JPS62225719A - Control device for variable capacity turbocharger - Google Patents

Abstract

PURPOSE:To ensure constantly stable supercharging characteristics and to improve torque performance, by a method wherein a feedback control region is learnt according to a deviation between the supercharging pressure of intake air and a desired supercharging pressure, and from the learning result, a present feedback control region is discriminated. CONSTITUTION:A correction amount computing means (c) is provided for computing the proportional part of a feedback correction amount, and the integral part thereof by which a deviation between a supercharging pressure detected by a supercharging pressure means (b) and a given desired supercharging pressure is decreased to zero, and a discriminating means (d) is provided for learning a feedback control region based on the deviation, and selecting a present feedback control region from the learning result, and selection the proportional part and the integrating part of a feedback correction amount according to the discriminating result. Based on an output from an operating state detecting means (a), a fundamental value for controlling a supercharging pressure is computed by a control means (e), correction is effected according to the selected feedback correction amount, and the result is outputted as a supercharging pressure control signal to a supercharging pressure control means (f).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a variable displacement turbocharger equipped with an exhaust bypass valve.

(Prior Art) Generally, in order to increase the output of an internal combustion engine, it is necessary to increase the weight of air that the engine uses for combustion per unit time.

Therefore, a method is adopted in which a turbocharger is used to force high-density air (supercharging).

In such turbochargers, an exhaust bypass valve is installed to suppress an excessive increase in boost pressure and keep it within a certain limit, and the intake capacity is varied depending on the operating range in order to meet the recent high level of drivability. (i.e.
variable capacity).

Here, in the variable displacement turbocharger with an exhaust bypass valve as described above, the displacement variable means and the exhaust bypass valve are controlled by a diaphragm and an actuator, respectively (see Japanese Patent Application Laid-Open No. 59-37228), and The control value of the capacity variable means is feedback-controlled so that the pressure matches the target supercharging pressure (see Japanese Patent Laid-Open No. 60-56126).

However, in such conventional control devices,
Since only the displacement variable means is subjected to feedback control, even if the displacement variable means can be controlled with high accuracy, if there are variations in the control value settings of the exhaust bypass valve, the overall control accuracy of the supercharging pressure will be reduced.

Moreover, if both are simply feedback controlled,
They interfere with each other, making suitable control difficult.

For example, control may be performed such that the exhaust bypass valve is opened in a state where the turbine capacity is small to make the supercharging pressure match the target pressure.

In order to solve this problem, for example, capacity variable means,
It is conceivable to enable feedback control of both the exhaust bypass valves, while determining the preferred mode of feedback and selectively controlling them. However, when air weight information such as air flow rate or boost pressure is used as a selection parameter for feedback control, the feedback switching timing and the range where the variable capacity is fully open (maximum capacity) and the boost pressure is controlled by the exhaust bypass valve. It is almost impossible to completely match the junction points (required switching points) of the two, considering variations in individual engine characteristics, variations in turbocharger flow characteristics, etc.

Therefore, the applicant of the present invention has proposed a device that appropriately uses open loop control and feedback control in combination for both of the above-mentioned controls (see Japanese Patent Application No. 178,586/1986). In this device, feedback control appropriately calculates so-called proportional and integral components depending on the situation, and also performs feedback correction using proportional components and integral components as appropriate depending on the operating range of the engine, thereby eliminating the above-mentioned problems. In other words, the turbocharging pressure is controlled by the exhaust bypass valve while the turbine capacity is small, preventing the problem of reducing the shaft torque, and if there is a slight shift in the switching point, it can be corrected by only the proportional amount. The boost pressure is also maintained at the specified value.

(Problems to be Solved by the Invention) By the way, the device according to the prior application was configured to use the intake air amount and supercharging pressure as parameters to determine the operating region in which integral control is performed. The integral control described above may also be executed in a region where the boost pressure is controlled by the exhaust bypass valve. In such a case, upper and lower limits are set for the correction amount by integral control to prevent hunting, so the value will not be very large.

Therefore, if the individual engine characteristics and the flow rate characteristics of the turbochargers are significantly different, it may become difficult to control the boost pressure to a constant level in the above range, and improvements in this respect are desirable.

In other words, engines and turbochargers are also a type of manufactured product, and when a large number of the same product is produced, the characteristics of the engine or turbocharger may vary more than initially expected. Under these conditions, if correction of only the proportional component is insufficient and correction of the integral component is also performed, for example, if the actual control switching point is set earlier than the required switching point. , even though the form of integral control is originally matched to the variable capacity region, the control shifts to the exhaust bypass region, and in this exhaust bypass region the variable capacitance 41i
Integral control matching the 817 area is executed. In this state, the boost pressure is limited to a predetermined value in the exhaust bypass area while the variable capacity means remains closed (small capacity), so it is gradually controlled to the full open side to prevent the shaft torque from decreasing. Soften. However, at this time, even if the exhaust bypass valve is fully closed, the decrease in supercharging pressure cannot be corrected by the proportional amount.

This is normally done so that the boost pressure can be maintained at the specified pressure even when the maximum value of the proportional correction amount is the maximum deviation of the switching point in consideration of characteristic variations in the original exhaust bypass region.
This is because the boost pressure is determined, and a decrease in supercharging pressure cannot be prevented in an unplanned variable capacity region. therefore,
In such a case, the boost pressure gradually decreases. Moreover, at this time, when the engine speed increases and passes the original required switching point, the integral control finally takes a form that matches the actual exhaust bypass region.

Therefore, since the supercharging pressure had been lower than the target value up to that point, in the integral control, the amount of correction in the pressure increasing direction is accumulated, and conversely, the supercharging pressure is increased beyond the target value at once. Then, the boost pressure is gradually controlled to the normal boost pressure. That is, the harmful effect of hunting due to integral control appears, and it becomes difficult to suppress the boost pressure within a certain range without fluctuation.

On the other hand, when the actual control switching point is set later than the required switching point, contrary to the above, the integral control mode is still in the variable capacity region even though it has shifted to the original exhaust bypass region. At this time, if the delay amount is small, the boost pressure can be controlled only by the proportional component even if the required switching point is exceeded, but if the delay amount is large, the boost pressure cannot be controlled by the proportional component alone. This becomes difficult to deal with, and the boost pressure gradually increases beyond the current set pressure.Then, when the control switching point is reached, the exhaust bypass valve opens and the boost pressure suddenly drops to the set pressure.

In this way, if the original required switching point and the actual control switching point for each engine or turbocharger are different, the integral control mode will not be in a desirable state, causing hunting, etc., and causing constant control of boost pressure. becomes difficult. As a result, it is not possible to obtain good torque characteristics with respect to changes in the operating range, and there is room for improvement in terms of improving drivability.

(Objective of the Invention) Therefore, the present invention learns a feedback control area based on the deviation between intake boost pressure and a predetermined target boost pressure, and determines the current feedback control area from this learning result. The purpose of the present invention is to provide appropriate integral control for each of the variable capacity region and the exhaust bypass region, achieve stable boost pressure characteristics, and improve the torque performance of the engine.

(Structure of the Invention) In order to achieve the above object, the control device for a variable displacement turbocharger according to the present invention has an operating state detection means a for detecting the operating state of the engine, as shown in FIG.
Then, the boost pressure detection means for detecting the intake boost pressure calculates the proportional and integral parts of the feedback correction amount to eliminate the deviation from the deviation between the intake boost pressure and the predetermined target boost pressure. The correction amount calculating means C calculates the feedback control area based on the deviation between the intake boost pressure and the predetermined target boost pressure, and uses this learning result to determine the current feedback system? a determining means d for determining the II region and selecting a proportional portion and an integral portion of the feedback correction amount according to the determined control region; and calculating a basic value for boost pressure control based on the operating state of the engine. , this is determined by means d
a control means e that corrects according to the feedback correction amount selected by and outputs a supercharging pressure control signal; a supercharging pressure operating means f that operates the supercharging pressure of intake air based on the supercharging pressure control signal; It is equipped with

(Function) In this device, the feedback control area is learned based on the deviation between the intake boost pressure and a predetermined target boost pressure, and the current feedback control area is determined based on the learning result. Control '4B' Appropriate feedback control is performed depending on the pH range. Therefore, regardless of the differences in the characteristics of individual engines and turbochargers, the form of integral control is appropriate for both the variable displacement region and the exhaust bypass region, preventing hunting in boost pressure control and keeping the control within a certain range. Precisely controlled.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 12 are diagrams showing an embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes an engine. Intake air is supplied to each cylinder from an air cleaner 2 through an intake pipe 3 and an intake manifold 4 sequentially, and fuel is injected by an injector (path shown). The air-fuel mixture in the cylinder is ignited and exploded at a predetermined ignition timing, and is discharged as exhaust through an exhaust manifold 5 and an exhaust pipe 6 in sequence.

A compressor 8 of an exhaust turbocharger 7 is installed in the intake pipe 3.
A compressor 8 is connected to a turbine 9 disposed in the exhaust pipe 6. The turbocharger 7 uses exhaust gas to drive a turbine 9, and the compressor 8 that works with the turbocharger 7 supercharges intake air.

The intake air flow rate Qa is detected by an air flow meter 10 and controlled by a throttle valve 11 in the intake pipe 3. The intake supercharging pressure Pa is detected by a supercharging pressure sensor (supercharging pressure detection means) 12, and the engine rotation speed Ne is detected by a crank angle sensor 13.

As the cross section of the turbocharger 7 is shown in FIG.
A scroll 14 formed to surround the turbine 9
The scroll 14 is formed so that its cross-sectional area gradually decreases as it goes downstream in the direction indicated by arrow F from the introduction passage 15.

A movable tongue portion 17, which is a capacity variable means constituting a flap valve, is provided at the confluence of the introduction passage 15 to the scroll 14 and the terminal end portion 16 of the scroll 14.
The proximal end portion thereof is rotatably supported by a shaft 18 so that the cross-sectional area of the introduction passage 15 can be expanded or contracted.

The movable tongue 17 is arranged in the exhaust pipe 6 upstream and near the introduction passage 15 to the turbine 9 in FIG. Further, a shaft 18 rotatably supporting the movable tongue portion 17 is connected to the upper end of a loft 20 via an arm 19, and a rod 2
0 is connected to a diaphragm 22 constituting an actuator 21 for driving the movable tongue portion. The case 23 housing the diaphragm 22 is divided into an atmospheric chamber 24 and a positive pressure chamber 25 by the diaphragm 22, and the atmospheric chamber 24 has a spring 26 biased to push the diaphragm 22 toward the positive pressure chamber 25. will be placed.

The boost pressure Pa downstream of the compressor 8 is supplied to the positive pressure chamber 25 through a connecting pipe 27, and a solenoid valve 28 is disposed in the middle of the connecting pipe 27. The electromagnetic valve 28 controls the opening ratio of the connecting pipe 27 to the atmosphere based on a variable capacity signal Sv having a duty control value, and the larger the duty value, the larger the opening ratio. Therefore, the duty value increases (as the pressure in the positive pressure chamber 25 decreases and the spring 2
6 moves the diaphragm 22 downward, and this movement is transmitted to the movable tongue 17 via the rod 20, the arm 19, and the shaft 18, and the movable tongue 17 connects the exhaust gas introduction passage 15 to the turbine 9. It rotates in the direction of making it smaller, that is, in the direction of closing. As a result, the flow rate supplied to the turbine 9 increases, and the supercharging pressure Pa applied to the engine 1 by the compressor 8 increases.

On the other hand, as the duty value decreases, the opening ratio of the solenoid valve 28 decreases and the pressure in the positive pressure chamber 25 increases, so the diaphragm 22 moves upward against the spring 26.
As a result, the movable tongue portion 17 rotates in the direction to open the introduction passage 15. As a result, the flow rate supplied to the turbine 9 becomes slower, and the supercharging pressure Pa to the engine 1 by the compressor 8 increases.
decreases.

Additionally, an exhaust bypass passage 29 that bypasses the turbine 9
A waste gate valve 30 is provided at the connection between the exhaust manifold 5 and the exhaust manifold 5. waste gate valve 30
is connected to one end of a rod 33 via an arm 31 and a connecting member 32, and the other end of the rod 33 is connected to a diaphragm 35 of an actuator 34 for driving a wastegate valve. Case 36 housing diaphragm 35
is divided into an atmospheric chamber 37 and a positive pressure chamber 38 by a diaphragm 35, and the diaphragm 35 is connected to a positive pressure chamber 38 in the atmospheric chamber 37.
A spring 39 is provided which is biased towards the side. A compressor 8 is connected to the positive pressure chamber 38 through a connecting pipe 40.
A downstream supercharging pressure Pa is supplied, and a solenoid valve 41 is disposed in the middle of the connecting pipe 40 . The solenoid valve 41 connects the connecting pipe 4 based on the bypass control signal SII having a duty control value.
The release ratio of o to the atmosphere is controlled, and the larger the duty value, the larger the release ratio. therefore,
When the duty value increases, the pressure in the connecting pipe 4o decreases and the diaphragm 35 moves downward under the action of the spring 39, and this movement is transmitted to the wastegate valve 30 via the rod 33, the connecting member 32, and the arm 31. is,
The valve 30 moves in the direction of closing the bypass passage 29. Furthermore, as the duty value decreases, the release rate of the solenoid valve 41 decreases and the pressure in the positive pressure chamber 38 increases.
The diaphragm 35 moves upward against the spring 39, which moves the wastegate valve 30 in the opening direction.

When the engine 1 is in a high speed and high load state, the waste gate valve 30 is operated by the turbocharger 7.
The supercharging pressure pa of the intake air supplied to becomes too high,
In order to prevent the engine 1 from being damaged, a portion of the exhaust gas from the engine 1 is discharged to the outside, and the exhaust gas supplied to the turbine 9 is reduced to introduce an appropriate boost pressure Pa into the engine 1. That's how I do it.

Signals from the air flow meter 10, boost pressure sensor 12 and crank angle sensor 13 are sent to the control unit (C
/U) 50, and the control unit 5
0 performs boost pressure control based on these sensor information.

That is, the control unit 50 has functions as a correction amount calculation means, a determination means, and a control means, and the CPU
, ROM, , RAM, I10 board, etc.

Then, by calculating the duty control value necessary for supercharging pressure control from the above sensor information and outputting the variable displacement signal Sv and bypass control signal S, the intake supercharging pressure Pa is adjusted appropriately according to the operating region. control to increase torque from low speed range to high speed range.

The air flow meter 10 and crank angle sensor 13
constitutes an operating state detection means 51. Further, both the movable tongue portion 17 and the wastegate valve 30 constitute a pair of supercharging pressure operating means 52 together with the actuator 21.34 and the solenoid valve 28.41. These pair of supercharging pressure operating means 52 have different operating ranges subject to feedback control. The present invention can be applied to any boost pressure operating means 52.

FIG. 4 is a circuit diagram of the control unit 50. In FIG. 4, the same numbers without a "'" indicate components of the variable capacity system, and those with a "'" indicate components of the exhaust bypass system. Reference numerals 56 and 56' denote basic control amount calculators that constitute the main parts of the control means 55 and 55', respectively. In this embodiment, the intake air amount Qa as an operating parameter detected by the air flow meter 10 is inputted and Qa is calculated. Accordingly, the basic control 1BAsE of the duty value for driving the solenoid valve 2 and 41 is determined by table lookup. By opening the electromagnetic valves 28 and 41 according to this basic control amount, the actuators 21 and 3
4. Control the supercharging pressure to a predetermined value via the movable tongue portion 17 and the wastegate valve 30. Specifically, solenoid valve 2
The drive duty values of 8 and 41 are determined experimentally in advance for the intake air 11Qa, and this data is stored in the basic control amount calculation means 56 or 56', and the drive duty values for each operating condition of the engine 1 are determined by table lookup. By doing this, the ordinary supercharging pressure can be set as the target supercharging pressure. Note that FIG. 5 shows a table of duty values used for table lookup.

Furthermore, in actual systems, feedback control is usually performed in order to eliminate steady-state deviations due to various variation factors. Reference numerals 53 and 53' denote correction amount calculation means for calculating the correction amount of feedback control, which includes a deviation calculation unit 57, a proportionality calculation unit 58, 58', and an integral calculation unit 5.
9.59'.

The deviation calculator 57 is composed of a subtractor, etc., and calculates the boost pressure Pa detected by the boost pressure sensor 12 and the set value P of the target boost pressure.
Deviation from a5et ΔP a (= Pa5et −P
Find a). In proportional-integral control based on this ΔPa, the proportional arithmetic operator 58.58' and the integral-integral operator 59.5
9' to find the feed pack correction amount. Here, the proportional computation unit 58 or 58' and the integral computation unit 59 or 59' vary the proportional component PROP, which has a magnitude proportional to the deviation ΔPa, and the integral component INT, which has a magnitude proportional to the integral value of the deviation ΔPa. Calculate each for the capacity system or exhaust bypass system. 60.60', and 61.
Adders 61' are part of the control means 55 and 55', and add PROP and INT to the BASE, respectively. Also, 62.62' and 63.63'
are switches that open and close according to signals from the determining means 54. The determining means 54 uses the intake air amount Qa representing the operating state of the engine and the boost pressure Pa detected by the boost pressure sensor 12.
The operating range in which integral control is to be performed is determined from the following.

Next, the action will be explained.

FIG. 6 is a flowchart showing a program for supercharging pressure control by the control unit 50, in which P, ~P
IT indicates each step of the flow. Note that this program is executed once every predetermined time. This flowchart is a control program for a variable displacement system, and the exhaust bypass system is controlled in the same way.

First, read the intake air amount Qa and boost pressure Pa with P+,
At P2, the basic control amount BASE of the duty value in the variable capacity signal Sv is determined by table lookup according to the intake air amount Qa. For this basic control [BASE, optimum values are prepared in advance as a data table through experiments using the intake air amount Qa as a parameter (see FIG. 5).

Next, at P3, it is determined whether the current supercharging pressure Pa is greater than 200 mHg, and when Pa > 2QQn+[g, it is determined that the operation is in the operating range where feedback control is performed, and feedback is performed at P, , ps. Calculate the proportional amount of correction. That is, in P4, the deviation ΔPa between the actual value and the target value is calculated according to the following equation (2).

Δp a = Pa5et −P a −− ■However,
Pa5et: Target boost pressure (for example, Pa5et"
375mCaHg) P, the proportional portion PROP of the feedback correction amount is calculated based on this deviation ΔPa according to the following equation (2).

PROP = 1・ΔPa ・・・・・・■ However, K1
:The constant proportional portion PROP becomes an appropriate boost pressure operation amount proportional to the magnitude of the deviation ΔPa.

Next, at P&, the boost pressure Pa is close to the target boost pressure at 320 m.
Determine whether it is greater than mHg, Pa > 320+
When it is uHg, it is determined that the operation region is in which integral feedback control is performed, and the integral of the feedback correction amount is calculated at Pl and P8. That is, in P7, the current integral INT is calculated according to the following equation.

I NT=Σ2・ΔPa...■ However, in order to prevent the integral INTO value from becoming too large at K2: constant P8, INT is limited within a predetermined value and the process proceeds to P. P
, the intake air 1iQa is at the control switching point air flow 4, which will be described later.
3 Determine whether Q is greater than 5vNrha, and
When a > Q, v, T, Jc, it is determined that the integral control amount is in the operating region where it is decreased, and the process proceeds to P+2.

Also, when Q a < Q 5vNr, 1a, it is determined that the operating region is in which integral control is performed, and P. Proceed to.

On the other hand, when pa≦200mHg in step P, it is determined that the operating range is in which open-loop control is performed, and P
At +4, proceed with the proportional portion PROP as zero.

In addition, when Pa≦320Hg in P6, the proportional amount PRO
It is determined that only P needs to be corrected, and the process proceeds to P+5. At P and 5, the integral INT is set to zero, and the process proceeds to Pl&.

Next, P. Now, BASE the correction amount PROP+INT
If it is the area to which the correction amount is to be added, the correction amount PROP+IN is determined based on the pH.
Calculate T and proceed to P+6. At P+6, a final duty value OUT is determined according to the following equation (2), and at Pl'l, a variable capacitance signal Sv having this final duty value OUT is output.

0UT=BASE+PROP+INT...
・■If it is not the area where the correction amount is added at P1°, PR
Setting OP=0 and INT=0, proceed to Pl&, obtain the final duty value 0UT=BASE at P+6, and proceed to Pl.

On the other hand, at P1□, the duty value OUT is calculated according to the above formula 0.
Find out and proceed to PI3. In PI3, the calculated duty value OUT is decreased by a fixed amount by □ at fixed time intervals, and P+
At step 7, the variable capacitance signal Sv having the final duty value 0UT- of 3 is output.

The above system JBM will be explained by returning to FIG. 4. In a variable displacement system, the operating range in which integral control of the boost pressure is performed is when the boost pressure Pa is close to the target boost pressure (for example, 320 m
mmm1f, and the intake air amount Qa is set to be less than or equal to a control switching point air flow rate QsvNrwa, which will be described later. At this time, the switch 61 is closed. Also, the intake air
j] Qa is the control switching point air flow rate Q! IVNT. When it exceeds the limit, the exhaust bypass system performs integral control of the boost pressure, so the switch 61 is opened and the switch 61' is closed.

On the other hand, when the boost pressure Pa is below a predetermined value close to the target boost pressure, proportional control is performed in both the variable displacement system and the exhaust bypass system, so the switches 61 and 61' are closed. Therefore, in the operating range where integral control is performed, proportional-integral control is performed in the variable displacement system or the exhaust bypass system, and in the operating range where integral control is not performed, proportional control is performed.

In this way, the operating range in which integral control of the boost pressure is performed is switched from the variable displacement system to the exhaust bypass system by the control switching air flow ff1QsVNT□6 corrected to eliminate the deviation from the required switching point.

Figure 7 shows the area where the boost pressure is controlled by the variable capacity means (movable tongue) (hereinafter referred to as the ■N area) on the overall performance curve of the engine, and the area where the boost pressure is controlled by the exhaust bypass valve (wastegate valve). The area where the W/G area is controlled (hereinafter referred to as the W/G area) is shown. The solid line B in the figure corresponds to the fully open position of the movable tongue, and the supercharging pressure control is switched around this line. That is, the original required switching point corresponds to this line, and it is necessary to make the actual control switching point coincide with this required switching point.

Here, based on FIGS. 8 and 9, it will be described how the deviation between the control switching point and the required switching point affects the boost pressure control.

Figure 8 shows the relationship between boost pressure, opening of the movable tongue (hereinafter referred to as VN) and waste gate valve (hereinafter referred to as W/G), and control duty with respect to engine speed during transient operation. be. Point A shown in the figure is a switching point for integral control, and when the engine speed exceeds switching point A, integral control shifts from VN to W/G. On the other hand, point B indicates the original request switching point. Considering variations in the performance of the parts or control parts that make up the turbocharger, this switching point A is usually set slightly earlier than the required switching point B, and the required VN opening line and the required W/G
If the duty line is b1b', the actual opening line and duty line are a and a', respectively.

However, depending on the performance variations of the control parts or the parts that make up the turbocharger,
) to (e), the boost pressure and the feedback correction amount change depending on the slowness of the control switching point relative to the required switching point. That is, in the figure, (a) and (b) show the case where the control switching point is too early than the required switching point, (C) shows the case where it is appropriate, and (d) and (6) show the case where it is too late.

In (a) and (b), since the control switching point is too early, VN opens early after switching, and the supercharging pressure drops once even though W/G is fully open. Therefore, the integral control is W/G
When transitioning to In Q), the control switching point is too late, so even though VN is fully open, W
W/G cannot be opened sufficiently with only proportional control on the /G side. Therefore, when the boost pressure increases and the integral control shifts to W/G, the correction amount between the integral and proportional components changes greatly in the direction of reducing the boost pressure (one direction in the figure), causing the boost Pressure fluctuations become large.

That is, as shown in FIG. 9(C), the supercharging pressure can be controlled most stably when there is no deviation between the control switching point and the required switching point.

Here, the control switching point air flow IQ3VNT of the integral control
The setting method of WG will be explained.

FIG. 10 shows the relationship between the integral amount of correction of VN and W/G within a constant air flow rate range before and after the control switching point, and the deviation between the control switching point and the actual required switching point. Point (C) shown in the figure shows points (a), (
Point b) indicates when the control switching point is too early relative to the required switching point, and points (d) and (e) indicate when the control switching point is too late relative to the required switching point.

That is, when the control switching point is too early with respect to the required switching point, the integral amount of the W/G correction amount becomes extremely large on the + side compared to the integral amount of the VN correction amount. On the other hand, when the control switching point is too late with respect to the required switching point, both the integral amount of the VN correction amount and the integral amount of the W/G correction amount greatly deviate to one side. The region indicated by diagonal lines in the figure indicates the range of the integral amount of the VN correction amount and the integral amount of the W/G correction amount in which the boost pressure can be controlled at a constant level, that is, the range in which the -penetration charge pressure can be controlled.

In this way, the integral amount of the VN correction amount and the integral amount of the W/G correction amount within the constant airflow range before and after the current control switching point are measured and compared.

As a result, the control switching point can be changed according to the difference from the -penetrating supply pressure controllable region A, and the changed switching point, that is, the control switching point air flow rate Qsvstwc can be set.

Next, a program for obtaining this control switching air flow il Q sv,4rsa will be explained. FIG. 11 is a flowchart showing a learning control program by the control unit 50, and PI8 to pz< in the figure indicate each step of the flow. Note that this program is executed once every predetermined time.

First, PI3 determines whether the learning conditions are satisfied. Which learning condition is the intake air MQa the current control switching point air flow rate Q, vN? □. It is satisfied only if it passes within the specified time. When the learning condition is satisfied in PI8, PI9 calculates the integral amount of VN correction (hereinafter referred to as VN correction amount), and Pzo calculates the integral amount of W/G correction amount (hereinafter referred to as W
/G correction amount) and proceed to PZI.

Here, FIG. 12 shows the control switching point air flow NQSVNfWG
It shows the relationship between the correction value of , and the above-mentioned VN and W/G correction amounts.

In PZI, the correction value of QsvNtwc is determined by the table lookup shown in FIG. 12 based on the VN and W/G correction amount, and in pzz, the correction value determined by PZI is added to the current Q3V)ITWG to obtain an appropriate Q for control. , v, lT. seek. Furthermore, Q3vN with PZI? 1. The range of lG values is limited so that it does not exceed a certain value.

On the other hand, if the learning condition is not satisfied in PI3, the process advances to P24, and both the VN correction amount and W/G correction are cleared in Pza.

Thus, the control switching point airflow it Q 5VNTWG
is always corrected to eliminate the deviation from the required switching point,
Therefore, the operating range in which the boost pressure is integrally controlled can be switched from the variable capacity system to the exhaust bypass system by setting an appropriate control switching point air flow rate QSVMTWG.

As discussed above, when the characteristics of individual engines and turbochargers vary, for example, even if the actual control switching point is set earlier than the required switching point, learning and discrimination The value of the control switching point is corrected and can be set as an appropriate control switching point. Therefore, an uncontrollable region in which the boost pressure does not rise to the target boost as in the example of the prior application does not occur, and the boost pressure quickly increases to the target boost pressure by executing the integral control.

In addition, as pointed out in the prior application, since the correction amount of integral control is accumulated when the original required switching point is exceeded, the boost pressure does not rise suddenly beyond the target boost pressure. The boost pressure can always be controlled to a constant value.

(Effects) According to the present invention, the control switching point can always be set to the optimal value regardless of the characteristics of individual engines and turbochargers or the performance variations of control system components.
Integral control for each of the variable capacity region and the exhaust bypass region can always be appropriate. As a result, stable supercharging pressure characteristics are obtained, which prevents damage to the engine and improves engine torque performance.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 12 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a main part of the turbocharger. 4 is a circuit configuration diagram of the control unit, FIG. 5 is a diagram showing the relationship between the basic control duty and air flow rate, FIG. 6 is a flowchart showing the boost pressure control program, and FIG. Figure 8 shows the region of boost pressure control, Figure 8 shows the relationship between valve opening, control duty and boost pressure with respect to engine speed during transient operation, Figure 9
FIG. 10 is a diagram showing the change in boost pressure and feedback correction amount due to the deviation of the control switching point, and FIG. 10 is a diagram showing the relationship between the feedback correction amount and the deviation of the control switching point.
FIG. 11 is a flowchart showing the learning control program, and FIG. 12 is a diagram showing the relationship between the correction value of the control switching point air flow rate and the feedback correction amount. 1...Engine, 7...Turbocharger, 12...Supercharging pressure sensor (supercharging pressure detection means), 5
1... Operating state detection means, 52... Boost pressure operation means, 53... Correction amount calculation means, 54... Discrimination means, 55... ...control means.

Claims (1)

[Claims] a) an operating state detection means for detecting the operating state of the engine; b) a supercharging pressure detecting means for detecting the supercharging pressure of intake air; c) a supercharging pressure of intake air and a predetermined target supercharging pressure d) a correction amount calculation means for calculating a proportional part and an integral part of a feedback correction amount to eliminate the deviation from the deviation from the supply pressure; The feedback control area is learned based on the feedback control area, and the current feedback control area is determined based on the learning result.
a discriminating means for selecting a proportional part and an integral part of the feedback correction amount according to the determined control region; and e) a discriminating means for calculating a basic value of boost pressure control based on the operating state of the engine and determining this value. f) a control means for correcting the boost pressure control signal according to the feedback correction amount selected by; f) a supercharging pressure operating means for manipulating the supercharging pressure of intake air based on the boost pressure control signal; A control device for a variable capacity turbocharger, comprising: