WO2021001669A1 - Method and device for controlling internal combustion engine - Google Patents

Abstract

An EGR system is provided, and an air intake passage is filled with an EGR gas when the internal combustion engine has temporarily stopped. When a prescribed restart condition is fulfilled after the internal combustion engine has stopped, an air intake shutter valve, which is provided in the air intake passage upstream of a point of connection with an EGR passage, is closed, the effective cross-sectional area of the air intake passage is reduced, and cranking of the internal combustion engine is started. The speed of the internal combustion engine increases after the start of cranking, and until the speed reaches a prescribed speed that is higher than before the start of cranking, cranking is continued and the air intake shutter valve remains closed. After the speed of the internal combustion engine has reached the prescribed speed, the air intake shutter valve is opened, a substantial amount of air is allowed into cylinders, and combustion is restarted.

Description

Internal combustion engine control method and control device

The present invention relates to an internal combustion engine control method and a control device including an EGR system and filling an intake passage with EGR gas when the internal combustion engine is temporarily stopped.

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

The technology of JP2005-330886A is that after the fuel supply is stopped by idle stop, the gas sent from the cylinder while the rotation due to coasting continues, and the gas flowing into the catalyst contains excess oxygen, so that the 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, and the cylinder from the start of the restart to the ignition. There is a problem that air (oxygen) via 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 purification rate of NOx (nitrogen oxide) by the catalyst decreases until the oxygen storage state is cleared.

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 internal combustion engine control method is provided that comprises an EGR system and fills an intake passage with EGR gas when the internal combustion engine is temporarily stopped. In the method according to this embodiment, when a predetermined restart condition is satisfied after the internal combustion engine is stopped, the intake shutter valve provided on the upstream side of the connection point of the EGR passage is closed, and the intake passage is opened. The effective cross-sectional area is reduced and the cranking of the internal combustion engine is started. Then, from the start of cranking until the rotation speed of the internal combustion engine rises and reaches a predetermined rotation speed higher than that before the start of cranking, the cranking is continued and the intake shutter valve is kept closed. .. Then, after the rotation speed of the internal combustion engine reaches a predetermined rotation speed, the intake shutter valve is opened to allow the introduction of substantial air into the cylinder, and the combustion is restarted.

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 a state of the internal combustion engine according to the same embodiment when the engine is stopped after the fuel is cut. 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 recovery (during cranking). 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 recovery (after the engine speed has increased). 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 recovery (after the lapse of the intake delay period). 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 content of the intake delay time lapse determination process of the control at the time of fuel cut recovery. FIG. 9 is an explanatory diagram of the operation of the internal combustion engine from the time when the engine is stopped due to the fuel cut to the time when the engine is restarted by the fuel cut recoverer 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 and fuel cut recovery 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, prior to stopping the supply of fuel, control is performed to fill the intake passage 11 and the inside of the cylinder on the downstream side of the admission valve 41 with EGR gas. This is because the admission valve 41 is closed, the effective cross-sectional area of the intake passage 11 is reduced compared to before the fuel cut condition is satisfied, and the EGR valve 33 is opened, so that the cylinder of the internal combustion engine 1 and the EGR passage 31 are connected. This can be achieved by circulating EGR gas between them.

Then, when the predetermined fuel cut recovery condition is satisfied, the fuel supply to the internal combustion engine 1 is restarted, and the fuel cut recovery is performed to restart the internal combustion engine 1.

Here, when the cranking of the internal combustion engine 1 is started and the admission valve 41 is opened at the same time after the fuel cut recovery condition is satisfied, that is, when the cranking is started and the admission valve 41 is opened. When the above is performed at the same time, the air (oxygen) introduced into the cylinder via the admission valve 41 is exhausted until the engine rotation speed rises to the predetermined rotation speed and the restart of combustion is allowed. It is sent to the passage 15 unreacted (that is, scavenged) and flows into the catalytic converter 16. When oxygen flows into the catalyst, the purification rate of NOx (nitrogen oxide) by the catalyst decreases after the combustion resumes until the oxygen adsorbed on the catalyst is sufficiently processed and the oxygen storage state is cleared. .. 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 recovery condition is satisfied, the EGR gas is circulated between the inside of the cylinder and the EGR passage 31 while the admission valve 41 is kept closed after the start of cranking, and the cylinder is used. Suppress the introduction of air into the interior. Then, when the engine speed has risen sufficiently and the predetermined speed at which combustion can be restarted is reached, the admission valve 41 is opened and the introduction of air is started. Further, after the start of air introduction, the execution of the fuel cut recovery is suspended 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, and the EGR is held. After the replacement of gas with air is completed, this is executed to restart the supply of fuel to the internal combustion engine 1 and 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 the time of stopping due to the fuel cut to the time of restarting by the fuel cut recovery cover. 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 presence or absence of the flow and its direction. Further, FIG. 9 shows the operation of the internal combustion engine 1 from before the fuel cut to after the fuel cut recovery 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. Further, the time Trcv indicates the time when the fuel cut recovery condition is satisfied, and the time Trst indicates the time when the fuel cut recovery 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 internal combustion engine 1 alone constitutes the drive source of the vehicle. However, the fuel cut (and the subsequent fuel cut recovery cover) will be described. ) Is not limited to this, and the vehicle may be temporarily stopped, for example, while waiting for a traffic light. Further, the deceleration fuel cut may be performed during so-called coastal operation from deceleration to stopping. 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 the state when the engine is stopped after the fuel is cut (time Tstp in FIG. 9). Due to the gas replacement performed when the fuel is cut, 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. The admission valve 41 is continuously closed from the time of fuel cut, and the EGR valve 33 is in the opened state. In the present embodiment, the admission valve 41 is fully closed and the EGR valve 33 is fully opened. By closing the admission valve 41, the introduction of air downstream thereof is suppressed.

FIG. 3 shows the state during cranking after the fuel cut recovery condition is satisfied (time Trcv to Trev). With the start of cranking, the rotation speed of the internal combustion engine 1 increases. The admission valve 41 is in the fully closed position, while the EGR valve 33 is in the fully open position, which promotes the introduction of EGR gas from the exhaust passage 15 to the intake passage 11 via the EGR passage 31, and promotes the introduction of EGR gas into the cylinder and in the EGR. EGR gas circulates with the passage 31. The throttle valve 13 is adjusted to maintain a fully closed state when the power of the engine controller 101 is turned off. However, in the present embodiment, the throttle valve 13 is controlled to a fully open position by turning on the power, and remains in the fully open position while cranking is continued. Be retained. Here, if the EGR gas filled in the intake passage 11 is sucked into the cylinder during the fuel cut and the engine speed during cranking described below rises sufficiently before being discharged, the EGR valve 33 By closing the EGR gas, the EGR gas may not be circulated.

FIG. 4 shows the state after the engine speed has sufficiently increased due to 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 preparation for the resumption of combustion. At the same time, the EGR valve 33 is closed to prevent the introduction of new EGR gas into the intake passage 11. In the present embodiment, the admission valve 41 is fully opened while the EGR valve 33 is fully closed. As a result, the EGR gas that was in the intake passage 11 when the fuel cut recovery condition is satisfied is sent out to the exhaust passage 15 by air, and 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 at the time of execution of the fuel cut recovery (time Trst). After the admission valve 41 is opened, the fuel supply to the internal combustion engine 1 is restarted when the air passes through the admission valve 41 and reaches the intake port, in other words, when the intake delay period ΔTdry elapses. And restart the combustion.

(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 present embodiment, the fuel cut condition is that 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, and the brake is applied by the driver. In addition, it is judged that it has been established. 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 electric motor supplied by the battery, even if the accelerator is on when the battery charge state SOC has a margin. 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). This promotes the circulation of EGR gas between the inside of the cylinder and the EGR passage 31.

In S105, it is determined whether or not the EGR gas transport delay time has elapsed. The transportation delay time 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 the internal combustion engine. It is possible to estimate based on the operating state of the engine 1. Similar to the estimation of the intake delay period ΔTdry described later, the flow rate of EGR gas passing through the intake valve (intake valve passing flow rate) is integrated per unit time 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 transport 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 elapse of the transportation delay time 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.

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 brake operated by the driver is released by the brake pedal being completely returned or returned to a state close to this. To. 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 battery charge state SOC decreases and the index value decreases to a predetermined value according to the accelerator opening, 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 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 ΔTdry has elapsed. The intake delay time ΔTdry is the time corresponding to the delay in transporting the air that has passed through the admission valve 41 to the intake port via the connection point Pm after the admission valve 41 is opened. It is possible to determine whether or not this has been done by estimation based on the operating state of the internal combustion engine 1. If the intake delay time ΔTdry has elapsed, the process proceeds to S209, and if not, the determination of S208 is repeated and the elapse is awaited.

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 intake 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 opened, and then the gas detected by the gas state sensor is used. When the behavior indicating the arrival of air occurs in the state, it is determined that the intake delay time ΔTdry has elapsed. As such a behavior, it can be exemplified that the oxygen concentration rises above a predetermined concentration when the oxygen concentration sensor is used. In this sense, the air transport delay is "the delay required to replace the EGR gas with air in the intake passage downstream of the intake shutter valve" or "the air occupied in the cylinder after opening the intake shutter valve ( It can be rephrased as "the delay until the ratio of oxygen) rises and reaches a predetermined value."

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.

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

First, when restarting the internal combustion engine 1 after a temporary stop, the air (oxygen) is admitted by keeping the admission valve 41 closed while continuing the cranking of the internal combustion engine 1. It is possible to prevent the air 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 prevent the catalyst from forming an excessive oxidizing atmosphere and deteriorating the purification rate of NOx (nitrogen oxide).

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

Secondly, after the start of cranking, the rotation speed of the internal combustion engine 1 rises, and after reaching a predetermined rotation speed, the fuel supply is restarted and the combustion is restarted, so that combustion is performed at a fuel-efficient operating point. It will be possible to restart. Here, even if it takes time for the rotation speed of the internal combustion engine 1 to reach a predetermined rotation speed, deterioration of the purification rate of NOx 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, so that the EGR gas is circulated between the cylinder and the EGR passage 31 while the cranking is continued. This makes it possible to reduce the load on the cranking motor and more reliably suppress the inflow of air into the catalyst.

Fourth, after the rotation speed of the internal combustion engine 1 reaches a predetermined rotation speed, combustion is restarted after a predetermined time has elapsed after the introduction of air through the admission valve 41 is permitted, so that the combustion is resumed in the cylinder. It is possible to avoid restarting combustion while the ratio of EGR gas to the filled gas is high, suppress the emission of unburned components due to unstable combustion, and reliably achieve restart. It becomes.

Here, after opening the admission valve 41, by waiting for the elapse of the intake delay period ΔTdry indicating the arrival of air to the intake port and restarting combustion, it is possible to set the intake delay period ΔTdry without excess or deficiency. It is possible to prevent the exhaust from being deteriorated due to the delay in the resumption of combustion and the inflow of air into the catalyst, or the supply of fuel in a state where the resumption of combustion is early and the ignition is unstable.

Fifth, by installing the catalyst converter 16 in the exhaust passage 15 on the upstream side 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 surely suppress the deterioration of the exhaust gas.

Sixth, 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, so that the existing low-pressure EGR system 3 is provided. The valve device (that is, the admission valve 41) makes it possible to realize an intake shutter valve and suppress an increase in the number of parts.

The control according to this embodiment is not limited to the so-called low pressure type EGR system, but can also be applied to the high pressure type EGR system. Specifically, when a catalyst is provided on the upstream side of the exhaust passage from the exhaust turbine, 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 for combustion. 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 without a supercharger, 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, and the throttle valve functions as an "intake shutter valve". Can be embodied.

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 (7)

An internal combustion engine control method that is equipped with an EGR system and fills the intake passage with EGR gas when the internal combustion engine is temporarily stopped.
When a predetermined restart condition is satisfied after the internal combustion engine is stopped,
Of the intake passages, the intake shutter valve provided on the upstream side of the connection point of the EGR passage is closed to reduce the effective cross-sectional area of the intake passage.
The cranking of the internal combustion engine is started,
A state in which the cranking is continued and the intake shutter valve is closed from the start of the cranking until the rotation speed of the internal combustion engine increases and reaches a predetermined rotation speed higher than that before the start of the cranking. Keep in
After the rotation speed of the internal combustion engine reaches the predetermined rotation speed, the intake shutter valve is opened to allow substantially air to be introduced into the cylinder and restart combustion.
Internal combustion engine control method. The method for controlling an internal combustion engine according to claim 1, 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.
When the predetermined restart condition is satisfied, the EGR valve is opened and then the cranking is started.
Internal combustion engine control method. The method for controlling an internal combustion engine according to claim 2.
After the rotation speed of the internal combustion engine reaches the predetermined rotation speed, the intake shutter valve is opened, the EGR valve is closed, and combustion is restarted after a predetermined time has elapsed.
Internal combustion engine control method. The method for controlling an internal combustion engine according to any one of claims 1 to 3.
During the cranking, the intake shutter valve is maintained at the minimum opening and the EGR valve is maintained at the maximum opening.
Internal combustion engine control method. The method for controlling an internal combustion engine according to any one of claims 1 to 4.
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. The method for controlling an internal combustion engine according to any one of claims 1 to 5, wherein the internal combustion engine includes a supercharger.
By the EGR system, the exhaust gas flowing through the exhaust passage downstream of the exhaust turbine of the supercharger is recirculated as the EGR gas to the intake passage upstream of the intake compressor of the supercharger.
Internal combustion engine control method. An EGR system that connects the intake passage and the exhaust passage so that fluid can communicate with each other via the EGR passage, and recirculates the exhaust gas after combustion as EGR gas into the cylinder through the EGR passage.
Of the intake passages, an intake shutter valve installed on the upstream side of the connection point of the EGR passage and capable of adjusting the effective cross-sectional area of the intake passage,
An internal combustion engine control device that controls an internal combustion engine.
When the internal combustion engine is temporarily stopped, the intake passage is filled with EGR gas.
When a predetermined restart condition is satisfied after the internal combustion engine is stopped,
The intake shutter valve is closed to reduce the effective cross-sectional area of the intake passage.
The cranking of the internal combustion engine is started,
From the start of the cranking until the rotation speed of the internal combustion engine reaches a predetermined rotation speed, the cranking is continued and the intake shutter valve is maintained in a closed state.
After the rotation speed of the internal combustion engine reaches the predetermined rotation speed, the intake shutter valve is opened to allow substantially air to be introduced into the cylinder and restart combustion.
Internal combustion engine control device.

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