JP2003027928A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of high-efficiently and reliably regenerating an occlusion type NOx catalyst as the size of a device is reduced by using a combustion heater, and, also capable of enabling improvement of catalyst durability performance. SOLUTION: The occlusion type NOx catalyst (24) is rotated by a catalyst rotating means (34), a space situated upper stream of the occlusion type NOx catalyst is partitioned centering around the central axis of the occlusion type NOx catalyst to form a first introduction region (27) and a second introduction region (28). High temperature combustion gas is supplied to the first introduction region from a combustion type heater (40) through a first passage (43), and low temperature combustion gas is supplied to the second introduction region through a second passage (42).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust purification system for an internal combustion engine, and more particularly to a technique for improving the efficiency of a storage type NOx catalyst.

[0002]

[Related Background Art] Exhaust gas emitted from diesel engines mounted on buses, trucks, etc., contains HC and C
In addition to O and particulate matter (abbreviated as PM), NOx which is a nitrogen oxide is contained. Therefore, it is considered to mount the NOx catalyst even in the vehicle equipped with the diesel engine.

As NOx catalysts, selective reduction type NOx catalysts and occlusion type NOx catalysts are known. Recently, even vehicles equipped with a diesel engine store NOx during normal operation in a lean atmosphere, After that, a rich atmosphere is generated in the vicinity of the catalyst by supplying unburned matter into the exhaust passage for a certain period of time, and the stored NOx is reduced and removed by the unburned matter as a reducing agent to regenerate the catalyst (NOx purge). These storage-type NOx catalysts are being widely used.

For example, in Japanese Unexamined Patent Publication No. 2000-186531, after NOx is stored in a storage type NOx catalyst, HC, CO, etc. in a combustion gas discharged from a combustion type heater are used as a reducing agent. An apparatus configured to regenerate an occlusion type NOx catalyst is disclosed.

[0005]

By the way, the combustion type heater disclosed in the above publication is originally used for heating the interior of a vehicle. Therefore, in the combustion type heater, the combustion gas that has undergone heat exchange with the heating medium (water or the like) is supplied to the occlusion type NOx catalyst, and the occlusion type Nx catalyst.
When regenerating the Ox catalyst, it is not possible to supply combustion gas at such a high temperature (about 370 ° C.), and there is a problem that the NOx purification efficiency cannot be stably maintained high.

Further, it is known that SOx is stored together with NOx in the storage type NOx catalyst (S poisoning),
This SOx cannot be reduced and removed unless it is in a high temperature atmosphere, and if the temperature of the combustion gas discharged from the combustion heater is low, S
There is also a problem that Ox cannot be removed sufficiently and the NOx purification efficiency is lowered. In this case, the combustion may be controlled so as to increase the heat generation amount of the combustion type heater, but in order to increase the heat generation amount, the combustion type heater must be increased in size and the fuel consumption amount must be increased, which is not preferable. .

Therefore, a combustion-type heater constructed so that high-temperature combustion gas can be taken out without heat exchange is disclosed in JP-A-2000-26.
No. 5826 is disclosed. However, in the combustion heater disclosed in the publication, a high temperature combustion gas is mixed with the exhaust gas from the engine, and the combustion gas supplied to the storage type NOx catalyst can be maintained at a high temperature depending on the exhaust temperature. Can not. At this time, even if an attempt is made to control the combustion gas temperature of the combustion heater according to the exhaust gas temperature, the response of the combustion heater is poor and control is difficult.

[0008] Further, since a diesel engine has a large intake air amount and is easy to generate NOx originally, and a diesel engine mounted on a bus, a truck, etc. is large in size, it is large in order to sufficiently process NOx. This type of large-scale storage NOx catalyst is required.
When trying to regenerate the catalyst, a large amount of reducing agent is required to make the catalyst atmosphere a rich atmosphere. Therefore, as disclosed in the above publication, when such a large amount of reducing agent is generated at one time, the combustion heater is inevitably increased in size, leading to cost increase and vehicle size increase. Not preferred.

Further, it has been confirmed that when the storage type NOx catalyst is regenerated, the stored NOx is once released and then undergoes a reduction reaction.
Further, during regeneration of the x catalyst, as shown in FIG. 9, there is a characteristic that the stored NOx is rapidly released in a short time immediately after the start of regeneration and is not released so much until the regeneration is completed. It has been confirmed. Therefore, when regenerating the storage type NOx catalyst, it is required to supply a large amount of reducing agent in a short time immediately after the regeneration is started. However, since the combustion heater takes a long time to ignite, the responsiveness is poor as described above, and there is a problem that it is difficult to stably supply the reducing agent when the regeneration of the occlusion type NOx catalyst is started. Further, it is not preferable to operate the combustion heater in advance before regenerating the catalyst because it leads to a reduction in energy efficiency.

The present invention has been made to solve the above problems, and an object of the present invention is to use a combustion heater to efficiently and surely store an occlusion type NOx catalyst while downsizing the apparatus. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can be regenerated and can improve catalyst durability performance.

[0011]

In order to achieve the above-mentioned object, according to the invention of claim 1, a plurality of through holes, which are interposed in the exhaust passage of the internal combustion engine and through which exhaust gas flows, are formed along the axis of the exhaust passage. Storage type NOx catalyst and the storage type NOx
A catalyst rotating means for rotating the catalyst around a central axis parallel to the axis of the exhaust passage, and an upstream space, which is an introduction region of the occlusion type NOx catalyst, is radially partitioned around the central axis of the occlusion type NOx catalyst, Introduction area partition means for forming the first introduction area and the second introduction area independently of the main introduction area of the exhaust gas flowing through the exhaust passage, and air is introduced to mix with the fuel, and the mixture is burned and reduced. A combustion type heater for discharging a high temperature combustion gas containing a chemical and a low temperature combustion gas; and a high temperature combustion gas discharged from the combustion type heater for the first
It is characterized in that it is provided with a first passage leading to the introduction region and a second passage leading to the second introduction region the low temperature combustion gas discharged from the combustion heater and having a temperature lower than the high temperature combustion gas.

As a result, the exhaust gas flowing through the exhaust passage is
Although the NOx in the exhaust gas is introduced from the main introduction region (the introduction region other than the first and second introduction regions) into the occlusion type NOx catalyst and passes through the through-holes, the occlusion type NOx catalyst absorbs NOx.
When the Ox catalyst rotates and a high-temperature (for example, 700 ° C.) combustion gas containing a reducing agent generated by the combustion heater is introduced from the first introduction region, SOx is generated together with NOx stored in the storage-type NOx catalyst. It is reduced and removed well. Then, when the storage type NOx catalyst further rotates, low-temperature (for example, 370 ° C.) combustion gas containing a reducing agent is introduced from the second introduction region, and NOx reduction and removal is continuously performed.

That is, according to the invention of claim 1, the occlusion type NOx catalyst is rotated, the high temperature combustion gas containing the reducing agent is introduced from the first introduction region, and the low temperature combustion containing the reducing agent is introduced from the second introduction region. Since gas is introduced, it is continuously NO at a fixed cycle when viewed partially, and always NO when viewed as a whole.
The NOx storage and reduction / removal and SOx reduction / removal are simultaneously performed in parallel, that is, the NOx storage / reduction / removal and SOx reduction / removal are repeated little by little to miniaturize the storage-type NOx catalyst itself. However, the amount of NOx and SOx released during one regeneration of the combustion gas that is always supplied continuously is small. Therefore, the amount of the combustion gas is suppressed to be small as a whole, and the combustion heater is downsized. However, with a simple structure, the low-temperature combustion gas containing the reducing agent and the high-temperature combustion gas containing the reducing agent are directly supplied to the NOx catalyst for a certain period of time directly, without performing complicated air-fuel ratio control and efficiently and reliably. Thus, NOx and SOx can be reduced and removed to regenerate the occlusion type NOx catalyst to improve the catalyst durability performance.

Further, in the invention of claim 2, the introduction area partition means adjoins the first introduction area to the second introduction area on the upstream side in the rotation direction of the storage type NOx catalyst with respect to the second introduction area. And the second introduction region is wider than the first introduction region. As a result, when the storage-type NOx catalyst rotates and the high-temperature combustion gas containing the reducing agent generated by the combustion heater is introduced from the first introduction region, SOx is improved together with the NOx stored in the storage-type NOx catalyst. It is reduced and removed. N
As for Ox, as shown in FIG. 9, storage type NOx
Although the NOx stored in the catalyst is rapidly released, it is well reduced and removed by the high temperature combustion gas containing the reducing agent. Then, when the storage-type NOx catalyst further rotates, the low-temperature combustion gas containing the reducing agent is continuously introduced into the storage-type NOx catalyst from the second introduction region, and the range of the second introduction region is wider than that of the first introduction region. During this period, NOx remaining without being reduced is sufficiently reduced and removed.

That is, according to the second aspect of the present invention, while reducing the size of the occlusion type NOx catalyst itself and the size of the combustion heater, the high temperature combustion gas and the low temperature combustion gas containing the reducing agent are made simple in structure. And NO are supplied at appropriate timing, and NO is efficiently and surely performed without performing complicated air-fuel ratio control.
By reducing and removing x and SOx, the occlusion type NOx catalyst can be regenerated and the catalyst durability performance can be improved.

Further, in the invention of claim 3, the combustion heater introduces air from the intake system of the internal combustion engine and controls the amount of air introduced from the intake system of the internal combustion engine under a constant fuel amount. And a combustion gas containing the reducing agent is generated. This makes it possible to easily and efficiently supply the reducing agents such as CO and HC necessary for the regeneration of the storage type NOx catalyst, and at the same time, to introduce the air used by the combustion heater from the intake system of the internal combustion engine, The auxiliary device such as an air filter can be commonly used to simplify the device.

Further, according to the invention of claim 4, there is provided an air supply passage for introducing air into the second passage, an opening / closing valve provided in the air supply passage, and an opening / closing valve control means for controlling the opening / closing valve. The on-off valve control means controls the on-off valve so that the air-fuel ratio of the combustion gas introduced into the second introduction region becomes close to the stoichiometric air-fuel ratio, and adjusts the air introduction amount.

As a result, as shown in FIG. 9, after the NOx is rapidly released, the amount of NOx released is reduced, and in accordance with this, the NOx is introduced into the storage type NOx catalyst from the second introduction region. The reducing agent is diluted with air, and the air-fuel ratio of the low temperature combustion gas is controlled to be close to the stoichiometric air-fuel ratio, and the reducing agents such as CO and HC are required and adequate amounts with respect to the NOx emission amount. , That is, CO in the low temperature combustion gas,
Since HC and the like almost completely contribute to the reduction reaction, the amount of CO, HC and the like that are surplus and discharged into the atmosphere can be minimized.

Further, in the invention of claim 5, the air supply passage is a branch passage branched from the exhaust passage, and the on-off valve control means controls the on-off valve to exhaust the exhaust air from the exhaust passage. It is characterized by adjusting the amount introduced. As a result, the storage type NOx from the second introduction region
By diluting the reducing agent introduced into the catalyst with the air in the exhaust gas and controlling the air-fuel ratio of the low-temperature combustion gas to near the stoichiometric air-fuel ratio, a fan, air filter, etc. required when an additional air supply passage is provided No additional device is required.

Further, according to the invention of claim 6, an oxygen sensor is provided in the second passage downstream of the connection portion with the air supply passage, and the on-off valve control means is provided with the information from the oxygen sensor. The on-off valve is controlled based on the above. As a result, the storage type NOx from the second introduction region
The air-fuel ratio of the low-temperature combustion gas introduced into the catalyst is properly controlled to be close to the stoichiometric air-fuel ratio, and the amount of surplus CO, HC, etc. discharged into the atmosphere is always minimized.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the structure of an engine 1 equipped with an exhaust gas purification device. Engine 1
Is a diesel engine, for example
Has an in-line 4-cylinder type cylinder layout. The intake passage 3 of the engine 1 is equipped with a turbocharger 2, and the supercharged intake air flows into the intake manifold 6 via the intercooler 4.

The fuel supply system of the engine 1 comprises, for example, a common rail system, and this system includes a common rail 8 and an injector 10 for each cylinder. The common rail system is publicly known, and the detailed description of the configuration of the common rail system is omitted here. The exhaust port of each cylinder of the engine 1 is connected to an exhaust pipe 18 which is integrated into one via an exhaust manifold 16. Then, the EGR passage 13 is connected to the exhaust manifold 16, and a part of the exhaust gas is removed from the EGR passage 1
It is returned to the intake system through 3. E in the EGR passage 13
The GR cooler 15 is inserted, and the EGR passage 13
An EGR valve 17 is installed in the.

A catalyst unit 20 is connected to the exhaust pipe 18, and the catalyst unit 20 is constructed by housing a NOx storage type catalyst (storage type NOx catalyst) 24 inside a casing 22. The catalyst 24 is composed of a carrier shaped like a cylinder, and a large number of exhaust gas flow passages (through holes) are formed inside the carrier. The exhaust gas flow passage has a catalyst 24
The exhaust gas can be circulated in the axial direction between the inlet and the outlet of the opening. The catalyst 24 carries a catalyst layer on a carrier, and the catalyst layer is formed so as to be exposed on the inner surface of each exhaust gas flow passage. As the carrier, for example, a monolith carrier composed of square cells or regular hexagonal cells is used.

The catalyst 24 is rotatably supported by the casing 22 about a central axis parallel to the axis of the exhaust passage, and the outer surface of the catalyst 24 and the inner surface of the casing 22 are hermetically sealed. A ring gear 30 is provided on the outer periphery of the catalyst 24, and a drive pinion 32 is meshed with the ring gear 30. The drive pinion 32 is housed in the casing 22 together with the catalyst 24, for example, and is rotatably supported by the casing 22.

A drive motor (catalyst rotating means) 34 is disposed adjacent to the catalyst unit 20, and the output shaft of the drive motor 34 is connected to the drive pinion 32. The drive motor 34 operates by receiving an operation signal from the electronic control unit (ECU) 70,
The drive pinion 32 is rotated. As a result, the catalyst 24 rotates in the casing 22 around the central axis at a constant rotation speed Nc.

Referring to FIG. 2, there is shown a sectional view of the catalyst unit 20 taken along the line AA of FIG. In this way, the upstream space of the catalyst 24 in the casing 22 is
An exhaust gas introduction chamber (main introduction region) 2 is defined by a partition wall 25 extending radially from the center axis of the exhaust gas 4, and the exhaust gas flowing through the exhaust pipe 18 is guided to the catalyst 24 in the upstream space.
6 together with fan-shaped rich gas introduction chamber (first introduction region)
27 and a stoichio gas introduction chamber (second introduction region) 28 are formed independently of the exhaust gas introduction chamber 26 (introduction region partitioning means).

More specifically, the rich gas introducing chamber 27 is formed upstream of the stoichio gas introducing chamber 28 in the rotational direction of the catalyst 24 and adjacent to the stoichio gas introducing chamber 28. The range of the stoichio gas introducing chamber 28 is the rich gas introducing chamber 27. Is set to a wider range than. Further, a combustion heater 40 is provided, and the combustion heater 40
Is for combusting air and fuel introduced from the intake manifold 6 through the intake pipe 41 to generate heat. Therefore, originally, the combustion heater 40 is used as a heat source for, for example, indoor heating. However, here, the combustion gas discharged from the combustion heater 40 is effectively used.

Referring to FIG. 3, there is shown a vertical cross-sectional view of the combustion type heater 40. As shown in the figure, the combustion type heater 40 has a water chamber 52 surrounding a combustion chamber 50. It is configured. Then, the air sucked from the intake passage 41 is supplied to the combustion chamber 50, and the fuel pipe 4
8 is configured to supply fuel. Specifically, the combustion chamber 50 is provided with a fan 46 that is driven by a drive motor 47, and when the drive motor 47 is driven by the command from the ECU 70 and the fan 46 rotates, the combustion chamber 5
Air is pumped to zero. Then, fuel is injected from the fuel pipe 48 toward the pressure-fed air, and the spark plug (glow plug or spark plug) 5 is instructed by the ECU 70.
When ignition is performed by 4, the flame is generated in the combustion chamber 50, whereby the combustion heater 40 functions as a heat exchanger, the water in the water chamber 52 is heated, and the water pipe 45 is circulated. A heater (not shown), for example, is interposed in the water pipe 45. A fuel valve 49 is provided in the fuel pipe 48 as shown in FIG. 1, and the fuel valve 49 is opened / closed in response to a command from the ECU 70 to carry out the flow and cutoff of the fuel.

On the other hand, a part of the combustion gas generated in the combustion chamber 50 is discharged to the high temperature combustion gas passage (first passage) 43, and the rest is discharged to the low temperature combustion gas passage (second passage) 42. At this time, the combustion gas discharged to the low-temperature combustion gas passage 42 is deprived of heat by the water in the water chamber 52 by heat exchange, so that the combustion gas temperature is low (for example,
About 350 ° C). On the other hand, the combustion gas discharged to the high-temperature combustion gas passage 43 has a structure in which the high-temperature combustion gas passage 43 penetrates the water chamber 52, so that the heat in the water in the water chamber 52 is scarcely taken away by the combustion gas. The gas temperature is high (for example, about 700 ° C.).

As shown in FIG. 1, the high temperature combustion gas passage 43 is connected to the rich gas introduction chamber (first introduction region) 27 of the catalyst unit 20, and the low temperature combustion gas passage 42 is connected to the stoichio gas introduction. It is connected to the chamber (second introduction area) 28. That is, the high temperature combustion gas from the combustion heater 40 is supplied to the rich gas introduction chamber 27, and the low temperature combustion gas from the combustion heater 40 is supplied to the stoichio gas introduction chamber 28.

The intake passage 41 is connected to the intake passage 3 of the engine 1. An electromagnetic intake throttle 60 is installed in the intake passage 41, and the ECU 7
By changing the opening degree of the intake throttle 60 according to a command from 0, the combustion air-fuel ratio in the combustion heater 40 can be changed under a constant fuel amount. That is, by adjusting the intake throttle 60, the combustion air-fuel ratio is set to, for example, the rich air-fuel ratio or the stoichiometric air-fuel ratio (Stoichio), and H
Combustion gas containing a large amount of reducing agents such as C and CO can be supplied to the rich gas introduction chamber 27 and the stoichio gas introduction chamber 28 as the high temperature combustion gas and the low temperature combustion gas through the high temperature combustion gas passage 43 and the low temperature combustion gas passage 42, respectively.

The intake passage 41 is connected to the engine 1 here.
By connecting to the intake passage 3 of the above, the auxiliary device such as an air filter can be shared and the device can be simplified.
The intake passage 41 may be opened to the atmosphere and the air used in the combustion heater 40 may be directly introduced from the atmosphere. Further, a branch pipe line (air supply passage, branch passage) 62 that branches from the exhaust pipe 18 and extends is connected to the low-temperature combustion gas passage 42. As a result, the low temperature combustion gas having a rich air-fuel ratio which is supplied to the stoichiometric gas introduction chamber 28 through the low temperature combustion gas passage 42 is diluted with the air in the exhaust gas. An electromagnetic exhaust throttle (open / close valve) 64 is provided in the branch pipe 62, and the opening of the exhaust throttle 64 is adjusted according to a command from the ECU 70 to dilute the low temperature combustion gas. It is possible to adjust the degree.

More specifically, an O ₂ sensor (oxygen sensor) 80 is provided downstream of the portion where the low temperature combustion gas passage 42 merges with the branch pipe 62, and the actual air-fuel ratio information from the O ₂ sensor 80 is provided. Based on this, the opening degree of the exhaust throttle 64, that is, the flow rate of the exhaust gas flowing through the branch pipe line 62 is adjusted, and the air-fuel mixture supplied to the stoichio gas introduction chamber 28 is subjected to stoichio feedback control. As a result, the air-fuel mixture flowing into the catalyst 24 from the stoichio gas introduction chamber 28 is always kept near the stoichio.

Since the exhaust gas from the engine 1 is mixed with the low-temperature combustion gas through the branch pipe line 62 here, an accessory such as a fan and an air filter, which is necessary when introducing air directly from the atmosphere, is provided. Although the device is not required and the device can be simplified, an intake pipe line (air supply passage) is provided in place of the branch pipe line 62 so that air in the atmosphere is directly introduced into the low temperature combustion gas passage 42. May be.

The ECU 70 is a control device for comprehensively controlling the exhaust emission control system for an internal combustion engine according to the present invention including the engine 1, and is composed of a CPU, a memory, a timer counter and the like. To the input side of the ECU 70, various sensors provided in the engine 1 for detecting the engine rotation speed and the like and the O ₂ sensor 80 are connected. Further, in the intake passage 41, an intake pressure sensor 72 for detecting the intake pressure Pi and an intake temperature sensor 74 for detecting the intake temperature Ti.
Is provided, an exhaust pressure sensor 76 for detecting the exhaust pressure Pe and an exhaust temperature sensor 78 for detecting the exhaust temperature Te are provided in the branch pipe line 62, and the intake pressures of these are provided on the input side of the ECU 70. The sensor 72, the intake air temperature sensor 74, the exhaust pressure sensor 76, and the exhaust temperature sensor 78 are also connected.

On the other hand, on the output side of the ECU 70, in addition to the fuel injection valve 10 and the like provided in the engine 1, the drive motor 34, drive motor 47, fuel valve 49, spark plug 54, intake throttle 60, exhaust throttle 64. Various devices such as are connected. Hereinafter, the operation of the exhaust gas purification device according to the present invention configured as described above will be described.

Referring to FIGS. 4 to 8, a control routine of the combustion heater 40, which is executed by the ECU 70, is shown in a flow chart, and the combustion heater control will be described below. According to the determination in step S10, the engine 1
If it is determined that the combustion type heater 40 has been started, it is determined in step S12 whether or not the combustion heater 40 is in the ignited state. Immediately after the engine 1 is started, the combustion heater 40
Has not been ignited, the process first proceeds to step S14 to perform ignition control. When the spark plug 54 is a glow plug, the ignition control is executed according to the flowchart of FIG.

In step S20, the drive motor 34 for rotating the catalyst is driven, and further the drive motor 47 for driving the fan is driven to operate the fan 46 to turn on the glow plug. Then, the timer counter is reset (t
= 0). In step S24, the intake pressure sensor 72,
Intake temperature sensor 74, exhaust pressure sensor 76, exhaust temperature sensor 7
The intake pressure Pi, the intake temperature Ti, the exhaust pressure Pe, and the exhaust temperature Te detected by 8 are read.

In step S26, the intake air amount Gi (= f (Pi, Ti)) is obtained based on the intake air pressure Pi and the intake air temperature Ti. Then, in step S28, it is determined whether or not the intake air amount Gi is larger than a predetermined value Git which is set in advance so that the combustion gas has a predetermined rich air-fuel ratio. The determination result is true (Y
es), it can be determined that the intake air amount Gi is too large,
In step S30, the intake throttle 60 is throttled. On the other hand, if the determination result is false (No), the process proceeds to step S32.

In step S32, it is determined whether or not the intake air amount Gi is smaller than a predetermined value Git. The determination result is true (Y
In the case of (es), it can be determined that the intake air amount Gi is too small, and the process proceeds to step S34 to open the intake throttle 60. On the other hand, if the determination result is false (No),
It proceeds to step S36. In step S36, it is determined whether or not the time t counted by the timer counter is equal to or longer than a predetermined time t0 (ignition time). The determination result is false (N
In the case of o), the process proceeds to step S22, and the time counting by the timer counter is continued (t = t + 1). On the other hand, if the determination result is true (Yes), the process proceeds to step S38.

In step S38, the fuel valve 49 is opened and the fuel supply from the fuel pipe 48 is started. The fuel supply amount is preset to a constant value. When the fuel is supplied together with the air as described above, the glow plug is turned on, so that ignition occurs and a flame is generated in the combustion chamber 50. As a result, combustion gas containing a large amount of reducing agents such as HC and CO is generated, a part of the high-temperature combustion gas that is not heat-exchanged is discharged to the high-temperature combustion-gas passage 43, and the remaining combustion gas is heat-exchanged to lower the temperature. Low temperature combustion gas passage 4 as combustion gas
It is discharged to 2.

When the spark plug 54 is a spark plug, the ignition control is executed according to the flowchart of FIG. Description of steps in FIG. 6 common to those in FIG. 5 is omitted. In step S20 ′, the drive motor 34 for rotating the catalyst is driven, the drive motor 47 for driving the fan is driven, and the fan 46 is operated. Then, the timer counter is reset (t = 0).

If the determination result of step S32 is false (No), the process proceeds to step S35, and the fuel valve 4
9 is opened, and fuel supply from the fuel pipe 48 is started. Then, if the determination result of step S36 is determined to be true (Yes), the process proceeds to step S42, and the ignition plug is turned on to perform spark ignition. When spark ignition is performed in the state where the fuel is supplied together with the air as described above, ignition is performed and a flame is generated in the combustion chamber 50. As a result, HC, C
Combustion gas containing a large amount of a reducing agent such as O is generated, a part of the high-temperature combustion gas that is not heat-exchanged is discharged to the high-temperature combustion gas passage 43, and the remaining combustion gas is heat-exchanged to become a low-temperature combustion gas. The low temperature combustion gas passage 42 is discharged. When the ignition is completed, the spark plug is turned off in step S44.

When the ignition is carried out in this manner, FIG.
The determination result of step S12 is true (Yes), and thereafter, A / F control is performed in step S16.
The A / F control is executed according to the flowchart of FIG. In step S50, the intake pressure sensor 72, the intake temperature sensor 74, the exhaust pressure sensor 76, the exhaust temperature sensor 78 are newly provided.
The intake pressure Pi, the intake temperature Ti, the exhaust pressure Pe, and the exhaust temperature Te detected by are read.

Then, similarly to the above, in step S52, the intake air amount Gi is determined based on the intake air pressure Pi and the intake air temperature Ti.
(= F (Pi, Ti)) is determined, and in step S54, it is determined whether or not the intake air amount Gi is larger than a predetermined value Git. If the determination result is true (Yes), the process proceeds to step S56. If the result of the determination is false (No), the process proceeds to step S58. In step S58, it is determined whether or not the intake air amount Gi is smaller than a predetermined value Git. If the determination result is true (Yes), step S58
In step 60, the intake throttle 60 is opened. On the other hand, if the determination result is false (No), the process proceeds to step S62.

In step S62, the exhaust gas amount Ge (= f (Pe, Te)) is obtained based on the exhaust gas pressure Pe and the exhaust gas temperature Te. Then, in step S64, it is determined whether or not the exhaust gas amount Ge is larger than a predetermined value Get. Here, the predetermined value G
et is a value that is appropriately set based on the actual air-fuel ratio information from the O ₂ sensor 80. If the determination result is true (Yes), it can be determined that the displacement Ge is too large, and step S66 is performed.
Then, proceed to step 7 to throttle the exhaust throttle 64. (Opening / closing valve control means) On the other hand, when the determination result is false (No),
It proceeds to step S68.

In step S68, it is determined whether or not the exhaust gas amount Ge is smaller than a predetermined value Get. The determination result is true (Y
In the case of es), it can be determined that the exhaust gas amount Ge is too small, and the process proceeds to step S70 to open the exhaust throttle 64 (open / close valve control means). When the combustion heater control is started in this way, first, the exhaust gas discharged from the engine 1 reaches the catalyst 24 from the exhaust pipe 18 through the exhaust gas introduction chamber 26. That is, the exhaust gas passes through the catalyst 24 within the exhaust gas introducing chamber 26 shown in FIG. In the case of a diesel engine, the exhaust gas discharged from the engine 1 usually has a lean air-fuel ratio and contains a large amount of NOx, so that the catalyst 24 is in a lean atmosphere within the range of the exhaust gas introduction chamber 26, and the exhaust gas is exhausted. NOx inside is
The catalyst 24 is stored in the exhaust gas introducing chamber 26 shown in FIG.

Since the catalyst 24 is rotated by the drive motor 34 in the constant direction (direction shown by the arrow in FIG. 2) at the constant rotation speed Nc, the catalyst 2 which has stored NOx.
The portion 4 is the HC and C from the rich gas introduction chamber 27 next.
A high-temperature combustion gas having a rich air-fuel ratio including O and the like is supplied to form a rich atmosphere. As described above, when the high temperature combustion gas having the rich air-fuel ratio is supplied and the catalyst 24 is brought into a high temperature and reducing atmosphere, the SOx stored in the catalyst 24 is instantaneously reduced and removed. According to the experiment, the rate of reduction and removal of SOx is higher as the atmospheric temperature is higher.
The SOx becomes about 100 times the ambient temperature, and SOx is reduced and removed almost in an instant.

When the high-temperature combustion gas is supplied, the regeneration of the catalyst 24 (NOx purge) is further started, and the stored NOx is released and reduced. That is, regarding NOx, as described above with reference to FIG.
Immediately after the catalyst 24 is regenerated, a large amount of NOx is suddenly released. Even if a large amount of NOx is released, the high temperature combustion gas introduced from the rich gas introduction chamber 27 has a rich air-fuel ratio. Since it contains a large amount of reducing agents such as HC and CO and is at a high temperature, NOx is reduced well.

Further, since the catalyst 24 rotates at a constant cycle Tc at a constant rotation speed Nc, and the storage and reduction of SOx and NOx are repeated cyclically, the exhaust gas introducing chamber 26
In this range, the amounts of SOx and NOx stored are not so large, and SOx and NOx are sufficiently reduced by the high temperature combustion gas with a relatively small amount of reducing agents such as HC and CO. That is, NOx and SOx can be sufficiently reduced even if the combustion heater 40 is downsized to reduce the fuel consumption.

When the catalyst 24 further rotates, the portion of the catalyst 24 supplied with the high temperature combustion gas having the rich air-fuel ratio from the rich gas introduction chamber 27 continues to be diluted with the low temperature combustion gas from the stoichio gas introduction chamber 28 into the vicinity of stoichiometry. Is supplied and the atmosphere is changed to Stoichio. That is, as described above with reference to FIG. 9, immediately after a large amount of NOx is released immediately after the start of the regeneration of the catalyst 24,
Until the regeneration of the catalyst 24 is completed, the amount of NOx released is not so large. Therefore, during this period, the amount of reducing agents such as HC and CO supplied to the catalyst 24 is suppressed to a necessary and sufficient amount. As a result, the NOx stored in the catalyst 24
Is continuously released satisfactorily and continues to be reduced, while most of the supplied CO and the like contributes to the reduction reaction, so that the surplus CO and the like discharged into the atmosphere can be minimized. Note that if only reducing and removing NOx, not so high an ambient temperature is required, and in this case, a low-temperature (for example, 350 ° C.) low-temperature combustion gas that has lost heat by heat exchange is sufficient. That is, the catalyst 24 can be satisfactorily regenerated while maintaining the original function (heating function or the like) of the combustion heater 40.

By rotating the catalyst 24 in this manner, NOx storage and reduction in the catalyst 24 and SOx reduction and removal are completed, and the regeneration of the catalyst 24 is completed. Then, the catalyst 24 receives the exhaust gas from the engine 1 again within the range of the exhaust gas introducing chamber 26, and receives NOx.
Is stored, and NOx storage and reduction and SOx reduction and removal are repeated at a constant cycle Tc.

By the way, referring to FIG. 8, there is shown the time ratio of the lean atmosphere time, the rich atmosphere time and the stoichio atmosphere time in the catalyst 24 obtained by the experiment corresponding to the NOx releasing characteristic of FIG. There is. According to this, it can be said that an ideal reproduction pattern has a lean atmosphere time of, for example, 30 seconds, a rich atmosphere time of, for example, 2 seconds, and a stoichiometric atmosphere time of, for example, 7.5 seconds. Further, since SOx is reduced and removed almost instantly in the high temperature combustion gas of high temperature (for example, 700 ° C.), it can be said that the rich atmosphere time is, for example, 2 seconds.

Therefore, here, each exhaust gas flow passage of the catalyst 24 is in the range of the exhaust gas introducing chamber 26, in the range of the rich gas introducing chamber 27, and in the stoichio gas introducing chamber 28 for 30 seconds and 2 seconds, respectively. , 7.5se
The ranges of the exhaust gas introducing chamber 26, the rich gas introducing chamber 27, and the stoichio gas introducing chamber 28 are set so as to be c (30: 2: 7.5).

That is, as shown in FIG. 2, the exhaust gas introducing chamber 26, the rich gas introducing chamber 27, and the stoichiometric gas introducing chamber 28 have a central angle a of the exhaust gas introducing chamber 26, a central angle b of the rich gas introducing chamber 27, and a stoichiometric gas introducing chamber 28, respectively. Central angle c
Are formed to have a division ratio of 30: 2: 7.5, respectively. That is, the central angle a of the exhaust gas introduction chamber 26 is set to 274 °, the central angle b of the rich gas introduction chamber 27 is set to 18 °, and the central angle c of the stoichio gas introduction chamber 28 is set to 68 °, for example.

The rotational speed Nc of the catalyst 24 is such that the cycle Tc of the catalyst 24 is, for example, 30 + 2 + 7.5 = 39.5 sec.
Is set to be The cycle Tc is 3
If it is less than 9.5 seconds, the time during which each exhaust gas flow passage of the catalyst 24 is within the range of the exhaust gas introduction chamber 26 is an ideal time of 30 se.
The period Tc may be shorter than 39.5 sec because the amount of NOx can be suppressed to less than c, that is, the NOx storage amount can be suppressed within the allowable range. However, the cycle Tc changes according to the capacity of the catalyst 24, and the smaller the capacity of the catalyst 24, the faster the storage limit and the earlier regeneration is required. Therefore, the cycle Tc needs to be shortened.

As a result, the high temperature combustion gas and the low temperature combustion gas containing a reducing agent such as HC and CO can be supplied to the catalyst 24 at an appropriate timing without waste, and the catalyst 24 can be efficiently regenerated and SOx is also generated. The catalyst 24 can be satisfactorily reduced and removed to improve the durability performance of the catalyst 24. Further, if the high-temperature combustion gas can be supplied to the catalyst 24 from the combustion heater 40, there is an effect that the temperature rise of the catalyst 24 can be promoted and the catalyst 24 can be activated early.

Although the description of the embodiment has been completed, the present invention is not limited to the above embodiment. For example, in the above embodiment, the air-fuel ratio of the combustion gas discharged by the combustion heater 40 is described as the rich air-fuel ratio, but the air-fuel ratio of the combustion gas may be stoichiometric. This is because even in stoichio, the combustion gas contains a reducing agent such as HC or CO.

The exhaust pressure Pe may be higher than the intake pressure Pi depending on the operating condition of the engine 1.
In such a case, it is preferable to increase the rotation speed of the fan 46 to correct the intake pressure Pi.

[0060]

As described in detail above, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 1 of the present invention, the storage type NO
x The catalyst is rotated, the high temperature combustion gas containing the reducing agent is introduced from the first introduction region, and the low temperature combustion gas containing the reducing agent is introduced from the second introduction region. As a whole, the storage and reduction removal of NOx and the reduction and removal of SOx are always carried out in parallel at the same time, that is, the storage and reduction removal of NOx and the reduction removal of SOx are repeated little by little. While reducing the size of the catalyst itself, the amount of NOx and SOx released during one regeneration of the combustion gas that is always supplied continuously is small. While aiming to downsize the heater, it is possible to supply a low temperature combustion gas containing a reducing agent as well as a high temperature combustion gas containing a reducing agent directly to the NOx catalyst for a fixed period with a simple structure, and to perform complicated air-fuel ratio control. Without also be implemented, occluded by efficiently and reliably reduce the NOx and SOx removal type NOx
It is possible to regenerate the catalyst and improve the catalyst durability performance.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 2, the first introduction region is more occluded than the second introduction region.
Since it is formed on the upstream side in the rotation direction of the Ox catalyst adjacent to the second introduction region, the storage type NOx catalyst itself and the combustion type heater can be downsized while the structure is simple and the high temperature containing the reducing agent is high. Combustion gas and low-temperature combustion gas can be supplied at appropriate timings, NOx and SOx can be efficiently and surely reduced and removed to regenerate the occluding NOx catalyst without complicated air-fuel ratio control, and catalyst durability can be achieved. The performance can be improved.

According to another aspect of the exhaust gas purifying apparatus for an internal combustion engine, the combustion heater introduces air from the intake system of the internal combustion engine, and supplies the air from the intake system of the internal combustion engine under a constant fuel amount. Since the combustion gas containing the reducing agent is generated by controlling the amount of air introduced, it is possible to easily and efficiently supply the reducing agents such as CO and HC necessary for regeneration of the storage type NOx catalyst, and to attach an air filter or the like. The device can be shared to simplify the device.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 4, NOx is controlled by controlling the air-fuel ratio of the low temperature combustion gas introduced from the second introduction region to near the stoichiometric air-fuel ratio.
The amount of reducing agents such as CO and HC can be adjusted to a necessary and adequate amount relative to the amount of CO2 emitted, that is, CO and HC in the low-temperature combustion gas can be substantially completely contributed to the reduction reaction, resulting in excess. It is possible to minimize the amount of CO, HC, etc. discharged into the atmosphere.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 5, the reducing agent introduced into the storage type NOx catalyst from the second introduction region is diluted with the air in the exhaust gas so that the air-fuel ratio of the low temperature combustion gas is increased. Since the air-fuel ratio is controlled in the vicinity of the theoretical air-fuel ratio, auxiliary devices such as a fan and an air filter, which are required when the air supply passage is separately provided, are unnecessary, and the device can be simplified.

According to the sixth aspect of the exhaust gas purifying apparatus for an internal combustion engine, an oxygen sensor is provided in the second passage downstream of the connection with the air supply passage, and the on-off valve is controlled based on the information from the oxygen sensor. Therefore, the air-fuel ratio of the low temperature combustion gas introduced from the second introduction region to the occlusion type NOx catalyst can be properly controlled to be close to the stoichiometric air-fuel ratio, and the excess C is discharged into the atmosphere.
The amount of O, HC, etc. can always be minimized.

[Brief description of drawings]

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

2 is a cross-sectional view of the catalyst unit taken along the line AA of FIG.

FIG. 3 is a vertical cross-sectional view of a combustion heater.

FIG. 4 is a flowchart showing a control routine of combustion heater control.

5 is a flowchart showing a control routine of ignition control (glow plug) in FIG.

FIG. 6 is a flowchart showing a control routine of ignition control (spark plug) in FIG.

7 is a flowchart showing a control routine of A / F control in FIG.

FIG. 8 is an experimental result showing a time ratio of a lean atmosphere time, a rich atmosphere time, and a stoichiometric atmosphere time.

FIG. 9 is a diagram showing NOx release characteristics during regeneration of an occlusion type NOx catalyst.

[Explanation of symbols]

1 Engine (Diesel Engine) 18 Exhaust Pipe 20 Catalyst Unit 24 Catalyst (Occlusion Type NOx Catalyst) 25 Partition Wall (Introducing Area Partitioning Means) 26 Exhaust Gas Introducing Chamber (Main Introducing Area) 27 Rich Gas Introducing Chamber (First Introducing Area) 28 Steiogas Introducing chamber (second introducing region) 30 Ring gear 32 Drive pinion 34 Drive motor (catalyst rotating means) 40 Combustion heater 41 Intake passage 42 Low temperature combustion gas passage (second passage) 43 High temperature combustion gas passage (first passage) 60 Intake Throttle 62 Branch pipe line (air supply passage) 64 Exhaust throttle 70 Electronic control unit (ECU) 80 O ₂ sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/08 F01N 3/24 L N 3/22 301 3/28 301C 3/24 3/36 J B01D 53 / 36 101A 3/28 301 ZAB 3/36 DF term (reference) 3G091 AA02 AA10 AA11 AA18 AB06 BA03 BA04 BA11 BA14 BA15 BA19 CA02 CA13 CA24 CA27 CB02 CB07 CB08 DA01 DA02 DB10 DC01 EA01 EA06 EA15 EA30 EA17 FA02 EA17 EA17 EA17 EA17 FA12 FA13 FB02 FB10 FB11 FB12 FC04 FC05 FC07 GA06 GA21 HA36 HA45 HB03 HB05 HB06 HB07 4D048 AA02 AA06 AB02 AB07 AC02 BB02 CA07 CB05 CC25 CC52 DA01 DA05 DA06 DA09 DA10 DA20 EA04

Claims (6)

[Claims] 1. An occlusion type NOx catalyst, which is provided in an exhaust passage of an internal combustion engine and has a plurality of through holes through which exhaust gas flows, formed along the axis of the exhaust passage, and the occlusion type NOx catalyst on the axis of the exhaust passage. A catalyst rotating means for rotating about a parallel central axis line, and an upstream space, which is an introduction region of the occlusion type NOx catalyst, is radially partitioned around the central axis line of the occlusion type NOx catalyst to form a first introduction region and a second introduction region. And an introduction region partitioning means that is formed independently of the main introduction region of the exhaust gas flowing through the exhaust passage, and introduces air to mix with fuel, and burns the mixture to form a high-temperature combustion gas containing a reducing agent and a low temperature. A combustion type heater that discharges combustion gas, a first passage that guides the high temperature combustion gas discharged from the combustion type heater to the first introduction region, a temperature lower than the high temperature combustion gas that is discharged from the combustion type heater And a second passage for guiding the low temperature combustion gas to the second introduction region. 2. The introduction region partitioning means forms the first introduction region on the upstream side in the rotational direction of the occlusion type NOx catalyst with respect to the second introduction region, adjacent to the second introduction region, and The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the second introduction region is wider than the first introduction region. 3. The combustion type heater introduces air from an intake system of an internal combustion engine, controls the amount of air introduced from the intake system of the internal combustion engine under a constant fuel amount, and combusts the fuel containing the reducing agent. The exhaust gas purification device for an internal combustion engine according to claim 1 or 2, which produces gas. 4. An air supply passage for introducing air into the second passage, an on-off valve provided in the air supply passage, and an on-off valve control means for controlling the on-off valve, the on-off valve control means comprising: The air introduction amount is controlled by controlling the on-off valve so that the air-fuel ratio of the combustion gas introduced into the second introduction region becomes close to the stoichiometric air-fuel ratio. Exhaust gas purification device for internal combustion engine. 5. The air supply passage is a branch passage branched from the exhaust passage, and the opening / closing valve control means controls the opening / closing valve to adjust the amount of exhaust gas introduced from the exhaust passage. The exhaust emission control device for an internal combustion engine according to claim 4, which is characterized in that. 6. An oxygen sensor is provided in the second passage downstream of a connection portion with the air supply passage, and the opening / closing valve control means controls the opening / closing valve based on information from the oxygen sensor. The exhaust emission control device for an internal combustion engine according to claim 4 or 5, characterized in that.