JP2014202140A - EGR device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR device capable of preventing soot compound from sticking and depositing onto the outlet side of an EGR cooler.SOLUTION: An EGR cooler 16 which connects between a pair of gas chambers 11, 12 with a plurality of tubes 13, surrounds respective tubes 13 with a shell 14 and, thereby, can charge and discharge cooling water 15 to and from the interior of the shell 14 is provided, and a control device 22 which connects each of respective gas chambers 11, 12 of the EGR cooler 16 with an exhaust manifold 9 (exhaust passage) via inlet valves 17, 18, branches an EGR pipe 19 guided from the neighborhood of an inlet (suction passage) of an intake manifold 6 and connects branched pipes respectively to each of the gas chambers 11, 12 via outlet valves 20, 21, controls the respective inlet valves 17, 18 and the respective outlet valves 20, 21 individually and can select a forward flow mode in which circulation gas 8' is caused to flow from one side gas chamber 11 toward the other side gas chamber 12 and a backward flow mode of reverse direction is provided.

Description

  The present invention relates to an EGR device.

  Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted as a recirculation gas from the exhaust side and returned to the intake side, and the recirculation gas returned to the intake side suppresses combustion of fuel in the engine and burns. Some have implemented so-called exhaust gas recirculation (EGR) in which the generation of NOx is reduced by lowering the temperature.

  In general, when this type of exhaust gas recirculation is performed, an EGR pipe is used between an appropriate position of the exhaust passage extending from the exhaust manifold to the exhaust pipe and an appropriate position of the intake passage extending from the intake pipe to the intake manifold. By connecting and opening / closing an EGR valve provided in the middle of the EGR pipe, the recirculated gas is recirculated from the exhaust side to the intake side by utilizing a differential pressure.

  Here, when the recirculated gas that is recirculated to the engine is cooled in the middle of the EGR pipe, the temperature of the recirculated gas decreases and the volume of the recirculated gas decreases, thereby reducing the combustion temperature without significantly reducing the engine output. Since generation of NOx can be reduced, a shell and tube type EGR cooler is provided in the middle of the EGR pipe for recirculating the reflux gas.

  As prior art document information related to this type of EGR apparatus, there are the following Patent Documents 1 and 2 and the like.

JP 2002-39019 A JP 2008-280867 A

  However, in vehicles with a mode of operation in which light-duty low-speed driving and stopping are repeated intermittently (such as buses that operate in congested routes in central Tokyo and trucks that perform delivery operations in areas where delivery destinations are dense), exhaust gas When the operation state with a low flow rate and temperature continues for a long time, the deposition of soot compound occurs on the outlet side of the EGR cooler, which may cause a reduction in efficiency and clogging of the EGR cooler.

  That is, when the reflux gas having a low temperature is further cooled at the outlet side of the EGR cooler and continues to flow in a state in which the temperature is greatly lowered, the SOF component (Soluble Organic Fraction: soluble organic Fraction) The component) remains in a wet state without volatilization, and a portion of the soot that cannot survive the flow of the reflux gas having a low flow velocity is attached thereto, and grows as a soot compound deposit as it is.

  Moreover, if a particulate filter is interposed in the middle of the exhaust pipe, and the control for regenerating the particulate filter is started in a light load low-speed running or idling stop state, the situation is likely to become worse. Post injection (fuel injection added at non-ignition timing later than compression top dead center following fuel main injection performed near compression top dead center) on the engine side increases SOF, There is a concern that the adhesion and deposition of compounds will become more prominent.

  Incidentally, the control for regenerating the particulate filter referred to here means that fuel is added by post injection on the engine side to the oxidation catalyst arranged in the preceding stage of the particulate filter, and the added fuel (HC) is added to the above-mentioned fuel (HC). This means that the oxidation reaction is performed with an oxidation catalyst, and the catalyst bed temperature of the particulate filter immediately after the reaction heat is increased to burn and remove the collected particulates.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an EGR device that can prevent deposition and deposition of soot compounds on the outlet side of the EGR cooler.

  The present invention is an EGR device that extracts a part of exhaust gas from an exhaust passage of an engine and recirculates it as a recirculation gas to an intake passage, and connects a pair of gas chambers with a plurality of tubes, and each tube is connected to each other. An EGR cooler that is surrounded by a shell so that cooling water can be sucked into and discharged from the shell, and each of the gas chambers of the EGR cooler is connected to an exhaust passage through an inlet valve, and is guided from an intake passage. A pipe is branched and connected to each of the gas chambers via an outlet valve, and a control device capable of individually controlling the inlet valve and the outlet valve is provided, and the inlet valve of one gas chamber and the other Only the outlet valve of the gas chamber is opened, the forward flow mode in which the reflux gas flows from one gas chamber to the other gas chamber, and one gas channel The controller is configured to select a reverse flow mode in which only the outlet valve of the gas chamber and the inlet valve of the other gas chamber are opened and the reflux gas flows backward from the other gas chamber toward the one gas chamber. It is characterized by.

  Thus, when the forward flow mode is selected by the control device, the inlet valve of one gas chamber and the outlet valve of the other gas chamber are opened so that the reflux gas flows from one gas chamber toward the other gas chamber. When the reverse flow mode is selected by the control device, the inlet valve of the other gas chamber and the outlet valve of the one gas chamber are opened so that the reflux gas flows backward from the other gas chamber toward the one gas chamber. Therefore, if the forward flow mode and the reverse flow mode are alternately selected by the control device, the low temperature region on the outlet side of the EGR cooler is changed to the inlet side to become a high temperature region. The attached SOF component volatilizes and the flow path wall surface returns to a dry state, so that the soot component, which is a precursor of the soot compound, is difficult to deposit.

  In practicing the present invention, only the inlet valve and the outlet valve of one gas chamber are opened, and the reflux gas is allowed to flow through one gas chamber without passing through the tube and flow to the EGR pipe. A first valve scavenging mode, and a second valve scavenging mode in which only the other gas chamber is allowed to pass through the other gas chamber without opening the inlet valve and the outlet valve of the other gas chamber and pass through the other gas chamber. It is preferable that the control device is configured so that the above can be selected.

  That is, even if the forward flow mode and the reverse flow mode are alternately selected as described above, only the reflux gas cooled through the tube is led to the outlet valve of each gas chamber. However, if the first valve scavenging mode and the second valve scavenging mode are alternately selected, the high-temperature recirculation gas extracted from the exhaust passage will be discharged from each outlet valve. It flows directly to any of the outlet valves, the temperature rises, the SOF component adhering to any channel wall surface of each outlet valve volatilizes, and the channel wall surface returns to a dry state. The apportionment is difficult to accumulate. Here, each outlet valve is scavenged with the reflux gas one by one in order to enhance the effect of scavenging the apportionment by keeping the flow rate of the reflux gas as high as possible.

  At this time, since the high-temperature reflux gas is also led to the EGR pipe, the SOF component adhering to the flow path wall surface of the EGR pipe is volatilized and the flow path wall surface becomes dry. Returning, the incidental merit that the soot content which is the precursor of the soot compound becomes difficult to accumulate is also obtained.

  In addition, when alternately selecting the first valve scavenging mode or the second valve scavenging mode, after injection is added at the combustible timing immediately after the main injection, or the intake air flow rate is narrowed as necessary. It is more effective to forcibly raise the exhaust temperature.

  In the present invention, when the engine is cold, all the inlet valves and outlet valves of the gas chambers are opened, and the recirculation gas is allowed to pass only through the gas chambers without passing through the tubes and flows to the EGR pipe. It is preferable that the control device is configured so that the mode can be selected.

  In this way, the warm-up mode is selected by the control device when the engine is cold-started, and all the inlet valves and outlet valves of each gas chamber are opened, and the recirculated gas is sucked at a high temperature without going through the tubes. Since it is recirculated to the passage, warm-up of the engine is positively promoted. Here, the recirculation gas is guided to the EGR pipe through both gas chambers in order to recirculate more warm recirculation gas without causing an extra pressure loss.

  Moreover, in a general EGR device, since the recirculation of the recirculated gas cooled by the EGR cooler at the time of cold start is likely to delay the warm-up of the engine, priority is given to the warm-up of the engine. Although the recirculation of the reflux gas is stopped as much as possible, in the EGR device of the present invention, it is possible to reduce the NOx during the warm-up by allowing the recirculation gas to be recirculated even at the time of cold start. .

  According to the EGR device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the direction of the reflux gas flow with respect to the EGR cooler can be reversed by alternately selecting the forward flow mode and the reverse flow mode by the control device. As a result, the low temperature region that was on the outlet side of the EGR cooler is changed to the high temperature region by changing it to the inlet side, and the SOF component adhering to the channel wall surface in the region is volatilized to dry the channel wall surface. It is possible to prevent the deposition of soot compounds on the outlet side of the EGR cooler, and to reduce the efficiency and clogging of the EGR cooler. It can be avoided in advance.

  (II) According to the invention described in claim 2 of the present invention, the first valve scavenging mode and the second valve scavenging mode are alternately selected by the control device, so that the high-temperature reflux gas extracted from the exhaust passage is Directly flow to any of the outlet valves to raise the temperature, volatilize the SOF component adhering to any flow path wall of each of the outlet valves to return the flow path wall to a dry state, and soot compound Therefore, it is possible to prevent deposition of soot compounds on each outlet valve, and to prevent malfunction of each outlet valve.

  (III) According to the invention described in claim 2 of the present invention, the high-temperature recirculated gas extracted from the exhaust passage is EGRed by alternately selecting the first valve scavenging mode and the second valve scavenging mode by the control device. Directly lead to the pipe to raise the temperature, volatilize the SOF component adhering to the flow wall surface of the EGR pipe to return the flow wall surface to a dry state, and deposit the water component precursor. Therefore, it is possible to prevent the deposition and deposition of soot compounds in the EGR pipe, and to avoid the reduction of the flow path cross-sectional area of the EGR pipe.

  (IV) According to the invention described in claim 3 of the present invention, the warm-up mode is selected by the control device at the time of cold start of the engine, so that the recirculation gas is kept at a high temperature without passing through the tube. Since the engine can be recirculated, warm-up of the engine can be actively promoted, and the recirculation of the recirculation gas is also performed during the cold start when the recirculation of the recirculation gas is generally stopped. NOx can be reduced.

It is the schematic which shows an example of the form which implements this invention. It is a table | surface which shows the action | operation of each inlet valve and each outlet valve according to mode. It is a flowchart which shows the specific control procedure in the control apparatus of FIG.

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

  FIG. 1 shows an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes an engine which is a diesel engine equipped with a turbocharger 2, and intake air 3 guided from an air cleaner (not shown) is passed through an intake pipe 4. Each cylinder of the engine 1 is sent to the compressor 2a of the turbocharger 2, the intake air 3 pressurized by the compressor 2a is sent to the intercooler 5 to be cooled, and the intake air 3 is further guided from the intercooler 5 to the intake manifold 6. 7 is distributed.

  The exhaust gas 8 discharged from each cylinder 7 of the engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 9, and the exhaust gas 8 driving the turbine 2b is discharged out of the vehicle through the exhaust pipe 10. I have to do it.

  In the vicinity of the exhaust manifold 9, a pair of gas chambers 11, 12 are connected by a plurality of tubes 13, and each tube 13 is surrounded by a shell 14 so that cooling water 15 is contained in the shell 14. An EGR cooler 16 that can be sucked and discharged is disposed, and each of the gas chambers 11 and 12 of the EGR cooler 16 is connected to an exhaust manifold 9 (exhaust passage) via inlet valves 17 and 18. At the same time, an EGR pipe 19 led from the vicinity of the inlet of the intake manifold 6 (intake passage) is branched and connected to the gas chambers 11 and 12 via outlet valves 20 and 21, respectively.

  Here, the opening and closing operations of the inlet valves 17 and 18 and the outlet valves 20 and 21 are individually controlled by a control device 22 that also serves as an engine control computer (ECU: Electronic Control Unit). A forward flow mode in which only the inlet valve 17 of the gas chamber 11 and the outlet valve 21 of the other gas chamber 12 are opened to allow the reflux gas 8 ′ to flow from one gas chamber 11 toward the other gas chamber 12, and one gas chamber The control device 22 is one of the reverse flow modes in which only the outlet valve 20 of 11 and the inlet valve 18 of the other gas chamber 12 are opened and the reflux gas 8 ′ flows backward from the other gas chamber 12 toward the one gas chamber 11. As a result, a part of the exhaust gas 8 extracted from the exhaust manifold 9 is converted into a recirculation gas 8 'and the EGR cooler. It is adapted to be recycled to near the inlet of the intake manifold 6 through the EGR pipe 19 after being cooled by 6.

  In addition, in the present embodiment, only the inlet valve 17 and the outlet valve 20 of one gas chamber 11 are opened, and the reflux gas 8 ′ is allowed to pass through only one gas chamber 11 without passing through the tube 13. The first valve scavenging mode to flow to the EGR, and only the other gas chamber 12 is allowed to pass through the other gas chamber 12 without passing through the tube 13 by opening only the inlet valve 18 and the outlet valve 21 of the other gas chamber 12. The second valve scavenging mode flowing to the pipe 19 can also be selected by the control device 22, and furthermore, the inlet valves 17, 18 and the outlet valves 20 of the gas chambers 11, 12 when the engine 1 is cold-started. 21 is opened, and the reflux gas 8 'is passed through each gas chamber 11 and 12 without passing through the tube 13, so that E Warm-up mode to flow into R pipe 19 is also adapted to be selected.

  FIG. 2 is a table in which the operations of the inlet valves 17 and 18 and the outlet valves 20 and 21 in the forward flow mode and the reverse flow mode, the first valve scavenging mode and the second valve scavenging mode, and the warm-up mode are arranged. Yes, in the forward flow mode, the recirculation gas 8 ′ is metered by the outlet valve 21, and in the reverse flow mode, the recirculation gas 8 ′ is metered by the outlet valve 20.

  A temperature sensor 23 is provided at the branch position of the EGR pipe 19 to detect the temperature (outlet gas temperature) of the reflux gas 8 ′ discharged from the EGR cooler 16 via the outlet valve 20 or the outlet valve 21. The detection values of these temperature sensors 23 are input to the control device 22.

  Here, since the control device 22 also serves as an engine control computer, various information for grasping the operating state of the engine 1 is also input. For example, the rotational speed of the engine 1 and the engine The water temperature and the like are input and grasped every moment.

  Further, reference numeral 24 in FIG. 1 denotes a particulate filter, and 25 denotes an oxidation catalyst arranged in the preceding stage, and the control is performed when an estimated value of the accumulated amount of particulates in the particulate filter 24 exceeds a specified value. The regeneration control is executed by the device 22, and more specifically, the fuel is added to the exhaust gas 8 by post injection on the engine 1 side, and the added fuel (HC) is used as the oxidation catalyst. By performing the oxidation reaction at 25, the catalyst bed temperature of the particulate filter 24 immediately after the reaction heat is increased, and the collected particulates are burned and removed.

  The specific control procedure in the control device 22 is as shown in the flowchart of FIG. 3. When the engine 1 is started in step S1, the warm-up mode is immediately selected in step S2, and the engine water temperature Tct is determined in step S3. The warm-up mode is continued until the engine temperature exceeds 50 ° C. When the engine water temperature Tct exceeds 50 ° C in this step S3, it is determined that the engine 1 has been warmed up and the process proceeds to step S4, where the engine 1 is stopped. It is confirmed whether or not the forward flow mode has been selected before. If the forward flow mode has been selected, the process proceeds to step S5, the reverse flow mode is selected, and if the forward flow mode has not been selected, step S6. Then, the forward flow mode is selected.

  Then, regardless of whether the forward flow mode or the reverse flow mode is selected, in the next step S7, the accumulated time during which the outlet gas temperature Tgo of the EGR cooler 16 detected by the temperature sensor 23 does not exceed 90 ° C. It is confirmed whether Ice exceeds 1 hour or whether the regeneration control Rce of the particulate filter 24 is performed in the light load operation state where the engine speed Ne is 1200 rpm or less, and any of the conditions is satisfied. In this case, the process proceeds to the next step S8, where it is confirmed whether the reverse flow mode is currently selected. If the reverse flow mode is selected, the process proceeds to step S9, where the first valve scavenging mode is selected and the reverse flow is selected. When the mode is not selected (when the forward flow mode is selected), the process proceeds to step S10 and the second valve scavenging mode is selected. It has become so.

  Regardless of whether the first valve scavenging mode or the second valve scavenging mode is selected, in the next step S11, after-injection is added at a combustible timing immediately after the main injection, and intake by the intake throttle valve 26 is performed. The exhaust gas temperature raising control for forcibly raising the exhaust gas temperature by reducing the flow rate of No. 3 was performed, and the outlet gas temperature Tgo of the EGR cooler 16 detected by the temperature sensor 23 in the next step S12 exceeded 300 ° C. In step S13, it is confirmed that 3 minutes have elapsed after the confirmation, and then, in step S14, it is confirmed whether or not the first valve scavenging mode is selected, and the first valve scavenging mode is selected. If the forward flow mode is selected and the first valve scavenging mode has not been selected, the process proceeds to step S16 and reverses. Mode is to be selected.

  Note that, regardless of whether the forward flow mode or the reverse flow mode is selected, in the next step S17, the accumulated time Ice traveled while the outlet gas temperature Tgo of the EGR cooler 16 does not exceed 90 ° C. is reset. 0 "and the same procedure is repeated by returning to the previous step S7.

Here, in the flowchart of FIG. 3, as a condition for selecting the first valve scavenging mode or the second valve scavenging mode, the accumulated time during which the outlet gas temperature of the EGR cooler 16 does not exceed a predetermined temperature (for example, 90 ° C.) A case where a specified time (for example, 1 hour) is exceeded and a case where the regeneration control of the particulate filter 24 is performed in a light load operation state at a predetermined rotation speed (for example, 1200 rpm) or less is adopted. Is established, the first valve scavenging mode or the second valve scavenging mode is executed. However, the conditions under which the soot compound is likely to accumulate on the outlet valves 20 and 21 are based on any event. The conditions themselves may be arbitrarily determined.

  Thus, when the EGR device is controlled according to the control procedure shown in the flowchart of FIG. 3, all of the inlet valves 17 and 18 and the outlet valves 20 and 21 of the gas chambers 11 and 12 are opened when the engine 1 is cold. Thus, the warm-up mode in which only the gas chambers 11 and 12 pass through the gas chambers 11 and 12 without passing through the tubes 13 and flow to the EGR pipe 19 is selected, and the inlet valves 17 and 18 of the gas chambers 11 and 12 are connected. Since all of the outlet valves 20 and 21 are opened and the reflux gas 8 ′ is recirculated to the vicinity of the inlet of the intake manifold 6 without passing through the tube 13, the engine 1 is actively warmed up. Will be promoted. Here, the reason why the recirculation gas 8 'is guided to the EGR pipe 19 through both the gas chambers 11 and 12 is to recirculate more warm recirculation gas 8' without causing extra pressure loss. is there.

  Further, in a general EGR device, the recirculation gas 8 ′ cooled by the EGR cooler 16 at the start of the cold engine may be recirculated, so that the warm-up of the engine 1 may be delayed. Although the recirculation of the reflux gas 8 ′ is stopped in order to give priority to the warm-up, the EGR device of the present embodiment can recirculate the reflux gas 8 ′ even at the time of cold start so that NOx during the warm-up can be obtained. Can be reduced.

  When the completion of warm-up is confirmed by the engine water temperature, a mode opposite to the mode before the engine 1 is stopped is selected from the forward flow mode and the reverse flow mode. For example, the forward flow mode is selected by the control device 22. In this case, the inlet valve 17 of one gas chamber 11 and the outlet valve 21 of the other gas chamber 12 are opened, and the reflux gas 8 ′ flows from one gas chamber 11 to the other gas chamber 12, When the reverse flow mode is selected by the control device 22, the inlet valve 18 of the other gas chamber 12 and the outlet valve 20 of the one gas chamber 11 are opened so that the reflux gas 8 ′ is sent from the other gas chamber 12 to the other gas chamber 12. The gas flows backward toward the gas chamber 11. As described above, when the forward flow mode and the reverse flow mode are alternately selected by the control device 22, the low temperature region which has been the outlet side of the EGR cooler 16 is changed to the inlet side to become a high temperature region. The SOF component adhering to the channel wall surface volatilizes and the channel wall surface returns to a dry state, so that the soot component, which is a precursor of the soot compound, is difficult to deposit.

  The mode selected here is continued until the condition that the deposition of the soot compound on the outlet valves 20 and 21 is concerned is satisfied, but the outlet gas temperature of the EGR cooler 16 is a predetermined temperature (for example, 90 ° C.). ) When the accumulated time of traveling without exceeding the specified time (for example, 1 hour) and when the regeneration control of the particulate filter 24 is performed in a light load operation state at a predetermined rotational speed (for example, 1200 rpm) or less. When either condition is satisfied, the first valve scavenging mode or the second valve scavenging mode is executed. That is, if the reverse flow mode is currently selected, the first valve scavenging mode is selected, and if the forward flow mode is currently selected, the second valve scavenging mode is selected.

  That is, even if the forward flow mode and the reverse flow mode are alternately selected as described above, only the reflux gas 8 ′ cooled through the tube 13 is guided to the outlet valves 20 and 21 of the gas chambers 11 and 12, respectively. Therefore, the temperature at each of the outlet valves 20 and 21 is always low, so that the SOF component easily adheres. Therefore, only the inlet valve 17 and the outlet valve 20 of one gas chamber 11 are opened and refluxed. Only the first valve scavenging mode in which the gas 8 ′ passes through only one gas chamber 11 without passing through the tube 13 and flows to the EGR pipe 19, and only the inlet valve 18 and the outlet valve 21 of the other gas chamber 12 are opened. The second gas flowing through the EGR pipe 19 through the other gas chamber 12 without passing through the tube 13 through the reflux gas 8 ′. A Bed scavenge mode, which of the forward flow mode and the backflow mode is to be selected based on whether the currently selected.

  As a result, the high-temperature recirculation gas 8 ′ extracted from the exhaust manifold 9 is directly circulated to any one of the outlet valves 20 and 21, and the temperature rises. The attached SOF component volatilizes and the flow path wall surface returns to a dry state, so that the soot component, which is a precursor of the soot compound, is difficult to deposit. Here, each outlet valve 20, 21 is scavenged one by one with the reflux gas 8 'in order to enhance the effect of scavenging the apportionment by keeping the flow velocity of the reflux gas 8' as high as possible. .

  At this time, since the high-temperature reflux gas 8 ′ is also guided to the EGR pipe 19, the SOF component adhering to the flow path wall surface of the EGR pipe 19 is volatilized and the flow path wall surface becomes There is also an attendant merit of returning to a dry state and making it difficult for the soot compound precursor to accumulate.

  In addition, when alternately selecting the first valve scavenging mode or the second valve scavenging mode, after injection is added at a combustible timing immediately after the main injection, or the flow rate of the intake air 3 is reduced as necessary. Thus, it is more effective to forcibly raise the exhaust gas temperature, so in this embodiment, the exhaust gas temperature raising control is used together.

  Then, the completion of the first valve scavenging mode or the second valve scavenging mode is determined based on the outlet gas temperature of the EGR cooler 16 and the passage of time, and whether the first valve scavenging mode or the second valve scavenging mode is currently selected. Based on the above, if the first valve scavenging mode is selected, the forward flow mode is selected this time, and if the second valve scavenging mode is selected, the reverse flow mode is selected this time.

  Therefore, according to the above-described embodiment, the flow direction of the recirculation gas 8 ′ with respect to the EGR cooler 16 can be reversed by alternately selecting the forward flow mode and the reverse flow mode by the control device 22, thereby the EGR cooler 16. The low temperature region that has been on the outlet side of the gas is changed to the high temperature region by changing it to the inlet side, and the SOF component adhering to the flow path wall surface of the region is volatilized to make the flow path wall surface dry. It is possible to make it difficult to deposit soot that is a precursor of the soot compound, so that adhesion deposition of soot compound on the outlet side of the EGR cooler 16 can be prevented, and reduction in efficiency and clogging of the EGR cooler 16 can be prevented. Can be avoided.

  Further, by alternately selecting the first valve scavenging mode and the second valve scavenging mode by the control device 22, the high-temperature recirculation gas 8 ′ extracted from the exhaust manifold 9 is directly applied to any one of the outlet valves 20 and 21. The temperature is raised by circulation, and the SOF component adhering to the flow path wall surface of each of the outlet valves 20 and 21 is volatilized to return the flow path wall surface to a dry state. Since it is possible to make it difficult to deposit soot, it is possible to prevent deposition of soot compounds on the outlet valves 20 and 21, and to prevent malfunction of the outlet valves 20 and 21.

  Further, by alternately selecting the first valve scavenging mode and the second valve scavenging mode by the control device 22, the high-temperature recirculation gas 8 ′ extracted from the exhaust manifold 9 is directly led to the EGR pipe 19 to raise the temperature, Since the SOF component adhering to the channel wall surface of the EGR pipe 19 is volatilized to return the channel wall surface to a dry state, it is possible to make it difficult to deposit soot as a precursor of the soot compound. It is possible to prevent deposition and deposition of soot compounds on the pipe 19, and to avoid a reduction in the cross-sectional area of the EGR pipe 19.

  Further, by selecting the warm-up mode by the control device 22 when the engine 1 is cold-started, the reflux gas 8 ′ can be recirculated to the vicinity of the inlet of the intake manifold 6 without passing through the tube 13. Therefore, the warm-up of the engine 1 can be actively promoted, and the recirculation gas 8 ′ is recirculated during the cold start when the recirculation of the recirculation gas 8 ′ is generally stopped. Reduction of NOx can be achieved.

  The EGR device of the present invention is not limited to the above-described embodiment. The first valve scavenging mode, the second valve scavenging mode, and the warm-up mode can be added as necessary. In addition, the exhaust passage may be an exhaust manifold or an exhaust pipe, the intake passage may be an intake manifold or an intake pipe, and does not depart from the gist of the present invention. Of course, various changes can be made within the range.

1 Engine 6 Intake manifold (intake passage)
8 Exhaust gas 8 'Reflux gas 9 Exhaust manifold (exhaust passage)
11 Gas chamber (one gas chamber)
12 Gas chamber (the other gas chamber)
13 Tube 14 Shell 15 Cooling water 16 EGR cooler 17 Inlet valve 18 Inlet valve 19 EGR pipe 20 Outlet valve 21 Outlet valve 22 Control device

Claims (3)

  An EGR device that extracts a part of exhaust gas from an exhaust passage of an engine and recirculates it as a recirculation gas to an intake passage, and connects a pair of gas chambers with a plurality of tubes and surrounds each tube with a shell. An EGR cooler capable of sucking and discharging cooling water in the shell and connecting each gas chamber of the EGR cooler to an exhaust passage through an inlet valve and branching an EGR pipe led from the intake passage. Each of the gas chambers is connected to each of the gas chambers via an outlet valve, and each of the inlet valves and each of the outlet valves is individually controlled, and includes an inlet valve of one gas chamber and an outlet of the other gas chamber. Only the valve is opened and the recirculation gas flows from one gas chamber to the other gas chamber, and the outlet bar of one gas chamber. And the control device is configured to select a reverse flow mode in which only the inlet valve of the other gas chamber is opened and the reflux gas is caused to flow backward from the other gas chamber toward the one gas chamber. EGR device.   A first valve scavenging mode in which only one of the gas chambers is opened and only one of the gas chambers is passed through the EGR pipe without passing through the tube by opening only the inlet valve and the outlet valve of the one gas chamber, and the inlet of the other gas chamber The control device is configured to select the second valve scavenging mode in which only the other gas chamber is passed through the other gas chamber without opening the valve and the outlet valve and passing through the other gas chamber. The EGR apparatus according to claim 1.   A warm-up mode can be selected in which all of the inlet and outlet valves of each gas chamber are opened at the time of engine cold start so that the recirculation gas passes through each gas chamber without passing through the tube and flows to the EGR pipe. The EGR device according to claim 1, wherein a control device is configured.

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