JP5533391B2 - EGR device - Google Patents

Description

  The present invention relates to an EGR device that recirculates a part of exhaust gas in an exhaust passage to an intake passage in order to reduce the NOx emission amount of an internal combustion engine.

  Regulations related to emissions of nitrogen oxides (hereinafter referred to as NOx) emitted from diesel engines have been strengthened year by year. As a measure to reduce NOx emissions, the space between the exhaust pipe and intake pipe of the diesel engine body In addition, an EGR (Exhaust Gas Recirculation) device provided with an EGR pipe having an EGR valve is used. With this EGR device, a part of the exhaust gas in the exhaust pipe is recirculated to the intake pipe via the EGR pipe to lower the combustion peak temperature in the engine body, thereby reducing the NOx emission amount of the diesel engine. . In order to cool the exhaust gas recirculated from the exhaust pipe to the intake pipe, a cooled EGR device in which an EGR cooler is provided in the middle of the EGR pipe has also been used.

JP 2008-88817 A

  Since exhaust gas flows through the EGR device, particulate matter (hereinafter referred to as PM) in the exhaust gas accumulates in the EGR device (in the EGR pipe, in the EGR cooler, and in the EGR valve), thereby reducing the EGR flow rate and EGR. There is a possibility that the cooling performance of the cooler is deteriorated, the EGR valve is not opened or closed, and the like. In order to suppress PM accumulation in the EGR apparatus, the EGR pipe shape is smoothed, the EGR cooler shape, and the EGR valve shape are optimized, but the effect is limited.

  It is known that the EGR deposit produced by depositing PM may change its properties with time after deposition, resulting in a stronger deposit. In addition, maintenance of the cooling performance of the EGR cooler is very important for proper operation of the EGR device, and it is required to maintain the cooling performance of the EGR cooler over a long period of time.

  Therefore, an object of the present invention is to prevent the cooling performance of the EGR cooler from being lowered by suppressing PM accumulation in the EGR cooler.

  In order to achieve the above object, the present invention provides a plurality of exhaust gases that are disposed in the middle of an EGR passage that communicates an exhaust passage and an intake passage of an internal combustion engine, and through which exhaust gas that recirculates from the exhaust passage to the intake passage flows. In an EGR apparatus equipped with an EGR cooler having a gas flow path, an exhaust gas is exhausted from the EGR passage by forming a porous layer on the inner wall surface of the exhaust gas flow path for collecting particulate matter in the exhaust gas. Forming an inner flow path inside the porous layer into which gas flows, and an outer flow path outside the porous layer into which exhaust gas that has passed through the porous layer flows from the inner flow path, and In order to remove the particulate matter deposited on the inner surface of the porous layer by supplying the exhaust gas from which the particulate matter has been removed by the porous layer to the inner passage from the outer passage, the adjacent exhaust gas Outside of the flow path An open / close means for opening and closing the exhaust gas flow channel is provided on the upstream side of the exhaust gas flow channel, and the particulate matter deposited on the inner surface of the porous layer is provided on the upstream side of the exhaust gas flow channel. Control means for closing the opening / closing means of the exhaust gas flow path to be removed and opening the opening / closing means of the exhaust gas flow path communicating with the exhaust gas flow path closed by the opening / closing means by the communication flow path is provided. It is a thing.

  The porous layer may be composed of sintered metal or porous ceramics.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an outstanding effect that the fall of the cooling performance of an EGR cooler and the increase in flow path resistance can be prevented by suppressing PM accumulation in an EGR cooler.

FIG. 1 is a schematic view of an engine in which an EGR device according to an embodiment of the present invention is used. FIG. 2A is a front sectional view showing an outline of an EGR cooler (shell tube type heat exchanger) according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along line A- of FIG. It is A sectional view. FIG. 3 is a front sectional view showing an outline of an EGR cooler (plate type heat exchanger) according to another embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an internal combustion engine (in this embodiment, a diesel engine) 1 in which an EGR device 10 according to this embodiment is used includes an engine body (diesel engine body) 1a and an exhaust port of the engine body 1a. An exhaust passage (exhaust pipe) 2 that communicates and an intake passage (intake pipe) 3 that communicates with the intake port of the engine body 1a are provided.

  An EGR device (cooled EGR device) 10 is disposed between the exhaust pipe 2 and the intake pipe 3 of the engine body 1a, and connects an EGR passage (EGR pipe) 11 that connects the exhaust pipe 2 and the intake pipe 3, and an EGR. An EGR valve 12 is provided in the middle of the pipe 11 to adjust the flow rate of exhaust gas recirculated from the exhaust pipe 2 to the intake pipe 3, and is provided in the EGR pipe 11 upstream of the EGR valve 12. , An EGR cooler 13 for cooling the exhaust gas flowing through the EGR pipe 11 and a controller 14 as a control means for controlling the EGR valve 12 are provided.

  The exhaust gas generated in the engine body 1a flows through the exhaust pipe 2 and is discharged. On the other hand, when EGR is required, the controller 14 opens the EGR valve 12 to a predetermined opening, thereby utilizing the negative pressure generated in the intake pipe 3 of the engine body 1a, A part of the exhaust gas is recirculated to the intake pipe 3 via the EGR pipe 11, the EGR cooler 13, and the EGR valve 12. Thereby, exhaust gas can be introduced into the air-fuel mixture in the engine body 1a to lower the combustion peak temperature, thereby reducing the NOx emission amount.

  FIG. 2 shows the EGR cooler 13 of the present embodiment.

  As shown in FIG. 2, the EGR cooler 13 is composed of a shell-and-tube heat exchanger. The EGR cooler 13 includes a substantially cylindrical (substantially cylindrical in this embodiment) shell 15 and a coolant flow path that is disposed in the shell 15 at a predetermined interval in the longitudinal direction of the shell 15 and through which coolant flows. A plurality of tubes 18 (in this embodiment, tubes) that are provided between a pair of end plates 17 that form a partition 16 and a pair of end plates 17 that form exhaust gas passages through which exhaust gas (EGR gas) flows. Are mainly composed of 18-1 to 18-4.

  The coolant flows into the coolant channel 16 in the shell 15 from the coolant inlet 13a, cools the exhaust gas flowing in the tube 18, and is discharged from the coolant outlet 13b. On the other hand, the exhaust gas flows into the tube 18 in the shell 15 from the exhaust gas inlet 13c, is cooled by the coolant flowing in the coolant flow path 16, and is discharged from the exhaust gas outlet 13d.

  In the present embodiment, by forming a porous layer 19 for collecting PM in the exhaust gas on the inner wall surface 18a of each tube 18, the inside of the porous layer 19 into which the exhaust gas flows from the EGR pipe 11 is formed. An inner channel 20 and an outer channel 21 outside the porous layer 19 into which exhaust gas that has passed through the porous layer 19 flows from the inner channel 20 are formed. The porous layer 19 is made of sintered metal or porous ceramics. The outer flow path 21 extends along the longitudinal direction of each tube 18 and is formed in plural (four in this embodiment) at a predetermined interval in the circumferential direction of each tube 18.

  In the present embodiment, the exhaust gas from which the PM is removed by the porous layer 19 is supplied from the outer channel 21 to the inner channel 20 to remove the PM deposited on the inner surface 19 a of the porous layer 19. The outer flow paths 21 of the tubes 18 to be communicated with each other by a communication flow path (communication pipe) 22. In the present embodiment, the outer flow path 21 of the tube 18-1 and the outer flow path 21 of the tube 18-2 are communicated by the communication pipe 22, and the outer flow path 21 and the tube 18 of the tube 18-3 are communicated by the communication pipe 22. -4. The communication pipe 22 is attached to the upstream end and the downstream end of each tube 18.

  Further, in the present embodiment, the partition between the exhaust gas inlet 13c and the upstream end of each tube 18 is divided into two by the partition plate 24 to divide the tube 18 into two groups, and the flow path is divided by the partition plate 24. A valve 25c1 and a valve 25c2 are installed. That is, valves 25c1 and 25c2 as opening / closing means for opening and closing each tube 18 are provided on the upstream side of each tube 18, respectively. Similarly, the space between the exhaust gas outlet 13d and the downstream end of each tube 18 is also divided into two by the partition plate 26, and the valves 25d1 and 25d2 are respectively installed in the flow paths divided by the partition plate 26. These valves 25c1, 25c2, 25d1, and 25d2 are controlled by the controller 14 and include, for example, butterfly valves.

  Next, the operation of this embodiment will be described.

  Hereinafter, although the operation | movement regarding the tubes 18-1 and 18-2 is demonstrated, since the operation | movement regarding the tubes 18-3 and 18-4 is performed similarly, description is abbreviate | omitted.

  In a normal case, first, the valve 25c1 is opened and the valve 25c2 is closed. At the same time, the valve 25d1 is closed and the valve 25d2 is opened. In this case, the EGR gas passes through the valve 25c1 from the exhaust gas inlet 13c, flows into the inner flow path 20 of the tube 18-1, passes through the porous layer 19 and flows into the outer flow path 21, and at that time, the EGR gas The PM inside is collected on the inner surface 19 a of the porous layer 19, while the EGR gas is cooled by heat exchange with the coolant flowing in the coolant channel 16. Further, the EGR gas from which PM has been removed by flowing into the outer flow path 21 of the tube 18-1 flows into the outer flow path 21 of the adjacent tube 18-2 through the communication pipe 22 and passes through the porous layer 19. Then, it flows into the inner channel 20 and is cooled by heat exchange with the coolant flowing in the coolant channel 16 during that time, and PM deposited on the inner surface 19 a of the porous layer 19 is removed. Thereby, the heat exchange efficiency of the tube 18-2 and the recovery effect of the flow path resistance are obtained. The EGR gas that has flowed into the inner flow path 20 of the tube 18-2 passes through the valve 25d2 and is discharged from the exhaust gas outlet 13d because the valve 25c2 on the exhaust gas inlet 13c side is closed.

  The above operation (EGR gas is introduced from the valve 25c1 and discharged from the valve 25d2) is continued for a predetermined period, PM in the EGR gas is collected on the inner surface 19a of the porous layer 19 of the tube 18-1, and the tube 18-2 is collected. After removing the PM collected on the inner surface 19a of the porous layer 19, the valves 25c1 and 25d2 are closed and the valves 25c2 and 25d1 are opened to reverse the EGR gas flow in the tubes 18-1 and 18-2. Thus, the PM deposited on the inner surface 19a of the porous layer 19 of the tube 18-1 is removed. Thereby, the heat exchange efficiency of the tube 18-1 and the recovery effect of the channel resistance can be obtained.

  By periodically repeating these operations (switching the flow paths of the tubes 18-1 and 18-2 by opening and closing the valves 25c1, 25c2, 25d1, and 25d2), excessive PM accumulation in the tube 18 It becomes possible to suppress the deposition of the EGR deposit generated by the subsequent modification.

  In short, according to the present embodiment, the PM accumulated on the inner surface 19a of the porous layer 19 of the tube 18 is removed from the exhaust gas from which the PM is removed by the porous layer 19 of the adjacent tube 18 on the inner wall surface 18a side of the tube 18. By supplying and removing from the (outer flow path 21) periodically (every predetermined period), PM accumulation in the EGR cooler 13 is suppressed, and deterioration of the cooling performance of the EGR cooler 13 is prevented. Is possible.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, in the above embodiment, the EGR cooler 13 is configured by a shell-and-tube heat exchanger. However, the same effect as that of the above-described embodiment can be obtained with a plate-type heat exchanger. For example, as shown in FIG. 3, the EGR cooler 30 formed of a plate heat exchanger includes a top plate 31 and a bottom plate 32 that define the coolant flow path 16, and a plate 33-1 that forms an exhaust gas flow path. 33-2.

  In the above embodiment, the EGR gas flow path in the EGR cooler 13 is switched periodically (every predetermined period), but the present invention is not limited to this. For example, the exhaust pipe 2 or the EGR cooler 13 is provided with differential pressure detection means (differential pressure sensor) for detecting the exhaust differential pressure upstream and downstream of the EGR cooler 13, and the exhaust differential pressure detected by the differential pressure detection means exceeds a predetermined pressure. The EGR gas flow path in the EGR cooler 13 may be switched by the valves 25c1, 25c2, 25d1, and 25d2. Further, the exhaust pipe 2 or the EGR cooler 13 is provided with temperature detecting means (temperature sensor) for detecting the exhaust temperature downstream of the EGR cooler 13, and when the exhaust temperature detected by the temperature detecting means exceeds a predetermined temperature, the valve 25c1 , 25c2, 25d1, and 25d2, the EGR gas flow path in the EGR cooler 13 may be switched.

1 Diesel engine (internal combustion engine)
2 Exhaust pipe (exhaust passage)
3 Intake pipe (intake passage)
10 EGR device 11 EGR pipe (EGR passage)
13 EGR cooler 14 Controller (control means)
18 Tube (exhaust gas flow path)
19 Porous layer 20 Inner flow path 21 Outer flow path 22 Communication pipe (communication flow path)
25c1, 25c2 valve (opening / closing means)
30 EGR cooler 33 plate (exhaust gas flow path)

Claims (2)

An EGR device provided with an EGR cooler having a plurality of exhaust gas passages arranged in the middle of an EGR passage communicating an exhaust passage and an intake passage of an internal combustion engine and through which exhaust gas recirculated from the exhaust passage to the intake passage flows In
By forming a porous layer for collecting particulate matter in the exhaust gas on the inner wall surface of the exhaust gas channel, the inner channel inside the porous layer into which the exhaust gas flows from the EGR passage And an outer flow path outside the porous layer into which exhaust gas that has passed through the porous layer flows from the inner flow path, and
In order to remove the particulate matter deposited on the inner surface of the porous layer by supplying the exhaust gas from which the particulate matter has been removed by the porous layer to the inner passage from the outer passage, the adjacent exhaust gas Communicating the outer channels of the channels with a communication channel; and
Opening / closing means for opening / closing the exhaust gas flow path is provided upstream of the exhaust gas flow path, and the opening / closing means of the exhaust gas flow path for removing particulate matter deposited on the inner surface of the porous layer is provided. An EGR apparatus comprising a control means for opening and closing the open / close means of the exhaust gas flow path which is closed and communicated by the communication flow path to the exhaust gas flow path closed by the open / close means.   The EGR device according to claim 1, wherein the porous layer is made of sintered metal or porous ceramics.

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