JP3204113B2 - Exhaust gas recirculation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device used in an internal combustion engine capable of switching a fuel injection mode, and more particularly to a direct injection internal combustion engine for directly injecting fuel into a combustion chamber of the internal combustion engine. The present invention relates to an exhaust gas recirculation control device suitable for use.

[0002]

2. Description of the Related Art In recent years, a lean burn engine in which a combustion air-fuel ratio is set to be higher than a stoichiometric air-fuel ratio has been proposed for an automobile engine from the viewpoint of improving fuel efficiency. By the way, in general, the higher the air-fuel ratio of the lean-burn engine is, the more the fuel efficiency can be improved.
Limitation due to deterioration of combustion occurs. As a method of maximizing this limit, a technique has been proposed in which the air-fuel ratio in the vicinity of the ignition point in the combustion chamber is made to be in a rich mixed state, while the overall air-fuel ratio in the combustion chamber is maintained large to perform stratified combustion.

[0003] Further, in order to be able to operate the engine with a leaner mixture of fuel, an in-cylinder injection engine in which fuel is directly injected into a cylinder has been developed. In particular, in such a direct injection type engine, fuel injection can be performed, for example, in the latter half of the compression stroke, so that a laminar vertical vortex such as a tumble flow is generated in the cylinder, and an ignition plug is ignited to the laminar vertical vortex. By performing the fuel injection immediately before (for example, in the latter half of the compression stroke), it is possible to realize a low fuel consumption operation with an extremely lean mixture as a whole, while ensuring the combustibility with only the vicinity of the ignition plug in a rich mixture state. .

[0004] When performing lean combustion,
It is known that the greater the combustion air-fuel ratio, the lower the NOx generation amount. However, when lean stratified combustion is performed, the air-fuel ratio near the ignition point is relatively small, so the NOx generation amount is reduced. Also have certain limitations. Therefore, as means for performing the NOx reduction, it is considered to perform a reflux of exhaust gases (EGR), for example, the compressed lean mode reflux a large amount of exhaust gas, NO _X
Is to be reduced.

In such an internal combustion engine, a target exhaust gas recirculation amount is set according to each operation mode (fuel injection mode). When the operation mode is switched, the exhaust gas recirculation amount is quickly increased to the target exhaust gas amount. E so that the amount of reflux
Control of the GR valve is performed.

[0006]

In the case where the EGR is operated before and after the switching of the fuel injection mode (operation mode), the target exhaust gas recirculation amount is set according to the fuel injection mode after the switching. If the switching is performed at once, the combustion state in the combustion chamber may be deteriorated.

That is, when switching the fuel injection mode, the target air-fuel ratio A / A is controlled by controlling the air amount by an air bypass valve (ABV) or the fuel injection amount by a fuel injection valve (injector) in order to suppress the torque fluctuation of the engine. F is changed, but in such a case, if only the target exhaust gas recirculation amount is switched at once according to the fuel injection mode, the combustion state fluctuates rapidly.

Further, when the operation mode is switched from an operation mode in which a large amount of exhaust gas is recirculated to an operation mode in which a small amount of exhaust gas is recirculated (including an operation mode in which no exhaust gas is recirculated), for example, from a stoichiometric mode to a compression lean mode At the time of switching, the recirculated exhaust gas remains in the exhaust gas recirculation passage and the intake passage. Therefore, if the target exhaust gas recirculation amount is simply switched in accordance with the operation mode, the actual exhaust gas recirculation amount is changed immediately after the operation mode is switched. The amount of exhaust gas recirculation increases from the target value, and the combustion state deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an exhaust gas recirculation control device for preventing deterioration of a combustion state due to a change in a target exhaust gas recirculation amount at the time of switching operation modes. The purpose is to provide.

[0010]

For this reason, the exhaust gas recirculation control device according to the present invention according to the first aspect of the present invention provides a system for controlling the exhaust gas recirculation ratio to a value higher than the stoichiometric air-fuel ratio.
A first fuel injection mode set to a lean air-fuel ratio and the second fuel injection mode;
The second mode is set to a richer air-fuel ratio than the first fuel injection mode.
An internal combustion engine capable of switching the fuel injection mode between a fuel injection mode and an exhaust gas recirculation device that recirculates a part of exhaust gas to intake air, and a target exhaust gas of the first fuel injection mode.
The gas recirculation amount is set to the first EGR flow value and
The target exhaust gas recirculation amount in the second fuel injection mode is
Target exhaust gas recirculation amount setting means for setting the EGR flow value to 2 and the first fuel injection mode and the second fuel injection mode.
When the fuel injection mode is switched between the first fuel
Set according to the injection mode or the second fuel injection mode
Exhaust gas recirculation amount correction to correct the set target exhaust gas recirculation amount
Correction means, wherein the exhaust gas recirculation amount correction means
The amount of exhaust gas recirculation is set at the time of switching the fuel injection mode.
The first EGR flow rate value and the second
To the third EGR flow value smaller than the EGR flow value
It is characterized in that.

[0011] The exhaust gas recirculation control device of the present invention according to claim 2, in addition to the above-described configuration according to claim 1, wherein
The exhaust gas recirculation amount correction means calculates the third EGR flow value.
It is characterized in that it is corrected to substantially zero .

According to a third aspect of the present invention, there is provided an exhaust gas recirculation control device according to the first aspect of the present invention, wherein the internal combustion engine is provided with the first fuel injection mode and the first fuel injection mode.
Supply to the combustion chamber of the internal combustion engine according to the second fuel injection mode;
Air volume setting method to set the target intake air volume to be supplied
And the first fuel at the time of switching the fuel injection mode.
Is set corresponding to the injection mode or the second fuel injection mode.
It is characterized by having air amount correcting means for correcting the target intake air amount .

Further, the exhaust gas recirculation control device of the present invention described in claim 4, in addition to the above-described configuration according to claim 1, wherein
When the fuel injection mode is switched, the internal combustion engine
Set the target air-fuel ratio before switching the injection mode to the fuel injection mode.
Change to the target air-fuel ratio after replacement, and
After executing the injection mode switching, the fuel injection mode is switched.
It is characterized and this <br/> be controlled so as to change the target air-fuel ratio after the de switching.

Further, in the exhaust gas recirculation control device according to the present invention , fuel is injected mainly in the compression stroke.
Operating with the air-fuel ratio leaner than the stoichiometric air-fuel ratio
In the stroke injection mode, fuel injection is performed mainly during the intake stroke.
Operating at a richer air-fuel ratio than the lean air-fuel ratio.
In-cylinder injection type that can switch between intake stroke injection mode
Exhaust that returns a part of exhaust gas to intake air in a fuel engine
A gas recirculation device, and a target exhaust gas in the compression stroke injection mode.
The recirculation amount is set to the first EGR flow value,
The target exhaust gas recirculation amount in the intake stroke injection mode is set to the second E
Target exhaust gas recirculation amount setting means for setting the GR flow value;
Between the compression stroke injection mode and the intake stroke injection mode.
When the fuel injection mode is switched during
Mode or the intake stroke injection mode
Exhaust gas recirculation amount correction means for correcting the target exhaust gas recirculation amount
Wherein the exhaust gas recirculation amount correcting means includes a target exhaust gas
At the predetermined time when the fuel injection mode is switched.
In the meantime, the first EGR flow value and the second EGR
The correction is made to a third EGR flow value smaller than the GR flow value . Further, according to the present invention described in claim 6,
The exhaust gas recirculation control unit uses air-fuel leaner than the stoichiometric air-fuel ratio.
A first fuel injection mode set to a ratio and the first fuel injection
The second fuel injection mode that is set to a richer air-fuel ratio than the mode
Internal combustion engine that can switch fuel injection mode between
Exhaust gas that returns part of the exhaust gas to the intake
Flow device and target exhaust gas recirculation in the first fuel injection mode
The amount is set to a first EGR flow value and the second
The target exhaust gas recirculation amount in the fuel injection mode is determined by the first EG
An eye to set a second EGR flow value smaller than the R flow value
Target exhaust gas recirculation amount setting means, and the first fuel injection mode
Fuel injection mode switching between the second fuel injection mode and the second fuel injection mode
At the time of replacement, the first fuel injection mode or the second fuel injection
The target exhaust gas recirculation amount set in accordance with the
Exhaust gas recirculation amount correcting means for correcting the exhaust gas
The recirculation amount correcting means is configured to switch from the first fuel injection mode to the second fuel injection mode.
2 When switching the fuel injection mode to the fuel injection mode,
Once the target exhaust gas recirculation amount is
And a third EGR flow smaller than the second EGR flow value
After correcting the flow rate to the second value, the flow rate is controlled to the second EGR flow rate value.
It is characterized by that. The present invention according to claim 7.
Of the exhaust gas recirculation control device is the air leaner than the stoichiometric air-fuel ratio.
A first fuel injection mode set to a fuel ratio and the first fuel injection
Fuel injection set to richer air-fuel ratio than injection mode
Internal combustion engine capable of switching fuel injection mode between the two modes
Exhaust gas that recirculates part of the exhaust gas to intake air in Seki
A recirculation device and a target exhaust gas return in the first fuel injection mode
The flow rate is set to a first EGR flow rate value, and the
The target exhaust gas recirculation amount in the two fuel injection mode is determined by the first E
Set to a second EGR flow value smaller than the GR flow value
A target exhaust gas recirculation amount setting means, the first fuel injection mode;
Mode between the fuel injection mode and the second fuel injection mode.
The first fuel injection mode or the second fuel
Set the target exhaust gas recirculation amount set for the injection mode
Exhaust gas recirculation amount correcting means for correcting the exhaust gas.
The recirculation amount correcting means is configured to switch from the second fuel injection mode to the
When switching the fuel injection mode to the first fuel injection mode
Once, the target exhaust gas recirculation amount is changed to the second EGR flow rate.
Value and a third EG smaller than the first EGR flow value
After the correction to the R flow value, the first EGR flow value is controlled.
An exhaust gas recirculation control device characterized by controlling the exhaust gas recirculation control device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust gas recirculation control device according to one embodiment of the present invention will be described below with reference to the drawings. This device is provided in a direct injection engine as shown in FIG. First, the configuration of the in-cylinder injection engine having the present device will be described with reference to FIG.
In the drawings, 1 is an engine body, 2 is an intake passage, 3 is a throttle valve installation portion, 4 is an air cleaner, 5 is a bypass passage (second bypass passage), and 6 is a regulator for adjusting an amount of air flowing through the second bypass passage 5. A second air bypass valve (# 2ABV). The intake passage 2 has a configuration in which an intake pipe 7, a surge tank 8, and an intake manifold 9 are connected in this order from the upstream side, and the second bypass passage 5 is provided on the upstream side of the surge tank 8. The second air bypass valve 6 is driven to a required opening degree by a stepper motor.
The opening degree may be adjusted using duty control by a solenoid valve.

Further, reference numeral 12 designates an idle speed control function, which comprises a bypass passage (first bypass passage) 13 and a first air bypass valve (# 1ABV) 14 as a bypass valve. The valve 14 is driven by a stepper motor (not shown). Reference numeral 15 denotes a throttle valve, and the first bypass passage 13 and the second bypass passage 5 have their upstream end and downstream end connected to the intake passage 2 so as to bypass the mounting portion of the intake passage 2 where the throttle valve 15 is mounted. It is connected.

Further, the opening and closing control of the first air bypass valve 14 and the second air bypass valve 6 is performed through an electronic control unit (ECU) 16 as control means. Reference numeral 17 denotes an exhaust passage, and reference numeral 18 denotes a combustion chamber. An intake valve 19 and an exhaust valve 20 are provided at openings of the intake passage 2 and the exhaust passage 17 to the combustion chamber 18, that is, at the intake port 2A and the exhaust port 17A. Have been.

Reference numeral 21 denotes a fuel injection valve (injector). In the present engine, the injector 21 is arranged so as to directly inject fuel into the combustion chamber 18.
Further, 22 is a fuel tank, 23A to 23E are fuel supply paths, 24 is a low-pressure fuel pump, 25 is a high-pressure fuel pump,
6 is a low pressure regulator, 27 is a high pressure regulator, 28
Reference numeral denotes a delivery pipe, which drives the fuel in the fuel tank 22 by the low-pressure fuel pump 24 and further pressurizes the fuel by the high-pressure fuel pump 25 to maintain the fuel supply paths 23A, 23B,
The fuel is supplied to the injector 21 through the delivery pipe 28. At this time, the fuel pressure discharged from the low-pressure fuel pump 24 is regulated by the low-pressure regulator 26, pressurized by the high-pressure fuel pump 25, and
The fuel pressure guided to 8 is regulated by a high-pressure regulator 27.

Reference numeral 29 denotes an exhaust gas recirculation passage (EGR passage) for recirculating exhaust gas (exhaust gas) in the exhaust passage 17 of the engine 1 into the intake passage 2, and reference numeral 30 denotes an EGR passage 29.
A stepper motor type valve (EGR valve) as exhaust gas amount adjusting means for adjusting the amount of exhaust gas returning to the intake passage 2 through the intake passage 2; 31 is a flow path for reducing blow-by gas; A passage for active ventilation of the room, 33 is a valve for active ventilation of the crankcase, and 3
Reference numeral 4 denotes a canister, and reference numeral 35 denotes an exhaust gas purifying catalyst (here, a three-way catalyst).

The exhaust gas recirculation device (EGR device) 200 is mainly connected to the EGR passage 29 and the EGR valve 30.
Is configured. By the way, the ECU 16 performs opening / closing control or opening control of the first air bypass valve 14 and the second air bypass valve 6, as shown in FIG.
Control of the injector 21, an ignition coil for an unillustrated ignition plug, the EGR valve 30, and the high-pressure regulator 2
7, the fuel pressure control is also performed. For these controls, as shown in FIG.
4, intake air temperature sensor 36, throttle position sensor (TPS) 37 for detecting throttle opening, idle switch 38, air conditioner switch (not shown), shift position sensor (not shown), vehicle speed sensor (not shown), power steering A power steering switch (not shown) for detecting an operating state, a starter switch (not shown), a first cylinder detection sensor 40, a crank angle sensor 41, a water temperature sensor 42 for detecting a cooling water temperature of the engine, and an oxygen concentration in exhaust gas are detected. An O ₂ sensor 43 is provided and connected to the ECU 16. The engine speed can be calculated based on the crank angle sensor 41. For example, such an engine speed calculation function is provided in the ECU 16.
Therefore, an engine speed sensor is constituted by the crank angle sensor 41 and the engine speed calculation function. Here, the crank angle sensor 41 is also referred to as an engine speed sensor for convenience.

As shown in FIG. 1, an operating state detecting means 101 for detecting an operating state of the engine is constituted by the throttle position sensor (TPS) 37 and the engine speed sensor 41. Where E
Regarding the control contents of the engine through the CU 16,
A description will be given based on the control block diagram of FIG.

In the present engine, premixed combustion which can be achieved by uniformly injecting fuel into the combustion chamber 18 and the combustion chamber 1
The engine switches between stratified lean combustion that can be achieved by unevenly distributing the injected fuel around a spark plug (not shown) facing the inside of the engine 8 in accordance with the operation state. In this engine, as an operation mode (fuel injection mode) of the engine, a late lean combustion operation mode (late lean mode) in which fuel is injected in a compression stroke to perform stratified lean combustion.
And the first-stage lean combustion operation mode (first-term lean mode) in which fuel injection is performed in the intake stroke to perform premixed combustion (first-term lean mode), the stoichiometric feedback operation combustion operation mode (stoichio operation mode), and the open-loop combustion operation mode (stoichio operation mode or enrichment Operating mode). In each mode, the case where the EGR is operated and the case where the EGR is stopped are set. One of these modes is selected according to the operating state of the engine, the running state of the vehicle, and the like, and the fuel supply is performed. Control is performed.

For this reason, as shown in FIG.
The operating state of the engine detected by the operating state detecting means 101, specifically, the load state Pe of the engine and the engine speed Ne of the engine are input. The operation modes as described above are selected by the operation mode selection means 300 according to the operation state of the engine (here, Pe, Ne). The ECU 16 further determines the operating state (P) of the engine based on the selected operation mode.
e, Ne), the air-fuel ratio is set, and the fuel supply by the fuel injection valves 21 provided for each cylinder is controlled based on the set air-fuel ratio.

In general, the enriched operation mode, the stoichiometric operation mode, the first lean mode, and the second lean mode are set with respect to the engine speed Ne and the engine load Pe in a region tendency as shown in FIG. Among the above-mentioned modes, the latter lean mode can realize the leanest combustion (air-fuel ratio is about 30 to 40), but in this mode, the fuel injection is performed at a stage very close to the ignition timing as in the latter half of the compression stroke. In addition, the fuel is collected near the spark plug to make it partially rich and lean as a whole so that the fuel-saving operation is performed while ensuring the ignitability and the combustion stability.

In the first lean mode, lean combustion (air-fuel ratio of about 20 to 24) can be realized. In this mode, fuel is injected in the intake stroke before the second lean mode to diffuse fuel into the combustion chamber. In this way, while maintaining the ignitability and combustion stability while keeping the overall air-fuel ratio lean, a certain amount of output is ensured, thereby performing the economizing operation.

In the stoichiometric operation mode, a sufficient engine output can be efficiently obtained based on the output of the O ₂ sensor while maintaining the air-fuel ratio at or near the stoichiometric ratio. Further, in the open loop combustion operation mode, combustion is performed by stoichiometry or an air-fuel ratio richer than the stoichiometric ratio by open loop control so that a sufficient output can be obtained at the time of acceleration or starting.

First, the control of the opening degree of each of the valves 6 and 14 will be described. The ECU 16 has a function of setting the required air amount according to the engine operating state. Fourteenth opening degree control is performed. Specifically, as shown in FIG. 3, first, the engine rotation based on throttle opening θth detected by a throttle sensor or accelerator opening information from an accelerator opening sensor (not shown) and detection information from a crank angle sensor. Speed N
e from the target engine load (target P) based on the map.
e) is set (block B1).

On the other hand, if the air conditioner is turned on based on the information from the air conditioner switch, the air conditioner correction amount ΔPe is determined from the engine speed Ne based on the map.
If power steering is ON based on information from the power steering switch, ac is set (block B2), a power steering corresponding correction amount ΔPeps is set based on the map from the engine rotation speed Ne (block B3), and the power from the inhibitor switch is set. At the time of starting based on the information, the inhibitor-corresponding correction amount ΔP based on the map from the engine rotation speed Ne.
einh is set (block B4).

Then, these corresponding correction amounts ΔPea
The target Pe is corrected by c, ΔPeps, and ΔPeinh. Then, the corrected target Pe is appropriately filtered through the switch S1 (block B5), and based on the target Pe and the engine speed Ne obtained in this manner,
Required air volume (or target intake air volume) based on the map
A control amount Pos related to the valve opening degree according to Q is set.

In setting the control amount Pos, a switch corresponding to the operating state of the engine is selected and used from a plurality of maps as shown in a block B7.
Through S2 and S3, a signal is output according to the operating state of the engine. Here, maps are provided for the three operating modes of the engine, the latter lean mode in which the leanest combustion is performed, the first lean mode in which the next lean combustion is performed, and the EGR operation in the stoichiometric operation mode. The required air volume is set only in these modes.

When the idling state is established by the switch S4, the required air amount (or target intake air amount) # 1 based on the feedback of the engine speed # 1 1A
BVPos (in this case, the target opening mainly based on the first air bypass valve) is set. The function part for setting the required air amount Q through the blocks B7 and B8 and the amount corresponding to # 1ABVQ corresponds to required air amount setting means (not shown).

According to the control amount Pos or # 1ABVPos thus obtained, the second air bypass valve 6
Setting of the opening position or setting of the duty ratio (Block B
10), the opening position of the first air bypass valve 14 is set (block B11), and the first air bypass valve 14 and the second air bypass valve 6 are controlled to required states.

Further, based on FIG.
1, each control of the ignition coil and the EGR will be described. In order to drive the injector 21, it is necessary to set the injection start time and the injection end time of the injector 21, but here, the injector drive time Tinj and the injection end time of the injector 21 are set, and While calculating the injection start timing of the injector 21 based on the
The timing for driving the injector 21 is determined.
These settings are made by the ECU 16 according to the engine operating state.

In setting the injector driving time Tinj,
First, an air-fuel ratio A / F is set based on a map from the corrected target Pe and the engine speed Ne subjected to the filtering process (block B6) (block B12). The setting maps in this case are also provided for the four modes of the late lean mode during the EGR operation, the late lean mode during the EGR stop, the first lean mode, and the open loop mode, according to the operating state of the engine. Select one to use.

The injector driving time Tinj is calculated from the air-fuel ratio A / F thus obtained and the intake air amount Qpb detected by the airflow sensor (block B13). Then, the injector driving time Tinj is subjected to the cylinder-specific injector unequal ratio correction (block B14) and the cylinder-specific dead time correction (block B15). On the other hand, the target Pe
Injection time TDEC for deceleration from the engine speed Ne
Is calculated (block B16), and at the time of deceleration and late lean operation, the block B13 is set through the switch S5.
The smaller one of the injector drive time Tinj and the deceleration injection time TDEC obtained in (1) is selected (block B17), and this is determined as the injector drive time.

As for the setting of the injection end timing of the injector 21, the injection end timing is set based on the map from the corrected target Pe and the engine speed Ne subjected to the filtering process (block B6) (block B18). The setting map in this case is also provided for the four modes of the late lean mode during the EGR operation, the late lean mode during the EGR stop, the first lean mode, and the open loop operation or the stoichiometric feedback operation mode. The one selected according to the operation state of the engine is used.

In the case of the latter-stage lean mode, the injection end timing obtained in this way is subjected to water temperature correction to obtain the injection end timing. The injector 21 is driven based on the injector drive time Tinj and the injection end timing obtained in this manner. The ignition timing of the ignition plug by the ignition coil is also set based on the map from the corrected target Pe and the engine speed Ne subjected to the filtering process (block B6) (block B20). In this case, the setting maps are the EGR operation in the late lean mode and the EG in the late lean mode.
The five modes are provided during R stop, during the first lean mode, during EGR operation during stoichiometric feedback operation, and during EGR stop during open loop operation or stoichiometric feedback operation. The ignition timing thus obtained is subjected to various retard corrections (block B21), and the ignition coil is controlled based on this.

Also, regarding the EGR flow rate control, the corrected target Pe Pe subjected to the filtering process (block B6) is used.
EG based on the map from
The flow rate of R is set (block B22). The setting map in this case includes four modes: a late lean mode in the D range, a late lean mode in the N range, a stoichiometric feedback operation mode in the D range, and a stoichiometric feedback operation mode in the N range. Is provided.

The EGR flow rate obtained in this way is subjected to water temperature correction (block B23), a control amount (duty ratio) corresponding to the opening is set (block B24), and the EGR flow rate control is performed. And these blocks B22,
The block B23 and the block B24 constitute a target exhaust gas recirculation amount setting means 100. For the water temperature correction (block B23), a map corresponding to the operating state of the engine (here, two modes of the late lean mode and the stoichiometric feedback operation mode) is used.

Next, the main parts of the present invention will be described with reference to FIGS.
This device relates to control of the exhaust gas recirculation amount when the EGR is operated before and after the switching of the operation mode (or the fuel injection mode). The gas recirculation amount is temporarily reduced from the target exhaust gas recirculation amount set by the target exhaust gas recirculation amount setting means 100.

For this reason, as shown in FIG.
Is provided with an exhaust gas recirculation amount correction means 100a. When the operation mode is switched as described above, the target exhaust gas recirculation amount correction means 100a sets the target exhaust gas recirculation amount set by the target exhaust gas recirculation amount setting means 100. The recirculation amount is corrected. Specifically, when switching from the stoichiometric operation mode to the late lean mode, and when switching from the late lean mode to the stoichiometric operation mode, the actual exhaust gas recirculation amount is temporarily smaller than the target exhaust gas recirculation amount. Exhaust gas recirculation system (EG
(R device) 200 is controlled.

Such control is mainly performed for the following reasons. That is, when the operation mode is switched, the target air-fuel ratio A / F is changed by controlling the air amount by the second air bypass valve (# 2ABV) 6 or the fuel injection amount by the injector 21 in order to suppress the torque fluctuation of the engine. However, in such a case, if only the target exhaust gas recirculation amount is switched at once according to the operation mode, the combustion state may fluctuate rapidly and the combustion state may deteriorate.

Therefore, in the present apparatus, as described above, when the operation mode is switched, the exhaust gas recirculation amount correcting means 1 is used.
00, the actual exhaust gas recirculation amount is corrected to be temporarily smaller than the target exhaust gas recirculation amount set by the target exhaust gas recirculation amount setting means 100, and deterioration of the combustion state in the combustion chamber 18 is reduced. They try to prevent it. Note that such adjustment of the exhaust gas recirculation amount is actually performed by the EG.
This is executed by correcting the operation of the R valve 30.

Hereinafter, the control of the exhaust gas recirculation amount at the time of switching the operation mode will be described with reference to FIGS. 5 (a) to 5 (d). First, control of the target air-fuel ratio A / F at the time of switching the operation mode will be described. Target air-fuel ratio A / F
When the operation mode is switched, is changed by the air amount control by the second air bypass valve (# 2ABV) 6 and the fuel injection amount control by the injector 21 as described above. Among them, the second air bypass valve 6 is configured as an air amount correction means for correcting the amount of air supplied to the combustion chamber 18 of the engine 1,
The change of the target air-fuel ratio A / F at the time of switching the operation mode is mainly executed by controlling the opening of the second air bypass valve 6.

At the time of switching from the stoichiometric operation mode to the late lean mode, and at the time of switching from the latter lean mode to the stoichiometric operation mode, the target air-fuel ratio A / F is determined by the air amount correcting means as shown in FIG. It is controlled as shown. That is, when switching from stoichiometric operation mode to the late lean mode, the target air-fuel ratio A / F is once (stepwise) rather than being changed, than the actual switching timing A at a predetermined time before (timing A ₁ Shown) to target air-fuel ratio A
/ F is gradually changed to the lean side, and the target air-fuel ratio A / F is changed at a stroke by a predetermined amount at the fuel injection switching timing A. Then, this switching timing A
During the period from to after a predetermined time (indicated by the timing A _2),
Further, the target air-fuel ratio A / F is gradually increased to switch to the target air-fuel ratio A / F in the late lean mode.

Similarly, at the time of switching from the late lean mode to the stoichiometric operation mode, the target air-fuel ratio A / F is not changed at once (in a stepwise manner), but is changed at the actual switching timing B. gradually changed to the rich side target air-fuel ratio a / F from the predetermined time before (shown in the timing B ₁₎ than is to change the stretch target air-fuel ratio a / F by a predetermined amount in the fuel injection switching timing B. Then, during the period from the switching timing B until after a predetermined time (indicated by the timing B _2), further gradually increasing the target air-fuel ratio A / F, to switch the target air-fuel ratio A / F of the stoichiometric operation mode Has become.

As a result, the amount of air supplied to the combustion chamber 18 becomes as shown in FIG. 5D. When the operation mode is switched, the amount of air does not suddenly change but increases or decreases gradually. I will be. As a result, torque fluctuation at the time of switching the operation mode is suppressed.
On the other hand, the exhaust gas recirculation amount at this time is controlled by adjusting the opening degree of the EGR valve 30 as shown in FIG.

That is, when the mode is switched from the stoichiometric operation mode to the late lean mode, normally, as shown in FIG.
(B) It is conceivable that the EGR valve 30 is opened to the target opening at a stretch in synchronization with the operation mode switching timing A as indicated by the one-dot chain line so that the target exhaust gas recirculation amount is obtained. in this apparatus, in order to prevent deterioration of the combustion state, as shown in solid line in FIG. 5 (b), in the timing a ₁ of a predetermined time period before switching timing a mode of operation, once the EGR valve 30 the opening substantially squeezed to the fully closed near the timing a ₂ after a predetermined time has elapsed from the switching timing a mode of operation, than it is set so as to obtain the target exhaust gas recirculation amount by opening the EGR valve 30 to the target opening degree .

Also, when switching from the late lean mode to the stoichiometric operation mode, the EGR valve 30 is normally reduced to the target opening at a stretch in synchronism with the operation mode switching timing B to obtain the target exhaust gas recirculation amount. it is conceivable to set so as to, in this apparatus, at the timing B ₁ of a predetermined time period before switching timing B operation mode, once aperture the opening of the EGR valve 30 to substantially fully closed near the operating mode At a timing B ₂ after a lapse of a predetermined time from the switching timing B, the EG
The setting is such that the R valve 30 is opened to the target opening to obtain the target exhaust gas recirculation amount.

Thus, the amount of exhaust gas (actual EGR amount) recirculated to the combustion chamber 18 has a characteristic as shown in FIG. That is, at the operation mode switching timing A, the actual EGR amount before the switching is reduced, and then increased to reach the normal target exhaust gas recirculation amount. Therefore, at the time of switching from the stoichiometric operation mode to the latter lean mode, the amount of exhaust gas once recirculated is reduced, so that the amount of exhaust gas recirculation does not suddenly increase when the operation mode is switched, and the combustion state is deteriorated. The operation mode can be switched quickly without any problem.

Further, at the switching timing B from the late lean mode to the stoichiometric operation mode, the amount of exhaust gas recirculation rapidly decreases, so that the influence of the residual EGR gas in the late lean mode can be eliminated. It is. Since the exhaust gas recirculation control device as one embodiment of the present invention is configured as described above, EGR
When switching from the stoichiometric operation mode to the late lean mode is performed while operating the device 200, EG
By once narrowing the opening of the R valve 30 to nearly full close,
The actual exhaust gas recirculation amount (the actual EGR amount) is larger than the target exhaust gas recirculation amount set by the target exhaust gas recirculation amount setting means 100.
Is temporarily set lower.

Thus, it is possible to suppress a sudden increase in the actual EGR amount, and to prevent deterioration of the combustion state due to such a sudden change in the EGR amount at the time of switching the operation mode. Also, in the case where switching from the late lean mode to the stoichiometric operation mode is performed while operating the EGR device 200, the opening degree of the EGR valve 30 is once narrowed to almost fully closed in the same manner as described above, thereby reducing the target exhaust gas return. The actual exhaust gas recirculation amount (actual EGR amount) is temporarily set smaller than the target exhaust gas recirculation amount set by the flow rate setting means 100.

In the late lean mode, the amount of exhaust gas recirculated is relatively large. On the other hand, the amount of EGR required in the stoichiometric operation mode is smaller than that in the latter lean mode. Therefore, immediately after switching from the late lean mode to the stoichiometric operation mode, the exhaust gas required in the late lean mode remains in the exhaust gas recirculation passage (EGR passage) 29 and the intake passage, and the stoichiometric operation mode It is conceivable that a larger amount of exhaust gas than the required EGR amount is supplied to the combustion chamber 18 in spite of the switching to the EGR valve 30. By once narrowing the opening to almost fully closed, such residual exhaust gas (residual E
The influence of GR on the combustion state can be eliminated as much as possible, and the deterioration of the combustion state can be prevented.

That is, when the air amount is reduced as in the case of switching from the late lean mode to the stoichiometric operation mode, there is a demand to reduce the EGR amount as described above. When the is driven in the closing direction, the amount of fresh air decreases, so the EGR rate tends to increase. In order to decrease the EGR rate, the degree of decrease in the EGR rate must be greater than the degree of decrease in the amount of fresh air. is there. However, due to the influence of the residual EGR gas as described above, the EGR amount tends to increase more than necessary immediately after the operation mode is switched.

On the other hand, when the operation mode is switched,
By narrowing the degree of opening of the EGR valve 30 to near full closure once, it is possible to prevent the deterioration of the combustion state at the time of such switching. At this time, if the opening degree of the EGR valve 30 at the time of switching the operation mode is temporarily fully closed, the operation mode switching time can be further shortened, and the deterioration of the exhaust gas performance can be reduced. There are advantages.

[0056]

As described in detail above, according to the exhaust gas recirculation control device of the present invention, when the fuel injection mode is switched while operating the exhaust gas recirculation device, it is set by the target exhaust gas recirculation amount setting means. Since the actual exhaust gas recirculation amount is temporarily set to be smaller than the target exhaust gas recirculation amount, it is possible to suppress a sudden increase in the actual exhaust gas recirculation amount, resulting in deterioration of the combustion state. Can be prevented.

Further, the influence of the residual exhaust gas on the combustion state before switching of the fuel injection mode can be eliminated as much as possible, and the deterioration of the combustion state can be prevented. Further, if the exhaust gas recirculation amount is set to 0 at the time of switching the fuel injection mode, there is an advantage that the operation mode switching time can be shortened and deterioration of the exhaust gas performance can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram focusing on main functions of an exhaust gas recirculation amount control device as one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an overall configuration of an internal combustion engine having an exhaust gas recirculation control device as one embodiment of the present invention.

FIG. 3 is a functional block diagram of an internal combustion engine having an exhaust gas recirculation control device as one embodiment of the present invention.

FIG. 4 is a diagram illustrating an operation mode of an internal combustion engine having an exhaust gas recirculation control device as one embodiment of the present invention.

FIG. 5 is a diagram for explaining an operation of the exhaust gas recirculation control device as one embodiment of the present invention when the fuel injection mode is switched.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Intake passage 2A Intake port 3 Throttle valve installation part 4 Air cleaner 5 Bypass passage (second bypass passage) 6 Second air bypass valve (# 2ABV) 7 Intake pipe 8 Surge tank 9 Intake manifold 12 Idle speed control function Provided 13 Bypass passage (first bypass passage) 14 First air bypass valve (# 1ABV) 15 Throttle valve 16 Electronic control unit (ECU) 17 Exhaust passage 17A Exhaust port 18 Combustion chamber 19 Intake valve 20 Exhaust valve 21 Fuel injection Valve (injector) 22 Fuel tank 23A to 23E Fuel supply path 24 Low pressure fuel pump 25 High pressure fuel pump 26 Low pressure regulator 27 High pressure regulator 28 Delivery pipe 29 Exhaust gas recirculation passage (EGR passage) 30 EGR valve DESCRIPTION OF SYMBOLS 1 Blow-by gas return flow path 32 Crank room positive ventilation passage 33 Crank room positive ventilation valve 34 Canister 35 Exhaust gas purification catalyst 36 Intake temperature sensor 37 Throttle position sensor (TPS) 38 Idle switch 40 First cylinder detection sensor 41 Crank Angle sensor 42 Water temperature sensor 43 O ₂ sensor 100 Target exhaust gas recirculation amount setting means 101 Operating state detection means 100a Exhaust gas recirculation amount correction means 200 Exhaust gas recirculation device (EGR device)

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI F02D 43/00 301 F02D 43/00 301E 301J 301K 301N 45/00 301 45/00 301F 301G 312 312A F02M 25/07 550 F02M 25 / 07 550F 550R (72) Inventor Hiroki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-5-113146 (JP, A) JP-A-6-10772 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/02 325 F02D 21/08 301 F02D 41/04 305 F02D 41/04 335 F02D 41/14 310 F02D 43/00 301 F02D 45/00 312 F02M 25/07 550

Claims (7)

(57) [Claims] An air-fuel ratio that is leaner than the stoichiometric air-fuel ratio is set.
The first fuel injection mode and the first fuel injection mode
Also between the second fuel injection mode in which the air-fuel ratio on the enrichment side is set.
In an internal combustion engine capable of switching the fuel injection mode, an exhaust gas recirculation device for recirculating a part of exhaust gas to the intake, the target exhaust gas recirculation amount of the first of the first fuel injection mode
In addition to setting the EGR flow value, the second fuel injection mode
And the target exhaust gas recirculation amount setting means for setting a target exhaust gas recirculation amount of over de in the second EGR flow rate value, and the first fuel injection mode and the second fuel injection mode
When the fuel injection mode is switched during the first fuel injection mode,
Mode or the second fuel injection mode.
Exhaust gas recirculation amount correction means for correcting the target exhaust gas recirculation amount
With the door, the exhaust gas recirculation amount compensation means, the target exhaust gas recirculation amount
For a predetermined time when the fuel injection mode is switched.
The first EGR flow rate value and the second EGR flow rate
An exhaust gas recirculation control device, wherein the third EGR flow value is smaller than the third EGR flow value . 2. The exhaust gas recirculation amount correction means includes:
3, wherein the EGR flow value is corrected to substantially zero .
The exhaust gas recirculation control device according to claim 1. 3. The engine according to claim 1 , wherein the internal combustion engine includes a first fuel injection mode.
And the internal combustion engine according to the second fuel injection mode.
Empty for setting the target intake air amount to be supplied to the combustion chamber
Air volume setting means; and the first fuel injection mode when the fuel injection mode is switched.
Target set according to the mode or the second fuel injection mode
3. The exhaust gas recirculation control device according to claim 1, further comprising air amount correction means for correcting an intake air amount . 4. An internal combustion engine according to claim 1 , wherein said fuel injection mode is switched off.
When switching, the target air-fuel ratio before switching the fuel injection mode
When changing to the target air-fuel ratio after switching the fuel injection mode
In both cases, after executing the actual fuel injection mode switch
The target air-fuel ratio after switching the fuel injection mode
And controls so that the exhaust gas recirculation control device according to claim 1. 5. When fuel is injected mainly in the compression stroke,
Both compression lines operate at a leaner air-fuel ratio than the stoichiometric air-fuel ratio
Injection mode and fuel injection mainly in the intake stroke
With the air-fuel ratio on the richer side than the lean air-fuel ratio
In-cylinder injection type internal combustion that can switch between intake stroke injection mode
In the engine, an exhaust gas recirculation device that recirculates a part of exhaust gas to intake air and a target exhaust gas recirculation amount in the compression stroke injection mode are set to a first value.
The EGR flow rate value is set and the intake stroke injection mode is set.
Set the target exhaust gas recirculation amount of the engine to the second EGR flow value
Target exhaust gas recirculation amount setting means for performing the compression stroke injection mode and the intake stroke injection mode.
When the fuel injection mode is switched during
Mode or the intake stroke injection mode
Exhaust gas recirculation amount correction means for correcting the target exhaust gas recirculation amount
With the door, the exhaust gas recirculation amount compensation means, the target exhaust gas recirculation amount
For a predetermined time when the fuel injection mode is switched.
The first EGR flow rate value and the second EGR flow rate
An exhaust gas recirculation control device, wherein the third EGR flow value is smaller than the third EGR flow value . 6. An air-fuel ratio which is set leaner than the stoichiometric air-fuel ratio.
The first fuel injection mode and the first fuel injection mode
Also between the second fuel injection mode in which the air-fuel ratio on the enrichment side is set.
In an internal combustion engine capable of switching the fuel injection mode, an exhaust gas recirculation device that recirculates a part of exhaust gas to intake air, and a target exhaust gas recirculation amount of the first fuel injection mode is set to a first value.
In addition to setting the EGR flow value, the second fuel injection mode
The target exhaust gas recirculation amount of the engine is calculated from the first EGR flow value.
Target exhaust gas set to a second EGR flow value smaller than
Recirculation amount setting means, and the first fuel injection mode and the second fuel injection mode
When the fuel injection mode is switched during the first fuel injection mode,
Mode or the second fuel injection mode.
Exhaust gas recirculation amount correction means for correcting the target exhaust gas recirculation amount
With the door, the exhaust gas recirculation amount compensation means, the first fuel injection mode
From the fuel injection mode to the second fuel injection mode
At the time of replacement, the target exhaust gas recirculation amount is temporarily set to the first E
A GR flow value and a second EGR flow value smaller than the second EGR flow value.
3, the second EGR flow rate is corrected.
Exhaust gas recirculation control device, characterized in that
Place. 7. An air-fuel ratio set leaner than the stoichiometric air-fuel ratio.
The first fuel injection mode and the first fuel injection mode
Also between the second fuel injection mode in which the air-fuel ratio on the enrichment side is set.
In an internal combustion engine capable of switching the fuel injection mode, an exhaust gas recirculation device that recirculates a part of exhaust gas to intake air, and a target exhaust gas recirculation amount of the first fuel injection mode is set to a first value.
In addition to setting the EGR flow value, the second fuel injection mode
The target exhaust gas recirculation amount of the engine is calculated from the first EGR flow value.
Target exhaust gas set to a second EGR flow value smaller than
Recirculation amount setting means, and the first fuel injection mode and the second fuel injection mode
When the fuel injection mode is switched during the first fuel injection mode,
Mode or the second fuel injection mode.
Exhaust gas recirculation amount correction means for correcting the target exhaust gas recirculation amount
And the exhaust gas recirculation amount correction means includes a second fuel injection mode.
From the fuel injection mode to the first fuel injection mode.
At the time of replacement, the target exhaust gas recirculation amount is temporarily set to the second E
A GR flow value and a first EGR flow value smaller than the first EGR flow value.
3, the first EGR flow rate is corrected to the first EGR flow rate.
Exhaust gas recirculation control device, characterized in that
Place.