JP2013253509A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of removing deposit accumulated in a compressor.SOLUTION: A control device for an internal combustion engine includes: a supercharger having a compressor disposed in an intake path in the internal combustion engine and a turbine disposed in an exhaust path of the internal combustion engine; a low pressure gas circulation path connecting the exhaust path more downstream than the turbine to the intake path more upstream than the compressor; a low pressure EGR valve capable of opening and closing the low pressure exhaust gas circulation path; and an intake throttle valve capable of opening and closing the intake path more upstream than a connection part of the low pressure exhaust gas circulation path with the intake path. When the internal combustion engine is stopped, the intake throttle valve is fully closed, the low pressure EGR valve is fully opened.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2012-007507), an internal combustion engine including a turbocharger, a low-pressure exhaust gas recirculation passage, a blow-by gas passage, and an intake throttle valve is known. . The turbocharger includes a turbine in the exhaust passage and a compressor in the intake passage. The low-pressure exhaust gas recirculation passage connects the exhaust passage on the downstream side of the turbine and the intake passage on the upstream side of the compressor. The blow-by gas passage connects the crank chamber of the internal combustion engine and the intake passage on the upstream side of the compressor. The intake throttle valve is disposed such that the intake throttle valve is located between the connection point of the low-pressure exhaust gas recirculation passage and the connection point of the blow-by gas passage in the intake passage. Patent Document 1 aims to reduce the influence of the pulsation of blow-by gas on the EGR rate by separating the location where blow-by gas flows in and the location where EGR gas recirculates from the intake throttle valve.
The applicant has recognized the following documents including the above-mentioned documents as related to the present invention.

JP 2012-007507 A JP 2008-309053 A JP 2012-013056 A

  When oil containing soot is supplied into the compressor by blow-by gas, deposits are accumulated in the compressor (for example, the diffuser surface) due to this. As a result, the compressor efficiency may be reduced and the supercharging performance may be reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of detaching deposits accumulated in a compressor.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A supercharger having a compressor disposed in an intake passage of the internal combustion engine and a turbine disposed in an exhaust passage of the internal combustion engine;
A low-pressure exhaust gas recirculation passage connecting the exhaust passage downstream of the turbine and the intake passage upstream of the compressor;
A low pressure EGR valve capable of opening and closing the low pressure exhaust gas recirculation passage;
An intake throttle valve capable of opening and closing the intake passage upstream of a connection portion between the low pressure exhaust gas recirculation passage and the intake passage;
Engine stop time valve control means for closing the intake throttle valve and opening the low pressure EGR valve when the internal combustion engine is stopped.

The second invention is the first invention, wherein
Further comprising soot amount estimating means for estimating the amount of soot contained in the engine oil of the internal combustion engine,
The engine stop time valve control means closes the intake throttle valve and stops the low pressure EGR valve when the internal combustion engine is stopped, provided that the amount of soot estimated by the soot amount estimating means is equal to or greater than a predetermined amount. It is characterized by opening.

The third invention is the first or second invention, wherein
Low-pressure EGR valve closing control means for closing the low-pressure EGR valve on the condition that after the low-pressure EGR valve is opened by the engine stop time valve control means and then the exhaust gas has spread into the compressor by the low-pressure exhaust gas recirculation passage, Is further provided.

According to a fourth invention, in any one of the first to third inventions,
A second intake throttle valve capable of opening and closing the intake passage on the downstream side of the compressor;
The engine stop valve control means further includes second intake throttle valve closing control means for closing the second intake throttle valve when the intake throttle valve is closed when the internal combustion engine is stopped.

  According to the first invention, when the internal combustion engine is stopped, the intake throttle valve is closed and the low-pressure EGR valve is opened. Therefore, the ratio of the exhaust gas (EGR gas) to the residual gas inside the compressor can be increased by closing the intake throttle valve to suppress gas exchange with fresh air and then opening the low-pressure EGR valve. By increasing the amount of exhaust gas inside the compressor, the amount of condensed water generated by condensation (condensation) of moisture contained in the exhaust gas increases in the process of cooling the internal combustion engine. Here, when condensed water is supplied to the deposit accumulated in the compressor, the deposit is easily detached. Therefore, the increased condensed water can suitably remove deposits inside the compressor after the internal combustion engine is restarted.

  In the first invention, “when the internal combustion engine is stopped, the intake throttle valve is closed and the low pressure EGR valve is opened” means that the intake throttle valve opening is 0 (that is, the intake throttle valve is fully closed). Then, not only the control for opening the low pressure EGR valve but also the control for closing the intake throttle valve and the control for opening the low pressure EGR valve are executed at the same time. In addition, the intake throttle valve is not only fully closed, but also means that the intake throttle valve is made smaller than the opening degree at that time. Furthermore, it means not only to fully open the low pressure EGR valve, but also to make the low pressure EGR valve larger than the opening degree at that time.

  According to the second invention, on the condition that the amount of soot contained in the engine oil of the internal combustion engine is a predetermined amount or more, the intake throttle valve is closed when the internal combustion engine is stopped, and the low pressure EGR valve is open. Since the above-mentioned condensed water may deteriorate the component parts, it is possible to achieve both the suppression of deterioration of the component parts and the removal of the deposit by positively generating the condensed water only when the above condition is satisfied. it can.

  According to the third invention, the low pressure EGR valve is closed on condition that exhaust gas (EGR gas) has spread into the compressor. Therefore, exhaust gas can be sufficiently supplied into the compressor.

  According to the fourth invention, when the internal combustion engine is stopped, the intake throttle valve is closed and the second intake throttle valve is closed. That is, in addition to the intake throttle valve on the upstream side of the compressor, the second intake throttle valve on the downstream side is also closed. Therefore, it is possible to increase the amount of exhaust gas in the compressor as compared with the case where only the upstream intake throttle valve is closed. As a result, the effect in the first invention can be further enhanced.

It is a conceptual diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the control routine which ECU50 performs in the system of Embodiment 1 of this invention. It is a flowchart of the control routine which ECU50 performs in the system of Embodiment 2 of this invention. It is a flowchart of the control routine which ECU50 performs in the system of Embodiment 3 of this invention. It is a conceptual diagram for demonstrating the system configuration | structure of Embodiment 4 of this invention. It is a flowchart of the control routine which ECU50 performs in the system of Embodiment 4 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a conceptual diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. The internal combustion engine 10 is mounted on a vehicle or the like and used as a power source. Although the internal combustion engine 10 shown in FIG. 1 is an in-line four-cylinder type, in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  An intake passage 12 for taking air into the cylinder and an exhaust passage 14 for discharging exhaust gas from the cylinder are connected to the internal combustion engine 10. In the vicinity of the inlet of the intake passage 12, an air flow meter 16 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 12 is provided. An electronically controlled intake throttle valve 18 for controlling the amount of air taken in is provided downstream of the air flow meter 16. A compressor 20 a of the supercharger 20 is disposed downstream of the intake throttle valve 18. The supercharger 20 includes a turbine 20b integrally connected to the compressor 20a. The compressor 20a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 20b.

  An intake manifold 22 constituting a part of the intake passage 12 is provided downstream of the compressor 20a. The intake manifold 22 is branched and connected to each cylinder. Each cylinder is provided with an injector 24 that directly injects fuel into the cylinder.

  An exhaust manifold 26 that constitutes a part of the exhaust passage 14 is connected to each cylinder. The exhaust manifold 26 joins downstream thereof, and a turbine 20b that is rotated by exhaust gas exhaust energy is disposed in the exhaust passage 14 after joining. A catalyst for purifying components in the exhaust gas is provided downstream of the turbine 20b.

  The system shown in FIG. 1 includes a low pressure exhaust gas recirculation passage (LPL: Low Pressure Loop) 28. The LPL 28 is configured to communicate the exhaust passage 14 downstream of the turbine 20b (downstream of the catalyst) and the intake passage 12 downstream of the intake throttle valve 18 and upstream of the compressor 20a. Yes. An LPL-EGR valve 30 for controlling the amount of recirculated exhaust gas (EGR gas) that flows back to the intake passage 12 through the LPL 28 is provided in the middle of the LPL 28.

  Furthermore, the system of the present embodiment includes a communication passage (not shown) that communicates the internal space (for example, the crank chamber) of the internal combustion engine 10 with the intake passage 12 on the upstream side of the compressor 20a. This communication passage functions as a blow-by gas passage for returning the blow-by gas existing inside the engine to the intake passage 12.

  Furthermore, the system of the present embodiment further includes an ECU (Electronic Control Unit) 50. ECU50 is comprised by the arithmetic processing apparatus provided with the memory circuit containing ROM, RAM, etc., for example. In addition to the air flow meter 16 described above, the ECU 50 includes an internal combustion engine 10 such as a crank angle sensor 52 for detecting the crank angle and the engine speed, and an engine start switch 54 for starting / stopping the internal combustion engine 10. Various sensors for detecting the driving state are connected. Further, various actuators for controlling the operating state of the internal combustion engine 10 such as the intake throttle valve 18, the injector 24, and the LPL-EGR valve 30 are connected to the output portion of the ECU 50. The ECU 50 controls the operating state of the internal combustion engine 10 by driving various actuators according to a predetermined program based on various sensor outputs.

  In the system of the present embodiment, when blow-by gas returns to the upstream side of the compressor 20a, deposits can be accumulated in the compressor 20a (inside the housing). The deposit is generated when the engine oil containing soot brought into the compressor 20a by the blow-by gas is exposed to a high temperature and is evaporated to increase the viscosity and accumulate on the diffuser surface. If the deposit accumulates, the compressor efficiency may decrease and the supercharging performance may decrease.

[Characteristic Control in Embodiment 1]
Therefore, in the present embodiment, by performing the characteristic control shown in FIG. 2 when the engine is stopped in the system configuration described above, the condensed water generated in the compressor 20a during the process of cooling the engine is increased, and when the engine is restarted. Thus, the deposit accumulated in the compressor 20a is desorbed and removed by the condensed water.

  FIG. 2 is a flowchart of a control routine executed by the ECU 50 in order to realize the characteristic control of the present invention. In the routine shown in FIG. 2, first, the ECU 50 detects that the engine 10 has been stopped (step S100). For example, when the engine start switch 54 shifts from an on state to an off state, it is detected that the engine 10 has stopped.

  When the engine stops, the intake throttle valve 18 is closed (step S110). Closing the intake throttle valve 18 preferably means that the opening degree of the intake throttle valve 18 is zero (that is, the intake throttle valve 18 is fully closed), but the present invention is not limited to this. . The opening of the intake throttle valve 18 may be made smaller than the opening at that time.

  Subsequently, the LPL-EGR valve 30 is opened (step S120). The opening of the LPL-EGR valve 30 preferably means that the opening of the LPL-EGR valve 30 is maximized (that is, the LPL-EGR valve 30 is fully opened). Not limited. It is good also as making the LPL-EGR valve 30 larger than the opening degree at that time.

  Thereafter, the LPL-EGR valve 30 is closed (step S130). The closing of the LPL-EGR valve 30 preferably means that the opening of the LPL-EGR valve 30 is set to 0 (that is, the LPL-EGR valve 30 is fully closed). Not limited to. It is good also as making the LPL-EGR valve 30 smaller than the opening degree at that time.

  As described above, according to the routine shown in FIG. 2, the actuators are operated in the order of the intake throttle valve 18 being fully closed, the LPL-EGR valve 30 being fully opened, and the LPL-EGR valve 30 being fully closed after the engine is stopped. Can do. When the engine is stopped, the intake throttle valve 18 is closed to suppress gas exchange with fresh air, and the LPL-EGR valve 30 is opened to increase the ratio of exhaust gas to the residual gas inside the compressor 20a. Thereby, dew condensation (condensed water) can be increased in the process of cooling the engine thereafter. The increased condensed water can suitably remove deposits inside the compressor 20a after the engine restarts.

  The engine to which the present invention is applied is not limited to the in-cylinder direct injection engine as in the above-described embodiment. The present invention can also be applied to a port injection type engine. Further, the present invention can be applied to both a compression self-ignition engine and a spark ignition engine. These points are the same in the following embodiments.

  In the first embodiment described above, the supercharger 20 is the “supercharger” in the first invention, the LPL 28 is the “low-pressure exhaust gas supply passage” in the first invention, and the LPL-EGR valve 30. Corresponds to the “low pressure EGR valve” in the first invention, and the intake throttle valve 18 corresponds to the “intake throttle valve” in the first invention. Here, the “engine stop valve control means” according to the first aspect of the present invention is implemented by the ECU 50 executing the processes of steps S100 to S120.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 3 described later in the configuration shown in FIG.

[Characteristic Control in Embodiment 2]
In the system of the first embodiment described above, the condensed water generated in the compressor 20a in the process of cooling the engine is increased, and the increased condensed water is used to desorb the deposit inside the compressor 20a after the engine is restarted. . However, condensed water can also deteriorate engine parts. Therefore, it is preferable to execute the control for increasing the condensed water only when deposits are likely to occur in the compressor 20a. Here, the accumulation of deposits becomes a problem when aging progresses and the amount of soot contained in the engine oil increases. Therefore, in the system of the present embodiment, the amount of soot contained in the engine oil is estimated, and control for increasing the condensed water is executed only when the amount is large.

  FIG. 3 is a flowchart of a control routine executed by the ECU 50 in order to realize the characteristic control of the present invention. This routine is the same as the routine shown in FIG. 2 except that the process of step S200 is added between the processes of step S100 and step S110. In FIG. 3, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 3, in step S200, the ECU 50 determines whether or not the amount of soot contained in the engine oil is larger than a predetermined amount. The amount of soot contained in the engine oil can be obtained by putting a sensor into the actual measurement or estimating from the operation history. As the predetermined amount, an amount in which deposit accumulation is a concern is set in advance through experiments and simulations. If the amount of soot acquired is larger than the predetermined amount, it can be determined that deposit accumulation is a problem, and therefore, the processing after step S110 described in FIG. 1 is executed, and the desorption of the deposit is promoted.

  On the other hand, when the amount of soot obtained is equal to or less than the predetermined amount, it can be determined that the amount of soot in the engine oil is still small and the deposit is not deposited so as to cause a problem. The Thereafter, if the determination establishment condition of step S200 is reached, the processing after step S110 is executed, and the desorption of the deposit is promoted.

  As described above, according to the routine shown in FIG. 2, the control for increasing the condensed water when the engine is stopped is executed only when the amount of soot in the engine oil is large. Thereby, desorption of the deposit can be promoted as necessary while minimizing deterioration (corrosion or the like) of the engine 10. In addition, oil and soot accumulate in the engine that has deteriorated over time as the soot concentration increases, and it works to neutralize acidic condensate. The risk of degradation is reduced.

  In the above-described second embodiment, the ECU 50 executes the process of step S200, so that the “soot amount estimation means” in the second aspect of the invention is the process of steps S100, S200, S110, and S120. By executing this, the “engine stop valve control means” in the second aspect of the present invention is realized.

Embodiment 3 FIG.
[System Configuration of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 4 described later in the configuration shown in FIG.

[Characteristic Control in Embodiment 3]
In the system of the first embodiment described above, the LPL-EGR valve 30 is opened in step S120 of FIG. 2 to increase the ratio of exhaust to the residual gas inside the compressor 20a, and then the LPL-EGR valve 30 is closed in step S130. I am going to do that. Here, the time when the LPL-EGR valve 30 is fully closed is optimal when the exhaust gas remaining in the exhaust passage 14 has sufficiently spread into the compressor 20a. Therefore, in the system of the present embodiment, this time is estimated and the LPL-EGR valve 30 is controlled to be fully closed.

  FIG. 4 is a flowchart of a control routine executed by the ECU 50 in order to realize the characteristic control of the present invention. This routine is the same as the routine shown in FIG. 2 except that the process of step S300 is added between the processes of step S120 and step S130. In FIG. 4, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 4, the ECU 50 opens the LPL-EGR valve 30 in step S120, and determines in step S300 whether or not exhaust gas has spread into the compressor 20a. As a method for determining whether or not the exhaust gas has spread in the compressor 20a, it is possible to determine by experimentally clarifying the necessary time and reaching the necessary time, or by measuring the temperature and determining by a temperature change. . If the determination condition is satisfied, it can be determined that the exhaust gas has sufficiently spread into the compressor 20a, and therefore the LPL-EGR valve 30 is controlled to be fully closed in step S130.

  On the other hand, if the determination condition is not satisfied, it can be determined that the exhaust gas has not yet sufficiently spread into the compressor 20a. In this case, the determination process of step S300 is executed again after a predetermined time, and if the determination condition is satisfied, the LPL-EGR valve 30 is controlled to be fully closed in step S130.

  As described above, according to the routine shown in FIG. 4, exhaust gas can be sufficiently supplied into the compressor, and the condensed water in the compressor can be suitably increased.

  In the system of the third embodiment described above, the process of step S200 of FIG. 3 described in the second embodiment may be added between the processes of step S100 and step S110 of FIG.

  In the third embodiment described above, the “low pressure EGR valve closing control means” according to the third aspect of the present invention is realized by the ECU 50 executing the processes of steps S300 and S130.

Embodiment 4 FIG.
[System Configuration of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 6 to be described later in the configuration shown in FIG.

  FIG. 5 is a conceptual diagram for explaining a system configuration according to the fourth embodiment of the present invention. The system shown in FIG. 5 is the same as the system shown in FIG. 1 except that a high pressure exhaust gas recirculation passage (HPL: High Pressure Loop) 40, an HPL-EGR valve 42, and an HPL path intake throttle valve 44 are provided. About the structure which is common in FIG. 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.

  The system shown in FIG. 5 includes an HPL 40. The HPL 40 is configured to communicate the exhaust manifold 26 located on the upstream side of the turbine 20b and the intake manifold 22 located on the downstream side of the compressor 20a. An HPL-EGR valve 42 for adjusting the amount of exhaust gas (EGR gas) that flows back to the intake manifold 22 through the HPL 40 is disposed in the middle of the HPL 40. An HPL path intake throttle valve 44 is provided in the intake passage 12 downstream of the compressor 20a and upstream of the connection portion between the HPL 40 and the intake manifold 22. Further, an HPL-EGR valve 42 and an HPL path intake throttle valve 44 are connected to the output portion of the ECU 50. In order to distinguish from the HPL path intake throttle valve 44, the intake throttle valve 18 is referred to as an LPL path intake throttle valve 18 in the following description.

[Characteristic Control in Embodiment 4]
In the system of the present embodiment including the LPL 28 and the HPL 40, the control for closing the HPL path intake throttle valve 44 is executed together with the control for closing the LPL path intake throttle valve 18 in the characteristic control of the first embodiment. The effect can be enhanced.

  FIG. 6 is a flowchart of a control routine executed by the ECU 50 in order to realize the characteristic control of the present invention. This routine is the same as the routine shown in FIG. 1 except that the process of step S110 is replaced with step S400. Hereinafter, in FIG. 6, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 6, the ECU 50 closes the HPL path intake throttle valve 44 simultaneously with closing the LPL path intake throttle valve 18 in step S400. The closing of the intake throttle valves 18 and 44 preferably means that the opening degree of the intake throttle valves 18 and 44 is 0 (that is, the intake throttle valves 18 and 44 are fully closed). The invention is not limited to this. It is good also as making the opening degree of the intake throttle valves 18 and 44 smaller than the opening degree at that time.

  As described above, according to the routine shown in FIG. 6, in addition to the LPL path intake throttle valve 18, the HPL path intake throttle valve 44 on the downstream side of the compressor 20a is also closed. Therefore, the amount of exhaust gas in the compressor 20a can be increased as compared with the case where only the LPL path intake throttle valve 18 is closed. As a result, the condensed water generated in the compressor 20a is increased as compared with the system of the first embodiment, and the deposit is more easily desorbed.

  By the way, in the system of the fourth embodiment described above, the process of step S200 of FIG. 3 described in the second embodiment may be added between the processes of step S100 and step S400 of FIG. Further, the process of step S300 of FIG. 4 described in the third embodiment may be added between the processes of step S120 and step S130 of FIG.

  In the above-described fourth embodiment, the HPL path intake throttle valve 44 corresponds to the “second intake throttle valve” in the fourth aspect of the invention. Here, the “second intake throttle valve closing control means” according to the fourth aspect of the present invention is realized by the ECU 50 executing the process of step S400.

10 Internal combustion engine
12 Intake passage 14 Exhaust passage 18 Intake throttle valve (LPL path intake throttle valve)
20 Supercharger 20a Compressor 20b Turbine 22 Intake manifold 26 Exhaust manifold 28 Low-pressure exhaust gas recirculation passage (LPL)
30 LPL-EGR valve 40 High pressure exhaust gas recirculation passage (HPL)
42 HPL-EGR valve 44 HPL path intake throttle valve 50 ECU (Electronic Control Unit)
52 Crank angle sensor 54 Engine start switch

Claims (4)

A supercharger having a compressor disposed in an intake passage of the internal combustion engine and a turbine disposed in an exhaust passage of the internal combustion engine;
A low-pressure exhaust gas recirculation passage connecting the exhaust passage downstream of the turbine and the intake passage upstream of the compressor;
A low pressure EGR valve capable of opening and closing the low pressure exhaust gas recirculation passage;
An intake throttle valve capable of opening and closing the intake passage upstream of a connection portion between the low pressure exhaust gas recirculation passage and the intake passage;
Engine stop time valve control means for closing the intake throttle valve and opening the low pressure EGR valve when the internal combustion engine is stopped;
A control device for an internal combustion engine, comprising: Further comprising soot amount estimating means for estimating the amount of soot contained in the engine oil of the internal combustion engine,
The engine stop time valve control means closes the intake throttle valve and stops the low pressure EGR valve when the internal combustion engine is stopped, provided that the amount of soot estimated by the soot amount estimating means is equal to or greater than a predetermined amount. Opening,
The control device for an internal combustion engine according to claim 1. Low-pressure EGR valve closing control means for closing the low-pressure EGR valve on the condition that after the low-pressure EGR valve is opened by the engine stop time valve control means and then the exhaust gas has spread into the compressor by the low-pressure exhaust gas recirculation passage,
The control device for an internal combustion engine according to claim 1, further comprising: A second intake throttle valve capable of opening and closing the intake passage on the downstream side of the compressor;
Second intake throttle valve closing control means for closing the second intake throttle valve when the intake throttle valve is closed when the internal combustion engine is stopped by the engine stop valve control means;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:

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