JP2010151111A - Egr system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of certainly removing clogging of a capturing device while suppressing deterioration of fuel economy, in an EGR system provided with the capturing device for capturing foreign matter in an EGR gas on a midway of an EGR passage. <P>SOLUTION: The EGR system for the internal combustion engine is provided with the EGR passage; the capturing device provided on the EGR passage and capturing the foreign matter contained in the EGR gas; an exhaust temperature obtaining means for obtaining a temperature of the exhaust gas flowing into the capturing device; a soot deposition amount obtaining means for obtaining a deposition amount of soot in the capturing device; a pressure loss obtaining means for obtaining pressure loss in the capturing device; a removal means for removing an exhaust component deposited in the capturing device by temperature-raising the capturing device when it is detected that the pressure loss obtained by the pressure loss obtaining means exceeds a predetermined reference value; and a setting means for setting a target temperature when the removal means temperature-raises the capturing device according to the temperature obtained by the exhaust temperature obtaining means and the deposition amount obtained by the soot deposition amount obtaining means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an EGR system for an internal combustion engine.

  2. Description of the Related Art An EGR device that makes a part of exhaust discharged from an internal combustion engine flow into an intake passage is known. By the way, parts such as the catalyst and turbine provided in the exhaust passage are damaged and the fragments flow into the exhaust, or foreign matters such as spatter generated during welding of the exhaust pipe piping are mixed into the exhaust. In this case, in the internal combustion engine equipped with the EGR device, the exhaust gas in which these foreign matters are mixed may be sucked into the internal combustion engine, causing an abnormality in the operation of the internal combustion engine. Further, when a large amount of EGR gas is required such as at high load, an internal combustion engine provided with a low-pressure EGR device that introduces EGR gas into an intake passage upstream of a relatively low-pressure compressor in order to introduce EGR gas. Then, there is a possibility that the exhaust gas mixed with foreign matter flows into the compressor and damages the compressor impeller.

  In order to solve such a problem, a technique has been proposed in which a collecting device that collects foreign substances in the EGR gas is provided in the middle of the EGR passage to prevent foreign substances from flowing into the intake system. As the collection device, a mesh filter, a device that separates foreign matters by the action of centrifugal force and gravity by turning EGR gas within a predetermined volume, and the like can be adopted.

  In Patent Document 1, a collecting part having a shape bent downward in the direction of gravity is provided in the middle of the low pressure EGR passage, and foreign matter in the EGR gas flowing through the low pressure EGR passage is collected in the collecting part. Describes a technique for suppressing inflow of air into the intake system.

  In Patent Document 2, in an internal combustion engine provided with a filter for collecting PM in the middle of an exhaust passage, when the front-rear differential pressure between the upstream side and the downstream side of the filter becomes a predetermined value or more, it is collected by the filter. A technique for performing a filter regeneration process for removing oxidized PM by oxidation is described.

  In Patent Document 3, in an internal combustion engine provided with a filter for collecting PM in the middle of an exhaust passage, when PM is continuously collected for a predetermined period or more under low exhaust temperature operating conditions, exhaust condensed water or low boiling point is collected. There is described a technique for removing condensed water and HC accumulated on a filter by raising the temperature of the filter to a temperature at which HC evaporates and lower than the combustion temperature of PM.

In Patent Document 4, in a configuration in which an EGR pipe that allows exhaust to flow into the intake system of the internal combustion engine from downstream of a filter or NOx catalyst is provided, a communication path that connects the vicinity of the lowermost part of the EGR pipe and the exhaust path is provided. A technique is disclosed in which condensed water in the piping is discharged to the exhaust passage through the communication passage to suppress accumulation of condensed water in the EGR piping.
JP 2008-150955 A JP 2008-223687 A Japanese Patent Laid-Open No. 11-081979 JP 2008-208721 A

In an EGR device equipped with a collection device that collects foreign substances in EGR gas in the middle of the EGR passage, substances other than foreign matters such as soot, HC, and condensed water in the exhaust accumulate on the collection device and collect them. The device may become clogged. When the collecting device is clogged, the pressure loss on the upstream side and the downstream side of the collecting device becomes large, and it becomes difficult for the EGR device to flow exhaust into the intake system.

  On the other hand, when clogging occurs in the collection device, it is conceivable to perform a process of removing these substances accumulated in the collection device by raising the temperature of the collection device. However, in order to surely eliminate the clogging of the collecting device by such treatment, it is necessary to raise the temperature of the collecting device to such a high temperature that it is possible to reliably remove the most difficult deposit (for example, soot). There is. Therefore, when the cause of the clogging of the collection device is the accumulation of substances that can be removed at a lower temperature (for example, condensed water or HC), the collection device is unnecessarily increased to an unnecessarily high temperature. There was a problem of deterioration of fuel consumption and deterioration of the collecting device due to the temperature increase process.

  The present invention has been made in view of such problems, and in the EGR system provided with a collection device that collects foreign substances in EGR gas in the middle of the EGR passage, the collection device while suppressing deterioration of fuel consumption. It is an object of the present invention to provide a technique that makes it possible to reliably remove clogging.

In order to achieve the above object, an EGR system for an internal combustion engine of the present invention communicates an exhaust passage of an internal combustion engine and an intake passage, and an EGR passage that allows a part of exhaust from the internal combustion engine to flow into the intake passage;
A collection device that is provided in the EGR passage and collects foreign substances contained in the EGR gas;
Exhaust temperature acquisition means for acquiring the temperature of the exhaust gas flowing into the collection device;
Soot accumulation amount acquisition means for acquiring the accumulation amount of soot in the collection device;
Pressure loss acquisition means for acquiring pressure loss on the upstream side and downstream side of the collection device;
Removal that removes exhaust components accumulated in the collecting device by raising the temperature of the collecting device when it is detected that the pressure loss obtained by the pressure loss obtaining means exceeds a predetermined reference value Means,
A setting for setting the target temperature when the removal means raises the temperature of the collection device according to the temperature acquired by the exhaust temperature acquisition means and the accumulation amount acquired by the soot accumulation amount acquisition means Means,
It is characterized by providing.

  In the configuration of the present invention described above, the trapping device is such that parts such as a catalyst and a turbocharger provided in the exhaust system downstream of the combustion chamber of the internal combustion engine are damaged and the fragments flow into the exhaust, When foreign matter such as spatter generated during pipe welding is mixed in the exhaust, the foreign matter is separated from the exhaust and can be collected.

  In addition to collecting the original purpose foreign matter, the collection device also deposits and accumulates exhaust components such as condensed water, HC, and soot (particulate matter, PM) in the exhaust, and clogs the collection device. May occur. In that case, the pressure loss between the upstream side and the downstream side of the collection device increases, and it becomes difficult to appropriately flow the EGR gas into the intake passage.

  In the EGR system of the present invention, when it is detected that the pressure loss between the upstream side and the downstream side of the collection device exceeds the reference value, it is determined that the collection device is clogged, and the collection is performed. The temperature of the device is raised to remove the exhaust components accumulated in the collection device. The reference value of the pressure loss can be determined based on the upper limit value of the pressure loss such that the influence on the fuel consumption is within the allowable range, the upper limit value of the pressure loss capable of appropriately controlling the EGR gas amount, or the like.

  By the way, the temperature of the temperature rise required for removing the exhaust component accumulated in the collection device by the temperature rise of the collection device varies depending on the type of the exhaust component. For example, when the condensed water is heated to 100 ° C. or higher, HC is 200 ° C. or higher, and soot is heated to 500 ° C. or higher, it can be suitably removed from the collecting device.

  Here, when it is determined that the collecting device is clogged (when it is detected that the pressure loss between the upstream side and the downstream side of the collecting device exceeds the reference value), the collecting device The type of exhaust component accumulated in the gas is related to the temperature of the exhaust gas flowing into the collection device and the amount of soot accumulated in the collection device.

  For example, when the temperature of the exhaust gas flowing into the collection device is lower than the temperature at which the condensed water in the exhaust gas evaporates (for example, around 100 ° C.), the condensed water mainly adheres and accumulates on the collection device. it is conceivable that. That is, under such a low exhaust temperature condition, it can be determined that the cause of the clogging of the collection device 10 is mainly condensed water.

  When the temperature of the exhaust gas flowing into the collection device is higher than the temperature at which condensed water in the exhaust gas evaporates but lower than the temperature at which HC evaporates (for example, around 200 ° C.), HC mainly adheres to the collection device. It is thought that it is accumulated. That is, under such a medium exhaust temperature condition, it can be determined that the cause of the clogging of the collecting device is mainly HC.

  When the temperature of the exhaust gas flowing into the collection device is higher than the temperature at which HC in the exhaust gas evaporates but lower than the temperature at which the soot oxidation reaction proceeds (for example, around 500 ° C.), It is considered that soot has accumulated. That is, it can be determined that the cause of the clogging of the collecting device is mainly the soot under such middle and high exhaust temperature conditions.

  However, even under such medium and high temperature exhaust temperature conditions, if exhaust at a temperature of a certain level (for example, around 400 ° C.) continuously flows into the collection device, soot in the collection device It is considered that the amount of deposition does not increase monotonously. That is, based on the engine operation history that the exhaust temperature condition at a certain temperature (for example, around 400 ° C.) is lower than a temperature at which the soot oxidation reaction easily proceeds (for example, around 500 ° C.) but continues for a certain period or more. It can also be determined that the cause of the clogging of the collecting device is not a soot.

  In addition, the travel time since the temperature of the collector was raised to remove the exhaust component last time, the integrated value of the fuel injection amount, the operating history under operating conditions such as acceleration transient with a large amount of soot discharge, EGR Based on the gas amount control history, etc., the amount of soot accumulated in the collector is estimated. Based on the estimated amount of soot accumulated, the exhaust that is the main cause of clogging in the collector The kind of component can be specified. When the amount of soot accumulated is so large as to cause clogging in the collecting device, it is possible to determine that the exhaust component accumulated in the collecting device is mainly soot regardless of the exhaust temperature conditions described above. it can.

  In addition, when the temperature of the exhaust gas flowing into the collection device is higher than the temperature at which the soot oxidation reaction proceeds (for example, around 500 ° C.), the collection device may be clogged with exhaust gases such as condensed water, HC, and soot. It is thought that it exists in addition to an ingredient. That is, under such a high exhaust temperature condition, the cause of the clogging of the trapping device is, for example, debris due to the damage of the exhaust purification catalyst provided in the exhaust passage upstream from the connection point of the EGR passage or the piping of the exhaust passage. It can be determined that foreign matter is accumulated such as welding spatter.

  Focusing on such relevance, in the EGR system of the internal combustion engine according to the present invention, according to the temperature of the exhaust gas flowing into the collection device and the amount of soot accumulated in the collection device, the collection device is The target temperature for raising the temperature was set.

  That is, in the EGR system of the present invention, the temperature at which the exhaust component can be removed from the collection device can be set as the target temperature for the temperature rise in accordance with the type of the exhaust component accumulated in the collection device. .

  For example, when it is determined that the exhaust component accumulated in the collection device is mainly condensed water, the minimum temperature increase temperature (for example, 100 ° C.) necessary for removing the condensed water from the collection device. Can be set as the target temperature. If the temperature of the collection device is raised according to the target temperature set in this way, the temperature rise temperature is reduced to the minimum temperature necessary for removing exhaust components actually accumulated in the collection device. In the process of removing the clogging of the collection device, it is deposited on the collection device while suppressing fuel consumption deterioration due to unnecessary energy consumption and thermal deterioration due to excessive temperature rise of the collection device. It is possible to suitably remove the exhaust components that are present and eliminate clogging of the collection device.

  As the collection device in the present invention, a mesh filter, a device for separating and collecting foreign substances from exhaust gas by the action of centrifugal force or gravity, and the like can be used.

  In the present invention, the exhaust temperature acquisition means measures the temperature of the exhaust on the upstream side of the collection device in the EGR passage, the temperature of the exhaust in the exhaust passage, the temperature of the exhaust in the exhaust manifold, the cooling water temperature of the internal combustion engine, the intake air temperature, etc. The temperature of the exhaust gas flowing into the collection device can be acquired by the calculation based on the above, the calculation based on the operating condition of the internal combustion engine, or the like.

  The soot accumulation amount acquisition means in the present invention is based on the operation history of the internal combustion engine, the operation conditions of the internal combustion engine, the exhaust gas temperature history, the elapsed time since the removal of clogging by the previous removal means, etc. The amount of soot accumulated can be acquired.

  The pressure loss acquisition means in the present invention is based on the pressure difference between the upstream side and the downstream side of the collection device, the gas flow rate difference, the temperature difference, etc., and the pressure between the upstream side and the downstream side of the collection device. You can get a loss.

  The removal means in the present invention may raise the temperature of the trapping device, for example, by increasing the fuel injection amount, performing after injection or post injection, advance of the exhaust valve opening timing, adding fuel to the exhaust, exhaust throttle valve In addition to various engine controls such as changing the opening degree to the valve closing side and changing the VN opening degree to the valve opening side, a method in which the collector is provided with a direct heating device such as an electric heater can also be employed. Whichever temperature raising method is used to raise the temperature of the collection device, according to the EGR system of the present invention, the exhaust component deposits causing the clogging of the collection device are removed from the collection device. Therefore, the temperature of the collecting device can be raised with the minimum temperature increase temperature as the target temperature, so that it is possible to reduce the amount of energy consumed for eliminating the clogging of the collecting device. Play.

  In the present invention, when it is determined that the collecting device is clogged, the temperature of the collecting device is increased and the exhaust components accumulated in the collecting device are removed. There is a possibility that the removed exhaust component is conveyed by the flow of exhaust gas flowing through the EGR passage and flows into the intake passage. In that case, exhaust components of high concentration may flow into the compressor or the internal combustion engine, which may cause malfunction of the turbocharger or combustion fluctuation of the internal combustion engine.

Therefore, in the present invention,
An EGR valve that is provided on the downstream side of the collection device in the EGR passage and adjusts the amount of EGR gas flowing from the EGR passage to the intake passage;
Control means for controlling the opening of the EGR valve;
Further comprising
The control means closes the EGR valve more when the temperature of the collecting device is increased by the removing means than when the temperature of the collecting device is not increased by the removing means. The valve may be opened at the opening on the side.

  Thereby, even when the temperature of the collecting device is raised by the removing means, it is possible to suppress the EGR gas containing the high-concentration exhaust component flowing out from the collecting device from flowing into the intake passage at once. Therefore, in the configuration in which the EGR passage is connected to the intake passage on the upstream side of the compressor, it is possible to suitably suppress the operation abnormality of the compressor. Further, intake of high concentration exhaust components into the internal combustion engine is suppressed, and combustion fluctuations can be suitably suppressed.

In the present invention,
A communication passage communicating the downstream side of the collection device in the EGR passage and the exhaust passage;
An EGR valve that is provided on the downstream side of the connection portion of the communication passage in the EGR passage, and adjusts the amount of EGR gas flowing from the EGR passage to the intake passage;
Control means for controlling the opening of the EGR valve;
Further comprising
The control means may close the EGR valve when the temperature of the collecting device is raised by the removing means.

  As a result, even when the temperature of the collecting device is raised by the removing means, the EGR gas containing the high concentration exhaust component flowing out from the collecting device flows into the exhaust passage via the communication passage, and the intake air It will not flow into the passage. Therefore, in the configuration in which the EGR passage is connected to the intake passage on the upstream side of the compressor, it is possible to more reliably prevent the compressor from operating abnormally. Further, intake of high concentration exhaust components into the internal combustion engine is suppressed, and combustion fluctuations can be suppressed more reliably.

  Further, since the downstream side of the collection device and the exhaust passage are always in communication with each other through the communication passage, the pressure loss in the collection device can be measured even when the EGR valve is closed. There are also the following effects. Therefore, it is possible to determine whether or not the collecting device is clogged even under operating conditions in which the EGR valve is closed and the recirculation of the EGR gas through the EGR passage is stopped.

  Deposits that can be removed from the collection device by the removal means raising the temperature of the collection device are exhaust components such as the condensed water, HC, and soot described above. If the cause of the clogging in the collector is not the accumulation of these exhaust components but the accumulation of foreign matter such as broken pieces of exhaust system parts that have been damaged, the removal means will raise the temperature of the collector. In some cases, it is difficult to eliminate clogging generated in the collecting device. Therefore, in such a case, it is considered that the pressure loss between the upstream side and the downstream side of the collection device does not sufficiently decrease even immediately after the temperature of the collection device is raised by the removing means. .

  Therefore, in the present invention, immediately after the temperature of the collection device is raised by the removing means, it is detected that the pressure loss acquired by the pressure loss acquiring means exceeds a predetermined second reference value. In this case, an engine abnormality determination means for determining that an abnormality has occurred in the internal combustion engine may be further provided.

  Here, “the abnormality has occurred in the internal combustion engine” means that an abnormality has occurred in the components of the exhaust system such as the turbine, the exhaust purification catalyst, the exhaust manifold, and various pipes arranged downstream of the combustion chamber of the internal combustion engine. Means comprehensively. In particular, when the EGR passage is configured to extract exhaust from the exhaust passage downstream of the exhaust purification catalyst, the foreign matter accumulated in the collection device is damaged by the excessive temperature rise. There is a possibility that it is a generated fragment.

  The second reference value is based on the pressure loss of the collector that is assumed to be realized if the temperature rise control of the collector is performed by the removing means when the deposit in the collector is an exhaust component. Can be determined. Even if foreign matter is accumulated in the collection device, it is considered that some exhaust components are also accumulated at the same time. The pressure loss is reduced by the amount corresponding to the amount. Therefore, the second reference value can be set to a value smaller than the first reference value.

  There is a certain amount of pressure loss between the upstream side and the downstream side of the collection device even if no foreign matter or exhaust components are accumulated. However, when the collection device is damaged, the pressure loss may be smaller than that of a normal collection device. For example, in a mesh-type filter collection device, if the filter breaks and a part of the mesh is perforated, the exhaust gas is easier to pass than the normal filter, so the pressure loss is Get smaller.

  Therefore, in the present invention, when it is detected that the pressure loss acquired by the pressure loss acquisition means is smaller than a predetermined third reference value, the collection device abnormality that determines that an abnormality has occurred in the collection device A determination unit may be further provided.

  Here, the third reference value can be determined based on a pressure loss between the upstream side and the downstream side of the collection device in a state where no foreign matter or exhaust components are accumulated in the collection device.

  When the collection device is damaged, there is a possibility that foreign matter in the exhaust gas is not collected by the collection device and flows into the intake passage via the EGR passage. Therefore, if it is determined by the collecting apparatus abnormality determining means having the above-described configuration that the collecting apparatus is damaged, the exhaust gas recirculation through the EGR passage may be stopped by closing the EGR valve. good. By doing so, it is possible to prevent foreign matters in the exhaust from flowing into the compressor or the internal combustion engine and causing problems.

  According to the present invention, in a low-pressure EGR system having a collection device that collects foreign substances in the middle of a low-pressure EGR passage, it is possible to suitably remove clogging of the collection device while suppressing an increase in fuel consumption.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a conceptual diagram schematically showing a schematic configuration of an internal combustion engine to which an EGR system for an internal combustion engine according to this embodiment is applied, and its intake system and exhaust system.

  The engine 1 in FIG. 1 is a diesel engine having four cylinders 30. A combustion chamber (not shown) of each cylinder 30 communicates with the intake manifold 17 via an intake port (not shown) opened and closed by an intake valve (not shown). The combustion chamber of each cylinder 30 communicates with the exhaust manifold 18 via an exhaust port (not shown) that is opened and closed by an exhaust valve (not shown).

An intake passage 19 is connected to the intake manifold 17. In the intake passage 19, from the downstream side to the upstream side with respect to the flow of intake air from the intake manifold 17, a connecting portion of a high pressure EGR passage 15 described later, a diesel throttle valve 9, an intercooler 2, a compressor 11 of a turbocharger 13, and a later described. A connecting portion of the low pressure EGR passage 24, an intake throttle valve 22, an air flow meter 7, and an air cleaner 3 are provided.

  An exhaust passage 20 is connected to the exhaust manifold 18. In the exhaust passage 20, from the upstream side toward the downstream side with respect to the flow of exhaust from the exhaust manifold 18, the connection portion of the high pressure EGR passage 15, the turbine 12 of the turbocharger 13, the PM filter 21, the connection portion of the low pressure EGR passage 24, the exhaust A throttle valve 6, a connecting portion of a communication passage 8 described later, and an exhaust purification device 5 are provided. The PM filter 21 has a filter that collects particulate matter in the exhaust and an oxidation catalyst supported on the filter. The exhaust purification device 5 has an NOx storage reduction catalyst.

  The engine 1 of the present embodiment is provided with an EGR system that allows a part of the exhaust from the engine 1 to flow into the intake passage 19. The EGR system of the present embodiment compares a part of the exhaust discharged from the engine 1 with the high pressure EGR device 32 that causes a part of the exhaust discharged from the engine 1 to flow into the intake passage 19 in a relatively high temperature and high pressure state. There are two systems of EGR devices, a low-pressure EGR device 33 that flows into the intake passage 19 in a state of low temperature and low pressure.

  The high-pressure EGR device 32 has a high-pressure EGR passage 15 that connects the exhaust passage 20 upstream of the turbine 13 and the intake passage 19 downstream of the compressor 11. A high pressure EGR valve 14 that adjusts the amount of exhaust gas flowing from the exhaust passage 20 into the intake passage 19 via the high pressure EGR passage 15 is provided in the middle of the high pressure EGR passage 15. The opening degree of the high pressure EGR valve 14 is controlled by an ECU 26 described later.

  The low pressure EGR device 33 has a low pressure EGR passage 24 that communicates the exhaust passage 20 downstream of the turbine 13 and the intake passage 19 upstream of the compressor 11. A low pressure EGR valve 23 that adjusts the amount of exhaust gas flowing from the exhaust passage 20 into the intake passage 19 via the low pressure EGR passage 24 is provided in the middle of the low pressure EGR passage 24. The opening degree of the low pressure EGR valve 23 is controlled by the ECU 26. In this embodiment, the low pressure EGR passage 24 corresponds to the “EGR passage” of the present invention. The low-pressure EGR valve 23 corresponds to the “EGR valve” of the present invention.

  The amount of exhaust gas recirculated to the intake passage 19 by the high pressure EGR device 32 (hereinafter referred to as high pressure EGR gas) and the amount of exhaust gas recirculated to the intake passage 19 by the low pressure EGR device 33 (hereinafter referred to as low pressure EGR gas) respectively. The target value is predetermined according to the operating conditions of the engine 1. FIG. 2 is a diagram schematically showing a switching control map of the high pressure EGR device 32 and the low pressure EGR device 33, which is determined according to the operation region (the rotation speed and the load) of the engine 1.

  As shown in FIG. 2, in the EGR system according to the present embodiment, when the operating conditions of the engine 1 belong to the low load / low rotation operating region, the exhaust gas is recirculated mainly by the high pressure EGR device 32. When belonging to the medium load / medium speed operation region, the exhaust gas is recirculated by using both the high pressure EGR device 32 and the low pressure EGR device 33, and when belonging to the high load / high rotation operation region, Exhaust gas is recirculated by the low pressure EGR device 33. In each EGR control region, the opening degree and the low pressure of the high pressure EGR valve 14 are set so that the amount of exhaust gas recirculated via the high pressure EGR passage 15 and the amount of exhaust gas recirculated via the low pressure EGR passage 24 become target values. The opening degree of the EGR valve 23 is controlled by the ECU 26.

  In addition to the above-described configuration, the low pressure EGR device 33 of the present embodiment cools the exhaust gas flowing through the low pressure EGR passage 24 from the low pressure EGR valve 23 of the low pressure EGR passage 24 toward the upstream side (exhaust passage 20 side). A low-pressure EGR cooler 4 and a collection device 10 that collects foreign substances contained in the low-pressure EGR gas flowing through the low-pressure EGR passage 24 are provided.

The collection device 10 is used when an exhaust system component such as the turbine 12, the PM filter 21, the exhaust passage 20, or the like has broken down and foreign matter such as debris generated from these components flows into the exhaust, This is a mesh-like filter capable of separating and collecting these foreign substances from the exhaust when sputters from pipe welding are mixed in the exhaust. By providing the collection device 10 in the low pressure EGR passage 24, the foreign matter can be prevented from flowing into the intake passage 19 through the low pressure EGR passage 24. The collecting device 10 is not limited to the mesh filter employed in the present embodiment, and a collecting device that separates and collects foreign matter from the exhaust gas by an action such as gravity or centrifugal force can also be used. . In the present embodiment, the collection device 10 corresponds to the “collection device” in the present invention.

  A communication passage 8 that connects the low pressure EGR passage 24 and the exhaust passage 20 is connected to a position of the low pressure EGR passage 24 downstream of the collection device 10 (intake passage 19 side) and upstream of the low pressure EGR cooler 4. Yes. The low pressure EGR device 33 includes a differential pressure sensor 25 that measures a differential pressure between the upstream side and the downstream side of the collection device 10, and an upstream side (exhaust passage 20) of the collection device 10 in the low pressure EGR passage 24. And an exhaust gas temperature sensor 16 for measuring the temperature of the exhaust gas flowing into the collection device 10 is provided.

  An exhaust gas temperature sensor 16 that measures the temperature of the exhaust gas flowing into the collection device 10 is provided on the upstream side (exhaust passage 20 side) of the collection device 10. Further, a differential pressure sensor 25 that measures the differential pressure between the upstream pressure and the downstream pressure of the collection device 10 is provided. In the present embodiment, the exhaust temperature sensor 16 corresponds to the “exhaust temperature acquisition means” in the present invention. The differential pressure sensor 25 corresponds to the “pressure loss acquisition means” in the present invention.

  The ECU 26 is a computer unit that controls the operating state of the engine 1. It includes known components such as a CPU, ROM, RAM, I / O port, communication bus, DAC, and ADC. The ECU 26 is connected to the intake throttle valve 22, the low pressure EGR valve 23, the diesel throttle valve 9, the high pressure EGR valve 14, the fuel injection valve 29, and the exhaust throttle valve 6 described above, and various kinds of devices are connected to the ECU 26. The operation of these devices is controlled by the signal. In addition to the exhaust temperature sensor 16 and the differential pressure sensor 25 described above, the ECU 26 includes an accelerator opening sensor 27 that measures the depression amount of the accelerator pedal 31, a crank angle sensor 28 that measures the rotation angle of the crankshaft, and the like. Sensors are connected, and measured values from these sensors are input to the ECU 26. The ECU 26 outputs a control signal for controlling the operation of various devices based on the operation state of the engine 1 acquired based on data input from these various sensors and the driver's request.

  The collection device 10 is installed for the purpose of collecting foreign matter in the exhaust as described above, but includes not only such foreign matter but also condensed water, HC, soot (particulate matter, PM) in the exhaust. In some cases, exhaust components such as) may also adhere and accumulate, and the trap 10 may be clogged. In that case, the pressure loss between the upstream side and the downstream side of the collection device 10 becomes large, and it may be difficult to appropriately recirculate the low pressure EGR gas to the intake passage 19 by the low pressure EGR device 33. .

  Therefore, in the EGR system of the present embodiment, when the pressure loss between the upstream side and the downstream side of the collection device 10 exceeds a predetermined reference value, the collection device 10 is clogged. When the temperature of the collection device 10 is increased, the exhaust component accumulated in the collection device 10 is removed. The reference value of the pressure loss is determined based on the upper limit value of the pressure loss so that the influence on the fuel consumption is within the allowable range. Or you may make it determine based on the upper limit of the pressure loss which can control low-pressure EGR gas amount appropriately.

In the present embodiment, whether or not the pressure loss between the upstream side and the downstream side of the collection device 10 exceeds the reference value is determined by the differential pressure sensor 25 before and after the differential pressure across the collection device 10. ΔP
Judgment based on. Specifically, when the front-rear differential pressure ΔP of the collection device 10 measured by the differential pressure sensor 25 exceeds a predetermined first reference differential pressure ΔP1, between the upstream side and the downstream side of the collection device 10 It is determined that the pressure loss has exceeded the reference value, and it is determined that the trap 10 is clogged. The first reference differential pressure ΔP1 is determined based on the differential pressure across the collection device 10 when the pressure loss between the upstream side and the downstream side of the collection device 10 is a reference value.

  Whether or not the pressure loss between the upstream side and the downstream side of the collection device 10 exceeds the reference value is determined by the low-pressure EGR gas flow rate on the downstream side of the collection device 10 and the air flow meter 7. It is also possible to carry out based on the pressure loss between the upstream side and the downstream side of the collection device 10 calculated based on the amount of intake air to be performed. Alternatively, the pressure loss may be determined based on the temperature of the exhaust on the downstream side of the collection device 10 and the temperature of the exhaust on the upstream side of the collection device 10. In this case, a temperature sensor is provided in each of the low pressure EGR passage 24 immediately downstream of the collection device 10 and the exhaust passage 20 immediately downstream of the PM filter 21, for example, away from the collection device 10 to some extent. It is preferable to calculate the pressure loss based on the difference. The determination can be made based on the pressure loss calculated using other known pressure loss estimation methods.

  In the present embodiment, the temperature of the collection device 10 is increased by increasing the temperature of the exhaust from the engine 1. The exhaust temperature is increased by increasing the fuel injection amount by the fuel injection valve 29 and performing sub-injection (after injection or post injection) by the fuel injection amount 29. In addition, in the configuration provided with the VVT that makes the opening / closing characteristics of the exhaust valve variable, the opening timing of the exhaust valve is advanced, or the fuel addition valve is provided upstream of the PM filter 21 in the exhaust passage 20. Various known exhaust temperature raising means such as adding fuel into the exhaust from the fuel addition valve, or changing the opening of the variable nozzle vane to the valve opening side in the configuration in which the turbine 12 includes the variable nozzle vane. Can be used. Moreover, you may make it raise the temperature of the collection apparatus 10 by supplying with electricity the said heater as the structure provided with the electric heater which heats the collection apparatus 10 directly. In short, any means that can raise the temperature of the collection device 10 can be used.

  By the way, the temperature of the temperature increase required to remove the exhaust component accumulated in the collection device 10 by raising the temperature of the collection device 10 varies depending on the type of the exhaust component accumulated. For example, it is sufficient to raise the temperature to 100 ° C. or higher for removing condensed water, but the collector is at a temperature of 200 ° C. or higher for removing unburned HC, and 500 ° C. or higher for removing soot. 10 needs to be heated.

  Conventionally, when exhaust components accumulated in the collection device 10 are removed by raising the temperature of the collection device 10, the exhaust components having the highest temperature required for removal are reliably removed from the collection device 10. Therefore, it was necessary to set a target temperature for raising the temperature. Specifically, assuming that the cause of the clogging of the collection device 10 is a soot, the target temperature of the temperature rise is removed so that the clogging of the collection device 10 can be surely eliminated. It was necessary to set the temperature to 500 ° C. or higher.

  Then, when the clogging of the collection device 10 is detected, the temperature of the collection device 10 is always raised to a temperature of 500 ° C. or higher, so that the clogging of the collection device 10 is eliminated. If the cause of the clogging is actually the accumulation of condensed water or HC, it means that the temperature of the collection device 10 has been raised to an unnecessarily high temperature. Therefore, there is a problem that energy consumed for eliminating the clogging of the collection device 10 is wasted and thermal deterioration of the collection device 10 is accelerated.

Here, when it is determined that the collecting device 10 is clogged, the types of exhaust components accumulated in the collecting device 10 are the temperature of the exhaust gas flowing into the collecting device 10 and the collecting device 10. It is related to the amount of soot accumulated in Japan.

  For example, when the temperature of the exhaust gas flowing into the collection device 10 is lower than the temperature at which condensed water in the exhaust gas evaporates (for example, around 100 ° C.), the condensed water mainly adheres and accumulates on the collection device 10. It is thought that. That is, under such a low exhaust temperature condition, it can be determined that the cause of the clogging of the collection device 10 is mainly condensed water.

  When the temperature of the exhaust gas flowing into the collection device 10 is higher than the temperature at which condensed water in the exhaust gas evaporates but lower than the temperature at which HC evaporates (for example, around 200 ° C.), the collection device 10 mainly contains HC. It is thought that is deposited and deposited. That is, under such an intermediate exhaust temperature condition, it can be determined that the cause of the clogging of the collection device 10 is mainly HC.

  When the temperature of the exhaust gas flowing into the collection device 10 is higher than the temperature at which HC in the exhaust gas evaporates but lower than the temperature at which the soot oxidation reaction proceeds (for example, around 500 ° C.), the collection device 10 It is thought that the cocoons are mainly accumulated. That is, it can be determined that the cause of the clogging of the collection device 10 is mainly soot under such medium and high temperature exhaust temperature conditions.

  However, in such a medium-high temperature exhaust temperature condition, when exhaust at a certain temperature (for example, around 400 ° C.) continuously flows into the collection device 10, The amount of soot deposits is not expected to increase monotonously. That is, it is determined that the cause of the clogging of the collection device 10 is not soot based on the engine operation history that the medium and high temperature exhaust temperature conditions lower than the temperature at which soot oxidation reaction easily proceeds continue for a certain period or more. You can also. In addition, the travel time since the temperature of the collecting device 10 was raised last time to remove the exhaust component, the integrated value of the fuel injection amount, the operation history under the operating condition such as acceleration transient with a large amount of soot discharge, Based on the control history of the low pressure EGR gas amount, etc., the amount of soot accumulated in the collection device 10 is estimated, and based on the estimated amount of soot accumulation, the main cause of causing clogging in the collection device 10 The type of exhaust component can be specified.

  Further, when it is determined that the trap 10 is clogged when the temperature of the exhaust gas flowing into the trap 10 is higher than the temperature at which the soot oxidation reaction easily proceeds, The cause of clogging is thought to be other than exhaust components such as condensed water, HC, and soot. That is, under such a high exhaust temperature condition, for example, it is determined that the cause of the clogging of the collecting device 10 is the catalyst debris of the PM filter 21 or the accumulation of foreign matters such as spatter of the pipe welding of the exhaust passage 20. be able to.

  In the EGR system of the present embodiment, on the basis of such a relationship, deposition is performed on the collection device 10 according to the temperature of the exhaust gas flowing into the collection device 10 and the amount of soot accumulated in the collection device 10. The target temperature for raising the temperature of the collection device 10 is set to remove the exhaust components. That is, in the EGR system of the present embodiment, when it is determined that the trap 10 is clogged, the temperature of the exhaust gas flowing into the trap 10, the amount of soot accumulated in the trap 10, Accordingly, the type of the exhaust component accumulated in the collection device 10 is specified, and the minimum necessary temperature for removing the exhaust component by raising the temperature of the collection device 10 is set as the target temperature. A temperature increase of 10 was performed.

Specifically, the temperature of the exhaust gas flowing into the collection device 10 is acquired by the exhaust temperature sensor 16, and the soot accumulation amount in the collection device 10 is acquired by estimation from the operation history of the engine 1,
(1) When the temperature of the exhaust is lower than a temperature T1 (for example, 100 ° C.) at which the condensation water is likely to evaporate and the amount of soot accumulated is equal to or less than a predetermined amount, the exhaust causing the clogging of the trap 10 It is determined that the component is mainly condensed water, and the target temperature for raising the temperature is the minimum necessary to evaporate the condensed water as a necessary and sufficient temperature for removing the condensed water by raising the temperature of the collection device 10. Temperature (for example, 100 ° C.).
(2) When the temperature of the exhaust gas is higher than the temperature T1 at which the evaporation of the condensed water is likely to proceed, lower than the temperature T2 (for example, 200 ° C.) at which the evaporation of the HC is likely to proceed, and the amount of soot is less than the predetermined amount, It is determined that the exhaust component causing the clogging of the collector 10 is mainly HC, and the target temperature of the temperature rise is set to HC as a temperature sufficient to remove HC by the temperature rise of the collector 10. The temperature is set to the minimum necessary temperature that can be evaporated (for example, 200 ° C.).
(3) When the temperature of the exhaust gas is higher than the temperature T2 at which HC evaporation is likely to proceed and is lower than a temperature T3 (for example, 400 ° C.) at which soot accumulation is suppressed when the temperature continues for a certain period of time, If there is no operation history in which the operating state where the temperature is T3 or higher but the temperature is T3 or higher continues for a certain period or more, it is determined that the exhaust component causing the clogging of the trap 10 is mainly soot. The target temperature for raising the temperature is set to a minimum necessary temperature (for example, 500 ° C.) that can oxidize the soot as a necessary and sufficient temperature for removing the soot by raising the temperature of the collection device 10.
(4) When the exhaust temperature is T3 or more and there is an operation history in which the operation state under the exhaust temperature condition continues for a certain period or more, or the temperature T4 (for example, 600 ° C.) at which the exhaust temperature is likely to proceed with soot oxidation ) If it is above, it is determined that the cause of the clogging of the collection device 10 is due to the accumulation of foreign matters other than the exhaust components, and the temperature of the collection device 10 is not increased.

  Thus, in the EGR system of the present embodiment, when the clogging of the collection device 10 is detected, the exhaust component is raised in temperature of the collection device 10 according to the type of the exhaust component causing the clogging. As the target temperature is set as the minimum temperature required for removal by the above, the temperature of the collection device 10 is increased, so that it is possible to suppress the temperature increase of the collection device 10 to an unnecessarily high temperature, It becomes possible to suppress energy consumption related to elimination of the clogging of the collection device 10.

  As described above, in the EGR system of the present embodiment, when it is determined that the collecting device 10 is clogged, the temperature of the collecting device 10 is increased and deposited on the collecting device 10. When the exhaust component is removed from the collection device 10, the exhaust component removed from the collection device 10 flows out to the low-pressure EGR passage 24 on the downstream side of the collection device 10. When the low-pressure EGR gas containing this high-concentration exhaust component flows through the low-pressure EGR passage 24 and flows into the intake passage 19 and is sucked into the compressor 11 and the engine 1, malfunction of the compressor 11 and combustion fluctuations of the engine 1 are caused. There is a risk of inviting.

  Therefore, in the EGR system of the present embodiment, when the temperature of the collecting device 10 is raised to eliminate the clogging of the collecting device 10, the low-pressure EGR valve 23 is closed regardless of the control map shown in FIG. The exhaust gas recirculation by the low pressure EGR device 33 is stopped. As a result, the low-pressure EGR gas containing the high-concentration exhaust component flowing out from the collection device 10 flows into the exhaust passage 20 via the communication passage 8 and does not flow into the intake passage 19. Therefore, it is possible to avoid problems such as malfunction of the compressor 11 and combustion fluctuations of the engine 1.

In this case, in order to avoid the EGR rate from deviating from the target value by stopping the exhaust gas recirculation by the low pressure EGR device 33, the exhaust gas recirculation amount by the high pressure EGR device 32 is corrected to be increased. Also good. Further, in the operation region in which the exhaust gas is recirculated using the low pressure EGR device 33 in the EGR control map of FIG. 2, when the temperature of the collection device 10 is raised, the exhaust gas by the low pressure EGR device 33 is reduced. Instead of completely stopping the recirculation, the opening degree is closer to the closing side than the opening degree of the low pressure EGR valve 23 during the normal operation in the operation region (that is, when the temperature of the collecting device 10 is not raised). The low-pressure EGR valve 23 may be opened so that the exhaust gas is recirculated by the low-pressure EGR device 33 while reducing the flow rate of the low-pressure EGR gas compared to the normal operation. In this case, the exhaust component flowing out from the collecting device 10 during the temperature rise flows into the intake passage 19 together with the low pressure EGR gas. However, since the flow rate of the low pressure EGR gas is reduced, malfunction of the compressor 11 Combustion fluctuations in the engine 1 can be suppressed.

  A specific execution procedure of the clogging removal processing of the collection device 10 in the EGR system of the present embodiment described above will be described with reference to FIG. FIG. 3 is a flowchart showing a routine for performing the clogging removal process of the collection device 10. This routine is periodically executed by the ECU 26 during operation of the engine 1 at predetermined intervals.

  In step S <b> 101, the ECU 26 acquires the operating state of the engine 1. The data acquired in this step is used as operation history data when estimating the amount of soot accumulation in the collection device 10 described above, and for example, the exhaust gas flowing into the collection device 10 such as the exhaust temperature sensor 16. It can also be used to estimate the temperature of the exhaust gas flowing into the collection device 10 in a configuration that does not include a device for measuring temperature.

  In step S <b> 102, the ECU 26 acquires the differential pressure ΔP between the upstream side and the downstream side of the collection device 10 based on the measurement value by the differential pressure sensor 25.

  In step S103, the ECU 26 determines whether or not the differential pressure ΔP acquired in step S102 exceeds the first reference differential pressure ΔP1. When the differential pressure ΔP exceeds the first reference differential pressure ΔP1 (ΔP> ΔP1, step S103: Yes), the ECU 26 proceeds to step S104. When the differential pressure ΔP is equal to or less than the first reference differential pressure ΔP1 (ΔP ≦ ΔP1, Step S103: No), the ECU 26 proceeds to Step S111 and performs normal control. The normal control means that the recirculation of the exhaust gas is controlled by the high pressure EGR device 32 and the low pressure EGR device 33 according to the control map shown in FIG.

  In step S104, the ECU 26 closes the low pressure EGR valve 23 and stops the exhaust gas recirculation by the low pressure EGR device 33. This prevents the exhaust component flowing out from the collection device 10 from flowing into the intake passage 19 when the temperature of the collection device 10 is raised in the subsequent processing.

  In step S <b> 105, the ECU 26 acquires the temperature of the exhaust gas flowing into the collection device 10 based on the measurement value by the exhaust temperature sensor 16 and calculates the amount of soot accumulated in the collection device 10.

  In step S <b> 106, the ECU 26 determines the type of the exhaust component that is causing clogging in the collection device 10 based on the above-described determination criteria based on the exhaust temperature and the soot accumulation amount acquired in step S <b> 105.

  When it is determined in step S106 that the exhaust component accumulated in the collection device 10 is mainly condensed water, the ECU 26 proceeds to step S107, and the minimum temperature (here, 100) at which the condensed water can be removed. The target temperature is set to (Centigrade) and the temperature of the collection device 10 is increased.

  If it is determined in step S106 that the exhaust component accumulated in the collection device 10 is mainly HC, the ECU 26 proceeds to step S108, and the minimum necessary temperature at which HC can be removed (here, 200 ° C.). Set the target temperature to raise the temperature of the collection device 10.

  In step S106, if it is determined that the exhaust component accumulated in the collection device 10 is mainly soot, the ECU 26 proceeds to step S109, and the minimum temperature (here, 500 ° C.) at which soot can be removed. Set the target temperature to raise the temperature of the collection device 10.

  In step S106, if it is determined that the cause of the clogging of the collection device 10 is not the accumulation of exhaust components but the accumulation of foreign matter, the ECU 26 proceeds to step S110 and performs MIL lighting to warn of engine abnormality. .

  By performing the clogging removal process of the collection device 10 according to the above routine, the clogging of the collection device 10 can be suitably removed while suppressing an increase in fuel consumption and thermal deterioration of the collection device. In this embodiment, the ECU 26 that calculates the soot accumulation amount in the collection device 10 in step S105 corresponds to the “soot accumulation amount acquisition means” in the present invention. In addition, when an affirmative determination is made in step S103, the ECU 26 that raises the temperature of the collection device 10 in any one of steps S107 to S109 corresponds to the “removing means” in the present invention. Further, the ECU 26 that selects any one of the temperature increasing processes in steps S107 to S109 according to the determination result in step S106 corresponds to the “setting unit” in the present invention. If the temperature raising process of the collection device 10 is not performed, EGR control according to the control map of FIG. 2 is performed in step S111, and if the temperature raising process of the collection device 10 is performed, in step S104. The ECU 26 that performs the process of closing the low pressure EGR valve 23 corresponds to the “control means” in the present invention.

  Deposits that can be removed from the collection device 10 by raising the temperature of the collection device 10 are exhaust components such as the condensed water, HC, and soot described above. If the cause of the clogging in the collection device 10 is not the accumulation of these exhaust components but the accumulation of foreign matters such as broken pieces of exhaust system parts, the temperature of the collection device 10 is increased. It is difficult to eliminate clogging that has occurred in the collection device 10. Therefore, in such a case, the pressure loss between the upstream side and the downstream side of the collection device 10 may not be sufficiently reduced even immediately after the temperature of the collection device 10 is increased.

  Therefore, in the EGR system of the present embodiment, immediately after performing the clogging removal processing of the collection device 10 as described above, the differential pressure between the upstream side and the downstream side of the collection device 10 is acquired again, When the acquired differential pressure exceeds the predetermined second reference differential pressure ΔP2, it is determined that the cause of the clogging of the collection device 10 is the accumulation of foreign matters. Here, it is estimated that the second reference differential pressure ΔP2 occurs before and after the collection device 10 immediately after the temperature increase process of the collection device 10 when the deposit in the collection device 10 is an exhaust component. Determine based on the differential pressure. Even if the cause of clogging of the collection device 10 is mainly due to the accumulation of foreign matter, it is considered that some exhaust components are also accumulated in the collection device 10, so that the temperature of the collection device 10 is increased. As a result, the pressure loss is reduced by an amount corresponding to the amount of exhaust component accumulated. Therefore, in the present embodiment, the second reference differential pressure ΔP2 is set to a value smaller than the first reference differential pressure ΔP1. More simply, the second reference differential pressure ΔP2 and the first reference differential pressure ΔP1 may be equalized.

  When such a determination is made, it is presumed that foreign matter generated due to some failure that has occurred in the exhaust system parts reaches the collection device 10 and accumulates. In particular, in the case of the EGR system of the present embodiment, since the low pressure EGR passage 24 is connected to the exhaust passage 20 downstream of the PM filter 21, this foreign matter is a catalyst or filter debris generated by the damage of the PM filter 21. There is a high possibility.

  Therefore, in the EGR system of this embodiment, when it is determined that the cause of the clogging occurring in the collection device 10 is the accumulation of foreign matter, the MIL is turned on to notify the driver of catalyst failure or engine abnormality. At the same time, the accelerator opening limit A is implemented for the operation control of the engine 1. The accelerator opening limit A is an operation limit intended for evacuation travel. As a result, the driver can take immediate measures against catalyst damage or engine abnormality.

  The collection device 10 of this embodiment is a mesh filter as described above. Therefore, there is a certain pressure loss even in a new state where no foreign matter or exhaust components are accumulated in the collection device 10. However, when the collection device 10 is damaged, the pressure loss may be smaller than that of the collection device 10 in a normal state. For example, when the filter is broken and a hole is formed in a part of the mesh, the exhaust gas passes more easily than the filter in the normal state, and the pressure loss is reduced.

  Therefore, in the EGR system of the present embodiment, the differential pressure between the upstream side and the downstream side of the collection device 10 acquired by the differential pressure sensor 25 is applied to the upstream side and the downstream side of the new collection device 10. When it is smaller than the third reference differential pressure ΔP3 determined based on the generated differential pressure, it is determined that the collecting device 10 is damaged.

  When such a determination is made, foreign matter in the exhaust gas cannot be suitably collected in the collection device 10, and therefore, when the exhaust gas is recirculated by the low pressure EGR device 33, the foreign matter becomes low pressure EGR gas. At the same time, the air may be guided to the intake passage via the low pressure EGR passage 24 and flow into the compressor 11.

  Therefore, in the EGR system of the present embodiment, when it is determined that the collecting device 10 is damaged, the MIL is turned on to notify the driver of the collecting device abnormality, and the low pressure is applied in all operation regions. The exhaust gas recirculation by the EGR device 33 is stopped, and the exhaust gas recirculation is performed by feedback control only by the high pressure EGR device 32. Further, the accelerator opening limit B is implemented for the operation control of the engine 1. The accelerator opening limit B is an operation restriction that restricts the operation control to a control that is possible under the condition that the EGR control is performed only by the high-pressure EGR device 32. The operation limit may be set to be milder than the accelerator opening limit A executed when the catalyst is damaged or the engine is abnormal.

  A specific execution procedure in the case of performing the catalyst abnormality determination and the collection device abnormality determination described above in the clogging removal processing of the collection device of the EGR system of the present embodiment will be described based on FIGS. 4 and 5. 4 and 5 are flowcharts showing a routine for performing catalyst abnormality determination and collection device abnormality determination in the clogging removal processing of the collection device 10. This routine is periodically executed by the ECU 26 during operation of the engine 1 at predetermined intervals.

  In step S201, the ECU 26 acquires the operating state of the engine 1. The data acquired in this step is used as operation history data when estimating the amount of soot accumulation in the collection device 10 described above, and for example, the exhaust gas flowing into the collection device 10 such as the exhaust temperature sensor 16. It can also be used to estimate the temperature of the exhaust gas flowing into the collection device 10 in a configuration that does not include a device for measuring temperature.

  In step S <b> 202, the ECU 26 acquires the differential pressure ΔP between the upstream side and the downstream side of the collection device 10 based on the measurement value by the differential pressure sensor 25.

  In step S203, the ECU 26 determines whether or not the differential pressure ΔP acquired in step S202 exceeds the first reference differential pressure ΔP1. When the differential pressure ΔP exceeds the first reference differential pressure ΔP1 (ΔP> ΔP1, step S203: Yes), the ECU 26 proceeds to step S204. When the differential pressure ΔP is equal to or lower than the first reference differential pressure ΔP1 (ΔP ≦ ΔP1, Step S203: No), the ECU 26 proceeds to Step S211 in FIG.

In step S204, the ECU 26 closes the low pressure EGR valve 23 and stops the exhaust gas recirculation by the low pressure EGR device 33. This prevents the exhaust component flowing out from the collection device 10 from flowing into the intake passage 19 when the temperature of the collection device 10 is raised in the subsequent processing.

  In step S205, the ECU 26 performs a clogging removal process for the collection device 10. Specifically, the processing from step S105 to step S110 in FIG. 3 is executed.

  In step S <b> 206, the ECU 26 acquires the differential pressure ΔP between the upstream side and the downstream side of the collection device 10 based on the measurement value by the differential pressure sensor 25. By this process, the differential pressure of the collection device 10 immediately after the temperature is raised to remove the clogging of the collection device 10 is acquired.

  In step S207, the ECU 26 determines whether or not the differential pressure ΔP acquired in step S206 exceeds the second reference differential pressure ΔP2. When the differential pressure ΔP exceeds the second reference differential pressure ΔP2 (ΔP> ΔP2, step S207: Yes), the ECU 26 proceeds to step S208, performs MIL lighting to warn of catalyst abnormality or engine abnormality, and in subsequent step S209. An accelerator opening limit A is imposed on the operation control of the engine 1. On the other hand, when the differential pressure ΔP is equal to or lower than the second reference differential pressure ΔP2 (ΔP ≦ ΔP2, step S207: No), the process proceeds to step S210 and normal control is performed. The normal control means that no control restriction is imposed on the operation control of the engine 1 and that the exhaust gas recirculation is controlled by the high pressure EGR device 32 and the low pressure EGR device 33 according to FIG.

  In step S211, the ECU 26 determines whether or not the differential pressure ΔP acquired in step S202 is smaller than the third reference differential pressure ΔP3. When the differential pressure ΔP is smaller than the third reference differential pressure ΔP3 (ΔP <ΔP3, Step S211: Yes), the ECU 26 proceeds to Step S212, performs MIL lighting that warns of the collection device abnormality, and continues to the low pressure EGR valve in Step S213. 23 is fully closed, and the exhaust gas recirculation by the low pressure EGR device 33 is stopped. Further, in step S214, the control of the high pressure EGR device 32 is controlled according to the EGR control map of FIG. 2 so that the exhaust gas recirculation control of the engine 1 is performed only by the high pressure EGR device 32, and the target EGR rate is changed to the high pressure EGR device. Switch to feedback control for realizing only 32. In step S215, an accelerator opening limit B is imposed on the operation control of the engine 1.

  On the other hand, when the differential pressure ΔP is greater than or equal to the third reference differential pressure ΔP3 (ΔP ≧ ΔP3, step S211: No), the process proceeds to step S216 and normal control is performed. The normal control means that no control restriction is imposed on the operation control of the engine 1 and that the exhaust gas recirculation is controlled by the high pressure EGR device 32 and the low pressure EGR device 33 according to FIG.

  In the clogging removal process in step S205, if it is determined that the cause of clogging in the collection device 10 is the accumulation of foreign matter (the result of the determination in step S106 in FIG. 3 is advanced to step S110). In this case, the processing of step S206 and step S207 may be skipped and the process may proceed to step S208.

  By performing the catalyst removal determination and the collection device abnormality determination together with the clogging removal processing of the collection device 10 according to the above routine, the catalyst abnormality and the collection device abnormality can be detected at an early stage.

  In this embodiment, the ECU 26 that determines that the catalyst is abnormal or the engine is abnormal when an affirmative determination is made in step S207 corresponds to the “engine abnormality determining means” in the present invention. In addition, when the determination in step S211 is affirmative, the ECU 26 that determines that the collection device is abnormal corresponds to the “collection device abnormality determination unit” in the present invention.

The above-described embodiment is an example for explaining the present invention, and various modifications can be made to the above-described embodiment without departing from the gist of the present invention. For example, in the above-described embodiment, the example in which the present invention is applied to the EGR system including the two systems of the EGR devices, the low-pressure EGR device 33 and the high-pressure EGR device 32 has been described. The invention can also be applied. However, in that case, if the exhaust gas recirculation by the low pressure EGR device 33 is stopped when the collection device abnormality is detected, it is necessary to impose a control restriction on the condition that the exhaust gas is not recirculated in the operation control of the engine 1. is there.

  Further, the communication path 8 in the above embodiment is not an essential component for the present invention. When the temperature of the collecting device 10 is increased in order to remove the clogging of the collecting device 10 in a configuration not provided with the communication passage 8, the low pressure EGR valve 23 is not fully closed but is closed more than during normal operation. You may make it open to the opening degree of a side. Thereby, the low-pressure EGR gas containing the high-concentration exhaust component flowing out from the collection device 10 flows into the intake passage 19, but the opening degree of the low-pressure EGR valve 23 is narrowed compared with that during normal operation. The low pressure EGR gas containing the exhaust component having a high concentration can be prevented from flowing into the compressor 11 and the engine 1 at a stretch, and the malfunction of the compressor 11 and the combustion fluctuation of the engine 1 can be suppressed.

  In the above embodiment, the example in which the temperature of the exhaust gas flowing into the collection device 10 is acquired by the exhaust temperature sensor 25 has been described. However, the exhaust temperature sensor 25 is not provided, and the collection device is estimated by estimation based on the operating conditions of the engine 1. The temperature of the exhaust gas flowing into the engine 10 may be acquired. Further, the temperature of the exhaust gas flowing into the collection device 10 may be acquired by estimation based on the cooling water temperature or the intake air temperature of the engine 1.

  Moreover, in the said Example, condensed water, HC, and soot are discriminate | determined as an exhaust component which has produced the clogging of the collection apparatus 10, and the minimum temperature which can remove each exhaust component is each 100 degreeC. The example of setting the target temperature for temperature rise as 200 ° C. and 500 ° C. has been described. However, it is also possible to determine the deposited material in consideration of exhaust components other than these, and in the determination of the deposited material, The temperature may be simplified such that HC is not discriminated, HC and soot are not discriminated, and the temperature (100 ° C.) used in this embodiment may be used as long as it can remove condensed water, HC, and soot. , 200 ° C., 500 ° C.) may be set as the target temperature. Further, when it is estimated that, for example, condensed water and HC are mixed and deposited in the collection device 10, the temperature necessary for removal of the exhaust components mixed and deposited is The target temperature may be set according to the higher exhaust component.

It is a figure which shows schematic structure of the engine in its Example, its intake system, and an exhaust system. It is a figure which shows an example of the EGR control map for controlling the high voltage | pressure EGR apparatus and low voltage | pressure EGR apparatus in an Example. It is a flowchart showing the clogging removal process routine of the collection apparatus in an Example. It is a flowchart showing the clogging removal process routine and catalyst abnormality determination routine of a collection apparatus in an Example. It is a flowchart showing the collection apparatus abnormality determination routine in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intercooler 3 Air cleaner 4 Low pressure EGR cooler 6 Exhaust throttle valve 7 Air flow meter 8 Communication passage 9 Diesel throttle valve 10 Collection device 11 Compressor 12 Turbine 13 Turbocharger 14 High pressure EGR passage 15 High pressure EGR passage 16 Exhaust temperature sensor 17 Intake Manifold 18 Exhaust manifold 19 Intake passage 20 Exhaust passage 21 DPF
22 Intake throttle valve 23 Low pressure EGR valve 24 Low pressure EGR passage 25 Differential pressure sensor 26 ECU
27 Accelerator opening sensor 28 Rotational speed sensor 29 Fuel injection valve 30 Cylinder 31 Accelerator pedal 32 High pressure EGR device 33 Low pressure EGR device

Claims (5)

An EGR passage that communicates an exhaust passage and an intake passage of the internal combustion engine, and causes a portion of the exhaust from the internal combustion engine to flow into the intake passage;
A collection device that is provided in the EGR passage and collects foreign substances contained in the EGR gas;
Exhaust temperature acquisition means for acquiring the temperature of the exhaust gas flowing into the collection device;
Soot accumulation amount acquisition means for acquiring the accumulation amount of soot in the collection device;
Pressure loss acquisition means for acquiring pressure loss on the upstream side and downstream side of the collection device;
Removal that removes exhaust components accumulated in the collecting device by raising the temperature of the collecting device when it is detected that the pressure loss obtained by the pressure loss obtaining means exceeds a predetermined reference value Means,
A setting for setting the target temperature when the removal means raises the temperature of the collection device according to the temperature acquired by the exhaust temperature acquisition means and the accumulation amount acquired by the soot accumulation amount acquisition means Means,
An EGR system for an internal combustion engine comprising: In claim 1,
An EGR valve that is provided on the downstream side of the collection device in the EGR passage and adjusts the amount of EGR gas flowing from the EGR passage to the intake passage;
Control means for controlling the opening of the EGR valve;
Further comprising
The control means closes the EGR valve more when the temperature of the collecting device is increased by the removing means than when the temperature of the collecting device is not increased by the removing means. An EGR system for an internal combustion engine that opens at a side opening. In claim 1,
A communication passage communicating the downstream side of the collection device in the EGR passage and the exhaust passage;
An EGR valve that is provided on the downstream side of the connection portion of the communication passage in the EGR passage, and adjusts the amount of EGR gas flowing from the EGR passage to the intake passage;
Control means for controlling the opening of the EGR valve;
Further comprising
The EGR system for an internal combustion engine, wherein the control means closes the EGR valve when the temperature of the collecting device is raised by the removing means. In any one of Claims 1-3,
If it is detected that the pressure loss acquired by the pressure loss acquisition means exceeds a predetermined second reference value immediately after the temperature of the collection device is raised by the removal means, the internal combustion engine An EGR system for an internal combustion engine, further comprising engine abnormality determination means for determining that an abnormality has occurred in the engine. In any one of Claims 1-4,
When it is detected that the pressure loss acquired by the pressure loss acquisition unit is smaller than a predetermined third reference value, the apparatus further includes a collection device abnormality determination unit that determines that an abnormality has occurred in the collection device. An EGR system for an internal combustion engine.

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