JPH01253527A - Supercharging pressure control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To control supercharging pressure stably and properly by starting feedback control in such a manner that the actual supercharging pressure comes to a target supercharging pressure in the lapse of a fixed time after the supercharging pressure exceeds a designated value when the supercharging pressure is in the transient state. CONSTITUTION:An air cleaner 6 is connected to an intake manifold 1 of an internal combustion engine E through an intake pipe 2, a throttle body 3, an inter cooler 4 and a variable-capacity turbo-charger 5. The turbo-charger 5 is driven by an actuator 60. A solenoid control valve 69 and a solenoid switch valve 72 respectively connected to the actuator 60 are respectively controlled according to a detection signal from a supercharging pressure sensor Sp 2 by control means C. In this case, when the supercharging pressure is in the transient state, feedback control is started in such a manner that the actual supercharging pressure comes to a target supercharging pressure in the lapse of a designated time after the supercharging pressure exceeds a designated value.

Description

Detailed Description of the Invention A2 Objective of the Invention (1) Industrial Application Field The present invention determines the controlled iTJ amount according to the deviation between the actual boost pressure and the target boost pressure, and adjusts the controlled amount to the controlled amount. The method relates to a supercharging pressure control method for an internal combustion engine that performs feedback control so that the boost pressure becomes the target boost pressure based on the target boost pressure, and in particular supercharging from a transient state to a steady state accompanied by a sudden change in the magnitude of the boost pressure. The present invention relates to a supercharging pressure control method for an internal combustion engine that enables stable and appropriate pressure control.

(2) Conventional technology In a so-called variable displacement turbocharger that uses exhaust gas flow as a turbine drive source and other supercharged internal combustion engines that can control boost pressure, an appropriate actuator (for example, to adjust boost pressure or negative pressure in the intake pipe) Feedback control has conventionally been used when boost pressure is controlled by a pressure-responsive actuation system including a diaphragm used as the actuation pressure, an actuation system using a step motor, etc.).

This is because the boost pressure is affected by individual openings such as manufacturing variations in the actuator and the components of the turbocharger body, and aging changes such as durability deterioration due to use. When operating with a preset control amount when controlling to the value of (The amount of adjustment operation may differ due to the opening of the lid or changes over time as mentioned above), but feedback control of boost pressure solves such problems. This is because it can be done. In other words, feedback control detects the deviation between the target boost pressure and the actual boost pressure, and performs control by determining the control amount according to the deviation so that the deviation becomes zero. Even if there are individual variations in the actuators or changes over time, these effects will be absorbed and corrected in the feedback control.

Therefore, when controlling the boost pressure to the required target pressure corresponding to the engine operating condition, the control amount is determined based on the above deviation so that the boost pressure becomes the target pressure. It is desirable to perform feedback control.

(3) Problems to be Solved by the Invention However, in some cases, the feedback described above may cause an undesirable abnormal increase in boost pressure.

In other words, in so-called transient states, such as when boost pressure suddenly increases, the control amount cannot follow the boost pressure adjustment due to a delay in the response of the control system, resulting in abnormal rises, drops, and hunting in boost pressure. Such phenomena occur.

Especially when it is necessary to rapidly increase the boost pressure to increase the engine output in response to acceleration, when the boost pressure increases toward the target boost pressure set high according to the operating condition, The boost pressure exceeds the target boost pressure and overshoots, and the larger the overshoot, the longer the hunting period becomes and the unstable boost pressure control. If this occurs, knocking will occur, which will also impede drivability during acceleration.

Therefore, in order to eliminate the above-mentioned problems with the feedback control in the transient state, the applicant has developed a supercharging pressure control method in which the supercharging pressure control is oven loop control in the transient state, and feedback control is performed in the steady state. (Japanese Unexamined Patent Publication No. 63-129126) has proposed this, and according to this, it is possible to perform more stable supercharging pressure control than the conventional one.

However, when oven loop control and feedback control are used separately for transient states and steady states, as in the control method proposed above, there is room for improvement in the following points, and if these are also improved, the results will be even better. It becomes possible to perform more stable supercharging pressure control.

In other words, when shifting to feedback control, if the decision to start feedback control is made only based on the state of boost pressure, satisfactory stability cannot be obtained. For example, when boost pressure increases, boost pressure is slightly less than the target boost pressure. If a steady state is determined and feedback control is started when the boost pressure exceeds a small predetermined value, a transient state will occur between when the boost pressure reaches the above predetermined value, that is, the feedback control start pressure, and when the target boost pressure is reached. Therefore, depending on the operating conditions, an abnormal increase in boost pressure or hunting may occur. On the other hand, if the target boost pressure and feedback control start pressure are set fairly close to each other in order to avoid this, the boost pressure will not rise to the feedback control start pressure and will be in a steady state, causing the boost pressure control to open loop. It may remain under control. In such a case, as a result of maintaining open loop control, it becomes difficult to correct variations among individual actuators used, changes over time, etc. by feedback control as described above.

The present invention has been made in view of the above circumstances, and it is possible to prevent abnormal increases in boost pressure and hunting even in cases where boost pressure increases dramatically, and to ensure reliable feedback control. It is an object of the present invention to provide a method of controlling boost pressure for an internal combustion engine, which enables the transition, thereby further stabilizing and optimizing the boost pressure from a transient state to a steady state.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the method of the present invention determines a control amount according to the deviation between the actual boost pressure and the target boost pressure, and controls the control amount. ?
In the boost pressure control method for an internal combustion engine that performs feedback control so that the boost pressure becomes the target boost pressure based on 111, when the boost pressure exceeds a predetermined value during a transient state of the boost pressure, The present invention is characterized in that the feedback control is started after a predetermined time has elapsed.

(2) Effect According to the above method, feedback control is not started until a predetermined time has elapsed after the boost pressure reaches a predetermined value.
By delaying the start of feedback control in this way, it is possible to suppress as much as possible overshoot, hunting, etc., from occurring when transitioning to feedback control.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. An intake manifold 1 is connected to the intake boat of each cylinder in the engine body E of a multi-cylinder internal combustion engine, and this intake manifold 1 is further connected to an intake pipe. 2, connected to an air cleaner 6 via a throttle body 3, an intercooler 4, and a variable displacement turbocharger 5. Further, an exhaust manifold 7 is connected to the exhaust boat of each cylinder, and this exhaust manifold 7 is connected to a catalytic converter 9 containing a three-way catalyst via an exhaust pipe 8 with a variable capacity turbocharger 5 interposed in the middle. be 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 displacement turbocharger 5 is provided with a water jacket 11, and the inlet of the water jacket 11 and the ink cooler 40 inlet are connected in parallel to the discharge port of a water pump 13 whose suction port is connected to the radiator 12. water pump 13
And the outlet of the ink cooler 4 is connected to the radiator 12. Furthermore, the radiator 12 is provided separately from the cooling water radiator on the side of the engine body.

Next, the configuration of the variable displacement turbocharger 5 will be explained with reference to FIGS. 2, 3, and 4. The turbocharger 5 includes a compressor casing 14 and a a plate 15; a bearing casing 17 that supports the main shaft 16;
A turbine casing 18 is provided.

A scroll passage 19 is defined between the compressor casing 14 and the back plate 15, and the compressor casing 1
An inlet passage 20 extending in the axial direction is formed in the central portion of 4. Moreover, a compressor wheel 21 is attached to one end of the main shaft 16 in the central portion of the scroll passage 19 and located at the inner end of the inlet passage 20.

The compressor casing 14 and the back plate 15 are fastened together with a plurality of bolts 22.

A bearing casing 17 is connected to the center of the bearing 15 .

A pair of bearing holes 23 and 24 are coaxially bored in the bearing casing 17 with an interval between them, and the main shaft 16 and the bearing holes 23 and 24 are inserted into these bearing holes 23 and 24, respectively.
Radial bearing metals 25 and 26 are interposed between them, respectively, so that the main shaft 16 is rotatably supported by the bearing casing 17. Further, a collar 27, a thrust bearing metal 28, and a bushing 29 are interposed between the step portion 16a of the main shaft 16 facing the compressor wheel 21 side and the compressor wheel 21 in this order from the step portion 16a side. By screwing and tightening a nut 30 that abuts the outer end of the main shaft 16 to one end of the main shaft 16, the main shaft 16 is supported in the thrust direction and the compressor wheel 21 is attached 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 a lubricating oil introducing hole 32 is provided in the bearing casing 17 to the radial bearing metal 25, 26 and the thrust bearing metal 28. A lubricating oil passage 33 is bored to guide the supplied lubricating oil.

Further, a lubricating oil outlet 34 is provided in the lower part of the bearing casing 17 for discharging the lubricating oil flowing out from each lubricating part downward. collected in the sump.

The bushing 29 is disposed through a through hole 35 bored in the center of the back plate 15, and is arranged through 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 in order to prevent lubricating oil flowing out from the bushing 8 from flowing toward the compressor wheel 21 side.

Further, a guide plate 37 is sandwiched between the back plate 15 and the thrust bearing metal 28 and allows the bushing 29 to pass therethrough. Therefore, the lubricating oil flowing out from the thrust bearing metal 28 is scattered radially outward from the bushing 29 and the guide plate 3
It is accepted at 7. Moreover, the lower part of the guide plate 37 is curved to smoothly guide the received lubricating oil to the lubricating oil outlet 34.

The bearing casing 17 is provided with a water jacket 11 around the main shaft 16, and a water supply port 38 for guiding water from the water pump 13 (see FIG. 1) to the water jacket l-11, as well as the water jacket 11. A water outlet 39 is provided for guiding water from the radiator 12 to the radiator 12 (see FIG. 1). In addition, the water jacket 11 is formed in a circular ring shape surrounding the main shaft 16 in a portion close to the turbine casing 18, and in a substantially U-shape that opens downward above the main shaft 16 in a portion corresponding to the upper part of the lubricating oil discharge port 34. The water supply port 38 is formed to have a cross-sectional shape, and the water supply port 38 is connected to the water jacket 1.
1 is bored in the bearing casing 17 to communicate with the lower part of the bearing casing 1,
A water outlet 39 is bored in the bearing casing 17 to communicate with the upper part of the water jacket 11.

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

Bearing casing 17 and turbine casing 18 are coupled to each other with back plate 44 sandwiched therebetween. That is, a plurality of stud bolts 45 are screwed into the turbine casing 18, and the bearing casing 17
The bearing casing 17 and the turbine casing 18 are mutually coupled by tightening the ring member 46 that engages with the stud bolt 45 with the nut 47, and the flange portion 44a provided on the outer periphery of the back plate 44 is connected to the bearing casing. 17 and the turbine casing 18.

A fixed vane member 48 is fixed to the back plate 44, and the fixed vane member 48 divides the inside of the scroll passage 41 into an outer circumferential passage 41a and an inflow passage 41b. The fixed vane member 48 has a cylindrical portion 4 that fits coaxially into the outlet passage 43.
8a, a disk portion 48b extending radially outward from the outer surface of the intermediate portion of the cylindrical portion 48a, and 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 side. A turbine wheel 50 provided at the other end of the main shaft 16 is housed within the fixed vane member 48. The cylindrical portion 48a is fitted into the outlet passage 43 through a seal ring 51 fitted on the outer surface thereof, and the fixed vane 49 is coupled to the back plate 44 by bolts 52.

The fixed vanes 49 are provided on the outer periphery of the turbine member 48 at equal intervals in the circumferential direction, and each fixed vane 49 is formed in an arc shape. Also, between each fixed vane 49, a back plate 4 is arranged parallel to the axis of the main shaft 16.
Movable vanes 54 having one end fixed to a rotation shaft 53 rotatably connected to the fixed vanes 4 are arranged, and the flow area of the gap between the fixed vanes 49 is adjusted by these movable vanes 54.

Each movable vane 54 is formed in an arc shape with the same curvature as the fixed vane 49, and is rotatable between a fully closed position shown by a solid line in FIG. 3 and a fully open position shown by a chain line. Moreover, each rotation shaft 53 is connected to the actuator 6 via a link mechanism 55 arranged between the back plate 44 and the bearing casing 17.
0, and each movable vane 54 is driven to open and close in synchronization with the operation of the actuator 60.

A shield plate 56 extending to the back of the turbine foil 50 is sandwiched between the back plate 44 and the bearing casing 17, and the heat of the exhaust gas flowing through the inflow path 41b is directly transmitted to the inside of the bearing casing 17 by this shield Fi, 56. This will be prevented as much as possible. In addition, in order to prevent exhaust gas from leaking into the bearing casing 17, the main shaft 16 should protrude into the turbine casing 18 (at a portion corresponding to the through hole 57 provided in the bearing casing 17, the main shaft 16 has a labyrinth). A plurality of annular grooves 58 functioning as grooves
is provided.

In such a variable capacity turbocharger 5, exhaust gas discharged from the engine body E flows from the inlet passage 42 to the outer peripheral passage 41a.
Exhaust gas flows into the inlet passage 41b at a flow rate corresponding to the flow area of the gap between the movable vane 54 and the fixed vane 49, which corresponds to the amount of rotation of the movable vane 54, and rotates the turbine wheel 50 to form the outlet. It is discharged from the passage 43. At this time, when the flow area of the gap between each movable vane 54 and the fixed vane 49 becomes smaller, the rotational speed of the turbine wheel 50, that is, the main shaft 16 becomes faster, and when the flow area of the gap between each movable vane 54 and the fixed vane 49 becomes larger. The rotational speed of the turbine wheel 50, ie, the main shaft 16, decreases. The compressor wheel 21 rotates in accordance with the rotation of the turbine wheel 50, and the compressor wheel 21 rotates from the air cleaner 6 to the inlet passage 2.
The air guided to the ink cooler 4 passes through the scroll passage 19 while being compressed by the compressor wheel 21.
It will be supplied to. Therefore, when the movable vane 54 is positioned at the outermost position in the radial direction of the turbine casing 18 to minimize the air gap circulation area between the movable vane 54 and the fixed vane 49, the supercharging pressure becomes maximum, and the movable vane 54 The supercharging pressure becomes the minimum when the gap circulation area between the fixed vane 49 and the fixed vane 49 is maximized by positioning the vane in the direction.

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

Referring again to FIG. 1, the actuator 60 for driving the movable vane 54 of the variable displacement turbocharger 5 is
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.
and the diaphragm 64 in the direction of contracting the first pressure chamber 62.
A return spring 65 is interposed between the housing 61 and the diaphragm 64 to bias the diaphragm 64 , and a return spring 65 is connected at one end to the center of the diaphragm 64 and passes through the housing 61 airtightly and movably on the second pressure chamber 62 side. and a drive rod 66 whose other end is connected to the link mechanism 55. Furthermore, the drive rod 66 and the link mechanism 55 are such that when the diaphragm 64 is bent in the direction to contract the second pressure chamber 63 and the drive rod 66 is extended, each movable vane 54 is moved inward in the radial direction of the turbine casing 18. It is connected so as to rotate and increase the air gap circulation area between the fixed vanes 49 and each fixed vane 49 .

An intake passage between the variable displacement turbocharger 5 and the inktor 94 is connected to the first pressure chamber 62 via a regulator 67, a throttle 68, and an electromagnetic control valve 69 to supply supercharging pressure P2, and the air cleaner 6 and Intake passages between the variable capacity turbochargers 5 are connected via a throttle 75. This electromagnetic control valve 69 is duty-controlled, and as the duty ratio of the solenoid 70 increases, the pressure in the first pressure chamber 62 increases, that is, it is variable via the drive rod 66 and the link mechanism 55. The movable portion of the turbocharger 5 -754 is rotated inward. In addition, the second pressure chamber 63 is provided with a check valve 7 so that an intake passage downstream of the throttle body 3 supplies the intake pressure P.
1 and an electromagnetic on-off valve 72. This electromagnetic on-off valve 72 opens in response to the excitation of the solenoid 73, and the second electromagnetic on-off valve 72 opens in response to the opening of the solenoid 73.
When the intake pressure P3 is supplied to the pressure chamber 63, the actuator 60 moves the movable vane 54 of the variable displacement turbocharger 5.
drive inward.

Solenoid 70 of electromagnetic control valve 69 and electromagnetic on-off valve 72
The excitation and demagnetization of the solenoid 73 is controlled by the control means C, and the control means C includes the engine main body E.
Water temperature T of a water jacket (not shown) provided inside. an intake air temperature sensor SA that detects the intake air temperature TA on the downstream side of the ink cooler 4, and an intake pressure sensor S7 that detects the intake pressure P between the air cleaner 6 and the variable displacement turbocharger 5. , a supercharging pressure sensor SP2 that detects the supercharging pressure P2 in the intake passage between the variable displacement turbocharger 5 and the intercooler 4, and an intake pressure sensor S□ that detects the intake pressure P on the downstream side of the throttle body 3. , engine rotation speed N, : a rotation speed detector S that detects
H, and a throttle opening detector STH that detects the opening θ7H of the throttle valve 74 in the throttle body 3;
A vehicle speed detector Sv for detecting vehicle speed V and a shift position detector S for detecting a shift position in the automatic transmission are connected. The control means C receives these input signals, that is, the water temperature T1. I, intake air temperature TA, intake pressure)) A%
Boost pressure P2, intake pressure PM, engine speed N.

, throttle opening θA□, vehicle speed ■, and automatic transmission shift position signals to control excitation and demagnetization of the solenoids 70 and 73.

Next, the control procedure in the control means C will be explained. First, the duty control of the solenoid 70 in the electromagnetic control valve 69 will be explained with reference to the main routine shown in FIG. However, in this main routine, duty D is used to control the excitation and demagnetization of the solenoid 70. As the value of UT increases, the duty ratio of the solenoid 70 decreases; DOUT=O corresponds to a duty ratio of 100%, and DooT-100 corresponds to a duty ratio of 0%.

In the first step S1, it is determined whether the engine is in the starting mode, that is, whether the engine is cranking. If the engine is in the starting mode, the duty is set to D in the second step S2. It is set so that Ua is 0, that is, the electromagnetic control valve 69 is fully opened, and the air gap circulation 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 supercharging pressure into the combustion chamber in such an unstable state will aggravate the instability. This is to avoid supercharging pressure being introduced into the combustion chamber by maximizing the air gap flow area between the two. Further, during cranking, the driver does not request supercharging of air supply, and there is no need to reduce the air gap circulation area between the movable vane 54 and the fixed vane 49. In the next third step S3, the timer tFIIDLY for delaying the start of feedback control is reset, and then the duty D is reset from the fourth step S4.

LIT is output.

The timer t FIIDLv is calculated according to the procedure shown in FIG. 6, and the three timers tFllDLYI+LPBDL are
One of YZ+L FRDLY:l is selected.

Here, the rate of change ΔP2 is the current supercharging pressure Pin and 6
Difference from previous supercharging pressure P2□6 (ΔP2 = P, -P2
It is found by □, ). That is, the main routine shown in FIG. 5 is updated by the TDC signal, but since the rate of change in supercharging pressure P2 is too small with only one TDC signal, the supercharging pressure behavior, that is, the rate of change ΔPl! In order to accurately read the supercharging pressure PZ+ and -6 six times earlier, the difference is calculated. Further, the set low rate of change ΔP ZPTL and the set high rate of change ΔP 2PTM are predetermined according to the engine speed Nt, and ΔP2≦ΔP ZPT
When it is L, tF111LN'l is set and ΔP
When zrtt <ΔP2≦ΔP gFTH, L□D
L'l□ is set, and when ΔP2P'Tll<ΔPt, tFIIOL7. is set. And L□DL
YI < t rmoLvt < t□DLY3,
When the supercharging pressure change rate ΔP2 is small, that is, when the supercharging pressure P2 is changing slowly, the delay time is set small, and when the supercharging pressure change rate ΔP2 is large, that is, the supercharging pressure P
2 is changing rapidly, the delay time is set to be large.

As a result, the correct time L□DLY is set when transitioning from oven loop control to feedback control.
It is possible to sufficiently avoid the hunting phenomenon occurring during the transition.

If it is determined in the first step SL that the starting mode is not set, the water temperature T, 1 is set to the set low water temperature T in the fifth step S5.
, it is determined whether it is less than IL, and the set low water temperature TW is set.
If it is less than L, the process proceeds to the second step S2. Here, the operating state of the engine that can be considered as a case where T, 1 < T, IL holds is, for example, when the engine is initially started or when the outside temperature is extremely low. continues to be unstable, and when the outside temperature is extremely low, the intake air density increases, which increases charging efficiency and causes abnormal combustion. In such a case, introducing supercharging pressure into the combustion chamber will promote an unstable state of the engine and abnormal combustion. Also, at extremely low temperatures, the solenoid control valve 6
9 itself may be malfunctioning, and there is a possibility that the electromagnetic control valve 69 may not behave as instructed by the control means C. Therefore, when T,4<T, the process proceeds to the second step S2. LI? ”=0.

In the fifth step S5, T1. , ≧ Tw1 or more, the process proceeds to the sixth step S6. In this sixth step S6, it is determined whether the water a'rw exceeds the set high water temperature T■, and when it exceeds the set high water temperature T□. Proceed to the second step S2. Here, possible cases where T w > T work are true are, for example, when the engine continues to operate under high load, when the outside temperature is extremely high, or when an abnormality occurs in the cooling water system of the engine body E. This is the case when there is a In all of these conditions, the intake air density decreases, that is, the charging efficiency decreases, which causes abnormal combustion such as non-combustion. Introducing supercharging pressure into the combustion chamber when the engine is in an unstable state will aggravate the unstable state, so the duty D is set in the second step S2.吋=0
That is. Furthermore, at extremely high temperatures, the inductance characteristics of the solenoid 70 are likely to change, and there is a risk that the solenoid 70 will behave differently from the set behavior under normal conditions.In order to avoid such a situation, the second step S2 is proceeded to. When it is determined in the sixth step S6 that TI4≧Twn, the process proceeds to the seventh step s7. That is, water temperature T
8 is in the range of not less than the set low water temperature T1 and not more than the set high water temperature T□, the process proceeds to the seventh step S7, and otherwise the process proceeds to the second step S2.

In the seventh step S7, the supercharging pressure P2 is set to a preset high supercharging pressure determination guard value PZN(i
It is determined whether Pt>PZNG, the process proceeds to the second step s2, and when P2≦PZHG, the process proceeds to the eighth step s8. Here, the high boost pressure determination guard value P tHG changes depending on the engine rotation speed N. (corresponding to the above) and is set so that the maximum output can be obtained below the link limit value. In the limit low speed range, the torque applied to the transmission member in the low gear is positive, and in the limit high speed range, the durability of the engine body E is positive, and P2HG is lower than in the middle speed range.
is set. This high boost pressure judgment guard value P 2N
When the supercharging pressure P exceeding G is detected, the second and third steps S2. In the fourth step S4 after passing through N3, the duty ratio is set to 100% to lower the supercharging pressure P2 and fuel injection is cut.

In the eighth step S8, a basic duty D as a basic boost pressure control amount is searched. This basic duty D is set in advance according to the engine speed N and the throttle opening 07N, and the basic duty ratio is searched from the setting table.

In this way, the basic duty D as the basic boost pressure control amount
0 is engine speed N, and throttle opening θT.

By searching using the map determined by , it is possible to accurately judge each operating state of the engine. This is because deceleration or transient operating conditions cannot be accurately determined by the engine speed N11 or the throttle opening θa alone.

Although the throttle opening θTH is used as a representative parameter indicating the engine load condition, the same effect can be obtained by replacing it with the intake pressure P or the fuel injection amount.

In the next ninth step S9, it is determined whether or not the shift position of the automatic transmission is in the first gear position. If it is in the first gear position, the process proceeds to a tenth step 310, and the automatic transmission is shifted to a shift position other than the first gear position. If so, the process proceeds to the eleventh step 311.

At the tenth step SlO, the basic duty D9 is subtracted according to the subroutine shown in FIG. In other words, a determination zone in which weight loss is required according to the operating condition determined by the engine speed N and intake pressure P is preset as shown by diagonal lines in FIG. Basic duty D depending on whether it is outside the zone
It is determined whether or not to perform subtraction of . By the way, the 9th
In the figure, changes in engine torque are observed based on the engine rotational speed N and intake pressure P, and the boundary line of the discrimination zone indicates the allowable torque of the gear shaft at the first speed position. That is, the first
To prevent the force applied to the gear shaft from becoming overloaded in the high speed position,
As shown in Figure 9, the discrimination in each operating range is determined by engine speed NE.
and the intake pressure P8. When it is outside the discrimination zone, the basic duty D is left unchanged and the process proceeds to step 12, but when it is within the discrimination zone, it is determined whether the flag F is 0, that is, whether the feedback control state is in effect. After that, when in the open control state, subtractions such as High, -〇, and Dr are performed, and when in the feedback control state, P2
The following subtraction is performed: □, =P2□, -ΔPZ11°. Here, D is a preset subtraction value. Also P
2REF is the target supercharging pressure used in the feedback control state, and ΔP2FF is a preset subtraction value, which will be explained in detail in the feedback control section below.

At the eleventh step Stt, the basic duty D is subtracted according to the subroutine shown in FIG. In other words, throttle opening θ, □ is the set throttle opening θT
HO3 is exceeded, the engine speed N exceeds the set speed NEO3, the intake pressure P exceeds the set intake pressure PR03, the rate of change ΔNE of the previous engine speed N is positive, and the current engine speed N , when the rate of change ΔN, is negative, the subtraction DH=DM Dos is performed in the open control state, and P ZR
The subtraction EF=P2REF-ΔP2□ros is performed, otherwise the basic duty is D. , and proceed to the twelfth step S12. Here it is. 5.
ΔPal! FO! l is a preset subtraction value.

In the twelfth step S12, it is determined whether the throttle opening degree θa exceeds a preset throttle opening degree θa□8. This set throttle opening degree θTN□ is set to determine whether to shift from open loop control to feedback control. By employing the throttle opening degree θ7 as a determination parameter in this way, it is possible to accurately determine whether the driver is requesting acceleration, that is, the supercharging zone. θ
When TH≦θT)IFB, that is, when open loop control is to be continued, in the 13th step S13, the delay timer tFBDLY shown in FIG. 6 is reset,
The process then proceeds to a fourteenth step 314.

In the fourteenth step S14, the duty correction coefficient KM
Search for ooi. This correction coefficient KMODij is searched using a map determined by the engine speed N and the intake air temperature TA, and is learned when the optimum boost pressure P2 falls within a predetermined deviation as described later. Updated from time to time. Here, the initial value of the correction coefficient K M OOi j is 1.

In the next 15th step S15, the duty atmospheric pressure correction coefficient KPATC (0.8 to 1.0) is determined corresponding to the intake pressure PA, and further in the next 16th step S16, the duty intake temperature correction coefficient KyAtc (0.8 to 1.0) is determined corresponding to the intake pressure PA. 0-8~1.3)
is determined corresponding to the intake air temperature TA.

In the seventeenth step S17, a set subtraction duty D7 corresponding to the rate of change ΔP2 of the supercharging pressure P2 is determined according to the subroutine shown in FIG. In other words, the throttle opening θT
l+ is the set throttle opening θ eye.

12 (a), ([)), (C
), the set subtraction duty D is selected based on the rate of change ΔP2 of the supercharging pressure P2 and the engine speed N, and when θT+(≦θT□, D1=0
It is said that

FIG. 12(a) shows the set subtraction duty D when the engine speed N is less than or equal to the preset first switching speed N, □ (for example, 3000 rpm).

12(b) shows the set subtraction duty D when the engine speed N exceeds the first switching speed N, □ and is below the second switching speed NF12 (for example, 4500 rpm), FIG. 12(C) shows the set subtraction duty DA when the engine speed N is less than the second switching speed NFIZ. Here, the set subtraction duty DT is the target supercharging pressure P ZI as shown in Fig. 19, which will be described later.
This is processed when the actual supercharging pressure P2 exceeds a set value pzs↑, which is lower than IEF, and is intended to prevent overshoot when the supercharging pressure Pi rises.

Moreover, as shown in FIG. 12 and as described above, D7 is changed depending on the engine speed N and the boost pressure change rate ΔP2, but this is the engine speed N at which the set value pisA is reached.
Since the overshade i differs depending on the boost pressure change rate ΔP2, the purpose of this is to optimize the duty control in each operating range by changing the holding position. Here, the larger ΔP2 and the larger N1, the larger D is set.

Furthermore, in the 18th step S18, the set addition duty D, □ is determined according to the subroutine shown in FIG. In other words, when the rate of change of supercharging pressure P2 is negative in open loop control, the 14th
As shown in Figures (a), (b), and (C), the set addition duty D and □ set by -P2 and engine speed N1 are selected, and the set subtraction duty DT is selected.
is set to 0.

Further, when the feedback control state is in effect and 8P2 is positive, the set addition duty DTR8 is set to 0. Like the setting subtraction duty D7 described above, this setting addition duty DTR is also switched as shown in FIG. The larger the −ΔPt, the larger the D
fill is set to be large, thereby making it possible to perform duty control such that a stable supercharging pressure P2 with little hunting can be obtained in each operating range. That is, the predetermined area P from the start of operation. Tight up to T. uy ”” 1
00, the air gap flow area between the movable vane 54 and the fixed vane 49 is minimized to increase the supercharging pressure P2, and the supercharging pressure P2 reaches the set pressure P. After exceeding T, it is necessary to prevent hunting that occurs as a reaction to the set subtraction duty DT for overshoot prevention (By adding the set addition duty DT □, stable boost pressure control is possible in each operating range. Therefore, the output duty D.UT outputted from the fourth step S4 is set by taking into consideration the above-mentioned contents and external factors, and also comprehensively considering the operating state of the engine.

In this way, the correction coefficient is +4oot= + Kratc
, KTATC1 After the set subtraction duty DT and the set addition duty DTRM are determined, the process advances to the nineteenth step S19.

In the nineteenth step S19, the duty DOt+T is corrected using the following equation.

DOLIT = KTATCX KPATCX Kso
otJx (DM +DT□-D?) Furthermore, in the 20th step S20, the flag F is set to 1 to indicate open loop control, and the duty D is set in the 21st step S21. , T is checked to see if it exceeds the limit value.

That is, a limit value of the duty Dt is set in advance according to the engine speed NE, and it is checked whether the duty Dt deviates from the limit value, and if it does not deviate from the limit value, the duty Dt is set in a fourth step S4. ut is output.

When it is determined in the twelfth step S12 that θI>θ□HF8, the process proceeds to the 22nd step 322. In this 22nd step S22, it is determined whether the previous flag F is 1, that is, whether or not the previous time was an open loop control state. It is determined whether the duty control start determination supercharging pressure P2,7 is exceeded. This duty control start determination supercharging pressure P 2
ST is P23? "Pff1ll!F-ΔP2S
T, and ΔP25. is shown in Figure 15 (
As shown in a), (b), and (C), they are set according to the engine speed Nt. Here, ΔP0a is the above-mentioned Da+
Similar to DTill, the engine speed NF and boost pressure change rate ΔPg are adjusted for optimal duty control.
It is set to increase as the engine speed N increases and as the boost pressure change rate ΔPt increases.

If pt>Pzsv in the 23rd step S23, it is determined in the 24th step S24 whether the boost pressure P2 exceeds the feedback control start determination boost pressure P2FB. This feedback control start determination supercharging pressure P2□ is obtained from P2Fl = Pz*vv-ΔP2F, and ΔP2□ is shown in FIGS. 16(a) and (b).
, as shown in (C), are set according to the engine speed N. That is, ΔP2FIl is the above-mentioned ΔPZ5a,
Similar to DA, D, and □, it is switched depending on the engine speed N and boost pressure change rate ΔP2 in order to perform optimal duty control, and as the engine speed N increases,
Further, the boost pressure change rate ΔP2 is set to become smaller as the rate of change ΔP2 becomes larger, and the feedback control start determination supercharging pressure P! □ increases as the engine speed N increases and as the boost pressure change rate ΔP2 increases. If Pt>p, □ in the twenty-fourth step 324, the process advances to the twenty-fifth step S25.

In the 25th step S25, the delay timer tF! It is determined whether or not 100 has elapsed, and if it has elapsed, the process advances to the 26th step S26. Also, the 22nd step 3
If F=0 in 22, the 23rd to 25th steps 3
23 to S25 and proceed to the 26th step 826.
If P2≦pzsT in the 23rd step S23, the process proceeds to the 27th step 327, and in the 24th step 324, P2
When ≦P2□, in the thirteenth step 313, the second
If the delay timer t_FIIDLY has not elapsed in step S25, the process proceeds to step 14, SI4.

In the 27th step S27, the duty is D. u7 is 100
Then, in the 28th step S28, the timer t FI
IDII is reset and the process proceeds to the fourth step S4.

In the 26th steno knob S26, it is determined whether the absolute value of the rate of change in supercharging pressure ΔP2 exceeds the feedback control determination supercharging differential pressure G6,2. This feedback control determination supercharging differential pressure cdrz is set to, for example, 30 mlIg, and when the progressive value of ΔP2 exceeds the feedback control determination supercharging differential pressure Gapt, the process returns to the 14th step S14, and the absolute value of ΔP2 is determined as the feedback control determination. Supercharging differential pressure G
If it is less than or equal to dP□, the process advances to the 29th step S29. If feedback control is started when 1ΔP21>G, +r□, it will cause hunting, so the process returns to step 14 and performs oven loop control.As mentioned above, in oven loop control, DT, Since hunting and overshoot are prevented by correction using DfRll, the main focus of the 26th step 326 is to perform a fail-safe function.

Feedback control is started from the 29th step 329, and first, at the 29th step S29, a target supercharging pressure PZREV that is preset based on the engine speed Nt and the intake air temperature TA is searched. Here, the feedback control first starts with θT in the twelfth step S12.
It is assumed that H>θTHFIl is satisfied,
Under these preconditions, the engine speed N and the target supercharging pressure ptme determined by the intake air temperature TA are searched as parameters that can accurately determine the operating state of the engine. θ7H〉θA, I□In other words, in the engine and under high load conditions, the engine speed N and the throttle opening θTH exhibit almost the same behavior, and NE is an effective parameter that indicates the operating state of the engine. It is something. Also, the intake air temperature TA
As shown in FIG. 1, is the intake air temperature on the downstream side of the ink cooler 4, and is a parameter that accurately indicates the state of the intake air introduced into the combustion chamber. Therefore, the target supercharging pressure P ZREF is determined by the map determined by the engine speed N and the intake air temperature TA.
By determining the value, it becomes possible to set a value that immediately corresponds to the operating state of the engine.

In the next 30th step 330, it is determined whether the shift position of the automatic transmission is the first gear position.

When the vehicle is in the first speed position, in the 31st step S31, according to the subroutine shown in FIG. 8 described in t4i1, when the operating state is in the determination zone (the shaded area in FIG. 9), pt*! The calculation r=pz□, -ΔP2□ is performed, and the process advances to the 33rd step S33. This ΔP 2Rt□ is a subtraction value that is set when the shift position is at the first speed position. Further, when it is determined in the 30th step S30 that the shift position is at a position other than the 1st speed position, in the 32nd step S32, P z++tv = P t according to the subroutine shown in FIG. 10 described above.
act-ΔPz*tv.

, is performed, and the process advances to the 33rd step S33.

Furthermore, ΔP 211EFO3 is a subtraction value that is set when the shift position is in a state other than the first speed position.

In the 33rd step S33, the boost pressure atmospheric pressure correction coefficient KPA and the duty atmospheric pressure correction coefficient set in advance according to the intake pressure PA are set to 11. is determined, and the next calculation is performed in a thirty-fourth step 334.

P z*ir = P tact X K rApt
X K t+tvts In the above formula, KR1FTl+ is a correction coefficient corresponding to the knock state of the engine.

In the 35th step 335, it is determined whether the absolute value of the deviation between the target boost pressure P2RfF and the current boost pressure P2 is greater than or equal to the set value G2□. The set value G, 2 is the dead zone defining pressure during feed bank control, for example, 20
It is set to about mm Hg. When the absolute value of the deviation between the target supercharging pressure P2□ and the actual supercharging pressure P2 is greater than or equal to the set value 012, the process proceeds to the 36th step S36, and when it is less than the set value G, □, the process proceeds to the 43rd step S43. Proceed to.

In the 36th step S36, the duty proportional control term is calculated using the following equation.

Dr = Kr In this FIG. 17, the engine rotation speed N. When is less than the first switching rotation speed N, □, KPI is obtained and the feedback coefficient Kl related to the integral control term described later
l is obtained and the engine speed NE exceeds the first switching speed N□1 and is equal to or less than the second switching speed NF12, then K
PZ is obtained, and when the engine speed N exceeds the second switching speed N□2, KPj+K13 is obtained.

In the 37th step 337, the above-mentioned 14th step S14
Similarly, the correction coefficient KMODij corresponding to the engine speed N and the intake air temperature TA is searched, and the correction coefficient KMODij is searched in the 38th step 33.
In step B, it is determined whether the previous flag F is 1, that is, whether this is the first feedback control state, and if F=1, in the 39th step S39, the previous integral control term DI (n-11 is Calculated according to the formula.

D++++-++=KtavcXKritcXD? 1X
(KPooijl) After this calculation is completed, the process proceeds to the 40th step S40, but if F=O in the 38th step 33B, the process bypasses the 39th step S39 and proceeds to the 40th step S40.

At the 40th step 340, the current integral control term Dln is calculated according to the following equation.

D+,=D++++-n+, + (Pz□FP2) Thereafter, the duty Dou□ is calculated in the 41st step S41. That is, Dour = KTATCX KPATCX DM +
DP + D 1. .

The following calculation is performed, and the flag F is set in the 42nd step S42.
After setting =O, the process proceeds to the 21st step S21.

Furthermore, if the absolute value of the deviation between the target supercharging pressure PZII■ and the actual supercharging pressure P2 is less than the set value GP□ in the 35th step S35, then in the 43rd step S43 DP=0.
D111=DIl11-11. Next, in the 44th step 344 to the 47th step S47, the water temperature T
1. A certain range consisting of l, that is, T-work. T-worker beyond office lady. K REF
It is determined whether or not the number of months is less than or equal to 0. If all of these conditions are satisfied, the process proceeds to the 48th step 348, and if even one of these conditions is not met, the process proceeds to the 41st step S41.

In the 48th step 34B, the duty correction coefficient KM
OD! The coefficient for learning J is calculated according to the following equation.

Ki − (KTATCXDH+D In)÷CKTA
TC×D, 4) Next, at the 49th step 349, calculations are performed to search and learn the correction coefficient KMO0,j, and further, at the 50th step S50, the 49th
K obtained with Stemp S49. 0Dij is written ↑a.

According to such duty control of the solenoid 70 in the electromagnetic control valve 69, the shift position of the automatic transmission is set to the first shift position.
If the engine is in the open-loop control state, the basic duty D4 is subtracted in the 10th step S10 when the operating state of the engine is in the discrimination zone shown in FIG.
In step 331, when the vehicle is in the discrimination zone, the target supercharging pressure P2□2 is subtracted by ΔP2111EF. Therefore, overload on the automatic transmission due to sudden start or overload when the shift position is at the first speed position can be prevented by reducing the supercharging pressure as the basic duty D decreases. Also, even if the shift is from open loop control to feedback control while maintaining the 1st speed position, the target boost pressure P
Since tNEW is subtracted, it is possible to prevent hunting from occurring during transition.

Further, assume that a shift change as shown in the lower part of FIG. 18 is performed. In this case, when changing gears,
While the engine speed N increases, there is a time lag in the operation of the actuator 60 by the control means C. Therefore, the boost pressure Pt does not correspond to the engine speed NE, and an overshoot occurs, causing the boost pressure P2 to reach the limit value, as shown by the broken line in Figure 18, especially during a shift change immediately after acceleration from a medium or high speed range. There is a risk that it will exceed. However,
At the 11th step Sll and the 32nd step 332, the duty D is executed according to a subroutine as shown in FIG. and target boost pressure P! A subtraction of IIF is performed. That is, at the time of a shift change, the throttle opening θT,I exceeds the predetermined value θT1os, and the engine speed N
, exceeds the predetermined value r'Jzos, and the intake pressure P, exceeds the predetermined value P.
When Bog is exceeded, that is, in accordance with the rate of change ΔPg of supercharging pressure P in the medium and high speed ranges, the basic duty D8 increases in open loop control. , and in feedback control, the target boost pressure P2□ becomes ΔP 211EFO
3 is subtracted.

As a result, as shown by the solid line in FIG. 18, overshoot at the time of shift change can be significantly reduced, hunting phenomenon can be avoided, and stable supercharging pressure control can be achieved.

Furthermore, when shifting from open-loop control to feedback control, the drop in supercharging pressure P2 can be covered, as shown in FIG. 19, and the shift can be quickly shifted to feedback control. In other words, duty is D at the start of operation. Ua is 100, that is, the duty ratio is 0%, and the throttle opening θa is the set throttle distance θ,
During open loop control when the voltage is less than H□, D is executed according to the subroutine of FIG.
It is assumed that A=O. Then, when θTH > θTNTI+, the transition from open loop control to feed puncture control begins, but when the boost pressure P2 exceeds pzst and θtH > θa□, DI4 = D, 4-D ,
to prevent overshoot.

However, when DT is subtracted as described above, the supercharging pressure P2 may drop as shown by the broken line in FIG. 19 due to the reaction. However, if 8P2≦0, D7=0, and D
Since only TRB is added, it is possible to cover the drop in supercharging pressure Pt and quickly shift to feedback control, making it possible to expand supercharging pressure control without the hunting phenomenon.

The duty control of the solenoid 70 in the electromagnetic control valve 69 described above is performed while the electromagnetic on-off valve 72 is closed, and when this electromagnetic on-off valve 72 is opened,
Intake pressure P is applied to the second pressure chamber 63 in the actuator 60.
, the actuator 60 is configured such that the movable vane 54 of the variable displacement turbocharger 5 is connected to the fixed vane 49 of the variable displacement turbocharger 5.
It operates in the direction of increasing the air gap circulation area between.

Next, referring to FIG. 20, the procedure in the control means C for controlling the solenoid 73 of the electromagnetic on-off valve 72 will be explained. Here, based on the main routine of FIG. 5, the supercharging pressure P! of the actuator 60 to the first pressure chamber 62 is increased! In addition to controlling the operation of the introduction electromagnetic control valve 69, more precise control is possible by introducing the intake pressure P into the second pressure chamber 63 of the actuator 60 via the electromagnetic on-off valve 72. This is because the supercharging pressure Pg is detected between the variable displacement turbocharger 5 and the intercooler 4, so the minute operation of the throttle valve 74 cannot be detected, whereas the intake pressure P□ is detected downstream of the throttle valve 74. This is because the minute actuation of the throttle valve 74 can be detected because it is derived from . In other words, the operation of the entire intake system including the turbocharger 5 is made more accurate by both the supercharging pressure sensor S0, which reliably detects the movement of the turbocharger 5, and the intake pressure sensor SPH, which reliably detects the movement of the throttle valve 74. It becomes possible to reflect.

In the first step L1, it is determined whether a predetermined time, for example, two minutes, has elapsed after the engine has been started. If the predetermined time has not elapsed, the process proceeds to a second step L2, where the solenoid 73 is energized and the actuator 60 controls the movable vane. 54 operates in a direction to increase the flow area between the fixed vane 49 and the fixed vane 49.

This is to deal with cold starting, prevents supercharging during cold times, and allows the catalyst temperature to rise gradually. If the predetermined time has elapsed in the first step L1, the process proceeds to the third step I, 3, where the vehicle speed (2) is set with hysteresis to determine the vehicle speed (2). It is determined whether the PI exceeds, for example, 90/87 km/h,
When V>VOP3, proceed to the fourth step L4,
(2) When ≦V OF2, the process proceeds to the fifth step L5.

In the fourth step I, 4, it is determined whether the throttle opening degree θTN is less than the set throttle opening degree change rate ΔθTHOP2. This set throttle opening change rate θTH
OP□ is set with hysteresis, and Δθ,
H〈Δθa,. , the process proceeds to the second step L2; otherwise, the process proceeds to the fifth step L5.

In the fifth step L5, the vehicle speed ■ is the set vehicle speed ■. It is determined whether it is less than □. The set vehicle speed ■OP+ has hysteresis, for example, 65/63 km.
/h. If V<Vo, . . ., the process proceeds to the seventh step L7, and if ■≧■o□, the process proceeds to the sixth step L6, where the solenoid 73 is demagnetized. Also, in the seventh step L7, the vehicle speed ■ is the set vehicle speed ■. It is determined whether it is less than 2. This set vehicle speed ■. P2 has hysteresis, and is set to +n/h at 4/3, for example. ■〉■. , 2, the process proceeds to the 12th step L12, and ■≦■. When it is 2□, the process advances to the eighth step L8.

In the eighth step L8, the previous vehicle speed ■ is the set vehicle speed ■.

It is determined whether it exceeds Pt, and ■>■OF! If so, the timer t is activated at the ninth step L9. , and then proceeds to the 10th step LIO, and when ■≦VoP□, proceeds to the 10th step 1°lO.
In step LIO, it is determined whether or not the previous state was in the excited state, and if it was in the de-energized state, the process proceeds to the sixth step L6.
If the state is excited, the process proceeds to the 11th step T-
11 now. P is the setting timer t. ,. If t01'>toro, the process goes to the sixth step L6, and t. P≦top. If so, the process proceeds to the second step L2.

In the twelfth step L12, it is determined whether the engine rotation speed N is less than the set rotation speed NEOF.This set rotation speed NtO has hysteresis.
For example, it is set to 2500/2:30 Or p m. If N, ≧N EOF, the process proceeds to the sixth step L6, and if NE<N fop, the process proceeds to the 13th step L13.

In the 13th step L13, the intake pressure P is set to the set intake pressure P.
It is determined whether it is less than lloF. This set intake pressure P. 2 has hysteresis, and is set to -100/-150 mmHg, for example. P3
≧P. , then go to the sixth step L6, and P
When H<PHOF, the process advances to the fourteenth step L14.

In the fourteenth step L14, it is determined whether the throttle opening θT11 is less than the set throttle opening θT, loP. This setting throttle opening θ? HOF is set to 20/15deg, for example. θT11≧θTll
When the value is 0F, the process proceeds to the sixth step L6, where θTH is reduced to θ.

,. When , the process proceeds to the fifteenth step L15.

Further, in the fifteenth step L15, it is determined whether the throttle opening change rate Δθ,H is positive and less than the set throttle opening change rate ΔθTHOP1 set with hysteresis, and 0<ΔθTH<ΔθTll.
If it is 0F+, the process proceeds to the second step L2, and otherwise, the process proceeds to the sixth step L6.

To summarize these steps, it is determined in the third step L3 and the fourth step L4 that at high vehicle speeds exceeding 90/87 km/h, the variable displacement turbocharger 5 is not movable in the slow acceleration state where ΔθTH<Δθ1H011. The vane 54 operates in a direction that increases the air gap circulation area between the vane 54 and the fixed vane 49. This makes it possible to prevent pumping loss.

In other words, when the vehicle is cruising at a high speed, acceleration is not required, and operating the movable vane 54 to increase the boost pressure is because pumping loss will occur due to the increase in back pressure caused by the high rotational speed of the engine. be.

Furthermore, in the fifth step L5, the solenoid 73 is demagnetized when the vehicle speed exceeds 65/63 km/h, but this is because the solenoid control valve 69 shown in FIG.
This is because control of is sufficient. Furthermore, the seventh step L
Step L 11 resets the timer when the vehicle is at a low speed of 4/3 km/h or less, that is, is almost stopped, and the previous vehicle speed was almost stopped;
While the timer elapses, for example, one minute, the solenoid 73 is energized and the movable vane 54 is operated to increase the flow area. This is when the movable vane 54 is restarted.
If the flow area is on the side where the flow area is small, the supercharging pressure P2 will temporarily increase and an overload will be applied to the starting gear etc., so this is to prevent this. Furthermore, the vehicle speed is 4/3 k
If the movable vane 54 is on the side where the flow area is small when the speed is less than m/h, the rotation of the variable capacity turbocharger 5 will be lengthened when the variable capacity turbocharger 5 is rotating for reconnaissance, etc. In this case, since the throttle openings θ and H are almost fully closed, the supercharging pressure increases the internal pressure of the intake passage upstream of the throttle valve. Therefore, by operating the movable vane 54 in a direction that increases the flow area, the occurrence of surging due to the pressure increase can be prevented. Moreover, it can also contribute to raising the catalyst temperature by 1-1 immediately after starting in a cold state.

Other 12th to 15th steps L12 to L15
According to the judgment condition, ■o p z < V < V O
PI,Nt<NEOF% pH<PIIOF,
θTH<θTHOF, 0<Δθ, HkuΔθa□. 2. When all of the above are satisfied, that is, in a slow acceleration state at partial load such as in 10 mode driving, the solenoid 73 is energized to lower the supercharging pressure P2, thereby preventing pumping loss.

In the above embodiment, the supercharging pressure Pt is detected by the supercharging pressure sensor Spz, but if the supercharging pressure is controlled with the throttle fully open, it will be detected by the intake pressure sensor S□. It is also possible to control the supercharging pressure so that the intake pressure P substantially matches the supercharging pressure P2.

Further, in the above embodiments, a variable displacement turbocharger in which the capacity is changed by operating the movable vane 54 has been described, but the present invention is applicable to a wastegate type and a boost pressure relief type variable displacement turbocharger. It is also applicable to a so-called supercharger driven by the output power of an engine.

C6 Effects of the Invention As described above, according to the method of the present invention, feedback control is started after a predetermined time has elapsed since the boost pressure exceeds a predetermined value during a transient state of the boost pressure. Even in a transient state where the boost pressure suddenly changes in magnitude, such as a sudden increase in boost pressure, it is possible to prevent abnormal increases in boost pressure and the occurrence of hunting phenomena, and ensure a smooth and prompt transition to feedback control. This makes it possible to control the supercharging pressure more stably and appropriately, especially during acceleration.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an overall schematic diagram showing the intake system and exhaust system of an internal combustion engine, FIG. 2 is an enlarged vertical side view of a variable displacement turbocharger, and FIG. 2 is a sectional view taken along the line ■-■, FIG. 4 is a sectional view taken along the TV-IV line in FIG. 2, FIG. 5 is a flowchart showing the main routine for controlling the solenoid control valve, and FIG. 7 is a graph showing the high boost pressure judgment guard value, FIG. 8 is a flowchart showing the basic duty at the 1st speed position and the target boost pressure subroutine, and FIG. 9 is a flow chart showing the subroutine for subtracting the target boost pressure. Fig. 8 is a diagram showing the discrimination zone used in the subroutine, Fig. 10 is a flowchart showing the subroutine for subtracting the basic duty and target boost pressure at positions other than the 1st speed position, and Fig. 11 is a subroutine for determining the set subroutine duty. A flowchart showing
Figure 12 is a diagram showing a map of the set subtraction duty.
3 is a flowchart showing a subroutine for determining the set addition duty, and FIGS. 14, 15, and 16.
The figure is I) t*s, ΔZS? , ΔP zym setting maps, FIG. 17 is a flowchart showing a subroutine for determining feedback coefficients related to the proportional control term and the integral control term, and FIG. 18 is a diagram showing changes in intake pressure at shift change. FIG. 19 is a diagram showing changes in duty and boost pressure at the time of transition from open loop control to feedback control, and FIG. 20 is a flowchart showing a main routine for controlling the electromagnetic on-off valve. 5...Variable displacement turbocharger P2...Supercharging pressure, P2□...Predetermined pressure, P□,...
Target boost pressure, 1. □L...Predetermined time Figure 4 '26 Figure 7 Figure 8 Figure 9 Figure 17

Claims (1)

[Claims] An overcharging system for an internal combustion engine that determines a control amount according to the deviation between an actual boost pressure and a target boost pressure, and performs feedback control based on the control amount so that the boost pressure becomes the target boost pressure. A boost pressure control method for an internal combustion engine, characterized in that feedback control is started after a predetermined time has elapsed after the boost pressure exceeds a predetermined value during a transient state of the boost pressure. Control method.