JPH11294145A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of torque shock at the time of recovering purifying performance of an exhaust emission control device. SOLUTION: In order to reactivate an NOx catalyst housed in a catalytic converter 22 of an exhaust emission control device, an opening of an exhaust throttle valve 20 is throttled for reducing a flow amount of exhaust gas. Reduction agent is added thereto from an addition nozzle 21. When the state is left, pumping loss is increased by the execution of exhaust throttling, and an output of an engine 1 is reduced. Torque shock may be caused. To cope with it, an opening of an EGR valve 29 is increased so as to obtain an engine output same as that prior to execution of exhaust throttling. In addition, a main fuel injection amount to be supplied to a combustion chamber of the engine 1 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to an exhaust gas purifying apparatus for an internal combustion engine that burns at a lean air-fuel ratio, such as a diesel engine or a gasoline engine burning a lean mixture. The present invention relates to an exhaust gas purification device that can be effectively removed.

[0002]

2. Description of the Related Art An exhaust gas purifying apparatus of this type is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-200740. In this device, a NOx catalyst that absorbs NOx in the presence of oxygen is disposed in an exhaust passage of a diesel engine, the NOx catalyst absorbs NOx in exhaust gas, and the NOx of the NOx catalyst
When the absorption efficiency is reduced, the flow rate of exhaust gas to the NOx catalyst is reduced to supply a gaseous reducing agent, so that the NOx
It releases NOx from the catalyst and reduces and purifies the released NOx. That is, in this device, the supplied reducing agent burns by the catalytic action of the NOx catalyst, consumes oxygen in the exhaust gas, and lowers the atmospheric oxygen concentration of the NOx catalyst, thereby reducing the NOx absorbed from the NOx catalyst. It is released and reduced and purified by a reducing agent.

[0003]

In the above-mentioned conventional exhaust gas purifying apparatus, the oxygen concentration in the atmosphere of the NOx catalyst is reduced to release the NOx absorbed from the NOx catalyst to perform reduction purification (hereinafter referred to as NOx release and reduction). NOx purification operation
In order to efficiently regenerate the NOx catalyst with a small amount of reducing agent, an exhaust throttle valve is installed upstream of the NOx catalyst, and the opening of the exhaust throttle valve is reduced. Thus, the flow rate of exhaust gas to the NOx catalyst is reduced.

[0004] However, when the opening degree of the exhaust throttle valve is reduced in this way, the pressure loss in the exhaust throttle valve becomes large, causing a decrease in output torque and a possibility of causing a torque shock.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and it is an object of the present invention to solve the above-mentioned problem. Thus, the driving performance is improved.

[0006]

The present invention has the following features to attain the object mentioned above.

According to the present invention, there is provided a purifying device provided in an exhaust passage of an internal combustion engine, reducing agent adding means for adding a reducing agent to the purifying device, and a reducing agent added to the purifying device by the reducing agent adding means. Exhaust gas flow control means for controlling the flow rate of exhaust gas flowing through the exhaust passage of the internal combustion engine to be reduced when the exhaust gas flows through the internal combustion engine, wherein a reducing agent is added to the purification device by the reducing agent adding means. A power reduction control means for controlling at least one of the parameters related to combustion to suppress a power reduction of the internal combustion engine.

[0008] In this exhaust gas purifying apparatus, in order to efficiently recover the purifying performance of the purifying apparatus, when the reducing agent is added from the reducing agent adding means to the purifying apparatus, the exhaust gas flow control means reduces the exhaust gas flow of the internal combustion engine. . If the exhaust flow rate is reduced, the pumping loss increases and the output of the internal combustion engine is reduced if left unchecked. Therefore, the output reduction suppression correcting means controls at least one of the parameters related to the combustion of the internal combustion engine so that the output does not decrease. I do. Accordingly, the internal combustion engine is maintained at the same engine output as before the purification performance recovery operation even when the purification performance recovery operation of the purification device is being performed.
Therefore, drivability is improved without generating torque shock.

The purifier may be of any type, for example, a DPF (Diesel Particulate Filter), a storage-reduction NOx catalyst or a storage-reduction type NOx catalyst, as long as it requires a reducing agent to restore the purification performance. It may be a selective reduction type NOx catalyst.

The storage-reduction NOx catalyst uses, for example, alumina as a carrier, and on the carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs; an alkaline earth such as barium Ba and calcium Ca; At least one selected from rare earth elements such as lanthanum La and yttrium Y and a noble metal such as platinum Pt are supported. When the ratio of air and fuel (hydrocarbon) supplied into the engine intake passage and the exhaust passage upstream of the NOx storage reduction catalyst is referred to as the air-fuel ratio of the exhaust gas flowing into the NOx storage reduction catalyst, The NOx catalyst absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases.

The selective reduction type NOx catalyst refers to a catalyst that reduces or decomposes NOx in the presence of hydrocarbons in an oxygen-excess atmosphere. A catalyst in which a transition metal such as Cu is ion-exchanged on zeolite, zeolite or alumina is used. And a catalyst supporting a noble metal.

[0012] The reducing agent adding means can be configured to inject a reducing agent into an exhaust passage using a nozzle, for example, and to guide the reducing agent to a purification device. If the fuel of the internal combustion engine is used as a reducing agent, a fuel injection device that injects fuel into the combustion chamber of the internal combustion engine is used as a reducing agent adding unit, and the fuel injection valve is used during the expansion stroke and the exhaust stroke of the internal combustion engine. , The fuel may be injected into the combustion chamber to add the reducing agent.

The reducing agent may be any as long as it generates a reducing component such as hydrocarbon or carbon monoxide in the exhaust gas, and may be a gas such as hydrogen or carbon monoxide, or a liquid or gas such as propane, propylene or butane. Liquid fuels such as hydrocarbons, gasoline, light oil, and kerosene can be used.

The exhaust flow control means may be of any form as long as it has a function of reducing the exhaust flow rate. For example, an exhaust throttle valve, an intake throttle valve, a waste gate valve (WGV), a variable displacement The variable turbine inlet area mechanism of the turbocharger can be adopted as the exhaust flow control means. When the opening of the exhaust throttle valve is reduced, when the opening of the intake throttle valve is reduced, when the opening of the WGV is increased, or when the turbine inlet area of the variable capacity turbocharger is reduced, The exhaust flow rate also decreases.

When the internal combustion engine is a diesel engine, the main fuel injection amount injected into the combustion chamber of the engine is exemplified as a parameter related to combustion and controlled by the output reduction suppression correcting means. If the internal combustion engine is a gasoline engine,
The air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine can be exemplified. In the case of an internal combustion engine equipped with a turbocharger, the opening degree of an exhaust gas recirculation control valve (EGR valve) may be used as the parameter.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the exhaust gas flow control means is provided upstream of the reducing agent adding means, and the exhaust gas and the reducing agent added from the upstream of the exhaust flow controlling means are added. Mixing means for mixing with a reducing agent may be provided. By doing so, atomization of the reducing agent is promoted, and the purification performance of the purification device is effectively recovered.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described below with reference to FIGS. Each embodiment described below is an embodiment applied to a diesel engine as an internal combustion engine.

[First Embodiment] FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purifying apparatus for an internal combustion engine according to a first embodiment. In this figure, a diesel engine 1 is an in-line four-cylinder, and fuel (light oil) is injected from a fuel injection valve 2 into a combustion chamber of each cylinder. Each fuel injection valve 2
Are connected to a common rail 3, and fuel is supplied to the common rail 3 from a fuel pump 4. Fuel pump 4
Is an electronic control unit (EC) for engine control so that the fuel pressure in the common rail 3 becomes a predetermined pressure.
U) The operation of each fuel injection valve 2 is controlled by EC5.
The valve opening timing and the valve opening time are controlled by U5 according to the operation state of the diesel engine 1.

An intake branch pipe 6 is connected to each cylinder of the diesel engine 1, and the intake branch pipe 6 is connected to an intake pipe 8 via an intake manifold 7. Intake pipe 8
Is connected to the compressor 10 of the turbocharger 9,
The compressor 10 is connected to an air cleaner 12 via an air flow meter 11. The air flow meter 11 outputs an output signal corresponding to the amount of air flowing therethrough to the ECU 5, and the ECU 5 calculates the intake air amount based on the output signal of the air flow meter 11. An intercooler 13 is provided in the middle of the intake pipe 8, and an intake throttle valve 14 is provided in the intake pipe 8 downstream of the intercooler 13. The opening degree of the intake throttle valve 14 is controlled by the ECU 5 according to the operating state of the diesel engine 1. Intake throttle valve 14
For example, a negative pressure driving type or a stepping motor driving type can be adopted.

Further, an exhaust branch pipe 15 is connected to each cylinder of the diesel engine 1, and each exhaust branch pipe 15 is provided with a DPF (Diesel Particulate Filter) 16. DPF 16 is a particulate matter (such as soot) in exhaust gas
Is a well-known filter that collects the air. Each exhaust branch 15 is connected to an exhaust manifold 17,
Is connected to the turbine 18 of the turbocharger 9,
The turbine 18 is connected to an exhaust pipe 19. In this embodiment, the exhaust branch pipe 15 and the exhaust manifold 17
, Turbine 18 and exhaust pipe 19 constitute an exhaust passage.

In the middle of the exhaust pipe 19, in order from the upstream side,
Exhaust throttle valve (exhaust flow rate control means) 20, addition nozzle 2
1. A catalytic converter 22 is provided. The catalytic converter 22 contains a storage reduction type NOx catalyst (hereinafter abbreviated as NOx catalyst). The NOx catalyst will be described later in detail. Exhaust temperature sensors 23 and 24 are provided on the upstream and downstream sides of the catalytic converter 22, respectively.
3 and 24 output to the ECU 5 output signals corresponding to the exhaust gas temperatures at the respective portions.

The addition nozzle 21 is for adding a reducing agent to exhaust gas when releasing and purifying the NOx absorbed by the NOx catalyst of the catalytic converter 22, that is, at the time of regeneration of the NOx catalyst. A reducing agent is supplied to the addition nozzle 21 from a reducing agent supply device 25. The reducing agent supply device 25 includes a pump and the like, and its operation is controlled by the ECU 5. In this embodiment, the addition nozzle 21 and the reducing agent supply device 25 constitute a reducing agent adding unit. Light oil which is the fuel of the diesel engine 1 is used as the reducing agent.

The opening of the exhaust throttle valve 20 is controlled by the ECU 5. The opening of the exhaust throttle valve 20 is kept fully open during normal operation, and is controlled to a predetermined opening during regeneration of the NOx catalyst. Reduce gas flow. As the exhaust throttle valve 20, a negative pressure drive type, a stepping motor drive type, or the like can be adopted.

The exhaust manifold 17 and the exhaust pipe 19 located upstream of the exhaust throttle valve 20 are connected by a bypass pipe 26 that bypasses the turbine 18.
The bypass pipe 26 is provided with a waste gate valve (hereinafter abbreviated as WGV) 27 for controlling the supercharging pressure. The WGV 27 can adopt a negative pressure drive type, a stepping motor drive type, or the like.

The exhaust gas of the diesel engine 1 is supplied from the exhaust manifold 17 to the turbine 18 of the turbocharger 9.
Through the exhaust pipe 19, at which time the turbine 18 drives the compressor 10. As a result, the intake air is boosted by the compressor 10 to become supercharged air, and the intake pipe 8
And supplied to the combustion chamber of each cylinder via the intake manifold 7. Here, by changing the opening of the WGV 27, the flow rate of the exhaust gas flowing through the turbine 18 of the turbocharger 9 can be changed, and the supercharging pressure can be changed. WG
The opening degree of V27 is controlled by the ECU 5 in accordance with the operating state of the diesel engine 1.

The intake manifold 7 and the exhaust manifold 17 are connected by an exhaust gas recirculation pipe 28.
An exhaust gas recirculation control valve (hereinafter referred to as EG)
(Abbreviated as R valve) 29 is provided. The EGR valve 29 is
The opening degree is controlled by the ECU 5 in accordance with the operation state of the diesel engine 1, and the exhaust gas having a flow rate corresponding to the opening degree of the EGR valve 29 flows from the exhaust manifold 17 to the intake manifold 7.
Reflux. As the EGR valve 29, a negative pressure drive type, a stepping motor drive type, or the like can be adopted.

The ECU 5 is composed of a digital computer and is connected to a ROM (Read-On-Memory), RAM (Random Access Memory),
It has a CPU (Central Processor Unit), an input port, and an output port, and performs basic control such as fuel injection amount control of the engine. In this embodiment, it controls the opening of the exhaust throttle valve 14 and regenerates the NOx catalyst. It performs correction control of the engine at the time of operation.

For these controls, an input signal from the air flow meter 11 and input signals from the exhaust gas temperature sensors 23 and 24 are input to input ports of the ECU 5.
An input signal from the rotation speed sensor 30 and an input signal from the accelerator opening sensor 31 are input. Rotation speed sensor 30
Outputs an output signal corresponding to the rotation speed of the diesel engine 1 as E
The ECU 5 calculates the engine speed from the output signal. The accelerator opening sensor 31 outputs an output signal corresponding to the accelerator opening to the ECU 5, and the ECU 5 calculates an engine load from the output signal.

NO stored in catalytic converter 22
An x-catalyst, that is, a storage-reduction-type NOx catalyst, uses, for example, alumina as a carrier, and on the carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs; , Lanthanum La, and at least one selected from rare earths such as yttrium Y, and a noble metal such as platinum Pt. When the air-fuel ratio of the inflowing exhaust gas (hereinafter referred to as the exhaust air-fuel ratio) is lean, this NOx catalyst is
It absorbs Ox and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases. Here, the exhaust air-fuel ratio means an exhaust passage upstream of the NOx catalyst, an engine combustion chamber,
It means the ratio of the sum of the amount of air supplied to the intake passage or the like to the sum of the fuel (hydrocarbon). Therefore, when no fuel, reducing agent, or air is supplied into the exhaust passage upstream of the NOx catalyst, the exhaust air-fuel ratio matches the air-fuel ratio of the air-fuel mixture supplied into the engine combustion chamber.

In this embodiment, a diesel engine is used as the internal combustion engine, and combustion is performed in a much leaner region than the stoichiometric condition (the stoichiometric air-fuel ratio, A / F = 13 to 14). In this state, the exhaust air-fuel ratio is very lean, and NOx in the exhaust gas is absorbed by the NOx catalyst. When the reducing agent is introduced into the exhaust gas by the operation described below and the oxygen concentration decreases, the NOx catalyst releases the absorbed NOx.

Although the mechanism of the NOx absorption / release operation of the NOx catalyst is not clear, it is considered that the mechanism is performed by the mechanism shown in FIG. The mechanism will be described by taking platinum Pt and barium Ba supported on a carrier as an example.
The same mechanism is obtained by using an alkali metal, an alkaline earth, or a rare earth.

First, when the exhaust gas becomes considerably lean, the exhaust gas is exhausted.
Since the oxygen concentration in the gas greatly increases, FIG.
Oxygen O as shown in_TwoIs O_Two ^-Or O^2-In the form of platinum Pt
Attaches to surface. Next, NO contained in the exhaust gas is white.
O on the surface of gold Pt_Two ^-Or O ^2-Reacts with NO_TwoBecomes
(2NO + O_Two→ 2NO_Two).

Thereafter, the generated NO_TwoIs the NOx catalyst
Oxidation on platinum Pt unless the NOx absorption capacity of
While being absorbed in the NOx catalyst and barium oxide Ba
O, and nitrate ions N as shown in FIG.
O_Three ^-And diffuses into the NOx catalyst. Thus N
Ox is absorbed in the NOx catalyst. In contrast, exhaust gas
NO when the oxygen concentration in the_TwoProduction is reduced
However, by the reverse reaction to the above reaction, the nitric acid in the NOx catalyst
Acid ion NO_Three ^-Is NO_Two Or NOx catalyst in the form of NO
Released.

On the other hand, HC in the exhaust gas, the reducing components such as CO are present, these components oxygen O ₂ on the platinum Pt ^-
Or, it is oxidized by reacting with O ²⁻ and consumes oxygen in the exhaust gas to lower the oxygen concentration in the exhaust gas. In addition, N2 released from the NOx catalyst due to a decrease in the oxygen concentration in the exhaust gas
O ₂ or NO is, as shown in FIG.
It reacts with O and is reduced. When NO ₂ or NO on the platinum Pt disappears in this way, NO ₂ or NO is released from the NOx catalyst one after another.

[0035] That is, HC in the exhaust gas, CO, first on the platinum Pt oxygen O ₂ ^- it is immediately reacted to oxidation or O ^2- and then oxygen O ₂ on the platinum Pt ^- or O ^2- is consumed If HC and CO still remain, the NOx released from the NOx catalyst and the NOx discharged from the engine are reduced by the HC and CO.

It is known that in order to efficiently regenerate the NOx catalyst with a small consumption of the reducing agent, it is better to reduce the flow rate of the exhaust gas to the NOx catalyst as compared with the normal operation. Therefore, in the exhaust purification device of this embodiment, the flow rate of the exhaust gas flowing into the catalytic converter 22 is reduced by reducing the opening of the exhaust throttle valve 20 during the regeneration of the NOx catalyst as compared with the normal operation.

However, when the opening degree of the exhaust throttle valve 20 is reduced during the regeneration of the NOx catalyst, the exhaust resistance increases, the pumping loss increases, and the engine output decreases. Therefore, a torque shock may be felt when the regeneration operation of the NOx catalyst is started from the normal operation state or when the normal operation state is shifted from the regeneration state of the NOx catalyst. Therefore, in this exhaust gas purification device, at least one of the parameters related to the combustion of the diesel engine 1 is corrected and controlled so that the engine output in the normal operation state before the regeneration operation is obtained even during the regeneration operation of the NOx catalyst. ing.

Next, a correction operation at the time of NOx catalyst regeneration in this embodiment will be described.

FIG. 2 is a flow chart showing the regeneration operation of the NOx catalyst and the engine control correction operation.

First, in step 101, the ECU 5 calculates the fresh air amount from the air flow meter 11, the engine speed from the speed sensor 30, the accelerator opening from the accelerator opening sensor 31, the catalyst input gas temperature and the catalyst output. The gas temperature is read from the exhaust temperature sensors 23 and 24, respectively, and the current operating state of the diesel engine 1 is detected.

Next, the ECU 5 determines in step 102 that N
It is determined whether the condition for executing the regeneration operation of the Ox catalyst is satisfied. In this embodiment, the condition for executing the NOx catalyst regeneration operation is that a predetermined time has elapsed since the last time the NOx catalyst regeneration operation was performed, and only when this condition is satisfied, Is performed, and if the condition is not satisfied, this routine ends.

The condition for executing the regeneration operation may be that the NOx absorption amount of the NOx catalyst is equal to or more than a predetermined value. The NOx absorption amount of the NOx catalyst is obtained, for example, by storing the NOx emission amount from the engine per unit time in advance in the ROM of the ECU 5 as a function of the engine load (accelerator opening), the engine speed, and the like. NOx is calculated from the accelerator opening and the engine speed by the above function.
The emission amount can be determined by multiplying the emission amount by a constant coefficient and integrating the result as the NOx absorption amount of the NOx catalyst within the fixed time period.

If the condition for executing the regeneration operation is satisfied in step 102, the ECU 5 proceeds to step 103 to change NOx from the current operating state of the diesel engine 1 to NOx.
When the opening of the exhaust throttle valve 20 is reduced for the catalyst regeneration operation, the combustion of the diesel engine 1 is performed so that the engine output of the diesel engine 1 becomes the same as before the opening of the exhaust throttle valve 20 is reduced. Calculate the correction amount of the involved parameter. Parameters relating to combustion will be described later using specific examples.

Next, the ECU 5 determines in step 104 that N
The amount of the reducing agent required to regenerate the Ox catalyst is calculated.

Next, at step 105, the ECU 5 executes the exhaust throttle by reducing the opening of the exhaust throttle valve 20 to an opening required for the regeneration operation of the NOx catalyst.

Next, the routine proceeds to step 106, where the ECU 5
Executes the correction of the corresponding parameter according to the correction amount calculated in step 103, and executes the engine control correction. Thus, even if the opening degree of the exhaust throttle valve 20 is reduced, the engine output of the diesel engine 1 does not decrease, and the engine output before the opening degree of the exhaust throttle valve 20 is reduced can be maintained.

Next, in step 107, the ECU 5 operates the reducing agent supply device 25 to execute addition of the reducing agent, and adds the reducing agent to the exhaust gas by the amount calculated in step 104. finish.

FIG. 3 shows the parameters related to the combustion of the diesel engine 1 in detail, and
In this embodiment, the opening degree of the EGR valve 29 and the fuel injection valve 2
The main fuel injection amount injected into the combustion chamber of each cylinder from
These are the parameters.

When the opening degree of the exhaust throttle valve 20 is reduced in step 105, the back pressure of the exhaust manifold 17 increases, so that the amount of exhaust gas recirculated from the exhaust manifold 17 to the intake manifold 8 via the exhaust gas recirculation pipe 28 ( Hereinafter, E
(Abbreviated as GR amount). If the EGR amount is too large, the oxygen concentration in the intake air of each cylinder decreases, so that smoke is likely to occur or the combustion efficiency is reduced. Thus, the ECU 5 corrects the opening of the EGR valve 29 by a predetermined opening reduction in step 106-1 and reduces the appropriate EGR amount so that the above-mentioned problem does not occur.

Next, the ECU 5 executes step 106-2.
Then, by increasing and correcting the main fuel injection amount injected from the fuel injection valve 2 into the combustion chamber of each cylinder, the same engine output as in the operating state before the execution of the exhaust throttle is obtained.

Therefore, in this embodiment, the ECU
5 is to calculate the correction amount for decreasing the opening degree of the EGR valve 29 and the correction amount for increasing the main fuel injection amount in step 103 of FIG. In this case, an experiment was conducted in advance when the NOx catalyst was regenerated from all operating states of the diesel engine 1, and the opening reduction correction amount of the EGR valve 29 and the main fuel injection amount increase required in each operating state The correction amount is calculated and mapped, and this map is used by the ECU.
5 is stored in the ROM.

It is conceivable that the engine output before the regeneration operation can be maintained only by executing the correction for decreasing the opening of the EGR valve 29 in step 106-1. In this case, step 106-2 is executed. The present routine can be terminated without executing.

In this embodiment, the fuel injection valve 2
Step 103, Step 106-1 and Step 1 in a series of signal processing by the ECU 5, the EGR valve 29, and the ECU 5.
The portion executing step 06-2 implements an output reduction suppression correction unit.

FIG. 4 shows N in the first embodiment.
5 is a timing chart at the time of a regeneration operation of an Ox catalyst. As shown in this figure, when the regeneration operation of the NOx catalyst is executed while the accelerator opening is kept constant, the engine speed and the engine output have the same magnitude before and after regeneration. Further, when the regeneration operation of the NOx catalyst is performed while the accelerator opening is being changed at a constant acceleration, the engine speed and the engine output change at a constant acceleration before and after the regeneration. Therefore, in any case, torque shock does not occur and driving performance is good. The decrease in the amount of oxygen in the exhaust gas during the regeneration of the NOx catalyst includes the fact that the intake air amount is reduced by the exhaust throttle, that the increased amount of the main injected fuel is burned in the combustion chamber, and that the reducing agent is burned. to cause.

[Second Embodiment] In a second embodiment, the parameters related to the combustion of the diesel engine 1 are defined as the opening degree of the intake throttle valve 14, the opening degree of the EGR valve 29, and the like.
This is an example when the main fuel injection amount is used. The difference from the first embodiment is only the details of step 103 and step 106 in FIG. 2, and the other points are the same as the first embodiment.

Hereinafter, the details of step 106 in the second embodiment will be described with reference to the flowchart of FIG. 6, and the same parts as those in the first embodiment will be denoted by the same reference numerals in the drawings. Is omitted.

In general, in the operation of the diesel engine 1, if the EGR amount is still insufficient even when the EGR valve 29 is fully opened, the opening degree of the intake throttle valve 14 is reduced to reduce the negative pressure on the intake manifold 7 side. Then, the exhaust gas is sucked using the negative pressure to increase the EGR amount. The second embodiment is an example of control in a case where a NOx catalyst regeneration operation is performed from such an operating state.

In this case, the pumping loss of the intake throttle valve 14 has already occurred in the normal operation state before the regeneration operation of the NOx catalyst. In this state, if the opening degree of the exhaust throttle valve 20 is reduced in step 105, the intake throttle The degree of output reduction is greater than when exhaust throttle is performed with the valve 14 fully open.

Accordingly, in this case, the ECU 5 proceeds from step 105 to step 106-3, in which the valve opening of the intake throttle valve 14 is corrected to increase by a predetermined opening, and the pumping loss due to the intake throttle valve 14 is reduced. And then E
The CU 5 corrects the opening degree of the EGR valve 29 in step 106-1 and performs the main injection amount increase correction in step 106-2. This makes it possible to reduce the increase correction amount of the main fuel injection amount for compensating for the output decrease.

FIG. 7 shows N in the second embodiment.
5 is a timing chart at the time of the regeneration operation of the Ox catalyst. Also in this case, the engine output at the time of the regeneration of the NOx catalyst can be made the same as the operation state before the regeneration operation.

In this embodiment, the ECU 5
In step 103 in FIG. 2, the correction amount for increasing the opening degree of the intake throttle valve 14, the correction amount for decreasing the opening degree of the EGR valve 29, and the correction amount for increasing the main fuel injection amount are calculated. In this case, an experiment is performed in advance when the regeneration operation of the NOx catalyst is performed from the operation state of the diesel engine 1 in which the opening degree of the intake throttle valve 14 is reduced, and an appropriate opening degree correction amount of the intake throttle valve 14 is obtained. This is mapped into a relationship with the operation state of the diesel engine 1, and this map is
In the ROM.

In this embodiment, step 1
In the case where the engine output before the regeneration operation can be held simply by executing the correction for increasing the opening of the intake throttle valve 14 at 06-3,
This routine may be ended without executing Steps 106-1 and 106-2.
If the engine output before the regeneration operation can be maintained only by executing the correction for increasing the opening of the intake throttle valve 14 at -3 and the correction for decreasing the opening of the EGR valve 29 at step 106-1,
This routine can be ended without executing Step 106-2.

In this embodiment, the fuel injection valve 2
Step 103 and Step 106 in a series of signal processing by the throttle valve 14, the EGR valve 29, and the ECU 5
-3, the step 106-1 and the step 106-2 perform an output reduction suppression correcting unit.

[Third Embodiment] A third embodiment is a modification of the first embodiment in which the opening degree of the EGR valve 29 and the main fuel injection amount are parameters related to the combustion of the diesel engine 1. It is an example.

In the third embodiment, the catalyst temperature in the operating state before the regeneration of the NOx catalyst is lower than the catalyst temperature required to regenerate the NOx catalyst. NOx
It is a control example when it is desired to increase the exhaust gas temperature when executing the catalyst regeneration operation.

In this embodiment, the pumping loss is increased by reducing the opening of the intake throttle valve 14 in addition to the reduction of the opening of the exhaust throttle valve 20, and the main injection amount increase correction amount is reduced in the first embodiment. The exhaust temperature is raised by increasing the exhaust temperature more than in the case of the embodiment. A decrease in the opening degree of the intake throttle valve 14 will decrease the exhaust flow rate,
Therefore, in this embodiment, the intake throttle valve 14 and the exhaust throttle valve 20 constitute exhaust flow rate control means.

Next, a correction control procedure will be described with reference to FIG. After executing the exhaust throttle at step 105, the ECU 5 corrects the opening of the intake throttle valve 14 to decrease at step 105-1, and then proceeds to step 106-1 to perform EGR.
Correction for decreasing the opening of the valve 29 is performed, and correction for increasing the main injection amount is performed in step 106-2. As a result, not only can the engine output during the regeneration of the NOx catalyst be made the same as the operating state before the regeneration operation,
x The temperature of the catalyst can be increased to a temperature required for regeneration.

Also, due to the decrease in the opening of the intake throttle valve 14,
Since the intake air amount is reduced and the exhaust flow rate is reduced, the amount of the reducing agent added during the regeneration of the NOx catalyst can be reduced.

The other points are the same as those in the first embodiment, and the description is omitted.

[Fourth Embodiment] The fourth embodiment is also a modification of the first embodiment in which the opening degree of the EGR valve 29 and the main fuel injection amount are parameters related to the combustion of the diesel engine 1. It is an example.

In the fourth embodiment, by increasing the opening of the WGV 27, the amount of the reducing agent added during the regeneration of the NOx catalyst is made smaller than in the first embodiment.

Hereinafter, a control procedure according to the fourth embodiment will be described with reference to a flowchart of FIG.

After executing the exhaust throttle in step 105, the ECU 5 increases and corrects the opening of the WGV 27 in step 105-2, and then proceeds to step 106-1 to perform EGR.
Correction for decreasing the opening of the valve 29 is performed, and correction for increasing the main injection amount is performed in step 106-2.

As described above, in step 105-1 the WGV
When the opening degree increase correction of 27 is performed, the supercharging pressure decreases.
The amount of intake air can be reduced. If the intake air amount decreases, the exhaust gas flow rate also decreases, so that the amount of the reducing agent added during the regeneration of the NOx catalyst can be reduced.

Further, since the exhaust flow rate is reduced by increasing the opening degree of the WGV 27, in this embodiment, the WGV 27 constitutes exhaust flow rate control means together with the exhaust throttle valve 20.

The other points are the same as those in the first embodiment, and the description is omitted.

[Fifth Embodiment] The fifth embodiment is a modification of the above-described first to fourth embodiments.

The difference between the fifth embodiment and the first to fourth embodiments lies in the installation position of the exhaust throttle valve 20.
As shown in FIG. 10, in the exhaust emission control device according to the fifth embodiment, the exhaust throttle valve 20 is installed downstream of the catalytic converter 22. With this arrangement, the energy of the exhaust gas can be effectively used to raise the temperature of the NOx catalyst housed in the catalytic converter 22, so that the NOx absorption performance of the NOx catalyst can be improved. Since the NOx catalyst can be installed under a high pressure, an atmosphere in which the reducing agent can be easily decomposed during regeneration of the NOx catalyst can be formed, and the regeneration efficiency can be improved.

The other structures and operations are the same as those of the first to fourth embodiments, and therefore the description is omitted.

[Sixth Embodiment] The sixth embodiment is a modification of the first embodiment, and includes a turbocharger 9.
Using a variable capacity turbocharger as the exhaust throttle valve 2
0 is omitted.

As is well known, in the variable capacity turbocharger, a movable vane is provided at the nozzle of the turbine 18 of the turbocharger 9, and the turbine inlet area can be varied by changing the angle of the vane. The supercharging pressure can be increased by reducing the turbine inlet area to increase the speed of the exhaust gas.

By the way, in this variable capacity turbocharger, if the turbine inlet area is extremely narrowed, the supercharging efficiency is reduced. Therefore, as shown in FIG. 14, the supercharging pressure (intake pipe pressure) is reduced and the exhaust pressure is reduced. Pressure increases and the turbine 18
The exhaust flow rate flowing through is reduced. This is the same operation as when the opening of the exhaust throttle valve 20 is reduced, and therefore,
The exhaust flow control means can be constituted by the variable capacity turbocharger.

FIG. 11 is a configuration diagram of a main part of an exhaust gas purifying apparatus according to the sixth embodiment. A variable displacement turbocharger is used for the turbocharger 9 without installing the exhaust throttle valve 20. The vane drive section 9a of the variable displacement turbocharger 9 is controlled by the ECU 5 at a predetermined vane angle, thereby controlling the turbine inlet area to a predetermined area. In FIG. 11, the bypass pipe 26 and the WGV 27
Are omitted, but the configuration other than the variable capacity turbocharger 9 is the same as that of the first embodiment.

The control procedure of the sixth embodiment is basically the same as that of the first embodiment, and the exhaust throttle method in step 105 in FIG. 5 is different from that of the first embodiment. Only.

Therefore, a portion corresponding to steps 105 and 106 in the first embodiment will be described with reference to the flowchart of FIG.

At step 105, the ECU 5 drives the vane driving section 9a to reduce the turbo inlet area of the variable capacity turbocharger 9 to a predetermined area, and executes the exhaust throttle. Subsequent steps are the same as in the first embodiment.
Performs the correction for decreasing the opening of the EGR valve 29 in step 106-1 and performs the correction for increasing the main injection amount in step 106-2. As a result, the same engine output as in the operating state before the execution of the exhaust throttle can be obtained.

In this case, the diesel engine 1
An experiment is performed in advance to determine the optimal throttle amount (ie, vane angle) of the turbo inlet area at the time of the NOx catalyst regeneration operation, and the operation of the vane drive unit 9a is controlled in step 105 so as to achieve the throttle amount.

Further, the variable capacity turbocharger can use a portion having a lower supercharging efficiency than a turbocharger which is not a variable capacity type, so that fresh air can be further reduced. Therefore, when the back pressure is made equal, the use of the variable-capacity turbocharger can reduce the exhaust flow rate more than the use of a non-variable-capacity turbocharger. As a result, the use of the variable capacity turbocharger can reduce the amount of the reducing agent to be added during the regeneration of the NOx catalyst, as compared with the case of using a non-variable capacity turbocharger.

The other points are the same as in the case of the first embodiment, and will not be described.

An exhaust throttle valve 20 is provided in the exhaust pipe 19, and a variable displacement turbocharger is used as a turbocharger. The exhaust throttle valve 20 and the exhaust throttle due to a decrease in the turbo inlet area of the variable capacity turbocharger are used. It is also possible to use together.

FIG. 13 is a flowchart of a part corresponding to steps 105 and 106 in the first embodiment in this case. The control procedure will be briefly described. The ECU 5 executes the exhaust throttle by reducing the opening degree of the exhaust throttle valve 20 in step 105, and then determines the turbo inlet area of the variable displacement turbocharger 9 in step 105-3. The exhaust area is reduced to a predetermined area and the exhaust throttle is further performed. Subsequent steps are the same as in the first embodiment.
In step U5, the opening degree of the EGR valve 29 is corrected to decrease in step 106-1, and the main injection amount increase correction is performed in step 106-2. As a result, the same engine output as in the operating state before the execution of the exhaust throttle can be obtained.

In each of the above-described second to fourth embodiments, a variable displacement turbocharger is used as the turbocharger 9 instead of executing the exhaust throttle with the exhaust throttle valve 20, and the turbo inlet area is made variable. By doing so, it is possible to execute the exhaust throttle, and it is also possible to execute the exhaust throttle by using both the exhaust throttle valve 20 and the variable displacement turbocharger.

[Seventh Embodiment] A seventh embodiment is a modification of the first to fourth embodiments described above, and differs from the first to fourth embodiments in that the addition nozzle 21 uses an exhaust gas and a reducing agent. And mixing means for mixing the two.

As shown in FIG. 15, the addition nozzle 21 of the exhaust gas purifying apparatus according to the seventh embodiment has a double pipe structure, and a reducing agent passage 21a is provided in the center of the inside thereof. An exhaust gas passage 21b is provided on the outside, and the tip of the exhaust gas passage 21b is connected to a reducing agent passage 21a.
The exhaust gas passage 21b is reduced in cross section by a throttle 21c. The reducing agent supply device 25 supplies the reducing agent to the reducing agent passage 21a, and the exhaust gas passage 21b receives the high-pressure exhaust gas from the upstream of the exhaust throttle valve 20 via the exhaust branch pipe 21d, as shown in FIG. Is supplied. In this addition nozzle 21, NO
At the time of x catalyst regeneration, exhaust gas is injected at a high speed from the distal end opening of the exhaust gas passage 21b, and at that time, the exhaust gas atomizes the reducing agent injected from the distal end opening of the reducing agent passage 21a. Thereby, the regeneration efficiency of the NOx catalyst can be improved.

Also, without using the addition nozzle 21 having such a special structure, the addition position of the reducing agent is set immediately upstream of the turbine 18 of the turbocharger 9 so that the reducing agent is atomized in the turbine 18. Even so, the same effect can be obtained. In this case, the turbine 18 constitutes the mixing means.

The other device configurations and control procedures are the same as those in the first to fourth embodiments, and therefore description thereof is omitted.

[Other Embodiments] In each of the above-described embodiments, the reducing agent is added to the exhaust passage downstream of the DPF 16 in each case.
A reducing agent may be added to the exhaust passage on the more upstream side. In such a case, when the reducing agent is added during the regeneration of the NOx catalyst, the added reducing agent becomes DPF1
6, soot and the like collected by the DPF 16 can be efficiently burned, so that the DPF 16 can be effectively regenerated. Further, since oxygen is consumed by burning soot and the like collected in the DPF 16, an atmosphere having a low oxygen concentration can be formed with a small amount of the reducing agent added.

In each of the above-described embodiments, the addition of the reducing agent is performed in the exhaust passage using the addition nozzle 21 in any case. However, the method of adding the reducing agent is not limited to this. For example, when each cylinder of the diesel engine 1 is in an expansion stroke or an exhaust stroke, fuel may be injected from the fuel injection valve 2 to add fuel as a reducing agent to exhaust gas.

[0099]

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, when the reducing agent is added to the purifying apparatus by the reducing agent adding means, at least one of the parameters relating to combustion is used to reduce the output of the internal combustion engine. By providing the output reduction suppression correction means for controlling to suppress, even when the purification performance recovery operation of the purification device is being performed, the internal combustion engine is maintained at the same engine output as before the purification performance recovery operation, Drivability is improved without generating torque shock.

Further, when the exhaust gas purifying apparatus for an internal combustion engine of the present invention is provided with a mixing means for mixing the exhaust gas and the reducing agent, it is possible to effectively recover the purifying performance of the purifying apparatus. The effect is achieved.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention.
It is a schematic structure figure in an embodiment.

FIG. 2 is a flowchart showing a procedure for regenerating a NOx catalyst and correcting an engine control in the exhaust gas purification apparatus according to the first embodiment.

FIG. 3 is a flowchart showing an engine control correction procedure in the exhaust gas purification apparatus according to the first embodiment.

FIG. 4 is a timing chart at the time of regeneration of a NOx catalyst in the exhaust gas purification apparatus of the first embodiment.

FIG. 5 is a diagram illustrating the NOx absorption / release / reduction action of a NOx catalyst.

FIG. 6 shows a second embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.
9 is a flowchart showing an engine control correction procedure in the embodiment.

FIG. 7 is a timing chart at the time of regeneration of a NOx catalyst in the exhaust gas purification apparatus according to the second embodiment.

FIG. 8 shows a third embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.
9 is a flowchart showing an engine control correction procedure in the embodiment.

FIG. 9 shows a fourth embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.
9 is a flowchart showing an engine control correction procedure in the embodiment.

FIG. 10 is a main part configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to a fifth embodiment of the present invention.

FIG. 11 is a main part configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to a sixth embodiment of the present invention.

FIG. 12 is a flowchart showing an engine control correction procedure in the exhaust gas purification apparatus according to the sixth embodiment.

FIG. 13 is a flowchart showing an engine control correction procedure in a modified example of the exhaust emission control device of the sixth embodiment.

FIG. 14 is a characteristic diagram of a variable displacement turbocharger used in the exhaust emission control device of the sixth embodiment.

FIG. 15 is an enlarged sectional view of a main part of an addition nozzle in a seventh embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention.

FIG. 16 is a main part configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to a seventh embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Diesel engine (internal combustion engine) 2 Fuel injection valve (output reduction suppression means) 3 Common rail 4 Fuel pump 5 Electronic control unit for engine control 9 Turbocharger 9a Vane drive unit (exhaust flow rate control means) 10 Compressor 14 Intake throttle valve ( Output drop suppression correcting means, exhaust flow control means) 15 exhaust branch pipe (exhaust passage) 16 DPF (purification device) 17 exhaust manifold (exhaust passage) 18 turbine 19 exhaust pipe (exhaust passage) 20 exhaust throttle valve (exhaust flow control means) 21) Addition nozzle (reducing agent addition means) 22 Catalytic converter (purification device) 25 Reducing agent supply device (reducing agent addition means) 27 WGV (exhaust flow rate control means) 29 EGR valve (output reduction suppression correction means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 9/04 ZAB F02D 9/04 ZABE 41/40 ZAB 41/40 ZABG

Claims (2)

[Claims] 1. A purifying device provided in an exhaust passage of an internal combustion engine, reducing agent adding means for adding a reducing agent to the purifying device, and when a reducing agent is added to the purifying device by the reducing agent adding device. An exhaust flow control device for controlling the exhaust flow rate flowing through the exhaust passage of the internal combustion engine so as to decrease the exhaust flow rate.When the reducing agent is added to the purification device by the reducing agent adding device, At least one of the parameters involved in combustion
An exhaust gas purification device for an internal combustion engine, comprising: output reduction suppression correction means for controlling at least one of the internal combustion engines to reduce the output reduction. 2. The exhaust gas flow control means is provided upstream of a reducing agent adding means, and comprises a mixing means for mixing exhaust gas upstream of the exhaust flow control means with a reducing agent. The exhaust gas purification device for an internal combustion engine according to claim 1.