JP2001182575A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily maintain an exhaust emission control performance by an EGR(exhaust gas recirculation) device and the like with appropriately controlling supercharging pressure in an engine control device. SOLUTION: In controlling the supercharging pressure of a supercharger 30 and an EGR valve 26 of an EGR 20, a target EGR rate is set according to an operation condition of the engine 1 by a target EGR setting means 41A, and an actual EGR rate is detected or estimated by an actual EGR rate detecting means 41B. A supercharging pressure control mechanism 34 and/or the EGR valve 26 are controlled by a control means 44 such that the actual EGR becomes the target EGR rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an engine control device for controlling a supercharging pressure control mechanism and / or an EGR valve by focusing on an EGR rate.

[0002]

2. Description of the Related Art In a supercharger (turbocharger) mounted on an engine (internal combustion engine), if the performance is set to ensure the low-speed side of the engine, the supercharging pressure becomes too high on the high-speed side of the engine. The engine may be damaged. For this reason, in recent years, a supercharging pressure adjusting mechanism (variable mechanism), such as a variable vane type supercharger, has been attached to the supercharger so that the supercharger performance can be compatible between the low-speed side and the high-speed side. Things are being developed. In such a supercharger in which the supercharging pressure is adjustable (that is, a variable-capacity supercharger), the low-speed torque can be improved while protecting the engine by preventing the supercharging pressure from increasing excessively on the high-speed side. In addition, the transient response of the engine can be improved.

[0003]

By the way, an engine provided with the above-described variable-capacity supercharger is further provided with an EG.
R (exhaust gas recirculation device)
NOx generated in exhaust gas by introducing R (exhaust gas recirculation)
To purify. However, a product error (manufacturing variation or deterioration over time) of a variable mechanism (for example, a variable vane) of a variable displacement turbocharger, a control error of the supercharging pressure control through the variable mechanism, or a supercharging pressure control that does not appropriately consider exhaust gas. For this reason, when EGR is introduced in the partial load region of the engine, the exhaust gas state may worsen.

[0004] For example, FIG. 9 illustrates a nozzle vane opening (a VG vane opening, here, a large opening VG _B , a medium opening VG _M , and a small opening VG _{S) in} a variable vane type supercharger. FIG. 9A is a diagram showing an example of smoke / NOx characteristics in the exhaust gas with respect to the engine speed when the engine is running at a low speed and a low load (fuel injection timing iT is fixed), and FIG. ) Shows the case when the engine is rotating at medium speed and under high load (injection timing iT is fixed). As shown in FIGS. 9 (a) and 9 (b), the NOx emission amount is substantially constant regardless of the VG vane opening degree in each operating range of the engine. At medium speed rotation and high load, the in-cylinder EGR rate (calculated from the amount of fresh air sucked into the cylinder plus the amount of air in the EGR gas and the burned gas amount of the EGR gas) It can be seen that large variations occur.

[0005] Fig. 10 shows an in-cylinder lambda (an excess amount of air in the cylinder calculated from the sum of the amount of fresh air sucked into the cylinder and the amount of air in the EGR gas and the fuel injection amount) and the cylinder. E
It is a figure which overlaps with the control range characteristic by the variable vane type supercharger (VG turbo) regarding the GR rate and the smoke characteristic in the exhaust gas. FIG. 10 shows the test results when the engine is rotating at medium speed and under a high load. In FIG. 10, the curve SL _B indicates the large smoke level, the curve SL _M indicates the middle smoke level, and the curve SL
_S indicates a small smoke level. Also, the curve VG
_B is VG vane large opening (substantially maximum opening), VG _M is VG
VG _S indicates a small VG vane opening (substantially the minimum opening).

As shown in FIG. 10, in a region Z1 where the in-cylinder lambda is large, the smoke generation rate changes in accordance with the in-cylinder EGR rate and increases as the in-cylinder EGR rate increases. Some characteristics are almost constant. Therefore, in this region, mainly, the change in the in-cylinder EGR rate largely affects the smoke generation rate. Further, in the region Z2 where the in-cylinder lambda is small, the smoke occurrence rate changes in accordance with the in-cylinder lambda, and increases as the in-cylinder lambda decreases, but has a characteristic that it is substantially constant with respect to the in-cylinder EGR rate. Therefore, in this region, mainly the change in the in-cylinder lambda greatly affects the smoke generation rate.

[0007] The control range of the VG turbo naturally has a region characteristic that the in-cylinder lambda becomes smaller as the EGR opening is increased. Furthermore, although not shown, when the engine speed and load were variously set and the control range characteristics of the VG turbo and the smoke characteristics in the exhaust gas were examined, the following characteristics were obtained according to the engine speed and load. It turned out that there is.

The smoke characteristic (curves SL _B and S in FIG. 10)
L _M , SL _S ) shifts to the lower side of the in-cylinder EGR rate at high load, and shifts to the higher side of the in-cylinder EGR rate at low load. VG turbo control characteristics (curves VG _B , V
G _M , V G _S ) shifts to the small side of the in-cylinder lambda at high load, shifts to the large side of the in-cylinder lambda at low load, shifts to the large side of the in-cylinder lambda at high rotation, Move to the small side of Inner Lambda.

On a low load side or a low rotation side where the operating flow rate (that is, the intake flow rate) is small, the control range of the VG turbo becomes narrow. Although not shown, the NOx emission amount (the emission amount per unit time) substantially corresponds to the in-cylinder EGR rate.
The higher the rate, the more NOx emissions can be reduced. For this reason, in the engine control, simply performing feedback control so that the in-cylinder lambda becomes the target lambda may cause an actual error due to a product error of the variable mechanism of the variable displacement supercharger or a control error of the supercharging pressure control by the variable mechanism. When the supercharging pressure is higher than the target supercharging pressure (for example, when the VG vane opening is smaller than the target opening), FIG.
As shown by an arrow A1 at 0, the in-cylinder EGR rate becomes larger than a target value, so that NOx decreases but smoke increases.

Conversely, when the actual supercharging pressure is lower than the target supercharging pressure (for example, when the VG vane opening is larger than the target opening), FIG. As shown by the arrow A2, the in-cylinder EGR rate becomes larger than the target value, and the smoke does not deteriorate but the NOx increases. That is, if the supercharging pressure control is not performed with high accuracy, the introduction of EGR leads to a situation in which the exhaust gas state worsens rather. This becomes remarkable, for example, in a partial load region of the engine in which the target opening of the VG vane is in an intermediate opening state.

The present invention has been made in view of the above-mentioned problems, and performs supercharging pressure control in consideration of the state of the EGR device, thereby purifying exhaust gas with an EGR device or the like while appropriately controlling the supercharging pressure. An object of the present invention is to provide an engine control device capable of maintaining good performance.

[0012]

Therefore, in the engine control apparatus according to the first aspect of the present invention, when controlling the supercharging pressure of the supercharger and the EGR valve of the EGR, the target EGR rate setting means is used. The target EGR rate is set according to the operating state of the engine, the actual EGR rate is detected or estimated by the actual EGR rate detecting means, and the supercharging pressure is adjusted by the control means so that the actual EGR becomes the target EGR rate. And controlling the control mechanism and / or the EGR valve. As a result, the supercharging pressure can be controlled while appropriately maintaining the EGR rate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 8 show an engine control device as an embodiment of the present invention. Will be explained. First, an engine (internal combustion engine) provided with the supercharging pressure control device will be described. As shown in FIGS. 1 and 3, the engine 1 is a direct-injection diesel engine. The nozzle 3 is disposed so that the injection port faces the inside of the combustion chamber 4. The fuel pressurized by the fuel pump 5 is directly injected into the combustion chamber 4 from the high-pressure injection nozzle 3 through the fuel pipe 6. Has become. A glow plug 7 is provided toward the combustion chamber 4.

An air cleaner 12 is provided at an upstream end of the intake passage 11, and a compressor section 31, an intercooler 13, a surge tank 14, a swirl control valve 15, an intake air A valve 16 is interposed. An exhaust valve 22, a turbine section 32 of a turbocharger 30, a catalytic converter (oxidation catalyst for diesel) 23, and an exhaust shutter 24 are interposed in the exhaust passage 21 from the upstream side.

An EGR device for recirculating exhaust gas (exhaust gas recirculation passage) is provided between the exhaust passage 21 and the intake passage 11.
20 are provided. The EGR device 20 includes an upstream portion (for example, an exhaust manifold) of the exhaust passage 21 and the intake passage 1.
An EGR passage (exhaust gas recirculation passage) 25 provided between the EGR passage 25 and the EGR control valve for controlling the EGR flow rate by adjusting the opening degree of the EGR passage 25. (Abbreviated EGR valve)
26. The opening of the EGR valve 26 is adjusted by duty-controlling a solenoid (EGR control solenoid) 26A.

Here, the turbocharger 30 will be described. The turbocharger 30 is a variable-capacity supercharger (also referred to as a variable vane type supercharger or a VG turbo). As shown, a number of nozzle vanes (supercharging pressure control mechanism) 34 are provided on the outer periphery of the turbine rotor 33, and each nozzle vane 34
It is configured to be rotatable about an axis parallel to the axis of the turbine rotor 33, and from a fully open degree as shown in FIG. 2A to a fully closed degree as shown in FIG. Up to this point, it is rotationally driven by the negative pressure type actuator 35. The supercharging pressure can be reduced as the opening degree of the nozzle vane 34 increases.

The negative pressure type actuator 35 has a rod 35A which takes an axial position according to a pressure state in an internal negative pressure chamber (not shown). The rod 35A is pivotally connected to the movable portion of each nozzle vane 34. In addition, the opening degree of the nozzle vane 34 is adjusted according to the axial position of the rod 35A. An electromagnetic nozzle vane control valve (nozzle vane valve) 36 is provided to adjust the pressure in the negative pressure chamber of the negative pressure actuator 35.

That is, the nozzle vane valve 36 is connected to a vacuum tank 38, which has been reduced in pressure by a vacuum pump 37, the air cleaner 12, and a negative pressure chamber of a negative pressure actuator 35.
The negative pressure in the vacuum tank 38 and the negative pressure in the air cleaner 12 are used to reduce the pressure in the negative pressure chamber.
By controlling the opening degree of the nozzle vane valve 36, the pressure in the negative pressure chamber of the negative pressure type actuator 35 is adjusted to operate the negative pressure type actuator 35.
The negative pressure supply path to the negative pressure type actuator 35 includes:
A vacuum damper 39 for stabilizing the pressure in the negative pressure chamber of the negative pressure actuator 35 is provided. The nozzle vane valve 36 is a valve whose opening is adjusted by duty control of a solenoid (solenoid for controlling a variable displacement supercharger) 36A.

The solenoid 2 of the EGR valve 26
6A and solenoid 36A of nozzle vane valve 36
Are the other control elements of the engine (for example, the fuel pump 4 or E
ECU 4 together with GR valve 26 and glow plug 7)
0 is controlled. In particular, for the EGR valve 26 and the nozzle vane valve 36, the duty control is performed by setting the drive duties Dγ, Dλ of the solenoids 26A, 36A.
An R rate (target in-cylinder EGR rate) γ _T is set so that the actual EGR rate (actual in-cylinder EGR rate) γ _R becomes the target EGR rate γ _T and a target lambda (target in-cylinder lambda, lambda :
Excess air ratio) λ _T to set actual lambda (actual in-cylinder lambda)
As lambda _R is the target lambda lambda _T, the driving duty d [gamma], is adapted to set a d [lambda].

The solenoid 26 of the EGR valve 26
When the drive duty Dγ of A is increased, the EGR amount is decreased, and when the drive duty Dγ is decreased, the EGR amount is set to increase. When the drive duty Dλ of the solenoid 36A of the nozzle vane valve 36 is increased, the supercharging is performed. The pressure is set to decrease, and when the drive duty Dλ is decreased, the supercharging pressure is set to increase. Therefore, under the condition that the components other than the solenoid 26A are kept constant, the EGR rate decreases when the drive duty Dγ increases, and the EGR rate increases when the drive duty Dγ decreases. Also,
Under the condition that the components other than the solenoid 36A are kept constant, when the drive duty Dλ of the solenoid 36A is increased (when the supercharging pressure is reduced), the excess air ratio (lambda) λ and the EGR ratio are reduced, and the driving of the solenoid 36A is performed. When the duty Dλ is decreased (when the supercharging pressure is increased), the excess air ratio (lambda) λ and the EGR ratio increase.

The driving duties Dγ and Dλ are controlled.
In order to control the ECU 40, as shown in FIG.
In-cylinder EGR rate γ_TTo set the target in-cylinder EGR rate
Stage (target EGR rate setting means) 41A and actual in-cylinder EGR rate
γ_RIn-cylinder EGR rate calculation means (actual EGR rate detection
Output means) 41B and the target in-cylinder lambda λ_TSet goals
In-cylinder lambda setting means 42A and actual in-cylinder lambda λ_RCalculate
The in-cylinder lambda calculating means 42B and the EGR valve 26
To set the drive duty Dγ of the solenoid 26A
GR drive duty setting means 43A, nozzle vane
The drive duty Dλ of the solenoid 36A of the valve 36 is
Nozzle vane drive duty setting means 43B to be set
And an EGR valve according to the set drive duty Dγ.
26 is controlled by the set drive duty Dλ.
And control means 44 for controlling the sulvane valve 36 is provided.
Have been. The ECU 40 also has a target in-cylinder EGR rate.
γ _TAnd target in-cylinder lambda λ_TSet the target fuel
Injection amount Q_fuelFuel injection amount setting means 40A for setting
Is provided.

The ECU 40 includes an engine speed sensor 46 for detecting an engine speed Ne (hereinafter, also referred to as a speed), an accelerator opening sensor 47 for detecting an accelerator opening corresponding to the engine load, and an intake manifold. Pressure sensor 48 for detecting the pressure _Pmani of the intake manifold, a temperature sensor 49 for detecting the temperature _Tmani in the intake manifold, and EGR
A pressure sensor 50 for detecting the upstream pressure P _egr of the valve 26,
An opening sensor 5 for detecting the opening V _egr of the EGR valve 26
The information of the engine operating state from each of the sensors 1 is input.

In the target fuel injection amount setting means 40A, the engine speed Ne measured by the engine speed sensor 46 is used.
And the accelerator opening V measured by the accelerator opening sensor 47
Based on the _APS , a target fuel injection amount Q _fuel is set from a first map (map1) as shown in FIG. That is, as shown in map1 of FIG. 4 (a), as the engine rotational speed Ne is low, also, as the accelerator opening degree V _APS is large, the target fuel injection amount Q _fuel is set to a large value.

In the target in-cylinder EGR rate setting means 41A, based on the engine speed Ne and the target fuel injection quantity Q _fuel set by the target fuel injection quantity setting means 40A, FIG.
From the second map (map2) as shown in FIG.
Set the R rate γ _T. The target in-cylinder EGR rate γ _T is, as shown in map 2 of FIG. 4B, in consideration of prevention of generation of smoke, and as a general tendency, the target fuel injection amount Q _fuel
Is set to a larger value as the engine speed Ne is smaller.

The target in-cylinder lambda setting means 42A uses a third map as shown in FIG. 4C based on the engine speed Ne and the target fuel injection quantity Q _fuel set by the target fuel injection quantity setting means 40A. The target in-cylinder lambda λ _T is calculated from (map3). This target in-cylinder lambda λ _T is shown in FIG.
As shown in map 3 of (c), as an approximate tendency,
The target fuel injection amount Q _fuel is set to a smaller value as it is larger, and is set to a larger value as the engine speed Ne goes to a lower speed range or a higher speed range than a middle range (medium speed range).

The actual in-cylinder EGR rate calculation means 41B calculates the previous actual lambda λ _n-1 and the total in-cylinder intake gas amount (total intake amount) Q _all per unit period (for example, one stroke) of the engine.
From the EGR flow rate Q _egr and the actual in-cylinder EG by the following equation (1).
The R rate γ _R is calculated. γ _R = [(1 / λ _n-1 ) × Q _egr ] / [Q _all − (1 / λ _n-1 ) × Q _egr ] (1) In the above equation (1), Total intake air quantity Q _all and EGR flow rate Q
_egr is obtained as follows.

First, the total intake air amount Q_allIs given by the following equation (2)
As shown in FIG.
Pressure P_maniAnd the volumetric efficiency correction coefficient Kη_v, Intake manifold
Temperature correction coefficient (manifold correction coefficient) K_Tmani， Pressure
Conversion coefficient K to convert to gas amount _vol(= Constant)
It is calculated by the following. Q_all= P_mani× Kη_v× K_Tmani× K_vol (2) The volume efficiency correction coefficient Kη_vIs measured by each sensor
Engine speed Ne and intake manifold pressure P_mani
And a sixth map (m) as shown in FIG.
ap6). As shown in map 6 in FIG.
As described above, the volume efficiency correction coefficient Kη_vIs the engine speed Ne
And intake manifold pressure P_maniIs bigger is smaller
The engine speed Ne and the intake manifold internal pressure
Force P_maniIs set to be larger as is smaller.

Also, the manifold temperature correction coefficient K_TmaniIs the temperature sensor
Intake manifold temperature T measured in step 49_maniBased on
Therefore, a seventh map (map) as shown in FIG.
Set from 7). As shown in map 7 of FIG.
And the manifold temperature correction coefficient K_TmaniIs the intake manifold internal temperature
Degree T_maniIs set to a smaller value as is higher. Next, EG
R flow rate Q_egrIs the EGR basic flow rate as in the following equation (3).
Q_egr0The EGR temperature correction coefficient K_Tegr， Straw time
Conversion factor t_Ne(= 30 / Ne, Ne
Is calculated by multiplying by (rpm).

Q_egr= Q_egr0× K_Tegr× t_Ne (3) EGR basic flow rate Q_egr0Is measured by the pressure sensor 50
Upstream pressure P of the EGR valve 26_egrAnd pressure sensor 4
Intake manifold pressure P measured at 8_maniDifferential pressure with
ΔP_egr(= P_egr−P_mani) And the opening sensor 51
The measured opening degree V of the EGR valve 26_egrAnd based on
From the eighth map (map8) as shown in FIG.
Set. As shown in map 8 of FIG.
Main flow Q _egr0Is the differential pressure ΔP_egrAnd opening degree V_egrIs bigger
Whichever value is set.

The EGR temperature correction coefficient K _Tegr is _{calculated based} on the engine speed Ne and the target fuel injection amount Q _fuel set by the target fuel injection amount setting means 40A as shown in a ninth map (FIG. 5D). Set from map 9). This EGR
The temperature correction coefficient K _Tegr is generally set to a smaller value as the target fuel injection amount Q _fuel is larger, as shown in map ₉ of FIG.
The larger the value of e, the larger the value is set.

The actual in-cylinder lambda calculating means 42B calculates the previous actual lambda λ _n-1 and the total intake air amount Q obtained as described above.
_all and EGR flow rate Q _egr and target fuel injection amount setting means 4
The target fuel injection amount Q _fuel set at 0A and the stoichiometric air-fuel ratio A
F _th (= constant) and the actual in-cylinder lambda λ
Calculate _R. λ _R = (1 / AF _th ) × [Q _all − (1 / λ _n−1 ) × Q _egr ] / Q _fuel (4) The EGR drive duty setting means 43A uses the following equation 5)
As shown in, the basic driving duty d [gamma] _B of the solenoid 26A of the EGR valve 26 P correction term (proportional action correction term) d [gamma] _P and I correction term of the solenoid 26A by correcting by the (integral operation correction term) d [gamma] _I Drive duty D
Set γ.

[0032] _{Dγ = Dγ B + Dγ P +} Dγ I ······ (5) Among them, the basic driving duty d [gamma] _B, the target fuel injection amount set by the engine speed Ne and the target fuel injection amount setting means 40A It is calculated from a fourth map (map4) as shown in FIG. 4D based on Q _fuel . That is, as shown in map4 of FIG. 4D, the basic drive duty Dγ _B is approximately a target fuel injection amount Q _fuel
Is set to a smaller value as is larger, and is set to a larger value as the engine speed Ne is higher.

The P correction term Dγ _P is given by the following equation (6):
The actual in-cylinder EG calculated by the actual in-cylinder EGR rate calculating means 41B
The difference Δγ between the R rate γ _R and the target in-cylinder EGR rate γ _T set by the target in-cylinder EGR rate setting means 41A is a P gain Gγ _P
Is calculated by multiplying Dγ _P = Δγ × Gγ _P (6) Further, the I correction term Dγ _I is obtained by adding the deviation Δγ and the I gain to the previous I correction term Dγ _{In−1 as} in the following equation (7). It is calculated by adding the multiplication value between G.gamma _I.

Dγ _I = Dγ _In-1 + Δγ × Gγ _I (7) The nozzle vane drive duty setting means 43B is configured to operate the solenoid 36A of the nozzle vane valve 36 as shown in the following equation (8). the basic driving duty d [lambda] _B to set the P correction term (proportional action correction term) d [lambda] _P and I correction term driving duty d [lambda] of the solenoid 36A by correcting by the (integral operation correction term) d [lambda] _I.

Dλ = Dλ _B + Dλ _P + Dλ _I (8) The basic drive duty Dλ _B is the engine speed Ne and the target fuel injection amount set by the target fuel injection amount setting means 40A. It is calculated from a fifth map (map5) as shown in FIG. 4E based on Q _fuel . That is, as shown in map5 of FIG. 4E, the basic drive duty Dλ _B is approximately changed to the target fuel injection amount Q _fuel
Is set to a smaller value as is larger, and is set to a larger value as the engine speed Ne is higher.

The P correction term Dλ _P is given by the following equation (9):
Calculated by multiplying the deviation Δλ between the actual in-cylinder lambda λ _R calculated by the actual in-cylinder lambda calculating means 42B and the target in-cylinder lambda λ _T set by the target in-cylinder lambda setting means 41A by a P gain Gλ _P. Is done. Dλ _P = Δλ × Gλ _P (9) Further, as shown in the following equation (10), the I correction term Dλ _I is obtained by adding the deviation Δλ and the I gain to the previous I correction term Dλ _In-1. It is calculated by adding the multiplication value between Gλ _I.

Dλ _I = Dλ _In-1 + Δλ × Gλ _I (10) The control means 44 controls the solenoid 26A of the EGR valve 26 with the set drive duty Dγ, and sets the set drive duty. Nozzle vane valve 3 by Dλ
No. 6 solenoid 36A is controlled. Since the supercharging pressure control device as one embodiment of the present invention is configured as described above, the solenoid 26A of the EGR valve 26 and the solenoid of the nozzle vane valve 36, for example, as shown in the flowcharts of FIGS. 36A is controlled.
6 and 7 are repeated at a predetermined cycle.

First, as shown in FIG. 6, the engine speed Ne is measured by the engine speed sensor 46, and the accelerator opening V _{APS is detected} by the accelerator opening sensor 47.
Is measured (step S10). Then, the engine speed N measured by the target fuel injection amount setting means 40A.
e and the accelerator opening degree V _APS and the target fuel injection amount from the first map (map1) as shown in FIG. 4 (a) based on the Q
_fuel [= map1 (Ne, V _APS )] is set (step S20).

The target in-cylinder EGR rate setting means 41A
And the measured engine speed Ne and step S2
FIG. 4 based on the target fuel injection amount Q _fuel set at 0.
The target in-cylinder EGR rate γ _T [= map2 (Ne, Q _fuel )] is set from the second map (map2) as shown in FIG.
Based on the measured engine speed Ne and the target fuel injection amount Q _fuel set in step S20, a target in-cylinder lambda λ _T [= map3 ( Ne, Q _fuel )] (step S30).

Further, the actual in-cylinder lambda (actual lambda) λ _R and the actual in-cylinder EGR rate (actual EGR rate) are calculated by the in-cylinder lambda calculating means 42B and the in-cylinder EGR rate calculating means 41B (step S40). ). In the process of step S40, specifically, each process as shown in the subroutine of FIG. 7 is performed.

That is, as shown in FIG. 7, first, the pressure inside the intake manifold P _mani is measured by the pressure sensor 48, and the temperature inside the intake manifold T _mani is measured by the temperature sensor 49 (step S410). Then, the engine speed Ne measured by each sensor and the intake manifold internal pressure P _mani
And a sixth map (m) as shown in FIG.
ap6) to the volume efficiency correction coefficient Kη _v [= map6 (N
e, P _mani )] (step S420), and based on the intake manifold temperature T _mani measured by the temperature sensor 49, a seventh map (map) as shown in FIG.
From 7), the _manifold temperature correction coefficient K _Tmani [= map7
(T _mani )] is set (step S422).

Further, as in the above equation (2), the volume efficiency correction coefficient Kη _v , the intake manifold temperature correction coefficient (manifold temperature correction coefficient) K _Tmani , are _added to the intake manifold pressure P _mani measured by the pressure sensor 48. The total intake air amount Q _all is calculated by multiplying the conversion coefficient K _vol (= constant) for converting the pressure into the gas amount (step S424). Further, the pressure sensor 50 measures the upstream pressure P _egr of the EGR valve 26, the opening sensor 51 measures the opening V _egr of the EGR valve 26 (step S430), and the upstream of the EGR valve 26 measured at step S430. Pressure P _egr and step S4
Differential pressure [Delta] P _egr the measured intake manifold pressure P _mani at 10 to calculate the _{(= P egr -P ma ni)} ( step S440), the differential pressure Δ calculated in step S440
Based on P _egr and the opening degree V _egr of the EGR valve 26 measured in step S430, the EGR basic flow rate Q _egr0 is set from an eighth map (map8) as shown in FIG. _5C (step S442). ).

Further, based on the engine speed Ne measured in step S10 and the target fuel injection amount Q _fuel set in step S20, a ninth fuel injection amount as shown in FIG.
An EGR temperature correction coefficient K _Tegr is set from the map (map 9) (step S444), and the EGR basic flow rate Q _egr0 calculated in step S442 and the EGR temperature correction calculated in step S444 are calculated as in equation (3). Coefficient K _Tegr
And the conversion coefficient t _Ne (= 30 / Ne, the unit of Ne is rpm)
To calculate the EGR flow rate Q _egr (step S446).

Then, the actual in-cylinder lambda calculating means 42B calculates the previous actual lambda λ _n−1 , the total intake air amount Q _all determined in step S424, and the EGR determined in step S446.
From the flow rate Q _egr , the target fuel injection amount Q _fuel set in step S20, and the stoichiometric air-fuel ratio AF _th (= constant), the actual in-cylinder lambda λ _R is calculated by the equation (4) (step S4).
50), by actual in-cylinder EGR rate calculating means 41B, before the an EGR flow rate Q _{eg r} obtained in total intake air amount Q _all the steps S446 obtained in the previous actual lambda lambda _n-1 and step S424 formula (1) calculates the actual in-cylinder EGR rate gamma _R (step S452), when for the period of setting, to set the current actual in-cylinder lambda lambda _R the actual lambda lambda _n-1 of the last time (step S454).

Referring again to FIG. 6, once the actual in-cylinder EGR rate γ _R and the actual in-cylinder lambda λ _R are calculated in step S40, the EGR drive duty setting means 43A measures them in step S10. Based on the engine speed Ne and the target fuel injection amount Q _fuel set in step S20, a fourth map (map) as shown in FIG.
4), the basic drive duty Dγ _B is calculated (step S50), and further, step S40 (step S45)
Actual in-cylinder EGR rate γ _R calculated in 2) and step S30
Δγ (= γ) from the target in-cylinder EGR rate γ _T set at
_R− γ _T ) is calculated (step S60), and a PI correction term [P correction term (proportional motion correction term) Dγ _P and I correction term (integral motion correction term) Dγ _I ] is calculated (step S7).
0).

That is, the P correction term Dγ _P is calculated by multiplying the deviation Δγ calculated in step S60 by the P gain Gγ _P as in the equation (6), and the I correction term Dγ _I
Is given by the previous I correction term Dγ _In-1 as in the previous equation (7).
Calculated by adding the multiplication value between the deviation Δγ and I gain G.gamma _I. Then, in the EGR drive duty setting means 43A, the EGR valve 26
Sets the driving duty d [gamma] of the solenoid 26A by the basic drive duty d [gamma] _B of the solenoid 26A corrected by the P correction term d [gamma] _P and I correction term d [gamma] _I (Step S80).

Also, setting the drive duty for the nozzle vanes
In the means 43B, the engine measured in step S10
The engine speed Ne and the target fuel injection set in step S20
Quantity Q _fuelAnd the fifth map as shown in FIG.
(Map5) to basic drive duty Dλ_BIs calculated
(Step S90), Step S40 (Step S45)
In-cylinder lambda λ calculated in 0)_RAnd in step S30
Set target in-cylinder lambda λ_TDeviation Δλ (= λ_R−
λ_T) (Step S100) to calculate the PI correction term.
[P correction term (proportional operation correction term) Dλ_PAnd I correction term (product
Minute operation correction term) Dλ_I] (Step S11)
0).

That is, the P correction term Dλ_PIs given by the equation (9)
As described above, the deviation Δλ calculated in step S60 is
Gλ_PIs multiplied by the I correction term Dλ_I
Is the previous I correction term Dλ as in the previous equation (10).
_In-1And the deviation Δλ and the I gain Gλ_IAdd the product value with
Is calculated. The drive data for the nozzle vanes
In the duty setting means 43B, as shown in the above equation (8),
The base of the solenoid 36A of the valve 36 for the nozzle vane
Main drive duty Dλ_BIs the P correction term (proportional operation correction term)
Dλ_PAnd I correction term (integral operation correction term) Dλ _IAnd supplement
By correcting the drive duty Dλ of the solenoid 36A,
It is set (step S120).

Thus, the solenoids 26A, 36A
After setting the drive duties Dγ and Dλ, the control means 44
EGR according to the set drive duty Dγ
By controlling the solenoid 26A of the valve 26, the set drive
The deflection of the nozzle vane valve 36 is controlled by the dynamic duty Dλ.
The control unit controls the solenoid 36A (step S130). This
Thus, in the present engine control device, the EGR valve 26
The drive duty Dγ for controlling the solenoid 26A is P
Correction term Dγ and I correction term Dγ_IAnd PI correction (proportional product
If Δγ is positive (ie, the actual in-cylinder EG
R rate γ_RIs the target in-cylinder EGR rate γ_TGreater than)
The drive duty Dγ is increased and corrected according to the magnitude of
Therefore, the actual in-cylinder EGR rate γ_RDecreases to the target in-cylinder EGR rate
γ _TApproach. If Δγ is negative (that is, the actual cylinder
EGR rate γ_RIs the target in-cylinder EGR rate γ_TLess than
And the drive duty according to the magnitude (−Δγ)
Since Dγ is corrected to decrease, the actual in-cylinder EGR rate γ_RIs increasing
And the target in-cylinder EGR rate γ_TApproach.

The drive duty Dλ for controlling the solenoid 36A of the nozzle vane valve 36 is determined by the P correction term D
By the PI correction (proportional-integral correction) using λ _P and the I correction term Dλ _I , if Δλ is positive, that is, the actual in-cylinder lambda λ
_{When R} is larger than the target in-cylinder lambda λ _T , the drive duty Dλ is increased and corrected according to the magnitude, so that the supercharging pressure decreases, and the excess air ratio (lambda) λ and the EGR ratio decrease. . Also, if Δλ is negative (i.e., an actual in-cylinder lambda lambda _R is smaller than the target cylinder lambda lambda _T), depending on its size (-.DELTA..lambda), the driving duty Dλ is reduced corrected As the supercharging pressure increases, the excess air ratio (lambda) λ and the EGR ratio increase.

Therefore, the EGR valve 26 and the nozzle vane valve 36 are controlled by the feedback control of the EGR rate deviation of the solenoid 26A of the EGR valve 26 and the excess air (lambda) deviation feedback control of the solenoid 36A of the nozzle vane valve 36. EG
R ratio and excess air ratio (lambda) are controlled,
While the supercharging pressure is controlled by the nozzle vane valve 36, the EGR rate and the excess air rate are appropriately maintained.

For example, FIG. 8 shows such an EGR valve 26.
FIGS. 7A and 7B are diagrams illustrating the effect of controlling the nozzle vane valve 36, wherein FIG. 8A is a diagram when the engine is running at low speed and low load, and FIG.
These correspond to FIGS. 10A and 10B, respectively. FIG.
As shown in (a) and (b), the EGR rate and the excess air rate λ are originally at points P11 and P21 with a predetermined control amount (that is, the basic drive duty Dλ _B of the solenoid 36A of the nozzle vane valve 36). Should be in the state of point P12, P2 due to a product error of the variable mechanism of the variable displacement supercharger or a control error of the supercharging pressure control by the variable mechanism.
If the actual supercharging pressure is lower than the target supercharging pressure as shown in FIG. 2, the points P13 and P13 are determined only by the feedback control of the excess air ratio deviation of the nozzle vane valve 36.
23, the in-cylinder EGR rate becomes excessive.
By adding the EGR rate deviation feedback control of the solenoid 26A of the GR valve 26, the EGR rate and the excess air rate λ can be made closer to the states of the points P11 and P21.

Conversely, a predetermined control amount (the basic driving duty D of the solenoid 36A of the nozzle vane valve 36)
λ _B ), the EGR rate and excess air rate λ are
However, due to a product error of the variable mechanism of the variable displacement supercharger or a control error of the supercharging pressure control by the variable mechanism, for example, points P14 and P24,
If the actual supercharging pressure is higher than the target supercharging pressure, the in-cylinder EGR rate becomes too small as shown at points P15 and P25 only by the feedback control of the excess air ratio of the nozzle vane valve 36. But the EGR valve 2
By adding the EGR rate deviation feedback control of the solenoid 26A of No. 6, the EGR rate and the excess air rate λ can be brought close to the states of the points P11 and P21.

Therefore, by appropriately controlling the EGR rate and the excess air rate (lambda), in particular, it is possible to improve the low-speed torque while protecting the engine by supercharging pressure control while maintaining good exhaust gas characteristics. Can be improved in transient response. FIG.
Comparing (a) and (b), as the engine speed and load increase, the error effect on the EGR rate and the excess air ratio λ due to product error and control error increases, and the control effect of the present engine control device increases. It turns out that it is big.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications without departing from the spirit of the present invention. For example, in the present embodiment, the EGR rate deviation feedback control is performed only on the solenoid 26A of the EGR valve 26.
Nozzle vane valve 36 for R rate deviation feedback control
May be applied to the solenoid 36A.

In this case, the P correction term Dλ _P for correcting the drive duty Dλ of the solenoid 36A and the I correction term Dλ _I
May be calculated by the following equation. Dλ _P = Δλ × Gλ _P + Δγ × Gγ _P ′ (11) Dλ _I = Dλ _In-1 + Δλ × Gλ _I + Dγ _In-1 + Δγ × Gγ _I ′ (12) Further, the excess air ratio deviation feedback control may be performed not only on the solenoid 36A of the nozzle vane valve 36 but also on the solenoid 26A of the EGR valve 26.

[0057] In this case, P correction term for correcting the driving duty d [gamma] of the solenoid 26A d [gamma] _P and I correction term d [gamma] _I
May be calculated by the following equation. _{Dγ P = Δγ × Gγ P +} Δλ × Gλ P '······ (13) Dγ I = Dγ In-1 + Δγ × Gγ I + Dλ In-1 + Δλ × Gλ I' ······ (14) Further, contrary to the present embodiment, the excess air ratio deviation feedback control may be performed only on the solenoid 26A of the EGR valve 26, and the EGR ratio deviation feedback control may be performed only on the solenoid 36A of the nozzle vane valve 36.

[0058]

As described above in detail, according to the engine control apparatus of the present invention, the EGR rate can be appropriately maintained while controlling the supercharging pressure. Even if an error or control error occurs, the supercharging pressure can be appropriately adjusted while ensuring the exhaust gas purification performance by EGR, and the low-speed torque can be reduced while protecting the engine by the supercharging pressure control. It is possible to achieve both the effect of improving the transient response of the engine and the effect of purifying the exhaust gas by EGR.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an engine control device as one embodiment of the present invention.

FIGS. 2A and 2B are schematic diagrams illustrating an open state of a variable vane type supercharger according to an embodiment of the present invention, wherein FIG. 2A illustrates a fully open state, and FIG. 2B illustrates a fully closed state; It is.

FIG. 3 is a schematic diagram showing a configuration of a main part of an engine control device as one embodiment of the present invention.

FIGS. 4A and 4B are diagrams showing a control map used in the engine control device as one embodiment of the present invention, wherein FIG. 4A shows a first map (map1) and FIG. 4B shows a second map (map2).
(C) shows the third map (map3), and (d) shows the fourth map (map3).
The map (map4) is shown, and (e) is the fifth map (map).
5) are respectively shown.

FIGS. 5A and 5B are diagrams showing a control map used in the engine control device as one embodiment of the present invention, wherein FIG. 5A shows a sixth map (map6), and FIG. 5B shows a seventh map (map7).
(C) shows the eighth map (map 8), and (d) shows the ninth map (map 8).
A map (map 9) is shown.

FIG. 6 is a flowchart illustrating engine control according to an embodiment of the present invention.

FIG. 7 is a flowchart illustrating engine control according to an embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation and effect of the present invention, and is a diagram showing smoke characteristics in exhaust gas superimposed on control range characteristics of a variable displacement turbocharger with respect to in-cylinder λ and in-cylinder EGR rate; (A) is a diagram at the time of low rotation and low load of the engine, and (b) is a diagram at the time of medium rotation and high load of the engine.

FIG. 9 is a diagram for explaining the problem of the present invention, and is a diagram showing an example of smoke / NOx characteristics in exhaust gas;
FIG. 4 is a diagram when the engine is running at a low speed and a low load, and FIG.

FIG. 10 is a view for explaining the problem of the present invention, and shows the in-cylinder λ.
FIG. 7 is a diagram showing smoke characteristics in exhaust gas superimposed on control range characteristics of a variable-capacity supercharger relating to an in-cylinder EGR rate.

[Explanation of symbols]

Reference Signs List 1 engine 20 EGR device (exhaust gas recirculation passage) 25 EGR passage (exhaust gas recirculation passage) 26 EGR control valve (EGR valve) 26A EGR control solenoid 30 turbocharger (supercharger) 33 turbine rotor 34 nozzle vane Supply pressure control mechanism) 35 Negative pressure actuator 36 Nozzle vane control valve (Nozzle vane valve) 36A Solenoid for variable capacity supercharger control 40A Target fuel injection amount setting means 41A Target EGR rate setting means 41B Actual cylinder EGR rate calculation means (actual EGR rate) Detecting means) 42A target in-cylinder lambda setting means 42B actual in-cylinder lambda calculating means 43A EGR drive duty setting means 43B nozzle vane drive duty setting means 44 control means 46 engine speed sensor (engine operating state Detecting means) 47 operating condition detecting means of the accelerator opening sensor (engine) 48, 50 pressure sensor 49 temperature sensor 51 opening sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 25/07 550 F02M 25/07 550F F-term (Reference) 3G062 AA05 BA04 EA10 FA05 FA10 GA01 GA02 GA04 GA06 GA08 GA12 GA14 3G084 BA07 BA20 DA01 DA02 DA05 DA10 EC06 FA02 FA07 FA10 FA11 FA12 FA20 FA33 3G092 AA17 AA18 BA04 BB03 DB03 DC09 DE01S EC08 EC10 FA01 FA06 FA15 GA05 GA06 GA17 HA01Z HA04Z HA05Z HA16Z HE01Z HF08Z

Claims (1)

[Claims] 1. A supercharger for supercharging air taken into a combustion chamber of an engine, a supercharging pressure control mechanism for controlling a supercharging pressure of the supercharger, and an EGR device for recirculating exhaust gas to an intake system. A target EGR rate setting means for setting a target EGR rate in accordance with an operation state of the engine; and an actual EGR rate detecting means for detecting or estimating the actual EGR rate. Controlling the supercharging pressure control mechanism and / or the EGR valve so that the actual EGR rate detected or estimated by the actual EGR rate detecting means becomes the target EGR rate set by the target EGR rate setting means. An engine control device, comprising: