JP2003074328A - Exhaust gas emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which can efficiently regenerate a purifying function of an exhaust gas emission control device. SOLUTION: An exhaust gas emission control unit 200 comprises a passage for exhaust including two branch passages 30b1, 30b2 branching in the halfway of a passage to join, two exhaust gas emission control parts 210, 220 provided in each branch passage for controlling exhaust gas, an adjusting part 230 including valves 231, 232 making partly a flow path sectional area changeable of each branch passage for adjusting a flow amount of exhaust gas in each branch passage, and a regeneration agent injection part 260 for injecting a regeneration agent for regenerating a control function of each controlling part into each branch passage. A control part 90 controls the adjusting part 230, in the case of adjusting the flow amount of exhaust gas in one branch passage provided with one controlling part so as to be almost a prescribed amount, the regeneration agent injection part 260 is controlled, to inject the regeneration agent into the one branch passage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for purifying exhaust gas from an internal combustion engine.

[0002]

2. Description of the Related Art In the exhaust gas of diesel engines, particulate matter such as black smoke (soot) and nitrogen oxides (NO
x) etc. are included. In recent years, reduction of these air pollutants has been strongly demanded. Therefore, the diesel engine is usually provided with an exhaust gas purifying device for purifying exhaust gas.

For example, the exhaust gas purifying apparatus described in Japanese Patent No. 2727906 is provided in each of the branch passages and an exhaust passage including two branch passages that branch and join in the middle of the passage, and Two purification units for purifying contained NOx are provided. Since the NOx purification function of the purification unit is limited, it is necessary to regenerate the purification function. Therefore, in this device, two shutoff valves provided on the upstream side of each purification unit for closing each branch passage,
And a reducing agent supply unit for supplying the reducing agent to each purification unit. Then, when the cutoff valve in the one branch passage provided with the selected one purification unit is shut off,
By supplying the reducing agent into the one branch passage, the purifying function of the one purifying section is regenerated.

[0004]

However, in the above-mentioned exhaust gas purifying apparatus, since the reducing agent is supplied with the shut-off valve shut off, the reducing agent is not fully utilized in the purifying section, so that the purifying section is not used. There is a problem that it is relatively difficult to efficiently regenerate the purification function of.

This problem is not limited to diesel engines, but is common to internal combustion engines such as so-called in-cylinder injection gasoline engines in which gasoline is directly injected into the combustion chamber.

The present invention has been made to solve the above-mentioned problems in the prior art, and an object thereof is to provide a technique capable of efficiently regenerating the purification function of the exhaust gas purification device.

[0007]

In order to solve at least a part of the above-mentioned problems, the device of the present invention is applied to an internal combustion engine having a combustion chamber, and exhaust gas discharged from the combustion chamber. An exhaust gas purifying apparatus for purifying gas, which is an exhaust passage through which exhaust gas discharged from the combustion chamber passes, and branches and joins in the middle of the passage 2
An exhaust passage including two branch passages, two purifying units provided in each of the branch passages for purifying at least nitrogen oxides contained in the exhaust gas, and a portion of each of the branch passages being cut off. An adjusting unit for adjusting the flow rate of exhaust gas in each branch passage and a regenerant for regenerating the purifying function of each purifying unit, which includes a valve whose area can be changed, are injected into each branch passage. A regenerant injecting section for controlling the adjusting section and the regenerant injecting section, and the control section controls the adjusting section such that one of the purifying sections is When the flow rate of exhaust gas in one of the branch passages provided is adjusted to be substantially a predetermined amount, the regenerant injection unit is controlled to inject the regenerant into the one branch passage. Characterize.

In this apparatus, when the flow rate of the exhaust gas in the one branch passage provided with the selected one purification section is adjusted to be substantially the predetermined amount, the regenerant is introduced into the one branch passage. Is injected. When the flow rate of the exhaust gas flowing through the purification unit is too large or too small, the injected regenerant may not be sufficiently used to regenerate the purification function of the purification unit. However, as described above, if the regenerant is injected when the exhaust gas flow rate becomes almost the predetermined amount, the regenerant is used relatively efficiently for regenerating the purifying function of the purifying unit. It becomes possible to regenerate the oxide purification function relatively efficiently.

In the above apparatus, the control unit includes a pressure measuring unit for measuring the pressure in each of the branch passages on the upstream side and the downstream side of the purifying unit, and the control unit includes:
The regenerant may be injected when the difference between the two pressures of the one purification section reaches a predetermined target value.

In this way, the regenerant can be injected in good timing when the flow rate of the exhaust gas flowing through the purification section becomes almost a predetermined amount.

Further, in the above apparatus, the control section further includes a temperature measuring section for measuring the temperature of each of the purification sections, and the control section, according to the temperature of the one purification section, It is preferable to change the predetermined target value.

If the temperature of the purifying section changes, it may be difficult to supply the regenerant to the purifying section, and it may be difficult to regenerate the purifying function of the purifying section. However, if the predetermined target value is changed according to the temperature of the purifying unit, the purifying function of the purifying unit can be reliably reproduced.

Alternatively, in the above apparatus, the control section may stop the operation of the valve when injecting the regenerant.

In this way, the regenerant can be injected with the flow rate of the exhaust gas flowing through the purification section maintained at a substantially predetermined amount.

In the above apparatus, the control unit includes a pressure measuring unit for measuring the pressure in each of the branch passages on the upstream side and the downstream side of the purifying unit, and the control unit includes:
The valve may be stopped and the regenerant may be injected when the difference between the two pressures of the one purification unit reaches a predetermined target value.

In this way, the regenerant can be injected with good timing while the flow rate of the exhaust gas flowing through the purification section is maintained at a substantially predetermined amount.

In the above apparatus, each of the purifying units may further have a function of purifying the particulate matter contained in the exhaust gas.

This makes it possible to purify the particulate matter and nitrogen oxides contained in the exhaust gas, which is suitable for diesel engines.

Further, in the above apparatus, another device for purifying at least a specific gaseous substance contained in the exhaust gas is provided in the exhaust passage downstream of the confluence of the two branch passages. A purifying unit may be provided.

In this way, the exhaust gas can be further purified.

In the above device, the exhaust passage includes two branch passages, but it may include a plurality of branch passages. That is, this device is applied to an internal combustion engine having a combustion chamber and is an exhaust gas purification device for purifying exhaust gas discharged from the combustion chamber, and exhaust gas through which exhaust gas discharged from the combustion chamber passes. Exhaust passage including N (N is an integer of 2 or more) branch passages that branch and join in the middle of the passage, and nitrogen contained in at least exhaust gas provided in each of the branch passages. An adjusting unit for adjusting the exhaust gas flow rate in each of the branch passages, which includes N purifying units for purifying oxides and a valve capable of changing a flow passage cross-sectional area of a part of each of the branch passages. And a control for controlling a regenerant injecting section for injecting a regenerant for regenerating the purifying function of each of the purifying sections into each of the branch passages, and the adjusting section and the regenerant injecting section. And a control unit that controls the adjustment unit. Then, when the exhaust gas flow rate in the M branch passages provided with M purification units (M is an integer of 1 or more and less than N) is adjusted to a substantially predetermined amount, the regenerant injection is performed. A portion is controlled to inject a regenerant into the M branch passages.

The present invention is directed to an exhaust gas purifying apparatus, an apparatus such as a moving body equipped with the exhaust gas purifying apparatus, an exhaust gas purifying method, a computer program for realizing the method or the function of the apparatus, and the computer program thereof. Can be realized in various forms such as a recording medium in which is recorded, a data signal including the computer program, and embodied in a carrier wave.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described based on examples in the following order. A. First Example: A-1. Overall configuration: A-2. Outline of combustion: A-3. Purification unit: A-4. Injection of reducing agent in purification unit: A-5. Regeneration process of purification unit: B. Second Embodiment: C.I. Third Example: D. Fourth Example: E. Fifth Example: F.I. Sixth Embodiment: G.I. Seventh embodiment:

A. First Example: A-1. Overall Configuration: FIG. 1 is an explanatory diagram showing a schematic configuration of a diesel engine 100 to which the exhaust gas purifying device of the present invention is applied. The diesel engine 100 is a so-called four-cylinder engine, and the engine body 10 including a cylinder block and a cylinder head has four combustion chambers #.
1 to # 4. Air is supplied to each of the combustion chambers # 1 to # 4 through the intake passage 20. When the fuel supplied from the fuel supply pump 13 is injected by the fuel injection nozzle 14 into each of the combustion chambers # 1 to # 4,
A mixed gas of air and fuel burns. The exhaust gas is discharged to the outside via the exhaust passage 30.

A supercharger 40 is provided between the exhaust passage 30 and the intake passage 20. The supercharger 40 includes a turbine 41 provided in the exhaust passage 30, a compressor 42 provided in the intake passage 20, and a turbine 41.
And a shaft 43 that connects the compressor 42 to the compressor 42. When the exhaust gas discharged from each of the combustion chambers # 1 to # 4 rotates the turbine 41, the compressor 42 rotates via the shaft 43. The compressor 42 compresses the air that has flowed in via the air cleaner 22 provided on the upstream side. In addition, the supercharger 40 is provided with an actuator 45 for adjusting the opening area of the inlet of the turbine 41.
The compressibility of air by 2 is improved. The air whose temperature has risen due to the compression is cooled by the intercooler 24 provided on the downstream side of the compressor 42, and then the combustion chambers # 1 to # 1
It is supplied in # 4.

An EGR passage 60 connects the exhaust passage 30 and the intake passage 20. Here, “EGR” means exhaust gas recirculation (Exhaust Gas Recirculation).
is an abbreviation for circulation. A part of the exhaust gas in the exhaust passage 30 passes through the EGR passage 60, and the intake passage 2
Reflux to 0. In this case, the maximum combustion temperature when the mixed gas burns becomes low, so that the amount of nitrogen oxide (NOx) produced can be reduced. The EGR passage 60 includes an EGR cooler 6 for cooling the recirculated exhaust gas.
2 and an EGR valve 64 for adjusting the exhaust gas recirculation amount
And are provided. A throttle valve 26 is provided in the intake passage 20, and by adjusting the opening degree of the EGR valve 64 and the opening degree of the throttle valve 26, the total intake amount of the combustion chambers # 1 to # 4 can be adjusted. The proportion of the exhaust gas recirculation amount can be adjusted.

A purification unit 200 for purifying the exhaust gas discharged from the combustion chambers # 1 to # 4 is provided on the downstream side of the exhaust passage 30. Purification unit 2
00 purifies particulate matter (hereinafter also referred to as “carbon-containing fine particles”) such as black smoke (soot) and nitrogen oxides (NOx) contained in the exhaust gas. The purification unit 200 will be described later.

The fuel supply pump 13, the fuel injection nozzle 14, the actuator 45, the EGR valve 64, the throttle valve 26 and the purification unit 200 are controlled by an electronic control unit (ECU) 90. The ECU 90 detects engine operating conditions such as engine speed and accelerator opening degree, and executes the above control according to the detection result.

A-2. Outline of Combustion: FIG. 2 is an explanatory diagram showing an outline of combustion of the diesel engine 100 (FIG. 1). FIG. 2 shows changes in the exhaust gas NOx concentration, smoke, CO (carbon monoxide) concentration, HC (hydrocarbon compound) concentration, and exhaust gas air-fuel ratio when the EGR rate is changed. Has been done.

Here, the EGR rate is the proportion of the exhaust gas recirculation amount in the total intake amount of the combustion chambers # 1 to # 4.
Smoke is an index showing the concentration of carbon-containing fine particles. The exhaust gas air-fuel ratio indicates the composition ratio of air in the exhaust gas and reducing substances (HC, CO, etc.). An exhaust gas composition in which oxygen remains even if all reducing substances in the exhaust gas are burned is referred to as “the exhaust gas air-fuel ratio is lean”. On the contrary, a composition of exhaust gas in which oxygen is insufficient when all reducing substances in the exhaust gas are burned is referred to as "rich exhaust gas air-fuel ratio". Further, the composition of the exhaust gas in which the reducing substance and oxygen are contained in the exhaust gas without excess or deficiency is referred to as “the exhaust gas air-fuel ratio is stoichiometric (theoretical air-fuel ratio)”. The value of the exhaust gas air-fuel ratio depends on the properties of the fuel, but in the case of stoichio, it is usually about 14.7-.
It is about 14.8.

As shown in FIG. 2, the exhaust gas air-fuel ratio is E
As the GR rate increases, it gradually decreases (shifts to the rich side). The oxygen concentration of exhaust gas is lower than the oxygen concentration of air. Therefore, when the EGR rate becomes high (that is,
When the exhaust gas recirculation amount increases), the oxygen concentration of the mixed gas supplied to the combustion chamber decreases. As a result, the oxygen concentration of the exhaust gas discharged from the combustion chamber decreases, and the exhaust gas air-fuel ratio decreases.

The NOx concentration gradually decreases as the EGR rate increases. This is because, as described above, the maximum combustion temperature when the mixed gas burns decreases.

The HC concentration and CO concentration gradually increase as the EGR rate increases. Further, the smoke (that is, carbon-containing fine particles) gradually increases as the EGR rate increases, and then gradually decreases. Specifically, the smoke starts to increase when the EGR rate exceeds about 40% and is about 6
It peaks at around 0%. When the EGR rate is further increased, the smoke is gradually reduced, and the smoke hardly occurs when the EGR rate is about 65%. The EGR rate is about 60
When it exceeds%, the smoke decreases sharply and C
O concentration and HC concentration are rapidly increasing. this is,
When the EGR rate is relatively high, the combustion temperature becomes low, and the fuel, which is a high-grade hydrocarbon-based compound, is converted into a low-grade hydrocarbon-based compound HC or CO before it is converted into carbon-containing fine particles such as soot by combustion. It is thought that this is because it is discharged.

In the conventional diesel engine, the EGR rate is set in a relatively low range of, for example, about 40% or less. On the other hand, in the diesel engine of this embodiment, E
The GR rate can be set to a relatively low range of, for example, about 40% or less, or a relatively high range of about 65% or more. Combustion when the EGR rate is set to a relatively low range is hereinafter referred to as "normal combustion". Further, the combustion when the EGR rate is set to a relatively high range will be described below.
Called "low temperature combustion".

If the exhaust gas that recirculates is cooled, the above low temperature combustion can be carried out with a relatively small EGR rate. Therefore, the diesel engine 10 of the present embodiment
At 0 (FIG. 1), the EGR cooler 62 is provided.

As described above, when normal combustion is performed in a diesel engine, the exhaust gas mainly contains carbon-containing fine particles and air pollutants such as NOx, and low-temperature combustion is performed. In the case, mainly HC and CO
Air pollutants such as are included. That is, if low-temperature combustion is performed, the emission amount of carbon-containing fine particles and NOx, which are particularly problematic in the conventional diesel engine, can be reduced. However, it is difficult to carry out low temperature combustion when the engine load is relatively high. This is because in order to operate the engine under high load, it is necessary to increase the fuel injection amount and the intake air amount, and to reduce the exhaust gas recirculation amount in order to increase the air amount. is there.

Therefore, the diesel engine 1 of this embodiment
00 (FIG. 1) executes normal combustion and low temperature combustion according to the engine operating conditions. And the purification unit 200
Irrespective of normal combustion and low temperature combustion, air pollutants are chemically converted into harmless gases and discharged.

A-3. Purification unit: FIG. 3 is an explanatory view showing the purification unit 200 of FIG. 1 in an enlarged manner. As shown in the figure, the purification unit 200 includes the upstream main passage 3
0a1 and two branch passages 30b that join after branching
1, 30b2 and the downstream main passage 30a2. In addition, each passage 30a1, 30a2, 30b1,
30b2 constitutes a part of the exhaust passage 30 shown in FIG.

The first and second branch passages 30b1 and 30
The b2 is provided with first and second purifying units 210 and 220 for purifying the exhaust gas, respectively. Two
The two purification units 210 and 220 mainly have a function of purifying carbon-containing fine particles and NOx contained in the exhaust gas. The purification units 210 and 220 will be described later.

An adjusting unit 230 for adjusting the flow rate of exhaust gas flowing through each of the branch passages 30b1 and 30b2 is provided on the downstream side of the two purifying units 210 and 220.
The adjusting unit 230 includes two adjusting valves 231 and 232 and two driving units 236 and 237 that drive the adjusting valves, respectively.
And are equipped with. The first regulating valve 231 is provided in the first branch passage 30b1, and the flow passage cross-sectional area on the downstream side of the first purifying unit 210 can be changed by the opening / closing operation of the first regulating valve 231. Similarly, the second regulating valve 232 is
It is provided in the branch passage 30b2, and the flow passage cross-sectional area on the downstream side of the second purification unit 220 can be changed by the opening / closing operation.

Further, on the upstream side of the two purification sections 210 and 220, a reducing agent injection section 260 for injecting a reducing agent for regenerating the purification function of each purification section into the respective branch passages 30b1 and 30b2. Is provided. Reductant injection part 2
60 includes two reducing agent injection nozzles 261 and 262 and one reducing agent supply pump 268. The reducing agent supplied from the reducing agent supply pump 268 is injected into the first branch passage 30b1 by the first reducing agent injection nozzle 261 and into the second branch passage 30b2 by the second reducing agent injection nozzle 262. Injected. As the reducing agent, a hydrocarbon compound can be used, and for example, the fuel of the diesel engine 100 (that is, light oil, etc.)
Can be used.

The adjusting section 230 and the reducing agent injecting section 260 are
It is controlled by the ECU 90 (FIG. 1). In particular,
The ECU 90 uses the two drive units 236, 2 of the adjustment unit 230.
It is connected to 37 and controls the opening / closing operations of the adjusting valves 231 and 232 by controlling the respective driving units. Further, the ECU 90 is connected to the two reducing agent injection nozzles 261 and 262 of the reducing agent injection unit 260, and controls the reducing agent injection nozzles to control the reducing agent injection operation.

Further, the purification unit 200 of this embodiment is
Two sets of pressure sensors 121 to 124 are provided. The two pressure sensors 121 and 122 of the first set are provided in the first branch passage 30 on the upstream side and the downstream side of the first purification unit 210, respectively.
Measure the pressure in b1. Second set of two pressure sensors 1
23 and 124 measure the pressure in the second branch passage 30b2 on the upstream side and the downstream side of the second purifying unit 220, respectively. The four pressure sensors 121 to 124 are the ECU 90.
Is connected to the ECU 90 and gives the measurement result to the ECU 90. E
The CU 90 determines the injection timing of the reducing agent using the given measurement result. The four pressure sensors 12
1 to 124 will be described later.

FIG. 4, FIG. 5 and FIG. 6 show a cleaning unit 200.
(FIG. 3) It is explanatory drawing which shows the flow of the exhaust gas inside.

FIG. 4 shows the flow of exhaust gas when both of the two adjusting valves 231 and 232 are set to the fully open state. At this time, the exhaust gas flowing through the upstream main passage 30a1 is divided into the first and second branch passages 30b1 and 30b.
Through b2, it flows into the downstream main passage 30a2.
That is, the exhaust gas passes through both of the two purification units 210 and 220.

FIG. 5 shows the flow of exhaust gas when the first adjusting valve 231 is set to the fully closed state and the second adjusting valve 232 is set to the fully open state. At this time, the exhaust gas flowing through the upstream main passage 30a1 flows into the downstream main passage 30a2 through the second branch passage 30b2. That is, the exhaust gas passes through only the second purification unit 220 of the two purification units.

FIG. 6 shows the flow of exhaust gas when the first adjusting valve 231 is set to the fully open state and the second adjusting valve 232 is set to the fully closed state. At this time, the exhaust gas flowing through the upstream main passage 30a1 flows into the downstream main passage 30a2 through the first branch passage 30b1. That is, the exhaust gas passes through only the first purification unit 210 of the two purification units.

As described above, the two adjusting valves 231 and 23
When both of the two are fully open, the exhaust gas passes through both of the two purification units 210 and 220. On the other hand, when one of the two adjusting valves 231 and 232 is in the fully closed state, the exhaust gas passes through one of the two purifying units 210 and 220. That is, the purification unit 200
The exhaust gas that has flowed into the exhaust gas always passes through at least one of the purification units and is discharged from the purification unit 200.

FIG. 7 is an explanatory view showing the first purifying section 210 (FIG. 3). FIG. 7 (A) shows the appearance of the first purification unit 210, and FIG. 7 (B) shows the first purification unit 210.
7 is a schematic cross section when the is cut along the exhaust gas flow direction (the x direction shown in FIG. 7A).

The first purifying section 210 is a monolith type filter capable of collecting carbon-containing fine particles in exhaust gas, and is made of porous ceramics. Specifically, the first
The purifying section 210 includes a plurality of small passages 212 arranged in a honeycomb shape. The partition wall 214 of the small passage 212 is
It has a porous structure through which exhaust gas can flow. Further, the sealing plates 216 are alternately provided at one end of each of the small passages 212. That is, two adjacent
Sealing plate 216 for one of the two small passages 212
Is provided on the first surface S1 side of the first purifying unit 210, and the sealing plate 216 of the other small passage is the first purifying unit 2
10 is provided on the second surface S2 side. The exhaust gas is
The inlet flows into a small passage that is not blocked by the sealing plate, but the outlet of this small passage is blocked by the sealing plate. For this reason,
The exhaust gas passes through the partition wall and flows out from the adjacent small passage whose outlet is not blocked. In this way, the exhaust gas always passes through the partition wall 214 when passing through the first purification unit 210, so the first purification unit 210 can efficiently collect the carbon-containing fine particles in the exhaust gas. You can

As the ceramic material, cordierite, silicon carbide, silicon nitride or the like can be used.

Further, the partition wall 214 of the first purifying section 210 carries an active component composed of a base material layer, an active metal and a cocatalyst. Specifically, in the partition wall 214, a base material layer containing alumina as a main component is formed, and platinum Pt as an active metal and potassium K as a cocatalyst are supported on the base material layer. Thereby, the first purification unit 210
Can oxidize the collected carbon-containing fine particles and store NOx in the exhaust gas.

As the active metal, in addition to platinum Pt, a noble metal having an oxidizing activity such as palladium Pd can be used. Further, as a co-catalyst, in addition to potassium K, lithium Li, sodium Na, rubidium Rb,
Alkali metals such as cesium Cs, calcium Ca,
At least one selected from alkaline earth metals such as strontium Sr and barium Ba, rare earths such as yttrium Y, lanthanum La and cerium Ce, and transition metals.
Different types of elements can be used. As the co-catalyst, it is preferable to use an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca.

FIG. 8 is an explanatory diagram schematically showing the functions of the active metal 218 and the cocatalyst 219 carried on the partition wall 214 of the first purification section 210 in a state where the oxygen concentration of the exhaust gas is relatively high. . Note that this state is realized when the normal combustion shown in FIG. 2 is performed. When normal combustion is carried out, the exhaust gas mainly contains carbon-containing fine particles and N
It contains Ox and almost no HC and CO. Further, when normal combustion is performed, the exhaust gas air-fuel ratio is lean, and excess oxygen exists in the exhaust gas.

In the figure, "NO" represents nitric oxide which constitutes most of NOx, and "C" represents carbon-containing fine particles.

As shown in the figure, NO in the exhaust gas reacts with oxygen O ₂ in the exhaust gas on the active metal 218 to form nitrate ion NO ₃ ⁻ . Nitrate ions move to the co-catalyst 219 by a phenomenon called “spillover”. The co-catalyst 219 converts nitrate ions into nitrate (KNO ₃ ).
In the form of, it releases active oxygen. Active oxygen is extremely reactive. Therefore, the collected carbon-containing fine particles C are oxidized by active oxygen (and oxygen in the exhaust gas) to become carbon dioxide CO ₂ .

As described above, the first purification section 210 can store NOx in the exhaust gas in a state where the oxygen concentration of the exhaust gas is relatively high. Then, the first purification unit 210 can oxidize and remove the collected carbon-containing fine particles C by using active oxygen generated when NOx is stored.

By the way, the NOx storage amount of the co-catalyst 219 is limited. Therefore, when the normal combustion is performed for a long period of time, the NOx purification function of the first purification unit 210 gradually decreases. The NOx purification function of the first purification unit 210 is performed by setting the oxygen concentration of exhaust gas to a relatively low state.
Is played.

FIG. 9 is an explanatory view schematically showing the functions of the active metal 218 and the cocatalyst 219 carried on the partition wall 214 of the first purification section 210 in a state where the oxygen concentration of the exhaust gas is relatively low. . Note that this state is realized, for example, when the low temperature combustion shown in FIG. 2 is performed. When low temperature combustion is performed, the exhaust gas mainly contains HC and C.
O is included, and carbon-containing fine particles and NOx are hardly included. Also, when low temperature combustion is carried out,
The exhaust gas air-fuel ratio shifts to the rich side (becomes stoichiometric or rich), and there is no excess oxygen in the exhaust gas.

As shown in the figure, when the oxygen concentration of the exhaust gas becomes relatively low, the active metal 218 becomes the co-catalyst 21.
Nitrate ion NO ₃ ⁻ stored in 9 is decomposed to release active oxygen. Specifically, the nitrate ion NO ₃ ⁻ stored in the co-catalyst 219 moves onto the active metal 218.
On the active metal 218, the bond between the nitrogen atom of the nitrate ion and the oxygen atom is easily broken. This state is
In FIG. 9, it is indicated by “N + 3 · O”. When a reducing substance such as HC or CO is present in this state, the bond between the nitrogen atom and the oxygen atom is broken, and nitrogen N ₂ and active oxygen are generated. Active oxygen is the reducing substance H in the exhaust gas.
Oxidizes C and CO, carbon dioxide CO ₂ and water (steam) H
₂ O is produced. Further, the active oxygen oxidizes the collected carbon-containing fine particles C to generate carbon dioxide CO ₂ .
Note that this phenomenon can also occur locally in FIG.
That is, the oxygen concentration of the exhaust gas is relatively high, but the same phenomenon may occur when the vicinity of the collected carbon-containing fine particles C is in an oxygen-deficient state.

As described above, the first purifying section 210 stores the stored N in the state where the oxygen concentration of the exhaust gas is relatively low.
NOx is reduced to nitrogen N ₂ and released to give NOx.
The purification function can be regenerated. Then, the first purification unit 210 can oxidize and remove the collected carbon-containing fine particles C by using the active oxygen generated at this time.

In FIGS. 7 to 9, the first purifying section 21 is used.
Although 0 has been focused on the description, the same applies to the second purifying unit 220.

A-4. Injection of reducing agent in the purification unit: As described above, the purification function of each of the purification units 210 and 220 is regenerated by performing low temperature combustion, but depending on the operating conditions of the engine 100, low temperature combustion may be performed. It can be difficult. Therefore, in the purification unit 200 of the present embodiment, the reducing agent injection part 260 has the branch passages 30b.
By injecting the reducing agent into 1, 30b2, it is possible to positively regenerate the purification function of each purification unit 210, 220.

FIG. 10 shows the first reducing agent injection nozzle 261.
It is explanatory drawing which shows the mode of injection | pouring of the reducing agent in the 1st branch passage 30b1 by. As illustrated, the first reducing agent injection nozzle 261 has the first branch passage 30b1 when the first adjustment valve 231 is set to an intermediate opening state between the fully open state and the fully closed state. The reducing agent is injected into the inside. When the first adjusting valve 231 is set to the intermediate opening state, the second adjusting valve 232 is maintained in the fully open state. Therefore, the exhaust gas flow rate in the first branch passage 30b1 is relatively smaller than the exhaust gas flow rate in the second branch passage 30b2.

The oxygen concentration of the exhaust gas inside the first purification section 210 is in a relatively high state (the exhaust gas air-fuel ratio is lean) until the reducing agent is injected, as shown in FIG. . Then, when the injected reducing agent is supplied to the first purification unit 210 by the flow of the exhaust gas, the reducing agent HC
Is reacted with oxygen O ₂ in the exhaust gas and burned by the action of the active metal 218 carried by the first purification section 210. As a result, the oxygen concentration of the exhaust gas inside the first purification section 210 becomes relatively low (the exhaust gas air-fuel ratio shifts to rich), as shown in FIG. 9. At this time, as described with reference to FIG. 9, the first purification unit 210 reduces the stored NOx to nitrogen N ₂ and releases the NOx, so that NO
x Regenerate purification function. Then, the first purification unit 210
Uses the active oxygen generated at this time to oxidize and remove the collected carbon-containing fine particles C.

As described above, the reducing agent injecting section 260 has the first
By supplying the reducing agent into the branch passage 30b1 of
The purification function of the first purification unit 210 can be regenerated.

The purification function of the first purification section 210 is
Regeneration is possible even when the first adjusting valve 231 is not set to the intermediate opening state, in other words, when the first adjusting valve 231 is set to the fully closed state or the fully opened state. However, in such a case, it becomes difficult to efficiently regenerate the first purification unit 210. That is, when the first adjustment valve 231 is set to the fully closed state, the exhaust gas in the first branch passage 30b1 stays, so the reducing agent diffuses into the exhaust gas and the first purification is performed. Part 2
It will take a considerable amount of time to be supplied to the whole 10.
Therefore, it takes a considerable time to regenerate the purification function of the first purification unit 210. On the other hand, when the first adjustment valve 231 is set to the fully open state, the first branch passage 3
The flow of exhaust gas in 0b1 is quite fast. When the reducing agent is injected in this state, most of the reducing agent passes through the first purification unit 210 as it is without being used for the regeneration process. Further, since the exhaust gas flow rate is large (that is, the amount of oxygen in the exhaust gas is large), it becomes relatively difficult to make the exhaust gas air-fuel ratio rich. Therefore, the first purification unit 2
In order to sufficiently regenerate the purification function of No. 10, a relatively large amount of reducing agent is required. Then, when fuel is used as the reducing agent, fuel efficiency is deteriorated.

Therefore, in this embodiment, as shown in FIG. 10, by injecting the reducing agent into the first branch passage 30b1 when the first adjusting valve 231 is set to the intermediate opening state, The purification function of the first purification unit 210 is efficiently regenerated.

In FIG. 10, the case where the purifying function of the first purifying unit 210 is reproduced has been described, but the same applies to the case where the purifying function of the second purifying unit 220 is reproduced. In this case, the second reducing agent injection nozzle 26
No. 2 injects the reducing agent into the second branch passage 30b2 when the second adjustment valve 232 is set to the intermediate opening state between the fully open state and the fully closed state. Then, when the second adjustment valve 232 is set to the intermediate opening state, the first adjustment valve 231 is maintained in the fully open state.

A-5. Regeneration process of the purifying unit: As described above, the opening / closing operation of each adjustment valve 231 and 232 and the reducing agent injection operation of each reducing agent injection nozzle 261 and 262 are performed by the ECU
0 (FIG. 3 (A)). Specifically, the ECU 90 estimates the emission amount of carbon-containing fine particles, NOx, etc. from the history of operating conditions of the engine 100. Then, the ECU 90 determines whether or not it is necessary to regenerate the purifying function of each of the purifying units 210 and 220, and if necessary, performs the opening / closing operation by each adjusting valve and the reducing agent injection operation by each reducing agent injection nozzle. Let At this time, the ECU 90 uses the measurement results of the four pressure sensors 121 to 124 to determine the reducing agent injection timing of each reducing agent injection nozzle.

For example, if the regeneration processing of the purification function of the first purification unit 210 is necessary, the ECU 90 causes the first purification unit 2
The opening / closing operation by the first adjusting valve 231 corresponding to 10 and the reducing agent injection operation by the first reducing agent injection nozzle 261 are executed. At this time, the ECU 90 determines that the first purifying unit 21
No. 0 upstream side and downstream side first branch passages 30b1 in the first set of two pressure sensors 121, 12 for measuring the pressure.
By using the measurement result of No. 2, the first reducing agent injection nozzle 261
Determines the injection timing of the reducing agent.

FIG. 11 is a flow chart showing the processing when the purification function of the first purification section 210 is reproduced. It should be noted that this process is executed according to a command from the ECU 90.

In step S101, the first adjusting valve 23
Opening / closing operation 1 is started. Specifically, first, the first regulating valve 231 operates from the fully open state to the fully closed state. In step S102, the difference between the measurement results Pf and Pr of the two pressure sensors 121 and 122 of the first set, that is, the differential pressure ΔP1 (= Pf−Pr) of the first purification unit 210.
Is determined to be equal to a preset target value Pa. When the differential pressure ΔP1 becomes equal to Pa, step S10
Go to 3. In step S103, the first reducing agent injection nozzle 261 injects the reducing agent into the first branch passage 30b1 for a predetermined period. At this time, the first adjustment valve 231
Is in an intermediate opening state between the fully open state and the fully closed state. The first adjustment valve 231 returns to the fully open state after shifting to the fully closed state, and the opening / closing operation of the first adjustment valve 231 ends in step S104.

FIG. 12 is an explanatory diagram showing changes in the exhaust gas flow rate Q1 in the first purification unit 210 and changes in the differential pressure ΔP1 in the first purification unit 210. Further, FIG. 13 is an explanatory diagram showing changes in the exhaust gas flow rate Q2 in the second purification unit 220 and changes in the differential pressure ΔP2 of the second purification unit 220. Note that FIGS. 12 and 13 show the case where the regeneration processing of the purification function of the first purification unit 210 is executed as shown in FIG. 11, that is, the first adjustment valve 231 is once moved from the fully open state to the fully closed state. Exhaust gas flow rate when returning to fully open state after
1 and Q2 and changes in the differential pressures ΔP1 and ΔP2. Here, the flow rate means the volume of the fluid (exhaust gas) flowing per unit time.

As shown in FIGS. 12 (A) and 13 (A), in the initial state in which both the first and second adjusting valves 231 and 232 are set to the fully open state, the first and second adjusting valves are set.
Exhaust gas having a flow rate of approximately Q0 flows in the purifying units 210 and 220. When the first regulating valve 231 shifts from the fully open state to the fully closed state, the exhaust gas flow rate Q1 in the first purification section 210 gradually decreases, and the exhaust gas flow rate Q2 in the second purification section 220 becomes It gradually increases. First adjusting valve 23
When 1 is fully closed, the exhaust gas flow rate Q1 becomes almost 0 and the exhaust gas flow rate Q2 becomes approximately 2 · Q0. And
When the first adjustment valve 231 shifts from the fully closed state to the fully opened state, the exhaust gas flow rate Q1 in the first purification section 210 gradually increases, and the exhaust gas flow rate Q2 in the second purification section 220.
Gradually decreases. When the first adjustment valve 231 returns to the fully open state, the exhaust gas flow rates Q1 and Q2 both return to approximately Q0.

As can be seen from FIGS. 12 (A) and 13 (A), upstream and downstream main passages 30a1,
30a2, regardless of the state of the first adjusting valve 231,
Almost 2.Q0 exhaust gas is constantly flowing.

Further, as shown in FIGS. 12 (B) and 13 (B), in the initial state in which both the first and second adjusting valves 231 and 232 are set to the fully open state, the first and second adjusting valves 231 and 232 are set to the fully opened state. The differential pressures ΔP1 and ΔP2 of the two purification units 210 and 220 are
It is almost P0. When the first adjustment valve 231 shifts from the fully open state to the fully closed state, the differential pressure ΔP1 of the first purification section 210 gradually decreases and the differential pressure ΔP2 of the second purification section 220 gradually increases. When the first regulating valve 231 is fully closed, the differential pressure ΔP1 becomes approximately 0 and the differential pressure ΔP2 becomes approximately 2 to 3 · P0. Then, the first adjustment valve 231
Is shifted from the fully closed state to the fully opened state, the differential pressure ΔP1 of the first purification unit 210 gradually increases, and the second purification unit 2
The differential pressure ΔP2 of 20 gradually decreases. First adjusting valve 23
When 1 returns to the fully open state, the differential pressures ΔP1 and ΔP2 both return to almost P0.

As shown in FIGS. 12A and 12B, as shown in FIG.
In step S102 of 1, the exhaust gas flow rate Q1 in the first purification unit 210 is substantially Qa at the time when the differential pressure ΔP1 of the first purification unit 210 becomes equal to the target value Pa. Therefore, if the injection of the reducing agent is started when the differential pressure ΔP1 reaches the target value Pa, it becomes possible to inject the reducing agent with good timing when the exhaust gas flow rate Q1 becomes substantially Qa.

As described above, the reducing agent is used in the first adjusting valve 2
It is injected when 31 goes from the fully open state to the fully closed state. At this time, the exhaust gas flow rate Q1 flowing through the first purification unit 210 is relatively small. Therefore, the first
As the adjusting valve 231 of FIG. 3 shifts to the fully closed state, the reducing agent passes through the first purifying section 210 relatively slowly while diffusing into the exhaust gas in the first branch passage 30b1. In other words, the exhaust gas having a rich exhaust gas air-fuel ratio passes through the first purification section 210 for a relatively long time. By doing so, the reducing agent is supplied to the first purifying unit 210.
Since it is efficiently used to regenerate the purification function of the first purification unit 210, it is possible to reduce the injection amount of the reducing agent required to regenerate the purification function of the purification unit and efficiently regenerate the purification function of the first purification unit 210. Become.

As shown in FIG. 12 (A), the time at which the differential pressure ΔP1 of the first purifying section 210 reaches the target value Pa during one opening / closing operation of the first adjusting valve 231 is 2 times. Exist. Therefore, in the present embodiment, the differential pressure ΔP1 is first set to the target value P during one opening / closing operation period of the first adjusting valve 231.
The reducing agent is to be injected at the time of a.

By the way, in FIGS. 12 (A) and 13 (A), in the initial state in which both of the two adjusting valves 231 and 232 are set to the fully open state, the two purifying sections 210,
Although the case where the exhaust gas flow rates Q1 and Q2 in 200 are almost Q0 has been described, the flow rate Q0 actually changes depending on the operating state of the engine 100.

FIG. 14 shows the change in the exhaust gas flow rate Q1 and the differential pressure Δ when the exhaust gas flow rate Q0 changes in the initial state.
It is explanatory drawing which shows the change of P1, and corresponds to FIG.
As shown in the figure, when the exhaust gas flow rate Q0 in the initial state is relatively large, the differential pressure P0 in the initial state also becomes relatively high. Exhaust gas flow rate Q in the first purification unit 210
1 is substantially determined by the differential pressure ΔP1 of the first purification section 210. Therefore, in step S102 of FIG. 11, when the injection of the reducing agent is started when the differential pressure ΔP1 becomes the target value Pa, the exhaust gas flow rate Q1 becomes approximately Qa regardless of the exhaust gas flow rate Q0 in the initial state. To
The reducing agent can be injected with good timing.

11 to 14, the case where the purifying function of the first purifying section 210 is reproduced is explained, but the same applies to the case where the purifying function of the second purifying section 220 is reproduced.

As described above, the exhaust gas purifying apparatus of this embodiment has the purifying unit 200. The purification unit 200 includes an exhaust passage 30 including two branch passages 30b1 and 30b2 that branch and join in the middle of the passage, and carbon-containing fine particles and NOx contained in the inflowing exhaust gas provided in each branch passage. Two purification units 210 for purification,
220, adjusting valves 231 and 232 capable of changing the flow passage cross-sectional area of a part of each branch passage, an adjusting portion 230 for adjusting the exhaust gas flow rate in each branch passage, and a purification function of each purification portion And a reducing agent injecting section 260 for injecting a reducing agent for regenerating the above into each branch passage. The adjustment unit 230 and the reducing agent injection unit 260 are connected to the ECU 9
Controlled by 0.

Thus, the purification unit 20 of this embodiment
At 0, since the reducing agent injection unit 260 is provided, the purification function of the purification unit 200 can be regenerated regardless of the operating conditions of the internal combustion engine.

Further, the purification unit 200 of this embodiment is
Four pressure sensors 121 to 124 for measuring the pressure in the branch passages 30b1 and 30b2 on the upstream side and the downstream side of the purification units 210 and 220 are provided. And E
The CU 90 is configured so that the differential pressures ΔP1 and ΔP of the purification units 210 and 220, respectively.
The reducing agent is injected when P2 reaches a predetermined target value. By doing so, the reducing agent can be injected in a timely manner when the flow rate of the exhaust gas flowing through the purifying units 210 and 220 reaches a substantially predetermined amount, and as a result, the purifying function of the purifying unit is efficiently regenerated. It becomes possible.

As can be seen from the above description, the four pressure sensors 121 to 124 of this embodiment correspond to the pressure measuring section in the present invention, and the ECU 90 and the four pressure sensors 121 to 124 control in the present invention. It corresponds to the department.

B. Second Embodiment: In the first embodiment (FIGS. 11 to 14), the differential pressures ΔP1 and Δ of the purification units 210 and 220, respectively.
The case where the injection of the reducing agent is started when P2 reaches a predetermined target value has been described, but when the temperature of each purifying unit (for example, the active component or the ceramic carrier) becomes high, the purifying function of each purifying unit is reduced. It may be difficult to surely reproduce. FIG. 15 shows changes in the exhaust gas flow rate Q1 and the differential pressure Δ when the temperature of the first purification section 210 becomes relatively high.
It is explanatory drawing which shows the change of P1. In addition, in FIG.
The target value of the differential pressure ΔP1 of the first purification unit 210 is Pa, and the reducing agent is the exhaust gas flow rate Q1 in the first purification unit 210.
Is injected when Q becomes approximately Qa. As shown in the figure, when the temperature of the first purification section 210 becomes relatively high, the exhaust gas flow rate Q0 in the initial state also becomes relatively large.
At this time, the time from the time when the exhaust gas flow rate Q1 in the first purification section 210 becomes substantially Qa to the time when the first adjustment valve 231 becomes fully closed becomes relatively short.
In such a case, most of the reducing agent is contained in the first purifying unit 2
There is a possibility that the reducing agent is consumed in the upstream side portion of 10, and the reducing agent is not so much supplied to the downstream side portion of the first purification section 210. Therefore, in the present embodiment, each of the purifying units 210 and 22
The temperature of 0 is used to change the target values of the differential pressures ΔP1 and ΔP2 of the respective purification units.

FIG. 16 is an explanatory view showing a purification unit 200B capable of measuring the temperature of each purification section 210, 220. 16 is almost the same as FIG. 3, but two temperature sensors 131 and 132 are added. The first temperature sensor 131 measures the temperature of the first purifying unit 210,
The temperature sensor 132 of measures the temperature of the second purifying unit 220. The two temperature sensors 131 and 132 are connected to the ECU 9
It is connected to 0 and gives a measurement result to ECU90.
The ECU 90 uses the given measurement result to determine the differential pressure ΔP.
1, change the target value of ΔP2.

FIG. 17 shows the first purifying unit 2 in FIG.
11 is an explanatory diagram showing a case where the target value of the differential pressure ΔP1 is changed according to the temperature of 10. FIG. In FIG. 17, the first purification unit 210
The target value of the differential pressure ΔP1 is changed from Pa to Pb. Then, the reducing agent is injected when the exhaust gas flow rate Q1 in the first purification section 210 becomes substantially Qb. The target value Pb of the differential pressure ΔP1 is larger than Pa. Therefore, the exhaust gas flow rate Qb when the reducing agent is injected is
It is larger than Qa. By doing this, the first
Since the time from the time when the exhaust gas flow rate Q1 in the purifying unit 210 becomes substantially Qb to the time when the first adjusting valve 231 is fully closed can be made relatively long, the first purifying unit 210 It is possible to reliably reproduce the purification function of.

As shown in FIG. 17, each of the purifying units 210, 2
When the temperature of 20 is relatively high, the differential pressure ΔP of each purification unit
It is preferable that the target values of 1 and ΔP2 are relatively large. On the contrary, when the temperatures of the purification units 210 and 220 are relatively low, the target values of the differential pressures ΔP1 and ΔP2 of the purification units may be relatively small. Generally, the ECU 9
For 0, the target value of the differential pressure may be changed according to the temperature of the one purification unit selected as the target of the regeneration process.

C. Third Embodiment: In the first embodiment, the reducing agent is injected when the adjusting valve shifts from the fully open state to the fully closed state. However, in the present embodiment, the opening / closing operation of the adjusting valve is performed in the intermediate opening state. Once stopped, the reducing agent is injected.

FIG. 18 is a flow chart showing the processing when the purifying function of the first purifying unit 210 is reproduced in the third embodiment. The process of FIG. 18 is executed in the purification unit 200 shown in FIG.

In step S201, the first adjusting valve 23
Opening / closing operation 1 is started. Specifically, the first regulating valve 231 operates from the fully open state to the fully closed state. In step S202, the first set of two pressure sensors 12
It is determined whether the difference between the measurement results Pf and Pr of 1,122, that is, the differential pressure ΔP1 (= Pf-Pr) of the first purification unit 210 is equal to the preset target value Ps. When the differential pressure ΔP1 becomes equal to Ps, the process proceeds to step S203. In step S203, the opening / closing operation of the first adjusting valve 231 is performed in the intermediate opening state between the fully open state and the fully closed state.
It is suspended for a predetermined period. Then, in step S204, the reducing agent is injected into the first branch passage 30b1 by the first reducing agent injection nozzle 261 for a predetermined period. When the reducing agent is injected, the opening / closing operation of the first adjusting valve 231 is restarted in step S205. First adjustment valve 231
Returns to the fully open state without shifting to the fully closed state, and step S
At 206, the opening / closing operation of the first adjusting valve 231 ends.

FIG. 19 shows changes in the exhaust gas flow rate Q1 in the first purification section 210 and changes in the differential pressure ΔP1 in the first purification section 210 when the first adjustment valve 231 is stopped at the intermediate opening state. FIG. 13 is an explanatory diagram showing and and corresponds to FIG. 12. Figure 20
Are explanatory diagrams showing changes in the exhaust gas flow rate Q2 in the second purification unit 220 and changes in the differential pressure ΔP2 in the second purification unit 220 when the first adjustment valve 231 is stopped in the intermediate opening state. And corresponds to FIG. In addition, FIG. 19 and FIG.
As shown in FIG. 18, when the regeneration process of the purification function of the first purification unit 210 is executed, that is, the first adjustment valve 231.
Of the exhaust gas flow rates Q1, Q2 and the differential pressure ΔP1, when the engine is stopped at an intermediate opening state between the fully open state and the fully closed state.
And changes in ΔP2.

As shown in FIGS. 19A and 19B, FIG.
In step S202 of 8, the exhaust gas flow rate Q1 in the first purification unit 210 is almost Qs at the time when the differential pressure ΔP1 of the first purification unit 210 becomes equal to the target value Ps. Therefore, if the opening / closing operation of the first adjusting valve is stopped and the injection of the reducing agent is started when the differential pressure ΔP1 reaches the target value Ps, the exhaust gas flow rate Q1 will be approximately Qs.
It becomes possible to inject the reducing agent while being maintained at. Note that when the first adjustment valve 231 is stopped in the intermediate opening state, the exhaust gas flow rates Q1 and Q2 and the differential pressures ΔP1 and ΔP1.
P2 is maintained at a substantially constant value.

18 to 20, the case where the purifying function of the first purifying unit 210 is reproduced is explained, but the same applies to the case where the purifying function of the second purifying unit 220 is reproduced.

The processing of this embodiment (FIG. 18) is the first
Similar to the embodiment (FIG. 14), it is also applicable when the operating state of the engine 100 changes. That is, regardless of the exhaust gas flow rate Q0 in the initial state, each purification unit 2
The reducing agent can be injected with the exhaust gas flow rates Q1 and Q2 in 10, 220 being maintained at approximately Qs.

Further, as in the second embodiment, the purification section 21
The target values of the differential pressures ΔP1 and ΔP2 may be changed according to the temperatures of 0 and 220.

As described above, in the present embodiment, the first
A purification unit 200 similar to that of the embodiment is provided. Then, the ECU 90 stops the operation of the adjusting valve and injects the reducing agent when the differential pressures ΔP1 and ΔP2 reach predetermined target values. In this way, the purification units 210, 20
It becomes possible to inject the reducing agent in a state where the flow rate of the exhaust gas flowing through 0 is maintained at a substantially predetermined amount.

D. Fourth Embodiment: As described above, the purification function of each purification unit 210, 200 is regenerated in a state where the exhaust gas air-fuel ratio is relatively low (stoichio or rich).
Therefore, for example, when the operating state of the engine 100 changes and the exhaust gas air-fuel ratio shifts to the lean side, it is necessary to increase the injection amount of the reducing agent in order to make the exhaust gas air-fuel ratio stoichiometric or rich. There is. In other words, when the air-fuel ratio of the exhaust gas before the reducing agent injection is relatively large, the injection amount of the reducing agent is adjusted so that the air-fuel ratio of the exhaust gas passing through each of the purifying units 210 and 220 becomes a predetermined value or less. Needs to be relatively large. The injection amount of the reducing agent can be changed by adjusting the injection pressure or the injection period of the reducing agent.

FIG. 21 is an explanatory view showing a purification unit 200D capable of measuring the exhaust gas air-fuel ratio. 21 is almost the same as FIG. 3, but the two air-fuel ratio sensors 141, 1
42 has been added. The first air-fuel ratio sensor 141 is
The air-fuel ratio of the exhaust gas flowing through the first branch passage 30b1 is measured, and the second air-fuel ratio sensor 142 measures the second branch passage 3
The air-fuel ratio of the exhaust gas flowing through 0b2 is measured. The two air-fuel ratio sensors 141, 142 are connected to the ECU 90 and give the measurement result to the ECU 90. The ECU 90
The given measurement results are used to determine the injection conditions such as the reducing agent injection pressure and the injection period. In FIG. 21, the ECU 9
0 is the reducing agent supply pump 268 and the reducing agent injection nozzle 26.
1 and 262, and a reducing agent is injected according to the determined injection conditions. Specifically, the ECU 90
Adjusts the injection pressure by adjusting the pressure of the reducing agent supply pump 268, and the reducing agent injection nozzles 261 and 26
Adjust the infusion period by adjusting the on-time of 2.

In the purifying unit 200D of FIG. 21, both the injection pressure of the reducing agent and the injection period can be adjusted, but generally, at least one of the injection pressure of the reducing agent and the injection period is adjusted. It should be possible.

As described above, the ECU 90 of this embodiment is
The reducing agent injection condition can be determined according to the exhaust gas air-fuel ratio. Generally, the reducing agent injection condition may be changed so that the air-fuel ratio of the exhaust gas flowing through each of the purifying units 210 and 220 becomes a predetermined value or less. In this way, the purification function of each of the purification units 210 and 220 can be purified more reliably, and the amount of reducing agent injected can be reduced.

E. Fifth Embodiment: FIG. 22 is an explanatory diagram showing a purification unit 200E of the fifth embodiment. FIG. 22 shows
Although it is almost the same as FIG. 3, the adjustment unit 230E is changed. That is, the adjusting unit 230 of FIG. 3 includes two adjusting valves 231, 232 and two driving units 236, 237, but the adjusting unit 230E of the present embodiment has one adjusting valve 231E and one driving unit. And section 236E. Then, the regulating valve 231E has two branch passages 30b1 and 30b.
It is provided at the confluence of b2.

The adjusting valve 231E is arranged in the first branch passage 30b1.
When the exhaust gas flowing through the upstream main passage 30a1 is set to the first state in which the outlet portion of the second main passage 30a1 is closed, the exhaust gas flows through the second branch passage 30b2 and the downstream main passage 30a1 as in FIG. Flows into 30a2. When the regulating valve 231E is set to the second state in which the outlet portion of the second branch passage 30b2 is closed, the exhaust gas flowing through the upstream main passage 30a1 is the same as in FIG. Through 30b1,
It flows into the downstream main passage 30a2. Further, in FIG. 22, when the regulating valve 231E is set to the third state which is substantially the center of the first and second states, the exhaust gas flowing through the upstream main passage 30a1 is the same as in FIG. It flows through the first and second branch passages 30b1 and 30b2 into the downstream main passage 30a2.

As described above, even when the adjusting portion 230E having the single adjusting valve 231E is used, the exhaust gas flow rate in each of the branch passages 30b1 and 30b2 can be adjusted as in the first embodiment.

F. Sixth Embodiment: FIG. 23 is an explanatory diagram showing a purification unit 200F of the sixth embodiment. FIG. 23 shows
Almost the same as FIG. 3, but with the first set of two pressure sensors 1
Only 21 and 122 are provided, and the two pressure sensors 123 and 124 of the second set are omitted.

As described with reference to FIGS. 12 (B) and 13 (B), during the opening / closing operation of the first adjusting valve 231, the
The differential pressure ΔP1 of the purifying section 210 becomes relatively small,
The differential pressure ΔP2 of the purifying section 220 becomes relatively large. On the contrary, during the opening / closing operation of the second adjusting valve 232, the differential pressure ΔP1 of the first purification unit 210 becomes relatively large, and the differential pressure ΔP2 of the second purification unit 220 becomes relatively small. In this way, if the adjustment valve that executes the opening / closing operation is changed, the two differential pressures ΔP1 and ΔP2 change in the opposite relationship. Therefore, if the differential pressure ΔP1 of the first purification unit 210 is known, the second pressure
It is possible to almost estimate the differential pressure ΔP2 of the purification unit 220. Therefore, in the purification unit 200F of this embodiment,
The second set of two pressure sensors 123, 124 shown in FIG. 3 is omitted.

The two pressure sensors 121 and 12 of this embodiment.
2 measures the differential pressure ΔP1 of the first purification section 210. Then, when the differential pressure ΔP1 of the first purifying unit 210 becomes equal to the first target value that is smaller than the initial state value P0, the reducing agent is injected into the first branch passage 30b1 to generate the first The purification function of the purification unit 210 can be regenerated. Further, when the differential pressure ΔP1 of the first purification section 210 becomes equal to the second target value which is larger than the value P0 in the initial state, the reducing agent is injected into the second branch passage 30b2, whereby the second The purification function of the purification unit 220 can be regenerated.

In this embodiment, the first purifying section 210
Pressure sensors 12 for measuring the differential pressure ΔP1 of
Although 1, 122 are used, two pressure sensors for measuring the differential pressure ΔP2 of the second purification section 220 may be used instead.

G. Seventh Embodiment: FIG. 24 is an explanatory diagram showing a purification unit 200G of the seventh embodiment. This purification unit 200G includes two pressure sensors 121G and 122G as in FIG.
1G and 122G measure the pressure in the upstream main passage 30a1 and the downstream main passage 30a2, respectively.
The two pressure sensors 121G and 122G are connected to the ECU 90 and give the measurement result to the ECU 90. EC
U90 determines the injection timing of the reducing agent using the given measurement result.

The ECU 90 uses the two pressure sensors 121.
When the difference between the measurement results of G and 122G, that is, the differential pressure ΔP3 of the purification unit 200G becomes equal to a preset target value, the reducing agent is injected. Purification unit 200G
The differential pressure ΔP3 of the control valve 231 or 232 is
When the opening / closing operation of is executed, it changes as shown in FIG. That is, when the flow rate of the exhaust gas flowing into the purification unit 200G is approximately 2 · Q0,
The differential pressure ΔP3 is almost P0 in the initial state. When the first adjusting valve 231 shifts from the fully open state to the fully closed state, the differential pressure ΔP3 gradually increases, and when the first adjusting valve 231 goes into the fully closed state, the differential pressure ΔP3 is approximately 2-3.
It becomes P0. Then, when the first adjusting valve 231 shifts from the fully closed state to the fully open state, the differential pressure ΔP3 gradually decreases, and when the first adjusting valve 231 returns to the fully open state, the differential pressure ΔP3.
3 returns to almost P0. The differential pressure ΔP3 changes similarly when the opening / closing operation of the second adjusting valve 232 is executed. Therefore, the target value of the differential pressure ΔP3 is set to the same value regardless of which of the opening / closing operations of the adjusting valves 231 and 232 is executed.

When selecting one of the purifying units to be subjected to the regeneration processing, the ECU 90 executes the opening / closing operation of the regulating valve corresponding to the selected purifying unit. Then, when the differential pressure ΔP3 reaches a predetermined target value, by controlling one of the reducing agent injection nozzles corresponding to the selected purifying unit, one of the branch passages in which the selected purifying unit is provided is controlled. Inject the reducing agent. This makes it possible to regenerate the purification function of the selected purification unit.

The present invention is not limited to the above-described examples and embodiments, but can be implemented in various modes without departing from the scope of the invention.
For example, the following modifications are possible.

(1) In the above embodiment, the two purification units 21
Although 0 and 220 are provided with a monolithic ceramic carrier as a carrier for the active ingredient, they may be provided with a monolithic metal carrier instead.

(2) In the above embodiment, the two purification units 21
In order to regenerate the purification function of 0, 220, the exhaust gas air-fuel ratio is made rich by injecting a reducing agent. Along with this, additional fuel is added into the combustion chamber during the latter half of the expansion stroke of the engine or during the exhaust stroke. You may make it eject.
In this way, it is possible to reduce the frequency of the opening / closing operation of the adjusting valves 231, 232, the frequency of reducing agent injection by the reducing agent injection nozzles 261, 262, the amount of reducing agent injection, and the like.

(3) In the above embodiment, each purifying section 210,
220 is carbon-containing fine particles or NOx contained in the exhaust gas
Has a function of purifying the
0 may have only the function of purifying NOx.
In this case, a filter for collecting carbon-containing fine particles may be separately provided in the exhaust passage 30 on the upstream side of the purifying units 210 and 220. Note that this filter is
For example, it is provided in a manifold passage portion of the exhaust passage 30 connected to the four combustion chambers # 1 to # 4.

Further, in the above embodiment, the purification unit 20
0 is equipped with the 1st and 2nd purification | cleaning part 210,220 in each of the 1st and 2nd branch passages 30b1 and 30b2, but may further be equipped with another purification | cleaning part. For example, the main passage 3 on the downstream side of the purification unit 200
A third purifying unit may be provided in 0a2. The third purification unit is, for example, a NOx storage reduction catalyst or a NOx selective reduction catalyst having a NOx purification function.
A catalyst may be supported. In addition, the third purification unit is N
Instead of the Ox catalyst, the reducing substance H contained in the exhaust gas
An oxidation catalyst (for example, platinum Pt or palladium Pd) capable of oxidizing C and CO into carbon dioxide and water (steam) may be supported.

That is, in the above embodiment, the two purification sections 210 and 220 have a function of purifying the particulate matter and the nitrogen oxides contained in the exhaust gas, but generally, at least the exhaust gas. It should have a function of purifying nitrogen oxides contained therein. Further, when the third purification unit is provided in the exhaust passage on the downstream side of the confluence portion of the two branch passages, the third purification unit removes at least the specific gaseous substance contained in the exhaust gas. It should have a function of purifying. In addition, if the third purification unit is provided, there is an advantage that the exhaust gas can be further purified.

(4) In the first embodiment (FIG. 3), the two adjusting valves 231 and 232 are provided on the downstream side of the two purification units 210 and 220, but on the upstream side of the two purification units. It may be provided. In addition, in the fifth embodiment (FIG. 22), one adjusting valve 231E has two branch passages 30b.
Although it is provided at the confluence portion of 1, 30b2, it may be provided at the branch portion to the two branch passages.

Generally, it is only necessary to include a valve capable of changing the flow passage cross-sectional area of a part of each branch passage and to provide an adjusting portion for adjusting the exhaust gas flow rate in each branch passage.

(5) In the first embodiment (FIG. 3), the control section is provided with two sets of pressure sensors 121 to 124, and the differential pressures ΔP1 and ΔP2 of the respective purification sections 210 and 220 are predetermined target values. At this time, the reducing agent is injected into each of the branch passages 30b1 and 30b2. In the sixth embodiment (FIG. 23), the control unit includes a pair of pressure sensors 121 and 122, and each branch passage 30b1 when the differential pressure ΔP1 of the first purification unit 210 reaches a predetermined target value. , 30b2 are injected with a reducing agent. In the seventh embodiment (FIG. 24), the control unit includes a pair of pressure sensors 121G and 122G, and inside the respective branch passages 30b1 and 30b2 when the differential pressure ΔP3 of the purification unit 200G reaches a predetermined target value. Is injecting a reducing agent.

Thus, the reducing agent injection timing is
It can be determined using the differential pressure of the purification unit, the differential pressure of the purification unit, or the like, but may be determined using another method.

For example, the control unit is provided with only one pressure sensor 121G for measuring the pressure (also called "back pressure") in the upstream main passage 30a1 shown in FIG. 24, and the back pressure has a predetermined target value. A reducing agent may be injected at the time. This makes it possible to configure the purification unit relatively easily.

Further, the control section may be provided with a flow meter capable of directly measuring the flow rate of the exhaust gas flowing through the first purification section 210. In this case, the control unit may inject the reducing agent when the flow rate of the exhaust gas reaches a predetermined target value.

Furthermore, the control unit controls each of the adjusting valves 231 and 23.
It is also possible to set a time from the time when the opening / closing operation of No. 2 is started to the injection start time of the reducing agent and adjust the time according to the operating state of the engine.

In this way, when the control unit controls the adjusting unit to adjust the exhaust gas flow rate in the one branch passage in which the selected one purifying unit is provided to be substantially the predetermined amount, The regenerant injection part may be controlled to inject the regenerant into one of the branch passages. As in the third embodiment, the control unit stops the operation of the regulating valve and injects the reducing agent when the flow rate of the exhaust gas flowing through one of the selected purification units becomes almost the predetermined amount. You may

In this way, if the regenerant is injected at such a time that the flow rate (or space velocity) of the exhaust gas flowing through one of the purification sections becomes almost a predetermined amount, the regenerant will be evenly distributed in the exhaust gas. The particle size of the regenerant can be adjusted to an appropriate size. Further, the injection amount of the regenerant for making the exhaust gas air-fuel ratio rich can be reduced. As a result, the purification function of each purification unit can be efficiently regenerated.

(6) In the above embodiment, the exhaust passage 30
Includes two branch passages 30b1 and 30b2, but may include three or more branch passages. In this case also, the purifying unit is provided in each branch passage.

(7) In the above embodiments, the case where the exhaust gas purifying apparatus of the present invention is applied to a diesel engine has been described, but instead of this, a gasoline engine of the type that directly injects gasoline into the combustion chamber, etc. It may be applied to other internal combustion engines.

Further, the exhaust gas purifying apparatus of the present invention can be applied to various internal combustion engines for vehicles, ships, and stationary.

That is, the exhaust gas purifying apparatus of the present invention is
It can be applied to an internal combustion engine including a combustion chamber.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a diesel engine 100 to which an exhaust gas purification device of the present invention is applied.

FIG. 2 is an explanatory diagram showing an outline of combustion of a diesel engine 100 (FIG. 1).

FIG. 3 is an explanatory view showing the purification unit 200 of FIG. 1 in an enlarged manner.

FIG. 4 is an explanatory diagram showing the flow of exhaust gas inside the purification unit 200 (FIG. 3).

5 is an explanatory diagram showing the flow of exhaust gas inside the purification unit 200 (FIG. 3). FIG.

FIG. 6 is an explanatory diagram showing the flow of exhaust gas inside the purification unit 200 (FIG. 3).

FIG. 7 is an explanatory diagram showing a first purification unit 210 (FIG. 3).

FIG. 8 is an explanatory diagram schematically showing the functions of an active metal 218 and a cocatalyst 219 carried on the partition wall 214 of the first purification section 210 in a state where the oxygen concentration of exhaust gas is relatively high.

FIG. 9 is an explanatory diagram schematically showing the functions of an active metal 218 and a cocatalyst 219 carried on the partition wall 214 of the first purification section 210 when the oxygen concentration of exhaust gas is relatively low.

FIG. 10 is an explanatory diagram showing how the first reducing agent injection nozzle 261 injects the reducing agent into the first branch passage 30b1.

FIG. 11 is a flowchart showing a process when reproducing the purification function of the first purification unit 210.

12 is an explanatory diagram showing changes in the exhaust gas flow rate Q1 in the first purification unit 210 and changes in the differential pressure ΔP1 of the first purification unit 210. FIG.

13 is an explanatory diagram showing changes in the exhaust gas flow rate Q2 in the second purification unit 220 and changes in the differential pressure ΔP2 of the second purification unit 220. FIG.

FIG. 14 is an explanatory diagram showing changes in the exhaust gas flow rate Q1 and changes in the differential pressure ΔP1 when the exhaust gas flow rate Q0 changes in the initial state, and corresponds to FIG.

FIG. 15 is an explanatory diagram showing changes in the exhaust gas flow rate Q1 and changes in the differential pressure ΔP1 when the temperature of the first purification section 210 becomes relatively high.

FIG. 16 is an explanatory diagram showing a purification unit 200B capable of measuring the temperatures of the purification units 210 and 220.

FIG. 17 is an explanatory diagram showing a case where the target value of the differential pressure ΔP1 is changed according to the temperature of the first purification section 210 in FIG.

FIG. 18 is a flowchart showing a process when regenerating the purification function of the first purification unit 210 in the third embodiment.

19 shows changes in the exhaust gas flow rate Q1 in the first purification unit 210 and changes in the differential pressure ΔP1 in the first purification unit 210 when the first adjustment valve 231 is stopped at the intermediate opening state. FIG. 13 is an explanatory diagram and corresponds to FIG. 12.

20 shows changes in the exhaust gas flow rate Q2 in the second purification unit 220 and changes in the differential pressure ΔP2 in the second purification unit 220 when the first adjustment valve 231 is stopped in the intermediate opening state. FIG. 14 is an explanatory diagram and corresponds to FIG. 13.

FIG. 21: Purification unit 2 capable of measuring exhaust gas air-fuel ratio
It is explanatory drawing which shows 00D.

FIG. 22 is an explanatory diagram showing a purification unit 200E of a fifth embodiment.

FIG. 23 is an explanatory diagram showing a purification unit 200F according to a sixth embodiment.

FIG. 24 is an explanatory diagram showing a purification unit 200G according to a seventh embodiment.

[Explanation of symbols]

10 ... Engine body 13 ... Fuel supply pump 14 ... Fuel injection nozzle 20 ... Intake passage 22 ... Air cleaner 24 ... Intercooler 26 ... Throttle valve 30 ... Exhaust passage 30a1, 30a2 ... Core passage 30b1, 30b2 ... Branch passage 40 ... Supercharger 41 ... Turbine 42 ... Compressor 43 ... Shaft 45 ... Actuator 60 ... EGR passage 62 ... EGR cooler 64 ... EGR valve 90 ... ECU (electronic control unit) 100 ... Diesel engine 121-124, 121G, 122G ... Pressure sensor 131, 132 ... Temperature sensor 141, 142 ... Air-fuel ratio sensor 200, B, D, E, F, G ... Purification unit 210 ... First purification section 212 ... Small passage 214 ... Partition wall 216 ... Sealing plate 218 ... Active metal 219 ... Promoter 220 ... Second purification section 230, 230E ... Adjustment unit 231, 232, 231E ... Regulator valve 236, 237, 236E ... Driving unit 260 ... Reducing agent injection part 261, 262 ... Reducing agent injection nozzle 268 ... Reductant supply pump

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/08 F01N 3/24 E 4D058 3/24 3/36 B 3/36 C 7/08 B 7 / 08 F02D 9/04 C F02D 9/04 E B01D 46/42 B // B01D 46/42 53/36 103B F term (reference) 3G004 BA06 BA09 DA24 EA01 3G065 AA01 AA03 AA04 AA09 AA10 CA12 DA04 EA07 GA06 GA08 GA10 GA46 KA03 3G090 AA02 AA03 AA06 BA02 CA02 CA03 CA04 CB02 CB25 DA04 DA09 DA13 DA18 EA02 EA05 EA06 3G091 AA10 AA11 AA18 AA28 AB06 AB13 BA04 BA11 BA14 CA18 CA27 HA06 HA46 HA06 HA16 EA02 EA08 EA08 EA02 EA08 EA08 EA02 EA08 EA02 AB01 AB02 AC00 AC02 BA14X BA30X BB02 BD03 CC24 CC26 CC27 CC33 CD05 DA01 DA02 DA07 DA10 4D058 JA32 JB06 MA41 PA04 SA08 TA02

Claims (8)

[Claims] 1. An exhaust gas purification device applied to an internal combustion engine having a combustion chamber, for purifying exhaust gas discharged from the combustion chamber, the exhaust gas purifying device passing through the exhaust gas discharged from the combustion chamber. An exhaust passage including two branch passages that are branched and merge in the middle of the passage, and two purifications provided in each of the branch passages for purifying at least nitrogen oxides contained in the exhaust gas. An adjusting unit for adjusting the flow rate of exhaust gas in each of the branch passages, and a purification function of each of the purifying units. Regenerant to
A regenerant injecting section for injecting into each of the branch passages, and a control section for controlling the adjusting section and the regenerant injecting section, wherein the control section controls the adjusting section. When the exhaust gas flow rate in one of the branch passages provided with the one of the purifying section is adjusted to be substantially a predetermined amount, the regenerant injection section is controlled so that the regenerant injection section An exhaust gas purification device characterized by injecting a regenerant. 2. The exhaust gas purifying apparatus according to claim 1, wherein the control unit includes a pressure measuring unit for measuring a pressure in each of the branch passages on the upstream side and the downstream side of the purifying unit. The exhaust gas purifying device, wherein the control unit causes the regenerant to be injected when the difference between the two pressures of the one purifying unit reaches a predetermined target value. 3. The exhaust gas purification device according to claim 2, wherein the control unit further includes a temperature measurement unit for measuring the temperature of each of the purification units, and the control unit An exhaust gas purification device that changes the predetermined target value according to the temperature of the purification unit. 4. The exhaust gas purification apparatus according to claim 1, wherein the control unit stops the operation of the valve when injecting a regenerant. 5. The exhaust gas purifying apparatus according to claim 4, wherein the control unit includes pressure measuring units for measuring pressures in the branch passages on the upstream side and the downstream side of the purifying units. The exhaust gas purifying apparatus, wherein the control unit stops the valve and injects a regenerant when a difference between the two pressures of the one purifying unit reaches a predetermined target value. 6. The exhaust gas purifying apparatus according to claim 5, wherein the control unit further includes a temperature measuring unit for measuring a temperature of each of the purifying units, and the control unit includes the one of An exhaust gas purification device that changes the predetermined target value according to the temperature of the purification unit. 7. The exhaust gas purifying apparatus according to claim 1, wherein each of the purifying units further has a function of purifying particulate matter contained in the exhaust gas. 8. The exhaust gas purifying apparatus according to claim 1, further comprising: an exhaust gas passage, which is provided in the exhaust passage downstream of a confluence portion of the two branch passages, and which is included in at least the exhaust gas. Equipped with another purification unit for purifying gaseous substances,
Exhaust gas purification device.