US20040177607A1 - Internal combustion engine with a fuel cell in an exhaust system - Google Patents

Abstract

In an internal combustion engine with a fuel cell in an exhaust system, fuel for power generation is able to be supplied to the fuel cell without regard to the operating condition of the internal combustion engine. The fuel cell has a fuel electrode side thereof connected with an exhaust passage of the engine. A fuel supply system supplies the power generation fuel to the exhaust passage at a location downstream of the engine and upstream of the fuel cell. A supply amount control part controls an amount of the power generation fuel supplied by the fuel supply system. According to such a construction, the power generation fuel can be supplied to the fuel cell by the fuel supply system so as to generate electricity without depending on the operating condition of the engine.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0001]
• The present invention relates to an internal combustion engine with a fuel cell in an exhaust system.[0002]
• 2. Description of the Related Art[0003]
• There has hitherto been known a technology in which a fuel cell is arranged in an exhaust system of an internal combustion engine so that unburnt components of fuel discharged from the internal combustion engine, which is caused to operate in a state of excessive fuel, are supplied, as fuel for electric power generation, to a fuel electrode side of the fuel cell (for example, see a first patent document: Japanese patent application laid-open No. 2002-175824 (pages 4-7 and FIG. 1)).[0004]
• However, it might sometimes be difficult to operate the internal combustion engine in the state of excessive fuel depending upon the operating condition of the internal combustion engine, and in this case, fuel cannot be supplied to the fuel cell. In addition, in such a case, when power generation of the fuel cell is given priority so as to cause the internal combustion engine to operate in the state of excessive fuel, the operating state of the internal combustion engine is deteriorated, thus giving rise to a fear that torque fluctuation and/or deterioration of emissions might be induced.[0005]
SUMMARY OF THE INVENTION
• Accordingly, the present invention has been made in view of the problems as referred to above, and has for its object to provide a technology in which in an internal combustion engine with a fuel cell in an exhaust system, fuel for power generation is able to be supplied to the fuel cell without regard to the operating condition of the internal combustion engine.[0006]
• In order to achieve the above object, according to one aspect of the present invention, there is provided an internal combustion engine with a fuel cell in an exhaust system, the engine comprising: a fuel cell having a fuel electrode side thereof connected with an exhaust passage of the internal combustion engine; a fuel supply system that supplies power generation fuel for the fuel cell to an exhaust passage at a location downstream of the internal combustion engine and upstream of the fuel cell; and a supply amount control part that controls an amount of power generation fuel supplied by the fuel supply system.[0007]
• The major feature of the present invention is that by the provision of the fuel supply system that supplies the power generation fuel to an intermediate portion of the exhaust passage, the power generation fuel can be supplied to the fuel cell without regard to the operating condition of the internal combustion engine.[0008]
• In the internal combustion engine with the fuel cell in the exhaust system as constructed in this manner, by the provision of the fuel supply system, the power generation fuel can be supplied to a fuel electrode side of the fuel cell without regard to the operating condition of the internal combustion engine. In addition, since the amount of supply of the power generation fuel is controlled by the supply amount control part, an appropriate amount of power generation fuel can be supplied to the fuel cell without regard to the operating condition of the internal combustion engine. On the other hand, the internal combustion engine can be caused to operate without regard to the state of power generation in the fuel cell, whereby torque fluctuation and the deterioration of emissions due to the deterioration of the operating state of the internal combustion engine can be suppressed.[0009]
• Preferably, the supply amount control part may control the amount of power generation fuel supplied by the fuel supply system in such a manner that an amount of electric power generation of the fuel cell becomes equal to a target amount of electric power generation. With this arrangement, it is possible to supply the power generation fuel to the fuel cell without regard to the operating condition of the internal combustion engine, as a result of which the amount of supply of the power generation fuel can be controlled based on the target amount of electric power generation of the fuel cell. Thus, an optimal amount of power generation fuel can be supplied to the fuel cell so as to achieve the target amount of electric power generation thereof.[0010]
• Preferably, the internal combustion engine may further comprise a fuel amount detection device that detects an amount of power generation fuel contributing to the power generation of the fuel cell, wherein the supply amount control part controls the amount of power generation fuel supplied by the fuel supply system based on the result of detection of the fuel amount detection device.[0011]
• Thus, the amount of supply of the power generation fuel can be controlled in a feedback manner based on the amount of power generation fuel actually detected that contributes to the power generation of the fuel cell, as a consequence of which an optimal amount of power generation fuel can be supplied to the fuel cell so as to achieve the target amount of electric power generation thereof.[0012]
• In the above control, for example, when the amount of power generation fuel contributing to the power generation of the fuel cell detected by the fuel amount detection device is smaller than a target amount, the supply amount control part increases the amount of power generation fuel supplied by the fuel supply system. On the other hand, when the amount of power generation fuel contributing to the power generation of the fuel cell detected by the fuel amount detection device is larger than the target amount, the supply amount control part may decrease the amount of power generation fuel supplied by said fuel supply system.[0013]
• Preferably, the internal combustion engine may further comprise a temperature detection device that detects a state of an element related to the temperature of the fuel cell, wherein the supply amount control part controls the amount of power generation fuel supplied by the fuel supply system based on the result of detection of the temperature detection device.[0014]
• The fuel cell has a suitable temperature for power generation, so it is possible to perform efficient power generation by supplying the power generation fuel when the fuel cell is at such a suitable temperature. In addition, when the temperature of the fuel cell is low, the amount of supply of the power generation fuel may be decreased. That is, when the temperature of the fuel cell is lower than a prescribed temperature, the supply amount control part may decrease the amount of power generation fuel supplied by the fuel supply system. Here, the prescribed temperature may be a suitable temperature for power generation. Thus, it is possible to suppress the power generation fuel exhausted from the fuel cell without contributing to power generation.[0015]
• Preferably, the internal combustion engine may further comprise a combustion device, wherein the fuel supply system supplies an exhaust gas discharged from the combustion device to the exhaust passage at a location downstream of the internal combustion engine and upstream of the fuel cell.[0016]
• By supplying the exhaust gas (burnt gas) from the combustion device to an intermediate portion of the exhaust passage, the burnt gas can be supplied to the fuel cell. Thus, by supplying the burnt gas from the combustion device to the fuel cell, the temperature of the fuel cell can be raised. Accordingly, even if the temperature of the exhaust gas discharged from the engine and the temperature of the fuel cell are low such as at the time of engine starting or the like, the fuel cell is able to start power generation at an earlier stage. Preferably, the exhaust gas (burnt gas) discharged from the combustion device may be supplied to the exhaust passage at a location downstream of the internal combustion engine and upstream of the fuel cell, while combustion in the combustion device is being performed in the state of an air fuel mixture containing excessive fuel (i.e., in a fuel rich state). By supplying the burnt gas to the fuel cell, the unburnt fuel in the combustion device can be supplied as the power generation fuel for the fuel cell. Preferably, the fuel supply system may supply an unburnt gas discharged from the combustion device to the exhaust passage at a location downstream of the internal combustion engine and upstream of the fuel cell, without combusting fuel in the combustion device. With such a construction, the unburnt fuel in the combustion device can also be supplied as the power generation fuel for the fuel cell.[0017]
• Preferably, the supply amount control part may control the amount of power generation fuel supplied by the fuel supply system by changing an air fuel ratio of a gas combusted in the combustion device.[0018]
• The amount of unburnt fuel contained in the burnt gas from the combustion device changes when the air fuel ratio of the gas combusted in the combustion device is changed. Thus, it is possible to change the amount of power generation fuel supplied to the fuel cell by changing the air fuel ratio of the mixture in the combustion device. As a result, the power generation fuel can be supplied in accordance with the target amount of electric power generation of the fuel cell.[0019]
• In cases where the main purpose is to raise the temperature of the fuel cell such as when the temperature of the fuel cell is lower than a prescribed temperature at which the fuel cell is able to generate electric power, it is desirable to make the air fuel ratio of the gas combusted in the combustion device to be a value in the vicinity of the stoichiometric air fuel ratio. With this measure, a gas of a relatively high temperature can be generated, so that the gas of such a high temperature (burnt gas) can be supplied to the fuel cell. In addition, it is possible to suppress the unburnt fuel exhausted from the combustion device.[0020]
• Preferably, the internal combustion engine may further comprise a catalyst having oxidation capability that is installed on the exhaust passage at a location upstream of the fuel cell and downstream of the fuel supply system.[0021]
• By this catalyst, the unburnt fuel from the internal combustion engine and/or the power generation fuel from the fuel supply system can be oxidized, so that the temperature of the fuel cell at the downstream side of the engine and fuel supply system can be raised by the heat of reactions at that time. Accordingly, even if the temperature of the exhaust gas discharged from the engine and the temperature of the fuel cell are low at the time of engine starting or the like, the fuel cell is able to start power generation at an earlier stage. Moreover, the unburnt fuel from the internal combustion engine and the power generation fuel from the fuel supply system react with oxygen in the catalyst to decrease the oxygen concentration of the exhaust gas, so that the amount of electric power generation of the fuel cell can be increased. Further, since the power generation fuel is reformed, it is possible to make the power generation fuel react easily in the fuel cell, as a result of which the electrical efficiency of the fuel cell can be improved.[0022]
• In case where a catalyst having oxidation capability is installed on the exhaust passage at a location upstream of the fuel cell and downstream of the fuel supply system, when the internal combustion engine is operated with a mixture of a rich air fuel ratio, the amount of power generation fuel supplied by the fuel supply system may be adjusted by making the air fuel ratio of the gas combusted in the combustion device to be a lean air fuel ratio.[0023]
• Oxygen is supplied to the catalyst having oxidation capability by combusting the mixture of a lean air fuel ratio in the combustion device. By supplying oxygen in this manner, the unburnt fuel from the internal combustion engine can be oxidized, thus making it possible to adjust the amount of power generation fuel supplied to the fuel cell.[0024]
• Preferably, the internal combustion engine may further comprise a catalyst having oxidation capability that is installed on the exhaust passage at a location downstream of the fuel cell.[0025]
• With this catalyst, it becomes possible to oxidize the power generation fuel exhausted from the fuel cell without contributing to power generation, whereby the power generation fuel can be suppressed from being discharged into the ambient atmosphere.[0026]
• Preferably, in case where a catalyst having oxidation capability is installed on the exhaust passage at a location downstream of the fuel cell, the internal combustion engine may further comprise an oxygen supply device that supplies oxygen to the catalyst having oxidation capability.[0027]
• In the case of the catalyst having oxidation ability, the higher the oxygen concentration of the exhaust gas passing through the catalyst, the higher does the oxidation capability of the catalyst becomes, and hence the oxidation capability of the catalyst can be improved by supplying oxygen to the catalyst. In this case, the oxygen discharged from an air electrode side of the fuel cell may be supplied to the catalyst.[0028]
• Preferably, the internal combustion engine may further comprise a heat exchanger installed on the exhaust passage at a location downstream of the fuel cell.[0029]
• The temperature of the gas exhausted from the fuel electrode side of the fuel cell operating at high temperature is high, so the heat of this gas can be collected by the heat exchanger. As a result, the system efficiency of the entire internal combustion engine can be improved. For example, by raising the temperature of cooling water for the internal combustion engine by use of the heat collected by the heat exchanger, the warming up of the internal combustion engine can be facilitated.[0030]
• Preferably, the internal combustion engine may further comprise an air supply passage that has the heat exchanger installed thereon and is connected with an inlet side of an air electrode of the fuel cell, wherein air whose temperature is raised due to the heat of an exhaust gas in the heat exchanger is supplied into the air electrode of the fuel cell through the air supply passage.[0031]
• Thus, air can be supplied to the fuel cell while suppressing a temperature drop thereof, as a result of which the electrical efficiency of the fuel cell can be improved.[0032]
• Preferably, an air supply passage with the heat exchanger installed thereon may be connected with the combustion device, so that air whose temperature is raised in the heat exchanger can be supplied into the combustion device through the air supply passage. With such an arrangement, the evaporation of the fuel in the combustion device can be facilitated with the result that the combustion state of the mixture in the combustion device can be stabilized.[0033]
• The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.[0034]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a first embodiment of the present invention.[0035]
• FIG. 2 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a second embodiment of the present invention.[0036]
• FIG. 3 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a third embodiment of the present invention.[0037]
• FIG. 4 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a fourth embodiment of the present invention.[0038]
• FIG. 5 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a fifth embodiment of the present invention.[0039]
• FIG. 6 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a sixth embodiment of the present invention.[0040]
• FIG. 7 is a view showing the flow of signals around an ECU according to the first embodiment of the present invention.[0041]
• FIG. 8 is a view showing the schematic construction of an internal combustion engine with intake and exhaust systems according to a seventh embodiment of the present invention.[0042]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Hereinafter, preferred embodiments of according to the present invention will be described while referring to the accompanying drawing. Here, reference will be made to the case where an internal combustion engine with a fuel cell according to the present invention is applied to a diesel engine used for driving a vehicle.[0043]
• <First Embodiment>[0044]
• FIG. 1 is a view that shows the schematic construction of an internal combustion engine with intake and exhaust systems according to a first embodiment of the present invention. The internal combustion engine (hereinafter also referred to simply as engine), generally designated at[0045]1 in FIG. 1, is a water-cooled four-cycle diesel engine. Connected with theengine1 is anexhaust passage2 for discharging an exhaust gas exhausted from theengine1 into the ambient atmosphere. Afuel cell3 is installed on a intermediate portion of theexhaust passage2. Thisfuel cell3 is electrically connected toaccessories4 through abattery5 for supplying electric power to theaccessories4. Here, note that in this embodiment, a solid oxide fuel cell, which is simple in structure and control and does require no catalyst for the fuel cell, and in which fuel can be reformed inside the fuel cell, is adopted as the fuel cell (hereinafter referred to as SOFC)3.
• The[0046]SOFC3 is constructed such that it includes three kinds of oxide electrolytes, i.e., a fuel electrode3a, anelectrolyte3b, and anair electrode3c.
• In addition, an[0047]air pump6 for sending air to theair electrode3cof theSOFC3 is connected with theSOFC3 through anair supply passage7. Theair pump6 receives electric power from thebattery5, and is thereby operated to discharge air to theair supply passage7.
• A[0048]combustion device9 is connected at its exhaust side with theexhaust passage2 at a location between theSOFC3 and theengine1 through anintroduction passage8. Theair pump6 is connected with an intake side of thecombustion device9 through theair supply passage7. Moreover, thecombustion device9 is provided with afuel injection valve10 for injecting fuel into thecombustion device9. Thefuel injection valve10 is connected to afuel pump11 which serves to feed fuel under pressure to thefuel injection valve10. In addition, thecombustion device9 is also provided with aspark plug12 for generating an electric spark based on a signal from an electronic control unit (ECU)13 to be described later.
• In the[0049]combustion device9 constructed in this manner, fuel is pressure fed from thefuel pump11 to thefuel injection valve10, so that it is injected from thefuel injection valve10 into thecombustion device9. The fuel thus injected mixes with air supplied from theair pump6 to thecombustion device9 to form an air fuel mixture therein. When an electric spark is generated by thespark plug12, the air fuel mixture is thereby ignited or fired to burn or combust in thecombustion device9. Thereafter, by means of air and fuel being further supplied into the gas (i.e., air fuel mixture) under combustion, the combustion can be made continuously with the gas under combustion acting as an ignition source. The burnt gas thus produced by combustion is introduced into theexhaust passage2 through theintroduction passage8.
• Here, note that in this embodiment, an electric spark may not be generated by the[0050]spark plug12, so that the air fuel mixture being unburnt can be discharged to theintroduction passage8 as it is.
• The gas introduced into the[0051]exhaust passage2 while being burnt or unburnt can be used as power generation fuel of theSOFC3.
• Here, the power generation fuel thus introduced into the[0052]SOFC3 reacts with steam or water vapor on the fuel electrode3a, so that it is reformed into hydrogen (H₂) and carbon monoxide (CO). Thus, in theSOFC3, it is possible to reform the power generation fuel therein. On the other hand, air is supplied from theair pump6 to theair electrode3c. In theair electrode3c, the atmospheric oxygen dissociates into oxygen ions (O²⁻) on an interface with theelectrolyte3b, and the oxygen ions (O²⁻) thus generated move toward the fuel electrode3aside in theelectrolyte3b. The oxygen ions (O²⁻) having arrived at an interface between theelectrolyte3band the fuel electrode3areact with hydrogen (H₂) and carbon monoxide (CO) to generate water (H₂O) and carbon dioxide (CO₂). The power generation of theSOFC3 is performed by taking out electrons discharged at this time. Thus, according to theSOFC3, the chemical energy of the power generation fuel is converted directly into electrical energy, so a loss due to the energy conversion is small, making it possible to generate electric power at high efficiency. Such power generation in theSOFC3 is performed at temperatures from 700 to 1,000° C., for example.
• Installed on the[0053]exhaust passage2 at the downstream side of theSOFC3 are an airfuel ratio sensor15 that outputs a signal corresponding to the air fuel ratio of the exhaust gas, and an exhaustgas temperature sensor16 that outputs a signal corresponding to the temperature of the exhaust gas.
• The[0054]ECU13 for controlling theengine1 is provided in conjunction with theengine1 as constructed above. TheECU13 controls the operating state of theengine1 according to the operating condition of theengine1 and the driver's request.
• A variety of kinds of sensors such as ones mentioned above are connected to the[0055]ECU13 through electric wiring, so that the output signals of the various sensors are input to theECU13. Also, thefuel injection valve10, thespark plug12 and thefuel pump11 are connected to theECU13 through electric wiring, so that the operations of these members are controlled by theECU13. For example, when a drive current is applied to thefuel injection valve10 under the control of a signal from theECU13, thefuel injection valve10 is driven to open, as a result of which fuel is injected from thefuel injection valve10 into thecombustion device9. In addition, an fuel cell ECU (hereinafter referred to as FC ECU)14 for controlling theSOFC3 is connected to theECU13, so that theSOFC3 is driven to operate under the control of a signal from theFC ECU14.
• A part of electric power provided by the power generation of the[0056]SOFC3 is once accumulated in thebattery5. Theaccessories4 such as an electric water pump, an electric compressor for use with an air conditioner, an electric oil pump, an electric pump for power steering and the like are electrically connected to thebattery5, so that electric power is supplied from thebattery5 to these accessories.
• However, in a conventional internal combustion engine with a fuel cell in an exhaust system, the unburnt fuel contained in the exhaust gas exhausted from the internal combustion engine has been used as power generation fuel of the fuel cell. Accordingly, when the fuel cell needs a large amount of power generation fuel, it is necessary to exhaust a larger amount of unburnt fuel from the internal combustion engine by making the internal combustion engine operate with a mixture of a rich air fuel ratio.[0057]
• However, for example, a conventional diesel engine is ordinarily operated with a mixture of a lean air fuel ratio, so the oxygen concentration of the exhaust gas is high and the amount of unburnt fuel is limited, thus making it difficult to obtain a necessary amount of electric power.[0058]
• Moreover, when an internal combustion engine has been operated at a rich-side air fuel ratio, in which the amount of fuel is more than that at the air fuel ratio at the time of ordinary operation, in order to supply the power generation fuel to the fuel cell, torque fluctuation and/or the deterioration of emissions has occasionally been induced.[0059]
• In addition, it might be difficult to operate the internal combustion engine at a rich-side air fuel ratio depending upon the operating condition of the internal combustion engine, and in such a case, it was impossible to secure required electric power.[0060]
• In the past, the main purpose was to use an internal combustion engine as a reformer for power generation fuel to obtain an output from a fuel cell in preference to obtaining an output from the internal combustion engine. Accordingly, the operating condition of the internal combustion engine had been changed so as to generate electricity with the fuel cell, and hence it was difficult to obtain enough power from the internal combustion engine. However, when a comparison is made between the internal combustion engine and the fuel cell with the same mass or the same volume, the output obtained from the internal combustion engine is greater than that obtained from the fuel cell. Therefore, considering the installation of the fuel cell on a vehicle, it is advantageous to mainly use the output from the internal combustion engine for the driving power of the vehicle from the point of view of the mass, size, etc.[0061]
• In this respect, according to this embodiment, the exhaust gas (i.e., burnt gas) discharged from the[0062]combustion device9 can be supplied to theSOFC3 as power generation fuel without changing the operating condition of theengine1.
• Further, in this embodiment, it is possible to adjust the amount of power generation fuel supplied to the[0063]SOFC3 by means of the amount of fuel injected from thefuel injection valve10 into thecombustion device9. That is, assuming that the amount of air supplied from theair pump6 is constant, the air fuel ratio of the mixture in thecombustion device9 is decided by the amount of fuel injected from thefuel injection valve10. Here, note that in this embodiment, thefuel injection valve10 is driven to open intermittently under the control of theECU13, so that the amount of fuel supplied to thecombustion device9 is controlled by adjusting the valve open time and the valve closure time of thefuel injection valve10 at this time. That is, the longer the valve open time of thefuel injection valve10, and the shorter the valve closure time thereof, the greater does the amount of fuel supplied to thecombustion device9 become. On the other hand, the shorter the valve open time of thefuel injection valve10, and the longer the valve closure time thereof, the smaller does the amount of fuel supplied to thecombustion device9 become. In addition, the amount of air supplied per unit time from theair pump6 to thecombustion device9 can be obtained beforehand by experiments or the like. Accordingly, the air fuel ratio of the mixture in thecombustion device9 can be controlled by adjusting the valve open time of thefuel injection valve10.
• In view of the above, the relation between the target air fuel ratio that is an air fuel ratio to be targeted or attained in the air fuel mixture in the[0064]combustion device9 and the valve open time and the valve closure time of thefuel injection valve10 is mapped beforehand, and the valve open time and the valve closure time of thefuel injection valve10 may be determined by substituting a desired target value for the target air fuel ratio in the map.
• Moreover, the relation between the target amount of electric power generation that is an amount of electric power generation to be targeted or obtained in the[0065]SOFC3 and the valve open time and the valve closure time of thefuel injection valve10 is mapped beforehand. The valve open time and the valve closure time of thefuel injection valve10 may be determined by substituting a desired target value for the target amount of electric power generation in the map.
• Here, note that when power generation fuel is supplied to the[0066]SOFC3, combustion may be carried out with the air fuel ratio of the mixture in thecombustion device9 being set to a fuel-excess air fuel ratio (rich air fuel ratio). The unburnt fuel at this time, i.e., hydrocarbon (HC) remaining unburnt, is supplied to theSOFC3 through theintroduction passage8 and theexhaust passage2. The hydrocarbon supplied at this time is reformed due to the high temperature in thecombustion device9, so it becomes easy to react in theSOFC3. Moreover, carbon monoxide (CO) generated during the combustion of the mixture of a rich air fuel ratio in thecombustion device9 also serves as power generation fuel for theSOFC3. Further, when there is steam or water vapor in thecombustion device9, hydrogen (H₂) is generated upon combustion of the mixture therein. The hydrogen thus generated also serves as power generation fuel for theSOFC3.
• Here, note that in this embodiment, when power generation fuel is supplied to the[0067]SOFC3, the mixture may be discharged from thecombustion device9 without being combusted or burnt therein. In this case, the amount of fuel injected from thefuel injection valve10 becomes equal to the amount of power generation fuel supplied to theSOFC3. Thus, the power generation fuel can be supplied to theSOFC3 by the fuel injection from thefuel injection valve10. In this connection, if the relation between the target amount of electric power generation and the valve open time and the valve closure time of thefuel injection valve10 is obtained and mapped beforehand, it is possible to generate a sufficient amount of electric power to meet a target power generation amount by adjusting the valve open time and the valve closure time of thefuel injection valve10 in an appropriate manner.
• Furthermore, the power generation in the[0068]SOFC3 is performed at temperatures from 700 to 1,000° C. for example, as stated above. Accordingly, when the temperature of theSOFC3 is low, it is necessary to raise the temperature of theSOFC3 to an appropriate temperature. Here, note that if the temperature of theSOFC3 is caused to rise due solely to the exhaust gas from theengine1, it takes time until theSOFC3 reaches a prescribed temperature at which theSOFC3 is able to carry out power generation since in the diesel engine, the combustion temperature is low and hence the temperature of the exhaust gas is low. In this respect, however, according to this embodiment, a high temperature gas discharged as a result of the mixture in thecombustion device9 being combusted can be supplied to theSOFC3, so the temperature of theSOFC3 can be raised more quickly than in the above case. As a consequence, power generation can be started at an earlier stage even when the temperature of theSOFC3 is low. Here, note that in case where it is the main purpose to raise the temperature of theSOFC3, it is desirable to combust or burn the mixture in thecombustion device9 at an air fuel ratio in the vicinity of the stoichiometric air fuel ratio. By combusting the mixture under such a condition, a gas of a relatively high temperature can be generated, so that the gas of such a high temperature (burnt gas) can be supplied to theSOFC3. In addition, it is possible to suppress the unburnt fuel exhausted from thecombustion device9 by combusting the mixture at an air fuel ratio in the vicinity of the stoichiometric air fuel ratio.
• Moreover, according to this embodiment, the exhaust gas from the[0069]engine1 is also supplied to the fuel electrode3a, so that the temperature of theSOFC3 can be raised due to the heat of the exhaust gas, and a part of the exhaust gas from theengine1 can be used as power generation fuel.
• Here, note that in this embodiment, the amount of power generation fuel supplied to the[0070]SOFC3, i.e., the valve open time and the valve closure time of thefuel injection valve10, may be controlled in a feedback manner based on the output signal of the airfuel ratio sensor15 installed on theexhaust passage2 at a location downstream of theSOFC3.
• That is, when the output signal of the air[0071]fuel ratio sensor15 is higher than a target air fuel ratio, the valve open time of thefuel injection valve10 is lengthened and the valve closure time thereof is shortened. On the other hand, when the output signal of the airfuel ratio sensor15 is lower than the target air fuel ratio, the valve open time of thefuel injection valve10 is shortened and the valve closure time thereof is lengthened.
• In other words, when the amount of fuel contributing to the power generation of the[0072]SOFC3 is small, the amount of power generation fuel to be supplied is increased, whereas when the amount of fuel contributing to the power generation of theSOFC3 is large, the amount of power generation fuel to be supplied is decreased. According to such fuel control, the amount of supply of the power generation fuel can be controlled based on the amount of power generation fuel that contributes to the power generation by theSOFC3. As a result, an optimal amount of power generation fuel can be supplied to theSOFC3 so as to achieve a target amount of electric power generation of theSOFC3.
• Similarly, in this embodiment, the valve open time and the valve closure time of the[0073]fuel injection valve10 may be controlled in a feedback manner based on the output signal of the exhaustgas temperature sensor16 installed on theexhaust passage2 at a location downstream of theSOFC3.
• That is, based on the output signal of the exhaust[0074]gas temperature sensor16, it is possible to determine whether the temperature of theSOFC3 has risen to a temperature at which theSOFC3 is able to perform electric power generation. The temperature of theSOFC3 is raised by combusting the mixture of the stoichiometric air fuel ratio in thecombustion device9 until theSOFC3 rises to a temperature at which it is able to perform power generation. After the temperature of theSOFC3 has risen up to the temperature at which theSOFC3 is able to carry out power generation, a mixture of a rich air fuel ratio is combusted in thecombustion device9, so that electricity is generated by theSOFC3.
• As a result, at cold engine start or the like, the temperature of the[0075]SOFC3 can be raised further rapidly up to the temperature at which electricity can be generated by theSOFC3. Further, the temperature of theSOFC3 can be controlled to be suitable for power generation, that is, a temperature at which theSOFC3 has high electrical efficiency. As a result, reduction in the electrical efficiency can be suppressed.
• Here, note that when the temperature of the[0076]SOFC3 is lower than the temperature suitable for power generation, the amount of supply of the power generation fuel may be decreased by reducing the amount of fuel to be injected from thefuel injection valve10. By doing so, it is possible to suppress the unburnt fuel exhausted from theSOFC3 without contributing to power generation.
• As described above, according to this embodiment, the power generation fuel can be supplied to the[0077]SOFC3 without regard to the operating condition of theengine1. In addition, an optimal amount of power generation fuel can be supplied to theSOFC3 so as to achieve a target amount of electric power generation thereof. Moreover, the temperature of theSOFC3 can be raised more quickly, whereby the power generation of theSOFC3 can be started at an earlier stage. Further, the amount of supply of the power generation fuel can be controlled in a feedback manner by the airfuel ratio sensor15 and/or the exhaustgas temperature sensor16. Here, reference will be made to the flow of signals around theECU13 in this embodiment while referring to FIG. 7.
• In FIG. 7, a dotted line arrow ([0078]1) represents the flow of a signal from theECU13 to thefuel injection valve10. A dotted line arrow (2) represents the flow of a signal from the airfuel ratio sensor15 to theECU13. A dotted line arrow (3) represents the flow of a signal from the exhaustgas temperature sensor16 to theECU13. A solid line arrow in FIG. 7 represents the supply of fuel from thefuel injection valve10 to thecombustion device9.
• In this embodiment, as stated above, fuel is injected from the[0079]fuel injection valve10 into thecombustion device9, and the unburnt fuel contained in the gas exhausted from thecombustion device9 is supplied as power generation fuel to theSOFC3. That is, thefuel injection valve10 and thecombustion device9 together constitute afuel supply system101 according to the present invention. The valve open time and the valve closure time of thefuel injection valve10 are controlled in the above-mentioned manner by running a control program stored in theECU13, so that the amount of fuel to be injected from thefuel injection valve10 can be controlled in an appropriate manner. As a result, the amount of power generation fuel supplied to theSOFC3 is adjusted. That is, the control program constitutes a supplyamount control part201 according to the present invention.
• Furthermore, in this embodiment, the supply[0080]amount control part201 may control the amount of fuel to be injected from thefuel injection valve10 based on the output signal of the airfuel ratio sensor15 and/or the output signal of the exhaustgas temperature sensor16, as mentioned above. That is, the airfuel ratio sensor15 constitutes a fuel amount detection device according to the present invention, and the exhaustgas temperature sensor16 constitutes a temperature detection device according to the present invention.
• <Second Embodiment>[0081]
• A second embodiment of the present invention is different from the first embodiment in that it is provided with an[0082]oxidation catalyst17 installed on theexhaust passage2 at a location between theintroduction passage8 and theSOFC3, as shown in FIG. 2. Here, note that in this second embodiment, the basic structure of the internal combustion engine, to which the present invention is applied, and the rest of hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 2 is a view that illustrates the schematic construction of the[0083]engine1 and its intake and exhaust systems according to this second embodiment.
• Unburnt fuel, which serves as power generation fuel for the[0084]SOFC3, is supplied from theengine1 and/or thecombustion device9 to theoxidation catalyst17, whereby the unburnt fuel is oxidized by theoxidation catalyst17. The temperature of the exhaust gas discharged from theengine1 is raised by the heat of reactions generated at this time, so that the temperature of theSOFC3 rises due to the exhaust gas flowing therein. As a result, even if the temperature of the exhaust gas discharged from theengine1 and the temperature of theSOFC3 are low, the temperature of theSOFC3 can be raised more quickly, so the power generation of theSOFC3 is able to be started at an earlier stage. In addition, a part of the unburnt fuel is reformed by theoxidation catalyst17, so that the unburnt fuel thus reformed can be supplied to theSOFC3. The reformed unburnt fuel is easy to react at the fuel electrode3a, so the electrical efficiency of theSOFC3 can be improved. Furthermore, the unburnt fuel from theengine1 and/or thecombustion device9 reacts with oxygen in theoxidation catalyst17, so the oxygen concentration of the exhaust gas is thereby decreased, thus making it possible to increase the amount of electric power generation of theSOFC3.
• Here, note that in this embodiment, the unburnt fuel discharged from the[0085]combustion device9 may be obtained by the combustion of a mixture containing therein an excessive amount of fuel, or it may also be obtained by discharging the fuel injected by thefuel injection valve10 from thecombustion device9 in its unburnt state.
• Moreover, in cases where the[0086]engine1 is operated with a mixture of a rich air fuel ratio, a mixture of a lean air fuel ratio may be combusted in thecombustion device9, so that theoxidation catalyst17 can be supplied with oxygen to oxidize the unburnt fuel from theengine1, thus making it possible to adjust the amount of unburnt fuel supplied to theSOFC3.
• Here, it is preferable to adopt a small-sized catalyst as the[0087]oxidation catalyst17 for the purpose of raising the temperature of theoxidation catalyst17 at an early stage.
• <Third Embodiment>[0088]
• A third embodiment of the present invention is different from the second embodiment in that it is provided with an[0089]oxidation catalyst18 installed on theexhaust passage2 at a location downstream of theSOFC3, as shown in FIG. 3. Here, note that in this third embodiment, the basic structure of the internal combustion engine, to which the present invention is applied, and the rest of hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 3 is a view that illustrates the schematic construction of the[0090]engine1 and its intake and exhaust systems according to this third embodiment.
• In case where the air[0091]fuel ratio sensor15 or the exhaustgas temperature sensor16 is installed on theexhaust passage2, the components of the exhaust gas are changed in theoxidation catalyst18 thereby to influence the output of thesensor15 or16. To avoid such an influence, theoxidation catalyst18 is arranged at the downstream side of thesensor15 or16.
• In the[0092]SOFC3, the whole of the power generation fuel (unburnt fuel fromengine1 and/or the combustion device9) supplied to the SOFC3 does not react, and some of the power generation fuel may pass through theSOFC3 without undergoing reactions. If a part of the power generation fuel is discharged into the atmosphere, the emissions discharged from theengine1 into the atmosphere are deteriorated. In this respect, however, according to this embodiment, by the provision of theoxidation catalyst18 arranged at the downstream side of theSOFC3, the power generation fuel discharged from theSOFC3 without undergoing reactions therein can be oxidized by theoxidation catalyst18, whereby the exhaust gas to be discharged into the atmosphere can be purified.
• Further, the[0093]oxidation catalyst18, being arranged at the downstream side of theSOFC3, is maintained at a high temperature by the heat from theSOFC3, so it is possible to carry out stable purification of the exhaust gas.
• <Fourth Embodiment>[0094]
• A fourth embodiment of the present invention is different from the third embodiment in that the gas (cathode off-gas) exhausted from the[0095]air electrode3cside of theSOFC3 is introduced into theoxidation catalyst18. Here, note that in this fourth embodiment, the basic structure of the internal combustion engine, to which the present invention is applied, and the rest of hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 4 is a view that illustrates the schematic construction of the[0096]engine1 and its intake and exhaust systems according to this fourth embodiment.
• In this embodiment, a portion of the[0097]exhaust passage2 between theSOFC3 and theoxidation catalyst18 is connected with an outlet side of theair electrode3cthrough anair introduction passage19, so that the oxygen discharged from theair electrode3cside is introduced into theoxidation catalyst18. In case where the airfuel ratio sensor15 or the exhaustgas temperature sensor16 is installed on theexhaust passage2, the components of the exhaust gas are changed in theoxidation catalyst18 thereby to influence the output of thesensor15 or16. To avoid such an influence, theair introduction passage19 is arranged at the downstream side of thesensor15 or16.
• Here, note that the exhaust gas from the fuel electrode[0098]3aside may have a low oxygen concentration depending upon the operating state of theengine1 or the power generation state of theSOFC3. Thus, when the oxygen concentration of the exhaust gas from the fuel electrode3aside is low, the oxidation ability of theoxidation catalyst18 might be reduced, making it difficult to oxidize the unburnt fuel. In this case, there is a fear that if oxygen is supplied to theoxidation catalyst18 with the operating condition of theengine1 or the power generation state of theSOFC3 being changed, necessary torque might not be obtained from theengine1, and a target amount of electric power generation of theSOFC3 might become unable to be achieved.
• In this connection, however, according to this embodiment, the oxygen contained in the air from the[0099]air electrode3cside can be introduced into theoxidation catalyst18, so it is possible to suppress the deterioration of emissions, which would otherwise be caused due to a lack of oxygen in theoxidation catalyst18. In addition, it is possible to supply oxygen to theoxidation catalyst18 without depending upon the operating condition of theengine1 and the power generation state of theSOFC3.
• Here, note that in this embodiment, air supplied by the[0100]air pump6 may be introduced into theoxidation catalyst18.
• Thus, in this embodiment, the[0101]air introduction passage19 or theair pump6 constitutes an air supply system according to the present invention.
• <Fifth Embodiment>[0102]
• A fifth embodiment of the present invention is different from the fourth embodiment in that it is provided with a[0103]heat exchanger20 installed on theexhaust passage2 at a location downstream of theoxidation catalyst18, as shown in FIG. 5. Here, note that in this fifth embodiment, the basic structure of the internal combustion engine, to which the present invention is applied, and the rest of hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 5 is a view that illustrates the schematic construction of the[0104]engine1 and its intake and exhaust systems according to this fifth embodiment.
• In this embodiment, the[0105]heat exchanger20 is arranged on theexhaust passage2 at a location downstream of theoxidation catalyst18, and abypass passage21 for bypassing the exhaust gas around theheat exchanger20 has one end and the other end thereof connected with theexhaust passage2 at locations on the upstream side and the downstream side of theheat exchanger20, respectively. A three-way valve22 for selectively passing the exhaust gas through either one of thebypass passage21 and theheat exchanger20 is installed on theexhaust passage2 at a location thereof at which thebypass passage21 is connected at the other end thereof with theexhaust passage2 on the downstream side of theheat exchanger20.
• A[0106]cooling water passage23 in which coolant or water for cooling theengine1 circulates is connected with theheat exchanger20. The coolingwater passage23 is connected with theengine1 and aheater core24.
• Here, note that the operating temperature of the[0107]SOFC3 is high, and hence a gas of high temperature is exhausted from the fuel electrode3aside of theSOFC3. Accordingly, during the time when theSOFC3 performs power generation, the temperature of the exhaust gas exhausted from theengine1, even if low, is raised in theSOFC3, and hence the temperature of the exhaust gas at the downstream side of theSOFC3 becomes high. On the other hand, even if the temperature of the exhaust gas from theengine1 is high, the heat from theengine1 can be collected by theheat exchanger20 arranged on theexhaust passage2. Thus, the heat of the exhaust gas from theengine1 and theSOFC3 can be collected by thesingle heat exchanger20. As a result, installability of the heat exchanger on the vehicle can be improved.
• In this embodiment, the cooling water of the[0108]engine1 is caused to circulate through theheat exchanger20, so that heat exchange is performed between the exhaust gas of high temperature and the cooling water thereby to raise the temperature of the cooling water. That is, as the exhaust gas of high temperature is introduced into theheat exchanger20, the temperature of the cooling water is raised by theheat exchanger20. Thus, it is possible to improve the heating performance of the vehicle by circulating the cooling water thus raised in temperature in theheater core24 through the coolingwater passage23. Moreover, when the temperature of theengine1 is low at the time of engine starting or the like, it is possible to heat theengine1 quickly by making the cooling water of high temperature circulate through theengine1. Further, even if theheat exchanger20 is reduced in size, such an advantageous effect can be achieved to a satisfactory extent since the exhaust gas of high temperature is circulated through theheat exchanger20.
• Here, note that when the cooling water temperature becomes too high, it becomes unable to cool the[0109]engine1 to a satisfactory extent, giving rise to so-called overheating. Accordingly, the three-way valve22 is driven to operate before the cooling water temperature becomes too high, so that the exhaust gas is passed to thebypass passage21. By doing so, it is possible to suppress the occurrence of overheating. Furthermore, in the case of the provision of the exhaustgas temperature sensor16, the exhaust gas may be passed through thebypass passage21 by means of the three-way valve22 when the temperature of the exhaust gas detected by the exhaustgas temperature sensor16 is higher than a prescribed temperature.
• <Sixth Embodiment>[0110]
• A sixth embodiment of the present invention is different from the fifth embodiment in that heat exchange between the exhaust gas and air is performed in the[0111]heat exchanger20. Here, note that in this sixth embodiment, the basic structure of the internal combustion engine, to which the present invention is applied, and the rest of hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 6 is a view that illustrates the schematic construction of the[0112]engine1 and its intake and exhaust systems according to this sixth embodiment.
• In this embodiment, the[0113]heat exchanger20 is arranged on theexhaust passage2 at a location downstream of theoxidation catalyst18, and abypass passage21 for bypassing the exhaust gas around theheat exchanger20 has one end and the other end thereof connected with theexhaust passage2 at locations on the upstream side and the downstream side of theheat exchanger20, respectively. A three-way valve22 for selectively passing the exhaust gas through either one of thebypass passage21 and theheat exchanger20 is installed on theexhaust passage2 at a location thereof at which thebypass passage21 is connected at the other end thereof with theexhaust passage2 on the downstream side of theheat exchanger20.
• The[0114]heat exchanger20 is connected at its inlet side with theair pump6 through theair supply passage7, and at its outlet side with an inlet side of theair electrode3cof theSOFC3 through theair supply passage7. Also, theair supply passage7 connected with the outlet side of theheat exchanger20 is branched on its way to theSOFC3 to be connected with thecombustion device9 through aheat exchanger25.
• A[0115]cooling water passage23 in which coolant or water for cooling theengine1 circulates is connected with theheat exchanger25. The clingwater passage23 is connected with theengine1 and theheater core24.
• Here, note that the operating temperature of the[0116]SOFC3 is high, and hence a gas of high temperature is exhausted from the fuel electrode3aside of theSOFC3. Accordingly, during the time when theSOFC3 performs power generation, the temperature of the exhaust gas exhausted from theengine1, even if low, is raised in theSOFC3, and hence the temperature of the exhaust gas at the downstream side of theSOFC3 becomes high. In this embodiment, heat exchange is performed between the exhaust gas of high temperature and the air discharged from theair pump6, whereby the temperature of the air supplied to theSOFC3 and thecombustion device9 can be raised.
• With such a construction, as the exhaust gas of high temperature is introduced into the[0117]heat exchanger20, the temperature of air is raised by theheat exchanger20. Thus, by introducing the air thus raised in temperature into theair electrode3cof theSOFC3, it is possible to supply the air to theSOFC3 while suppressing a temperature drop thereof, as a result of which the electrical efficiency of theSOFC3 can be improved.
• In addition, the evaporation of fuel in the[0118]combustion device9 is facilitated by supplying the air of high temperature to thecombustion device9, so that combustion in thecombustion device9 can be further stabilized. However, when the temperature of the air supplied to thecombustion device9 becomes too high, the oxygen concentration of the air is reduced. To avoid this, according to this embodiment, after heat exchange between the air of high temperature and the cooling water has been made in theheat exchanger25, the air thus lowered in temperature is supplied to thecombustion device9. As a result, combustion in thecombustion device9 can be further stabilized. On the other hand, when the mixture is caused to discharge from thecombustion device9 without undergoing combustion therein, the evaporation of the fuel in the mixture can be facilitated, so that the fuel can be made easy to react in theSOFC3.
• As can be seen from the foregoing discussion, in an internal combustion engine with a fuel cell in an exhaust system according to the present invention, it is possible to supply power generation fuel to the fuel cell without regard to the operating condition of the internal combustion engine. In addition, the amount of power generation fuel supplied to the fuel cell can be increased or decreased without regard to the operating condition of the internal combustion engine, so that an amount of power generation fuel corresponding to a target amount of power generation can be supplied. Further, by introducing the exhaust gas from a combustion device into the fuel cell, the temperature of the fuel cell can be raised more quickly, whereby the power generation of the fuel cell can be accordingly started at an earlier stage.[0119]
• While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.[0120]
• <Seventh Embodiment>[0121]
• A seventh embodiment of the present invention is different from the first embodiment in that, in place of the[0122]combustion device9 in the first embodiment, this embodiment includes afuel adding injector26 disposed between theengine1 and theSOFC3 in theexhaust passage2 for adding the fuel thereto. Further, theheat exchanger20 is disposed at the downstream side of theSOFC3 in theexhaust passage2. Here, note that in this embodiment, the basic structure of the internal combustion engine, to which the invention is applied and rest hardware are common with those of the above-mentioned first embodiment, and hence an explanation thereof is omitted.
• FIG. 8 is a view that illustrates the schematic construction of the[0123]engine1 and its intake and exhaust systems according to this seventh embodiment.
• This embodiment includes the[0124]fuel adding injector26 between theengine1 and theSOFC3 in theexhaust passage2. The fuel is supplied from thefuel pump11 to thisfuel adding injector26. Further, thisfuel adding injector26 is electrically connected with theECU13 and operated by the signals from theECU13, thereby the fuel adding is controlled. Thus, the fuel added to theexhaust passage2 can be used as power generation fuel for theSOFC3.
• Accordingly, with this embodiment, the fuel added by the[0125]fuel adding injector26 can be supplied to theSOFC3 as power generation fuel without changing the operation condition of theengine1. Further, the exhaust gas from theengine1 can be introduced into theSOFC3, thereby the temperature of theSOFC3 can be raised by a high temperature of the exhaust gas, and, still further, portion of the exhaust gas from theengine1 can be used as the power generation fuel.
• Here, a quantity of power generation fuel supplied to the[0126]SOFC3 can be adjusted by a quantity of the fuel injected from thefuel adding injector26. Specifically, with this embodiment, a valve of thefuel adding injector26 is opened intermittently, and the fuel quantity to be added to theexhaust passage2 is adjusted by adjusting the valve open time and the valve closure time he valve of thefuel adding injector26. At this time, as the longer the valve open time and the shorter the valve closure time, the greater does the amount of fuel quantity to be supplied to theSOFC3 become. On the other hand, as the shorter the valve open time and the longer the valve closure time, the smaller does the amount fuel quantity to be supplied to theSOFC3 become.
• Thus, a relationship between the target amount of electric power generation of the[0127]SOFC3 and the valve open and closure times of thefuel adding injector26 may be prepared in a map form in advance, and the valve open time and the valve closure time of thefuel adding injector26 may be determined by substitution of the target amount of electric power generation. In this manner, it becomes possible to perform power generation to meet the target amount of electric power generation.
• Further, this embodiment includes the[0128]heat exchanger20 at the downstream side of theSOFC3 in theexhaust passage2. Moreover, and abypass passage21 for bypassing the exhaust gas around theheat exchanger20 has one end and the other end thereof connected with theexhaust passage2 at locations on the upstream side and the downstream side of theheat exchanger20, respectively. A three-way valve22 for selectively passing the exhaust gas through either one of thebypass passage21 and theheat exchanger20 is installed on theexhaust passage2 at a location thereof at which thebypass passage21 is connected at the other end thereof with theexhaust passage2 on the downstream side of theheat exchanger20.
• The[0129]heat exchanger20 is provided with an unillustrated air intake port, and heat exchange is performed in theheat exchanger20 between the air taken through the air intake port and the exhaust gas.
• Further, one end of the[0130]air supply passage7 is connected to theheat exchanger20. The other end of theair supply passage7 is connected to theexhaust passage2 between theengine1 and thefuel adding injector26. Theair supply passage7 includes at its midway anair pump27 for discharging the air under a predetermined pressure from the side of theheat exchanger20 towards theexhaust passage2 at the upstream of theSOFC3.
• With the above-described construction, the air with its temperature raised in the[0131]heat exchanger20 is introduced into theexhaust passage2 at the upstream side of theSOFC3 through theair supply passage7. Consequently, the wall surface temperature of theexhaust passage2 and the temperature of the exhaust gas can be raised. Thus, evaporation of the fuel added from thefuel adding injector26 can be advanced.
• Further, in the low-load region, a degree of raising the temperature of the wall surface of the[0132]exhaust passage2 with the heat of the exhaust gas from theengine1 is small, thereby the fuel added from thefuel adding injector26 is liable to adhere to the wall surface of theexhaust passage2. However, with the above-described construction, the temperature of the wall surface of theexhaust passage2 and of the exhaust gas can be raised, thereby evaporation of the fuel adhered to the wall surface can be advanced. Consequently, even at the time of low-load operation, the power generation fuel can be supplied stably to theSOFC3.
• Note that, in this embodiment, the other end of the[0133]air supply passage7 may be connected to theexhaust passage2 at more downstream from thefuel adding injector26. Specifically, it is sufficient to raise the temperature of a location in theexhaust passage2 where the fuel is adhered, by supplying the air from theair supply passage7.
• With this embodiment, the[0134]fuel adding injector26 constitutes the fuel supply system of the present invention.

Claims (19)

What is claimed is:

1. An internal combustion engine with a fuel cell in an exhaust system, said engine comprising:

a fuel cell having a fuel electrode side thereof connected with an exhaust passage of said internal combustion engine;

a fuel supply system that supplies power generation fuel for said fuel cell to an exhaust passage at a location downstream of said internal combustion engine and upstream of said fuel cell; and

a supply amount control part that controls an amount of power generation fuel supplied by said fuel supply system.

2. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, wherein said supply amount control part controls the amount of power generation fuel supplied by said fuel supply system in such a manner that an amount of electric power generation of said fuel cell becomes equal to a target amount of electric power generation.

3. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 2, further comprising a fuel amount detection device that detects an amount of power generation fuel contributing to the power generation of said fuel cell, wherein said supply amount control part controls the amount of power generation fuel supplied by said fuel supply system based on the result of detection of said fuel amount detection device.

4. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 3, wherein when the amount of power generation fuel contributing to the power generation of said fuel cell detected by said fuel amount detection device is smaller than a target amount, said supply amount control part increases the amount of power generation fuel supplied by said fuel supply system.

5. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, further comprising a temperature detection device that detects a state of an element related to the temperature of said fuel cell, wherein said supply amount control part controls the amount of power generation fuel supplied by said fuel supply system based on the result of detection of said temperature detection device.

6. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 5, wherein when the temperature of said fuel cell is lower than a prescribed temperature, said supply amount control part decreases the amount of power generation fuel supplied by said fuel supply system.

7. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, further comprising a combustion device, wherein said fuel supply system supplies an exhaust gas discharged from said combustion device to said exhaust passage at a location downstream of said internal combustion engine and upstream of said fuel cell.

8. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 7, wherein said fuel supply system supplies the exhaust gas discharged from said combustion device to said exhaust passage at a location downstream of said internal combustion engine and upstream of said fuel cell, with combustion in said combustion device being performed with a mixture of a rich air fuel ratio which is a lower air fuel ratio than the stoichiometric air fuel ratio.

9. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 7, wherein said fuel supply system supplies an unburnt gas discharged from said combustion device to said exhaust passage at a location downstream of said internal combustion engine and upstream of said fuel cell, without combusting fuel in said combustion device.

10. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 7, wherein said supply amount control part controls the amount of power generation fuel supplied by said fuel supply system by changing an air fuel ratio of a gas combusted in said combustion device.

11. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 10, wherein when the temperature of said fuel cell is raised, said supply amount control part makes the air fuel ratio of said gas combusted in said combustion device to be a value in the vicinity of the stoichiometric air fuel ratio.

12. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, further comprising a catalyst having oxidation capability that is installed on said exhaust passage at a location upstream of said fuel cell and downstream of said fuel supply system.

13. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 7, further comprising a catalyst having oxidation capability that is installed on said exhaust passage at a location upstream of said fuel cell and downstream of said fuel supply system, wherein when said internal combustion engine is operated with a mixture of a rich air fuel ratio, said supply amount control part adjusts the amount of power generation fuel supplied by said fuel supply system by making an air fuel ratio of a gas combusted in said combustion device to be a lean air fuel ratio which is a higher air fuel ratio than the stoichiometric air fuel ratio.

14. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, further comprising a catalyst having oxidation capability that is installed on said exhaust passage at a location downstream of said fuel cell.

15. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 14, further comprising an oxygen supply device that supplies oxygen to said catalyst having oxidation capability.

16. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 15, wherein said oxygen supply device supplies the oxygen discharged from an air electrode side of said fuel cell to said catalyst having oxidation capability.

17. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 1, further comprising a heat exchanger installed on said exhaust passage at a location downstream of said fuel cell.

18. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 17, further comprising an air supply passage that has said heat exchanger installed thereon and is connected with an inlet side of an air electrode of said fuel cell, wherein air whose temperature is raised due to the heat of an exhaust gas in said heat exchanger is supplied into said air electrode of said fuel cell through said air supply passage.

19. The internal combustion engine with a fuel cell in an exhaust system as set forth inclaim 7, further comprising: a heat exchanger installed on said exhaust passage at a location downstream of said fuel cell; and an air supply passage that has said heat exchanger installed thereon and is connected with said combustion device, wherein air whose temperature is raised due to the heat of an exhaust gas in said heat exchanger is supplied into said combustion device through said air supply passage.

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