JP2632184B2 - Control method of variable capacity turbocharger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Industrial application field The present invention controls the supercharging pressure based on a basic supercharging pressure control amount set according to the operating state of the engine. And a control method of the variable capacity turbocharger.

(2) Prior Art Conventionally, such a control method is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-164142.
It is publicly known from Japanese Patent Publication No.

(3) Problems to be Solved by the Invention By the way, when a specific operation of the engine is performed, for example, when the intake air temperature and the cooling water temperature are abnormally low or high, or when the supercharging pressure is abnormally high, the supercharging pressure is not supplied to the engine. It is desirable to avoid this, even in the control method proposed earlier by the applicant,
In such a specific operation, the supercharging pressure is forcibly reduced. However, if the supercharging pressure is immediately increased based on the basic supercharging pressure control amount when the specific operating state is canceled, the specific operating state may return to the specific operating state near the boundary between the specific operating state and the non-specific operating state. Therefore, the supercharging pressure control becomes unstable, which is not preferable in terms of engine durability.

The present invention has been made in view of such circumstances,
Provided is a variable displacement turbocharger control method capable of performing a stable supercharging pressure control by increasing a supercharging pressure after an operating state of an engine reliably shifts from a specific state to a non-specific state. The purpose is to:

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the method of the present invention provides a method for controlling the supercharging pressure based on a basic supercharging pressure control amount set according to the operating state of the engine. In the variable displacement turbocharger control method, the supercharging pressure is forcibly reduced regardless of the basic supercharging pressure control amount when the operating state of the engine is in the specific state, and the specific state is released. Sometimes, first, the basic supercharging pressure control amount is corrected so as to decrease over a predetermined time by a certain correction coefficient, and after the predetermined time elapses, the correction coefficient is corrected every predetermined period, and the correction coefficient is corrected by the correction coefficient. The reduction amount of the basic supercharging pressure control amount is gradually reduced.

(2) Operation According to the above method, when the specific operating state of the engine is canceled, first, the basic supercharging pressure control amount is corrected to decrease by a certain correction coefficient over a predetermined time. When the supercharging pressure fluctuates on the boundary between the non-specific state and the supercharging pressure, the supercharging pressure is reduced, and after the specific state is reliably released, the supercharging pressure control based on the basic supercharging pressure control amount corresponding to the operating state is performed. It is performed stably.

After the elapse of the predetermined time during such a correction of the basic supercharging pressure control amount, the correction coefficient is corrected every predetermined cycle, so that the reduction amount of the basic supercharging pressure control amount by the correction coefficient gradually decreases. Therefore, the reduced-corrected basic supercharging pressure control amount gradually approaches the normal (i.e., uncorrected) basic supercharging pressure control amount, whereby the control can be shifted to the normal control very smoothly without hunting.

(3) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, in FIG. 1 showing an overall schematic configuration of an intake system and an exhaust system of an internal combustion engine, each cylinder in an engine body E of a multi-cylinder internal combustion engine is shown. Is connected to an air cleaner 6 via an intake pipe 2, a throttle body 3, an intercooler 4, and a variable capacity turbocharger 5.
An exhaust manifold 7 is connected to an exhaust port of each cylinder. The exhaust manifold 7 is connected to a catalytic converter 9 containing a three-way catalyst through an exhaust pipe 8 having a variable capacity turbocharger 5 provided at an intermediate portion. Is done. Further, a fuel injection valve 10 for injecting fuel toward the intake port of each cylinder is attached to a portion of the intake manifold 1 close to each intake port.

The variable capacity turbocharger 5 is provided with a water jacket 11, and an inlet of the water jacket 11 and an inlet of the intercooler 4 are connected in parallel to a discharge port of a water pump 13 having a suction port connected to a radiator 12, The outlets of the water pump 13 and the intercooler 4 are connected to the radiator 12. Moreover, the radiator 12 is provided separately from the radiator for cooling water in the engine body E.

Next, the configuration of the variable-capacity turbocharger 5 will be described with reference to FIGS. 2, 3 and 4.
And a back plate for closing a back surface of the compressor casing 14.
15, a bearing casing 17 that supports the main shaft 16, and a turbine casing 18.

A scroll passage 19 is defined between the compressor casing 14 and the back plate 15, and an inlet passage 20 extending in the axial direction is formed at the center of the compressor casing 14. In addition, a compressor wheel 21 is attached to one end of the main shaft 16 at a portion located at the center of the scroll passage 19 and at the inner end of the entrance passage 20.

Compressor casing 14 and back plate 15 have multiple bolts
The bearing casing 17 is connected to the center of the back plate 15. A pair of bearing holes 23, 24 are coaxially formed in the bearing casing 17 at an interval from each other, and are provided between the main shaft 16 inserted in these bearing holes 23, 24 and the bearing holes 23, 24. Radial bearing metals 25 and 26 are interposed therebetween, whereby the main shaft 16 is rotatably supported by the bearing casing 17. A collar 27, a thrust bearing metal 28, and a bushing 29 are interposed between the stepped portion 16a of the main shaft 16 facing the compressor wheel 21 and the compressor wheel 21 in this order from the stepped-down 16a side. By screwing a nut 30 in contact with the outer end of the main shaft 16 to one end of the main shaft 16 to fasten the main shaft 16 in the thrust direction and mounting the compressor wheel 21 to the main shaft 16.

A lubricating oil introduction hole 32 connected to a lubricating oil pump (not shown) is provided in the upper part of the bearing casing 17, and inside the bearing casing 17, radial lubricating metal 25, 26 and thrust bearing metal 28 A lubricating oil passage 33 for guiding the supplied lubricating oil is provided. Further, a lubricating oil discharge port 34 for discharging the lubricating oil flowing out of each lubricating portion downward is provided at a lower portion of the bearing casing 17, and the lubricating oil discharged from the lubricating oil discharge port 34 is an oil (not shown). Collected by sump.

The bushing 29 has a through hole 35 formed in the center of the back plate 15.
A seal ring 36 is interposed between the outer surface of the bushing 29 and the inner surface of the through hole 35 to prevent the lubricating oil flowing out of the thrust bearing metal 28 from flowing to the compressor wheel 21 side. Is done. In addition, a guide plate 37 for penetrating the bushing 29 is sandwiched between the back plate 15 and the thrust bearing metal 28. Therefore, the lubricating oil flowing out of the thrust bearing metal 28 scatters radially outward from the bushing 29 and is received by the guide plate 37. In addition, the lower portion of the guide plate 37 is formed to be curved so as to guide the received lubricating oil to the lubricating oil discharge port 34 smoothly.

The bearing casing 17 has a water jacket around the main shaft 16.
11 and a water pump is provided on the water jacket 11.
A water supply port 38 for guiding water from 13 (see FIG. 1) and a water outlet 39 for guiding water from water jacket 11 to radiator 12 (see FIG. 1) are provided. In addition, the water jacket 11 is formed in an annular shape surrounding the main shaft 16 in a portion near the turbine casing 18 and has a lubricating oil discharge port 34.
The water supply port 38 is formed in the bearing casing 17 so as to communicate with the lower part of the water jacket 11 at a portion corresponding to the upper part of the water jacket 11 so as to have a substantially U-shaped cross-sectional shape opened downward above the main shaft 16. The water outlet 39 is provided in the bearing casing 17 so as to communicate with the upper part of the water jacket 11.

In the turbine casing 18, a scroll passage 41,
An inlet passage 42 communicating with the scroll passage 41 and extending in a tangential direction and an outlet passage 43 communicating with the scroll passage 41 and extending in the axial direction are provided.

The bearing casing 17 and the turbine casing 18 are mutually connected so that the back plate 44 is sandwiched therebetween. That is, a plurality of stud bolts 45 are screwed to the turbine casing 18, and a nut 47 for screwing a ring member 46 engaged with the bearing casing 17 to the stud bolt 45.
As a result, the bearing casing 17 and the turbine casing 18 are connected to each other, and the flange portion 44a provided on the outer peripheral portion of the back plate 44 is sandwiched between the bearing casing 17 and the turbine casing 18.

A fixed vane member 48 is fixed to the back plate 44, and the inside of the scroll passage 41 is fixed to the outer peripheral path 41 by the fixed vane member 48.
a and an inflow passage 41b. The fixed vane member 48 includes
A cylindrical portion 48a coaxially fitted in the outlet passage 43;
A disk portion 48b extending radially outward from the outer surface of the intermediate portion of
A plurality of, for example, four fixed vanes 49 extending from the outer peripheral end of the disk portion 48b toward the back plate 44, and a turbine wheel 50 provided at the other end of the main shaft 16 is provided with the fixed vane member 48.
Is stored inside. The cylindrical portion 48a is fitted into the outlet passage 43 via a seal ring 51 fitted on the outer surface thereof, and the fixed vane 49 is connected to the back plate 44 by bolts 52.

The fixed vanes 49 are provided on the outer peripheral portion of the turbine member 48 at equal intervals in the circumferential direction, and each of the fixed vanes 49 is formed in an arc shape. A movable vane having one end fixed to a rotating shaft 53 rotatably pivotally attached to the back plate 44 in parallel with the axis of the main shaft 16 between the fixed vanes 49.
The movable vanes 54 adjust the flow area of the gap between the fixed vanes 49.

Each movable vane 54 is formed in an arc shape having a curvature equivalent to that of the fixed vane 49, and includes a fully closed position indicated by a solid line in FIG.
It is rotatable between all positions shown by the dashed lines. Moreover, each rotating shaft 53 is connected to an actuator 60 via a link mechanism 55 disposed between the back plate 44 and the bearing casing 17.
54 is opened and closed in synchronization.

A shield plate 56 extending to the back of the turbine wheel 50 is sandwiched between the back plate 44 and the bearing casing 17, and the heat of the exhaust gas flowing through the inflow passage 41b is directly transmitted to the inside of the bearing casing 17 by the shield plate 56. Is prevented as much as possible. In order to prevent the exhaust gas from leaking into the bearing casing 17, a main shaft is installed inside the turbine casing 18.
Through-hole provided in bearing casing 17 to project 16
At a portion corresponding to 57, the main shaft 16 is provided with a plurality of annular grooves 58 that function as labyrinth grooves.

In such a variable capacity turbocharger 5, the engine body E
Exhaust gas discharged from the inlet passage 42 flows into the outer peripheral path 41a from the inlet passage 42, and the exhaust gas flows at an inflow path 41b at a flow rate corresponding to the flow area of the gap between the movable vane 54 and the fixed vane 49 according to the amount of rotation of the movable vane 54. And is driven out of the outlet passage 43 by rotating the turbine wheel 50. At this time, when the flow area of the gap between each movable vane 54 and the fixed vane 49 decreases, the rotation speed of the turbine wheel 50, that is, the main shaft 16 increases, and the flow area of the gap between each movable vane 54 and the fixed vane 49 increases. Turbine wheel 50 or main shaft
16 rotation speed slows down. The compressor wheel 21 rotates in accordance with the rotation of the turbine wheel 50, and the air guided from the air cleaner 6 to the inlet passage 20 is supplied to the intercooler 4 through the scroll passage 19 while being compressed by the compressor wheel 21. become. Accordingly, when the movable vane 54 is located at the outermost position in the radial direction of the turbine casing 18 to minimize the air flow area between the movable vane 54 and the fixed vane 49, the supercharging pressure is maximized. The supercharging pressure becomes minimum when the air flow area between the stationary vane 49 and the stationary vane 49 is maximized by being positioned at the innermost position in the direction.

The temperature rise of the bearing casing 17 due to the temperature rise during the air compression in the variable capacity turbocharger 5 is prevented as much as possible by the supply of the cooling water to the water jacket 11, and the rise of the intake air temperature is prevented by the supply of the cooling water to the intercooler 4. Is prevented.

Referring again to FIG. 1, an actuator 60 for driving the movable vane 54 of the variable capacity turbocharger 5 includes a housing 61, and a diaphragm 64 that partitions the inside of the housing 61 into a first pressure chamber 62 and a second pressure chamber 63. , 1st pressure chamber
A return spring 65 interposed between the housing 61 and the diaphragm 64 to urge the diaphragm 64 in a direction to contract the 62
And a drive rod having one end connected to the center of the diaphragm 64 and the other end connected to the link mechanism 55 through the housing 61 airtightly and movably on the second pressure chamber 62 side.
66. Further, when the drive rod 66 and the link mechanism 55 are extended in the direction in which the diaphragm 64 contracts the second pressure chamber 63 and the drive rod 66 extends, the movable vanes
54 are connected to each other so as to rotate inward in the radial direction of the turbine casing 18 so as to increase the gap flow area between the fixed vanes 49.

The first pressure chamber 62, together with the intake passage between the variable capacity turbocharger 5 and the intercooler 4 is a regulator 67 to supply the supercharging pressure P _2, it is connected via a throttle 68 and the electromagnetic control valve 69, an air cleaner 6 The intake passage between the variable capacity turbocharger 5 and the variable capacity turbocharger 5 is connected via a throttle 75.
This electromagnetic control valve 69 is duty-controlled,
The pressure in the first pressure chamber 62 increases as the duty ratio of the solenoid 70 increases, that is, the movable vane 54 of the variable turbocharger 5 rotates inward via the drive rod 66 and the link mechanism 55. Driven. The second pressure chamber 63
The intake passage on the downstream side is connected through a check valve 71 and the solenoid valve 72 to supply the intake air pressure P _B of the throttle Boti 3. The electromagnetic switching valve 72 is adapted to open in response to excitation of the solenoid 73, when the intake pressure P _B supplied to the second pressure chamber 63 in accordance with the opening of the electromagnetic switching valve 72, the actuator 60 drives the movable vane 54 of the variable capacity turbocharger 5 inward.

Excitation and demagnetization of the solenoid 70 of the electromagnetic control valve 69 and the solenoid 73 of the electromagnetic on-off valve 72 are controlled by control means C. The control means C includes a water jacket (see FIG. a temperature detector S _W for detecting the cooling water temperature T _W of Shimese not), the intake air temperature sensor S _a for detecting the intake air temperature T _a of the downstream side of the intercooler 4, an air cleaner 6
And an intake pressure sensor S _PA for detecting the intake air pressure P _A between the variable capacity turbocharger 5, the variable geometry turbocharger 5
And a supercharging pressure sensor S _P2 for detecting the supercharging pressure P ₂ in the intake passage between the intercooler 4, an intake pressure sensor S _PB for detecting an intake pressure P _B on the downstream side of the throttle body 3, the engine speed N
A rotation speed detector S _N for detecting the _E, the throttle opening detector S _TH for detecting an opening theta _TH of the throttle valve 74 in the throttle body 3, a vehicle speed detector S _V for detecting the vehicle speed V,
Shift position detector and S _S is connected to detect the shift position of the automatic transmission. Thus, the control means C receives these input signals, that is, the water temperature T _W , the intake temperature T _A , and the intake pressure.
P _A, the supercharging pressure P _2, the intake pressure P _B, the engine speed N _E, the throttle opening theta _TH, controls the excitation and demagnetization of the solenoid 70, 73 based on the shift position signal of the vehicle speed V and the automatic transmission I do.

Next, the control procedure of the control means C will be described. First, the duty control of the solenoid 70 in the electromagnetic control valve 69 will be described with reference to the main routine of FIGS. 5A and 5B. However, the duty in this main routine
D _OUT is such that the duty ratio of the solenoid 70 decreases as its value increases, and D _OUT = 0 corresponds to a duty ratio of 100%, that is, a state where the movable vane 54 is driven inward to the maximum. D _OUT = 100 is 0% duty ratio
That is, this corresponds to a state in which the movable vane 54 is driven at the maximum outward.

In a first step S1, it is determined whether or not the engine is in a start mode, that is, whether or not the engine is being cranked. When the engine is in a start mode, a setting corresponding to the completion of the warm-up state of the engine is made in a second step S2. Time t _BTWCO (eg, 96
After the timer t _BTWC for counting the second) is reset, and the timer t _FBDLY for delaying the start of the feedback control in the next third step S3 is reset,
In the fourth step S4, the duty _DOUT is set to 0, that is, the electromagnetic control valve 69 is fully opened so that the gap flow area between the movable vane 54 and the fixed vane 49 is maximized. This is because the engine is in an unstable state during cranking, and introducing the supercharging pressure into the combustion chamber in such an unstable state promotes instability, so that the movable vane 54 and the fixed vane 49
This is to avoid introducing the supercharging pressure into the combustion chamber by maximizing the air gap flow area between them. Also, during the cranking, the driver does not request supercharging of the air supply, and there is no need to reduce the gap flow area between the movable vane 54 and the fixed vane 49. In the next fifth step S5, the duty D _OUT
Is output.

The timer t _FBDLY is intended to be computed in accordance with the procedure shown in FIG. 6, one of the supercharging pressure P by ₂ rate of change [Delta] P ₂ 3 two timers t _FBDLY1, t _FBDLY2, t _FBDLY3 is selected. Here, the rate of change ΔP ₂ is the supercharging pressure P _{2n of} this time,
It is determined by the difference from the supercharging pressure P _2n-6 six times before (ΔP ₂ = P _2n −P _2n-6 ). That is the main routine shown in FIGS. 5A and Figure 5B but is updated by the TDC signal, since only one TDC signal is too small, the rate of change of the supercharging pressure P _2, supercharged圧挙dynamic i.e. the rate of change [Delta] P ₂ In order to read the pressure accurately, the difference from the supercharging pressure P _2n-6 six times before is calculated. The set low change rate [Delta] P _2PTL and set high change rate [Delta] P _2PTH are those that are predetermined in accordance with the engine speed N _E, [Delta] P ₂
When ≦ ΔP _2PTL , t _FBDLY1 is set, and ΔP _2PTL <ΔP
_{When 2} ≦ ΔP _2PTH , t _FBDLY2 is set, and ΔP _2PTH <Δ
T _FBDLY3 is set at the time of P _2. And t _FBDLY1 <t
_FBDLY2 <a t _FBDLY3, i.e. if the supercharging pressure P ₂ when the supercharging pressure change rate [Delta] P ₂ is small is changing slowly is set small delay time, i.e. if excessive supercharging pressure change rate [Delta] P ₂ greater delay time is set larger when the Kyu圧P ₂ is changing rapidly. As a result, a time t _FBDLY is set for the transition axis from the open loop control to the feedback control without excess or shortage, and it is possible to sufficiently avoid occurrence of a hunting phenomenon at the transition.

If it is determined in the first step S1 that the current mode is not the start mode, it is determined in a sixth step S6 whether the current mode is the first TDC signal by entering the basic mode, that is, the first processing cycle, If it is the first time, the process proceeds to the seventh step S7.
Proceed to step SS11. In the seventh step S7, the intake air temperature T _A exceeds the set low intake air temperature T _AL, for example, −8 ° C. (T _A > T _AL )
Is determined, and when T _A > T _AL , the eighth step S
The process proceeds to step S10 when T _A ≦ T _AL , and to the tenth step S10.
In the eighth step S8, the cooling water temperature T _W is set to the set low cooling water temperature T _WL.
For example, it is determined whether the temperature exceeds 60 ° C. (T _W > T _WL ), and if T _W > T _WL , the process proceeds to the ninth step S9, and T _W ≦ T _WL
If it is _WL , go to the tenth step S10.

In a ninth step S9, a timer t _BTWC for counting the time until the warm-up of the engine is completed is set to a value FF greater than 96 seconds, for example, a set time t _BTWCO set corresponding to the completion of the warm-up. After that, proceed to the thirteenth step S13,
In step S10, after the timer _tBTWC is reset, the process proceeds to a third step S3.

The processing procedure up to this point is summarized as follows. That is, when the engine is started, it is determined in each first TDC signal whether or not the engine is cranking in the first step S1, and when it is determined that the engine is in the starting mode, the timer t _BTWC is reset in the second step S2. I do. In addition, at the time of processing according to the first TDC signal after entering the basic mode, the seventh and eighth steps S7 and S8 elapse so that T _A > T _AL and T _W > T
_When both _WL are established, it is determined that the engine is continuing to run after the warm-up is completed, and the timer t _BTWC is set to a time FF _{equal to} or _longer than t _BTWCO , and T _A ≦ T _AL , T _W ≦ T _WL When at least one of the conditions is satisfied, the timer t _BTWC is reset and time counting is started. Therefore, the time for determining that the engine has completed warm-up is started after the basic mode is entered.

In an eleventh step S11, the intake air temperature T _A is set to the set low intake air temperature T.
_It is determined whether it is less than _AL (T _A <T _AL ). If T _A <T _AL , the process proceeds to the second step S2, and if T _A ≧ T _AL , the process proceeds to a twelfth step S12. At 12th step S12, whether the preset coolant temperature T _W is lower cooling below temperature _{T WL (T W <T WL} ) is determined, the second step S2 to walk in T _W <T _WL, also T _W ≧ T
_If it is _WL , go to the thirteenth step S13. That is,
When it is determined in the sixth step S6 that the cycle is the second or later cycle, the intake air temperature T _A and the cooling water temperature T _W are compared with the set values in the eleventh and twelfth steps S11 and S12, and according to the determination result. The second step S2 or the thirteenth step S1
Proceed to 3.

Here, the operating state of the engine considered as a case where T _W <T _WL and T _A <T _AL is satisfied is, for example, at the initial stage of the engine start or when the outside air temperature is in a very low temperature state. The operation state is unstable, and when the outside air temperature is extremely low, the intake air density increases, so that the charging efficiency increases and causes abnormal combustion. In such a case, introducing the supercharging pressure into the combustion chamber promotes an unstable state of the engine and abnormal combustion. In addition, when the temperature is extremely low, malfunction of the electromagnetic control valve 69 itself may be considered, and the electromagnetic control valve 69 may not behave as instructed by the control means C. Therefore, when at least one of T _W <T _WL and T _A <T _AL is satisfied, D _OUT = 0 is set in the fourth step S4 after the second and third steps S2 and S3.

In a thirteenth step S13, the engine speed _NE becomes equal to the set speed N _DO
For example, whether more than 500rpm (N _E> N _DO) is determined. In the thirteenth step S13, when N _E > N _DO , the process proceeds to a fourteenth step S14. When N _E ≦ N _DO , the process proceeds to the fifteenth step S15 bypassing the first step S14. In the fourteenth step S14, it is determined whether or not the timer t _BTWC exceeds the set time t _BTWCO (t _BTWC > t _BTWCO ), that is, whether or not a time that can be determined that the engine has completed warm-up has elapsed. In the fourteenth step S14, when it is determined that t _BTWC > t _BTWCO , the process proceeds to the fifteenth step S15, where t _BTWC
When it is determined that ≦ t _BTWCO , the process proceeds to the third step S3.

Therefore, when the cooling water temperature T _{W of the} engine is less than the set temperature, that is, the set low cooling water temperature T _WL , the duty D _{OUT is set} to 0 and the supercharging pressure P ₂ is reduced, and even if the cooling water temperature T _W exceeds the set water temperature T _WL. when the engine speed N _E exceeds the set rotation speed N _DO is until the elapse of the set time t _BTWCO as the time that may be determined that the engine warm-up has been completed, since the D _OUT remains set to 0 , supercharging pressure P ₂ is not increased when the engine speed N _E in the middle warmed up rises.

In the fifteenth step S15, the intake air temperature T _A is set to the set high intake air temperature T _AH
For example, it is determined whether or not the temperature exceeds 100 ° C. (T _A > T _AH ). If T _A > T _AH , the process proceeds to the third step S3, and T _A again.
When a ≦ T _AH proceeds to a sixteenth step S16. Next 16
In step S16, it is determined whether the cooling water temperature T _W exceeds a set high cooling water temperature T _WH, for example, 120 ° C. (T _W > T _WH ), and T _W >
When T _WH , the process proceeds to the third step S3, and when T _W ≦ T _WH , the process proceeds to a seventeenth step S17. Here, it is considered that T _A > T _AH and T _W > T _WH are satisfied, for example, when the engine continues to perform high-load operation, when the outside air temperature is extremely high, and when the cooling water system of the engine body E is used. Is abnormal. In all these states, the intake air density decreases, that is, the charging efficiency decreases, which causes abnormal combustion such as unburned combustion. In this way, when the supercharging pressure is introduced into the combustion chamber when the engine is in an unstable state, the unstable state is promoted. Therefore, the duty D _OUT = 0 is set in the fourth step S4. is there. At extremely high temperatures, the inductance characteristic of the solenoid 70 is liable to change, and may behave differently from the set behavior in the normal state. To avoid such a situation, the third step S3 is followed by the fourth step. It is what advances to S4.

In a 17 step S17, when the supercharging pressure P ₂ whether more than a high boost pressure determination guard value P _2HG which is set in advance as shown in FIG. 7 is determined, a P _2> P _2HG is first Proceed to 3 _stap S3, and if P ₂ ≦ P _2HG , the 18th step
Proceed to S18. Here high boost pressure determination guard value P _2HG is to vary according to the engine rotational speed N _E, which is set so that the highest output can be obtained by the following knock limit value corresponding to the engine speed N _E Things. In its limit low speed range torque exerted on the transmission member at a low speed gear stage positive, the durability of the engine body E in the critical high speed range becomes positive, P _2HG in less than the rotational speed range respectively are set. This high when more than boost pressure determination guard value P _2HG supercharging pressure P ₂ is detected, supercharging pressure as 100% duty ratio of the solenoid 70 in the control valve 69 in the fourth step S4 that has passed through the third step S3 with decreasing P ₂ is achieved, the fuel injection is cut.

Basic duty D _M as a 18 base supercharging pressure control amount in step S18 is searched. This basic duty D _M is
Are previously set depending on the engine speed N _E and the throttle opening theta _TH, basic duty D _M is retrieved from the settings table. By searching the map in this way defined by the basic duty D _M the engine speed N _E and the throttle opening theta _TH as a basic supercharging pressure control amount, it is possible to accurately determine the respective operating state of the engine . This is because the engine speed _NE alone or the throttle opening θ _TH alone cannot accurately determine the deceleration or the transient operation state. Incidentally it employs a throttle opening theta _TH as a representative of a parameter indicating the load state of the engine, but in which the same effect can be obtained by alternative to the intake pressure P _B and the fuel injection amount.

In the next nineteenth step S19, it is determined whether or not the shift position of the automatic transmission is at the first speed position. When the shift position is at the first speed position, the process proceeds to step S20, where the shift position is shifted to a shift position other than the first speed position. When there is, the process proceeds to the 21st step S21.

In a 20 step S20, the subtraction of the basic duty D _M is performed according to a subroutine shown in FIG. 8. That the engine speed N _E and determination zones are required weight loss according to the operation state determined by the intake pressure P _B is set in advance as shown by oblique lines in FIG. 9, it is within the determination zone, determination whether to subtract the basic duty D _M is determined depending on whether outside zone. Meanwhile in the Figure 9 and looking at the torque variation of the engine by the engine speed N _E and the intake pressure P _B, the boundary line determination zone shows the allowable torque of the gear shaft in the first speed position. That is, as the force on the gear shaft is not overloaded in the first speed position, the engine speed determination for each operating region as shown in FIG. 9 N _E and the intake pressure
P _B makes the right decision. When it is outside the discrimination zone, the process proceeds to the 22nd step S22 while keeping the basic duty D _M , but when it is inside the discrimination zone, it is determined whether the flag F is 0, that is, whether it is in the feedback control state. In the open control state, the subtraction of D _M = D _M -D _F is performed, and in the feedback control state, the subtraction of P _2REF = P _2REF -ΔP _2REFF is performed. Here, _DF is a preset subtraction value. P _2REF is a target supercharging pressure used in the feedback control state, and ΔP _2RFF is a preset subtraction value, which will be described in detail later in the section on feedback control.

In a 21 step S21, the subtraction of the basic duty D _M is performed according to a subroutine shown in Figure 10. That is, the throttle opening θ _TH exceeds the set throttle opening θ _THOS ,
Exceeded the engine speed N _E is the set rotational speed N _EOS, the intake pressure P _B exceeds the set intake pressure P _BOS, change rate .DELTA.N _E is positive in the previous engine rotational speed N _E, the current engine speed N _E when the rate of change .DELTA.N _E is negative, D _M = D _M -D _OS becomes subtraction is performed when in the open control state, P when it is in the feedback control state
_2REF = P _{2REF -ΔP 2REFOS} becomes subtraction is performed, the process proceeds to a 22 step S22 to the basic duty D _M as it is otherwise. Here, D _OS and ΔP _2REFOS are preset subtraction values.

In a twenty-second step S22, a duty correction coefficient is set.
K _MODij , duty atmospheric pressure correction coefficient K _PATC (0.8 to 1.
0) and the intake air temperature correction coefficient K _TATC for duty (0.8 to 1.
3) Search for each. Duty correction coefficient K _MODij
Is intended to be searched in the map determined by the engine speed N _E and the intake air temperature T _A, are learned when the optimum supercharging pressure P ₂ as described below are within a predetermined deviation, from time to time by the learning Be updated. Here, the initial value of the correction coefficient K _MODij is 1. The duty atmospheric pressure correction coefficient K _PATC is the intake pressure P _A
Determined for the further intake air temperature correction coefficient K _TATC duty is determined in accordance with the intake air temperature T _A.

In the twenty-third step S23, the correction coefficient K _DOWN is searched according to the subroutine shown in FIG. This subroutine interrupts the main routine of FIGS. 5A and 5B for each TDC signal. When the duty D _OUT is 0, the timer t _DOWN is reset and the duty D _OUT is no longer 0. From the correction coefficient K according to the first TDC signal
_DOWN is set to an initial value, for example, 0.5, and after the time counted by the timer t _DOWN has passed a predetermined time (for example, 5 seconds), the added value ΔK _DOWN, for example, every predetermined period, that is, for each TDC signal,
The correction coefficient K _DOWN is obtained by adding 0.1, and is set to 1.0 after the correction coefficient K _DOWN exceeds 1.0.

The correction coefficient K _DOWN determined in this manner is used in a correction equation of the duty D _OUT described later, and when the engine is in a specific operation range, that is, the intake air temperature T _A is abnormally high or low,
Or a cooling water temperature T _W is abnormally high or low temperature, when the state of forced to zero the duty D _OUT is released in a particular operating range of the supercharging pressure P ₂ is or a high-pressure abnormality, the duty This contributes to D _OUT stability control. That is, when the duty D _OUT is immediately returned to an abnormal value when the specific operation state in which D _OUT = 0 has been returned to the normal operation state, the duty D _OUT on the boundary between the specific operation area and the normal operation area can be reduced. Since irregular control occurs, in order to avoid such irregular control, the correction coefficient K _DOWN is set to a fixed initial value (for example, 0.5 seconds) until, for example, 5 seconds have elapsed after returning to the normal operation range as described above. ), The duty D _OUT is gradually returned to the normal control by increasing the correction coefficient K _DOWN at predetermined intervals, for example, by 0.1 after 5 seconds have elapsed.

In the next 24th step S24, it is determined whether or not the throttle opening θ _TH exceeds a preset throttle opening θ _THFB . This set throttle opening θ _THFB is set to determine whether to shift from open loop control to feedback control. By employing the throttle opening θ _TH as a determination parameter in this way, it is possible to accurately determine whether the driver is requesting acceleration, that is, a supercharging zone. θ _TH ≦ θ
_When it is _THFB, that is, when the open loop control is continued, the delay timer t _FBDLY shown in FIG. 6 is reset in a 25th step S25, and the process further proceeds to a 26th step S26.

In the 26th step S26, the set subtraction duty _DT and the set addition duty D _TRB are searched. The set subtraction duty _DT depends on the rate of change ΔP ₂ of the supercharging pressure P ₂ ,
It is determined according to the subroutine shown in the figure. That Figure 13 when the throttle opening theta _TH is greater than the set throttle opening _{θ THFB (a), (b} ), the change rate [Delta] P ₂ and the engine speed of the supercharging pressure P ₂ as shown by (c) setting subtraction duty D _T set by N _E is selected, when a θ _TH ≦ θ _THFB are D _T = 0.

13 (a) shows a set subtraction duty D _T when the engine speed N _E is less than the first switching rotational speed is preset N _FB1 (e.g. 3000 rpm), Figure 13 (b) is the engine rotational speed N _E exceeds the first switching speed N _FB1 second switching speed N
_FB2 (e.g. 4500 rpm) shows the setting subtraction duty D _T when it is less, FIG. 13 (C) is intended to indicate a set subtraction duty D _T when the engine speed N _E exceeds the second switching rotational speed N _FB2 It is. Here, the set subtraction duty _DT is equal to the set value P lower than the target supercharging pressure P _{2REF as} shown in FIG.
Intended to be processed from the time beyond the actual supercharging pressure P ₂ of _2ST, it is intended to prevent an overshoot when the rising of the supercharging pressure P _2. Moreover the D _T, as in the FIG. 13 and described above, but instead lifting in accordance with the engine rotational speed N _E and the supercharging pressure change rate [Delta] P _2, the engine speed when it is to reach the set value P _2ST the N _E, and because there is a difference in overshoot amount by the supercharging pressure change rate [Delta] P _2, it is an aim to optimize the duty control of each operation range by said lifting replacement. Greater the [Delta] P ₂ here, also the more N _E larger, D _T is set large.

Further, the set addition duty D _TRB is determined according to a subroutine shown in FIG. That Figure 15 when the change rate [Delta] P ₂ of the open loop control is a by addition supercharging pressure P ₂ is a negative state (a), (b), -ΔP 2 and the engine speed as shown by (c) setting summing duty D _TRB which is set by the N _E is selected and a further set subtraction duty D _T is 0. When ΔP ₂ is positive in the feedback control state, the set addition duty D _TRB is set to 0. The set addition duty D _{TRB is} also switched as shown in FIG. 15 according to the engine speed NE and the negative supercharging pressure change rate −ΔP ₂ similarly to the above-described set subtraction duty D _T , and N D _TRB increases as _E increases and -ΔP ₂ increases.
It is set to be larger, thereby it is possible to duty control, such as the boost pressure P ₂ which less stable hunting is obtained in each operation range. That is, in the operation range by adding a set sum duty D _TRB order to prevent the hunting from the boost pressure P ₂ exceeds the set pressure P _2ST generated as a reaction setting subtraction duty D _T for preventing overshoot This enables stable supercharging pressure control.

After the correction coefficients K _MODij , K _PATC , K _TATC , K _DOWN , the set subtraction duty _DT and the set addition duty D _TRM are determined in this way, the process proceeds to the 27th step S27, and in this 27th step S27, the duty D _OUT Is corrected by the following equation.

D _OUT = K _TATC × K _PATC × K _MODij × K _DOWN × (D _M + D _TRB −
D _T ) Therefore, the output duty D _OUT output from the fifth step S5 is set in consideration of the above-described contents and the operating state of the engine in consideration of external factors. Further, in a 28th step S28, the flag F is set to 1 to indicate that the control is open loop control.

In the following twenty-ninth step S29 and thirtieth step S30, it is determined whether or not the operating state of the engine is in a region where traveling in the second speed hold is possible. That is, the engine speed at the 29th step S29 N _E is first set rotation speed N _SEC1 e.g. 4500rpm
With the above, the second set rotation speed N _SEC2, for example, 6000 rpm or less (N
_SEC1 ≦ N _E ≦ N _SEC2 ), and in a thirtieth step S30, the vehicle speed V is set to the first set vehicle speed V _SEC1 for example, 70 km.
/ h or more and the second set vehicle speed V _SEC2 or less (V _SEC1 ≤ V ≤ V
_SEC2 ). These conditions are:
This is for determining whether or not the operating state of the engine is in a region where the vehicle can run in the second speed hold. If both conditions are satisfied, the duty D _{OUT is set} to 0 in the 31st step S31 and the process proceeds to the 32nd step S32. . Whereby force exerted on the gear shaft in the second speed position to lower the supercharging pressure P ₂ is prevented from being overloaded.

In the 29th and 30th step _{S29, S30, N E <N} SEC1,
N _SEC2 <N _E, when was _{V <V SEC1, V SEC2 <} V is,
Proceed to the 32nd step S32.

In the 32nd step S32, it is determined whether or not the shift position of the automatic transmission is in the first speed position. When the shift position is in the first speed position, the process proceeds to step 33, and when the shift position is in a shift position other than the first speed position. And the timer t in the 37th step S37
After resetting the _KDF , the process proceeds to the 38th step S38.

In a thirty-third step S33, it is determined whether or not the last time was at the first speed position, and if it was the first speed position, the process proceeds to the thirty-fourth step S34. In the 34th step S34, the timer t _KDF
Is determined to have passed a set time t _KDF0, for example, 5 seconds. If t _KDF > t _KDF0 , the process proceeds to the 38th step S38, and if t _KDF ≦ t _KDF0 , the process proceeds to the 36th step S36.

When it is determined in the 33rd step S33 that the previous time was at a shift position other than the first speed position, the 35th step S35
In After resetting the timer t _TFBDLY, the process proceeds to 38th step S38 the duty D _OUT as 0 in the 36 step S36.

The processing of the 32nd step S32 to the 37th step S37 is for kick down countermeasures, and is performed when the shift position is kicked down from a position other than the first speed position to the first speed position, and when the kick down is performed. Until a predetermined time, for example, 5 seconds, elapses, the duty D _{OUT is set} to ₀ and the first
The overload of the high speed gear shaft is prevented.

In the next 38th step S38, it is checked whether the duty D _OUT has not exceeded the limit value. That is set limit value of the duty D _OUT in advance according to the engine rotational speed N _E, checks whether deviate from the limit value, when not deviate from the limit value, the fifth
In step S5, the duty D _OUT is output.

_If it is determined in the 24th step S24 that θ _TH > θ _THFB , the process proceeds to the 39th step S39. This 39th step S
In 39, whether the last flag F is 1, i.e., the last time is determined whether an open loop control condition, the supercharging pressure P ₂ in the 40th step S40 when the F = 1 the duty control start in the open-loop Judgment boost pressure
It is determined whether _P2ST is exceeded. This duty control start determination supercharging pressure P _2ST is obtained by P _2ST = P _2REF −ΔP _2ST , and ΔP _2ST is _{calculated as} shown in FIGS.
Depending on the engine speed N _E as shown in (c) are set. Here [Delta] P _2ST is above D _T, similarly to the D _TRB, is intended to be replaced lifting in accordance with the engine rotational speed N _E and the supercharging pressure change rate [Delta] P ₂ in order to best duty control, the engine speed N _E
Is set so as to increase as the pressure change rate ΔP ₂ increases.

When a P _2> P _2ST at the 40th step S40 whether the boost pressure P ₂ in the 41 step S41 is greater than the feedback control start determination supercharging pressure P _2FB is determined. This feedback control start determination supercharging pressure P _2FB is expressed as P _2FB = P _2REF −ΔP _2FB
ΔP _2FB is obtained from FIG. 17 (a),
(B), it is set according to the engine rotational speed N _E as shown in (c). This feedback control start determination supercharging pressure P
_2FB is also the [Delta] P _2ST, D _T, similarly to the D _TRB, is intended to be replaced lifting in accordance with the engine rotational speed N _E and the supercharging pressure change rate [Delta] P ₂ in order to best duty control, the engine speed N _It is set to increase as _E increases and as the supercharging pressure change rate ΔP ₂ increases. This is when a P _2> P _2FB at the 41 step 41 proceeds to a 42 step S42.

In the forty-second step S42, it is determined whether or not the delay timer t _FBDLY has elapsed, and if it has elapsed, the process proceeds to the forty-third step S43. When F = 0 in the 39th step S39, the process goes to the 43rd step S43 bypassing the 40th to 42nd steps S40 to S42, and proceeds to the 44th step S44 when P ₂ ≦ P _2ST in the 41st step S41. If P ₂ ≦ P _2FB in the 41st step S41, the operation _proceeds to a 25th step S25, and if the delay timer t _FBDLY has not elapsed in the 42nd step S42, the 26th step
Proceed to S26.

At 44th step S44, settings are set in advance in accordance with the engine speed N _E as shown in Figure 18 the duty D _SCRB
Is found, and in the next forty-fifth step S45, the duty D _OUT is calculated according to the following equation.

D _OUT = D _SCRB × K _TATC × K _PATC Further, in a _forty- sixth step S46, the timer t _FBDLY is reset, and thereafter, the process proceeds to the thirty-eighth step S38.

Such first 44 to 46 step S46 is the supercharging pressure P ₂ is P
It is intended to be obtained in the operation range until reaching _2REF stable supercharging pressure control, output duty D with respect to the duty D _SCRB has set in advance in accordance with the engine speed N _E
By defining the _OUT, regardless of the change rate [Delta] P ₂ of supercharging pressure P _2, it is possible to prevent the overshoot occurs.

In a 43 step S43, the absolute value of the supercharging pressure change rate [Delta] P ₂ whether more than feedback control determination supercharging pressure difference G _dP2 is determined. This feedback control judgment supercharging differential pressure G
_dP2 is set to, for example, 30 mmHg, back to the 26 step S26 when the absolute value [Delta] P ₂ exceeds the feedback control determination supercharging pressure difference G _dP2, the absolute value of the feedback control determination supercharging pressure difference G of [Delta] P _{2 dP2} If it is below, the process proceeds to the 47th step S47. Here, if feedback control is started when | ΔP ₂ |> G _dP2 , hunting may occur. Therefore, the process returns to the 26th step S26 to perform open loop control. _T and D _{TRB are} corrected to prevent hunting and overshoot.
The focus of the 47 step S47 is to fulfill the fail-safe function.

Feedback control is started from the 47th step S47. First, in a 47th step S47, the engine speed N _E
And the target boost pressure preset by the intake air temperature T _A
P2REF is searched. Here the feedback control, first 24 serves θ _TH> θ _THFB assumed to satisfy the in step S24, the engine speed N _E as a parameter that can accurately determine the operating state of the engine in this premise conditions And a target boost pressure P _2REF determined by the intake air temperature T _A. Among θ _TH> θ _THFB i.e. engine, the engine speed N _E and the throttle opening theta _TH in the high-load state is intended to exhibit substantially the same behavior, N _E becomes valid parameter indicating the operating state of the engine Things. Also, the intake air temperature T _A
Is the intake air temperature on the downstream side of the intercooler 4 as shown in FIG. 1 and is a parameter that accurately indicates the state of the intake air introduced into the combustion chamber. Therefore, by determining a target supercharge pressure P _2ref a map defined by the engine speed N _E and the intake air temperature T _A, thereby capable of setting a value responsive to the operating state of the engine.

In the next forty-eighth step S48, it is determined whether the shift position of the automatic transmission is at the first speed position. When a first speed position is P _2REF = P _2REF -ΔP _2REFF when the operation state according to a subroutine shown in FIG. 8 described above in the 49th step S49 is in the determination zone (shaded area in FIG. 9) operation Is performed, and the process proceeds to a 51st step S51. This ΔP
_2REFF is an operation value set corresponding to when the shift position is at the first speed position. If it is determined in step 48 that the shift position is in a position other than the first speed position, then in step 50, the operation of P _2REF = P _2REF −ΔP _{2 REFOS is performed} according to the subroutine shown in FIG. Is performed, and the process proceeds to a 51st step S51. Moreover, ΔP2
_REFOS is a subtraction value set correspondingly when the shift position is in a state other than the first speed position.

51st step supercharging pressure has been set in advance according to S51 in the intake air pressure P _A the atmospheric pressure correction coefficient K _PAP2 is determined, the next operation is carried out further in the 52 step S52.

P _2REF = P _2REF × K _PAP2 × K _{REFTB In the} above equation, K _REFTB is a correction coefficient corresponding to the knock state of the engine.

In a 53 step S53, whether the absolute value of the deviation between the target supercharging pressure P _2ref and the present boost pressure P ₂ is the set value G _P2 or not is determined. The set value G _P2 is a dead zone defined pressure during feedback control is set to, for example, about 20 mmHg. When the absolute value of the difference between the supercharging pressure P ₂ and the actual target supercharging pressure P _2ref is the set value G _P2 or more, the first 54 step S
Proceeds to step 54, and when it is less than the set value _GP2 ,
Go to 61.

In a 54 step S54, the proportional control term D _P of the duty is calculated by the following equation.

D _P = K _P × (P _2REF −P ₂ ) In the above equation, K _P is a feedback coefficient relating to the proportional control term, and is obtained according to a subroutine shown in FIG. In this Figure 19, obtained feedback coefficient K _I1 according to the integral control term of the later with K _P1 is obtained when the engine speed N _E is less than or equal to the first switching rotational speed N _FB1, the engine speed N _E When the rotation speed exceeds the first switching rotation speed N _FB1 and is equal to or lower than the second switching rotation speed N _FB2 , K _P2 and K _I2 are obtained.
Furthermore the engine speed N _E exceeds the second switching rotational speed N _FB2 When K
_P3 and K _I3 are obtained.

55 In step S55 the engine speed N _E and the intake air temperature T _A
The correction coefficient K _MODij corresponding to is retrieved, and the 56th step S56
Then, it is determined whether or not the previous flag F is 1, that is, whether or not it is the first feedback control state. When F = 1, the previous integral control term DI _(n-1) is determined in a 57th step S57. Is calculated according to the following equation.

_{D I (n-1) =} K TATC × K PATC × D M × (K MODij -1) after the calculation end the process proceeds to 58th step S58, the first 56
If F = 0 in step S56, the 57th step S57
And goes to the 58th step S58.

In the fifty-eighth step S58, the current integral control term D _In is calculated according to the following equation.

_{D In = D I (n-} 1) + K I + (P 2REF -P 2) Then, the duty D _OUT at 59th step S59 is calculated. That is, an operation of D _OUT = K _TATC × K _PATC × K _DOWN × D _M + D _P + D _In is performed, and the flag F = 0 in the 60th step S60.
After that, the process proceeds to the 38th step S38.

Further when the absolute value of the deviation of the actual supercharging pressure P ₂ between the target supercharging pressure P _2ref is less than the set value G _P2 in the 53 step S53 D _P = 0 in the 61 step S61, D _In = D _{I (n-1)} .
Next, at # 62 step R62 to 66th step S66, the whether the atmospheric pressure P _A exceeds the set pressure P _AMOD example 650 mmHg, the water temperature T _W exceeds the certain range i.e. T _WMODL T
It is determined whether it is less than _WMODH, whether the retard amount T _ZRET is 0, that is, whether it is out of the knock state, whether the shift position is other than the first speed position, whether K _REFTB is 1.0 or less, When all of these conditions are satisfied, the flow proceeds to the 67th step S67, and when any of the conditions is not satisfied, the flow proceeds to the 59th step S59.

In a 67th step S67, a duty correction coefficient K _MODij
Coefficient K _R for learning is calculated according to the following equation.

K _R = (K _TATC × D _M + D _In ÷ (K _TATC × D _M )) Next, in a 68th step S68, in order to search and learn the correction coefficient K _MODij , Is performed, and in the 69th step S69, the 68th
After the limit check of K _MODij obtained in step S68 is performed, the correction coefficient K _MODij is stored in the backup RAM in step S70, and then the process proceeds to step 59.

Such first 64 to second 70 step S64~S70 is in storing the result of the learning control when the supercharging pressure P ₂ is stable feedback control with dead band G _P2 as the correction coefficient K _MODij, special Correction factor K _MODij
Is prohibited to avoid adversely affecting the operation state.

According to the duty control of the solenoid 70 in the electromagnetic control valve 69 as described above, the shift position of the automatic transmission is set to the first position.
When the engine is in the open loop control state, the basic duty _DM is subtracted by _DF in the twentieth step S20 when the operating state of the engine is in the determination zone in FIG. 49 In step S9, when in the determination zone, the target supercharging pressure P _2REF is reduced by ΔP _2RFE . Therefore, the shift position is
Rapid transmission of time is fast position, it is possible to prevent a decrease in the supercharging pressure with decreasing basic duty D _M overloading the automatic transmission due to an overload or the like. Further, even if the control is shifted from the open loop control to the feedback control in the first speed position, the hunting can be prevented from occurring at the shift because the target boost pressure _P2REF is subtracted.

It is also assumed that a shift change as shown in the lower part of FIG. 20 is performed. In this case, at the time of shift change,
While the engine speed _NE increases, the operation of the actuator 60 by the control means C has a time lag. Therefore, the boost pressure P ₂ is not corresponding to the engine speed N _E, in overshoot occurs supercharging pressure P ₂ in particular, as indicated by a broken line in FIG. 20, shift change immediately after acceleration from the high-speed range Sometimes the limit may be exceeded. However, step 21
In S21 and the 50th step S50, according to a subroutine shown in FIG. 10 is performed the subtraction of the duty D _M and the target supercharging pressure P _2ref. That is, at the time of a shift change, the throttle opening θ _TH exceeds the predetermined value θ _THOS ,
Exceeds a predetermined value N _EOS is the engine speed N _E, the intake pressure P _B is a predetermined value P
When it exceeds _BOS, i.e. within, in accordance with the change rate [Delta] P ₂ of supercharging pressure P ₂ in the high speed range, it is subtracted basic duty D _M is an open loop control only D _OS, the target supercharging pressure P in the feedback control _2REF is subtracted by ΔP _2REFOS . As a result, as shown by the solid line in FIG. 20, overshoot at the time of a shift change can be greatly reduced, hunting phenomenon can be avoided, and stable supercharging pressure control can be performed.

When further transition from open loop control in the field back control is to cover the drop in the supercharging pressure P ₂ as shown in FIG. 21, it is possible to shift quickly to feedback control. That is, when the operation is disclosed, the duty
In the open loop control in which D _OUT is 100, that is, the duty ratio is 0%, and the throttle opening θ _TH is less than the set throttle opening θ _THFB , the 26th step S26
Is set to D _T = 0 according to the subroutine of FIG. Then, when θ _TH > θ _THTB , the shift from the open loop control to the feedback control starts, but when θ _TH > θ _THFB when the supercharging pressure P ₂ exceeds P _2ST ,
D _M = D _M -D _T to prevent overshoot.

However, when only subtracting D _T as described above, may be in the reaction supercharging pressure P ₂ falls as shown by the dashed line in FIG. 21. However, if ΔP ₂ ≦ 0, D _T = 0, and only D _{TRB is} added, so that it is possible to cover the drop in the supercharging pressure P ₂ and quickly shift to feedback control.
The supercharging pressure control without the hunting phenomenon can be expanded.

The duty control of the solenoid 70 in the above-described electromagnetic control valve 69 is performed while the electromagnetic on-off valve 72 is closed. When the electromagnetic on-off valve 72 is opened, the second pressure chamber 63 in the actuator 60 is opened. intake pressure P _B is supplied to the actuator 60 is movable vanes 54 of the variable displacement turbocharger 5 is operated in the direction of the large voids flow area between the fixed vane 49. Thus, the actuator 60 is controlled based on the main routine of FIGS. 5A and 5B.
In addition to controlling the operation of the first to the pressure chamber 62 the boost pressure P ₂ for introducing electromagnetic control valve 69, when the second pressure chamber 63 of the actuator 60 via the electromagnetic switching valve 72 to introduce the intake air pressure P _B , More precise control becomes possible. This is because the supercharging pressure P ₂ is detected between the variable capacity turbocharger 5 and the intercooler 4, so that the minute operation of the throttle valve 74 cannot be detected.
Intake pressure P _B is because since it is derived from the downstream of the throttle valve 74 is capable of detecting a minute operation of the throttle valve 74. That is, the operation of the entire intake system including the turbocharger 5 is controlled by both the supercharging pressure sensor S _P2 that reliably detects the movement of the turbocharger 5 and the intake pressure sensor S _PB that reliably detects the movement of the throttle valve 74. It is possible to reflect more accurately.

In the above embodiment, the variable capacity turbocharger in which the capacity is changed by operating the movable vane 54 has been described, but the present invention relates to a fusible capacity turbocharger of a wastegate type and a supercharging pressure relief type. Is also applicable.

C. Effects of the Invention As described above, according to the present invention, when the operating state of the engine is in the specific state, the supercharging pressure is forcibly reduced regardless of the basic supercharging pressure, and when the specific state is released. First, since the basic supercharging pressure control amount is corrected so as to decrease over a predetermined time by a certain correction coefficient, the supercharging pressure is reduced when the operating state of the engine fluctuates on the boundary between the specific state and the non-specific state. It is possible to stably perform the supercharging pressure control based on the basic supercharging pressure control amount corresponding to the operating state after the specific state is surely released, and thus the durability of the engine can be maintained. Improvement and drivability can be achieved.

After the elapse of the predetermined time, the correction coefficient is corrected at predetermined intervals during such a correction of the basic supercharging pressure control amount, and the reduction amount of the basic supercharging pressure control amount by the correction coefficient gradually increases. Since it is made smaller, the reduced-corrected basic boost pressure control amount can gradually approach the normal basic boost pressure control amount, and therefore, the transition to the normal boost pressure control can be performed very smoothly without hunting. It can be carried out.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is an overall schematic view showing an intake system and an exhaust system of an internal combustion engine, FIG. 2 is an enlarged vertical sectional side view of a variable capacity turbocharger, and FIG. FIG. 2 is a sectional view taken along line III-III, FIG. 4 is a sectional view taken along line IV-IV in FIG. 2, FIGS. 5A and 5B are flowcharts showing a main routine for controlling the electromagnetic control valve, and FIG. Is a flowchart showing a subroutine for selecting a timer, FIG. 7 is a graph showing a guard value for determining a high boost pressure, FIG. 8 is a flowchart showing a subroutine for subtracting the basic duty and the target boost pressure at the first speed position, FIG. 9 is a diagram showing a discrimination zone used in the subroutine of FIG. 8, and FIG.
FIG. 11 is a flowchart showing a subroutine for subtracting a basic duty and a target supercharging pressure at a position other than the speed position. FIG. 11 is a flowchart showing a subroutine for obtaining a correction coefficient corresponding to cancellation of a specific operating state of the engine. A flowchart showing a subroutine for determination,
FIG. 13 is a diagram showing a map of the setting subtraction duty, FIG. 14 is a flowchart showing a subroutine for determining the setting addition duty, FIGS. 15, 16, and 17 are D _TRB ,
FIGS. 18A and 18B are diagrams showing setting maps of ΔP _2ST and ΔP _2FB , respectively. FIG. 18 is a diagram showing a map of duty set according to the engine speed, and FIG. 19 is a diagram showing feedback coefficients related to a proportional control term and an integral control term. FIG. 20 is a flowchart showing a subroutine for determination, FIG. 20 is a diagram showing a change in intake pressure at the time of a shift change, and FIG. 21 is a diagram showing a change in duty and supercharging pressure at the time of transition from open loop control to feedback control. . 5: Variable capacity turbocharger D _M …… Basic duty as basic boost pressure control amount

Claims (1)

(57) [Claims] 1. A variable displacement turbocharger control method for controlling a supercharging pressure based on a basic supercharging pressure control amount set according to an operating state of an engine, wherein the operating state of the engine is set to a specific state. In some cases, the supercharging pressure is forcibly reduced irrespective of the basic supercharging pressure control amount. When the specific state is released, the basic supercharging pressure control amount is first reduced by a fixed correction coefficient over a predetermined time. And the correction coefficient is corrected at predetermined intervals after the predetermined time has elapsed, so that the reduction amount of the basic supercharging pressure control amount by the correction coefficient gradually decreases. To control a variable capacity turbocharger.