JP2005327672A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To circulate cooling water only to a specific cell in a fuel cell having a plurality of cells.
A fuel cell system including a plurality of cells, wherein cooling water is circulated through a cooling water passage corresponding to each of the plurality of cells and a cooling water passage corresponding to only a specific cell among the plurality of cells. Circulation means. The specific cell is, for example, a cell determined to be a predetermined temperature or higher. In addition, the circulation means includes, for example, a check valve that is provided in each cooling water flow path and allows only the flow from outside the cell to the inside of the cell, and the circulation means that is provided in each cooling water flow path only from the inside of the cell to the outside of the cell. A check valve that is allowed, and an element that is provided in a cooling water flow path between the check valves and changes in volume when energized.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system including a plurality of cells.

  Conventionally, in the field of a fuel cell system, a stack in which a plurality of cells (also referred to as single cells or single cells) are stacked in series is provided, and electricity is generated by reaction of anode gas and cathode gas supplied in each cell. For example, a polymer electrolyte fuel cell is known. In such a fuel cell system, since each cell generates heat due to a reaction, a cooling water flow path is provided for the purpose of cooling each cell. This cooling water flow path is generally configured to circulate cooling water to each cell by a pump provided outside the cell (see, for example, Patent Document 1).

  However, in the fuel cell system including a plurality of cells, the idea of circulating the cooling water only to specific cells has not been proposed. For this reason, for example, if the cooling water is circulated while the fuel cell is being operated for the purpose of raising the temperature to a predetermined temperature (for example, warm-up operation in an environment below freezing), new cooling water (usually, There is a problem that all the cells are cooled by being circulated), which is lower in temperature than the cooling water in the middle of raising the temperature. This is because even though each cell generates heat, the temperature of all the cells does not rise uniformly, for example, the cell in the center part is easy to heat up and the temperature at the end part is difficult to heat up. This is because the cooling water cannot be circulated only to a specific cell (in this case, the central cell).

In addition, as a thing considered to be related to the present invention, there is a fuel cell in which at least one of a fuel gas channel and an oxidant gas channel is provided with a vibrating means including a diaphragm and a piezoelectric element (see, for example, Patent Document 2). ).
JP-A-7-122280 JP 2002-184430 A

  The subject of this invention is providing the technique for circulating a cooling water only to a specific cell in a fuel cell system provided with a some cell.

  The present invention has been made to solve the above-described problem, and is a fuel cell system including a plurality of cells, a cooling water flow path corresponding to each of the plurality of cells, and a specific one of the plurality of cells. Circulation means for circulating the cooling water in the cooling water flow path corresponding only to the cell.

  According to the present invention, the cooling water can be circulated only to a specific cell (for example, a cell that has been previously determined to reach the maximum temperature or a cell that has been determined to be at or above a predetermined temperature). Therefore, for example, at the time of starting the fuel cell, it is possible to circulate cooling water only to a specific cell while the fuel cell is being operated for the purpose of raising the temperature to a predetermined temperature (for example, warm-up operation in a sub-freezing environment). It becomes. Therefore, in this case, as in the conventional case, new cooling water (usually at a lower temperature than the cooling water that is being heated) is circulated through all the cells, so that all the cells are not cooled.

In the fuel cell system, for example, the circulation means is provided in each cooling water flow path and allows only a flow from outside the cell to the inside of the cell, and provided in each cooling water flow path from the inside of the cell. And a check valve that allows only the flow outside the cell, and an element that is provided in the cooling water flow path between the check valves and changes in volume when energized.

  This specifies an example of the circulation means. Therefore, the circulation means of the present invention is not limited to this. For example, a conventional circulation pump may be provided for each cooling water flow path, and this may be used as the circulation means.

  In the fuel cell system, for example, the circulating means functions as a pump when the volume of the element is changed by energization.

  This specifies the usage example of the circulation means. Therefore, the circulation means of the present invention can function not only as a pump but also for various other purposes.

  In the fuel cell system, for example, the element is set so that its volume is maximized or minimized when de-energized.

  In this way, if the volume is set to be maximized when the power is not supplied, the amount of cooling water in each cooling water flow path is reduced (that is, the heat capacity is reduced). ), The temperature rise characteristic of the cooling water in each cooling water channel can be improved. Similarly, if the volume is set to be minimum when the power is not supplied, the amount of cooling water in each cooling water passage increases (that is, the heat capacity increases), so that it is relatively difficult to cool even after the operation is stopped. A fuel cell can be obtained.

  According to the present invention, it is possible to circulate cooling water only in specific cells. Therefore, for example, while the fuel cell is being operated for the purpose of raising the temperature to a predetermined temperature (for example, warm-up operation in an environment below freezing), the cooling water can be circulated only to the cells that have exceeded the predetermined temperature. Therefore, in this case, as in the conventional case, new cooling water (usually at a lower temperature than the cooling water that is being heated) is circulated through all the cells, so that all the cells are not cooled.

  Hereinafter, a polymer electrolyte fuel cell system (hereinafter simply referred to as a fuel cell) according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the fuel cell 10 of this embodiment includes a stack 30 configured by stacking a plurality of cells (also referred to as single cells or single cells) 20 in series, and the stacked cells 20. A cooling water (also referred to as a refrigerant) flow path 40 for cooling, a temperature detector 50 for detecting a cell 20 exceeding a predetermined value (predetermined temperature), and a cooling water flow path 40 corresponding to the detected cell 20 Circulation means 60 for circulating the cooling water. FIG. 1 is a cross-sectional view mainly showing one of the cells 20 constituting the stack 30 for convenience of explanation, and the other cells 20 are not shown. .

The cell 20 is configured by laminating a separator 21, an MEA (membrane electrode assembly) 22, and a separator 23. In FIG. 1, the separator 21 has a plurality of concave grooves 21 a extending in the direction orthogonal to the paper surface, and each concave groove 21 a and the lower surface of the MEA 22 form a cathode channel 21 a. Similarly, the separator 23 has a plurality of concave grooves 23a extending in the direction orthogonal to the paper surface, and each concave groove 23a and the upper surface of the MEA 22 form an anode flow path 23a. In the cell 20, an anode gas that is a fuel such as hydrogen and a cathode gas such as air that is an oxidant are supplied to each cathode channel 21 a and each anode channel 23 a and reacts in the MEA 22 to generate power. Since the anode gas and cathode gas supply systems are known, the configuration thereof is omitted.

  Each cell 20 is laminated with its separator 21 facing the separator 23 of another cell 20. Since each of the stacked cells 20 generates heat due to the above reaction, a cooling water channel 40 is provided between the cells 20 for the purpose of cooling each cell 20 (a cooling water channel corresponding to each of the plurality of cells of the present invention). Equivalent). The cooling water flow path 40 is provided between the stacked cells 20, that is, between the separator 21 of a certain cell 20 and the separator 23 of the cell 20 stacked adjacent thereto. Therefore, for example, in the stack 30 configured by stacking the five cells 20, there are four cooling water flow paths 40. Since this is an example of installation of the cooling water flow path 40, for example, the cooling water passage 40 may be provided for every two cells 20, or may be installed in other forms.

  Each cooling water channel 40 is configured so that the cooling water is circulated by the circulation means 60. Alternatively, when an external cooling water pump (not shown) is provided, the cooling of the average cell is left to the external pump, and only specific cells (for example, the end cell and the lowermost cell) are cooled by the circulation means 60. You may comprise.

  A temperature detector 50 is provided to detect the cell 20 exceeding a predetermined value (predetermined temperature). The temperature detector 50 includes a temperature sensor, and is provided, for example, in the cooling water channel 40. Alternatively, it may be provided at the anode gas outlet of each cell 20. Alternatively, the temperature of the cell 20 may be estimated based on the voltage and current obtained from the cell 20. Since the relationship between the voltage and current is generally determined by the environmental temperature (the temperature of the cell 20), the temperature of the cell 20 can be estimated based on the voltage and current obtained from the cell 20.

  FIG. 1 shows an example in which the temperature detector 50 is provided in the upper part of the element in the cooling water channel 40. The temperature detector 50 is connected to a control unit 70 such as a CPU. The control unit 70 executes a predetermined program to compare a value (temperature) detected by the temperature detector 50 with a predetermined value (predetermined temperature such as a warning temperature or an upper limit temperature), and whether or not the predetermined value is exceeded. (Or whether or not a predetermined value or more). Thereby, the cell 20 exceeding the predetermined value can be detected. When the temperature detector 50 is provided in the cooling water channel 40, the temperature detector 50 actually detects not the temperature of the cell 20 but the temperature of the cooling water in the cooling water channel 40. However, the temperature of the cooling water in the cooling water channel 40 can also be said to be the temperature of the cell 20 adjacent to the cooling water channel 40. Accordingly, if the correspondence between the cooling water flow path 40 and the cell 20 adjacent thereto is held in the memory, the correspondence relation is referred to when the cooling water temperature in the specific cooling water flow path 40 is detected. Thus, the temperature of the specific cell 20 can be detected.

  The cooling water passage 40 is also one of the elements constituting the circulation means 60 for circulating the cooling water. That is, as shown in FIG. 1, the circulation means 60 includes a check valve 61 that is provided in the cooling water flow path 40 (on one end thereof) and allows only circulation from the outside of the cell 20 to the inside of the cell 20, and the cooling water passage 40. A check valve 62 that is provided on the other end of the cell 20 and allows only the flow from the inside of the cell 20 to the outside of the cell 20, and the control unit 70 that is provided in the cooling water flow path 40 between the check valves 61 and 62. Element 63 whose volume is changed by the control (energization or the like) and a film 64 that covers the element 63 and separates the cooling water in the cooling water passage 40 from the air layer.

  For example, in the stack 30 configured by stacking five cells 20, there are four cooling water flow paths 40, and thus usually four circulation means 60 are configured. In this example, the four elements 63 constituting the four circulation means 60 are connected to the control unit 70 via the drive circuit 80 corresponding to each element 64. The power supply for the element 63 may be supplied from the cell V detection circuit 81 that obtains the voltage generated in the cell 20, or may be supplied from an external power supply.

  The control unit 70 controls a specific element 63 via the drive circuit 80. For example, if the element 63 is a piezoelectric element whose volume is changed by energization / non-energization, energization / non-energization (on / off) is repeated. Then, the controlled element 63 repeats the volume change (the shape shown by the solid line or the shape shown by the wavy line in FIG. 1 is repeated), so that the film 64 covering this element 63 also moves up and down in conjunction with it. Therefore, in FIG. 1, the cooling water in the cooling water flow path 40 flows from the left (check valve 61) to the right (check valve 62). That is, the cooling water channel 40 functions as a pump. In this sense, the circulation means 60 can be said to be a pump. Thereby, it becomes possible to circulate cooling water only to the specific cell 20. In addition, the flow rate of the circulating cooling water can be adjusted by appropriately setting the interval between energization / non-energization (on / off). As the element 63, for example, an artificial muscle or the like whose length or volume is changed by energization / non-energization can be applied. Further, as the film 64, for example, a thin film such as rubber or stainless steel can be applied.

  Assuming that the fuel cell 10 is operated in a sub-freezing environment, the element 63 is set to have the largest volume when no power is supplied (when the power is turned off) (for example, the original shape is restored when no power is supplied). It is desirable to make the element 63 so as to. By doing so, the amount of cooling water in each cooling water channel 40 is reduced (that is, the heat capacity is reduced). Therefore, when the fuel cell 10 is operated next time, the cooling water in each cooling water channel 40 is operated. The temperature rise characteristic can be improved. From this point of view, the element 63 is not necessarily changed in volume by energization or the like like a piezoelectric element, and may be a balloon, for example. On the other hand, if there is a request to obtain a fuel cell 10 that is difficult to cool even after the operation is stopped, it is desirable to set the element 63 so that the volume becomes the smallest when no power is supplied (when the power is off). In this way, since the amount of cooling water in each cooling water channel 40 increases (that is, the heat capacity increases), it is possible to obtain a fuel cell that is relatively difficult to cool even after operation is stopped.

  Next, the operation of the fuel cell 10 configured as described above will be described with reference to FIG.

  In the fuel cell 10, when anode gas or cathode gas is supplied and power generation is started (S10), the temperature of each cell 20 (or a specific cell such as the cell 20 that has been previously known to reach the maximum temperature) is detected. (S11). This temperature detection is performed by each temperature detector 50, for example.

  In the present embodiment, the cell 20 to be temperature-detected is set in the monitoring cell list 90. The monitoring cell list 90 is a correspondence relationship between a cell 20 and an identifier indicating whether or not the cell 20 is a temperature detection target cell. The monitoring cell list 90 is held in a memory accessible by the control unit 70.

  The control unit 70 refers to the monitoring cell list 90 by executing a predetermined program, and the temperature detector 50 detects the cell 20 in which an identifier indicating that the cell is a target of temperature detection is set. The determined value is compared with a predetermined value (warning temperature) to determine whether or not the predetermined value is exceeded. Thereby, the cell 20 exceeding a predetermined value (warning temperature) can be detected (corresponding to the detection means of the present invention).

As a result, when the control unit 70 detects a cell 20 that exceeds a predetermined value (warning temperature), only the cooling water flow path 40 corresponding to the cell 20 is caused to function as a pump (S12). That is, the control unit 70 controls the element 63 in the cooling water flow path 40 corresponding to the cell 20 via the drive circuit 80 corresponding to the cell 20 (for example, energization / non-energization is repeated). Then, the controlled element 63 repeats the volume change (the shape shown by the solid line in FIG. 1 or the shape shown by the wavy line is repeated), so that the film 64 covering the element 63 also moves up and down in conjunction with it. Therefore, in FIG. 1, the cooling water in the cooling water flow path 40 flows from the left (check valve 61) to the right (check valve 62). That is, the cooling water channel 40 functions as a pump. Thereby, it becomes possible to circulate cooling water only to the cell 20 which exceeded the predetermined value (warning temperature). It does not circulate to other cells 20 that do not exceed the predetermined value.

  Thus, since the cooling water for each cell 20 can be circulated individually, for example, the following effects are produced.

  First, as in the prior art, new cooling water (usually at a lower temperature than the cooling water being heated) is circulated through all the cells 20 so that all the cells 20 are not cooled. Second, it is possible to raise the temperature of the fuel cell 10 to a predetermined temperature relatively early (for example, early completion of warm-up operation in a sub-freezing environment). Third, each cell 20 can be adjusted to a uniform temperature. Fourth, it is not necessary to newly develop a cooling water pump even if the number of stacked cells 20 is changed. Fifth, by integrating the drive circuit 80 with the cell V detection circuit 81, the pump driver (drive circuit 80) can be downsized. Sixth, depending on the performance of the stack 30, an external pump is not required. Seventh, it is possible to reduce the load of the cooling water pump, the FC output cable, and the contactor.

  Next, the control unit 70 removes the cell 20 in which the circulation unit 60 is activated as a pump from the monitoring cell list 90 (S13). That is, the control unit 70 refers to the monitoring cell list 90 and sets an identifier indicating that the cell 20 whose circulation means 60 is activated as a pump is a cell whose temperature is to be detected as such a target. It is rewritten with an identifier indicating that the cell is not set. When all the cells 20 are removed from the monitoring cell list 90 (S14: Yes), the process (start-up mode) of this flowchart is ended (S17).

  On the other hand, when all the cells 20 are not removed from the monitoring cell list 90 (S14: No), the control unit 70 executes the predetermined program to thereby detect the value detected by the temperature detector 50 and the predetermined value ( (Upper limit temperature) and a determination is made as to whether or not a predetermined value has been reached (S15). As a result, when it is determined that there is a cell 20 that has reached a predetermined value (upper limit temperature) (S15: Yes), the control unit 70 operates an external cooling water pump (not shown) (S16). Then, cooling water is supplied to each cooling water flow path 40 (when an external cooling water pump is provided). This makes it possible to protect the cell that has reached the upper limit temperature.

  On the other hand, when it is not determined that there is a cell 20 that has reached a predetermined value (upper limit temperature) (S15: No), the control unit 70 repeats the processes after S11.

  As described above, according to the fuel cell 10 of the present embodiment, it is possible to circulate the cooling water only to the specific cell 20.

(Modification)
In the fuel cell system of the above embodiment, the example in which the external cooling water pump is provided has been described, but the present invention is not limited to this. For example, the fuel cell 10 may be configured without providing an external cooling water pump. In this case, the processes of S15 and S16 are not necessary.

Further, in the fuel cell system of the above embodiment, the value detected by the temperature detector 50 and the predetermined value for the cell 20 in which the identifier indicating that the cell is a target of temperature detection is set in the monitoring cell list 90. Although the value (predetermined temperature) is compared and the cooling water flow path 40 corresponding to the cell 20 exceeding the predetermined value is explained to function as a pump, the present invention is not limited to this. For example, for a specific cell (for example, a cell in the central portion that is known to reach the maximum temperature in advance), the temperature detection by the temperature detector 50 (and the detected value and a predetermined value (predetermined temperature)) Without comparison, the fuel cell 10 is always started at the beginning (for example, the fuel cell 10
For a predetermined time after activation, the cooling water flow path 40 corresponding only to the specific cell 20 may be caused to function as a pump (S12). In this case, the detection means 50 becomes unnecessary. If it does in this way, it will become possible to circulate cooling water only about the specific cell 20 first at the time of fuel cell 10 start-up.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, said embodiment is only a mere illustration in all points. The present invention is not construed as being limited by these descriptions.

  According to the present invention, it is possible to circulate cooling water only in specific cells. Therefore, for example, while the fuel cell is being operated for the purpose of raising the temperature to a predetermined temperature (for example, warm-up operation in a sub-freezing environment), it is possible to circulate cooling water only to cells that exceed the predetermined temperature. . Therefore, unlike the prior art, new cooling water (usually at a lower temperature than the cooling water that is being heated) is circulated through all the cells, so that all the cells are not cooled.

It is a figure for demonstrating schematic structure of the polymer electrolyte fuel cell which is embodiment of this invention. It is a flowchart for demonstrating operation | movement of the polymer electrolyte fuel cell which is embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 20 Cell 30 Stack 40 Cooling water flow path 50 Temperature detector 60 Circulating means 70 Control part 80 Drive circuit 90 Monitoring cell list

Claims (5)

A fuel cell system comprising a plurality of cells,
A cooling water flow path corresponding to each of the plurality of cells;
A circulating means for circulating cooling water to a cooling water flow path corresponding to only a specific cell among the plurality of cells;
A fuel cell system comprising:   The fuel cell system according to claim 1, wherein the specific cell is a cell determined to be equal to or higher than a predetermined temperature. The circulating means is
A check valve that is provided in each cooling water flow path and allows only the flow from outside the cell to the inside of the cell, and a check valve that is provided in each cooling water flow path and allows only the flow from the inside of the cell to the outside of the cell; An element that is provided in the cooling water flow path between the check valves and changes its volume when energized;
The fuel cell system according to claim 1, comprising: The circulating means functions as a pump by changing the volume of the element when energized.
The fuel cell system according to claim 3.   The fuel cell system according to claim 3, wherein the element has a volume that is maximized or minimized when de-energized.

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