JP2019194460A - Internal combustion engine control apparatus, internal combustion engine, and internal combustion engine control method - Google Patents

Abstract

To provide an internal combustion engine control apparatus, an internal combustion engine, and an internal combustion engine control method, which are capable of preventing PM from entering an EGR mechanism and an intake system.SOLUTION: An internal combustion engine control apparatus includes: a capturing efficiency determination part that is used in an internal combustion engine that has a capturing filter, disposed in an exhaust channel of the engine, for capturing particulate materials contained in an exhaust gas and a first EGR channel for refluxing an exhaust gas flowing downstream of the capturing filter to upstream of a compressor of a turbo charger and that determines whether a capturing efficiency of the capturing filter is equal to or better than a predetermined value; and an EGR control part for performing control to close the first EGR channel in a case where the capturing efficiency determination part determines that the capturing efficiency of the capturing filter is less than the predetermined value.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an internal combustion engine control apparatus, an internal combustion engine, and an internal combustion engine control method.

  Patent Document 1 discloses an internal combustion engine provided with a turbocharger and an exhaust gas recirculation (EGR) mechanism.

  In this document, exhaust gas from a diesel engine is exhausted to the outside through an exhaust passage after driving a turbine of a turbocharger.

  A diesel particulate filter (hereinafter referred to as Diesel Particle Filter: DPF) that collects particulate matter (hereinafter referred to as PM) in the exhaust gas is disposed in the exhaust passage. If the DPF continues to collect PM, problems such as clogging of the DPF, an increase in back pressure, and a decrease in fuel consumption occur. For this reason, when PM is collected to some extent, the exhaust gas temperature is raised, the PM is forcibly burned and removed, and the DPF is regenerated.

  The EGR mechanism also recirculates the exhaust gas from the DPF to the upstream side of the turbocharger compressor.

JP 2010-223040 A

  By the way, for example, when PM combustion progresses due to regeneration of the DPF, blow-off in which the PM collection efficiency is reduced occurs, and PM flows out downstream of the DPF. Under this circumstance, when the EGR mechanism is used, PM enters the EGR mechanism and the intake system. As a result, the EGR mechanism and the intake system may become dirty. Similar problems can occur with gasoline engines.

  An object of the present disclosure is to provide a control device for an internal combustion engine, an internal combustion engine, and a control method for the internal combustion engine that can prevent PM from entering the EGR mechanism and the intake system.

An internal combustion engine control apparatus according to an aspect of the present disclosure includes:
A collection filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas;
A first EGR passage that recirculates exhaust gas flowing downstream of the collection filter to the upstream side of the compressor of the turbocharger, and used in an internal combustion engine.
A collection efficiency determination unit for determining whether the collection efficiency of the collection filter is equal to or greater than a predetermined value;
An EGR control unit that performs control to close the first EGR passage when the collection efficiency determination unit determines that the collection efficiency of the collection filter is less than a predetermined value;
Is provided.

  An internal combustion engine according to an aspect of the present disclosure includes the control device.

An internal combustion engine control method according to an aspect of the present disclosure includes:
A collection filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas; an EGR passage for returning the exhaust gas flowing downstream of the collection filter to the upstream side of the compressor of the turbocharger; An internal combustion engine control method comprising:
Determining whether the collection efficiency of the collection filter is a predetermined value or more,
When it is determined that the collection efficiency of the collection filter is less than a predetermined value, control is performed to close the EGR passage.

  According to the present disclosure, it is possible to prevent PM from entering the EGR mechanism and the intake system.

Schematic configuration diagram of a diesel engine according to an embodiment of the present disclosure A graph representing the temperature of the exhaust gas according to the present embodiment The graph showing the collection efficiency of PM by DPF concerning this embodiment Block diagram of a control device for an internal combustion engine The flowchart which shows an example of the low voltage | pressure EGR control which concerns on this Embodiment. Timing chart showing an example of EGR control according to a modification The flowchart which shows an example of EGR control concerning a modification

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  In the present embodiment, a case where the present invention is applied to a diesel engine (internal combustion engine) mounted on an automobile will be described.

  First, a schematic structure of a diesel engine (hereinafter simply referred to as an engine) according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of an engine 1 according to the embodiment.

  As shown in FIG. 1, the engine 1 corresponds to an intake manifold 11, an exhaust manifold 12, a turbocharger 13, an air cleaner 17, an intercooler 18, an exhaust pipe 20, and a low pressure EGR passage 21L (the “first EGR passage” of the present invention). ), High pressure EGR passage 21H (corresponding to “second EGR passage” of the present invention), exhaust passage 30, PM sensor 35, and ECU 100 (corresponding to “control device” of the present invention).

  The intake manifold 11 is connected to an intercooler 18 via a downstream intake pipe 16b.

  The intercooler 18 is connected to the compressor 14 of the turbocharger 13 through an intermediate intake pipe 16c. The compressor 14 is connected to an air cleaner 17 via an upstream side intake pipe 16a.

  The air from the air cleaner 17 is sucked into the compressor 14 through the upstream side intake pipe 16a and pressurized, cooled through the intercooler 18, and supplied from the intake manifold 11 to the engine 1 through the downstream side intake pipe 16b. Is done.

  The exhaust manifold 12 is connected to the turbine 15 of the turbocharger 13.

  The turbine 15 is connected to the exhaust pipe 20 via the exhaust passage 30. Exhaust gas from the engine 1 is exhausted to the exhaust pipe 20 through the exhaust passage 30 after driving the turbine 15.

  The low pressure EGR passage 21L recirculates exhaust gas from the DPF 32 (described later) to the upstream side of the compressor 14. An EGR cooler 22L and an EGR valve 23L are provided in the low pressure EGR passage 21L. By returning a part of the exhaust gas to the intake air through the low pressure EGR passage 21L, the amount of oxygen entering the engine 1 can be suppressed, and the NOx emission amount can be reduced by lowering the combustion temperature. The path from the compressor 14 to the intermediate intake pipe 16c, the intercooler 18, the downstream intake pipe 16b, the intake manifold 11, the intake valve (not shown), and the inside of the engine 1 may be referred to as an “intake system”.

  The high pressure EGR passage 21 </ b> H recirculates exhaust gas from the upstream side of the turbine 15 to the upstream side of the intake manifold 11 and downstream of the intercooler 18. The high pressure EGR passage 21H is provided with an EGR cooler 22H and an EGR valve 23H. Note that the high-pressure EGR passage 21 </ b> H may recirculate the exhaust gas upstream of the intake manifold 11 and downstream of the compressor 14.

  The exhaust passage 30 is provided with an oxidation catalyst (Diesel Oxidation Catalyst: DOC) 31 and a DPF 32.

  The DOC 31 oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas.

  The DPF 32 is a filter that collects PM in the exhaust gas. In the forced regeneration of the DPF 32, the temperature of the exhaust gas is raised by performing fuel injection after the combustion process, and the collected PM is combined (combusted) with oxygen at a high temperature. Further, the DOC 31 oxidizes the fuel injected after the combustion process when the DPF 32 is regenerated, thereby raising the temperature of the exhaust gas and promoting the combustion of PM.

  FIG. 2 is a diagram illustrating an example of the temperature of the exhaust gas when the DPF 32 is regenerated. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the exhaust gas temperature. As shown in FIG. 2, the temperature of the exhaust gas rises from the regeneration start time ta of the DPF 32, and reaches the PM combustion temperature after a predetermined time has elapsed.

  FIG. 3 is a diagram illustrating an example of the PM collection efficiency when the DPF 32 is regenerated. In FIG. 3, the horizontal axis represents time, and the vertical axis represents PM collection efficiency. The PM collection efficiency may be simply referred to as “collection efficiency”. As shown in FIG. 3, when the combustion of PM proceeds due to regeneration of the DPF 32, blow-off that lowers the collection efficiency occurs. The collection efficiency continues to decrease until the end of regeneration tc.

  Due to the occurrence of blow-off, PM passes through the DPF 32 and flows downstream. Under this situation, when the low pressure EGR passage 21L is opened, exhaust gas containing PM enters the intake system from the low pressure EGR passage 21L. As a result, the low pressure EGR passage 21L and the intake system may become dirty.

  Therefore, in the present embodiment, as shown in FIG. 1, the PM sensor 35 is provided on the downstream side of the DPF 32 in the exhaust passage 30. The PM sensor 35 detects in real time the PM that passes through the DPF 32 and flows downstream. Specifically, the PM sensor 35 outputs a detection value corresponding to the amount of PM deposited on the element. The PM sensor 35 may burn and remove the PM deposited on the element by supplying a high-voltage current to the element when the amount of PM deposition exceeds a predetermined value.

  Next, the ECU 100 will be described with reference to FIG. The ECU 100 includes a microcomputer (not shown) composed of a CPU, ROM, RAM, and the like and an input / output circuit. A PM sensor 35 is connected to the input circuit of the ECU 100. An EGR valve 23L and an EGR valve 23H are connected to the output circuit of the ECU 100.

  FIG. 4 is a block diagram of the control device for the internal combustion engine. The ECU 100 includes a storage unit 110, a collection efficiency calculation unit 120, a collection efficiency determination unit 130, and an EGR control unit 140, as shown in FIG.

  The storage unit 110 stores a PM emission amount map indicating a predetermined relationship between the operating state of the engine 1 and the PM emission amount. The operating state of the engine 1 includes, for example, the engine speed and the fuel injection amount. The PM emission amount map is created based on, for example, simulations or experimental results.

  The collection efficiency calculation unit 120 calculates the PM emission amount based on the operating state of the engine 1 with reference to the above-described PM emission amount map. Note that the PM discharge amount corresponds to the PM inflow amount in the exhaust gas flowing into the DPF 32. The collection efficiency calculation unit 120 calculates the collection efficiency in real time based on the calculated PM emission amount and the detection value detected by the PM sensor 35. The collection efficiency (%) is a value obtained by dividing the PM outflow amount in the exhaust gas flowing out from the DPF 32 by the PM inflow amount (PM discharge amount) in the exhaust gas flowing into the DPF 32 from 1. Indicated by subtracted number.

  The collection efficiency determination unit 130 determines whether the collection efficiency calculated by the collection efficiency calculation unit 120 is equal to or greater than a specified value ηa (see FIG. 3). Here, the prescribed value ηa refers to the minimum allowable collection efficiency.

  The EGR control unit 140 controls the opening degree of the EGR valve 23L so as to adjust the recirculation amount in the low pressure EGR passage 21L.

  The EGR control unit 140 controls the EGR valve 23L so as to close the low-pressure EGR passage 21L when the collection efficiency is less than the specified value ηa. Here, “closing the low pressure EGR passage 21L” means both closing the low pressure EGR passage 21L completely and partially closing the low pressure EGR passage 21L. In the following description, “close the low pressure EGR passage 21L” means full closure of the low pressure EGR passage 21L. Thereby, when the collection efficiency is less than the specified value ηa, the exhaust gas containing PM is prevented from flowing into the intake system through the low pressure EGR passage 21L.

  In the configuration in which the low pressure EGR passage 21L is partially closed, the flow rate of exhaust gas containing PM flowing in the intake system can be reduced.

<Control of low pressure EGR>
Next, an example of the control of the low pressure EGR will be described with reference to FIG. “Implementing EGR” shown in FIG. 5 means opening the low-pressure EGR passage 21L, and “stopping EGR” means closing the low-pressure EGR passage 21L. Note that the control of the low pressure EGR is started by starting the engine 1. Hereinafter, the collection efficiency calculation unit 120, the collection efficiency determination unit 130, and the EGR control unit 140 will be described as the ECU 100.

  In step S100, the ECU 100 determines whether or not the low pressure EGR is being performed. When the low pressure EGR is being performed (step S100: YES), the process proceeds to step S110. When the low pressure EGR is not being performed (step S100: NO), the process returns to step S100.

  In step S110, the ECU 100 determines whether or not the collection efficiency is equal to or higher than a specified value.

  When the collection efficiency is equal to or higher than the specified value (step S110: YES), in step S120, the ECU 100 controls the EGR valve 23L so as to continue the execution of the low pressure EGR.

  When the collection efficiency is less than the specified value (step S110: NO), in step S130, the ECU 100 controls the EGR valve 23L so as to stop the execution of the low pressure EGR.

<Effects of the present embodiment>
As described above, the control apparatus for an internal combustion engine according to the present embodiment includes the DPF 32 provided in the exhaust passage 30 of the engine 1 for collecting PM in the exhaust gas, and the exhaust gas from the DPF 32 to the exhaust gas of the turbocharger 13. The low-pressure EGR passage 21L that recirculates to the upstream side of the compressor 14, the collection efficiency determination unit 130 that determines whether the collection efficiency of the DPF 32 is equal to or higher than a specified value, and the collection efficiency determination unit 130 that collects the DPF 32 An EGR control unit 140 that performs control to close the low-pressure EGR passage 21L when it is determined that the efficiency is less than the specified value.

  When blow-off occurs during regeneration of the DPF 32, PM flows out downstream of the DPF 32. However, since the collection efficiency is less than a specified value, the low-pressure EGR passage 21L is closed. This prevents the exhaust gas containing PM from flowing into the intake system through the low pressure EGR passage 21L. As a result, the low pressure EGR passage 21L and the intake system can be prevented from being contaminated.

  In the above embodiment, the ECU 100 controls the EGR valve 23L so as to close the low-pressure EGR passage 21L when the collection efficiency is less than the specified value. By the way, as shown in FIG. 3, at the time of regeneration of the DPF 32, the collection efficiency falls below a specified value at tb immediately before the end of regeneration, and recovers to a specified value or more at td immediately after the end of regeneration. The time required for regenerating the DPF 32 (regeneration time) is obtained based on the operating state of the engine 1. A reproduction end time tc is obtained from the obtained reproduction time and reproduction start time ta. Further, tb immediately before the end of regeneration when the collection efficiency is less than the specified value and td immediately after the end of regeneration when the collection efficiency is equal to or higher than the specified value can be obtained from the result of simulation or experiment.

  The collection efficiency determination unit 130 determines that the collection efficiency is less than the specified value when the elapsed time from the reproduction start time ta is from tb immediately before the reproduction end to td immediately after the reproduction ends. The EGR control unit 140 controls the EGR valve 23L so as to close the low pressure EGR passage 21L based on the determination result of the collection efficiency determination unit 130. Specifically, tb immediately before the end of reproduction and td immediately after the end of reproduction obtained from the result of the experiment or the like are stored in advance in the storage unit 110. The EGR control unit 103 closes the low-pressure EGR passage 21L when the collection efficiency determination unit 130 determines that the elapsed time from the regeneration start time ta is within the period from tb immediately before the regeneration end to td immediately after the regeneration end. The EGR valve 23L is controlled.

<Modification of the present embodiment>
Next, a modification of the present embodiment will be described with reference to FIGS. In the modification, the configuration different from the above embodiment is mainly described, and the description of the same configuration is omitted. FIG. 6 is a timing chart showing an example of EGR control. FIG. 6 shows a time tb when the collection efficiency is less than the specified value and a time td when the collection efficiency is equal to or higher than the specified value.

  In the above embodiment, the ECU 100 controls the EGR valve 23L so that the low-pressure EGR passage 21L is closed when the collection efficiency is less than the specified value ηa.

  On the other hand, in the modification, as shown in FIG. 6, when the collection efficiency is less than the specified value ηa, the ECU 100 controls the EGR valve 23L so as to close the low pressure EGR passage 21L, while the high pressure EGR. The EGR valve 23H is controlled so as to open the passage 21H.

  Next, an example of EGR control in the modification will be described with reference to FIG. Note that steps S100 to S120 shown in FIG. 7 are the same as steps S100 to S120 shown in FIG.

  In the modification, when the collection efficiency is less than the specified value (step S110: NO), the process proceeds to step S140. In step S140, the ECU 100 controls the EGR valve 23L so as to close the low pressure EGR passage 21L, and controls the EGR valve 23H so as to open the high pressure EGR passage 21H.

  As a result, instead of the low pressure EGR passage 21L, a part of the exhaust gas is returned to the intake air using the high pressure EGR passage 21H, so that the amount of oxygen sucked into the engine 1 is suppressed and the combustion temperature is lowered. Can be reduced.

  In this embodiment, a diesel engine is used as an example of the internal combustion engine, but the type of the internal combustion engine to which the EGR mechanism is applied is not limited to this. As another example, the EGR mechanism can be applied to a gasoline engine. Even when the EGR mechanism is applied to a gasoline engine, the effects of the present embodiment can be achieved.

  Moreover, in the said embodiment, although the collection efficiency of DPF32 is used for the control determination of low pressure EGR, this invention is not limited to this. For example, since the collection efficiency is low when the PM accumulation amount is small, the PM accumulation amount of the DPF 32 may be used instead of the collection efficiency by the PM sensor. In this case, the ECU 100 controls to close the low pressure EGR when the PM accumulation amount falls below the threshold value. The PM accumulation amount estimation means calculates the PM amount discharged from the engine and the PM amount combusted by the DPF 32 based on the operating conditions, and calculates the difference between the two PM amounts as the PM accumulation amount.

  The control device for an internal combustion engine of the present disclosure is useful as a vehicle equipped with an engine that is required to prevent the EGR mechanism and the intake system from being contaminated.

DESCRIPTION OF SYMBOLS 1 Engine 11 Intake manifold 12 Exhaust manifold 13 Turbocharger 14 Compressor 15 Turbine 16a Upstream intake pipe 16b Downstream intake pipe 16c Intermediate intake pipe 17 Air cleaner 18 Intercooler 20 Exhaust pipe 21L Low pressure EGR passage 21H High pressure EGR passage 22L EGR cooler 22L EGR cooler 23L EGR valve 23H EGR valve 30 Exhaust passage 31 DOC
32 DPF
35 PM sensor 100 ECU
DESCRIPTION OF SYMBOLS 110 Storage part 120 Collection efficiency calculation part 130 Collection efficiency determination part 140 EGR control part

Claims (6)

A collection filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas;
A first EGR passage that recirculates exhaust gas flowing downstream of the collection filter to the upstream side of the compressor of the turbocharger, and used in an internal combustion engine.
A collection efficiency determination unit for determining whether the collection efficiency of the collection filter is equal to or greater than a predetermined value;
An EGR control unit that performs control to close the first EGR passage when the collection efficiency determination unit determines that the collection efficiency of the collection filter is less than a predetermined value;
An internal combustion engine control device comprising: A PM sensor that detects PM discharged from the collection filter, and a collection efficiency calculation unit that calculates the collection efficiency based on the detection result of PM by the PM sensor,
The control apparatus for an internal combustion engine according to claim 1. The collection efficiency determination unit determines that the collection efficiency is less than a predetermined value when the elapsed time from the start of regeneration of the collection filter is within a period from immediately before the end of regeneration to immediately after the end of regeneration. To
The control device for an internal combustion engine according to claim 1. A second EGR passage through which exhaust gas from the internal combustion engine is recirculated from the upstream side of the turbine of the turbocharger to the downstream side of the compressor;
4. The control device for an internal combustion engine according to claim 1, wherein the EGR control unit performs control for closing the first EGR passage, and performs control for opening the second EGR passage. 5.   An internal combustion engine comprising the control device for an internal combustion engine according to any one of claims 1 to 4. A collection filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas; an EGR passage for returning the exhaust gas flowing downstream of the collection filter to the upstream side of the compressor of the turbocharger; An internal combustion engine control method comprising:
Determining whether the collection efficiency of the collection filter is a predetermined value or more,
When it is determined that the collection efficiency of the collection filter is less than a predetermined value, a control for closing the EGR passage is performed.
A method for controlling an internal combustion engine.

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