JP2009048974A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which a response delay of a fuel gas supplying system can be reduced and moreover an excess supply of the fuel gas can be prevented. <P>SOLUTION: The fuel cell system 1 is provided with a fuel gas supply volume controlling unit 41 which supplies the fuel gas to an anode side electrode arranged on one surface of an electrolyte membrane of a fuel cell 10 and supplies oxidant gas to a cathode side electrode arranged on the other surface of the electrolyte membrane and generates power and controls a fuel gas supply volume, an anode voltage potential detecting unit 42 which detects, as an anode voltage potential, a voltage potential difference between the anode side electrode and a predetermined reference electrode, and an anode voltage potential change ratio calculating unit 43 which calculates a change ration of the detected anode voltage potential. The fuel gas supply volume controlling unit 41 increases the fuel gas supply volume in proportion to the change ratio of the calculated anode voltage potential. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system. In detail, it is related with the fuel cell system mounted in a motor vehicle.

  In recent years, fuel cell systems have attracted attention as a new power source for automobiles. The fuel cell system includes, for example, a fuel cell that generates power by chemically reacting a reaction gas, a reaction gas supply device that supplies the reaction gas to the fuel cell via a reaction gas flow path, and a control that controls the reaction gas supply device. An apparatus.

  The fuel cell has, for example, a stack structure in which several tens to several hundreds of cells are stacked. Here, each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators, and the membrane electrode structure includes two electrodes, an anode side electrode (anode) and a cathode side electrode (cathode), A solid polymer electrolyte membrane sandwiched between these electrodes.

  When a fuel cell as a reaction gas is supplied to the anode side electrode (anode) and an oxidant gas as a reaction gas is supplied to the cathode side electrode (cathode), the fuel cell generates electricity by an electrochemical reaction.

By the way, in the above fuel cell, when the amount of the fuel gas actually supplied is insufficient with respect to the amount of the fuel gas required by the power generation request, the absolute potential of the anode side electrode rises. It has been found that battery degradation is accelerated.
Therefore, a reference electrode serving as a ground potential is provided on the electrolyte membrane, and the potential difference between the reference electrode and the anode side electrode is monitored. If the potential difference is greatly different from the predetermined reference line, it is determined that the fuel gas is insufficient. Thus, a method for increasing the supply amount of fuel gas has been proposed (see, for example, Patent Document 1).
JP 2003-331895 A

  However, since the fuel gas is supplied to the fuel cell through the pipe, if the supply amount of the fuel gas is increased after it is determined that the fuel gas is insufficient as in Patent Document 1, the supply amount of the fuel gas is increased. It may take time until the increased fuel gas is actually used in the fuel cell. That is, there may be a delay in the response time of the fuel gas supply system.

  In order to reduce this delay in response time, a method is considered in which a reference line is set so that it can be easily determined that the fuel gas is insufficient, and a method for determining the shortage of the fuel gas at an early stage is considered. Depending on changes in the situation, fuel gas may be supplied excessively.

  An object of the present invention is to provide a fuel cell system that can reduce delay in response of a fuel gas supply system and can prevent excessive supply of fuel gas.

  The fuel cell system of the present invention supplies fuel gas to the anode side electrode provided on one surface of the electrolyte membrane of the fuel cell and oxidant gas to the cathode side electrode provided on the other surface of the electrolyte membrane. The fuel gas supply control means (for example, a fuel gas supply amount control unit 41 to be described later) that controls the supply amount of the fuel gas, and generates a potential difference between the anode side electrode and the predetermined reference electrode An anode potential detecting means (for example, an anode potential detecting section 42 described later) that detects the potential, and an anode potential change rate calculating means (for example, an anode potential change rate calculating section 43 described later) that calculates the change rate of the detected anode potential. The fuel gas supply control means increases the supply amount of the fuel gas as the calculated change rate of the anode potential increases. That.

  According to the present invention, the potential difference between the anode side electrode of the fuel cell and the predetermined reference electrode is detected as the anode potential, and the change rate of the anode potential is calculated. Then, the larger the calculated change rate of the anode potential, the greater the supply amount of the fuel gas.

  Therefore, since the supply amount of the fuel gas is controlled based on the change rate of the anode potential, the shortage of the fuel gas can be predicted more quickly than in the case where the supply amount of the fuel gas is controlled based on the anode potential. The delay in the response of the gas supply system can be reduced, and an excessive supply of fuel gas can be prevented. As a result, deterioration of the fuel cell can be suppressed, and further, the utilization rate of the fuel gas can be improved.

  The fuel cell system of the present invention supplies fuel gas to the anode side electrode provided on one surface of the electrolyte membrane of the fuel cell and oxidant gas to the cathode side electrode provided on the other surface of the electrolyte membrane. The generated current control means (for example, a generated current control unit 45 described later) that controls the generated current of the fuel cell and the potential difference between the anode side electrode and the predetermined reference electrode is set as the anode potential. An anode potential detecting means for detecting (for example, an anode potential detecting section 42 described later), an anode potential change rate calculating means for calculating a change rate of the detected anode potential (for example, an anode potential change rate calculating section 43 described later), The generated current control means reduces the generated current more as the calculated change rate of the anode potential is larger.

  According to the present invention, the potential difference between the anode side electrode of the fuel cell and the predetermined reference electrode is detected as the anode potential, and the change rate of the anode potential is calculated. The generated current is greatly decreased as the calculated change rate of the anode potential is larger. Therefore, according to this invention, there exists an effect similar to the above-mentioned.

  According to the present invention, since the supply amount of the fuel gas is controlled based on the change rate of the anode potential, the shortage of the fuel gas can be predicted more quickly than in the case where the supply amount of the fuel gas is controlled based on the anode potential. Therefore, the delay in the response of the fuel gas supply system can be reduced, and an excessive supply of fuel gas can be prevented. As a result, deterioration of the fuel cell can be suppressed, and further, the utilization rate of the fuel gas can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a configuration of a fuel cell system 1 according to an embodiment of the present invention.
The fuel cell system 1 includes a fuel cell 10 that generates power by reacting a fuel gas and an oxidant gas as a reaction gas, a supply device 50 that supplies the fuel cell 10 with the fuel gas, and the fuel cell 10 and the supply. And a control device 40 that controls the device 50.

The fuel cell 10 includes a membrane electrode structure 14 and a pair of separators 16 and 18 that sandwich the membrane electrode structure 14.
A seal member 19 is interposed between the membrane electrode structure 14 and the separators 16 and 18.

FIG. 2 is a perspective view of the membrane electrode structure 14.
The membrane electrode structure 14 includes an electrolyte membrane 26 and an anode side electrode 28 and a cathode side electrode 30 provided with the electrolyte membrane 26 interposed therebetween.

The electrolyte membrane 26 is provided with a fuel gas supply hole 24a and a fuel gas discharge hole 24b. The fuel gas is supplied to the anode side electrode 28 through the fuel gas supply hole 24a, and the anode is connected to the anode through the fuel gas discharge hole 24b. Used fuel gas is discharged from the side electrode 28.
A reference electrode 32 having a ground potential is attached to the anode side electrode 28 side of the electrolyte membrane 26. A conductive wire 34 is connected to the reference electrode 32.

  Returning to FIG. 1, the supply device 50 includes a fuel gas tank 51 that supplies fuel gas to the fuel cell 10, an ejector 52, a flow rate control valve 53, and a pressure control valve 54.

The fuel gas tank 51 is connected to the fuel gas supply hole 24 a via the fuel gas supply path 61.
The ejector 52 is provided in the fuel gas supply path 61.
The flow rate control valve 53 is provided between the fuel gas tank 51 and the ejector 52 in the fuel gas supply path 61, and the amount of fuel gas supplied from the fuel gas tank 51 is adjusted by the flow rate control valve 53.

  In addition, a fuel gas discharge path 62 is connected to the fuel gas discharge hole 24b, and this fuel gas discharge path 62 is connected to the above-described ejector 52. The ejector 52 collects the fuel gas from the fuel gas discharge path 62 and returns to the fuel gas supply path 61.

  The pressure control valve 54 is provided in the fuel gas discharge passage 62, and adjusts the pressure of the fuel gas supplied to the fuel cell 10 by the opening degree of the pressure control valve 54.

The fuel gas tank 51, the flow rate control valve 53, and the pressure control valve 54 are controlled by the control device 40.
The conducting wire 34 extending from the reference electrode 32 is connected to the control device 40. As a result, the potential of the reference electrode 32 is input to the control device 40.
Further, the separator 18 is connected to the control device 40. The separator 18 has the same potential as that of the anode side electrode 28, whereby the potential of the anode side electrode 28 is input to the control device 40.

FIG. 3 is a block diagram of the control device 40.
The control device 40 includes a fuel gas supply amount control unit 41 as a fuel gas supply control unit, an anode potential detection unit 42 as an anode potential detection unit, and an anode potential change rate calculation unit 43 as an anode potential change rate calculation unit. A fuel gas increase amount calculation unit 44 as a fuel gas increase amount calculation unit, a power generation current control unit 45 as a power generation current control unit, and a power generation current decrease amount calculation unit 46 as a power generation current decrease amount calculation unit. .

  The fuel gas supply amount control unit 41 controls the supply amount of the fuel gas to the fuel cell 10 by adjusting the opening degree of the flow control valve 53 and the pressure control valve 54 described above. Specifically, the shortage of fuel gas supply is resolved by increasing the fuel gas supply amount.

  The anode potential detector 42 detects a potential difference between the anode side electrode 28 and the reference electrode 32 as an anode potential. Here, even if the potential of the anode side electrode 28 changes, the potential of the reference electrode 32 does not change. Therefore, the anode potential detected by the anode potential detection unit 42 is the absolute potential of the anode side electrode 28.

Anode potential change rate calculating section 43, based on the anode potential calculated by the anode potential detection unit 42 calculates the potential rise of alpha _E as the rate of change of the detected anode potential.

  Here, it has been found that the anode potential changes as shown in FIG. 4 according to the amount of fuel gas supplied.

FIG. 4 is a diagram showing the relationship between the stoichiometry of fuel gas and the anode potential at a predetermined current value.
When the stoichiometry of the fuel gas is low, the supply amount of the fuel gas is insufficient with respect to the power generation request of the fuel cell 10, and the anode potential is high. When the stoichiometry of the fuel gas increases from this state, the anode potential decreases, and when the stoichiometry of the fuel gas is high, sufficient fuel gas is supplied to the power generation request of the fuel cell 10 and the anode potential decreases. ing.

Thus, since the anode potential increases when the fuel gas stoichiometry decreases and the fuel gas is insufficient, the potential increase degree α _E which is the change rate of the anode potential is obtained, and this potential increase degree α based on _E, to control the amount of reduction of the increase and the power generation current of the fuel gas.

As a specific example, determine the potential increase of alpha _E at time t0 in FIG.
FIG. 5 is a diagram showing a specific example of a change in anode potential with time.
When a short time at time t0 and Delta] t, the potential rise of alpha _E is an increase amount ΔE of the anode potential in the minute time Delta] t, it is calculated by dividing the short time Delta] t.

Fuel gas increase amount calculation unit 44, based on the potential increase of alpha _E calculated by the anode potential change rate calculating section 43 calculates the increase amount of the fuel gas to be controlled by the fuel gas supply amount control unit 41 in accordance with FIG. 6 .

Figure 6 is a diagram showing a potential increase of alpha _E, the increase amount of the fuel gas to be commanded to the fuel gas supply amount control unit 41, the relationship.
As shown in FIG. 6, the amount of increase in fuel gas increases as the potential increase degree α _E increases.
Therefore, the fuel gas increase amount calculating section 44, the larger the potential increase of alpha _E, to increase the increase amount of the fuel gas.

  When it is determined that the amount of fuel gas supplied to the fuel cell 10 cannot be increased, the generated current control unit 45 controls the generated current by the fuel cell 10. Specifically, the amount of fuel gas required is reduced by reducing the generated current.

Power current decrease amount calculation unit 46, based on the potential increase of alpha _E calculated by the anode potential change rate calculating section 43 calculates a decrease amount of the power generation current controlled by the generated current controller 45 in accordance with FIG.

Figure 7 is a diagram showing the above-mentioned potential rise of alpha _E, and decrease the amount of power generation current command to the generator current controller 45, a relationship. Power current decrease amount calculation unit 46, the larger the potential increase of alpha _E, increasing calculates the decrease of the power generation current.

FIG. 8 is a flowchart showing the operation of the fuel cell system 1.
In S1, the anode potential detection unit 42 detects the anode potential.
Subsequently, in S <b> 2, the anode potential change rate calculation unit 43 calculates the detected change rate of the anode potential, that is, the potential increase degree.

In S3, the increase amount of the fuel gas supplied to the fuel cell 10 is calculated by the fuel gas increase amount calculation unit 44, and in S4, it is determined whether or not an increase in the fuel gas is necessary.
If the determination in S4 is YES, the process proceeds to S5, and if this determination is NO, there is no need to increase the fuel gas, and the process returns to S1.

  In S5, the fuel gas supply amount control unit 41 determines whether or not the fuel gas supply amount can be increased. When this determination is YES, the process proceeds to S6, the fuel gas supply amount control unit 41 increases the fuel gas supply amount, and then returns to S1. On the other hand, if this determination is NO, the amount of fuel gas supplied cannot be increased, and the process proceeds to S7.

In S <b> 7, the power generation current decrease amount calculation unit 46 calculates the power generation current decrease amount in the fuel cell 10.
In S8, the generated current control unit 45 determines whether or not the generated current can be reduced by the calculated reduction amount. When this determination is YES, the process proceeds to S9, the generated current is reduced by the generated current control unit 45, and then the process returns to S1. On the other hand, if this determination is NO, the shortage of fuel gas cannot be resolved by controlling the amount of fuel gas supplied or the generated current, so the process moves to S10, and in S10, the fuel cell system 1 is stopped.

FIG. 9 is a timing chart of the fuel cell system 1.
During the period from time t0 to t1, the required output for the generated current of the fuel cell is a constant value d1. Therefore, during this period, the required amount of fuel gas is a constant value g1, so the anode potential is a constant value e1, and the command value for increasing the fuel gas is zero.
Here, the command value of the fuel gas increase amount is a command value indicating an increase amount to be supplied in addition to the necessary fuel gas amount.

During the period from time t1 to t2, the required output of the fuel cell increases from d1 to d2. Then, the required amount of fuel gas increases from g1 to g2 in accordance with the magnitude of the required output. However, if only this required amount of fuel gas is supplied, the fuel gas becomes insufficient due to a delay in response.
Conventionally, as shown by the broken line, even if the fuel gas is insufficient, the command value for the fuel gas increase amount does not change, so the anode potential rises rapidly and reaches e3. Thereafter, when the shortage of the fuel gas amount is improved, the anode potential converges to the anode potential e2 commensurate with the required output d2 at time t2.

However, in this embodiment, when the fuel gas is insufficient and the anode potential increases greatly, the command value for the fuel gas increase amount is increased to c1, as indicated by the solid line, in accordance with the change rate of the anode potential. Thereafter, when the shortage of the supply amount of the fuel gas is improved and the increase rate of the anode potential is decreased, the command value for the increase amount of the fuel gas is decreased. Therefore, the anode potential gradually increases to e2 as compared with the conventional case.
As described above, in this embodiment, it is detected in advance that the anode potential greatly increases, and the supply amount of the fuel gas is increased.

According to this embodiment, there are the following effects.
(1) The potential difference between the anode side electrode 28 of the fuel cell 10 and the predetermined reference electrode 32 is detected as the anode potential, and the change rate of the anode potential is calculated. Then, the larger the calculated change rate of the anode potential, the greater the supply amount of the fuel gas.
Therefore, since the supply amount of the fuel gas is controlled based on the change rate of the anode potential, the shortage of the fuel gas can be predicted more quickly than in the case where the supply amount of the fuel gas is controlled based on the anode potential. The delay in the response of the gas supply system can be reduced, and an excessive supply of fuel gas can be prevented. As a result, deterioration of the fuel cell 10 can be suppressed, and further, the utilization rate of the fuel gas can be improved.

  (2) The potential difference between the anode side electrode 28 of the fuel cell 10 and the predetermined reference electrode 32 is detected as the anode potential, and the change rate of the anode potential is calculated. The generated current is greatly decreased as the calculated change rate of the anode potential is larger. Therefore, there is an effect similar to (1).

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

1 is a schematic diagram illustrating a configuration of a fuel cell system according to an embodiment of the present invention. It is a perspective view of the membrane electrode structure which concerns on the said embodiment. It is a block diagram of a control device concerning the embodiment. It is a figure which shows the relationship between the stoichiometry of fuel gas and anode potential which concern on the said embodiment. It is a figure which shows the specific example of the time-dependent change of the anode potential which concerns on the said embodiment. It is a figure which shows the relationship between the electric potential rise degree which concerns on the said embodiment, and the increase amount of fuel gas. It is a figure which shows the relationship between the electric potential rise degree which concerns on the said embodiment, and the amount of reduction | decrease of generated electric current. It is a flowchart which shows operation | movement of the fuel cell system which concerns on the said embodiment. 4 is a timing chart of the fuel cell system according to the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 26 Electrolyte membrane 28 Anode side electrode 30 Cathode side electrode 32 Reference electrode 40 Control apparatus 41 Fuel gas supply amount control part (fuel gas supply control means)
42 Anode potential detection unit (anode potential detection means)
43 Anode potential change rate calculation unit (anode potential change rate calculation means)
44 Fuel gas increase amount calculation unit (fuel gas increase amount calculation means)
45 Generated current control unit (generated current control means)
46 Generation Current Reduction Amount Calculation Unit (Generation Current Reduction Amount Calculation Means)

Claims (2)

A fuel that supplies fuel gas to an anode-side electrode provided on one surface of an electrolyte membrane of a fuel cell and supplies an oxidant gas to a cathode-side electrode provided on the other surface of the electrolyte membrane to generate power A battery system,
Fuel gas supply control means for controlling the supply amount of fuel gas;
Anode potential detection means for detecting a potential difference between the anode side electrode and a predetermined reference electrode as an anode potential;
An anode potential change rate calculating means for calculating a change rate of the detected anode potential,
The fuel gas supply control means increases the fuel gas supply amount as the calculated change rate of the anode potential increases. A fuel that supplies fuel gas to an anode-side electrode provided on one surface of an electrolyte membrane of a fuel cell and supplies an oxidant gas to a cathode-side electrode provided on the other surface of the electrolyte membrane to generate power A battery system,
Generated current control means for controlling the generated current of the fuel cell;
Anode potential detection means for detecting a potential difference between the anode side electrode and a predetermined reference electrode as an anode potential;
An anode potential change rate calculating means for calculating a change rate of the detected anode potential,
The fuel cell system according to claim 1, wherein the generated current control means greatly reduces the generated current as the calculated change rate of the anode potential is larger.

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