JP3460635B2 - Control unit for diesel engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine control device, and more particularly to an EGR device (device for recirculating a part of exhaust gas to an intake passage) and a supercharger.

[0002]

2. Description of the Related Art A turbocharger and an EGR valve capable of controlling an EGR flow rate are provided, and an area for supercharging by operating the turbocharger and an area for performing EGR by opening the EGR valve are separated. There is one (see Japanese Patent Laid-Open No. 7-139413).

Further, a variable capacity turbocharger having a variable nozzle in a turbine and an EGR valve are provided, and a method for controlling the EGR amount and the nozzle opening of the variable nozzle during a transition is studied (IMechE 1997 C524 / 12).
7/97), a variable capacity turbocharger, and an EGR valve that is not continuous in setting but can be set in several stages in stages,
There is one in which the amount of EGR is controlled by the opening area of the variable nozzle, etc. (Preprints 965, 1996-10, published by the Society of Automotive Engineers of Japan, pages 193 to 19).
(See page 6).

[0004]

By the way, in all of these conventional devices, basically, when changing the EGR amount, the nozzle opening of the variable nozzle is held at a constant value and the supercharging pressure is changed. At this time, the EGR valve opening is held at a constant value to obtain the optimum value of exhaust emission.

The reason why one of the nozzle opening and the EGR valve opening is held and the other is changed is as follows. From the perspective of boost pressure control, EGR control also physically fulfills the role of boost pressure control. That is, the supercharging pressure also changes by changing the EGR amount. On the contrary, when the supercharging pressure is changed, the exhaust pressure also changes, so the EGR amount also changes, and the supercharging pressure and the EGR amount cannot be controlled independently. Has become a disturbance of. As a result, in the conventional technology, the usage must be compromised to some extent.

It should be noted that when one is changed, the other is re-adapted in order to ensure control accuracy, but after the other is re-adapted, the other must be re-adapted. Therefore, with this method, it is difficult to secure control accuracy during a transition.

As described above, since the supercharging pressure and the EGR amount influence each other, if the EGR amount is changed, it is difficult to properly adjust the nozzle opening and the like, and especially during a transition. The control accuracy of both is reduced.

On the other hand, in the case of a diesel engine,
Each of the supercharging pressure and the EGR amount is sensitive to the emission amount of harmful substances in the exhaust gas, and it is necessary to set these to optimal values in order to reduce the harmful emission substances in the exhaust gas. In particular, in order to achieve these target values of each other at the time of transition and to achieve both exhaust emission and drivability, it is desired to actively change each.

Further, when a catalyst such as a NOx reduction catalyst is provided in the exhaust passage, if the catalyst deteriorates, the exhaust pressure rises, and due to such an increase in the exhaust pressure and the operation variation of the variable capacity turbocharger. When the EGR amount increases due to the fluctuation of the intake air amount, the excess air ratio decreases and the smoke characteristic deteriorates. Therefore, feedback control is performed so that the actual intake air amount matches the target intake air amount (Japanese Patent Laid-Open No. Hei 1
1-82183) or the actual EGR amount is the target EGR
There is one that performs feedback control so as to match the amount (see Japanese Patent Laid-Open No. 11-50917).

However, the mere feedback control is not sufficient for the target followability during the transition, and the setting of the feedback gain becomes complicated.

Further, the relationship between the deviation of the actual intake air amount from the target intake air amount and the EGR valve opening degree is not linear but changes depending on the differential pressure before and after the EGR valve and the EGR flow rate, so that it depends on the operating conditions. Therefore, it is necessary to change the feedback gain, and a large amount of feedback occurs depending on the conditions, and it is difficult to ensure sufficient control accuracy.

Therefore, when various experiments were conducted, as shown in FIG. 65, the cylinder EGR amount Qec, the target EGR rate Megr, and the flow velocity of EGR gas (gas flowing through the EGR valve) (the flow velocity of this EGR gas Hereinafter, simply "EG
It was newly discovered that there is a strong correlation between Cqe (referred to as “R flow velocity”) regardless of the nozzle opening degree of the variable nozzle.

Therefore, according to the present invention, the target EGR amount and the target EG
The EGR flow rate (or the differential pressure across the EGR valve that has a constant relationship with this flow rate) is predicted based on the R ratio, and the EGR valve is controlled based on this predicted value, and the actual intake air amount and the target intake air amount By feedback-correcting the EGR flow rate or the parameter (target EGR amount or target EGR rate) used in the calculation of the EGR flow rate or the EGR flow rate based on the difference (error amount) or the ratio (error ratio), the exhaust pressure rise due to deterioration of the catalyst or Even if there is a fluctuation in the intake air amount due to variation in operation when a variable capacity turbocharger is used, it is possible to reliably prevent the excess air ratio from decreasing and further improve the robustness to exhaust gas. .

[0014]

The first invention is, as shown in FIG. 75, a supercharger 61 and an EGR capable of controlling the EGR amount.
Means 63 for detecting an engine operating condition (for example, engine speed and load), and means 64 for calculating a target EGR rate Megr based on the detected value of the operating condition.
Means 65 for setting the target EGR amount based on the target EGR rate Megr and the detected value of the operating condition, and the target E
Means 66 for calculating the EGR flow rate Cqe based on the GR amount and the target EGR rate Megr, and the EGR flow rate Cqe
And the opening area A of the EGR valve 62 from the target EGR amount
ev calculation means 67 and this EGR valve opening area Ae
means 68 for controlling the EGR valve 62 so that
A means 69 for calculating the target intake air amount tQac, a means 70 for controlling the supercharger 61 so as to obtain the target intake air amount tQac, and a means 71 for calculating the actual intake air amount Qac. A parameter (that is, the target EGR amount or the target EGR) used for calculating the EGR flow rate Cqe or the EGR flow rate Cqe based on the difference (error amount) or the ratio (error ratio) between the actual intake air amount and the target intake air amount.
And means 72 for feedback-correcting the rate).

As shown in FIG. 76, the second aspect of the present invention comprises a supercharger 61 and an EGR valve 62 capable of controlling the EGR amount, and means 63 for detecting engine operating conditions (for example, rotational speed and load). , The target EG based on the detected value of this operating condition
A means 64 for calculating the R rate Megr and a target EGR based on the target EGR rate Megr and the detected value of the operating condition.
Means 65 for setting the amount, means 66 for calculating the EGR flow rate Cqe based on the target EGR amount and the target EGR rate Megr, and the EGR flow rate Cqe and the target EGR
A means 67 for calculating the opening area Aev of the EGR valve 62 from the amount, a means 68 for controlling the EGR valve 62 so that the EGR valve opening area Aev is obtained, and a means 81 for storing a learning value for each operating region. A means 82 for correcting the parameter (that is, a target EGR amount or a target EGR rate) used for the calculation of the EGR flow rate Cqe or the EGR flow rate with this learning value, and a means 6 for calculating the target intake air amount tQac.
9, a means 70 for controlling the supercharger 61 so as to obtain the target intake air amount tQac, and an actual intake air amount Qa.
A means 71 for calculating c and a means 83 for updating the learning value based on the difference (error amount) or ratio (error ratio) between the actual intake air amount Qac and the target intake air amount tQac are provided.

As shown in FIG. 77, the third aspect of the invention comprises a supercharger 61 and an EGR valve 61 capable of controlling the EGR amount, and means 63 for detecting engine operating conditions (for example, engine speed and load). , The target EG based on the detected value of this operating condition
Means 64 for calculating the R rate, means 65 for setting the target EGR amount based on the target EGR rate and the detected value of the operating condition, and EGR flow velocity calculation based on the target EGR amount and the target EGR rate A means 66, a means 67 for calculating an opening area of the EGR valve 62 from the EGR flow velocity and the target EGR amount, a means 68 for controlling the EGR valve 62 so that the EGR valve opening area is obtained, and a target intake air. Means 69 for calculating the amount and the target intake air amount tQac
70 for controlling the supercharger 61 so that
And means 71 for calculating the actual intake air amount, and means 91 for feedback-correcting the target EGR amount based on the difference (error amount) or ratio (error ratio) between the actual intake air amount and the target intake air amount. Was set up.

In the fourth invention, instead of the target intake air amount tQac used for the feedback correction in the first or third invention, this target intake air amount tQac is used.
The value tQacd obtained by subjecting the intake system to the delay process is used.

In the fifth invention, instead of the target intake air amount used for updating the learning value in the second invention,
A value tQacd obtained by delaying the intake system with respect to the target intake air amount tQac is used.

In a sixth aspect of the present invention, the feedback correction amount for the feedback correction in the first aspect is a value proportional to the integral value of the difference or ratio (instantaneous error amount or instantaneous error ratio).

In a seventh invention, a feedback correction amount Kq when performing the feedback correction in the third invention.
ac00 is a value proportional to the difference or ratio (instantaneous error amount or instantaneous error rate).

[0021]

In the first and sixth aspects of the present invention, feedback correction is performed so that the actual intake air amount matches the target intake air amount. Therefore, when a catalyst is provided in the exhaust passage, the exhaust pressure rises due to deterioration of the catalyst and Even if there is a fluctuation in the intake air amount due to operational variations when using a variable capacity turbocharger,
Although it is possible to prevent the decrease of the excess air ratio and improve the robustness to the exhaust gas, in the first and sixth inventions, the target of the feedback correction is the EGR flow velocity, which is different from the conventional technique. .

Here, as shown in FIG. 65, the cylinder E
GR amount Qec, target EGR rate Megr, and EGR flow velocity Cq
From the first finding that there is a strong correlation between e regardless of the nozzle opening of the variable nozzle,
As in the sixth invention, by predicting the EGR flow velocity and controlling the EGR valve based on this predicted value, even in an engine equipped with a variable capacity turbocharger, the target is irrespective of the nozzle opening degree of the variable nozzle. Since the EGR amount can be calculated accurately and the EGR gas flow velocity is a value that is not related to steady state and transient, the target EGR amount including transient can be calculated accurately.

As a result, in setting the feedback gain in the first and sixth aspects of the present invention, since the steady state and the transient state can be uniformly treated, the feedback gain of the feedback gain is set higher than that of the prior art in which the EGR amount or the intake air amount is the object of the feedback correction. The setting becomes easier and the robustness to exhaust gas is further improved.

According to the second aspect of the invention, the difference between the actual intake air amount and the target intake air amount becomes zero or the ratio of the actual intake air amount and the target intake air amount becomes 1 by the learned value for each operation region. Therefore, the change in the feedback correction amount is reduced, and the controllability is improved.

The characteristic of the EGR flow velocity with the target EGR amount and the target EGR rate as parameters is as shown in FIG. 64, and in the same figure, the portion near the right end where the inclination of the characteristic becomes steep is a region where a conformance error is likely to occur. Therefore, if there is a matching error,
Although the EGR valve opening area changes due to the influence of the matching error, according to the third and seventh inventions, even if there is the matching error, the actual intake air amount is changed to the target intake air amount. Can be converged.

During a transition, the actual intake air amount deviates from the target intake air amount. Since this deviation is due to the delay of the intake system volume, the EGR flow velocity, the parameter used to calculate the EGR flow velocity, or the target EGR amount is fed back based on the difference or ratio between the actual intake air amount and the target intake air amount even during the transition. If the correction or the feedback correction amount of the EGR flow velocity is calculated, the feedback amount becomes excessive due to the delay of the intake system volume.
According to the fifth aspect, the feedback amount is not excessively increased even during the transition.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structure for performing a so-called low temperature premixed combustion in which a heat generation pattern is a single stage combustion. The structure itself is disclosed in Japanese Patent Laid-Open No. 8-86.
It is known from, for example, Japanese Patent No. 251.

Now, the production of NOx largely depends on the combustion temperature, and it is effective to lower the combustion temperature to reduce it. In the low temperature premixed combustion, in order to realize low temperature combustion by reducing the oxygen concentration by EGR, the negative pressure control valve 5 controls the negative pressure in the EGR passage 4 connecting the exhaust passage 2 and the collector portion 3a of the intake passage 3. A diaphragm type EGR valve 6 that responds to the above is provided.

The negative pressure control valve 5 is the control unit 4
It is driven by the duty control signal from 1.
Thereby, a predetermined EGR rate according to the operating condition is obtained. For example, the EGR rate is set to 100% at the maximum in the low rotation and low load range, and the EGR rate is decreased as the rotation speed and the load increase. Since the exhaust temperature rises on the high load side, if a large amount of EGR gas is recirculated, the effect of reducing NOx is reduced due to the rise in intake air temperature, or the ignition delay period of the injected fuel is shortened and premixed combustion cannot be realized. Therefore, the EGR rate is gradually reduced.

A cooling device 7 for EGR gas is provided in the middle of the EGR passage 4. This is composed of a water jacket 8 formed around the EGR passage 4 in which a part of the engine cooling water is circulated, and a flow rate control valve 9 provided in the cooling water inlet 7a and capable of adjusting the circulation amount of the cooling water. Therefore, according to the command from the control unit 41, the cooling degree of the EGR gas increases as the circulation amount increases via the control valve 9.

A swirl control valve (not shown) having a predetermined notch is provided in the intake passage near the intake port for promoting combustion. When the control unit 41 closes the swirl control valve in the low rotation and low load region, the flow velocity of the intake air sucked into the combustion chamber is increased and swirl is generated in the combustion chamber.

The combustion chamber is a large diameter toroidal combustion chamber (not shown). In this, the piston cavity is formed in a cylindrical shape from the crown of the piston to the bottom without restricting the inlet, and at the center of the bottom, resistance is given to the swirl flowing from the outside of the piston cavity while swirling from the outside of the compression stroke. A cone is formed so as to further improve the mixing of air and fuel. With this cylindrical piston cavity that does not throttle the inlet, the swirl generated by the swirl valve described above diffuses from the inside of the piston cavity to the outside of the cavity as the piston descends during the combustion process. The swirl is sustained.

The engine is equipped with a common rail fuel injection device 10. The configuration of the common rail type fuel injection device 10 is also publicly known (see Proceedings of the 13th Internal Combustion Engine Symposium, pp. 73 to 77), and will be outlined with reference to FIG.

This fuel injection device 10 mainly includes a fuel tank 11, a fuel supply passage 12, a supply pump 14, a common rail (accumulation chamber) 16, and a nozzle 17 provided for each cylinder.
After the fuel pressurized by the supply pump 14 is temporarily stored in the pressure accumulating chamber 16 through the fuel supply passage 15, the high pressure fuel in the pressure accumulating chamber 16 has the same number of nozzles 1 as the number of cylinders.
It is divided into seven.

The nozzle 17 includes a needle valve 18, a nozzle chamber 19,
Fuel supply passage 20 to nozzle chamber 19, retainer 21, hydraulic piston 22, return spring 23 for urging needle valve 18 in the valve closing direction (downward in the figure), fuel supply passage 24 to hydraulic piston 22, this passage 24 A three-way valve (solenoid valve) 25, etc. installed in the nozzle
When the three-way valve 25 in which the high pressure fuel is guided to both the upper portion of the hydraulic piston 22 and the nozzle chamber 19 is OFF (ports A and B communicate, ports B and C are cut off), the pressure receiving area of the hydraulic piston 22 is Is larger than the pressure receiving area of the needle valve 18, the needle valve 18 is in the seated state, but the three-way valve 25 is ON.
When the state (ports A and B are cut off, ports B and C are in communication), the fuel above the hydraulic piston 22 is returned to the fuel tank 11 via the return passage 28, and the fuel pressure acting on the hydraulic piston 22 is reduced. . As a result, the needle valve 18 rises and fuel is injected from the injection hole at the tip of the nozzle. Three-way valve 2
When 5 is returned to the OFF state again, the high pressure fuel in the pressure accumulating chamber 16 is guided to the hydraulic piston 22 and the fuel injection ends. That is, if the fuel injection start timing is adjusted by the switching timing of the three-way valve 25 from ON to OFF and the fuel injection amount is adjusted by the ON time, and the pressure in the pressure accumulating chamber 16 is the same,
The fuel injection amount increases as the ON time increases. Reference numeral 26 is a check valve, and 27 is an orifice.

The fuel injection device 10 is further provided with a pressure adjusting valve 31 in the passage 13 for returning the fuel discharged from the supply pump 14 in order to adjust the pressure of the pressure accumulating chamber. The adjusting valve 31 opens and closes the flow path of the passage 13, and adjusts the pressure of the pressure accumulating chamber by adjusting the amount of fuel discharged to the pressure accumulating chamber 16. The fuel injection rate changes depending on the fuel pressure (injection pressure) in the pressure accumulating chamber 16, and the higher the fuel pressure in the pressure accumulating chamber 16, the higher the fuel injection rate.

In the control unit 41 to which signals from the accelerator opening sensor 33, the sensor 34 for detecting the engine speed and the crank angle, the sensor 35 for discriminating the cylinder, and the water temperature sensor 36 are input, the engine speed and the accelerator opening are set. The target fuel injection amount and the target pressure of the pressure accumulating chamber 16 are calculated according to the degree, and the fuel of the pressure accumulating chamber 16 is adjusted via the pressure adjusting valve 31 so that the pressure accumulating chamber pressure detected by the pressure sensor 32 matches the target pressure. Feedback control the pressure.

Further, the ON time of the three-way valve 25 is controlled according to the calculated target fuel injection amount, and the O of the three-way valve 25 is controlled.
By controlling the switching timing to N, the predetermined injection start timing according to the operating conditions is obtained. For example, the fuel injection timing (injection start timing) is delayed to the piston top dead center (TDC) so that the ignition delay period of the injected fuel becomes longer on the side of low rotation and low load with a high EGR rate. Due to this delay, the temperature in the combustion chamber at the ignition timing is set to a low temperature state and the premixed combustion ratio is increased, thereby suppressing the occurrence of smoke in the high EGR rate region. On the other hand, the injection timing is advanced as the rotation speed and the load increase. This is the ignition delay crank angle (a value obtained by converting the ignition delay time into a crank angle) even if the ignition delay time is constant.
Becomes larger in proportion to the increase in engine speed, and low EG
The injection timing is advanced to obtain a predetermined ignition timing at the R rate.

Returning to FIG. 1, a variable capacity turbocharger is provided in the exhaust passage 2 downstream of the opening of the EGR passage 4. this is,
A variable nozzle 53 driven by a negative pressure actuator 54 is provided at the scroll inlet of the exhaust turbine 52. The variable nozzle 53 is controlled by the control unit 41.
Is a nozzle opening (tilt state) that increases the flow velocity of the exhaust gas introduced into the exhaust turbine 52 on the low rotation side so that a predetermined boost pressure can be obtained from the low rotation range, and the exhaust gas is exhausted without resistance on the high rotation side. It is introduced into the turbine 52 to control the nozzle opening (fully open state).

The negative pressure actuator 54 comprises a diaphragm actuator 55 that drives the variable nozzle 53 in response to the control negative pressure, and a negative pressure control valve 56 that adjusts the control negative pressure to the actuator 55. The duty control signal is generated so that the opening ratio of the nozzle 53 becomes the target opening ratio Rvnt obtained as described later, and this duty control signal is output to the negative pressure control valve 56.

From the perspective of supercharging pressure control,
The EGR control also physically plays the role of supercharging pressure control. That is, the supercharging pressure also changes by changing the EGR amount. On the contrary, when the supercharging pressure is changed, the exhaust pressure also changes, so the EGR amount also changes, and the supercharging pressure and the EGR amount cannot be controlled independently. In addition, it is a control disturbance for each other. Note that if one is changed, the other is re-adapted to ensure control accuracy, but after re-adapting the other, the other must be re-adapted. With the method, it is difficult to secure the control accuracy during the transition.

As described above, the supercharging pressure and the EGR amount have an influence on each other, and when the EGR amount is changed, it is difficult to properly adjust the nozzle opening and the like. Therefore, the control unit 41 controls the target intake air amount tQac according to the operating conditions.
Is calculated and the target intake air amount tQac and the target EGR amount and the target EGR rate Megr are subjected to delay processing, and the variable nozzle that is the operation target value of the turbocharger is calculated from the actual EGR amount Qec and the actual EGR rate Megrd. Target opening ratio R of 53
Set vnt.

Further, the EGR flow rate Cqe is predicted, and the opening Aev of the EGR valve 6 is controlled based on this predicted value.

Further, the EGR flow velocity feedback correction coefficient Kqac0 is calculated so that the actual intake air amount Qac matches the target intake air amount delay processing value tQacd, and this feedback correction coefficient Kqac0 and EGR flow velocity learning correction coefficient Kqac (= Rqac + 1). And correct the actual EGR amount Qec, which is a parameter used to calculate the EGR flow velocity Cqe. At that time, the error rate learning value Rqac for each operating region
Is updated based on the EGR flow velocity feedback correction amount Kqac0.

The EGR amount feedback correction coefficient Kqac00 is calculated so that the actual intake air amount Qac matches the target intake air amount delay processing value tQacd, and the target EGR amount is corrected by this feedback correction coefficient Kqac0.

The contents of these controls executed by the control unit 41 will be described with reference to the following flow chart. In addition, FIG. 3, FIG. 4, and FIG.
Is a prior application device (see Japanese Patent Application No. 9-92306), and FIG. 7 (except that Kqac00 is introduced in step 6) is another prior application device (see Japanese Patent Application No. 9-125892).
Is the same as that already proposed in.

First, FIG. 3 is for calculating the target fuel injection amount Qsol. The REF signal (reference position signal of the crank angle, which is every 180 degrees in a 4-cylinder engine and every 120 degrees in a 6-cylinder engine). ) Is executed for each input.

In steps 1 and 2, the engine speed Ne and the accelerator opening Cl are read, and in step 3, these N
Based on e and Cl, the basic fuel injection amount Mqdrv is calculated by searching a map having the contents of FIG.
In step 4, the basic fuel injection amount Mqdrv is increased and corrected by the engine cooling water temperature or the like, and the corrected value is set as the target fuel injection amount Qsol.

FIG. 5 is for calculating the opening area Aev of the EGR valve 6, which is executed every time the REF signal is input. In step 1, the target EGR amount Tqek is calculated. This T
The calculation of qek will be described with reference to the flow of FIG.

In FIG. 7 (subroutine of step 1 in FIG. 5), in steps 1 and 2, the intake air amount Qacn per cylinder and the target EGR rate Megr are calculated.

Here, the calculation of Qacn will be described with the flow of FIG. 8, and the calculation of Megr will be described with the flow of FIG.

First, in FIG. 8, in step 1, the engine speed Ne is read, and based on this engine speed Ne and the intake air amount Qas0 obtained from the air flow meter.

[0053]

## EQU1 ## Qac0 = (Qas0 / Ne) × KCON # where KCON # is a constant, and the intake air amount Qac0 per cylinder is calculated.

The above air flow meter 39 (see FIG. 1)
Is provided in the intake passage 3 upstream of the compressor, and performs delay processing for the transportation delay from the air flow meter 39 to the collector portion 3a. Therefore, in step 3, the value of Qac0 before L (where L is a constant) times is collected. It is calculated as the intake air amount Qacn per cylinder at the position of the inlet portion 3a. Then, in step 4, for this Qacn

[0055]

(2) Qac = Qac _n-1 × (1-KIN × KVO
L) + Qacn × KIN × KVOL where KIN: volumetric efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, Qac _n-1 : previous Qac, The intake air amount per cylinder at the intake valve position (this intake air amount is abbreviated as “cylinder intake air amount” below) Qac is calculated by the equation (first-order lag equation).
This is for compensating the dynamics from the collector inlet portion 3a to the intake valve.

The detection of the intake air amount Qas0 on the right side of the above equation 1 will be described with reference to the flow chart of FIG. The flow of FIG. 9 is executed every 4 msec.

In step 1, the output of the air flow meter 39 is output.
The force voltage Us is read, and from this Us, step 2 is performed.
Retrieving a voltage-flow rate conversion table containing 0
Intake air amount Qas0 Calculate d. further,
This Qas0 in step 3 Performs weighted average processing on d
The weighted average processed value is set as the intake air amount Qas0.
Set.

Next, in FIG. 11, in step 1, the engine speed Ne, the target fuel injection amount Qsol, and the engine cooling water temperature Tw are read. In step 2, the basic target EGR rate Me is obtained by searching the map including the content of FIG. 12 from the engine speed Ne and the target fuel injection amount Qsol.
Calculate grb. In this case, the basic target EGR rate increases in a region where the engine is frequently used, that is, a low turning point and a low load (low injection amount), and is reduced at high output where smoke is likely to occur.

Next, in step 3, from the cooling water temperature Tw, as shown in FIG.
The water temperature correction coefficient Kegr of the basic target EGR rate is searched by searching a table having Calculate tw.
Then, in step 4, from the basic target EGR rate and this water temperature correction coefficient,

[0060]

[Equation 3] Megr = Megrb × Kegr The target EGR rate Megr is calculated by the formula of tw.

In step 5, it is determined whether the engine is in the complete explosion state. However, the judgment of this complete explosion is
It will be described later in the flow of FIG.

At step 6, it is judged whether or not the state is the complete explosion state. If the complete explosion state, the current processing is ended. If it is determined that the complete explosion state is not reached, the target EGR rate Megr is set to 0 and the current processing is performed. finish.

As a result, the EGR control is performed after the complete explosion of the engine, and the EGR is not performed before the complete explosion in order to secure a stable startability.

FIG. 14 is for determining the complete explosion of the engine. The engine speed Ne is read in step 1, and this engine speed Ne is compared with the complete explosion determination slice level NRPMK corresponding to the complete explosion speed in step 2. When Ne is larger, it is judged that the explosion is complete,
Go to step 3. Here, the counter Tmrkb is compared with the predetermined time TMRKBP, and when the counter Tmrkb is larger than the predetermined time, the process proceeds to step 4, and the process is terminated assuming that the complete explosion has occurred.

On the other hand, when Ne is smaller in step 2, the process proceeds to step 6 and the counter Tmrkb
Is cleared, and in step 7, it is determined that the complete explosion has not occurred, and the processing ends. Further, even if it is larger than Ne in step 2, if the counter Tmrkb is smaller than the predetermined time in step 3, the counter is incremented in step 5 and it is judged that the complete explosion is not completed.

From these, it is determined that the complete explosion has occurred when the engine speed is equal to or higher than a predetermined value (for example, 400 rpm) and this state is continued for a predetermined time.

In this way, when the calculation of the cylinder intake air amount Qacn according to FIG. 8 and the target EGR rate Megr according to FIG. 11 are completed, the process returns to step 3 of FIG.

[0068]

(4) Mqec = Qacn × Megr The required EGR amount Mqec is calculated by the following equation.

In step 4, for this Mqec, K
Let IN × KVOL be the weighted average coefficient

[0070]

[Equation 5] Rqec = Mqec × KIN × KVOL + Rq
ec _n-1 × (1-KIN × KVOL) where KIN: volume efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, Rqec _n-1 : The intermediate processing value (weighted average value) Rqec is calculated by the formula of the previous intermediate processing value, and the calculated Eq amount and the requested EGR amount Mqec are used in step 5.

[0071]

[Equation 6] Tqec = Mqec × GKQEC + Rqec
_n-1 × (1-GKQEC) However, the target EGR amount Tqec per cylinder is calculated by performing the advance correction according to the formula GKQEC: advance correction gain. Since there is a delay of the intake system with respect to the required value (that is, a delay corresponding to the capacity of the EGR valve 6 → the collector portion 3a → the intake manifold → the intake valve), steps 4 and 5 carry out advance processing for this delay. .

In step 6,

[0073]

## EQU00007 ## Tqek = Tqec.times. (Ne / KCON #) /
Kqac00 However, the target EGR amount Tqek is obtained by performing unit conversion (per cylinder → per unit time) according to the equations Kqac00: EGR amount feedback correction coefficient, KCON #: constant. In addition,
The calculation of the EGR amount feedback correction coefficient Kqac00 will be described later (see FIG. 54).

When the calculation of the target EGR amount Tqek is completed in this way, the process returns to step 2 of FIG. 5 to calculate the EGR flow velocity Cqe, and the EGR flow velocity Cqe and the target EGR amount Tqek are calculated.

[0075]

## EQU8 ## The EGR valve opening area Aev is calculated by the equation Aev = Tqek / Cqe. EG
The calculation of the R flow velocity Cqe will be described later (see FIG. 63).

The EGR valve opening area Aev thus obtained is converted into the lift amount of the EGR valve 6 by searching a table having the contents of FIG. 6 in a flow not shown, and becomes this EGR valve lift amount. Thus, a duty control signal for the negative pressure control valve 5 is created, and this duty control signal is output to the negative pressure control valve 5.

Next, FIGS. 15 and 16 show the control command duty value Dt given to the negative pressure control valve 56 for driving the turbocharger.
This is for calculating yvnt, and is executed at regular time intervals (for example, every 10 msec).

When FIG. 15 is the first embodiment and FIG. 16 is the second embodiment, there are differences between the two embodiments in the parameters used to calculate the target opening ratio Rvnt of the variable nozzle 53 (see FIG. 15). In one embodiment, the actual EGR amount Qe
c, and in the second embodiment of FIG. 16, the actual EGR
The target opening ratio Rvnt of the variable nozzle 53 is calculated based on the ratio Megrd).

Note that FIGS. 15 and 16 are main routines, and a large control flow follows the illustrated steps, and a subroutine is prepared for the processing of each step. Therefore, in the following, the subroutine will be mainly described.

FIG. 17 (subroutine of step 1 in FIGS. 15 and 16) is for calculating the actual EGR rate.
It is executed every time the EF signal is input. Target EGR in step 1
The rate Megr (which has already been obtained in FIG. 11) is read, and in step 2, the time constant equivalent value Kkin for the collector capacitance is calculated. The calculation of Kkin will be described with reference to the flow of FIG.

In FIG. 18 (subroutine of step 2 in FIG. 17), in step 1, the engine speed Ne, the target fuel injection amount Qsol, and Megrd _n-1 [%] which is the previous value of the actual EGR rate, which will be described later, are read, Of these, Ne and Q
The volume efficiency equivalent basic value Kinb is obtained by searching a map having the contents of FIG.
Is calculated, and in step 3,

[0082]

Equation 9 Kin = Kinb × 1 / (1 + Megrd _n−1)
/ 100) to calculate the volumetric efficiency equivalent value Kin. This is E
Since GR reduces the volumetric efficiency, the correction is made accordingly.

The value obtained by multiplying Kin thus obtained by KVOL (see step 4 in FIG. 8) which is a constant corresponding to the ratio of the intake system volume to the cylinder volume in step 4 corresponds to the time constant for the collector capacity. The value is calculated as Kkin.

When the calculation of Kkin is completed in this way, the process returns to step 3 of FIG. 17, and this Kkin and the target EG
Using the R rate Megr,

[0085]

[Equation 10] Megrd = Megr × Kkin × Ne × K
E2 # + Megrd _n-1 x (1-Kkin x Ne x KE
2 #) However, Kkin: Kin × KVOL #, KE2 #: constant, Megrd _n−1 : previous Megrd, delay processing and unit conversion (per cylinder → per unit time) are performed at the same time, and intake valve position The EGR rate Megrd at is calculated. Ne × KE2 on the right side of Expression 10
# Is the value for unit conversion. Target EGR rate Megr
On the other hand, since this Megrd responds with a first-order delay, this Megrd is hereinafter referred to as “actual EGR rate”.

FIG. 20 (subroutine of step 2 in FIGS. 15 and 16) is for calculating the target intake air amount tQac. Engine speed Ne, actual E in step 1
The GR rate Megrd and the target fuel injection amount Qsol are read, and in step 2, Megrd and a predetermined value MEGRLV # are compared.

Here, the predetermined value MEGRLV # is a value (for example, 0.5) for determining whether or not the EGR is operating,
When Megrd> MEGRLV #, it is judged that it is in the EGR operation range, and the routine proceeds to steps 3, 4 and 5, whereas when Megrd ≦ MEGRLV #, EGR
It is judged that it is in the non-operation area of No., and the routine proceeds to step 6. MEG
If the RLV # is not 0, there is a demand for handling the same even when a small amount of EGR is performed as when the EGR is not performed.

If it is in the EGR operating range, step 3
Then, the target intake air amount basic value tQacb is calculated by searching a map having, for example, FIG. 21 based on the engine speed Ne and the actual EGR rate Megrd. If the engine speed is constant, the target intake air amount is increased as the actual EGR rate is larger as shown in FIG.

In step 4, the correction coefficient ktQac of the target intake air amount is calculated by searching a map having the contents of FIG. 22 from Ne and Qsol, and this correction coefficient is multiplied by the target intake air amount basic value. The calculated value is calculated as the target intake air amount tQac. Correction coefficient ktQac
Is to meet the demand for changing the target intake air amount depending on the operating conditions (Ne, Qsol).

On the other hand, when it is in the non-operating range of EGR, the routine proceeds to step 6, where the target intake air amount tQac is calculated by searching a map having the contents of FIG. 23 from Ne and Qsol, for example.

FIG. 24 (subroutine of step 3 in FIG. 15) is for calculating the actual EGR amount. In step 1, the intake air amount Qacn per cylinder at the position of the collector inlet 3a (already obtained in step 3 of FIG. 8), the target EGR rate Megr, and the time constant equivalent value Kkin for the collector capacity are read. Of these, Qacn and Me
from gr in step 2

[0092]

[Equation 11] The EGR amount Qec0 per cylinder at the position of the collector inlet portion 3a is calculated by the equation of Qec0 = Qacn × Megr, and this Qec0 and K
In step 3 using kin,

[0093]

[Equation 12] Qec = Qec0 × Kkin × Ne × KE #
+ Qec _n-1 x (1-Kkin x Ne x KE #) However, Kkin: Kin x KVOL, KE #: constant, Qec _n-1 : Qec of the previous time. The process and the unit conversion (per cylinder → per unit time) are simultaneously performed to calculate the cylinder intake EGR amount Qec. Ne × KE # on the right side of Expression 12 is a value for unit conversion. Since this Qec responds to the target EGR amount Tqek with a first-order lag, this Qec is hereinafter referred to as “actual EGR amount”. Further, the above Qac that responds with a first-order lag to the target intake air amount tQac is hereinafter referred to as “actual intake air amount”.

FIG. 25 (subroutine of step 4 in FIG. 15) and FIG. 27 (subroutine of step 3 in FIG. 16) are for calculating the target opening ratio Rvnt of the variable nozzle 53 (FIG. 25 is the first embodiment). FIG. 27 shows a second embodiment).

Here, the opening ratio of the variable nozzle 53 is
It is the ratio of the current nozzle area to the nozzle area when the variable nozzle 53 is fully opened. Therefore, the variable nozzle 5
No. 3 has an opening ratio of 100% when fully opened, and has an opening ratio of 0% when fully closed. The reason for adopting the opening ratio is to provide versatility (a value that has no relation to the capacity of the turbocharger). Of course, the opening area of the variable nozzle may be adopted.

Since the turbocharger of the embodiment is of the type in which the supercharging pressure is the smallest when fully opened and the supercharging pressure is highest when fully closed, the smaller the opening ratio, the higher the supercharging pressure. Become.

First, referring to FIG. 25 of the first embodiment, in step 1, the target intake air amount tQac, the actual E
GR amount Qec, engine speed Ne, target fuel injection amount Q
Read sol.

In steps 2 and 3,

[0099]

[Equation 13] tQas0 = (tQac + Qsol × QFG
AN #) × Ne / KCON # Qes0 = (Qec + Qsol × QFGAN #) × Ne
/ KCON # where QFGAN #: gain, KCON #: constant, two intake air amount equivalent values tQas0 for setting the target opening ratio (hereinafter, this intake air amount equivalent value is referred to as "the set intake air amount "Equivalent value") and the EGR amount equivalent value Qes0 (hereinafter, referred to as "equivalent value") for setting the target opening ratio.
This EGR amount equivalent value is referred to as a “set EGR amount equivalent value”)
Is calculated. In Equation 13, Q is added to tQac and Qec.
The reason for adding sol × QFGAN # is that the load correction can be performed on the set intake air amount equivalent value and the set EGR amount equivalent value, and the sensitivity is adjusted by the gain QFGAN #. . Also, Ne / KCON #
Is a value for converting the intake air amount and the EGR amount per unit time.

From the set intake air amount equivalent value tQas0 and the set EGR amount equivalent value tQes0 thus obtained, in step 4, the target opening ratio Rvnt of the variable nozzle 53 is set by searching a map having the contents shown in FIG. To do.

On the other hand, in FIG. 27 of the second embodiment,
In step 1, the target intake air amount tQac and the actual EGR rate Me
grd, engine speed Ne, target fuel injection amount Qsol
28, and in step 2, the set intake air amount equivalent value tQas0 is calculated by the upper equation of the above equation 13, and the set intake air amount equivalent value tQas0 and the actual EGR rate Megrd are calculated in step 3 as shown in FIG. The target opening ratio Rvnt of the variable nozzle 53 is set by retrieving the map.

The characteristics shown in FIGS. 26 and 28 are set with emphasis on fuel consumption. However, the difference from the setting example of emphasizing exhaust gas described below is only specific numerical values, so the characteristics common to both will be described first, and then the differences between the two. Note that the characteristics of FIG. 28 are different from those of FIG. 26 in the vertical axis (the inclination from the origin indicates the EGR rate in FIG. 26), but are basically the same as those of FIG.
It will be explained in item 6.

As shown in FIG. 26, the target opening ratio is reduced as the set EGR amount corresponding value Qes0 increases in the right region where the set intake air amount corresponding value tQas0 is large. This is for the following reason. When the EGR amount increases, the fresh air decreases accordingly, and when the air-fuel ratio leans toward the rich side, smoke is generated. Therefore, as the EGR amount increases, it is necessary to reduce the target opening ratio and increase the supercharging pressure.

On the other hand, in the region on the left side where tQas0 is small, the supercharging effect cannot be obtained so much. TQ in this area
The smaller the as0, the smaller the target opening ratio. This is for the following reason. This is because if the target opening ratio is increased in this region as well, the exhaust pressure is hard to rise, so it is desirable to avoid this, and for the full-open acceleration, the opening ratio should be small at the initial stage.
Thus, the characteristics shown in FIG. 26 are basically determined from two different requirements. Therefore, the change in the target opening ratio differs depending on whether the change in the target intake air amount is small or large.

The tendency of the target opening ratio represented in FIG. 26 is common to the emphasis on fuel consumption and the emphasis on exhaust gas, and the difference between the two lies in a specific numerical value. In the figure, the numerical value at a position of "small" is the minimum value at which the turbocharger works efficiently, and is the same in both the fuel consumption-oriented setting example and the exhaust-oriented setting example, for example, about 20. On the other hand, the numerical value of a certain position, which is “large”, differs between the two, and in the case of the setting example of emphasizing fuel efficiency, 60
In the example of setting with emphasis on exhaust gas, the value is about 30.

The setting of the target opening ratio is not limited to the above. In the first embodiment, the target opening ratio is set from the set intake air amount equivalent value tQas0 and the set EGR amount equivalent value tQes0, but instead of this, it is set from the target intake air amount tQac and the actual EGR amount Qec. I don't care. Further, instead of this, the target intake air amount tQ
It may be set from ac and the target EGR amount (Qec0). Similarly, in the second embodiment, the target opening ratio is set from the set intake air amount equivalent value tQas0 and the actual EGR rate Megrd, but instead of this, the target intake air amount t
It may be set from Qac and the actual EGR rate Megrd. Further, instead of this, the target intake air amount tQac and the target EGR rate Megr may be set.

FIG. 29 (subroutine of step 5 in FIG. 15 and step 4 in FIG. 16) shows a negative pressure actuator 54 (negative pressure control) for driving the variable nozzle with respect to the target opening ratio Rvnt obtained as described above. In order to compensate for the dynamics of the valve 56 and the diaphragm actuator 55), advance processing is performed. This is because when the actuator of the variable nozzle 53 is a negative pressure actuator, there is a response delay that cannot be ignored, unlike when it is a step motor.

In step 1, the target opening ratio Rvnt is read, and this Rvnt and the previously predicted opening ratio Cav
nt _n-1 are compared in step 2. Here, the expected opening ratio Cavnt is a weighted average value of the target opening ratio Rvnt, as described later (see step 10).

If Rvnt> Cavnt _n-1 (when the variable nozzle 53 is moved to the opening side), the process proceeds to steps 3 and 4 to advance the predetermined value GKVNTO # and advance the correction gain Gkvnt and the predetermined value TCVNTO # to advance the correction. Is set as the time constant equivalent value Tcvnt of
When t <Cavnt _n−1 (when the variable nozzle 53 is moved to the closing side), the process proceeds to steps 6 and 7.
The correction gain Gkvnt is advanced by a predetermined value GKVNTC #, and the time constant equivalent value Tcvn of the correction is advanced by a predetermined value TCVNTC #.
Set as t. If Rvnt and Cavnt _n-1 are the same, the process proceeds to steps 8 and 9, and the previous advance correction gain and the time constant equivalent value of the advance correction are maintained.

Advance correction gain Gk depending on whether the variable nozzle 53 is moved to the open side or to the closed side.
vnt, the time constant equivalent value Tcvnt for advance correction are made different, and GKVNTO # <GKVNTC #, TCVNTO #
<TCVNTC #. This is the variable nozzle 53
Since it is necessary to resist the exhaust pressure when the valve is moved to the closing side, the gain Gkvnt is accordingly increased and the time constant is decreased (the time constant equivalent value Tcvnt, which is in inverse relation to the time constant, is increased). It is necessary.

In step 10, the time constant equivalent value Tcvnt of the advance correction thus obtained and the target opening ratio Rvn are obtained.
using t

[0112]

[Equation 14] Cavnt = Rvnt × Tcvnt + Cav
nt _n-1 × (1-Tcvnt) where Cavnt _{n-1 is the} previous Cavnt, the expected opening ratio Cavnt is calculated, and from this value and the target opening ratio Rvnt,

[0113]

[Equation 15] Avnt f = Gkvnt × Rvnt− (G
kvnt-1) × Cavnt _n-1 where Cavnt _{n-1 is the} previous Cavnt, the advance correction is performed, and the feedforward amount Avnt of the target opening ratio is calculated. Calculate f. Steps 10 and 1
The advance processing of 1 itself is basically the same as the advance processing shown in steps 4 and 5 of FIG.

FIG. 30 (subroutines of step 6 in FIG. 15 and step 5 in FIG. 16) shows the feedback amount Avnt of the target opening ratio. It is for calculating fb.
In step 1, target intake air amount tQac and target EGR rate M
egr, engine speed Ne, target fuel injection amount Qso
1, the actual intake air amount Qac is read, and in step 2, the target EGR rate Megr and the predetermined value MEGRLV # are compared.

When Megr ≧ MEGRLV # (E
(In the operating range of GR), in step 4

[0116]

## EQU16 ## The error ratio dQac from the target intake air amount is calculated by the equation dQac = tQac / Qac-1. The value of dQac is centered around 0, and becomes a positive value when Qac as an actual value is smaller than tQac as a target value, and conversely becomes a negative value when Qac is larger than tQac.

On the other hand, when Megr <MEGRLV # (in the non-operating range of EGR), the routine proceeds to step 3, where the error ratio dQac = 0 (that is, feedback is prohibited).

In step 5, the correction coefficient Kh of the feedback gain is calculated by searching a predetermined map from Ne and Qsol, and this value is calculated in step 6 with each constant (proportional constant KPB #, integral constant KIB #, differential constant K).
Feedback gain K by multiplying DB #)
p, Ki, Kd are calculated, and the feedback amount Avnt of the target opening ratio is calculated using these values. fb is calculated in step 7. The method of calculating the feedback amount is a well-known PID process.

The above correction coefficient Kh is determined by the operating condition (Ne,
Qsol) was introduced in response to a change in the appropriate feedback gain, and becomes larger as the load and the rotational speed increase.

FIG. 31 (subroutines of step 7 in FIG. 15 and step 6 in FIG. 16) is for performing linearization processing on the target opening ratio. Feedforward amount Avnt of the target opening ratio in step 1 f and the feedback amount Avnt fb is read, and a value obtained by adding both of them in step 2 is calculated as a command opening ratio Avnt. In step 3, this command opening ratio Avnt
Then, the command opening ratio linearization processing value Ratdty is set by searching, for example, a table (linearization table) having the contents of FIG.

This linearization processing is required when the command signal to the actuator for driving the turbocharger has a non-linear characteristic with respect to the opening ratio (or opening area) as shown in FIG. Is. For example, as shown in FIG. 33, even if the variation range of the air amount (supercharging pressure) is the same, the variation range of the opening area is significantly different from dA0 and dA1 in the region where the air amount is small and the region where the air amount is large (( However, EG
Without R). Furthermore, the presence or absence of EGR (in the figure, "w / o"
The change width of the opening area also changes depending on whether "EGR" indicates no EGR and "w / EGR" indicates EGR. Therefore, if the same feedback gain is used regardless of the operating conditions, the target intake air amount (supercharging pressure) cannot be obtained.
Therefore, in order to facilitate the adaptation of the feedback gain, the feedback gain correction coefficient Kh according to the operating conditions is introduced as described above.

34 (step 8 in FIG. 15, each subroutine in step 7 in FIG. 16) sets a control command value Dtyvnt which is an ON duty value (hereinafter simply referred to as “duty value”) given to the negative pressure control valve 56. It is for doing. First, in step 1, the engine speed Ne, the target fuel injection amount Qsol, the command opening ratio linearization processing value Ra
tdty, advance correction time constant equivalent value Tcvnt, water temperature T
read w

In step 2, the duty selection signal flag is set. This flag setting will be described with reference to the flow of FIG. In FIG. 35, the command opening ratio Avnt and the advance correction time constant equivalent value Tcvnt are read in step 1, and from these, in step 2,

[0124]

[Expression 17] Adlyvnt = Avnt × Tcvnt + A
dlyvnt _n-1 x (1-Tcvnt) where Adlyvnt _{n-1 is the} previous Adlyvnt, and the expected aperture ratio Adlyvn
In step 3, t is calculated, and this value is compared with Adlyvnt _nM which is the value M (where M is a constant) times before the previous expected opening ratio.

When Adlyvnt ≧ Adlyvnt _nM (in the increasing tendency or in the steady state), the operation direction command flag fvnt = 1 is set in step 4 to indicate that the increasing tendency or in the steady state, and otherwise in step 5 The operating direction command flag fvnt = 0 is set. In step 6, in order to separate the case where there is an increasing tendency from the steady state, Adlyvnt and Adlyvnt _nM are compared. When Adlyvnt = Adlyvnt _nM , the duty holding flag fvnt2 =
1 and otherwise, the duty holding flag fvnt2 = 0 is set in step 8.

Thus, the two flags fvnt, f
When the setting of vnt2 is completed, the process returns to step 3 of FIG. 34 and the temperature correction amount Dty of the duty value is returned. Calculate t.
This calculation will be described with reference to the flow of FIG.

In FIG. 36, the engine speed Ne, the target fuel injection amount Qsol, and the water temperature Tw are read in step 1, and a basic map is obtained by searching, for example, a map having FIG. 37 in step 2 from Ne and Qsol. The exhaust temperature Texhb is calculated. Where Tex
hb is the exhaust temperature after completion of warming up. On the other hand, since the exhaust temperature after warming up is different during warming up, the water temperature correction coefficient for the exhaust temperature can be obtained by searching the water temperature Tw in step 3, for example, in a table having the content shown in FIG. Ktexh tw is calculated, and this value is calculated in step 4
At the exhaust temperature T
Calculate as exhi.

At step 5, from this exhaust temperature Texhi

[0129]

[Expression 18] Texhdly = Texhi × KEXH # +
Texhly _n-1 x (1-KEXH #) where KEXH # is a constant, Texhdly _{n-1 is the} previous Texhdly, and the value subjected to the delay process is the actual exhaust temperature Texhd.
Calculate as ly. This is to perform a delay process for the thermal inertia component.

At step 6, the basic exhaust temperature Texhb and
Calculate the difference dTexh from this actual exhaust temperature Texhdly
Then, from this difference dTexh, in step 7
By searching a table having the contents of FIG.
Temperature correction amount of duty value Dty Calculate t. Step
Maps 6 and 7 are used for the hysteresis correspondence described later.
(Duty h p, Duty h n, Duty l
p, Duty l n map) after completion of warm-up
With the setting in mind, the difference from that state (
(DTexh).
The temperature correction amount Dty Correction by t is the ambient temperature
Actuator for driving turbocharger with temperature characteristics
This is the process required when using the data (see Fig. 40).
See).

In this way, the temperature correction amount Dty When the calculation of t is completed, the process returns to step 4 in FIG.

Steps 4 to 9 in FIG. 34 are for performing hysteresis processing. This process will be described first with reference to FIG. 45. This is because the command opening ratio linearization process value Ra
When tdty is increasing, the upper characteristic (Duty
l p is a command signal when the variable nozzle is fully opened, Duty h
p is used as a command signal when the variable nozzle is fully closed), while the command opening ratio linearization processing value Ratd is used.
When ty tends to decrease, another lower characteristic (Duty l n is a command signal when the variable nozzle is fully opened, D
uty The h n is to use a linear characteristic) to the command signal of the variable nozzle is fully closed. Ratdty is 1
There is a region in which two characteristics are turned over in the region close to, but this region is not actually used.

Returning to FIG. 34, in step 4, the flag fvn is set.
Look at t1. When fvnt = 1 (that is, when the opening ratio tends to increase or is in a steady state), the process proceeds to steps 5 and 6, and, for example, a map (Duty) including FIG. h p map) and a map (Duty) with the contents of FIG. 42. l p-map), the duty value Duty when the variable nozzle is fully closed h and the duty value Duty when the variable nozzle is fully opened Set l respectively. On the other hand, when fvnt = 0 (that is, when the opening ratio tends to decrease), the process proceeds to steps 7 and 8 and, for example, a map (Duty) having FIG. h n map) and a map (Duty) having the contents of FIG. 44. l n map) to retrieve the duty value Duty when the variable nozzle is fully closed. h and the duty value Duty when the variable nozzle is fully opened Set l respectively.

The duty value Duty when the variable nozzle is fully closed, set in this way h, duty value Duty when the variable nozzle is fully opened In step 9, using 1 and the command opening ratio linearization processing value Ratdty described above,

[0135]

[Equation 18] Dty h = (Duty h-Duty
l) × Ratdty + Duty l + Dty t Linear duty calculation is performed using the formula
Value Dty Compute h. That is, used for linear interpolation calculation
The linearization characteristics of the commanded opening ratio are linearized.
Or in steady state and commanded aperture ratio linear
When the digitized value is decreasing, it is changed (hysterical
By performing cis processing), the command opening ratio linearization processing value is
Even if it is the same, the command opening ratio linearization processing value tends to increase.
(Or steady state) tends to decrease
Command duty value basic value Dty h is large
Become.

At step 10, another flag fvn is set.
Look at t2. If fvnt2 = 1 (that is, there is no change in the command opening ratio linearization processing value), the process proceeds to step 11, and the previous control command duty value (described later) D
If tyvnt _n-1 is put into the normal command duty value Dtyv (holding the duty value) and fvnt2 = 0 (that is, the opening ratio tends to decrease), step 12
To Dty, which is the latest calculated value. Let h be Dtyv.

In step 13, operation confirmation control processing is performed. This processing will be described with reference to the flow of FIG.
In FIG. 46, in step 1, the normal command duty value D
tyv, engine speed Ne, target fuel injection amount Qso
Read the water temperature Tw.

The conditions for entering the operation confirmation control are determined by checking the contents of steps 2, 3, 4, and 5 one by one, and when all of the items are satisfied, the time until the control is further executed. Enter the measurement of. That is, step 2: Qsol is less than a predetermined value QSOLDIZ # (that is, at the time of fuel cut), step 3: Ne is less than a predetermined value NEDIZ # (that is, the middle rotation range), step 4: Tw is less than a predetermined value TWDIZ #. (That is, before completion of warm-up), Step 5: Operation confirmation control completed flag fdiz = 0 (Operation confirmation control is not yet performed), When, Operation confirmation control counter Ctrdiz in Step 6
Is incremented.

At step 7, this operation confirmation control counter is compared with predetermined values CTRDIZH # and CTRDIZL #. Here, the predetermined values CTRDIZL #, CTRDIZH
# Defines a lower limit and an upper limit of the operation confirmation control counter. CTRDIZL # is a value of about 2 seconds, and CTRDIZH # is a value of about 7 seconds, for example. Therefore, from the timing when the operation confirmation control counter matches the lower limit CTRDIZL #, the operation confirmation control counter reaches the upper limit CTR.
While it is less than DIZH #, the process proceeds to step 9 and the operation confirmation control command duty value is set. That is, CTR
DIZH # -CTRDIZL # is the operation confirmation control execution time.

The setting of the operation confirmation control command duty value will be described with reference to the flow chart of FIG. In FIG. 47, the operation confirmation control counter Ctrdiz and the engine speed Ne are read in step 1 and Ctr is read in step 2.
From diz-CTRDIZL # (≧ 0), for example, FIG.
Control pattern Duty by searching the table that contains Set pu. This is to move the variable nozzle 53 to a fully closed position and a fully opened position in a short cycle.

In step 3, the duty value Duty is determined by searching a table having the contents of FIG. 49, for example, from the engine speed Ne. p Set ne, this D
uty p In step 4, the control pattern Duty A value multiplied by pu is calculated as a control command duty value Dtyvnt. As shown in FIG. 49, the control pattern Duty Duty value Duty to be multiplied by pu
p Ne is set to a value corresponding to the engine speed Ne.
This assumes that the duty command value for confirming the opening / closing operation of the variable nozzle 53 differs depending on the engine speed. For example, the variable nozzle 53 needs to be closed against the exhaust pressure, but the exhaust pressure increases as the rotation speed increases, so the duty command value is increased accordingly. On the higher rotation side, the value is lowered so as not to be adversely affected by this control.

Returning to FIG. 46, when the operation confirmation control counter is less than CTRDIZL # as the lower limit, the routine proceeds from step 8 to step 15 where the normal command duty value Dtyv is made the control command duty value Dtyvnt.

When the operation confirmation control counter reaches or exceeds CTRDIZH # as the upper limit, step 7
Then, the process proceeds to step 10, where Ctrdiz _n-1 which is the previous operation confirmation control counter and CTR as the upper limit.
Compare DIZH #. Ctrdiz _n-1 <CTRDI
If it is ZH #, it is determined that the operation confirmation control counter has just reached CTRDIZH # or higher as the upper limit,
In order to end the operation confirmation control, the control command duty value Dtyvnt = 0 is set in step 11. This is because the variable nozzle 53 is fully opened once at the end of the operation confirmation control to ensure the control accuracy during normal control. Step 1
In 2, in the operation confirmation control completion flag fdiz = 1,
This processing ends. Because of this flag fdiz = 1, it is not possible to proceed to step 6 and subsequent steps from the next time onward, so that the operation confirmation control is not performed twice after the engine is started.

If it is not immediately after the operation confirmation control counter reaches or exceeds CTRDIZH # as the upper limit,
The process proceeds from step 10 to step 14 to set the operation check control counter Ctrdiz = 0 to prepare for the next time, and then the process of step 15 is executed.

On the other hand, Qsol is a predetermined value QSOLDIZ #
When it is above (not during fuel cut), Ne is above a predetermined value NEDIZ # (high speed range), and when Tw is above a predetermined value TWDIZ # (after completion of warm-up), operation confirmation control is prohibited. Therefore, the process proceeds from Steps 2, 3 and 4 to Step 13, and after the flag fdiz = 0 is set, the processes of Steps 14 and 15 are executed.

As described above, when the operation of the actuator for driving the turbocharger is unstable, especially when the temperature is low, the operation confirmation control is performed, so that the movement of the variable nozzle becomes smooth, and the operation for driving the turbocharger is performed. The operation of the actuator can be made more reliable.

With the above, the description of FIGS. 15 and 16 is completed.

Next, FIG. 50 shows two feedback correction coefficients Kqa used to calculate the EGR amount and the EGR flow velocity.
c00, Kqac0 and EGR flow velocity learning correction coefficient Kqac
And is executed every time the REF signal is input.

First, at step 1, the target intake air amount tQa
c, actual intake air amount Qac, engine speed Ne, and target fuel injection amount Qsol are read. In step 2, from the target intake air amount tQac

[0150]

TQacd = tQac × KIN × KVOL ×
KQA # + tQac d _n-1 x (1-KIN x KVOL x
KQA #) However, KIN: volume efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, KQA #: constant, tQacdn _-1 : previous Qacd, The target intake air amount delay processing value tQacd is calculated by the following equation (first-order delay equation). In this case, a delay process is performed so that two feedback correction coefficients Kqac00 and Kqac0 and an error rate learning value Rqac, which will be described later, do not become large due to the air supply delay due to the presence of the intake system volume.

In step 3, various feedback-related flags are read. These settings will be described with reference to the flows of FIGS. 51, 52 and 53.

51, 52, and 53 are executed at fixed time intervals (for example, every 10 msec) independently of FIG.

FIG. 51 shows a feedback permission flag fef.
It is for setting b. In step 1, the engine speed Ne, the target fuel injection amount Qsol, the actual EGR rate Me
The grd and the water temperature Tw are read.

The determination of the feedback permission condition is performed by checking the contents of steps 2 to 5 and 8 one by one. When all of the items are satisfied, the feedback is permitted. Prohibit That is, Step 2: Megrd exceeds a predetermined value MEGRFB # (that is, an EGR operation range), Step 3: Tw is a predetermined value TWFBL # (for example, 30).
℃), Step 4: Qsol exceeds the specified value QSOLLFBL # (no fuel cut), Step 5: Ne exceeds the specified value NEFBL # (not in the engine stall range) Step 8: When the feedback start counter Ctrfb exceeds a predetermined value TMRFB # (for example, a value of less than 1 second), the feedback permission flag fefb = 1 is set to permit feedback in Step 9, and otherwise, to Step 10. After that, the feedback permission flag fefb = 0 is set in order to prohibit feedback.

The feedback start counter counts up when steps 2 to 5 are satisfied (step 6), and the feedback start counter is reset when steps 2 to 5 are not satisfied (step 7).

FIG. 52 shows the learning value reflection permission flag ferln.
It is for setting 2. In step 1, the engine speed Ne, the target fuel injection amount Qsol, the actual EGR rate Me
The grd and the water temperature Tw are read.

The determination of the learning value reflection permission condition is also performed in step 2
It is performed by checking the contents of 5 to 8 one by one, and the reflection of the learning value is permitted when all of the items are satisfied, and the reflection of the learning value is prohibited when even one is not satisfied. That is, Step 2: Megrd exceeds a predetermined value MEGRLN2 # (that is, an EGR operation range), Step 3: Tw is a predetermined value TWLNL2 # (for example, 2).
0 ° C), Step 4: Qsol exceeds a predetermined value QSOLNLNL2 # (fuel is not cut), Step 5: Ne exceeds a predetermined value NELNL2 # (not in the engine rotation range) ), Step 8: When the learning value reflection counter Ctrln2 exceeds a predetermined value TMRLN2 # (for example, about 0.5 seconds), the learning value reflection permission flag feln2 = 1 is set to permit reflection of the learning value in Step 9, If not, the process proceeds to step 10 and the learning value reflection permission flag feln2 = 0 is set in order to prohibit the reflection of the learning value.

It should be noted that the learning value reflection counter is set in steps 2 to 2.
The count is incremented when 5 is satisfied (step 6), and the count is reset when steps 2 to 5 are not satisfied (step 7).

FIG. 53 is for setting the learning permission flag ferln. Engine speed N in step 1
e, target fuel injection amount Qsol, actual EGR rate Megrd,
Read the water temperature Tw.

The learning permission condition is determined in steps 2 to 7,
It is performed by checking the contents of 10 one by one, and learning is permitted when all of the items are satisfied, and learning is prohibited when even one of them is violated. That is, Step 2: Megrd exceeds a predetermined value MEGRLN # (that is, an EGR operation range), Step 3: Tw is a predetermined value TWLNL # (for example, 70).
˜80 ° C.), Step 4: Qsol exceeds a predetermined value QSOLNLNL # (no fuel cut), Step 5: Ne exceeds a predetermined value NELNL # (engine rotation range) Step 6: feedback permission flag fefb = 1, step 7: learning value reflection permission flag ferln2 = 1, step 10: learning delay counter Ctrln exceeds a predetermined value TMRLN # (for example, about 4 seconds) If so, the learning permission flag feln = 1 is set to permit learning in step 11, and if not, the process proceeds to step 12 and the learning permission flag feln = 0 is set to prohibit learning.
And

The learning delay counter is set in step 2.
The count is incremented when the conditions (1) to (7) are satisfied (step 8), and reset when the conditions (2) to 7 are not satisfied (step 9).

Returning to FIG. 50, the feedback permission flag fefb is checked in step 4 among the three flags thus set. When fefb = 1, the feedback correction coefficient Kqac0 of the EGR amount is calculated in steps 5 and 6.
0 and the feedback correction coefficient Kqac0 of the EGR flow velocity are calculated. On the other hand, when fefb = 0 (when feedback is prohibited), the process proceeds from step 4 to steps 7 and 8 where Kqac00 = 1 and Kqac0 = 1.

Here, regarding the calculation of the EGR amount feedback correction coefficient Kqac00, according to the flow of FIG.
The calculation of the EGR flow velocity feedback correction coefficient Kqac0 will be described with reference to the flow chart of FIG.

54 (subroutine of step 5 in FIG. 50), the target intake air amount delay processing value tQacd, the actual intake air amount Qac, the engine speed Ne, the target fuel injection amount Qsol, and the water temperature Tw are read in step 1. .

In step 2, E is obtained from Ne and Qsol by searching a map having the contents of FIG. 55, for example.
The correction gain Gkfb of the GR flow rate, and in step 3, the water temperature correction coefficient Kgfbtw of the correction gain is calculated from Tw, for example, by searching a table having the contents of FIG. 54, and these are used in step 4

[0166]

## EQU20 ## Kqac00 = (tQacd / Qac-1)
The EGR amount feedback correction coefficient Kqac00 is calculated by the formula of × Gkfb × Kgfbtw + 1.

(TQacd / Qa) of the first term on the right side of this equation.
c-1) is the error rate from the target intake air amount delay processing value, and by adding 1 to this, Kqac00 becomes a value centered on 1. Formula 20 is for calculating the EGR amount feedback correction coefficient Kqac00 in proportion to the error rate from the target intake air amount delay processing value.

Next, in FIG. 57 (subroutine of step 6 in FIG. 50), in step 1, target intake air amount delay processing value tQacd, actual intake air amount Qac, engine speed Ne, target fuel injection amount Qsol, water temperature Tw. Read.

In step 2, E is obtained from Ne and Qsol by retrieving a map having, for example, FIG.
The correction gain Gkfbi of the GR flow velocity, and in step 3, the water temperature correction coefficient Kgfbitw of the correction gain is calculated from Tw, for example, by searching a table having the contents of FIG. 59, and these are used in step 4

[0170]

## EQU21 ## Rqac0 = (tQacd / Qac-1) ×
Gkfbi × kGfbitw + Rqac0 _n-1 , where Rqac0 _{n-1 is the} previous Rqac0, the error ratio Rqac0 is updated, and the value obtained by adding 1 to this error ratio Rqac0 in step 5 is used as the EGR flow velocity feedback correction coefficient Kqac0. calculate.

This is proportional to the integrated value (integral value) of the error ratio (tQacd / Qac-1) from the target intake air amount delay processing value, and the EGR flow velocity feedback correction coefficient K is calculated.
qac0 is calculated (integral control).

The reason why the correction gain is set to a value corresponding to the operating condition (Ne, Qsol) as shown in FIGS. 55 and 58 is as follows. This is because hunting may or may not occur depending on operating conditions even with the same gain, so that the correction gain is reduced in the region where hunting occurs. FIG. 56,
As shown in FIG. 59, the reason why the value is made small when the water temperature is low (before the completion of warm-up) is to stabilize the engine in the low water temperature region where the engine rotation is unstable.

When the calculation of the EGR amount feedback correction coefficient Kqac00 and the EGR flow velocity feedback correction coefficient Kqac0 is completed in this way, the process returns to FIG. 50 and the learning value reflection permission flag feltrn2 is checked in step 9. When the learning reflection permission flag ferln2 = 1 (when the reflection of the learning value is permitted), the process proceeds to step 10, where Ne and Q
The error ratio learning value Rqac is read by searching the learning map of FIG. 60 from sol, and a value obtained by adding 1 to this is calculated as the EGR flow velocity learning correction coefficient Kqac. On the other hand, when the learning reflection permission flag ferln2 = 0 (when the reflection of the learning value is prohibited), the process proceeds from step 9 to step 12, and the EGR flow velocity learning correction coefficient Kqac
= 1.

Subsequently, at step 13, the learning permission flag ferln is checked. If the learning permission flag ferlrn = 1 (when learning is permitted), the process proceeds to step 14 and E
The error ratio Rqacn is obtained by subtracting 1 from the GR flow velocity feedback correction coefficient Kqac0. On the other hand, when the learning permission flag feltr = 0 (when learning is prohibited)
Proceeds from step 13 to step 15 and the error ratio R
Let qacn = 0.

Error rate Rqacn thus obtained
In step 16, the error rate learning value Rqac is updated based on the above. The update of the learning value will be described with reference to the flow of FIG.

In FIG. 61 (subroutine of step 16 in FIG. 50), the error ratio Rqacn, the engine speed Ne, and the target fuel injection amount Qsol are read in step 1. Learning speed Tclr in step 2 from Ne and Qsol
For example, n is calculated by searching a map having the contents shown in FIG. In step 3, the error rate learning value Rqac is read from Ne and Qsol from the learning map of FIG. In step 4

[0177]

(22) Rqac _n = Rqacn × Tclrn + Rq
ac _n-1 × (1−Tclrn) where Rqac _n : error rate learning value after updating, Rqac _n-1 : error rate learning value before updating (= learning value read value), The learned value after update is stored in the learning map of FIG. 60 in step 5 (the value after update is overwritten on the value before update).

FIG. 63 (subroutine of step 2 in FIG. 5) is for calculating the EGR flow velocity Cqe.

In steps 1 and 2, the actual EGR amount Qec, the actual E
The GR rate Megrd, the actual intake air amount Qac, the EGR flow velocity feedback correction coefficient Kqac0, and the EGR flow velocity learning correction coefficient Kqac are read, and in step 3,

[0180]

[Equation 23] Qec From the equation of h = Qec × Kqac × Kqac0, the actual EGR amount Qec is calculated by Kqac0 and Kqac.
The corrected actual EGR amount Qec calculated as h, and the corrected actual EGR amount Qec h and actual EGR rate Meg
In step 8 from rd, the EGR flow rate Cqe is calculated by searching a map having the content shown in FIG. 64, for example. In addition, steps 4 to 7 which have not been described will be described later.

The EGR flow velocity characteristic of FIG. 64 shows that the non-linearity is strong and the sensitivity of the EGR feedback differs depending on the operating condition, so that the difference in the feedback amount with respect to the operating condition becomes small. The EGR flow velocity feedback correction coefficient Kqac0 is used as feedback to the actual EGR amount Qec used for searching the flow velocity map.

However, in FIG. 64, the portion near the right end where the slope of the characteristic becomes steep is a region in which a matching error of the map is likely to occur. Therefore, if there is a matching error, the EGR valve is affected by the matching error. The opening area Aev changes.
That is, A that is an expression for calculating the EGR valve opening area Aev
In ev = Tqek / Cqe, there is a matching error in Cqe.
It is necessary to correct the flow rate error for the amount Tqek as well. Therefore, the above-mentioned EGR amount feedback correction coefficient Kqac00 is newly introduced, and the target EGR amount Tqek is corrected in step 6 of FIG. 7 by this Kqac00.

In this case, the equation (20) for calculating Kqac00 calculates Kqac00 in proportion to the error rate from the target intake air amount delay processing value, and therefore, by this proportional control, the EGR flow velocity map of FIG. It will be possible to immediately correct the conformance error of. For example, for the sake of simplicity, in the equation (20), if the correction gain Gkfb = 1 and the completion of warm-up are considered, Kqac00 = (tQacd / Q
ac-1) +1. In this case, t as the target value
If the actual intake air amount Qac is smaller than Qacd, Kqac
00 becomes a value larger than 1, which causes Tqec to be immediately reduced. When the target EGR amount is immediately reduced, the fresh air amount (intake air amount) relatively increases, whereby the actual intake air amount Qac converges to tQacd as the target value.

Steps 4 to 7 in FIG. 63, which have not been described, are the parts for setting the initial value at the start of the EGR operation. Specifically, in step 4, the corrected actual EGR amount Qec Compare h with 0. Qec When h = 0 (that is, when the EGR is not operating), go to step 5,

[0185]

[Equation 24] Qec h = Qac × MEGRL # where MEGRL # is a constant, and the corrected actual EGR amount Qec Set h. Similarly, in step 6, the actual EGR rate Megrd is compared with 0, and when Megrd = 0, in step 7

[0186]

(25) Megrd = MEGRL # The actual EGR rate Megrd is set by the following equation.

The EGR flow velocity passing through the EGR valve 6 when the EGR valve 6 is fully closed is naturally zero, but
The equation (25) sets the initial values of the parameters used to calculate the flow velocity in consideration of the start of EGR operation. ME
The value of GRL # is, for example, 0.5 as described above.
Further, since the differential pressure before and after the EGR valve (and therefore also the EGR flow velocity) at the start of the EGR operation is different depending on the operating condition, this is dealt with. In this case, EG
The differential pressure across the EGR valve at the start of R operation is the actual intake air amount Q
Related to ac. Therefore, according to the equation 24, Qec is proportional to Qac. By giving the initial value of h, the calculation accuracy of the EGR flow velocity at the start of the EGR operation is improved.

Here, the operation of this embodiment will be described.

The target intake air amount tQac is calculated according to the operating conditions (Ne, Qsol), and is calculated based on the target intake air amount tQac and the actual EGR amount Qec in the first embodiment, and in the second embodiment. Target intake air amount tQac
Since the target opening ratio Rvnt which is the operation target value of the supercharger is set based on the actual EGR rate Megrd and the actual EGR rate Megrd, the target EGR amount (Qe
Even if c0) or the target EGR rate Megr changes, the target intake air amount that optimizes the fuel consumption is obtained, and the controllability of the turbocharger and the EGR device including the transition is improved. The performance of can be fully demonstrated. Further, simplification of adaptation and simplification of logic are also possible.

Especially during a transition, the target EGR amount and the target EG
Even if the R rate Megr changes stepwise, the actual EGR amount Q
ec and the actual EGR rate Megrd are the target EGR amount and the target EG.
There is a delay in catching up with the R rate Megr, and the target EGR
The target opening ratio Rvnt may have an error due to the amount of deviation from the target EGR ratio Megr and the target intake air amount that optimizes fuel consumption may not be obtained.
In setting vnt, according to the first embodiment, the actual EGR amount Qec, which is a value obtained by delaying the target EGR amount.
Further, according to the second embodiment, since the actual EGR amount Megrd, which is a value obtained by delaying the target EGR rate Megr, is used, it is possible to obtain the target intake air amount that optimizes fuel consumption even during a transition. Can control turbocharger.

Further, the feedback correction is performed so that the actual intake air amount Qac matches the target intake air amount delay processing value tQacd. Therefore, when a catalyst is provided in the exhaust passage, the exhaust pressure rises due to the deterioration of the catalyst and the variable capacity turbocharger. Even if the intake air amount fluctuates due to the operation variation when the supercharger is used, it is possible to prevent the excess air ratio from decreasing and improve the robustness to the exhaust gas. Then, the target of the feedback correction is the EGR flow rate Cqe, which is different from the conventional technique.

Here, as shown in FIG. 65, the cylinder E
GR amount Qec, target EGR rate Megr, and EGR flow velocity Cq
From the first finding that there is a strong correlation between e regardless of the nozzle opening of the variable nozzle, the EGR flow rate Cqe is predicted as in the present embodiment, and based on this predicted value. By controlling the EGR valve opening degree, the target EGR amount can be accurately calculated regardless of the nozzle opening degree of the variable nozzle, and the EGR gas flow rate Cqe is kept steady even in an engine equipped with a variable displacement turbocharger. Since the value has no relation to the transient, the target EGR amount including the transient can be calculated accurately.

As a result, in setting the feedback gain, since the steady state and the transient state can be uniformly treated, it becomes easier to set the feedback gain than the prior art in which the target of the feedback correction is the EGR amount or the intake air amount.
Robustness to exhaust is further improved.

For example, FIG. 66 shows a simulation result when operating in the 10-15 mode, targeting the case where the exhaust pressure is standard (base) and the case where the exhaust pressure is higher than this due to individual variation or the like. As shown in FIG. 67, when the control accuracy is poor, the waveforms of the actual EGR rate and the actual intake air amount Qac should be greatly different between them. However, according to the present embodiment, the actual EGR rate and the actual intake air amount Q
The waveforms of ac almost overlap with each other (the actual EGR rate is shown in the bottom of FIG. 66, and the actual intake air amount Qac is shown in FIG. 6).
7). In other words, even if the exhaust pressure is high due to individual variations, etc.
The GR rate and the actual intake air amount Qac are obtained.

The error rate learning value Rqa for each operating region
By introducing c, the actual EGR amount Qec, which is a parameter used for the calculation of the EGR flow velocity Cqe, is also corrected by the EGR flow velocity learning correction coefficient Kqac created from this. Since the update is performed based on the correction amount Kqac0, the learning value for each operating region is absorbed so that the ratio (error ratio) between the actual intake air amount Qac and the target intake air amount delay processing value tQacd becomes 1, and the feedback correction is accordingly performed. Coefficient K
The change in qac0 is reduced, which improves the controllability of EGR and boost pressure.

The map characteristic of the EGR flow velocity using the actual EGR amount and the actual EGR rate as parameters is as shown in FIG. 64, and the portion near the right end where the slope of the characteristic is steep in the figure is the conformance error of the map. Therefore, if there is a matching error, the EGR valve opening area Aev changes due to the matching error. However, in the present embodiment, the actual intake air amount Qac and the target intake air amount Qac Since the target EGR amount Tqek is feedback-corrected based on the ratio (error ratio) of the air amount delay processing value tQacd, even if there is a matching error in the EGR flow velocity map, the actual intake air amount Qac is changed to the target intake air amount delay processing value tQacd. Can be converged to.

During the transition, the actual EGR amount is the target E
The actual EGR rate and the target EGR rate deviate from the GR amount. Since this deviation is due to the delay of the intake system volume, the EG can be calculated from the target EGR amount and the target EGR rate even during the transition.
The calculation of the R flow velocity shows that E due to the delay of the intake system volume
Although a GR flow velocity error occurs, according to the present embodiment, the actual EGR amount Qec and the actual EGR amount that are values obtained by subjecting the target EGR amount and the target EGR rate to delay processing of the intake system.
Since the EGR flow rate Cqe is calculated from the rate Megrd, the EGR flow rate Cqe can be calculated accurately even during a transition.

The flowchart of FIG. 68 is the third embodiment.
In FIG. 63, which is common to the first and second embodiments,
It replaces. This embodiment is an EGR flow velocity learning supplement.
The first and second embodiments in that only a positive coefficient Kqac is given.
Is different from. Therefore, this learning supplement is added to the actual EGR amount Qec.
The value obtained by multiplying the positive coefficient Kqac is the corrected actual EGR amount Qec h
As a result, the EGR flow velocity Cqe is calculated (see FIG. 6).
8 steps 4, 5). Although not shown, it corresponds to FIG.
In the calculation flow of the target EGR amount Tqek, Kqac00 =
It is 1.

Further, the method of obtaining the actual EGR rate and the actual EGR amount is slightly different from that of the first and second embodiments. To explain this, in step 1 of FIG. 68, the required EGR amount Mq
ec (already obtained in step 3 of FIG. 7), target EGR
The rate Megr (which has already been obtained in FIG. 11) and the cylinder intake air amount Qac (which has already been obtained in FIG. 8) are read, and from these, from the required EGR amount Mqec and the target EGR rate Megr,
In steps 2 and 3,

[0200]

[Equation 26] Qec = Mqec × KIN × KVOL × KQ
E # + Qec _n-1 x (1-KIN x KVOL x KQE
#) Regr = Megr × KIN × KVOL × KME # + R
egr _n-1 × (1-KIN × KVOL × KME #) where KIN: volumetric efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, KQE # : Constant, KME #: constant, Qec _n-1 : previous Qec, Regr _n-1 : previous Regr (Equation of first-order lag) EGR amount Qec per cylinder at intake valve position The EGR rate Regr at the intake valve position is calculated.

Here, as can be seen by comparing the second equation of the equation 26 and the arithmetic expression of Megrd in step 3 of FIG. 17, the difference between Megrd and Regr is that Megrd is a unit conversion (per cylinder → unit time). It is a value after that, but Regr is only a point before the unit conversion. Therefore, this Regr that responds with a first-order lag to the target EGR rate Megr is also the actual EGR rate. Similarly, the Qec of the first equation of the equation 26 also responds with a first-order delay to Mqec as the target value, and can therefore be regarded as the actual EGR amount.

Calculation of the learning correction coefficient Kqac will be described with reference to the flow chart of FIG. In FIG. 69, steps 1 to 4 are the parts for calculating the target intake air amount as in FIG. In step 1, the target EGR rate Megr,
The target intake air amount basic value tQac is read by reading the target fuel injection amount Qsol, the engine speed Ne, and the actual intake air amount Qac, and by searching the map having the contents of FIG.
b, and the correction coefficient Kqaqf of the target intake air amount is calculated by searching a table having the content of FIG. 71 from Qsol in step 3, and this correction coefficient is multiplied by the target intake air amount basic value. The value is calculated as the target intake air amount Qact0. In step 5, from this target intake air amount Qact0

[0203]

[Equation 27] Qact = Qact0 × KIN × KVOL ×
KQA # + Qact _n-1 x (1-KIN x KVOL x K
QA #) where KIN: volumetric efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, KQA #: constant, Qact _n-1 : previous Qact, The target intake air amount delay processing value Qact is calculated by the following equation (first-order delay equation). This is because the air supply delay due to the presence of the intake system volume causes the error rate learning value R to be described later.
Delay processing is performed so that qac1 does not become large.

At step 6, the actual EGR rate Regr (Fig. 6
8 already obtained from step 3) and 0 are compared. Real E
When the GR rate Regr is not 0 (when the EGR is operating),
Go to steps 7 and 8

[0205]

The error ratio Rqac0 is calculated by the equation Rqac0 = Qact / Qac-1, and from this error ratio Rqac0

[0206]

(29) Rqac1 = Rqac0 × Tclrn1 + R
qac1 _n-1 × (1-Tclrn1) where Tclrn1: learning speed (fixed value), Rqac1 _n-1 : previous error rate learning value, and the error rate learning value Rqa
Update c1. In step 9, a value obtained by adding 1 to this is calculated as the EGR flow velocity learning correction coefficient Kqac.

On the other hand, when the actual EGR rate Regr = 0, (E
Since the correction is not necessary (when the GR is not operated), step 6
Then, the process proceeds to step 10, Kqac = 0 is set, and the current process is terminated.

The flowchart of FIG. 72 is the fourth embodiment and replaces FIG. 69 of the third embodiment. In FIG. 72, when the actual EGR rate Regr is not 0 (E
(When the GR is operating), from step 7 to steps 22 and 23
74, the error ratio learning value Rqac2 is read from the learning map of FIG. 74 from Ne and Qsol, and 1 is added to this to calculate the EGR flow velocity learning correction coefficient Kqac.
In FIG. 72, the same parts as those in FIG. 69 are designated by the same step numbers, and the description thereof will be omitted.

The flowchart of FIG. 73 is for updating the learning value. Steps 1 to 7 are the same as those in FIG. 69 of the third embodiment. In step 8, the error rate learning value Rqac2 is read from the learning map of FIG. 74 from Ne and Qsol, and in step 9,

[0210]

Rqac2 _n = Rqac0 × Tclrn2 +
Rqac2 _n-1 × (1-Tclrn2) where Tclrn2: learning speed (fixed value), Rqac2 _n : error rate learning value after update, Rqac2 _n-1 : error rate learning value before update (= learning value read value) ), And the weighted average processing is performed by the following equation, and the updated learning value is stored in the learning map of FIG. 74 in step 10 (the value before updating is overwritten with the value before updating).

Error rate learning value Rqac1 of the third embodiment
However, in the fourth embodiment, a different error ratio learning value Rqac2 is provided for each operating condition, which is different from the first and second embodiments. A similar effect is produced.

In the embodiment, the case where the EGR flow velocity is predicted and the EGR valve is controlled based on this predicted value has been described. However, the differential pressure across the EGR valve which has a constant relationship with the EGR flow velocity (the differential pressure across the EGR valve is the flow velocity). May be predicted.

In the embodiment, EG is set so that the actual intake air amount Qac matches the target intake air amount delay processing value tQacd.
The R flow velocity feedback correction coefficient Kqac0 is calculated, and the EGR flow velocity C is calculated by the feedback correction coefficient Kqac0 and the EGR flow velocity learning correction coefficient Kqac (= Rqac + 1).
The case where the cylinder EGR amount Qec, which is a parameter used to calculate qe, is corrected has been described, but the EGR flow rate feedback correction coefficient Kqac0 and the EGR flow rate learning correction coefficient Kqac are another parameter that is the actual EGR rate M.
Even if the egrd is corrected, the actual intake air amount Q
so that ac matches the target intake air amount tQac
The flow velocity feedback correction coefficient Kqac0 is calculated, and the feedback correction coefficient Kqac0 and the EGR flow velocity learning correction coefficient Kqac are used to correct the cylinder EGR amount Qec and the actual EGR rate Megrd used to calculate the EGR flow velocity Cqe, and further the EGR flow velocity Cqe itself. But it doesn't matter. As for the learning value, the learning correction coefficient can be used as the learning value.

Further, the feedback correction coefficients Kqac0 and Kqac00 were calculated based on the ratio (error ratio) between the actual intake air amount Qac and the target intake air amount delay processing value tQacd, but the actual intake air amount Qac and the target intake air amount delay were calculated. The feedback correction coefficient Kqac is calculated based on the difference (error amount) between the processed value tQacd (or the target intake air amount tQa).
0 and Kqac00 may be calculated.

In the embodiment, the case of performing so-called low temperature premix combustion in which the heat generation pattern is single-stage combustion has been described, but in the case of normal diesel combustion in which diffusion combustion is added after premix combustion However, it goes without saying that the present invention can be applied.

[Brief description of drawings]

FIG. 1 is a control system diagram of an embodiment.

FIG. 2 is a schematic configuration diagram of a common rail fuel injection device.

FIG. 3 is a flowchart for explaining calculation of a target fuel injection amount.

FIG. 4 is a map characteristic diagram of a basic fuel injection amount.

FIG. 5 is a flowchart for explaining calculation of an EGR valve opening area.

FIG. 6 is a characteristic diagram of an EGR valve drive signal with respect to an EGR valve opening area.

FIG. 7 is a flowchart for explaining calculation of a target EGR amount.

FIG. 8 is a flowchart for explaining calculation of a cylinder intake air amount.

FIG. 9 is a flowchart for explaining detection of intake air amount.

FIG. 10 is a characteristic diagram of an intake air amount with respect to an air flow meter output voltage.

FIG. 11 is a flowchart for explaining calculation of a target EGR rate.

FIG. 12 is a map characteristic diagram of a basic target EGR rate.

FIG. 13 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 14 is a flowchart for explaining a complete explosion determination.

FIG. 15 is a flowchart for explaining calculation of a control command duty value given to the negative pressure control valve of the first embodiment.

FIG. 16 is a flowchart for explaining calculation of a control command duty value given to the negative pressure control valve of the second embodiment.

FIG. 17 is a flowchart for explaining calculation of an actual EGR rate.

FIG. 18 is a flowchart for explaining calculation of a time constant equivalent value for a collector capacitance.

FIG. 19 is a map characteristic diagram of a basic value equivalent to volumetric efficiency.

FIG. 20 is a flowchart for explaining calculation of a target intake air amount.

FIG. 21 is a map characteristic diagram of a target intake air amount basic value during EGR operation.

FIG. 22 is a map characteristic diagram of a target intake air amount correction coefficient.

FIG. 23 is a map characteristic diagram of a target intake air amount when EGR is not operating.

FIG. 24 is a flowchart for explaining calculation of an actual EGR amount.

FIG. 25 is a flowchart for explaining calculation of a target opening ratio according to the first embodiment.

FIG. 26 is a map characteristic diagram of a target opening ratio.

FIG. 27 is a flowchart for explaining calculation of a target opening ratio according to the second embodiment.

FIG. 28 is a map characteristic diagram of a target opening ratio.

FIG. 29 is a flowchart for explaining calculation of a feedforward amount of a target opening ratio.

FIG. 30 is a flowchart for explaining calculation of a feedback amount of a target opening ratio.

FIG. 31 is a flowchart illustrating linearization processing.

FIG. 32 is a table characteristic diagram of linearization.

FIG. 33 is a characteristic diagram showing the relationship between the opening area and the supercharging pressure.

FIG. 34 is a flowchart for explaining signal conversion.

FIG. 35 is a flowchart for explaining setting of a duty selection signal flag.

FIG. 36 is a flowchart for explaining the calculation of the temperature correction amount of the duty value.

FIG. 37 is a map characteristic diagram of basic exhaust temperature.

FIG. 38 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 39 is a table characteristic diagram of a temperature correction amount.

FIG. 40 is a temperature characteristic diagram of a turbocharger drive actuator.

FIG. 41 is a map characteristic diagram of a duty value when the variable nozzle is fully closed.

FIG. 42 is a map characteristic diagram of a duty value when the variable nozzle is fully opened.

FIG. 43 is a map characteristic diagram of duty values when the variable nozzle is fully closed.

FIG. 44 is a map characteristic diagram of duty values when the variable nozzle is fully opened.

FIG. 45 is a hysteresis diagram when converting a command aperture ratio linearization processing value into a duty value.

FIG. 46 is a flowchart for explaining operation confirmation control.

FIG. 47 is a flowchart for explaining the setting of the operation confirmation control command duty value.

FIG. 48 is a table characteristic diagram of control patterns.

FIG. 49 is a table characteristic diagram of duty values during operation confirmation control.

FIG. 50 is a flowchart for explaining calculation of two feedback correction coefficients and learning correction coefficient of EGR control.

FIG. 51 is a flowchart for explaining the setting of a feedback permission flag.

FIG. 52 is a flowchart for explaining setting of a learning value reflection permission flag.

FIG. 53 is a flowchart for explaining setting of a learning permission flag.

FIG. 54 is a flowchart for explaining calculation of an EGR amount feedback correction coefficient.

FIG. 55 is a map characteristic diagram of the correction gain of the EGR flow rate.

FIG. 56 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 57 is a flowchart for explaining calculation of an EGR flow velocity feedback correction coefficient.

FIG. 58 is a map characteristic diagram of an EGR flow velocity correction gain.

FIG. 59 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 60 is a table diagram of a learning map of error rate learning values.

FIG. 61 is a flowchart for explaining updating of learning values.

FIG. 62 is a map characteristic diagram of learning speed.

FIG. 63 is a flowchart for explaining calculation of EGR flow velocity.

FIG. 64 is a map characteristic diagram of EGR flow velocity.

FIG. 65 is a characteristic diagram showing a relationship among an EGR amount, an EGR rate, and an EGR flow velocity.

FIG. 66 is a waveform chart showing a simulation result when operating in the 10-15 mode.

FIG. 67 is a waveform chart showing simulation results when operating in the 10-15 mode.

FIG. 68 is a flowchart for explaining calculation of EGR flow velocity according to the third embodiment.

FIG. 69 is a flowchart for explaining calculation of an EGR flow rate learning correction coefficient according to the third embodiment.

FIG. 70 is a map characteristic diagram of a target intake air amount basic value.

71 is a table characteristic diagram of a target intake air amount correction coefficient. FIG.
chart.

FIG. 72 is a flowchart for explaining calculation of an EGR flow velocity learning correction coefficient according to the fourth embodiment.

FIG. 73 is a flowchart for explaining updating of learning values according to the fourth embodiment.

FIG. 74 is a table of a learning map of error rate learning values according to the fourth embodiment.

FIG. 75 is a diagram corresponding to the claim of the first invention.

FIG. 76 is a diagram corresponding to the claim of the second invention.

FIG. 77 is a diagram corresponding to the claim of the third invention.

[Explanation of symbols]

4 EGR passage 6 EGR valve 41 Control unit 52 Exhaust turbine 53 variable nozzle

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/02 360 F02D 41/02 360 F02M 25/07 550 F02M 25/07 550F 570 570P (72) Inventor Miura Manabu Yokohama, Kanagawa Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Japan (56) References JP-A-11-132049 (JP, A) JP-A-6-336938 (JP, A) JP-A-11-62720 (JP, A) JP, 2000-87782 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 43/00 F02B 37/00 F02D 21/08 F02D 23/00 F02D 41/02 F02M 25/07

Claims (7)

(57) [Claims] 1. A supercharger and an EGR valve capable of controlling an EGR amount, means for detecting an operating condition of an engine, means for calculating a target EGR rate based on a detected value of the operating condition, and this target. Means for setting a target EGR amount based on the detected value of the EGR rate and the operating condition, and EGR based on the target EGR amount and the target EGR rate
A means for calculating the flow velocity, a means for calculating the opening area of the EGR valve from the EGR flow velocity and the target EGR amount, a means for controlling the EGR valve so that the EGR valve opening area is obtained, and a target intake air amount A means for calculating the target intake air amount, a means for controlling the supercharger so as to obtain the target intake air amount, a means for calculating the actual intake air amount, and a difference between the actual intake air amount and the target intake air amount or A control device for a diesel engine, comprising: means for feedback-correcting the EGR flow velocity or a parameter used for calculation of the EGR flow velocity based on the ratio. 2. A supercharger and an EGR valve capable of controlling an EGR amount, means for detecting an operating condition of an engine, means for calculating a target EGR rate based on a detected value of the operating condition, and this target. Means for setting a target EGR amount based on the detected value of the EGR rate and the operating condition, and EGR based on the target EGR amount and the target EGR rate
Means for calculating a flow velocity, means for calculating an opening area of the EGR valve from the EGR flow velocity and the target EGR amount, means for controlling the EGR valve so that the EGR valve opening area is obtained, and A means for storing a learned value, a means for correcting the EGR flow velocity or a parameter used for calculation of the EGR flow velocity with the learned value, a means for computing a target intake air amount, and a means for obtaining the target intake air amount. A means for controlling the supercharger, a means for calculating the actual intake air amount, and a means for updating the learning value based on the difference or ratio between the actual intake air amount and the target intake air amount are provided. Diesel engine control device featuring. 3. A supercharger and an EGR valve capable of controlling an EGR amount, means for detecting an engine operating condition, means for calculating a target EGR rate based on a detected value of the operating condition, and this target. Means for setting a target EGR amount based on the detected value of the EGR rate and the operating condition, and EGR based on the target EGR amount and the target EGR rate
A means for calculating the flow velocity, a means for calculating the opening area of the EGR valve from the EGR flow velocity and the target EGR amount, a means for controlling the EGR valve so that the EGR valve opening area is obtained, and a target intake air amount Means for controlling the supercharger so as to obtain the target intake air amount, means for calculating the actual intake air amount, and a difference between the actual intake air amount and the target intake air amount. And a means for feedback-correcting the target EGR amount based on the ratio. 4. The target intake air amount used for the feedback correction is replaced by a value obtained by subjecting the target intake air amount to delay processing of the intake system. Diesel engine control device described. 5. The target intake air amount used for updating the learning value is replaced by a value obtained by subjecting the target intake air amount to delay processing of the intake system.
Diesel engine control device described in. 6. The control device for a diesel engine according to claim 1, wherein the feedback correction amount in the feedback correction is a value proportional to an integral value of the difference or the ratio. 7. The control device for a diesel engine according to claim 3, wherein the feedback correction amount when performing the feedback correction is a value proportional to the difference or the ratio.