JP2516790B2 - Variable capacity turbocharger control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention controls the capacity of a variable capacity turbocharger based on a basic boost pressure control amount corresponding to an operating state of an engine. The present invention relates to a control method for a variable displacement turbocharger, which corrects a basic boost pressure control amount according to a deviation between an actual boost pressure and a target boost pressure when an engine operating state is in a feedback control region.

(2) Conventional Technology Conventionally, for example, Japanese Patent Application Laid-Open No. 58-192942 discloses a method for improving the engine output by changing the capacity of a variable capacity turbocharger according to the operating state of the engine. .

(3) Problems to be Solved by the Invention By the way, the torque applied to the transmission member in the power transmission mechanism differs depending on the shift position in the transmission, and is particularly excessive at the first speed position. Therefore, in the above-mentioned conventional one, the supercharging pressure is reduced at the first speed position to reduce the torque applied to the transmission member, thereby reducing the size of the transmission. However, when the engine speed decreases during a shift change of the transmission, the supercharging pressure corresponds to the engine speed despite the engine speed decreasing due to the time lag with the operation of the means for adjusting the supercharging pressure. Otherwise, overshoot may occur, making stable control difficult.

The present invention has been made in view of such circumstances,
An object of the present invention is to provide a control method for a variable displacement turbocharger that detects a shift change by the behavior of the engine speed to reduce the amount of overshoot and enables stable supercharging pressure control.

B. Configuration of the Invention (1) Means for Solving Problems According to the method of the present invention, when the engine speed changes from the acceleration state to the deceleration state under a preset operating condition of the engine, the target excess is exceeded. The supply pressure and the basic boost pressure control amount are reduced.

(2) Operation According to the above method, it is detected that the engine speed is changing from the speed increasing state to the speed reducing state, and the shift change is detected, and the basic boost pressure control amount and the feedback control are performed in the open loop control region. Since the target supercharging pressure is reduced in each region, the amount of overshoot can be reduced as the supercharging pressure according to the engine speed, and stable supercharging pressure control can be performed.

(3) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings. An intake manifold 1 is connected to an intake port of each cylinder in an engine body E of a multi-cylinder internal combustion engine, and the intake manifold 1 further includes an intake pipe. 2, throttle body 3,
It is connected to an air cleaner 6 via 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 in the central portion 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
It is fastened by 22 and the bearing casing 17 is connected to the central portion 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 step 16a facing the compressor wheel 21 side of the main shaft 16 and the compressor wheel 21 in this order from the step 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, at the bottom of the bearing casing 17, there is provided a lubricating oil discharge port 34 for discharging the lubricating oil flowing out from each lubricating portion downward, and the lubricating oil discharged from this lubricating oil discharge port 34 is an oil (not shown). Collected in sump.

The bushing 29 has a through hole 35 formed in the central portion 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 the 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 coupled to each other so that the back plate 44 is sandwiched between them. 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 stat 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.
It is stored inside. The cylindrical portion 48a is fitted into the outlet passage 43 via a seal ring 51 fitted to the outer surface thereof, and the fixed vane 49 is joined to the back plate 44 by the bolt 52.

The fixed vanes 49 are provided on the outer peripheral portion of the turbine member 48 at positions equidistantly arranged in the circumferential direction, and each fixed vane 49 is formed in an arc shape. Between each fixed vane 49, a movable vane whose one end is fixed to a rotary shaft 53 which is rotatably pivotally attached to the back plate 44 in parallel with the axis of the main shaft 16.
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 a fully open position indicated by a chain line. Moreover, each rotating shaft 53 is connected to the actuator 60 via the link mechanism 55 arranged between the back plate 44 and the bearing casing 17, and the movable vanes 54 are synchronously opened and closed by the operation of the actuator 60. It

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 becomes slow. 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 at the time of 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 supplied by the cooling water to the intercooler 4. To be 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 whose one end is connected to the central portion of the diaphragm 64 and which penetrates the housing 61 airtightly and movably on the second pressure chamber 63 side and is connected to the link mechanism 55 at the other end.
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.
The 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 body 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 opening / closing valve 72 are controlled by the control means C, and the control means C includes a water jacket (Fig. a temperature detector S _W to detect the 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 intake pressure between the air cleaner 6 and the variable geometry turbocharger 5 The intake pressure sensor S _PA that detects P _A , the supercharging pressure sensor S _P2 that detects the supercharging pressure P ₂ in the intake passage between the variable capacity turbocharger 5 and the intercooler 4, and the suction pressure sensor downstream of the throttle body 3 An intake pressure sensor S _PB that detects the atmospheric pressure P _B , a rotation speed detector S _N that detects the engine speed N _E, and a throttle opening detector S that detects the opening θ _TH of the throttle valve 74 in the throttle body 3. Detects _TH and vehicle speed V The vehicle speed detector S _V and the shift position detector S _S for detecting the shift position in the automatic transmission are connected. Then, the control means C receives those input signals, that is, the water temperature T _W , the intake temperature T _A , the intake pressure P _A , the supercharging pressure P ₂ , the intake pressure P _B , the engine speed N _E , the throttle opening θ _TH , Excitation and demagnetization of the solenoids 70 and 73 are controlled based on the vehicle speed V and the shift position signal of the automatic transmission.

Next, the control procedure in 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 FIG. However, the duty D _OUT for controlling the excitation and demagnetization of the solenoid 70 in this main routine 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%. _However , D _OUT = 100 corresponds to a duty ratio of 0%.

In the first step S1, it is determined whether or not the engine is in the starting mode, that is, whether or not the engine is cranking. If the engine is in the starting mode, the duty D is determined in the second step S2.
_OUT is set to 0, that is, the electromagnetic control valve 69 is fully opened so that the void 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 promotes instability, so that the movable vanes 54 and the fixed vanes 49 are This is for maximizing the void circulation area between and to prevent the boost pressure from being introduced into the combustion chamber. 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 third step S3, the timer t _FBDLY for delaying the start of the feedback control is reset, and then the fourth step S4
The duty D _OUT is output from.

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 change rate ΔP ₂ is the boost pressure P of this time.
_2n and the boost pressure P _2n-6 six times before (ΔP ₂ = P _2n −
P _2n-6 ). That is, the main routine shown in FIG. 5 is updated by the TDC signal, but since the change rate of the supercharging pressure P ₂ is too small with only one TDC signal, the supercharging pressure behavior, that is, the change rate ΔP ₂ is accurately read. In order to avoid this, the difference from the supercharging pressure P _2n-6 6 times before is determined. 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, the time t _FBDLY without excess or deficiency is set at the time of the transition from the open loop control to the feedback control, and it becomes possible to sufficiently prevent the hunting phenomenon from occurring at the time of the transition.

When it is determined not to be a starting mode in the first step S1, the water temperature T _W in the fifth step S5, it is determined whether setting is less than the low water temperature T _WL, the second step when setting is less than the low water temperature T _WL Proceed to S2. Here, the operating state of the engine considered as the case where T _W <T _WL is satisfied is, for example, when the engine is initially started or when the outside air temperature is extremely low. When the stable state continues and the outside air temperature is extremely low, the intake 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 T _W <T _WL ,
In the second step S2, D _OUT = 0.

When it is determined in the fifth step S5 that T _W ≧ T _WL or more, the process proceeds to a sixth step S6. The At step S6 whether the water temperature T _W is higher than the set high temperature T _WH is determined and when exceeds the set high water temperature T _WH proceeds to the second step S2. Here, when T _W > T _WH is satisfied, for example, when the engine continues to operate under high load,
This is the case when the outside air temperature is extremely high and when there is an abnormality in the cooling water system of the engine body E. In all these states, the intake air density decreases, that is, the charging efficiency decreases, which causes abnormal combustion such as unburned combustion. Introducing the supercharging pressure into the combustion chamber when the engine is unstable as described above promotes the unstable state.
The duty is D _OUT = 0 in S2. In addition, the inductance characteristic of the solenoid 70 is likely to change at extremely high temperatures, which may cause a behavior different from the setting behavior in the normal state. The second step is also to avoid such a behavior.
It is to advance to S2. When it is determined in the sixth step S6 that T _W ≦ T _WH , the process proceeds to a seventh step S7. That is, the water temperature T _W is _{equal to} or higher than the set low water temperature T _WL and the set high water temperature T _WH
If it is within the following range, the process proceeds to the seventh step S7, and if not, the process proceeds to the second step S2.

In the seventh step S7, it is judged whether or not the supercharging pressure P ₂ exceeds a preset high supercharging pressure judgment guard value P _2HG as shown in FIG. 7, and when P ₂ > P _{2HG Go} to 2 step S2, and if P _{2 ≤P 2HG} , step 8 S8
Proceed to. 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 boost pressure judgment guard value P
_{When the} supercharging pressure P ₂ exceeding _2HG is detected, the supercharging pressure P ₂ is reduced by setting the duty ratio to 100% in the fourth step S4 after the second and third steps S2 and S3, and the fuel injection is performed. Is cut.

In the eighth step S8, the basic duty D _M as the basic boost pressure control amount is searched. The basic duty D _M is previously set according to the engine speed N _E and the throttle opening theta _TH, basic duty D _M from the setting table is searched. 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.

At the next ninth step S9, it is determined whether or not the shift position of the automatic transmission is at the first speed position. When it is at the first speed position, the process proceeds to tenth step S10, at a shift position other than the first speed position. If there is, the process proceeds to the eleventh step S11.

In the tenth step S10, the basic duty D _M is subtracted according to the subroutine shown in FIG. 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. By the way, the torque acting on the transmission from the engine is proportional to the engine load, and the torque changes depending on the engine speed N _E.
FIG. 9 shows changes in the torque, that is, the intake pressure P _B , depending on the engine speed N _E and the intake pressure P _B which is a parameter representing the engine load. Moreover, the torque acting on the transmission from the engine becomes maximum when the transmission is in the first speed position, and the boundary line of the discrimination zone in FIG.
It shows the allowable torque amount of the gear shaft in the high speed position. That is, in order to prevent the force applied to the gear shaft from being overloaded in the first speed position, the judgment in each operating range is accurately made based on the engine speed N _E and the intake pressure P _B as shown in FIG. . When it is outside the discrimination zone, the basic duty D _M is left as it is and the process proceeds to the twelfth step S12. However, when it is in the discrimination zone, after it is judged whether the flag F is 0, that is, whether the feedback control state is established or not. , In the open loop control state, the subtraction D _M = D _M −D _F is performed, and in the feedback control state, P _2REF
= P _2REF -ΔP _2REFF becomes subtraction is performed. Where D _F
Is a preset subtraction value. P 2 _REF is the target boost pressure used when in feedback control, ΔP
_2REF is a preset subtraction value, which will be described in detail later in the section of feedback control.

In the eleventh step S11, the basic duty D _M is subtracted according to the subroutine shown in FIG. 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
_A subtraction of _2REF = _P2REF − _ΔP2REFOS is performed. In other _cases , the basic duty D _M is left unchanged and the process proceeds to the 12th step S12. Here, D _OS and ΔP _2REFOS are preset subtraction values.

In the twelfth step S12, it is determined whether the throttle opening θ _TH exceeds a preset throttle opening θ _THFB . The 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 _THFB
When the open loop control is continued, the delay timer t shown in FIG.
_FBDLY is reset and the process proceeds to the 14th step S14.

In the 14th step S14, the duty correction coefficient K _MODij
To search. This correction coefficient K _MODij is searched using a map determined by the engine speed N _E and the intake air temperature T _A, and is learned when the optimum boost pressure P ₂ falls within the predetermined deviation as described later. , It will be updated from time to time with the learning. Here, the initial value of the correction coefficient K _MODij is 1.

In the next fifteenth step S15, the duty atmospheric pressure correction coefficient K _PATC (0.8 to 1.0) is determined corresponding to the intake pressure P _A ,
Further, in the next 16th step S16, the duty intake air temperature correction coefficient K _TATC (0.8 to 1.3) is determined corresponding to the intake air temperature T _A. In the seventeenth step S17, the set subtraction duty D _T according to the rate of change ΔP ₂ of the supercharging pressure P ₂ is determined according to the subroutine of FIG. That Figure 12 when the throttle opening theta _TH is greater than the set throttle opening _{θ THFB (a), (b} ), the change rate of the supercharging pressure P ₂ as shown by (c) [Delta] P ₂ and the engine speed N _When the set subtraction duty D _T set by _E is set and θ _TH ≤ θ _THFB , D _T
= 0.

FIG. 12 (a) shows the set subtraction duty D _T when the engine speed N _E is less than or equal to the preset first switching speed N _FB1 (for example, 3000 rpm), and FIG. 12 (b) shows the engine. The rotation speed N _E exceeds the first switching rotation speed N _FB1 and the second switching rotation speed N
_FB2 (e.g. 4500 rpm) shows the setting subtraction duty D _T when less, Fig. 12 (c) shows a set subtraction duty D _T when the engine speed N _E exceeds the second switching rotational speed N _FB2 It is a thing. Here, the set subtraction duty D _T is a set value P lower than the target boost pressure P _{2REF as} shown in FIG. 19 described later.
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, as shown in FIG. 12 and above, the D _T is changed depending on the engine speed N _E and the supercharging pressure change rate ΔP ₂ , which is the engine speed when the set value P _2ST is reached. Since there is a difference in the amount of overshoot depending on N _E and the rate of change in supercharging pressure ΔP ₂ , the purpose is to optimize the duty control in each operating range by the above holding change. Here, D _T is set to be larger as ΔP ₂ is larger and N _E is larger.

Furthermore, in the 18th step S18, the set addition duty D
_TRB is determined according to the subroutine shown in FIG. That is, open loop control and supercharging pressure
Figure 14 is when the change rate [Delta] P ₂ of P ₂ is a negative state (a), (b), -ΔP 2 and set set by the engine speed N _E adder duty D as shown in (c)
_TRB is selected, and the set subtraction duty D _T is set to 0. When ΔP ₂ is positive in the feedback control state, the set addition duty D _TRB is set to 0. This setting addition duty D _TRB is also the setting subtraction duty described above.
Similar to D _T , supercharging pressure change rate at engine speed N _E and-
It can be replaced as shown in Fig. 14 according to P ₂ .
It is set so that D _TRB becomes larger as N _E becomes larger and −ΔP ₂ becomes larger, which enables duty control such that stable supercharging pressure P ₂ with less hunting is obtained in each operating range. That is, from the start of operation to the predetermined region P _2ST , D _OUT = 100 is set to increase the supercharging pressure P ₂ by minimizing the void circulation area between the movable vane 54 and the fixed vane 49, and supercharging pressure P ₂ After the pressure exceeds the set pressure P _2ST , the set addition duty D is set to prevent hunting that occurs as a reaction of the set subtraction duty D _T for overshoot prevention.
By adding _TRB , stable supercharging pressure control is possible in each operating range. Therefore, the fourth step S4
The output duty D _OUT output from is set in consideration of the operating conditions of the engine in consideration of the above contents and external factors.

After the correction coefficients K _MODij , K _PATC , K _TATC , the set subtraction duty D _T, and the set addition duty D _TRM are thus determined, the process proceeds to the 19th step S1.

In the 19th step S19, the duty D _OUT is corrected by the following equation.

D _OUT = K _TATC × K _PATC × K _MODij × (D _M + D _TRB −D _T ) Further, in the twentieth step S20, the flag F = 1 is set to indicate the open loop control, and the twenty-first step S21.
Check to see if the duty D _OUT has exceeded the limit value. That is, the limit value of the duty D _OUT is preset according to the engine speed N _E , and it is checked whether or not the limit value is out of the limit value. If the limit value is not exceeded, the duty D _OUT is determined in the fourth step S4.
_OUT is output.

When it is determined in the twelfth step S12 that θ _TH > θ _THFB , the process proceeds to a 22nd step S22. This 22nd Step S
At 22, it is determined whether or not the previous flag F is 1, that is, whether or not the previous time was the open loop control state, and when F = 1, the boost pressure P ₂ starts the duty control in the open loop in the 23rd step S23. Distinguishing 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 shown in FIGS. 15 (a), (b),
As shown in (c), it is set according to the engine speed N _E. Here, ΔP _2ST is, like D _T and D _TRB described above, changed over depending on the engine speed N _E and the supercharging pressure change rate ΔP ₂ for optimum duty control. N _E
Is set to be larger, and as the supercharging pressure change rate ΔP ₂ is set to be larger.

When P ₂ > P _2ST in the 23rd step S23, it is _determined in a 24th step S24 whether or not the boost pressure P ₂ exceeds the feedback control start determination _boost pressure P _2FB . This feedback control start determination supercharging pressure P _2FB is P _2FB = P _{2REF −} ΔP _2FB
And ΔP _2FB is obtained from Fig. 16 (a),
As shown in (b) and (c), it is set according to the engine speed N _E. This feedback control start determination supercharging pressure P
_{2FB is} also similar to the above-mentioned ΔP _2ST , D _T , and D _TRB , in order to perform optimum duty control, engine speed N _E and supercharging pressure change rate ΔP ₂
It is intended to be replaced lifting depending on, enough the engine speed N _E increases and is set to be larger as the supercharging pressure change rate [Delta] P ₂ increases. In this 24th step S24, P ₂ > P
_If it is _2FB , the process proceeds to the 25th step S25.

In the 25th step S25, it is determined whether or not the delay timer t _FBDLY has elapsed, and when it has elapsed, the process proceeds to the 26th step S26. When F = 0 in the 22nd step S22, the 23rd to _25th steps S23 to S25 are bypassed to the 26th step S26, and when P _{2 ≤P 2ST} in the 23rd step S23, the 27th step S27 is performed. , In the 24th step S24, if P ₂ ≦ P _2FB , in the 13th step S13; in the 25th step S25, if the delay timer t _FBDLY has not elapsed, the 14th step
Proceed to S14 respectively.

In the 27th step S27, the duty D _OUT is set to 100, then in the 28th step S28, the timer t _FBDLY is reset and the process proceeds to the fourth step S4.

In the 26th step S26, it is determined whether or not the absolute value of the supercharging pressure change rate ΔP ₂ exceeds the feedback control determination supercharging differential pressure G _dP2 . This feedback control judgment supercharging differential pressure G
_dP2 is set to 30 mmHg, for example, and when the absolute value of ΔP ₂ exceeds the feedback control determination supercharging differential pressure G _dP2 , the process returns to the 14th step S14, and the absolute value of ΔP ₂ returns to the feedback control determination supercharging differential pressure. When it is below G _dP2 , the process proceeds to the 29th step S29. Here, starting feedback control when | ΔP ₂ |> G _dP2 causes hunting, so the process returns to the 14th step S14 to perform open-loop control. _Since the hunting and the overshoot are prevented by performing the correction by _T and D _TRB ,
26 The main purpose of step S26 is to fulfill the fail-safe function.

Feedback control is started from the 29th step S29. First, at the 29th step S29, the engine speed N _E
And the target boost pressure preset by the intake air temperature T _A
P 2 _REF is searched. Here, the feedback control is based on the premise that θ _TH > θ _THFB is satisfied in the twelfth step S12, and the engine speed N _{E is a} parameter that can accurately determine the operating state of the engine under this precondition. The target boost pressure P _2REF determined by the intake air temperature T _A and the intake air temperature T _A is searched. 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 temperature on the downstream side of the intercooler 4 as shown in FIG. 1 and is a parameter that accurately indicates the intake state introduced into the combustion chamber. Therefore, by determining the target supercharging pressure P _{2REF based} on the map determined by the engine speed N _E and the intake air temperature T _A , it is possible to set a value that immediately corresponds to the operating state of the engine.

In the next thirtieth step S30, it is determined whether or not the shift position of the automatic transmission is the first speed position. When in the first speed position, in the 31st step S31, P _2REF = P _2REF -ΔP _{2REFF is} calculated according to the subroutine shown in FIG. 8 when the operating state is in the discrimination zone (hatched portion in FIG. 9). Is performed and the process proceeds to the 33rd step S33. This ΔP
_2REFF is a subtraction value that is set corresponding to 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 in a position other than the first speed position, the calculation of P _2REF = P _2REF −ΔP _2REFOS is _executed in the 32nd step S32 according to the subroutine shown in FIG. After that, the process proceeds to the 33rd step S33. And ΔP
_2REFOS is a subtraction value that is set correspondingly when the shift position is in a state other than the first speed position.

33 step supercharging pressure has been set in advance in accordance with S33 in the intake air pressure P _A atmospheric pressure correction coefficient K _PAP2 and the atmospheric pressure correction coefficient K _PATC duty is determined, the following additional operations performed at the 34 step S34 P _2REF = P _2REF × K _PAP2 × K _{PEFTB In the} above equation, K _PEFTB is a correction coefficient corresponding to the knock state of the engine.

At 35th step S35, 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. If the absolute difference in deviation between the target boost pressure P _2REF and the actual boost pressure P ₂ is greater than or equal to the set value G _P2 , the 36th step S
Proceed to 36, and if the set value is less than G _P2 , the 43rd step S
Continue to 43.

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

D _P = K _P × (P _2REF −P ₂ ) In the above equation, K _P is a feedback coefficient related to the proportional control term, and is _calculated according to the subroutine shown in FIG. In FIG. 17, when the engine speed N _E is less than or equal to the first switching speed N _FB1 , K _P1 is obtained and a feedback coefficient K _I1 related to an integral control term described later is obtained,
When the engine speed N _E exceeds the first switching speed N _FB1 and is less than or equal to the second switching speed N _FB2 , K _P2 and K _I2 are obtained, and further the engine speed N _E is the second switching speed N _{FB. When} it exceeds _FB2 , K _P3 , K
_I3 is obtained.

In the 37th step S37, as in the 14th step S14 described above,
Correction coefficient K _MODij according to engine speed N _E and intake air temperature T _A
Is searched, and the previous flag F is set to 1 in the 38th step S38.
It is determined whether or not it is the first feedback control state. When F = 1, the previous integral control term D _{I (n-1)} is calculated in the 39th step 39 according to the following equation.

D _{I (n-1)} = K _TATC x K _PATC x D _M x (K _MODij -1) After the completion of this calculation, the process proceeds to the 40th step S40, but if F = 0 in the 38th step S38, the 39th The process bypasses step S39 and proceeds to step 40.

In the 40th step S40, 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 the 41 step S41 is calculated. That is, the operation of D _OUT = K _TATC × K _PATC × D _M + D _P + D _In is performed, and the flag F = 0 at the 42nd step S42.
After that, the process proceeds to the 21st step S21.

Further, when the absolute value of the deviation between the target supercharging pressure P _2REF and the actual supercharging pressure P ₂ is less than the set value G _{P2 in} the 35th step S35, D _P = 0, D _In = D _{I in} the 43rd step S43. _(n-1) .
Next, in 44th step S44 to 47th step S47, whether the water temperature T _W is above a certain fixed range, that is, T _WMODL and less than T _WMODH, and whether the retard amount T _ZRET is 0, that is, whether it is out of the knock state , It is determined whether or not the shift position is other than the first speed position and whether or not K _REFTB is 1.0 or less. If all of these conditions are satisfied, the 48th step S48 is proceeded to, and even one of these conditions is deviated. If so, the process proceeds to the 41st step S41.

In the 48th step S48, the 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 _forty-ninth step S49, in order to search and learn the correction coefficient K _MODij , Then, in the 50th step S50, K _MODij obtained in the 49th step S49 is stored.

According to the duty control of the solenoid 70 in the electromagnetic control valve 69, when the shift position of the automatic transmission is at the first speed position, if the open loop control state is established,
In the tenth step S10, the basic duty D _M is subtracted by _DF when the engine operating state is in the discrimination zone of FIG. 9, and in the feedback control state, the target supercharging is performed in the 31st step S31 when the engine is in the discrimination zone. Pressure P 2 _REF is ΔP
Only _{2REF is} subtracted. Therefore, when the shift position is the first speed position, it is possible to prevent an excessive load on the automatic transmission due to a sudden start, an overload, or the like, by reducing the supercharging pressure as the basic duty D _M decreases. Also, when the control shifts from the open loop control to the feedback control while maintaining the first speed position, the basic duty D _M is subtracted by D _F in the open loop control region based on the fact that the operating state of the engine is in the discrimination zone of FIG. 9. On the other hand, if the target boost pressure P _2REF is not subtracted in the initial _stage of the transition to the feedback control, the difference between the target boost pressure P _2REF and the actual boost pressure P _2REF becomes relatively large, and control hunting is performed. May occur. However, when the operating condition of the engine is in the first speed position and in the discrimination zone shown in FIG. 9, the target boost pressure P _2REF is also _reduced by ΔP _2REF , so the target excess pressure is changed when the open loop control is changed to the feedback control. Supply pressure P _{2 REF} and actual boost pressure P ₂
It is possible to prevent the control hunting from occurring by making the difference between and relatively small.

It is also assumed that the shift change shown in the lower part of FIG. 18 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 supercharging pressure P ₂ does not correspond to the engine speed N _E , and overshoot occurs, so that the supercharging pressure P ₂ is particularly high at the time of a shift change immediately after acceleration from the middle-high speed range as shown by the broken line in FIG. 18. There is a risk of exceeding the limit value. However, the 11th step
In S11 and the 32nd step S32, the basic duty D _M and the target supercharging pressure P _2REF are subtracted according to the subroutine shown in FIG. That is, at the time of a shift change, when the throttle opening θ _TH exceeds a predetermined value θ _THOS , the engine speed N _E exceeds a predetermined value N _EOS , and the intake pressure P _B exceeds a predetermined value P _BOS , that is, medium and high speed. Boost pressure P _{2 in range}
Depending on the rate of change [Delta] P _2, basic duty D _M is decremented by D _OS is an open-loop control, the target supercharging pressure P _2ref is subtracted [Delta] P _2REFOS the feedback control. As a result, as shown by the solid line in FIG. 18, overshoot at the time of shift change can be significantly reduced, the occurrence of hunting phenomenon can be avoided, and stable supercharging pressure control can be performed.

Further, when shifting from the open loop control to the feedback control, it is possible to swiftly shift to the feedback control by covering the fall of the supercharging pressure P ₂ as shown in FIG. That is, when the operation starts, D
_During open loop control in which _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 , D _T = 0 according to the subroutine of FIG. 13 in step S18. To be done. Then, when θ _TH > θ _THTB , the shift from the open loop control to the feedback control starts, but the supercharging pressure P ₂ becomes P
When θ _TH > θ _THFB when _2ST is exceeded, D _M = D _M
-D _T prevents overshoot.

However, when only D _{T is} subtracted as described above, the boost pressure P ₂ may drop due to the reaction as shown by the broken line in FIG. 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 electromagnetic control valve 69 described above is performed in a state where the electromagnetic opening / closing valve 72 is closed. When the electromagnetic opening / closing valve 72 is opened, the second pressure chamber 63 in the actuator 60 is opened. The intake pressure P _B is supplied to the actuator 60, and the actuator 60 operates in the direction in which the movable vane 54 in the variable displacement turbocharger 5 increases the gap flow area between the movable vane 54 and the fixed vane 49.

Next, referring to FIG. 20, the solenoid of the solenoid on-off valve 72
The procedure in the control means C for controlling 73 will be described. Here, in addition to controlling the operation of the electromagnetic control valve 69 for introducing the boost pressure P ₂ into the first pressure chamber 62 of the actuator 60 based on the main routine of FIG.
By introducing the intake pressure P _B into the pressure chamber 63 via the electromagnetic opening / closing valve 72, more precise control becomes possible. This is supercharging pressure
P ₂ is variable capacity turbocharger 5 and intercooler 4
Since the minute operation of the throttle valve 74 cannot be detected because it is detected during the period, the intake pressure P _B is derived from the downstream side of the throttle valve 74, so the minute operation of the throttle valve 74 can be detected. Because it is. 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 first step L1, it is determined whether or not a predetermined time, for example, 2 minutes has elapsed after the engine was started. If the predetermined time has not elapsed, the process proceeds to the second step L2, the solenoid 73 is excited, and the actuator 60 moves 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 cope with the start-up in the cold state, supercharging in the cold state can be prevented, and the catalyst temperature can be gradually raised. When the predetermined time has elapsed in the first step L1, the routine proceeds to a third step L3, where the vehicle speed V is set to have a hysteresis and the determination vehicle speed V _OP3, for example,
It is determined whether or not it exceeds 90/87 km / h, and if V> V _OP3 , proceed to the fourth step L4, and if V ≦ V _OP3 , proceed to the fifth step L5.

In the fourth step L4, it is determined whether the throttle opening change rate Δθ _TH is less than the set throttle opening change rate Δθ _THOP2 . This set throttle opening change rate Δθ
_THOP2 is set with hysteresis and θ _TH <
When it is θ _THOP2 , it proceeds to the second step L2, and otherwise it proceeds to the fifth step L5.

In the fifth step L5, it is determined whether the vehicle speed V is less than the set vehicle speed V _OP1 . The set vehicle speed V _OP1 has a hysteresis and is set to, for example, 65/63 km / h. If V / V _OP1 , proceed to 7th step L7, and V ≧ V
_If it is _OP1 , proceed to the sixth step L6 and solenoid 73
Degauss. In the seventh step L7, it is determined whether the vehicle speed V exceeds the set vehicle speed V _OP2 . This set vehicle speed V
_OP2 has hysteresis, for example 4 / 3km
It is set to / h. 12th step when V> V _OP2
Proceed to L12, and if V ≦ V _OP2 , proceed to eighth step L8.

In the eighth step L8, the previous vehicle speed V is the set vehicle speed V _OP2
If it is determined that V> V _OP2 , the timer t _OP is reset in the ninth step L9 when V> V _OP2 , and then the process proceeds to the tenth step L10. If V ≦ V _OP2 , the tenth step L10
Go to 10. In the tenth step L10, it is determined whether or not the previous state was the excitation state. If the state is the demagnetization state, the process proceeds to the sixth step L6, and if it is the excitation state, the timer t _OP sets the set timer t _{OPO in} the eleventh step L11. If t _OP > t _OPO , the sixth step L
In 6 and when t _OP ≤t _OPO , proceed to the second step L2.

In the 12th step L12, the engine speed N _E is set to the set speed N _EOP
Is determined to be less than. This set speed N _EOP
Have hysteresis, for example 2500/2
It is set to 300 rpm. The sixth when N _E ≧ N _EOP
To step L6, and when N _E <N _EOP , proceed to the 13th step L13.

In the thirteenth step L13, it is judged if the intake pressure P _B is less than the set intake pressure P _BOP . This set intake pressure P _BOP has hysteresis, for example, −100 / −150 mmH
Set to g. When P _B ≧ P _BOP , the sixth step L
If 6 or P _B <P _BOP , the process proceeds to the 14th step L14.

In the 14th step L14, it is determined whether the throttle opening θ _TH is less than the set throttle opening θ _THOP . The set throttle opening θ _THOP is set to, for example, _20/15 deg. When θ _TH ≧ θ _THOP, the process proceeds to the sixth step L6, and when θ _TH <θ _THOP , the process proceeds to the fifteenth step L15.

Further, in the fifteenth step L15, it is determined whether or not the throttle opening change rate Δθ _TH is positive and is less than the set throttle opening change rate Δθ _THOP1 set with hysteresis, and 0 <Δθ _TH < _If it is Δθ _THOP1 , the process _proceeds to the second step L2, and otherwise, proceeds to the sixth step L6.

According to the procedure described above, the variable capacity turbo is used in the slow acceleration state where 0 <Δθ _TH <Δθ _THOP2 at the high vehicle speed exceeding 90 / 87km / h as judged by the third step L3 and the fourth step L4. The movable vanes 54 of the charger 5 are fixed vanes 49.
It operates in the direction of increasing the void circulation area between and. Thereby, pumping loss can be prevented. That is, acceleration is not required in the high vehicle speed creasing state, and actuating the movable vane 54 to the boost pressure increasing side causes pumping loss due to back pressure increase caused by the high engine speed. is there.

Also, in the fifth step L5, the solenoid 73 is demagnetized in the vehicle speed state of 65/63 km / h or more. However, in such a high vehicle speed state, the control of the electromagnetic control valve 69 shown in FIG. 5 is sufficient. Because. Further, in the seventh step L7 to the eleventh step L11, at a low vehicle speed of 4/3 km / h or less, that is, almost stopped, the timer is reset when the previous vehicle speed is almost stopped, and the timer, for example, 1 minute During the passage of time, the solenoid 73 is excited to move the movable vanes 54 so that the flow area becomes large. This is to prevent that when the movable vanes 54 are on the side that reduces the flow area when restarting, the boost pressure P ₂ temporarily rises and overloads the starting gear, etc. is there. Furthermore, the vehicle speed is 4 /
If the movable vane 54 is on the side that reduces the flow area when the speed is 3 km / h or less, it will help the variable capacity turbocharger 5 to rotate when it is rotating due to inertia, etc. Since the degree θ _TH is almost fully closed, the supercharging pressure causes the intake passage pressure upstream of the throttle valve to rise. Therefore, by operating the movable vane 54 in the direction in which the flow area becomes large, the occurrence of surging due to the above-described pressure increase is prevented. Moreover, it can also contribute to the temperature rise of the catalyst immediately after starting in cold weather.

V _OP2 <V <V _OP1 , N _E <N _EOP , P _B <P _BOP , θ _{TH according to the} other judgment conditions of the 12th to 15th steps L12 to L15.
When <θ _THOP and 0 <Δθ _TH <Δθ _THOP are all satisfied,
That is, in the slow acceleration state under partial load such as in 10-mode traveling, the solenoid 73 is excited to reduce the supercharging pressure P ₂ , and thereby pumping loss can be prevented.

In the above embodiments, the variable capacity turbocharger in which the movable vane 54 is operated to change the capacity has been described. However, the present invention is applicable to wastegate type and supercharging pressure relief type variable capacity turbochargers. Applicable.

C. Effects of the Invention As described above, according to the method of the present invention, when the engine speed changes from the acceleration state to the deceleration state under the preset operating conditions of the engine, the basic supercharging is performed in the open loop control region. Since the pressure control amount and the target supercharging pressure in the feedback control region are both reduced, the shift change is detected by the behavior of the engine speed, and the supercharging pressure is reduced.
As a result, overshoot can be avoided and stable supercharging pressure control can be performed.

[Brief description of drawings]

1 shows an embodiment of the present invention. FIG. 1 is an overall schematic diagram showing an intake system and an exhaust system of an internal combustion engine, FIG. 2 is an enlarged vertical side view of a variable capacity turbocharger, and FIG. 2 is a sectional view taken along the line III-III in FIG. 4, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, FIG. 5 is a flowchart showing a main routine for controlling the electromagnetic control valve, and FIG. 7 is a graph showing a high boost pressure determination guard value, FIG. 8 is a flow chart showing a subroutine for subtracting the basic duty and the target boost pressure at the first speed position, and FIG. FIG. 8 is a diagram showing a discrimination zone used in the subroutine of FIG. 8, FIG. 10 is a flowchart showing a subroutine for subtracting the basic duty and the target supercharging pressure at positions other than the first speed position, and FIG. 11 is a serve for determining the set subtraction duty. routine 12 is a flowchart showing a map of the set subtraction duty, FIG. 13 is a flowchart showing a subroutine for determining the set addition duty, FIGS. 14, 15 and 16 are D _TRB , ΔP _2ST ,
FIG. 17 is a diagram showing a setting map of ΔP _2FB , FIG. 17 is a flowchart showing a subroutine for determining a feedback coefficient relating to a proportional control term and an integral control term, and FIG. 18 is a diagram showing changes in intake pressure during a shift change, FIG. 19 is a diagram showing changes in duty and supercharging 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 opening / closing valve. 5: Variable capacity turbocharger, D _M : Basic duty as a basic boost pressure control amount, P ₂ ... Boost pressure, P _2REF ...
… Target boost pressure

Claims (1)

(57) [Claims] 1. A control system for controlling the capacity of a variable displacement turbocharger based on a basic supercharging pressure control amount corresponding to an operating state of an engine, and when the operating state of the engine is in a feedback control region, the actual supercharging pressure and In a variable capacity turbocharger control method that corrects the basic boost pressure control amount according to the deviation from the target boost pressure, the engine speed decelerates from an accelerating state under preset engine operating conditions. A control method for a variable displacement turbocharger, characterized in that when the state changes, the basic boost pressure control amount is reduced in the open loop control region, and the target boost pressure is reduced in the feedback control region.