JP2008255940A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology more efficiently warming up a catalyst of an exhaust emission control device under a condition where an internal combustion engine is stopped. <P>SOLUTION: This device is provided with the exhaust emission control device including the catalyst in an exhaust gas passage. When the internal combustion engine is stopped and temperature of the catalyst is lower than activation temperature (S101, S102), an EGR loop can be formed with parts of an intake pipe and an exhaust pipe, and a low pressure EGR passage by closing a second throttle valve and am exhaust throttle valve (S103). Gas in the EGR loop is forcibly re-circulated in the EGR loop by driving a compressor of a supercharger by a motor (S105). When the internal combustion engine is stopped and temperature of the catalyst is not less than activation temperature, the second throttle valve and the exhaust throttle valve are fully closed (S106), and only heat insulation of the catalyst is performed by not driving the compressor by the motor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine that recirculates a part of exhaust gas passing through an exhaust passage of the internal combustion engine to an intake passage.

  As a technique for reducing the amount of nitrogen oxide (hereinafter referred to as “NOx”) discharged from the internal combustion engine into the atmosphere, an exhaust gas recirculation device that recirculates part of the exhaust gas in the exhaust system of the internal combustion engine to the intake system. And an exhaust purification catalyst such as a NOx catalyst (hereinafter abbreviated as “catalyst”) or a particulate filter (hereinafter referred to as “filter”) carrying a catalyst is known. ing.

  In the exhaust emission control device described above, it is an important issue to promote catalyst warm-up when the internal combustion engine is stopped, such as before the internal combustion engine is started, when an eco-run is stopped, or during an internal combustion engine stop period in a hybrid vehicle. ing. That is, if the temperature of the catalyst is not sufficiently raised when the internal combustion engine is stopped, the catalyst cannot be activated immediately after the internal combustion engine is started, and there is a risk of causing deterioration of emissions after the internal combustion engine is started. Because there is.

  In relation to this, as a technology to promote early warm-up of the system including the catalyst, for example, the supercharger of the internal combustion engine can be driven electrically and the compressor of the supercharger is driven before the internal combustion engine is started. Then, a technology (Patent Document 1) for warming up a specific part with intake air whose temperature has been increased by supercharging, and a supercharger of an internal combustion engine can be driven electrically, At the time of start-up, a technique for increasing the intake air temperature by supercharging the intake air supplied to the internal combustion engine a plurality of times by a supercharger (see Patent Document 2), or at the time of cold start of the internal combustion engine. A technique (see Patent Document 3) that increases the intake air temperature more reliably by restricting the intake air amount when the feeder is electrically driven is known.

However, in the above-described technology, the intake air whose temperature has been increased passes through the internal combustion engine and the exhaust passage and is directly dissipated to the outside, and the energy provided by supercharging by the supercharger is used to warm the catalyst and the internal combustion engine. It was not always available effectively for the machine.
JP 2003-307134 A JP 2004-332715 A JP 2004-340122 A

  An object of the present invention is to provide a technique capable of warming up the catalyst of the exhaust emission control device more efficiently when the internal combustion engine is stopped.

In order to achieve the above object, the present invention provides an exhaust gas recirculation system for an internal combustion engine that recirculates a part of the exhaust gas to the intake system in an exhaust system of an internal combustion engine equipped with an exhaust gas purification device having a catalyst. Therefore, the following features are the greatest features. That is, when the internal combustion engine is stopped, the exhaust throttle valve is actuated so that an EGR path can be formed by the exhaust passage and part of the intake passage of the internal combustion engine and the EGR passage. In addition, a circulating flow generating means for forcibly recirculating the gas in the EGR path through the EGR path is provided. And, when the temperature of the catalyst is lower than a predetermined temperature when the internal combustion engine is stopped, the exhaust throttle valve is throttled to form an EGR path and the circulating flow generating means recirculates the gas in the EGR path, Warm-up is promoted by allowing the catalyst to pass through without letting hot gas escape to the outside.

More specifically, an exhaust purification device having a catalyst provided in an exhaust passage of an internal combustion engine and purifying exhaust gas passing through the exhaust passage;
An EGR passage communicating the exhaust passage downstream of the exhaust purification device and the intake passage of the internal combustion engine;
An exhaust throttle valve that is provided on the downstream side of a connection portion between the EGR passage and the exhaust passage in the exhaust passage and controls the amount of exhaust gas passing through the exhaust passage;
Provided in an EGR path formed including the intake passage and a part of the exhaust passage and the EGR passage, and recirculates the EGR path to the gas in the EGR path even when the internal combustion engine is stopped. A circulating flow generating means capable of generating a flow;
With
When the temperature of the catalyst is lower than a predetermined temperature while the internal combustion engine is stopped, the exhaust throttle valve is closed and a flow is generated in the gas in the EGR path by the circulation flow generation means, And forcibly recirculating the EGR path.

  According to this, when the internal combustion engine is stopped, the gas existing in the EGR path can be recirculated through the EGR path to allow the catalyst to pass therethrough, so that the heat accumulated in the internal combustion engine and the exhaust gas purification device is 1 The catalyst can be effectively used for warming up the catalyst without escaping outside. As a result, the catalyst can be warmed up more efficiently.

  In the present invention, the intake passage further includes an intake throttle valve that is provided upstream of a connection portion between the EGR passage and the intake passage in the intake passage and controls the amount of intake air that passes through the intake passage. When the temperature of the catalyst is lower than the predetermined temperature while the engine is stopped, the intake throttle valve and the exhaust throttle valve are closed and a flow is generated in the gas in the EGR path by the circulating flow generation means. Thus, the gas may be forcibly recirculated through the EGR path.

  In other words, by closing the intake throttle valve provided on the upstream side of the connection portion between the EGR passage and the intake passage together with the exhaust throttle valve, it is possible to further improve the sealing performance of the EGR passage. As a result, low temperature fresh air can be prevented from flowing into the EGR path, and the catalyst of the exhaust emission control device can be warmed up more efficiently.

  In the above, the valve closing does not necessarily mean full closing. In general, it includes operating the intake throttle valve or the exhaust throttle valve so that the opening degree changes to the closed side.

  In the present invention, when the temperature of the catalyst is equal to or higher than the predetermined temperature while the internal combustion engine is stopped, the intake throttle valve and the exhaust throttle valve are closed and the circulating flow generating means The generation of the gas flow may be stopped.

  That is, when the internal combustion engine is stopped, the exhaust throttle valve and the intake throttle valve are throttled, and the hot gas is recirculated in the EGR path so that the temperature of the catalyst becomes a predetermined temperature or more. Consider a case where the catalyst of the exhaust emission control device is already at a predetermined temperature or higher when it is stopped. In this case, if the flow is forcibly generated in the gas in the EGR path by the circulating flow generation means, the temperature of the catalyst may be lowered.

Therefore, in the present invention, in such a case, the intake throttle valve and the exhaust throttle valve are closed to seal the EGR path, and the operation of the circulating flow generating means is stopped to keep the catalyst warm. If it does so, while being able to suppress that a low temperature fresh air flows in into an EGR path | route, it can suppress that the flow of an unnecessary gas takes the heat of a catalyst, and the temperature of a catalyst is more reliably more than predetermined temperature. Can be maintained.

  In this case as well, the term “closed valve” includes all operations of restricting the intake throttle valve or the exhaust throttle valve so that the opening degree changes to the closed side. However, if the intake throttle valve or exhaust throttle valve is fully closed and the EGR path is more reliably sealed, the heat retaining effect of the catalyst can be further enhanced.

  In the present invention, a turbocharger is provided in which a compressor is provided downstream of the connection portion between the EGR passage and the intake passage in the intake passage and a turbine is provided upstream of the exhaust purification device in the exhaust passage. The circulating flow generation means may be an electric supercharger capable of generating a flow of gas in the EGR path by operating a compressor of the supercharger by an electric motor.

  According to this, it is not necessary to newly provide a circulating flow generation means in the EGR path, and gas can be recirculated using an existing compressor. Therefore, it is advantageous in terms of cost and space.

  Further, since the gas temperature can be increased by the compression work of the compressor every time the gas in the EGR path passes through the compressor, warming up of the catalyst can be promoted more reliably. For example, even when the temperature of the gas in the EGR path is low, such as before the start of the internal combustion engine, it is possible to increase the temperature of the gas and promote the warm-up of the catalyst.

  In the present invention, the downstream side of the compressor in the intake passage and the portion of the exhaust passage between the turbine and the exhaust purification device are communicated, and the turbine is bypassed to the gas passing through the intake passage. A turbine bypass passage may be further provided.

  In this case, the gas in the EGR path is allowed to pass through the turbine bypass passage as part of the path. If it does so, the loss of the energy by the expansion work at the time of the gas in an EGR path | route passing a turbine can be suppressed, and it can suppress that the gas temperature in an EGR path | route falls. As a result, the calorie | heat amount of the gas in an EGR path | route can be supplied to the said catalyst more efficiently, and the said catalyst can be warmed up more efficiently.

Further, in the present invention, a turbine front communication passage that communicates the turbine bypass passage and a portion upstream of the turbine in the exhaust passage;
Of the gas passing through the turbine bypass passage, a turbine bypass amount control valve that controls the amount of intake air flowing into the turbine front communication passage;
Further comprising
When the remaining power amount of the battery as the power source of the electric supercharger is smaller than a predetermined amount, the amount of gas flowing into the turbine front communication path may be increased by the turbine bypass amount control valve. .

  Here, a case is considered where a flow is generated in the gas in the EGR path by the compressor of the electric supercharger and the gas in the EGR path is passed through the turbine bypass passage. In this case, the turbine of the supercharger is also rotated by the rotation of the compressor, so that the upstream side of the turbine is in a negative pressure state. As a result, the drive power of the electric motor may increase.

Therefore, in the present invention, a turbine pre-communication passage that communicates the turbine bypass passage and the upstream portion of the exhaust passage with respect to the turbine is provided. And when the residual electric energy of the battery as the electric power source of the electric supercharger is smaller than a predetermined amount, the amount of gas flowing into the turbine front communication passage among the gas passing through the turbine bypass passage by the turbine bypass amount control valve As a result, an increase in the negative pressure on the upstream side of the turbine is suppressed, and an increase in the driving power of the electric motor is suppressed.

  If it does so, since it can suppress that the drive electric power of an electric motor becomes large further in the state where the amount of residual electric power of the battery of an electric supercharger is low, it can control that a battery runs out and a malfunction of an electric supercharger arises. .

  Here, the predetermined amount of residual electric power means that if the residual electric energy of the battery of the electric turbocharger is less than this, if the gas in the EGR path continues to bypass the turbine, the battery will go up or the electric overcharge This is the amount of residual power that may cause malfunction of the feeder, and may be obtained in advance by experiments.

  In the present invention, an intercooler for cooling the gas supercharged by the compressor is provided on the downstream side of the compressor in the intake passage, and the turbine bypass passage includes the compressor in the intake passage and the compressor. You may make it connect to the part between intercoolers.

  Then, by passing the gas in the EGR path through the turbine bypass passage, it is possible to prevent the gas from being cooled by the intercooler and the catalyst warm-up efficiency from being lowered.

  In the present invention, the EGR cooler that is provided in the EGR passage and cools the gas passing through the EGR passage communicates with the upstream side and the downstream side of the EGR cooler in the EGR passage, and passes through the EGR passage. An EGR cooler bypass passage that allows the gas to bypass the EGR cooler may be further provided.

  That is, when the gas in the EGR path passes through the EGR cooler, the gas temperature for warming up the catalyst may be inadvertently lowered. Therefore, when an EGR cooler is provided in the EGR passage, an EGR cooler bypass passage that bypasses the EGR cooler is further provided, and the gas that recirculates in the EGR passage passes through the EGR cooler bypass passage. And If it does so, it can suppress that the temperature of the gas in an EGR path | route falls carelessly. According to this, it can suppress that the warming-up efficiency of a catalyst falls by an EGR cooler.

  Further, in the present invention, the exhaust purification device has a plurality of catalysts arranged in series with the exhaust passage, is branched from the EGR passage, and is downstream of at least a part of the plurality of catalysts in the exhaust passage. One or a plurality of EGR branch passages connected to the EGR branch passage, and the EGR branch passage among the gas that is provided at a connection portion between the EGR branch passage and the EGR passage and recirculates to the intake passage through the EGR passage. And an EGR switching valve capable of controlling the amount of gas flowing into each of the EGR passages.

  Then, by controlling the amount of gas that passes through each EGR branch passage, the amount of gas that passes through each of the plurality of catalysts in the exhaust purification device can be controlled. Then, warming up of the plurality of catalysts in the exhaust purification device can be promoted with a higher degree of freedom.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, the catalyst of the exhaust gas purification device can be warmed up more efficiently when the internal combustion engine is stopped.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine, an intake / exhaust system, and a control system to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a diesel engine having four cylinders 2 and four fuel injection valves 3 that inject fuel into each cylinder 2.

  An intake manifold 8 is connected to the internal combustion engine 1, and each branch pipe of the intake manifold 8 is communicated with a combustion chamber of each cylinder 2 through an intake port. In the vicinity of the connection portion between the intake manifold 8 and the intake pipe 9, a throttle valve 12 capable of changing the flow passage cross-sectional area of the intake pipe 9 is provided. The throttle valve 12 is an example of an intake throttle valve, and is connected to an ECU 22 described later via an electrical wiring. The throttle valve 12 can adjust the flow rate of the intake air flowing through the intake pipe 9 by controlling the valve opening degree based on a control signal from the ECU 22. An intercooler 13 that cools the gas flowing through the intake pipe 9 is provided upstream of the throttle valve 12.

  A compressor housing 6 in which the compressor of the supercharger 10 is stored is provided upstream of the intercooler 13. The rotation shaft of the compressor in this embodiment is connected to the output shaft of the motor 6a. The motor 6a is supplied with electric power from the battery 40, and the rotation speed is controlled based on a command signal from the ECU 22. That is, by controlling the rotational speed of the motor 6a, the compressor can be driven by the motor, and the supercharging pressure of the intake air can be controlled. The motor 6a corresponds to the electric motor in this embodiment, and the supercharger 10 in this embodiment is an example of the electric supercharger. Further, the supercharger 10 is an example of a circulating flow generating means in the present embodiment.

  Further, a second throttle valve 17 capable of changing the cross-sectional area of the intake pipe 9 is provided further upstream of the compressor housing 6. The second throttle valve 17 is also connected to the ECU 22 and adjusts the flow rate of the intake air flowing through the intake pipe 9 based on a control signal from the ECU 22. An air flow meter 24 for detecting the amount of intake air passing through the intake pipe 9 and an air cleaner 25 for removing dust floating in the fresh air are provided further upstream of the second throttle valve 17 in the intake pipe 9. Here, the intake pipe 9 and the intake manifold 8 constitute an intake passage in this embodiment.

On the other hand, an exhaust manifold 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust manifold 18 communicates with the combustion chamber of each cylinder 2 through an exhaust port. A turbine housing 7 in which the turbine of the supercharger 10 is stored is connected to the exhaust manifold 18 via a collecting pipe 16. An exhaust pipe 19 is connected to an opening through which the exhaust of the turbine housing 7 flows out. The exhaust pipe 19 is provided with an NSR 20 as an exhaust purification device that purifies NOx in the exhaust.

The NSR 20 absorbs (sucks and adsorbs) NOx in the exhaust gas when the oxygen concentration of the inflowing exhaust gas is high when the temperature rises above the activation temperature, and the oxygen concentration of the inflowing exhaust gas decreases and is reduced. reduced to N ₂ while releasing the NOx which has been absorbed when the agent is present. A fuel addition valve 26 is provided immediately upstream of the NSR 20 to add fuel as a reducing agent to the exhaust when reducing and releasing NOx absorbed by the NSR 20.

  An exhaust throttle valve 11 capable of changing the cross-sectional area of the exhaust pipe 19 is provided downstream of the NSR 20. The exhaust pipe 19 is open to the atmosphere downstream of the exhaust throttle valve 11. The exhaust throttle valve 11 is connected to the ECU 22 via electrical wiring, and the flow rate of the exhaust gas flowing through the exhaust pipe 19 can be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. . Here, the exhaust manifold 18, the collecting pipe 16, and the exhaust pipe 19 constitute an exhaust passage in this embodiment.

  A portion of the exhaust pipe 19 downstream of the NSR 20 and upstream of the exhaust throttle valve 11 and a portion of the intake pipe 9 upstream of the compressor housing 6 are communicated by a low pressure EGR passage 23. The low-pressure EGR passage 23 is provided with a low-pressure EGR cooler 14 that cools the gas flowing through the low-pressure EGR passage 23 and a low-pressure EGR valve 5 that can change the cross-sectional area of the low-pressure EGR passage 23. The low pressure EGR valve 5 is connected to the ECU 22 through an electrical wiring. The low-pressure EGR valve 5 is capable of adjusting the amount of gas flowing through the low-pressure EGR passage 23 by controlling the valve opening degree based on a control signal from the ECU 22 (hereinafter referred to as the low-pressure EGR passage 23). The flowing gas is sometimes referred to as “low pressure EGR gas” and the amount thereof is sometimes referred to as “low pressure EGR gas amount”. The low pressure EGR passage 23 functions as an EGR passage in the present embodiment.

  On the other hand, the exhaust manifold 18 and the intake manifold 8 are communicated with each other by a high pressure EGR passage 15. The high-pressure EGR passage 15 is provided with a high-pressure EGR valve 21 that can change the flow path cross-sectional area of the high-pressure EGR passage 15. The high-pressure EGR valve 21 is connected to the ECU 22 via electrical wiring, and the amount of gas flowing through the high-pressure EGR passage 15 may be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. (Hereinafter, the gas flowing through the high pressure EGR passage 15 may be referred to as “high pressure EGR gas” and the amount thereof may be referred to as “high pressure EGR gas amount”.)

  The internal combustion engine 1 is also provided with an ECU 22 that is an electronic control computer that controls the internal combustion engine 1. The ECU 22 includes a ROM, a RAM, a CPU, an input port, an output port, and the like (not shown), and performs known control such as fuel injection according to the operation state of the internal combustion engine 1 detected by the various sensors and a request from the driver. At the same time, an opening degree command signal is output to the high pressure EGR valve 21, the low pressure EGR valve 5, the throttle valve 12, the second throttle valve 17, the exhaust throttle valve 11, and the like.

  In the above configuration, the air introduced into the intake pipe 9 passes through the air flow meter 24 after dust is removed by the air cleaner 25, and is supercharged by the compressor in the compressor housing 6, and is also intercooler 13, intake manifold 8 is introduced into each cylinder 2 of the internal combustion engine 1.

  The gas discharged from each cylinder 2 flows into the turbine housing 7 via the exhaust manifold 18 and the collecting pipe 16 to drive the turbine. Thereafter, the exhaust gas passes through the exhaust pipe 19, and the NOx in the exhaust gas is purified by the NSR 20, and finally exhausted into the atmosphere.

  Here, when the low pressure EGR valve 5 is opened, the low pressure EGR passage 23 becomes conductive, and a part of the gas passing through the exhaust pipe 19 flows into the intake pipe 9 via the low pressure EGR passage 23. The low pressure EGR gas flowing into the intake pipe 9 is supercharged by the compressor in the compressor housing 6 and introduced into the cylinder 2 of the internal combustion engine 1 via the intake manifold 8 (EGR performed via the low pressure EGR passage 23). Hereinafter may be referred to as “low pressure EGR”).

Further, when the high-pressure EGR valve 21 is opened, the high-pressure EGR passage 15 becomes conductive, and part of the gas flowing through the exhaust manifold 18 flows into the intake manifold 8 via the high-pressure EGR passage 15, and the internal combustion engine 1. Is recirculated to the second cylinder. Here, the amount of high-pressure EGR gas can also be adjusted by adjusting the opening of the throttle valve 12 to increase or decrease the pressure at the branch point of the high-pressure EGR passage 15 in the intake manifold 8 (via the high-pressure EGR passage 15). Hereinafter, the EGR performed may be referred to as “high pressure EGR”.)

  Thus, by recirculating a part of the exhaust gas to the cylinder 2 of the internal combustion engine 1 by the low pressure EGR and the high pressure EGR, the combustion temperature in the combustion chamber is lowered, and the amount of NOx generated in the combustion process is lowered. Can do.

  In this embodiment, the low pressure EGR passage 23, the intake pipe 9, the intake manifold 8, the internal combustion engine 1, the exhaust manifold 18, the collecting pipe 16, and the exhaust pipe 19 form an EGR loop. This EGR loop corresponds to an EGR path.

  In the internal combustion engine 1, when the operating state is a low load and a low rotation speed, the high-pressure EGR having excellent responsiveness is preferentially used to ensure the responsiveness of the entire EGR. Further, when the operating state of the internal combustion engine is high load or high speed, the recirculation of the low pressure EGR gas by the low pressure EGR is promoted and the recirculation of the high pressure EGR gas by the high pressure EGR is suppressed, and the temperature of the EGR gas is increased. Suppressing excessively high temperatures. As a result, the exhaust gas can be recirculated in a wider range of operating conditions.

  Next, the actual operation during operation of the internal combustion engine 1 and its intake / exhaust system and control system will be described. Here, in response to demands for saving fuel resources and protecting the air environment, the internal combustion engine 1 is instructed by a command from the ECU 22 when the vehicle is temporarily stopped, for example, in an intersection even during operation of the vehicle on which the internal combustion engine 1 is mounted. The eco-run operation is temporarily stopped. During the stop of the internal combustion engine 1 due to the eco-run operation, high-temperature exhaust gas is not discharged from the internal combustion engine 1, and the temperature of, for example, the NSR 20 that is a component of the exhaust system may be lowered.

Then, in the state after the warm-up of the NSR 20 is completed, there is a possibility that the NSR 20 that has been activated at the corner may be deactivated. Further, activation of the NSR 20 may be delayed at the time of cold start. As a result, the NOx purification ability of the NSR 20 could not be ensured, and the emission may be deteriorated.

  On the other hand, in the present embodiment, when the internal combustion engine 1 is stopped and the temperature of the NSR 20 is lower than the activation temperature, the exhaust throttle valve 11 and the second throttle valve 17 are closed, and the motor 6a The compressor in the compressor housing 6 was operated electrically.

  According to this, it is possible to increase the hermeticity of the EGR loop and to form a high-temperature gas flow that recirculates through the EGR loop. As a result, the NSR 20 can be passed through the high-temperature gas, and the high-temperature gas can be prevented from being released to the outside as it is and then dissipating energy after passing through the NSR 20. Further, every time gas in the EGR loop passes through the compressor housing 6, the temperature of the gas can be raised by the compression work of the compressor, and the temperature of the gas recirculated in the EGR loop can be maintained at a high temperature. . As a result, even when the internal combustion engine 1 is stopped, warming up of the NSR 20 can be promoted, and deterioration of emissions can be suppressed.

Next, the case where the temperature of the NSR 20 when the internal combustion engine 1 is stopped is equal to or higher than the activation temperature will be described. When the recirculation of the gas in the EGR loop is continued while the temperature of the NSR 20 is equal to or higher than the activation temperature while the internal combustion engine 1 is stopped, the gas passes through the NSR 20 because the gas temperature is relatively low. On the contrary, there is a risk of cooling. Therefore, in the present embodiment, when the internal combustion engine 1 is stopped and the temperature of the NSR 20 is equal to or higher than the activation temperature, the second throttle valve 17 and the exhaust throttle valve 11 are fully closed, and the compressor Decided to stop. According to this, the gas tightness of the EGR loop can be further improved and the gas flow in the EGR loop can be stopped. Then, the NSR 20 in the EGR loop can be suitably kept warm. In the above, the activation temperature of the NSR 20 corresponds to a predetermined temperature in the present embodiment.

  FIG. 2 shows a flowchart of a catalyst warm-up routine when the engine is stopped in the present embodiment. This routine is a program stored in the ROM of the ECU 22, and is a routine that is executed at predetermined intervals when the vehicle in which the internal combustion engine 1 is mounted is turned on.

  When this routine is executed, it is first determined in S101 whether the internal combustion engine 1 is stopped. Specifically, while the internal combustion engine 1 is stopped, the determination may be made by reading the value of the flag that is ON, or may be determined from the drive signal of the fuel injection valve 3. Here, when it is determined that the internal combustion engine 1 is not stopped, this routine is ended as it is. On the other hand, when it is determined that the internal combustion engine 1 is stopped, the process proceeds to S102.

  In S102, it is determined whether the temperature of the NSR 20 is lower than the activation temperature. This is determined by detecting the temperature of the exhaust exhausted from the NSR 20 by an exhaust temperature sensor (not shown) provided downstream of the NSR 20 and comparing the detected temperature with a preset activation temperature value. May be.

  If it is determined in S102 that the temperature of the NSR 20 is equal to or higher than the activation temperature, the process proceeds to S106. On the other hand, if it is determined that the temperature of the NSR 20 is lower than the activation temperature, the process proceeds to S103.

  In S103, the second throttle valve 17 and the exhaust throttle valve 11 are operated to the valve closing side. Thereby, the sealing property with the outside in the EGR loop is improved. When the process of S103 ends, the process proceeds to S104.

  In S104, the throttle valve 12 and the low pressure EGR5 are operated in the valve opening direction. As a result, the EGR passage 23 can be brought into a conducting state, and the downstream side of the compressor in the intake pipe 9 can be brought into a conducting state, whereby the gas circulation property in the EGR loop can be improved. When S104 ends, the process proceeds to S105.

  In S105, the motor 6a is energized and the compressor is activated. When the process of S105 ends, this routine is temporarily ended.

  If it is determined in S102 of this routine that the temperature of the NSR 20 is equal to or higher than the activation temperature, the process proceeds to S106. In S106, the second throttle valve 17 and the exhaust throttle valve 11 are fully closed. When the process of S106 ends, this routine is temporarily ended.

As described above, in the present embodiment, when the temperature of the NSR 20 is lower than the activation temperature while the internal combustion engine 1 is stopped, the second throttle valve 17 and the exhaust throttle valve 11 are closed to perform the EGR loop. The compressor was driven by the motor 6a while being closed. According to this, the gas can be recirculated in the EGR loop, and the exhaust discharged from the NSR 20 can be prevented from being diffused to the outside as it is. Therefore, it is possible to prevent energy from being wasted outside. Further, the gas temperature can be raised by the compression work of the compressor every time the gas in the EGR loop passes through the compressor. Thereby, warming-up of NSR20 can be accelerated | stimulated more efficiently and it can be activated earlier.

  In this embodiment, when the temperature of the NSR 20 is equal to or higher than the activation temperature while the internal combustion engine 1 is stopped, the second throttle valve 17 and the exhaust throttle valve 11 are fully closed to close the EGR loop and the compressor. The driving by the motor 6a is stopped. According to this, since the sealing performance of the EGR loop can be further improved and the gas recirculation in the EGR loop can be stopped, the once raised NSR 20 can be more efficiently kept warm.

  In this embodiment, when the temperature of the NSR 20 is lower than the activation temperature when the internal combustion engine is stopped, in the process of S104, the second throttle valve 17 and the exhaust throttle valve are used in order to increase the sealing performance of the EGR loop. Both 11 were closed. However, it is not always necessary to close both the second throttle valve 17 and the exhaust throttle valve 11. For example, even if only the exhaust throttle valve 11 is closed, high temperature exhaust after passing through the NSR 20 can be prevented from being released to the outside as it is, and an EGR loop is formed. Can play.

  Next, a second embodiment of the present invention will be described. In this embodiment, a turbine bypass pipe that communicates the downstream side of the compressor in the intake pipe and the downstream side of the turbine in the exhaust pipe to bypass the turbine, and a communication pipe before the turbine that communicates the turbine bypass pipe and the exhaust manifold. And an EGR loop is formed including these. Then, depending on the state of the battery of the motor that drives the compressor, whether to recirculate the gas in the EGR loop from the turbine bypass pipe to the downstream side of the turbine, or to the upstream side of the turbine via the turbine front communication pipe Switch whether to introduce.

  FIG. 3 shows a schematic diagram of the entire internal combustion engine 1, intake / exhaust system, and control system in this embodiment. The difference between the present embodiment and the overall view of the first embodiment shown in FIG. 1 is that, as described above, the intake pipe 9 on the downstream side of the compressor housing 6, the turbine housing 7 of the exhaust pipe 19, and the fuel addition valve. 26 is provided with a turbine bypass pipe 30 that communicates with a portion between the turbine 26 and a turbine front communication pipe 31 that communicates with the turbine bypass pipe 30 and the exhaust manifold 18. In this embodiment, the turbine bypass pipe 30 corresponds to a turbine bypass passage, and the turbine front communication pipe 31 corresponds to a turbine front communication path.

  The turbine bypass pipe 30 is provided with a first bypass valve 33 that adjusts the amount of gas passing through the turbine bypass pipe 30. In addition, a connecting portion between the turbine bypass pipe 30 and the turbine front communication pipe 31 is a three-way valve, and the gas flowing into the turbine bypass pipe 30 is introduced into the exhaust manifold 18 via the turbine front communication pipe 31. A second bypass valve 34 is provided that adjusts the amount of gas that passes through the turbine bypass pipe 30 and is introduced into the exhaust pipe 19 as it is. In the present embodiment, the second bypass valve 34 corresponds to a turbine bypass amount control valve.

  In the present embodiment, the EGR bypass pipe 28 that communicates the upstream side and the downstream side of the EGR cooler 14 in the low-pressure EGR passage 23 and the gas that passes through the EGR cooler 14 out of the gas that passes through the low-pressure EGR passage 23. A second EGR valve 29 capable of controlling the amount and the amount passing through the EGR bypass pipe 28 is provided. In this embodiment, the EGR bypass pipe 28 corresponds to an EGR cooler bypass passage.

In this embodiment, when the temperature of the NSR 20 is lower than the activation temperature while the internal combustion engine 1 is stopped, and the remaining amount of the battery 40 is sufficiently large, the second throttle valve 17 and the exhaust throttle valve 11 are used. Is closed. At that time, the EGR valve 6 is opened and the throttle valve 12 is closed. Further, the first bypass valve 33 is opened, and the EGR gas passing through the turbine bypass valve 30 is directly introduced into the exhaust pipe 19 in the second bypass valve 34 that is a three-way valve.

  If it does so, it can suppress that the gas which recirculates an EGR loop will be cooled by the expansion work in a turbine, and can warm up NSR20 more efficiently.

  Here, as described above, consider a case where the gas recirculated through the EGR loop is passed through the turbine bypass pipe 30 and directly introduced to the downstream side of the turbine housing 7 in the exhaust pipe 19. In this case, since the exhaust passage on the upstream side of the turbine housing 7 such as the exhaust manifold 18 and the collecting pipe 16 has a negative pressure, the driving power for driving the compressor and the turbine connected to the compressor by the motor 6a. Will increase. Therefore, if the remaining amount of charge of the battery 40 is less than 30%, for example, if this state is continued, there is a possibility that the charge amount of the battery 40 is insufficient (including battery exhaustion) or the motor 6a malfunctions. .

  Therefore, in this embodiment, when the remaining amount of charge of the battery 40 is less than 30%, the gas passing through the turbine bypass pipe 30 is caused to flow into the turbine front communication pipe 31 into the second bypass valve 34. I made it.

  If it does so, the increase in the negative pressure in the exhaust manifold 18 and the collecting pipe 16 on the upstream side of the turbine can be suppressed, and the shortage of the charge amount of the battery 40 and the occurrence of malfunction of the motor 6a can be suppressed.

  Further, in this embodiment, when the temperature of the NSR 20 is equal to or lower than the activation temperature, the gas recirculated through the low pressure EGR passage 23 is passed through the EGR bypass pipe 28 and the temperature of the gas is reduced by the EGR cooler 14. We decided to suppress it.

  FIG. 4 shows a flowchart for the engine stop-time catalyst warm-up routine 2 in the present embodiment. This routine is a program stored in the ROM of the ECU 22, and is a routine that is executed at predetermined intervals while the vehicle in which the internal combustion engine 1 is mounted is turned on.

  The difference between this routine and the engine warming-up routine at the time of engine stop shown in FIG. 1 is that the processing of S201 and S202 is executed instead of the processing of S104, and the processing of S203 to S207 after the processing of S105. Is the point where is executed. Only the differences between this routine and the engine stop-time catalyst warm-up routine will be described below.

  In this routine, after the processing of S103 is completed, instead of opening the throttle valve 12 and the low pressure EGR valve 5 in S104, first, in S201, the throttle valve 12 is closed and the low pressure EGR valve 5 is opened. Is done. Then, when the process of S201 ends, the process proceeds to S202.

  In S202, the first bypass valve 33 is opened and the EGR bypass valve 29 is closed. As a result, the turbine bypass pipe 30 enters a conductive state, and the EGR gas can pass through the EGR bypass pipe 28 without passing through the EGR cooler 14. When the process of S202 ends, the process proceeds to S105.

  In S105, since the motor 6a is energized and the compressor starts operating, an EGR loop in which gas is recirculated through the EGR bypass pipe 28 and the turbine bypass pipe 30 is formed. When the process of S105 ends, the process proceeds to S203.

  In S203, the remaining amount of the battery 40 is detected, and it is determined whether this is 10% or more of the maximum charge. Specifically, the remaining amount of charge of the battery 40 may be detected by reading the output of a remaining charge sensor (not shown) provided in the battery 40 into the ECU 22. Here, when it is determined that the remaining charge of the battery 40 is less than 10% of the maximum charge, it is determined that the motor 6a does not operate normally even if the motor 6a is driven, or the battery runs out. In S205, the motor 6a is stopped or the routine is temporarily terminated without driving the motor 6a. On the other hand, when it is determined that the charged amount of the battery 40 is 10% or more, the process proceeds to S204.

  In S204, the remaining amount of the battery 40 is detected, and it is determined whether this is 30% or more of the maximum charge. The details of the determination method are the same as those shown in S203. Here, when it is determined that the remaining amount of the battery 40 is 30% or more, the gas recirculated through the EGR loop passes through the turbine bypass passage 30 and is directly introduced into the exhaust pipe 19, thereby Even if the negative pressure on the side increases, it is determined that the driving of the motor 6a and the compressor can be continued without any problem, and the process proceeds to S206. On the other hand, when it is determined that the remaining amount of the battery 40 is lower than 30%, the gas that recirculates through the EGR loop passes through the turbine bypass passage 30 and is directly introduced into the exhaust pipe 19, so that the upstream side of the turbine When the negative pressure increases, it is determined that the motor 6a and the compressor do not operate normally or there is a possibility that the battery will run out.

  In S206, the second bypass valve 34 is operated, and the EGR gas flowing into the turbine bypass pipe 30 bypasses the turbine and flows into the exhaust pipe 19 as it is. Thereby, it can suppress that the gas which recirculates an EGR loop passes a turbine, and can suppress that temperature falls when gas passes a turbine. At this time, the negative pressure on the upstream side of the turbine increases. However, since the remaining amount of the battery 40 is sufficient, normal operation of the motor 6a and the compressor is ensured, and there is no fear of the battery running out. When the process of S206 is finished, this routine is once finished.

  In S207, the second bypass valve 34 is operated, and the EGR gas flowing into the turbine bypass pipe 30 passes through the turbine front communication pipe 31 and flows into the exhaust manifold 18. As a result, an increase in the negative pressure on the upstream side of the turbine is suppressed, normal operation of the motor 6a and the compressor is ensured, and a battery rise is suppressed. When the process of S207 is completed, this routine is temporarily ended.

  As described above, in the present embodiment, first, the downstream side of the compressor housing 6 in the intake pipe 9 and the portion of the exhaust pipe 19 between the turbine housing 7 and the fuel addition valve 26 are communicated to each other, and the EGR loop. An intercooler 13 and a turbine bypass pipe 30 for bypassing the turbine are provided in the gas that is recirculated.

  Thereby, when the temperature of NSR20 is lower than activation temperature, it can suppress that the gas which recirculates an EGR loop will be cooled by passing the intercooler 13 and the turbine in the turbine housing 7. FIG.

  Further, in the present embodiment, since the EGR bypass pipe 28 that similarly bypasses the EGR cooler 14 is provided, it is possible to suppress the gas passing through the low pressure EGR passage 23 from being cooled by the EGR cooler 14.

Further, in the present embodiment, a turbine front communication pipe 31 that communicates the turbine bypass pipe 30 and the exhaust manifold 18 is provided, and when the remaining amount of the battery 40 is less than 30%, the turbine bypass pipe 30 passes through. The gas to be flown into the exhaust manifold 18 is not allowed to bypass the turbine. Therefore, when the remaining amount of the battery 40 is small, an increase in the negative pressure on the upstream side of the turbine can be suppressed, the normal operation of the motor 6a can be ensured, and the occurrence of battery exhaust can be suppressed.

  In the present embodiment, the operation of the second bypass valve 34 is switched, and the gas introduced into the turbine bypass pipe 30 is introduced directly into the exhaust pipe 19 downstream of the turbine or exhausted through the turbine front communication pipe 31. Although switching to the manifold 18 is switched, the switching by the second bypass valve 34 may be an intermediate switching. That is, of the gas introduced into the turbine bypass pipe 30 according to the remaining amount of the battery 40, the amount of gas introduced directly into the exhaust pipe 19 downstream of the turbine and the exhaust manifold 18 through the turbine front communication pipe 31 are introduced. Control that continuously changes the amount of gas may be performed. When the remaining amount of the battery 40 is less than 30%, the amount of gas flowing into the turbine front communication pipe 31 may be increased by the second bypass valve 34.

  In the present embodiment, the remaining amount of 30% at the time of maximum charging of the battery 40 corresponds to a predetermined amount of residual power. The value of the predetermined amount is not limited to 30%, and may be appropriately determined according to battery performance, the rating of the motor 6a, and the characteristics of the internal combustion engine 1.

  Next, Embodiment 3 of the present invention will be described. In this embodiment, a filter unit that combines a filter that collects particulate matter in the exhaust and an HC catalyst that absorbs HC that is an unburned component in the exhaust is provided upstream of the NSR in the exhaust pipe, and An example in which a portion of the exhaust pipe between the filter unit and the NSR and the low pressure EGR passage are communicated will be described. The other parts of the internal combustion engine, the intake / exhaust system, and the control system in the present embodiment are the same as those described in the first embodiment.

  FIG. 5 shows a schematic diagram of the internal combustion engine, the intake / exhaust system, and the control system in the present embodiment. In this embodiment, as shown in the figure, on the upstream side of the NSR 20 in the exhaust pipe 19, a filter that collects particulate matter in the exhaust and an HC catalyst that absorbs HC, which is an unburned component in the exhaust, are provided. A combined filter unit 35 is provided. Further, the portion of the exhaust pipe 19 between the filter unit 35 and the NSR 20 and the low pressure EGR passage 23 are communicated with each other by an EGR communication pipe 37. Here, the upstream side (in the EGR loop) of the low pressure EGR passage 23 connected to the EGR communication pipe 37 is connected to the upstream low pressure EGR passage 23a and the connection portion of the low pressure EGR passage 23 to the EGR communication pipe 37 (in the EGR loop). The downstream side is a downstream low pressure EGR passage 23b. Further, a second exhaust throttle valve 36 is provided between the connection portion of the exhaust pipe 19 and the EGR communication pipe 37 and the NSR 20, and a three-way valve is provided at the connection section of the EGR communication pipe 37 and the low pressure EGR passage 23. The second low pressure EGR valve 38 is provided. Note that the exhaust emission control device of this embodiment includes a filter unit 35 and an NSR 20, and the HC catalyst and the NSR 20 correspond to a plurality of catalysts.

  In this embodiment, when the temperature of the NSR 20 is lower than the activation temperature when the internal combustion engine 1 is stopped, the second throttle valve 17 and the exhaust throttle valve 11 are throttled. Further, the second exhaust throttle valve 36 is opened. Further, the second low-pressure EGR valve 38 is blocked between the EGR communication pipe 37 and the downstream low-pressure EGR passage 23b, and is opened between the upstream low-pressure EGR passage 23a and the downstream low-pressure EGR passage 23b. As a result, the gas passing through the exhaust pipe 19 is recirculated through the upstream low pressure EGR passage 23a and the downstream low pressure EGR passage 23b after passing through both the filter unit 35 and the NSR 20.

On the other hand, when the temperature of the NSR 20 is equal to or higher than the activation temperature when the internal combustion engine 1 is stopped and the temperature of the HC catalyst of the filter unit 35 is lower than the activation temperature, the second exhaust throttle valve 36 is used.
Is closed. At the same time, the second low-pressure EGR valve 38 is opened between the EGR communication pipe 37 and the downstream low-pressure EGR passage 23b, and the upstream low-pressure EGR passage 23a and the downstream low-pressure EGR passage 23b are blocked. Thus, the gas passing through the exhaust pipe 19 is recirculated through the EGR communication pipe 37 and the downstream low-pressure EGR passage 23b without passing the NSR 20 after passing through the filter unit 35. In this case, the NSR 20 can be suitably kept warm by closing the exhaust throttle valve 11.

  Further, when the temperature of the NSR 20 is equal to or higher than the activation temperature and the temperature of the HC catalyst of the filter unit 35 is equal to or higher than the activation temperature when the internal combustion engine 1 is stopped, the exhaust throttle valve 11 is fully closed and the second throttle valve is closed. 17 is fully closed, and the motor 6a is stopped.

  According to this, depending on whether the temperature of the HC catalyst and NSR 20 of the filter unit 35 is equal to or higher than the respective activation temperature, the EGR loop can be changed, and a high-temperature gas can be selectively passed through the catalyst to be warmed up. The HC catalyst of the filter unit 35 and the warm-up of the NSR 20 can be promoted more efficiently. In this embodiment, the upstream low pressure EGR passage 23a and the EGR communication pipe 37 correspond to an EGR branch passage. The second low pressure EGR valve 38 corresponds to an EGR switching valve.

  FIG. 6 shows a flowchart of the engine stop-time catalyst warm-up routine 3 in this embodiment. This routine is a program stored in the ROM of the ECU 22, and is a routine that is executed at predetermined intervals while the vehicle in which the internal combustion engine 1 is mounted is turned on.

  The difference between this routine and the engine warming-up routine at the time of engine stop shown in FIG. 1 is that the processing of S301 is inserted between the processing of S104 and S105, and after the processing of S106 is finished, S302 to S305. This process is added. Only the differences between this routine and the engine stop-time catalyst warm-up routine will be described below.

  In this routine, when the process of S104 ends, the process of S301 is executed. In S301, the second exhaust throttle valve 36 is opened and the second low pressure EGR valve 38 opens the upstream low pressure EGR passage 23a and the downstream low pressure EGR passage 23b. Further, the EGR communication pipe 37 and the downstream low pressure EGR passage 23b are blocked.

  In this routine, when the process of S106 is completed, the process proceeds to S302, where it is determined whether or not the temperature of the HC catalyst of the filter unit 35 is lower than its activation temperature. If it is determined that the temperature of the HC catalyst is equal to or higher than the activation temperature, it is determined that both the HC catalyst and the NSR 20 are equal to or higher than the activation temperature. On the other hand, if it is determined in S302 that the temperature of the HC catalyst is lower than its activation temperature, it is necessary to keep the NSR 20 warm and promote warm-up of the HC catalyst, so the process proceeds to S303.

  In S303, the throttle valve 12 and the low pressure EGR valve 5 are opened. When the process of S303 ends, the process proceeds to S304.

  In S304, the second exhaust throttle valve 36 is closed, and the second low pressure EGR valve 38 opens the space between the EGR communication pipe 37 and the downstream low pressure EGR passage 23b, and the upstream low pressure EGR passage 23a and the downstream low pressure EGR. The passage 23b is blocked. When the process of S304 ends, the process proceeds to S305.

  In S305, the motor 6a is energized, and the operation of the compressor by electric operation is started. When the processing of S305 ends, this routine is temporarily ended.

  As described above, in the present embodiment, the control of the exhaust system while the internal combustion engine 1 is stopped is changed according to the activation state of the HC catalyst of the filter unit 35 and the NSR 20. Specifically, first, when the temperature of the NSR 20 is lower than the activation temperature, the exhaust throttle valve 11 and the second throttle valve 17 are closed, and the throttle valve 12, the second exhaust throttle valve 36, and the low pressure EGR valve 5 are turned on. The valve was opened, and the second low pressure EGR valve 38 was opened between the upstream low pressure EGR passage 23a and the downstream low pressure EGR passage 23b.

  As a result, an EGR loop including the filter unit 35 and NSR 20 can be formed. When the motor 6a is energized, both the filter unit 35 and NSR 20 are allowed to pass through the gas recirculated through the EGR loop to warm both. The machine can be promoted.

  On the other hand, when the temperature of the HC catalyst of the filter unit 35 is lower than the activation temperature and the temperature of the NSR 20 is equal to or higher than the activation temperature, the exhaust throttle valve 11 and the second throttle valve 17 are fully closed, and the throttle valve 12 and The low pressure EGR valve 5 was opened, the second exhaust throttle valve 36 was closed, and the second low pressure EGR valve 38 was opened between the EGR communication pipe 37 and the downstream low pressure EGR passage 23b.

  As a result, the exhaust throttle valve 11 and the second exhaust throttle valve 36 are closed, and the upstream low-pressure EGR passage 23a and the downstream low-pressure EGR passage 23b are blocked, so that the activated NSR 20 It is possible to keep the heat by confining in a nearby region and stopping the flow. Further, an EGR path including the HC catalyst of the filter unit 35 can be formed, and by energizing the motor 6a, warming up of the HC catalyst can be promoted by allowing the high-temperature gas to pass through the filter unit 35. .

  Further, when both the HC catalyst and the NSR 20 of the filter unit 35 are at the activation temperature or higher, the exhaust throttle valve 11 and the second throttle valve 17 are fully closed, and the energization of the motor 6a is stopped.

  Thereby, about both the filter unit 35 and NSR20, while confining a high temperature gas to the area | region of the vicinity, a flow can be stopped and heat insulation can be carried out.

  Here, in this embodiment, the opening and closing of the second exhaust throttle valve 36 and the second low pressure EGR valve 37 are switched depending on whether the temperatures of the HC catalyst and the NSR 20 of the filter unit 35 are equal to or higher than the respective activation temperatures. However, the operation of these two valves is not limited to the operation of switching between fully open and fully closed. For example, the amount of these two valves can be changed while maintaining the recirculated gas through a plurality of loops by switching the operation between a relatively large opening state and a relatively small opening state. The details of the control can be changed.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention may be configured by combining both the configuration according to FIG. 3 described in the second embodiment and the configuration according to FIG. 5 described in the third embodiment. it can. Then, the exhaust gas recirculation device can have the effects described in the respective embodiments. The configuration of the internal combustion engine 1, the intake / exhaust system, and the control system in that case is shown in FIG.

In the above embodiment, the case where the internal combustion engine 1 is stopped during the eco-run operation of the internal combustion engine 1 has been described as an example. However, the stop of the internal combustion engine 1 may be caused by other causes. For example, the present invention may be applied to catalyst warm-up before the internal combustion engine 1 is started. In this case, the gas can pass through the EGR loop and the compression work can be performed by the compressor, so that the temperature can be increased, and the warm-up can be promoted by introducing the gas whose temperature has increased to the catalyst. it can. Further, the present invention may be applied to a period during which the internal combustion engine 1 is stopped in a hybrid vehicle.

  In the above embodiment, the supercharger having a compressor that can be driven by the motor 6a functions as the circulating flow generating means. However, the circulating flow generating means is not limited to this. For example, an electric pump as a circulating flow generating means may be separately provided in the EGR loop.

1 is a schematic diagram of an internal combustion engine, an intake / exhaust system, and a control system thereof according to Embodiment 1 of the present invention. It is a flowchart about the catalyst warm-up routine at the time of engine stop which concerns on Example 1 of this invention. It is the schematic of the internal combustion engine which concerns on Example 2 of this invention, its intake-exhaust system, and a control system. It is a flowchart about the catalyst warm-up routine 2 at the time of engine stop which concerns on Example 2 of this invention. It is the schematic of the internal combustion engine which concerns on Example 3 of this invention, its intake-exhaust system, and a control system. It is a flowchart about the catalyst warm-up routine 3 at the time of engine stop which concerns on Example 3 of this invention. It is the schematic about the example which combined the internal combustion engine which concerns on Example 2 and Example 3 of this invention, its intake-exhaust system, and a control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 5 ... Low pressure EGR valve 6 ... Compressor housing 6a ... Motor 7 ... Turbine housing 8 ... Intake manifold 9. ..Intake pipe 10 ... supercharger 11 ... exhaust throttle valve 12 ... throttle valve 13 ... intercooler 14 ... EGR cooler 15 ... high pressure EGR passage 16 ... collection pipe 17 ... Second throttle valve 18 ... Exhaust manifold 19 ... Exhaust pipe 20 ... Filter 21 ... High pressure EGR valve 22 ... ECU
23 ... Low pressure EGR passage 23a ... Upstream low pressure EGR passage 23b ... Downstream low pressure EGR passage 24 ... Air flow meter 25 ... Air cleaner 26 ... Fuel addition valve 30 ... Turbine bypass pipe 31 ..Turbine front communication pipe 33 ... first bypass valve 34 ... second bypass valve 35 ... filter unit 36 ... second exhaust throttle valve 37 ... EGR communication pipe 38 ... second Low pressure EGR valve 40 ... Battery

Claims (9)

An exhaust purification device having a catalyst provided in an exhaust passage of an internal combustion engine and purifying exhaust gas passing through the exhaust passage;
An EGR passage communicating the exhaust passage downstream of the exhaust purification device and the intake passage of the internal combustion engine;
An exhaust throttle valve that is provided on the downstream side of a connection portion between the EGR passage and the exhaust passage in the exhaust passage and controls the amount of exhaust gas passing through the exhaust passage;
Provided in an EGR path formed including the intake passage and a part of the exhaust passage and the EGR passage, and recirculates the EGR path to the gas in the EGR path even when the internal combustion engine is stopped. A circulating flow generating means capable of generating a flow;
With
When the temperature of the catalyst is lower than a predetermined temperature while the internal combustion engine is stopped, the exhaust throttle valve is closed and a flow is generated in the gas in the EGR path by the circulation flow generation means, An exhaust gas recirculation device for an internal combustion engine, wherein the exhaust gas is forcibly recirculated in the EGR path. An intake throttle valve that is provided upstream of the connection portion between the EGR passage and the intake passage in the intake passage and controls the amount of intake air that passes through the intake passage;
When the temperature of the catalyst is lower than the predetermined temperature while the internal combustion engine is stopped, the intake throttle valve and the exhaust throttle valve are closed and the circulation flow generating means allows the gas in the EGR path to flow. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the gas is forcibly recirculated through the EGR path.   When the temperature of the catalyst is equal to or higher than the predetermined temperature while the internal combustion engine is stopped, the intake throttle valve and the exhaust throttle valve are closed and the generation of the gas flow by the circulating flow generation means is stopped. The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein A turbocharger further comprising a compressor provided downstream of a connection portion between the EGR passage and the intake passage in the intake passage and a turbine provided upstream of the exhaust purification device in the exhaust passage;
The said circulating flow production | generation means is an electric supercharger which can produce | generate a flow in the gas in the said EGR path | route by operating the compressor of the said supercharger with an electric motor. An exhaust gas recirculation device for an internal combustion engine according to any one of the above.   A turbine bypass passage is further provided that communicates a downstream side of the compressor in the intake passage with a portion of the exhaust passage between the turbine and the exhaust purification device, and bypasses the turbine with a gas passing through the intake passage. The exhaust gas recirculation device for an internal combustion engine according to claim 4. A turbine pre-communication passage that communicates the turbine bypass passage and a portion of the exhaust passage upstream of the turbine;
Of the gas passing through the turbine bypass passage, a turbine bypass amount control valve that controls the amount of intake air flowing into the turbine front communication passage;
Further comprising
When the residual electric energy of the battery as the electric power source of the electric supercharger is smaller than a predetermined amount, the amount of gas flowing into the turbine front communication path is increased by the turbine bypass amount control valve. The exhaust gas recirculation device for an internal combustion engine according to claim 5. On the downstream side of the compressor in the intake passage, an intercooler for cooling the gas supercharged by the compressor is provided,
The exhaust gas recirculation device for an internal combustion engine according to claim 5 or 6, wherein the turbine bypass passage is connected to a portion of the intake passage between the compressor and the intercooler. An EGR cooler provided in the EGR passage for cooling gas passing through the EGR passage;
An EGR cooler bypass passage that connects an upstream side and a downstream side of the EGR cooler in the EGR passage, and bypasses the EGR cooler with a gas passing through the EGR passage;
The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 7, further comprising: The exhaust purification device has a plurality of catalysts arranged in series in the exhaust passage,
One or more EGR branch passages branched from the EGR passage and connected to the downstream side of at least some of the plurality of catalysts in the exhaust passage;
Of the gas that is provided at the connection portion between the EGR branch passage and the EGR passage and recirculates through the EGR passage to the intake passage, the amount of gas flowing into the EGR passage from each of the EGR branch passages is determined. A controllable EGR switching valve;
The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 8, further comprising:

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