JP7287464B2 - Control method and control device for internal combustion engine - Google Patents

Description

The present invention relates to a control method and control apparatus for an internal combustion engine that has an EGR system and fills an intake passage with EGR gas when the internal combustion engine is temporarily stopped.

In JP2005-330886A, in an internal combustion engine equipped with an EGR system, when the internal combustion engine is temporarily stopped by idling stop, the EGR valve is opened, and the air sent from the cylinder during rotation due to inertia after the fuel supply is stopped is Introduction to the intake passage is disclosed (paragraphs 0029-0037).

The technique of JP2005-330886A is that the gas sent from the cylinder while the rotation due to inertia continues after stopping the supply of fuel by idling stop and flowing into the catalyst contains excess oxygen, resulting in an oxidizing atmosphere in the catalyst. It suppresses the formation of

In other words, the above technology focuses on the period after the fuel supply is stopped, and does not specifically assume the restart after the idle stop. There is a problem that the air (oxygen) through the cylinder flows into the catalyst unreacted during ranking or motoring. This is because when oxygen flows into the catalyst, the oxygen adsorbed on the catalyst is sufficiently processed, and the NOx (nitrogen oxide) purification rate of the catalyst decreases until the oxygen storage state is eliminated.

Furthermore, since it results in an increase in the input amount of the reducing agent required to eliminate the oxygen storage state, there is concern that it may cause deterioration of exhaust gas.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control method and control apparatus for an internal combustion engine in which the above problems are taken into account.

In one aspect, the EGR system includes an EGR valve interposed in the EGR passage so as to be able to adjust the effective cross-sectional area of the EGR passage, and fills the intake passage with EGR gas when the internal combustion engine is temporarily stopped. A method of controlling an engine is provided. In the method according to the present embodiment, the control device closes the intake shutter valve provided upstream of the connection point of the EGR passage in the intake passage when a predetermined restart condition is satisfied after the internal combustion engine is stopped. to reduce the effective cross-sectional area of the intake passage, and after opening the EGR valve, cranking of the internal combustion engine is started. Cranking is continued and the intake shutter valve is kept closed until the rotational speed of the internal combustion engine increases from the start of cranking until it reaches a predetermined rotational speed higher than before the start of cranking. . Then, after the number of rotations of the internal combustion engine reaches a predetermined number of rotations, the intake shutter valve is opened to allow the substantial introduction of air into the cylinder, and the EGR valve is closed and a predetermined time elapses. to resume combustion.

In another aspect, a control system for an internal combustion engine is provided.

FIG. 1 is a schematic diagram showing the overall configuration of an internal combustion engine according to one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the state of the internal combustion engine according to the embodiment when the engine is stopped after fuel cut. FIG. 3 is an explanatory diagram showing the operation of the internal combustion engine according to the embodiment during fuel cut recovery (during cranking). FIG. 4 is an explanatory diagram showing the operation of the internal combustion engine according to the above embodiment during fuel cut recovery (after the engine speed is increased). FIG. 5 is an explanatory diagram showing the operation of the internal combustion engine according to the above embodiment during fuel cut recovery (after the intake delay period has elapsed). FIG. 6 is a flow chart showing the contents of control during fuel cut of the internal combustion engine according to the embodiment. FIG. 7 is a flow chart showing the contents of control during fuel cut recovery in the internal combustion engine according to the embodiment. FIG. 8 is an explanatory diagram showing the contents of the intake delay time elapse determination process of the control during fuel cut recovery. FIG. 9 is a time chart for explaining the operation of the internal combustion engine from when the engine is stopped due to fuel cut to when it is restarted due to fuel cut recovery.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Overall Configuration of Internal Combustion Engine)
FIG. 1 shows the overall configuration of an internal combustion engine 1 according to one embodiment of the invention.

An internal combustion engine (hereinafter referred to as "internal combustion engine", sometimes simply referred to as "engine") 1 according to the present embodiment is mounted on a vehicle and constitutes a drive source that generates driving force for the vehicle. The internal combustion engine 1 can be configured as a single vehicle drive source, or can be configured in cooperation with an electric motor or a motor generator. The drive source in the latter case may be either series or parallel.

The internal combustion engine 1 has a turbocharger 2 . The supercharger 2 includes an intake compressor 21 and an exhaust turbine 22. The intake compressor 21 is installed in the intake passage 11 of the internal combustion engine 1, and the exhaust turbine 22 is installed in the exhaust passage 15, respectively. The intake compressor 21 and the exhaust turbine 22 are coupled by a shaft 23, and the rotation of the exhaust turbine 22 is transmitted to the intake compressor 21 via the shaft 23, causing the intake compressor 21 to rotate.

In the intake passage 11, an air cleaner 12 is installed upstream of the intake compressor 21 with respect to the flow of intake air, a throttle valve 13 is installed downstream, and a fuel injection valve 14 is installed further downstream. . The air cleaner 12 removes foreign substances contained in the air taken into the intake passage 11 from the atmosphere, and the throttle valve 13 enlarges the substantial cross-sectional area (hereinafter sometimes referred to as "effective cross-sectional area") of the intake passage 11. Or reduce it to adjust the amount of air taken into the cylinder. The fuel injection valve 14 is arranged so as to be able to supply fuel into the cylinder, and in this embodiment, is embedded in the cylinder head and injects fuel toward the intake port.

On the other hand, in the exhaust passage 15, catalytic converters 16 and 17 are installed downstream of the exhaust turbine 22 with respect to the flow of exhaust gas, and a muffler 18 is installed further downstream. In this embodiment, an example is shown in which two catalytic converters 16 and 17 having the same type of catalyst with different capacities are provided. may be As a type of catalyst, a three-way catalyst can be exemplified, but it is also possible to adopt other catalysts having oxygen storage capacity. Furthermore, there may be only one catalytic converter (for example, catalytic converter 16), or there may be three or more.

The internal combustion engine 1 further includes an EGR system 3 that recirculates exhaust gas after combustion as EGR gas into the cylinder.

The EGR system 3 includes an EGR passage 31 connected between the intake passage 11 and the exhaust passage 15 . In the present embodiment, the EGR passage 31 is located downstream of the exhaust turbine 22 in the exhaust passage 15 , specifically, a portion (branch point Pd) between the two catalytic converters 16 and 17 and the intake passage 11 Among them, the portion (connection point Pm) on the upstream side of the intake compressor 21 is connected between them. An EGR cooler 32 and an EGR valve 33 are installed in the EGR passage 31 as elements other than the EGR passage 31 that constitute the EGR system. The EGR cooler 32 cools the exhaust gas branched from the exhaust passage 15, and the EGR valve 33 expands or reduces the substantial cross-sectional area (effective cross-sectional area) of the EGR passage 31 so that the exhaust gas recirculated into the cylinder ( EGR gas) is adjusted.

In addition to the above, the internal combustion engine 1 includes an intake shutter valve 41 installed in the intake passage 11 upstream of the connection point Pm of the EGR passage 31 with respect to the flow of intake air. The intake shutter valve 41 is configured such that the effective cross-sectional area of the intake passage 11 can be adjusted. It is configured as an admission valve (hereinafter collectively referred to as “admission valve”) that increases the differential pressure between the inlet side (branch point Pd) and the outlet side (connection point Pm) of 31 . The "intake shutter valve" according to this embodiment is configured as the admission valve 41 so that the degree of opening can be adjusted stepwise or continuously. may be possible. An example of such a case is a case where the operation of the EGR system does not require an expansion of the differential pressure. For example, the maximum opening degree is the opening degree at the time of full opening (fully open opening degree), and the minimum opening degree is the opening degree at the time of fully closing (fully closed opening degree). Similarly to the admission valve 41, the EGR valve 33 should not only be configured so that the degree of opening can be adjusted stepwise or continuously, but also be configured to be switchable only between the maximum degree of opening and the minimum degree of opening. is possible.

(Basic configuration of control system)
The operation of the entire internal combustion engine 1 including the EGR system 3 is controlled by an engine controller 101 .

The engine controller 101 is configured as an electronic control unit, and is composed of a microcomputer having a central processing unit (CPU), various storage devices such as RAM and ROM, an input/output interface, and the like.

The engine controller 101 receives detection signals from various operating state sensors that detect the operating state of the internal combustion engine 1, and executes predetermined calculations based on the detected operating state to determine the fuel injection amount of the internal combustion engine 1, Set the fuel injection timing, ignition timing, etc.

In the present embodiment, as driving state sensors, an accelerator sensor 111 that detects an operation amount of an accelerator pedal by a driver (hereinafter referred to as "accelerator opening") APO, a rotation speed sensor 112 that detects a rotation speed NE of the internal combustion engine 1, A cooling water temperature sensor 113 for detecting the temperature TW of the engine cooling water is provided, as well as an air flow meter, a throttle sensor, an air-fuel ratio sensor and the like (not shown).

(Overview of fuel cut control and fuel cut recovery control)
In this embodiment, the supply of fuel to the internal combustion engine 1 is temporarily stopped when a predetermined fuel cut condition is satisfied while the engine controller 101 is operating, in other words, while the start switch (not shown) is turned on. fuel cut Prior to stopping the supply of fuel, control is performed to fill the intake passage 11 downstream of the admission valve 41 and the inside of the cylinder with EGR gas. This is done by closing the admission valve 41 to reduce the effective cross-sectional area of the intake passage 11 compared to before the fuel cut condition is satisfied, and by opening the EGR valve 33 to allow the cylinder of the internal combustion engine 1 to communicate with the EGR passage 31. It can be realized by circulating EGR gas between them.

After that, when a predetermined fuel cut recovery condition is satisfied, the supply of fuel to the internal combustion engine 1 is resumed, and the fuel cut recovery for restarting the internal combustion engine 1 is performed.

Here, when the admission valve 41 is opened at the same time as the cranking of the internal combustion engine 1 is started after the fuel cut recovery condition is satisfied, that is, the cranking is started and the admission valve 41 is opened. are performed at the same time, the air (oxygen) introduced into the cylinder through the admission valve 41 is exhausted until the engine speed rises to a predetermined speed and combustion is allowed to resume. The unreacted gas is delivered (that is, scavenged) to the passage 15 and flows into the catalytic converter 16 . When oxygen flows into the catalyst, the NOx (nitrogen oxide) purification rate of the catalyst decreases until the oxygen stored in the catalyst is sufficiently processed after combustion is resumed and the oxygen storage state is eliminated. . Furthermore, since it results in an increase in the input amount of the reducing agent required to eliminate the oxygen storage state, it can also be a cause of worsening the exhaust gas. Elimination of the oxygen storage state is generally achieved, for example, by operating the fuel injection valve 14 to temporarily increase the air-fuel ratio of the exhaust above the theoretical value (rich spike operation).

Therefore, in this embodiment, when the fuel cut recovery condition is satisfied, the admission valve 41 is kept closed after cranking is started, and the EGR gas is circulated between the cylinder interior and the EGR passage 31 to Suppress the introduction of air inside. Then, when the engine speed has sufficiently increased to reach a predetermined speed at which combustion is allowed to resume, the admission valve 41 is opened to start introducing air. Furthermore, after the introduction of air is started, until the introduced air reaches the intake port and the EGR gas in the intake passage 11 downstream of the admission valve 41 is replaced with air, execution of fuel cut recovery is suspended and EGR is performed. After the replacement of gas with air is completed, it is carried out to restart the supply of fuel to the internal combustion engine 1 and to restart combustion.

(Basic operation of fuel cut recovery)
FIGS. 2 to 5 show, in chronological order, the operation of the internal combustion engine 1 according to the present embodiment from when it is stopped due to fuel cut to when it is restarted due to fuel cut recovery. In each of FIGS. 2 to 5, thick dotted lines conceptually indicate the behavior of exhaust gas or EGR gas, and the directions of arrows indicate the presence or absence of flow and its direction. Furthermore, FIG. 9 shows the operation of the internal combustion engine 1 from before the fuel cut to after the fuel cut recovery by means of a time chart. In FIG. 9, time Toff indicates when the accelerator is off, time Treq indicates when the fuel cut condition is satisfied, and time Tcut indicates when fuel cut is executed. Furthermore, the time Trcv indicates when the fuel cut recovery condition is satisfied, and the time Trst indicates when the fuel cut recovery is executed. The operation of the internal combustion engine 1 will now be described with reference to FIGS. 2 to 5 with appropriate reference to FIG.

In the present embodiment, on the premise that the internal combustion engine 1 alone constitutes the driving source of the vehicle, a case of so-called deceleration fuel cut, in which fuel is cut during deceleration of the vehicle, will be described. ) is not limited to this, and may be, for example, while the vehicle is temporarily stopped, such as while waiting for a traffic light. Further, the deceleration fuel cut may be performed during so-called coast driving from deceleration to stop. In this sense, "fuel cut" according to the present embodiment refers to general operations for temporarily stopping the supply of fuel to the internal combustion engine 1 (in other words, while the engine controller 101 is operating). It also includes the case of so-called idle stop. Furthermore, the case where the internal combustion engine 1 cooperates with the electric motor to constitute the drive source may include the case of switching to a mode in which the vehicle runs only with the electric motor.

FIG. 2 shows the state when the engine is stopped after fuel cut (time Tstp in FIG. 9). In addition to the exhaust passage 15 and the EGR passage 31, the intake passage 11 downstream of the admission valve 41 is also filled with EGR gas due to the gas replacement performed when the fuel is cut. The admission valve 41 continues to be closed after the fuel cut, and the EGR valve 33 is in an open state. In this embodiment, the admission valve 41 is fully closed and the EGR valve 33 is fully opened. By closing the admission valve 41, introduction of air downstream thereof is suppressed.

FIG. 3 shows the state during cranking after the fuel cut recovery condition is established (time Trcv to Trev). With the start of cranking, the rotational speed of the internal combustion engine 1 increases. Since the admission valve 41 is in the fully closed position and the EGR valve 33 is in the fully open position, the introduction of EGR gas from the exhaust passage 15 to the intake passage 11 via the EGR passage 31 is promoted, and the inside of the cylinder and the EGR EGR gas circulates between the passages 31 . The throttle valve 13 is adjusted so as to keep the fully closed state when the power of the engine controller 101 is turned off. retained. Here, when the EGR gas filled in the intake passage 11 is sucked into the cylinder during fuel cut and the engine speed during cranking, which will be described below, sufficiently increases before it is discharged, the EGR valve 33 may be closed to prevent the EGR gas from circulating.

FIG. 4 shows the state after the engine speed has sufficiently increased by cranking (time Trev to Trst). The admission valve 41 is opened in order to replace the EGR gas filled in the intake passage 11 with air in order to prepare for the restart of combustion. At the same time, the EGR valve 33 is closed to prevent new EGR gas from being introduced into the intake passage 11 . In this embodiment, the admission valve 41 is fully opened and the EGR valve 33 is fully closed. As a result, the EGR gas that was in the intake passage 11 at the time when the fuel cut recovery condition was satisfied is sent to the exhaust passage 15 by the air, and the air is introduced into the cylinder. When the air reaches the intake port, it can be considered that the replacement with air is completed. In FIG. 4, a thick dotted line with an arrow indicates the behavior of EGR gas, and a two-dot chain line with an arrow indicates the behavior of air.

FIG. 5 shows the state during execution of fuel cut recovery (time Trst). After the admission valve 41 is opened, the supply of fuel to the internal combustion engine 1 is resumed when the air passes through the admission valve 41 and reaches the intake port, in other words, when the intake delay period ΔTdly has elapsed. to resume combustion.

(Explanation by flow chart)
6 and 7 show the operation of the engine controller 101 by means of flowcharts, with FIG. 6 showing the operation related to fuel cut control and FIG. 7 showing the operation related to fuel cut recovery control. The engine controller 101 is programmed to execute fuel cut control when a predetermined fuel cut condition is satisfied, and to execute fuel cut recovery control when a predetermined fuel cut recovery condition is satisfied after execution of fuel cut. ing.

In the flow chart shown in FIG. 6, in S101, it is determined whether or not the accelerator is off. If the accelerator pedal is completely returned or in a position close to it and the accelerator is off, the process proceeds to S102, and if not, the process proceeds to S108.

In S102, it is determined whether or not the fuel cut condition is satisfied. In this embodiment, the fuel cut condition is that the rotational speed of the internal combustion engine 1 is equal to or higher than a predetermined rotational speed when the accelerator is off for a predetermined time or longer, and the brake is applied by the driver. shall be deemed to have been established. If the fuel cut condition is satisfied, the process proceeds to S103, and if not satisfied, the processes of S101 and S102 are repeated.

Here, in a hybrid vehicle that is equipped with a battery and that can generate a driving force with an electric motor fed by the battery, if the state of charge SOC of the battery has a margin, even if the accelerator is on. A fuel cut may be performed to automatically stop the internal combustion engine 1 . In this case, as the processing of S101 and S102, based on the state of charge of the battery and the degree of accelerator opening, it is determined whether or not the automatic stop condition of the internal combustion engine 1 (that is, the EV driving mode condition) as the fuel cut condition is established. Is possible.

In S103, the admission valve 41 is closed (specifically, fully closed).

In S104, the EGR valve 33 is opened (specifically, fully opened). This promotes circulation of EGR gas between the cylinder and the EGR passage 31 .

In S105, it is determined whether or not the EGR gas transportation delay time has elapsed. The transportation delay time is a time corresponding to the transportation delay of EGR gas from the connection point Pm of the EGR passage 31 to the intake port after the admission valve 41 is closed. It is possible to estimate based on the operating state of the engine 1 . Similar to the estimation of the intake delay period ΔTdly, which will be described later, the flow rate of EGR gas passing through the intake valve per unit time (intake valve passing flow rate) is integrated to calculate the volume passing through the intake valve (intake valve passing volume). Then, when this reaches a predetermined volume corresponding to the volume of the intake passage 11, it is estimated that the transportation delay time has elapsed. If the transportation delay time has elapsed, the process proceeds to S107, and if not, the process proceeds to S106.

In S106, it is determined whether or not the fuel cut cancellation condition is satisfied. The fuel cut cancellation condition is satisfied, for example, when the accelerator pedal is depressed while waiting for the transportation delay time to pass, and the fuel supply is continued. If the fuel cut cancellation condition is satisfied, the process proceeds to S108, and if not satisfied, the process returns to S105 and continues to wait for the transportation delay time to elapse.

In S107, a fuel cut is executed. Specifically, the operation of the fuel injection valve 14 is stopped and the supply of fuel to the internal combustion engine 1 is stopped. Along with this, the operation of the ignition plug (not shown) is also stopped.

In S108, normal fuel injection control is executed to continue the supply of fuel to the internal combustion engine 1.

Moving on to the flowchart shown in FIG. 7, in S201, it is determined whether or not the fuel cut recovery condition is satisfied. In this embodiment, the fuel cut recovery condition is determined to be satisfied when the brake operated by the driver is released by the brake pedal being fully returned or returned to a state close to it. be. If the fuel cut recovery condition is satisfied, the process proceeds to S202, and if not satisfied, the process of S201 is repeated.

In the hybrid vehicle described above, instead of the above, the fuel cut recovery condition (that is, the internal combustion engine 1 It is possible to determine that the restart condition) has been met.

In S202, the admission valve 41 is closed (specifically, fully closed). In this embodiment, since the admission valve 41 is already closed when the fuel is cut, the closed state is continued.

In S203, the EGR valve 33 is opened (specifically, fully opened). As with the admission valve 41, the fuel cut state (valve open state) is maintained.

In S204, cranking of the internal combustion engine 1 is started. Cranking (sometimes called "motoring") is by an electric motor, such as an ISG (Integrated Starter Generator). When the internal combustion engine 1 cooperates with an electric motor or a motor generator to form a drive source, cranking can be performed by these rotating electric machines. Here, since the admission valve 41 is in the closed state and the EGR valve 33 is in the open state, the exhaust gas in the exhaust passage 15 flows through the branch point Pd in the downstream direction of the exhaust passage 15 during cranking. , but is guided to the intake passage 11 via the EGR passage 31 .

In S205, it is determined whether or not the rotation speed of the internal combustion engine 1 has reached a predetermined rotation speed. If the predetermined number of revolutions has been reached, the process proceeds to S206, and if not, the cranking is continued and the predetermined number of revolutions is reached.

In S206, the admission valve 41 is opened (for example, fully opened). This allows air to pass through the admission valve 41 and the connection point Pm and be introduced into the cylinder.

In S207, the EGR valve 33 is closed (for example, fully closed). As a result, the introduction of EGR gas into the intake passage 11 is blocked, and as the introduction of air through the admission valve 41 progresses, the gas occupying the intake passage 11 is replaced from the EGR gas by air.

In S208, it is determined whether or not the intake delay time ΔTdly has elapsed. The intake delay time ΔTdly refers to the time corresponding to the air transport delay from the time the admission valve 41 is opened until the air passing through the admission valve 41 reaches the intake port via the connection point Pm. It is possible to make a determination as to whether or not the internal combustion engine 1 has performed by estimation based on the operating state of the internal combustion engine 1 . If the intake delay time ΔTdly has passed, the process proceeds to S209.

FIG. 8 shows the principle of determination of progress in the case of estimation.

As shown in FIG. 8(a), the flow rate of air passing through the intake valve (intake valve passing flow rate) is given for each opening degree of the throttle valve 13 (hereinafter referred to as "throttle opening degree") THO. It is possible to predetermine the degree THO as a function of the engine speed NE, eg as a monotonically increasing function. Then, the intake valve passage volume of air is calculated by integrating the intake valve passage flow rate. At (time T1), it is determined that the intake delay time ΔTdly has elapsed.

Whether or not the transportation delay time ΔTdly has elapsed can be determined not only by such estimation but also by actual measurement using a sensor. For example, in the intake passage 11, a gas state sensor (for example, an oxygen concentration sensor) is installed at a position near the combustion chamber or the intake port, and after the admission valve 41 is opened, the gas detected by the gas state sensor It is determined that the intake delay time ΔTdly has elapsed when a behavior indicating arrival of air occurs in the state. Such a behavior can be exemplified by an increase in oxygen concentration above a predetermined concentration in the case of an oxygen concentration sensor. In this sense, the air transportation delay is defined as "the delay required for the gas occupying the intake passage downstream of the intake shutter valve to be replaced with air from EGR gas" or "the air occupying the cylinder after the intake shutter valve is opened ( oxygen) rises and reaches a predetermined value".

In S209, fuel cut recovery is executed, fuel supply by the fuel injection valve 14 is restarted, and the internal combustion engine 1 is started.

(Description of Action and Effect)
In this embodiment, the engine controller 101 constitutes a "control device for an internal combustion engine". The internal combustion engine 1 and its control device according to this embodiment have the above configurations, and the effects obtained by this embodiment will be described below.

First, when the internal combustion engine 1 is restarted after being temporarily stopped, the admission valve 41 is maintained in a closed state while the cranking of the internal combustion engine 1 is continued, so that air (oxygen) is admitted. It is possible to prevent the gas from flowing into the intake passage 11 downstream of the valve 41, passing through the cylinder unreacted, and flowing into the catalyst. As a result, it is possible to avoid the formation of an excessively oxidizing atmosphere in the catalyst and the deterioration of the purification rate of NOx (nitrogen oxides).

Furthermore, by suppressing the formation of an oxidizing atmosphere in the catalyst, it is possible to reduce the input amount of the reducing agent required to eliminate the oxygen storage state, thereby improving fuel efficiency.

Second, after the start of cranking, the rotation speed of the internal combustion engine 1 increases, and after reaching a predetermined rotation speed, the supply of fuel is restarted and combustion is restarted. It is possible to restart. Here, even if it takes time for the rotation speed of the internal combustion engine 1 to reach the predetermined rotation speed, the deterioration of the NOx purification rate can be suppressed by suppressing the inflow of air into the catalyst.

Third, at the start of cranking, the EGR valve 33 is opened to expand the effective cross-sectional area of the EGR passage 31, thereby circulating EGR gas between the cylinder and the EGR passage 31 while cranking is continued. As a result, the load on the cranking motor can be reduced, and the inflow of air to the catalyst can be suppressed more reliably.

Fourthly, after the number of rotations of the internal combustion engine 1 reaches a predetermined number of rotations, the intake of air through the admission valve 41 is permitted, and combustion is restarted after a predetermined period of time has passed. It is possible to avoid restarting combustion while EGR gas accounts for a high proportion of the charged gas, suppress the emission of unburned fuel due to unstable combustion, and achieve a reliable restart. becomes.

Here, after the admission valve 41 is opened, combustion is resumed after waiting for the passage of the intake delay period ΔTdly indicating the arrival of air to the intake port, so that the proper intake delay period ΔTdly can be set. In addition, it is possible to avoid the deterioration of exhaust gas caused by the inflow of air into the catalyst due to the delayed resumption of combustion, or the supply of fuel in a state where the resumption of combustion is early and the ignition is unstable.

Fifth, by installing the catalytic converter 16 in the exhaust passage 15 upstream of the branch point Pd of the EGR passage 31, the gas discharged from the cylinder passes through the catalyst before reaching the branch point Pd. It will be. According to the present embodiment, in such a situation, it is possible to suppress the inflow of air into the catalyst and reliably suppress the deterioration of the exhaust gas.

Sixthly, the EGR system 3 recirculates the exhaust gas flowing through the exhaust passage 15 downstream of the exhaust turbine 22 to the intake passage 11 upstream of the intake compressor 21 as EGR gas. (that is, the admission valve 41) makes it possible to realize an intake shutter valve, thereby suppressing an increase in the number of parts.

The control according to the present embodiment can be applied not only to a so-called low-pressure EGR system, but also to a high-pressure EGR system. Specifically, when a catalyst is provided on the upstream side of the exhaust turbine in the exhaust passage, the exhaust passage on the downstream side of the catalyst and the intake passage on the downstream side of the throttle valve are connected by an EGR passage to By closing the throttle valve when restarting after cutting, the introduction of air into the intake passage is suppressed.

Furthermore, in an internal combustion engine not equipped with a supercharger, an EGR passage connects the exhaust passage downstream of the catalyst and the intake passage downstream of the throttle valve, and the throttle valve functions as an "intake shutter valve". can be embodied.

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. not on purpose. Various changes and modifications can be made to the above-described embodiment within the scope of matters described in the claims.

Claims (5)

A control method for an internal combustion engine comprising an EGR system having an EGR valve interposed in an EGR passage so as to be able to adjust the effective cross-sectional area of the EGR passage, and filling the intake passage with EGR gas when the internal combustion engine is temporarily stopped. and
The controller is
After the internal combustion engine stops, when a predetermined restart condition is satisfied,
closing an intake shutter valve provided upstream of a connection point of the EGR passage in the intake passage to reduce an effective cross-sectional area of the intake passage;
After opening the EGR valve, starting cranking of the internal combustion engine;
A state in which the cranking is continued and the intake shutter valve is closed until the rotational speed of the internal combustion engine increases from the start of the cranking and reaches a predetermined rotational speed higher than before the start of the cranking. to maintain
After the number of rotations of the internal combustion engine reaches the predetermined number of rotations, the intake shutter valve is opened to allow substantial introduction of air into the cylinder, and a predetermined time has passed since the EGR valve was closed. wait to resume combustion,
A control method for an internal combustion engine. A control method for an internal combustion engine according to claim 1, comprising:
maintaining the intake shutter valve at a minimum opening and maintaining the EGR valve at a maximum opening during the cranking;
A control method for an internal combustion engine. A control method for an internal combustion engine according to claim 1 or 2,
The internal combustion engine includes an exhaust purification catalyst installed upstream of a branch point of the EGR passage from the exhaust passage in the exhaust passage,
A control method for an internal combustion engine. The method of controlling an internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine comprises a supercharger,
The EGR system causes the exhaust gas flowing through the exhaust passage downstream of the exhaust turbine of the supercharger to recirculate as the EGR gas to the intake passage upstream of the intake compressor of the supercharger.
A control method for an internal combustion engine. An EGR valve is provided in the EGR passage so as to be able to adjust the effective cross-sectional area of the EGR passage, and the intake passage and the exhaust passage are connected to each other through the EGR passage so as to be in fluid communication with each other through the EGR passage. , an EGR system that recirculates the exhaust gas after combustion as EGR gas into the cylinder;
an intake shutter valve installed upstream of a connection point of the EGR passage in the intake passage and capable of adjusting an effective cross-sectional area of the intake passage. and
filling the intake passage with EGR gas when the internal combustion engine is temporarily stopped;
After the internal combustion engine stops, when a predetermined restart condition is satisfied,
closing the intake shutter valve to reduce the effective cross-sectional area of the intake passage;
After opening the EGR valve, starting cranking of the internal combustion engine;
continuing the cranking and maintaining the intake shutter valve in a closed state from the start of the cranking until the rotational speed of the internal combustion engine reaches a predetermined rotational speed;
After the number of rotations of the internal combustion engine reaches the predetermined number of rotations, the intake shutter valve is opened to allow substantial introduction of air into the cylinder, and a predetermined time has passed since the EGR valve was closed. wait to resume combustion,
A control device for an internal combustion engine.

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