JP2004273354A - Internal combustion engine having fuel cell in exhaust system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which can supply fuel for power generation to a fuel cell irrespective of the operation conditions of the internal combustion engine, in an internal combustion engine having a fuel cell in an exhaust system. <P>SOLUTION: The internal combustion engine is provided with a fuel cell 3 whose fuel electrode 3a side is connected to an exhaust passage 2 of the internal combustion engine 1, a fuel supplying means 10 which supplies fuel for power generation for the fuel cell 3 into the exhaust passage 2 on the downstream side of the internal combustion engine 1 and on the upstream side of the fuel cell 3, and a supply amount controlling means 13 which controls the amount of the fuel to be supplied by the fuel supplying means 10. By such a construction, irrespective of the operation conditions of the internal combustion engine 1, the fuel supplying means 10 can supply the fuel for power generation to the fuel cell 3 to generate power. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal combustion engine having a fuel cell in an exhaust system.
[0002]
[Prior art]
There is a technology in which a fuel cell is provided in an exhaust system, and an internal combustion engine is operated in an excessive fuel state to supply unburned components discharged to the fuel electrode side of the fuel cell as fuel for power generation (for example, see Patent Document 1). Are known.
[0003]
[Patent Document 1]
JP-A-2002-175824 (page 4-7, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, depending on the operating conditions of the internal combustion engine, it may be difficult to operate in a fuel-rich state, and in such a case, it becomes impossible to supply fuel to the fuel cell. Further, in such a case, if the internal combustion engine is operated in an excessive fuel state by giving priority to power generation by the fuel cell, the operation state of the internal combustion engine is deteriorated, and torque fluctuation and emission deterioration are induced.
[0005]
The present invention has been made in view of the above-described problem, and has been made in view of the above-mentioned circumstances. In an internal combustion engine having a fuel cell in an exhaust system, a technology capable of supplying fuel for power generation to the fuel cell regardless of operating conditions of the internal combustion engine. Is to provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an internal combustion engine having a fuel cell in an exhaust system according to the present invention employs the following means. That is,
A fuel cell having a fuel electrode connected to an exhaust passage of an internal combustion engine,
Fuel supply means for supplying fuel for power generation of the fuel cell into an exhaust passage downstream of the internal combustion engine and upstream of the fuel cell;
Supply amount control means for controlling the supply amount of fuel by the fuel supply means,
It is characterized by having.
[0007]
The most significant feature of the present invention is that the fuel supply means for supplying the fuel for power generation in the middle of the exhaust passage allows the fuel for power generation to be supplied to the fuel cell regardless of the operating conditions of the internal combustion engine. is there.
[0008]
In the internal combustion engine having the fuel cell in the exhaust system configured as described above, the fuel supply unit is provided, so that the fuel for power generation can be supplied to the fuel electrode side of the fuel cell regardless of the operation state of the internal combustion engine. It becomes. Further, since the supply amount of the fuel for power generation is controlled by the supply amount control means, an appropriate amount of fuel for power generation can be supplied to the fuel cell regardless of the operation state of the internal combustion engine. On the other hand, the internal combustion engine can be operated regardless of the power generation state of the fuel cell.
[0009]
In the present invention, the supply amount control means can control the amount of fuel for power generation based on a power generation target value of the fuel cell.
[0010]
Since the fuel for power generation can be supplied regardless of the operating state of the internal combustion engine, it is possible to control the fuel supply amount based on the power generation target. This makes it possible to supply an optimal amount of fuel to the fuel cell in order to achieve the power generation target of the fuel cell.
[0011]
In the present invention, the fuel cell further includes a fuel amount detecting unit that detects a fuel amount contributing to power generation of the fuel cell, and controls a power generation fuel supplied to the fuel cell based on a detection result of the fuel amount detecting unit. Can be.
[0012]
Based on the actually detected fuel amount, feedback control of the supplied fuel amount becomes possible, and it becomes possible to supply an optimal amount of fuel to the fuel cell to achieve the power generation target of the fuel cell.
[0013]
In the present invention, the fuel cell system may further include a temperature detecting means for detecting a state of an element relating to a temperature of the fuel cell, and the power generation fuel supplied to the fuel cell can be controlled based on a detection result of the temperature detecting means.
[0014]
The fuel cell has an optimum temperature for power generation, and if fuel is supplied at that temperature, efficient power generation can be performed. Further, when the temperature of the fuel cell is low, it is possible to reduce the supply amount of the fuel and suppress the fuel from being discharged from the fuel cell without contributing to power generation.
[0015]
In the present invention, the apparatus further includes a combustion device, and the fuel supply unit can supply exhaust gas from the combustion device to an exhaust passage.
[0016]
By supplying the burned gas from the combustion device to the fuel cell, it is possible to raise the temperature of the fuel cell, such as when starting the engine and when the exhaust gas temperature and the fuel cell temperature are low. It is also possible to start power generation promptly. In addition, by supplying burned gas burned in a fuel-rich (rich) state to the fuel cell in the combustion device, it becomes possible to supply unburned fuel in the combustion device as fuel for power generation of the fuel cell. .
[0017]
In the present invention, the supply amount control means can control the fuel supply amount to the fuel cell by changing the air-fuel ratio of the gas burned by the combustion device.
[0018]
When the air-fuel ratio of the gas burned by the combustion device is changed, the amount of unburned fuel contained in the exhaust gas from the combustion device changes. Therefore, by changing the air-fuel ratio in the combustion device, it is possible to change the amount of power generation fuel to be supplied to the fuel cell, and to supply power generation fuel in accordance with the power generation target.
[0019]
In the present invention, a catalyst having an oxidizing ability can be provided in an exhaust passage upstream of the fuel cell and downstream of the fuel supply means.
[0020]
With this catalyst, it is possible to oxidize unburned fuel from the internal combustion engine and fuel for power generation from the fuel supply means, and to raise the temperature of the downstream fuel cell by the reaction heat at that time. Therefore, even when the engine is started or the like and the temperature of the exhaust gas and the temperature of the fuel cell are low, it is possible to start power generation quickly. Further, since oxygen reacts in the catalyst and the oxygen concentration in the exhaust gas decreases, the power generation amount of the fuel cell can be improved. Further, the fuel for power generation can be reformed, and the fuel easily reacts in the fuel cell, so that the power generation efficiency with respect to the supplied fuel can be improved.
[0021]
In the present invention, an oxidizing catalyst can be provided in the exhaust passage downstream of the fuel cell.
[0022]
With this catalyst, it is possible to oxidize the fuel for power generation discharged from the fuel cell without contributing to the power generation, and it is possible to suppress the fuel from being released into the atmosphere.
[0023]
In the present invention, an oxygen supply means for supplying oxygen to the oxidizing catalyst can be provided.
[0024]
A catalyst having an oxidizing ability has a higher oxidizing ability as the oxygen concentration in the exhaust gas passing through the catalyst is higher. Therefore, it is possible to increase the oxidizing ability by supplying oxygen from upstream of the catalyst. Note that oxygen released from the air electrode of the fuel cell may be supplied.
[0025]
In the present invention, a heat exchanger may be provided in an exhaust passage downstream of the fuel cell.
[0026]
The temperature of gas discharged from the fuel electrode side of a fuel cell operating at a high temperature is high, and this heat can be recovered by a heat exchanger. This makes it possible to improve system efficiency. For example, by raising the temperature of the cooling water of the internal combustion engine, the warm-up of the internal combustion engine can be completed quickly.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
Hereinafter, specific embodiments of the internal combustion engine according to the present invention will be described with reference to the drawings. Here, an example in which the internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described.
[0028]
FIG. 1 is a diagram showing a schematic configuration of an engine 1 and an intake / exhaust system thereof according to the present embodiment.
[0029]
The engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine.
[0030]
An exhaust passage 2 for discharging burned gas from the engine 1 to the atmosphere is connected to the engine 1. A fuel cell 3 is provided in the exhaust passage 2. The fuel cell 3 is electrically connected to accessories 4 via a battery 5 and supplies power to the accessories 4. In the present embodiment, a solid oxide fuel cell (Solid Oxide Fuel Cell: hereinafter) that has a simple structure and control, does not require a catalyst for a fuel cell, and is capable of reforming the fuel inside the fuel cell. , SOFC).
[0031]
The SOFC 3 includes three types of oxide electrolytes, ie, a fuel electrode 3a, an electrolyte 3b, and an air electrode 3c.
[0032]
An air pump 6 for sending air to the air electrode 3 c of the SOFC 3 is connected to the SOFC 3 via an air supply passage 7. The air pump 6 operates by receiving power supply from the battery 5 and discharges air.
[0033]
An exhaust side of a combustion device 9 is connected to an exhaust passage 2 between the SOFC 3 and the engine 1 via an introduction pipe 8. An air pump 6 is connected to an intake side of the combustion device 9 via an air supply passage 7. Further, the combustion device 9 includes a fuel injection valve 10 for injecting fuel into the combustion device 9. The fuel injection valve 10 is connected to a fuel pump 11 for pumping fuel. Further, the combustion device 9 is provided with a spark plug 12 that generates an electric spark according to a signal from the ECU.
[0034]
In the combustion device 9 configured as described above, the fuel is pumped from the fuel pump 11 to the fuel injection valve 10. When a drive current is applied to the fuel injection valve 10, the fuel injection valve 10 opens, and as a result, fuel is injected from the fuel injection valve 10 into the combustion device 9. This fuel forms an air-fuel mixture with the air supplied by the air pump 6. Then, when an electric spark is generated by the ignition plug 12, the mixture is ignited, and combustion is performed in the combustion device 9. Thereafter, by further supplying air and fuel to the burning gas, continuous burning using the burning gas as an ignition source becomes possible. The burned gas thus burnt is introduced into the exhaust passage 2 through the introduction pipe 8.
[0035]
In the present embodiment, the unburned air-fuel mixture can be directly discharged to the introduction pipe 8 without generating an electric spark in the ignition plug 12.
[0036]
In this way, the gas introduced into the exhaust passage 2 with or without combustion can be used as fuel for power generation of the SOFC 3.
[0037]
Here, the fuel for power generation introduced into the SOFC 3 reacts with water vapor on the fuel electrode 3a to generate hydrogen (H ₂ ) And carbon monoxide (CO). As described above, in the SOFC 3, it is possible to reform the fuel in the battery. On the other hand, air is supplied from the air pump 6 to the air electrode 3c. At the air electrode 3c, oxygen in the air dissociates at the interface with the electrolyte 3b and oxygen ions (O ^2- ), And moves to the fuel electrode 3a side in the electrolyte 3b. Oxygen ions (O 2) reaching the interface between the electrolyte 3 b and the fuel electrode 3 a ^2- ) Is hydrogen (H ₂ ) And carbon monoxide (CO) to form water (H ₂ O) and carbon dioxide (CO ₂ ). Power generation by the SOFC 3 is performed by extracting electrons emitted at this time. In this way, the chemical energy of the fuel is directly converted into electric energy, so that the loss due to the energy conversion is small and the power generation can be performed with high efficiency. Such power generation is performed, for example, at a temperature of 700 to 1000 ° C.
[0038]
An air-fuel ratio sensor 15 that outputs a signal corresponding to the air-fuel ratio of the exhaust gas and an exhaust temperature sensor 16 that outputs a signal corresponding to the temperature of the exhaust gas are mounted in the exhaust passage 2 downstream of the SOFC.
[0039]
Such an engine 1 is provided with an electronic control unit (ECU: Electronic Control Unit) 13 for controlling the engine 1. The ECU 13 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and a driver's request.
[0040]
Various sensors are connected to the ECU 13 via electric wiring, and output signals of the various sensors are input to the ECU 13. The ECU 13 is connected to an FC ECU 14 for controlling the SOFC 3.
[0041]
The SOFC 3 is operated by a signal from the FC ECU 14. Part of the power obtained by the power generation is temporarily stored in the battery 5. Auxiliary equipment 4 such as an electric water pump, an electric compressor for an air conditioner, an electric oil pump, and an electric pump for power steering are electrically connected to the battery 5, and power is supplied to these devices.
[0042]
By the way, in a conventional internal combustion engine having a fuel cell in an exhaust system, unburned fuel contained in exhaust gas of the internal combustion engine has been used as fuel for power generation of the fuel cell. Therefore, when a fuel cell requires a large amount of fuel for power generation, it is necessary to operate the internal combustion engine at a rich air-fuel ratio to discharge a large amount of unburned fuel.
[0043]
However, since a diesel engine is usually operated at a lean air-fuel ratio, the oxygen concentration in the exhaust gas is high, and it has been difficult to obtain required power.
[0044]
On the other hand, when attempting to supply fuel for power generation to the fuel cell and operating the internal combustion engine at a richer air-fuel ratio with more fuel than the air-fuel ratio during normal operation, torque fluctuations and emission deterioration may be induced. there were.
[0045]
Further, depending on the operating state of the internal combustion engine, it may be difficult to operate at an air-fuel ratio closer to rich, and in such a case, it has not been possible to secure required electric power.
[0046]
Conventionally, the main purpose has been to use an engine as a reformer for a fuel for generating electricity and to obtain an output from a fuel cell rather than an output from the engine. Along with this, the operating state of the engine has been changed in order to generate power with the fuel cell, so it was difficult to obtain sufficient power from the engine. However, when the engine and the fuel cell are compared, when the same mass or the same volume is used, the output obtained from the engine is larger than that of the fuel cell. Therefore, in consideration of mounting on a vehicle, it is more advantageous to mainly use the output from the engine in terms of mass, size, and the like.
[0047]
In this regard, in the present embodiment, the exhaust gas from the combustion device 9 can be introduced as fuel for power generation into the SOFC 3 without changing the operation state of the engine.
[0048]
The amount of fuel for power generation introduced into the SOFC 3 can be adjusted by the amount of fuel injected from the fuel injection valve 10. That is, assuming that the amount of air supplied from the air pump 6 is constant, the air-fuel ratio of the air-fuel mixture in the combustion device 9 is determined by the amount of fuel injected from the fuel injection valve 10. Here, in the present embodiment, the fuel injection valve 10 is intermittently opened, and the fuel injection valve 10 is supplied into the combustion device 9 by adjusting the valve opening time and the valve closing time at this time. The fuel amount is adjusted. That is, the longer the valve opening time and the shorter the valve closing time, the higher the fuel concentration in the air-fuel mixture. On the other hand, the shorter the valve opening time and the longer the valve closing time, the lower the fuel concentration in the air-fuel mixture. In addition, the amount of air supplied from the air pump 6 to the combustion device 9 per unit time can be obtained in advance by experiments or the like. Therefore, by adjusting the valve opening time of the fuel injection valve 10, the air-fuel ratio of the air-fuel mixture in the combustion device 9 can be adjusted.
[0049]
Then, the relationship between the target air-fuel ratio in the combustion device 9 and the valve opening or closing time of the fuel injection valve 10 is mapped in advance, and the target air-fuel ratio is substituted into the map to change the fuel injection valve 10. The valve opening time or the valve closing time can be obtained.
[0050]
Further, the relationship between the target power generation amount in the SOFC 3 and the valve opening or closing time of the fuel injection valve 10 is mapped in advance, and the target power generation amount is substituted into the map to open the fuel injection valve 10. The time or the valve closing time may be obtained.
[0051]
Here, when supplying the fuel to the SOFC 3, the air-fuel mixture in the combustion device 9 is burned at an air-fuel ratio (rich air-fuel ratio) with excess fuel. At this time, the remaining hydrocarbons (HC) are introduced into the SOFC 3 via the introduction pipe 8 and the exhaust passage 2. The HC supplied at this time is reformed due to high temperature in the combustion device 9 and easily reacts in the SOFC 3. Further, carbon monoxide (CO) generated during combustion at a rich air-fuel ratio also acts as fuel for the SOFC 3. Furthermore, if steam is present in the combustion device 9, when fuel is burned in the combustion device 9, hydrogen (H ₂ ) Occurs. This H ₂ Also act as fuel for the SOFC 3.
[0052]
In the present embodiment, when the fuel for power generation is supplied to the SOFC 3, the air-fuel mixture can be directly discharged from the combustion device 9 without burning. Thereby, the amount of fuel injected from the fuel injection valve 10 becomes equal to the amount of fuel supplied to the SOFC 3. In this manner, the fuel for power generation can be supplied by fuel injection from the fuel injection valve 10. If the required power generation amount and the valve opening time or valve closing time of the fuel injection valve 10 are obtained and mapped in advance, the required power generation amount can be changed by changing the valve opening time or valve time of the fuel injection valve 10. Can be generated.
[0053]
The power generation in the SOFC 3 is performed at a temperature of, for example, 700 to 1000 ° C., as described above. Therefore, when the temperature of the SOFC 3 is low, the temperature of the SOFC 3 needs to be increased. Here, since the combustion temperature of the diesel engine is low and the temperature of the exhaust gas is low, if it is attempted to raise the temperature of the SOFC 3 only by the exhaust gas from the engine 1, it takes a long time to reach the temperature at which power can be generated by the SOFC 3. . In this regard, in the present embodiment, since the high-temperature gas discharged as a result of burning the air-fuel mixture in the combustion device 9 can be supplied to the SOFC 3, the temperature of the SOFC 3 can be quickly increased. It becomes. Thereby, it becomes possible to start power generation from the cold state early. Here, when the main purpose is to increase the temperature of the SOFC 3, the combustion is performed such that the air-fuel mixture in the combustion device 9 becomes stoichiometric. By burning under such conditions, a relatively high-temperature gas can be generated, and this high-temperature gas can be supplied to the SOFC 3. Further, by burning with stoichiometry, the outflow of unburned components from the combustion device 9 can be suppressed.
[0054]
Further, since the exhaust gas from the engine 1 can also be introduced into the fuel electrode 3a, the temperature of the SOFC 3 can be increased by the temperature of the exhaust gas, and a part of the exhaust gas from the engine 1 is used as fuel for power generation. You can also.
[0055]
In the present embodiment, based on the output signal of the air-fuel ratio sensor 15 attached to the exhaust passage 2 downstream of the SOFC 3, the amount of fuel for power generation, that is, the opening time and closing time of the fuel injection valve 10, The valve time may be feedback controlled.
[0056]
That is, when the output signal of the air-fuel ratio sensor 15 is higher than the target air-fuel ratio, the valve opening time of the fuel injection valve 10 is lengthened or the valve closing time is shortened. If it is also low, the valve opening time of the fuel injection valve 10 is shortened or the valve closing time is lengthened.
[0057]
Similarly, in the present embodiment, the valve opening time and the valve closing time of the fuel injection valve 10 are feedback-controlled based on the output signal of the exhaust gas temperature sensor 16 attached to the exhaust passage 2 downstream of the SOFC 3. Is also good.
[0058]
That is, the exhaust temperature sensor 16 can determine whether the SOFC 3 has risen to a temperature at which power can be generated. Until the temperature of the SOFC 3 rises to a temperature at which power can be generated, the stoichiometric mixture is burned in the combustion device 9 to raise the temperature of the SOFC 3. Then, after the temperature of the SOFC 3 has risen to a temperature at which power can be generated, the combustion device 9 burns the air-fuel mixture having a rich air-fuel ratio, and the SOFC 3 generates power.
[0059]
Thereby, the temperature of the SOFC 3 can be set to a temperature at which power generation efficiency is good, and a decrease in power generation efficiency can be suppressed. Further, at the time of the cold start of the SOFC 3, the temperature can be quickly raised to a temperature at which power can be generated.
[0060]
As described above, according to the present embodiment, fuel can be supplied to SOFC 3 regardless of the operating state of engine 1. Further, the temperature of the SOFC 3 can be quickly raised, and power generation can be started at an early stage. Feedback control by the air-fuel ratio sensor 15 and the exhaust gas temperature sensor 16 can be performed on the supply amount of the fuel for power generation and the temperature of the SOFC 3, respectively.
<Second embodiment>
The present embodiment is different from the first embodiment in that an oxidation catalyst 17 is provided in the exhaust passage 2 between the introduction pipe 8 and the SOFC 3. In the present embodiment, the basic configuration of the engine and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0061]
FIG. 2 is a diagram showing a schematic configuration of the engine 1 and the intake / exhaust system thereof according to the present embodiment.
[0062]
By supplying the unburned fuel component from the combustion device 9 to the oxidation catalyst 17, the unburned fuel reacts on the oxidation catalyst 17 and generates reaction heat. Due to this heat, the temperature of the exhaust gas rises, and the temperature of the SOFC 3 into which the exhaust gas flows rises. Thus, even when the temperature of the SOFC 3 is low, the temperature can be quickly increased. Further, a part of the unburned fuel is reformed by the oxidation catalyst 17, and the reformed fuel can be supplied to the SOFC 3. Since the reformed fuel easily reacts at the fuel electrode 3a, the power generation efficiency can be improved. Further, since oxygen reacts in the oxidation catalyst 17, the oxygen concentration in the exhaust gas can be reduced, and the power generation efficiency of the SOFC 3 can be improved.
[0063]
In the present embodiment, the unburned fuel component discharged from the combustion device 9 may be obtained by burning an air-fuel mixture, and the fuel injected from the fuel injection valve 10 is not burned. It may be obtained by discharging as it is.
[0064]
When the engine 1 is operated at a rich air-fuel ratio, the combustion device 9 may burn fuel at a lean air-fuel ratio. Thus, oxygen may be supplied to the oxidation catalyst 18 to oxidize unburned fuel from the engine 1 and adjust the amount of unburned components flowing into the SOFC 3.
[0065]
In order to raise the temperature of the oxidation catalyst 17 at an early stage, it is preferable to employ a small catalyst.
<Third embodiment>
The present embodiment is different from the second embodiment in that an oxidation catalyst 18 is provided in the exhaust passage 2 downstream of the SOFC 3. In the present embodiment, the basic configuration of the engine and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0066]
FIG. 3 is a diagram showing a schematic configuration of the engine 1 and the intake / exhaust system thereof according to the present embodiment.
[0067]
Here, when the air-fuel ratio sensor 15 or the exhaust gas temperature sensor 16 is attached to the exhaust passage 2, components in the exhaust gas change in the oxidation catalyst 18 and affect the sensor output. 18 is provided.
[0068]
Here, not all of the supplied power generation fuel reacts in the SOFC 3, and some fuel passes without reacting in the SOFC 3. If this fuel is released into the atmosphere, emission performance will deteriorate. In this regard, in the present embodiment, by providing the oxidation catalyst 18 downstream of the SOFC 3, the fuel for power generation discharged without reacting in the SOFC 3 can be oxidized and purified.
[0069]
Further, since the oxidation catalyst 18 is provided downstream of the SOFC 3, it is maintained at a high temperature by the heat from the SOFC 3, and can perform stable exhaust gas purification.
<Fourth embodiment>
The present embodiment is different from the third embodiment in that a gas (cathode off-gas) discharged from the air electrode side is introduced into the oxidation catalyst 18. In the present embodiment, the basic configuration of the engine and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0070]
FIG. 4 is a diagram showing a schematic configuration of the engine 1 and the intake / exhaust system thereof according to the present embodiment.
[0071]
In the present embodiment, the outlet side of the air electrode 3c and the upstream of the oxidation catalyst downstream of the SOFC 3 are connected by an air introduction pipe 19, and exhaust gas from the air electrode 3c is introduced into the oxidation catalyst. Here, when the air-fuel ratio sensor 15 or the exhaust gas temperature sensor 16 is attached to the exhaust passage 2, the components in the exhaust gas change in the oxidation catalyst 18 and affect the sensor output. The tube 19 is connected.
[0072]
Here, the oxygen concentration of the exhaust gas from the fuel electrode 3a may be low depending on the operation state of the engine 1 and the power generation state of the SOFC 3. As described above, when the oxygen concentration is low, the oxidizing ability of the oxidation catalyst 18 becomes low, and it may be difficult to oxidize the unburned fuel. In such a case, if an attempt is made to supply oxygen to the oxidation catalyst 18 by changing the operating state of the engine 1 or the operating state of the SOFC 3, the required torque may not be obtained from the engine 1. It may not be possible to achieve this.
[0073]
In this regard, according to the present embodiment, oxygen contained in exhaust gas from air electrode 3c can be introduced into oxidation catalyst 18, and deterioration of emission performance due to lack of oxygen in oxidation catalyst 18 can be suppressed. it can. Further, oxygen can be supplied to the oxidation catalyst 18 regardless of the operating states of the engine 1 and the SOFC 3.
[0074]
In the present embodiment, air supplied by the air pump 6 may be introduced into the oxidation catalyst 18.
<Fifth embodiment>
The present embodiment is different from the fourth embodiment in that a heat exchanger 20 is provided downstream of the oxidation catalyst 18. In the present embodiment, the basic configuration of the engine and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0075]
FIG. 5 is a diagram showing a schematic configuration of the engine 1 and the intake / exhaust system thereof according to the present embodiment.
[0076]
A heat exchanger 20 is provided in the exhaust passage 2 downstream of the oxidation catalyst 18. Further, a bypass 21 for bypassing the heat exchanger 20 and flowing exhaust gas is connected to the upstream side and the downstream side of the heat exchanger 20. At a connection portion where the bypass passage 21 is connected to the exhaust passage 2 on the downstream side of the heat exchanger 20, a three-way valve 22 for selecting either the bypass passage 21 or the heat exchanger 20 and flowing exhaust gas is provided. I have.
[0077]
A cooling water passage 23 through which cooling water circulates is connected to the heat exchanger 20, and the cooling water passage 23 is connected to the heater core 24 and the engine 1.
[0078]
Here, the operating temperature of the SOFC 3 is high, and a high-temperature gas is discharged from the fuel electrode 3a. Therefore, while the SOFC 3 is generating power, even if the temperature of the exhaust gas discharged from the engine 1 is low, the temperature of the SOFC 3 is increased and the temperature of the exhaust gas downstream of the SOFC 3 is increased. Further, even when the temperature of the exhaust gas from the engine 1 is high, the heat from the engine 1 can be recovered because the heat exchanger 20 is provided in the exhaust passage 2. Further, since the heat of the exhaust gas from the engine 1 and the SOFC 3 can be recovered by the single heat exchanger 20, the mountability on the vehicle can be improved. Furthermore, since high-temperature exhaust gas can flow through the heat exchanger 20, a sufficient effect can be obtained even if the heat exchanger 20 is downsized.
[0079]
In the present embodiment, the cooling water of the engine 1 is circulated through the heat exchanger 20, and heat exchange is performed between the high-temperature exhaust gas and the cooling water to increase the temperature of the cooling water. When the high-temperature exhaust gas is introduced into the heat exchanger 20, the temperature of the cooling water is increased in the heat exchanger 20. Heating performance can be improved by flowing the cooling water whose temperature has increased through the cooling water passage 23 to the heater core 24. Further, when the temperature of the engine 1 is low, for example, at the time of starting the engine 1, by circulating high-temperature cooling water through the engine 1, the engine 1 can be warmed up early.
[0080]
If the temperature of the cooling water is too high, the engine 1 cannot be sufficiently cooled and so-called overheating occurs. Therefore, the three-way valve 22 is driven before the temperature of the cooling water becomes too high, and Allow the exhaust to flow. When the exhaust gas temperature sensor 16 is provided, the exhaust gas is allowed to flow through the bypass passage 21 when the temperature of the exhaust gas detected by the exhaust gas temperature sensor 16 is higher than a predetermined temperature. May be.
<Sixth Embodiment>
The present embodiment is different from the fifth embodiment in that the heat exchange between the exhaust gas and the air is performed in the heat exchanger 20. In the present embodiment, the basic configuration of the engine and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0081]
FIG. 6 is a diagram showing a schematic configuration of the engine 1 and the intake / exhaust system thereof according to the present embodiment.
[0082]
A heat exchanger 20 is provided in the exhaust passage 2 downstream of the oxidation catalyst 18. Further, a bypass 21 for bypassing the heat exchanger 20 and flowing exhaust gas is connected to the upstream side and the downstream side of the heat exchanger 20. At a connection portion where the bypass passage 21 is connected to the exhaust passage 2 on the downstream side of the heat exchanger 20, a three-way valve 22 for selecting either the bypass passage 21 or the heat exchanger 20 and flowing exhaust gas is provided. I have.
[0083]
The inlet side of the heat exchanger 20 is connected to the air pump 6 via the air supply passage 7. On the other hand, the outlet side of the heat exchanger 20 is connected to the inlet side of the air electrode 3 c of the fuel cell 3 via the air supply passage 7. The air supply passage 7 connected to the outlet side of the heat exchanger 20 branches off in the middle and is connected to the combustion device 9 via the heat exchanger 25.
[0084]
Here, the operating temperature of the SOFC 3 is high, and a high-temperature gas is discharged from the fuel electrode 3a side. Therefore, while the SOFC 3 is generating power, even if the temperature of the exhaust gas discharged from the engine 1 is low, the temperature of the SOFC 3 is increased and the temperature of the exhaust gas downstream of the SOFC 3 is increased. In the present embodiment, heat exchange is performed between the high-temperature exhaust gas and the air discharged from the air pump 6 to increase the temperature of the air supplied to the SOFC 3 and the combustion device 9.
[0085]
With such a configuration, when high-temperature exhaust gas is introduced into the heat exchanger 20, the temperature of the air is increased in the heat exchanger 20. By introducing the air with the increased temperature into the air electrode 3c of the SOFC 3, air can be supplied while suppressing the temperature decrease of the SOFC 3, and as a result, the power generation efficiency can be improved.
[0086]
Further, by supplying high-temperature air to the combustion device 9, the evaporation of the fuel in the combustion device 9 is promoted, and the combustion state in the combustion device 9 can be stabilized. By the way, if the temperature of the air supplied to the combustion device 9 is too high, the oxygen concentration will decrease. In this regard, in the present embodiment, heat is exchanged between the high-temperature air and the cooling water in the heat exchanger 25, and the temperature of the air is reduced and then supplied to the combustion device 9. Thereby, the combustion state in the combustion device 9 can be stabilized. When the air-fuel mixture is discharged without being burned by the combustion device 9, the fuel can be evaporated and easily reacted by the SOFC 3.
[0087]
【The invention's effect】
In the internal combustion engine having a fuel cell in the exhaust system according to the present invention, fuel for power generation can be supplied to the fuel cell regardless of the operating state of the internal combustion engine. In addition, the amount of fuel for power generation to be supplied to the fuel cell can be increased or decreased regardless of the operation state of the internal combustion engine, and an amount of fuel corresponding to the required power generation amount can be supplied. Furthermore, by introducing exhaust gas from the combustion device to the fuel cell, the temperature of the fuel cell can be quickly raised, and power generation can be started at an early stage.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a first embodiment.
FIG. 2 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a second embodiment.
FIG. 3 is a view showing a schematic configuration of an engine and an intake / exhaust system thereof according to a third embodiment.
FIG. 4 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a fourth embodiment.
FIG. 5 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a fifth embodiment.
FIG. 6 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a sixth embodiment.
[Explanation of symbols]
1 engine
2 Exhaust passage
3 Fuel cell
3a Fuel electrode
3b electrolyte
3c air electrode
4 Auxiliary equipment
5 Battery
6 air pump
7 Air supply passage
8 Introduction pipe
9 Combustion device
10 Fuel injection valve
11 Fuel pump
12 Spark plug
13 ECU
14 FC ECU
15 Air-fuel ratio sensor
16 Exhaust gas temperature sensor
17 Oxidation catalyst
18 oxidation catalyst
19 Air inlet pipe
20 heat exchanger
21 Detour passage
22 Three-way valve
23 Cooling water passage
24 heater core
25 heat exchanger

Claims (10)

A fuel cell having a fuel electrode connected to an exhaust passage of an internal combustion engine,
Fuel supply means for supplying fuel for power generation of the fuel cell into an exhaust passage downstream of the internal combustion engine and upstream of the fuel cell;
Supply amount control means for controlling the supply amount of fuel by the fuel supply means,
An internal combustion engine having a fuel cell in an exhaust system, comprising: The internal combustion engine having a fuel cell in an exhaust system according to claim 1, wherein the supply amount control means controls an amount of fuel for power generation based on a power generation target value of the fuel cell. The fuel cell system according to claim 1, further comprising a fuel amount detecting means for detecting an amount of fuel contributing to the power generation of the fuel cell, wherein the fuel for power generation supplied to the fuel cell is controlled based on a detection result of the fuel amount detecting means. Item 3. An internal combustion engine having a fuel cell in the exhaust system according to Item 2. 3. The fuel cell according to claim 2, further comprising a temperature detecting unit configured to detect a state of an element related to a temperature of the fuel cell, and controlling a power generation fuel supplied to the fuel cell based on a detection result of the temperature detecting unit. 4. An internal combustion engine having a fuel cell in the exhaust system according to 3. The internal combustion engine having a fuel cell in an exhaust system according to any one of claims 1 to 4, further comprising a combustion device, wherein the fuel supply unit supplies exhaust gas from the combustion device to an exhaust passage. The fuel supply system according to claim 5, wherein the supply amount control means controls a fuel supply amount to the fuel cell by changing an air-fuel ratio of gas burned by the combustion device. Having an internal combustion engine. The internal combustion engine having a fuel cell in an exhaust system according to any one of claims 1 to 6, further comprising an oxidizing catalyst in an exhaust passage upstream of the fuel cell and downstream of the fuel supply means. . The internal combustion engine having a fuel cell in an exhaust system according to any one of claims 1 to 7, further comprising a catalyst having an oxidizing ability in an exhaust passage downstream of the fuel cell. 9. The internal combustion engine having a fuel cell in an exhaust system according to claim 8, further comprising oxygen supply means for supplying oxygen to the catalyst having oxidizing ability. 10. The internal combustion engine having a fuel cell in an exhaust system according to claim 1, wherein a heat exchanger is provided in an exhaust passage downstream of the fuel cell.

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