JP5318180B2 - Engine exhaust purification system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine exhaust purification device that can remove PMs from a DPF, and can recirculate exhaust gas during the regeneration of the DPF. <P>SOLUTION: The exhaust gas purification device includes: the DPF 60 which is arranged in a branched passage 50 out of branched passages 50, 52 which are formed by branching the middle of an exhaust passage 40 of an engine 10; a first valve 50a and a second valve 52a which open and close the branched passages 50, 52 at the upstream side of the DPF 60, respectively; an EGR pipe 54 which makes the branched passage 50 at the downstream side of the first valve 50a and an air-intake passage 20 of the engine 10 communicate with each other at the upstream side of the DPF 60; and an ECU 80 which controls the first valve 50a and the second valve 52a so as to close the branched passage 50 and to open the branched passage 52 at the regeneration of the DPF 60. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an exhaust emission control device for an engine that removes particulate matter (PM) from exhaust gas.

  As an exhaust gas purification device for purifying exhaust gas discharged from a diesel engine, there is one in which a diesel particulate filter (DPF) that collects and removes PM contained in exhaust gas is provided in an exhaust pipe. Since such a DPF is clogged due to an increase in collected PM, periodic regeneration processing such as incineration and oxidation removal of the collected PM is indispensable. However, in the forced regeneration type in which PM is ignited and incinerated, for example, when PM burns all at once, the DPF may overheat, which may cause heat damage such as melting or breakage. In addition, the continuous regeneration method in which PM is removed by oxidation may result in an insufficient regeneration process because a sufficient oxidation reaction cannot be obtained depending on the catalyst temperature. For this reason, as described in Japanese Patent Application Laid-Open No. 2004-108194 (Patent Document 1), the DPF is back-washed with high-pressure gas in the direction opposite to the flow downstream of the exhaust gas, thereby preventing the occurrence of heat damage. On the other hand, a DPF regeneration technique that is independent of the catalyst temperature has been proposed.

JP 2004-108194 A

  However, in the conventional proposed technique, PM can be removed even at a low temperature at which oxidation reaction does not easily occur while preventing the occurrence of thermal damage, but the backwashed PM is collected in a container provided on the upstream side of the DPF. Therefore, the DPF regeneration process could not be executed unless the engine was stopped. In addition, the process for removing the collected PM involves the removal of the container, and the work is complicated.

  Therefore, in view of the conventional problems as described above, the present invention provides an engine that can regenerate the PM by removing the PM from the DPF by backwashing the DPF with the exhaust, and can make the exhaust including the separated PM EGR. An object is to provide an exhaust emission control device.

Therefore, an exhaust emission control device for an engine according to claim 1 is disposed in a branch passage excluding at least one branch passage among a plurality of branch passages branched in the middle of the exhaust passage of the engine, and the PM in the exhaust gas And a branch passage that opens and closes a branch passage upstream of the filter in a branch passage in which the filter is disposed, and a branch passage that opens and closes the branch passage in a branch passage in which the filter is not disposed An opening / closing means, an EGR pipe communicating with the branch passage upstream of the filter and downstream of the branch passage opening / closing means and the intake passage of the engine, and a branch passage in which the filter is disposed when the filter is regenerated And the control means for controlling the branch passage opening / closing means so as to open the branch passage where the filter is not disposed, and the branch passages join when the filter is regenerated. And characterized in that the opening of the downstream side of the exhaust passage than the flow section, which is configured to include a degree of opening adjustment means for adjusting a multi-stage or continuously over the fully opened - fully closed according to the engine operating conditions, the To do.

The engine exhaust gas purification apparatus according to claim 2 is characterized in that the EGR pipe communicates with an intake passage upstream of a compressor of a supercharger provided in the engine.
According to a third aspect of the present invention, the control means integrates the operating time of the engine, and determines that it is the time to start the regeneration of the filter when the accumulated time exceeds a predetermined time.

  According to a fourth aspect of the present invention, the control means estimates the PM discharge flow rate according to the engine operating state, and when the integrated value of the discharge flow rate is equal to or higher than a first predetermined value, it is at the start of filter regeneration. It is characterized by determining.

  The invention according to claim 5 further includes differential pressure detection means for detecting the differential pressure between the upstream side and the downstream side of the filter, and the control means is configured so that if the detected differential pressure is equal to or higher than a predetermined pressure, It is characterized in that it is determined that the filter reproduction is started.

  According to a sixth aspect of the present invention, the control means estimates the separation flow rate of PM that separates from the filter in response to the engine operating state or the high-pressure gas supply flow rate from the start of the regeneration of the filter, and integrates the separation flow rate. When the value is equal to or greater than a second predetermined value, it is determined that the filter regeneration is completed.

According to the first aspect of the present invention, when the filter is regenerated, the upstream side of the branch passage where the filter is disposed is closed from the filter, while the branch passage where the filter is not disposed is opened. As a result, the exhaust gas flows to the branch passage where the filter is not arranged, and a part of the exhaust gas is diverted at the junction where the branch passage joins, and flows back to the branch passage where the filter is arranged. Then, this backflow exhaust gas backwashes the filter to release the collected PM, and is returned to the intake passage of the engine via the EGR pipe. For this reason, it is possible to regenerate the filter while the engine is operating without causing heat damage and without being influenced by the exhaust temperature, and it is possible to remove the collected PM by EGR. In addition, when the filter is regenerated, the opening degree of the exhaust passage downstream from the junction of the branch passages is adjusted in multiple stages or continuously from fully open to fully closed according to the engine operating state, thereby Since the exhaust gas flow rate flowing back to the branch passage in which the filter is disposed can be adjusted, the EGR rate can be adjusted.

  According to the invention described in claim 2, the EGR pipe communicates with the intake passage upstream of the compressor of the supercharger. Since the intake pressure here is lower than that of the intake passage downstream of the compressor, the exhaust gas including the separated PM can be easily recirculated in a wide range of engine operating conditions.

  According to the third to fifth aspects of the present invention, when the accumulated engine operation time becomes a predetermined time or more, and the integrated value of the PM discharge flow rate estimated according to the engine operation state becomes the first predetermined value or more. When the detected differential pressure is equal to or higher than the predetermined pressure, it can be determined that the regeneration of the filter is started, and the regeneration of the filter can be started.

  According to the sixth aspect of the present invention, it is determined that the regeneration of the filter is completed when the integrated value of the PM separation flow rate estimated according to the engine operating state is equal to or greater than the second predetermined value. For this reason, it is possible to perform filter regeneration that fluctuates the completion of regeneration in accordance with the flow rate of the fluid that backwashes the filter.

1 is an overall view of an exhaust emission control device for an engine according to a first embodiment. Flowchart explaining filter regeneration processing Overall view of an exhaust emission control device for an engine according to a second embodiment Overall view of an exhaust emission control device for an engine according to a third embodiment (A) PM emission map, (b) PM removal map explanatory diagram

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of an engine exhaust purification device. The diesel engine 10 includes a turbocharger 30 including a compressor 30 a interposed in the intake passage 20 and a turbine 30 b interposed in the exhaust passage 40.

  The exhaust passage 40 has a branch structure in which the middle is branched into a plurality of, for example, two branches, a first branch passage 50 and a second branch passage 52. A branch passage excluding at least one of the two branch passages, for example, the first branch passage 50, includes a first valve 50a that can be remotely operated to open and close the passage along the exhaust flow direction, and an exhaust. The DPF 60 that collects the PM therein is arranged in this order. In addition, an EGR pipe in which a check valve 54a that opens only in a direction in which exhaust gas is recirculated to the intake passage 20 of the diesel engine 10 is disposed in the first branch passage 50 positioned between the first valve 50a and the DPF 60. 54 is connected. On the other hand, the second branch passage 52 is provided with a remotely operable second valve 52a for opening and closing the passage. As the branch passage opening / closing means, two valves 50a and 52a are provided in the two branch passages 50 and 52, respectively, but the branch portion 40a branching to the two branch passages 50 and 52 is like a three-way switching valve. A multidirectional switching valve may be provided.

  In addition, a butterfly valve 42 that controls the exhaust passage area in multiple stages or continuously from fully open to fully closed is arranged in the exhaust passage 40 located downstream of the joining portion 40b where the two branch passages join. Established.

  As a differential pressure detection means for detecting the differential pressure between the upstream side and the downstream side of the DPF 60, a pressure sensor 70a for detecting the exhaust pressure in the exhaust passage 40 located upstream of the exhaust of the branching portion 40a, and the exhaust downstream of the junction 40b And a pressure sensor 70b for detecting an exhaust pressure in the exhaust passage 40 located at the position. Note that the differential pressure detection means may be one that detects the differential pressure between the upstream side and the downstream side of the DPF 60 with a single sensor. The diesel engine 10 includes an engine speed sensor 72 that detects the engine speed Ne, and an engine load Q that detects an engine load Q such as a fuel injection amount, an intake air flow rate, an intake negative pressure, a required torque, and a boost pressure. A sensor 74 is attached.

  The pressure signals Pa and Pb, the rotational speed Ne, and the engine load Q output from the sensors 70a, 70b, 72, and 74 are input to an electronic control unit (ECU) 80 built in the computer. The ECU 80 executes a control program stored in a ROM (Read Only Memory) or the like, for example, an engine operating state such as a differential pressure P obtained from the pressure signals Pa and Pb, a rotational speed Ne, and an engine load Q. Accordingly, the first valve 50a, the second valve 52a, the butterfly valve 42 and the like are appropriately driven and controlled.

  The initial state of the valve at the time of starting the diesel engine 10 is, for example, that the first valve 50a is in an open state and the second valve 52a is in a closed state. When exhaust gas is discharged from the diesel engine 10 in this state, the exhaust gas rotates from the exhaust manifold to the turbine 30b and flows to the exhaust passage 40, and is led from the branch portion 40a to the first branch passage 50 to be the EGR pipe. 54 and DPF 60. The exhaust gas guided to the EGR pipe 54 is returned to the intake passage 20 on the downstream side of the supercharger 30 through the check valve 54a. The exhaust guided to the DPF 60 flows from the junction 40b to the exhaust passage 40 after PM is collected. At this time, the opening degree of the butterfly valve 42 is adjusted, and the EGR rate is controlled.

FIG. 2 shows the contents of a control program that is repeatedly executed in the ECU 80 of FIG.
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), it is determined whether or not the regeneration of the DPF 60 is started. Here, if the differential pressure P between the detected pressure signals Pa and Pb is equal to or higher than a first predetermined pressure that does not affect the engine output, it is determined that the regeneration of the DPF 60 is started, and the process proceeds to Step 2 (Yes). On the other hand, otherwise, it is determined that it is not at the start of regeneration of the DPF 60, and the process proceeds to Step 6 (No). In step 6, the EGR rate is calculated according to the engine operating state, and the opening degree of the butterfly valve 42 is adjusted based on the EGR rate, thereby adjusting the EGR rate.

  In step 2, the first valve 50a is closed, the second valve 52a is opened, and valve switching control at the start of filter regeneration is executed. By this valve switching control, the exhaust gas flowing through the exhaust passage 40 during the regeneration of the filter flows from the branching portion 40a to the second branching passage 52, and a part thereof is diverted at the joining portion 40b to the first branching passage 50. And backflow. Then, this backflow exhausts the DPF 60 by backwashing to regenerate the trapped PM, and the exhaust containing the detached PM flows to the EGR pipe 54 and is recirculated. As a result, the DPF 60 can be sufficiently regenerated and the separated PM can be removed while the diesel engine 10 is in an operating state without causing heat damage and without being influenced by the exhaust temperature.

  In step 3, the EGR rate is calculated according to the engine operating state, and the opening degree of the butterfly valve 42 is adjusted based on the EGR rate to adjust the EGR rate. For example, when the diesel engine 10 is in an operation state of complete combustion, since the generation of PM is small, the EGR rate is increased to reduce the NOx emission amount. In this case, the opening degree of the butterfly valve 42 is controlled so as to reduce the opening degree of the exhaust passage 40, and the EGR rate is increased. The EGR rate is obtained by, for example, measuring the NOx concentration by providing a NOx sensor in the intake manifold to which the EGR pipe 54 communicates, or calculating the NOx concentration in the exhaust gas from the exhaust NOx map according to the engine operating state. You may make it calculate based on. In this case, the parameter of the intake flow rate used for the calculation of the EGR rate is obtained, for example, by providing an air flow sensor to measure the intake flow rate or calculating the intake flow rate from the intake flow rate map according to the engine operating state. Can do.

  In step 4, it is determined whether or not the regeneration of the DPF 60 is completed. Here, if the differential pressure P becomes less than the second predetermined pressure which is smaller than the first predetermined pressure, it is determined that the regeneration of the DPF 60 is completed, and the process proceeds to Step 5 (Yes). On the other hand, otherwise, it is determined that the regeneration of the DPF 60 has not been completed, and the process returns to Step 3 (No), and the opening degree adjustment of the butterfly valve 42 is repeated.

In step 5, the first valve 50a is opened, the second valve 52a is closed, and the valve switching control at the completion of filter regeneration is executed to return the valve to the initial state.
The exhaust purification device described above has a branched structure in which the middle of the exhaust passage 40 is branched into two, but may be a branched structure in which the exhaust passage 40 is branched into two or more. The DPF 60 may be a CSF (Catalyzed Soot Filter), and a diesel oxidation catalyst (DOC) is arranged upstream of the DPF 60, or a CSF and a catalyzed DPF are arranged upstream of the DPF 60. Also good. Further, when a filter is disposed in a plurality of branch passages, for example, the CSF is disposed in the first stage of the branch passage, and the CSF, the DPF, and the catalyzed DPF are disposed in the order of the second stage. Combinations can be applied as appropriate. This is the same in each embodiment described later.

  FIG. 3 shows a second embodiment of the engine exhaust gas purification apparatus. Here, based on the configuration of the first embodiment, a DPF is provided in each of two branch passages, and one of them is properly regenerated while collecting the other PM. Hereinafter, the description of the configuration common to the first embodiment will be omitted as appropriate.

  In the first branch passage 50, a remotely operable first valve 50a for opening and closing the passage and a first DPF 62 for collecting PM in the exhaust are arranged in this order along the exhaust flow direction. . Similarly, in the second branch passage 52, a second valve 52a that can be remotely operated to open and close the passage and a second DPF 64 that collects PM in the exhaust are arranged in this order along the exhaust flow direction. Established.

  The first independent shape of the EGR pipe 54 having a first independent shape portion 56 and a second independent shape portion 58 which are independent at least on the branch passage side in the first branch passage 50 located between the first valve 50a and the first DPF 62. The second independent shape portion 58 is connected to the second branch passage 52 that is connected to the portion 56 and is located between the second valve 52 a and the second DPF 64. The first independent shape portion 56 is provided with a first EGR valve 56a that can be remotely operated to open and close the flow path, and the second independent shape portion 58 can also be a remotely operated second EGR valve that opens and closes the flow path. 58a is disposed. As the EGR pipe opening / closing means, two EGR valves 56a and 58a are arranged in the two independent shape portions 56 and 58. However, it is like a three-way switching valve at the junction where the two independent shape portions 56 and 58 merge. A multidirectional switching valve may be provided.

  The initial state of the valve when starting the diesel engine 10 is, for example, that the first valve 50a and the first EGR valve 56a are open, and the second valve 52a and the second EGR valve 58a are closed. Exhaust gas follows the same flow path as in the first embodiment.

  The regeneration process of the first DPF 62 and the second DPF 64 is basically the same as the regeneration process of the DPF 60 in the first embodiment. However, since the two DPFs are alternately regenerated, the valve at the start of regeneration in step 2 in FIG. The switching control and the valve switching control at the time of completion of regeneration in step 5 are different.

  In the valve switching control at the start of regeneration of the first DPF 62, the first valve 50a is closed and the second valve 52a is opened. By this valve switching control, exhaust gas follows the same path as in the first embodiment, and PM is collected by the second DPF 64 and becomes exhaust gas including separated PM from the first DPF 62, and the first independent shape portion 56. To be refluxed. Thus, PM can be collected by the second DPF 64 while regenerating the first DPF 62 and removing the detached PM while maintaining the operation state of the diesel engine 10 without causing thermal damage and being influenced by the exhaust temperature. it can.

In the valve switching control upon completion of regeneration, the first EGR valve 56a is closed and the second EGR valve 58a is opened. Thereby, it switches to PM collection which made 2nd DPF64 the main.
In the valve switching control at the start of regeneration of the second DPF 64 and at the completion of regeneration, the backflow exhausted during the filter regeneration backwashes the second DPF 64 and recirculates it, and the first DPF 62 collects PM after the filter regeneration is completed. The valve switching control similar to the filter regeneration process of the first DPF 62 is executed.

  FIG. 4 shows a third embodiment of the engine exhaust gas purification apparatus. Here, based on the configuration of the second embodiment, the filter is regenerated alternately using high-pressure gas. Hereinafter, the description of the same configuration as that of the second embodiment will be omitted as appropriate.

  The first branch passage 50 is provided with a third valve 50b that can be remotely operated on the downstream side of the first DPF 62, and the second branch passage 52 also has a passage downstream of the second DPF 64. A fourth valve 52b that can be remotely operated is disposed.

  The first branch passage 50 located between the first DPF 62 and the third valve 50b is connected to a first supply passage 92 connected to an air reservoir 90 as high pressure gas supply means for supplying high pressure gas. Similarly, a second supply passage 94 connected to the air reservoir 90 is connected to the second branch passage 52 located between the second DPF 64 and the fourth valve 52b. The supply passages 92 and 94 have a manifold shape that merges on the air reservoir 90 side. Further, the first supply passage 92 is provided with a first switch valve 92a that can be remotely operated to introduce the high-pressure gas from the air reservoir 90 into the first branch passage 50. The second supply passage 94 is also connected to the first supply passage 92 from the air reservoir 90. The second switching valve 94a that can be remotely operated to introduce the high pressure gas into the second branch passage 52 is provided. The two branch passages 50 and 52 are provided as two branch passages 50 and 52 as branch passage blocking means, and the two switching valves 92a and 94a are provided as two supply passages 92 and 94 as supply passage switching means. However, a multi-directional switching valve such as a three-way switching valve may be disposed in the merging portion 40b and the merging portions of the two supply passages 92 and 94, respectively.

  The initial state of the valve at the time of starting the diesel engine 10 is, for example, that the third valve 50b and the fourth valve 52b are open, and the first switching valve 92a and the second switching valve 94a are closed.

  The regeneration processing of the first DPF 62 and the second DPF 64 is basically the same as the filter regeneration processing in the second embodiment, but the two DPFs are alternately regenerated using high-pressure gas, so that valve switching control at the start of regeneration is performed. The valve switching control upon completion of regeneration is different.

  In the regeneration process of the first DPF 62, in addition to the valve switching control at the start of regeneration in the second embodiment, the third valve 50b is closed, the first switching valve 92a is opened, and the supply of high-pressure gas by the air reservoir 90 is started. Thereby, instead of the backflow exhaust of 2nd Embodiment, high pressure gas backwashes and reproduces | regenerates 1st DPF60, and can acquire the effect similar to 2nd Embodiment. Thereafter, in addition to the valve switching control at the completion of regeneration in the second embodiment, the third valve 50b is opened, the first switching valve 92a is closed, and the supply of high-pressure gas is stopped.

The valve switching control similar to the regeneration process of the first DPF 62 is also performed in the valve switching control at the start of regeneration and at the completion of regeneration in the regeneration process of the second DPF 64.
In the configuration of each embodiment, the EGR pipe 54 may be connected to the intake passage 20 upstream of the compressor 30a of the supercharger 30. According to this, since the exhaust gas including the separated PM is returned to the intake air before being compressed by the compressor 30a, it is easily EGRed. Similarly, a high-pressure gas containing separated PM can be easily introduced.

  In each of the above-described embodiments, the condition at which the differential pressure P is equal to or higher than the first predetermined pressure is used for the determination at the start of regeneration of the DPF, but other conditions can also be applied. For example, (1) when the travel distance reaches a predetermined distance, (2) the engine operating time is integrated, and this integrated time is equal to or longer than a predetermined time at which the filter is considered to be clogged in an average engine operating state. (3) The PM discharge flow rate is estimated with reference to a PM discharge map in which the PM discharge flow rate per unit time according to the rotational speed Ne and the engine load Q as shown in FIG. When the integrated value becomes equal to or higher than the PM discharge flow rate (first predetermined value) at which the filter is considered to be clogged, etc. can be applied.

  In addition, for the determination at the completion of the regeneration of the DPF, the condition that the differential pressure P is less than the second predetermined pressure is used, but other conditions can be applied. For example, (1) PM separation flow rate per unit time for separation from the DPF is set according to the rotational speed Ne, the engine load Q, and the high-pressure gas supply flow rate as shown in FIG. 5B. Estimated from the PM departure map, and when the accumulated value is equal to or greater than the PM separation flow rate (second predetermined value) considered to be complete filter regeneration, (2) Accumulate engine operating time from the start of DPF regeneration In addition, when the accumulated time is equal to or longer than a predetermined time considered that the regeneration of the filter is completed, it is possible to apply.

Further, in the determination at the start of DPF regeneration, two or more of the above conditions may be arbitrarily combined, and when any of the conditions is satisfied, it may be determined as the start of regeneration. These conditions may be combined, and when all the conditions are satisfied, it may be determined that the reproduction has been completed. Thereby, the reliability of the DPF regeneration process can be improved.
Furthermore, the above embodiments may be appropriately combined.

10 diesel engine 20 intake passage 30 supercharger 30a compressor 30b turbine 40 exhaust passage
42 Butterfly valve 50, 52 Branch passage 50a, 52a Valve 54 EGR pipe 60 DPF
70a, 70b Pressure sensor 72 Rotational speed sensor 74 Engine load sensor 80 ECU

Claims (6)

A filter that is disposed in a branch passage excluding at least one branch passage among a plurality of branch passages branched in the middle of the exhaust passage of the engine, and collects particulate matter in the exhaust;
A branch passage opening and closing means for opening and closing a branch passage upstream of the filter in the branch passage where the filter is disposed; and a branch passage opening and closing means for opening and closing the branch passage in the branch passage where the filter is not disposed;
An EGR pipe communicating with the branch passage upstream of the filter and downstream of the branch passage opening and closing means and the intake passage of the engine;
Control means for controlling the branch passage opening and closing means so as to close a branch passage where the filter is disposed while opening a branch passage where the filter is not disposed during regeneration of the filter;
Opening degree adjusting means for adjusting the opening degree of the exhaust passage downstream from the merging portion where the branch passages merge at the time of regeneration of the filter in a multistage or continuous manner from fully open to fully closed according to the engine operating state ; ,
An exhaust emission control device for an engine characterized by comprising:   2. The engine exhaust gas purification apparatus according to claim 1, wherein the EGR pipe communicates with an intake passage upstream of a compressor of a supercharger provided in the engine.   3. The engine according to claim 1, wherein the control unit integrates the operation time of the engine, and determines that it is a filter regeneration start time when the integration time exceeds a predetermined time. Exhaust purification equipment.   The control means estimates the discharge flow rate of the particulate matter according to the engine operating state, and determines that it is at the start of filter regeneration when the integrated value of the discharge flow rate is equal to or higher than a first predetermined value. The engine exhaust gas purification device according to any one of claims 1 to 3. Further comprising a differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the filter,
The engine exhaust according to any one of claims 1 to 4, wherein if the detected differential pressure is equal to or greater than a predetermined pressure, the control means determines that the filter is at the start of regeneration. Purification equipment.   The control means estimates the detachment flow rate of particulate matter that detaches from the filter in response to the engine operating state from the start of the regeneration of the filter, and when the integrated value of the detachment flow rate exceeds a second predetermined value, The engine exhaust gas purification apparatus according to any one of claims 1 to 5, wherein it is determined that the regeneration is completed.