JP2015178786A - Egr gas scavenging device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR gas scavenging device for engines that can scavenge EGR gas remaining within an intake system of the engine and that can prevent corrosion or the like of the intake system due to condensation water generated by condensation of the EGR gas within the intake system.SOLUTION: An EGR gas scavenging device 1 includes: a low pressure EGR device 50 for recirculating part of exhaust gas from a downstream side of a turbine 23 to an upstream side of a compressor 21; a vacuum pump 11 for providing the inside of a negative pressure tank 70 with negative pressure when an engine 10 is in an operating state; a first solenoid valve 71 interposed in piping 73 for communicating an intercooler 34 with the negative pressure tank 70; a second solenoid valve 72 interposed in piping 74 for communicating the vacuum pump 11 with the negative pressure tank 70; and a valve control section 82 that, after the engine is operated, closes the solenoid valve 71 and opens the second solenoid valve 72 and that, after the engine is stopped, opens the first solenoid valve 71 and closes the second solenoid valve 72.

Description

  The present invention relates to an engine EGR gas scavenger.

  Conventionally, in order to reduce NOx (nitrogen oxides) discharged from the engine, an exhaust gas recirculation device (hereinafter referred to as “the exhaust gas recirculation device”) that recirculates part of the exhaust gas discharged from the engine to the intake passage (intake system). An engine equipped with an “EGR device” is widely put into practical use.

  As a technique for increasing the amount of exhaust gas (hereinafter also referred to as “EGR gas”) to be recirculated to the engine, a part of the exhaust gas flowing in the exhaust passage downstream of the turbocharger turbine is upstream of the turbocharger compressor. A low-pressure EGR (LP-EGR) device that recirculates to the intake passage is also put into practical use.

  By the way, in the EGR device, when the EGR gas is returned to the intake passage and cooled, the moisture in the EGR gas is condensed and condensed water is generated. In particular, since a large amount of EGR gas is returned to the intake passage (intake system) in the low-pressure EGR device, the amount of condensed water generated also increases.

  Here, in Patent Document 1, in an exhaust gas purification system for an internal combustion engine equipped with a low-pressure EGR device, condensed water staying inside the low-pressure EGR device is preferably removed, and an increase in pressure loss or a decrease in performance of the low-pressure EGR device is reported. A technique for suppressing the occurrence of defects is disclosed.

  The technique described in Patent Document 1 (exhaust gas purification system for an internal combustion engine) includes a compressor that supplies pressurized intake air to the internal combustion engine, and an EGR that recirculates part of the exhaust gas flowing through the exhaust passage to the intake passage upstream of the compressor. A passage and a bypass passage for guiding a part of the intake air pressurized by the compressor to the EGR passage downstream from the EGR cooler are provided. Then, when the internal combustion engine is in an operation state in which the EGR is stopped, the intake air introduced into the EGR passage through the bypass passage is caused to flow backward from the downstream to the upstream of the EGR passage, and the condensed water and unburned fuel in the EGR passage are blown away. Remove.

JP 2007-198310 A

  By the way, the above-described condensed water is generated not only in the EGR device but also in the intake system of the engine. Therefore, the condensed water generated in the intake system during the soak (while the engine is stopped) may cause corrosion, freezing, deposit, or the like of the intake system (for example, an intercooler). However, although the technique described in Patent Document 1 described above can remove the condensed water in the EGR passage, it has not been considered to remove the condensed water in the intake system of the engine.

  The present invention has been made in order to solve the above-described problems, and is capable of scavenging EGR gas remaining in the intake system of the engine and condensing produced by condensing the EGR gas in the intake system. An object of the present invention is to provide an EGR gas scavenging device for an engine that can prevent corrosion of an intake system due to water.

  An EGR gas scavenging device for an engine according to the present invention communicates with an EGR device that recirculates a part of exhaust gas discharged from the engine to the intake system of the engine, a negative pressure tank, and a negative pressure tank. A vacuum pump that sucks air in the negative pressure tank to make the inside of the negative pressure tank negative, a first valve interposed in a pipe that communicates the intake system of the engine and the negative pressure tank, and a vacuum pump A second valve interposed in a pipe communicating with the negative pressure tank, detection means for detecting whether or not the engine is operating, and control of opening and closing of each of the first valve and the second valve Control means for closing the first valve when the engine is operating, opening the second valve, and opening the first valve when the engine is stopped. Both Characterized by closing the second valve.

  According to the EGR gas scavenging device for an engine according to the present invention, the first valve is closed and the second valve is opened when the engine is operating, whereby the negative pressure tank is held in a negative pressure state by the vacuum pump. Is done. Then, after the engine is stopped, the first valve is opened and the second valve is closed, so that the EGR gas staying in the intake system of the engine communicates between the intake system of the engine and the negative pressure tank. It is sucked into the negative pressure tank through the pipe and the first valve. As a result, the EGR gas remaining in the intake system of the engine can be scavenged, and corrosion of the intake system due to condensed water generated by the condensation of the EGR gas in the intake system can be prevented. .

  The engine EGR gas scavenger according to the present invention has a turbine provided on the exhaust passage of the engine and a compressor provided on the intake passage and connected to the turbine by a shaft, and uses the energy of the exhaust gas. It is preferable to further include a supercharger that supercharges the intake air, and the EGR device recirculates the exhaust gas from the downstream side of the turbine to the upstream side of the compressor.

  In this case, by applying to an engine equipped with an EGR device (so-called low-pressure EGR device) that recirculates exhaust gas from the downstream side of the turbine to the upstream side of the compressor, a large amount of EGR gas with a large amount of water flows into the intake system. It is possible to scavenge EGR gas remaining in the intake system of an engine equipped with a low-pressure EGR device capable of preventing the generation of condensed water in the intake system.

  An engine EGR gas scavenger according to the present invention is disposed downstream of a compressor, an intercooler that cools intake air compressed by the compressor, and an air amount that is disposed downstream of the intercooler and is sucked into the engine. And a throttle valve for adjusting the air pressure, the first valve is interposed in a pipe communicating the intercooler and the negative pressure tank, and the control means scavenges the EGR gas in the intake system upstream from the intercooler. In this case, it is preferable to close the throttle valve and open the throttle valve when scavenging EGR gas in the intake system upstream and downstream of the intercooler.

  In this way, it is possible to select and scavenge the location where the EGR gas is to be scavenged (that is, the intake system upstream from the intercooler or the intake system upstream and downstream of the intercooler). Therefore, it is possible to scavenge EGR gas remaining in the intake system more effectively and prevent the generation of condensed water.

  The engine EGR gas scavenger according to the present invention further includes a second EGR device for recirculating exhaust gas from the upstream side of the turbine to the downstream side of the compressor, and the control means stops the engine and opens the throttle valve. When the valve is operated, it is preferable to close the EGR valve that adjusts the exhaust gas recirculation amount of the second EGR device.

  In this way, it is possible to prevent the EGR gas staying in the second EGR device from being sucked into the negative pressure tank. Therefore, only the EGR gas staying in the intake system of the engine can be scavenged efficiently.

  The engine EGR gas scavenger according to the present invention includes crank position detection means for detecting a stop position of the crank when the engine is stopped, and the control means includes a valve between the intake valve and the exhaust valve based on the stop position of the crank. It is preferable to determine whether or not there is an overlap, and close the throttle valve when there is a valve overlap, and open the throttle valve and close the EGR valve when there is no valve overlap.

  In this way, even if valve overlap occurs, it is possible to prevent the residual gas in the cylinder and the exhaust system from being sucked into the negative pressure tank. Therefore, only the EGR gas staying in the intake system of the engine can be scavenged efficiently.

  In the engine EGR gas scavenger according to the present invention, the control means is provided with an EGR valve that adjusts the exhaust gas recirculation amount of the EGR device when the engine is stopped, and an exhaust pressure disposed on the downstream side of the turbine. It is preferable to close each of the exhaust pressure adjusting valves for adjusting the pressure. This makes it possible to efficiently scavenge the EGR gas in the intake system.

  In the engine EGR gas scavenger according to the present invention, the engine is preferably a diesel engine, and the vacuum pump is preferably driven by the engine and used to create a negative pressure for operating the brake booster. .

  In this way, a vacuum pump that creates a negative pressure inside the negative pressure tank and a vacuum pump that produces a negative pressure for operating the brake booster can be used in common. Can be achieved.

  According to the present invention, EGR gas remaining in the intake system of the engine can be scavenged, and corrosion of the intake system due to condensed water generated by condensation of the EGR gas in the intake system can be prevented. It becomes possible.

It is a figure which shows the structure of the diesel engine provided with the EGR gas scavenger of the engine which concerns on embodiment, and this EGR gas scavenger. It is a flowchart which shows the process sequence of the EGR gas scavenging process by the EGR gas scavenger of the engine which concerns on embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are used for the same or corresponding parts. Moreover, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  First, the configuration of an EGR gas scavenging device 1 for an engine according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an engine EGR gas scavenger 1 and an engine 10 including the EGR gas scavenger 1.

  The engine 10 is, for example, a horizontally opposed type diesel engine that obtains output by injecting fuel into a cylinder by an injector after compression of intake air to cause spontaneous ignition. A common rail type is preferably used as the injector. The engine 10 can achieve high output and low fuel consumption by supercharging intake air by a turbocharger 20 described later.

  A vacuum pump (vacuum pump) 11 is attached to the cam shaft of the engine 10. The vacuum pump 11 is driven by the engine 10 (cam shaft) and generates negative pressure for operating a brake booster (a booster, not shown). Further, when the vacuum pump 11 communicates with a negative pressure tank 70 described later, the vacuum pump 11 sucks air in the negative pressure tank 70 to make the inside of the negative pressure tank 70 a negative pressure.

  In the intake passages 31A, 31B, 31C, 31D (hereinafter collectively referred to as the intake passage 31) of the engine 10, an air cleaner 32, a turbocharger 20 (compressor 21), an intercooler 34, an electronically controlled throttle valve (from the upstream side) In the following, 35 or the like is also arranged. The air cleaner 32 is a filter that removes dust and dirt in the intake air.

  The turbocharger 20 is a supercharger that is disposed between the intake passage 31 and the exhaust passage 41 and performs supercharging. The turbocharger 20 includes a turbine 22 provided in an exhaust passage 41 and a compressor 21 provided in an intake passage 31 and connected to the turbine 22 by a rotary shaft 23, and drives the turbine 22 with exhaust energy. As a result, the air is compressed by the coaxial compressor 21.

  The intercooler 34 cools the intake air that has been compressed by the turbocharger 20 (compressor 21) to a high temperature by heat exchange. A throttle valve 35 that adjusts the intake air amount of the engine 10 is disposed downstream of the intercooler 34. In a diesel engine, the engine output is controlled by the fuel injection amount, so that the throttle valve 35 is normally operated in an open state. However, for example, when it is desired to put a large amount of EGR gas at a light load, when it is desired to stop the engine smoothly, or when it is desired to increase the exhaust temperature by reducing the intake air during DPF regeneration, the opening of the throttle valve 35 is reduced.

  Further, when scavenging EGR gas staying in the intake system of the engine 10, when scavenging the upstream side (that is, the intercooler 34 and the intake passages 31 </ b> A, 31 </ b> B, 31 </ b> C) from the intercooler 34, the throttle valve 35 is closed. On the other hand, when scavenging is performed not only on the upstream side of the intercooler 34 but also on the downstream side (that is, the intake passage 31D (intake manifold)), the throttle valve 35 is opened. Details of the operation of the throttle valve 35 will be described later. The opening degree of the throttle valve 35 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 80 described later.

  A pipe 73 that connects the intercooler 34 (or the intake passage 31C) and the negative pressure tank 70 is connected to the intercooler 34 (or the intake passage 31C that connects the intercooler 34 and the throttle valve 35). The negative pressure tank 70 is a tank made of resin, for example, having a predetermined tank capacity. The negative pressure tank 70 is held at a negative pressure by the vacuum pump 11 when the engine is operating. Further, when the engine is stopped, the sucked (scavenged) EGR gas, condensed water, and the like are stored.

  A first electromagnetic valve 71 is interposed in a pipe 73 that connects the intercooler 34 (or the intake passage 31 </ b> C) and the negative pressure tank 70 described above. That is, the first electromagnetic valve 71 corresponds to the first valve described in the claims. The first electromagnetic valve 71 is a valve that can be electrically controlled to open / close, and is controlled by the ECU 80.

  The negative pressure tank 70 is connected to a pipe 74 that communicates the negative pressure tank 70 and the vacuum pump 11. A second electromagnetic valve 72 is interposed in the pipe 74. That is, the second electromagnetic valve 72 corresponds to the second valve described in the claims. Similarly to the first electromagnetic valve 71 described above, the second electromagnetic valve 72 is a valve that can be electrically controlled to open / close, and is controlled by the ECU 80.

  On the other hand, on the exhaust passages 41A and 41B (collectively referred to as the exhaust passage 41), in order from the upstream side (engine 10 side), the diesel particulates provided with the turbine 22 (turbocharger 20) and the oxidation catalyst 42A. A filter 42B, an exhaust pressure adjusting valve 43, a muffler 44, and the like are provided.

  As the oxidation catalyst (DOC: Diesel Oxidation Catalyst) 42A, a platinum-based catalyst is preferably used, and oxidizes and removes CO, HC, etc. in the exhaust gas. A diesel particulate filter (DPF) 42B is disposed downstream of the oxidation catalyst 42A.

  The diesel particulate filter 42B is a filter that collects PM (particulate matter) contained in the exhaust gas. That is, HC and CO are oxidized by the oxidation catalyst 42A, and then PM is collected by passing through the diesel particulate filter 42B. As the diesel particulate filter 42B, for example, heat resistant ceramics such as cordierite is formed in a honeycomb structure, and a large number of cells serving as gas flow paths are sealed on the end face so that the inlet side and the outlet side are staggered. A so-called closed type (wall flow type) formed by performing the above process is preferably used.

  Further, in the diesel particulate filter 42B, when clogging is detected or at a predetermined timing, HC is supplied into the exhaust gas by adding fuel to the post injection or the exhaust gas, and the reaction in the oxidation catalyst 42A. So-called filter regeneration is performed, in which PM accumulated on the diesel particulate filter 42B is burned by heat.

  On the downstream side of the diesel particulate filter 42B, an exhaust pressure adjusting valve 43 that adjusts exhaust pressure (exhaust gas flow rate) by opening and closing the valve is disposed. The exhaust pressure adjusting valve 43 is driven to open and close by an electric motor (not shown) disposed in association therewith. By controlling the electric motor by the ECU 80, the exhaust pressure adjusting valve 43 can be set to an arbitrary opening degree. The exhaust pressure adjusting valve 43 is fully opened by a return spring when not driven.

  Further, between the intake passage 31 and the exhaust passage 41, exhaust gas is mixed into the intake air and is re-inhaled (recirculation of exhaust gas) by the engine 10 to reduce NOx (nitrogen oxide). A low pressure EGR (LP-EGR) apparatus 50 and a high pressure EGR (HP-EGR) apparatus 60 are provided.

  The low-pressure EGR device 50 transfers a part of the exhaust gas between the diesel particulate filter 42B and the exhaust pressure adjusting valve 43 on the exhaust passage 41B and between the air cleaner 32 and the compressor 21 on the intake passage 31A. A low-pressure EGR pipe 51 to be introduced is provided. The low pressure EGR device 50 corresponds to the EGR device described in the claims.

  On the low-pressure EGR pipe 51, an EGR cooler 52 that cools the gas after combustion recirculated to the intake passage 31A and an EGR valve (hereinafter also referred to as “LP-EGR valve”) 53 that adjusts the exhaust gas recirculation amount are attached. ing. The opening degree control (Duty control) of the LP-EGR valve 53 is performed by the ECU 80.

  The high-pressure EGR device 60 includes a high-pressure EGR pipe 61 that introduces a part of the exhaust gas between the engine 10 and the turbine 22 in the exhaust passage 41A between the throttle 35 and the engine 10 on the intake passage 31D. Yes. The high-pressure EGR gas has a higher pressure and a higher temperature than the above-described low-pressure EGR gas. The high-pressure EGR device 60 corresponds to the second EGR device described in the claims.

  On the high-pressure EGR pipe 61, an EGR cooler 62 that cools the burned gas recirculated to the intake passage 31D and an EGR valve (hereinafter also referred to as “HP-EGR valve”) 63 that adjusts the exhaust gas recirculation amount are attached. ing. The opening degree control (Duty control) of the HP-EGR valve 63 is also performed by the ECU 80.

  Here, a crank angle sensor 91 for detecting the rotational position of the crankshaft 10a is attached in the vicinity of the crankshaft 10a of the engine 10. At the end of the crankshaft 10a, for example, a timing rotor 91a in which 34-tooth projections with two missing teeth are formed at intervals of 10 ° is attached. By detecting the rotational position of the crankshaft 10a.

  By the way, when the engine is stopped, the rotational torque may decrease and the piston may reverse without being able to get over the compression top dead center. Therefore, in order to accurately detect the crank stop position (crank angle) when the engine is stopped, a crank angle sensor capable of detecting the reverse rotation of the crankshaft 10a (with a reverse rotation detection function) is used as the crank angle sensor 91. . That is, the crank angle sensor 91 functions as a crank position detection unit described in the claims. As the crank angle sensor 91, for example, a sensor using a Hall element or MR element is preferably used.

  The crank angle sensor 91 is connected to the ECU 80. Further, the ECU 80 is also connected with various sensors such as an accelerator pedal opening sensor 92 for detecting the depression amount of the accelerator pedal, that is, the opening degree of the accelerator pedal.

  The ECU 80 includes a microprocessor that performs calculations, a ROM that stores programs for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, and a backup RAM in which the stored contents are held by a 12V battery. And an input / output I / F and the like. The ECU 80 includes an injector driver that drives the injector, a motor driver that drives an electric motor that opens and closes the throttle valve 35, a motor driver that drives an electric motor that opens and closes the exhaust pressure adjustment valve 43, and the like. The ECU 80 further includes a driver for driving the first electromagnetic valve 71, the second electromagnetic valve 72, the LP-EGR valve 53, and the HP-EGR valve 63 described above.

  In the ECU 80, the cylinder is determined from the output of the cam angle sensor, and the rotational angular velocity and the engine speed are obtained from the output of the crank angle sensor 91. Further, the ECU 80 acquires various information such as the accelerator pedal opening and the water temperature of the engine 10 based on the detection signals input from the various sensors described above. Then, the ECU 80 comprehensively controls the engine 10 by controlling the fuel injection amount and various devices based on the acquired various information.

  In particular, the ECU 80 is generated by condensing the EGR gas in the intake system in the soak by scavenging EGR gas remaining in the intake system (the intake passage 31 and the intercooler 34) of the engine 10 when the engine is stopped. It has a function to prevent corrosion, freezing, deposit generation, etc. of the intake system due to the condensed water. Therefore, the ECU 80 functionally includes an operation detection unit 81 and a valve control unit 82. In the ECU 80, the functions stored in the ROM are executed by the microprocessor, whereby the functions of the operation detection unit 81 and the valve control unit 82 are realized.

  The operation detection unit 81 detects whether or not the engine 10 is operating. That is, the operation detection unit 81 functions as detection means described in the claims. Specifically, the operation detection unit 81 determines that the engine 10 is stopped, for example, when the engine speed calculated from the detection signal of the crank angle sensor 91 is zero. On the other hand, when the engine speed is not zero, it is determined that the engine 10 is operating. Information indicating the operating state (whether or not the engine 10 is operating) detected by the operation detecting unit 81 is output to the valve control unit 82.

  The valve control unit 82 controls the opening and closing of the first electromagnetic valve 71 and the second electromagnetic valve 72. The valve control unit 82 also controls the respective opening degrees of the throttle valve 35, the LP-EGR valve 53, the HP-EGR valve 63, and the exhaust pressure adjustment valve 43. That is, the valve control unit 82 functions as a control unit described in the claims.

  More specifically, the valve control unit 82 closes the first electromagnetic valve 71 and opens the second electromagnetic valve 72 when the engine 10 is operating. Thereby, the vacuum pump 11 and the negative pressure tank 70 are connected, and the inside of the negative pressure tank 70 is kept at a negative pressure.

  On the other hand, the valve controller 82 opens the first electromagnetic valve 71 and closes the second electromagnetic valve 72 when the engine 10 is stopped. As a result, the EGR gas staying in the intake system of the engine 10 is sucked into the negative pressure tank 70 and scavenged. At that time, the valve control unit 82 closes the throttle valve 35 when scavenging EGR gas upstream from the intercooler 34 (that is, the intercooler 34 and the intake passages 31A, 31B, 31C).

  On the other hand, when scavenging the EGR gas in the downstream intake passage 31D (intake manifold) in addition to the upstream side of the intercooler 34, the throttle valve 35 is opened and the HP-EGR valve 63 is closed. In this case, however, the valve control unit 82 determines whether or not there is a valve overlap between the intake valve and the exhaust valve based on the crank stop position detected by the crank angle sensor 91, and there is a valve overlap. In this case, it is preferable to close the throttle valve 35. On the other hand, when there is no valve overlap, as described above, the throttle valve 35 is opened and the HP-EGR valve 63 is closed.

  The valve controller 82 closes the LP-EGR valve 53 and the exhaust pressure adjustment valve 43 in order to improve scavenging efficiency when the engine 10 is stopped and the EGR gas is scavenged.

  Next, the operation of the engine EGR gas scavenger 1 will be described with reference to FIG. FIG. 2 is a flowchart showing a processing procedure of EGR gas scavenging processing by the engine EGR gas scavenging device 1 according to the embodiment. This process is repeatedly executed at a predetermined timing in the ECU 80.

  First, in step S100, it is determined whether or not the engine 10 is stopped. Here, when the engine 10 is stopped, the process proceeds to step S104. On the other hand, when the engine 10 is operating, the process proceeds to step S102.

  In step S102, the first electromagnetic valve 71 is closed and the second electromagnetic valve 72 is opened. Therefore, the vacuum pump 11 and the negative pressure tank 70 are communicated, and the negative pressure tank 70 is held at a negative pressure. Thereafter, the process is temporarily exited.

  In step S104, the second electromagnetic valve 72 is closed. Subsequently, in step 106, it is determined whether or not only the upstream side of the intercooler 34 (that is, the intercooler 34 and the intake passages 31A, 31B, 31C) is set to be scavenged. Here, when it is set to scavenge only the upstream side from the intercooler 34, the process proceeds to step S108. On the other hand, when the downstream side (intake passage 31D) is set to scavenge from the intercooler 34 in addition to the upstream side, the process proceeds to step S110.

  In step S108, the throttle valve 35 is closed. Thereafter, the process proceeds to step S114.

  In step S110, a determination is made as to whether there is a valve overlap between the intake valve and the exhaust valve. Here, if there is an overlap, the process proceeds to step S114 after the throttle valve 35 is closed in step S108. On the other hand, when there is no overlap, the process proceeds to step S112.

  In step S112, the throttle valve 35 is opened and the HP-EGR valve 63 is closed. Thereafter, the process proceeds to step S114.

  In step S114, the exhaust pressure adjustment valve 43 is closed and the LP-EGR valve 53 is closed.

  Subsequently, in step S116, the first electromagnetic valve 71 is opened. Thereby, the EGR gas staying in the exhaust system of the engine 10 is sucked into the negative pressure tank 70 and scavenged.

  As described above in detail, according to the present embodiment, when the engine is operating, the first electromagnetic valve 71 is closed and the second electromagnetic valve 72 is opened, whereby the vacuum pump 11 causes the negative pressure tank to open. The inside of 70 is maintained in a negative pressure state. Then, after the engine is stopped, the first electromagnetic valve 71 is opened and the second electromagnetic valve 72 is closed, so that the EGR gas staying in the intake system of the engine 10 becomes the piping 73 and the first electromagnetic valve. 71 is sucked into the negative pressure tank 70 through 71. As a result, EGR gas remaining in the intake system of the engine 10 can be scavenged when the engine is stopped, and an intake system (for example, an intercooler) using condensed water generated by condensing the EGR gas in the intake system during the soak. Etc.), corrosion, freezing, deposit formation, etc. can be prevented.

  According to the present embodiment, by applying the engine 10 having the low pressure EGR device 50 that recirculates the exhaust gas from the downstream side of the turbine 23 to the upstream side of the compressor 21, a large amount of EGR gas with a large amount of moisture is taken into the intake system. It is possible to scavenge the EGR gas remaining in the intake system of the engine 10 equipped with the low pressure EGR device 50 that can flow into the intake system, thereby preventing the generation of condensed water in the intake system.

  According to the present embodiment, it is possible to select and scavenge a location where the EGR gas is to be scavenged (that is, the intake system upstream from the intercooler 34 or the intake system upstream and downstream of the intercooler 34). Therefore, it is possible to scavenge EGR gas remaining in the intake system more effectively and prevent the generation of condensed water.

  According to the present embodiment, by closing the HP-EGR valve 63, it is possible to prevent the EGR gas staying in the high pressure EGR device 60 from being sucked into the negative pressure tank 70. Therefore, only the EGR gas staying in the intake system of the engine 10 can be scavenged efficiently.

  According to the present embodiment, it is possible to prevent the residual gas in the cylinder and the exhaust system from being sucked into the negative pressure tank 70 even when valve overlap occurs. Therefore, only the EGR gas staying in the intake system of the engine 10 can be scavenged efficiently.

  According to this embodiment, when the engine 10 is stopped, the LP-EGR valve 53 and the exhaust pressure adjustment valve 43 are each closed. Therefore, it is possible to efficiently scavenge the EGR gas in the intake system.

  According to the present embodiment, the vacuum pump 11 that creates a negative pressure inside the negative pressure tank 70 and the vacuum pump 11 that creates a negative pressure for operating the brake booster are shared, so the apparatus can be reduced in size and size. Costs can be reduced.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the first embodiment, the type of vacuum pump 11 that is directly driven by the camshaft of the engine 10 is used, but instead of this type, for example, the vacuum pump 11 is driven by a crankshaft. Alternatively, a type driven by an intermediate transmission such as a gear or a chain may be used. Further, a type driven by an electric motor or the like can be used instead of the engine.

  In the above-described embodiment, the vacuum pump that creates a negative pressure in the negative pressure tank 70 and the vacuum pump that generates the negative pressure for operating the brake booster are used in common. However, different vacuum pumps are used. It can also be.

  In the above embodiment, a type that is electrically controlled by the ECU 80 is used as the second electromagnetic valve 72. However, instead of this type, for example, a negative pressure generated by the vacuum pump 11 is used. A check valve that is opened only when the negative pressure in the negative pressure tank 70 is higher may be used. In this case, for example, a spring coil or the like for setting the valve opening pressure of the check valve corresponds to the control means described in the claims.

DESCRIPTION OF SYMBOLS 1 EGR gas scavenging apparatus 10 Engine 11 Vacuum pump 20 Turbocharger 21 Compressor 22 Turbine 23 Rotating shaft 31, 31A, 31B, 31C, 31D Intake passage 34 Intercooler 35 Electronically controlled throttle valve 41, 41A, 41B Exhaust passage 42A Oxidation catalyst (DOC)
42B Diesel particulate filter (DPF)
43 Exhaust pressure adjusting valve 50 Low pressure EGR device 53 LP-EGR valve 60 High pressure EGR device 63 HP-EGR valve 70 Negative pressure tank 71 First electromagnetic valve 72 Second electromagnetic valve 73, 74 Piping 80 ECU
81 Operation detection unit 82 Valve control unit 91 Crank angle sensor

Claims (7)

An EGR device that recirculates part of the exhaust gas discharged from the engine to the intake system of the engine;
A negative pressure tank,
A vacuum pump that sucks air in the negative pressure tank to make the negative pressure inside the negative pressure tank negative when communicated with the negative pressure tank;
A first valve interposed in a pipe communicating the intake system of the engine and the negative pressure tank;
A second valve interposed in a pipe communicating the vacuum pump and the negative pressure tank;
Detecting means for detecting whether or not the engine is operating;
Control means for controlling the opening and closing of each of the first valve and the second valve,
The control means closes the first valve when the engine is operating and opens the second valve, and opens the first valve when the engine is stopped. An EGR gas scavenger for an engine, wherein the second valve is closed. A turbocharger having a turbine provided on an exhaust passage of the engine and a compressor provided on an intake passage and connected to the turbine by a shaft, and supercharging intake air using energy of exhaust gas Further equipped with
The engine EGR gas scavenger according to claim 1, wherein the EGR device recirculates exhaust gas from a downstream side of the turbine to an upstream side of the compressor. An intercooler that is disposed downstream of the compressor and cools the intake air compressed by the compressor;
A throttle valve that is arranged downstream of the intercooler and adjusts the amount of air taken into the engine;
The first valve is interposed in a pipe communicating the intercooler and the negative pressure tank,
The control means closes the throttle valve when scavenging EGR gas in the intake system upstream from the intercooler, and scavenges EGR gas in the intake system upstream and downstream of the intercooler. 3. The engine EGR gas scavenger according to claim 2, wherein the throttle valve is opened. A second EGR device for recirculating exhaust gas from the upstream side of the turbine to the downstream side of the compressor;
The control means closes an EGR valve that adjusts an exhaust gas recirculation amount of the second EGR device when the engine is stopped and the throttle valve is opened. An EGR gas scavenger for an engine as described. Crank position detection means for detecting the stop position of the crank when the engine is stopped,
The control means determines whether or not there is a valve overlap between the intake valve and the exhaust valve based on the stop position of the crank. If there is a valve overlap, the control means closes the throttle valve, and the valve overlap is 5. The engine EGR gas scavenging device according to claim 4, wherein when there is no engine, the throttle valve is opened and the EGR valve is closed.   The control means includes an EGR valve that adjusts an exhaust gas recirculation amount of the EGR device when the engine is stopped, and an exhaust pressure adjustment valve that is disposed downstream of the turbine and adjusts the exhaust pressure. The EGR gas scavenging device for an engine according to any one of claims 2 to 5, wherein the valve is closed. The engine is a diesel engine;
The engine EGR according to any one of claims 1 to 6, wherein the vacuum pump is driven by the engine and is used to create a negative pressure for operating a brake booster. Gas scavenger.

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