JP2006286525A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of precisely monitoring the temperature of fuel cell, even when operation of the fuel cell stops, by suppressing the energy consumption, as much as possible. <P>SOLUTION: The fuel cell system comprises a fuel cell 10, a cooling liquid circulating device (20, 21) for supplying and circulating the cooling liquid to the fuel cell 10, and a temperature detection means 22 for detecting the temperatures of the cooling liquid. The system has a cooling liquid circulation driving control means 30 (S5, S6, S7) for driving the cooling liquid circulation device intermittently, when operation of the fuel cell 10 is stopped and a temperature acquisition means 30 (S8) which obtains the temperature of the cooling liquid detected by the temperature detection means 22 as the temperature of the fuel cell; while the cooling liquid circulation device is driven by the cooling liquid circulation drive control means 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system having a fuel cell that is cooled by circulating a coolant and that detects the temperature of the coolant as the temperature of the fuel cell.

  For example, in a polymer electrolyte fuel cell, a fuel gas (for example, hydrogen gas) and an oxidant gas (for example, an oxygen-containing gas (air)) react in a process of permeating the polymer electrolyte membrane to generate an electromotive force. . In order to suppress an increase in temperature of the fuel cell due to heat generated during the operation of the fuel cell, the fuel cell system generally includes a cooling water circulation device (cooling water) for supplying and circulating cooling water to the fuel cell. Including a circulation path and a water pump.

  In such a fuel cell system, the temperature of the fuel cell is monitored in order to determine whether or not the fuel cell is operating normally. In this case, normally, the temperature of the fuel cell is indirectly detected by detecting the temperature of the cooling water discharged through the fuel cell. Thus, when the detected temperature of the cooling water deviates from the normal temperature range, it can be determined that the operation of the fuel cell is not normal.

  By the way, when the fuel cell and the secondary battery are provided, and the required power (output) is in a range where the power generation efficiency of the fuel cell is not good, the operation of the fuel cell is stopped and the load from the secondary battery is reduced. A system for supplying power to (for example, a motor) has been proposed (see, for example, Patent Document 1). According to such a system, waste of power generation in the fuel cell can be suppressed, and the efficiency of the entire system having the fuel cell and the secondary battery can be improved.

In a system in which a fuel cell operates intermittently, such as a system including a fuel cell and a secondary battery as described above, in order to save energy when the operation of the fuel cell is stopped It is common to stop the operation of the cooling water circulation device. On the other hand, there is also a demand for monitoring the temperature state of the fuel cell even when the operation of the fuel cell is stopped.
JP 2001-307758 A JP 2003-36874 A

  However, as in a fuel cell system in which the operation of the fuel cell is intermittent, the operation of the fuel cell is stopped and the operation of the cooling water circulation device is stopped. Even if detected as a temperature, the detected temperature does not represent an accurate fuel cell. Therefore, it is conceivable that the operation of the cooling water circulation device is not stopped even when the operation of the fuel cell is stopped. However, in this case, there is a problem that energy (electric power) consumption for operating the cooling water circulation device is increased.

  The present invention has been made in order to solve the above-described conventional problems, so that energy consumption can be minimized and the temperature of the fuel cell can be accurately monitored even when the operation of the fuel cell is stopped. A fuel cell system is provided.

A fuel cell system according to the present invention is a fuel cell system including a fuel cell, a coolant circulation device that supplies and circulates a coolant to the fuel cell, and a temperature detection means that detects the temperature of the coolant. The coolant circulation operation control means for intermittently operating the coolant circulation device when the operation of the fuel cell is stopped, and the coolant circulation device is operated by the coolant circulation control means. In the meantime, the temperature detecting means acquires the temperature of the coolant detected by the temperature detecting means as the temperature of the fuel cell.

  With such a configuration, when the operation of the fuel cell is stopped, the coolant circulation device is intermittently operated, and the temperature of the coolant is detected while the coolant circulation device is operating. The detected temperature is acquired as the temperature of the fuel cell.

  In the fuel cell system according to the present invention, the coolant circulation operation control means may operate the coolant circulation device at regular time intervals.

  With such a configuration, when the coolant circulating apparatus is operated at regular time intervals, the detected temperature of the coolant is acquired as the temperature of the fuel cell. Thus, the temperature of the fuel cell is acquired at regular time intervals while the operation of the fuel cell is stopped.

  In addition, the fuel cell system according to the present invention may be configured to include interval control means for controlling a time interval for operating the coolant circulation device in accordance with the temperature detected by the temperature detection means.

  With such a configuration, it is possible to control the frequency of acquiring the temperature of the fuel cell in accordance with the detected temperature of the cooling water that can represent the state of the fuel cell. For example, the higher the detected temperature, the smaller the time interval for operating the coolant circulation device, that is, the operation frequency of the coolant circulation device can be increased, and the frequency of fuel cell temperature acquisition can be increased accordingly. become able to.

  In the fuel cell system according to the present invention, the interval control unit may control the time interval for operating the coolant circulation device to be shorter as the rate of change of the detected temperature per time is larger. With such a configuration, finer temperature detection becomes possible as the rate of change of detected temperature per time increases.

  In the fuel cell system according to the present invention, the fuel cell operates the coolant circulation device with a coolant supply output corresponding to the required power when the required power at the time of starting power generation becomes a predetermined amount or more. It can be set as the structure which has a means to make.

  With such a configuration, the fuel cell can be forcibly cooled when the required power exceeds a predetermined value. Therefore, even if the fuel cell is started with the required power of a predetermined value or more, it is possible to suppress a rapid temperature rise at the time of starting.

  According to the fuel cell system of the present invention, when the operation of the fuel cell is stopped, the coolant circulation device is operated only intermittently, so that energy consumption associated with the operation of the coolant circulation device is minimized. Can do. In addition, since the detected temperature of the coolant is acquired as the temperature of the fuel cell during the operation period of the coolant circulating apparatus that is intermittently operated, the temperature of the fuel cell is adjusted even when the operation of the fuel cell is stopped. It becomes possible to monitor accurately.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The fuel cell system according to one embodiment of the present invention is configured as shown in FIG. The fuel cell system is mounted on a vehicle, for example, and supplies power from the fuel cell to a load (for example, a drive motor) and supplies power from the secondary battery to the load according to an accelerator operation amount (required power). Included in the system for switching between and. That is, this fuel cell system repeats a normal operation in which power is supplied from the fuel cell to the load and an intermittent operation in which the fuel cell is stopped and power is supplied from the secondary battery to the load in accordance with the accelerator operation amount.

  In FIG. 1, the fuel cell system includes a fuel cell 10 having a structure (stack) in which a plurality of single cells that are solid polymer fuel cells are stacked, for example. The fuel cell 10 is provided with a cooling water circulation path 20, and the cooling water circulation path 20 is provided with a water pump 21 for circulating the cooling water. The coolant circulation path 20 and the water pump 21 correspond to the coolant circulation device of the present invention. The cooling water circulation path 20 and the water pump 21 constitute a cooling water circulation device. Further, a temperature detector 22 (corresponding to the temperature detecting means of the present invention) is installed at the end of the coolant circulation path 20 connected to the discharge port of the fuel cell 10.

  The control unit 30 includes an operation control signal (FC operation control signal) indicating whether the fuel cell 10 supplied from the host system is operating or has stopped, and the fuel cell 10 from the temperature detector 22. A detection signal indicating the temperature of the discharged cooling water is input. The control unit 30 controls the operation of the water pump 21 based on the FC operation control signal and the detection signal from the temperature detector 22, and also controls the temperature (startup) of the fuel cell 10 based on the detection signal from the temperature detector 22. (FC temperature) to the upper system.

  The control unit 30 executes processing according to the procedure shown in FIG.

  In FIG. 2, the control unit 30 determines whether or not the operation of the fuel cell 10 is stopped based on the FC operation control signal from the host system (S1). When the fuel cell 10 is in operation (NO in S1), the control unit 30 sets the detected temperature of the cooling water based on the detection signal from the temperature detector 22 at a predetermined period, although not shown. And the temperature is provided to the host system as the temperature when the fuel cell 10 starts up (FC temperature at startup).

  When the control unit 10 determines that the operation of the fuel cell 10 is stopped based on the state of the FC operation control signal when the power supply source to the load is switched from the fuel cell 10 to the secondary battery (in S1) YES), it is determined whether or not the coolant temperature based on the detection signal from the temperature detector 22 is lower than a predetermined threshold Tth (for example, 60 ° C.) (S2). When the cooling water temperature is equal to or higher than the threshold value Tth, the above-described processing (S1, S2) is repeatedly executed. Thus, immediately after the operation of the fuel cell 10 is stopped, if the temperature, that is, the cooling water temperature is still relatively high, the operation of the water pump 10 is maintained and the circulation of the cooling water is continued.

  When the cooling water temperature becomes lower than the threshold value Tth (YES in S2), the control unit 30 determines the cooling water temperature based on the detection signal from the temperature detector 22 as the temperature at startup of the fuel cell 10 (FC temperature at startup). ) Is acquired (S3). Then, the control unit 30 stops the water pump 21 (S4). Thereby, the circulation of the cooling water is stopped. After stopping the water pump 21, the control unit 30 checks whether or not the operation of the fuel cell 10 is stopped based on the state of the FC operation control signal (S5), and for a certain period of time (for example, , About 20 seconds) is repeatedly determined (S6).

In the process, when the predetermined time has elapsed (YES in S6), the control unit 30 operates the water pump 21 for a predetermined time (S7). Then, the control unit 30 updates the startup FC temperature with the cooling water temperature based on the detection signal from the temperature detector 22 while the cooling water is circulating by the operation of the water pump 21 (S8). Thereafter, the control unit 30 repeatedly executes the same processing (S5 to S8) as described above, and sets the water pump 21 at predetermined intervals while the operation of the fuel cell 10 is stopped (NO in S5). The start-up FC temperature is updated with the cooling water temperature based on the detection signal from the temperature detector 22 while circulating the cooling water for a period of time. The control unit 30 that executes the processes of S5 to S7 corresponds to the coolant circulation operation control means of the present invention. Further, the control unit 30 that executes the process of S8 corresponds to the temperature acquisition means of the present invention.

  When the control unit 30 determines that the operation (power generation operation) of the fuel cell 10 has started based on the state of the FC operation control signal in the process described above (YES in S5), the control unit 30 returns to the initial state (S1). . Thereafter, the control unit 30 repeatedly executes the above-described processing (S1 to S8).

  According to such a fuel cell system, when the operation of the fuel cell 10 is stopped, the water pump 21 is operated only at regular time intervals, so that the water pump 21 is operated as compared with the case where the water pump 21 is always operated. The power consumption accompanying the operation of the pump 21 can be kept low. Further, the temperature of the cooling water detected while circulating the cooling water during the operation period (predetermined time) in which the water pump 21 is operated at regular time intervals is the temperature of the fuel cell 10 (FC at start-up). Temperature), the temperature of the fuel cell 10 can be accurately monitored even when the operation of the fuel cell 10 is stopped.

  The start-up FC temperature that is updated at regular time intervals while the operation of the fuel cell 10 is stopped may be provided from the control unit 30 to the host system each time it is updated. When the operation of the fuel cell 10 is resumed (YES in S5), the startup FC temperature at that time may be provided to the host system. Thus, the host system monitors the temperature expected when the operation of the fuel cell 10 is resumed while the operation of the fuel cell 10 is stopped, or immediately the temperature of the fuel cell 10 when the operation is resumed. Will be able to get.

  The control unit 30 can also execute processing according to the procedure shown in FIG. This example differs from the example shown in FIG. 2 in that the operation interval of the water pump 22, that is, the temperature detection interval of the cooling water is controlled according to the temperature when the operation of the fuel cell 10 is stopped.

  The control unit 30 has a table representing the correspondence between the temperature difference ΔT between the outside air temperature and the cooling water temperature and the set time as shown in FIG. 4 (stored in a storage unit not shown). . In this table, the corresponding set times t1, t2, and t3 increase as the temperature difference ΔT between the outside air temperature and the cooling water temperature increases (t1 <t2 <t3).

  In FIG. 3, as described above (see FIG. 2), the control unit 30 sets the detected temperature of the cooling water at the time of activation when the detected temperature of the cooling water becomes lower than the threshold value Tth after the operation of the fuel cell 10 is stopped. Obtained as the FC temperature, the water pump 21 is stopped (S1 to S4). Then, the control unit 30 calculates the temperature difference ΔT between the outside air temperature and the cooling water temperature based on the detection signal from the outside air temperature detector (not shown) and the detection signal from the temperature detector 22, and is shown in FIG. A set time corresponding to the temperature difference ΔT is acquired with reference to the table (S11). The control unit 30 that executes the process of S11 corresponds to the interval control means of the present invention.

  Thereafter, the control unit 30 confirms whether or not the operation of the fuel cell 10 is resumed (S5), operates the water pump 21 for a predetermined time at the set time interval, and operates the water pump 21 for cooling water. The start-up FC temperature is updated with the coolant temperature based on the detection signal from the temperature detector 22 in a state where the temperature is circulated (S6 to S8).

  According to the processing shown in FIG. 3, the frequency at which the temperature of the fuel cell 10 is acquired is controlled according to the detected temperature of the cooling water that can represent the situation immediately before the fuel cell 10 is stopped. Specifically, the higher the detected temperature, the smaller the time interval for operating the water pump 10, and accordingly, the frequency of acquiring the temperature of the fuel cell can be increased.

  In the above-described embodiment, during the intermittent operation in the fuel cell system in which the normal operation for supplying power from the fuel cell 10 to the load and the intermittent operation for stopping the fuel cell and supplying power from the secondary battery to the load are repeated. The temperature detection process has been described. However, the implementation of the present invention is not limited to such temperature detection processing during intermittent operation. For example, the present invention can be applied to a system temperature detection process in which the water pump 10 is not started to increase the temperature at the start of operation after the fuel cell stops at a low temperature.

  In the above embodiment, the water pump 21 is operated for a predetermined time at different set time intervals according to the temperature difference ΔT between the outside air temperature and the cooling water temperature, and the cooling water is circulated by the operation of the water pump 21. The cooling water temperature was detected based on the detection signal from the temperature detector 22. Instead of such a temperature difference ΔT between the outside air temperature and the cooling water temperature, the water pump 21 is operated for a predetermined time at different set time intervals according to the change rate Δt of the cooling water temperature per hour, and the cooling water temperature is set to It may be detected. For example, if the set time interval is shortened as the rate of change Δt increases, temperature detection that is more detailed than usual can be performed when the rate of change Δt is large. The control procedure in that case is the same as the flowchart of FIG.

  Further, the control unit 30 can also execute processing according to the procedure shown in FIG. In this example, the accelerator operation amount of the vehicle becomes a predetermined value or more in the process of detecting the coolant temperature by operating the water pump 21 at regular time intervals while the operation of the fuel cell 10 is stopped. 2 differs from the example shown in FIG. 2 in that the water pump 21 is forcibly operated at the maximum rotation speed.

  In FIG. 5, as described above (see FIG. 2), when the detected temperature of the cooling water becomes lower than the threshold Tth after the operation of the fuel cell 10 is stopped, the control unit 30 sets the detected temperature of the cooling water at the time of activation. Obtained as the FC temperature, the water pump 21 is stopped (S1 to S4). Thereafter, the control unit 30 confirms whether or not the accelerator operation amount is equal to or greater than a predetermined value (S21) and whether or not the operation of the fuel cell 10 is started (S5), as described above (FIG. 2). The water pump 21 is operated at a predetermined time interval for a predetermined time (S7), and the start-up FC temperature is updated with the cooling water temperature detected while the cooling water is circulating by the operation of the water pump 21. (S8).

  In the above-described process, when the accelerator operation amount is equal to or greater than a predetermined value (for example, 50% of the full operation amount), that is, when the required power is equal to or greater than the predetermined value and the operating condition of the fuel cell 10 is satisfied, the control unit 30 The forcible processing (S22) is executed. This forcing process is performed according to the procedure shown in FIG.

  In FIG. 6, the control unit 30 operates the water pump 21 at the maximum rotational speed (S221). By operating the water pump 21 at the maximum rotational speed in this manner, the cooling effect of the fuel cell 10 is enhanced, and in this state, the control unit 30 performs cooling water based on the detection signal from the temperature detector 22. The start-up FC temperature is updated with the temperature (S222). Thereafter, the control unit 30 determines whether or not the operation of the fuel cell 10 has been started based on the state of the FC operation control signal (S223), and if the operation of the fuel cell 10 has not yet started (in S223) NO), and the startup FC temperature is updated with the detected coolant temperature (S222).

  The fact that the accelerator operation amount is equal to or greater than the predetermined value means that the required power is a condition for starting the operation of the fuel cell 10, and therefore the fuel has a slight time lag from when the accelerator operation amount becomes equal to or greater than the predetermined value. The operation of the battery 10 is started. When the operation of the fuel cell 10 is thus started, the control unit 10 returns to the initial state (S1).

  According to the processing shown in FIGS. 5 and 6, when the accelerator operation amount becomes a predetermined value or more in a situation where the operation of the fuel cell 10 is stopped, the water pump 21 predicts the start of operation of the fuel cell and Since the operation is forcibly performed at the maximum rotation speed, the cooling effect of the fuel cell 10 is enhanced immediately before the operation of the fuel cell 10 is started. Therefore, the FC temperature at the start-up when the operation of the fuel cell 10 is started can be further lowered, and a rapid temperature rise at the start-up of the fuel cell 10 can be suppressed.

In the forcible processing shown in FIG. 5 (see FIG. 6), the water pump 21 is operated at the maximum rotational speed. You may make it drive | operate at a rotational speed.
That is, when the required power is small at the time of starting power generation, it is not always necessary to operate the water pump 21 at the maximum rotation speed. Therefore, for example, the water pump 21 may be controlled by selecting a rotation speed parameter corresponding to the magnitude of the required power at the start of power generation of the fuel cell, that is, the accelerator operation amount. With such a configuration, finer control is possible than in the case of the above-described embodiment, depending on the required power at the start of power generation.

  The fuel cell system described above is applied to a system that switches a power supply source for a load (for example, a vehicle drive motor) to either the fuel cell 10 or the secondary battery. The present invention can be applied to a system that operates the fuel cell 10 intermittently. Moreover, this fuel cell system is not limited to the one mounted on the vehicle, and can be applied to a system using a fuel cell as a power source for various loads.

  As described above, the fuel cell system according to the present invention has the effect of minimizing energy consumption and accurately monitoring the temperature of the fuel cell even when the operation of the fuel cell is stopped. And a fuel cell that is cooled by circulating a coolant, and is useful as a fuel cell system that detects the temperature of the coolant as the temperature of the fuel cell.

1 is a diagram showing a fuel cell system according to an embodiment of the present invention. 3 is a flowchart showing a first example of a processing procedure in a control unit in the fuel cell system shown in FIG. 1. 6 is a flowchart showing a second example of a processing procedure in a control unit in the fuel cell system shown in FIG. 1. It is a figure which shows an example of the table used by the process shown in FIG. 6 is a flowchart showing a third example of a processing procedure in a control unit in the fuel cell system shown in FIG. 1. It is a flowchart which shows the procedure of the forced process in the process procedure shown in FIG.

Explanation of symbols

10 Fuel cell (stack)
20 Cooling water circulation system 21 Water pump 22 Temperature detector 30 Control unit

Claims (5)

A fuel cell system comprising: a fuel cell; a coolant circulating device for supplying and circulating a coolant to the fuel cell; and a temperature detecting means for detecting the temperature of the coolant.
A coolant circulation operation control means for intermittently operating the coolant circulation device when the operation of the fuel cell is stopped;
Temperature acquisition means for acquiring, as the temperature of the fuel cell, the temperature of the coolant detected by the temperature detection means while the coolant circulation device is operating by the coolant circulation control means. A fuel cell system.   2. The fuel cell system according to claim 1, wherein the coolant circulation operation control means operates the coolant circulation device at regular time intervals.   2. The fuel cell system according to claim 1, further comprising interval control means for controlling a time interval for operating the coolant circulation device in accordance with a temperature detected by the temperature detection means.   4. The fuel cell system according to claim 3, wherein the interval control means controls the time interval for operating the coolant circulation device to be shorter as the rate of change of the detected temperature per time is larger.   2. The fuel cell according to claim 1, further comprising means for operating the coolant circulation device with a coolant supply output corresponding to the required power when the required power at the time of starting power generation exceeds a predetermined amount. The fuel cell system according to any one of 1 to 4.

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