JP3508594B2 - Internal combustion engine having lean NOx catalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A catalytic converter used in an exhaust system as an exhaust purification means for an internal combustion engine such as a gasoline direct-injection lean-burn engine or a diesel engine, which has high thermal efficiency and has an atmosphere in the exhaust system with excess oxygen and a small amount of hydrocarbons and carbon monoxide. Contains, for example, a storage reduction lean NOx catalyst. The storage reduction lean NOx catalyst releases the stored nitrogen oxides from the catalyst by temporarily storing nitrogen oxides in the catalyst in a lean atmosphere and then supplying exhaust gas in a rich atmosphere having a low oxygen concentration to the lean NOx catalyst. The reduction component in the exhaust gas reduces and purifies it all at once. That is, the lean NOx catalyst does not continuously perform reduction purification of nitrogen oxides, and alternately repeats execution and stop of reduction purification. Therefore, the storage reduction lean NOx catalyst can also be said to be an intermittent treatment lean NOx catalyst.

Further, the lean NOx catalyst is activated in a predetermined temperature range, and sufficient activation cannot be expected below a predetermined temperature. Therefore, the lean NOx catalyst must be raised to above the activation temperature which is the predetermined temperature.

[0004]

By the way, in a diesel engine and other internal combustion engines that directly inject fuel into cylinders, during deceleration due to structural reasons such as the mounting position of the fuel injection device on the engine, etc. Do not inject fuel.
However, if the vehicle is running, the piston will move whether or not there is injection. For this reason, the air that has entered the cylinder from the intake port during deceleration does not undergo combustion and flows from the exhaust port to the exhaust passage as it is and eventually reaches the catalytic converter. That is, at the time of deceleration, since it is at the time of non-combustion, air having a temperature considerably lower than that at the time of combustion flows through the catalytic converter. Therefore, the catalyst temperature decreases, and if the catalyst was activated before the deceleration, the catalyst temperature becomes lower than the activation temperature. Then, even if the vehicle shifts from the decelerating traveling to the normal traveling in this state, the temperature of the lean NOx catalyst does not immediately reach the activation temperature or higher in accordance with it. Therefore, the nitrogen oxides may not be reduced and purified until the catalyst reaches the activation temperature or higher again.

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

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

In order to supply the reducing agent, for example, as described in Japanese Patent Laid-Open No. 6-117225,
The original role has been achieved by 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 means fuel injection in which the injector injects between the expansion stroke and the exhaust stroke.

On the other hand, the fuel injection originally injected by the injector is called main injection, and the main injection is performed in the compression stroke. Therefore, the secondary injection is secondary. For this reason, the injector is set so that the main injection, which is the original role of the injector, 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. Then, in order to realize this, the injector is attached to the cylinder head with a constant injection angle. However, since the sub-injection is fuel injection performed between the expansion stroke and the exhaust stroke as described above, the timing of injecting fuel from the injector for the sub-injection is when the piston is below the top dead center. . In this relationship, the fuel injected by the sub-injection is unlikely to be vaporized or atomized. Therefore, the fuel injected by the sub-injection may be supplied to the exhaust system in the liquefied state. However, even if the fuel is guided to the exhaust system by sub-injection,
It is preferable that this is in a vaporized or atomized state in order to reduce and purify nitrogen oxides.

However, it is impossible to expect a sufficient effect for the secondary injection from the injector whose original role is focused on the main injection.

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

[0011]

In order to solve the above problems, the internal combustion engine having the lean NOx catalyst of the present invention employs the following means.

An intake throttle valve installed in the intake passage for restricting intake air passing through the intake passage, a lean NOx catalyst installed in the exhaust passage for purifying gas passing through the exhaust passage, and an engine using heat obtained by burning fuel A combustion heater that raises the temperature of related elements, a combustion gas discharge passage through which combustion gas of the combustion heater is discharged to the intake passage, and a lean N in the exhaust passage.
A combustion gas introduction passage for guiding the combustion gas toward the upstream side of the Ox catalyst without passing through the cylinder; and a switching valve for selectively opening either the combustion gas introduction passage or the combustion gas discharge passage. The lean NOx that opens the combustion gas introduction path by closing the intake passage by the intake throttle valve and switching the switching valve when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating.
Internal combustion engine with x-catalyst.

Here, the "engine-related element" is, for example, the engine cooling water, the cylinder block, the cylinder head, or the internal combustion engine itself.

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

The "combustion type heater" is a heater attached to an internal combustion engine as a separate entity from the internal combustion engine body, and burns by performing its own combustion without being affected by the combustion in the cylinder of the internal combustion engine body. It discharges gas. By separately providing this, the exhaust system temperature can be raised 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. Therefore, the combustion fuel for the combustion type heater is fuel for internal combustion engine such as gasoline or light oil. It is preferably used. This is because fuels such as gasoline generate unburned gas unless they are completely burned, and the unburned gas contains hydrocarbons and carbon monoxide as reducing agents. It should be noted that the combustion gas emitted by the combustion heater is hereinafter referred to as combustion gas unless otherwise specified.

The "combustion gas introduction passage" is a lean NOx that does not allow heat to escape to the other while the combustion gas passes through the passage.
Advantageously, the passage is dedicated to warming the x catalyst. 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.

"When requesting regeneration processing of lean NOx catalyst"
Is when the 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 lean NOx catalyst regeneration process is required and the vehicle is decelerating, the intake throttle valve installed in the intake passage is throttled to open the intake passage. With the closing, that is, at the same time or almost the same time as closing the intake passage, the combustion gas introduction passage is opened by operating the switching valve. Opening the combustion gas introduction path means simultaneously closing the combustion gas discharge path with the switching valve as a boundary.

When the intake throttle valve is closed, almost no intake air flows toward the cylinder through at least the intake throttle valve. In other words, low temperature gas (substantially intake air)
Does not flow towards the lean NOx catalyst. Therefore, this alone can prevent the temperature of the lean NOx catalyst from decreasing.

In addition, in the present invention, the combustion gas introduction passage is opened by operating the gas passage switching valve, and the opened combustion gas introduction passage does not pass through the engine body, in other words, the cylinder, Combustion gas is guided to 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 decelerating, the lean NOx catalyst is not cooled by the intake air as in the prior art. Rather it warms the lean NOx catalyst. Therefore, when the vehicle is in the deceleration range, the combustion amount of the combustion type heater is increased so that the temperature of the lean NOx catalyst becomes equal to or higher than the activation temperature so that the lean NOx catalyst effectively functions when shifting from the deceleration running to the normal running. If so, the lean NOx catalyst is already in an activated state when the vehicle starts to run normally. Therefore, if an appropriate amount of reducing agent is supplied to the lean NOx catalyst at this time, reduction purification of nitrogen oxides can be performed without interruption during transition from deceleration traveling to normal traveling. As a result, suitable regeneration of the lean NOx catalyst can be achieved.

Further, even if soot or the like adheres to the lean NOx catalyst, the soot or the like can be removed by combustion by raising the temperature of the combustion gas.

As a further preferable means, an exhaust gas recirculation device is provided, and the exhaust gas recirculation device is operated when the regeneration processing is requested and the vehicle is decelerating to extend the exhaust gas recirculation 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, the intake passage is closed and the combustion gas introduction passage is opened as described above when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating. In addition, at this time, the exhaust gas recirculation device is activated to open the exhaust gas recirculation passage extending from the exhaust system to the intake system. At this time, since the vehicle is decelerating, fuel is not injected into the cylinder from the fuel injection device. Therefore, even if the intake air on the downstream side of the intake throttle valve in the intake passage before the intake throttle valve is closed flows into the cylinder, this intake air is not used for 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 discharged from the exhaust port returns to the intake side through the exhaust gas recirculation passage. Therefore, when the lean NOx catalyst regeneration process is requested and the intake throttle valve is closed when the vehicle is decelerating, almost no cold intake air flows toward the lean NOx catalyst. Therefore, lean NOx
The temperature decrease of the catalyst can be further prevented.

As a further preferable means, the lean NO
It is preferable to make the air-fuel ratio of the combustion gas rich when the regeneration processing of the x catalyst is requested.

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 heater increases and the reducing gas component such as hydrocarbon increases in the exhaust gas. , NOx reduction of lean NOx catalyst is possible. Further, since the combustion gas of the combustion type heater is used for the reduction of nitrogen oxides, the conventional auxiliary injection becomes unnecessary.

As a further preferable means, it is desirable that the junction of the combustion gas introduction passage and the exhaust passage is located in front of the lean NOx catalyst.

In the internal combustion engine having the lean NOx catalyst of the present invention, the combustion gas emitted from the combustion type heater is directly passed through the combustion gas introduction path to a position in front of the lean NOx catalyst, that is, immediately near the lean NOx catalyst. Can be sent. Therefore, the combustion gas heat can be used without waste to activate the lean NOx catalyst.

As a further preferable means, the combustion gas introducing passage may have a heat insulating material.

If the combustion gas introducing passage is made adiabatic, it can be used only for warming the catalyst without releasing the heat of the combustion gas to the other while the combustion gas is passing through the combustion gas introducing passage. Therefore, since the lean NOx catalyst can be further warmed, the nitrogen oxides can be reduced more quickly.

[0032]

DETAILED DESCRIPTION OF THE INVENTION 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 sending air required for combustion into the cylinder 2, and a cylinder 2.
An exhaust device 4 for discharging exhaust gas emitted from the exhaust gas to the atmosphere.

A cylinder head 2a is mounted and fixed on the upper portion of the cylinder 2, 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 of.

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

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

The injector 10 receives the pump pressure of an injection pump (not shown) which is a drive source of the injector 10 and ejects fuel.

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

The intake device 3 has an air cleaner (not shown) for filtering the outside air as the starting end and the intake port 8 as the ending end. Between the air cleaner and the intake port 8, a compressor 15 of a turbocharger, which is an intake system structure, is provided.
a, a combustion heater 17 for heating the engine-related elements, an intercooler (not shown) that is an intake cooling device, an intake manifold that is a suction branch pipe, and the like are arranged on the intake passage 11.

The exhaust device 4 is an exhaust port 9 in the engine body.
Is the starting point and the muffler (not shown) is the ending point.
Between the exhaust port 9 and the muffler, a turbine 15b of a turbocharger, a catalytic converter 19 as a gas purifying device, which is an exhaust system structure, and the like are provided on the exhaust passage 12. The catalytic converter 19 is a gas purification device that encloses a storage-reduction lean NOx catalyst therein to mainly purify the exhaust gas of the engine I and also purifies the combustion gas of the combustion heater 17. Further, the catalytic converter 19 can be used in the sense of a lean NOx catalyst, and the occlusion reduction type lean NOx catalyst is simply referred to as a lean NOx catalyst unless otherwise specified. further,
The time when the lean NOx catalyst requires NOx reduction will be referred to as the lean NOx catalyst regeneration processing request.

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 connected to the combustion heater 17
Is a pipe that guides the combustion gas from the intake passage 11 side toward the exhaust passage 12 side while bypassing 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 the nitrogen oxides generated in the cylinder 2, and the EGR passage 23a as an exhaust gas recirculation passage that substantially connects the intake device 3 and the exhaust device 4, and the 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
Reference numeral 7 has an air supply passage 33 for supplying air from the intake passage 11 to the combustion heater 17, and a combustion gas discharge passage 35 for outputting the combustion gas produced by 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 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 heater 17. Further, the reference numeral 17c indicates an oxygen sensor,
By using the oxygen sensor 17c, the air-fuel ratio of the combustion gas can be obtained.

Regarding the connection points C1 and C2 of the air supply passage 33 and the combustion gas discharge passage 35 to the intake passage 11, the connection portion C1 is located upstream of the connection portion C2. A known three-way valve 36 is provided in the middle of the combustion gas discharge passage 35.
Is provided. One end of the combustion gas introduction passage 21 is connected to the three-way valve 36. Further, the other end of the combustion gas introduction passage 21 is
The exhaust passage 12 is connected to a location C3 on the upstream side of the catalytic converter 19. This upstream side front portion C3 is also a junction point of the combustion gas introduction passage 21 with the exhaust passage 12, in other words, a portion near an inlet (not shown) of the catalytic converter 19. A heat insulating material (not shown) is attached to the wall surface of the combustion gas introduction passage 21 so that the heat of the combustion gas passing through the combustion gas introduction passage 21 is not released to the other.

Further, when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating, the three-way valve 36 opens the combustion gas introducing passage 21. As a result, the combustion gas of the combustion heater 17 flows into the catalytic converter 19 via the combustion gas introduction passage 21. Then, when the vehicle is decelerating, fuel is not injected from the injector 10 to the cylinder 2.

Further, the connection point C1 in the intake passage 11
An intake throttle valve 38 that throttles the intake air passing through the intake passage 11 is provided between the connection point C2 and the connection point C2. This intake throttle valve 38
Like the three-way valve 36, the lean NO of the catalytic converter 19
The x-catalyst functions when the regeneration process is requested and the vehicle is decelerating. The intake throttle valve 38 is operated to close the intake passage 11.

FIG. 1 shows the engine operating state when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating.

In this case, the combustion gas is the combustion gas introduction passage 2
C3 upstream of the catalytic converter 19 via 1
And then warms the lean NOx catalyst of the catalytic converter 19. In addition, when the lean NOx catalyst regeneration process is requested and the vehicle is decelerating, the EGR device 23 is operated to open the EGR passage 23a. Further, when a request for regeneration of the lean NOx catalyst is made, the air-fuel ratio of the combustion heater 17 is adjusted to make the air-fuel ratio of the combustion gas rich in the lean NOx catalyst as in the reducing atmosphere.

On the contrary, FIG. 2 shows the engine operating state when the vehicle is in normal running, not when the regeneration processing of the lean NOx catalyst is requested.

In this case, the three-way valve 36 and the intake throttle valve 3
8 acts in the opposite manner to the case where the lean NOx catalyst regeneration process is requested and the vehicle is decelerating. As a result, the three-way valve 36 closes the combustion gas introduction passage 21, and the intake throttle valve 38 opens the intake passage 11. The combustion gas in this case flows into the intake passage 11 via the combustion gas discharge passage 35 as shown by the solid line arrow in FIG. 2, then enters the cylinder 2 and acts to warm up the engine. Note that the fuel is injected from the injector 10 because the vehicle is not decelerated but is normally traveling. When the air-fuel mixture formed by mixing the injected fuel with the intake air is combusted, it becomes exhaust gas from the exhaust port 9 of the cylinder 2. Further, since the vehicle is traveling normally, the EGR device 23 operates normally, and the exhaust gas discharged from the exhaust port 9 becomes a flow indicated by a dashed arrow in FIG.
The GR passage 23a is recirculated from the exhaust side toward the intake side. The opening degree 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 decelerating.

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

Further, in the intake passage 11, the intake throttle valve 38
An intake pressure sensor 39 is mounted between the compressor and the compressor 15a. If the combustion heater 17 is operated when the pressure of the intake system exceeds a predetermined value, the combustion gas emitted from the combustion heater 17 is exhausted through the combustion gas introduction passage 21 even when the engine I is operating. Can be flowed to passage 12. The "predetermined value" means that the pressure of the engine intake system is equal to or higher than 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 be sent to the engine exhaust system,
A value that does not cause backflow.

In the exhaust passage 12, the catalytic converter 19
An NOx sensor (not shown) is attached near the both ends of the inlet and the outlet. Whether or not the lean NOx catalyst is in the reduction period can be obtained from the difference between the detection values of both NOx sensors.

It is the computer, that is, the engine control unit EC, that determines when the lean NOx catalyst regeneration process is requested.
It is a central processing control unit CPU which is a component of U. C
The PU detects various sensors provided in the engine I for each operating state of the engine I and
It is determined whether or not the lean NOx catalyst regeneration process is requested and the vehicle is decelerating based on various electric signals sent to the vehicle. Then, according to the determination result, the CPU operates the three-way valve 36 and the intake throttle valve 38 to cause the combustion gas introduction passage 21
Also, the intake passage 11 is opened / closed to distribute the combustion gas to a required location, or 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 the catalyst regeneration process is requested and the vehicle is decelerating, the intake throttle valve 38 installed in the intake passage 11 is operated to close the intake passage 11. Simultaneously or almost at the same time, the combustion gas introducing 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 it larger than when the vehicle is normally traveling in the EGR passage 23a. Open the street of gas well. Combustion gas introduction passage 21
Opening means that the combustion gas discharge passage 35 is closed at the same time with the three-way valve 36 as a boundary.

After closing the intake passage 11 by operating the intake throttle valve 38, the amount of intake air flowing toward the cylinder 2 via at least the intake throttle valve 38 is very small. In other words, low-temperature gas (substantially intake air) is lean NO
x does not flow towards the catalyst. Therefore, this alone can prevent the temperature of the lean NOx catalyst from decreasing.

A three-way valve 36 which is a gas flow path switching valve
When the combustion gas introduction passage 21 is opened by the operation of, the opened combustion gas introduction passage 21 is
The combustion gas is guided to the upstream side C3 of the Ox catalyst. At this time, the combustion gas bypasses the engine body (cylinder 2) and flows in the combustion gas introduction passage 21 as shown by the solid arrow in FIG. Therefore, if the temperature of the combustion gas is high at this time, the temperature of the lean NOx catalyst also rises.

That is, even when the vehicle is decelerating, the lean NOx catalyst is not cooled by the intake air as in the prior art, but the lean NOx catalyst is warmed up. Therefore, when the vehicle is in the deceleration range, the combustion amount of the combustion type heater is increased to increase the lean NOx catalyst so that the lean NOx catalyst effectively functions when shifting from the deceleration running to the normal running.
If the temperature of the x-catalyst is kept above the activation temperature, the lean NOx catalyst is already in the activated state when the vehicle starts to run normally. Therefore, lean N at this time
If an appropriate amount of 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 and lean NOx is obtained.
If the catalyst is in the reducing atmosphere, the reduction and purification of nitrogen oxides can be performed without interruption during the transition from decelerating traveling to normal traveling. As a result, suitable regeneration of the lean NOx catalyst can be achieved.

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

Further, fuel is not injected from the injector 10 when the vehicle is decelerating. Therefore, the above-mentioned intake air on the downstream side of the installation location of the intake throttle valve 38 in the intake passage 11 before closing the intake throttle valve 38 is
It leaves the exhaust port 9 without being subjected to combustion, that is, in a state where there is almost no temperature change. And at this time EGR
Since the passage 23a is open, the gas (substantially intake air) emitted from the exhaust port 9 is returned from the exhaust side to the intake side through the EGR passage 23a as indicated by the broken line arrow in FIG. Therefore, after closing the intake throttle valve 38, almost no cold intake air flows toward the catalytic converter 19. Therefore, the temperature decrease of the lean NOx catalyst can be further prevented.

Further, in the engine I, the combustion heater 17
The combustion gas from the exhaust gas passes through the combustion gas introduction passage 21 to the point C3 before the lean NOx catalyst, that is, the lean NOx.
x Can be sent directly to the immediate vicinity of the catalyst. Therefore, the combustion gas heat can be used without waste to activate the lean NOx catalyst. In addition, since the combustion gas introduction passage 21 is insulated, the heat of the combustion gas does not escape to the other while the combustion gas passes through the combustion gas introduction passage 21. Therefore, the combustion gas heat can be used only for warming the catalyst. Therefore, since the lean NOx catalyst can be further warmed, the exhaust gas can be purified more quickly, and the nitrogen oxides can be reduced.

Further, since the combustion gas of the combustion type heater is used for the reduction of nitrogen oxides, the conventional auxiliary injection becomes unnecessary.

[0064]

According to the internal combustion engine having the lean NOx catalyst of the present invention, since the temperature of the lean NOx catalyst can be raised in advance to the activation temperature or higher when the vehicle shifts from decelerating traveling to normal traveling, the vehicle decelerates traveling. Even after shifting from normal to normal driving, reduction purification of nitrogen oxides and removal of soot etc. can be performed without interruption.

[Brief description of 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 operating state when a vehicle is decelerating.

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 operating state when a vehicle is normally traveling.

[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 adjusting valve 17b Blower fan 17c Oxygen sensor 19 Catalytic converter (lean NOx catalyst) 21 ... Combustion gas introduction passage 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 ... Connection point between air supply passage 33 and intake passage 11 C2 ... upstream front portion of the connection point C3 ... catalytic converter 19 and the combustion gas discharge passage 35 and the intake passage 11 (the junction of the exhaust passage 12 of the combustion gas introducing passageway 33)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI 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 570J 570Z (56) Reference JP-A-6-317142 (JP, A) JP-A 64-24118 (JP, A) JP-A 60-79149 (JP, A) JP-A 61-54313 (JP, A) Actual Kaihei 1-152069 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 3/08-3/28 F02D 21/08 F02D 41/12 F02M 25/07

Claims (5)

(57) [Claims] 1. An intake throttle valve installed in an intake passage for throttling intake air passing through the intake passage, a lean NOx catalyst installed in an exhaust passage for purifying gas passing through the exhaust passage, and heat obtained by burning fuel. A combustion type heater for raising the temperature of engine-related elements by means of a combustion gas, a combustion gas discharge passage for discharging the combustion gas of the combustion type heater to the intake passage, and an exhaust passage without passing through the cylinder toward the upstream side of the lean NOx catalyst. A combustion gas introducing passage for guiding the combustion gas; and a switching valve for selectively opening either the combustion gas introducing passage or the combustion gas discharging passage, and a regeneration processing request for the lean NOx catalyst is made. Further, when the vehicle is decelerating, a lean NOx catalyst that closes the intake passage by the intake throttle valve and switches the switching valve to open the combustion gas introduction passage is provided. Internal combustion engine that. 2. An exhaust gas recirculation device is provided, and the exhaust gas recirculation device is operated to open an exhaust gas recirculation passage extending from the exhaust gas system to the intake gas system when the regeneration process is requested and the vehicle is decelerating. The lean NOx according to claim 1, wherein
Internal combustion engine with catalyst. 3. The internal combustion engine having a lean NOx catalyst according to claim 1, wherein the air-fuel ratio of the combustion gas is made rich when a request for regeneration processing of the lean NOx catalyst is made. 4. The lean NO according to claim 1, wherein a junction of the combustion gas introducing passage and the exhaust passage is a portion in front of the 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 introducing passage has a heat insulating material.