JP2797646B2 - Exhaust gas recirculation system for a supercharged lean internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas recirculation device for a supercharged lean burn internal combustion engine.

(Prior art)

Japanese Patent Application No. 1-156685 discloses a gasoline-fueled internal combustion engine in which a large turbocharger is used to perform supercharging and increase the air density to realize lean combustion during high-load operation (hereinafter referred to as high-density supercharging). Lean burn). By performing supercharging at a high density, the amount of fuel per unit volume is maintained even when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. Efficiency can be improved.

[Problems to be solved by the invention]

The air-fuel ratio is set to the stoichiometric air-fuel ratio on the low-speed and low-load side where the turbocharger does not provide a sufficient supercharging effect in the high-density supercharged lean-burn system, and the air-fuel ratio on the high-speed and high-load side is lean Is set. In switching from the stoichiometric air-fuel ratio range to the lean air-fuel ratio range, it is ideally preferable to switch the air-fuel ratio stepwise from the stoichiometric air-fuel ratio (14.5) to 19.0.
At such an intermediate air-fuel ratio (for example, 16.0), the emission amount of the nitrogen oxide component in the exhaust gas increases. However, since the torque of the engine suddenly changes due to the stepwise change in the setting of the air-fuel ratio, the air-fuel ratio is actually set to continuously change from the stoichiometric air-fuel ratio to the target lean air-fuel ratio. Therefore, there is a problem that the emission amount of the nitrogen oxide component in the exhaust gas increases.

An object of the present invention is to realize switching from a stoichiometric air-fuel ratio to a lean air-fuel ratio quickly without reducing the torque and without increasing the emission of nitrogen oxide components.

[Means for solving the problem]

According to the present invention, in FIG. 1, the supercharger A controls the air-fuel ratio to the lean side during operation in which the supercharging effect is achieved, and the exhaust gas recirculation passage B connecting the exhaust system and the intake system is provided. Means D for determining an operating range in which the air-fuel ratio should be controlled to a lean side in an internal combustion engine provided with an exhaust gas recirculation control valve C
Means E for increasing the supercharging pressure by the supercharger when it is determined that the air-fuel ratio is in the lean air-fuel ratio control range, and means F for detecting an increase in the supercharging pressure.
And the exhaust gas recirculation passage B when it is detected that the boost pressure has increased.
Means for controlling the exhaust gas recirculation control valve C such that the amount of recirculated exhaust gas passing through the exhaust gas recirculation gas increases.

[Action]

When the lean air-fuel ratio control range determining means D determines a region where the air-fuel ratio should be set to be lean, the supercharging pressure increasing means E increases the supercharging pressure by the supercharger A.

When the supercharging pressure detecting means F detects that the supercharging pressure is increased, the exhaust gas recirculation control means G controls the exhaust gas recirculation control valve C so that the amount of the recirculated exhaust gas passing through the exhaust gas recirculation passage B increases. Control.

〔Example〕

FIG. 2 shows the whole of a high-density supercharged gasoline internal combustion engine according to the present invention. Reference numeral 10 denotes an engine body, and an intake pipe 12 and an exhaust pipe 14 are connected. In the internal combustion engine of the embodiment, each intake port 10-1 is divided into two parts, one of which is provided with a swirl control valve 10-2, and when the control valve 10-2 is closed, only the other part is opened. The air-fuel mixture is introduced into the cylinder, and the air-fuel mixture forms a swirl in the cylinder. On the other hand, when the control valve 10-2 is opened, the air-fuel mixture is introduced from both portions of the intake port, and the swirl disappears. It is intended to favorably burn a mixture leaner than the stoichiometric air-fuel ratio by swirl.

A large turbocharge 17 and a small turbocharger 18 are arranged in series. The large turbocharger 17 includes a compressor 20, a turbine 22, and a rotating shaft 24.
The small turbocharger 18 has a compressor 26 and a turbine
28 and a rotating shaft 25. In the intake pipe 12, the compressor 20 of the large turbocharger 17 and the compressor 26 of the small turbocharger 18 are arranged in this order in the flow direction of the intake air, and the intercooler 29 is arranged downstream thereof. In the exhaust pipe, the turbine 28 of the small turbocharger 18 and the turbine 22 of the large turbocharger 17 are arranged in this order in the flow direction of the exhaust gas.

A first exhaust bypass passage 30 is connected to the exhaust pipe bypassing the turbine of the large turbocharger 17, and a wastegate valve 32, which is a swing door valve, is disposed in the first exhaust bypass passage 30. The waste gate valve 32 is connected to a diaphragm actuator 34, and the diaphragm 34
a is connected to the bypass valve 32. The bypass valve 32 is normally urged to close by the spring 34b, but the waste gate valve 32 is opened against the spring 34b by a positive pressure replacing the diaphragm 34a.

The second bypassing the turbine 28 of the small turbocharger 18
The exhaust bypass passage 36 is provided, and the second bypass passage 36 is provided with an exhaust switching valve 38 as a butterfly valve. The exhaust switching valve 38 is connected to the actuator 40, and the actuator 40 is configured as a two-stage diaphragm mechanism.
The actuator 40 is operated by the exhaust switching valve 38 until the large turbocharger 17 exhibits the full supercharging capacity, as described later.
And the exhaust gas switching valve 38 is quickly opened when the large turbocharger 17 reaches its full supercharging capacity. The actuator 40 is a diaphragm 40a,
40b and springs 40c and 40d, one diaphragm
40a is connected to an exhaust switching valve 38 via a rod 40e, and another diaphragm 40b is connected to a rod 40f. Apply supercharging pressure to the diaphragm 40a or
By applying a supercharging pressure to the exhaust gas, a stepwise opening characteristic of the exhaust gas switching valve 38 can be obtained. That is, when the supercharging pressure is applied to the diaphragm 40b, the exhaust switching valve 38 is opened against the force of the spring 40c and the resultant force of the spun ring 40d, so that the opening is performed slowly. When the supercharging pressure acts on the diaphragm 40a, the exhaust switching valve 38 is opened only against the force of the spring 40c, so that the valve opening operation is quick.

An intake bypass passage 44 that bypasses the compressor 26 of the small turbocharger 18 is provided.
An intake bypass valve 46 is arranged at 44. The switching valve 46 is connected to a diaphragm actuator 48, and the diaphragm
The operation of the intake bypass valve 46 is controlled by the pressure applied to 48a. This intake bypass valve 46 is a large turbocharger
Although the intake bypass passage 44 is closed in the operating range of the small turbocharger 18 where the startup of the compressor 17 is not completed, after the completion, the boost pressure acts on the diaphragm 48a from below, and the intake bypass valve 46 is opened. Will be

The internal combustion engine is equipped with an exhaust gas recirculation (EGR) device,
The GR device has an exhaust gas recirculation passage (EGR passage) 50 and an EGR passage
An exhaust gas recirculation control valve (EGR valve) 52 above
The GR valve 52 has a diaphragm 52a and a valve body 52b, and the opening and closing of the valve body 52b are controlled according to the pressure applied to the diaphragm 52a. The EGR passage 50 has an upstream end (exhaust gas outlet) 50A connected to the exhaust pipe 14 upstream of the turbine 28 of the small turbocharger 18 and a downstream end (exhaust gas inlet 50).
B) is connected to the intake pipe downstream of the intercooler 29.

A three-way solenoid valve (VSV1) 54 is provided for controlling the pressure of the waste gate valve 32 to the actuator 34.
Reference numeral 54 switches between a position where the atmospheric pressure is introduced into the diaphragm 34a and a position where the supercharging pressure is introduced at a position 56 downstream of the small turbocharger 26 and upstream of the intercooler 29. When introducing atmospheric pressure, the waste gate valve 3
The closing gate 2 is driven to open the waste gate valve 32 against the spring 34b when the supercharging pressure is introduced.

A three-way solenoid valve (VSV2) 58 is provided for controlling the pressure of the actuator 40 of the exhaust switching valve 38 to the diaphragm 40a,
The solenoid valve 58 switches between a position for introducing atmospheric pressure to the diaphragm 40a and a position for introducing supercharging pressure at the outlet 60 of the small turbocharger 26. Further, the pressure of the small turbocharger outlet 60 is constantly introduced into the diaphragm 40b.

Two three-way solenoid valves 64 and 66 are provided for controlling the pressure of the intake bypass valve 46 to the actuator 48. A three-way solenoid valve (VSV3) 64 is provided above the diaphragm 48a of the actuator 48 of the intake bypass valve 46 for pressure control. This solenoid valve 64 is provided with a position for introducing atmospheric pressure above the diaphragm 48a and a small turbocharger. 18 compressor outlets 60
It switches with the position where the supercharging pressure is introduced. The three-way solenoid valve (VSV4) 66 is connected to the actuator 48 of the intake bypass valve 46.
The solenoid valve 66 is provided for controlling the pressure below the diaphragm 48a, and is connected to a negative pressure port downstream of the throttle valve 16.
The position is switched between the position where the negative pressure of 68 is introduced and the position where the supercharging pressure at the compressor outlet of the large turbocharger 66 is introduced.

A three-way solenoid valve (VSV5) 70 is provided for controlling the operation of the EGR valve 52. This solenoid valve 70 controls the position for introducing atmospheric pressure to the diaphragm 52a and the negative pressure at the negative pressure port 68 downstream of the throttle valve 16. Switches depending on the position to be introduced. The electromagnetic valve 70 is driven by a pulse signal, and can be controlled to an arbitrary EGR amount by controlling the duty ratio.

The solenoid valve 71 (VSV6) is provided to rapidly increase the supercharging pressure by closing the exhaust switching valve 38 when the air-fuel ratio is switched from the stoichiometric air-fuel ratio setting to the lean air-fuel ratio setting. The solenoid valve 71 has a position for introducing atmospheric pressure to the side of the diaphragm 40a on the side of the spring 40c and a negative pressure port downstream of the throttle valve 16.
It switches at the position where 68 negative pressure is introduced.

The control circuit 72 is provided for supercharging control in the present invention, and the solenoid valves 54 (VSV1), 58 (VSV2), 64 (VSV3), 66 (V
SV4), 70 (VSV5), and 71 (VSV6) drive signals are generated.
Further, an ignition plug (not shown) is controlled via an igniter 74 and a distributor 76 to control the ignition timing.
The control circuit 72 is connected to various sensors for executing the control according to the present invention. First, a large turbocharger
The first pressure sensor 78 for detecting the outlet pressure P ₁ of the compressor 20 of 17 is provided, also small turbocharger 18
The second pressure sensor 80 is provided for detecting the outlet pressure P ₂ of the compressor 26. The air-fuel ratio sensor 82 generates a signal corresponding to the air-fuel ratio. Although not shown, a sensor for detecting the intake air amount Q to the engine and a crankshaft
A crank angle sensor is provided for generating a pulse signal every time the motor rotates by ゜ and 720 °.

Hereinafter, the operation of the control circuit 72 will be described with reference to the flowcharts of FIGS. FIG. 3 shows a supercharging control routine. In step 100, the ratio of intake air amount to engine speed Q / N
It is determined whether E is greater than a predetermined value X. The predetermined value X is a value of an intake air amount-engine speed ratio which is a reference when switching the air-fuel ratio from the stoichiometric air-fuel ratio to the lean air-fuel ratio. The switching point from the stoichiometric air-fuel ratio to the lean air-fuel ratio may be the intake manifold pressure or a factor other than switching based on the intake air amount-engine speed ratio as in the embodiment. When Q / NE ≦ X, that is, when the air-fuel ratio should be set to the stoichiometric air-fuel ratio, the routine proceeds to step 102, where the solenoid valve 71 (VSV6)
N, and therefore the negative pressure port 68 downstream of the throttle valve 16
Is introduced to the side of the spring 40c of the diaphragm 40a, and the diaphragm 40a moves to the left against the spring 40c,
The exhaust switching valve 38 is opened.

When it is determined in step 100 that Q / NE> X, that is, when the air-fuel ratio should be controlled to the lean side, the process proceeds to step 104, where the solenoid valve 71 (VSV6) is turned off, and the atmospheric pressure is reduced by the spring of the diaphragm 40a. Introduced to the side of 40c, the diaphragm 40a is biased rightward against the spring 40c, and the exhaust switching valve 38 is biased to close. The switching control of the exhaust switching valve 38 from the open state to the closed state at the switching point of the air-fuel ratio from the stoichiometric air-fuel ratio setting to the lean setting is to cancel the tendency of the torque reduction due to the rapid increase of the supercharging pressure and the leaning of the air-fuel ratio. .

In step 106, the ratio of intake air amount to engine speed Q / NE
> Y is determined. This predetermined value Y (> X) detects an actual increase in the supercharging pressure due to the switching of the exhaust switching valve 38 from open to closed. When Q / NE ≦ Y, it is considered that the supercharging pressure has not yet risen, and the routine proceeds to step 108, where the flag F is cleared. When F = 0, leaning of the air-fuel ratio is prohibited by an air-fuel ratio control routine described later, and the air-fuel ratio is set to the stoichiometric air-fuel ratio. Next, the routine proceeds to step 110, where the EGR rate correction coefficient K = 1.
It is set to 0. K is a coefficient for correcting the EGR rate as much as possible from the map value in a switching region of the air-fuel ratio from the stoichiometric air-fuel ratio to the lean air-fuel ratio. By setting K = 1.0, the EGR rate becomes the map value.

When it is determined in step 106 that Q / NE> Y, that is, when it is considered that the supercharging pressure has increased, the routine proceeds to step 111, where the flag F is set. When F = 1, leaning of the air-fuel ratio is permitted by an air-fuel ratio control routine described later. Steps
At 112, the EGR rate correction coefficient K is calculated. The EGR rate correction coefficient is used to correct the EGR rate so that it becomes higher than the normal value at the time of transition from the stoichiometric air-fuel ratio to the lean air-fuel ratio, and to suppress the emission of nitrogen oxide components that often occur at the time of the air-fuel ratio transition. is there. In step 114, the ratio of intake air amount to engine speed Q / N
E> It is determined whether or not the value is greater than a predetermined value Z. This predetermined value Z (> Y) is a threshold value at the upper limit boundary of the region where the EGR rate is increased in the switching region from the stoichiometric air-fuel ratio to the lean air-fuel ratio. Q
When / NE ≦ Z, the process exits from step 110. Therefore, EGR
The rate is increased. When Q / NE> Z, it is determined that the nitrogen oxide rise region has been exceeded in switching from the stoichiometric air-fuel ratio to the lean air-fuel ratio, and the routine proceeds to step 110, where the EGR rate correction coefficient K
= 1.0, and the EGR rate is the original map value.

The processing after step 120 is a routine for switching from two-stage supercharging to one-stage supercharging. Compressor outlet pressure P ₁ of the compressor outlet pressure P _2> large turbocharger 17 in step 120 the small turbocharger 18 is determined whether or not satisfied. Figure 7 shows the relationship between the engine speed NE and the supercharge pressure in case of fixing the opening degree of the throttle valve 16 to a constant (turbocharger outlet pressure), the rise of the small turbocharger outlet pressure P ₂ is large It is earlier than the rise of the turbocharger outlet pressure P _1. Therefore, in a state where the rotation of the engine has not yet risen, P ₂ > P ₁ is satisfied, and the routine proceeds to step 122 and subsequent steps. In step 122, the solenoid valve 54 (VSV1) is turned off, and the diaphragm
Atmospheric pressure is introduced to 34a, and the waste gate valve 32 is closed by a spring 34b. In step 124, the solenoid valve 58 (VSV2) for controlling the actuator 40 is turned off. Therefore, the atmospheric pressure acts on the diaphragm 40a of the actuator 40. On the other hand, since the compressor outlet pressure of the small turbocharger 18 is always introduced into the diaphragm 40b, the exhaust switching valve 38 is controlled by the compressor outlet pressure of the small turbocharger 18 which opposes the spring force corresponding to the resultant force of the springs 40c and 40d. Operation is controlled. That is, as long as the spring force is dominant in the supercharging pressure P ₂ is the exhaust switching valve 38 is maintained fully closed, the supercharging pressure P ₂ is a predetermined value P _SET
Up to the rotation speed (NE _{1 in} FIG. 7)
Maintains a fully closed, P ₂ = predetermined value P _SET exhaust switching when it reaches the valve 38 is caused to start the gradual opening against the closing biasing force is spring 40c, 40d force of. Note that P ₂ <P ₁
However, when the intake air amount-engine speed ratio Q / NE ≦ X (Yes in step 100), the exhaust switching valve 38 is opened by the introduction of the negative pressure to the diaphragm 40a, and the actual exhaust switching valve 38 is closed. Occurs after Q / NE> X (No in step 100). With respect to the operation of the intake bypass valve 46 at the time of low rotation, the compressor outlet pressure P ₁ of the solenoid valve 64 (VSV3) is turned ON turbocharger 20 diaphragm in step 126
The intake bypass valve 46 is closed to act on the upper side of 48a. In step 128, the solenoid valve 66 (VSV4) is turned off, so that the negative pressure from the negative pressure pump 67 acts on the lower side of the diaphragm 48a, so that the diaphragm 48a is pulled downward and the intake bypass valve 46 is closed. The power has been raised to ensure that the valve is closed.

During acceleration, the engine speed NE increases to NE ₂ and the compressor outlet pressure of the large turbocharger 17
Rise of P ₁ catches up to the compressor outlet pressure P ₂ of the small turbocharger 18, when the P ₂ = P ₁ step 120
When the solenoid valve 54 (VSV1) is turned on, the boost pressure from the position 56 is introduced to the diaphragm 34a, and the waste gate valve 32 is urged in the opening direction against the spring 34b. . In step 132, the operating solenoid valve 58 (VSV2) of the exhaust switching valve 38 is turned on. For this reason, since the supercharging pressure acts on the diaphragm 40a, the spring 40d does not participate in the closing force of the exhaust switching valve 38 against the supercharging pressure, and only the weak urging force of the spring 40c participates in the closing force. Therefore, the actuator 40 opens the exhaust switching valve 38 at a stretch. In step 134, the solenoid valve 64 (VSV
3) is turned off, the atmospheric pressure acts on the upper side of the diaphragm 48a, the solenoid valve 66 (VSV4) is turned on in step 136, and the supercharging pressure acts on the lower side of the diaphragm 48b. When pressed, the intake bypass valve 46 is opened at a stretch.

FIG. 4 shows an exhaust gas recirculation control routine. In step 140, it is determined whether or not the engine is in an operating range in which exhaust gas recirculation is performed. At the time of high rotation and high load operation, the EGR is stopped, and the routine proceeds to step 142, where the duty ratio DUTY = 0 in the drive signal of the solenoid valve 70 (VSV5) for driving the EGR valve 52 is set. Therefore, the electromagnetic valve 70 (VSV5) is continuously turned off, and the atmospheric pressure is introduced into the diaphragm 52a, so that the EGR valve 52 is closed. If it is determined in step 140 that the area is an EGR area, step
Proceed to 144, solenoid valve 70 responsible for EGR rate in normal state
(VSV5) drive signal duty ratio DUTY maps
Calculated from MAP. This map has a duty ratio DUTY value according to an optimal EGR rate according to a load at that time (for example, intake air amount-engine speed ratio Q / NE),
The duty ratio DUTY corresponding to the EGR rate suitable for the current operation condition is calculated by the interpolation calculation. Step 146
Is the duty ratio DUTY multiplied by the correction coefficient K.
TY. FIG. 9 schematically shows a map of the EGR rate correction coefficient K with respect to the rotation speed and the air-fuel ratio A / F when the throttle valve opening is kept constant. The line with K = 1 indicates the boundary region for executing the correction of the EGR rate in switching from the two-stage supercharging to the one-stage supercharging, and the air-fuel ratio (AF = AF ₀ ) at which the nitrogen oxide emission peaks. The correction coefficient is set to be large. Further, the correction coefficient is reduced as the number of rotations increases. Step 148 shows the output of the duty ratio signal, so that the solenoid valve 70 (VSV5) is operated at that duty ratio, and the calculated EGR rate can be obtained.

In FIG. 7, the EGR rate map set in step 144 (FIG. 4) is schematically shown by contour lines. Q / NE =
The shaded area between Y and Q / NE = Z is the area of the intermediate air-fuel ratio where the emission of nitrogen oxides is large, and the EGR rate is increased by the EGR rate correction coefficient K according to the map of FIG. .

FIG. 5 shows a fuel injection routine in which the fuel injection timing of the cylinder is determined by the crank angle sensor from 30 ° CA, 720 °.
Determined and executed by CA signal. In step 150, the basic fuel injection amount Tp is calculated. The basic fuel injection amount is a standard value at which the air-fuel ratio is the stoichiometric air-fuel ratio at the load and the rotation speed. In step 152, it is determined whether or not the air-fuel ratio control flag F = 1. When F = 0, that is, when the air-fuel ratio should be controlled to the stoichiometric air-fuel ratio, the process proceeds from step 152 to step 154.
Then, the air-fuel ratio correction coefficient KLEAN = 1.0 and the feedback flag FB = 1 are set. KLEAN is a coefficient for correcting the air-fuel ratio to a leaner side than the stoichiometric air-fuel ratio. By setting KLEAN = 1.0, the setting of the air-fuel ratio becomes the stoichiometric air-fuel ratio. The feedback control of the air-fuel ratio is executed by setting the feedback flag FB = 1. In step 156, the air-fuel line correction coefficient FAF is directly entered into the FAF. FAF is a coefficient that corrects the air-fuel ratio to the stoichiometric air-fuel ratio during the air-fuel ratio feedback.

When F = 1, that is, when the air-fuel ratio should be controlled to the lean air-fuel ratio, the process proceeds from step 152 to step 158, where the air-fuel ratio correction coefficient KLEAN is calculated from the map. The air-fuel ratio is controlled to be as lean as possible from the fuel consumption rate, and there is a demand from the output to suppress the degree of leanness, and it is appropriately set in harmony. A well-known interpolation operation is performed to obtain a value of KLEAN suitable for the operating condition. In step 160, the feedback correction coefficient FAF is corrected to 1.0. That is, the feedback control of the air-fuel ratio is not performed during the lean air-fuel ratio control.

 In step 162, the final fuel injection amount is calculated by TAU = Tp × KLEAN × FAF.

Step 164 shows the output of the fuel injection signal to the injector 15 so that the fuel injection of the amount calculated in step 162 is performed.

FIG. 6 schematically shows an air-fuel ratio feedback control routine. In step 170, it is determined whether or not the feedback flag FB = 1, and when FB = 0, that is, when there is no feedback, the process proceeds to step 171, where FAF = 1.0. FB =
Step 17, when performing air-fuel ratio feedback
From 0, the process proceeds to step 172, where a signal is input to the air-fuel ratio sensor 82.At step 174, it is determined whether the air-fuel ratio is leaner than the stoichiometric air-fuel ratio based on the signal of the air-fuel ratio sensor. Then, the process proceeds to step 178, where the feedback correction coefficient FAF is increased.

FIG. 8 is a timing chart for schematically explaining the operation of the embodiment of the present invention. (A) is the EGR rate, (b) is the amount of nitrogen oxide (NOx) emissions, (c) is the fuel amount Gf, (d) is the operation of the exhaust switching valve 38, (e) is the intake air amount-engine speed The number ratio Q / NE indicates the air-fuel ratio A / F. Assuming that the time t ₀ is the start timing of the transition region from the stoichiometric air-fuel ratio to the lean air-fuel ratio (Yes in step 100 in FIG. 3), the exhaust gas switching valve
A signal is generated to switch 38 from open to closed. It is detected that the intake air amount-engine speed ratio Q / NE increases (No. 3
EGR rate correction coefficient in terms of FIG step 106) t ₁ is set (step 112 of FIG. 3), the EGR rate (a) is rapidly and the air-fuel ratio is gradually increased toward the lean air-fuel ratio of the target (F). By increasing the EGR rate, it is possible to suppress the emission of nitrogen oxide components in the transition region of the air-fuel ratio (b). (B) Dashed line is conventional (when EGR is not increased)
Figure 5 shows NOx emissions. Increase in the EGR rate at the time of t ₂ past the transition zone is returned to the map value is stopped (step 144 of FIG. 4) (b).

In the above embodiment, the control is to increase the EGR rate from the normal map value at the time of shifting from the stoichiometric air-fuel ratio operation to the lean air-fuel ratio operation. It is possible to perform control such that EGR is performed only at the time of transition from the stoichiometric air-fuel ratio operation to the lean air-fuel ratio operation, which is a problem (control using only k in the embodiment).

Further, the swirl control valve 10-2 is closed in the intermediate air-fuel ratio region where the EGR rate is increased, and the intake swirl is generated in the cylinder, so that the combustibility can be improved in the EGR rate increased region.

〔effect〕

According to the present invention, in the transition region from the stoichiometric air-fuel ratio to the lean air-fuel ratio operation, by increasing the supercharging pressure and simultaneously performing the exhaust gas recirculation, the generation of nitrogen oxides is suppressed while suppressing the torque decrease. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a functional configuration of the present invention. FIG. 2 is a diagram showing a configuration of an embodiment of the present invention. 3 to 6 are flowcharts for explaining the operation of the control circuit. FIG. 7 is a graph showing a change of a supercharging pressure with respect to an engine speed. FIG. 8 is a timing chart schematically explaining the operation of the control circuit. FIG. 9 is a diagram schematically illustrating a map of an EGR rate correction coefficient. 10 ... engine body, 12 ... intake pipe, 14 ... exhaust pipe, 17 ... large turbocharger, 18 ... small turbocharger, 30 ... first exhaust bypass passage, 32 ... waste gate valve, 36 ... … Second exhaust bypass passage, 38… Exhaust switching valve, 44 …… Intake bypass passage, 50… EGR passage, 52… EGR valve, 54,58,64,66,70 …… Solenoid valve (VSV), 78,80 ... Pressure sensor.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301N 301R F02M 25/07 550 F02M 25/07 550C (72) Inventor Toshiyuki Maehara Toyota City, Aichi Prefecture No. 1 Toyota Town Inside Toyota Motor Co., Ltd. (56) References JP-A-62-85148 (JP, A) JP-A-56-2433 (JP, A) JP-A-56-124664 (JP, A) 61-268845 (JP, A) JP-A-4-17743 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-43/00 F02D 21 / 08,23 / 00 F02B 37/00 F02M 25/07

Claims (1)

(57) [Claims] An exhaust gas recirculation control valve is provided in an exhaust gas recirculation passage connecting an exhaust system and an intake system to control the air-fuel ratio to a lean side when the supercharger operates to achieve a supercharging effect. Means for determining the operating range in which the air-fuel ratio should be controlled to the lean side, means for increasing the supercharging pressure by the supercharger when the air-fuel ratio is determined to be the lean air-fuel ratio control area, and increasing the supercharging pressure. A supercharged lean internal combustion engine comprising: means for detecting; and means for controlling an exhaust gas recirculation control valve such that the amount of recirculated exhaust gas passing through an exhaust gas recirculation passage increases when the supercharging pressure is detected to be increased. Exhaust gas recirculation device.