JP2002115572A - Control device for supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous determination of over-boost caused by operating an EGR(exhaust gas recirculation) device during controlling the boost pressure. SOLUTION: A turbo supercharger 61 is provided with an actuator 62 for driving a booster pressure variable mechanism. A set means 63 sets a target intake air quantity or a target booster pressure according to the operation conditions and a control means 64 controls the actuator 62 so as to obtain the target intake air quantity or the target booster pressure. The EGR device 65 is provided. In this case, a detection means 66 detects an actual intake air quantity, a detection means 67 detects the accrual EGR quantity of the EGR device 65, a determination means 68 determines whether the over-boost is generated or not based on the actual intake air quantity and the actual EGR quantity, and a booster pressure suppressing means 69 suppresses the booster pressure so as not to cause the over-boost based on the determination result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercharger control device, and more particularly, to a device having an EGR device (a device for recirculating a part of exhaust gas to an intake passage) in addition to a variable supercharging pressure mechanism.

[0002]

2. Description of the Related Art There is a type in which a command value given to an actuator for driving a supercharging pressure variable mechanism is feedback controlled so that an actual supercharging pressure coincides with a target supercharging pressure (see Japanese Patent Application Laid-Open No. 8-338256). ).

[0003]

Since the target supercharging pressure is increased with respect to a change in the operating range, the variable supercharging pressure mechanism is driven so as to obtain the increased target supercharging pressure. If the phenomenon that the actual value of the supercharging pressure exceeds the supercharging limit (hereinafter, this phenomenon is referred to as “overboost”) occurs when the actuator for performing the operation is operated (refer to the one-dot chain line at the bottom of FIG. 108) , Noise and exhaust performance deteriorate.

Further, when the EGR device is operated during the supercharging pressure control as in the prior application device of Japanese Patent Application No. 11-233124 (hereinafter simply referred to as "first application device"), the EGR device is When the above-described over-boost occurs in the operating range of, the intake pressure and the exhaust pressure fluctuate due to instability of control on the supercharger side due to the over-boost. Emissions will also worsen.

In order to avoid such over-boost in the supercharging pressure control, when the variation of the actual supercharging pressure exceeds a predetermined value or the variation of the actual intake air amount (corresponding to the actual supercharging pressure) is reduced to a predetermined value. When the above occurs, it is determined that overboost occurs, and the actuator for driving the supercharging pressure variable mechanism may be moved to the side where the supercharging pressure decreases.

However, according to this method, when the EGR device is operated during the supercharging pressure control, an erroneous determination that overboost has occurred may occur.

[0007] This will be described more specifically with reference to a case where the amount of change in the actual intake air amount is changed. The upper part of FIG. When moved, the actual intake air amount Qac becomes 500 mg / st. From cyl to supercharging limit of 65
0 mg / st. cyl to 700 mg / st. cy
1. In this case, the change amount ΔQac of the actual intake air amount from the timing of t2 is 10
0 mg / st. If cyl is present, it can be determined that overboost occurs at this time.

On the other hand, in the lower part of FIG. 113, although the variable nozzle does not move, the exhaust pressure increases due to the opening of the EGR valve due to the operation of the EGR device, which increases the supercharging work and increases the actual intake air. When the amount Qac is 200 mg / st. c
yl to 500 mg / st. cyl. In this case, the change amount ΔQac of the actual intake air amount from the timing of t4 is 100
mg / st. Cyl does not cause over-boost. However, the change amount ΔQ of the actual intake air amount is
In the method of determining whether or not overboost occurs based only on ac, the upper case and the lower case in FIG. 113 cannot be separated from each other. Therefore, it is erroneously determined that overboost occurs even in the lower case.

Accordingly, the present invention employs the supercharging pressure itself based on a value including not only the actual intake air amount but also the actual EGR amount in the case of the type employing the intake air amount equivalent to the supercharging pressure. Erroneous determination of overboost due to the operation of the EGR device during the boost pressure control by determining whether or not overboost occurs based on the actual boost pressure in the operating range of the EGR device The purpose is to prevent.

Next, FIG. 110 shows the case of the type employing the intake air amount, and FIG. 111 shows the case of the type employing the supercharging pressure itself. This is a summary of the results of steady-state experiments with various changes in the engine speed and the engine load. The actual intake air amount Qac and the actual EGR are shown in FIG. 110 due to the difference in the operating conditions (engine load, engine speed) even if the opening ratio of the variable nozzles is the same, or the difference in the opening ratio even if the operating conditions are the same. It can be seen that the total value of the amount Qec and the actual exhaust amount Qexh, and in FIG. 111, the actual supercharging pressure and the actual exhaust amount Qexh vary considerably.
This variation is caused by variations in the production of the means for detecting the amount of intake air and the actuator for driving the supercharging pressure variable mechanism in the case of the type employing the intake air amount, and in the case of the type employing the supercharging pressure itself. This is due to manufacturing variations such as a means for detecting the supercharging pressure and an actuator for driving the variable supercharging pressure mechanism. Such Qac in the case of the type that adopts the intake air amount
+ Qec and Qexh, and the actual supercharging pressure and Qe in the case of the type using the supercharging pressure itself.
Due to the variation of xh, an over-boost occurs under the conditions plotted beyond the illustrated supercharging limit.

Therefore, the present invention is based on the actual exhaust air amount in addition to the actual intake air amount and the actual EGR amount in the case of the type employing the intake air amount, and also in the case of the type employing the supercharging pressure itself. By determining whether overboost occurs based on the actual displacement in addition to the supercharging pressure, the sum of the actual intake air amount and the actual EGR amount and the actual displacement in the case of the type employing the intake air amount are determined. It is also an object of the present invention to prevent an over boost caused by a variation of the actual supercharging pressure or the actual displacement in the case of a type employing the supercharging pressure itself.

[0012]

The first invention is shown in FIG.
As shown in FIG. 5, a turbocharger 61 having an actuator 62 for driving a supercharging pressure variable mechanism, a means 63 for setting a target intake air amount or a target supercharging pressure according to operating conditions, Means 64 for controlling said actuator 62 so as to obtain an air amount or a target supercharging pressure
, An EGR device 65, a means 66 for detecting the actual intake air amount, a means 67 for detecting the actual EGR amount of the EGR device 65, and an over-boost based on the actual intake air amount and the actual EGR amount. Means 68 for determining whether or not the pressure is generated, and means 69 for suppressing the supercharging pressure based on the determination result so as not to cause overboost are provided.

In the second invention, as shown in FIG. 115, a turbocharger 61 having an actuator 62 for driving a supercharging pressure variable mechanism, and a target intake air amount or a target supercharging pressure are set to operating conditions. A means 63 for controlling the actuator 62 so as to obtain the target intake air amount or the target supercharging pressure; and an EGR device 65
Means 66 for detecting the actual intake air amount;
The means 67 for detecting the actual EGR amount of the GR device 65, the means 71 for calculating the actual exhaust amount, the actual intake air amount, the actual E
Means 72 for determining whether or not overboost is generated based on the GR amount and the actual exhaust amount, and means 69 for suppressing the supercharging pressure so as not to generate overboost based on the determination result are provided.

In the third aspect, the means 72 for determining whether or not overboost occurs in the second aspect is
The sum of the actual EGR amount and the actual intake air amount is calculated as the cylinder intake gas amount Q
cyl, means for setting the determination value TQcyl in accordance with the actual exhaust amount Qexh, and when the cylinder intake gas amount Qcyl is equal to or greater than the determination value TQcyl, an over-boost occurs. Means for determining that overboost does not occur when TQcyl is less than TQcyl.

In a fourth aspect of the present invention, as shown in FIG. 116, a turbocharger 61 having an actuator 62 for driving a supercharging pressure variable mechanism, and a target intake air amount or a target supercharging pressure as operating conditions. A means 63 for controlling the actuator 62 so as to obtain the target intake air amount or the target supercharging pressure; and an EGR device 65
Means 81 for detecting the actual boost pressure in the operating range of the EGR device 65, means 82 for determining whether or not overboost is generated based on the actual boost pressure, and Means 69 for suppressing the supercharging pressure so that overboost does not occur.

In a fifth aspect of the present invention, as shown in FIG. 117, a turbocharger 61 having an actuator 62 for driving a supercharging pressure variable mechanism, and a target intake air amount or a target supercharging pressure are set as operating conditions. A means 63 for controlling the actuator 62 so as to obtain the target intake air amount or the target supercharging pressure; and an EGR device 65
Means 71 for calculating the actual displacement, and the EGR
Means 81 for detecting the actual boost pressure in the operating range of the device 65;
Means 91 for determining whether or not overboost is generated based on the actual supercharging pressure and the actual displacement are provided, and means 69 for suppressing the supercharging pressure so as not to generate overboost based on the determination result. .

In the sixth invention, the means 91 for determining whether or not overboost occurs in the fifth invention is as follows.
Means for setting the determination value TPa in accordance with the actual displacement Qexh, and an overboost when the actual supercharging pressure is equal to or higher than the determination value TPa, and no overboost when the actual supercharging pressure is less than the determination value TPa. Determining means.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, the means 64 for controlling the actuator 62 includes the target intake air amount or the target supercharging pressure and E
An operation target value of the supercharger 61 (for example, in a type in which the geometric shape of the exhaust turbine can be variably adjusted) based on a control target value (for example, a target EGR rate or a target EGR amount) of the GR device 65, for example, Means for setting a target value of the opening area or a value corresponding to the opening area, for example, in a type having a waste gate valve, a target value of the valve opening degree) and the actuator 62 so that the operation target value of the supercharger 61 becomes the target value. In the case where the system includes the control unit, the supercharging pressure suppressing unit 69 changes the set value of the unit for setting the operation target value of the supercharger 61 to a condition under which the overboost does not occur when the overboost occurs. This is a means for switching to a value that weakens the supercharging pressure from time to time.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, a period (for example, a time) TTMRO in which the supercharging pressure is suppressed so that overboost does not occur.
B0 is determined by an engine load (for example, target fuel injection amount Qso).
The setting is made according to the change amount DQSOL per predetermined time or the change amount DNE of the engine rotation speed NE per predetermined time.

In the ninth aspect, in any one of the first to third aspects, a period (for example, a time) TTMRO in which the supercharging pressure is suppressed so that overboost does not occur.
B0 is set according to the change amount DQAC of the actual intake air amount Qac per predetermined time.

In the tenth invention, the period (for example, time) TTMROB0 in which the supercharging pressure is suppressed so that overboost does not occur in the third invention is determined by the amount of deviation of the cylinder intake gas amount Qcyl from the determination value TQcyl or Set according to the displacement.

According to an eleventh aspect of the present invention, the operation of the actuator is delayed when returning the actuator to a side where the supercharging pressure rises after the supercharging pressure is suppressed in any one of the first to tenth aspects.

According to a twelfth aspect, in the eleventh aspect, the period for delaying the movement of the actuator is set according to the atmospheric pressure or the displacement.

According to a thirteenth aspect, in the third aspect, the determination value TQcyl is set so as to have an approximately mountain-shaped characteristic with respect to the displacement.

[0025]

In order to avoid over-boost in the supercharging pressure control, when the amount of change in the actual intake air amount exceeds a predetermined value in the case of the type employing the intake air amount, the supercharging pressure itself is reduced. In the case of the adopted type, it is determined that overboost occurs when the amount of change in the actual supercharging pressure exceeds a predetermined value, and the actuator for driving the supercharging pressure variable mechanism is moved to the side where the supercharging pressure decreases. According to the method, when the EGR device is operated during the supercharging pressure control, an erroneous determination that an over-boost occurs may occur. According to the first and seventh aspects, according to the fourth and seventh aspects, in the case of a type employing the supercharging pressure itself based on a value including not only the actual intake air amount but also the actual EGR amount, E
Since it is determined whether overboost occurs based on the actual boost pressure in the operating range of the GR device, it is possible to prevent erroneous determination of overboost due to the operation of the EGR device during the boost pressure control.

According to the second, third and seventh aspects of the present invention, the actual intake air amount, the actual EGR
Since it is determined whether or not the over-boost has occurred based on the actual exhaust amount in addition to the amount, in addition to the effect of the first invention, a means for detecting the intake air amount in the case of the type employing the intake air amount, It is possible to prevent over-boost caused by manufacturing variations of the actuator for driving the supercharging pressure variable mechanism.

According to the fifth, sixth and seventh aspects of the present invention, in the case where the supercharging pressure itself is adopted, in addition to the actual supercharging pressure in the operating range of the EGR device, the overpressure is based on the actual displacement. Since it is determined whether or not a boost has occurred, in addition to the effect of the fourth invention, a means for detecting the supercharging pressure in the case of the type employing the supercharging pressure itself or an actuator for driving the supercharging pressure variable mechanism It is possible to prevent over-boost caused by manufacturing variations such as the above.

The overboost is more likely to occur as the change in the engine load, the engine speed, and the actual intake air amount is larger, or as the deviation from the determination value of the cylinder intake gas amount or the exhaust amount is larger. Therefore, these three periods (engine load, engine speed,
Matching when the change amount of the actual intake air amount) is small, or when the displacement amount from the determination value of the cylinder intake gas amount or the exhaust amount is small, if these three change amounts are large or the determination of the cylinder intake gas amount When the amount of deviation from the value or the exhaust amount is large, the period during which the boost pressure is suppressed is too short to cause over-boost.On the contrary, when the change amount of these three members is large, Matching when the amount of deviation from the cylinder intake gas amount determination value or the exhaust amount is large means that when these three changes are small or when the amount of deviation or the exhaust amount from the cylinder intake gas amount determination value is small, Although the period for suppressing the supercharging pressure is too long, the unnecessary supercharging pressure is suppressed. However, according to the eighth, ninth, and tenth aspects, the engine load, the engine rotation speed, the actual intake Any one of the air volume Variation or by more suppress time boost pressure deviation amount or the exhaust amount from the judgment value of the cylinder intake gas amount is large is made to be longer, it is possible to avoid such a situation.

If the actuator is quickly moved to the side where the boost pressure rises in order to return to the state before the suppression of the boost pressure after the suppression of the boost pressure, an over-boost may occur due to the cause. However, according to the eleventh invention, such a situation can be avoided.

Since the exhaust amount increases in accordance with the differential pressure between the exhaust pressure and the atmospheric pressure, the exhaust amount increases under a condition where the atmospheric pressure is low, such as at high altitude, and accordingly, the work performed by the turbocharger increases. (Overboost is likely to occur). Therefore, if the period during which the movement of the actuator is delayed is matched to the condition where the atmospheric pressure is not low, such as at low altitude, the period during which the movement of the actuator is delayed under the condition where the atmospheric pressure is low is too short, and overboost occurs.
Conversely, if the period during which the movement of the actuator is delayed is matched to a condition where the atmospheric pressure is low, such as at high altitudes, the period during which the movement of the actuator is delayed at low altitudes is unnecessarily too long. According to the twelfth aspect of the invention, in which the period for delaying is set according to the atmospheric pressure, such a situation can be avoided.

Since the over-boost is likely to occur when the displacement exceeds the predetermined value, it is necessary to match the period during which the movement of the actuator is delayed under the condition that the displacement does not exceed the predetermined value. If the period during which the movement of the actuator is delayed is too short, an over-boost occurs, and conversely, if the period during which the movement of the actuator is delayed under the condition where the displacement exceeds the predetermined value is matched, the Although the period of delaying the movement of the actuator becomes uselessly long, such a situation can be avoided according to the twelfth invention in which the period of delaying the movement of the actuator is set according to the displacement.

According to the thirteenth aspect, the efficiency (new air amount) increases as the displacement increases from a small value, and the efficiency decreases as the displacement further increases. It can be performed.

[0033]

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. This configuration itself is disclosed in Japanese Patent Application Laid-Open No. 8-86.
251 and the like.

Now, the generation of NOx greatly 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, in response to the control pressure from the pressure control valve 5, the EGR passage 4 connecting the exhaust passage 2 and the collector 3a of the intake passage 3 is operated. A diaphragm type EGR valve 6 is provided.

The pressure control valve 5 includes a control unit 4
Driven by a duty control signal from 1
As a result, a predetermined EGR rate corresponding to the operating conditions is obtained. For example, the EGR rate is set to a maximum of 100% in a low-speed low-load region, and the EGR rate is reduced as the rotational speed and the load increase. Since the exhaust gas temperature increases on the high load side, if a large amount of EGR gas is recirculated, the effect of reducing NOx decreases due to the increase in the intake air temperature,
The EGR rate is reduced stepwise because the ignition delay period of the injected fuel becomes short and premixed combustion cannot be realized.

In the middle of the EGR passage 4, an EGR gas cooling device 7 is provided. This is because the water jacket 8 is formed around the EGR passage 4 and circulates a part of the engine cooling water, and the flow control valve 9 provided at the cooling water inlet 7 a and capable of adjusting the circulation amount of the cooling water. In other words, according to a 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 to promote combustion. When the swirl control valve is closed in the low rotation and low load range by the control unit 41, the flow velocity of the intake air taken into the combustion chamber increases, 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 surface to the bottom of the piston without narrowing the inlet.At the center of the bottom, a resistance is given to the swirl flowing from the outside of the piston cavity while rotating from the outside of the piston cavity in the latter half of the compression stroke To avoid mixing, a conical portion is formed to further improve the mixing of air and fuel. The swirl generated by the above-described swirl valve or the like due to the cylindrical piston cavity that does not restrict the inlet is diffused from the inside of the piston cavity to the outside as the piston descends in the combustion process, and even outside the cavity. Swirl is maintained.

The engine is provided with a common rail type fuel injection device 10. The configuration of the common rail type fuel injection device 10 is also known (refer to the 13th Internal Combustion Engine Symposium Lecture Papers, pp. 73-77), and is outlined with reference to FIG.

The fuel injection device 10 mainly includes a fuel tank 11, a fuel supply passage 12, a supply pump 14, a common rail (accumulator) 16, and a nozzle 17 provided for each cylinder.
The fuel pressurized by the supply pump 14 is temporarily stored in the accumulator 16 via the fuel supply passage 15, and then the high-pressure fuel in the accumulator 16 is supplied to the nozzles 1 for the number of cylinders.
7 is distributed.

The nozzle 17 includes a needle valve 18, a nozzle chamber 19,
A fuel supply passage 20 to the nozzle chamber 19, a retainer 21, a hydraulic piston 22, a return spring 23 for urging the needle valve 18 in a valve closing direction (downward in the figure), a fuel supply passage 24 to the hydraulic piston 22, this passage 24 And a three-way valve (electromagnetic valve) 25 interposed in the
When the three-way valve 25 is turned off (ports A and B are connected and ports B and C are shut off), the pressure receiving area of the hydraulic piston 22 is turned off. 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.
In the state (the ports A and B are shut off and the ports B and C communicate), 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 decreases. . 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 the valve 5 is returned to the OFF state again, the high-pressure fuel in the accumulator 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 OFF to ON, and the fuel injection amount is adjusted by the ON time, and the pressure in the accumulator 16 is the same,
The fuel injection amount increases as the ON time increases. 26 is a check valve, and 27 is an orifice.

The fuel injection device 10 further includes 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 accumulator. The adjusting valve 31 opens and closes the flow path of the passage 13, and adjusts the pressure of the accumulator by adjusting the amount of fuel discharged to the accumulator 16. The fuel injection rate changes depending on the fuel pressure (injection pressure) in the accumulator 16, and the fuel injection rate increases as the fuel pressure in the accumulator 16 increases.

A control unit 41 to which signals from an accelerator opening sensor 33, a sensor 34 for detecting an engine speed and a crank angle, a sensor 35 for distinguishing a cylinder, and a water temperature sensor 36 are inputted, has a function of the engine speed and the accelerator opening. The target fuel injection amount and the target pressure of the accumulator 16 are calculated in accordance with the pressure, and the pressure regulating valve 31 is adjusted so that the accumulator pressure detected by the pressure sensor 32 matches the target pressure.
The feedback control of the fuel pressure in the pressure accumulating chamber 16 is performed via the.

The ON time of the three-way valve 25 is controlled in accordance with the calculated target fuel injection amount.
By controlling the switching timing to N, a predetermined injection start timing according to the operating conditions is obtained. For example, the fuel injection timing (injection start timing) is delayed up to the piston top dead center (TDC) so that the ignition delay period of the injected fuel becomes longer on the low-rotation low-load side with a high EGR rate. Due to this delay, the temperature in the combustion chamber at the time of ignition is set to a low temperature state, and the generation of smoke in the high EGR rate region is suppressed by increasing the premixed combustion ratio. On the other hand, the injection timing is advanced as the rotational 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.
Increases in proportion to the increase in the engine speed, and the low E
In order to obtain a predetermined ignition timing at the GR rate, the injection timing is advanced.

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 an actuator 54 is provided at a scroll inlet of the exhaust turbine 52.
By the control unit 41, the variable nozzle 53 is set at a high nozzle opening (tilting state) to increase the flow velocity of the exhaust gas introduced into the exhaust turbine 52 on the low rotation speed side so that a predetermined supercharging pressure is obtained from the low rotation speed region. On the rotating side, the exhaust gas is introduced into the exhaust turbine 52 without resistance and is controlled to the nozzle opening degree (fully opened state).

The actuator 54 includes a diaphragm actuator 55 for driving the variable nozzle 53 in response to the control pressure, and a diaphragm actuator 55
A duty control signal is generated such that the opening ratio of the variable nozzle 53 becomes a target opening ratio Rvnt obtained as described later. Is the pressure control valve 5
6 is output.

From the viewpoint of supercharging pressure control, EGR
Control also physically fulfills the role of boost pressure control. That is, by changing the EGR amount, the supercharging pressure also changes. Conversely, when the supercharging pressure is changed, the exhaust pressure changes, so that the EGR amount also changes.
It cannot be controlled independently of quantity. In addition, it is somewhat a control disturbance. In addition, if one is changed, in order to ensure control accuracy, the other must be re-adapted, but after the other is re-adapted, the other must be re-adapted. With the method, it is difficult to ensure control accuracy during transition.

As described above, the supercharging pressure and the EGR amount affect each other, and if the EGR amount is changed, it is difficult to appropriately adapt the nozzle opening degree, for example, it is necessary to change the nozzle opening degree. Control unit 41 reduces the target intake air amount tQac according to the operating conditions.
Is calculated from the target intake air amount tQac, the target EGR amount, and the target EGR rate Megr, the actual EGR amount Qec and the actual EGR rate Megrd, which are the variable target values of the turbocharger operation target. 53 target opening ratio R
vnt is set.

Further, feedback control is performed so that the actual intake air amount matches the target value. At this time, the target intake air amount tQ set according to the operating conditions (rotational speed, load)
A value obtained by performing delay processing on ac in accordance with the delay of the intake system is set as a target value in feedback control.

The supercharging limit may be exceeded depending on manufacturing variations of the air flow meter 39 and the actuator 54 and the use environment (for example, atmospheric pressure) of the vehicle. And real EG
It is determined whether or not the supercharging limit is reached based on the total value of the R amount and the actual displacement, and if the supercharging limit is exceeded, the boost pressure is reduced for a predetermined period to suppress overboost. The actuator 54 is moved.

Further, if the actuator 54 is suddenly moved to the side where the supercharging pressure is increased just because the overboost suppression is terminated and the operation is returned to the normal operation, the overboost is likely to occur again. When the operation is ended and the operation is returned to the normal operation, the actuator 54 is returned slowly.

In this case, the optimum value of the time for suppressing the over-boost changes depending on the degree of acceleration, and is set according to the degree of transition. In addition, since the optimum value of the time until the shift to the normal operation changes after the suppression of the overboost is changed depending on the use environment and the exhaust amount, this is set according to the atmospheric pressure and the exhaust amount.

The contents of the control executed by the control unit 41 will be described with reference to the following flowchart. 3 to 40, FIG. 54 (steps 1 to 3 only), FIG. 59 (steps 1 and 2 only), FIG.
2. FIGS. 87 to 102 are the same as those already proposed in the prior application.

First, FIG. 3 is for calculating the target fuel injection amount Qsol. The REF signal (a reference position signal of the crank angle, which is a signal at every 180 degrees for a 4-cylinder engine and every 120 degrees for 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, a map having the contents shown in FIG. 4 is searched based on these Ne and Cl to obtain the basic fuel injection amount. Mqdrv is calculated, and in step 4, the basic fuel injection amount Mqdrv is increased by the engine coolant 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, and is executed every time the REF signal is input.

FIG. 5 shows a main routine, in which a large control flow follows the illustrated steps, and a subroutine is prepared for the processing of each step. Accordingly, the subroutine will be mainly described below.

FIG. 7 (subroutine of step 1 in FIG. 5)
Is for calculating the target EGR amount Tqec per cylinder, and is executed every time a REF signal is input.

In steps 1 and 2, the intake air amount Qacn per cylinder and the target EGR rate Megr are calculated.

Here, the operation of Qacn will be described with reference to the flow of FIG. 8, and the operation of Megr will be described with reference to the flow of FIG.

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

[0062]

## 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 delays the transport delay from the air flow meter 39 to the collector 3a. Therefore, in step 3, the value of Qac0 L (where L is an integer) times before Is the intake air amount Qac per cylinder at the position of the collector inlet 3a.
n. Then, in step 4, this Qa
for cn

[0064]

## EQU2 ## Qac = Qac _n-1 × (1-KIN × KVO
L) + Qacn × KIN × KVOL, where KIN: value corresponding to volumetric efficiency, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, Qac _n−1 : previous Qac, (The first-order lag equation) is used to calculate the amount of intake air per cylinder at the intake valve position (the amount of intake air is hereinafter abbreviated as “cylinder intake air amount”) Qac.
This is for compensating the dynamics from the collector inlet 3a to the intake valve.

The detection of the intake air amount Qas0 on the right side of Expression 1 will be described with reference to the flowchart of FIG. The flow of FIG. 9 is executed every 4 ms.

In step 1, the air flow meter 39 is
The power voltage Us is read, and from this Us, at step 2 in FIG.
Searching the voltage-flow rate conversion table containing 0
The intake air amount Qas0 Calculate d. further,
In step 3, this Qas0 Perform weighted average processing on d
The weighted average processing 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 coolant temperature Tw are read. In step 2, the basic target EGR rate Megrb is calculated by searching a map having the contents shown in FIG. 12 from the engine speed Ne and the target fuel injection amount Qsol. In this case, the basic target EGR rate is increased in a region where the engine is frequently used, that is, in a low rotation point and a low load (low injection amount), and is reduced at a high output where smoke is likely to occur.

Next, at step 3, the cooling water temperature Tw is calculated from FIG.
By searching a table containing the following information, a water temperature correction coefficient Kegr of the basic target EGR rate is obtained. tw is calculated.
Then, in step 4, from the basic target EGR rate and the water temperature correction coefficient,

[0069]

## EQU3 ## Megr = Megrb × Kegr The target EGR rate Megr is calculated by the equation of tw.

In step 5, it is determined whether or not the state of the engine is a complete explosion state. However, this complete explosion judgment
This will be described later with reference to the flow of FIG.

In step 6, it is checked whether the state is complete explosion. If the state is complete explosion, the current processing is terminated. If it is determined that the state is not complete explosion, the target EGR rate Megr is set to 0 and the current processing is performed. finish.

Thus, 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. In step 1, the engine rotation speed Ne is read, and the engine rotation speed Ne and the complete explosion determination slice level NRPMK corresponding to the complete explosion rotation speed are determined in step 2.
Will be compared. If Ne is larger, it is determined that the explosion is complete, and the process proceeds to step 3. Here, the counter Tmrk
b and a predetermined time TRMKBP, and a counter Tmr
If kb is longer than the predetermined time, the process proceeds to step 4 and ends assuming that the explosion has been completed.

On the other hand, if Ne is smaller in step 2, the process proceeds to step 6, where the counter Tmrkb
Is cleared, and the process is terminated in step 7 assuming that it is not in the complete explosion state. 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 determined that the explosion is not complete.

Thus, 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, it is determined that a complete explosion has occurred.

After the calculation of the cylinder intake air amount Qacn according to FIG. 8 and the target EGR rate Megr according to FIG. 11, the process returns to step 3 in FIG.

[0077]

The required EGR amount Mqec is calculated by the following equation: Mqec = Qacn × Megr

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

[0079]

Rqec = Mqec × KIN × KVOL + Rq
ec _n-1 × (1-KIN × KVOL), where KIN: equivalent value of volumetric efficiency, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, Rqec _n-1 : Intermediate processing value (weighted average value) Rqec is calculated by the following intermediate processing value: Rqec, and using this Rqec and the required EGR amount Mqec in step 5

[0080]

## EQU6 ## Tqec = Mqec × GKQEC + Rqec
_n-1 × (1−GKQEC), where GKQEC: advance correction gain, the advance correction is performed, and the target EGR amount Tqec per cylinder is calculated. Since there is a delay in the intake system relative to the required value (that is, a delay corresponding to the capacity of the EGR valve 6 → the collector unit 3a → the intake manifold → the intake valve), steps 4 and 5 perform processing for advancing the delay. .

Next, FIGS. 15 and 16 show the target intake air amount t.
This is for calculating Qac, and is executed at regular intervals (for example, every 10 ms).

If FIG. 15 is the first embodiment and FIG. 16 is the second embodiment, there is a difference between the two embodiments in the parameters used to calculate the target opening ratio Rvnt of the variable nozzle 53 (the first embodiment). Then, the target opening ratio Rvnt of the variable nozzle 53 is calculated based on the actual EGR amount Qec, and in the second embodiment, based on the actual EGR rate Megrd.)

Note that FIGS. 15 and 16 are also main routines, and a subroutine is prepared for the processing of each step.

FIG. 17 (subroutine of step 1 in FIGS. 15 and 16) is for calculating the actual EGR rate.
Execute every 0 ms. In step 1, the target EGR rate Meg
r (obtained in FIG. 11) is read, and in step 2, a time constant equivalent value Kkin for the collector capacitance is calculated. This K
The calculation of kin 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 the previous value of the actual EGR rate, Megrd _n-1 [%], which will be described later, are read. Of these, Ne and Qsol are searched in step 2 for a map having the contents shown in FIG.
b, and in step 3,

[0086]

## EQU7 ## Kin = Kinb × 1 / (1 + Megrd _n−1)
/ 100) is calculated by the following equation. This is E
Since the volume efficiency is reduced by GR, the correction is made accordingly.

The value obtained by multiplying the thus determined Kin by KVOL (see step 4 in FIG. 8) which is a constant corresponding to the ratio between the intake system volume and the cylinder volume in step 4 is equivalent to a time constant corresponding to the collector capacity. The calculation is performed as the value Kkin.

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

[0089]

Equation 8: Megrd = Megr × Kkin × Ne × KE
2 # + Megrd _n-1 × (1-Kkin × Ne × KE2
#), Where Kkin: Kin × KVOL #, KE2 #: constant, Megrd _n-1 : previous Megrd, delay processing and unit conversion (per cylinder → per unit time) are performed simultaneously to obtain the intake valve position. Of the EGR rate Megrd at is calculated. Ne × KE2 # on the right side of Equation 8
Is a value for unit conversion. Since this Megrd responds to the target EGR rate Megr with a first-order lag, 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. In step 1, the engine speed Ne, the actual EGR rate Megrd, and the target fuel injection amount Qsol are read, and in step 2, Megrd is compared with a predetermined value MEGLV #.

Here, the predetermined value MEGLV # is a value (for example, 0.5) for determining whether or not EGR is activated.
When Megrd> MEGRLV #, it is determined that the operating range of the EGR is in effect, and the process proceeds to steps 3, 4, and 5. On the other hand, when Megrd ≦ MEGRLV #, the EGR is performed.
And the process proceeds to step 6. MEG
The reason why RLV # is not 0 is to respond to the case where there is a request to treat a small amount of EGR in the same manner as when no EGR is performed.

If it is within the operating range of EGR, step 3
A target intake air amount basic value tQacb is calculated by searching a map having the contents shown in FIG. 21, for example, from the engine rotation speed Ne and the actual EGR rate Megrd. If the engine speed is constant, the actual EGR as shown in FIG.
The target intake air amount increases as the rate increases.

In step 4, a correction coefficient ktQac of the target intake air amount is calculated by searching a map having the contents shown in FIG. 22, for example, 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 for responding to a request to change the target intake air amount according to the operating conditions (Ne, Qsol).

On the other hand, if it is in the EGR non-operating range, the routine proceeds to step 6, where the target intake air amount tQac is calculated by searching a map containing 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 (obtained in step 3 in FIG. 8) at the position of the collector inlet 3a, the target EGR rate Megr, and the time constant equivalent value Kkin for the collector capacity are read. Of these, Qacn and Meg
r from step 2

[0096]

## EQU9 ## The EGR amount Qec0 per cylinder at the position of the collector inlet 3a is calculated by the following equation: Qec0 = Qacn × Megr
In step 3 using kin

[0097]

## EQU10 ## Qec = Qec0 × Kkin × Ne × KE #
+ Qec _n-1 × (1−Kkin × Ne × KE #) where Kkin: Kin × KVOL, KE #: constant, Qec _n−1 : previous Qec, The delay processing and the unit conversion (per cylinder / per unit time) are performed simultaneously to calculate the cylinder intake EGR amount Qec. Ne × KE # on the right side of Expression 10 is a value for unit conversion. This Q
Since ec responds to the target EGR amount Tqek (described later with reference to FIG. 40) with a first-order lag, this Qec is hereinafter referred to as “real E
It is called GR amount. The above-described Qac that responds to the target intake air amount tQac with a first-order delay is hereinafter referred to as “actual intake air amount”.

FIG. 25 (subroutine of step 2 in FIG. 5) calculates the EGR amount and the flow rate of the EGR gas (gas flowing through the EGR valve).
This is for calculating two feedback correction coefficients Kqac00 and Kqac0 and an EGR flow rate learning correction coefficient Kqac used for the calculation of the “GR flow velocity”, and is executed every time the REF signal is input.

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

In step 2, the target intake air amount tQac
From

[0101]

## EQU11 ## tQacd = tQac × KIN × KVOL ×
KQA # + tQacd _n-1 × (1-KIN × KVOL ×
KQA #), where KIN: volume efficiency equivalent value, KVOL: VE / NC / VM, VE: displacement, NC: number of cylinders, VM: intake system volume, KQA #: constant, tQacd _n-1 : previous Qaccd The target intake air amount delay processing value tQacd is calculated by the following equation (first-order lag equation). This is because of the delay in air supply due to the presence of the intake system volume, two feedback correction coefficients Kqac00 and Kqac0, which will be described later, and a learning value Rq.
The delay processing is performed so that ac does not become large.

In step 3, various feedback-related flags are read. These settings will be described with reference to the flowcharts of FIGS. 26, 27, and 28.

26, 27, and 28 are executed at fixed time intervals (for example, every 10 ms) independently of FIG.

FIG. 26 shows a feedback permission flag fef.
b is set. In step 1, the engine speed Ne, the target fuel injection amount Qsol, and the actual EGR rate M
egrd 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. Feedback is permitted when all of the items are satisfied, and feedback is performed when even one is not satisfied. Ban. That is, Step 2: Megrd exceeds a predetermined value MEGRFB # (that is, the operating range of EGR). Step 3: Tw becomes a predetermined value TWFBL # (for example, 30).
Step 4: Qsol exceeds a predetermined value QSOLFBL # (no fuel cut), Step 5: Ne exceeds a predetermined value NEFBL # (rotational speed range where engine stalls) Step 8: When the feedback start counter Ctrfb exceeds a predetermined value TMRFB # (for example, a value of less than one second), a feedback permission flag fefb = 1 is set to permit feedback in Step 9, otherwise, Step 10 is performed. Then, the feedback permission flag fefb = 0 is set to prohibit the feedback.

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

FIG. 27 shows a learning value reflection permission flag felrn.
2 is set. In step 1, the engine speed Ne, the target fuel injection amount Qsol, and the actual EGR rate M
egrd and the water temperature Tw are read.

The determination of the learning value reflection permission condition is also performed in step 2
This is performed by checking the contents of .about.5 and 8 one by one. 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 any one of them is contrary. That is, Step 2: Megrd is a predetermined value MEG
RLN2 # is exceeded (that is, the operating range of EGR), Step 3: Tw is a predetermined value TWLNL2 # (for example, 2
Step 4: Qsol exceeds a predetermined value QSOLLNL2 # (no fuel cut), Step 5: Ne exceeds a predetermined value NELNL2 # (rotation speed range where engine stalls) Step 8: When the learning value reflection counter Ctrln2 exceeds a predetermined value TMRLN2 # (for example, about 0.5 seconds), a learning value reflection permission flag feln2 = 1 is set in Step 9 to permit reflection of the learning value. Otherwise, the process proceeds to step 10, where the learning value reflection permission flag feln2 = 0 is set to prohibit the reflection of the learning value.

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

FIG. 28 is for setting the learning permission flag felrn. In step 1, the engine speed Ne, the target fuel injection amount Qsol, and the actual EGR rate Megr
d, The water temperature Tw is read.

The determination of the learning permission condition includes steps 2 to 7,
This is done 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 is wrong. That is, Step 2: Megrd exceeds a predetermined value MEGRLN # (that is, the operating range of EGR). Step 3: Tw becomes a predetermined value TWLNL # (for example, 70
Step 4: Qsol exceeds a predetermined value QSOLNLNL # (no fuel cut), Step 5: Ne exceeds a predetermined value NELNL # (rotation speed at which engine stalls) Range), step 6: feedback permission flag fefb = 1, step 7: learning value reflection permission flag feldrn2 = 1, step 10: learning delay counter Ctrln exceeds predetermined value TMRLN # (for example, about 4 seconds). If so, in step 11, the learning permission flag feln = 1 is set to permit learning, otherwise, the process proceeds to step 12, where the learning permission flag feln = 0 is set to prohibit learning.

The learning delay counter is set in step 2
It counts up when the conditions are satisfied (step 8) and resets when the conditions are not satisfied (step 9).

Returning to FIG. 25, of the three flags set in this way, the feedback permission flag fefb is checked in step 4. When fefb = 1, the feedback correction coefficient Kqac0 of the EGR amount is determined in steps 5 and 6.
0 and a feedback correction coefficient Kqac0 for 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.

The calculation of the EGR amount feedback correction coefficient Kqac00 will now be described with reference to the flow chart of FIG.
The calculation of the EGR flow velocity feedback correction coefficient Kqac0 will be described with reference to the flowchart of FIG.

First, in FIG. 29 (subroutine of step 5 in FIG. 25), in step 1, the target intake air amount delay processing value tQacd, actual intake air amount Qac, engine speed Ne, target fuel injection amount Qsol, and water temperature Tw are read. .

In step 2, for example, a map having the contents shown in FIG.
A GR flow rate correction gain Gkfb is calculated, and in step 3, a water temperature correction coefficient Kgfbtw of the correction gain is calculated from Tw by searching a table containing, for example, FIG.

[0117]

Kqac00 = (tQacd / Qac-1)
× Gkfb × Kgfbtw + 1, the EGR amount feedback correction coefficient Kqac0
Calculate 0.

The first term on the right side of this equation, (tQacd / Qa
c-1) is the error ratio from the target intake air amount delay processing value. By adding 1 to this, Kqac00 becomes a value centered on 1. Equation 12 calculates the EGR amount feedback correction coefficient Kqac00 in proportion to the error ratio from the target intake air amount delay processing value.

Next, in FIG. 32 (subroutine of step 6 in FIG. 25), in step 1, 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. Read.

In step 2, by searching a map having the contents shown in FIG. 33 from Ne and Qsol, for example, E
The GR flow velocity correction gain Gkfbi is calculated, and in step 3, the water temperature correction coefficient Kgfbitw of the correction gain is calculated from Tw by searching a table containing, for example, FIG.

[0121]

Rqac0 = (tQacd / Qac-1) ×
Gkfbi × kGfbitw + Rqac0 _n−1 , where Rqac0 _n−1 : the previous error rate Rqac0, the error rate Rqac0 is updated, and the value obtained by adding 1 to the error rate Rqac0 in step 5 in the EGR flow rate Cqe (FIG. 38) (Described later) will be calculated as the feedback correction coefficient Kqac0.

The EGR flow rate feedback correction coefficient K is proportional to the integrated value (integral value) of the error ratio (tQacd / Qac-1) from the target intake air amount delay processing value.
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. 30 and 33 is as follows. Even if the gain is the same, hunting may or may not occur depending on the operating conditions, so that the correction gain is reduced in a region where hunting occurs. FIG.
The reason why the value is reduced at the time of low water temperature (before the completion of warm-up) as shown in FIG. 34 is to stabilize the engine in a low water temperature region where engine rotation is unstable.

After the calculation of the EGR amount feedback correction coefficient Kqac00 and the EGR flow velocity feedback correction coefficient Kqac0 is completed, the flow returns to FIG. 25, and in step 9, the learning value reflection permission flag felrn2 is checked. When the learning reflection permission flag felrn2 = 1 (when the reflection of the learning value is permitted), the process proceeds to step 10, where Ne and Q
For example, a learning map shown in FIG. 35 is retrieved from the sol to read an error rate learning value Rqac, and a value obtained by adding 1 to this is calculated as an EGR flow rate learning correction coefficient Kqac. On the other hand, when the learning reflection permission flag feldrn2 = 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.

Next, at step 13, the learning permission flag felrn is checked. If the learning permission flag felrn = 1 (when learning is permitted), the process proceeds to step 14 and E
Subtract 1 from the GR flow velocity feedback correction coefficient Kqac0 to obtain an error rate Rqacn. On the other hand, when the learning permission flag feldrn = 0 (when learning is prohibited)
Goes from step 13 to step 15 to calculate the error rate R
It is assumed that qacn = 0.

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

In FIG. 36 (subroutine of step 16 in FIG. 25), in step 1, the error ratio Rqacn, the engine speed Ne, and the target fuel injection amount Qsol are read. Learning speed Tclr in step 2 from Ne and Qsol
n is calculated, for example, by searching a map having the contents shown in FIG. In step 3, the error ratio learning value Rqac is read from Ne and Qsol from the learning map of FIG. In step 4

[0128]

Rqac _n = Rqacn × Tclrn + Rq
ac _n-1 × (1-Tclrn), where Rqac _n : error ratio learning value after update, Rqac _n-1 : error ratio learning value before update (= learning value read value), weighted average processing Is stored in the learning map of FIG. 35 in step 5 (the value before update is overwritten with the value before update) in step 5.

FIG. 38 (subroutine of step 3 in FIG. 5) is for calculating the EGR flow velocity Cqe.

In steps 1 and 2, the actual EGR amount Qec and the actual EGR
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.

[0131]

(Equation 15) 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 h, and the corrected actual EGR amount Qec h and actual EGR rate Meg
In step S8, the EGR flow velocity Cqe is calculated by searching a map having the contents shown in FIG. 39, for example. Steps 4 to 7, which have not been described, will be described later.

Since the characteristic of the EGR flow velocity in FIG. 39 shows that the nonlinearity is strong and the sensitivity of the EGR feedback differs according to the operating condition, the difference in the feedback amount with respect to the operating condition is reduced. 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. 39, the portion near the right end where the slope of the characteristic is steep is a region in which a matching error of the map tends to occur, and if there is a matching error, the EGR valve is affected by the matching error. The opening area Aev changes.
That is, A is a formula for calculating the EGR valve opening area Aev.
Since eq = Tqek / Cqe (which will be described later with reference to FIG. 40) causes an adaptation error in Cqe, it is necessary to correct the flow rate error in the target EGR amount Tqek to cope with this. Therefore, the newly introduced EGR amount feedback correction coefficient Kqac00
Thus, the target EGR amount Tqek is corrected in step 2 of FIG.

In this case, since the above equation (12), which is an equation for calculating Kqac00, calculates Kqac00 in proportion to the error ratio from the target intake air amount delay processing value, the EGR flow rate map shown in FIG. Can be immediately corrected for the matching error. For example, in Expression 12, for simplicity, when the correction gain Gkfb = 1 and the warm-up is completed, 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 and thus the target EGR
The quantity Tqek is immediately reduced. Target EGR amount Tqek
Is reduced immediately, the relative fresh air volume (intake air volume)
Increases, whereby the actual intake air amount Qac converges to tQacd as the target value.

Steps 4 to 7 in FIG. 38, which have not been described, are for setting initial values at the start of EGR operation. Specifically, in step 4, the corrected actual EGR amount Qec Compare h with 0. Qec When h = 0 (that is, when EGR is not operating), the process proceeds to step 5, and

[0136]

(Equation 16) h = Qac × MEGRL #, where MEGRL #: 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,

[0137]

## EQU17 ## The actual EGR rate Megrd is set according to the equation: Megrd = MEGRL #.

When the EGR valve 6 is fully closed, the flow rate of the EGR passing through the EGR valve 6 is naturally zero.
Equation (17) sets the initial values of the parameters used for the calculation of the flow velocity in consideration of the start of the EGR operation. ME
The value of GRL # is, for example, 0.5 as described above.
More specifically, the differential pressure before and after the EGR valve (and therefore the EGR flow rate) at the start of the EGR operation differs depending on the operating conditions. 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 equation 16, Qec is proportional to Qac. By giving the initial value of h, the calculation accuracy of the EGR flow speed at the start of the EGR operation is improved.

FIG. 40 (subroutine of step 4 in FIG. 5) is for calculating the EGR valve opening area Aev. In step 1, the target EGR amount T per cylinder is set.
qec, EGR amount feedback correction coefficient Kqac0
0, the EGR flow velocity Cqe is read. In step 2, the target EGR amount per cylinder Tqec is corrected by an EGR amount feedback correction coefficient Kqac00 (Tqec /
Kqac00)

[0140]

[Equation 18] Tqek = Tqec × (Ne / KCON #)
/ Kqac00, where Kqac00: EGR amount feedback correction coefficient, KCON #: constant, unit conversion (per cylinder → per unit time) is performed to determine the target EGR amount Tqek, and this target EGR amount Tqek and EGR Step 3 from the flow rate Cqe
In

[0141]

The EGR valve opening area Aev is calculated by the following equation: Aev = Tqek / Cqe.

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

Next, FIG. 41 is for calculating a control command duty value Dtyvnt to be given to the actuator 54, and is executed at regular intervals (for example, every 10 ms). Since FIG. 41 is also a main routine, a description will be given focusing on subroutines prepared for the processing of each step.

FIG. 42 (subroutine of step 1 in FIG. 41) is for setting the overboost determination flag FOVBST.

First, at step 1, the engine speed N
e, the target fuel injection amount Qsol, the actual intake air amount Qac, and Ne, which is the value before k (integer constant) cycle.
_nk , Qsol _nk , Qac _{nk and} actual EGR rate Meg
Read rd.

In Step 2, the actual intake air amount Qac and the actual E
Using GR rate Megrd

[0147]

[Equation 20] Qcyl = Qac × (1 + Megrd / 10
0), the gas amount Qcyl [m
g / st. cyl]. The second term (Qac × Megrd / 100) on the right side of Expression 20 is the actual EGR amount,
The sum of the actual intake air amount Qac (new air amount) and the actual EGR amount is defined as the gas amount sucked into the cylinder.

The actual EGR amount is the actual EG amount in FIG.
The R amount Qec may be used (therefore, at this time, Qcyl = Qac + Qec).

In step 3,

[0150]

## EQU21 ## Qexh = (Qac + Qsol × GKQFV)
NT #) × Ne / KCON #, where GKQFVNT #: conversion coefficient, KCON #: constant, the actual displacement Qexh [mg / st. cyl]. This assumes that the total of the amount of the fuel of Qsol burning and becoming exhaust and the actual intake air amount Qac is the exhaust amount (ignoring the rise in temperature). Where Qsol
Is [mm ³ / st. cyl], the unit of Qexh is multiplied by a conversion coefficient GKQFVNT # [mg / mm ³ ], so that the unit of Qexh is Qac [mg / st.
cyl]. Ne / KC
ON # is multiplied by [mg / st. cyl] to [g
/ S].

In step 4, Ne, Qsol, Qac
Is calculated as an engine speed change amount DNE, a fuel injection amount change amount DQSOL, and an actual intake air amount change amount DQAC, respectively, based on these engine speed Ne and the target fuel injection amount Qsol. In steps 5 to 7, it is determined whether or not overboost occurs. That is, Step 5: Ne ≧ predetermined value KNEOB # and DNE ≧ predetermined value KDNEOB #. Step 6: Qsol ≧ predetermined value KQFOB # and DQS
OL ≧ predetermined value KDQFOB #, Step 7: When DQAC ≧ predetermined value KDQACOB # is satisfied, it is determined that overboost occurs, and the process proceeds to steps 11 and 12 to set the overboost determination flag FOVBT = 1. At the same time, the over-boost timer TMROB is reset (TMROB =
0).

As will be described later with reference to FIGS. 54 and 59, this flag FOVBST is used for calculating the target ratio basic value Rvnt0. When the flag FOVBT = 1 when the intake air amount and the EGR amount are the same, the flag FOVBT = 0. The target ratio basic value Rvnt0 having a larger value than the time is calculated. As the target ratio basic value Rvnt0 decreases, the variable nozzle 53 is closed and the supercharging pressure increases as the value decreases. Therefore, when the flag FOVBT = 1, the variable nozzle 53 is opened more than when the flag FOVBT = 0 (supercharging). This makes it difficult for pressure to rise), thereby suppressing overboost. That is, the flag FOVBT
When = 1, the over-boost is suppressed, and when FOVBT = 0, the normal operation is performed.

The over-boost timer TMROB is for measuring the time elapsed since the flag FOVBT was switched to 1. Although not shown, the timer TMROB is reset by setting the flag FOVBT from 0 to 1
And the second and subsequent times are skipped (the processing of step 12 is skipped). The timer TMROB may be constituted by, for example, an internal timer of the CPU, and the timer value increases with time by resetting the timer.

FIG. 43 schematically shows the change when the accelerator pedal is suddenly depressed. The timing for determining the occurrence of overboost is determined by the target fuel injection amount Qsol,
The flag FOVBT is set to “1” each time the engine speed Ne and the actual intake air amount Qac are earlier. This is because, when it is attempted to determine the occurrence of overboost based only on the actual intake air amount Qac, the timing of the determination is late, and when the accelerator pedal is depressed rapidly, the response to overboost is delayed and overboost occurs. The target fuel injection amount Qsol
And the engine rotation speed Ne are added as parameters for the over-boost determination, so that the timing of the over-boost determination is advanced as much as possible.

Note that FIG. 43 shows three persons (Qsol, Ne,
In order to clearly understand the time lag of the signal of Qac), the case where Qsol is small due to the limitation of the smoke limit in the initial stage of the transition is shown. Therefore, when the occurrence of overboost is determined only based on the actual intake air amount Qac in the case where the smoke limit is accompanied by the fuel limitation, the determination timing is greatly delayed. However, according to the present embodiment, Even in the case where the fuel limit of the smoke limit is involved, there is ample time to cope with the over-boost suppression, and the over-boost can be reliably prevented.

If none of the above three conditions shown in steps 5 to 7 are satisfied, steps 5, 6, 7 in FIG.
Then, the process proceeds to steps 8 and 9.

Steps 8 and 9 correspond to the cylinder intake gas amount Qc.
This is a section for determining whether or not overboost occurs based on yl and the actual displacement Qexh. To explain this, FIG. 110 shows one result of a steady-state experiment in which the opening ratio of the variable nozzle 53 (described later), the engine rotation speed Ne, and the target fuel injection amount Qsol as the engine load are variously changed in one engine. The cylinder intake gas amount Qcyl (= Qac + Qec) due to the difference in the operating conditions (Ne, Qsol) even if the opening ratio of the variable nozzle 53 is the same, or the difference in the opening ratio even if the operating conditions are the same even for the same engine. ) And the actual displacement Qexh vary considerably. This variation is due to manufacturing variations of the air flow meter 39, the actuator 54, and the like. Due to such variations in Qcyl and Qexh, overboost occurs when the conditions are plotted beyond the supercharging limit. Therefore, Qc
In order to prevent overboost due to variations in yl and Qexh, a supercharging limit that changes according to the actual displacement Qexh is set in a table in advance as a determination value, and Qcyl calculated during operation and Qcyl at that time are set. Actual displacement Qex
From the result of comparison with the determination value obtained by searching the table from h, if overboost occurs when Qcyl is equal to or greater than the determination value, it is determined that overboost does not occur when Qcyl is less than the determination value.

Although the two embodiments are of the type in which the intake air amount is adopted as the supercharging pressure, the cylinder intake gas amount Qcyl is plotted on the vertical axis. The shaft becomes the actual boost pressure. This is shown in FIG. 111. Also in this case, similarly to FIG. 110, due to manufacturing variations of the supercharging pressure sensor and the actuator, the opening ratio of the variable nozzle and the operating conditions (Ne, Qsol ), The actual supercharging pressure and the actual exhaust amount Qexh vary considerably. Due to such variations of the actual supercharging pressure and Qexh, overboost occurs under the conditions plotted beyond the supercharging limit. Therefore, in order to prevent the overboost due to the variation of the actual supercharging pressure or Qexh, a supercharging limit that changes according to the actual displacement Qexh is set in advance as a determination value in a table and detected during operation. If the actual boost pressure is equal to or higher than the determination value and an over-boost occurs based on the result of comparison between the actual boost pressure and the determination value obtained by searching the table from the actual exhaust amount Qexh at that time, the reverse occurs. When the boost pressure is less than the determination value, it may be determined that overboost does not occur.

More specifically, at step 8 in FIG. 42, a map containing, for example, FIG. 44 is retrieved from the actual exhaust amount Qexh to find the overboost determination intake gas amount TQc.
yl (judgment value), and calculates the cylinder intake gas amount Q
cyl and this TQcyl are compared in step 9 of FIG. When Qcyl is equal to or larger than TQcyl, it is determined that overboost occurs, and the processes of steps 11 and 12 are executed.

On the other hand, when Qcyl is less than TQcyl, overboost does not occur, so the routine proceeds from step 9 to step 10 and the overboost determination flag FOV
BST = 0.

As shown in FIG. 44, the overboost determination intake gas amount TQcyl has a characteristic that becomes substantially mountain-shaped with respect to the actual exhaust amount Qexh. This takes into account the efficiency characteristics of the turbocharger shown in FIG. That is, in FIG. 45, in the turbocharger, the efficiency η (fresh air amount) increases as the actual exhaust amount Qexh increases from a small value,
When the actual displacement Qexh further increases, the efficiency η decreases. Therefore, TQcyl is set accordingly. The vertical axis is the pressure ratio (manifold pressure Pm / atmospheric pressure Pa).

At the same actual displacement Qexh, the atmospheric pressure P
It is preferable to make TQcyl smaller as a becomes lower (see FIG. 44).

FIG. 46 (step 2 subroutine in FIG. 41) shows an over-boost release transition flag FCLROB.
It is for setting. This flag FCLROB
The reason for introducing is as follows. The over-boost is suppressed for a predetermined time (over-boost suppression time TTMROB described later). However, if the variable nozzle 53 is immediately returned to the closing side (the side where the boost pressure rises) just after the elapse of the time, there is a possibility that overboost may occur due to this. Therefore, this over-boost release transition flag FCLROB is introduced,
As shown in FIG. 47, the overboost determination flag F
At the timing when OVBST is changed from 1 to 0 (that is, when the timing of overboost suppression ends), the overboost release shift flag FCLROB is switched from 0 to 1 and the overboost release shift flag FCLROB = 1
The variable nozzle 53 is slowly returned to the position before the start of the over-boost suppression during the period.

More specifically, in step 1 of FIG. 46, the overboost timer TMROB and the overboost determination flag FOVBST are checked. When the over-boost timer TMROB is equal to or shorter than the over-boost suppression time TTMROB or when the over-boost determination flag FOVBST = 1, the over-boost is being suppressed, so the process proceeds to step 4 and the state of the over-boost determination flag FOVBST = 1 is continued.

On the other hand, at other times (for example, when the overboost timer TMROB exceeds the overboost suppression time TTMROB, or when the condition for overboost generation while suppressing the overboost is no longer satisfied), step 1 is executed. Go to steps 2 and 3
In order to end the over-boost suppression and return to the normal operation, the over-boost determination flag FOVBST = 0 and the over-boost clear timer TMCLR
OB is reset (TMRCLROB = 0).

Overboost clear timer TMRCL
ROB is the over-boost determination flag FOVBST = 0
This is for measuring the elapsed time from the start.
Although not shown, the reset of the timer TMRCLROB is also performed when the overboost determination flag FOVBST is set to 1
Only the timing of switching to 0 is set, and the second and subsequent times are skipped (step 3 is skipped). This timer TMR
The CLROB may be constituted by, for example, an internal timer of the CPU, and the timer value increases with time by resetting the timer.

In step 5, the timer TMRCLROB
And the over-boost release transition time TTMRCLROB. Immediately after resetting the timer TMRCLROB, since TMRCLROB <TTMRCLROB, the routine proceeds to step 7, where the over-boost release transition flag FC
It is assumed that LROB = 1.

From the next time (that is, after 10 ms), the process proceeds to steps 1, 2, and 5, and the timer TMRCLROB is compared with the overboost release transition time TTMRCLROB.
As long as TMRCLROB is equal to or smaller than TTMRCLROB, the processing of step 7 is repeated, and the timer TMRCL
If the ROB exceeds TTMRCLROB, the process proceeds from step 5 to step 6, where the overboost release transition flag FCLROB = 0. This causes a transition during normal operation.

The over-boost suppression time TTMROB and the over-boost release transition time T used in FIG.
TMRCLROB is always calculated (for example, every 10 ms) as shown in FIGS.

First, referring to FIG. 48, in step 1, the engine rotational speed change amount DNE and the fuel injection amount change amount D
For example, by searching a map having the contents shown in FIG. 49 from QSOL, basic value TT of overboost control time is obtained.
MROB0 and the actual intake air amount change amount D in step 2
For example, a correction coefficient KTMROB of the over-boost control time is calculated from the QAC and the deviation of the cylinder intake gas amount Qcyl from the deviation from the over-boost determination intake gas amount TQcyl by searching a map containing, for example, FIG. In step 3, the calculation is performed as the overboost suppression time TTMROB. Note that DQSO
The calculation method of L, DNE, DQAC, Qcyl, and TQcyl is the same as that of FIG. 42, and is not shown in the flow of FIG.

As shown in FIG. 49, DNE and DQSOL
Is larger, the over-boost control time basic value TTMR
The reason why OB0 is increased is as follows. Engine speed Ne and target fuel injection amount Q as engine load
The larger the change in sol, the more likely overboost occurs. Therefore, the overboost suppression time is made longer as the change in Ne or Qsol is larger (that is, as DNE or DQSOL is larger). As shown in FIG. 50, the larger the DQAC or Qcyl-TQcyl, the larger the value of the correction coefficient KTMROB is because the change in the actual intake air amount Qac (that is, DQAC) and the deviation from the determination value (that is, Qcyl-TQcyl). The larger the value is, the more the over-boost is likely to occur, and accordingly, the over-boost suppression time is made longer.

Next, referring to FIG. 51, in step 1, the atmospheric pressure P detected by the atmospheric pressure sensor 38 (see FIG. 1) is detected.
52, a table containing the contents shown in FIG. 52 is retrieved, and the overboost release transition time basic value TTM is retrieved.
RCLROB0 and the actual displacement Qexh in step 2
For example, by retrieving a table having the contents shown in FIG. 53 from (obtained in step 3 in FIG. 42), a correction coefficient KTMRCLROB of the overboost release transition time is calculated, and the product of these is calculated in step 3 as the overboost release transition time TTMRCLROB. Is calculated as

The reason for increasing the over-boost release transition time basic value TTMRCLROB0 under the condition where the atmospheric pressure Pa becomes low (for example, at high altitude) as shown in FIG. 52 is as follows. Since the exhaust amount increases in accordance with the difference between the exhaust pressure and the atmospheric pressure, the exhaust amount increases under low atmospheric pressure conditions, and the work performed by the turbocharger increases accordingly (overboost is likely to occur. ). Therefore, under the condition where the atmospheric pressure Pa is low, the over-boost release transition time basic value TTMR
CLROB0 is increased. FIG.
In the region where the actual displacement Qexh is equal to or larger than the predetermined value, as shown in FIG.
The reason for increasing B is that overboost is likely to occur when the actual displacement Qexh exceeds a predetermined value.
Accordingly, the over-boost release transition time is increased in a region where the actual displacement Qexh exceeds a predetermined value.

FIGS. 54 and 59 (the subroutine of step 3 in FIG. 41) show the target opening ratio Rvnt of the variable nozzle 53.
(FIG. 54 shows the first embodiment,
FIG. 59 shows the second embodiment.

Here, the opening ratio of the variable nozzle 53 is
This 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
3, the opening ratio is 100% when fully opened, and the opening ratio is 0% when fully closed. The reason why the opening ratio is adopted is to provide versatility (a value irrelevant to the capacity of the turbocharger). Of course, the opening area of the variable nozzle may be adopted.

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

First, from FIG. 54 of the first embodiment, at step 1, the target intake air amount tQac and the actual E
The GR amount Qec, the engine speed Ne, the target fuel injection amount Qsol, and the target EGR rate Megr are read.

In steps 2 and 3,

[0179]

TQas0 = (tQac + Qsol × QFG)
AN #) × Ne / KCON #, Qes0 = (Qec + Qsol × QFGAN #) × Ne
/ KCON #, where QFGAN #: gain, KCON #: constant, an intake air amount equivalent value tQas0 for setting the target opening ratio basic value (hereinafter, this intake air amount equivalent value is set by EGR amount equivalent value Q for setting the target opening ratio basic value.
es0 (hereinafter, this EGR amount equivalent value is referred to as “set EGR amount equivalent value”) is calculated. In Equation 22, tQa
The reason why Qsol × QFGAN # is added to c and Qec is that 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 Q
The adjustment is made with FGAN #. Also, N
e / KCON # is the amount of intake air per unit time, EGR
Value to convert to quantity.

Steps 4 to 10 correspond to the target EGR rate Megr
<1> Megr ≧ predetermined value KEMRAV # and FOV
<2> Megr ≧ predetermined value KEMRAV # and FOVBST = 0 (EGR operating range and normal operation) when BST = 1 (EGR operating range and over boost suppression), <3> Megr <predetermined value KEMV # and F
When OVBST = 1 (when EGR is not in operation and over boost is suppressed), <4> Megr <predetermined value KEMRA
When V # and FOVBST = 0 (EGR non-operating range and normal operation), the four cases are classified, and the optimum opening ratio in each of the four cases is determined as the target opening ratio basic value Rvnt0 (the turbocharger operation target Value). That is, in the case of <1>, a map having, for example, the contents shown in FIG. 55 is searched in step 7 from the set intake air amount equivalent value tQas0 and the set EGR amount equivalent value tQes0.
In the case of <2>, the target opening ratio basic value Rvnt0 is set in step 8 by searching a map having the contents shown in FIG. 56 from tQas0 and tQes0. Similarly, in the case of <3>, at step 10 tQ
57 is searched from as0 and the target fuel injection amount Qsol. In the case of <4>, a map containing, for example, FIG. 58 is searched from tQas0 and Qsol in step 9. An opening ratio basic value Rvnt0 is set.

On the other hand, in FIG. 59 of the second embodiment,
The target EGR rate Me instead of the set EGR amount equivalent value Qes0
The only difference from the first embodiment is that gr is used (therefore, there is no step 3 in FIG. 54). That is, in step <1>, a map containing, for example, FIG. 60 is retrieved from tQas0 and Megr in step 7, and in <8>, a map containing, for example, FIG. 61 is retrieved from tQas0 and Megr in step 8. Is set to set the target opening ratio basic value Rvnt0.

Since the other parts are the same as those of the first embodiment, the description of the flow is omitted.

The characteristics shown in FIGS. 60 and 61 are different from those shown in FIGS. 55 and 56 on the vertical axis, but are basically the same as those shown in FIGS. 55 and 56. The characteristic of the target opening ratio basic value Rvnt0 will be described.

As shown in FIGS. 55 and 56, in the right region where the set intake air amount equivalent value tQas0 is large, the target opening ratio basic value decreases as the set EGR amount equivalent value Qes0 increases. This is because the fresh air decreases as the EGR amount increases, and smoke occurs when the air-fuel ratio leans to the rich side. Therefore, as the EGR amount increases, the target opening ratio basic value is reduced to increase the supercharging pressure. It is necessary.

The tendency of the target opening ratio basic value represented in FIG. 55 and FIG. 56 is common to the emphasis on fuel consumption and the exhaust, and the difference between them is a specific numerical value. For example, the minimum value in the figure is the value at which the turbocharger works efficiently, and thus is the same in both the fuel efficiency setting example and the exhaust setting setting example. TQas0 differs from the setting example in which
When Qes0 and Qes0 are the same condition, the setting example focusing on fuel efficiency becomes larger. Note that the target opening ratio basic value may be set as an example in which acceleration is emphasized.

FIG. 62 shows which of the three characteristics of fuel efficiency, exhaust emission, and acceleration is important.
(Except <1> and <2> above)
FIG. 7 shows that the fuel consumption, exhaust gas (NOx and PM), and the intake air amount are different when the EGR rate is different between large and small under the condition that the engine speed and the engine torque are constant. It shows how it changes. As can be seen from the figure, even if the engine speed and the engine torque are the same, the opening area of the variable nozzle that provides the best fuel efficiency, the opening area of the variable nozzle that provides the best exhaust, and the intake air amount become the maximum (that is, the acceleration is the best It can be seen that the opening areas of the variable nozzles differ. Therefore, for example, in order to create a characteristic with an emphasis on fuel economy, a large number of data of the opening area (opening ratio) at which the fuel economy is the best is obtained by making the engine rotational speed and the engine torque different, and these data are renewed.
That is, it is only necessary to assign Qas0 and Qes0 (Megr) to a map having parameters as parameters.

Next, the target opening ratio basic value during overboost suppression (see FIGS. 55 and 57 in the first embodiment, and FIGS. 60 and 57 in the second embodiment) is converted to the target opening ratio basic value during normal operation. (In the first embodiment, FIGS. 56 and 58, the second
In the embodiment, it is larger than those shown in FIGS. 61 and 58). This is because the over-boost can be suppressed by reducing the supercharging pressure, that is, opening the variable nozzle 53 (increase Rvnt0).

The setting of the target opening ratio basic value is not limited to the above. In the first embodiment, FIG.
Although the target opening ratio basic value is set from the set intake air amount equivalent value tQas0 and the set EGR amount equivalent value Qes0 as shown in FIG. 56, the target intake air amount tQac is used instead.
And the actual EGR amount Qec. Further, instead of this, the target intake air amount tQac and the target EGR
It may be set from the amount (Qec0). Similarly, in the second embodiment, as shown in FIGS. 60 and 61, the target opening ratio basic value is set from the set intake air amount equivalent value tQas0 and the target EGR rate Megr. It may be set from the amount tQac 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.

As described above, based on the target intake air amount tQac and the actual EGR amount Qec, and based on the target intake air amount tQac.
When a target opening ratio basic value Rvnt0 which is an operation target value of the supercharger is set based on ac and the actual EGR rate Megrd, a target EGR amount (Qe) which is a control target value of the EGR device is set.
Even if c0) or the target EGR rate Megr changes, a target intake air amount that optimizes fuel efficiency, exhaust, and acceleration can be obtained, and controllability of the turbocharger and the EGR device including transients is improved. However, this allows the performance of each other to be sufficiently exhibited. It is also possible to simplify the adaptation and the logic.

Particularly during 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 before catching up with the R rate Megr, and the target EGR
An error may occur in the target opening ratio basic value Rvnt0 due to the amount of deviation from the target amount and the target EGR rate Megr, and it may not be possible to obtain a target intake air amount that optimizes fuel consumption, exhaust, and acceleration. When setting the value Rvnt0, the actual EG is a value obtained by delaying the target EGR amount.
By using the R amount Qec and the actual EGR amount Megrd, which is a value obtained by delaying the target EGR rate Megr, it is possible to obtain a target intake air amount that optimizes fuel consumption, exhaust, and acceleration even in a transient state. Can control the turbocharger.

In FIG. 54, at step 11, the over-boost release transition flag FCLROB is checked. FCLR
When OB = 1 (at the time of shift to overboost cancellation), the process proceeds to step 13, and

[0192]

Rvnt = (1 / TMRCROB #) × R
vnt0 + (1− (1 / TMRCROB #)) × Rv
nt _n−1 , where TMRCLROB #: time constant, Rvnt _n−1 : previous Rvnt, the target opening ratio basic value Rvnt0 is delayed to calculate the target opening ratio Rvnt. The process at the time of shifting to the over-boost release is such that after the variable nozzle 53 is opened (the side where the boost pressure does not rise) when the over-boost is suppressed, the variable nozzle 53 is suddenly closed (the side where the boost pressure rises). If the variable nozzle 53 is returned to, there is a risk of causing over-boost due to this, so the variable nozzle 53 is returned slowly to the closed side.

When the flag FCLROB becomes 0 (the over-boost release transition is completed), the process proceeds from step 11 to step 12, where the target opening ratio basic value Rv is set.
nt0 is directly used as the target opening ratio Rvnt.

FIG. 63 (subroutine of step 4 in FIG. 41) performs advance processing to compensate for the dynamics of the intake system with respect to the target opening ratio Rvnt obtained as described above.

The response delay of the fresh air amount to the control command value to the actuator 54 includes the response delay of the intake and exhaust gas flows,
In this embodiment, the turbo lag is included in the response delay of the intake and exhaust gas flows, and is separated from the response delay of the actuator 54 itself. A response delay (hereinafter, this delay is referred to as a “supercharger / intake / exhaust response delay”) and a response delay of the actuator 54 itself are independently advanced and processed.

In FIG. 63, the advance processing is performed by considering only the response delay of the supercharger / intake / exhaust (actuator 5
(See FIG. 85 for the advance processing taking into account only the response delay of No. 4).
In this case, since the time constant of the response delay of the supercharger / intake / exhaust greatly depends on the exhaust amount, the advance correction gain Gkvnt and the time constant equivalent value Tcvnt of the advance correction are set using the exhaust amount as a parameter. Furthermore, since the time constant of the response differs between the case where the variable nozzle 53 is moved to the open side and the case where the variable nozzle 53 is moved to the close side, it is assumed that the response is made in each case. The details will be described below.

In FIG. 63, at step 1, the target opening ratio Rvnt, the target intake air amount delay processing value tQacd, the target fuel injection amount Qsol, and the engine speed Ne are read.

[0198]

Tqexh = (tQacd + Qsol × QF)
GAN #) × Ne / KCON #, where QFGAN #: gain, KCON #: constant, Tqexh [mg / st. cy
l] is calculated. This Tqexh is a value obtained by using the target intake air amount delay processing value tQacd in place of the target intake air amount tQac in the upper equation for obtaining the set intake air amount equivalent value tQas0 in the equation (22). This is a signal that changes with substantially the same time constant as the time constant when the actual displacement is responded. For example, FIG. 64 shows a change when the target fuel injection amount Qsol is increased in a stepwise manner. In response to an actual change in the exhaust amount (see the broken line at the bottom), an actual exhaust amount equivalent value Tqexh (bottom line) (See the solid line in FIG. 3) responds with good response.

In step 3 of FIG. 63, the target opening ratio Rv
Compare nt with Cavnt _n−1 which is the previous expected opening ratio. Here, the expected opening ratio Cavnt is a weighted average value of the target opening ratio Rvnt, as described later (see step 11 in FIG. 63).

Rvnt> Cavnt_n-1If (variable
When the nozzle 53 is moving to the open side), the step
Proceed to 4 and 5, and from the actual displacement amount equivalent value Tqexhd
For example, a value TGK obtained by searching a table having the contents shown in FIG.
Advancing vnto, the correction gain Gkvnt, the actual displacement
From the equivalent value Tqexhd, for example,
To the value TTCVNTO obtained by searching the cable for correction
It is set as a constant equivalent value Tcvnt.
vnt <Cavnt_n-1(When the variable nozzle 53 is
When moving to the closing side), proceed to steps 7 and 8.
From FIG. 66, for example, based on the actual displacement amount Tqexhd,
The value TGKVNTC obtained by searching the table as the contents is
Advance correction gain Gkvnt, also equivalent to actual exhaust amount Tq
Exhd, for example, a table having the contents shown in FIG.
Advances the value TTCVNTC obtained by searching and the time constant equivalent value of the correction
Set as Tcvnt. Also, Rvnt and Cavn
t_{n- 1}If they are the same, proceed to steps 9 and 10
The previous advance correction gain and advance to ensure stability
The value corresponding to the time constant of the correction is maintained.

The above table values TGKVNTO and TGKVNTC which determine the advance correction gain Gkvnt are shown in FIG.
As shown in FIG. 66, the value increases as the actual exhaust amount equivalent value Tqexhd decreases. This is because the smaller the displacement, the greater the response delay of the turbocharger, intake and exhaust,
The advance correction gain Gkvnt is increased in the smaller displacement area. When the variable nozzle 53 is moved to the closing side even if the actual exhaust amount equivalent value Tqexhd is the same (FIG. 66).
The reason why the table value is set to be larger than that in the case of moving to the open side (FIG. 65) is that moving to the close side makes it more difficult to increase the supercharging pressure, so that it is necessary to increase the correction gain.

The above table values TTCVNTO and TTCVNTC which determine the time constant equivalent value Tcvnt of the advance correction are the actual exhaust amount equivalent value Tqex as shown in FIGS.
The value becomes smaller as hd becomes smaller. This is because the smaller the displacement, the larger the time constant of the response delay of the supercharger / intake / exhaust, so the smaller the displacement, the larger the time constant (therefore, the time constant equivalent value Tcvn which is inversely related to the time constant).
t is smaller in the smaller displacement range). Even when the actual exhaust amount equivalent value Tqexhd is the same, the table value is smaller on the closing side than when the variable nozzle 53 is moved to the closing side (FIG. 68) than when the variable nozzle 53 is moved to the opening side (FIG. 67). Moving it has a larger time constant, so it is in line with this.

In step 11 of FIG. 63, the value Tcvnt corresponding to the time constant for advance correction and the target opening ratio Rvnt thus obtained are used.

[0204]

Cavnt = Rvnt × Tcvnt + Cav
nt _n-1 × (1-Tcvnt), where Cavnt _n-1 : the previous opening ratio Cavnt, and the expected opening ratio Cavnt is calculated, and from this value and the target opening ratio Rvnt, in step 12,

[0205]

[Equation 26] Avnt f = Gkvnt × Rvnt− (G
kvnt-1) × Cavnt _n−1 , where Cavnt _n−1 : the previous Cavnt, advance correction is performed, and the feedforward amount Avnt of the target opening ratio is calculated. Calculate f. Step 11, 1
The advance processing itself of 2 is basically the same as the advance processing shown in steps 4 and 5 in FIG.

In step 13 of FIG.

[0207]

Rvnt = Rvnt × TCVNT # + (1
−TCVNT #) × Rvnt _n−1 , where TCVNT #: the time constant of the response delay of the actuator 54, Rvnt _n−1 : the previous Rvnt, and the delay processing is performed on the target opening ratio Rvnt, and the actual processing is performed. The aperture ratio Rvnte is calculated. The time constant TCVNT # of the response delay of the actuator 54 itself is a constant value because it does not change whether the actuator 54 is moved to the open side or the closed side of the variable nozzle 53.

The actual aperture ratio Rvnte is calculated by calculating the PI gain aperture ratio correction coefficient Gkvavnt (step 7 in FIG. 72, FIG. 76) when setting a feedback gain, which will be described later, and by using the aperture ratio used in the reflection area of the aperture ratio learning value. It is used for calculating the reflection coefficient Gkvntlav (step 9 in FIG. 80, FIG. 83).

FIG. 69 (subroutine of step 5 in FIG. 41) shows an opening ratio correction value (opening ratio feedback amount A).
vnt fb and the opening ratio learning value Ravlr), and are executed at regular intervals (every 10 ms).
FIG. 69 is a subroutine for FIG. 41, but FIG.
Since a lower-order subroutine is prepared for the processing of each step of No. 9, the following subroutine will be mainly described.

FIG. 70 (subroutine of step 1 in FIG. 69) is for determining permission of feedback of the opening ratio.

First, in step 1, it is checked whether the aperture ratio is in the feedback area. As shown in FIG. 71, the feedback area (abbreviated as F / B area in the figure) is the remaining area excluding the low load and low flow rate area. The reason for excluding the region of low load and low flow rate is that in this region, even if the opening ratio of the variable nozzle 53 is changed, the fresh air amount can hardly be changed (that is, the sensitivity of the new air amount to the change in the opening ratio is low). Small). Thus, the stability of the intake air amount control (supercharging pressure control) in a region where the sensitivity of the exhaust amount to the change in the opening ratio is small can be improved.

A hysteresis area is provided at the boundary between the feedback area and the non-feedback area.

If the operating condition (Ne, load) is in the feedback region, the feedback region flag FVNFBNEQF is set to 1 in step 2 of FIG. 70, and if not, the flag is set to FVNFBNEQF = 0 in step 3.

In steps 4 to 6, the target EGR rate Meg
r, command opening ratio clamp flag FCLPVNDTY
FCLPVNDT which is the previous value (described later in FIG. 85)
Based on Y _n-1 and the air flow meter failure flag FDGMAF, it is determined whether the condition is a feedback permission condition for the opening ratio. Step 4: Megr> predetermined value KVNFBMEGR # (operating range of EGR) Step 5: FCLPVNDTY _n-1 = 1 (when clamping the command opening ratio Avnt) Step 6: FDGMAF = 1 ( When either of the above cases is satisfied, the process proceeds to step 8 where the feedback permission flag FVNFB is set to 0 to prohibit the feedback of the opening ratio, and otherwise, the process proceeds to step 7 and the flag FVNFB is set to 1. .

The reason why the feedback of the opening ratio is prohibited in the operation range of the EGR is as follows. Since the EGR valve opening is feedback-controlled in the EGR operating region, if the opening ratio of the variable nozzle 53 is also feedback-controlled in this region, hunting due to interference between the two feedback controls occurs.

The reason why the feedback is prohibited when the command opening ratio Avnt is clamped is as follows. The command opening ratio Avnt is clamped when the change in the command opening ratio Avnt converges as described later (see steps 2 and 9 in FIG. 85). Therefore,
This is because when the command opening ratio Avnt is clamped, there is no need to further feedback control the opening ratio. Prohibiting the feedback when the air flow meter fails is for fail-safe.

FIG. 72 (subroutine of step 2 in FIG. 69) is for setting a feedback gain used for feedback control of the opening ratio.

In step 1, the target intake air amount delay processing value tQacd, the actual intake air amount Qac, and the actual exhaust amount equivalent value Tq
exhd, the actual opening ratio Rvte is read.

In step 2, the feedback permission flag FVNFB is checked. If the flag FVNFB = 1 (feedback control of the opening ratio is performed), step 4
At

[0220]

[Equation 28] The target value (tQac) of the actual intake air amount Qac is obtained from the equation of Eqac0 = Qac-tQacd.
The control error Eqac0 from d) is calculated.

Here, in normal feedback control,
The target intake air amount tQac set according to the operating conditions is the target in the feedback control as it is. However, in this embodiment, since the dead time and the time constant of the response are both large control targets, the target intake air amount The control error Eqac0 is determined using the amount delay processing value tQacd as the target value in the feedback control (the same applies to step 4 in FIG. 77 described later).

On the other hand, when the flag FVNFB = 0 (no feedback control of the opening ratio is performed), the routine proceeds to step 3, where the control error Eqac0 = 0.

In step 5, a basic proportional gain value Gkvntp0 and a basic integral gain value Gkvnti0 are calculated from the control error Eqac0 by searching a table containing, for example, FIGS. 73 and 74. The dead zone is provided in FIGS. 73 and 74 in order to obtain control stability near the target value.

In steps 6 and 7 of FIG. 72, a table containing, for example, the contents shown in FIG.
kvqexh and Pv by searching a table containing the contents of FIG.
Calculate the aperture ratio correction coefficient Gkvavnt of the I gain,
In step 8

[0225]

Gkvntp = Gkvntp0 × Gkvqe
xh × Gkvavnt, Gkvnti = Gkvnti0 × Gkvqexh × Gk
vavnt, proportional gain Gkvntp, integral gain Gkv
Compute nti. As shown in FIG. 75, the displacement correction coefficient Gkvqexh of the PI gain is the actual displacement amount Tq.
The value becomes smaller as exhd becomes larger. This is because, even if the variation width of the opening ratio of the variable nozzle 53 is the same, the larger exhaust volume side is easier to approach the target than the small exhaust volume side (see FIG. 103). This is because it may be smaller than the quantity side.

As shown in FIG. 76, the aperture ratio correction coefficient Gkvavnt of the PI gain is a value that becomes smaller as the actual aperture ratio Rvnt becomes smaller. Since the supercharging pressure is higher on the side where the variable nozzle 53 is closed (the side where the actual opening ratio Rvnt is smaller) than on the side where the variable nozzle 53 is open (the side where the actual opening ratio Rvnt is larger), the variable nozzle 5 is closed.
Since the fresh air amount changes more sensitively by slightly changing the opening ratio of the variable nozzle 53 on the side where the variable nozzle 53 is closed (see FIG. 104), the correction coefficient increases as the variable nozzle 53 is closed. Is required to be smaller.

A more accurate view of FIGS. 75 and 76 is shown in FIGS.

FIG. 77 (subroutine of step 3 in FIG. 69) shows a feedback amount Avnt of the opening ratio. This is for calculating fb.

In steps 1 to 4, steps 1 to 4 in FIG.
After calculating the control error Eqac according to the value of the feedback permission flag FVNFB in the same manner as in step 4,

[0230]

## EQU30 ## The proportional correction value Ravfbp is calculated by the following equation: Ravfbp = Gkvntp × Eqac.
so

[0231]

Ravfbi = Ravfbi _n-1 + Gkvn
ti × Eqac−dTravrr, where Ravfbin ₋₁ : the previous Ravfbi, dTravrr: the change in the opening ratio learning value, and the integral correction value Ravfbi is calculated according to the following equation. A
vnt It is calculated as fb.

Here, up to the second term on the right side of Expression 31 is a normal learning operation. In the present embodiment, a third term on the right side is newly added, and Ravfbin ₋₁ +
The opening ratio learning value Travl is obtained from Gkvti × Eqac.
dTravlr, which is the change in r from the previous time to the present time, is subtracted (the calculation cycle of the integral correction value and the aperture ratio learning value is the same at 10 ms). Opening ratio learning value Rav
lr is updated based on the integral correction value Ravfbi as described later (see steps 2 to 6 in FIG. 80). Thus, all or a part of the integral correction value Ravfbi is replaced with the opening ratio learning value Ravlr. The difference from the integral correction value in the next cycle by the amount replaced with the opening ratio learning value Ravlr is that the total opening ratio correction value (= Avnt fb + Travl
This is because r) is kept constant during the learning of the aperture ratio.

FIG. 78 (subroutine of step 4 in FIG. 69) shows a learning permission flag FVNLR used for opening ratio learning.
It is for setting. In step 1, target EGR
Rate Megr, atmospheric pressure Pa, water temperature Tw, control error Eqac
0 (obtained from FIG. 72), the target intake air amount delay processing value tQacd is read.

The determination of the learning permission condition is performed by checking the contents of steps 2 to 9 one by one. When all the items are satisfied, the opening ratio learning is permitted. Prohibit learning. That is, Step 2: in the learning area, Step 3: Feedback permission flag FVNFB = 1
Step 4: Megr is equal to or less than a predetermined value KVNLLRMEGR # (that is, an EGR non-operating region). Step 5: Pa is equal to or more than a predetermined value KVNLRPA # (not high altitude). Step 6: Tw is a predetermined value KVNLRTW #. Step 7: Absolute value of ratio of Eqac0 to tQacd is equal to or less than predetermined value KVNLREQA # (no disturbance is present). Step 8: Overboost determination flag FOVRBS
T = 0 and over-boost release transition flag FCLRO
B = 0, Step 9: Air flow meter failure determination flag FDGM
When all of AF = 0 are satisfied, the learning permission flag FVNLR is set to 1 in step 10 to permit the opening ratio learning, otherwise, the process proceeds to step 11, and the learning permission flag is set to prohibit the opening ratio learning. It is assumed that FVNLR = 0.

The reason why the ratio between the control error Eqac0 and the target (tQacd) is adopted in step 7 is that the ratio of the control error to the target is desired to be constant even if the target changes. In brief, the absolute value of the control error may be compared with a predetermined value.

As shown in FIG. 79, a predetermined area is previously provided for the target fuel injection amount Qsol as the engine load and the engine speed Ne as the learning area. However, FIG. 79 shows only a model, and is actually provided in a part of the feedback region of the aperture ratio as shown in FIG. A desirable condition for the learning region is that the sensitivity of the opening ratio learning is good (the amount of fresh air changes greatly with respect to the opening ratio).

FIG. 80 (subroutine of step 5 in FIG. 69) is for calculating the opening ratio learning value Ravlr.

In step 1, the aperture ratio learning value Ravl stored in the memory EEPROM (non-volatile RAM)
r is read, and Ravlr, which is the previous aperture ratio learning value
After storing as z, the learning permission flag F
Look at VNLR. When the learning permission flag FVNLR = 1, the process proceeds to steps 3 to 6 to calculate (update) the opening ratio learning value in the same manner as in the normal learning method. That is, in Steps 3 and 4, the integral correction value Ravfbi as the feedback amount of the opening ratio is put into the opening ratio learning initial value Ravlr0, and learning is performed by searching a map including, for example, FIG. 81 from the operating conditions (Ne, Qsol). Speed Kvn
tlrn is calculated, and these opening ratio learning initial values Ravl are calculated.
Using r0 and learning speed Kvntrln, in step 5,

[0239]

Ravlr = Ravlr0 × Kvntrln
+ (1−Kvntrln) × Ravrln ₋₁ , where Ravlr: aperture ratio learning value after updating, Ravlrn ₋₁ : aperture ratio learning value before updating (= learning value read value), and weighted averaging process The updated aperture ratio learning value is stored in the memory EEPROM in step 6 (the updated value is overwritten with the updated value). Thereby, for example, the learning speed Kvntrln is 1 which is the maximum.
If the learning speed Kvntrln is smaller than 1, the integral correction value Ravfbi is equal to
A part of avfbi is replaced with an opening ratio learning value Ravlr.

As shown in FIG. 81, the learning speed Kvntl
rn is a value that increases as Qsol and Ne increase (however, Kvntrln ≦ 1). this is,
In response to the higher Qsol and Ne, the higher the sensitivity (the greater the change in fresh air amount with respect to the opening ratio),
This is because the opening ratio learning is completed earlier as ol and Ne increase.

On the other hand, when the learning permission flag FVNLR = 0, it is out of the learning area, so that the aperture ratio learning value cannot be calculated (updated).

In this case, however, in this embodiment, steps 7 to 10 in FIG. 80 are newly added, and the opening ratio learning value for reflecting the opening ratio learning value Ravlr obtained in the learning region outside the learning region is calculated. I do. However, the opening ratio learning value calculated outside the learning region also uses the same Ravlr as the opening ratio learning value updated in the learning region as a symbol of the learning value. The area in which the opening ratio learning value for reflecting the opening ratio learning value is calculated is the region excluding the learning region in the opening ratio feedback region.

More specifically, in step 7 of FIG. 80, the previous opening ratio learning value Ravrln _-1 (the opening ratio learning value stored in the memory EEPROM immediately before executing the processing in step 7) is used as the opening ratio. It is set to the learning initial value Ravlr0. In steps 8 and 9, the operating conditions (Qsol, N
For example, by searching a map having the contents shown in FIG. 82 from e), the operating area reflection coefficient Gkvn of the opening ratio learning value is obtained.
For example, a table containing the contents shown in FIG. 83 is retrieved from tlnq and the actual opening ratio Rvnte (actual boost pressure operation value) to obtain the opening ratio reflection coefficient G of the opening ratio learning value.
kvntlav is calculated, and in step 10 of FIG.

[0244]

Ravlr = Ravlr0 × Gkvntln
The opening ratio learning value Ravlr in the reflection area is obtained by the equation of q × Gkvntlav.
Is calculated.

Since the aperture ratio learning value obtained by equation 33 is used only to reflect the aperture ratio learning value outside the learning region, unlike the aperture ratio learning value updated in the learning region, the memory EEPROM is used. Is not stored (there is no step corresponding to step 6).

As shown in FIG. 82, the operating area reflection coefficient G
kvntlnq is a value that becomes smaller than 1 as it goes out of the learning region (1 being the maximum in the learning region). This is because it is considered that a learning value that is almost equal to the learning region is sufficient near the learning region, but if the learning ratio is the same as the learning region even in a region that largely deviates from the learning region, the true opening ratio is obtained. Since the deviation from the learning value is too large and there is a possibility that an over-boost occurs, the reflection coefficient is set to be smaller as the distance from the learning region is exceeded in order to avoid this.

As shown in FIG. 83, the aperture ratio reflection coefficient Gkvn
tlav is a value that becomes smaller in a region where the actual aperture ratio Rvnte is small. This is a characteristic in which the characteristic of the fresh air amount with respect to the opening ratio is substantially similar to the inverse proportional characteristic. Even in a region where the opening ratio is small (a region where the boost pressure rises sharply), a region where the opening ratio is large (the charging pressure Given the same aperture ratio learning value as that of the region with a poor rise), the aperture ratio learning value is too large and may cause over-boost. Therefore, the reflection coefficient is smaller in the region with the smaller aperture ratio than in the region with the larger aperture ratio. Is given.

In step 11 of FIG. 80, the opening ratio learning value Ravlr obtained in this manner and the previous opening ratio learning value Ravlrz are used.

[0249]

The change amount of the opening ratio learning value (operation period 10 ms) is calculated by the equation dTavlr = Ravlr-Ravlrz.
Calculate dTravlr). The change dTravlr is the feedback amount Avn of the opening ratio.
t It is used for calculating fb (see step 6 in FIG. 77). Therefore, in the present embodiment, the total aperture ratio correction value is kept constant not only in the learning region but also in the reflection region.

The description of FIG. 69 has been completed.

Next, FIG. 84 (subroutine of step 6 in FIG. 41) is for calculating the final command opening ratio Trvnt.

In step 1, the feedforward amount Avnt of the target opening ratio f, feedback amount A of aperture ratio
vnt fb, the opening ratio learning value Ravlr is read,
The value obtained by adding these in step 2 is calculated as the command opening ratio Avnt.

In step 3, advance processing is performed to compensate for the dynamics of the actuator 54. this is,
This is because, when the actuator 54 is a pressure actuator, there is a non-negligible response delay unlike the case of a step motor. This actuator 5
The advance processing of No. 4 will be described with reference to FIG.

In FIG. 85 (subroutine of step 3 in FIG. 84), the command opening ratio Avnt (FIG.
4), and the absolute value of the difference between this value and the previous command opening ratio Avnt _n-1 is compared with a predetermined value EPSDTY #. Avnt and Avnt
_If the absolute value of the difference from _n-1 is equal to or greater than the predetermined value EPSDTY # (the command opening ratio is in the process of changing), the clamp flag FCLPVNDTY of the command opening ratio is set to 0 in step 3, and Avnt and Avnt _n-1 Is the predetermined value E
If it is less than PSDTY #, then from step 2 to step 9
To the command opening ratio clamp flag FCLPVND
It is assumed that TY = 1.

The clamp flag FCLPVNDTY is newly introduced in the present embodiment, and is used to inhibit feedback control of the opening ratio (see FIG. 70).
That is, when the clamp flag FCLPVNDTY = 1, the feedback control is prohibited from the next time. This is because it is determined that the change in the command opening ratio Avnt has converged from the clamp flag FCLPVNDTY = 1 (that is, the change in the command opening ratio Avnt has become less than the predetermined value). In this case, the opening ratio is further feedback-controlled. It is not necessary.

Step 3 Clamp flag FCLPVND
After setting TY = 0, the process proceeds to step 4 and subsequent steps.

In step 4, the command opening ratio Avnt and the previous
Avnt which is the command opening ratio of times_{n- 1}Compare. Av
nt> Avnt_n-1(If the actuator 54 is
When moving to the open side of the changing nozzle 53), step
Proceed to steps 5 and 6 to actuate the predetermined value GKVACTP #
Data gain correction gain Gkact, predetermined value TCVACTP #
With the time constant equivalent value Tact of the actuator advance correction.
And, in contrast, Avnt <Avnt_n-1so
At some point (actuator 54 closes variable nozzle 53
Move to steps 7 and 8)
The constant value GKVACTN # is set to the actuator advance correction gain.
Gkact, a predetermined value TCVACTN # is used as an actuator
It is set as a time constant equivalent value Tcact for advance correction.

The actuator advance correction gain Gkact and the time constant equivalent value Tcact of the actuator advance correction differ between when the actuator 54 is moving to the open side and when it is moving to the close side of the variable nozzle 53.
GKVACTP # <GKVACTN #, TCVACTP
# <TCVACTN #. This is because, when the actuator 54 is moved to the closing side of the variable nozzle 53, it is necessary to resist the exhaust pressure.
This is because it is necessary to increase t and reduce the time constant (increase the time constant equivalent value Tcact, which is inversely related to the time constant).

On the other hand, in step 9, the clamp flag FCL
After setting PVNDTY = 1, the process proceeds to steps 10 and 11 to secure the stability of the pressure actuator advance processing, and the previous actuator advance correction gain and the time constant equivalent value of the actuator advance correction are maintained.

In step 12, using the time constant equivalent value Tcact and the command opening ratio Avnt thus obtained for the actuator advancement correction,

[0261]

[Expression 35] Cvact = Avnt × Tcact + Cva
ct _n-1 × (1−Tcact), where Cvact _{n-1 is the} expected opening ratio Cvact by the following equation:

[0262]

Tvnt = Gkact × Avnt− (Gk
act-1) × Cvact _n−1 , where Cvact _n−1 : the previous Cvact, advance correction is performed, and the final command opening ratio Trvn
Calculate t. The advance processing itself in steps 12 and 13 is basically the same as the advance processing shown in steps 4 and 5 in FIG.

As described above, in the flow of FIG. 85, the advance processing is performed in consideration of only the response delay of the actuator 54 (the advance processing in consideration of only the response delay of the supercharger / intake / exhaust is described above with reference to FIG. 63).

After calculating the final command opening ratio Trvnt, which is the value after performing the advance processing in consideration of the response delay of the actuator 54 itself, returning to FIG. 84, in step 4, the final command opening ratio Trvnt is calculated from this final command opening ratio Trvnt. Table containing FIG. 86 (linearized table)
To obtain the command opening ratio linearization processing value Rat
Set dty.

This linearization processing is necessary when the command signal to the actuator has a non-linear characteristic with respect to the opening ratio (or opening area) as shown in FIG.

FIG. 87 (subroutine of step 7 in FIG. 41) is for setting a control command duty value Dtyvnt which is an ON duty value (hereinafter simply referred to as “duty value”) given to the pressure control valve 56. First, in step 1, the engine rotation speed Ne, the target fuel injection amount Qsol, the command opening ratio linearization processing value Ratdty,
Time constant equivalent value Tact of actuator 54, water temperature T
Read w.

In step 2, a duty selection signal flag is set. This flag setting will be described with reference to the flow of FIG. In FIG. 88, the command opening ratio Avnt and the time constant equivalent value Tcact of the actuator 54 are read in Step 1, and from these, in Step 2,

[0268]

(37) Addlyvnt = Avnt × Tact + A
dlyvnt_n-1× (1-Tcact), where Addlyvnt_n-1: Delay processing is performed by the formula of the previous Adlyvnt, and the expected opening ratio Adlyvn
t, this value and M of the previous expected opening ratio (however,
M is an integer constant) Adlyvnt is the value before _nMWhen
Are compared in step 3.

When Adlyvnt ≧ Adlyvnt _nM (when increasing or in a steady state), the operation direction command flag fvnt is set to 1 in step 4 to indicate that it is increasing or in a steady state, and otherwise, step 5 is performed. To set the operation direction command flag fvnt = 0. In step 6, Adlyvnt and Adlyvnt _nM are compared in order to separate the case of a further increase from the steady state. If Adlyvnt = Adlyvnt _nM , the duty holding flag fvnt2 =
In other cases, the duty holding flag fvnt2 is set to 0 in step S8.

Thus, the two flags fvnt, fvnt
When the setting of vnt2 is completed, the process returns to step 3 of FIG. Calculate t.
This calculation will be described with reference to the flow of FIG.

In FIG. 89, the engine speed Ne, the target fuel injection amount Qsol, and the water temperature Tw are read in step 1, and a map having the contents shown in FIG. 90 is searched in step 2 from Ne and Qsol. The exhaust temperature Texhb is calculated. Where Te
xhb is the exhaust gas temperature after the warm-up is completed. On the other hand, if the exhaust temperature is different from the exhaust temperature after the warm-up is completed during the warm-up, the water temperature correction coefficient of the exhaust temperature is searched in step 3 by searching a table containing, for example, FIG. Ktexh tw, and calculates this value in step 4
At the exhaust gas temperature T
The calculation is performed as exhi.

In step 5, the exhaust temperature Texhi is

[0273]

Texhdly = Texhi × KEXH # +
Texhdly _n-1 × (1-KEXH #), where KEXH #: a constant, Texhdly _n-1 : the value obtained by performing the delay processing according to the expression of the previous Texhdly, and the actual exhaust temperature Texhd
Calculate as ly. This is to perform delay processing for thermal inertia.

In step 6, the basic exhaust gas temperature Texhb
The difference dTexh from this actual exhaust gas temperature Texhdly is calculated.
Then, from the difference dTexh in step 7, for example,
By searching a table having the contents shown in FIG.
Temperature correction amount Dty of the duty value Calculate t. Step
Maps 6 and 7 are maps used for hysteresis described below.
(Duty h p, Duty h n, Duty l
p, Duty l n map) after completion of warm-up
Keep in mind that you need to set
DTexh).
Note that the temperature correction amount Dty Correction by t is the ambient temperature
When using an actuator with temperature characteristics due to
(See FIG. 93).

Thus, the temperature correction amount Dty Upon completion of the calculation of t, the process returns to the step 4 of FIG.

Steps 4 to 9 in FIG. 87 perform a hysteresis process. This processing will be described earlier with reference to FIG. 98. This is because the command opening ratio linearization processing value Ra
When dtty is increasing, the upper characteristic (Duty)
l p is the command signal for fully opening the variable nozzle, Duty h
p is a command signal when the variable nozzle is fully closed, whereas the command opening ratio linearization processing value Ratd
When ty is decreasing, another lower characteristic (Duty) l n is the command signal for fully opening the variable nozzle, D
uty The h n is to use a linear characteristic) to the command signal of the variable nozzle is fully closed. In addition, Ratdty is 1
There is a region where the two characteristics are turned upside down, but this region is not actually used.

Returning to FIG. 87, in step 4, the flag fvn
Look at t1. When fvnt = 1 (that is, when the opening ratio is increasing or 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) containing FIG. l p map) to obtain a duty value Duty when the variable nozzle is fully closed. h and duty value when the variable nozzle is fully open 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 the contents shown in FIG. 96 is used. h n map) and a map (Duty) containing FIG. l n map) to obtain the duty value Duty when the variable nozzle is fully closed. h and duty value when the variable nozzle is fully open Set l respectively.

The duty value Duty at the time when the variable nozzle is fully closed set in this way. h, Duty value when variable nozzle is fully open In step 9 using l and the above-described command opening ratio linearization processing value Ratdty,

[0279]

[Formula 39] Dty h = (Duty h-Duty
l) × Rattdy + Duty l + Dty The command duty value is calculated based on the linear interpolation calculation using the formula t.
Value Dty Calculate h. In other words, used for linear interpolation calculation
The characteristic of the straight line is changed, the command opening ratio linearization processing value is increasing
At or in steady state and command opening ratio linear
(When the hysteresis value is decreasing)
Cis processing), the command opening ratio linearization processing value
Even if they are the same, the command opening ratio linearization processing value tends to increase
(Or steady state)
Command duty value basic value Dty h is large
Become.

At step 10, another flag fvn
Look at t2. When fvnt2 = 1 (that is, there is no change in the command opening ratio linearization processing value), the process proceeds to step 11, where D is the previous control command duty value (to be described later).
tyvnt _n-1 is set in the normal command duty value Dtyv (duty value is held), and when fvnt2 = 0 (that is, the opening ratio is decreasing), step 12 is executed.
To the latest operation value Dty Let h be Dtyv.

At step 13, an operation confirmation control process is performed. This processing will be described with reference to the flow of FIG.
In FIG. 99, in step 1, the normal command duty value D
tyv, engine speed Ne, target fuel injection amount Qso
1. Read the water temperature Tw.

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

In step 7, the operation check control counter is compared with predetermined values CTRDIZH # and CTRDIZL #. Here, the predetermined values CTRDIZL #, CTRDIZH
# Defines the lower limit and the upper limit of the operation check control counter, respectively. CTRDIZL # is, for example, about 2 seconds, and CTRDIZH # is, for example, about 7 seconds. Therefore, from the timing when the operation check control counter matches the lower limit CTRDIZL #, the CTR whose operation check control counter is the upper limit
While it is less than DIZH #, the routine proceeds to step 9, where an 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 flowchart of FIG. In FIG. 100, in step 1, the operation confirmation control counter Ctrdiz,
The engine rotation speed Ne is read, and a control pattern Duty is retrieved in step 2 by searching a table having, for example, the contents shown in FIG. 101 from Ctrdiz-CTRDIZL # (≧ 0). Set pu. This is to move the variable nozzle 53 between the fully closed position and the fully opened position in a short cycle.

In step S3, a table containing, for example, the contents shown in FIG. 102 is searched from the engine speed Ne to obtain the duty value Duty. p ne, and this Duty p ne in step 4 the above control pattern Duty The value multiplied by pu is calculated as the control command duty value Dtyvnt. As shown in FIG.
Control pattern Duty Duty value Du multiplied by pu
ty p ne is a value corresponding to the engine rotation speed Ne. This is because the variable nozzle 5 depends on the engine speed.
It is assumed that the duty command values for confirming the opening / closing operation of No. 3 are different. For example, the variable nozzle 53 needs to be closed against the exhaust pressure, but the exhaust pressure increases as the rotation speed increases, and accordingly the duty command value is increased. Further, on the high rotation speed side, the value is reduced so as not to be adversely affected by this control.

Returning to FIG. 99, when the operation confirmation control counter is less than CTRDIZL # as the lower limit, the process proceeds from step 8 to step 15, where the normal command duty value Dtyv is set as the control command duty value Dtyvnt.

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

If the operation confirmation control counter has not become immediately after the count becomes higher than or equal to CTRDIZH # as the upper limit,
The process proceeds from step 10 to step 14, where the operation confirmation control counter Ctrdiz = 0 is set 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 #
The operation confirmation control is prohibited when Ne is equal to or greater than (not during fuel cut), when Ne is equal to or greater than a predetermined value NEDIZ # (high rotation range), and when Tw is equal to or greater than a predetermined value TWDZ # (after completion of warm-up). Therefore, the process proceeds from Steps 2, 3, and 4 to Step 13, sets the flag fdiz = 0, and executes the processing of Steps 14 and 15.

As described above, when the operation of the actuator 54 is unstable, particularly when the temperature is low, the operation confirmation control is performed, whereby the movement of the variable nozzle 53 becomes smooth, and the operation of the actuator 54 is made more reliable. Can be.

Thus, the description of FIG. 41 is completed.

Here, the operation of the two embodiments will be described.

In the case of the prior application apparatus in which advance processing is performed on the target opening ratio Rvnt of the variable nozzle 53 in consideration of the response delay of the supercharger / intake / exhaust, the target suction set in accordance with the operation conditions. It is physically impossible to follow the actual intake air amount Qac without delay with respect to the air amount tQac by feedback control, and the variable nozzle 53 is closed on the change side of the operation range (the boost pressure rise side). When the actuator 54 is moved to the next position, an over-boost occurs (see FIG. 108).

On the other hand, according to the present embodiment, the target intake air amount tQac set according to the operating conditions is the target intake air amount which is a value obtained by performing a delay process corresponding to the delay of the intake system. Since the amount delay processing value tQacd is set as the target value in the feedback control, the area between tQacd as the target value in the new feedback control and the actual intake air amount Qac performs the conventional feedback control on the prior application. In this case (see the bottom part of FIG. 108), the value becomes smaller (see the bottom part of FIG. 109). Accordingly, the integral correction value Ravfbi calculated based on the difference between tQacd and Qac does not increase so much that the feedback gain is reduced. (Integral gain basic value Gkvn
ti0) can be increased. As a result, in this embodiment, no overshoot occurs, and the response value converges to the target value (tQacd) with good response (FIG. 10).
9 See the dot-dash line at the bottom.) That is, in the case of the present embodiment, the target value in the feedback control is set within the operable range of the actuator 54 even for a control object having a large dead time and a response time constant. Even if the dead time and the response time constant are both large, such as the order and the response time constant being on the order of several seconds, it is possible to achieve both the stability and the responsiveness during the transition of the supercharging pressure control.

According to FIG. 103 (experimental result) showing the relationship between the displacement [kg / s] and the opening ratio of the variable nozzle 53 when the engine rotation speed and the load are changed (the same rotation speed is assumed to be the same). On the other hand, the presence of a plurality of lines is due to the difference in load. At a low rotation speed, the change in the exhaust amount with respect to the opening ratio is small, but the change in the exhaust amount increases as the rotation speed and the load increase. As shown in FIG. 104, when the closed side and the open side of the variable nozzle 53 are compared, when the displacement is the same, the change in the actual intake air amount Qac is slow with respect to the opening ratio on the open side, It has high sensitivity on the closed side. Therefore, the actual displacement amount Tq
exhd, PI gain displacement correction coefficient Gkvqe
xh and the PI gain opening ratio correction coefficient Gkvavnt are set in accordance with the actual opening ratio Rvnte, and the integral correction gain basic value Gkvnti0 is corrected by the PI gain exhaust amount correction coefficient Gkvqexh and the PI gain opening ratio correction coefficient Gkvavnt ( By correcting the feedback gain according to the displacement and the opening ratio), an appropriate feedback gain can be given in the entire operation range even if the displacement and the opening ratio are different.

In the low load and low flow rate region, the feedback control is prohibited by setting this as a non-feedback region. Therefore, the sensitivity of the fresh air amount to a change in the opening ratio (a change in the command value given to the actuator 54) is reduced. The stability of intake air amount control (supercharging pressure control) in a small region can be improved.

Further, in the case of the present embodiment in which EGR control is performed in addition to supercharging pressure control, if the intake pressure and the exhaust pressure fluctuate due to control instability on the supercharger side in the EGR operating range, the EG
Although the R amount fluctuates, which also increases the NOx emission amount, according to the present embodiment, the intake air system tQac set according to the operating conditions as described above differs from the intake system. By performing feedback control using a target intake air amount delay processing value tQacd, which is a value obtained by performing a delay processing corresponding to the delay amount, as a target value in the feedback control, control instability on the turbocharger side can be avoided. At the same time in the region where the feedback control is performed.
Even if the control is performed, the NOx emission amount does not deteriorate.

Also, the cylinder intake gas amount Qcyl and the actual exhaust amount Qexh vary due to manufacturing variations of the air flow meter 39 (means for detecting the intake air amount) and the actuator 54 (actuator for driving the supercharging pressure variable mechanism). As described above with reference to FIG. 110, there is a possibility that overboost occurs beyond the supercharging limit. According to the present embodiment, the actual intake air amount Qac and the actual EGR amount Q
ec and the over-boost determination intake gas amount TQcyl that changes according to the actual exhaust amount Qexh.
The result of the comparison shows that Qcyl is equal to or greater than TQcyl,
When it is less than cyl, it is determined that overboost does not occur, so that it is possible to reliably prevent overboost from occurring due to manufacturing variations of the air flow meter 39, the actuator 54, and the like.

FIG. 109 shows a case where Qcyl does not exceed TQcyl when the supercharging pressure is changed to a higher side, and FIG. 112 shows a case where Qcyl exceeds TQcyl. I will explain it. In addition,
Since the operation and effect in this case are the same as those of the first and second embodiments, the case of the first embodiment will be mainly described.

When the supercharging pressure is changed to a higher side in accordance with a change in the operating conditions, while Qcyl is less than TQcyl (that is, between t1 and t2), the target opening ratio basic value in normal operation is reduced. The target opening ratio basic value Rvnt0 is calculated by searching the map (FIG. 56) (steps 5 and 8 in FIG. 54), whereas Qcyl is TQc.
From the timing of t2 when yl or more, the map of the target opening ratio basic value during normal operation (FIG. 56) to the map of the target opening ratio basic value during overboost suppression (FIG. 55)
(Steps 5 and 7 in FIG. 54), and even if the set intake amount equivalent value tQas0 and the set EGR amount equivalent value Qes0 do not substantially change before and after the map change, the target opening ratio after the map change is larger than before the change. The basic value becomes Rvnt0. That is, the command duty value Dtyvnt calculated based on the target opening ratio basic value decreases stepwise at t2, which is the timing of map switching (since the command duty value decreases when the opening ratio increases, the reverse). Since the supercharging pressure is reduced, the occurrence of overboost is prevented (see the thick solid line in the fourth row in FIG. 112).

In this case, the greater the change in each of the target fuel injection amount Qsol as the engine load, the engine rotation speed Ne, and the actual intake air amount Qac, or the greater the deviation of the cylinder intake gas amount Qcyl from the determination value TQcyl. Over boost is likely to occur. Therefore, the over-boost suppression time TTMROB (between t2 and t3), which is the period for selecting the map for over-boost suppression, is used when the variation of each of these three factors Qsol, Ne and Qac is small, or the cylinder intake gas amount Qcyl is determined. Value TQ
When matching is performed when the deviation from cyl is small, when the amount of change between these three is large, or when Tcc of Qcyl is large,
When the deviation from yl is large, the overboost suppression time is too short to cause overboost. On the other hand, when the overboost suppression time has a large variation between these three factors, or the deviation of Qcyl from TQcyl is large. In the case where matching is performed in the case, when the change amount of these three is small or when the deviation amount of Qcyl from TQcyl is small, the overboost suppression time is too long and the unnecessary boost pressure is suppressed. According to the embodiment, Qso
Change amount DQSO of l, Ne and Qac per predetermined time
Since L, DNE, DQAC, and Qcyl-TQcyl are larger, the overboost suppression time (the period during which the supercharging pressure is suppressed) is set longer (FIGS. 48 and 49,
50), such a situation can be avoided.

In FIG. 112, the map of the target opening ratio basic value is switched from the one at the time of the overboost suppression to the one at the time of the normal operation so as to return to the normal operation at the timing t3 when the overboost suppression is finished. Then
This time, the command duty value Dtyvnt increases stepwise. Since this means that the actuator 54 is quickly moved to the side where the boost pressure rises, there is a possibility that the operation of the actuator 54 causes overboost. In this case, according to the present embodiment, the target opening ratio becomes smaller with a first-order lag than the timing of t3 (steps 11 and 13 in FIG. 54). As a result, the command duty value Dtyvnt slowly increases (the movement of the actuator 54 is delayed) (see the thick solid line in the fourth row in FIG. 112). It is possible to avoid over-boost caused by quickly moving the actuator 54 to the side where the pressure rises.

[0303] Also, since the exhaust amount increases in accordance with the differential pressure between the exhaust pressure and the atmospheric pressure, the exhaust amount increases under conditions of low atmospheric pressure such as high altitude, and the work performed by the turbocharger accordingly. Large (over-boost is likely to occur). Accordingly, the over-boost release transition time TTMCLR is used for a condition such as lowland where the atmospheric pressure is not low.
By matching OB (between t3 and t4),
If the over-boost release transition time is too short under conditions where the atmospheric pressure is low, over-boost will occur.On the other hand, if the over-boost release transition time is matched for low atmospheric pressure conditions such as high altitude, The over-boost release transition time is unnecessarily too long, but the over-boost release transition time (the period during which the movement of the actuator for driving the supercharging pressure variable mechanism is delayed) is set according to the atmospheric pressure Pa. According to the embodiment (FIGS. 51 and 52), such a situation can be avoided.

Also, since over-boost is likely to occur when the exhaust amount exceeds a predetermined value, if the over-boost release transition time is matched under the condition that the exhaust amount does not exceed the predetermined value, the exhaust amount exceeds the predetermined value. Under the condition, the over-boost release transition time is too short and over-boost occurs.On the contrary, if the over-boost release transition time is matched under the condition that the displacement exceeds the predetermined value, the over-boost does not exceed the prescribed value. Although the release transition time becomes unnecessarily long, according to the present embodiment in which the overboost release transition time is set according to the actual displacement Qexh (FIGS. 51 and 53), such a situation can be avoided.

In the embodiment, the case where the actual EGR amount Qec and the actual exhaust amount Qexh are calculated has been described.
The amount Qec and the actual exhaust amount Qexh may be actually detected.

In this embodiment, the means for determining whether or not overboost occurs is a means for calculating the sum of the actual EGR amount Qec and the actual intake air amount Qac as a cylinder intake gas amount Qcyl, and a means for calculating the actual exhaust amount Qexh. Overboost determination means for setting the intake gas amount TQcyl (determination value) and means for determining that overboost occurs when Qcyl is equal to or greater than TQcyl, and that no overboost occurs when Qcyl is less than TQcyl. As described above, in the case of the type that employs the supercharging pressure itself, the means for determining whether or not overboost occurs is a means for setting the determination value TPa in accordance with the actual displacement Qexh, If overboost occurs at or above the judgment value TPa, the actual supercharging pressure becomes
If it is less than the above, a means for determining that overboost does not occur may be used.

In the embodiment, the over-boost suppression time T
TMROB to DQSOL, DNE, DQAC, Qcyl
−TQcyl has been described (FIG. 4
9, see FIG. 50), and may be set in accordance with the actual displacement Qexh (at this time, the actual displacement Qe).
The larger xh, the longer the overboost suppression time.)

In the embodiment, the case where the operation target value of the supercharger is the target opening ratio Rvnt has been described. However, the present invention is not limited to this, and the target opening area may be used.

In the embodiment, the case where the target intake air amount tQac is calculated has been described. However, the target supercharging pressure may be used instead of the target intake air amount tQac.

[0310] In the embodiment, the turbocharger in which the supercharging pressure changes according to the opening ratio of the variable nozzle has been described. However, the present invention is not limited to this. That is, in the exhaust turbine, if the area through which the gas passes is changed, the supercharging pressure changes. Therefore, the supercharging pressure changes even if the opening ratio of the scroll or the diffuser is changed in addition to the nozzle. Since these can eventually change the geometry of the exhaust turbine, they are variable geometry turbochargers (Variable Geometries).
c Turbocharger). The present invention has application to such variable geometric turbochargers. Further, the present invention is also applicable to a turbocharger having a constant capacity and having a wastegate valve. In the variable geometric turbocharger, for example, the target value of the opening area or the opening area equivalent value of the turbocharger, and the target value of the constant-capacity turbocharger provided with the wastegate valve, for example, the target value of the valve opening thereof are set as the turbocharger. Becomes the operation target value.

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

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a common rail type 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 the 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 per cylinder.

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

FIG. 9 is a flowchart for explaining detection of an 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 illustrating a complete explosion determination.

FIG. 15 is a flowchart illustrating a calculation of a target intake air amount according to the first embodiment.

FIG. 16 is a flowchart illustrating a calculation of a target intake air amount according to 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 corresponding to volume 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 operated.

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

FIG. 25 is a flowchart for explaining calculation of two feedback correction coefficients and a learning correction coefficient of EGR control.

FIG. 26 is a flowchart illustrating the setting of a feedback permission flag.

FIG. 27 is a flowchart illustrating the setting of a learning value reflection permission flag.

FIG. 28 is a flowchart for explaining setting of a learning permission flag.

FIG. 29 is a flowchart illustrating the calculation of an EGR amount feedback correction coefficient.

FIG. 30 is a map characteristic diagram of a correction gain of the EGR flow rate.

FIG. 31 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 32 is a flowchart for explaining the calculation of an EGR flow velocity feedback correction coefficient.

FIG. 33 is a map characteristic diagram of an EGR flow velocity correction gain.

FIG. 34 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 35 is a table showing a learning map of an error ratio learning value.

FIG. 36 is a flowchart illustrating updating of a learning value.

FIG. 37 is a map characteristic diagram of learning speed.

FIG. 38 is a flowchart for explaining the calculation of the EGR flow velocity.

FIG. 39 is a map characteristic diagram of the EGR flow velocity.

FIG. 40 is a flowchart for explaining the calculation of the EGR valve opening area.

FIG. 41 is a flowchart for explaining calculation of a control command duty value given to the pressure control valve.

FIG. 42 is a flowchart illustrating the setting of an overboost determination flag.

FIG. 43 is a model diagram showing a change in an overboost determination flag when the accelerator pedal is rapidly depressed.

FIG. 44 is a map characteristic diagram of an overboost determination intake gas amount.

FIG. 45 is an efficiency characteristic diagram of a turbocharger.

FIG. 46 is a flowchart for explaining setting of an over-boost release transition flag.

FIG. 47 is a waveform chart of an overboost determination flag and an overboost release transition flag.

FIG. 48 is a flowchart illustrating the calculation of the overboost suppression time.

FIG. 49 is a map characteristic diagram of an overboost control time basic value.

FIG. 50 is a map characteristic diagram of an overboost control time correction coefficient.

FIG. 51 is a flowchart for explaining the calculation of the overboost release transition time.

FIG. 52 is a table characteristic diagram of an overboost release transition time basic value.

FIG. 53 is a table characteristic diagram of an overboost release transition time correction coefficient.

FIG. 54 is a flowchart for explaining the calculation of a target opening ratio according to the first embodiment;

FIG. 55 is a map characteristic diagram of a target opening ratio in an EGR operation region and overboost suppression.

FIG. 56 is a map characteristic diagram of an EGR operating region and a target opening ratio during normal operation.

FIG. 57 is a map characteristic diagram of a target opening ratio in an EGR non-operating region and at the time of suppressing overboost.

FIG. 58 is a map characteristic diagram of a target opening ratio in a non-operating region of the EGR and in a normal operation.

FIG. 59 is a flowchart illustrating the calculation of a target opening ratio according to the second embodiment.

FIG. 60 is a map characteristic diagram of a target opening ratio in an EGR operation region and overboost suppression.

FIG. 61 is a map characteristic diagram of an EGR operating region and a target opening ratio during normal operation.

FIG. 62 is a characteristic diagram of fuel efficiency, exhaust gas, and intake air amount with respect to an EGR rate and an opening area.

FIG. 63 is a flowchart for explaining the calculation of the feedforward amount of the target opening ratio.

FIG. 64 is a waveform chart showing a change in an actual exhaust flow rate equivalent value when the fuel injection amount is increased stepwise.

FIG. 65 is a table characteristic diagram of an advance correction gain when the variable nozzle is moved to the open side.

FIG. 66 is a table characteristic diagram of an advance correction gain when the variable nozzle is moved to the closing side.

FIG. 67 is a table characteristic diagram of a time constant equivalent value of advance correction when the variable nozzle is moved to the open side.

FIG. 68 is a table characteristic diagram of a time constant equivalent value of advance correction when the variable nozzle is moved to the closing side.

FIG. 69 is a flowchart for explaining calculation of an opening ratio correction value.

FIG. 70 is a flowchart illustrating the setting of a feedback permission flag.

FIG. 71 is a feedback area diagram.

FIG. 72 is a flowchart for explaining setting of a feedback gain;

FIG. 73 is a table characteristic diagram of a basic proportional gain basic value.

FIG. 74 is a table characteristic diagram of a basic integral gain basic value.

FIG. 75 is a table characteristic diagram of a displacement correction coefficient of a PI gain.

FIG. 76 is a table characteristic diagram of an aperture ratio correction coefficient of a PI gain.

FIG. 77 is a flowchart for explaining the calculation of the feedback amount of the aperture ratio.

FIG. 78 is a flowchart illustrating the setting of a learning permission flag.

FIG. 79 is a learning region diagram.

FIG. 80 is a flowchart for explaining the calculation of an opening ratio learning value.

FIG. 81 is a map characteristic diagram of learning speed.

FIG. 82 is a map characteristic diagram of an operating region reflection coefficient.

FIG. 83 is a table characteristic diagram of an aperture ratio reflection coefficient.

FIG. 84 is a flowchart for explaining the calculation of the final command opening ratio.

FIG. 85 is a flowchart for explaining advance processing of the actuator itself.

FIG. 86 is a table characteristic diagram of linearization.

FIG. 87 is a flowchart for explaining signal conversion;

FIG. 88 is a flowchart for describing setting of a duty selection signal flag;

FIG. 89 is a flowchart for explaining the calculation of the temperature correction amount of the duty value.

FIG. 90 is a map characteristic diagram of a basic exhaust gas temperature.

FIG. 91 is a table characteristic diagram of a water temperature correction coefficient.

FIG. 92 is a table characteristic diagram of a temperature correction amount.

FIG. 93 is a temperature characteristic diagram of an actuator.

FIG. 94 is a map characteristic diagram of the duty value when the variable nozzle is fully closed.

FIG. 95 is a map characteristic diagram of the duty value when the variable nozzle is fully opened.

FIG. 96 is a map characteristic diagram of the duty value when the variable nozzle is fully closed.

FIG. 97 is a map characteristic diagram of the duty value when the variable nozzle is fully opened.

FIG. 98 is a hysteresis diagram for converting a command opening ratio linearization processing value into a duty value;

FIG. 99 is a flowchart for explaining operation check control;

FIG. 100 is a flowchart for describing the setting of an operation check control command duty value.

FIG. 101 is a table characteristic diagram of a control pattern.

FIG. 102 is a table characteristic diagram of a duty value during operation check control.

FIG. 103 is a characteristic diagram showing the relationship between the displacement and the opening ratio of the variable nozzle when the engine speed and the load are changed.

FIG. 104 is a characteristic diagram of an actual intake air amount when an opening ratio and an exhaust amount are changed.

FIG. 105 is a more accurate characteristic diagram for FIG. 75;

FIG. 106 is a more accurate characteristic diagram for FIG. 76;

FIG. 107 is a waveform chart for explaining the operation of the present invention in comparison with a conventional device.

FIG. 108 is a waveform chart for explaining the operation when normal feedback control is performed on the premise of the prior application device.

FIG. 109 is a waveform chart for explaining the operation of the first and second embodiments when the cylinder intake gas amount is smaller than the overboost determination intake gas amount.

FIG. 110 is a characteristic diagram showing variations in the total value of the actual intake air amount and the actual EGR amount and the actual exhaust amount in the case of the type employing the intake air amount.

FIG. 111 is a characteristic diagram showing variations in the actual supercharging pressure and the actual displacement in the case of the type employing the supercharging pressure itself.

FIG. 112 is a waveform chart for explaining the operation of the first and second embodiments when the cylinder intake gas amount is equal to or larger than the overboost determination intake gas amount.

FIG. 113 is a waveform chart showing changes in the actual intake air amount when only the EGR valve opening changes when only the opening ratio of the variable nozzle changes.

FIG. 114 is a diagram corresponding to claims of the first invention.

FIG. 115 is a view corresponding to claims of the second invention.

FIG. 116 is a diagram corresponding to the claims of the fourth invention.

FIG. 117 is a view corresponding to claims of the fifth invention.

[Explanation of symbols]

 41 Control Unit 52 Exhaust Turbine 53 Variable Nozzle 54 Actuator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301R 45/00 364 45/00 364E F02M 25/07 570 F02M 25/07 570P // F02B 37/00 302 F02B 37/00 302F F term (reference) 3G005 DA02 EA04 EA15 FA06 GA05 GB12 GC05 GD13 GD14 GE03 GE08 GE10 HA12 JA03 JA12 JA39 JA45 JB02 JB05 3G062 AA01 BA02 CA07 CA08 DA02 EA12 FA02 FA02 FA15 GA01 GA04 GA06 GA08 GA13 GA15 GA21 3G084 BA08 BA20 DA08 DA11 EA11 EB12 EB20 EC01 EC03 FA07 FA20 FA33 FA34 FA37 3G092 AA17 AA18 DB03 DC09 EA10 EA16 EA17 EC01 EC05 FA05 HA01Z HD07Z HE01Z NE02 HA10 NE04 NC04 NE22 PA01Z PD15Z PE01Z PE02Z PE08Z

Claims (13)

[Claims] A turbocharger having an actuator for driving a supercharging pressure variable mechanism; a means for setting a target intake air amount or a target supercharging pressure according to operating conditions; A means for controlling the actuator so as to obtain a target supercharging pressure; an EGR device; a means for detecting an actual intake air amount; a means for detecting an actual EGR amount of the EGR device; A means for determining whether or not an over-boost occurs based on the amount and the actual EGR amount; and a means for suppressing the supercharging pressure so as to prevent the over-boost based on the determination result. Feeder control device. 2. A turbocharger having an actuator for driving a supercharging pressure variable mechanism, means for setting a target intake air amount or a target supercharging pressure according to operating conditions, A means for controlling the actuator so as to obtain a target supercharging pressure; an EGR device; a means for detecting an actual intake air amount; a means for detecting an actual EGR amount of the EGR device; Means for calculating, means for determining whether or not over-boost occurs based on the actual intake air amount, actual EGR amount and actual exhaust amount, and supercharging pressure for preventing over-boost based on the determination result. A control device for a supercharger, comprising: a control unit. 3. A means for determining whether or not an over-boost occurs is means for calculating a sum of an actual EGR amount and an actual intake air amount as a cylinder intake gas amount, and means for setting a determination value in accordance with an actual exhaust amount. Means for determining that overboost occurs when the cylinder intake gas amount is equal to or greater than the determination value and that no overboost occurs when the cylinder intake gas amount is less than the determination value. A control device for a supercharger according to claim 2. 4. A turbocharger having an actuator for driving a variable supercharging pressure mechanism, means for setting a target intake air amount or a target supercharging pressure according to operating conditions, Means for controlling the actuator so as to obtain a target supercharging pressure; an EGR device; a means for detecting an actual supercharging pressure in an operating range of the EGR device; A control device for a supercharger, comprising: means for determining whether a boost is generated; and means for suppressing a supercharging pressure so as not to generate an overboost based on a result of the determination. 5. A turbocharger having an actuator for driving a supercharging pressure variable mechanism, means for setting a target intake air amount or a target supercharging pressure according to operating conditions, Means for controlling the actuator so as to obtain a target supercharging pressure; means for calculating an actual exhaust amount provided with an EGR device; means for detecting an actual supercharging pressure in an operating range of the EGR device; Means for determining whether or not overboost occurs based on the actual supercharging pressure and the actual displacement, and means for suppressing the supercharging pressure based on the determination result so as not to generate overboost. Characteristic supercharger control device. 6. A means for determining whether or not an over-boost occurs. A means for setting a determination value in accordance with an actual displacement, and a means for setting an over-boost when the actual boost pressure is equal to or more than the determination value. 6. The supercharger control device according to claim 5, comprising means for determining that overboost does not occur when the supply pressure is less than a determination value. 7. A means for controlling the actuator, the means for setting an operation target value of a supercharger based on a target intake air amount or a target supercharging pressure and a control target value of an EGR device;
Means for controlling the actuator so as to attain the operation target value of the supercharger, the means for suppressing the supercharging pressure, when the setting value of the means for setting the operation target value of the supercharger is exceeded. 7. The turbocharger according to claim 1, wherein the booster is a means for switching to a value on the side where the supercharging pressure is weakened in a condition under which boosting occurs, compared with a condition in which overboost does not occur. Control device. 8. A period in which the supercharging pressure is suppressed so that overboost does not occur is set according to a change amount of the engine load per predetermined time or a change amount of the engine rotation speed per predetermined time. The control device for a turbocharger according to any one of claims 1 to 7, wherein 9. The system according to claim 1, wherein a period during which the supercharging pressure is suppressed so that overboost does not occur is set according to a change amount of the actual intake air amount per predetermined time.
The supercharger control device according to any one of the above. 10. A method according to claim 3, wherein a period during which the supercharging pressure is suppressed so that overboost does not occur is set according to a deviation amount of the cylinder intake gas amount from the determination value or an exhaust amount. The control device of the supercharger according to the above. 11. The supercharger according to claim 1, wherein the operation of the actuator is delayed when returning the actuator to a side where the supercharge pressure rises after the supercharging pressure is suppressed. Feeder control device. 12. The supercharger control device according to claim 11, wherein a period during which the movement of the actuator is delayed is set according to the atmospheric pressure or the displacement. 13. The supercharger control device according to claim 3, wherein the determination value is set with a characteristic which becomes substantially mountain-shaped with respect to the displacement.