JP2012149558A - Exhaust gas recirculation system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation system of an internal combustion engine, which effectively controls the formation of a water film in an impurity collection filter that prevents impurities from entering a recirculating exhaust gas, to reliably prevent an exhaust recirculation path from being blocked by the impurity collection filter, at low cost.SOLUTION: The exhaust gas recirculation system of an internal combustion engine, is installed in an engine 10 that has a diesel particulate filter (DPF) unit 45 in the middle of an exhaust pipe 42. The exhaust gas recirculation system of an internal combustion engine, includes: a low pressure loop-exhaust gas recirculation (LPL-EGR) pipe 71 for recirculating the exhaust gas cleaned-up by the DPF unit 45 to a side of an aspiration passage 32w from a side of an exhaust gas passage 42w; and the impurity collection filter 80 formed in a convex shape that is protruded inside the exhaust gas passage 42w from an interior wall of the LPL-EGR pipe 71 or of the exhaust pipe 42.

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine, and more particularly to an exhaust gas recirculation device for an internal combustion engine provided with a foreign matter collecting filter in an exhaust gas recirculation path.

  In a vehicle engine (internal combustion engine), an exhaust gas recirculation device is provided to perform exhaust gas recirculation (hereinafter also referred to as EGR (Exhaust Gas Recirculation)) effective in reducing NOx (nitrogen oxide). However, the HPL (High Pressure Loop) -EGR system, which recirculates some of the hot exhaust gas to the intake side, has passed through the turbocharger exhaust turbine and exhaust aftertreatment device. An exhaust gas recirculation device of LPL (Low Pressure Loop) -EGR system that enables exhaust gas recirculation at a low temperature by recirculating exhaust gas upstream of the compressor of the turbocharger has become widespread.

  In this LPL-EGR system, foreign matter such as spatter (spatters at the time of welding) and dropping pieces from the exhaust gas purification device can be generated in the exhaust pipe that recirculates the exhaust gas to the intake passage side. Generally, a foreign matter collecting filter is provided in the exhaust gas recirculation path so as not to cause damage by entering the compressor of the supercharger.

  As an LPL-EGR system equipped with such a foreign matter collecting filter, for example, an EGR filter for collecting exhaust foreign matter in EGR gas flowing through a low pressure EGR passage, and a state in which the EGR filter rattles against a low pressure EGR pipe There are known ones including a holding part that holds the exhaust system and a capturing part that captures exhaust system foreign matter shaken off from the EGR filter (see, for example, Patent Document 1).

  In addition, an EGR gas pickup pipe provided with a foreign matter collecting filter is inserted downstream of the exhaust turbine of the turbocharger and upstream of the filter portion in the DPF (diesel particulate filter) device. There is also known one in which EGR gas is recirculated upstream from the compressor of the turbocharger by using the back pressure obtained by the filter unit of the DPF device in the axial direction (see, for example, Patent Document 2). ).

JP 2010-138745 A JP 2003-535264 A

  However, in the conventional exhaust gas recirculation device for an internal combustion engine as described above, the foreign matter collecting filter in the low pressure EGR pipe is easy to form a water film with a fine mesh, so that the exhaust gas recirculation passage is a water film. The foreign matter collecting filter that forms the gas is likely to be clogged, and a required amount of exhaust gas is not recirculated, so that the NOx reduction effect may be reduced.

  In addition, when heat transfer and moisture evaporation to the foreign matter collecting filter are promoted by welding the foreign matter collecting filter or a pickup pipe to which the foreign matter collecting filter is fixed to a DPF case having a large heat capacity, the structure becomes complicated and the cost increases. There was a problem of inviting.

  Furthermore, if the exhaust pipe flow passage is easily blocked by the foreign matter collecting filter, it is difficult to evaporate or neutralize acidic condensate generated in the EGR cooler or the like on the exhaust passage side. There is also a concern that the metal parts of the system are easily corroded by condensed water.

  Therefore, the present invention effectively suppresses the formation of a water film on the foreign matter collecting filter that prevents foreign matter from entering the recirculated exhaust gas, and the passage in the exhaust recirculation pipe is blocked by the foreign matter collecting filter. It is an object of the present invention to provide an exhaust gas recirculation device for an internal combustion engine that can reliably prevent the above-mentioned problem.

  In order to solve the above problems, an exhaust gas recirculation device for an internal combustion engine according to the present invention is (1) exhaust gas recirculation for an internal combustion engine equipped in an internal combustion engine having an exhaust gas purification unit in the middle of an exhaust pipe forming an exhaust gas passage. An exhaust gas recirculation pipe that recirculates the exhaust gas purified by the exhaust gas purification unit from the exhaust gas passage side to the intake passage side of the internal combustion engine, and the exhaust recirculation pipe or the inner wall surface of the exhaust pipe A convex foreign matter collecting filter protruding into the exhaust gas passage.

  In this invention, since the foreign matter collecting filter has a convex shape protruding into the exhaust gas passage from the exhaust recirculation pipe or the inner wall surface of the exhaust pipe, the foreign matter is collected even when the recirculated exhaust gas does not flow into the exhaust recirculation passage. The collection filter is constantly exposed to the exhaust gas passing through the exhaust gas passage in a relatively large area and intersects the direction of the exhaust gas flow in the exhaust gas passage, and the foreign matter collection filter is exhausted. Heat transfer from the exhaust pipe side to the foreign matter collecting filter is improved without welding to large parts on the pipe side. Therefore, the evaporation of water adhering to the foreign matter collecting filter is promoted, the formation of a water film on the foreign matter collecting filter is effectively suppressed, and the passage in the exhaust gas recirculation pipe is blocked by the foreign matter collecting filter. Can be reliably prevented, and the complexity and cost of the structure can be avoided.

  In the exhaust gas recirculation device for an internal combustion engine according to the present invention, (2) the exhaust purification unit can purify the exhaust gas passing through the cylindrical case portion disposed in the exhaust pipe and the cylindrical case portion. The exhaust gas recirculation pipe recirculates the exhaust gas that has passed through the exhaust gas purification filter portion of the exhaust gas purification unit from the exhaust gas passage side to the intake passage side, and the foreign matter collecting filter Preferably, in the vicinity of the upstream end portion of the exhaust gas recirculation pipe, the exhaust gas passage projects into the exhaust gas passage from the inner wall surface of the cylindrical case portion on the downstream side of the exhaust gas purification filter portion of the exhaust gas purification unit.

  With this configuration, the foreign matter collecting filter can be exposed to the exhaust gas passing through the cylindrical case portion with a large area, and the gas passage surface that intersects the direction of the exhaust gas flow in the cylindrical case portion can be easily provided. In addition, sufficient heat transfer from the cylindrical case portion having a large heat capacity to the foreign matter collecting filter becomes possible. Therefore, the formation of a water film on the foreign matter collecting filter is prevented, so that a required exhaust gas recirculation amount can be secured.

  In the case of having the configuration described in (2) above, (3) an exhaust cooler that cools exhaust gas that is installed in the middle of the exhaust gas recirculation pipe and recirculates to the intake pipe side, and that has an upstream end of the exhaust gas recirculation pipe The exhaust cooler is configured to discharge the condensed water generated in the exhaust cooler through the foreign matter collecting filter into the exhaust gas passage on the downstream side of the exhaust purification filter portion of the exhaust purification unit. It is preferable to descend from the inlet portion toward the inner wall surface side of the cylindrical case portion downstream of the exhaust purification filter portion. With this configuration, acidic condensed water generated by cooling the exhaust gas in the exhaust gas recirculation pipe flows down from the inlet portion of the exhaust cooler toward the inner wall surface side of the cylindrical case portion downstream of the exhaust purification filter portion. As a result, it becomes difficult to flow into the intake passage and the intake system parts are hardly corroded.

  When having the configuration described in (2) or (3) above, (4) the exhaust purification filter portion of the exhaust purification unit is configured by a particulate matter collection filter, and the cylindrical case portion is It has an inclined inner wall surface inclined in the direction of diameter reduction with respect to the wall surface around the particulate matter collection filter so as to reduce the cross-sectional area of the exhaust gas passage on the downstream side of the particulate matter collection filter. Is preferred. With this configuration, the angle and range at which the foreign matter collecting filter intersects the flow of exhaust gas from the upstream side can be increased, and the action of suppressing the formation of a water film in the foreign matter collecting filter can be strengthened, and Inflow of exhaust gas can be facilitated.

  In the case of having any one of the constitutions (2) to (4), (5) the foreign matter collecting filter is disposed between the upstream end portion of the exhaust gas recirculation pipe and the cylindrical case portion of the exhaust gas purification unit. It is preferable to have an annular base end portion that is sandwiched and a convex surface forming portion that is supported by the annular base end portion and protrudes into the exhaust gas passage to form the convex surface. As a result, sufficient heat transfer from the cylindrical case portion of the exhaust purification unit having a large heat capacity to the foreign matter collecting filter can be performed, and the foreign matter collecting filter can convert the exhaust gas passing through the exhaust gas passage in a relatively large area. It is exposed and crosses the direction of the exhaust gas flow in the exhaust gas passage.

  When having the configuration of (5) above, (6) a reflux pipe side flange portion that forms the upstream end of the exhaust gas reflux pipe, and the tubular shape of the exhaust gas purification unit corresponding to the reflux pipe side flange part A case-side flange portion provided in the case portion, and the annular base end portion of the foreign matter collecting filter includes the return-tube side flange portion of the exhaust gas recirculation tube and the case-side flange of the exhaust gas purification unit. The convex surface forming portion of the foreign matter collecting filter is supported by the annular base end portion and protrudes into the exhaust gas passage through the inside of the reflux pipe side flange portion. Even if it is, it is preferable. In this case, the foreign matter collecting filter can be easily attached, and sufficient heat transfer from the cylindrical case portion of the exhaust purification unit having a large heat capacity to the foreign matter collecting filter can be performed. Exhaust gas flowing into the pipe is allowed to pass through a wide gas passage area.

  In the case of having any one of the above configurations (2) to (6), (7) the foreign matter collecting filter is fixed to the upstream end of the exhaust recirculation pipe, and the upstream end of the exhaust recirculation pipe It is preferable to be sandwiched between the cylindrical case portion of the exhaust purification unit. As a result, when the upstream end portion of the exhaust gas recirculation pipe is connected to the cylindrical case portion of the exhaust gas purification unit, the foreign matter collecting filter is automatically sandwiched between them, so that the foreign matter collecting filter is assembled. Improves.

  In the case of having any one of the constitutions (5) to (7), (8) a part of the foreign matter collection filter sandwiched between the exhaust purification unit and the cylindrical case portion is the exhaust gas recirculation. It is preferable that the gasket is disposed between the upstream end portion of the pipe and the cylindrical case portion of the exhaust purification unit. In this case, the assembly of the foreign matter collecting filter can be further facilitated and the manufacturing cost can be reduced without substantially increasing the number of parts.

  In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, (9) the internal combustion engine includes an exhaust turbine that rotates by energy of exhaust gas flowing in the exhaust gas passage, and the intake passage connected to the exhaust turbine. A turbocharger having an intake air compressor for compressing the intake air therein is mounted, and the exhaust gas recirculation pipe is located upstream of the intake air compressor in the intake pipe forming the intake passage of the internal combustion engine. It is preferable to be connected to the intake pipe. With this configuration, it is possible to effectively suppress the formation of a water film on the foreign matter collecting filter at the inlet portion of the exhaust gas recirculation pipe in the low pressure EGR circuit in which the amount of condensed water generated increases, and the passage in the exhaust gas recirculation pipe is blocked. The required low pressure EGR amount can be secured.

  According to the present invention, the foreign matter collecting filter is disposed so as to form a convex shape protruding into the exhaust gas passage from the exhaust gas recirculation pipe or the inner wall surface of the exhaust pipe, and the foreign matter collecting filter has a relatively large area and the exhaust gas is exhausted. It is always exposed to the exhaust gas passing through the passage, intersects with the direction of the exhaust gas flow in the exhaust gas passage, and heat transfer from the exhaust pipe side to the foreign matter collecting filter is improved. Therefore, it is possible to effectively suppress the formation of a water film on the foreign matter collecting filter that prevents foreign matters from entering the recirculated exhaust gas, and to prevent the passage in the exhaust recirculation pipe from being blocked by the foreign matter collecting filter. It is possible to provide a low-cost exhaust gas recirculation device for an internal combustion engine that can be reliably prevented.

1 is an overall schematic configuration diagram of an exhaust gas recirculation device for an internal combustion engine according to a first embodiment of the present invention. It is a principal part block diagram including the partial cross section of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 1st Embodiment of this invention. It is a principal part expanded sectional view of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 1st Embodiment of this invention. 1 is a schematic external perspective view of a foreign matter collecting filter in an exhaust gas recirculation device for an internal combustion engine according to a first embodiment of the present invention. It is a principal part block diagram containing the partial cross section of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention. It is a principal part expanded sectional view of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention. It is a general | schematic external appearance perspective view of the foreign material collection filter in the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
1 to 4 show a first embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention.

  In this embodiment, the present invention is applied to an in-line four-cylinder diesel engine 10 (hereinafter simply referred to as the engine 10) which is a multi-cylinder internal combustion engine.

  As shown in FIG. 1, the engine 10 of the present embodiment has a plurality of cylinders 11 in a main body block 10M. The engine 10 includes combustion chambers (details are not shown) in each cylinder 11. A common rail fuel injection device 12 for injecting fuel into the combustion chamber, an intake device 13 for inhaling air into the combustion chamber, an exhaust device 14 for exhausting exhaust gas from the combustion chamber, and exhaust energy in the exhaust device 14 Then, the turbocharger 15 that compresses the intake air in the intake device 13 and supercharges the air into the combustion chamber, and returns a part of the high-pressure side exhaust gas upstream from the turbocharger 15 to the intake side. HPL (High Pressure Loop) -EGR device 16 which is an exhaust gas recirculation device on the high pressure side to be recirculated and a part of the low pressure exhaust gas downstream from the turbocharger 15 is recirculated to the intake side and recirculated. Circulating low pressure side exhaust And LPL (Low Pressure Loop) -EGR device 17 is a circular device is equipped.

  The fuel injection device 12 includes a supply pump 21 that pumps fuel from a fuel tank (not shown), pressurizes the fuel to a high fuel pressure (fuel pressure), and discharges the fuel, a common rail 22 into which fuel from the supply pump 21 is introduced, and the common rail And a fuel injection valve 23 that injects the fuel supplied through the cylinder 22 into the combustion chamber at a timing and opening degree (duty ratio) corresponding to an injection command signal from an ECU (electronic control unit) (not shown). The supply pump 21 is driven using, for example, the rotational power of the engine 10, and the common rail 22 distributes and supplies the high-pressure fuel supplied from the supply pump 21 to the plurality of fuel injection valves 23 while keeping it even. The fuel injection valve 23 is composed of a known needle valve that is electromagnetically driven, and the valve opening time is controlled in accordance with the injection command signal, whereby a fuel (for example, light oil) of a fuel injection amount corresponding to the injection command signal is supplied. It can be injected and supplied into the combustion chamber.

  The intake device 13 includes an intake manifold 31, an intake pipe 32 upstream of the intake manifold 31, an air cleaner 33 that cleans intake air by a filter at the most upstream portion of the intake pipe 32, and a downstream side of the turbocharger 15. An intercooler 34 that cools the intake air heated by compression / supercharging by the intake air compressor 15a in the intake pipe portion 32b, an air flow meter 35 that detects the intake flow rate of fresh air, and an intake air amount into the engine 10 A throttle valve 36 for adjustment, an intake air temperature sensor 37 for detecting the intake air temperature, and an intake pipe pressure sensor 38 for detecting the boost pressure of the engine 10 near the inlet of the intake manifold 31 are mounted.

  The exhaust device 14 has an exhaust manifold 41, an exhaust pipe 42 downstream from the exhaust manifold 41, and an exhaust throttle that can increase the exhaust temperature during idling or light load and can control the back pressure of the LPL-EGR device 17. A valve 43 and an exhaust aftertreatment device 46 including a known oxidation catalytic converter 44 and a DPF (diesel particulate filter) unit 45 mounted on an exhaust pipe 42 downstream of the turbocharger 15. ing.

  The turbocharger 15 includes an intake air compressor 15a and an exhaust turbine 15b that are integrally coupled to each other in the rotational direction. The intake air compressor 15a is rotated by rotating the exhaust turbine 15b and exhaust air compressor 15a by exhaust energy. The intake air can be compressed by the compressor 15 a to supply positive pressure air into the engine 10.

  The HPL-EGR device 16 is mounted between the HPL-EGR pipe 61 and the HPL-EGR pipe 61 interposed between the exhaust manifold 41 and the intake pipe 32, and adjusts the recirculation amount of the exhaust gas. An HPL-EGR valve 62 that can be used, and an HPL-EGR cooler 63 that can cool the exhaust gas passing through the HPL-EGR pipe 61 on the way. The HPL-EGR pipe 61 bypasses the combustion chamber in the engine 10, and a part of the exhaust passage in the exhaust pipe 42 upstream of the exhaust turbine 15 b (inside the exhaust pipe part 42 a on the upstream side) or the exhaust manifold 41. The high-pressure side exhaust recirculation passage P1 that connects the exhaust passage inside and the portion of the intake passage 32w in the intake pipe 32 downstream of the intake air compressor 15a (inside the intake pipe portion 32b on the downstream side) is formed. It is a side passage forming member. Further, the HPL-EGR valve 62 is in an open state in which the high pressure side exhaust gas recirculation passage P1 is opened, and in a closed state in which the opening of the high pressure side exhaust gas recirculation passage P1 is restricted, for example, the high pressure side exhaust gas recirculation passage P1 is shut off. It is possible to switch to. Although not shown in detail, the HPL-EGR cooler 63 is provided with a cooling water pipe portion that contacts the EGR gas in a case portion that forms a part of the high-pressure side exhaust gas recirculation passage P1, and is used for cooling that is introduced into the cooling water pipe portion. The high-pressure side recirculated exhaust gas can be cooled by heat exchange between the fluid (for example, engine cooling water) and the high-pressure recirculated exhaust gas passing through the case portion. The high-pressure side exhaust gas recirculation passage P <b> 1 forms a main part of the high-pressure side exhaust gas recirculation path in the HPL-EGR device 16.

  The LPL-EGR device 17 is installed in the middle of the LPL-EGR pipe 71 interposed between the exhaust pipe 42 and the intake pipe 32 and adjusts the recirculation amount of the exhaust gas. An LPL-EGR valve 72 that can be used, an LPL-EGR cooler 73 that serves as an exhaust cooler that can cool the exhaust gas that passes through the LPL-EGR pipe 71, and an exhaust passage in the exhaust pipe 42 on the downstream side. Of these, the exhaust throttle valve 43 that can reduce the opening degree so as to reduce the cross-sectional area of the passage in the exhaust passage portion downstream of the DPF unit 45 is provided.

  The LPL-EGR pipe 71 bypasses the combustion chamber in the engine 10, and a portion of the exhaust gas passage 42 w in the exhaust pipe 42 downstream of the exhaust turbine 15 b (inside the exhaust pipe portion 42 b on the downstream side) and the intake air A low-pressure side exhaust recirculation passage P2 (low-pressure side exhaust recirculation path) that communicates with a portion upstream of the intake air compressor 15a (inside the upstream intake pipe portion 32a) in the intake passage 32w in the pipe 32 is formed. The exhaust gas recirculation pipe is configured to recirculate the exhaust gas purified by the oxidation catalyst converter 44 and the DPF unit 45 from the exhaust gas passage 42w side to the intake passage 32w side. The LPL-EGR valve 72 is in an open state in which the low pressure side exhaust gas recirculation passage P2 is opened, and in a closed state in which the opening of the low pressure side exhaust gas recirculation passage P2 is restricted, for example, the low pressure side exhaust gas recirculation passage P2 is shut off. It is possible to switch to. Furthermore, the LPL-EGR cooler 73 includes a case portion 73a that forms part of the low-pressure side exhaust recirculation passage P2, and a cooling water pipe portion 73b that contacts the EGR gas passing through the case portion 73a and forms a cooling fluid passage. And the low-pressure side recirculated exhaust gas by heat exchange between the cooling fluid (for example, engine cooling water) introduced into the cooling water pipe portion 73b and the recirculated exhaust gas passing through the case portion 73a. Can be cooled. The low-pressure side exhaust recirculation passage P2 is a low-pressure in the LPL-EGR device 17 together with a portion of the intake passage 32w in the intake pipe 32 downstream of the connection position j where the LPL-EGR pipe 71 is connected to the intake pipe 32. Side exhaust gas recirculation path.

On the other hand, the oxidation catalyst converter 44 and the DPF unit 45 are disposed in the middle of the exhaust pipe 42 of the engine 10 and serve as an exhaust purification unit that purifies exhaust gas passing through the inside. That is, the oxidation catalytic converter 44 has an oxidation performance that can change, for example, hydrocarbon (HC) and carbon monoxide (CO) into carbon dioxide (CO ₂ ) and water (H ₂ O). The DPF unit 45 has a honeycomb structure made of, for example, porous ceramics. The DPF unit 45 collects particulate matter (PM) contained in the exhaust gas of the engine 10 and burns PM deposited by the collection. The playback process can be performed.

  As shown in FIGS. 2 to 4, the DPF unit 45 specifically includes a cylindrical case portion 51 that is disposed in the middle of the exhaust pipe 42 and extends the exhaust gas passage 42 w in a specific passage section, and the cylinder. PM collection filter unit 52 (exhaust gas purification filter unit) housed in the cylindrical case unit 51 so as to collect PM in the exhaust gas passing through a specific passage section in the cylindrical case unit 51 and purify the exhaust gas And have.

  The cylindrical case portion 51 of the DPF unit 45 has a passage cross-sectional area on the downstream side of the PM collection filter portion 52 on the downstream side of the PM collection filter portion 52 in the extended specific passage section of the exhaust gas passage 42w. The inner wall surface 51a (inclined inner wall surface) that inclines and intersects with the cylindrical wall surface 51b around the PM collection filter portion 52 in the direction of diameter reduction (direction in which the diameter decreases) is reduced.

  In addition, the inside of the cylindrical case portion 51 on the downstream side of the PM collection filter portion 52 is a downstream portion of a specific passage section of the exhaust gas passage 42 w extended corresponding to the PM collection filter portion 52. An exhaust gas distribution chamber 53 is defined, and an exhaust gas passage portion 42wx downstream of the exhaust gas distribution chamber 53 in the exhaust gas passage 42w is, for example, on the vehicle rear side from the exhaust gas distribution chamber 53 in FIG. While extending to the near side, the low pressure side exhaust recirculation passage P2 is curved while extending from the exhaust gas distribution chamber 53 to the upper side in FIG.

  On the other hand, in the vicinity of the upstream end 71u of the LPL-EGR pipe 71 forming the low pressure side exhaust recirculation passage P2, a cylindrical case portion 51 constituting a part of the inner wall surface of the upstream end 71u or the adjacent exhaust pipe 42 is provided. A convex foreign matter collecting filter 80 protruding from the inner wall surface 51a into the exhaust gas passage 42w is provided.

  The foreign matter collecting filter 80 is formed of a metal mesh (a net made of metal wire, or a porous body having a porosity) that is sufficiently finer than the honeycomb-shaped PM collecting filter portion 52 of the DPF unit 45. In addition, spatter (spattering during welding) existing in the exhaust pipe 42, falling pieces from the PM collection filter 52, or foreign matters moving with the exhaust gas from the upstream side of the PM collection filter 52 are generated. The foreign matter is captured at the time, and such foreign matter is prevented from entering the intake air compressor 15a of the turbocharger 15 and causing damage.

  Further, the foreign matter collecting filter 80 is disposed in the vicinity of the upstream end 71u of the LPL-EGR pipe 71 and from the inner wall surface 51a of the cylindrical case portion 51 on the downstream side of the PM collecting filter portion 52 of the DPF unit 45 to the exhaust gas passage. It protrudes into the exhaust gas distribution chamber 53 which is a part of 42w.

  Specifically, the upstream end portion 71u of the LPL-EGR pipe 71 is connected to an annular insertion portion 71i held in an opening peripheral portion 51p formed in the cylindrical case portion 51 of the DPF unit 45, and the annular insertion portion 71i. It has a flange portion 71f that is adjacent and airtightly fixed and held to the cylindrical case portion 51.

  As shown in FIG. 4, the foreign matter collecting filter 80 includes an annular outer peripheral edge portion 81 sandwiched between the opening peripheral portion 51p of the cylindrical case portion 51 and the flange portion 71f of the LPL-EGR pipe 71, A short cylindrical portion 82 sandwiched between the opening peripheral portion 51p of the cylindrical case portion 51 and the annular insertion portion 71i of the LPL-EGR pipe 71, and a substantially conical shape from the short cylindrical portion 82 into the exhaust gas passage 42w. And a convex filter portion 83 that protrudes into the center.

  Here, the annular outer peripheral edge portion 81 and the short cylindrical portion 82 are each an annular base having a substantially L-shaped cross section sandwiched between the upstream end 71 u of the LPL-EGR pipe 71 and the cylindrical case portion 51 of the DPF unit 45. The convex filter portion 83 is an end portion, and is a convex surface forming portion that is supported by a short cylindrical portion 82 as an annular base end portion and protrudes into the exhaust gas passage 42w.

  At least one of the annular outer peripheral edge 81 and the short cylindrical portion 82 is previously welded to the upstream end 71u of the LPL-EGR pipe 71, and in this state, the upstream end 71u of the LPL-EGR pipe 71 is connected to the DPF. When connected to the cylindrical case portion 51 of the unit 45, it is held in a sandwiched state as shown in FIGS.

  By the way, in the engine 10 of the present embodiment, the low pressure side exhaust gas recirculation passage P2 formed by the LPL-EGR device 17 with respect to the recirculation exhaust gas in the high pressure side exhaust gas recirculation passage P1 formed by the HPL-EGR device 16. The recirculated exhaust gas in the low-pressure side and the low-temperature side of the recirculated exhaust gas is cooled by the LPL-EGR cooler 73 in the low-pressure side exhaust recirculation passage P2, so that the LPL-EGR Acidic condensed water is easily generated in the cooler 73. Further, since the foreign matter collecting filter 80 is made of metal and has a fine mesh, a water curtain is easily applied to the surface of the foreign matter collecting filter 80 due to surface tension.

  Therefore, the upstream end 71u of the LPL-EGR pipe 71 passes through the foreign matter collection filter 80 through the foreign matter collection filter 80 and the exhaust gas passage 42w on the downstream side of the PM collection filter 52 of the DPF unit 45 through the LPL-EGR pipe 71. At least vertically in the vertical direction so as to descend from the inlet portion 73e of the LPL-EGR cooler 73 toward the inner wall surface 51a side of the cylindrical case portion 51 downstream of the PM collection filter portion 52 so as to be discharged into the interior. It extends to.

  More specifically, as shown in FIGS. 2 and 3, the upstream end portion 71u of the LPL-EGR pipe 71 is curved from the vicinity of the flange portion 71f toward the upper side in the vertical direction. The remaining part of the LPL-EGR pipe 71 connected to 71u is composed of flange portions at both ends, a plurality of other tubular members 71j, 71k having bellows-like undulations, a part of the LPL-EGR cooler 73, and the like.

  The operation of the engine 10 is controlled by an ECU (electronic control unit) (not shown) based on sensor information of various sensor groups. For example, discharge control of the supply pump 21 (for example, control of the electromagnetic spill valve) ), Fuel injection amount control by the fuel injection valve 23, opening degree control of the throttle valve 36, opening degree (EGR rate) control of the HPL-EGR valve 62 and LPL-EGR valve 72, and opening degree control of the exhaust throttle valve 43 Control and the like are executed. The various sensor groups referred to here include, for example, the known air flow meter 35, intake temperature sensor 37, intake pipe pressure sensor 38, exhaust oxygen concentration sensor 47, exhaust temperature sensors 48a and 48b, exhaust temperature sensor 49, DPF shown in FIG. In addition to the front-rear differential pressure sensor 91, the low pressure EGR differential pressure sensor 92, and the like, there are an accelerator opening sensor, a throttle opening sensor, a crank angle sensor, a water temperature sensor, a vehicle speed sensor, and the like (not shown). Further, instead of the exhaust throttle valve 43 or in combination with the exhaust throttle valve 43, a low pressure EGR intake throttle valve 93 may be provided in the upstream intake pipe portion 32a.

  Next, the operation will be described.

  In the exhaust gas recirculation device for an internal combustion engine of the present embodiment configured as described above, the foreign matter collecting filter 80 is located in the vicinity of the upstream end portion 71u of the LPL-EGR pipe 71, and the inner wall surface or cylinder of the upstream end portion 71u. When the exhaust gas is discharged to the exhaust pipe 42 by the operation of the engine 10, it is formed by the LPL-EGR device 17 because it has a convex shape protruding from the inner wall surface 51 a of the cylindrical case portion 51 into the exhaust gas passage 42 w. Even when the recirculated exhaust gas does not flow in the low-pressure side exhaust recirculation passage P2 or when the flow rate is small, the foreign matter collecting filter 80 is in the exhaust gas flow passing through the exhaust gas passage 42w in a relatively wide area. While being always exposed, the exhaust gas passage 42w intersects the direction of the exhaust gas flow in the exhaust gas passage 42w without closing the exhaust gas passage 42w. Further, at this time, the foreign matter collecting filter 80 is always in contact with the cylindrical case portion 51 having a large heat capacity at the annular outer peripheral edge portion 81 and the short cylindrical portion 82, so that the recirculation exhaust gas is introduced into the low pressure side exhaust recirculation passage P2. Even when the gas does not flow, good heat transfer from the cylindrical case 51 side to the foreign matter collecting filter 80 is possible.

  Therefore, the exhaust gas distribution chamber 53 in the cylindrical case portion 51 on the exhaust gas passage 42w side and the low pressure side exhaust recirculation passage P2 side in the LPL-EGR device 17 are partitioned by a foreign matter collecting filter 80 having a wide gas passage surface. However, by promoting the evaporation of water adhering to the foreign matter collecting filter 80, formation of a water film on the foreign matter collecting filter 80 is effectively suppressed, and the LPL-EGR pipe 71 The passage is reliably prevented from being blocked by the foreign matter collecting filter 80.

  In the present embodiment, the LPL-EGR pipe 71 upstream of the LPL-EGR pipe 71 that recirculates the exhaust gas that has passed through the PM collection filter portion 52 of the DPF unit 45 from the exhaust gas passage 42w side to the intake passage 32w side. In the vicinity of the end 71u, the foreign matter collecting filter 80 that partitions the exhaust gas passage 42w side and the intake passage 32w side is exhausted from the inner wall surface 51a of the cylindrical case portion 51 on the downstream side of the PM collection filter portion 52. Since it protrudes into the passage 42w, the foreign matter collecting filter 80 can be formed so as to be exposed to the exhaust gas passing through the cylindrical case part 51 with a larger area, and the flow of the exhaust gas in the cylindrical case part 51 It is possible to easily form a gas passage surface that intersects the direction of the gas from the cylindrical case portion 51 having a large heat capacity to the foreign matter collecting filter 80. Minute heat transfer is possible. Therefore, the formation of a water film on the foreign matter collecting filter 80 is surely prevented, and a required exhaust gas recirculation amount in the LPL-EGR device 17 can be secured.

  Furthermore, in the present embodiment, the upstream end 71u of the LPL-EGR pipe 71 passes the condensed water generated in the LPL-EGR cooler 73 through the foreign matter collection filter 80 and is downstream of the PM collection filter 52 of the DPF unit 45. The exhaust gas is cooled in the LPL-EGR pipe 71 because it descends from the inlet 73e of the LPL-EGR cooler 73 into the cylindrical case 51 so as to be discharged into the exhaust gas passage 42w. The acidic condensate generated by this becomes easy to flow down from the inlet portion 73e of the LPL-EGR cooler 73 to the downstream side of the PM collection filter portion 52 of the DPF unit 45 and hardly flows into the intake passage 32w side. Accordingly, the metal parts of the intake system (valves, parts of the intake air compressor 15a, etc.) are not easily corroded. The condensed water flowing down into the DPF unit 45 can be easily evaporated, and can be neutralized using a known neutralization means for acid.

  In addition, in the present embodiment, the cylindrical case portion 51 is formed on the cylindrical wall surface 51b around the PM collection filter portion 52 so as to reduce the cross-sectional area of the exhaust gas passage 42w on the downstream side of the PM collection filter portion 52. Since the inner wall surface 51a is inclined in the direction of diameter reduction, the angle and range at which the foreign matter collecting filter 80 intersects the flow of exhaust gas from the upstream side is increased according to the shape of the inner wall surface 51a. It is possible to make adjustments, and it is possible to enhance the water film formation suppressing action in the foreign matter collecting filter 80 and to facilitate the inflow of exhaust gas to the LPL-EGR pipe 71. Further, the foreign matter collecting filter 80 is supported by the annular outer peripheral edge portion 81 and the short cylindrical portion 82 having a substantially L-shaped cross section as an annular base end portion, and protrudes into the exhaust gas passage 42w. Since the convex filter 83 having a substantially conical shape or a substantially hemispherical shape is provided, the effect of suppressing the above-described heat transfer and water curtain formation can be sufficiently obtained.

  Furthermore, in the present embodiment, the LPL-EGR pipe 71 is connected to the upstream side of the intake air compressor 15a in the intake pipe 32 of the engine 10 to configure the LPL-EGR device 17 that generates a large amount of condensed water. At the upstream end 71u that is the inlet of the LPL-EGR pipe 71, water film formation on the foreign matter collecting filter 80 can be effectively suppressed, so that the passage in the LPL-EGR pipe 71 is prevented from being blocked. Therefore, a required low pressure EGR amount can be ensured.

  Further, at least one of the annular outer peripheral edge portion 81 and the short cylindrical portion 82 of the foreign matter collecting filter 80 is previously welded to the upstream end portion 71u of the LPL-EGR pipe 71, and the upstream end portion 71u of the LPL-EGR pipe 71 is When connected to the cylindrical case portion 51 of the DPF unit 45, the foreign matter collecting filter 80 is automatically sandwiched between them, so that the assembling property of the foreign matter collecting filter 80 is excellent. In addition, since it is not necessary to weld the foreign matter collecting filter 80 to the cylindrical case portion 51 or the like, it is possible to avoid a complicated configuration and high cost.

  As described above, in the present embodiment, the foreign matter collecting filter 80 is formed so as to protrude from the upstream end portion 71u of the LPL-EGR pipe 71 or the inner wall surface 51a of the cylindrical case portion 51 into the exhaust gas passage 42w. And the foreign matter collecting filter 80 is exposed to the exhaust gas passing through the exhaust gas passage 42w in a relatively large area and intersects the direction of the exhaust gas flow in the exhaust gas passage 42w. Since heat transfer from the cylindrical case portion 51 side to the collection filter 80 is improved, the exhaust gas passage 42w side and the exhaust recirculation passage side are partitioned by a foreign matter collection filter 80 having a wide gas passage surface. However, it is possible to effectively suppress the formation of a water film on the foreign matter collecting filter 80, and the low pressure side exhaust recirculation passage P2 in the LPL-EGR pipe 71 can collect the foreign matter. It is possible to provide an exhaust recirculation device with low cost internal combustion engine capable of reliably prevented from being closed by filter 80.

(Second Embodiment)
5-7 has shown the principal part of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention.

  This embodiment has an overall configuration substantially similar to that of the above-described first embodiment, and only the configuration of the mounting portion of the foreign matter collecting filter is different from the first embodiment. Accordingly, the same or similar configurations as those of the first embodiment are denoted by the same reference numerals in FIG. 5 to FIG. 7 as the corresponding components in FIG. 1 to FIG. 4, and particularly different from the first embodiment. Is described below.

  As shown in FIGS. 5 and 6, in the exhaust gas recirculation device for the internal combustion engine of the present embodiment, the LPL-EGR device 17 (see FIG. 1) returns to form the upstream end 71 u of the LPL-EGR pipe 71. It has a pipe-side flange portion 111. Further, the cylindrical case portion 51 of the DPF unit 45 projects the opening peripheral portion 51p, which is a part of the inner wall surface 51a on the downstream side of the PM collection filter portion 52, outwardly, and the reflux pipe side flange is formed at the tip portion thereof. The case side flange portion 121 corresponding to the portion 111 is provided.

  The foreign matter collecting filter 180 that divides the exhaust gas passage 42 w side and the intake passage 32 w side is sandwiched between the reflux pipe side flange portion 111 of the LPL-EGR pipe 71 and the case side flange portion 121 of the DPF unit 45. An annular base end portion 181 as a gasket, and a convex surface forming portion 183 integrally coupled to the annular base end portion 181 and projecting into the exhaust gas passage 42w through the inside of the reflux pipe side flange portion 111; ,have.

  As shown in FIGS. 6 and 7, the annular base end portion 181 of the foreign matter collecting filter 180 is integrally provided with a seal ring portion 181 r for sealing between the reflux pipe side flange portion 111 and the case side flange portion 121. Is formed. Further, as shown in FIG. 7, a plurality of bolts (not shown) for fastening the reflux pipe side flange portion 111 and the case side flange portion 121 integrally to each other outside the seal ring portion 181r of the annular base end portion 181. A plurality of bolt holes 185 are formed through the. Of course, the reflux pipe side flange portion 111 and the case side flange portion 121 may be interconnected by a fastening method other than the bolt fastening or by another connecting method.

  In the present embodiment, when connecting the LPL-EGR pipe 71 to the cylindrical case portion 51 of the DPF unit 45, the foreign matter collecting filter 80 is oriented so that the convex surface forming portion 183 faces the inside of the DPF unit 45. Therefore, the foreign matter collecting filter 80 can be easily attached only by arranging the annular base end portion 181 so as to be sandwiched between the reflux pipe side flange portion 111 and the case side flange portion 121. Moreover, sufficient heat transfer from the cylindrical case portion 51 of the DPF unit 45 having a large heat capacity to the foreign matter collecting filter 80 becomes possible, and the foreign matter collecting filter 80 widens the exhaust gas flowing into the LPL-EGR pipe 71. Since the gas is passed through the gas passage area, the same effect as in the first embodiment can be expected.

  Furthermore, in this embodiment, since the foreign material collection filter 180 also functions as a gasket for the flange coupling portion, the foreign material collection filter 180 can be easily assembled without substantially increasing the number of parts. .

  Note that the annular outer peripheral edge 81 of the foreign matter collecting filter 80 in the first embodiment and the annular base end 181 of the foreign matter collecting filter 180 in the second embodiment are the convex filter portion 83 or the convex surface forming portion 183. The periphery of the metal mesh to be formed is held by holding with a metal ring or the like, and the metal ring or the like can be used as a gasket. As in the second embodiment, an annular shape in which the periphery of the metal mesh is fixed It can also be configured by providing an annular unevenness for sealing on the metal plate. Needless to say, the convex shape of the foreign matter collecting filter is not limited to a substantially conical shape, a hemispherical shape, a substantially truncated cone shape, or the like.

  As described above, the exhaust gas recirculation device for an internal combustion engine according to the present invention arranges the foreign matter collecting filter so as to form a convex shape protruding into the exhaust gas passage from the inner wall surface of the exhaust gas recirculation pipe or the exhaust pipe, The foreign matter collecting filter is always exposed to the exhaust gas passing through the exhaust gas passage over a relatively large area and intersects with the direction of the exhaust gas flow in the exhaust gas passage, and further to the foreign matter collecting filter. Since heat transfer from the exhaust pipe side is improved, a low-cost internal combustion engine that can effectively suppress the formation of a water film on the foreign matter collecting filter that prevents foreign matter from entering the recirculated exhaust gas. The exhaust gas recirculation device can be provided, and is useful for exhaust gas recirculation devices for internal combustion engines in which a foreign matter collecting filter is provided in the exhaust gas recirculation path.

10 engine (diesel engine, internal combustion engine)
DESCRIPTION OF SYMBOLS 15 Turbocharger 15a Intake air compressor 15b Exhaust turbine 16 HPL-EGR device 17 LPL-EGR device 32 Intake pipe 32w Intake passage 42 Exhaust pipe 42w Exhaust gas passage 43 Exhaust throttle valve 44 Oxidation catalytic converter 45 DPF unit (Exhaust purification unit) )
51 Cylindrical case part 51a Inner wall surface (inclined inner wall surface)
51b Tubular wall surface (wall surface around the exhaust purification filter section)
51p Opening peripheral part 52 PM collection filter part (exhaust gas purification filter part)
71 LPL-EGR pipe (exhaust gas recirculation pipe)
71u Upstream end 72 LPL-EGR valve 73 LPL-EGR cooler (exhaust cooler)
73e Inlet portion 80; 180 Foreign matter collecting filter 81 Annular outer peripheral edge (annular base end)
82 Short cylinder (annular base end)
83 Convex filter part (convex surface forming part)
111 Reflux Pipe Side Flange 121 Case Side Flange 181 Annular Base End (Gasket)
183 Convex surface forming portion P1 High pressure side exhaust recirculation passage P2 Low pressure side exhaust recirculation passage

Claims (9)

An exhaust gas recirculation device for an internal combustion engine equipped in an internal combustion engine having an exhaust gas purification unit in the middle of an exhaust pipe forming an exhaust gas passage,
An exhaust gas recirculation pipe for recirculating the exhaust gas purified by the exhaust gas purification unit from the exhaust gas passage side to the intake passage side of the internal combustion engine;
An exhaust gas recirculation device for an internal combustion engine, comprising: the exhaust gas recirculation pipe or a convex foreign matter collecting filter protruding into the exhaust gas passage from an inner wall surface of the exhaust pipe. The exhaust purification unit has a cylindrical case part disposed in the middle of the exhaust pipe and an exhaust purification filter part capable of purifying exhaust gas passing through the cylindrical case part,
The exhaust gas recirculation pipe recirculates the exhaust gas that has passed through the exhaust gas purification filter portion of the exhaust gas purification unit from the exhaust gas passage side to the intake passage side;
The foreign matter collecting filter protrudes into the exhaust gas passage from the inner wall surface of the cylindrical case portion downstream of the exhaust purification filter portion of the exhaust purification unit in the vicinity of the upstream end portion of the exhaust gas recirculation pipe. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation device is an internal combustion engine. An exhaust cooler that cools exhaust gas that is installed in the middle of the exhaust gas recirculation pipe and recirculates to the intake pipe side;
An upstream end portion of the exhaust gas recirculation pipe discharges condensed water generated in the exhaust cooler into the exhaust gas passage on the downstream side of the exhaust gas purification filter portion of the exhaust gas purification unit through the foreign matter collecting filter. The exhaust of the internal combustion engine according to claim 2, wherein the exhaust gas is descending from an inlet portion of the exhaust cooler toward an inner wall surface side of the cylindrical case portion downstream of the exhaust purification filter portion. Recirculation device. The exhaust purification filter portion of the exhaust purification unit is constituted by a particulate matter collection filter,
The cylindrical case portion is inclined in the direction of diameter reduction with respect to the wall surface around the particulate matter collection filter so as to reduce the cross-sectional area of the exhaust gas passage on the downstream side of the particulate matter collection filter. The exhaust gas recirculation device for an internal combustion engine according to claim 2 or 3, further comprising a wall surface.   The foreign matter collecting filter is supported by the annular base end portion between the upstream end portion of the exhaust gas recirculation pipe and the cylindrical case portion of the exhaust purification unit, and the exhaust gas is supported by the annular base end portion. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 2 to 4, further comprising: a convex surface forming portion having a convex surface shape protruding into the gas passage. A reflux pipe side flange portion forming the upstream end portion of the exhaust gas reflux pipe, and a case side flange portion provided in the cylindrical case portion of the exhaust gas purification unit corresponding to the reflux pipe side flange portion, In addition,
The annular base end of the foreign matter collecting filter is sandwiched between the reflux pipe side flange part of the exhaust gas reflux pipe and the case side flange part of the exhaust gas purification unit;
The convex surface forming portion of the foreign matter collecting filter is supported by the annular base end portion and protrudes into the exhaust gas passage through the inside of the reflux pipe side flange portion. An exhaust gas recirculation device for an internal combustion engine according to claim 5.   The foreign matter collecting filter is sandwiched between the upstream end portion of the exhaust gas recirculation pipe and the cylindrical case portion of the exhaust gas purification unit in a state of being fixed to the upstream end portion of the exhaust gas recirculation pipe. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 2 to 6, wherein the exhaust gas recirculation device is an internal combustion engine.   A part of the foreign matter collecting filter sandwiched between the exhaust purification unit and the cylindrical case portion is between the upstream end of the exhaust gas recirculation pipe and the cylindrical case portion of the exhaust purification unit. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 5 to 7, wherein the exhaust gas recirculation device is an arranged gasket. The internal combustion engine includes a turbocharger having an exhaust turbine that is rotated by energy of exhaust gas flowing in the exhaust gas passage, and an intake air compressor that is connected to the exhaust turbine and compresses intake air in the intake passage. Is installed,
The exhaust gas recirculation pipe is connected to an intake pipe upstream of the intake air compressor among the intake pipes forming the intake passage of the internal combustion engine. An exhaust gas recirculation device for an internal combustion engine according to claim 1.

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