JP2003222018A - Exhaust purification device for internal combustion engine - Google Patents

Abstract

(57) Abstract: In an exhaust gas purification device for an internal combustion engine, there is provided a technique capable of supplying a reducing agent to an exhaust gas purification catalyst while suppressing deterioration of fuel efficiency. An exhaust purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for extracting chemical energy generated when fuel is oxidized as electric energy, and a gaseous fuel for the fuel cell and the exhaust purification catalyst. And a fuel supply means 11 for supplying the fuel of the present invention to the exhaust gas purification catalyst 9 by supplying gaseous fuel before being oxidized by the fuel cell 11 as a reducing agent, regardless of the operating state of the internal combustion engine. Reduction of NOx, temperature rise of the exhaust purification catalyst 9, and the like can be performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust emission control device for an internal combustion engine.

[0002]

2. Description of the Related Art As an exhaust gas purification apparatus for purifying exhaust gas of an internal combustion engine, for example, a NOx catalyst may be arranged in an exhaust passage.

The NOx catalyst is a catalyst capable of purifying exhaust gas emitted from a lean-burn internal combustion engine such as a diesel engine or a lean burn gasoline engine, and a NOx catalyst of selective reduction type or a NOx catalyst of storage reduction type is included in this catalyst. Can be mentioned.

For example, the NOx storage reduction catalyst stores NOx when the oxygen concentration of the inflowing exhaust gas is high, and reduces the stored NOx when the oxygen concentration of the inflowing exhaust gas decreases.

In the case of this NOx storage reduction catalyst, the NOx in the exhaust is stored in the NOx catalyst because the air-fuel ratio of the exhaust gas in the normal operation of the internal combustion engine becomes lean. However, if exhaust gas having a lean air-fuel ratio is continuously supplied to the NOx catalyst, the NOx storage capacity of the NOx catalyst becomes saturated, NOx cannot be stored any more, and NOx is leaked. Therefore, in the NOx storage reduction catalyst, the oxygen concentration of the inflowing exhaust gas is reduced at a predetermined timing before the NOx storage capacity is saturated, and a reducing agent component such as hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas. It is necessary to increase the amount and reduce the NOx stored in the NOx catalyst to N ₂ to eliminate the NOx storage capacity of the storage reduction type NOx catalyst.

As described above, in the exhaust gas purification apparatus using the lean NOx catalyst, it is necessary to intermittently reduce the oxygen concentration of the exhaust gas and supply the reducing agent component in order to purify NOx. Then, as a method of intermittently reducing the oxygen concentration of the exhaust gas, there are a fuel addition in the exhaust gas and a sub-injection in which the fuel is further injected during the expansion stroke after the main injection of the fuel in the cylinder.

For example, in Japanese Unexamined Patent Publication No. 6-117225, in an exhaust gas purifying apparatus for an internal combustion engine equipped with an electronically controlled fuel injection valve for injecting fuel into a cylinder, the in-cylinder is used in the expansion stroke or exhaust stroke of the engine. I am trying to execute the injection. By electronically controlling the fuel injection valve in this way,
The timing and amount of sub-injection can be finely adjusted, it is possible to respond to changes in operating conditions, and it is possible to improve the NOx purification rate and suppress deterioration of HC emissions.

On the other hand, the NOx storage reduction catalyst has sulfur oxides (SO
x) is also stored by the same mechanism as NOx. SOx stored in this way is less likely to be released than NOx, and NOx
Accumulates in the catalyst. This is called sulfur poisoning (SOx poisoning), and the NOx purification rate decreases, so SOx is added at an appropriate time.
It is necessary to perform poisoning elimination processing that eliminates poisoning. This poisoning elimination processing is performed by circulating exhaust gas, in which the oxygen concentration is lowered while the NOx catalyst is at a high temperature, through the NOx catalyst.

However, since the temperature of the exhaust gas during the lean burn operation is low, it is difficult to raise the temperature of the catalyst to the temperature required to eliminate SOx poisoning.

Further, the catalyst has a temperature range in which exhaust gas can be effectively purified, and it is important to raise the temperature of the catalyst within this temperature range at the early stage of engine startup and then maintain that temperature. Become.

By the way, while the diesel engine is excellent in economic efficiency, it is a particulate matter (Particulat) typified by soot which is a suspended particulate matter contained in exhaust gas.
e Matter: Hereinafter referred to as "PM" unless otherwise specified. ) Is an important issue. Therefore, P
A technique is well known in which a particulate filter (hereinafter, simply referred to as “filter”) that traps PM is provided in an exhaust system of a diesel engine so that M is not released.

This filter can prevent PM in the exhaust gas from being once collected and released into the atmosphere. However, PM trapped in the filter may be deposited on the filter and may cause clogging of the filter. If this clogging occurs, the pressure of the exhaust gas upstream of the filter may increase, which may lead to a decrease in the output of the internal combustion engine or damage to the filter. In such a case, the PM accumulated on the filter can be removed by igniting and burning the PM. The removal of PM deposited on the filter in this way is called filter regeneration.

However, in order to ignite and burn the PM collected in the filter, it is necessary to raise the temperature of the filter, but since the temperature of the exhaust gas of the diesel engine is usually lower than this temperature, the PM is burned. It was difficult to remove.

As described above, when it is necessary to raise the temperature of the catalyst or the like and further maintain the temperature, an electric heater, a burner, or the like is used to reach the temperature required to eliminate SOx poisoning, or to catch the SOx poisoning. It is conceivable to raise the temperature of the catalyst and the like to a temperature at which ignited combustion of the collected PM occurs, and further to a temperature at which the catalyst purification rate is high. It is also possible to raise the temperature and maintain the temperature by utilizing the heat of oxidation reaction in the catalyst due to the addition of fuel or the auxiliary injection.

[0015]

However, when a large amount of exhaust gas is discharged from the engine, a large amount of fuel is required in order to reduce the oxygen concentration of the exhaust gas due to secondary injection, etc., which leads to deterioration of fuel efficiency. I will leave.

Further, in order to heat the filter with an electric heater or the like, it is necessary to supply a large amount of energy,
It is difficult to obtain a large amount of energy required by an exhaust gas purification device for an internal combustion engine mounted on a vehicle.

The present invention has been made in view of the above problems, and in an exhaust gas purification apparatus for an internal combustion engine,
An object of the present invention is to provide a technique capable of supplying a reducing agent to an exhaust purification catalyst while suppressing deterioration of fuel efficiency.

[0018]

In order to achieve the above object, the exhaust gas purifying apparatus for an internal combustion engine of the present invention employs the following means. That is, the first invention provides an exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for taking out chemical energy generated when fuel is oxidized as electric energy, a fuel cell and the exhaust gas purification catalyst. And a fuel supply means for supplying a gaseous fuel.

The greatest feature of the present invention is that the fuel before being oxidized in the fuel cell is supplied to the exhaust purification catalyst so that N
The purpose is to improve the catalyst purification rate by reducing Ox and raising the temperature of the catalyst.

In the exhaust gas purifying apparatus for an internal combustion engine thus configured, the fuel cell receives the fuel supplied by the fuel supply means to generate power. Here, since the fuel supplied by the fuel supply means has an oxidizing effect, it becomes possible to act as a reducing agent by supplying the fuel to the exhaust purification catalyst. The exhaust purification catalyst may be a filter carrying a catalyst.

In order to achieve the above object, the exhaust gas purifying apparatus for an internal combustion engine of the present invention employs the following means. That is, the second invention is an exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for extracting chemical energy generated when fuel is oxidized as electrical energy, and a fuel for supplying fuel to the fuel cell. And a fuel electrode side exhaust gas supply means for supplying exhaust gas from the fuel electrode side of the fuel cell to the exhaust gas purification catalyst.

The greatest feature of the present invention is to improve the catalyst purification rate by supplying the exhaust gas from the fuel electrode side of the fuel cell to the exhaust purification catalyst.

In the exhaust gas purifying apparatus for an internal combustion engine configured as described above, the fuel cell receives the supply of fuel from the fuel supply means to generate electricity. At this time, exhaust gas having a high temperature is discharged from the fuel electrode side of the fuel cell. By thus supplying the exhaust gas discharged from the fuel electrode side to the exhaust gas purification catalyst, the temperature of the exhaust gas purification catalyst can be raised or maintained regardless of the operating state of the internal combustion engine.

In the first and second inventions, the fuel reforming means for reforming the fuel is provided, and the fuel supply means can supply the fuel reformed by the fuel reforming means. The fuel reforming means can reform fuel for operating the internal combustion engine to hydrogen. Therefore, the fuel used for operating the internal combustion engine can be supplied to the fuel cell, and the fuel can be shared.

In order to achieve the above object, the exhaust gas purifying apparatus for an internal combustion engine of the present invention employs the following means. That is, the third invention is an exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for taking out chemical energy generated when fuel is oxidized as electric energy, and electric energy taken out by the fuel cell. Is supplied to heat the exhaust purification catalyst.

The greatest feature of the present invention is that the temperature of the exhaust purification catalyst is raised by supplying the electric power generated by the fuel cell to the heater for heating the exhaust purification catalyst to generate heat. .

In the exhaust gas purifying apparatus for an internal combustion engine configured as described above, the fuel cell supplied with the fuel generates electric power.
By supplying the electric power obtained at this time to the heater, it is possible to raise the temperature of the exhaust purification catalyst early before and immediately after the engine is started by the heater, and it is possible to maintain this temperature. Become.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> Specific embodiments of an internal combustion engine according to the present invention will be described below with reference to the drawings. Here, a case where the internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.

FIG. 1 is a diagram showing a schematic structure of an engine 1 and its intake and exhaust system according to the present embodiment.

The engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine.

The engine 1 is connected to a fuel pump 3 via a fuel supply pipe 2. The fuel pump 3 is a pump that operates by receiving power supply from the battery 4.
The fuel pump 3 is further connected via a fuel supply pipe 2 to a fuel tank 5 which stores fuel.

In the fuel supply system configured as described above, when electric power is supplied from the battery 4 to the fuel pump 3, the fuel pump 3 operates to suck up the fuel from the fuel tank 5 and then discharge the fuel. .

The fuel discharged from the fuel pump 3 is
The fuel is distributed to a fuel injection valve (not shown) through the fuel supply pipe 2, and the fuel is injected from the fuel injection valve into the cylinder.

Next, an intake pipe 6 is connected to the engine 1, and in the middle of the intake pipe 6, a centrifugal supercharger (turbocharger) 7 that operates using the energy of exhaust gas as a drive source.
The compressor housing 7a is provided.

In the intake system thus constructed, the intake air flows into the compressor housing 7a via the intake pipe 6. The intake air that has flowed into the compressor housing 7a is compressed by the rotation of the compressor wheel installed in the compressor housing 7a. The intake air that has been compressed in the compressor housing 7a and has a high pressure is distributed to the combustion chamber of each cylinder, and is combusted using the fuel injected from the fuel injection valve of each cylinder as an ignition source.

On the other hand, an exhaust pipe 8 is connected to the engine 1, and the exhaust pipe 8 communicates with a combustion chamber of each cylinder via an exhaust port (not shown).

The exhaust pipe 8 is connected to the turbine housing 7b of the centrifugal supercharger 7. The turbine housing 7b is connected to an exhaust pipe 8 and the exhaust pipe 8
Is connected downstream to a muffler (not shown).

In the middle of the exhaust pipe 8, a storage reduction type NO
A particulate filter 9 carrying an x catalyst is provided. A heater 10 that receives power from the battery 4 and generates heat is provided on the upstream side of the filter 9.

In the exhaust system configured as described above, the air-fuel mixture (burnt gas) burned in each cylinder of the engine 1 is discharged to the exhaust pipe 8 through the exhaust port, and then the centrifugal supercharge is performed from the exhaust pipe 8. It flows into the turbine housing 7b of the machine 7. The exhaust gas that has flowed into the turbine housing 7b uses the energy of the exhaust gas to rotate the turbine wheel that is rotatably supported in the turbine housing 7b. At that time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 7a described above.

The exhaust gas discharged from the turbine housing 7b flows into the filter 9 through the exhaust pipe 8, and the particulate matter (hereinafter referred to simply as PM) in the exhaust gas is collected. Further, the NOx storage reduction catalyst carried by the filter 9 (hereinafter, simply referred to as NOx catalyst).
Stores (absorbs, adsorbs) nitrogen oxides (NOx) in the exhaust gas when the oxygen concentration of the exhaust gas flowing into the NOx catalyst is high.
To do. On the other hand, the NOx catalyst releases the stored nitrogen oxides (NOx) when the oxygen concentration of the exhaust flowing into the NOx catalyst decreases. At that time, hydrocarbons (H
If a reducing component such as C) or carbon monoxide (CO) is present, nitrogen oxides (NOx) are reduced to nitrogen (N ₂ ).

Then, the exhaust gas having the PM collected by the filter 9 is discharged into the atmosphere through the muffler.

When it becomes necessary to heat the filter 9, the heater 10 receives power from the battery 4 to generate heat.

The exhaust gas purification apparatus for an internal combustion engine according to this embodiment includes a fuel cell 11. This fuel cell 11
Is electrically connected to the auxiliary components 19 such as the electric air conditioner compressor, the electric oil pump, and the electric power steering pump in addition to the electric water pump 14 through the battery 4, and supplies electric power to the auxiliary devices 19. . In the present embodiment, the structure and control are simple, and a solid oxide fuel cell (solid oxide fuel cell: solid oxide fuel cell: solid oxide fuel cell: , SOFC).

The SOFC 11 includes a fuel electrode 11a and an electrolyte 1
1b and the air electrode 11c are provided with three types of oxide electrolytes. The SOFC 11 is connected to the FC fuel pump 12 via the fuel supply pipe 2, and the FC fuel pump 12 is further connected to the fuel tank 5 via the fuel supply pipe 2.

A cooling water passage 13 for circulating cooling water in the SOFC 11 is connected to the SOFC 11. The cooling water passage 13 includes an electric water pump 14,
It is connected to the engine 1 and the heater core 15 for heating. The electric water pump 14 receives power from the battery 4 and operates to circulate cooling water.

Further, an air pump 16 for sending air to the air electrode 11c of the SOFC 11 is connected to the SOFC 11 via an air supply passage 17. The air pump 1
6 receives electric power from the battery 4 to operate and discharges air.

As the fuel necessary for operating the SOFC 11, the same light oil as the engine 1 is used. The fuel supplied to the SOFC 11 by the FC fuel pump 12 reacts with water vapor on the fuel electrode 11a to be reformed into hydrogen (H ₂ ) and carbon monoxide (CO). In this way, SOFC11
It is possible to reform the fuel in the cell. On the other hand, air is supplied to the air electrode 11c by the air pump 16. In the air electrode 11c, the oxygen in the air is the electrolyte 11
At the interface with b, it dissociates into oxygen ions (O ²⁻ ) and moves in the electrolyte 11b toward the fuel electrode 11a. The oxygen ions (O ²⁻ ) that have reached the interface between the electrolyte 11b and the fuel electrode 11a react with hydrogen (H ₂ ) and carbon monoxide (CO) to produce water (H ₂ O) and carbon dioxide (CO ₂ ). ) Is generated. Power generation by the SOFC 11 is performed by taking out the electrons emitted at this time. In this way
Since the chemical energy of the fuel is directly converted into electric energy, loss due to energy conversion is small, and highly efficient power generation is possible. Such power generation is, for example, 700 to 1
It is carried out at a temperature of 000 ° C.

The SOFC 11 thus constructed is
It operates by the signal from CU18. A part of the electric power obtained by the power generation is temporarily stored in the battery 4. In addition to the electric water pump 14, an auxiliary equipment 19 such as an electric air conditioner compressor, an electric oil pump, an electric power steering pump, etc. is electrically connected to the battery 4, and electric power is supplied to these devices.

Further, in the SOFC 11 according to the present embodiment, the reducing agent supply passage for supplying hydrogen (H ₂ ) and carbon monoxide (CO) generated as a result of reforming the fuel on the fuel electrode 11a side to the filter 9. 21 is connected to one end, and the other end of the reducing agent supply passage 21 is connected to the exhaust pipe 8 upstream of the filter 9. At the connection between the SOFC 11 and the reducing agent supply passage 21, a shutoff valve 20 that opens and closes according to a signal from the ECU 18 is provided.

In the reducing agent supply mechanism thus constructed, the ECU 18 activates the SOFC 11 when the reducing agent needs to be supplied to the filter 9. SOFC
Hydrogen (H ₂ ) and carbon monoxide (CO) generated by the reforming of the fuel at 11 pass through the cutoff valve 20 that has been opened and flow through the reducing agent supply passage 21, and from the upstream side of the filter 9 to the filter 9 Flows into. In this way, the reducing agent can be supplied to the filter 9.

Further, hydrogen (H ₂ ) supplied at this time
Also, since the temperature of carbon monoxide (CO) is high, it is possible to raise the temperature of the filter 9.

In such an engine 1, the engine 1
Electronic control unit (ECU: Electron) for controlling
ic Control Unit) 18 is attached. This ECU
Reference numeral 18 denotes a unit that controls the operating state of the engine 1 according to the operating conditions of the engine 1 and the driver's request.

Various sensors are connected to the ECU 18 through electrical wiring, and the output signals of the various sensors described above are EC.
It is designed to be input to U18. Also, the ECU 1
8 is an FC ECU 2 for controlling the SOFC 11.
2 is connected.

By the way, when the engine 1 is in the lean burn operation, the air-fuel ratio of the exhaust gas discharged from the engine 1 becomes a lean atmosphere and the oxygen concentration of the exhaust gas becomes high.
Nitrogen oxides (NOx) contained in the exhaust gas will be stored in the NOx catalyst, but if the lean burn operation of the engine 1 is continued for a long period of time, the NOx storage capacity of the NOx catalyst will be saturated, and Nitrogen oxides (NOx) are released into the atmosphere without being removed by the NOx catalyst.

In particular, in a diesel engine such as the engine 1, a lean air-fuel ratio mixture is burned in most operating regions, and accordingly, the exhaust air-fuel ratio becomes lean air-fuel ratio in most operating regions. , N of NOx catalyst
Ox storage capacity is easily saturated. Incidentally, the lean air-fuel ratio here is, for example, 20 to 50 in a diesel engine,
It means a region where the three-way catalyst cannot purify NOx.

Therefore, when the engine 1 is in the lean burn operation, the concentration of oxygen in the exhaust flowing into the NOx catalyst is reduced and the concentration of the reducing agent is increased before the NOx storage capacity of the NOx catalyst is saturated, and NOx is increased. It is necessary to reduce the nitrogen oxides (NOx) stored in the catalyst.

Here, in the conventional exhaust gas purification apparatus for an internal combustion engine, when it is necessary to supply the reducing agent to the filter or the NOx catalyst, fuel is added to the exhaust gas, or the fuel is expanded in the engine expansion and exhaust strokes. A secondary injection was performed. However, in addition of these fuels and secondary injection, it is necessary to supply a large amount of fuel, resulting in deterioration of fuel efficiency.
In addition, in the fuel addition, hydrogen (H ₂ ) and carbon monoxide (CO) are not directly supplied to the filter or the NOx catalyst, and further it is difficult to uniformly supply them to the filter or the like unless they are gasified. In such a state, the reduction efficiency is low, and again a large amount of fuel needs to be supplied.

Therefore, in the present embodiment, the reformed fuel generated at the time of SOFC power generation is supplied to the filter. As described above, by using the reformed fuel generated during the SOFC power generation, it becomes possible to supply the reducing agent to the filter regardless of the operating state of the internal combustion engine. Therefore, since it is not necessary to change the fuel injection control to the engine, the operating condition of the engine is not deteriorated. Further, it becomes possible to supply a gas having a strong reducing power such as hydrogen (H ₂ ) and carbon monoxide (CO) to the filter. Since hydrogen (H ₂ ) and carbon monoxide (CO) at this time are gasified, it is possible to uniformly supply the reducing agent to the filter. As described above, by using the reformed fuel generated during the SOFC power generation as the reducing agent, it is possible to suppress the deterioration of fuel efficiency.

Next, the flow of the reducing agent supply control according to this embodiment will be described.

FIG. 2 is a flowchart showing the flow of the reducing agent supply control according to this embodiment.

In step S101, it is determined whether the reduction process of the filter 9 is necessary. For the determination, a NOx sensor (not shown) that detects the NOx concentration in the exhaust gas may be provided downstream of the filter 9, and the reduction process of the filter 9 may be necessary when the NOx concentration becomes a predetermined value or more. This is because when the NOx storage amount of the filter 9 increases, the NOx that passes through the filter 9 without being stored increases.
This is because the NOx concentration downstream of the filter 9 becomes high.
The predetermined value used for the determination is obtained in advance by experiments or the like. In addition, the NOx occlusion amount is due to the vehicle traveling distance being a predetermined distance or more, the operating time of the engine 1 being a predetermined time or more, the cumulative value of the injection amount being a predetermined value or more. May be estimated.

If an affirmative judgment is made in step S101, the routine proceeds to step S102, while if a negative judgment is made, this routine is ended.

In step S102, it is determined whether or not the bed temperature of the filter 9 has exceeded a predetermined temperature. The temperature of the catalyst can be obtained by the filter temperature sensor 23 provided in the filter 9. Alternatively, the electric resistance of the heater 10 may be obtained from the energization current of the heater 10 and the voltage of the battery 4, and the heater 10 temperature may be obtained from a map of the resistance of the heater 10 and the heater 10 temperature which is obtained in advance. Further, it may be estimated from the energization time of the heater 10. The predetermined temperature at this time is 250 ° C., for example.

If an affirmative decision is made in step S102, the operation proceeds to step S103, while if a negative decision is made, the operation proceeds to step S104.

In step S103, the reformed fuel generated by the SOFC 11 is supplied upstream of the filter 9. E
The CU 18 sends a signal to the FC ECU 22 to send the SOFC1
1 is operated and the shutoff valve 20 is opened to supply the reformed fuel upstream of the filter 9.

In step S104, the filter 9 is heated by the heater 10. By heating with the heater 10, the NOx storage reduction catalyst is raised to a temperature required for releasing NOx.

In step S105, it is determined whether or not the return processing termination condition is satisfied. Here, the reduction process termination condition means that the NOx concentration in the exhaust gas obtained from the NOx sensor provided downstream of the filter 9 is equal to or lower than a predetermined value, or the reformed fuel is supplied to the filter 9 for a predetermined time. This indicates that the reduction ability of the NOx storage reduction catalyst has been restored.

In step S106, the supply of the reducing agent is stopped. The ECU 18 closes the shutoff valve 20 to stop the supply of the reformed fuel. If you don't need to generate electricity,
A signal is sent to the FC ECU 22 to stop the operation of the SOFC 11 at the same time.

In this way, it becomes possible to supply the reforming fuel as the reducing agent to the filter 9.

Further, the supply of the reformed fuel is not limited to the release of NOx from the NOx storage reduction catalyst, but a reducing agent may be supplied when SOx poisoning is eliminated, or when SOx poisoning is eliminated and PM is eliminated.
It is also possible to raise the temperature of the filter 9 during the removal.

Next, the poisoning elimination control will be described.

Here, sulfur (S) is used as the fuel for the engine 1.
When such a fuel is burned in the engine 1, sulfur oxides (SOx) such as sulfur dioxide (SO ₂ ) and sulfur trioxide (SO ₃ ) are generated.

The sulfur oxide (SOx) flows into the filter 9 together with the exhaust gas and is stored in the filter 9 by the same mechanism as the nitrogen oxide (NOx).

Specifically, when the oxygen concentration of the exhaust gas flowing into the filter 9 is high, the sulfur oxides (SO ₂ ) such as sulfur dioxide (SO ₂ ) and sulfur trioxide (SO ₃ ) in the inflowing exhaust gas are
x) is oxidized on the surface of platinum (Pt) and stored in the filter 9 in the form of sulfate ions (SO ₄ ²⁻ ). Further, the sulfate ions (SO ₄ ²⁻ ) stored in the filter 9 combine with barium oxide (BaO) to form a sulfate salt (BaSO ₄ ).

By the way, the sulfate (BaSO ₄ ) is more stable than barium nitrate (Ba (NO ₃ ) ₂ ) and difficult to decompose, and is decomposed even when the oxygen concentration of the exhaust gas flowing into the filter 9 becomes low. Instead, they remain in the filter 9.

Sulfate (BaSO ₄ ) in the filter 9
As the amount of nitrogen increases, nitrogen oxides (NOx) correspondingly increase.
Oxide (BaO) that can be involved in the storage of
Since the amount of NOx is reduced, so-called SOx poisoning occurs in which the NOx storage capacity of the filter 9 is reduced.

As a method of eliminating SOx poisoning of the filter 9, the ambient temperature of the filter 9 is set to about 600 to 6
By raising the temperature to a high temperature range of 50 ° C. and reducing the oxygen concentration of the exhaust gas flowing into the filter 9, the barium sulfate (BaSO ₄ ) stored in the filter 9 is reduced to S.
A method of thermally decomposing into O ₃ ⁻ or SO ₄ ⁻ and then reacting SO ₃ ⁻ or SO ₄ ⁻ with hydrocarbons (HC) or carbon monoxide (CO) in the exhaust gas to reduce to gaseous SO ₂ ^−. Can be illustrated.

Therefore, in the poisoning elimination processing according to the present embodiment, the ECU 18 first executes the catalyst temperature raising control for raising the bed temperature of the filter 9 and then lowers the oxygen concentration of the exhaust gas flowing into the filter 9. I did it.

In the catalyst temperature raising control, the ECU 18 sends a signal to the FC ECU 22 to operate the SOFC 11, and at the same time, opens the shut-off valve 20 to add the reformed fuel to the exhaust gas, so that the filter 9 controls them. Oxidize. The filter 9 is heated by the heat generated during the oxidation.
Can raise the floor temperature.

When the bed temperature of the filter 9 rises to a high temperature range of about 600 ° C. to 650 ° C. by the catalyst temperature increasing process as described above, the ECU 18 intermittently supplies the reformed fuel to the filter 9.

When the poisoning elimination processing is executed in this way,
When the bed temperature of the filter 9 is high, the oxygen concentration of the exhaust gas flowing into the filter 9 becomes low, so that barium sulfate (BaSO ₄ ) stored in the filter 9 becomes SO ₃ ⁻ or SO ₄ ^−.
Is thermally decomposed into SO ₃ ⁻ and SO ₄ ^{−, which} are reduced by reacting with hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas,
As a result, SOx poisoning of the filter 9 is eliminated.

On the other hand, depending on the operating condition of the engine, the PM captured by the filter 9 remains unburned and accumulated, which causes the filter 9 to be clogged. As one of the methods for effectively removing the unburned PM, the temperature increase control by the fuel addition is effective. The active oxygen is released by the reformed fuel that has flowed into the filter 9, so that the PM is transformed into a substance that is easily oxidized, and the amount that can be oxidized and removed per unit time is improved. Further, by adding the reforming fuel, oxygen poisoning of the catalyst is removed and the activity of the catalyst is increased, so that active oxygen is easily released. Further, the temperature of the filter 9 rises due to the oxidation reaction of the reformed fuel. Then, PM is oxidatively burned and removed by the active oxygen.

On the other hand, since the exhaust gas from the fuel electrode 11a side has a high temperature, the temperature of the filter 9 can be raised by supplying this exhaust gas to the filter 9. Here, an exhaust passage is provided which is connected to the exhaust pipe 8 upstream of the filter 9 via a flow path switching valve (not shown) in the middle of a passage (not shown) for discharging exhaust from the fuel electrode 11a side. Thus, the exhaust gas from the fuel electrode 11a side is supplied to the upstream side of the filter 9. The ECU 18 sends a signal to the flow path switching valve when it is necessary to raise the temperature of the filter 9 and the fuel electrode 1
Exhaust gas from the 1a side is supplied to the filter 9.

In this way, the temperature of the filter 9 can be raised. Therefore, it is possible to activate the filter 9 even before the engine is started and immediately after the engine is started, and it is possible to suppress the deterioration of the emission immediately after the engine is started. It is also possible to raise the temperature of the filter 9 when SOx poisoning is eliminated or PM is removed by high-temperature exhaust from the fuel electrode 11a side. The temperature control of the filter 9 can be performed as in the case of supplying the reformed fuel.

In the conventional exhaust gas purifying apparatus for an internal combustion engine, when it is necessary to supply the reducing agent to the filter or the catalyst, or when it is necessary to raise the temperature of the filter or the catalyst, the fuel is discharged into the exhaust gas. Secondary injection was performed in which fuel was added, or fuel was injected during expansion and exhaust stroke of the engine. However, with these fuel additions and secondary injections,
It was necessary to supply a large amount of fuel, resulting in deterioration of fuel efficiency. Further, in the fuel addition, hydrogen (H ₂ ) and carbon monoxide (CO) are not directly supplied to the filter or the catalyst, and further it is difficult to uniformly supply to the filter 9 unless gasified. In such a state, the reduction efficiency is low and it is necessary to supply a large amount of fuel.

In this respect, in this embodiment, the SOFC 11
By supplying the reformed fuel generated at the time of power generation of the filter 9 to the filter 9, regardless of the operating state of the internal combustion engine,
It becomes possible to supply the reducing agent to. Therefore, since it is not necessary to change the fuel injection control to the engine, the operating condition of the engine is not deteriorated. Further, it is possible to supply a gas having a strong reducing power such as hydrogen (H ₂ ) and carbon monoxide (CO) to the filter 9. Since hydrogen (H ₂ ) and carbon monoxide (CO) at this time are gasified, it is possible to uniformly supply the reducing agent to the filter 9. As described above, by using the reformed fuel generated during the power generation of the SOFC 11 as the reducing agent, it is possible to suppress the deterioration of fuel efficiency.

Further, the SOFC 11 is used to generate electric power, and the electric power is used to drive the auxiliary machinery, whereby the drive loss of the auxiliary machinery can be eliminated and the engine efficiency can be improved.
Further, if the required output is the same, the displacement of the internal combustion engine can be reduced, and the fuel consumption can be improved.

Since the cooling water for the engine 1 can be used for cooling the SOFC 11, the cost can be reduced and the reliability can be improved as compared with the case where a cooling system for the SOFC 11 is newly provided. be able to. Second Embodiment In the present embodiment, the electric power obtained by the power generation of the SOFC 11 is supplied to the heater 10 to raise the temperature of the filter 9.

The basic configuration of the engine 1 and other hardware to which the present embodiment is applied is the same as that of the first embodiment, and the description thereof is omitted.

Here, in the conventional exhaust gas purifying apparatus for an internal combustion engine, exhaust gas is not sufficiently purified when the temperature of the catalyst is low immediately after the engine is started. This is because the catalyst requires a certain temperature to be activated, and the purifying ability of the catalyst is lowered until this temperature is reached. Furthermore, in a direct injection diesel engine or the like equipped with a turbocharger, it takes time to raise the temperature to a temperature at which the catalyst is activated because the exhaust temperature is low. Further, in such an engine, when the NOx storage reduction catalyst is provided, it becomes difficult to raise the temperature to the temperature required for eliminating SOx poisoning. On the other hand, when a filter for collecting PM in exhaust gas is provided, it is necessary to raise the temperature of the filter to burn and remove the PM. However, raising the temperature of the filter to such a temperature is still necessary. Have difficulty.

When the temperature of the exhaust gas from the engine is raised or the reducing agent is supplied to the catalyst in order to raise the temperature of the catalyst or the filter, a direct injection diesel engine equipped with a turbocharger is used. Etc., the temperature of the exhaust gas is low and the amount of the exhaust gas is large, so that the reducing agent is consumed in a large amount, and when fuel is used as the reducing agent, the fuel consumption deteriorates.

Further, it is possible to provide a heater for the catalyst and the like to heat the catalyst and the like by the electric power from the battery, but the deterioration of the battery is accelerated and early replacement is required. Further, it is necessary to increase the capacity of the battery, which makes it difficult to mount the battery on a vehicle. Further, fuel consumption may deteriorate due to consumption of fuel for power generation.

Therefore, in the present embodiment, the filter is equipped with an electric heater, and the electric power generated by the SOFC is supplied to this heater to generate heat to raise the temperature of the filter. Where S
Power generation by OFC is generally more efficient than an alternator (generator) mounted on a vehicle. Therefore, it is possible to suppress deterioration of fuel efficiency. Further, since it is possible to generate power even when the engine is stopped, it is not necessary to increase the capacity of the battery. Further, the temperature of the filter can be raised regardless of the engine operating state. Therefore, the temperature of the filter 9 can be raised before the engine is started. Further, it does not affect the engine operating state. Since the efficiency of the catalyst can be increased by raising the temperature of the catalyst, the capacity of the catalyst can be reduced, the size can be reduced, and the amount of the precious metal used for the catalyst can be reduced.

Next, the catalyst temperature raising control for raising the temperature of the catalyst in advance when the engine is started according to the present embodiment will be described.

FIG. 3 is a flow chart showing a flow for raising the temperature of the catalyst in advance when the engine is started.

In step S201, it is determined whether or not the door (not shown) on the driver's seat side is opened. For the trigger signal which is the condition for starting execution of the control, for example, a door opening / closing signal on the driver's side transmitted by a door opening / closing sensor (not shown) is used. Before the vehicle driver starts the engine 1 mounted on the vehicle, the operation of opening the vehicle door and getting on the vehicle is naturally involved. Therefore, when it is detected that the vehicle door is opened, the ECU 18 is activated to raise the temperature of the filter 9 so that the filter 9 is in an active state when the vehicle driver starts the engine 1.

If an affirmative judgment is made in step S201, the routine proceeds to step S202, while if a negative judgment is made, this routine is ended.

In step S202, the SOFC 11 is activated. The ECU 18 sends a signal to the FC ECU 22 to activate the SOFC 11 and start power generation.

In step S203, the heater 10 is energized.

In step S204, it is determined whether or not the bed temperature of the catalyst has exceeded a predetermined temperature. The catalyst bed temperature can be obtained by, for example, the filter temperature sensor 23 provided in the filter 9. Further, the electric resistance of the heater 10 may be obtained from the energization current of the heater 10 and the voltage of the battery 4, and the heater 10 temperature may be obtained from the map of the heater 10 resistance and the heater 10 temperature which are obtained in advance. Further, it may be estimated from the energization time of the heater 10. Here, the predetermined temperature is, for example, 250 ° C.

If an affirmative decision is made in step S204, the operation proceeds to step S205, while if a negative decision is made, the operation returns to step S203.

In this way, it becomes possible to raise the temperature of the filter 9 and activate the NOx storage reduction catalyst even before the engine is started.

Next, the temperature rise control required for eliminating SOx poisoning of the NOx storage reduction catalyst will be described.

FIG. 4 is a flow chart showing the control flow when the temperature of the filter 9 is raised.

In step S301, it is determined whether the filter 9 regeneration (SOx poisoning elimination) process is necessary.
For the determination, a NOx sensor (not shown) that detects the NOx concentration in the exhaust gas may be provided downstream of the filter 9, and the regeneration process of the filter 9 may be necessary when the NOx concentration becomes equal to or higher than a predetermined value. This is the SO stored in the filter 9.
This is because when the amount of x increases, the amount of NOx that passes through the filter 9 without being stored increases, and the NOx concentration downstream of the filter 9 increases. The predetermined value used for the determination is obtained in advance by experiments or the like. Further, the storage amount of SOx may be estimated when the traveling distance of the vehicle is equal to or greater than a predetermined distance, the operating time of the engine 1 is equal to or greater than a predetermined time, or the like.

If an affirmative decision is made in step S301, the operation proceeds to step S302, while if a negative decision is made, this routine is ended.

In step S302, the SOFC 11 is activated. The ECU 18 sends a signal to the FC ECU 22 to activate the SOFC 11 and start power generation.

In step S303, the heater 10 is energized.

In step S304, it is determined whether the bed temperature of the catalyst has reached a predetermined temperature or higher. The catalyst bed temperature can be obtained, for example, by a temperature sensor (not shown) provided in the filter 9. Further, the electric resistance of the heater 10 may be obtained from the energization current of the heater 10 and the voltage of the battery 4, and the heater 10 temperature may be obtained from the map of the heater 10 resistance and the heater 10 temperature which are obtained in advance. Further, it may be estimated from the energization time of the heater 10. Here, the predetermined temperature is, for example, 500 ° C.

If an affirmative decision is made in step S204, the operation proceeds to step S305, while if a negative decision is made, the operation returns to step S303.

In this way, it becomes possible to raise the temperature of the filter 9 to the temperature required for eliminating SOx poisoning. Thereafter, the oxygen concentration in the exhaust gas is reduced to regenerate the NOx storage reduction catalyst.

In the present embodiment, the temperature rise control during catalyst regeneration has been described, but the temperature rise control during PM regeneration for removing the PM trapped in the filter 9 can also be applied. In this case, in step S301, it is determined whether the PM regeneration process of the filter 9 is necessary. For the determination, a differential pressure sensor (not shown) that measures the pressure difference between the exhaust gas upstream and downstream of the filter 9 may be provided, and the amount of PM trapped in the filter 9 may be determined based on this output signal. In addition, it is possible to determine the amount of trapped PM by, for example, reducing the front pressure of the filter 9 (back pressure upstream of the filter 9) or the intake air amount.

The predetermined value used for the determination is previously obtained by experiments or the like. Alternatively, the amount of collected PM may be estimated based on that the traveling distance of the vehicle is equal to or greater than a predetermined distance, the operating time of the engine 1 is equal to or greater than a predetermined time, or the like.

In this way, the temperature of the filter 9 is raised and PM
It is possible to burn and remove. <Others> In the first and second embodiments described above, the filter 9 and the NOx storage reduction type carried by the filter 9 are used.
Although the catalyst has been described, it may be applied instead of this in the case of raising the temperature of the exhaust purification catalyst having an oxidizing function.

Further, in the first and second embodiments, the example of using the solid oxide fuel cell capable of reforming the fuel inside the fuel cell has been described, but instead of this, another type of fuel is used. A battery such as a polymer fuel cell may be used. In this case, the fuel reforming means may not be provided, and a means capable of storing hydrogen may be separately provided so that the hydrogen is directly supplied to the fuel cell, the exhaust purification catalyst and the like. Further, a reformer for reforming fuel for operating the internal combustion engine, methanol, natural gas, or the like into hydrogen may be separately provided to supply hydrogen to the fuel cell, the exhaust purification catalyst, or the like.

[0116]

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the gaseous fuel used for power generation in the fuel cell is purified by the exhaust gas regardless of the operating state of the internal combustion engine and without deteriorating the operating state. It can be fed to the catalyst. Since this fuel is gaseous, it can be uniformly supplied to the entire exhaust purification catalyst. Further, since the gaseous fuel acts as a reducing agent having a strong reducing power on the catalyst, the fuel consumption can be suppressed to a small amount. Therefore, in the fuel of the fuel cell,
When the fuel used for operating the internal combustion engine is used, fuel consumption can be improved.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the exhaust gas from the fuel electrode, which is discharged when the fuel cell performs power generation, is supplied to the catalyst so that the exhaust gas can be discharged regardless of the operating state of the internal combustion engine. The temperature of the catalyst can be raised. Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the temperature of the catalyst can be raised before the engine is started by supplying the electric energy obtained from the fuel cell to the heater, and the operating state after the engine is started. The temperature of the catalyst can be raised or maintained regardless of the temperature. Therefore, the exhaust gas purification rate of the catalyst can be increased and the exhaust emission deterioration can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention is applied and an intake / exhaust system thereof.

FIG. 2 is a flowchart showing a flow of reducing agent supply control according to the first embodiment.

FIG. 3 is a flowchart showing a flow for raising the temperature of the catalyst in advance when the engine is started.

FIG. 4 is a flowchart showing a control flow when the temperature of the filter is raised.

[Explanation of symbols]

1 ... Engine 2 ... Fuel supply pipe 3 ... Fuel pump 4 ... Battery 5 ... Fuel tank 6 ... Intake pipe 7 ... Centrifugal turbocharger 8 ... Exhaust pipe 9 ... Particulate filter 10 ... Heater 11 ... Fuel cell (SOFC) 12 ... FC fuel pump 13 ... Cooling water passage 14 ... Electric water pump 15: Heater core 16 ... Air pump 17 ... Air supply passage 18 ... ECU 19 ... Auxiliary equipment 20 ... Shut-off valve 21 ... Reductant supply passage 22 ... FC ECU 23 ... Filter temperature sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 9/00 H01M 8/00 ZABZ H01M 8/00 ZAB 8/06 G 8/06 8/12 // H01M 8/12 B01D 53/36 103B F term (reference) 3G091 AA02 AA10 AA18 AB06 AB13 AB14 BA03 BA04 BA11 BA14 CA03 CA18 CA19 CB08 DB10 EA15 EA18 HA14 4D048 AA06 AA18 AB01 BB02 CC53 CD05 DA02 DA08 DA13 5H027 A06 5H027 A06 5H027 AA06 5H027 A06

Claims (4)

[Claims] 1. An exhaust purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for taking out chemical energy generated when fuel is oxidized as electrical energy, and a gaseous state for the fuel cell and the exhaust purification catalyst. An exhaust gas purification apparatus for an internal combustion engine, comprising: a fuel supply unit that supplies fuel. 2. An exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for taking out chemical energy generated when fuel is oxidized as electric energy, and a fuel supply means for supplying fuel to the fuel cell. An exhaust gas purification apparatus for an internal combustion engine, comprising: a fuel electrode side exhaust gas supply means for supplying exhaust gas from the fuel electrode side of the fuel cell to the exhaust gas purification catalyst. 3. The internal combustion engine according to claim 1, further comprising fuel reforming means for reforming the fuel, wherein the fuel supply means supplies the fuel reformed by the fuel reforming means. Exhaust gas purification device for engines. 4. An exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine, a fuel cell for taking out chemical energy generated when fuel is oxidized as electric energy, and electric energy taken out by the fuel cell. And a heater for heating the exhaust gas purification catalyst, and an exhaust gas purification device for an internal combustion engine.