JP6969308B2 - Fuel cell system - Google Patents

Description

The techniques disclosed herein relate to fuel cell systems. More specifically, the present invention relates to a technique for preventing freezing of a fuel cell system.

A fuel cell system that uses hydrogen gas to generate electricity has been developed. The fuel cell system includes a fuel cell, a hydrogen tank for storing hydrogen gas, a hydrogen introduction path for guiding hydrogen gas to the fuel cell, an on-off valve for opening and closing the hydrogen introduction path, and a control unit for controlling the on-off valve. In fuel cell systems, the on-off valve freezes when the outside air temperature drops, making it impossible to open the valve when necessary. In the fuel cell system of Patent Document 1, the outside air temperature is detected at predetermined time intervals. Then, when it is detected that the temperature is below the predetermined temperature, the control unit causes the on-off valve to flow a current within the range in which the on-off valve does not open. This current causes the on-off valve to generate heat and suppresses the on-off valve from freezing.

Japanese Unexamined Patent Publication No. 2013-125626

In the fuel system of Patent Document 1, the temperature is detected at predetermined predetermined time intervals, and it is determined whether or not the detected temperature is equal to or lower than the predetermined temperature. Therefore, even if it is not necessary to detect the temperature frequently, for example, when the outside air temperature drops slowly, the temperature is detected after a predetermined time, and the power consumption is large. There was a problem of becoming. The present specification discloses a technique for reducing the power consumption required for the freeze prevention function of the on-off valve.

The fuel cell system disclosed in the present specification includes a fuel cell, a hydrogen tank for storing hydrogen gas, a hydrogen introduction path for connecting the fuel cell and the hydrogen tank to introduce hydrogen gas into the fuel cell, and a hydrogen introduction path. It includes an on-off valve that opens and closes, a control unit that controls the on-off valve, a housing that houses the fuel cell and the on-off valve, and a temperature detection unit that detects the temperature outside the housing. The control unit has a temperature acquisition time storage means that stores the time for acquiring the detected temperature from the temperature detection unit, a time measuring means that measures the elapsed time since the detection temperature is acquired from the temperature detection unit, and a temperature acquisition time. When the time stored by the storage means and the time measured by the time measuring means match, the temperature acquisition means that acquires the detected temperature from the temperature detection unit and the detection temperature acquired by the temperature acquisition means are equal to or less than the predetermined temperature. Calculate the difference between the detected temperature acquired this time and the detected temperature acquired last time, and the energization means that allows a current smaller than the current required to open the on-off valve to the on-off valve, and at least the detected temperature acquired this time and the calculated difference. Based on the above, a determination means for determining the next temperature acquisition time and storing it in the temperature acquisition time storage means, and a previous temperature storage means for storing the detected temperature acquired this time as the previous detection temperature are provided.

The above fuel cell system is provided with a determination means for determining the next temperature acquisition time based on at least the temperature acquired this time and the difference between the temperature acquired last time and the temperature acquired this time. For this reason, the temperature is set when it is not necessary to detect the temperature frequently, such as when the temperature acquired this time is relatively high, or when the amount of change in temperature from the acquisition of the previous temperature to the acquisition of the temperature this time is small. The number of detections can be reduced. Therefore, it is possible to avoid unnecessary temperature detection processing and reduce the power consumption required for the on-off valve freeze prevention processing.

The figure which shows typically the schematic structure of the fuel cell system which concerns on Example. The block diagram which shows the structure of the control system of the fuel cell system which concerns on Example. It is a figure explaining the magnitude of the electric current supplied to an on-off valve, (a) is a figure which holds the valve open state after changing the on-off valve from the valve closed state to the valve open state at the time of power generation of a fuel cell. The magnitude of the current supplied to the on-off valve is shown, and (b) shows the magnitude of the current supplied to the on-off valve during the freeze prevention process of the on-off valve when the power generation of the fuel cell is stopped. There is. The figure which shows the relationship between the temperature detected this time, the difference between the temperature detected last time and the temperature detected this time, and the time until the next temperature is detected. The flowchart which shows an example of the freeze prevention process of an on-off valve when the power generation of a fuel cell is stopped.

Hereinafter, the fuel cell system 10 according to the embodiment will be described. As shown in FIG. 1, the fuel cell system 10 includes a fuel cell 12, a hydrogen tank 14, a hydrogen introduction path 16, an on-off valve 18 installed in the hydrogen introduction path 16, a gas discharge path 20, and gas. An on-off valve 22 installed in the discharge path 20, a compressor 24, an on-off valve 26 installed between the compressor 24 and the fuel cell 12, a temperature sensor 28, a housing 30, and a control unit 32 (FIG. 2) is provided.

The fuel cell 12 uses the hydrogen gas in the hydrogen tank 14 to generate electric power. The hydrogen tank 14 stores hydrogen gas. The hydrogen introduction path 16 connects the fuel cell 12 and the hydrogen tank 14. The on-off valve 18 is installed in the hydrogen introduction path 16, and the hydrogen introduction path 16 is opened and closed by opening and closing the on-off valve 18. Therefore, when the on-off valve 18 is opened, the hydrogen gas in the hydrogen tank 14 is supplied to the fuel cell 12 through the hydrogen introduction path 16. The on-off valve 18 is connected to the control unit 32.

The gas discharge path 20 discharges exhaust gas, water, and the like generated when electric power is generated by the fuel cell 12. The on-off valve 22 is installed in the gas discharge path 20, and the gas discharge path 20 is opened and closed by opening and closing the on-off valve 22. The compressor 24 is connected to the fuel cell 12. The on-off valve 26 is installed between the compressor 24 and the fuel cell 12. Therefore, when the compressor 24 is operated with the on-off valve 26 opened, air is sent to the fuel cell 12, and the fuel cell 12 generates electricity by hydrogen and oxygen. Then, the exhaust gas, moisture, and the like generated in the fuel cell 12 are discharged through the gas discharge path 20. The on-off valves 22, 26 and the compressor 24 are connected to the control unit 32.

The temperature sensor 28 is installed outside the housing 30 and detects the temperature outside the housing 30. The housing 30 is directly arranged outdoors. Therefore, the temperature sensor 28 detects the outside air temperature. The housing 30 may be housed in another housing. In this case, the temperature sensor 28 may detect the temperature between the housing 30 and the other housing, and the temperature sensor 28 is installed outside the other housing and the temperature outside the other housing, that is, , The outside temperature may be detected. Further, in the present embodiment, the housing 30 accommodates the fuel cell 12, the on-off valve 18, and the hydrogen tank 14, but is not limited to such a configuration. The housing 30 may contain at least the fuel cell 12 and the on-off valve 18, and may not contain the hydrogen tank 14.

As shown in FIG. 2, the control unit 32 is configured by using a computer including a memory 40 and a CPU 50. The memory 40 is provided with a temperature acquisition time storage unit 42 and a previous temperature storage unit 44.

The temperature acquisition time storage unit 42 stores the time for acquiring the temperature detected by the temperature sensor 28 from the temperature sensor 28. The time for acquiring the detected temperature from the temperature sensor 28 is determined by the temperature acquisition time determining unit 58, which will be described later.

The previous temperature storage unit 44 stores the detected temperature acquired by the temperature acquisition unit 54, which will be described later. In the freeze prevention process of the on-off valve 18 when the power generation of the fuel cell 12 is stopped, which will be described in detail later, it is possible to acquire the detected temperature from the temperature sensor 28 a plurality of times from the stop of the power generation of the fuel cell 12 to the start of the power generation. be. The previous temperature storage unit 44 stores the detected temperature acquired this time for use as the "previous detected temperature" when acquiring the next detected temperature. For example, when the detection temperature acquired this time by the temperature acquisition unit 54 is the "nth detection temperature acquired", the previous temperature storage unit 44 describes it as the "previous detection temperature" when the detection temperature is acquired at the n + 1th time. In order to do so, the detected temperature acquired at the nth time is stored.

An arithmetic program is stored in the memory 40, and when the CPU 50 executes the arithmetic program, the CPU 50 functions as a timing unit 52, a temperature acquisition unit 54, a valve opening holding current supply unit 56, and a temperature acquisition time determination unit 58. do.

The timekeeping unit 52 measures the time elapsed since the previous acquisition of the detected temperature. The temperature acquisition unit 54 acquires the detected temperature from the temperature sensor 28 at a set time. Specifically, the temperature acquisition unit 54 acquires the detected temperature from the temperature sensor 28 when the time stored in the temperature acquisition time storage unit 42 and the time measured by the timekeeping unit 52 match.

The valve opening holding current supply unit 56 causes the valve opening holding current to flow through the on-off valve 18. The valve open holding current is a current of a magnitude required to hold the valve open state when the on-off valve 18 is in the valve open state. As shown in FIG. 3A, when the on-off valve 18 is opened to supply hydrogen gas to the fuel cell 12 during power generation of the fuel cell 12, it is opened / closed to change from the closed state to the open state. A large current (hereinafter, also referred to as valve opening current) is passed through the valve 18. Then, after the valve is opened, a current smaller than the valve opening current (hereinafter, also referred to as a valve opening holding current) is passed through the on-off valve 18 in order to maintain the valve opening state. As shown in FIG. 3B, the valve opening holding current supply unit 56 supplies the valve opening holding current to the on-off valve 18. When the valve opening holding current supply unit 56 supplies the valve opening holding current to the on-off valve 18, the on-off valve 18 is in a closed state because the power generation of the fuel cell 12 is stopped. By supplying the valve opening holding current to the on-off valve 18 in the closed state, the temperature of the on-off valve 18 can be raised without opening the on-off valve 18. This makes it possible to prevent the on-off valve 18 from freezing.

The temperature acquisition time determination unit 58 determines the time until the next acquisition of the detected temperature from the temperature sensor 28. If the outside air temperature is dropping sharply, it is necessary to monitor the outside air temperature frequently. Therefore, the time until the next time to acquire the detected temperature from the temperature sensor 28 is shortened. On the other hand, when the falling speed of the outside air temperature is slow, the on-off valve 18 does not freeze even if it is left for a while. Therefore, the time from the temperature sensor 28 to the acquisition of the detected temperature can be set relatively long. Further, when the current temperature is low, the on-off valve 18 may freeze unless the time until the next temperature acquisition is shortened, but when the current temperature is not low, until the next temperature acquisition. The on-off valve 18 does not freeze even if the time is lengthened. Therefore, the temperature acquisition time determination unit 58 calculates the difference between the detected temperature acquired this time and the previous detected temperature stored in the previous temperature storage unit 44, and is based on the difference between the detected temperature acquired this time and the calculated difference. , Next, determine the time until the detection temperature is acquired.

FIG. 4 shows the relationship between the time until the next detection temperature is acquired (vertical axis) and the difference between the previous detection temperature and the current detection temperature (horizontal axis). In the following, the detected temperature acquired this time may be referred to as "T2", the detected temperature acquired last time may be referred to as "T1", and the difference between T1 and T2 (specifically, T1-T2) may be referred to as "ΔT". .. Graph A shows when T2 is 0 ° C. or lower, which is a predetermined temperature, graph B shows when T2 is larger than 0 ° C. and 10 ° C. or lower, and graph C shows when T2 is 10 or less. Indicates when the temperature is higher than ° C. As shown in FIG. 4, in any of the graphs A to C, as ΔT increases, the time until the next detection temperature is acquired becomes shorter. Further, in the case of Graph A, since the outside air temperature is already below the predetermined temperature, the on-off valve 18 tends to freeze. Therefore, the time until the next detection temperature is acquired is shortened as a whole. On the other hand, in the case of the graph B, since the outside air temperature is higher than that in the case of the graph A, the time until the next detection temperature is acquired is generally longer than that in the case of the graph A. Since the outside air temperature is higher in the case of the graph C than in the case of the graph B, the time until the next detection temperature is acquired is made longer as a whole than in the case of the graph B.

In this way, the temperature acquisition time determination unit 58 determines the time until the next detection temperature is acquired based on ΔT and T2. As a result, the outside air temperature can be monitored so that the on-off valve 18 does not freeze, and it is possible to prevent the number of times of monitoring from increasing more than necessary. Therefore, the power consumption used for the antifreeze treatment can be reduced. In this embodiment, the predetermined temperature is set to 0 ° C., but the present invention is not limited to such a configuration. The predetermined temperature may be a temperature higher than 0 ° C. or a temperature lower than 0 ° C.

Further, the control unit 32 is connected to the on-off valves 18, 22, 26 and the compressor 24. The control unit 32 controls the opening and closing of the on-off valves 18, 22, and 26, and controls the compressor 24. Further, the control unit 32 is connected to the temperature sensor 28 and acquires the temperature detected by the temperature sensor 28.

Further, the control unit 32 controls a parking purge process for scavenging exhaust gas, water, etc. from the gas discharge path 20 when the power generation of the fuel cell 12 is stopped. In the parking purge process, the control unit 32 acquires the detected temperature from the temperature sensor 28 at preset time intervals. This time interval is longer than the temperature detection time interval required for the freeze prevention treatment of the on-off valve 18. Then, when the detected temperature is lower than a predetermined temperature (for example, 0 ° C.), the control unit 32 opens the on-off valves 22 and 26 and operates the compressor 24. Then, the exhaust gas, water, etc. remaining in the fuel cell 12 are discharged through the gas discharge path 20. This makes it possible to prevent the fuel cell 12 and the gas discharge path 20 from freezing while the power generation of the fuel cell 12 is stopped.

Next, the freeze prevention process of the on-off valve 18 when the power generation of the fuel cell 12 is stopped will be described. FIG. 5 is a flowchart showing an example of the freeze prevention process of the on-off valve 18 when the power generation of the fuel cell 12 is stopped. If the outside air temperature drops when the power generation of the fuel cell 12 is stopped, the inside of the fuel cell system 10 may freeze. In particular, when the on-off valve 18 freezes, the on-off valve 18 cannot be opened when the power generation of the fuel cell 12 is started, and hydrogen cannot be supplied to the fuel cell 12. Therefore, if the on-off valve 18 freezes when the power generation of the fuel cell 12 is stopped, the power generation cannot be started promptly when the fuel cell 12 is started. In order to prevent this, a process of preventing the on-off valve 18 from freezing is executed while the power generation of the fuel cell 12 is stopped. In the following description, temperature detection from the second time onward after the fuel cell 12 is stopped will be described as an example. Therefore, if a process different from the second and subsequent temperature detections is executed at the time of the first temperature detection from the stop of the fuel cell 12, the difference will be described together in the corresponding step in the following explanation. do.

As shown in FIG. 5, the timekeeping unit 52 measures the elapsed time from the previous temperature acquisition (S12). If the temperature has never been detected since the power generation of the fuel cell 12 was stopped, the elapsed time from the power generation stop of the fuel cell 12 is measured.

Next, the control unit 32 determines whether or not the elapsed time measured by the time measuring unit 52 coincides with the time stored in the temperature acquisition time storage unit 42 (S14). The time stored in the temperature acquisition time storage unit 42 is the time determined by the temperature acquisition time determination unit 58 by the processing by the previous temperature acquisition. The time determination by the temperature acquisition time determination unit 58 will be described later. If the temperature has never been detected since the power generation of the fuel cell 12 was stopped, the control unit 32 determines whether or not the elapsed time measured by the time measuring unit 52 matches the preset time. .. If the elapsed time measured by the time measuring unit 52 does not match the time stored in the temperature acquisition time storage unit 42 (or the preset time) (NO in step S14), the previous temperature acquisition It is determined that the time determined by the process (or the preset time) has not been reached, and the process waits until the time stored in the temperature acquisition time storage unit 42 (or the preset time) is reached.

On the other hand, when the elapsed time measured by the time measuring unit 52 matches the time stored in the temperature acquisition time storage unit 42 (or the preset time) (YES in step S14), the previous temperature. Determining that the time determined by the acquisition process (or the preset time) has been reached, the temperature acquisition unit 54 acquires the detected temperature (that is, the current detected temperature T2) from the temperature sensor 28 (S16). ..

Next, the control unit 32 determines whether or not T2 acquired in step S16 is lower than the predetermined temperature (S18). Specifically, it is determined whether or not T2 is lower than 0 ° C.

If T2 is lower than 0 ° C. (YES in step S18), it is determined that the on-off valve 18 may freeze, and the process proceeds to step S20. On the other hand, when T2 is 0 ° C. or higher (NO in step S18), step S20 is skipped and the process proceeds to step S22.

When T2 is lower than 0 ° C. (YES in step S18), the valve opening holding current supply unit 56 causes the valve opening holding current to flow through the on-off valve 18 (S20). As described above, the valve opening holding current supplied by the valve opening holding current supply unit 56 to the on-off valve 18 is a relatively small current shown in FIG. 3 (b). Therefore, the temperature of the on-off valve 18 is raised without opening the on-off valve 18. Thereby, even if the outside air temperature becomes lower than 0 ° C., the on-off valve 18 can be prevented from freezing.

Next, the temperature acquisition time determination unit 58 calculates the difference (that is, ΔT) between the previously acquired detection temperature (that is, T1) and the currently acquired detection temperature T2 (S22). T1 is stored in the temperature storage unit 44 last time. The step of storing T1 in the previous temperature storage unit 44 will be described later. The temperature acquisition time determination unit 58 calculates ΔT from T1 stored in the temperature storage unit 44 last time and T2 acquired by the temperature acquisition unit 54 in step S16. If the detected temperature is acquired only once from the stop of power generation of the fuel cell 12, the previous temperature T1 does not exist, so step S22 is omitted. Alternatively, the temperature at the time when the power generation is stopped is stored in the previous temperature storage unit 44 as T1 and ΔT is calculated.

Next, the temperature acquisition time determination unit 58 determines the time until the next acquisition of the detected temperature from the temperature sensor 28 based on the T2 acquired by the temperature acquisition unit 54 in step S16 and the ΔT calculated in step S22. (S24). Specifically, the relationship shown in FIG. 4 is used. Then, the temperature acquisition time storage unit 42 stores the acquisition time of the detection temperature determined by the temperature acquisition time determination unit 58 in step S24 (S26). If the detected temperature is acquired only once from the stop of power generation of the fuel cell 12, the time until the next acquisition of the detected temperature from the temperature sensor 28 is determined based only on T2, and the determined time is determined. It is stored in the temperature acquisition time storage unit 42.

Next, the previous temperature storage unit 44 stores the detected temperature acquired in step S16 (S28). The detected temperature acquired in step S16 is used not only as T2 in the current processing of steps S18, S22 and S24, but also as T1 in the next processing. Therefore, the previous temperature storage unit 44 stores the detected temperature acquired in step S16 as T1.

Next, the control unit 32 determines whether or not to carry out the parking purge process (S30). As described above, the parking purge process acquires the detected temperature from the temperature sensor 28 at preset time intervals, and is performed when the detected temperature is lower than 0 ° C. In other words, the parking purge process is performed at a preset time and when the temperature detected at that time is lower than 0 ° C. The time interval preset here is longer than the time interval determined in step S24 described above. Therefore, the frequency of temperature detection for the parking purge process is lower than the frequency of temperature detection for the freeze prevention process of the on-off valve 18. Therefore, the power consumption required for the parking purge process is smaller than the power consumption required for the freeze prevention process of the on-off valve 18. When the parking purge process is performed (YES in step S30), that is, when the preset time is reached and the temperature detected at that time is lower than 0 ° C., the process proceeds to step S32 and parking is performed. Perform a purge process. After that, the process returns to step S12, and the processes of steps S12 to S32 are repeated until the power generation of the fuel cell 12 starts. On the other hand, when the parking purge process is not performed (NO in step S30), that is, the preset time has not been reached, or the preset time has been reached, but the temperature detected at that time is If the temperature is 0 ° C. or higher, the process returns to step S12. Then, the processes of S12 to S32 are repeated until the power generation of the fuel cell 12 is started.

In the fuel cell system 10 of this embodiment, the time from the acquisition of the detected temperature from the temperature sensor 28 to the acquisition of the next detected temperature is the current detection temperature T2, the previous detection temperature T1, and the current detection temperature. It is calculated based on the difference ΔT of T2. Therefore, when the on-off valve 18 is not likely to freeze even if the outside air temperature is not frequently monitored, such as when T2 is relatively high or ΔT is small, the number of times the freeze prevention process is executed can be reduced. can. When the power generation of the fuel cell 12 is stopped, the control unit 32 is also stopped together with the fuel cell 12, but the control unit 32 is activated during the antifreezing process. Therefore, power consumption can be reduced by reducing the number of unnecessary antifreezing treatments.

In this embodiment, the time until the next detection temperature is acquired is determined based on T2 and ΔT, but the configuration is not limited to this. For example, the time until the next detection temperature is acquired may be determined based on the amount of change (that is, the rate of change) of the difference between T2 and T1 and T2 per time. That is, the time until the next detection temperature is acquired may be determined by taking into consideration the time interval in addition to T2 and T1-T2.

The points to be noted about the fuel cell system 10 described in the examples will be described. The temperature sensor 28 of the embodiment is an example of the "temperature detection unit", the temperature acquisition time storage unit 42 is an example of the "temperature acquisition time storage means", and the timekeeping unit 52 is an example of the "timekeeping means". The acquisition unit 54 is an example of "temperature acquisition means", the valve opening holding current supply unit 56 is an example of "energization means", and the temperature acquisition time determination unit 58 is an example of "determination means". Part 44 is an example of the "previous temperature storage means".

Although specific examples of the disclosed techniques have been described in detail in the present specification, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above. Further, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

10: Fuel cell system 12: Fuel cell 14: Hydrogen tank 16: Hydrogen introduction path 18: On-off valve 20: Gas discharge path 22: On-off valve 24: Compressor 26: On-off valve 28: Temperature sensor 30: Housing 32: Control unit 42: Temperature acquisition time storage unit 44: Previous temperature storage unit 52: Measuring unit 54: Temperature acquisition unit 56: Valve opening holding current supply unit 58: Temperature acquisition time determination unit

Claims (1)

With a fuel cell
A hydrogen tank that stores hydrogen gas and
A hydrogen introduction path for connecting the fuel cell and the hydrogen tank and introducing the hydrogen gas into the fuel cell,
An on-off valve that opens and closes the hydrogen introduction path,
A control unit that controls the on-off valve and
A housing that houses the fuel cell and the on-off valve,
It is equipped with a temperature detection unit that detects the temperature outside the housing.
The control unit
A temperature acquisition time storage means that stores the time for acquiring the detected temperature from the temperature detection unit, and
A timekeeping means for measuring the elapsed time since the detection temperature was acquired from the temperature detection unit, and
When the time stored by the temperature acquisition time storage means and the time measured by the timekeeping means match, the temperature acquisition means for acquiring the detected temperature from the temperature detection unit and the temperature acquisition means.
When the detected temperature acquired by the temperature acquisition means is equal to or lower than a predetermined temperature, an energizing means for passing a current smaller than the current required for opening the on-off valve through the on-off valve, and an energizing means.
The difference between the detected temperature acquired this time and the detected temperature acquired last time is calculated, and the next temperature acquisition time is determined based on at least the detected temperature acquired this time and the calculated difference, and the temperature acquisition time storage means is used. The deciding means to remember,
A fuel cell system including a previous temperature storage means for storing the detected temperature acquired this time as the previous detected temperature.

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