JP2010071186A - Control device for internal combustion engine, and control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, removing foreign matter deposited in an EGR cooler during operation of the internal combustion engine. <P>SOLUTION: This control device is applied to the internal combustion engine including the EGR cooler cooling EGR gas, and an EGR valve (flow rate regulating valve) regulating a flow rate of EGR gas flowing in the EGR cooler, and controls operation of the EGR valve in order to remove PM (particulate matter) by the EGR gas flowing in the EGR cooler (S40) when it is determined as such a foreign matter deposition state that the predetermined amount of the PM (particulate matter) or more is deposited inside of the EGR cooler (S10:YES). Specifically, the EGR valve (flow rate regulating valve) is fully opened after being temporarily fully closed, thereby allowing the EGR gas to flow at a breath into the EGR cooler to remove the PM. Alternatively, pressure pulsation is generated in the EGR gas by repeatedly opening/closing the EGR valve in a predetermined cycle, thereby removing the PM by the pressure pulsation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that includes an EGR cooler that cools EGR gas.

  Conventionally, an EGR system in which a part of exhaust gas discharged from an internal combustion engine is recirculated as an exhaust gas recirculation (EGR) gas to the intake system of the internal combustion engine to reduce the combustion temperature and reduce NOX in the exhaust gas. It has been known.

Here, since the exhaust gas is high in temperature, there is a concern that if the exhaust gas is directly flowed into the intake system as EGR gas, the intake air temperature rises, the mass flow rate that can be sucked into the combustion chamber decreases, and the intake efficiency decreases. Therefore, it is common to suppress the reduction in intake efficiency by providing an EGR cooler that cools by exchanging heat with EGR gas (see Patent Document 1 and the like).
JP 54-23825 A

  However, as the operating time of the internal combustion engine becomes longer, foreign matters such as PM (particulate matters (fine particles)) contained in the exhaust gas adhere to and accumulate on the internal flow path of the EGR cooler. Then, the internal flow path is blocked with PM, which causes an increase in pressure loss and a problem that the flow rate of EGR gas decreases. In addition, since PM having a heat insulating effect adheres to the entire surface of the internal flow path, the amount of heat transfer from the EGR gas to the EGR cooler decreases, resulting in a problem that the cooling efficiency by the EGR cooler decreases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine control device and an internal combustion engine control system that are designed to remove foreign matter accumulated in an EGR cooler during operation of the internal combustion engine. It is to provide.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

In the first aspect of the present invention, a part of the exhaust gas discharged from the internal combustion engine is recirculated as EGR gas to the intake system of the internal combustion engine, and cooling is performed by exchanging heat with the EGR gas provided in the EGR pipe. And an EGR cooler, and a flow rate adjustment valve that variably controls the flow area of the EGR pipe so as to adjust the flow rate of the EGR gas flowing through the EGR cooler.
Deposition determination means for determining whether or not a predetermined amount or more of foreign matter has accumulated inside the EGR cooler, and EGR gas flowing through the EGR cooler when determined to be in the foreign matter accumulation state And foreign matter removal control means for controlling the operation of the flow rate adjusting valve so as to remove the foreign matter.

  According to this, when a predetermined amount or more of foreign matter accumulates in the EGR cooler, the foreign matter is removed by the EGR gas flowing through the EGR cooler by the operation of the flow rate adjustment valve, so the foreign matter deposited on the EGR cooler. Can be easily realized during operation of the internal combustion engine, and the above-described problem of the decrease in the flow rate of the EGR gas and the problem of the decrease in the cooling efficiency of the EGR cooler can be solved.

  The invention according to claim 2 is characterized in that the flow rate adjusting valve is a circulating flow rate adjusting valve for adjusting a circulating flow rate of the EGR gas recirculated to the intake system. According to a third aspect of the present invention, the flow rate adjusting valve is configured to flow the EGR gas through the EGR cooler and bypass the bypass pipe so as to adjust the temperature of the EGR gas recirculated to the intake system. It is the distribution | circulation ratio adjustment valve which adjusts the ratio with.

  According to these inventions, since the flow of EGR gas can be controlled so as to remove foreign matter using the existing circulation flow rate adjustment valve or existing flow rate adjustment valve, the number of parts required for foreign matter removal can be increased. Can be suppressed.

  The invention according to claim 4 is characterized in that the foreign matter removal control means causes pressure pulsation in the EGR gas by repeatedly opening and closing the flow rate adjusting valve so that the EGR gas is circulated intermittently at a predetermined cycle. To do.

  According to this, the foreign matter deposited on the EGR cooler due to the pressure pulsation of the EGR gas is removed, and the removal of the foreign matter with the EGR gas can be easily realized.

  Here, pulsation is generated in the exhaust gas in synchronization with the combustion cycle of the internal combustion engine, that is, in synchronization with the rotation speed of the output shaft (for example, the crankshaft) of the internal combustion engine. The invention according to claim 5, wherein the exhaust gas pulsation is used to increase the pressure pulsation of the EGR gas, and the foreign matter removal control means is configured to control the flow rate adjusting valve according to the rotational speed of the output shaft of the internal combustion engine. It is characterized in that the opening / closing cycle of the is changed.

  According to this, for example, the flow adjustment valve is closed when the exhaust gas pressure is low, and the opening and closing cycle of the flow adjustment valve is changed according to the rotation speed of the output shaft so that the flow adjustment valve is opened when the exhaust gas pressure is high Then, the pressure pulsation of the EGR gas can be increased. Therefore, it is possible to more reliably remove the foreign matter with the EGR gas.

  The invention according to claim 6 is characterized in that the foreign matter removal control means increases the instantaneous flow rate of EGR gas by controlling the flow rate adjusting valve to the open side. According to this, by controlling the flow rate adjusting valve to the open side, the EGR gas flows into the EGR cooler at a stretch, and the instantaneous flow rate of the EGR gas increases. That is, the foreign matter accumulated in the EGR cooler is removed by causing the EGR gas to flow to the EGR cooler at once (increasing the instantaneous flow rate), and it is possible to easily remove the foreign matter with the EGR gas.

  In addition, when controlling the flow rate adjustment valve to the open side as described above, it is desirable to control to the open side until it is fully opened. In addition, prior to controlling to the opening side, it is desirable to control the flow rate adjusting valve to the closing side and then to the opening side. Furthermore, when controlling to the closed side, it is desirable to control to the closed side until the fully closed state is reached. For example, once the fully-closed state and then the fully-open state, the EGR gas is blocked by temporarily closing the flow rate adjusting valve, and then when the fully-opened state is reached, The instantaneous flow rate of the EGR gas can be further increased by flowing to the EGR cooler at once.

  The invention according to claim 7 is characterized in that the foreign matter removal control means makes the operating speed of the flow rate adjusting valve when controlling to the opening side faster than when controlling to the closing side. Furthermore, the invention according to claim 8 is characterized in that the foreign matter removal control means sets the operation speed of the flow rate adjusting valve at the time of control to the opening side to the maximum capability speed of the flow rate adjusting valve.

  According to these inventions, since the instantaneous flow rate when the damped EGR gas flows to the EGR cooler at once can be increased, it is possible to further reliably remove foreign matters with the EGR gas.

  In a ninth aspect of the invention, prior to the execution of the control by the foreign matter removal control means, there is provided differential pressure increase control means for controlling the operating state of the internal combustion engine so as to increase the differential pressure across the EGR cooler. Features.

  According to this, since the control by the foreign matter removal control means is executed in a state in which the differential pressure across the EGR cooler is increased, it is possible to more reliably remove the foreign matter with the EGR gas. For example, in the case where foreign matter is removed by the pressure pulsation of the EGR gas described above, the pressure pulsation of the EGR gas is increased due to an increase in the differential pressure across the EGR cooler, so that the foreign matter is easily removed. Further, in the case of removing foreign matter by increasing the instantaneous flow rate of EGR gas described above, the instantaneous flow rate of EGR gas is increased by increasing the differential pressure across the EGR cooler, so that the foreign matter is easily removed.

  The invention according to claim 10 is characterized in that the differential pressure increase control means reduces the intake pressure, which is the pressure downstream of the EGR cooler, by controlling the opening of the electric throttle valve to be small. To do. In the invention according to claim 11, the differential pressure increase control means controls the capacity variable device of the supercharger so as to increase the conversion ratio to the rotational driving force, whereby the pressure on the upstream side of the EGR cooler is controlled. The exhaust pressure is increased.

  According to these inventions, it is possible to increase the differential pressure across the EGR cooler using an existing electric throttle valve or an existing turbocharger variable capacity device. The increase in points can be suppressed.

  Here, when the operation of the flow rate adjustment valve is controlled so as to remove foreign substances, there is a concern that emission may deteriorate, for example, NOX in exhaust gas cannot be sufficiently reduced by recirculating EGR gas to the intake system. With respect to this concern, the invention according to claim 12 is characterized in that the control by the foreign matter removal control means is executed at the time of fuel injection cut for operating the internal combustion engine while stopping the injection of fuel for combustion of the internal combustion engine. And

  According to this, since the control by the foreign matter removal control means is executed at the time of the fuel injection cut, it is possible to eliminate the concern about the deterioration of the emission caused by controlling the operation of the flow rate adjusting valve so as to remove the foreign matter.

  By the way, as foreign matter accumulation on the EGR cooler proceeds, the differential pressure across the EGR cooler increases. Further, as the vehicle travel distance and the operation time of the internal combustion engine become longer, the accumulation of foreign matter on the EGR cooler proceeds. That is, the differential pressure across the EGR cooler, the travel distance of the vehicle, and the operation time of the internal combustion engine are highly correlated with the amount of foreign matter accumulated on the EGR cooler. In view of this point, in the invention according to claim 13, when the differential pressure across the EGR cooler is greater than a specified differential pressure, the accumulation determining means determines that a travel distance of the vehicle on which the internal combustion engine is mounted is a specified distance. When it becomes longer or when the operation time of the internal combustion engine becomes longer than a specified time, it is determined that the foreign matter is accumulated. Therefore, it is possible to easily determine whether or not the EGR cooler is in a foreign matter accumulation state in which a predetermined amount or more of foreign matter has accumulated.

  A fourteenth aspect of the invention is an internal combustion engine control system comprising the internal combustion engine control device and at least one of the EGR pipe, the EGR cooler, and the flow rate adjusting valve. According to this internal combustion engine control system, the various effects described above can be exhibited in the same manner.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
First, an outline of an engine (internal combustion engine) on which the internal combustion engine control apparatus according to the present embodiment is mounted will be briefly described. In this embodiment, a diesel engine for a four-wheeled vehicle is targeted, and an engine of a system in which high pressure fuel (for example, light oil having an injection pressure of “1000 atm” or more) is directly supplied to the combustion chamber by injection (direct injection supply). is there. The engine is assumed to be a multi-cylinder (for example, in-line four-cylinder) four-stroke, reciprocating diesel engine.

  Next, the configuration of the intake / exhaust system of the engine will be described with reference to FIG.

  The engine includes an EGR pipe 10 that recirculates exhaust gas from the exhaust system to the intake system. By returning a part of the exhaust gas to the intake pipe 11, the combustion temperature in the combustion chamber 12 is lowered to reduce NOX in the exhaust gas. I am trying. The EGR pipe 10 is provided with an EGR flow rate adjusting device 13 that adjusts the flow rate of EGR gas (EGR flow rate). The EGR flow rate adjusting device 13 includes an EGR valve 13a (circulation flow rate adjusting valve) that adjusts the flow path cross-section opening degree of the EGR pipe 10, and an electric motor 13b that drives the EGR valve 13a. When the EGR valve 13a is fully opened, the EGR flow rate becomes maximum, and when the EGR valve 13a is fully closed, the EGR flow rate becomes zero.

  An EGR cooler 14 that cools the EGR gas is provided in a portion of the EGR pipe 10 downstream of the EGR valve 13a. By cooling the EGR gas in this way, the volume of the EGR gas is reduced (density increase), thereby improving the charging efficiency of the intake air flowing into the combustion chamber 12. Incidentally, the EGR cooler 14 is formed with a coolant passage through which the coolant circulates and a gas passage 14a through which the EGR gas circulates, and the EGR gas that circulates through the gas passage cools through the coolant passage. It is cooled by exchanging heat with the liquid. Note that engine coolant is applied to the coolant, and the coolant is cooled by exchanging heat with outside air by a radiator (not shown).

  A throttle valve 17 a that adjusts the flow rate of fresh air out of the intake air flowing into the combustion chamber 12 is provided upstream of the portion of the intake pipe 11 to which the EGR pipe 10 is connected. The throttle valve 17a is opened / closed by an electric motor 17b, and the fresh air amount is maximized when fully opened, and the fresh air amount becomes zero when fully closed.

  A turbocharger 19 (supercharger) is disposed between the intake pipe 11 and the exhaust pipe 18. The turbocharger 19 has a compressor impeller 19a provided in the intake pipe 11 and a turbine wheel 19b provided in the exhaust pipe 18, which are connected by a shaft 19c. In the turbocharger 19, the turbine wheel 19b is rotated by the exhaust gas flowing through the exhaust pipe 18, and the rotational force is transmitted to the compressor impeller 19a via the shaft 19c. Then, the intake air flowing through the intake pipe 11 is compressed by the compressor impeller 19a, and supercharging is performed.

  The turbocharger 19 according to the present embodiment employs a variable capacity turbocharger that can change the ratio of converting the exhaust fluid energy into the rotational driving force of the shaft 19c. Specifically, the turbine wheel 19b is provided with a plurality of variable vanes 19d (capacity variable devices) for making the flow rate of the exhaust gas sprayed variable. These variable vanes 19d open and close in synchronization with each other. Then, the exhaust flow rate is adjusted by changing the size of the gap between the adjacent variable vanes 19d, that is, the opening degree of the variable vane 19d, thereby adjusting the rotational speed of the turbine wheel 19b. Then, by adjusting the rotational speed of the turbine wheel 19b, the amount of air forcibly supplied to the combustion chamber 12, that is, the supercharging pressure is adjusted.

  The air supercharged by the turbocharger 19 is cooled by the intercooler 20 and then fed downstream. The intake air is cooled by the intercooler 20 to reduce the volume (increase in density), thereby improving the charging efficiency of the intake air flowing into the combustion chamber 12.

  A mass flow rate MAF of intake air flowing in per unit time (hereinafter simply referred to as intake air amount or intake air amount) is detected in the intake pipe 11 upstream of the compressor impeller 19a and downstream of the air cleaner 21. An air flow meter 22 (intake air amount sensor) is attached. The air flow meter 22 according to the present embodiment employs a hot wire type air flow meter that indirectly detects the intake air amount by detecting a change in the heat amount taken from the heating element in accordance with the intake air flow rate.

  A purification device 23 for purifying exhaust gas is attached to the exhaust pipe 18 on the downstream side of the turbine wheel 19b. Specific examples of the purification device 23 include a DPF (diesel particulate filter) for collecting PM in exhaust, a NOx catalyst for purifying NOx in exhaust, an oxidation catalyst for purifying HC and CO in exhaust, and the like. Can be mentioned.

  An A / F sensor 24 for detecting the oxygen concentration in the exhaust is attached to the exhaust pipe 18 downstream of the purification device 23. The A / F sensor 24 is an oxygen concentration sensor that outputs an oxygen concentration detection signal O2 corresponding to the oxygen concentration in the exhaust gas from time to time. The oxygen concentration detection signal as the sensor output of the A / F sensor 24 is adjusted so as to change linearly according to the oxygen concentration. Instead of the A / F sensor 24, an electromotive force output type O2 sensor that outputs an electromotive force signal that differs depending on whether the exhaust gas is rich or lean may be employed.

  An intake pressure sensor 25 for detecting an intake pressure P1 (also a turbocharger pressure to be described later) is provided in a portion of the intake pipe 11 to which the EGR pipe 10 is connected and downstream of the throttle valve 17a. It has been. An exhaust pressure sensor 26 for detecting the exhaust pressure P2 is provided in a portion of the exhaust pipe 18 where the EGR pipe 10 is branched and upstream of the turbine wheel 19b.

  An EGR temperature sensor 27 that detects the temperature of the EGR gas cooled by the EGR cooler 14 is provided on the downstream side of the EGR cooler 14 in the EGR pipe 10. An intake air temperature sensor (not shown) that is disposed in a portion of the intake pipe 11 to which the EGR pipe 10 is connected and detects the intake air temperature may also be used as the EGR temperature sensor 27.

  The detection signals output from the various sensors 22, 24, 25, 26, 27 and the crank angle sensor 28 described above are input to an engine ECU 29 (electronic control unit) as an internal combustion engine control device. Based on these detection signals, the ECU 29 controls the engine by controlling the fuel injection amount, the supercharging pressure, the opening degree of the EGR valve 13a, the opening degree of the throttle valve 17a, and the like as follows.

  The microcomputer 29 a provided in the ECU 29 calculates the rotational speed (engine rotational speed NE) of the engine output shaft (crankshaft) based on the detection signal input from the crank angle sensor 28. Further, based on a detection signal input from an accelerator sensor (not shown), an operation amount (depression amount) of the accelerator pedal by the driver is calculated. The microcomputer 29a calculates the fuel target injection amount Qfin based on the engine operating state (for example, engine speed NE), the accelerator pedal operation amount, and the like, and controls the operation of the injector 30 so as to be the target injection amount Qfin. .

  The microcomputer 29 a of the ECU 29 controls the supercharging pressure by adjusting the capacity of the variable capacity turbocharger 19. That is, the target opening of the variable vane 19d is calculated using a map or the like using the target injection amount Qfin and the engine rotational speed NE as parameters. Then, the variable vane 19d is controlled to have the target opening by driving and controlling an actuator (not shown) so as to have the target opening. Note that the higher the engine speed NE or the larger the target injection amount Qfin, the larger the target opening, and thus the supercharging pressure. Further, the ECU 29 feedback-controls the opening degree of the variable vane 19d so that the value of the supercharging pressure P1 detected by the intake pressure sensor 25 or the value of the exhaust pressure P2 detected by the exhaust pressure sensor 26 approaches the target value.

  The microcomputer 29a of the ECU 29 controls the opening degree of the EGR valve 13a, thereby controlling the EGR flow rate flowing into the EGR pipe 10 from the exhaust pipe 18 and returning. That is, the target value (target exhaust oxygen concentration) of the oxygen concentration (exhaust oxygen concentration) in the exhaust gas is calculated using a map or the like using the target injection amount Qfin and the engine rotational speed NE as parameters. Then, the target EGR flow rate is set so that the exhaust oxygen concentration detected by the A / F sensor 24 approaches the target exhaust oxygen concentration, and the EGR opening EGRP of the EGR valve 13a is calculated so as to be the target EGR flow rate. That is, it can be said that the EGR opening degree EGRP is feedback-controlled based on the deviation between the exhaust oxygen concentration and the target exhaust oxygen concentration. Based on the calculated EGR opening degree EGRP, the electric motor 13b is driven to control the opening degree of the EGR valve 13a.

  Incidentally, when the EGR flow rate is too low, a sufficient NOx reduction effect cannot be obtained, and when the EGR flow rate is too high, oxygen in the cylinder becomes insufficient and smoke due to an increase in PM occurs. In order to avoid this, it is required to increase the EGR flow rate to the limit of the smoke generation limit and to reduce NOx without the generation of smoke. Therefore, by controlling the EGR valve opening, the target exhaust oxygen concentration is set so that the exhaust gas oxygen concentration having a strong correlation with the smoke generation amount is set to a predetermined value or more so that the EGR flow rate is increased to the limit of smoke generation. . Further, the target exhaust oxygen concentration is set according to the state of the purification device 23.

  In this way, the above-described control for controlling the operation of the EGR valve 13a based on the target injection amount Qfin (engine load), the engine rotational speed NE, and the like in order to suppress the deterioration of the emission is hereinafter referred to as normal control of the EGR valve 13a. Call it.

  By the way, as the engine operating time becomes longer, foreign matters such as PM (hereinafter simply referred to as PM) contained in the exhaust gas adhere to and accumulate on the gas passage 14a (internal passage) of the EGR cooler 14. . Then, the gas passage 14a is blocked with PM, thereby causing an increase in pressure loss, and there is a concern about a decrease in the flow rate of EGR gas. Further, since PM having a heat insulating effect adheres to the entire surface of the gas passage 14a, the amount of heat transferred from the EGR gas to the coolant through the gas passage 14a is reduced, and there is a concern that the cooling efficiency of the EGR cooler 14 may be reduced. The

  With respect to these concerns, in the present embodiment, when it is estimated that PM of a predetermined amount or more is accumulated (PM accumulation state), the EGR valve 13a is removed so that PM is removed by the EGR gas flowing through the EGR cooler 14. Operate. Specific details of the operation will be described later. Controlling the operation of the EGR valve 13a to remove the PM accumulated in the gas passage 14a in this way is hereinafter referred to as PM removal control of the EGR valve 13a. That is, when controlling the operation of the EGR valve 13a, the normal control and the PM removal control are switched and executed in accordance with whether or not the PM accumulation state.

  Hereinafter, the processing procedure of the PM removal control executed by the microcomputer 29a of the ECU 29 will be described with reference to FIGS. The series of processes shown in FIG. 2 is a process repeatedly executed by the microcomputer 29a at a predetermined cycle (for example, a calculation cycle of the CPU included in the microcomputer 29a) or every predetermined crank angle. The series of processes shown in FIG. 3 is a subroutine process of PM removal control (step S40) in FIG.

  First, in step S10 (deposition determination means) in FIG. 2, it is determined whether or not a PM accumulation state in which a predetermined amount or more of PM has accumulated in the gas passage 14a of the EGR cooler 14 is determined. Specifically, when the differential pressure between the exhaust pressure P2 detected by the exhaust pressure sensor 26 and the supercharging pressure P1 detected by the intake pressure sensor 25 is greater than the specified differential pressure TH1, the PM accumulation state is assumed. judge. Alternatively, when the travel distance of the vehicle becomes longer than the specified distance TH2, it is determined that the PM accumulation state. Alternatively, when the engine operating time is longer than the specified time TH3, it is determined that the PM is in the accumulated state.

  If it is determined that the PM accumulation state is present (S10: YES), it is determined in subsequent step S20 whether or not a fuel injection cut described below is being executed. That is, when the engine speed NE is at or above a predetermined value (cut rotation speed) during deceleration travel, a fuel injection cut that stops fuel injection from the injector 30 is executed. Further, when the engine speed NE exceeds the upper limit value (for example, 7000 rpm) and the engine speed is high, or when the vehicle speed exceeds the upper limit value (for example, 180 km / h), the fuel is injected from the injector 30. A fuel injection cut is executed to stop the operation.

  When it is determined that it is not in the PM accumulation state (S10: NO), or when it is determined that the fuel injection cut is not being executed (S20: NO), in step S30, an EGR valve is set to suppress emission deterioration. The normal control 13a is executed as described above. On the other hand, when it is determined that the fuel is in the PM accumulation state and the fuel injection cut is being executed (S20: YES), the PM accumulated in the gas passage 14a in step S40 (PM removal control means (foreign matter removal control means)). PM removal control of the EGR valve 13a is executed according to the subroutine processing of FIG.

  First, in step S41 of FIG. 3, the EGR valve 13a is fully closed to operate so that the EGR flow rate becomes zero. In executing the fully closed operation, the EGR valve 13a is controlled so that the operating speed (valve closing speed) becomes a predetermined first speed V1. In addition, although the operating speed of the EGR valve 13a increases as the applied voltage to the electric motor 13b is increased, in the following description, the operating speed of the EGR valve 13a when the applied voltage is maximized is the maximum capability of the EGR valve 13a. Called velocity Vmax.

  In subsequent step S42, it is determined whether or not a predetermined time has elapsed since the EGR valve 13a is fully closed, and the fully closed operation in step S41 is executed until the predetermined time elapses, and it is determined that the predetermined time has elapsed. If this is the case (S42: YES), in the following step S43, the EGR valve 13a is fully opened and the EGR flow rate is maximized. In executing this full opening operation, control is performed so that the operating speed (opening speed) of the EGR valve 13a becomes a predetermined second speed V2. In the present embodiment, the second speed V2 is set to be faster than the first speed, and it is desirable to set the second speed V2 to the maximum capability speed Vmax. Further, it is desirable to set the second speed V2 so as to be faster than the operating speed (normal speed) of the EGR valve 13a in step S30.

  In subsequent step S44, it is determined whether or not a predetermined time has elapsed since the EGR valve 13a is fully opened, and the fully open operation in step S43 is executed until the predetermined time elapses, and it is determined that the predetermined time has elapsed. In (S44: YES), the subroutine processing of FIG. 3 in step S40 is terminated.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) In PM removal control according to the present embodiment, the EGR valve 13a is once fully closed and then fully opened. According to this, the EGR gas is dammed by the EGR valve 13a once in the fully closed state, and then the damped EGR gas flows into the gas passage 14a of the EGR cooler 14 all at once when the valve is fully opened. As a result, the instantaneous flow rate of EGR gas increases. That is, the PM accumulated in the gas passage 14a is removed by causing the EGR gas to flow through the gas passage 14a at once (increasing the instantaneous flow rate). Therefore, PM deposited on the EGR cooler 14 can be easily removed, and the above-described concerns about the decrease in the flow rate of EGR gas and the decrease in cooling efficiency can be solved.

  (2) Since the flow of EGR gas can be controlled to remove PM using the existing EGR valve 13a, increase in the number of parts required for PM removal can be suppressed, and PM can be removed during engine operation. Can be realized easily.

  (3) When performing PM removal control, the valve opening speed of the EGR valve 13a according to step S43 is set faster (or set to the maximum capacity speed Vmax) than the valve closing speed of the EGR valve 13a according to step S41. The instantaneous flow rate when the EGR gas blocked by the EGR valve 13a in the closed state flows to the EGR cooler 14 at once can be increased. Therefore, it is possible to more reliably remove the foreign matter with the EGR gas.

(Second Embodiment)
In the PM removal control of the first embodiment, the EGR valve 13a is once fully closed and then fully opened, so that EGR gas flows into the gas passage 14a all at once and PM is removed. In the embodiment, pressure pulsation is generated in the EGR gas by repeatedly opening and closing the EGR valve 13a at a predetermined cycle, and PM is removed by the pressure pulsation.

  FIG. 4 shows a processing procedure of PM removal control according to this embodiment, and the difference from FIG. 3 will be mainly described below. The hardware configuration of the engine intake / exhaust system and the like in this embodiment is the same as that of the first embodiment shown in FIG.

  First, the engine speed NE is acquired in step S45 of FIG. Next, in step S46, the opening / closing cycles t1, t2 (the predetermined cycle) and the opening / closing timing of the EGR valve 13a are calculated based on the acquired engine rotational speed NE. Then, in the following step S47, as shown in FIG. 5A, the EGR valve 13a is opened during the t1 period, and is closed during the t2 period, and these opening and closing operations are repeated at a cycle of t1 + t2. Also, the solid line in FIG. 5 (a) shows the change of the exhaust pressure in the upstream portion of the EGR pipe 10 upstream of the EGR valve 13a over time, and the valve is opened at the optimum timing when the exhaust pressure increases. The valve is closed at the optimal timing when the exhaust pressure is lowered.

  The exhaust pressure in the EGR pipe 10 pulsates in synchronization with the combustion cycle as shown by the solid line in FIG. In synchronization with this pulsation, the opening / closing valve periods t1, t2 and the opening / closing timing are calculated in step S46. Note that the alternate long and short dash line in FIG. 5A indicates the change in the exhaust pressure at the outlet portion (exhaust port portion) of the combustion chamber 12 in the exhaust pipe 18. The exhaust pressure change indicated by the solid line is shifted from the exhaust pressure change indicated by the alternate long and short dash line.

  Then, since the pulsation of the exhaust pressure also changes in accordance with the engine speed NE, in step S46, a map in which the relationship between the engine speed NE, the optimum opening / closing valve periods t1, t2 and the opening / closing timing is stored is used. With reference to the map, the open / close valve periods t1 and t2 and the open / close timing are calculated based on the engine speed NE.

  Next, in step S48, it is determined whether or not the opening / closing operation of the EGR valve 13a performed in step S47 has passed a predetermined time or more, or whether the opening / closing operation has been performed a predetermined number of times or more. If it is determined that the predetermined time has elapsed or the predetermined number of times has been performed (S48: YES), the subroutine processing of FIG. 4 in step S40 is terminated.

  Note that when the drive response of the EGR valve 13a is slow and switching between opening and closing cannot be performed in a short period t1, t2 as shown in FIG. 5A, the exhaust pressure is compared as shown in FIG. 5B. The optimal opening / closing valve periods t10 and t20 and the opening / closing timing may be set so that the valve is opened in the time region t10 where the exhaust pressure is relatively high and is closed in the time region t20 where the exhaust pressure is relatively low. For example, the integrated value of the exhaust pressure during the valve opening period t10 (the area of the hatched portion S1 in FIG. 5B) is the integrated value of the exhaust pressure during the valve closing period t20 (the halftone dot in FIG. 5B). The opening / closing valve periods t10 and t20 and the opening / closing timing may be set so as to be larger than the area of the portion S2.

  According to the embodiment described in detail above, the effect (2) is obtained and the following effect is obtained.

  (4) In the PM removal control according to the present embodiment, the EGR valve 13a is repeatedly opened and closed at a predetermined cycle t1 + t2, thereby causing a pressure pulsation in the EGR gas, and the PM accumulated in the gas passage 14a is removed by the pressure pulsation. Will be. Therefore, PM deposited on the EGR cooler 14 can be easily removed, and the above-described concerns about the decrease in the flow rate of EGR gas and the decrease in cooling efficiency can be solved.

(Third embodiment)
FIG. 6 is a diagram illustrating a hardware configuration of the intake / exhaust system according to the present embodiment. In FIG. 6, the same reference numerals as those in FIG. Explained.

  In the present embodiment, an intake / exhaust system having a configuration including a bypass pipe 15 and a switching device 16 described below is targeted. That is, a bypass pipe 15 that bypasses the EGR gas with respect to the EGR cooler 14 is provided in the EGR pipe 10 at a downstream portion of the EGR valve 13a. In addition, a switching device 16 that switches the flow of EGR gas between the EGR cooler 14 and the bypass pipe 15 is provided at a portion of the EGR pipe 10 upstream of the EGR cooler 14 and where the bypass pipe 15 branches. . The switching device 16 includes a switching valve 16a that switches between the inlet 10a to the EGR cooler 14 and the inlet 10b to the bypass pipe 15 in the EGR pipe 10, and an electric motor 16b that drives the switching valve 16a. Configured.

  Further, the switching valve 16a (distribution ratio adjusting valve) not only simply switches between the two inlets 10a and 10b, but also adjusts the opening degree at an intermediate opening position where both the inlets 10a and 10b are opened. Thus, the flow ratio of the flow rate for circulating EGR gas to the EGR cooler 14 and the flow rate for bypassing by the bypass pipe 15 is adjusted. As a result, the temperature of the EGR gas is adjusted at the portion where the bypass pipe 15 joins on the downstream side of the EGR cooler 14. According to this, it is possible to improve the NOX reduction effect by adjusting the temperature of the EGR gas to the optimum value and refluxing the EGR gas.

  Next, the processing procedure of PM removal control according to the present embodiment will be described with reference to FIG.

  First, in steps S10 and S20, as in the first embodiment shown in FIG. 2, it is determined whether or not it is in the PM accumulation state, and it is determined whether or not the fuel injection cut is being executed. When it is determined that the fuel is in the PM accumulation state and the fuel injection cut is being executed (S20: YES), the switching valve 16a is operated to the side where the EGR gas is circulated to the EGR cooler 14. That is, the switching valve 16a is operated so that the inlet 10a to the EGR cooler 14 is fully opened and the inlet 10b to the bypass pipe 15 is fully closed.

  In the subsequent step S40, the PM removal control of the EGR valve 13a is executed according to the subroutine processing of FIG. 3 or FIG. 4 in order to remove the PM accumulated in the gas passage 14a in the same manner as in the first embodiment shown in FIG. . That is, the operation of the EGR valve 13a is controlled so that the EGR gas flows through the gas passage 14a at once, or the pressure pulsation is generated in the EGR gas.

  On the other hand, when it is determined not to be in the PM accumulation state (S10: NO), or when it is determined that the fuel injection cut is not being executed (S20: NO), in step S300, in order to suppress emission deterioration. Normal control of the EGR valve 13a is executed in the same manner as in the first embodiment. Furthermore, in step S300, the opening degree of the switching valve 16a is feedback-controlled (normal control) so that the actual EGR gas temperature detected by the EGR temperature sensor 27 approaches the target gas temperature.

  According to the present embodiment described in detail above, even in the intake / exhaust system having a configuration including the bypass pipe 15 and the switching device 16, the same effects as those of the first and second embodiments can be obtained. .

(Fourth embodiment)
The present embodiment is directed to an intake / exhaust system having a configuration including a bypass pipe 15 and a switching device 16 as in the third embodiment shown in FIG. In the PM removal control of the third embodiment, the EGR valve 13a is controlled, and the EGR valve 13a is once fully closed and then fully opened or repeatedly opened and closed. On the other hand, in the PM removal control of this embodiment, the switching valve 16a is a control target, and the switching valve 16a is once fully closed and then fully opened or repeatedly opened and closed.

  In more detail using FIG. 8, first, in steps S10 and S20, as in the first embodiment shown in FIG. 2, it is determined whether or not it is in the PM accumulation state, and the fuel injection cut is being executed. It is determined whether or not there is. When it is determined that the fuel is in the PM accumulation state and the fuel injection cut is being executed (S20: YES), in the subsequent step S400 (PM removal control means (foreign matter removal control means)), the EGR valve 13a is Normal control of the EGR valve 13a is executed in the same manner as in the first embodiment in order to suppress emission deterioration. For the switching valve 16a, PM removal control similar to that in FIG. 3 such as once fully closed and then fully opened, or PM removal control similar to FIG. 4 such as repeated opening and closing is performed.

  On the other hand, when it is determined that it is not in the PM accumulation state (S10: NO), or when it is determined that the fuel injection cut is not being executed (S20: NO), in step S300, the third state shown in FIG. Similarly to the embodiment, normal control is performed on the EGR valve 13a and feedback control (normal control) is performed on the switching valve 16a.

  According to this embodiment described above in detail, the same effects as those of the first to third embodiments can be obtained, and the following effects can be obtained.

  (5) In the PM removal control according to the present embodiment, it is realized that the EGR gas is caused to flow into the gas passage 14a at once or the pressure pulsation is generated in the EGR gas by the operation of the switching valve 16a. Can perform normal control. Therefore, PM removal can be achieved while setting the EGR flow rate to an optimal flow rate in order to suppress the deterioration of emissions. In particular, when it is desired to execute PM removal when the fuel injection cut is not being executed, it is possible to suitably suppress the deterioration of emissions during execution of PM removal control.

(Fifth embodiment)
This embodiment is characterized in that step S25 (differential pressure increase control means) and step S26 described below with reference to FIG. 9 are added to the first embodiment shown in FIG.

  First, in steps S10 and S20, as in the first embodiment shown in FIG. 2, it is determined whether or not it is in the PM accumulation state, and it is determined whether or not the fuel injection cut is being executed. If it is determined that the fuel is in the PM accumulation state and the fuel injection cut is being executed (S20: YES), the differential pressure across the EGR cooler 14 is increased in the subsequent step S25 (differential pressure increase control means). Controls the operating state of the engine. Specifically, at least one of the variable vane 19d and the throttle valve 17a of the turbocharger 19 is controlled (differential pressure increase control) as follows.

  That is, the opening degree of the variable vane 19d during normal operation is determined based on the engine operating state such as the engine rotational speed NE and the engine load. When executing the PM removal control in step S40, prior to the execution. Thus, the opening degree of the variable vane 19d is controlled (differential pressure increase control) so that the opening degree is smaller than the opening degree during normal operation. According to this, the exhaust pressure, which is the pressure upstream of the EGR cooler 14, is increased, and consequently the differential pressure across the EGR cooler 14 is increased. It should be noted that the opening degree of the variable vane 19d during the differential pressure increase control is desirably set to the smallest opening degree in terms of increasing the front-rear differential pressure.

  Further, the opening of the throttle valve 17a during normal operation is determined based on the engine operating state such as the engine speed NE and the engine load. When executing the PM removal control in step S40, prior to the execution. Thus, the opening of the throttle valve 17a is controlled (differential pressure increase control) so that the opening is smaller than the opening during normal operation. According to this, the intake pressure that is the pressure on the downstream side of the EGR cooler 14 is reduced, and consequently, the differential pressure across the EGR cooler 14 is increased. In addition, it is desirable that the opening of the throttle valve 17a during the differential pressure increase control is set to be small so as to be the opening during the idling operation of the engine from the viewpoint of increasing the front-rear differential pressure.

  Next, in step S26, it is determined whether or not a predetermined time has elapsed since the execution of the differential pressure increase control is started, and the differential pressure increase control in step S25 is executed until the predetermined time elapses. If it is determined that the time has elapsed (S26: YES), in the subsequent step S40, PM removal control is executed according to the subroutine processing of FIG. 3 or FIG. 4 in the same manner as in the first embodiment shown in FIG.

  According to this embodiment described in detail above, the same effects as those of the first and second embodiments can be obtained, and the following effects can be obtained.

  (6) According to the present embodiment, the PM removal control is executed in a state where the differential pressure across the EGR cooler 14 is increased, so that it is possible to more reliably remove the deposited PM with the EGR gas. For example, when PM is removed by the pressure pulsation of the EGR gas described above, the pressure pulsation of the EGR gas is increased due to an increase in the differential pressure across the EGR cooler 14, so that the PM is easily removed. Further, in the case where PM is removed by increasing the instantaneous flow rate of EGR gas described above, the instantaneous flow rate of EGR gas is increased by increasing the differential pressure across the EGR cooler 14, so that PM is easily removed.

(Other embodiments)
The present invention is not limited to the description of the above-described embodiments, and the characteristic configurations of the respective embodiments may be arbitrarily combined. In addition, each of the above embodiments may be modified as follows.

  In the PM removal control according to the first embodiment, the EGR valve 13a is once fully closed and then fully opened, so that EGR gas flows to the EGR cooler 14 all at once, and PM is removed. As described above, when PM is removed by flowing EGR gas at a stroke, the opening operation may be performed toward the fully open position without operating the fully opened position. Further, the closing operation may be performed toward the fully closed position without operating to the front closing position. Moreover, you may make it operate-control (or open-activate) a fully-open state, without once making it a fully-closed state (or closing-operation).

  As shown in FIG. 1, in the intake / exhaust system having a configuration not including the bypass pipe 15, in the example of FIG. 1, the EGR flow rate adjustment device 13 is arranged on the upstream side of the EGR cooler 14. An intake / exhaust system in which 13 is disposed on the downstream side of the EGR cooler 14 may be the target.

  In step S41 in FIG. 3, the first speed V1 is set to be smaller than the maximum capacity speed Vmax, but the first speed V1 may be set to the maximum capacity speed Vmax in the same manner as the second speed V2. .

  Here, when the fuel injection is not cut, if the valve closing speed of the EGR valve 13a is set to the maximum capacity speed Vmax in step S41, there is a concern that PM in the exhaust gas increases. Therefore, it is desirable to solve the above-mentioned concern by setting the first speed V1 smaller than the maximum capacity speed Vmax.

  In the above embodiment, the present invention is applied to a self-ignition diesel engine, but may be applied to an ignition gasoline engine.

1 is a configuration diagram of an intake / exhaust system of an engine to which an internal combustion engine control device according to a first embodiment of the present invention is applied. The flowchart which shows the process sequence of PM removal control concerning 1st Embodiment. The flowchart which shows the subroutine processing of FIG. The flowchart which shows the process sequence of PM removal control concerning 2nd Embodiment of this invention. The figure explaining the opening-and-closing cycle and opening-and-closing timing of an EGR valve in PM removal control concerning a 2nd embodiment. The block diagram of the intake-exhaust system of an engine to which the internal combustion engine control apparatus concerning 3rd Embodiment of this invention was applied. The flowchart which shows the process sequence of PM removal control concerning 3rd Embodiment. The flowchart which shows the process sequence of PM removal control concerning 4th Embodiment of this invention. The flowchart which shows the process sequence of PM removal control concerning 5th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... EGR piping, 13a ... EGR valve (circulation flow rate adjustment valve (flow rate adjustment valve)), 14 ... EGR cooler, 15 ... Bypass piping, 16a ... Switching valve (flow rate adjustment valve (flow rate adjustment valve)), 17a ... Electric Throttle valve, 19 ... turbocharger (supercharger), 19d ... variable vane (capacity variable device), 29 ... ECU (internal combustion engine control device), S10 ... accumulation determination means, S25 ... differential pressure increase control means, S40, S400 ... PM removal control means (foreign matter removal control means).

Claims (14)

An EGR pipe for recirculating a part of the exhaust gas discharged from the internal combustion engine to the intake system of the internal combustion engine as EGR gas;
An EGR cooler that is provided in the EGR pipe and cools by exchanging heat with EGR gas;
A flow rate adjusting valve for variably controlling the flow area of the EGR pipe so as to adjust the flow rate of the EGR gas flowing through the EGR cooler;
Applied to an internal combustion engine comprising:
Deposition determination means for determining whether or not a predetermined amount or more of foreign matter has accumulated inside the EGR cooler;
Foreign matter removal control means for controlling the operation of the flow rate adjusting valve so as to remove the foreign matter by EGR gas flowing through the EGR cooler when it is determined that the foreign matter is accumulated.
An internal combustion engine control device comprising:   2. The internal combustion engine control device according to claim 1, wherein the flow rate adjusting valve is a circulating flow rate adjusting valve that adjusts a circulating flow rate of EGR gas to be recirculated to the intake system. A bypass pipe that bypasses the EGR gas to the EGR cooler is connected to the EGR pipe,
The flow rate adjustment valve adjusts a ratio of a flow rate for circulating the EGR gas to the EGR cooler and a flow rate for bypassing the bypass pipe so as to adjust a temperature of the EGR gas recirculated to the intake system. The internal combustion engine control device according to claim 1, wherein the internal combustion engine control device is a valve.   4. The foreign matter removal control means causes pressure pulsation in EGR gas by repeatedly opening and closing the flow rate adjusting valve so that EGR gas is circulated intermittently at a predetermined cycle. An internal combustion engine control device according to claim 1.   5. The internal combustion engine control device according to claim 4, wherein the foreign matter removal control means changes an opening / closing cycle of the flow rate adjusting valve according to a rotation speed of an output shaft of the internal combustion engine.   The internal combustion engine control device according to any one of claims 1 to 3, wherein the foreign matter removal control means increases the instantaneous flow rate of EGR gas by controlling the flow rate adjustment valve to the open side. .   7. The internal combustion engine controller according to claim 6, wherein the foreign matter removal control means makes the operating speed of the flow rate adjusting valve when controlling to the opening side faster than when controlling to the closing side.   8. The internal combustion engine control device according to claim 6, wherein the foreign matter removal control means sets the operating speed of the flow rate adjusting valve when controlling to the opening side to a maximum capability speed of the flow rate adjusting valve. .   9. A differential pressure increase control means for controlling an operating state of the internal combustion engine so as to increase a differential pressure across the EGR cooler prior to execution of the control by the foreign matter removal control means. The internal combustion engine control device according to any one of the above. The internal combustion engine is provided with an electric throttle valve that is operated by an electric actuator to adjust the intake air amount,
The said differential pressure increase control means reduces the intake pressure which is a pressure of the downstream of the said EGR cooler by controlling so that the opening degree of the said electric throttle valve may be made small. Internal combustion engine control device. The internal combustion engine includes a compressor impeller provided in an intake pipe, a turbine wheel provided in an exhaust pipe, a shaft connecting the compressor impeller and the turbine wheel, and exhaust fluid energy as rotational driving force of the shaft. A turbocharger is provided that has a variable capacity device that can change the rate of conversion.
The differential pressure increase control means increases the exhaust pressure, which is the pressure on the upstream side of the EGR cooler, by controlling the variable capacity device so as to increase the conversion ratio to the rotational driving force. Item 11. The internal combustion engine control device according to Item 9 or 10.   The control by the foreign matter removal control means is executed at the time of fuel injection cut for operating the internal combustion engine while stopping the injection of fuel to be used for combustion of the internal combustion engine. An internal combustion engine control device according to claim 1.   The accumulation determination means may be configured such that when the differential pressure across the EGR cooler is greater than a specified differential pressure, when the travel distance of a vehicle on which the internal combustion engine is mounted is longer than a specified distance, or the operation time of the internal combustion engine. The internal combustion engine control device according to any one of claims 1 to 12, wherein it is determined that the foreign matter is accumulated when the time becomes longer than a predetermined time. An internal combustion engine control device according to any one of claims 1 to 13,
At least one of the EGR pipe, the EGR cooler, and the flow rate adjustment valve;
An internal combustion engine control system comprising:

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