JP2011058428A - Exhaust gas recirculation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely return PM collected by a cyclone type dust collection device to an exhaust system while relaxing restriction of layout. <P>SOLUTION: The cyclone type duct collection device 34 is disposed so as to collect PM of EGR gas flowing in an EGR passage 30 and to discharge PM at a communication passage 38 communication between an intake pipe 14 at an exhaust gas downstream of a turbocharger 18 and an exhaust pipe 24 at exhaust gas upstream of an oxidation catalyst 26. A first open close valve 40 opening and closing the communication passage 38 in a direction toward the exhaust pipe 24 from the intake pipe 14, and a check valve 42 opening only in this direction are disposed at the communication passage 38 in this order. A second open close valve 46 opening and closing a drain passage 44 discharging PM from the cyclone type duct collection device 34 to the communication passage 38 is provided. The first open close valve 40 is closed and the second open close valve 46 is opened when DPF 28 is not forcibly regenerated, and the first open close valve 40 is opened and the second open close valve 46 is closed when DPF 28 is forcibly regenerated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation (EGR) device that introduces a part of exhaust gas into an intake system and recirculates the exhaust gas to reduce the generation amount of nitrogen oxides (NOx) through a decrease in combustion temperature.

In an EGR device for a diesel engine, particulate matter (PM: PM: Soluble Organic Fraction) is mainly contained in soot and soluble organic components (SOF) in the EGR gas extracted from the exhaust system.
Since Particulate Matter) is included, as described in JP 2009-97441 A (Patent Document 1), a technique for removing PM with a cyclone dust collector has been proposed. In this proposed technology, a configuration is adopted in which the PM removed by the cyclone type dust collector is returned to the exhaust system using gravity.

JP 2009-97441 A

  However, in the configuration in which the PM is returned to the exhaust system using gravity, the exhaust system needs to be positioned vertically below the cyclone dust collector, which is subject to layout restrictions and can reliably return the PM to the exhaust system. Not necessarily. Further, when the intake pressure varies, there is no denying that the PM removed by the cyclone dust collector may flow back into the intake system.

  Therefore, in view of the problems of the prior art, the present invention utilizes the intake air supercharged by the turbocharger, and removes the PM removed by the cyclone type dust collector in the exhaust upstream of the diesel particulate filter (DPF: Diesel Particulate Filter). An object of the present invention is to provide an EGR device that can reliably return PM to the exhaust system while relaxing the constraints on the layout.

  For this reason, the EGR device according to the present invention includes an EGR passage that communicates an intake passage located upstream of the turbocharger with an exhaust passage located downstream of the turbocharger, and an intake passage located downstream of the turbocharger. And a communication passage communicating with the exhaust passage located downstream of the DGR disposed in the exhaust passage and upstream of the DPF disposed in the exhaust passage, and PM contained in the EGR gas flowing through the EGR passage. A cyclone type dust collector arranged to collect dust and discharge the collected PM to the communication path, a connection point of the communication path to the intake passage, and a part from which the PM is discharged from the cyclone type dust collector The first on-off valve that opens and closes the communication passage located between the first passage, the location where PM is discharged from the cyclone type dust collector, and the connection location of the communication passage to the exhaust passage A check valve that is disposed in the communication passage located between them and opens only in a direction toward the exhaust passage, and a second on-off valve that opens and closes a passage that discharges PM from the cyclone dust collector to the communication passage; And determining means for determining whether or not the forced regeneration process of the DPF is being executed, and opening the first on-off valve when the determining means determines that the forced regeneration process is being executed and Control means for closing the first open / close valve and opening the second open / close valve when the determination means determines that the forced regeneration process is not being executed, It is comprised including.

  According to the present invention, if the DPF is not in the forced regeneration process, the first on-off valve is closed and the second on-off valve is opened, so that the PM collected by the cyclone dust collector is It collects inside the communication path. At this time, since the check passage that opens only in the direction toward the exhaust passage is disposed in the communication passage, it is possible to prevent PM from flowing back to the cyclone dust collector due to the exhaust pressure in the exhaust passage.

  On the other hand, if the DPF forced regeneration process is in progress, the first on-off valve opens and the second on-off valve closes, so that part of the intake air supercharged by the turbocharger is introduced into the communication path. Is done. Then, using this intake air, the PM accumulated in the communication passage is forcibly returned to the exhaust upstream of the DPF through the check valve. At this time, since the passage for discharging PM from the cyclone dust collector to the communication passage is closed by the second on-off valve, the backflow of PM to the cyclone dust collector is prevented by intake air. Thereafter, the PM returned to the upstream side of the DPF is incinerated while being collected by the DPF. Here, as the condition for returning the PM to the exhaust upstream of the DPF, the fact that the DPF forced regeneration process is in progress is adopted, so that the clogging of the DPF can be suppressed even if the PM is returned to the exhaust.

  Therefore, the PM separated and collected by the cyclone type dust collector can be surely returned to the exhaust system while relaxing the constraints on the layout.

1 is an overall configuration diagram showing a first embodiment of an EGR device that embodies the present invention; The concrete composition of a cyclone type dust collector is shown, (A) is a longitudinal section, and (B) is a transverse section. Flow chart showing contents of control program The whole block diagram which shows 2nd Embodiment of the EGR apparatus which actualized this invention. The specific structure of a plasma generator is shown, (A) is a longitudinal sectional view, (B) is a transverse sectional view, and (C) is an explanatory view of a PM particle size growth mechanism.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of an EGR device constructed by applying the present invention to a diesel engine equipped with a turbocharger.

An intake pipe 14 (intake passage) connected to the intake manifold 12 of the diesel engine 10 is provided with an air cleaner 16 that removes dust and the like in the air along the intake flow direction, a compressor 18A of the turbocharger 18 and a turbocharger 18. An intercooler 20 that cools the intake air that has become hot is arranged in this order. On the other hand, in the exhaust pipe 24 (exhaust passage) connected to the exhaust manifold 22 of the diesel engine 10, the turbine 18B of the turbocharger 18 and nitrogen monoxide (NO) in the exhaust gas are nitrogen dioxide (NO) along the exhaust circulation direction. An oxidation catalyst 26 that oxidizes to NO ₂ ) and a DPF 28 that collects and removes PM in the exhaust are disposed in this order. The oxidation catalyst 26 and the DPF 28 constitute a continuous regeneration type DPF device, but only the DPF 28 may be used. Further, instead of DPF 28, CSF (Catalyzed Soot Filter) in which an active component and an additive component are supported on the surface of DPF 28 can be used.

  The intake pipe 14 positioned upstream of the intake air of the turbocharger 18 and the exhaust pipe 24 positioned downstream of the exhaust thereof are connected in communication via an EGR passage 30. Specifically, one end of the EGR passage 30 is connected to the intake pipe 14 positioned between the air cleaner 16 and the compressor 18 </ b> A of the turbocharger 18, while between the turbine 18 </ b> B of the turbocharger 18 and the oxidation catalyst 26. The other end of the EGR passage 30 is connected to the exhaust pipe 24 positioned. The EGR passage 30 includes an EGR cooler 32 that cools the EGR gas along the flow direction of the EGR gas, a cyclone dust collector 34 that separates and collects PM from the EGR gas, and an engine operating state. The EGR valve 36 for changing the EGR rate is arranged in this order. As shown in FIG. 2, the cyclone type dust collecting apparatus 34 includes a substantially truncated cone-shaped outer cylinder part 34 </ b> A having a small diameter in the vertically lower part, and an introduction cylinder part 34 </ b> B connected tangentially at the upper part and the outer peripheral part thereof. A discharge cylinder part 34C extending vertically through the top plate of the outer cylinder part 34A and a drain cylinder part 34D extending vertically downward from the bottom plate of the outer cylinder part 24A are configured. The EGR passage 30 is connected to the introduction cylinder portion 34B and the discharge cylinder portion 34C of the cyclone dust collector 34, respectively.

  The intake pipe 14 positioned downstream of the intake air of the turbocharger 18 and the exhaust pipe 24 positioned downstream of the exhaust gas from the connection portion of the EGR passage 30 to the exhaust pipe 24 and upstream of the oxidation catalyst 26 are connected via the communication path 38. Communication connection. Specifically, one end of the communication passage 38 is connected to the intake pipe 14 located between the compressor 18A of the turbocharger 18 and the intercooler 20, while the connection portion of the EGR passage 30 to the exhaust pipe 24 and the oxidation catalyst are connected. The other end of the communication path 38 is connected to the exhaust pipe 24 located between the exhaust pipe 24 and the exhaust pipe 24. In addition, the communication passage 38 includes an electromagnetic first on-off valve 40 that opens and closes the communication passage 38 along the direction from the connection point to the intake pipe 14 to the connection point to the exhaust pipe 24, and the exhaust pipe 24. And a check valve 42 that opens only in the direction toward the front.

  Further, a drain passage 44 communicating with the drain cylinder portion 34D of the cyclone type dust collector 34 is connected to the communication passage 38 positioned between the first on-off valve 40 and the check valve 42, and the drain passage is connected thereto. An electromagnetic second on-off valve 46 that opens and closes 44 is disposed. In short, the cyclone type dust collector 34 is arranged to collect PM contained in the EGR gas flowing through the EGR passage 30 and to discharge the collected PM to the communication passage 38.

  In order to electronically control the EGR valve 36, the first on-off valve 40, and the second on-off valve 46, an EGR control unit 48 incorporating a computer is provided. The EGR control unit 48 is connected to the engine control unit 50 via a CAN (Controller Area Network) or the like so that the rotational speed Ne and the load Q of the diesel engine 10 can be read. Here, as the load Q, a state quantity closely related to the torque, such as a fuel injection amount, an intake pressure, a supercharging pressure, and an accelerator opening, can be used. Further, the rotational speed Ne and the load Q of the diesel engine 10 are not limited to the configuration read from the engine control unit 50, and may be directly detected by a known rotational speed sensor and load sensor. Further, the EGR control unit 48 may be incorporated into the engine control unit 50 or another control unit.

  The EGR control unit 48 executes a control program stored in a ROM (Read Only Memory) or the like, thereby electronically controlling the EGR valve 36 according to the rotational speed Ne and the load Q as the engine operating state. The first on-off valve 40 and the second on-off valve 46 are electronically controlled according to whether or not the forced regeneration process of the DPF 28 is in progress. Here, whether or not the forced regeneration process of the DPF 28 is being performed may be inquired of, for example, the engine control unit 50 that executes control for increasing the exhaust temperature during the forced regeneration process. The EGR control unit 48 executes the control program, so that the determination unit and the control unit are realized.

FIG. 3 shows the contents of a control program that the EGR control unit 48 repeatedly executes at predetermined time intervals when the diesel engine 10 is started.
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), it is determined whether or not the DFP 28 is in the forced regeneration process. If the DPF 28 is in the forced regeneration process, the process proceeds to step 2 (Yes), whereas if the DPF 28 is not in the forced regeneration process, the process proceeds to step 4 (No).

In step 2, the first on-off valve 40 is opened.
In step 3, the second on-off valve 46 is closed.
In step 4, the first on-off valve 40 is closed.

In step 5, the second on-off valve 46 is opened.
According to such an EGR device, a part of the exhaust gas that has passed through the turbine 18B of the turbocharger 18 is introduced into the EGR cooler 32 through the EGR passage 30 as EGR gas. The EGR gas introduced into the EGR cooler 32 is cooled by the EGR cooler 32, so that the SOF is condensed and easily collected, and is introduced into the cyclone type dust collector 34. In the cyclone type dust collector 34, the EGR gas introduced into the outer cylinder part 34A from the introduction cylinder part 34B is swung downward around the discharge cylinder part 34C along the inner peripheral surface of the outer cylinder part 34A. It flows into the discharge cylinder part 34C from the opening located below, and is discharged. At this time, the EGR gas swirls at a high speed inside the outer cylinder portion 34A, so that a large centrifugal force acts on the PM contained in the EGR gas, and this is separated and collected at the bottom of the outer cylinder portion 34A.

  If the DPF 28 is not in the forced regeneration process, the first on-off valve 40 is closed and the second on-off valve 46 is opened, so that the PM separated and collected by the cyclone dust collector 34 is collected. Then, it accumulates in the communication passage 38 through the drain passage 44. At this time, since the check valve 42 that opens only in the direction toward the exhaust pipe 24 is disposed in the communication path 38, PM flows backward to the cyclone dust collector 34 due to the exhaust pressure of the exhaust pipe 24. Can be prevented.

  If the DPF 28 is in the forced regeneration process, the first on-off valve 40 is opened while the second on-off valve 46 is closed, so that a part of the intake air supercharged by the compressor 18A of the turbocharger 18 is partially discharged. It is introduced into the communication path 38. Then, using this intake air, the PM accumulated in the communication passage 38 is forcibly returned to the exhaust upstream of the oxidation catalyst 26 through the check valve 42. At this time, since the second on-off valve 46 that opens and closes the drain passage 44 is closed, PM is prevented from flowing back to the cyclone dust collector 34 due to intake air. The PM returned to the upstream side of the exhaust of the oxidation catalyst 26 is incinerated while being collected by the oxidation catalyst 26 and the DPF 28. Here, as the condition for returning PM to the upstream side of the exhaust of the oxidation catalyst 26, the fact that the DPF 28 is being forcedly regenerated is adopted, so that the clogging of the DPF 28 is prevented from proceeding even if PM is returned to the exhaust. it can.

Therefore, the PM separated and collected by the cyclone dust collector 34 can be reliably returned to the exhaust system while relaxing the constraints on the layout.
FIG. 4 shows a second embodiment of an EGR device constructed by applying the present invention to a diesel engine equipped with a turbocharger. In addition, the structure which is common in the first embodiment will be omitted or simplified by attaching the same reference numerals.

  In the second embodiment of the EGR device, particle size growth means for growing PM by combining PM contained in EGR gas with the EGR passage 30 positioned between the EGR cooler 32 and the cyclone dust collector 34. As a result, a plasma generator 52 is further provided.

  Here, as shown in FIGS. 5A and 5B, the plasma generator 52 includes a substantially cylindrical ground electrode 52A disposed along the peripheral wall of the EGR passage 30, and a ground electrode 52A. And a linear discharge electrode 18B disposed substantially at the center of the cross section over the entire length.

  According to such an EGR device, when the EGR gas that has passed through the EGR cooler 32 is introduced into the plasma generator 52, the PM contained in the EGR gas is charged to approximately the same number of positive and negative charges, and the charges having different polarities are charged. When the charged PMs are attracted and bonded by electrical attraction, the particle size grows. That is, as shown in FIG. 5C, the PM contained in the EGR gas is charged to the negative electrode by the discharge of the discharge electrode 52B and receives an electric attractive force acting between the ground electrode 52A and the ground electrode 52A. To be collected. The PM collected by the ground electrode 52A loses its charge, and then is charged to a reverse polarity (positive electrode) by induction charging. The PM is discharged from the ground electrode 52A under the force of the electric field and is pulled back into the EGR gas. The PM drawn back into the EGR gas is charged to the negative electrode again by the discharge of the discharge electrode 52B. By repeating such a phenomenon, the PMs collide with each other and bond, and the particle size grows. For this reason, the PM contained in the EGR gas collides with each other when the PMs having different polarities are attracted and combined by the electric attractive force, and collide when they are repeatedly collected by the ground electrode 52A. Can be further grown. And the PM dust collection capability in the cyclone type dust collector 34 can further be improved because the particle size of PM grows.

14 Intake pipe 18 Turbocharger 24 Exhaust pipe 28 DPF
Reference Signs List 30 EGR passage 32 EGR cooler 34 cyclone dust collector 38 communication passage 40 first on-off valve 42 check valve 44 drain passage 46 second on-off valve 48 EGR control unit 50 engine control unit 52 plasma generator

Claims (5)

An EGR passage communicating the intake passage located upstream of the turbocharger with the exhaust passage located downstream of the turbocharger;
The intake passage located downstream of the turbocharger and the exhaust passage located downstream of the EGR passage connected to the exhaust passage and upstream of the diesel particulate filter disposed in the exhaust passage communicate with each other. A communication path
A cyclone type dust collector arranged to collect particulate matter contained in EGR gas flowing through the EGR passage and to discharge the collected particulate matter to the communication passage;
A first on-off valve that opens and closes a communication passage located between a connection portion of the communication passage to the intake passage and a portion from which the particulate matter is discharged from the cyclonic dust collector;
A reverse passage that is disposed in a communication passage located between a location where particulate matter is discharged from the cyclone dust collector and a connection location of the communication passage to the exhaust passage and opens only in the direction toward the exhaust passage. A stop valve,
A second on-off valve for opening and closing a passage for discharging particulate matter from the cyclone dust collector to the communication passage;
Determination means for determining whether or not forced regeneration processing of the diesel particulate filter is being executed;
When the determination unit determines that the forced regeneration process is being executed, the first opening / closing valve is opened and the second opening / closing valve is closed, while the determination unit performs the forced regeneration process. Control means for closing the first on-off valve and opening the second on-off valve when it is determined that is not being executed,
An exhaust gas recirculation device comprising:   An EGR cooler for cooling EGR gas flowing through the EGR passage is further disposed in an EGR passage located between the cyclone type dust collector and a connection portion of the EGR passage with respect to the exhaust passage. Item 2. An exhaust gas recirculation device according to Item 1.   The particle size growing means for combining the particulate matter contained in the EGR gas flowing into the cyclone type dust collector and growing the particle size thereof is further provided. Exhaust recirculation device.   4. The exhaust gas recirculation device according to claim 3, wherein the particle size growth means comprises a plasma generator.   The plasma generator includes a cylindrical ground electrode disposed along a peripheral wall of the EGR passage, and a linear discharge electrode disposed in the center of a transverse section over the entire length of the ground electrode. The exhaust gas recirculation device according to claim 4, comprising:

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