WO2021001670A1

WO2021001670A1 - Control method and control device for internal combustion engine

Info

Publication number: WO2021001670A1
Application number: PCT/IB2019/000646
Authority: WO
Inventors: 越後亮
Original assignee: 日産自動車株式会社; ルノーエス．ア．エス．
Priority date: 2019-07-04
Filing date: 2019-07-04
Publication date: 2021-01-07
Also published as: JP7287465B2; JPWO2021001670A1

Abstract

The present invention discloses a control method for an internal combustion engine in which exhaust gas after combustion is circulated inside a cylinder as EGR gas. The control method involves determining whether a fuel cut condition has been established for performing a fuel cut to temporarily stop the supply of fuel to the internal combustion engine, and when the fuel cut condition is established, closing an intake shutter valve installed on an upstream side in an intake passage from a connection point of an EGR passage, reducing the effective cross-sectional area of the intake passage compared to that before the establishment of the fuel cut condition, and furthermore, after the intake shutter valve is closed, continuing the combustion inside the cylinder during a delay in the transport of the EGR gas from the connection point of the EGR passage to an intake port of the internal combustion engine.

Description

Internal combustion engine control method and control device

The present invention relates to a control method and a control device for an internal combustion engine provided with an EGR system and replacing the gas occupying the intake passage with EGR gas when fuel is cut.

In the JP2015-068274A, in an internal combustion engine equipped with an EGR system, the intake shutter valve and the exhaust shutter valve are closed when the fuel is cut to temporarily stop the supply of fuel to the internal combustion engine, and the exhaust passage, the EGR passage and the intake passage are changed. It is disclosed to replace the occupying gas with EGR gas (paragraph 0047).

In the technology of JP2015-068274A, when the intake shutter is closed and the fuel supply is stopped at the same time after the fuel cut condition is satisfied, that is, the intake shutter valve is closed and the fuel supply to the internal combustion engine is stopped. If you do and at the same time, the following problems will occur.

Until the gas occupying the intake passage downstream of the intake shutter valve is replaced by EGR gas, the air (oxygen) in the intake passage is sent from the cylinder to the exhaust passage unreacted and becomes a catalyst provided in the exhaust passage. It is to flow in. When oxygen flows into the catalyst, the oxygen adsorbed on the catalyst is sufficiently processed when restarting after the fuel is cut, and the purification rate of NOx (nitrogen oxide) by the catalyst is until the oxygen storage state is cleared. Is reduced.

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

An object of the present invention is to provide a control method and a control device for an internal combustion engine in consideration of the above problems.

In one aspect, an EGR system is provided, and a control method for an internal combustion engine is provided in which exhaust gas after combustion is returned as EGR gas into a cylinder. The method according to this embodiment determines whether or not the fuel cut condition for performing the fuel cut for temporarily stopping the supply of fuel to the internal combustion engine is satisfied, and when the fuel cut condition is satisfied, among the intake passages, Close the intake shutter valve installed on the upstream side of the connection point of the EGR passage. As a result, the effective cross-sectional area of the intake passage is reduced compared to before the fuel cut condition is satisfied, and after the intake shutter valve is closed, the EGR gas from the connection point of the EGR passage to the intake port of the internal combustion engine Continue combustion in the cylinder during transport delays.

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

FIG. 1 is a schematic view showing an overall configuration of an internal combustion engine according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the operation of the internal combustion engine according to the same embodiment at the time of fuel cut (during constant speed running before the start of deceleration). FIG. 3 is an explanatory diagram showing the operation of the internal combustion engine according to the same embodiment at the time of fuel cut (after the start of deceleration and before the establishment of the fuel cut condition). FIG. 4 is an explanatory diagram showing the operation of the internal combustion engine according to the same embodiment at the time of fuel cut (after the fuel cut condition is satisfied). FIG. 5 is an explanatory diagram showing the operation of the internal combustion engine according to the same embodiment at the time of fuel cut (after execution of fuel cut). FIG. 6 is a flowchart showing the content of control of the internal combustion engine according to the same embodiment at the time of fuel cut. FIG. 7 is a flowchart showing the content of control of the internal combustion engine according to the same embodiment at the time of fuel cut recovery. FIG. 8 is an explanatory diagram showing the contents of the transportation delay time lapse determination process of the control at the time of fuel cut. FIG. 9 is an explanatory diagram of the operation at the time of fuel cut by a time chart.

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 an embodiment of the present invention.

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

The internal combustion engine 1 includes a turbocharger 2. The supercharger 2 includes an intake compressor 21 and an exhaust turbine 22, and the intake compressor 21 is interposed in the intake passage 11 of the internal combustion engine 1, and the exhaust turbine 22 is interposed in the exhaust passage 15. 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 to rotate the intake compressor 21.

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

On the other hand, in the exhaust passage 15, the

catalytic converters

16 and 17 are installed on the downstream side of the exhaust turbine 22 with respect to the flow of exhaust gas, and the muffler 18 is installed further on the downstream side thereof. In the present embodiment, an example including two

catalytic converters

16 and 17 having the same type of catalyst having different capacities is shown, but the catalysts contained in the

catalytic converters

16 and 17 may be of different types or have the same capacity. It may be. A three-way catalyst can be exemplified as the type of catalyst, but other catalysts having oxygen storage capacity can also be adopted. Further, the number of catalytic converters may be only one (for example, the catalytic converter 16), or may be three or more.

The internal combustion engine 1 further includes an EGR system 3 that recirculates the 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, and the intake passage 11 and the exhaust passage 15 are connected to each other by the EGR passage 31 so that fluid can communicate with each other. In the present embodiment, the EGR passage 31 is the portion of the exhaust passage 15 downstream of the exhaust turbine 22, specifically, the portion between the two

catalytic converters

16 and 17, (branch point Pd), and the intake passage 11. Of these, it is connected between the portion on the upstream side (connection point Pm) of the intake compressor 21. In the EGR passage 31, an EGR cooler 32 and an EGR valve 33 are installed as elements other than the EGR passage 31 constituting the EGR system. The EGR cooler 32 cools the exhaust gas branched from the exhaust passage 15, and the EGR valve 33 expands or contracts the substantial cross-sectional area (effective cross-sectional area) of the EGR passage 31 and returns the exhaust gas (effective cross-sectional area) to the inside of the cylinder. Adjust the amount of EGR gas).

In addition to the above, the internal combustion engine 1 includes an intake shutter valve 41 installed in the intake passage 11 on the upstream side of the connection point Pm of the EGR passage 31 with respect to the intake flow. The intake shutter valve 41 is configured so that the effective cross-sectional area of the intake passage 11 can be adjusted. In the present embodiment, the pressure on the downstream side of the intake passage 11 is reduced by reducing the effective cross-sectional area of the intake passage 11, and the EGR passage is reduced. It is configured as an admission valve (hereinafter unified by the name of "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 the present embodiment is configured as an admission valve 41 so that the opening degree can be adjusted stepwise or continuously, but it is adjusted only to two positions, the maximum opening degree and the minimum opening degree. It may be possible. As such a case, a case where the expansion of the differential pressure is not required for the operation of the EGR system can be exemplified. Then, for example, the maximum opening degree is the opening degree when fully opened (fully opened opening degree), and the minimum opening degree is the opening degree when fully closed (fully closed opening degree). Like the admission valve 41, the EGR valve 33 is not only configured so that the opening degree can be adjusted stepwise or continuously, but is also configured so that the opening degree can be switched only between the maximum opening degree and the minimum opening degree. Is possible.

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

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

The engine controller 101 inputs detection signals of various operating state sensors that detect the operating state of the internal combustion engine 1, executes a predetermined calculation based on the detected operating state, and determines the fuel injection amount of the internal combustion engine 1. Set the fuel injection timing, ignition timing, etc.

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

(Overview of fuel cut control)
In the present embodiment, during the operation of the engine controller 101, in other words, while the start switch (not shown) is on, when a predetermined fuel cut condition is satisfied, the supply of fuel to the internal combustion engine 1 is temporarily stopped. Make a fuel cut. Then, when the fuel is cut, the admission valve 41 is closed to reduce the effective cross-sectional area of the intake passage 11 as compared with that before the fuel cut condition is satisfied, and the EGR valve 33 is opened to open the cylinder and the EGR passage of the internal combustion engine 1. The EGR gas is circulated between the EGR gas and the intake passage 11 on the downstream side of the admission valve 41, and the gas occupied in the cylinder is replaced with the EGR gas.

Here, when the operation of the fuel injection valve 14 is stopped at the same time as closing the admission valve 41 after the fuel cut condition is satisfied, that is, when the admission valve 41 is closed and the fuel is supplied to the internal combustion engine 1. When stopped at the same time, the air (oxygen) in the intake passage 11 is transferred from the cylinder to the exhaust passage until the gas occupying the intake passage 11 downstream of the admission valve 41 is replaced with the EGR gas. It is sent to 15 unreacted (that is, scavenged) and flows into the catalytic converter 16. At the time when the fuel cut condition is satisfied, the internal combustion engine 1 is in the accelerator-off state in which the accelerator pedal is completely returned or close to it, and the EGR is stopped. Therefore, the gas existing in the intake passage 11 is air. This is because, if there is, or not, the proportion of EGR gas is extremely low. Then, when oxygen flows into the catalyst, when restarting after the fuel is cut, the oxygen adsorbed on the catalyst is sufficiently processed, and NOx (nitrogen oxide) produced by the catalyst is used until the oxygen storage state is eliminated. The purification rate is reduced. Further, since it results in an increase in the amount of reducing agent input required to eliminate the oxygen storage state, it may cause deterioration of exhaust gas. The elimination of the oxygen storage state is generally performed by, for example, operating the fuel injection valve 14 (rich spike operation) that temporarily increases the air-fuel ratio of the exhaust gas from the theoretical value.

Therefore, in the present embodiment, when the fuel cut condition is satisfied, not only the admission valve 41 is closed, but also the EGR from the connection point Pm of the EGR passage 31 to the intake port after the admission valve 41 is closed. During the gas transportation delay, fuel is continuously supplied by the fuel injection valve 14 to continue combustion in the cylinder. In other words, the exhaust gas in the EGR passage 31 when the fuel cut condition is satisfied reaches the intake port via the connection point Pm, and burns until the air in the intake passage 11 is replaced with the EGR gas. By continuing the above, oxygen in the intake air is consumed. Then, after the replacement of air with EGR gas is completed, the fuel cut is executed and the supply of fuel to the internal combustion engine 1 is stopped.

(Basic operation of fuel cut)
FIGS. 2 to 5 show the operations of the internal combustion engine 1 according to the present embodiment from before the fuel cut to after the fuel cut in chronological order. In each of FIGS. 2 to 5, the thick dotted line conceptually shows the behavior of the exhaust gas or the EGR gas, and the direction of the arrow indicates the direction of the flow. Further, FIG. 9 shows the operation of the internal combustion engine 1 before and after the fuel cut by a time chart. In FIG. 9, the time Toff indicates the time when the accelerator is off, the time Treq indicates the time when the fuel cut condition is satisfied, and the time Tcut indicates the time when the fuel cut is executed. The operation of the internal combustion engine 1 will be described with reference to FIGS. 2 to 5 with reference to FIG. 9 as appropriate.

In the present embodiment, the case of so-called deceleration fuel cut, in which the fuel is cut when the vehicle is decelerated, is described on the premise that the drive source of the vehicle is configured by the internal combustion engine 1 alone, but the application of the fuel cut is applied to this. The vehicle is not limited, and the vehicle may be temporarily stopped, for example, while waiting for a traffic light. In this sense, the "fuel cut" according to the present embodiment means a general operation of temporarily stopping the supply of fuel to the internal combustion engine 1 (in other words, during the operation of the engine controller 101), and the vehicle is stopped. It shall also include the case of so-called idle stop. Further, when the internal combustion engine 1 forms a drive source in cooperation with an electric motor, it may include a case of switching to a mode in which the internal combustion engine 1 travels only by the electric motor.

FIG. 2 shows a state during constant speed running at a relatively low speed before the start of deceleration (time Tstd in FIG. 9). The operating state of the internal combustion engine 1 is in the region where EGR is performed (that is, the EGR region), and both the throttle valve 13 and the EGR valve 33 are in the fully open position. Since the rotation speed of the internal combustion engine 1 is low and there is not a sufficient differential pressure between the branch point Pd and the connection point Pm, the admission valve 41 is slightly closed with respect to the fully open position in order to expand the pressure. Let me.

FIG. 3 shows the state after the start of deceleration due to the accelerator off and before the fuel cut condition is satisfied (time Tdec). The rotation speed of the internal combustion engine 1 decreases at the start of deceleration, and the operating state of the internal combustion engine 1 deviates from the EGR range, so that the EGR valve 33 is controlled to the fully closed position, and the admission valve 41 is also fully opened accordingly. Controlled by position. The throttle valve 13 is adjusted to a slight opening degree that allows the passage of a very small amount of air by completely returning the accelerator pedal.

FIG. 4 shows the state after the fuel cut condition is satisfied (time Trip). In order to fill the intake passage 11 and the cylinder with EGR gas in preparation for the execution of the fuel cut, the admission valve 41 is closed and the EGR valve 33 is opened. In the present embodiment, the admission valve 41 is fully closed, while the EGR valve 33 is fully opened. As a result, the exhaust gas that was in the EGR passage 31 when the fuel cut condition is satisfied is guided to the intake passage 11 and introduced into the cylinder. When the EGR gas reaches the intake port, it can be considered that the replacement with the EGR gas is completed.

FIG. 5 shows the state after the execution of the fuel cut (time Tpst). The fuel for the internal combustion engine 1 is filled with exhaust gas or EGR gas in the cylinder, the exhaust passage 15, the EGR passage 31, and the intake passage 11 (specifically, the portion downstream of the admission valve 41). The supply is stopped and the internal combustion engine 1 is stopped.

(Explanation by flowchart)
6 and 7 show the operation of the engine controller 101 by a flowchart, FIG. 6 shows the operation related to the fuel cut control, and FIG. 7 shows the operation related to the fuel cut recovery control, respectively. The engine controller 101 is programmed to execute the fuel cut control when the predetermined fuel cut condition is satisfied, and to execute the fuel cut recovery control when the predetermined fuel cut recovery condition is satisfied after the execution of the fuel cut. ing.

In the flowchart shown in FIG. 6, in S101, it is determined whether or not the accelerator is off. If the accelerator pedal is fully released or close to it and the accelerator is off, the process proceeds to S102, and if the accelerator pedal is not in the accelerator off state, the process proceeds to S108.

In S102, it is determined whether or not the fuel cut condition is satisfied. In the deceleration fuel cut, it can be determined that the fuel cut condition is satisfied when the rotation speed of the internal combustion engine 1 at the time when the accelerator off state continues for a predetermined time or longer is equal to or higher than the predetermined rotation speed. It is possible. If the fuel cut condition is satisfied, the process proceeds to S103, and if not, the processes of S101 and 102 are repeated.

Here, in a hybrid vehicle equipped with a battery and capable of generating driving force by an internal combustion engine 1 or an electric motor supplied by the battery, the accelerator is turned on when the battery charge state SOC is sufficient. Even in this state, the fuel may be cut and the internal combustion engine 1 may be automatically stopped. In this case, as the processing of S101 and 102, the success or failure of the automatic stop condition of the internal combustion engine 1 (that is, the EV driving mode condition) is determined as the fuel cut condition based on the battery charge state and the accelerator opening. It is possible.

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

In S104, the EGR valve 33 is opened (specifically, fully opened).

In S105, it is determined whether or not the transportation delay time ΔTdry has elapsed. The transportation delay time ΔTdry refers to the time corresponding to the transportation delay of the EGR gas from the connection point Pm of the EGR passage 31 to the intake port after the admission valve 41 is closed, and whether or not this has elapsed is determined. It is possible to estimate based on the operating state of the internal combustion engine 1. If the transport delay time ΔTdry has elapsed, the process proceeds to S107, and if not, the process proceeds to S106.

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

As shown in FIG. 8A, the flow rate of air passing through the intake valve (flow rate passing through the intake valve) is given for each opening of the throttle valve 13 (hereinafter referred to as “throttle opening”) THO, and each throttle is opened. It is possible to predetermine the degree THO as a function with respect to the engine speed NE, for example, a monotonically increasing function. Then, the intake valve passing volume of air is calculated by integrating the intake valve passing flow rate, and when the intake valve passing volume reaches a predetermined volume Vthr corresponding to the volume of the intake passage 11 after the start of integration (time T0). It is determined that the transportation delay time ΔTdry has elapsed at (time T1).

Whether or not the transportation delay time ΔTdry has elapsed can be determined not only by such an 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 near the combustion chamber or the intake port, the admission valve 41 is closed, and then the gas detected by the gas state sensor is used. When the behavior indicating the passage of EGR gas occurs in the state, it is determined that the transport delay time ΔTdry has elapsed. As such a behavior, it can be exemplified that the oxygen concentration is lowered to a predetermined concentration or less when the oxygen concentration sensor is used. In this sense, the transport delay of EGR gas is "the delay required to replace the gas in the intake passage downstream of the intake shutter valve with EGR gas" or "the delay of EGR gas occupied in the cylinder after closing the intake shutter valve". It can be rephrased as "the delay until the ratio rises and reaches a predetermined value".

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 elapse of the transportation delay time ΔTdry to continue the fuel supply. If the fuel cut cancellation condition is satisfied, the process proceeds to S108, and if the fuel cut cancellation condition is not satisfied, the process returns to S105 and continues to wait for the elapse of the transportation delay time ΔTdry.

In S107, 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 spark plug (not shown) is also stopped.

In S108, normal fuel injection control is executed to continue supplying 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 the present embodiment, it is determined that the fuel cut recovery condition is satisfied when the accelerator pedal is depressed by the driver from the accelerator off state, the accelerator opening APO reaches a predetermined value, and the accelerator is turned on. Will be done. If the fuel cut recovery condition is satisfied, the process proceeds to S202, and if not, the process of S201 is repeated.

In the hybrid vehicle described above, instead of the above, when the charge state SOC of the battery decreases and the index value decreases to a predetermined value, for example, to a predetermined value according to the accelerator opening APO, the fuel cut recovery cover It is possible to determine that the condition (that is, the restart condition of the internal combustion engine 1) is satisfied.

In S202, the admission valve 41 is closed (specifically, fully closed). In the present embodiment, since the admission valve 41 is already closed at the time of fuel cut, the closed state is continued.

In S203, the EGR valve 33 is opened (specifically, fully opened). Similar to the admission valve 41, the state at the time of fuel cut (valve open state) is continued.

In S204, cranking of the internal combustion engine 1 is started. Cranking (sometimes called "motoring") is done 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, it is possible to perform cranking 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 during cranking is directed toward the branch point Pd downstream of the exhaust passage 15. Is guided to the intake passage 11 via the EGR passage 31 without passing through.

In S205, it is determined whether or not the rotation speed of the internal combustion engine 1 has reached a predetermined rotation speed. When the predetermined rotation speed is reached, the process proceeds to S206, and when the predetermined rotation speed is not reached, cranking is continued and the predetermined rotation speed is waited for.

In S206, the admission valve 41 is opened (for example, fully opened). As a result, air is allowed 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 the EGR gas into the intake passage 11 is prevented, and as the introduction of air through the admission valve 41 progresses, the gas occupying the intake passage 11 is replaced with air from the EGR gas.

In S208, it is determined whether or not the intake delay time has elapsed. The intake delay time refers to the time corresponding to the air transport delay from the connection point Pm of the EGR passage 31 to the intake port after the admission valve 41 is opened, and it is determined whether or not this has elapsed. Similar to the determination regarding the EGR gas transport delay time ΔTdry, it can be estimated or actually measured. For example, the flow rate of air passing through the admission valve 41 per unit time is obtained, and this is sequentially integrated, and whether or not the passing volume, which is the integrated value, reaches a predetermined volume corresponding to the volume of the intake passage 11. Is determined. If the intake delay time has elapsed, the process proceeds to S209, and if not, the determination of S208 is repeated and the elapse is awaited.

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

In the present embodiment, the engine controller 1 constitutes an "internal combustion engine control device". Then, in the flowchart shown in FIG. 6, the processes of S101 and 102 realize the function of the "condition determination unit", and the processes of S103 and S105 to 107 realize the function of the "fuel cut control unit".

(Explanation of action and effect)
The internal combustion engine 1 and its control device (engine controller 101) according to the present embodiment have the above configurations, and the effects obtained by the present embodiment will be described below.

First, when the fuel cut condition is satisfied, the admission valve 41 is continued to burn in the cylinder during the delay in transporting the EGR gas to the intake port even after the admission valve 41 is closed. The air (oxygen) that was on the downstream side at the time of closing is sent out to the exhaust passage 15 without reacting through the cylinder, and it becomes possible to suppress the inflow to the catalyst, particularly the catalytic converter 16. ..

As a result, an oxidizing atmosphere is formed in the catalyst, and it is possible to suppress a decrease in the purification rate of NOx (nitrogen oxide) at the time of restarting after the fuel is cut, and to improve the exhaust properties. Furthermore, it is possible to reduce the amount of reducing agent input required to eliminate the oxygen storage state, thereby improving fuel efficiency. Here, the engine torque generated during the transportation delay of EGR gas, that is, during the continuation of fuel, is converted into electric power by a power generation motor such as ISG, and is used for supplying electric power to an electric machine or for filling a battery. It is possible to allocate it.

Secondly, the time corresponding to the transport delay of the EGR gas (transport delay time ΔTdry) is measured or estimated, and after that time has elapsed, the fuel supply is stopped and the combustion is stopped, so that the combustion is excessive. It can be continued without any shortage, and the fuel consumption can be suppressed as much as possible to prevent the air from being sent from the cylinder to the exhaust passage 15 without reacting.

FIG. 9 shows the transportation delay time ΔTdry, which corresponds to the time from the time Treq where the fuel cut condition is satisfied to the time Tcut when the replacement with EGR gas is completed and the fuel cut is executed. In the present embodiment, during this period, combustion in the cylinder is continued to maintain the engine torque, but the engine torque may be reduced during this transportation delay. FIG. 9 shows the change in engine torque in this case by a chain double-dashed line.

Third, by increasing the opening degree of the EGR valve 33 and expanding the effective cross-sectional area of the EGR passage 31 in conjunction with closing the admission valve 41, the recirculation of the EGR gas is positively promoted and transported. It is possible to shorten the delay time ΔTdry and stop the fuel supply at an earlier stage. As a result, fuel efficiency can be further improved.

Fourth, by setting a branch point Pd on the downstream side of the catalyst converter 16 and recirculating the exhaust gas after passing through the catalyst converter 16 as EGR gas, combustion is performed during the transportation delay when the fuel is cut. It is possible to suppress the inflow of air into the catalyst when the above is not continued. Thereby, the decrease in the purification rate of NOx due to the formation of the oxidizing atmosphere can be suppressed more effectively.

Further, in the present embodiment, after the fuel cut is executed, the engine torque is gradually reduced to give a gradient to the decrease in the engine speed. However, in the case of using a hybrid drive source that cooperates with an electric motor or the like. In particular, in the case of a series hybrid type drive source, when the internal combustion engine 1 is stopped, the engine torque may be instantaneously reduced and the rotation of the internal combustion engine 1 may be stopped immediately. In FIG. 9, the changes in the engine torque and the engine speed in this case are shown by dotted lines.

Although the embodiment of the present invention has been described above, the above-described embodiment shows only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above-described embodiment. Not the purpose. Various changes and modifications can be made to the above embodiments within the scope of the matters described in the claims.

Claims

It is a control method for an internal combustion engine equipped with an EGR system and recirculating the exhaust gas after combustion as EGR gas into the cylinder.
It is determined whether or not the fuel cut condition for performing the fuel cut for temporarily stopping the supply of fuel to the internal combustion engine is satisfied.
When the above fuel cut condition is satisfied,
Of the intake passages, the intake shutter valve installed on the upstream side of the connection point of the EGR passage is closed, and the effective cross-sectional area of the intake passage is reduced as compared with that before the fuel cut condition was satisfied.
After closing the intake shutter valve, combustion in the cylinder is continued during the transportation delay of the EGR gas from the connection point to the intake port of the internal combustion engine.
Internal combustion engine control method.
The method for controlling an internal combustion engine according to claim 1.
Measure or estimate the time corresponding to the transport delay and
Continue burning in the cylinder for the measured or estimated time.
After the lapse of the measured or estimated time, the fuel supply is stopped.
Internal combustion engine control method.
The method for controlling an internal combustion engine according to claim 1 or 2.
The intake shutter valve can adjust the opening degree stepwise or continuously.
Internal combustion engine control method.
The method for controlling an internal combustion engine according to any one of claims 1 to 3, wherein the EGR system includes an EGR valve in which the effective cross-sectional area of the EGR passage is adjustablely interposed in the EGR passage. hand,
When the fuel cut condition is satisfied, the opening degree of the EGR valve is increased in conjunction with closing the intake shutter valve.
Internal combustion engine control method.
The method for controlling an internal combustion engine according to claim 4.
The EGR valve can adjust the opening degree stepwise or continuously.
Internal combustion engine control method.
The method for controlling an internal combustion engine according to any one of claims 1 to 5.
The internal combustion engine includes an exhaust purification catalyst installed in the exhaust passage on the upstream side of the branch point of the EGR passage from the exhaust passage.
Internal combustion engine control method.
An EGR system having an EGR passage that connects an intake passage and an exhaust passage so that fluids can communicate with each other, and an EGR system configured so that exhaust after combustion can be returned to the cylinder as EGR gas through the EGR passage.
An intake shutter valve, which is installed upstream of the connection point of the EGR passage in the intake passage so that the effective cross-sectional area of the intake passage can be adjusted,
A fuel injection valve arranged so that fuel can be supplied in the cylinder,
An internal combustion engine control device that controls an internal combustion engine.
A condition determination unit for determining whether or not a fuel cut condition for performing a fuel cut for temporarily stopping the supply of fuel to the internal combustion engine is satisfied.
A fuel cut control unit that controls the intake shutter valve and the fuel injection valve when the fuel cut condition is satisfied.
By closing the intake shutter valve, the effective cross-sectional area of the intake passage is reduced as compared with that before the fuel cut condition was satisfied.
After closing the intake shutter valve, the fuel injection valve is continuously operated during the delay in transporting the EGR gas from the connection point to the intake port of the internal combustion engine to continue combustion in the cylinder. Fuel cut control unit and
A control device for an internal combustion engine.