JP2001210338A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which can prevent superheating of combustor without using a huge one. SOLUTION: By-pass passages 37, 39 which lead discharge reforming gas and discharge air drained from a fuel cell stack 9 to a combustor 13 directly without a capacitor 11, and valves 45, 47 which open and close the by-pass passages 37, 39 have been installed, and the superheating state of the combustor 13 is judged based on the temperature of the combustor 13, and in the case the combustor 13 is judged that it is under superheated state, for example, respective valves 41, 43, 45, and 47 are controlled in order to lead the exhaust gas drained from the fuel cell stack 9 to the by-pass 37, 39.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system capable of preventing a combustor from overheating.

[0002]

2. Description of the Related Art A conventional fuel cell system includes a fuel cell stack that generates electricity using a reformed gas containing hydrogen reformed in a reformer and a gas (air) containing oxygen, and a fuel cell stack. 2. Description of the Related Art A fuel cell system including a water recovery device that recovers water from excess discharged exhaust gas (exhaust reformed gas and exhaust air) and a combustor that burns the exhaust gas whose water is recovered by the water recovery device is known. Have been.

[0003]

However, in such a conventional fuel cell system, when the load of the fuel cell stack changes stepwise (output level decreases), the reformer performs the stepdown. Until following the load fluctuation, an excess of reformed gas which is not required to be used for power generation in the fuel cell stack is generated temporarily.

[0004] At this time, when the battery is not fully charged, the fuel cell stack generates electric power using the surplus reformed gas, and charges the battery with the generated surplus electric power. It is possible to handle the increment. However, if the battery is fully charged,
Since the battery cannot be charged with the surplus power generated by the fuel cell stack using the surplus reformed gas, a large amount of surplus reformed gas that cannot be used for power generation in the fuel cell stack, including the increased amount, is burned. However, there is a problem that the combustor is overheated.

In order to prevent overheating of the combustor, it is conceivable to use a large combustor having a large combustion output with a margin against overheating. However, when a large combustor having a large combustion output is used, However, there has been a problem that the fuel cell system itself becomes large and cannot be mounted as a fuel cell system used for a moving body.

[0006] The present invention has been made in view of the above,
An object of the present invention is to provide a fuel cell system that can prevent overheating of a combustor without using a large-sized combustor.

[0007]

According to the first aspect of the present invention,
In order to solve the above problems, a fuel reformer for reforming fuel using water, and a fuel for generating electricity using a reformed gas containing hydrogen and a gas containing oxygen reformed by the fuel reformer A fuel cell system comprising: a battery stack, a water recovery device that recovers water from exhaust gas discharged from the fuel cell stack, and a combustor that burns the exhaust gas from which water is recovered by the water recovery device. A bypass passage that directly guides the exhaust gas discharged from the fuel cell stack to the combustor without passing through the water recovery unit, an opening / closing unit that opens and closes the bypass passage, and whether the combustor is in an overheated state Determination means for determining whether the combustor is in an overheated state, and control means for controlling the opening / closing means to guide exhaust gas discharged from the fuel cell stack to the bypass passage. And summarized in that a.

According to a second aspect of the present invention, in order to solve the above-mentioned problems, there is provided a temperature detecting means for detecting a temperature of the combustor, and the judging means is provided based on a signal value from the temperature detecting means. The gist is to determine whether or not the combustor is in an overheated state.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, there is provided a temperature detecting means for detecting a temperature of the combustor, wherein the judging means comprises a signal value from the temperature detecting means and a signal value of the signal value. The gist is to determine whether or not the combustor is in an overheated state based on the time differential value of.

According to a fourth aspect of the present invention, there is provided an electric vehicle, comprising: a state-of-charge detecting means for detecting a state of charge of a battery; and an amount-of-step detecting means for detecting an amount of depression of an accelerator. Is to judge whether the combustor is overheated based on the signal value from the charged state detecting means, the signal value from the stepping amount detecting means, and the time derivative of the signal value. And

[0011]

According to the first aspect of the present invention, a bypass passage for guiding exhaust gas discharged from a fuel cell stack directly to a combustor without passing through a water recovery unit, and an opening / closing means for opening and closing the bypass passage It is determined whether the combustor is in an overheated state, and when it is determined that the combustor is in an overheated state, the exhaust gas discharged from the fuel cell stack is guided to a bypass passage. By controlling the opening and closing means, overheating of the combustor can be prevented without using a large combustor.

According to the second aspect of the present invention, temperature detecting means for detecting the temperature of the combustor is provided, and the combustor is overheated based on a signal value (temperature of the combustor) from the temperature detecting means. By determining whether the state is in the state or not, the current overheating state of the combustor can be determined.

According to the third aspect of the present invention, temperature detecting means for detecting the temperature of the combustor is provided, and a signal value (temperature of the combustor) from the temperature detecting means and a time differential value of the signal value are provided. By determining whether or not the combustor is in an overheated state, it is possible to predict a future overheated state of the combustor, and it has been detected in advance that the combustor is approaching the overheated state. At this time, a measure for lowering the temperature of the combustor can be taken.

According to the fourth aspect of the present invention, there are provided a charged state detecting means for detecting a charged state of the battery and a stepped amount detecting means for detecting a stepped amount of an accelerator,
Signal value from charge state detection means (battery charge state)
And determining whether or not the combustor is in an overheated state based on a signal value (accelerator stepping amount) from the stepping amount detecting means and a time differential value of the signal value. Of the combustor can be predicted in accordance with the fluctuation of the battery and the state of charge of the battery, and a measure to reduce the temperature of the combustor when it is previously detected that the combustor is approaching the overheated state. Can be applied.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a hybrid fuel cell vehicle of a fuel cell system having a fuel reformer and a battery as a structure applicable to a fuel cell system according to a first embodiment of the present invention. Is shown.

In FIG. 1, a fuel reformer (hereinafter simply referred to as a reformer) 1 steam-reforms methanol in a methanol tank 3 using water in a water tank 5 as fuel.
Generates reformed gas containing hydrogen. At this time, if necessary, air is sent from the compressor 7 and reforming by partial oxidation of methanol is also performed. Steam reforming is an endothermic reaction, and partial oxidation is an exothermic reaction.

The reformed gas generated in the reformer 1 and the air from the compressor 7 are sent to the anode and the cathode of the fuel cell stack 9, where hydrogen in the reformed gas and oxygen in the air are supplied. Is used to generate power. At this time, the hydrogen in the reformed gas and the oxygen in the air are not all consumed in the fuel cell stack 9 but are discharged leaving a part thereof, and the condenser 11 is discharged as the reformed gas and the discharged air. The fuel is sent to the combustor 13 via the compressor 7 and, if necessary, is combusted with the air from the compressor 7 and the methanol in the methanol tank 3.

The condenser 11 is a device that functions as a water recovery unit, and cools the discharged reformed gas and the discharged air, which are the discharged gas from the fuel cell stack 9, with cooling water to form the discharged reformed gas and the discharged air. The water vapor contained in is condensed and recovered. At this time, since the condenser 11 has two chambers, the exhaust reformed gas, which is the exhaust gas from the fuel cell stack 9, and the exhaust air are not mixed inside. The recovered water condensed and recovered by the condenser 11 is returned to the water tank 5.

The heat generated by the combustion reaction in the combustor 13 is transferred to the evaporator 15 by the exhaust gas whose temperature has increased after the combustion reaction. At this time, the exhaust gas is used in the evaporator 15 as a heat source for evaporating methanol and water supplied from the methanol tank 3 and the water tank 5 to the reformer 1, respectively, or as steam reforming in the reformer 1. Is reused as a heat source for the endothermic reaction.

The battery 17 stores the surplus electric power generated by the fuel cell stack 9 and the regenerative electric power generated by the motor 19 when the fuel cell vehicle decelerates. If the fuel cell stack 9 does not generate enough power to supply the auxiliary equipment power consumed by the burner 1, the combustor 13, and the like, the fuel cell stack 9 discharges and discharges the motor 19 and the auxiliary equipment (the compressor 7, the reformer 1 , The combustor 13, etc.) to compensate for the lack of power. The distribution of these powers is performed via the power regulator 21.

The controller 23 controls the power distribution by the power regulator 21 based on a signal (accelerator depression amount) detected by the position sensor (depression amount detection means) 27 of the depression amount of the accelerator pedal 25. Further, the control device 23 is based on the signals (the exhaust reformed gas pressure and the exhaust air pressure) detected by the pressure sensors 29 and 31 that detect the pressure of the exhaust reformed gas and the exhaust air supplied to the combustor 13, respectively. The operating pressure of the fuel cell stack 9 is controlled by adjusting the opening of the pressure adjusting valves 33 and 35 for adjusting the pressures of the reformed gas and the air supplied to the fuel cell stack 9 respectively.

A bypass passage between the inlet and outlet of the condenser 11 leads the exhaust gas (exhaust reformed gas and exhaust air) discharged from the fuel cell stack 9 directly to the combustor 13 without passing through the condenser 11. 37 and 39 are provided. The bypass passage 37 is for exhaust gas reformed from the fuel cell stack 9 (exhaust gas from the fuel electrode), and the bypass passage 39 is for exhaust air from the fuel cell stack 9 (exhaust gas from the air electrode).

Exhaust gas (exhaust reformed gas and exhaust air) flowing into the condenser 11 passes through valves (hereinafter referred to as condenser valves) 41 and 43, respectively, and the condenser 1
Exhaust gas (exhaust reformed gas and exhaust air) flowing into the condenser 1 and bypassing the condenser 11 passes through valves (hereinafter referred to as bypass valves) (opening / closing means) 45 and 47 provided in the bypass passages 37 and 39, respectively. Direct combustor 1
Flow into 3

The combustor 13 is provided with a temperature sensor (temperature detecting means) 49 for detecting the temperature of the combustor 13. The temperature sensor 49 is connected to the control device 23 for controlling the fuel cell system, and outputs a detection signal to the control device 23.

The control device 23 (judgment means, control means)
It has a control ROM in which a control program is stored and a RAM serving as a work area for control.
3 based on the signal value (temperature of the combustor) from the temperature sensor 49, it is determined whether or not the combustor 13 is overheated;
The control signal according to the result of this determination is transmitted
The overheating of the combustor 13 is prevented by outputting to the first and third valves 43 and the bypass valves 45 and 47 to perform switching control of these valves 41, 43, 45 and 47.

Next, with reference to the control characteristics shown in FIG. 3, a control operation for preventing the combustor overheating of the fuel cell system for a mobile body will be described according to a control flowchart shown in FIG. Note that the control flowchart shown in FIG. 2 is stored as a control program in the internal ROM of the control device 23.

First, in step S100, the control device 2
3 reads the signal value (temperature Tb of the combustor 13) from the temperature sensor 49 of the combustor 13. Then, step S1
At 10, the control device 23 sets the combustor temperature Tb read from the temperature sensor 49 to the preset upper limit temperature T2.
It is determined whether it is higher than (see FIG. 3).

If the result of this determination is that the combustor temperature Tb is higher than the upper limit temperature T2, it is determined that the combustor 13 is in an overheated state, and the routine proceeds to step S120. In this step S120, the bypass valves 45 and 47 are opened,
At the same time, a control signal for closing the condenser valves 41, 43 is sent to the valves 41, 43, 45, 47. In response to this, the bypass valves 45 and 47 open according to the control signal to open the bypass passages 37 and 39, and the condenser valves 41 and 43 close according to the control signal to open the bypass passages 37 and 39. Close the passage.

As a result, the exhaust gas (exhaust reformed gas and exhaust air) discharged from the fuel cell stack 9 flows into the combustor 13 through the bypass passages 37 and 39 without passing through the condenser 11. That is, the exhaust gas (exhaust reformed gas and exhaust air) discharged from the fuel cell stack 9 is guided to the combustor 13 without collecting a large amount of water vapor contained in the exhaust gas, and is subjected to the combustion processing. .

Therefore, a large amount of water vapor is contained in the exhaust gas subjected to the combustion treatment, and the specific heat of the combustion gas is increased.
3 is prevented from overheating. For example, the exhaust gas from the fuel cell stack 9 is directly passed through the combustor 1 without passing through the condenser 11.
The combustion temperature in the combustor 13 when the combustion is led to 3 is lowered by about 85 ° C. because the amount of steam introduced into the combustor 13 is about twice as large.

On the other hand, when the combustor temperature Tb is equal to the upper limit temperature T
If it is less than or equal to 2, the process proceeds to step S130. In this step S130, it is further determined whether or not the combustor temperature Tb is lower than a preset lower limit temperature T1 (see FIG. 3).

If the result of this determination is that the combustor temperature Tb is lower than the lower limit temperature T1, it is determined that the combustor 13 is not in an overheated state, and the routine proceeds to step S140. In this step S140, a control signal for opening the condenser valves 41, 43 and closing the bypass valves 45, 47 is sent to the valves 41, 43, 45, 47. In response to this, the condenser valves 41 and 43 open according to the control signal to open the passage to the condenser 11, and the bypass valves 45 and 47 close according to the control signal to close the bypass passages 37 and. Close 39.

As a result, the exhaust gas (exhausted reformed gas and exhaust air) exhausted from the fuel cell stack 9 is guided to the condenser 11, and the steam contained in the exhaust gas (exhausted reformed gas and exhaust air) is discharged. After being recovered by condensation, it is guided to the combustor 13 where it is subjected to combustion processing.

On the other hand, when the combustor temperature Tb is lower than the lower limit temperature T
If the temperature is equal to or higher than 1, that is, if the combustor temperature Tb is equal to or higher than the lower limit temperature T1 and equal to or lower than the upper limit temperature T2, the routine immediately returns to maintain the current open / closed state of each of the valves 41, 43, 45, and 47. That is, the control device 23
When the temperature Tb of the combustor 13 becomes higher than the upper limit temperature T2 as in the control characteristics shown in FIG. 3, the bypass passages 37 and 39 are opened to allow the exhaust gas from the fuel cell stack 9 to bypass the condenser 11. Thus, the overheat of the combustor 13 is prevented. On the other hand, when the combustor temperature Tb becomes lower than the lower limit temperature T1, the bypass passages 37 and 39 are closed to discharge the exhaust gas from the fuel cell stack 9 to the condenser 1.
1 to prevent overcooling of the combustor 13.

As described above, the respective steps from step S100 to step S140 are repeated.
The temperature of the combustor 13 can be controlled within a certain range while preventing overheating of the combustor 13.

As a result, the effect of the first embodiment is that when the temperature of the combustor read from the temperature sensor 49 provided in the combustor 13 exceeds the preset upper limit temperature, Is determined to be in an overheated state, the bypass passages 37 and 39 are opened, and the exhaust gas from the fuel cell stack 9 is guided to the combustor 13 by bypassing the condenser 11 without using a large-sized combustor. Thus, overheating of the combustor can be prevented.

(Second Embodiment) FIG. 4 is a control flowchart for explaining a control operation for preventing a combustor from overheating in a fuel cell system according to a second embodiment of the present invention. In the second embodiment, the first embodiment shown in FIG.
It has the same configuration as that of the fuel cell system corresponding to the embodiment, and the description thereof will be omitted.

A feature of the second embodiment is that, in the first embodiment, a measure is taken to lower the temperature of the combustor 13 when the combustor temperature exceeds a predetermined value (upper limit temperature). On the other hand, on the basis of the combustor temperature and its time differential value (hereinafter simply referred to as the differential value), a measure for lowering the temperature of the combustor 13 even when it is detected in advance that the combustor 13 is approaching an overheated state. To be applied.

FIG. 5 is a control map for that purpose. The region A of the control map is a region in which the action of lowering the temperature of the combustor 13 is performed in the second embodiment, and it is determined that the combustor 13 is currently in a superheated state or is predicted to be in a future superheated state. Area. Control map area B
Is a region in which the action of lowering the temperature of the combustor 13 is not performed in the second embodiment, and is a region where it is determined that the combustor 13 is not currently in a superheated state and is predicted not to be in a future superheated state. . The control flowchart shown in FIG. 4 and the control map shown in FIG. 5 are stored in the internal ROM of the control device 23a as a control program and a data table.

First, in step S200, the control device 2
3a reads the signal value (temperature of the combustor 13) from the temperature sensor 49 of the combustor 13. Then, step S21
0, the combustor temperature Tb read from the temperature sensor 49
Is calculated. Note that this differential value ΔTb is
For example, it is obtained by calculating the difference between the current and previous combustor temperatures Tb.

In step S220, the control device 23a determines whether or not the combination of the combustor temperature Tb read from the temperature sensor 49 and its differential value ΔTb is the area A of the control map shown in FIG. to decide. If the result of this determination is that the area is the area A of the control map, it is determined that the combustor 13 is in an overheated state or is approaching an overheated state, and the process proceeds to step S230.

In step S230, the bypass valves 45 and 47 are opened, and the condenser valves 41 and 4 are opened.
The control signal for closing 3 is transmitted to each of the valves 41, 43, 45, 47.
Send to In response to this, the bypass valves 45 and 47
The bypass valves 37 and 39 are opened according to the control signal to open the bypass passages 37 and 39, and the condenser valves 41 and 43 are closed according to the control signal to close the passage to the condenser 11.

As a result, the exhaust gas (exhaust reformed gas and exhaust air) discharged from the fuel cell stack 9 flows into the combustor 13 through the bypass passages 37 and 39 without passing through the condenser 11. That is, the exhaust gas (exhaust reformed gas and exhaust air) discharged from the fuel cell stack 9 is guided to the combustor 13 without collecting a large amount of water vapor contained in the exhaust gas, and is subjected to the combustion processing. . Therefore, a large amount of water vapor is contained in the exhaust gas subjected to the combustion treatment, and the specific heat of the combustion gas is increased. As described above, the combustion temperature is significantly reduced, and the overheating of the combustor 13 is prevented. You.

On the other hand, if it is the area B of the control map, it is determined that the combustor 13 is not in the overheated state and is not going to the overheated state, and the process proceeds to step S240.

In step S240, the condenser valves 41 and 43 are opened, and the bypass valves 45 and 4 are opened.
The control signal for closing the valve 7 is transmitted to each of the valves 41, 43, 45, 47.
Send to In response to this, the condenser valves 41 and 43 open according to the control signal to open the passage to the condenser 11, and the bypass valves 45 and 47 close according to the control signal to close the bypass passages 37 and. Close 39.

As a result, the exhaust gas (exhausted reformed gas and exhaust air) exhausted from the fuel cell stack 9 is guided to the condenser 11 and the steam contained in the exhaust gas (exhausted reformed gas and exhaust air) is discharged. After being recovered by condensation, it is guided to the combustor 13 where it is subjected to combustion processing.

As described above, the steps S200 to S240 are repeated, so that the combustor 13
The temperature of the combustor 13 can be controlled within a certain range while preventing overheating of the combustor 13.

As a result, the effect of the second embodiment is the same as that of the first embodiment.
By determining whether the combustor 13 is in an overheated state based on the combustor temperature Tb read from the temperature sensor 49 and the derivative ΔTb thereof, a future overheated state of the combustor 13 is also predicted. Therefore, when it is detected in advance that the combustor 13 is approaching an overheated state, a measure for lowering the temperature of the combustor 13 can be taken.

In the first and second embodiments, the case where the temperature sensor 49 is provided in the combustor 13 has been described as an example. However, the present invention is not limited to this. For example, a temperature sensor may be provided at the exhaust gas outlet of the combustor 13 or the exhaust gas inlet of the evaporator 15.

(Third Embodiment) FIG. 6 is a diagram showing a configuration of a fuel cell system according to a third embodiment of the present invention. The third embodiment has the same basic configuration as the fuel cell system corresponding to the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals. , The description of which will be omitted.

The feature of the third embodiment is that, as shown in FIG. 6, the battery 17 has a charging rate (SOC) of the battery 17.
Is provided based on the SOC value from the battery sensor 51, the accelerator depression amount from the position sensor 27, and the time derivative thereof (hereinafter simply referred to as the derivative value). It is also to take a measure to lower the temperature of the combustor 13 even when it is detected in advance that the fuel cell 13 is approaching an overheated state.

Next, referring to the control map shown in FIG.
The control operation for preventing the combustor from overheating in the fuel cell system will be described with reference to the control flowchart shown in FIG. The control flowchart shown in FIG. 7 and the control map shown in FIG. 8 are stored in the internal ROM of the control device 23b as a control program and a data table.

First, in step S300, the control device 2
3b reads the signal value from the position sensor 27 (the operation amount of the accelerator pedal 25, that is, the accelerator depression amount). Then, in step S310, a differential value (here, the accelerator release speed) of the accelerator depression amount read from the position sensor 27 is obtained.

Then, in step S320, the control device 23b sets the combination of the accelerator depression amount read from the position sensor 27 and its differential value (accelerator release speed) in the area C of the control map shown in FIG. It is determined whether or not.

If the result of this determination is that the area is the area C of the control map, it is determined that the load fluctuation of the fuel cell stack 9 has stepped down and the combustor 13 may be overheated. The process proceeds to step S330.

In step S330, the signal value from the battery sensor 51 (the SOC of the battery 17)
Value). Then, in step S340, the SOC of the battery 17 read from the battery sensor 51
Based on the value, it is determined whether or not battery 17 is fully charged.

As a result of this determination, when the battery 17 is in a fully charged state, even if the fuel cell stack 9 generates electric power using the surplus reformed gas, the surplus electric power is supplied to the battery 17.
, The process proceeds to step S350. In step S350, the power generation in the fuel cell stack 9 is stopped, and the bypass valves 45 and 4 are stopped.
7 and a control signal to close the condenser valves 41, 43 is sent to the valves 41, 43, 45, 47. In response to this, the bypass valves 45, 47 open in response to the control signal to open the bypass passages 37, 39.
The condenser valves 41 and 43 close in response to the control signal to close the passage to the condenser 11.

As a result, the exhaust gas (exhausted reformed gas and exhaust air) from the fuel cell stack 9 containing a large amount of surplus reformed gas does not pass through the condenser 11 but passes through the bypass passage 37,
It flows into the combustor 13 through 39. That is, the exhaust gas (the exhaust gas and the exhaust gas) discharged from the fuel cell stack 9 is guided to the combustor 13 without collecting a large amount of water vapor contained in the exhaust gas, and is subjected to a combustion process. . Therefore, a large amount of water vapor is contained in the exhaust gas subjected to the combustion treatment, and the specific heat of the combustion gas is increased. As described above, the combustion temperature is significantly reduced, and the overheating of the combustor 13 is prevented. You.

On the other hand, when the battery 17 is not in the fully charged state, the fuel cell stack 9 can generate electric power by using the surplus reformed gas and charge the surplus electric power to the battery 17, so that step S360 is performed. Proceed to. In this step S360, the power generation in the fuel cell stack 9 is maintained, and a control signal for opening the condenser valves 41, 43 and closing the bypass valves 45, 47 is sent to the valves 41, 43, 45, 47. In response to this, the condenser valves 41 and 43 open according to the control signal to open the passage to the condenser 11, and the bypass valves 45 and 47 close according to the control signal to close the bypass passages 37 and. Close 39.

As a result, the exhaust gas (exhausted reformed gas and exhaust air) discharged from the fuel cell stack 9 is guided to the condenser 11 and the steam contained in the exhaust gas (exhausted reformed gas and exhaust air) is discharged. After being recovered by condensation, it is guided to the combustor 13 where it is subjected to combustion processing. During this time, since the power generation in the fuel cell stack 9 is maintained, the surplus reformed gas is consumed in the fuel cell stack 9. Therefore, the hydrogen concentration in the reformed gas exhausted from the fuel cell stack 9 is reduced by the power generation of the fuel cell stack 9, and the overheating of the combustor 13 is prevented. At this time, the surplus power generated by the fuel cell stack 9 charges the battery 17.

If the result of determination in step S320 is that the area is the area D of the control map, the fuel cell stack 9
No load fluctuation during the step-down of
Then, it is determined that there is no possibility that 3 will be overheated, and the process proceeds to step S370.

In step S370, the condenser valves 41 and 43 are opened, and the bypass valves 45 and 4 are opened.
The control signal for closing the valve 7 is transmitted to each of the valves 41, 43, 45, 47.
Send to In response to this, the condenser valves 41 and 43 open according to the control signal to open the passage to the condenser 11, and the bypass valves 45 and 47 close according to the control signal to close the bypass passages 37 and. Close 39.

As a result, the exhaust gas (exhausted reformed gas and exhaust air) discharged from the fuel cell stack 9 is guided to the condenser 11 and the steam contained in the exhaust gas (exhausted reformed gas and exhaust air) is discharged. After being recovered by condensation, it is guided to the combustor 13 where it is subjected to combustion processing.

As described above, the steps from step S300 to step S370 are repeated.
The temperature of the combustor 13 can be controlled within a certain range while preventing overheating of the combustor 13. As a result, in addition to the effects of the first embodiment described above, the effects of the third embodiment include the SOC value of the battery read from the battery sensor 51, the accelerator depression amount from the position sensor 27, and the Derivative value (accelerator release speed)
By determining whether the combustor 13 is in an overheated state on the basis of the above, the future load of the combustor according to the change in the load required for the fuel cell system (particularly, step-down) and the state of charge of the battery 17 is determined. An overheating state can be predicted, and a measure for lowering the temperature of the combustor 13 can be taken when it is previously detected that the combustor 13 is approaching the overheating state. In the first, second and third embodiments, the exhaust gas (exhaust reformed gas and exhaust air) from the fuel cell stack 9 is led to the condenser 11 or
The switching control for determining whether to bypass is described as an example, but the present invention is not limited to this. For example, the amount of bypass may be made variable in accordance with the temperature of the combustor 13 and / or its differential value or deviation by using a variable flow valve whose opening degree can be adjusted.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a control flowchart for describing a control operation for preventing overheating of a combustor of the fuel cell system according to the first embodiment.

FIG. 3 is a diagram illustrating control characteristics according to the first embodiment.

FIG. 4 is a control flowchart illustrating a control operation for preventing a combustor from overheating in a fuel cell system according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a control map according to the second embodiment.

FIG. 6 is a diagram showing a configuration of a fuel cell system according to a third embodiment of the present invention.

FIG. 7 is a control flowchart for explaining a control operation for preventing a combustor from overheating in the fuel cell system according to the third embodiment.

FIG. 8 is a diagram showing a control map according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel reformer 7 Compressor 9 Fuel cell stack 11 Capacitor 13 Combustor 15 Evaporator 17 Battery 23, 23a, 23b Control device 25 Accelerator pedal 27 Position sensor 37, 39 Bypass passage 41, 43, 45, 47 Valve 49 Temperature sensor 51 Battery sensor

Claims (4)

[Claims] 1. A fuel reformer for reforming a fuel using water, and a fuel cell stack for generating electricity using a reformed gas containing hydrogen and a gas containing oxygen reformed by the fuel reformer A water recovery device that recovers water from exhaust gas discharged from the fuel cell stack; and a combustor that burns the exhaust gas from which water has been recovered by the water recovery device. A bypass passage that directly guides the exhaust gas discharged from the stack to the combustor without passing through the water recovery unit; an opening / closing unit that opens and closes the bypass passage; and determines whether the combustor is in an overheated state. And a control unit that controls the opening / closing unit to guide the exhaust gas discharged from the fuel cell stack to the bypass passage when it is determined that the combustor is in an overheated state. Fuel cell system, characterized in that. 2. A temperature detecting means for detecting a temperature of the combustor, wherein the judging means judges whether or not the combustor is overheated based on a signal value from the temperature detecting means. The fuel cell system according to claim 1, wherein: 3. A temperature detecting means for detecting a temperature of the combustor, wherein the judging means overheats the combustor based on a signal value from the temperature detecting means and a time differential value of the signal value. 2. The fuel cell system according to claim 1, wherein it is determined whether or not the fuel cell is in a state. 4. A charge state detection means for detecting a charge state of a battery, and a depression amount detection means for detecting a depression amount of an accelerator, wherein the determination means includes a signal value from the charge state detection means and 2. The fuel cell system according to claim 1, wherein whether or not the combustor is in an overheated state is determined based on a signal value from the stepping amount detecting means and a time differential value of the signal value.