat exchanger 42.

  Next, it is determined whether the internal temperature of the fuel cell 10 has increased to the activation temperature (step 130). When the internal temperature of the fuel cell 10 does not reach the activation temperature, it can be determined that the temperature should still be raised and that the cooling water should not flow into the fuel cell 10. For this reason, when reaching | attaining to activation temperature is not recognized, the pump 18 is maintained in an OFF state, As a result, the state (state shown to FIG. 4 (A)) at the time of a low temperature start is maintained.

  If it is determined that the internal temperature of the fuel cell 10 has reached the activation temperature, the pump 18 is turned on to prevent overheating of the internal temperature (step 132). As a result, instead of the operation at the low temperature start, the operation of the low warmer process shown in FIG. 4B is started. That is, the operation of separating and extracting pure water from the antifreeze liquid tank 30 and distributing the pure water to the reserve tank 26 via the fuel cell 10 is started.

  Next, it is determined whether or not the water separation completion condition is satisfied (step 134). The condition for completing the water separation is when it can be determined that a sufficient amount of pure water has been taken out of the antifreeze liquid tank 30, and more specifically, a sufficient amount of pure water is reserved to perform operations during normal operation. When it can be determined that the fuel has been stored in the tank 26, its establishment is recognized. This condition is determined to be satisfied when, for example, the elapsed time after the pump 18 is turned on reaches a predetermined time.

  When it is determined that the water separation completion condition is satisfied, the second switching is performed to stop the operation of the low warming process (see FIG. 4B) and start the operation in the normal operation (see FIG. 2). The valve 36 is switched from the second state to the first state (step 136). As a result, a circulation path necessary for normal operation, that is, a circulation path that forms a circulation path without including the antifreeze liquid tank 30 and the separation membrane unit 38 is formed. Thereafter, in step 124, the starting flag is turned OFF, and then the current routine is terminated.

  According to the above processing, only when the fuel cell 10 is stopped in a low-temperature environment, that is, when there is a possibility that the cooling water of the pure water may freeze, the antifreeze is mixed with the cooling water, If water freezing is not expected, the pure water can be left as it is without being mixed with the antifreeze. For this reason, according to the system of this embodiment, it is possible to keep the fuel cell 10 generating electric power stably and efficiently while sufficiently reducing the burden on the separation membrane unit 38. According to this system, since the burden on the separation membrane unit 38 is small, the deterioration with time can be sufficiently suppressed, and the durability of the system itself can be greatly improved.

  By the way, in the first embodiment described above, when the fuel cell 10 is stopped in a warm environment, the pump 18 is stopped with pure water cooling water remaining in the circulation path. (Operation at the time of warm stop), the stop method in the warm environment is not limited to this. That is, even when stopping in a warm environment, the pump 18 may be stopped after the cooling water in the circulation path is collected in the reserve tank 26 in order to extract the cooling water from the inside of the fuel cell 10. According to such a method, it is possible to reduce the heat capacity around the fuel cell 10 even when starting in a warm environment, as in the case of starting in a low temperature environment. The time required for the machine can be shortened.

  In the first embodiment described above, the circulation path used during normal operation is the “cooling mechanism” in the first invention, the humidifying unit 16 is the “humidifying mechanism” in the first invention, and the antifreeze liquid tank 30 is. The first switching valve 24, the second switching valve 26 and the CPU 50 correspond to the “antifreeze mixing mechanism” in the first invention, and the separation membrane unit 38 corresponds to the “cooling water separation mechanism” in the first invention. ing.

Next, a modified example of the present invention will be described with reference to FIG. In the modification shown in FIG. 6, (1) the antifreeze liquid tank 30 and the separation membrane unit 30 and the branch mechanism (the first switching valve 24, the second switching valve 36, and the pipes 32 and 40) connected to them are omitted. The system of Embodiment 1 except that (2) the switching valve 60 is disposed between the reserve tank 26 and the heat exchanger 42, and (3) the humidifying unit 16 is removed. It has the same hardware configuration. In the system shown in FIG. 6, it is assumed that cooling water containing antifreeze is used to avoid freezing.

  In the system shown in FIG. 6, the switching valve 60 can selectively realize either the valve opening state or the valve closing state in response to a command from the CPU 50. The fuel cell system shown in FIG. 6 operates the pump 18 with the switching valve 60 opened during normal operation. In this case, since the cooling water circulates in the circulation path, the inside of the fuel cell 10 can be appropriately cooled.

  In the system shown in FIG. 6, when the fuel cell 10 is stopped in a warm environment, specifically, in an environment where the outside air temperature exceeds 5 ° C., the pump 18 is immediately turned off and the cooling water is turned off. Stop circulation. On the other hand, when a low temperature environment is detected when the fuel cell 10 is stopped or during the stop, specifically, an environment in which the outside air temperature falls below a predetermined determination value set between 0 to 5 ° C. is detected. If so, an extraction process for extracting the cooling water from the fuel cell 10 is started at that time.

  Specifically, the cooling water extraction process can be executed by closing the switching valve 60 and turning on the pump 18. According to such a process, the cooling water existing downstream of the switching valve 60 can be recovered in the reserve tank 26. When it is determined that the cooling water has been collected (for example, when it is determined that a predetermined execution time has elapsed), at that time, the pump 18 is turned off to end the extraction process.

  Thereafter, the cooling water does not flow into the fuel cell 10 until the switching valve 60 is opened. The switching valve 60 is maintained in the closed state until the fuel cell 10 is restarted when the fuel cell 10 is stopped in a low temperature environment, and then the internal temperature of the fuel cell 10 reaches the activation temperature. According to such a process, the heat capacity of the fuel cell 10 can be reduced by the amount of no cooling water when restarting in a low temperature environment. For this reason, according to the system shown in FIG. 6, the warm-up of the fuel cell 10 can be quickly terminated after starting in a low temperature environment, and the situation in which the fuel cell 10 efficiently generates electric power can be shortened. Can be produced in time.

It is a figure for demonstrating the structure of the fuel cell system of Embodiment 1 of this invention. It is a figure showing the state which the system of Embodiment 1 of this invention implement | achieves in "at the time of normal operation", "at the time of warm stop", and "at the time of warm start". FIG. 3A shows a state realized by the system according to the first embodiment of the present invention at “during cold stop”. FIG. 3B shows a state realized by the system according to the first embodiment of the present invention in “during cold stop”. FIG. 4A shows a state that the system according to the first embodiment of the present invention realizes at “at the time of cold start”. FIG. 4B shows a state realized by the system according to the first embodiment of the present invention in the “low warming process”. 3 shows a flowchart of a routine executed in Embodiment 1 of the present invention. It is a figure for demonstrating the structure of the fuel cell system of the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 16 Humidification part 18 Pump 24 1st switching valve 26 Reserve tank 30 Antifreeze liquid tank 36 2nd switching valve 38 Separation membrane unit

Claims (3)

A fuel cell;
A cooling mechanism for cooling the fuel cell with pure water cooling water;
A humidifying mechanism for humidifying the reaction gas supplied to the fuel cell with the cooling water;
An antifreeze mixing mechanism that mixes the cooling water with the antifreeze only under a low temperature environment in which the fuel cell is stopped and the cooling water is expected to freeze;
A cooling water separation mechanism for separating the cooling water mixed by the antifreezing liquid mixing mechanism from the antifreezing liquid under a situation where separation of the cooling water and the antifreezing liquid is required;
A fuel cell system comprising:   The fuel cell system according to claim 1, wherein the cooling water separation mechanism separates the cooling water from the antifreeze when the humidification mechanism humidifies the reaction gas. The cooling mechanism includes a cooling water circulation path including the fuel cell,
3. The fuel cell system according to claim 1, wherein the antifreeze liquid mixing mechanism includes an antifreeze liquid tank that collects the cooling water in the cooling water circulation path and stores the cooling water in a mixed state with the antifreeze liquid. .

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