U.S. patent application number 10/784958 was filed with the patent office on 2004-09-16 for internal combustion engine with a fuel cell in an exhaust system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Oba, Takahiro, Suzuki, Makoto.
Application Number | 20040177607 10/784958 |
Document ID | / |
Family ID | 32911466 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040177607 |
Kind Code |
A1 |
Suzuki, Makoto ; et
al. |
September 16, 2004 |
Internal combustion engine with a fuel cell in an exhaust
system
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.
Inventors: |
Suzuki, Makoto;
(Mishima-shi, JP) ; Oba, Takahiro; (Mishima-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
471-8571
|
Family ID: |
32911466 |
Appl. No.: |
10/784958 |
Filed: |
February 25, 2004 |
Current U.S.
Class: |
60/286 ;
60/285 |
Current CPC
Class: |
Y02T 10/12 20130101;
Y02T 90/32 20130101; H01M 8/0662 20130101; H01M 8/0612 20130101;
F01N 2240/32 20130101; Y02T 90/40 20130101; H01M 2250/20 20130101;
F01N 5/00 20130101; H01M 2008/1293 20130101; Y02E 60/50 20130101;
Y02E 60/525 20130101; Y02T 10/16 20130101 |
Class at
Publication: |
060/286 ;
060/285 |
International
Class: |
F01N 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2003 |
JP |
2003-065030 |
May 20, 2003 |
JP |
2003-142164 |
Claims
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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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 in claim 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.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an internal combustion
engine with a fuel cell in an exhaust system.
[0003] 2. Description of the Related Art
[0004] 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)).
[0005] 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.
SUMMARY OF THE INVENTION
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] Preferably, the internal combustion engine may further
comprise a heat exchanger installed on the exhaust passage at a
location downstream of the fuel cell.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] FIG. 7 is a view showing the flow of signals around an ECU
according to the first embodiment of the present invention.
[0042] 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.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] 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.
[0044] <First Embodiment>
[0045] 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 1 in FIG. 1, is a water-cooled
four-cycle diesel engine. Connected with the engine 1 is an exhaust
passage 2 for discharging an exhaust gas exhausted from the engine
1 into the ambient atmosphere. A fuel cell 3 is installed on a
intermediate portion of the exhaust passage 2. This fuel cell 3 is
electrically connected to accessories 4 through a battery 5 for
supplying electric power to the accessories 4. 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.
[0046] The SOFC 3 is constructed such that it includes three kinds
of oxide electrolytes, i.e., a fuel electrode 3a, an electrolyte
3b, and an air electrode 3c.
[0047] In addition, an air pump 6 for sending air to the air
electrode 3c of the SOFC 3 is connected with the SOFC 3 through an
air supply passage 7. The air pump 6 receives electric power from
the battery 5, and is thereby operated to discharge air to the air
supply passage 7.
[0048] A combustion device 9 is connected at its exhaust side with
the exhaust passage 2 at a location between the SOFC 3 and the
engine 1 through an introduction passage 8. The air pump 6 is
connected with an intake side of the combustion device 9 through
the air supply passage 7. Moreover, the combustion device 9 is
provided with 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 which serves to feed fuel under pressure to the fuel
injection valve 10. In addition, the combustion device 9 is also
provided with a spark plug 12 for generating an electric spark
based on a signal from an electronic control unit (ECU) 13 to be
described later.
[0049] In the combustion device 9 constructed in this manner, fuel
is pressure fed from the fuel pump 11 to the fuel injection valve
10, so that it is injected from the fuel injection valve 10 into
the combustion device 9. The fuel thus injected mixes with air
supplied from the air pump 6 to the combustion device 9 to form an
air fuel mixture therein. When an electric spark is generated by
the spark plug 12, the air fuel mixture is thereby ignited or fired
to burn or combust in the combustion device 9. 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 the
exhaust passage 2 through the introduction passage 8.
[0050] Here, note that in this embodiment, an electric spark may
not be generated by the spark plug 12, so that the air fuel mixture
being unburnt can be discharged to the introduction passage 8 as it
is.
[0051] The gas introduced into the exhaust passage 2 while being
burnt or unburnt can be used as power generation fuel of the SOFC
3.
[0052] Here, the power generation fuel thus introduced into the
SOFC 3 reacts with steam or water vapor on the fuel electrode 3a,
so that it is reformed into hydrogen (H.sub.2) and carbon monoxide
(CO). Thus, in the SOFC 3, it is possible to reform the power
generation fuel therein. On the other hand, air is supplied from
the air pump 6 to the air electrode 3c. In the air electrode 3c,
the atmospheric oxygen dissociates into oxygen ions (O.sup.2-) on
an interface with the electrolyte 3b, and the oxygen ions
(O.sup.2-) thus generated move toward the fuel electrode 3a side in
the electrolyte 3b. The oxygen ions (O.sup.2-) having arrived at an
interface between the electrolyte 3b and the fuel electrode 3a
react with hydrogen (H.sub.2) and carbon monoxide (CO) to generate
water (H.sub.2O) and carbon dioxide (CO.sub.2). The power
generation of the SOFC 3 is performed by taking out electrons
discharged at this time. Thus, according to the SOFC 3, 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 the SOFC 3 is performed at
temperatures from 700 to 1,000.degree. C., for example.
[0053] Installed on the exhaust passage 2 at the downstream side of
the SOFC 3 are an air fuel ratio sensor 15 that outputs a signal
corresponding to the air fuel ratio of the exhaust gas, and an
exhaust gas temperature sensor 16 that outputs a signal
corresponding to the temperature of the exhaust gas.
[0054] The ECU 13 for controlling the engine 1 is provided in
conjunction with the engine 1 as constructed above. The ECU 13
controls the operating state of the engine 1 according to the
operating condition of the engine 1 and the driver's request.
[0055] A variety of kinds of sensors such as ones mentioned above
are connected to the ECU 13 through electric wiring, so that the
output signals of the various sensors are input to the ECU 13.
Also, the fuel injection valve 10, the spark plug 12 and the fuel
pump 11 are connected to the ECU 13 through electric wiring, so
that the operations of these members are controlled by the ECU 13.
For example, when a drive current is applied to the fuel injection
valve 10 under the control of a signal from the ECU 13, the fuel
injection valve 10 is driven to open, as a result of which fuel is
injected from the fuel injection valve 10 into the combustion
device 9. In addition, an fuel cell ECU (hereinafter referred to as
FC ECU) 14 for controlling the SOFC 3 is connected to the ECU 13,
so that the SOFC 3 is driven to operate under the control of a
signal from the FC ECU 14.
[0056] A part of electric power provided by the power generation of
the SOFC 3 is once accumulated in the battery 5. The accessories 4
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 the
battery 5, so that electric power is supplied from the battery 5 to
these accessories.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] In this respect, according to this embodiment, the exhaust
gas (i.e., burnt gas) discharged from the combustion device 9 can
be supplied to the SOFC 3 as power generation fuel without changing
the operating condition of the engine 1.
[0063] Further, in this embodiment, it is possible to adjust the
amount of power generation fuel supplied to the SOFC 3 by means of
the amount of fuel injected from the fuel injection valve 10 into
the combustion device 9. That is, assuming that the amount of air
supplied from the air pump 6 is constant, the air fuel ratio of the
mixture in the combustion device 9 is decided by the amount of fuel
injected from the fuel injection valve 10. Here, note that in this
embodiment, the fuel injection valve 10 is driven to open
intermittently under the control of the ECU 13, so that the amount
of fuel supplied to the combustion device 9 is controlled by
adjusting the valve open time and the valve closure time of the
fuel injection valve 10 at this time. That is, the longer the valve
open time of the fuel injection valve 10, and the shorter the valve
closure time thereof, the greater does the amount of fuel supplied
to the combustion device 9 become. On the other hand, the shorter
the valve open time of the fuel injection valve 10, and the longer
the valve closure time thereof, the smaller does the amount of fuel
supplied to the combustion device 9 become. In addition, the amount
of air supplied per unit time from the air pump 6 to the combustion
device 9 can be obtained beforehand by experiments or the like.
Accordingly, the air fuel ratio of the mixture in the combustion
device 9 can be controlled by adjusting the valve open time of the
fuel injection valve 10.
[0064] 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 combustion device 9 and the valve open
time and the valve closure time of the fuel injection valve 10 is
mapped beforehand, and the valve open time and the valve closure
time of the fuel injection valve 10 may be determined by
substituting a desired target value for the target air fuel ratio
in the map.
[0065] 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 SOFC 3 and the valve open time and
the valve closure time of the fuel injection valve 10 is mapped
beforehand. The valve open time and the valve closure time of the
fuel injection valve 10 may be determined by substituting a desired
target value for the target amount of electric power generation in
the map.
[0066] Here, note that when power generation fuel is supplied to
the SOFC 3, combustion may be carried out with the air fuel ratio
of the mixture in the combustion device 9 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 the SOFC 3 through the introduction passage 8 and the exhaust
passage 2. The hydrocarbon supplied at this time is reformed due to
the high temperature in the combustion device 9, so it becomes easy
to react in the SOFC 3. Moreover, carbon monoxide (CO) generated
during the combustion of the mixture of a rich air fuel ratio in
the combustion device 9 also serves as power generation fuel for
the SOFC 3. Further, when there is steam or water vapor in the
combustion device 9, hydrogen (H.sub.2) is generated upon
combustion of the mixture therein. The hydrogen thus generated also
serves as power generation fuel for the SOFC 3.
[0067] Here, note that in this embodiment, when power generation
fuel is supplied to the SOFC 3, the mixture may be discharged from
the combustion device 9 without being combusted or burnt therein.
In this case, the amount of fuel injected from the fuel injection
valve 10 becomes equal to the amount of power generation fuel
supplied to the SOFC 3. Thus, the power generation fuel can be
supplied to the SOFC 3 by the fuel injection from the fuel
injection valve 10. 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 the fuel injection valve 10 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 the fuel injection valve 10 in an appropriate
manner.
[0068] Furthermore, the power generation in the SOFC 3 is performed
at temperatures from 700 to 1,000.degree. C. for example, as stated
above. Accordingly, when the temperature of the SOFC 3 is low, it
is necessary to raise the temperature of the SOFC 3 to an
appropriate temperature. Here, note that if the temperature of the
SOFC 3 is caused to rise due solely to the exhaust gas from the
engine 1, it takes time until the SOFC 3 reaches a prescribed
temperature at which the SOFC 3 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 the combustion device
9 being combusted can be supplied to the SOFC 3, so the temperature
of the SOFC 3 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 the SOFC 3 is low. Here, note that in
case where it is the main purpose to raise the temperature of the
SOFC 3, it is desirable to combust or burn the mixture in the
combustion device 9 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 the SOFC 3. In addition, it is possible to
suppress the unburnt fuel exhausted from the combustion device 9 by
combusting the mixture at an air fuel ratio in the vicinity of the
stoichiometric air fuel ratio.
[0069] Moreover, according to this embodiment, the exhaust gas from
the engine 1 is also supplied to the fuel electrode 3a, so that the
temperature of the SOFC 3 can be raised due to the heat of the
exhaust gas, and a part of the exhaust gas from the engine 1 can be
used as power generation fuel.
[0070] Here, note that in this embodiment, the amount of power
generation fuel supplied to the SOFC 3, i.e., the valve open time
and the valve closure time of the fuel injection valve 10, may be
controlled in a feedback manner based on the output signal of the
air fuel ratio sensor 15 installed on the exhaust passage 2 at a
location downstream of the SOFC 3.
[0071] That is, when the output signal of the air fuel ratio sensor
15 is higher than a target air fuel ratio, the valve open time of
the fuel injection valve 10 is lengthened and the valve closure
time thereof is shortened. On the other hand, when the output
signal of the air fuel ratio sensor 15 is lower than the target air
fuel ratio, the valve open time of the fuel injection valve 10 is
shortened and the valve closure time thereof is lengthened.
[0072] In other words, when the amount of fuel contributing to the
power generation of the SOFC 3 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 the SOFC 3
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
the SOFC 3. As a result, an optimal amount of power generation fuel
can be supplied to the SOFC 3 so as to achieve a target amount of
electric power generation of the SOFC 3.
[0073] Similarly, in this embodiment, the valve open time and the
valve closure time of the fuel injection valve 10 may be controlled
in a feedback manner based on the output signal of the exhaust gas
temperature sensor 16 installed on the exhaust passage 2 at a
location downstream of the SOFC 3.
[0074] That is, based on the output signal of the exhaust gas
temperature sensor 16, it is possible to determine whether the
temperature of the SOFC 3 has risen to a temperature at which the
SOFC 3 is able to perform electric power generation. The
temperature of the SOFC 3 is raised by combusting the mixture of
the stoichiometric air fuel ratio in the combustion device 9 until
the SOFC 3 rises to a temperature at which it is able to perform
power generation. After the temperature of the SOFC 3 has risen up
to the temperature at which the SOFC 3 is able to carry out power
generation, a mixture of a rich air fuel ratio is combusted in the
combustion device 9, so that electricity is generated by the SOFC
3.
[0075] As a result, at cold engine start or the like, the
temperature of the SOFC 3 can be raised further rapidly up to the
temperature at which electricity can be generated by the SOFC 3.
Further, the temperature of the SOFC 3 can be controlled to be
suitable for power generation, that is, a temperature at which the
SOFC 3 has high electrical efficiency. As a result, reduction in
the electrical efficiency can be suppressed.
[0076] Here, note that when the temperature of the SOFC 3 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 the fuel injection valve 10.
By doing so, it is possible to suppress the unburnt fuel exhausted
from the SOFC 3 without contributing to power generation.
[0077] As described above, according to this embodiment, the power
generation fuel can be supplied to the SOFC 3 without regard to the
operating condition of the engine 1. In addition, an optimal amount
of power generation fuel can be supplied to the SOFC 3 so as to
achieve a target amount of electric power generation thereof.
Moreover, the temperature of the SOFC 3 can be raised more quickly,
whereby the power generation of the SOFC 3 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 air
fuel ratio sensor 15 and/or the exhaust gas temperature sensor 16.
Here, reference will be made to the flow of signals around the ECU
13 in this embodiment while referring to FIG. 7.
[0078] In FIG. 7, a dotted line arrow (1) represents the flow of a
signal from the ECU 13 to the fuel injection valve 10. A dotted
line arrow (2) represents the flow of a signal from the air fuel
ratio sensor 15 to the ECU 13. A dotted line arrow (3) represents
the flow of a signal from the exhaust gas temperature sensor 16 to
the ECU 13. A solid line arrow in FIG. 7 represents the supply of
fuel from the fuel injection valve 10 to the combustion device
9.
[0079] In this embodiment, as stated above, fuel is injected from
the fuel injection valve 10 into the combustion device 9, and the
unburnt fuel contained in the gas exhausted from the combustion
device 9 is supplied as power generation fuel to the SOFC 3. That
is, the fuel injection valve 10 and the combustion device 9
together constitute a fuel supply system 101 according to the
present invention. The valve open time and the valve closure time
of the fuel injection valve 10 are controlled in the
above-mentioned manner by running a control program stored in the
ECU 13, so that the amount of fuel to be injected from the fuel
injection valve 10 can be controlled in an appropriate manner. As a
result, the amount of power generation fuel supplied to the SOFC 3
is adjusted. That is, the control program constitutes a supply
amount control part 201 according to the present invention.
[0080] Furthermore, in this embodiment, the supply amount control
part 201 may control the amount of fuel to be injected from the
fuel injection valve 10 based on the output signal of the air fuel
ratio sensor 15 and/or the output signal of the exhaust gas
temperature sensor 16, as mentioned above. That is, the air fuel
ratio sensor 15 constitutes a fuel amount detection device
according to the present invention, and the exhaust gas temperature
sensor 16 constitutes a temperature detection device according to
the present invention.
[0081] <Second Embodiment>
[0082] A second embodiment of the present invention is different
from the first embodiment in that it is provided with an oxidation
catalyst 17 installed on the exhaust passage 2 at a location
between the introduction passage 8 and the SOFC 3, 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.
[0083] FIG. 2 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this second embodiment.
[0084] Unburnt fuel, which serves as power generation fuel for the
SOFC 3, is supplied from the engine 1 and/or the combustion device
9 to the oxidation catalyst 17, whereby the unburnt fuel is
oxidized by the oxidation catalyst 17. The temperature of the
exhaust gas discharged from the engine 1 is raised by the heat of
reactions generated at this time, so that the temperature of the
SOFC 3 rises due to the exhaust gas flowing therein. As a result,
even if the temperature of the exhaust gas discharged from the
engine 1 and the temperature of the SOFC 3 are low, the temperature
of the SOFC 3 can be raised more quickly, so the power generation
of the SOFC 3 is able to be started at an earlier stage. In
addition, a part of the unburnt fuel is reformed by the oxidation
catalyst 17, so that the unburnt fuel thus reformed can be supplied
to the SOFC 3. The reformed unburnt fuel is easy to react at the
fuel electrode 3a, so the electrical efficiency of the SOFC 3 can
be improved. Furthermore, the unburnt fuel from the engine 1 and/or
the combustion device 9 reacts with oxygen in the oxidation
catalyst 17, so the oxygen concentration of the exhaust gas is
thereby decreased, thus making it possible to increase the amount
of electric power generation of the SOFC 3.
[0085] Here, note that in this embodiment, the unburnt fuel
discharged from the combustion device 9 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 the fuel injection valve 10 from the combustion device 9 in its
unburnt state.
[0086] Moreover, in cases where the engine 1 is operated with a
mixture of a rich air fuel ratio, a mixture of a lean air fuel
ratio may be combusted in the combustion device 9, so that the
oxidation catalyst 17 can be supplied with oxygen to oxidize the
unburnt fuel from the engine 1, thus making it possible to adjust
the amount of unburnt fuel supplied to the SOFC 3.
[0087] Here, it is preferable to adopt a small-sized catalyst as
the oxidation catalyst 17 for the purpose of raising the
temperature of the oxidation catalyst 17 at an early stage.
[0088] <Third Embodiment>
[0089] A third embodiment of the present invention is different
from the second embodiment in that it is provided with an oxidation
catalyst 18 installed on the exhaust passage 2 at a location
downstream of the SOFC 3, 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.
[0090] FIG. 3 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this third embodiment.
[0091] In case where the air fuel ratio sensor 15 or the exhaust
gas temperature sensor 16 is installed on the exhaust passage 2,
the components of the exhaust gas are changed in the oxidation
catalyst 18 thereby to influence the output of the sensor 15 or 16.
To avoid such an influence, the oxidation catalyst 18 is arranged
at the downstream side of the sensor 15 or 16.
[0092] In the SOFC 3, the whole of the power generation fuel
(unburnt fuel from engine 1 and/or the combustion device 9)
supplied to the SOFC3 does not react, and some of the power
generation fuel may pass through the SOFC 3 without undergoing
reactions. If a part of the power generation fuel is discharged
into the atmosphere, the emissions discharged from the engine 1
into the atmosphere are deteriorated. In this respect, however,
according to this embodiment, by the provision of the oxidation
catalyst 18 arranged at the downstream side of the SOFC 3, the
power generation fuel discharged from the SOFC 3 without undergoing
reactions therein can be oxidized by the oxidation catalyst 18,
whereby the exhaust gas to be discharged into the atmosphere can be
purified.
[0093] Further, the oxidation catalyst 18, being arranged at the
downstream side of the SOFC 3, is maintained at a high temperature
by the heat from the SOFC 3, so it is possible to carry out stable
purification of the exhaust gas.
[0094] <Fourth Embodiment>
[0095] A fourth embodiment of the present invention is different
from the third embodiment in that the gas (cathode off-gas)
exhausted from the air electrode 3c side of the SOFC 3 is
introduced into the oxidation catalyst 18. 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.
[0096] FIG. 4 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this fourth embodiment.
[0097] In this embodiment, a portion of the exhaust passage 2
between the SOFC 3 and the oxidation catalyst 18 is connected with
an outlet side of the air electrode 3c through an air introduction
passage 19, so that the oxygen discharged from the air electrode 3c
side is introduced into the oxidation catalyst 18. In case where
the air fuel ratio sensor 15 or the exhaust gas temperature sensor
16 is installed on the exhaust passage 2, the components of the
exhaust gas are changed in the oxidation catalyst 18 thereby to
influence the output of the sensor 15 or 16. To avoid such an
influence, the air introduction passage 19 is arranged at the
downstream side of the sensor 15 or 16.
[0098] Here, note that the exhaust gas from the fuel electrode 3a
side may have a low oxygen concentration depending upon the
operating state of the engine 1 or the power generation state of
the SOFC 3. Thus, when the oxygen concentration of the exhaust gas
from the fuel electrode 3a side is low, the oxidation ability of
the oxidation catalyst 18 might be reduced, making it difficult to
oxidize the unburnt fuel. In this case, there is a fear that if
oxygen is supplied to the oxidation catalyst 18 with the operating
condition of the engine 1 or the power generation state of the SOFC
3 being changed, necessary torque might not be obtained from the
engine 1, and a target amount of electric power generation of the
SOFC 3 might become unable to be achieved.
[0099] In this connection, however, according to this embodiment,
the oxygen contained in the air from the air electrode 3c side can
be introduced into the oxidation catalyst 18, so it is possible to
suppress the deterioration of emissions, which would otherwise be
caused due to a lack of oxygen in the oxidation catalyst 18. In
addition, it is possible to supply oxygen to the oxidation catalyst
18 without depending upon the operating condition of the engine 1
and the power generation state of the SOFC 3.
[0100] Here, note that in this embodiment, air supplied by the air
pump 6 may be introduced into the oxidation catalyst 18.
[0101] Thus, in this embodiment, the air introduction passage 19 or
the air pump 6 constitutes an air supply system according to the
present invention.
[0102] <Fifth Embodiment>
[0103] A fifth embodiment of the present invention is different
from the fourth embodiment in that it is provided with a heat
exchanger 20 installed on the exhaust passage 2 at a location
downstream of the oxidation catalyst 18, 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.
[0104] FIG. 5 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this fifth embodiment.
[0105] In this embodiment, the heat exchanger 20 is arranged on the
exhaust passage 2 at a location downstream of the oxidation
catalyst 18, and a bypass passage 21 for bypassing the exhaust gas
around the heat exchanger 20 has one end and the other end thereof
connected with the exhaust passage 2 at locations on the upstream
side and the downstream side of the heat exchanger 20,
respectively. A three-way valve 22 for selectively passing the
exhaust gas through either one of the bypass passage 21 and the
heat exchanger 20 is installed on the exhaust passage 2 at a
location thereof at which the bypass passage 21 is connected at the
other end thereof with the exhaust passage 2 on the downstream side
of the heat exchanger 20.
[0106] A cooling water passage 23 in which coolant or water for
cooling the engine 1 circulates is connected with the heat
exchanger 20. The cooling water passage 23 is connected with the
engine 1 and a heater core 24.
[0107] Here, note that the operating temperature of the SOFC 3 is
high, and hence a gas of high temperature is exhausted from the
fuel electrode 3a side of the SOFC 3. Accordingly, during the time
when the SOFC 3 performs power generation, the temperature of the
exhaust gas exhausted from the engine 1, even if low, is raised in
the SOFC 3, and hence the temperature of the exhaust gas at the
downstream side of the SOFC 3 becomes high. On the other hand, even
if the temperature of the exhaust gas from the engine 1 is high,
the heat from the engine 1 can be collected by the heat exchanger
20 arranged on the exhaust passage 2. Thus, the heat of the exhaust
gas from the engine 1 and the SOFC 3 can be collected by the single
heat exchanger 20. As a result, installability of the heat
exchanger on the vehicle can be improved.
[0108] In this embodiment, the cooling water of the engine 1 is
caused to circulate through the heat exchanger 20, 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 the heat exchanger 20, the temperature of the
cooling water is raised by the heat exchanger 20. Thus, it is
possible to improve the heating performance of the vehicle by
circulating the cooling water thus raised in temperature in the
heater core 24 through the cooling water passage 23. Moreover, when
the temperature of the engine 1 is low at the time of engine
starting or the like, it is possible to heat the engine 1 quickly
by making the cooling water of high temperature circulate through
the engine 1. Further, even if the heat exchanger 20 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 the heat exchanger 20.
[0109] Here, note that when the cooling water temperature becomes
too high, it becomes unable to cool the engine 1 to a satisfactory
extent, giving rise to so-called overheating. Accordingly, the
three-way valve 22 is driven to operate before the cooling water
temperature becomes too high, so that the exhaust gas is passed to
the bypass passage 21. By doing so, it is possible to suppress the
occurrence of overheating. Furthermore, in the case of the
provision of the exhaust gas temperature sensor 16, the exhaust gas
may be passed through the bypass passage 21 by means of the
three-way valve 22 when the temperature of the exhaust gas detected
by the exhaust gas temperature sensor 16 is higher than a
prescribed temperature.
[0110] <Sixth Embodiment>
[0111] 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 heat exchanger 20. 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.
[0112] FIG. 6 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this sixth embodiment.
[0113] In this embodiment, the heat exchanger 20 is arranged on the
exhaust passage 2 at a location downstream of the oxidation
catalyst 18, and a bypass passage 21 for bypassing the exhaust gas
around the heat exchanger 20 has one end and the other end thereof
connected with the exhaust passage 2 at locations on the upstream
side and the downstream side of the heat exchanger 20,
respectively. A three-way valve 22 for selectively passing the
exhaust gas through either one of the bypass passage 21 and the
heat exchanger 20 is installed on the exhaust passage 2 at a
location thereof at which the bypass passage 21 is connected at the
other end thereof with the exhaust passage 2 on the downstream side
of the heat exchanger 20.
[0114] The heat exchanger 20 is connected at its inlet side with
the air pump 6 through the air supply passage 7, and at its outlet
side with an inlet side of the air electrode 3c of the SOFC 3
through the air supply passage 7. Also, the air supply passage 7
connected with the outlet side of the heat exchanger 20 is branched
on its way to the SOFC 3 to be connected with the combustion device
9 through a heat exchanger 25.
[0115] A cooling water passage 23 in which coolant or water for
cooling the engine 1 circulates is connected with the heat
exchanger 25. The cling water passage 23 is connected with the
engine 1 and the heater core 24.
[0116] Here, note that the operating temperature of the SOFC 3 is
high, and hence a gas of high temperature is exhausted from the
fuel electrode 3a side of the SOFC 3. Accordingly, during the time
when the SOFC 3 performs power generation, the temperature of the
exhaust gas exhausted from the engine 1, even if low, is raised in
the SOFC 3, and hence the temperature of the exhaust gas at the
downstream side of the SOFC 3 becomes high. In this embodiment,
heat exchange is performed between the exhaust gas of high
temperature and the air discharged from the air pump 6, whereby the
temperature of the air supplied to the SOFC 3 and the combustion
device 9 can be raised.
[0117] With such a construction, as the exhaust gas of high
temperature is introduced into the heat exchanger 20, the
temperature of air is raised by the heat exchanger 20. Thus, by
introducing the air thus raised in temperature into the air
electrode 3c of the SOFC 3, it is possible to supply the air to the
SOFC 3 while suppressing a temperature drop thereof, as a result of
which the electrical efficiency of the SOFC 3 can be improved.
[0118] In addition, the evaporation of fuel in the combustion
device 9 is facilitated by supplying the air of high temperature to
the combustion device 9, so that combustion in the combustion
device 9 can be further stabilized. However, when the temperature
of the air supplied to the combustion device 9 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 the heat
exchanger 25, the air thus lowered in temperature is supplied to
the combustion device 9. As a result, combustion in the combustion
device 9 can be further stabilized. On the other hand, when the
mixture is caused to discharge from the combustion device 9 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 the SOFC 3.
[0119] 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.
[0120] 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.
[0121] <Seventh Embodiment>
[0122] A seventh embodiment of the present invention is different
from the first embodiment in that, in place of the combustion
device 9 in the first embodiment, this embodiment includes a fuel
adding injector 26 disposed between the engine 1 and the SOFC 3 in
the exhaust passage 2 for adding the fuel thereto. Further, the
heat exchanger 20 is disposed at the downstream side of the SOFC 3
in the exhaust passage 2. 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.
[0123] FIG. 8 is a view that illustrates the schematic construction
of the engine 1 and its intake and exhaust systems according to
this seventh embodiment.
[0124] This embodiment includes the fuel adding injector 26 between
the engine 1 and the SOFC 3 in the exhaust passage 2. The fuel is
supplied from the fuel pump 11 to this fuel adding injector 26.
Further, this fuel adding injector 26 is electrically connected
with the ECU 13 and operated by the signals from the ECU 13,
thereby the fuel adding is controlled. Thus, the fuel added to the
exhaust passage 2 can be used as power generation fuel for the SOFC
3.
[0125] Accordingly, with this embodiment, the fuel added by the
fuel adding injector 26 can be supplied to the SOFC 3 as power
generation fuel without changing the operation condition of the
engine 1. Further, the exhaust gas from the engine 1 can be
introduced into the SOFC 3, thereby the temperature of the SOFC 3
can be raised by a high temperature of the exhaust gas, and, still
further, portion of the exhaust gas from the engine 1 can be used
as the power generation fuel.
[0126] Here, a quantity of power generation fuel supplied to the
SOFC 3 can be adjusted by a quantity of the fuel injected from the
fuel adding injector 26. Specifically, with this embodiment, a
valve of the fuel adding injector 26 is opened intermittently, and
the fuel quantity to be added to the exhaust passage 2 is adjusted
by adjusting the valve open time and the valve closure time he
valve of the fuel adding injector 26. 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 the SOFC
3 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 the SOFC 3 become.
[0127] Thus, a relationship between the target amount of electric
power generation of the SOFC 3 and the valve open and closure times
of the fuel adding injector 26 may be prepared in a map form in
advance, and the valve open time and the valve closure time of the
fuel adding injector 26 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.
[0128] Further, this embodiment includes the heat exchanger 20 at
the downstream side of the SOFC 3 in the exhaust passage 2.
Moreover, and a bypass passage 21 for bypassing the exhaust gas
around the heat exchanger 20 has one end and the other end thereof
connected with the exhaust passage 2 at locations on the upstream
side and the downstream side of the heat exchanger 20,
respectively. A three-way valve 22 for selectively passing the
exhaust gas through either one of the bypass passage 21 and the
heat exchanger 20 is installed on the exhaust passage 2 at a
location thereof at which the bypass passage 21 is connected at the
other end thereof with the exhaust passage 2 on the downstream side
of the heat exchanger 20.
[0129] The heat exchanger 20 is provided with an unillustrated air
intake port, and heat exchange is performed in the heat exchanger
20 between the air taken through the air intake port and the
exhaust gas.
[0130] Further, one end of the air supply passage 7 is connected to
the heat exchanger 20. The other end of the air supply passage 7 is
connected to the exhaust passage 2 between the engine 1 and the
fuel adding injector 26. The air supply passage 7 includes at its
midway an air pump 27 for discharging the air under a predetermined
pressure from the side of the heat exchanger 20 towards the exhaust
passage 2 at the upstream of the SOFC 3.
[0131] With the above-described construction, the air with its
temperature raised in the heat exchanger 20 is introduced into the
exhaust passage 2 at the upstream side of the SOFC 3 through the
air supply passage 7. Consequently, the wall surface temperature of
the exhaust passage 2 and the temperature of the exhaust gas can be
raised. Thus, evaporation of the fuel added from the fuel adding
injector 26 can be advanced.
[0132] Further, in the low-load region, a degree of raising the
temperature of the wall surface of the exhaust passage 2 with the
heat of the exhaust gas from the engine 1 is small, thereby the
fuel added from the fuel adding injector 26 is liable to adhere to
the wall surface of the exhaust passage 2. However, with the
above-described construction, the temperature of the wall surface
of the exhaust passage 2 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 the SOFC 3.
[0133] Note that, in this embodiment, the other end of the air
supply passage 7 may be connected to the exhaust passage 2 at more
downstream from the fuel adding injector 26. Specifically, it is
sufficient to raise the temperature of a location in the exhaust
passage 2 where the fuel is adhered, by supplying the air from the
air supply passage 7.
[0134] With this embodiment, the fuel adding injector 26
constitutes the fuel supply system of the present invention.
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