JP3520789B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device for an internal combustion engine equipped with a combustion heater.

2. Description of the Related Art In recent years, internal combustion engines mounted on automobiles have been required to reduce harmful gas components in exhaust gas for reasons such as environmental protection. In response to such a demand, a combustion device (combustion type heater) independent of the internal combustion engine is provided, and the combustion heat generated by the combustion type heater is used to heat intake air and cooling water of the internal combustion engine, thereby Techniques have been proposed for promoting vaporization, raising the temperature of the combustion chamber of an internal combustion engine, and warming up, and reducing unburned HC and white smoke emitted from the internal combustion engine during cold start. The combustion heater as described above is configured to take in a part of the intake air and a part of the fuel of the internal combustion engine into the combustion chamber in the heater to ignite and combust it, and discharge the combustion gas to the engine intake system. .
Further, a heater internal water passage for circulating engine cooling water is formed around the heater internal combustion chamber. According to the combustion heater configured as described above, since the high temperature combustion gas burned in the combustion chamber in the heater is discharged to the intake system of the internal combustion engine, the intake air flowing through the intake system receives the heat of the combustion gas. Raise the temperature. When the intake air temperature is raised in this way, the temperature in the combustion chamber of the internal combustion engine rises, and fuel vaporization is promoted.
As a result, combustion of the air-fuel mixture is promoted. Further, in the combustion type heater, the engine cooling water flowing through the heater internal water channel receives the combustion heat to increase its temperature. Therefore, by circulating the engine cooling water whose temperature has been increased in this way through the cooling water channel in the internal combustion engine,
The temperature of the internal combustion engine rises, and warm-up is promoted. Therefore,
According to the combustion heater as described above, it is possible to reduce the amount of unburned HC and white smoke generated when the internal combustion engine is cold-started and to accelerate the warm-up of the internal combustion engine. In the combustion heater as described above, the heat of the cooling water warmed by the combustion heater is used by disposing the heater core for indoor heating in the cooling water passage extending from the combustion heater to the internal combustion engine. It is possible to heat the air for heating, and it is also possible to improve the heating performance at the cold start. Also, in the case of diesel engines, soot and unburned fuel components (unburned hydrocarbons (HC)) contained in the exhaust gas
It is also important to reduce particulate matter (PM; Particulate Matter) and nitrogen oxides (NO _x ). In response to such a demand, conventionally, N in the exhaust gas is exhausted under predetermined conditions.
Development of an internal combustion engine equipped with an NO _x catalyst for reducing and purifying O _x , a DPF (Diesel Particulate Filter) for trapping PM in exhaust gas, and the like in an exhaust system is underway. As the NO _X catalyst, when the exhaust gas flowing into the catalyst is in an oxygen excess state and HC is present, NO _X is used as a reducing agent to convert NO _X to nitrogen (N ₂ ), water (H _2
2 O), carbon dioxide (CO ₂ ) and other selective reduction type NO _X catalysts, or when the air-fuel ratio of the exhaust gas flowing into the catalyst is lean, NO _X in the exhaust gas is stored and A storage-reduction type NO that releases the stored NO _x when the oxygen concentration decreases and reacts the released NO _x with unburned HC, carbon monoxide (CO), etc. to reduce and purify it into N ₂ etc. _X catalyst and the like are known. On the other hand, the DPF is formed of a porous ceramic or the like, traps PM in the exhaust gas when the exhaust gas passes through the holes, and traps the captured PM in an air-fuel ratio of the inflowing exhaust gas that is in a lean atmosphere and has a high exhaust gas temperature (for example, , 500 ° C. to 700 ° C.), a catalyst is supported on the surface of the exhaust flow passage in the DPF,
It is known that the above substances are reacted with oxygen as a reducing agent and the trapped PM is burned by the heat of reaction at that time.
By the way, since a diesel engine generally burns an air-fuel mixture in an oxygen-excessive state, the amount of HC in the exhaust gas is small, and it has been difficult to supply a sufficient amount of HC as a reducing agent to the NO _X catalyst and DPF. For such a problem, an "exhaust gas purification device for an internal combustion engine" described in Japanese Patent Laid-Open No. 6-117225 is known. The exhaust emission control device described in this publication is a common rail in-cylinder injection type diesel engine, in which the fuel is injected (sub-injection) from the fuel injection valve in the expansion stroke or exhaust stroke of each cylinder to cause the existing fuel in the combustion chamber. The heat of the fuel gas is used to partially oxidize the HC in the fuel, and the partially oxidized HC is exhausted along with the NO _X.
It is intended to reduce and process NO _X and PM is supplied to the catalyst and DPF.

By the way, the above-mentioned exhaust emission control device has a problem that the load on the fuel injection valve, the fuel pump, etc. becomes large because the auxiliary injection is performed in addition to the normal fuel injection. . Further, since the above-described exhaust gas purification device needs to inject fuel into the combustion chamber during the expansion stroke and exhaust stroke, it is effective for a cylinder injection internal combustion engine in which the fuel injection valve injects fuel directly into the combustion chamber. However, there is a problem that it cannot be applied to other internal combustion engines. The present invention has been made in view of the above problems, and is provided with an exhaust gas purification unit that purifies harmful gas components in exhaust gas when an additive is supplied under predetermined conditions, and a combustion heater It is an object of the present invention to provide a technology capable of purifying harmful gas components in exhaust gas while reducing the amount of energy required for supply processing of an additive in a provided internal combustion engine.

The present invention adopts the following means in order to solve the above problems. That is, an exhaust gas purification apparatus for an internal combustion engine according to the present invention is provided with a combustion type heater that raises the temperature of a related element of the internal combustion engine and an exhaust system of the internal combustion engine, and exhausts when an additive is supplied under a predetermined condition. Exhaust purification means for purifying harmful gas components inside,
If the combustion heater is in an operating state when the predetermined condition is satisfied, the gas burned by the combustion heater is introduced as an additive into the exhaust system upstream of the exhaust gas purification means, and the combustion heater is deactivated. If there is, a purification control means for supplying fuel to the combustion heater to vaporize the fuel and introduce the vaporized fuel as an additive into an exhaust system upstream of the exhaust purification means. In the exhaust emission control device configured as described above, the purification control unit is configured such that the combustion heater is in the operating state or the combustion heater is not in operation when the condition that enables the exhaust purification unit to purify the harmful gas component is satisfied. Determine if it is working. When it is determined that the combustion heater is in the operating state, the purification control means introduces the gas burned by the combustion heater as an additive into the exhaust system upstream of the exhaust purification means. In this case, the fuel component contained in the combustion gas discharged from the combustion type heater is exposed to combustion heat in the combustion type heater and is thermally decomposed into a fuel component having a relatively small molecular size to purify harmful gas components. It becomes an additive suitable for. On the other hand, when it is determined that the combustion heater is in the inoperative state, the purification control means supplies the fuel to the combustion heater, vaporizes the fuel by using the residual heat of the combustion heater, and adds the vaporized fuel. It is introduced as an agent into the exhaust system upstream of the exhaust purification means. In this case, the vaporized fuel discharged from the combustion type heater is exposed to the residual heat of the combustion type heater and is thermally decomposed into a fuel component having a relatively small molecular size, and is added as an additive suitable for purifying harmful gas components. Become. That is, since the exhaust gas purification device according to the present invention supplies the fuel component in the gas discharged from the combustion type heater to the exhaust gas purification means as an additive, the combustion heat of the combustion type heater is used during the operation of the combustion type heater. However, when the combustion heater is not in operation, the residual heat of the combustion heater can be used to vaporize or thermally decompose the fuel, and it is not necessary to provide a dedicated device for supplying the additive, and It is possible to reduce the energy required for the agent supply process. Here, the exhaust gas purifying means described above, selective reduction type lean NO _X catalyst inflow exhaust gas is reduced and purify nitrogen oxides in the exhaust and a hydrocarbon is added during the lean atmosphere, the inflow exhaust gas is lean atmosphere Is a storage reduction type lean N that stores the nitrogen oxides in the exhaust gas and releases and purifies the stored nitrogen oxides when the additive concentration is added to the inflowing exhaust gas and the oxygen concentration decreases.
O _X catalyst or a particulate matter in the exhaust was trapped, combustion inflow exhaust particulate matter that has been captured with the temperature of the lean atmosphere and the inflow exhaust hydrocarbons is added at a predetermined temperature or higher and A particulate filter or the like to be processed can be exemplified. Further, the purification control means may change the state of the combustion gas or vaporized fuel of the combustion heater according to the state of the exhaust purification means. At that time, the purification control means may determine the state of the exhaust purification means according to at least one of the exhaust temperature downstream of the exhaust purification means, the engine speed, and the engine torque.

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. In FIG. 1, an internal combustion engine 1 is a multi-cylinder water-cooled diesel engine. An intake branch pipe 2 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 2 communicates with a combustion chamber of each cylinder via an intake port (not shown). The intake branch pipe 2 is connected to an intake pipe 3, and the intake pipe 3 is connected to an air cleaner box 4 containing an air filter. In the intake system configured as described above, the fresh air that has flowed into the air cleaner box 4 is removed of dust and dirt by the air filter, and then is guided to the intake branch pipe 2 through the intake pipe 3 and is introduced into the intake branch pipe 2. It is distributed to the combustion chamber of each cylinder through each branch pipe. On the other hand, the internal combustion engine 1 has an exhaust branch pipe 6
Are connected, and each branch pipe of the exhaust branch pipe 6 communicates with the combustion chamber of each cylinder via an exhaust port (not shown). The exhaust branch pipe 6 is connected to the exhaust pipe 7, the selective reduction type lean NO _X catalyst 8 as an exhaust gas purification device according to the way to the present invention the exhaust pipe 7 is provided. The selective reduction type lean NO _X catalyst 8 is located an air-fuel ratio of the exhaust gas flowing into the selective reduction type lean NO _X catalyst 8 in a lean atmosphere, and reducing the NO _X in the exhaust gas in a situation where the hydrocarbon HC is present Alternatively, it is a catalyst that decomposes, and examples thereof include a carrier made of zeolite carrying a transition metal such as Cu by ion exchange, and a carrier made of zeolite or alumina carrying a noble metal. In the exhaust system configured as described above, the air-fuel mixture burned in the combustion chamber of each cylinder is guided to the exhaust pipe 7 through each branch pipe of the exhaust branch pipe 6,
It flows into the selective reduction lean NO _x catalyst 8. At that time, if the air-fuel ratio of the exhaust gas flowing into the selective reduction lean NO _x catalyst 8 is in a lean atmosphere and HC exists in the exhaust gas, part of the HC in the selective reduction lean NO _x catalyst 8 will be present. Partial oxidation generates active species, and the active species react with NO _X in the exhaust gas to reduce NO _X to N ₂ , H ₂ O, CO _2, etc. Next, the internal combustion engine 1 is provided with one fuel injection valve 10 for each cylinder. Each fuel injection valve 10 is attached so that its injection hole faces the combustion chamber of each cylinder, and fuel can be directly injected into the combustion chamber. The fuel injection valve 10 communicates with a pressure accumulating chamber (common rail) 12 via a fuel distribution pipe 11, and the common rail 12 communicates with a fuel pump (not shown) via a fuel passage 13. In the fuel injection system configured as described above, the fuel discharged from the fuel pump is accumulated in the common rail 12 to a predetermined pressure, and the accumulated fuel is applied to the fuel injection valve 10 via the fuel distribution pipe 11. Then, when the fuel injection valve 10 is opened, the accumulated fuel is injected into the combustion chamber. Further, the internal combustion engine 1 is provided with a combustion heater 14. The combustion heater 14 has an intake passage 1
5 and the combustion gas discharge passage 17 are connected. The intake introduction passage 15 is connected to the intake pipe 3, and the combustion gas discharge passage 17 is connected to the exhaust pipe 7 upstream of the selective reduction lean NO _X catalyst 8. Intake passage 15
An air pump 16 that pumps a part of the intake air flowing through the intake pipe 3 to the combustion heater 14 is provided in the middle of the above.
Subsequently, in the combustion heater 14, a cooling water introduction passage 18 for guiding the cooling water of the internal combustion engine 1 to the combustion heater 14 and a cooling water for guiding the cooling water warmed in the combustion heater 14 to the internal combustion engine 1. The discharge passage 19 is connected. Further, a fuel introduction passage 20 is connected to the combustion heater 14, and the fuel introduction passage 20 is connected to the fuel passage 13 described above. This makes it possible to supply a part of the fuel flowing through the fuel passage 13 to the combustion heater 14.
Here, a specific configuration of the combustion heater 14 is shown in FIG.
It will be described based on. The combustion heater 14 is used for the internal combustion engine 1
Not shown water jacket and cooling water introduction passage 18
And the cooling water discharge passage 19, the inside of the combustion type heater 14 is formed with a heater internal cooling water passage 14a for flowing cooling water from the water jacket. The heater internal cooling water passage 14a is configured to circulate around a combustion chamber 14d formed inside the combustion heater 14, and the cooling water flowing in the heater internal cooling water passage 14a receives heat from the combustion chamber 14d. It is designed to heat up. This will be described sequentially. The combustion chamber 14d is a combustion cylinder 1 as a combustion source that generates flames.
4b and a cylindrical partition wall 14c that covers the combustion cylinder 14b to prevent the flame from leaking to the outside. By covering the combustion cylinder 14b with the partition wall 14c in this manner, the combustion chamber 14d is defined within the partition wall 14c. The partition wall 14c is covered by the outer wall 43a of the combustion chamber main body 43 of the combustion heater 14, and an annular gap is provided between the partition wall 14c and the outer wall 43a. It functions as the cooling water passage 14a. The combustion heater 14 has an air supply port 14d.
₁ and the exhaust discharge port 14d ₂ are formed, and the air supply port 14d ₁ and the exhaust discharge port 14d ₂ communicate with the combustion chamber 14d. The above-mentioned intake introduction passage 15 is connected to the air supply port 14d _1, and the above-mentioned combustion gas discharge passage 17 is connected to the exhaust discharge port 14d ₂ . Subsequently, the combustion heater 14 is provided with a cooling water introduction port 14a ₁ and a cooling water discharge port 14a ₂ and these cooling water introduction port 14a ₁ and cooling water discharge port 14a ₂ are connected to the heater internal cooling water. It communicates with the passage 14a. The cooling water inlet 14
The aforesaid cooling water introduction passage 18 is connected to a _1, and the aforesaid cooling water discharge passage 19 is connected to the cooling water discharge port 14a _2.
Are connected. Further, the above-described fuel introduction passage 20 is connected to the combustion cylinder 14b so that a part of the fuel discharged from the fuel pump is supplied to the combustion cylinder 14b. The combustion cylinder 14b has a vaporization glow plug (not shown) for vaporizing the fuel supplied through the fuel introduction passage 20 and an ignition glow plug (not shown) for igniting the vaporized fuel. ing. A single glow plug may be used as both the vaporization glow plug and the ignition glow plug. In the combustion heater 14 thus configured, the intake air flowing from the intake introduction passage 15 to the air supply port 14d ₁ is guided to the combustion chamber 14d, and the fuel supplied to the combustion cylinder 14b by the fuel introduction passage 20 is illustrated. Not vaporized by a glow plug. Then, the intake air and the vaporized fuel are mixed to form an air-fuel mixture, and the air-fuel mixture is ignited and burned by an ignition glow plug (not shown) in the combustion chamber 14d.
The gas combusted in the combustion chamber 14d is guided from the combustion chamber 14d to the exhaust gas outlet 14d ₂ and then the exhaust gas outlet 14d.
It is led from d ₂ to the exhaust pipe 7 upstream of the selective reduction lean NO _x catalyst 8 via the combustion gas discharge passage 17. that time,
The heat of the combustion gas discharged from the combustion chamber 14d is applied to the partition wall 14c.
Is transmitted to the cooling water flowing in the heater internal cooling water passage 14a via the heater, and the temperature of the cooling water rises. Therefore, the combustion chamber 1
Reference numeral 4d denotes a heat exchange passage, in other words, a heat transfer portion for transmitting the heat of the combustion gas discharged from the combustion chamber 14d of the combustion type heater 14 to the cooling water and raising the temperature of the cooling water flowing through the heater internal cooling water passage 14a. I can say. Returning now to FIG. 1, the internal combustion engine 1
Includes an electronic control unit (ECU: Electr) for engine control.
onic Control Unit) 21 is installed side by side. ECU2
1 is a CP, interconnected by a bidirectional bus
The input interface circuit includes a U, a ROM, a RAM, an input interface circuit, an output interface circuit, and the like, and various sensors are connected to the input interface circuit through electrical wiring. The various sensors described above include an air flow meter 5 attached to the intake pipe 3, a selective reduction lean NO.
An exhaust gas temperature sensor 9 attached to the exhaust pipe 7 downstream of the _X catalyst 8, a crank position sensor 22 and a water temperature sensor 23 attached to the internal combustion engine 1, an accelerator pedal (not shown), or an accelerator lever that operates in conjunction with the accelerator pedal, etc. The attached accelerator position sensor 24 etc. can be illustrated. The air flow meter 5 is a sensor that outputs an electric signal corresponding to the mass of intake air flowing through the intake pipe 3. The exhaust temperature sensor 9 is
This sensor outputs an electric signal corresponding to the temperature of the exhaust gas discharged from the selective reduction lean NO _x catalyst 8. The crank position sensor 22 is a sensor that outputs a pulse signal every time a crankshaft (not shown) of the internal combustion engine 1 rotates by a predetermined angle. The water temperature sensor 23 is a sensor that outputs an electric signal corresponding to the temperature of the cooling water flowing through the water jacket of the internal combustion engine 1. The accelerator position sensor 24 is a sensor that outputs an electric signal corresponding to the operation amount of the accelerator pedal. The ECU 21 determines the operating state of the internal combustion engine 1 based on the output signal values of various sensors as described above, and based on the determination result, the fuel injection valve 10, the combustion heater 14, or the air pump 1
The control signal value for 6 is calculated. The various control signal values calculated in this way are output from the output interface circuit via the electric line to the fuel injection valve 10 and the combustion heater 1.
4 or to the air pump 16. Next, the exhaust gas purification control in this embodiment will be described. The exhaust gas purification control according to the present embodiment is performed by using H contained in the gas supplied from the combustion heater 14 to the exhaust pipe 7.
By adjusting the amount of C, H that is required for NO _x purification
The amount of C is supplied to the selective reduction type lean NO _x catalyst 8. As a method of adjusting the amount of HC contained in the gas supplied from the combustion heater 14 to the exhaust pipe 7, a method of controlling the amount of fuel supplied to the combustion heater 14 and a method of supplying the fuel to the combustion heater 14 A method of controlling the intake air amount, a method of controlling the combustion state in the combustion type heater 14 or the like can be exemplified. However, in the present embodiment, the amount of fuel supplied to the combustion type heater 14 is controlled so that the combustion gas An example of adjusting the amount of HC contained in is described. ECU2
1 performs exhaust gas purification control according to an exhaust gas purification control routine as shown in FIG. The exhaust gas purification control routine is a routine executed every predetermined time (for example, every time the crank position sensor 22 outputs a pulse signal). In the exhaust gas purification control routine, the ECU 21 first executes the selective reduction lean NO in S301 to S302.
It is determined whether the _X catalyst 8 is in a state capable of purifying NO _X , that is, whether the NO _X purification condition is satisfied. The NO _X purification condition here is that the temperature of the exhaust gas discharged from the selective reduction lean NO _X catalyst 8 is within a predetermined temperature range (catalyst purification window). Therefore, the ECU 21
In step S301, the output signal value (exhaust gas temperature) of the exhaust gas temperature sensor 9 is input, and then in step S302, it is determined whether or not the exhaust gas temperature is within the catalyst purification window. When it is determined in S302 that the exhaust temperature is within the catalyst purification window, the ECU 21 determines in S30
In 3 to S305, the addition amount of HC (required HC addition amount) required for the selective reduction lean NO _X catalyst 8 to purify NO _X in the exhaust gas is calculated. Here, the request HC amount will vary depending on the amount of NO _X in the exhaust gas, NO _X in the exhaust gas
Since the amount changes according to the operating state of the internal combustion engine 1 (engine speed, engine torque), in the present embodiment, the relationship between the engine speed, the engine torque, and the required HC addition amount is previously obtained by experiments or the like. In advance, map those relationships and EC
It is stored in the ROM or the like of U21. And the ECU 2
1 is the crank position sensor 22 in S303.
Also, the output signal value of the accelerator position sensor 24 is input. In S304, the ECU 21 calculates the engine speed of the internal combustion engine 1 based on the time interval at which the crank position sensor 22 outputs a pulse signal, and the internal combustion engine 1 outputs the engine speed based on the output signal value of the accelerator position sensor 24. Calculate the output torque. In S305, the ECU 21 calculates the required HC addition amount by accessing the ROM map using the engine speed and torque calculated in S304 as parameters. In S306,
The ECU 21 determines whether the combustion heater 14 is in an operating state or a non-operating state. When it is determined in S306 that the combustion heater 14 is in the operating state, the ECU 21 proceeds to S307 and proceeds to S307.
The amount of fuel required for combustion (the amount of fuel calculated in a separate control routine, hereinafter referred to as the amount of fuel for combustion) is input. In S308, the ECU 21 adds the fuel amount corresponding to the required HC addition amount calculated in S305 to the combustion fuel amount input in S307, and the combustion heater 14
The amount of fuel to be supplied to the vehicle (hereinafter referred to as the required fuel amount) is calculated. Then, the ECU 21 proceeds to S309 and supplies the required fuel amount calculated in S308 to the combustion heater 14. At this time, the amount of intake air supplied to the combustion heater 14 is the amount of intake air required to completely burn the above-mentioned combustion fuel amount. In this case, the combustion heater 14 burns the fuel corresponding to the combustion fuel amount, and the remaining fuel amount, that is, the fuel amount corresponding to the required HC addition amount is discharged from the combustion heater 14 in an unburned state. . The unburned fuel contains HC that is thermally decomposed into a relatively small molecular size when exposed to high-temperature combustion heat in the combustion heater 14. Combustion gas containing such HC is supplied to the selective reduction type lean NO _X catalyst 8 upstream of the exhaust pipe 7 via the combustion gas discharge passage 17. As a result, exhaust gas containing HC having a small molecular size and a high NO _x purification rate flows into the selective reduction lean NO _x catalyst 8,
Part of the HC is partially oxidized to generate active species, and the active species react with NO _X in the exhaust gas to convert NO _X to N ₂ , H ₂ O,
Reduce to CO ₂ . On the other hand, if it is determined in S306 that the combustion heater 14 is in the inoperative state, the EC
U21 advances to S310 and energizes the vaporization glow plug of the combustion heater 14. However, immediately after the combustion heater 14 stops operating, when the temperature inside the combustion heater 14 is sufficiently high (for example, 300 to 400 ° C.), the vaporization glow plug may not be energized. Then ECU
In step 21, the process proceeds to step S311, in which the fuel amount corresponding to the required HC addition amount calculated in step S305 and the intake air as a carrier gas for carrying the fuel from the combustion heater 14 to the exhaust pipe 7 are supplied to the combustion heater 14. Supply. In this case, the gas discharged from the combustion heater 14 contains vaporized fuel corresponding to the required HC addition amount. The vaporized fuel contains HC that is thermally decomposed when heated by a vaporized glow plug to have a smaller molecular size.
The gas containing such HC is used in the combustion gas discharge passage 1
It is supplied to the exhaust pipe 7 upstream of the selective reduction type lean NO _x catalyst 8 via 7. As a result, selective reduction type lean NO _x
The catalyst 8 has H with a small molecular size and a high NO _x purification rate.
The exhaust gas containing C will flow in, and a part of the HC will be partially oxidized to generate active species, which will react with NO _x in the exhaust gas to convert NO _x to N ₂ , H ₂ O. , Reduce to CO ₂ . In this way, the ECU 21 executes the exhaust gas purification control routine, whereby the purification control means according to the present invention is realized. Therefore, according to the present embodiment, in the internal combustion engine equipped with the combustion heater, by supplying HC contained in the gas discharged from the combustion heater as an additive to the selective reduction lean NO _x catalyst, Since HC contained in the gas can be pyrolyzed or vaporized by using combustion heat or residual heat of a combustion heater to generate HC having a high NO _x purification rate, it is exclusively used for supplying an additive. It is possible to reduce the amount of energy required for the additive supply process, without providing the above device. In the present embodiment, the selective reduction type lean NO _X catalyst as lean NO _X catalyst according to the present invention has been described as an example, it is of course not limited to, occlusion reduction type lean N
O _X catalyst or oxidation catalyst may be a supported particulate filter or the like. In short, it is sufficient that the harmful gas component in the exhaust gas can be purified by using HC as an additive.

The exhaust gas purifying apparatus for an internal combustion engine according to the present invention supplies the fuel component contained in the exhaust gas by supplying the fuel component in the gas discharged from the combustion heater as an additive to the exhaust gas purifying means. The components can be pyrolyzed and vaporized by using the combustion heat and residual heat of the combustion heater, and it is not necessary to provide a dedicated device for supplying the additive, and the amount of energy required for the additive supply processing. Can be reduced.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an internal configuration of a combustion heater.

FIG. 3 is a flowchart showing an exhaust gas purification control routine.

[Explanation of symbols]

1 ... internal combustion engine 2 ... intake branch pipe 3 ... intake pipe 6 ... exhaust manifold 7 ... exhaust pipe 8 ... selective reduction type lean NO _X catalyst 9 ... exhaust temperature sensor 14 ... Combustion heater 15 ... Intake introduction passage 16 Air pump 17 Combustion gas discharge passage 20 Fuel introduction passage 21 ECU

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01N 3/08-3/36 B60H 1/00

Claims (6)

(57) [Claims] 1. A combustion type heater for raising the temperature of a related element of an internal combustion engine, and an exhaust gas which is provided in an exhaust system of the internal combustion engine and purifies harmful gas components in the exhaust gas when an additive is supplied under a predetermined condition. Purifying means, and if the combustion heater is in an operating state when the predetermined condition is satisfied, the gas burned by the combustion heater is introduced as an additive into the exhaust system upstream of the exhaust purification means, and the combustion heater is If it is in a non-operating state, it supplies fuel to the combustion type heater to vaporize the fuel, and introduces the vaporized fuel as an additive into the exhaust system upstream of the exhaust purification means. Exhaust gas purification device for internal combustion engine. Wherein said exhaust gas purification means, wherein the inflow exhaust gas when the hydrocarbon is added during the lean atmosphere, a selective reduction type lean NO _X catalyst for reducing and purifying nitrogen oxides in the exhaust The exhaust emission control device for an internal combustion engine according to claim 1. 3. The exhaust gas purifying means occludes nitrogen oxides in the exhaust gas when the inflowing exhaust gas is in a lean atmosphere and occludes the nitrogen oxide in the exhaust gas when an additive is added to the inflowing exhaust gas to reduce the oxygen concentration. An exhaust emission control device for an internal combustion engine according to claim 1, which is a storage reduction lean NO _x catalyst that releases and purifies nitrogen oxides. 4. The particulate matter trapped by the exhaust gas purifying means when a hydrocarbon is added when the inflowing exhaust gas is in a lean atmosphere and the temperature of the inflowing exhaust gas is equal to or higher than a predetermined temperature. The exhaust gas purification device for an internal combustion engine according to claim 1, which is a particulate filter that burns and processes particulate matter. 5. The exhaust purification of an internal combustion engine according to claim 1, wherein the purification control means changes the state of the combustion gas or vaporized fuel of the combustion heater in accordance with the state of the exhaust purification means. apparatus. 6. The purification control means determines the state of the exhaust purification means according to at least one of an exhaust temperature downstream of the exhaust purification means, an engine speed and an engine torque. An exhaust emission control device for an internal combustion engine according to claim 5.