JP2000186530A - INTERNAL COMBUSTION ENGINE HAVING LEAN NOx CATALYST - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine having a lean NOx catalyst, capable of increasing the temperature of a catalyst above an active temperature, starting from the time when a vehicle in deceleration area, so that the lean NOx catalyst effectively functions in synchronism with the transition of the vehicle from deceleration travel to normal travel. SOLUTION: The internal combustion engine having a lean NOx catalyst is provided with an inlet throttle valve 38, a lean NOx catalyst 19 for purifying exhaust gas, a combustion heater 17, a combustion gas discharge path 35, for sending combustion gas of the combustion heater 17 to an intake passage 11, a combustion gas introducing path 21 for bypassing an engine body to introduce combustion gas to the upstream side of the lean NOx catalyst in an exhaust passage 12, and a three-way valve 36 for selecting either of the combustion gas introducing path 21 or the combustion gas discharge path 35 to switch the paths for combustion gas. When the vehicle is decelerated and the regeneration-treatment of the lean NOx catalyst is required, the intake passage 11 is closed by the inlet throttle valve, and the combustion gas introducing path 21 is opened by the three-way valve 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a lean NOx catalyst, and more particularly, to an exhaust system of an internal combustion engine in which the atmosphere in the exhaust system is particularly in an oxygen excess state.
The present invention relates to an internal combustion engine having a lean NOx catalyst for purifying nitrogen oxides NOx contained in exhaust gas of an exhaust system using a reducing agent.

[0002]

2. Description of the Related Art A catalytic converter used in an exhaust gas system as an exhaust gas purifying means for an internal combustion engine such as a gasoline direct-injection lean burn engine or a diesel engine, which has a high thermal efficiency, an atmosphere in the exhaust system which has an excessive amount of oxygen and a small amount of hydrocarbons and carbon monoxide. Contains, for example, an occlusion reduction type lean NOx catalyst. The storage-reduction type lean NOx catalyst stores nitrogen oxides in the catalyst once in a lean atmosphere, and then discharges the stored nitrogen oxides from the catalyst by supplying exhaust gas in a rich atmosphere having a low oxygen concentration to the lean NOx catalyst. In this method, the reducing components in the exhaust gas are reduced and purified at once. That is, the lean NOx catalyst does not continuously perform reduction and purification of nitrogen oxides, and alternately repeats execution and stop of reduction and purification. Therefore, the storage reduction type lean NOx catalyst can be said to be an intermittent treatment type lean NOx catalyst.

[0003] Further, the lean NOx catalyst is activated in a predetermined temperature range, and sufficient activation cannot be expected below a predetermined temperature. For this purpose, the lean NOx catalyst must be raised to a temperature equal to or higher than the predetermined temperature, that is, the activation temperature.

[0004]

In the case of a diesel engine or other internal combustion engine that directly injects fuel into a cylinder, the speed of the fuel injection device is reduced during deceleration due to structural reasons such as the mounting position of the fuel injection device on the engine. Do not perform fuel injection.
However, when the vehicle is running, the piston moves regardless of the presence or absence of injection. For this reason, the air that has entered the cylinder from the intake port at the time of deceleration flows from the exhaust port to the exhaust passage without being subjected to combustion, and eventually reaches the catalytic converter. That is, during deceleration, non-combustion is performed, so that much lower temperature air flows through the catalytic converter than during combustion. For this reason, the catalyst temperature decreases, and if the catalyst was activated before deceleration, the catalyst temperature would be lower than the activation temperature. Then, even if the vehicle shifts from deceleration traveling to normal traveling in this state, the temperature of the lean NOx catalyst does not immediately become higher than the activation temperature in accordance with the transition. Therefore, it may not be possible to reduce and purify nitrogen oxides until the catalyst returns to the activation temperature or higher.

When the temperature of the lean NOx catalyst is low,
Not only is it difficult to reduce and purify nitrogen oxides, but if diesel fuel is used as a reducing agent for the lean NOx catalyst and supplied to the exhaust system, soot or the like is generated, and the lean NOx catalyst may be clogged.

The present invention has been made under such a technical background, and when the vehicle is in a deceleration range so that the lean NOx catalyst functions effectively when the vehicle shifts from deceleration traveling to normal traveling. Therefore, it is an object to increase the lean NOx catalyst to an activation temperature or higher and to suppress generation of soot and the like.

[0007] In order to supply the reducing agent, for example, as described in JP-A-6-117225,
Its primary role has been to perform so-called sub-injection by an injector, which is a fuel injection device that injects fuel for driving the engine. As is well known, the sub-injection is a fuel injection that the injector injects between an expansion stroke and an exhaust stroke.

On the other hand, the fuel injection originally injected by the injector is called a main injection, and the main injection is performed in a compression stroke. Thus, the sub-injection is secondary. For this reason, the injector is set so that the main injection, which is its original role, is first suitable. For example, in order to suitably perform engine combustion, it is preferable to vaporize or atomize the fuel. Therefore, in order to easily vaporize the fuel, the main injection is usually performed when the piston is near the top dead center. To achieve this, the injector is attached to the cylinder head at a fixed injection angle. However, since the sub-injection is a fuel injection performed between the expansion stroke and the exhaust stroke as described above, the timing of injecting the fuel from the injector for the sub-injection is when the piston is below the top dead center. . In this connection, the fuel injected by the sub-injection is not easily vaporized or atomized. Therefore, the fuel injected by the sub-injection may be supplied to the exhaust system in a liquefied state. However, even with fuel guided to the exhaust system by sub-injection,
It is preferable that this is in a vaporized or atomized state in performing reduction purification of nitrogen oxides.

[0009] However, it is impossible to expect the injector whose primary role is focused on the main injection to have a sufficient effect on the sub-injection.

An object of the present invention is to provide an internal combustion engine having a lean NOx catalyst which can cope with such a problem.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, an internal combustion engine having a lean NOx catalyst according to the present invention employs the following means.

An intake throttle valve provided in the intake passage for restricting intake air passing through the intake passage; a lean NOx catalyst provided in the exhaust passage for purifying gas passing through the exhaust passage; and an engine using heat obtained by burning fuel. A combustion heater for raising the temperature of related elements; a combustion gas discharge passage for discharging combustion gas from the combustion heater to the intake passage; and a lean N in the exhaust passage.
A combustion gas introduction path that guides the combustion gas without passing through the cylinder toward the upstream side of the Ox catalyst, and a switching valve that selectively opens and opens either the combustion gas introduction path or the combustion gas discharge path. When the lean NOx catalyst regeneration process is requested and the vehicle is running at a reduced speed, the lean throttle valve closes the intake passage and switches the switching valve to open the combustion gas introduction passage.
Internal combustion engine with x catalyst.

Here, the "engine-related element" refers to the internal combustion engine itself such as engine cooling water, a cylinder block, and a cylinder head.

The term "internal combustion engine" refers to an internal combustion engine in which fuel is not injected into a cylinder from a fuel injection device during deceleration of a gasoline direct injection lean burn engine, a diesel engine, or the like.

A "combustion heater" is a heater attached to an internal combustion engine as a separate component from the internal combustion engine main body, and performs its own combustion without being affected by the combustion in the cylinder of the internal combustion engine main body. It emits gas. By providing this separately, the exhaust system temperature can be increased and the catalyst can be activated before the engine is started. .

The "lean NOx catalyst" may be an occlusion reduction type lean NOx catalyst or a selective reduction type lean NOx catalyst.

The "combustion gas" preferably contains hydrocarbons, carbon monoxide and the like as necessary in its components. For this reason, the fuel for combustion of the combustion type heater includes fuel for internal combustion engines such as gasoline and light oil. It is preferably used. If the fuel such as gasoline does not completely burn, it generates unburned gas, and the unburned gas contains hydrocarbons and carbon monoxide that serve as reducing agents. The combustion gas emitted by the combustion heater is hereinafter referred to as combustion gas unless otherwise specified.

[0018] The "combustion gas introduction path" has a lean NO.
Preferably, the passage is dedicated to warming the x catalyst only. Further, it is desirable that the combustion gas introduction path is a detour that bypasses the engine body while connecting the intake passage and the exhaust passage.

"At the time of request for regeneration processing of lean NOx catalyst"
Is the time when NOx reduction of the lean NOx catalyst is required.

In the internal combustion engine having the lean NOx catalyst according to the present invention, when the regeneration process of the lean NOx catalyst is requested and the vehicle is running at a reduced speed, the intake throttle valve provided in the intake passage is throttled to restrict the intake passage. At the same time as closing, that is, at or almost simultaneously with closing the intake passage, the switching valve is operated to open the combustion gas introduction passage. Opening the combustion gas introduction passage means closing the combustion gas discharge passage at the same time at the switching valve.

When the intake throttle valve is closed, there is almost no intake air going to the cylinder via at least the intake throttle valve. In other words, low-temperature gas (essentially intake air)
Does not flow toward the lean NOx catalyst. Therefore, the temperature of the lean NOx catalyst can be prevented from dropping by itself.

In addition, according to the present invention, the combustion gas introduction passage is opened by operating the gas passage switching valve, and the opened combustion gas introduction passage is passed through the engine body, in other words, without passing through the cylinder. The combustion gas is guided toward the upstream side of the lean NOx catalyst in the exhaust passage while bypassing the engine body. Therefore, if the temperature of the combustion gas is high at this time,
The temperature of the lean NOx catalyst also increases. That is, in the present invention, even when the vehicle is running at a reduced speed, the lean NOx catalyst is not cooled by the intake air unlike the related art. Rather, it warms the lean NOx catalyst. Therefore, when the vehicle is in the deceleration range, the combustion amount of the combustion heater is increased from when the vehicle is in the deceleration range so that the temperature of the lean NOx catalyst is equal to or higher than the activation temperature so that the lean NOx catalyst functions effectively when shifting from deceleration traveling to normal traveling. If this is done, the lean NOx catalyst is already in an activated state when the vehicle starts running normally. Therefore, at this time, if the reducing agent is supplied to the lean NOx catalyst in an appropriate amount, the reduction and purification of nitrogen oxides can be continuously performed during the transition from the deceleration running to the normal running. As a result, a suitable lean NOx catalyst can be regenerated.

Even if soot or the like is attached to the lean NOx catalyst, the soot or the like can be removed by combustion by increasing the temperature of the combustion gas.

As a further preferred means, an exhaust gas recirculation device is provided, and the exhaust gas recirculation device is operated at the time of the regeneration process request and when the vehicle is running at a reduced speed, and the exhaust gas recirculation device extends from the exhaust system to the intake system. It is desirable to open the circulation passage.

In the internal combustion engine having the lean NOx catalyst of the present invention, when the regeneration process of the lean NOx catalyst is requested and the vehicle is running at a reduced speed, the intake passage is closed and the combustion gas introduction passage is opened as described above. In addition, at this time, the exhaust gas recirculation device is operated to open the exhaust gas recirculation passage extending from the exhaust system to the intake system. At this time, since the vehicle is traveling at a reduced speed, no fuel is injected from the fuel injection device into the cylinder. Therefore, even if the intake air downstream of the intake throttle valve in the intake passage before closing the intake throttle valve flows into the cylinder, the intake air is not subjected to combustion, that is, at least in a state where there is almost no temperature change. It only comes out of the exhaust port. At this time, since the combustion gas introduction passage is open, the gas that has exited from the exhaust port returns to the intake side via the exhaust gas recirculation passage. Therefore, after the intake throttle valve is closed when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating, the cold intake air hardly flows toward the lean NOx catalyst. Therefore, lean NOx
The temperature of the catalyst can be further prevented from lowering.

As a more preferable means, the lean NO
When the x-catalyst regeneration process is requested, the air-fuel ratio of the combustion gas may be made rich.

In the internal combustion engine having the lean NOx catalyst of the present invention, when the air-fuel ratio of the combustion gas is made rich, the combustion heat of the combustion type heater increases, and the reducing gas components such as hydrocarbons increase in the exhaust gas. Thus, NOx can be reduced by the lean NOx catalyst. Further, since the combustion gas of the combustion type heater is used for reducing nitrogen oxides, the conventional auxiliary injection becomes unnecessary.

As a further preferred means, it is desirable that the junction of the combustion gas introduction passage and the exhaust passage is located at a position before the lean NOx catalyst.

In the internal combustion engine having the lean NOx catalyst according to the present invention, the combustion gas emitted from the combustion type heater is directed to a position immediately before the lean NOx catalyst via the combustion gas introduction path, that is, immediately near the lean NOx catalyst. Can be sent. For this reason, the combustion gas heat can be used without waste to activate the lean NOx catalyst.

As a further preferred means, the combustion gas introduction passage may have a heat insulating material.

If the combustion gas introduction path is made insulated, it can be used only for warming the catalyst without escaping the heat of the combustion gas while the combustion gas passes through the combustion gas introduction path. Therefore, the lean NOx catalyst can be further warmed, so that nitrogen oxides can be reduced earlier.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An internal combustion engine having a lean NOx catalyst according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

A diesel engine I as an internal combustion engine to which the present invention is applied includes a cylinder 2, an intake device 3 for feeding air required for combustion into the cylinder 2, and a cylinder 2
And an exhaust device 4 for discharging exhaust gas emitted from the exhaust gas to the atmosphere.

The cylinder 2 has a cylinder head 2a mounted and fixed on an upper portion thereof, and a piston 5 is provided inside the cylinder 2 so as to be vertically movable.

The piston 5 is connected to a crankshaft (not shown) via a connecting rod 5a. Piston 5
A combustion chamber 6 is formed in the piston head.

The cylinder head 2a is provided with an intake port 8 and an exhaust port 9 that face the combustion chamber 6 when the piston 5 comes up.

An intake valve 8a and an exhaust valve 9a are incorporated in the intake port 8 and the exhaust port 9, respectively. An injector 10 for injecting fuel into the cylinder 2 is disposed between the two valves so as to face the cylinder 2. It is.

The injector 10 receives a pump pressure of an unillustrated injection pump, which is a driving source of the injector 10, and ejects fuel.

The intake port 8 is connected to an intake passage 11, and the exhaust port 9 is connected to an exhaust passage 12.

The intake device 3 has an air cleaner (not shown) for filtering outside air as a start end and an intake port 8 as an end. A compressor 15 of a turbocharger, which is an intake system structure, is provided between the air cleaner and the intake port 8.
a, a combustion heater 17 for raising the temperature of an engine-related element, an intercooler (not shown) serving as an intake cooling device, an intake manifold serving as a suction branch pipe, and the like are arranged on the intake passage 11.

The exhaust device 4 is provided with an exhaust port 9 in the engine body.
Is the start end, and the muffler (not shown) is the end from there.
Further, between the exhaust port 9 and the muffler, an exhaust system structure such as a turbine 15b of a turbocharger, a catalytic converter 19 as a gas purification device, and the like are provided on the exhaust passage 12. The catalytic converter 19 is a gas purification device that contains a lean NOx storage-reduction type catalyst therein, purifies mainly the exhaust gas of the engine I, and purifies the combustion gas of the combustion heater 17 together. Further, the catalytic converter 19 can be used in the sense of a lean NOx catalyst, and unless otherwise specified, the lean NOx storage reduction catalyst is simply referred to as a lean NOx catalyst. further,
The time when the lean NOx catalyst requires NOx reduction is referred to as a request for the lean NOx catalyst regeneration process.

The intake device 3 and the exhaust device 4 are connected by two connecting pipes that connect the two separately, that is, a combustion gas introduction passage 21 and an exhaust gas recirculation device (EGR device) 23.

The combustion gas introduction passage 21 is provided with a combustion heater 17.
Is a pipe that guides the combustion gas from the intake passage 11 toward the exhaust passage 12 to bypass the engine body, in other words, the cylinder 2. The EGR device 23 returns the exhaust gas to the intake system in order to reduce nitrogen oxides generated in the cylinder 2, and an EGR passage 23a as an exhaust recirculation passage which substantially connects the intake device 3 and the exhaust device 4, and an EGR passage 23a. And an EGR valve 23b for adjusting the amount of exhaust gas passing through.

On the other hand, the combustion type heater 1 belonging to the intake device 3
7 has an air supply passage 33 for supplying air to the combustion heater 17 from the intake passage 11 and a combustion gas discharge passage 35 for discharging combustion gas from the combustion heater 17 to the intake passage 11. The combustion heater 17 is attached to the intake passage 11 by the air supply passage 33 and the combustion gas discharge passage 35. Further, the combustion type heater 17 has an adjustment valve 17a and a blower fan 17b for adjusting the amount of air flowing through an air flow passage (not shown) of the combustion type heater 17. Also, what is indicated by reference numeral 17c is an oxygen sensor,
By using the oxygen sensor 17c, the air-fuel ratio of the combustion gas can be obtained.

The connection points C1 and C2 of the air supply path 33 and the combustion gas discharge path 35 with the intake passage 11 are such that the connection point C1 is located upstream of the connection point C2. In the middle of the combustion gas discharge passage 35, a well-known three-way valve 36 is provided.
Is provided. One end of the combustion gas introduction passage 21 is connected to the three-way valve 36. The other end of the combustion gas introduction path 21 is
The exhaust passage 12 is connected to a position C3 on the upstream side of the catalytic converter 19 in the exhaust passage 12. This upstream side location C3 is also a junction point of the combustion gas introduction path 21 with the exhaust path 12, and in other words, is a location near the entrance (not shown) of the catalytic converter 19. The combustion gas introduction passage 21 is provided with a heat insulating material (not shown) on its wall surface so that heat of the combustion gas passing through the combustion gas introduction passage 21 is not escaping.

Further, when the regeneration process of the lean NOx catalyst is required and the vehicle is running at a reduced speed, the three-way valve 36 opens the combustion gas introduction passage 21. Thereby, the combustion gas of the combustion heater 17 flows to the catalytic converter 19 via the combustion gas introduction path 21. When the vehicle is running at a reduced speed, fuel is not injected from the injector 10 into the cylinder 2.

Further, the connection point C1 in the intake passage 11
An intake throttle valve 38 for restricting intake air passing through the intake passage 11 is provided between the intake port 11 and the connection point C2. This intake throttle valve 38
Like the three-way valve 36, the lean NO of the catalytic converter 19
It acts when the x-catalyst is at the time of the regeneration request and the vehicle is running at a reduced speed. The intake throttle valve 38 is operated to close the intake passage 11.

FIG. 1 shows the operating state of the engine when a request for regeneration of the lean NOx catalyst is required and the vehicle is running at a reduced speed.

In this case, the combustion gas is supplied to the combustion gas introduction path 2
1, upstream upstream side of the catalytic converter 19, C3
After that, the lean NOx catalyst of the catalytic converter 19 is warmed. In addition, when the lean NOx catalyst regeneration process is requested and the vehicle is running at a reduced speed, the EGR device 23 is operated to open the EGR passage 23a. Further, when the lean NOx catalyst is requested to be regenerated, the air-fuel ratio of the combustion heater 17 is adjusted in order to make the air-fuel ratio of the combustion gas rich as in a reducing atmosphere.

On the other hand, FIG. 2 shows the engine operating state when the vehicle is in normal running, not when the lean NOx catalyst regeneration process is requested.

In this case, the three-way valve 36 and the intake throttle valve 3
Reference numeral 8 denotes a time when a request for a regeneration process of the lean NOx catalyst is made and the operation is opposite to the case where the vehicle is running at a reduced speed. As a result, the combustion gas introduction passage 21 is closed by the three-way valve 36, and the intake passage 11 is opened by the intake throttle valve 38. The combustion gas in this case flows through the combustion gas discharge passage 35 into the intake passage 11 as shown by the solid arrow in FIG. 2, and then enters the cylinder 2 to act as an engine warm-up. Note that the fuel is injected from the injector 10 because the vehicle is traveling normally instead of being decelerated. When the air-fuel mixture formed by mixing the injected fuel with the intake air burns, the air-fuel mixture comes out of the exhaust port 9 of the cylinder 2 as exhaust gas. In addition, since the vehicle is traveling normally, the EGR device 23 operates normally, and the exhaust gas flowing out of the exhaust port 9 flows as indicated by a broken arrow in FIG.
The GR passage 23a is recirculated from the exhaust side to the intake side. Note that the opening of the EGR valve 23b at this time is lean N
It is smaller than when the Ox catalyst regeneration process is requested and when the vehicle is running at a reduced speed.

As described above, the three-way valve 36 is provided with the lean NOx
The three-way valve 36 is a switching valve that selectively switches either the combustion gas introduction path 21 or the combustion gas discharge path 35 to open the gas passage according to the state of the catalyst and the running state of the vehicle. It is called a gas flow switching valve.

The intake throttle valve 38 in the intake passage 11
An intake pressure sensor 39 is mounted between the compressor and the compressor 15a. If the combustion type heater 17 is operated when the pressure of the intake system becomes equal to or higher than a predetermined value, the combustion gas exiting from the combustion type heater 17 is exhausted through the combustion gas introduction passage 21 even when the engine I is operating. It can flow into the passage 12. The "predetermined value" means that the pressure of the engine intake system is higher than or equal to the predetermined value, and the pressure of the engine intake system is higher than the pressure of the engine exhaust system when the combustion heater is operated. Combustion gas can flow to the engine exhaust system,
A value that does not cause backflow.

In the exhaust passage 12, a catalytic converter 19
NOx sensors (not shown) are attached to the vicinity of both ends of the entrance and exit. From the difference between the detected values of the two NOx sensors, it is determined whether the lean NOx catalyst is in the reduction time.

It is determined by the computer, that is, the engine control unit EC, that it is determined that the lean NOx catalyst regeneration process is required.
U is a central processing control unit CPU which is a component of U. C
The PU detects various sensors provided for the engine I for each operating state of the engine I, regardless of whether or not the description is given.
It is determined whether or not the vehicle is decelerating at the time of the request for the regeneration processing of the lean NOx catalyst, based on the various electric signals sent to the vehicle. Then, in accordance with the result of the determination, the CPU operates the three-way valve 36 and the intake throttle valve 38 to set the combustion gas introduction passage 21
In addition, by opening and closing the intake passage 11, the combustion gas is distributed to a necessary portion, and the air-fuel ratio of the combustion gas is adjusted. <Operation and Effect of Embodiment> Next, the operation and effect of the embodiment will be described.

In the diesel engine I, lean NOx
When a catalyst regeneration process is requested and the vehicle is running at a reduced speed, the intake throttle valve 38 provided in the intake passage 11 is operated to close the intake passage 11. Simultaneously or almost at the same time, the combustion gas introduction passage 21 is opened by operating the three-way valve 36, which is a gas passage switching valve, and the EGR valve 23b is operated to make the EGR passage 23a larger than when the vehicle normally travels. Open the gas well. Combustion gas introduction path 21
Is to simultaneously close the combustion gas discharge passage 35 with the three-way valve 36 as a boundary.

After the intake throttle valve 38 is actuated and the intake passage 11 is closed, the amount of intake air flowing toward the cylinder 2 via the intake throttle valve 38 is very small. In other words, the low-temperature gas (essentially, the intake) is lean NO
It does not flow toward the x catalyst. Therefore, it is possible to prevent the temperature of the lean NOx catalyst from lowering by itself.

Further, a three-way valve 36 serving as a gas flow switching valve is provided.
When the combustion gas introduction passage 21 is opened by the operation described above, the opened combustion gas introduction passage 21
The combustion gas is guided toward the upstream upstream location C3 of the Ox catalyst. At this time, the combustion gas bypasses the engine body (cylinder 2) and flows through the combustion gas introduction passage 21 as indicated by the solid arrow in FIG. Therefore, at this time, if the temperature of the combustion gas is high, the temperature of the lean NOx catalyst also increases.

That is, even when the vehicle is running at a reduced speed, the lean NOx catalyst is not only cooled by the intake air as in the prior art, but is also warmed. Therefore, when the vehicle is in the deceleration range, the combustion amount of the combustion type heater is increased from when the vehicle is in the deceleration range so that the lean NOx catalyst functions effectively when shifting from deceleration traveling to normal traveling.
If the temperature of the x catalyst is set to be equal to or higher than the activation temperature, the lean NOx catalyst is already activated when the vehicle starts to run normally. Therefore, at this time lean N
If an appropriate amount of the reducing agent is supplied to the Ox catalyst, that is, the air-fuel ratio of the combustion gas of the combustion type heater is made rich to make lean NOx
If the catalyst is in a reducing atmosphere, the reduction and purification of nitrogen oxides can be continuously performed during the transition from deceleration running to normal running. As a result, a suitable lean NOx catalyst can be regenerated.

Even if soot or the like is attached to the lean NOx catalyst, if the air-fuel ratio of the combustion gas is enriched, the heat of the combustion gas increases, so that the soot or the like can be removed by combustion.

Further, when the vehicle is running at a reduced speed, no fuel is injected from the injector 10. Therefore, the intake air downstream of the installation location of the intake throttle valve 38 in the intake passage 11 before closing the intake throttle valve 38 is
The gas leaves the exhaust port 9 without being subjected to combustion, that is, with almost no change in temperature. At this time, EGR
Since the passage 23a is open, the gas (substantially, intake) that has exited from the exhaust port 9 is returned from the exhaust side to the intake side through the EGR passage 23a as indicated by a broken arrow in FIG. Therefore, after the intake throttle valve 38 is closed, cold intake air hardly flows toward the catalytic converter 19. Therefore, a decrease in the temperature of the lean NOx catalyst can be further prevented.

In the engine I, the combustion heater 17
Of the combustion gas exiting through the combustion gas introduction passage 21 to a point C3 just before the lean NOx catalyst, that is, the lean NOx catalyst.
x Can be sent directly to the immediate vicinity of the catalyst. For this reason, the combustion gas heat can be used without waste to activate the lean NOx catalyst. In addition, since the combustion gas introduction path 21 is insulated, the heat of the combustion gas does not escape to other parts while the combustion gas passes through the combustion gas introduction path 21. Therefore, the combustion gas heat can be used only for warming the catalyst. Therefore, the lean NOx catalyst can be further warmed, so that the exhaust gas can be purified earlier and the nitrogen oxides can be reduced.

Since the combustion gas of the combustion heater is used for reducing nitrogen oxides, the conventional auxiliary injection becomes unnecessary.

[0064]

According to the internal combustion engine having the lean NOx catalyst of the present invention, when the vehicle shifts from deceleration running to normal running, the temperature of the lean NOx catalyst can be raised in advance to the activation temperature or higher, so that the vehicle runs at reduced speed. Even when the vehicle shifts to normal running, reduction and purification of nitrogen oxides and removal of soot and the like can be performed without interruption.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an internal combustion engine having a lean NOx catalyst according to the present invention, showing an operation state when a vehicle is running at a reduced speed.

FIG. 2 is a schematic configuration diagram of an embodiment of an internal combustion engine having a lean NOx catalyst according to the present invention, showing an operation state when the vehicle is running normally.

[Explanation of symbols]

I ... Diesel engine (internal combustion engine) 2 ... Cylinder 3 ... Intake device 4 ... Exhaust device 5 ... Piston 5a ... Connecting rod 6 ... Combustion chamber 7 ... Cylinder head 8 ... Intake port 8a ... Intake valve 9 ... Exhaust port 9a ... Exhaust valve 10 ... Injector 11 ... Intake passage 12 ... Exhaust passage 15a ... Turbocharger compressor 15b ... Turbocharger turbine 17 ... Combustion heater 17a ... Air amount adjustment valve 17b ... Blower fan 17c ... Oxygen sensor 19 ... Catalyst converter (lean NOx catalyst) Reference Signs List 21: combustion gas introduction path 23: exhaust gas recirculation device (EGR device) 23a: EGR passage (exhaust gas recirculation passage) 23b: EGR valve 33: air supply passage 35: combustion gas discharge passage 36: three-way valve (switching valve) 38 ... intake throttle valve 39 ... intake pressure sensor C1 ... air supply passage 33 and intake passage Connection point to the passage 11 C2: Connection point between the combustion gas discharge path 35 and the intake passage 11 C3 ... Near point upstream of the catalytic converter 19 (junction point of the combustion gas introduction path 33 with the exhaust passage 12)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 21/08 301 F02D 21/08 301A 301C 311 311B 41/12 305 41/12 305 310 310 F02M 25/07 F02M 25 / 07 B 570 570 J 570 Z F term (reference) 3G062 AA01 AA05 AA06 BA00 CA00 GA02 GA04 GA09 GA21 3G091 AA02 AA10 AA11 AA17 AA18 AA24 AB05 AB06 BA03 BA04 BA14 BA33 CA02 CA13 CA18 CB02 FA03 CB03 FA03 CB03 FA03 CB03 FA03 FB10 FB11 FB12 FC07 HA36 HA37 HA42 HB03 HB05 HB06 3G092 AA01 AA02 AA06 AA09 AA17 AA18 AB02 AB03 BA04 BA06 BB10 DB03 DC03 DC10 DC15 DF01 DF02 DF09 EA05 EA11 EA28 EA29 FA17 HA03 HA03 HD03 HA03 LA01 LB04 MA01 NE13 PA07Z PD01Z

Claims (5)

[Claims] 1. An intake throttle valve installed in an intake passage to restrict intake air passing through the intake passage; a lean NOx catalyst installed in an exhaust passage to purify gas passing through the exhaust passage; and heat obtained by burning fuel. A combustion-type heater that raises the temperature of an engine-related element, a combustion-gas exhaust passage that emits combustion gas from the combustion-type heater to the intake passage, and without passing through a cylinder toward an upstream side of a lean NOx catalyst in the exhaust passage. A combustion gas introduction path for guiding the combustion gas, and a switching valve for selectively switching and opening either the combustion gas introduction path or the combustion gas discharge path. When the vehicle is running at a reduced speed, a lean NOx catalyst for closing the intake passage by the intake throttle valve and switching the switching valve to open the combustion gas introduction passage is provided. Internal combustion engine that. 2. An exhaust gas recirculation device, wherein the exhaust gas recirculation device is operated to open an exhaust gas recirculation passage extending from an exhaust system to an intake system when the regeneration process is requested and the vehicle is running at a reduced speed. The lean NOx according to claim 1, characterized in that:
An internal combustion engine having a catalyst. 3. The internal combustion engine having a lean NOx catalyst according to claim 1, wherein an air-fuel ratio of the combustion gas is made rich when a request for regeneration of the lean NOx catalyst is made. 4. The lean NO according to claim 1, wherein a junction of the combustion gas introduction passage with the exhaust passage is located in front of a lean NOx catalyst.
Internal combustion engine with x catalyst. 5. The internal combustion engine having a lean NOx catalyst according to claim 1, wherein the combustion gas introduction path has a heat insulating material.