JP2006073451A - Control device of fuel cell and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a fuel cell enhancing a starting ability, together with improvement of the durability of the fuel cell. <P>SOLUTION: When starting the fuel cell, a fuel control part 10c is made to supply reaction gas to the fuel cell, and when anode pressure and cathode pressure of the fuel cell have reached prescribed values, a cell voltage detecting part 10a detects cell voltage of a cell a, a cell b, a cell c,... a cell n constituting the fuel cell; when the fuel cell is started based on the detected cell voltage, a deficiency inferring part 10d infers the deficiency of the power generation performance; and if there is deficiency, a load control part 10b makes the temperature of the fuel cell raised, the deficiency is dissolved, load is applied to the fuel cell, and the fuel cell is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a fuel cell and a control method thereof, and more particularly to control when starting a fuel cell.

  A fixed polymer fuel cell is configured by stacking cells in which a membrane electrode structure (MEA) comprising a polymer electrolyte membrane sandwiched between a cathode and an anode is further sandwiched between separators. Here, the membrane electrode structure is configured, for example, by adhering a catalyst layer mainly composed of carbon powder carrying a platinum-based metal catalyst on both sides of a polymer electrolyte membrane composed of a resin having a sulfone group. ing. Further, in order to smoothly supply the reaction gas to the catalyst layer and discharge the reaction product water, a gas diffusion layer having high gas diffusibility and electronic conductivity is provided outside the catalyst layer as necessary. Yes. These electrode layer and electrolyte assembly are mechanically fixed as a membrane electrode structure, and a conductive separator plate for electrically connecting adjacent junctions in series is arranged on the electrode surface of the separator. On the opposite surface, a groove-like channel for supplying the reaction gas uniformly to the electrode layer is provided.

  In the fuel cell configured as described above, a malfunctioning cell that exhibits power generation performance malfunction may appear due to an individual difference of the cell, particularly when starting at a low temperature. This malfunctioning cell is considered to be caused by a difference in diffusivity and distribution of reaction gas due to a slight difference in freezing conditions at the time of freezing, a gas flow path between cells. For example, once a fuel cell in which such a malfunctioning cell exists is frozen, the reaction gas distribution and diffusion further deteriorate in the malfunctioning cell, and the startability of the fuel cell becomes extremely worse as a result of a vicious cycle. There is a problem that needs to be addressed. That is, if the fuel cell is forcibly generated by ignoring the presence of the malfunctioning cell, the shortage of reaction gas causes corrosion of the electrode near the malfunctioning cell and deterioration of the separator, and the durability of the fuel cell deteriorates. Therefore, it is necessary to prevent a shortage of reaction gas particularly when starting the fuel cell.

As a control method of the fuel cell, for example, there is one disclosed in Patent Document 1. Here, when increasing the load on the fuel cell, a reaction gas shortage state locally generated in the fuel cell is detected at an early stage to protect the fuel cell from the reaction gas shortage.
JP-A-6-243882 (Claims, Claim 1)

However, in the above conventional method, the lack of reaction gas is detected by actually pulling the load and observing the power generation status of the fuel cell. Otherwise, there was a problem that it could not be detected.
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a fuel cell control apparatus and method that can improve startability while improving the durability of the fuel cell.

The invention according to claim 1 is a control device for a fuel cell in which a plurality of cells are stacked, and is generated in each cell by supplying reaction gas to the fuel cell, and reaction gas supply means for supplying the reaction gas to the fuel cell. A cell voltage detecting means for detecting a cell voltage; a malfunction estimating means for estimating a malfunction of the power generation performance of the fuel cell when the fuel cell is started by applying a load based on the detected cell voltage; A start acceleration means for accelerating the start of the fuel cell; and a start means for starting the fuel cell by applying a load to the fuel cell, wherein the start means is assumed to be inferior in power generation performance of the fuel cell. The fuel cell is started after starting the start promoting means.
According to the first aspect of the present invention, when starting the fuel cell, if the fuel cell is started, a failure in the power generation performance of the fuel cell is estimated, and if there is a failure, the startability of the fuel cell is reduced. Since the starting is performed after the improvement, it is possible to prevent the starting with the reaction gas being insufficient at the local portion of the fuel cell.

According to a second aspect of the present invention, the failure estimation means estimates the failure based on a cell voltage after the pressure of the reaction gas supplied to the fuel cell reaches a predetermined value.
According to the invention described in claim 2, in addition to having the same effect as that of claim 1, it is possible to accurately estimate the defect.

According to a third aspect of the present invention, the start acceleration means accelerates the start of the fuel cell by raising the temperature of the fuel cell.
According to the invention described in claim 3, in addition to having the same effect as that of claim 1 or 2, it is possible to start quickly even when a malfunction is estimated.

The invention according to claim 4 is a control method of a fuel cell in which a plurality of cells are stacked, and after the reaction gas is supplied to the fuel cell and the reaction gas is supplied, the cell voltage of each cell is detected. Based on the detected cell voltage, when the fuel cell is loaded and started, a fault in the power generation performance of the fuel cell is estimated, and if there is a fault, the fuel cell is raised. After the temperature was raised, the fuel cell was loaded and started.
According to the invention described in claim 4, as in the case of claim 1, when starting the fuel cell, a failure in the power generation performance of the fuel cell is estimated by starting, and if there is a failure, Since the start-up is performed after the startability is improved, it is possible to prevent the start-up with the reactive gas shortage at the local portion of the fuel cell.

  According to the present invention, when starting the fuel cell, there is no shortage of reactive gas at the local portion of the fuel cell. As a result, there is no possibility that the time required until the power generation performance is further deteriorated due to the start-up, and as a result, the startability is improved. Further, when a malfunction is estimated, if the startability is promoted, the startability can be further improved, performance deterioration can be prevented, and durability can be improved.

Hereinafter, an embodiment in which the present invention is applied to a fuel cell electric vehicle will be described with reference to the drawings.
First, the principle of detecting a malfunction at the start in the present invention will be described.
FIG. 5 is a diagram showing a cell voltage and an output current of the fuel cell when the fuel cell is started in a frozen state, and FIG. 6 is an enlarged view of a portion A and a portion B in FIG. Part A is a change in voltage of each cell after the pressure of the reaction gas reaches a predetermined value in the fuel cell, and part B is a change in voltage of each cell when the fuel cell is started.
When the reaction gas is supplied to the fuel cell, a cell voltage (open voltage) is generated in each cell (Start). As shown in FIG. 5, a high voltage is once generated, and then the cell voltage changes with a slight decrease due to a gas leak (so-called cross leak) between the anode and the cathode. At this time, for example, if there is a cell temperature variation due to some reason or a cell in which the supply of the reaction gas is not sufficient, as shown in the enlarged view of FIG. A large variation occurs between the voltages of each cell. Here, the drop of cell a and cell b is particularly large with respect to other cells. When the fuel cell in such a state is started with a load as usual, the problem is amplified as shown by the dotted line in FIG. 6B, and the cells a and b are more than the other cells. Cell voltage drops further.

  At this time, if the power generation is forcibly generated, the separator sandwiching the cells will be deteriorated. In the present invention, as shown in FIG. 6 (a), paying attention to the variation in the cell voltage before starting by applying a load, if there is a malfunction, the malfunction of the power generation performance is estimated due to the presence of the malfunctioning cell. The temperature of the fuel cell is raised and the power generation performance, that is, the startability of the malfunctioning cell is recovered, and then the start is performed. By doing so, for example, even when the fuel cell is started in a state where the cell voltage variation between the cells is large, the power generation performance (starting performance) is recovered as shown in FIG. 6B. Thus, the cell voltages of the cells including the cell a and the cell b, which have been malfunctioning, change in a uniform manner, and power can be generated without the output current dropping as shown in FIG.

FIG. 1 is a diagram showing a fuel cell system to which the present invention is applied. This fuel cell system is mounted on an automobile.
The fuel cell 1 is configured by stacking cells in which a membrane electrode assembly (MEA) having a polymer electrolyte membrane 1a sandwiched between a cathode and an anode is further sandwiched between separators. As its structure, for example, a catalyst layer mainly composed of carbon powder carrying a platinum-based metal catalyst is adhered to both surfaces of a polymer electrolyte membrane composed of a resin having a sulfone group. In order to smoothly supply the reaction gas to the catalyst layer and discharge the reaction product water, a gas diffusion layer having high gas diffusibility and electronic conductivity is provided outside the catalyst layer. These electrode layer and electrolyte assembly are mechanically fixed as a membrane electrode structure, and a conductive separator plate for electrically connecting adjacent junctions in series is arranged on the electrode surface of the separator. Groove-shaped flow paths for uniformly supplying the reaction gas to the electrode layers are provided on the opposing surfaces.

A hydrogen supply source 5 is connected to the anode side of the fuel cell 1 through a gas line 2a. The hydrogen supply source 5 is, for example, a fuel tank that stores high-pressure pure hydrogen.
The gas line 2a is provided with an electromagnetic valve 2b, and hydrogen gas can be supplied to the anode of the fuel cell 1 by opening and closing the electromagnetic valve 2b.

A compressor 4 is connected to the cathode of the fuel cell 1 through a gas line 3a. The gas line 3a is provided with an electromagnetic valve 3b, and air as an oxidant gas can be supplied to the cathode of the fuel cell 1 by opening and closing the electromagnetic valve 3b.
Pressure sensors P2 and P1 for detecting anode pressure and cathode pressure when hydrogen gas and oxidant gas are supplied are provided in the vicinity of the fuel cell 1 of the gas lines 2a and 3a.
Exhaust gas lines 2c and 3c are provided at the anode and cathode of the fuel cell 1 for exhausting the reacted gas, respectively. A load 6 is connected to the two electrodes of the fuel cell 1. The load 6 is, for example, a motor that drives the vehicle and other auxiliary machines.
In order to raise the temperature of the fuel cell 1, the fuel cell 1 is provided with a heater 7 as a start acceleration means.
A control device 10 arranged to control the fuel cell 1 controls the solenoid valves 2b and 3b, the compressor 4, the heater 7 and the load 6. In addition, detection values of the pressure sensors P <b> 2 and P <b> 1 are input to the control device 10 in order to perform control. The control device 10, the compressor 4 and the heater 7 are electrically supplied from a battery (not shown).

FIG. 2 is a block diagram illustrating a configuration of the control device.
a, b, c,..., n are each cell of the fuel cell 1. The control device 10 includes a cell voltage detection unit (cell voltage detection unit) 10a, a load control unit (starting unit) 10b, a fuel control unit 10c, and a defect estimation unit (problem estimation unit) 10d.
The fuel control unit 10c controls the electromagnetic valves 2b and 3b and the compressor 4 to supply hydrogen gas and oxidant to the fuel cell 1 or to cut off the supply.
The cell voltage detector 10a detects the cell voltage of each cell. When the fuel cell 1 is started, the load control unit 10b instructs the fuel control unit 10c to supply the fuel cell 1 with hydrogen gas and oxidant gas. When the failure estimation unit 10d determines that the anode pressure and the cathode pressure have reached predetermined values based on the detection values of the pressure sensors P2 and P1, based on the cell voltage detected by the cell voltage detection unit 10a, When 1 is started, it is determined whether or not there is a defect in power generation performance. In some cases, the load controller 10b energizes the heater 7 to raise the temperature of the fuel cell 1. When it is determined that there is no problem due to the temperature rise, the load 6 is controlled so that a current flows from the fuel cell 1 to the load 6. Next, the flow when starting the fuel cell 1 will be described according to a flowchart.

FIG. 3 is a flowchart showing a flow when starting the fuel cell in the control device.
When it is determined from the vehicle side that the ignition switch signal is an ON signal (S1), the fuel control unit 10c operates the compressor 4 and opens the electromagnetic valves 2b and 3b. As a result, the compressor rotates and hydrogen gas and oxidant gas are supplied to the fuel cell 1 (S2).
The defect estimation unit 10d inputs the detection values of the pressure sensors P2 and P1, respectively, and determines whether or not the boosting of the anode pressure and the cathode pressure has been completed based on the detection values as shown in FIG. (S3). When the bipolar step-up is completed (S3, Yes), the failure estimation unit 10d inputs the cell voltages of the cells a, b, c,..., N detected by the cell voltage detection unit 10a.

  FIG. 4 is a graph showing the relationship between anode pressure, cathode pressure and cell voltage. According to this, since the increase in the anode pressure and the cathode pressure is completed (time a), the cell voltages of the cell a and the cell b which are malfunctioning cells are larger than the other cells, so that they are distinguished from normal cells. A malfunctioning cell can be easily detected. Note that the cell voltage drops due to the influence of the cross leak of the reaction gas through the polymer electrolyte membrane as described above. By the way, when the flow of reaction gas is small for both the anode and the cathode, or when the cross leak is large (for example, there is a hole in the electrolytic membrane), the drop in cell voltage is considered to increase, and detection of a malfunctioning cell is detected. It becomes easier.

Based on the input cell voltage, the failure estimation unit 10d estimates a failure in power generation performance when a load is applied to the fuel cell 1 to generate power (S5). If there is no malfunction (No in S5), the fuel cell 1 is started by controlling the load 6 so that a current flows from the fuel cell 1 to the load 6 (S6). After starting, the fuel cell 1 is controlled as usual based on a power generation command from the automobile side.
For example, the defect can be estimated by determining whether there is a cell whose cell voltage is equal to or lower than a predetermined value. Further, it can be estimated by the degree of variation with respect to the average value of the cell voltages.
If there is a problem (S5, Yes), the load control unit 10b energizes the heater 7 (S8). Thereby, the temperature of the fuel cell 1 is raised. As a result, as shown in FIG. 4, the cell voltages of cells a and b, which were malfunctioning cells, gradually approach the cell voltages of other cells, and the power generation performance, that is, the startability is restored. At this time, no load is drawn from the fuel cell 1.

After that, the cell voltage detection unit 10a detects the cell voltage again, and the failure estimation unit 10d inputs the detected cell voltage (S9), and checks whether or not the failure is solved by checking the variation in the cell voltage. (S10). If the problem is not resolved (S10), the process returns to step S9, and a new cell voltage is detected (S9).
If it is determined that the problem has been resolved (S10, Yes), the load control unit 10b cuts off the power to the heater 7 (S11). Thereafter, in step S6, the load 6 is controlled and started so that current flows from the fuel cell 1 to the load 6, and control is performed as usual. Here, the determination as to whether or not the problem has been resolved can be made based on, for example, the temperature of the fuel cell 1 without using the cell voltage.

According to the embodiment, when the fuel cell 1 is started, when the fuel cell 1 is started, a failure in the power generation performance of the fuel cell 1 is estimated, and if there is a failure, the fuel cell is heated to improve the power generation performance. Since starting is performed, it is possible to prevent the corrosion of the electrode and the deterioration of the separator due to the lack of the reaction gas in the local part of the fuel cell while improving the startability.
In addition, in the estimation of the problem, since the cell voltage when the anode pressure and the cathode pressure reach predetermined values is estimated, the problem can be accurately estimated.
In the above embodiment, the decrease in the temperature of the cell is caused as a cause of the problem, and the temperature is raised by the heater 7 to be solved. However, the cause may be that the flow of the reaction gas is hindered by the produced water. In such a case, the start-up can be accelerated by purging the fuel cell 1 to discharge moisture. Alternatively, the stoichiometric value of the reaction gas can be increased, and the anode pressure and the cathode pressure can be increased. That is, the promotion means is not limited to the heater. Alternatively, the temperature of the fuel cell 1 may be raised by power generation while pulling a load from only normal cells.

It is a figure which shows the fuel cell system to which this invention is applied. It is a block diagram which shows the structure of a control apparatus. It is a flowchart which shows the flow when starting the fuel cell in a control apparatus. It is a figure which shows the relationship between an anode pressure, a cathode pressure, and a cell voltage. It is a figure which shows the cell voltage in the case of starting a fuel cell in the frozen state, and the output current of a fuel cell. FIG. 6 is an enlarged view of a portion A and a portion B in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2a Gas line 2b Solenoid valve 2c Exhaust gas line 3a Gas line 3b Solenoid valve 4 Compressor 5 Hydrogen supply source 6 Load 7 Heater 10 Controller 10a Cell voltage detection part 10b Load control part 10c Fuel control part 10d Problem estimation part

Claims (4)

A fuel cell control device comprising a plurality of stacked cells,
Reactive gas supply means for supplying a reactive gas to the fuel cell;
Cell voltage detection means for detecting a cell voltage generated in each cell by the supply of the reaction gas;
Based on the detected cell voltage, when the fuel cell is loaded and started, a failure estimation means for estimating a failure in the power generation performance of the fuel cell;
Start acceleration means for accelerating the start of the fuel cell;
Starting means for applying a load to the fuel cell to start the fuel cell,
The fuel cell control device according to claim 1, wherein when the malfunction of the power generation performance of the fuel cell is estimated, the start unit starts the fuel cell after starting the start promoting unit.   2. The fuel cell according to claim 1, wherein the failure estimation unit estimates the failure based on a cell voltage after a pressure of a reaction gas supplied to the fuel cell reaches a predetermined value. Control device.   3. The fuel cell control device according to claim 1, wherein the start acceleration unit accelerates the start of the fuel cell by raising the temperature of the fuel cell. 4. A fuel cell control method comprising a plurality of stacked cells,
After supplying the reaction gas to the fuel cell, and supplying the reaction gas, the cell voltage of each cell is detected, and when the fuel cell is started by applying a load based on the detected cell voltage, the fuel cell If it is estimated that there is a problem with the power generation performance of the fuel cell, the temperature of the fuel cell is increased to promote the start of the fuel cell, and then the fuel cell is started with a load applied. A control method for a fuel cell.

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