JPH0598932A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To use a filter continuously by eliminating the exhaust particulate piled on a filter without using a reconditioning device for recondition a filter with a burner, which gives a damage to the fuel economy and a heater, which invites the increase of the capacity of a buttery or a motor. CONSTITUTION:A first after-treatment device 34 provided with a filter 31 and the catalyst 33 and a second after-treatment device 36 provided with a filter 35 are located in parallel with each other. When the collection quantity of the exhaust particulate exceeds a predetermined quantity, and at the time of reconditioning the filter 31 and 35, a part of the exhaust passed through one after-treatment device is passed through the other after-treatment device by the inverted flow, and with this passed exhaust, the particulate collected by the other after-treatment device is fed back to an intake system to burn it in a combustion chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine having an exhaust aftertreatment device for purifying the exhaust gas by passing the exhaust gas therethrough.

[0002]

2. Description of the Related Art Of the particulate components in exhaust gas emitted from diesel engines, soluble organic substances (SOF) components are partially oxidized and removed by an oxidation catalyst, and other carbon particles appear as so-called black smoke. Are adhered and collected by a filter made of ceramic foam or the like. The adhered and collected carbon particles gradually accumulate as the amount of collection increases, and if they remain as they are, the exhaust pressure rises and the engine performance is adversely affected, so that they cannot be used. For this reason, it is necessary to combust and remove the deposited carbon particles by a regeneration device such as a heater or a burner to regenerate the filter.

An example of an exhaust gas purifying device having such a filter regenerating device is disclosed in Japanese Utility Model Publication No. 63-38328. As shown in FIG. 7, this is because the honeycomb type filter 3 housed in the connecting pipe 1 is arranged so that the flow direction of the exhaust gas is alternately inverted.
The exhaust pipe 4 is branched into a first branch pipe 5 and a second branch pipe 7,
A flow control valve 9, at the connection between each branch pipe 5, 7 and the connecting pipe 1,
A burner 1 for combusting and removing carbon particles is provided inside the connecting pipe 1 near both ends of the filter 3 as well.
3 and 15 are provided respectively.

In this case, as shown in FIG. 7, the exhaust gas flows in through the first branch pipe 5 from one end face of the filter 3 and flows out from the other end face thereof, and when a predetermined amount of carbon particles are accumulated, the exhaust gas flows in. The burner 13 on the side end face is ignited to burn and remove the carbon particles adhering and collected in the vicinity of the burner 13.
Play back one side. After that, the flow control valves 9, 1
By changing 1 as shown by the broken line position, the exhaust gas passes through the second branch pipe 7 and the flow direction with respect to the filter 3 is reversed. When the collection proceeds in this state and the accumulated amount becomes equal to or more than a predetermined amount, the burner 15 on the opposite side to the above is ignited to regenerate the other surface of the filter 3.

[0005]

In such a conventional exhaust emission control device, the exhaust gas flows out after the regeneration because the filter is alternately collected and regenerated by reversing the flow direction of the exhaust gas with respect to the filter. Fine particles remaining on the side end faces are also burned and removed during regeneration after reversal, and the filter is efficiently regenerated. However, it is generally necessary to raise the temperature to 600 ° C. or higher during regeneration, which requires a large amount of fuel for the burner, which impairs the fuel economy of the diesel engine. Further, even when a heater is used as a regenerator, there are many problems to be solved in practical use, such as an increase in battery and generator capacity accompanying an increase in power consumption in order to maintain a high temperature.

Therefore, the object of the present invention is to make it possible to continuously use the post-treatment device without using a burner which impairs fuel economy or a regeneration device by a heater which causes an increase in battery or generator capacity. I am trying.

[0007]

In order to achieve the above object, the present invention has a first exhaust passage and a second exhaust passage which are connected in parallel with each other in the middle of the exhaust passage. A first aftertreatment device and a second aftertreatment device for cleaning the exhaust gas are provided in the second exhaust passage, and the first exhaust passage is provided at an upstream side branch portion between the first exhaust passage and the second exhaust passage. Is provided and an upstream side control valve that switches between a state in which the second exhaust passage is closed and a state in which the first exhaust passage is closed at the downstream confluence of the first exhaust passage and the second exhaust passage are provided. A downstream side control valve that switches between a state in which the exhaust passage is closed and a state in which the exhaust passage is in an intermediate position is provided, and the intake passage, the first post-treatment device, and the second exhaust valve are provided via an exhaust gas recirculation passage.
A first exhaust passage and a second upstream of each of the aftertreatment devices
An exhaust valve is connected to the exhaust gas recirculation passage, and an on-off valve is provided in the exhaust gas recirculation passage to allow or block the recirculation of the recirculated exhaust gas from the first exhaust passage and the second exhaust passage.
When one of the post-treatment devices has a collection amount of exhaust particulates of a predetermined amount or more, the exhaust gas discharged from the engine is passed to the other post-treatment device, and a part of the passed exhaust gas A control means for controlling the opening / closing of each of the upstream side control valve, the downstream side control valve, and the opening / closing valve is provided so that the post-processing device is allowed to flow backward, pass through, and be returned to the intake system.

[0008]

According to the exhaust emission control device having such a configuration, for example, when the amount of particulates deposited by the second post-treatment device exceeds a predetermined amount, the upstream side control valve closes the second exhaust passage and controls the downstream side. The valve is at the intermediate position, and the opening / closing valve of the exhaust gas recirculation passage connected to the second exhaust passage is opened. As a result, exhaust is the first
After passing through the aftertreatment device, the fine particles are collected by the first aftertreatment device, and the exhaust gas flows back through the second aftertreatment device through the downstream side control valve at the intermediate position and passes through the second aftertreatment device. The particulates accumulated in the processing device are carried away by the exhaust gas passing therethrough, flow into the intake passage through the exhaust gas recirculation passage, and are reburned in the combustion chamber.

Further, when the amount of fine particles deposited by the first post-treatment device exceeds a predetermined amount, the upstream side control valve is set to the first control valve.
The exhaust passage is closed and the downstream side control valve is at the intermediate position.
The opening / closing valve of the exhaust gas recirculation passage connected to the exhaust passage opens. As a result, the exhaust gas passes through the second aftertreatment device, the exhaust particulates are collected by the second aftertreatment device, and the exhaust gas flows backward through the downstream side control valve at the intermediate position, so that the exhaust gas flows through the first aftertreatment device. The exhaust particulate matter that has passed through and is deposited in the first post-treatment device at this time is carried away by the exhaust gas passing therethrough, flows into the intake passage through the exhaust gas recirculation passage, and is reburned in the combustion chamber.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

An exhaust passage 23 and an intake passage 25 are connected to the engine body 21 of the diesel engine, and the exhaust passage 23 is branched into a first exhaust passage 27 and a second exhaust passage 29 on the way. In the first exhaust passage 27, a filter 31 that mainly collects and collects carbon particles of exhaust particles in the exhaust, and an SOF that is arranged downstream of the filter 31.
A catalyst 33 for oxidizing and removing a part of the components is arranged in series with each other. The filter 31 and the catalyst 33 make the first
The post-processing device 34 is configured. On the other hand, the second exhaust passage 2
9 is provided with a filter 35 similar to the filter 31. With this filter 35, the second post-processing device 3
6 is composed.

An upstream control valve 37 is provided at a branch portion of the first exhaust passage 27 and the second exhaust passage 29 on the exhaust upstream side. The upstream control valve 37 is switched between a state of A position for closing the second exhaust passage 29 shown by a solid line and a state of B position for closing the first exhaust passage 27 shown by a two-dot chain line. On the other hand, a downstream side control valve 39 is provided at the confluence portion of the first exhaust passage 27 and the second exhaust passage 9 on the exhaust downstream side. The downstream side control valve 39 is in the A position for closing the second exhaust passage 29, which is indicated by the solid line, in the B position for closing the first exhaust passage 27, which is indicated by the alternate long and two short dashes line, and in the A and B positions, which are indicated by the alternate long and short dash line. It switches to the state of the C position intermediate between and.

A first merging passage 41 and a second merging passage 43 are connected in communication with the first exhaust passage 27 near the upstream side of the filter 31 and the second exhaust passage 29 near the upstream side of the filter 35, respectively. Both meet at the upstream end. The merging portion and the intake passage 25 are connected to each other by a communication passage 47 having a first exhaust gas recirculation amount control valve 45 on the way, and the communication passage 47 and the first and second merging passages 41, 4 are connected.
3 constitutes a first exhaust gas recirculation passage 49. First,
A merging control valve 50 is provided at the merging portion between the second respective merging passages 41 and 43. The merging control valve 50 switches between a state of the A position for closing the first merging passage 41 indicated by the solid line and a state of the B position for closing the second merging passage 43 indicated by the two-dot chain line. Therefore, the merging control valve 50 includes an opening / closing valve that allows / blocks the recirculation of the recirculated exhaust gas from the first exhaust passage 27 in the exhaust gas recirculation passage including the communication passage 47 and the first merging passage 41. Allowing the recirculation of the recirculated exhaust gas from the second exhaust passage 29 into the exhaust gas recirculation passage formed of the two merging passages 43.
Configure an on-off valve that shuts off. In addition, the exhaust passage 23 upstream of the upstream control valve 37 and the first exhaust gas recirculation amount control valve 45.
The first exhaust gas recirculation passage 49 on the upstream side is communicatively connected by a second exhaust gas recirculation passage 53 having a second exhaust gas recirculation amount control valve 51 in the middle thereof.

In the exhaust passage 23 near the second exhaust gas recirculation passage 53, the first and second aftertreatment devices 3 are provided.
An upstream temperature sensor 55 for detecting the exhaust temperature T ₁ on the upstream side of the exhaust gas 4, 36 is mounted, and the exhaust temperature T on the downstream side of the catalyst 33 is installed in the first exhaust passage 27 on the downstream side of the first aftertreatment device 36.
A downstream temperature sensor 57 for detecting ₂ is attached.

The temperature detected by each of the temperature sensors 55 and 57 serves as a criterion for determining the catalyst conversion temperature and the catalyst heat resistant temperature of the catalyst 33 of the first post-treatment device 34, and the temperature signal thereof is, for example, from a microcomputer or the like. It is input to the configured control unit 59. In addition to the above, the control unit 59 includes a rotation sensor 61 that detects the engine speed, an opening sensor 61 that detects the opening of a control lever that controls the amount of fuel supplied to the engine body 21, and the like.
Each detection signal of engine operating conditions is input. Based on these input signals, the control unit 59 controls the upstream and downstream control valves 37 and 39, the merge control valve 50, and the first and second exhaust gas recirculation amount control valves 45 and 51, respectively. Open and close control.

The first and second post-processing devices 34 and 3 are also provided.
The filters 31 and 35 of No. 6 remove the collected fine particles by a regeneration control described later so that they can be continuously used when the amount of collected fine particles exceeds a predetermined amount. It may be based on when the exhaust pressure difference before and after the filter becomes a predetermined value or more.

The control operation of the control unit 59 for each control valve is set in four cases as shown in Table 1.

[0018]

[Table 1]

Case 1 (see FIG. 2) ... The catalyst inlet exhaust temperature T ₁ detected by the upstream temperature sensor 55 is equal to or higher than the catalyst conversion temperature, and the catalyst outlet exhaust temperature T ₂ detected by the downstream temperature sensor 57.
Is equal to or lower than the heat resistant temperature of the catalyst, the upstream side control valve 37 and the downstream side exhaust valve 39 are both in the A position for closing the second exhaust passage 29, and the merging side control valve 50 is in the A position for closing the first merging passage 41. The first exhaust gas recirculation amount control valve 45 is closed and the second exhaust gas recirculation amount control valve 51 is opened.

Case 2 (see FIG. 3) ... Catalyst inlet exhaust temperature T ₁
Is below the catalyst conversion temperature or above the catalyst heat resistance temperature, and the catalyst outlet exhaust temperature T ₂ is above the catalyst heat resistance temperature, the upstream side control valve 3
7 and the downstream side exhaust valve 39 are both in the B position for closing the first exhaust passage 27, the merging side control valve 50 is in the B position for closing the second merging passage 43, the first exhaust gas recirculation amount control valve 45 is closed, and the second exhaust gas recirculation amount control valve 45 is closed.
The exhaust gas recirculation amount control valve 51 is opened.

Case 3 (see FIG. 4) ... Catalyst inlet exhaust temperature T ₁
And both of the catalyst outlet exhaust temperature T ₂ are below the catalyst heat resistant temperature,
The upstream side control valve 37 is in the A position for closing the second exhaust passage 29, the downstream side exhaust valve 39 is in the neutral position C position, and the merging side control valve 50 is in the A position for closing the first merging passage 41. The recirculation amount control valve 45 opens and the second exhaust gas recirculation amount control valve 51
Closes.

Case 4 (see FIG. 5) ... Similar to case 3, when both the catalyst inlet exhaust temperature T ₁ and the catalyst outlet exhaust temperature T ₂ are below the catalyst heat resistant temperature, the upstream side control valve 37 causes the first exhaust passage 27 to operate.
B, the downstream side exhaust valve 39 is in the neutral position C, and the merging side control valve 50 closes the second merging passage 43.
At the position, the first exhaust gas recirculation amount control valve 45 is opened and the second exhaust gas recirculation amount control valve 51 is closed.

Such four control operation examples are selectively controlled by the procedure of the flowchart shown in FIG. First, it is determined whether the engine speed exceeds 50 rpm (step S1), and if it exceeds 50 rpm, the present system operates. When the engine speed exceeds 50 rpm, the upstream side sensor 55 and the downstream side sensor 57 respectively read the catalyst inlet exhaust temperature T ₁ and the catalyst outlet exhaust temperature T ₂ (steps S2 and S3).

Next, the deceleration operation condition for fuel cut and the exhaust gas recirculation (EGR) region in which exhaust gas is recirculated to the intake system are determined (steps S4 and S5), and the filter of the first aftertreatment device 34 is further determined. It is judged whether it is the regeneration time of 31 (step S6) and whether it is the regeneration time of the filter 35 of the second post-processing device 36 (step S7). Deceleration operation condition or EGR
If it is not in the range, or it is not in the deceleration operation condition and EG
In the R region, when neither of the first and second aftertreatment devices 34 and 36 is in the regeneration timing, the exhaust temperature T ₁ detected by the upstream sensor 55 is compared with the catalyst conversion temperature (step S
8) The exhaust gas temperature T ₂ detected by the downstream side sensor 57 is compared with the catalyst heat resistant temperature (step S9). Here, when the exhaust temperature T ₁ is equal to or higher than the catalyst conversion temperature and the exhaust temperature T ₂ is equal to or lower than the catalyst heat resistant temperature, that is, in this case, the operation range in which the particulates in the exhaust are reduced by the filter and the conversion of the catalyst 33 is performed. Since the exhaust gas temperature is within the temperature range in which the temperature can be controlled, case 1 in FIG. 2 is controlled.

At this time, the exhaust gas flowing through the exhaust passage 23 flows into the first exhaust passage 27 and passes through the filter 31 of the first post-treatment device 34 to collect carbon particles, and further passes through the catalyst 33. At this time, the SOF component adheres and is oxidized and removed, and the exhaust gas purified in this way is released into the atmosphere. Further, a part of the exhaust gas flowing through the exhaust passage 23 is
It is recirculated from the intake passage 25 to the combustion chamber through the second exhaust gas recirculation passage 53. In this case, since the exhaust gas to be recirculated is from the upstream side of the first aftertreatment device 34, the engine body 21
The fine particles that have just been generated are condensed and recirculated before they are enlarged, so that the re-combustion of these fine particles in the combustion chamber is ensured, and the discharge amount of the particles is reduced.

In step S8, the exhaust temperature T ₁ is lower than the catalyst conversion temperature, or in step S9 the exhaust temperature T ₂
When the temperature exceeds the heat resistant temperature of the catalyst, the control of case 2 in FIG. 3 is performed in order to prevent the catalyst 33 from being overcooled by the low temperature exhaust and the catalyst 33 from being burnt out by the high temperature exhaust.

At this time, the exhaust gas flowing through the exhaust passage 23 flows into the second exhaust passage 29, passes through the filter 35 of the second post-treatment device 36, and the carbon particles are collected and released into the atmosphere. Since the exhaust gas flowing through the exhaust passage 23 bypasses the catalyst 33 of the first post-treatment device 34, supercooling of the catalyst 33 due to low temperature exhaust and burnout of the catalyst 33 due to high temperature exhaust are avoided. In this case, oxidation at the catalyst 33 is not problematic at low temperatures below the catalyst conversion temperature, and therefore there is no problem. At high temperatures above the catalyst heat resistance temperature, the catalyst 33 is prevented from being burnt out and durability is improved.

When the amount of carbon particles collected in the filter 31 of the second post-treatment device 36 in step S6 becomes a predetermined amount or more and it is time to regenerate the filter 35 (at this time, exhaust temperatures T ₁ , T ₂ Is under the catalyst heat resistant temperature), the control of Case 3 in FIG. 4 is performed.

At this time, the exhaust gas flowing through the exhaust passage 23 flows into the first exhaust passage 27, the carbon particles are collected by the filter 31, and the SOF component is oxidized and removed by the catalyst 33. Since the second exhaust gas recirculation amount control valve 45 is open, a part of the exhaust gas that has passed through the catalyst 33 flows back to the second exhaust passage 29 side via the downstream side control valve 39 at the C position. .. The exhaust gas that has flowed backward flows through the filter 3 of the second post-treatment device 36.
5, the carbon particles deposited on the filter 35 at this time are carried away by the exhaust gas passing therethrough, flow into the intake passage 25 through the first exhaust gas recirculation passage 49 including the second merging passage 43, and are burned. Burned out indoors.

Further, when the amount of carbon particles collected in the filter 31 of the first post-treatment device 34 in step S7 becomes a predetermined amount or more and it is time to regenerate the filter 31 (at this time, exhaust temperatures T ₁ , T _2). Is under the catalyst heat resistant temperature), the control of Case 4 in FIG. 5 is performed.

At this time, the exhaust gas flowing through the exhaust passage 23 flows into the second exhaust passage 29, and carbon particles are collected by the filter 35. Part of the exhaust gas that has passed through the filter 35 is
Since the second exhaust gas recirculation amount control valve 45 is open, the first exhaust passage 27 passes through the downstream side control valve 39 that is in the C position.
Backflow to the side. The backflowed exhaust gas passes through the catalyst 33 and the filter 31 of the first post-treatment device 34, and the carbon particles accumulated on the filter 31 at this time are carried away by the passing exhaust gas, and together with the exhaust gas, the first confluence passage 41 is included. 1
It flows into the intake passage 25 through the exhaust gas recirculation passage 49 and is burned and removed in the combustion chamber.

As described above, during the regeneration of the second and first post-treatment devices 36 and 34 shown in the cases 3 and 4, the carbon particles deposited on the filter 35 or the filter 31 flow backward through the exhaust gas. Since it is carried away to the combustion chamber side and reburned and removed, a special burner or heater dedicated to regeneration is not required at the time of regeneration, which does not impair fuel economy and increases the capacity of the battery or generator. The regeneration of the post-processing device can be efficiently performed without inviting.

When the case 3 or 4 is regenerated, it is feared that the fine particles recirculated to the combustion chamber will not be recombusted and will be discharged to the exhaust passage 23 again. Since it is collected by either of the filters 31, 35, there is no concern that it will be released into the atmosphere.

[0034]

As described above, according to the present invention, two post-treatment devices for purifying the exhaust gas by passing the exhaust gas are arranged in parallel with each other, and one of the post-treatment devices is regenerated when the post-treatment device is regenerated. Part of the exhaust gas that has passed through the device is made to flow backward through the other aftertreatment device by opening the exhaust gas recirculation amount control valve, and the particulates are returned to the intake system along with the exhaust gas that has passed and are burned in the combustion chamber. , A dedicated burner or heater for burning and removing fine particles accumulated in the aftertreatment device to regenerate becomes unnecessary, and as a result, the fuel economy is reduced by using the burner, and the battery or power generation by using the heater is eliminated. It is possible to avoid an increase in machine capacity.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an exhaust emission control device showing an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the exhaust gas purification device of FIG.

FIG. 3 is an operation explanatory view of the exhaust gas purification device of FIG. 1.

FIG. 4 is an operation explanatory view of the exhaust gas purification device of FIG. 1.

5 is an explanatory view of the operation of the exhaust emission control device of FIG.

6 is a flowchart showing a control operation of the exhaust emission control device of FIG.

FIG. 7 is an overall configuration diagram of an exhaust emission control device showing a conventional example.

[Explanation of symbols]

 23 Exhaust passage 27 First exhaust passage 29 Second exhaust passage 31, 35 Filter 33 Catalyst 34 First post-treatment device 36 Second post-treatment device 37 Upstream control valve 39 Downstream control valve 41 First merging passage 43 Second merging passage Passage 45 First exhaust gas recirculation amount control valve 49 First exhaust gas recirculation passage 50 Merge control valve 55 Upstream temperature sensor 57 Downstream temperature sensor 59 Control unit (control means)

Claims (1)

[Claims] 1. A first exhaust passage and a second exhaust passage, which are connected in parallel to each other in the middle of the exhaust passage, are interposed, and a first exhaust passage and a second exhaust passage are provided for cleaning the exhaust gas. A post-treatment device and a second post-treatment device are respectively provided, and switching between a state in which the first exhaust passage is closed and a state in which the second exhaust passage is closed is performed at an upstream branch portion of the first exhaust passage and the second exhaust passage. An upstream control valve is provided, and a state in which the first exhaust passage is closed and a state in which the second exhaust passage is closed is an intermediate position between these two states at the downstream merging portion of the first exhaust passage and the second exhaust passage. A downstream side control valve for switching to the state is provided, and the intake passage, the first post-treatment device, and the second exhaust passage are provided via an exhaust gas recirculation passage.
A first exhaust passage and a second upstream of each of the aftertreatment devices
An exhaust valve is connected to the exhaust gas recirculation passage, and an on-off valve is provided in the exhaust gas recirculation passage to allow or block the recirculation of the recirculated exhaust gas from the first exhaust passage and the second exhaust passage.
When one of the post-treatment devices has a collection amount of exhaust particulates of a predetermined amount or more, the exhaust gas discharged from the engine is passed to the other post-treatment device, and a part of the passed exhaust gas Exhaust gas purification of an internal combustion engine, characterized in that control means is provided for controlling opening / closing of each of the upstream side control valve, the downstream side control valve and the opening / closing valve so that the aftertreatment device is allowed to flow backward and to be passed back to the intake system. apparatus.