JPH0610424B2 - Supercharging pressure control method for internal combustion engine - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (1) Field of Industrial Application The present invention determines a control amount according to a deviation between an actual supercharging pressure and a target supercharging pressure, and based on the control amount, the supercharging pressure is the target. TECHNICAL FIELD The present invention relates to a supercharging pressure control method for an internal combustion engine that performs feedback control so as to obtain supercharging pressure, and particularly relates to a supercharging pressure control method for an internal combustion engine that can appropriately perform supercharging pressure control from a transient state to a steady state. .

(2) Conventional technology In a so-called variable displacement turbocharger or other internal combustion engine with a supercharger whose exhaust gas flow is used as a turbine drive source and which can control supercharging pressure, an appropriate actuator (for example, supercharging pressure or negative pressure in intake pipe) Feedback control has heretofore been used in the case of controlling the supercharging pressure by a pressure-responsive type operating system including a diaphragm used as an operating pressure or an operating system utilizing a step motor or the like.

This is because the supercharging pressure is affected by individual differences such as variations in manufacturing the above-mentioned actuators and components of the supercharger main body during manufacturing, or secular change such as deterioration in durability due to use. When operating with a preset control amount when controlling to a value of (1), a large change in supercharging pressure will occur (even if the same control amount is applied, the operation control system of the actuator etc. that should normally operate correspondingly) However, the feedback control of the supercharging pressure solves such a problem. Because you can do it. That is, the feedback control detects the deviation between the target supercharging pressure and the actual supercharging pressure, determines the control amount according to the deviation so that the deviation becomes zero, and performs control. Even if there are individual variations in the actuators, or if there is a secular change, those effects are absorbed and corrected in the feedback control.

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

(3) Problems to be Solved by the Invention However, the above feedback may cause an undesired abnormal increase in the boost pressure in some cases.
That is, in a so-called transient state such as when the boost pressure rises abruptly, the control amount cannot follow the boost pressure adjustment due to the response delay of the control system, resulting in an abnormal rise in boost pressure, abnormal drop, and hunting. Such phenomenon occurs.

In particular, at the time of acceleration, when it is necessary to sharply decrease the supercharging pressure to increase the engine output in response thereto, when the supercharging pressure rises toward the target supercharging pressure set high according to the operating state, The boost pressure exceeds the target boost pressure and overshoots.The larger the overshoot, the longer the hunting period and the unstable boost pressure control, and excessive overshoot causes overboost. If so, knocking or the like will occur, which also hinders drivability during acceleration.

Therefore, in order to eliminate the problem of the feedback control in the transient state, the present applicant first proposed a supercharging pressure control method in which the boost pressure control is an open loop control in the transient state and the feedback control is performed in the steady state. (Japanese Patent Application Laid-Open No. 63-129126), it becomes possible to perform stable supercharging pressure control as compared with the conventional one.

However, when the open loop control and the feedback control are selectively used in the transient state and the steady state as in the control method according to the above proposal, there is room for improvement in the following points, and if it is also improved, it is more possible. It becomes possible to perform more stable supercharging pressure control.

That is, when the feedback control start is judged only by the boost pressure state when shifting to the feedback control, the feedback control state may be entered too early depending on the operating state, or in some cases, the feedback control state may be entered. There is also a situation where there is no.

In this way, in the process of changing from the transient state to the steady state,
Depending on the situation, the timing of transition to feedback control may not be appropriate, and if the feedback control state is entered too early when the boost pressure rises, the deviation from the target boost pressure at that time may be larger. Since the control is started by entering the feedback control region, overboost and hunting are likely to occur. Further, when the feedback control state is difficult to enter, the later the transition to the feedback control is delayed, the more difficult it becomes during that time to correct the variation among the actuators used by the feedback control and the aging. .

The present invention has been made in view of the above circumstances, and optimizes the timing of transition to feedback control according to the operating condition of the engine, and thus, the internal combustion engine that always obtains an optimum control state is provided. An object is to provide a supply pressure control method.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the first feature of the present invention, in a predetermined operating state of the engine, the actual supercharging pressure and the target supercharging pressure are In the supercharging pressure control method for the internal combustion engine, which performs the feedback control so that the supercharging pressure becomes the target supercharging pressure based on the deviation of, the supercharging pressure is determined to be the first predetermined value when it is determined that the feedback control should be performed. When the value is less than or equal to a value, the basic supercharging pressure control amount is set to the maximum supercharging pressure control amount, and feedback control is started when the supercharging pressure exceeds a second predetermined value higher than the first predetermined value. The second predetermined value is changed to a larger value as the supercharging pressure change rate is higher. According to a second aspect of the present invention, in addition to the first feature, when the boost pressure is larger than the first predetermined value and smaller than the second predetermined value, the basic pressure A predetermined amount is subtracted from the boost pressure control amount when the boost pressure change rate is positive, and a predetermined amount is added when the change rate is negative.

(2) Operation According to the above method, when it is determined that the feedback control should be performed, the feedback control is started in response to the boost pressure exceeding the second predetermined value, and the second predetermined value is exceeded. Since the larger the supply pressure change rate is, the larger the value is changed, the timing of transition to the feedback control can be optimized according to the change in the supercharging pressure. Moreover, when the supercharging pressure is equal to or lower than the first predetermined value lower than the second predetermined value, the basic supercharging pressure control amount is set to the maximum supercharging pressure control amount, so that the transition to the feedback control is quick.

Further, according to the second feature, when the supercharging pressure is between the two predetermined values, the basic supercharging pressure control amount is subtracted by the predetermined amount when the supercharging pressure change rate is positive, and the same change rate. Since a predetermined amount is added when is negative, not only can the overshoot at the rise of boost pressure be effectively prevented by subtracting the predetermined amount,
The drop in the boost pressure due to the reaction is covered by the addition of the predetermined amount.

(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 the exhaust port of the modified cylinder, and the exhaust manifold 7 is connected to a catalytic converter 9 containing a three-way catalyst via an exhaust pipe 8 in which a variable capacity turbocharger 5 is provided in an intermediate portion. To be done. Further, a fuel injection valve 10 for respectively injecting fuel toward the intake port of each cylinder is attached to a portion of the intake manifold 1 in the vicinity of each intake port.

The variable-capacity turbocharger 5 is provided with a water jacket 11, and the inlet of the water jacket 11 and the inlet of the intercooler 4 are connected in parallel to the outlet of the water pump 13 whose inlet is connected to the radiator 12, Water pump 13
And the outlet of the intercooler 4 is 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 FIG. 2, FIG. 3 and FIG.
A back plate 15 that closes the back surface of the compressor casing 14, and 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 the compressor casing 1
An inlet passage 20 extending in the axial direction is formed in the central portion of 4. Moreover, the compressor wheel 21 is attached to one end of the main shaft 16 in the central portion of the scroll passage 19 and at the inner end of the inlet passage 20.

The compressor casing 14 and the back plate 15 are fastened together by a plurality of bolts 22, and the bearing casing 17 is connected to the central portion of the back plate 15. Bearing casing 17
A pair of bearing holes 23 and 24 are coaxially formed at a distance from each other, and the radial direction is provided between the main shaft 16 and the bearing holes 23 and 24 which are inserted into these bearing holes 23 and 24. Bearing metals 25 and 26 are respectively interposed, so that the main shaft 16 is rotatably supported by the bearing casing 17. Further, between the step portion 16a facing the compressor wheel 21 side of the main shaft 16 and the compressor wheel 21, the collar 27 and the thrust bearing metal 2 are arranged in order from the step portion 16a side.
8 and a bushing 29 are interposed, and a nut 30 that comes into contact with the outer end of the compressor wheel 21 is screwed onto one end of the main shaft 16 and tightened to support the thrust direction of the main shaft 16 and the main shaft 16 of the compressor wheel 21.
Is installed.

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

The bushing 29 is arranged so as to pass through a through hole 35 formed in the central portion of the back plate 15, and the thrust bearing metal 2
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 the lubricating oil flowing out of the compressor 8 from flowing to the compressor wheel 21 side.
A guide plate 37 is inserted between the back plate 15 and the thrust bearing metal 28 to allow the bushing 29 to pass therethrough. Therefore, the lubricating oil flowing out from the thrust bearing metal 28 is scattered outward from the bushing 29 in the radial direction, and the guide plate 3
Accepted at 7. Moreover, the lower part of the guide plate 37 is curved so as to smoothly guide the received lubricating oil to the lubricating oil discharge port 34.

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

A scroll passage 41 is provided in the turbine casing 18.
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 onto the turbine casing 18, and the bearing casing 17
The bearing casing 17 and the turbine casing 18 are coupled to each other 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 peripheral portion of the back plate 44 forms the bearing casing. It is sandwiched between 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 peripheral passage 41a and an inflow passage 41b. The fixed vane member 48 has a cylindrical portion 4 coaxially fitted in the outlet passage 43.
8a, a disk portion 48b extending outward in the radial direction 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. The turbine wheel 50 provided at the other end of the main shaft 16 is housed in the fixed vane member 48. The cylindrical portion 48a is fitted into the outlet passage 43 through a seal ring 51 fitted to the outer surface of the cylindrical portion 48a, and the fixed vanes 49 are joined to the back plate 44 by bolts 52.

The fixed vanes 49 are provided on the outer peripheral portion of the turbine member 48 at positions equidistantly arranged in the circumferential direction, and each fixed vane 49 is formed in an arc shape. Between the fixed vanes 49, the back plate 4 is made parallel to the axis of the main shaft 16.
Movable vanes 54, one end of which is fixed to a rotary shaft 53 that is rotatably pivotally mounted on the shaft 4, are arranged. 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 is rotatable between a fully closed position shown by a solid line in FIG. 3 and a fully opened position shown by a chain line. Moreover, the rotary shafts 53 have the back plate 44 and the bearing casing 17 respectively.
It is connected to an actuator 60 via a link mechanism 55 arranged between them, and the movable vanes 54 are synchronously opened and closed by the operation of the actuator 60.

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 addition, the exhaust gas is bearing casing 1
In order to prevent the main shaft 16 from leaking into the turbine casing 18, at a portion corresponding to the through hole 57 provided in the bearing casing 17 so as to project the main shaft 16 into the turbine casing 18, the main shaft 16
A plurality of annular grooves 58 functioning as labyrinth grooves are provided in the.

In the variable capacity turbocharger 5 as described above, the exhaust gas discharged from the engine body E passes from the inlet passage 42 to the outer peripheral passage 41a.
Exhaust gas flows into the inflow passage 41b at a flow velocity corresponding to the flow area of the gap between the movable vane 54 and the fixed vane 49 depending on the amount of rotation of the movable vane 54, and rotationally drives the turbine wheel 50 to exit. It is discharged from the passage 43. At this time, when the flow area of the gap between the movable vanes 54 and the fixed vanes 49 becomes smaller, the rotation speed of the turbine wheel 50, that is, the main shaft 16 becomes faster, and the flow area of the gap between the movable vanes 54 and the fixed vane 49 becomes larger. The rotation speed of the turbine wheel 50, that is, the main shaft 16 is reduced. The compressor wheel 21 is rotated in accordance with the rotation of the turbine wheel 50, and the air cleaner 6 moves to the inlet passage 2
The air guided to 0 passes through the scroll passage 19 while being compressed by the compressor wheel 21, and the intercooler 4
Will be supplied to. Therefore, when the movable vane 54 is positioned on the outermost side in the radial direction of the turbine casing 18 to minimize the void flow area between the movable vane 54 and the fixed vane 49, the supercharging pressure becomes maximum, and the movable vane 54 is moved to the radius of the turbine casing 18. The supercharging pressure is minimized when it is positioned at the innermost side in the direction to maximize the void circulation area with the fixed vane 49.

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 temperature is supplied to the intercooler 4. Is prevented by.

Referring again to FIG. 1, the actuator 60 for driving the movable vanes 54 of the variable capacity turbocharger 5 is
A housing 61 and a first pressure chamber 6 inside the housing 61.
2 and the diaphragm 64 which divides into the 2nd pressure chamber 63
And the diaphragm 64 in the direction of contracting the first pressure chamber 62.
And a return spring 65 interposed between the housing 61 and the diaphragm 64 for urging the housing 61, and one end of the diaphragm 64 is connected to the central portion of the diaphragm 64, and the housing 61 is pierced movably in an airtight manner on the side of the second pressure chamber 62. And a drive rod 66 having the other end connected to the link mechanism 55. Moreover, the drive rod 66 and the link mechanism 55 cause the movable vanes 54 to move inward in the radial direction of the turbine casing 18 when the diaphragm 64 bends in the direction in which the second pressure chamber 63 contracts and the drive rod 66 extends. It is connected so as to rotate so as to increase the void circulation area between each fixed vane 49.

The intake passage between the variable displacement turbocharger 5 and the intercooler 4 is connected to the first pressure chamber 62 via the regulator 67, the throttle 68 and the electromagnetic control valve 69 to supply the supercharging pressure P ₂ , and the air cleaner 6 is also provided. An intake path 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, and the pressure of the first pressure chamber 62 increases as the duty ratio of the solenoid 70 increases, that is, the pressure is changed via the drive rod 66 and the link mechanism 55. The movable vane 54 of the turbocharger 5 is rotationally driven inward. Further, in the second pressure chamber 63, the check valve 7 is provided so that the intake passage downstream of the throttle body 3 supplies the intake pressure P _B.
1 and the electromagnetic on-off valve 72. The electromagnetic opening / closing valve 72 opens in response to the excitation of the solenoid 73, and the second opening / closing valve 72 opens in response to the opening of the electromagnetic opening / closing valve 72.
When the intake pressure P _B is supplied to the pressure chamber 63, the actuator 60 causes the movable vane 54 of the variable capacity turbocharger 5 to move.
Drive inward.

Solenoid 70 of solenoid control valve 69 and solenoid on-off valve 72
Excitation and demagnetization of the solenoid 73 of the engine is controlled by the control means C.
A temperature detector S _w for detecting the water temperature T _w of the provided water jacket (not shown) within the intake air temperature sensor S _A for detecting the intake air temperature T _A of the downstream side of the intercooler 4, an air cleaner 6 and an intake pressure sensor S _PA for detecting the intake air pressure P _a between the variable capacity turbocharger 5, a supercharging pressure sensor S _P2 for detecting the supercharging pressure P ₂ in the intake passage between the variable capacity turbocharger 5 and the intercooler 4, an intake pressure sensor S _PB for detecting an intake pressure P _B on the downstream side of the throttle body 3, the rotation speed detector S for detecting the engine speed N _E
N, and a throttle opening detector S _TH for detecting the opening θ _TH of the throttle valve 74 in the throttle body 3,
A vehicle speed detector S _V for detecting the vehicle speed V, a shift position detector S _S for detecting a shift position of the automatic transmission is connected. Thus, 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 , and the throttle opening θ.
Excitation and demagnetization of the solenoids 70 and 73 are controlled based on _TH , 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. When the engine is in the starting mode, the duty D _OUT is 0 in the second step S2, that is, the electromagnetic control valve 69. Is set to be 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. Further, during cranking, the driver does not request the supercharging of the air supply, and it is not necessary to reduce the gap flow area between the movable vanes 54 and the fixed vanes 49. In the next third step 3, the timer t _FBDLY for delaying the start of the feedback control is reset, and then the duty D _{OUT is changed} from the fourth step S4.
Is output.

The timer t _FBDLY is calculated according to the procedure shown in FIG. 6, and three timers t _FBDLY1 , t _FBDLY2 , t are calculated according to the change rate ΔP ₂ of the supercharging pressure P _2.
One of _FBDLY3 is selected. Here, the change rate ΔP ₂ is obtained by comparing the current boost pressure P _2n and the boost pressure P 6 times before.
Determined by the difference between the _{2n-6 (ΔP 2 = P} 2n -P 2n-6). That is, the main routine shown in FIG. 5 is TDC.
Although it is updated by the signal, since the rate of change of the supercharging pressure P ₂ is too small with only one TDC signal, the supercharging pressure P _2n 6 times before is changed in order to accurately read the supercharging pressure behavior, that is, the rate of change ΔP _2. The difference from ₋₆ is obtained. In addition, the setting change rate ΔP _2PTL and the setting high change rate ΔP
_2PTH is predetermined according to the engine speed N _E , and when ΔP ₂ ≦ ΔP _2PTL , t
_FBDLY1 is set, and ΔP _2PTL <ΔP ₂ ≦ ΔP
_{When 2PTH} , t _FBDLY2 is set, and ΔP
_{When 2PTH} <ΔP ₂ , t _FBDLY3 is set. Moreover, t _FBDLY1 <t _FBDLY2 <t
_FBDLY3 , the delay time is set small when the supercharging pressure change rate ΔP ₂ is small, that is, when the supercharging pressure P ₂ is slowly changing, and when the supercharging pressure change rate ΔP ₂ is large, that is, the supercharging pressure P _{When 2} rapidly changes, the delay time is set large. 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 is possible to sufficiently prevent the hunting phenomenon from occurring at the time of the transition.

When it is determined in the first step S1 that the starting mode is not set, the water temperature T _W is set to the set low water temperature T in the fifth step S5.
_It is judged whether it is less than _WL , and the set low water temperature T _WL
When it is less than, it proceeds to the second step S2. Where T
The operating state of the engine that is considered as a case where _W <T _WL is satisfied is, for example, when the engine starts or when the outside air temperature is extremely low, and the operating state is unstable at the beginning of the engine. In addition, when 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 boost pressure into the combustion chamber promotes an unstable state of the engine and abnormal combustion. Further, when the temperature is extremely low, the electromagnetic control valve 69 itself may malfunction, and the electromagnetic control valve 69 may not behave as instructed by the control means C. So _TW
If <T _WL , proceed to the second step S2 and set 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. In this sixth step S6, it is judged whether or not the water temperature T _W exceeds the set high water temperature T _WH, and if it exceeds the set high water temperature T _WH , the second
Go to step S2. Here, when T _W > T _WH is satisfied, for example, when the engine continues to operate under high load, when the outside air temperature is extremely high, or when an abnormality occurs in the cooling water system of the engine body E. When there is. In all of these states, the intake density decreases, that is, the charging efficiency decreases, which causes abnormal combustion such as unburned. Introducing the supercharging pressure into the combustion chamber when the engine is in the unstable state as described above promotes the unstable state. Therefore, the duty D _OUT = 0 in the second step S2. is there. Further, the inductance characteristic of the solenoid 70 is likely to change at an extremely high temperature, and there is a possibility that the behavior may be different from the setting behavior in the normal state. To avoid such a situation, the second step S2 is also proceeded.
When it is determined in the sixth step S6 that T _W ≧ T _WH , the process proceeds to a seventh step S7. That process proceeds to a seventh step S7 when in the water temperature T _W is set low temperature T A at _WL above setting high temperature T _WH the range, the process proceeds to the second step S2 at other times.

In a seventh step S7, it is determined whether or not the supercharging pressure P ₂ exceeds a preset high supercharging pressure determination guard value P _2HG as shown in FIG. 7, and when P ₂ > P _2HG , The process proceeds to step S2, and if P _{2 ≤P 2HG} , the process proceeds to step S8. Here high boost pressure determination guard value P _2HG is to vary according to the engine rotational speed N _E, it is set so that the highest output can be obtained by the following knock limit value corresponding to the engine speed N _E It is a thing. In the limit low speed range, the torque applied to the transmission member at the low speed shift stage is positive, in the limit high speed range, the durability of the engine body E is positive, and P _2HG lower than the middle speed range is set. This high when more than boost pressure determination guard value P _2HG supercharging pressure P ₂ is detected, the supercharging pressure P _2, the duty ratio of 100% in the fourth step S4 that has passed through the second and third steps S2, S3 Is reduced and fuel injection is cut.

In the eighth step S8, the basic duty D _M as the basic boost pressure control amount is searched. This basic duty D
_M is preset according to the engine speed N _E and the throttle opening θ _TH, and the basic duty D _M is searched from the setting table. As described above, by searching the basic duty D _M as the basic boost pressure control amount with the map determined by the engine speed N _E and the throttle opening θ _TH , each operating state of the engine can be accurately determined. .
This is the engine speed N _E alone or the throttle opening θ
_{This is because TH} alone cannot accurately determine the deceleration or the transient operating state. The throttle opening θ _TH is adopted as a representative parameter indicating the load condition of the engine.
Even if the intake pressure P _B or the fuel injection amount is substituted, the same effect can be obtained.

In the following ninth step S9, it is determined whether or not the shift position of the automatic transmission is in the first speed position. If the shift position is in the first speed position, the process proceeds to tenth step S10 to shift to 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 is, the discrimination zone that needs to be reduced according to the operating state determined by the engine speed N _E and the intake pressure P _B is preset as shown by the hatched line in FIG. 9, and whether it is in this discrimination zone or not. Basic duty D _M depending on whether it is outside
Is determined. Meanwhile FIG. 9 in the engine speed N _E - is viewing a torque variation of the engine by the intake pressure P _B, the boundary line determination zone shows the allowable torque of the gear shaft in the first speed position. That is, in order to prevent the force applied to the gear shaft from being overloaded in the first speed position, the determination 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 unchanged and the first duty
2 Go to step S12, but when it is in the discrimination zone, it is judged whether the flag F is 0, that is, whether it is in the feedback control state, and when it is in the open control state, D _M = D _M −D _F Is subtracted, and when in the feedback control state, P
_2HEF = _{P 2REF -ΔP 2REFF} becomes subtraction is performed. Here, D _F is a preset subtraction value.
Further, P _2REF is a target supercharging pressure used in the feedback control state, and 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 is the set throttle opening θ
_The engine speed N _E exceeds _THOS and the engine speed N _E is the set speed N _EOS.
Beyond the intake pressure P _B exceeds the set intake pressure P _BOS, previous engine rotational speed N _E of the change rate .DELTA.N _E is positive, when the change rate .DELTA.N _E of this engine rotational speed N _E is negative, open In the control state, the subtraction D _M = D _M −D _0S is performed, and in the feedback control state, P _2REF
= P _2REF −ΔP _2REFOS
Otherwise, the basic duty D _M is left unchanged and the process proceeds to the twelfth step S12. Where D _0S , ΔP
_2REFOS is a preset subtraction value.

In the twelfth step S12, it is determined whether or not the throttle opening θ _TH exceeds a preset throttle opening θ _THFB . This set throttle opening θ _THFB
Is set to determine whether to shift from open loop control to feedback control.
Thus, the throttle opening θ _{TH is used} as the determination parameter.
By adopting, it is possible to accurately determine whether or not the driver is requesting acceleration, that is, the supercharging zone.
When θ _TH ≦ θ _THFB, that is, when the open loop control is continued, the delay timer t _FBDLY shown in FIG. 6 is reset in the thirteenth step S13, and the process proceeds to the fourteenth step S14.

In the fourteenth step S14, the duty correction coefficient K
Search _MODij . This correction coefficient K _MODij is
It is searched by a map determined by the engine speed N _E and the intake air temperature T _A, and is learned when the optimum supercharging pressure P ₂ is within a predetermined deviation as described later, and is updated at any time by the learning. It Here, the initial value of the correction coefficient K _MODij is 1
Is.

The next 15th step S15, the atmospheric pressure correction coefficient _K PATC duty (0.8-1.0) is determined in accordance with the intake pressure _{P A,} further intake air temperature correction coefficient duty at the 16 step S16 follows K _TATC (0.8-1.3)
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 is, when the throttle opening θ _TH is larger than the set throttle opening θ _THFB, FIG.
(a), (b), the supercharging pressure P ₂ of the change rate [Delta] P ₂ as shown by (c)
And the set subtraction duty D _T set by the engine speed N _E is selected, and when θ _TH ≦ θ _THFB , D _T = 0.

FIG. 12 (a) shows a set subtraction duty D _T when the engine speed N _E is equal to or lower than a preset first switching speed N _FB1 (for example, 3000 rPm), and FIG.
(b) shows that the engine speed N _E exceeds the first switching speed N _FB1 and the second switching speed N _FB2 (for example, 4500 rpm).
The set subtraction duty D _T when
FIG. 2 (c) shows the set subtraction duty D _T when the engine speed N _E is less than the second switching speed N _FB2 . Here, the set subtraction duty D _T is a set value P lower than the target supercharging pressure P _{2REF as} shown in FIG. 19 described later.
It is processed from the time when the actual supercharging pressure P ₂ exceeds _2ST , and is for preventing overshoot at 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 set value P _2ST.
Since there is a difference in the overshoot amount depending on the engine speed N _E when reaching the engine speed and the supercharging pressure change rate ΔP ₂ ,
The purpose is to optimize the duty control in each operation range by the above-mentioned replacement. Here ΔP
_The larger ₂ is and the larger N _E is, the larger D _T is set.

Further, in the eighteenth step S18, the set addition duty _DTRS is determined according to the subroutine shown in FIG. That first when the change rate [Delta] P ₂ of the open loop control is a by addition supercharging pressure P ₂ is a negative state
As shown in FIGS. 4A, 4B, and 4C, the set addition duty D set by −ΔP ₂ and the engine speed N _E.
TRB is selected, and the set subtraction duty D _T is 0.
It is said that In the feedback control state, ΔP ₂
Is positive, the set addition duty _DTRB is set to zero. Like the set subtraction duty D _T also above the setting summing duty D _TRB, it is intended to be replaced lifting as shown in FIG. 14 according to the engine rotational speed N _E and one supercharging pressure change rate -ΔP _2, the larger N _E, is set such -DerutaP ₂ is more D _TRB is large increases, thereby it is possible to duty control, such as the boost pressure P ₂ which less stable hunting is obtained in each operation range. That is, D _OUT = 1 from the start of operation to the predetermined region P _2ST
00, the supercharging pressure P ₂ is increased by minimizing the gap flow area between the movable vane 54 and the fixed vane 49, and overshoot is prevented after the supercharging pressure P ₂ exceeds the set pressure P _2ST. By adding the set addition duty D _{TRB in} order to prevent hunting that occurs as a reaction of the set subtraction duty D _T for use, stable supercharging pressure control can be performed in each operation range. Therefore, the output duty D _OUT output from the fourth step S4 is set in consideration of the operating conditions of the engine in consideration of the above-mentioned contents and external factors.

Thus, the correction coefficients K _MODij , K _PATC , K
_{After the TATC} , the setting subtraction duty _DT, and the setting addition duty _DTRM are determined, the 19th step S
Proceed to 19.

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 ) Furthermore, in the twentieth step S20, a flag F = 1 is set to indicate that the loop control is open loop, and in the twenty-first step S21, it is checked whether or not the duty D _OUT exceeds the limit value. To do. That is, engine speed N
The limit value of the duty _DT is set in advance according to _E , and it is checked whether or not it is out of the limit value. When it is not out of the limit value, the duty _DOUT is output in the fourth step S4.

When it is determined in the 12th step S12 that θ _TH > θ _THFB , the process proceeds to a 22nd step S22. In the 22nd step S22, it is determined whether or not the previous flag F is 1, that is, whether the previous time was the open loop control state, and when F = 1, the supercharging pressure P ₂ is open loop in the 23rd step S23. It is determined whether or not the duty control start determination supercharging pressure P _{2ST in} 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), (c).
It is set according to the engine speed N _E as shown by.
Here, ΔP _2ST is similar to D _T and D _TRB described above,
The engine speed N _E and the supercharging pressure change rate ΔP ₂ are changed over in order to perform the optimum duty control. As the engine speed N _E increases, the supercharging pressure change rate ΔP ₂ increases.
Is set to be larger as is 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 obtained by P _2FB = P _2REF −ΔP _2FB , and ΔP _2FB is shown in FIGS. 16 (a), (b),
As shown in (c), it is set according to the engine speed N _E. That is, ΔP _2FB is _equal to ΔP _2ST , D _T , D
Similar to the _TRB , the duty ratio is changed according to the engine speed N _E and the supercharging pressure change rate ΔP ₂ for optimal duty control. As the engine speed N _E increases, the supercharging pressure change rate increases. It is set so as to decrease as ΔP ₂ increases, and feedback control start determination supercharging pressure P _2FB
Is the supercharging pressure change rate Δ as the engine speed N _E increases.
It increases as P ₂ increases. This 24th step S
If P ₂ > P _2FB at 24, the 25th step S
Go to 25.

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. In addition, the 22nd step S2
When F = 0 in 2nd, the 23rd to 25th steps S2
By detouring from 3 to S25, the process proceeds to the 26th step S26, and when P ₂ ≦ P _2ST in the 23rd step S23, the 27th step S27 is performed, and the P ₂ ≦ in the 24th step S24.
When it is P 2 _FB , the second step is performed in the thirteenth step S13.
If the delay timer t _FBDLY has not elapsed in step S25, the process proceeds to fourteenth step S14.

In the 27th step S27, the duty D _OUT is 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 . The feedback control determination supercharging differential pressure G _dP2 is set to, for example, 30 mmHg, 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 is When the feedback control determination supercharging differential pressure G _dP2 or less, the process proceeds to the 29th step S29. Here, starting feedback control when | ΔP ₂ |> G _dP2 causes hunting. Therefore, the process returns to the fourteenth step S14 to perform open loop control. _Since the hunting and the overshoot are prevented by performing the correction by _T , D _TRB , the 26th step S26 is mainly to perform the fail-safe function.

The feedback control is started from the 29th step S29, and first, in a 29th step S29, the target supercharging pressure P _2REF preset by the engine speed N _E and the intake air temperature T _A is searched. Here, in the feedback control, first, in the 12th step S12, θ _TH
It is premised that> _θTHFB is satisfied, and the target supercharging pressure P _2REF determined by the engine speed N _E and the intake air temperature T _A is searched as a parameter that can accurately determine the operating state of the engine under this precondition. It is what is done. θ
_TH > _{θTHFB In other} words, the engine speed N _E and the throttle opening θ _TH exhibit almost the same behavior in a medium and high load state of the engine, and N _E is an effective parameter indicating the operating state of the engine. Is. Also, the intake air temperature T _A 2
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 from 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, P _2REF = P when the operating state is in the discrimination zone (hatched portion in FIG. 9) according to the subroutine shown in FIG. 8 in the 31st step S31.
_2REF− ΔP _2REFF is performed, and the 33rd
It proceeds to step S33. This ΔP _2REFF is a subtraction value that is set in correspondence with the shift position at the first speed position. If it is determined in the 30th step S30 that the shift position is in a position other than the first speed position, the third position is set.
2 In step S32, P _2REF = P _2REF −ΔP according to the subroutine shown in FIG. 10 described above.
_The operation of _2REFOS is performed, and the 33rd step S3
Go to 3. Moreover, ΔP2 _REFOS has the first shift position.
It is a subtraction value that is set corresponding to a state other than the 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 Be done.

P _2REF = P _2REF × K _{REFTB In the} above equation, K _REFTB is a correction coefficient corresponding to the knocked 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 defining pressure during feedback control, for example, 20 mmH
It is set to about g. When the absolute value of the deviation between the target supercharging pressure P _2REF and the actual supercharging pressure P ₂ is greater than or equal to the set value G _{P2, the routine} proceeds to the 36th step S36, where the set value G
When it is less than _P2 , the process proceeds to the 43rd step S43.

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) K P in the above formula is feedback coefficient according to the proportional control term is determined according to a subroutine shown in FIG. 17. In FIG. 17, the engine speed N _E is the first
When it is below the switching speed N _FB1 , K _P1 is obtained and at the same time, a feedback coefficient K ₁₁ relating to an integral control term described later is obtained, and the engine speed N _E is the first switching speed N.
_{When FB1} is exceeded and the second switching speed N _FB2 or less, K _P2 and K ₁₂ are obtained, and the engine speed N _{E is} further obtained.
_Exceeds the second switching speed N _FB2 , K _P3 and K ₁₃ are obtained.

In the 37th step S37, the 14th step S14 described above is performed.
Similarly, the correction coefficient K _MODij according to the engine speed N _E and the intake air temperature T _A is retrieved, and the 38th step S3
At 8, it is determined whether the previous flag F is 1, that is, whether it is the first feedback control state, and when F = 1, at the 39th step S39, the previous integral control term D _{I (n-1).} Is calculated according to the following equation.

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

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 is calculated in the 41st step S41. That is, D _OUT = K _TATC × K _PATC × D _M + D _P + D
_In is performed, and the flag F is set in the 42nd step S42.
After setting = 0, 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 the 43rd step S43.
_In = DI _(n-1) . Next, in the 44th step S44 to the 47th step S47, the water temperature T _W exceeds a certain fixed range, that is, T _WMODL , and T _WMODH
Whether the retard amount T _2RET is 0, that is, out of the knock state, whether the shift position is other than the first gear position, and whether K _REFTB is 1.0 or less is determined. When all the conditions are satisfied, the process proceeds to the 48th step S48, and when any one of these conditions is not satisfied, the process proceeds to the 41st step S41.

In the 48th step S48, the duty correction coefficient K
The coefficient K _R for learning _MODij 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, the correction coefficient K
_In order to search and learn _MODij , Then, in the 50th step S50, the K _MODij obtained in the 49th step S49 is stored.

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 position.
If the open loop control state is set in the speed position, the basic duty D _M is D when the operating state of the engine is in the determination zone in FIG. 9 in step S10.
_In the feedback control state, the target supercharging pressure P _2REF is subtracted by ΔP _{2REF in} the 31st step S31 in the determination zone. Therefore, when the shift position is the first speed position, overload on the automatic transmission due to rapid advance, overload, etc.
_This can be prevented by reducing the supercharging pressure as _M decreases. Further, even if the open-loop control is changed to the feedback control in the first speed position, the target boost pressure P _2REF is subtracted, so that hunting can be prevented from occurring during the change.

It is also assumed that the shift change shown in the lower part of FIG. 18 is performed. In this case, when shifting
While the engine speed N _E increases, there is a time lag in the operation of the actuator 60 by the control means C. Therefore, the supercharging pressure P ₂ does not correspond to the engine speed N _E , and an overshoot occurs, so that the supercharging pressure P ₂ is changed as shown by a broken line in FIG. Sometimes the limit may be exceeded. However,
In the 11th step S11 and the 32nd step S32, the duty D _M and the target supercharging pressure P _2REF are subtracted according to the subroutine shown in FIG. 10. 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. According to the rate of change ΔP ₂ of the supercharging pressure P _{2 in} the region, the basic duty D _M is subtracted by D _{OS in} the open loop control, and the target supercharging pressure P _2REF is subtracted by ΔP _2REFOS in 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, as shown in FIG. 19, it is possible to cover the fall of the supercharging pressure P ₂ and shift to the feedback control promptly. That is, at the start of operation, the duty D _OUT is 100, that is, the duty ratio is 0%, and the throttle opening θ _TH is the set throttle opening θ.
_In open loop control with less than _THFB , the 18th
According to the subroutine in FIG. 13 in step S18, D _T = 0. Then, when θ _TH > θ _THTB , the transition from the open loop control to the feedback control side starts, but when θ _TH > θ _THFB when the supercharging pressure P ₂ exceeds P _2ST , D _M = D _M -D _T
To prevent overshoot.

However, when only 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, then D _T = 0 and D
_Since only _{TRB is} added, it is possible to cover the fall of the supercharging pressure P ₂ and quickly shift to the feedback control, and it is possible to expand the supercharging pressure control without the hunting phenomenon.

By the way, a feedback control start determination supercharging pressure P _2FB (= P _2REF −ΔP for determining whether to shift from open loop control to feedback control)
_2FB ) is changed according to the operating state and environmental conditions of the engine, so that an appropriate control state can always be obtained according to the situation.

That is, the feedback control start determination supercharging pressure P
_2FB is set so as to increase as the change rate ΔP _{2 of the} supercharging pressure increases. As a result, the rate of change in boost pressure ΔP
_{When 2} is large, it is possible to make the feedback control start determination supercharging pressure P _2FB larger than when the rate of change ΔP _{2 of the} supercharging pressure is small and shift to the feedback control at an appropriate timing. Etc. can be prevented.

Further, when the gear position of the transmission is at the low speed, that is, the first speed position, the target supercharging pressure P _2REF is set to be lower in the 10th step S10 and the 31st step S31 than in the other shift positions. As a result, the feedback control start determination supercharging pressure P _2FB is set to a lower value when in the low speed gear, and even if the supercharging pressure characteristic is changed according to the shift position, the feedback control is always performed at an appropriate timing. It becomes possible to shift.

Further, the feedback control start determination _boost pressure P _2FB is
E is changed by the intake air temperature T _A as an environmental condition and the intake pressure P _A immediately after passing through the air cleaner 6 as an index indicating the atmospheric pressure. That is, the target boost pressure P _2REF is
It is set by the engine speed N _E and the intake air temperature T _A , and the target supercharging pressure P _2REF is the atmospheric pressure correction coefficient K.
_Corrected by _PATC . Thus, the feedback control start determination supercharging pressure P _2FB changes depending on the intake air temperature T _A and the intake pressure P _A. That is, if the intake air temperature T _A is low, the feedback control start determination supercharging pressure P _2FB is also lowered, and the lower the intake pressure P _A is, the higher the intake pressure P _A is. Thus, the feedback control start determination for determining the feedback control start is performed. By changing the supercharging pressure P _{2FB according} to the environmental conditions, the timing for shifting to the feedback control can be appropriately performed.

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 opens,
The intake pressure P is applied to the second pressure chamber 63 in the actuator 60.
_{When B} is supplied, the movable vanes 54 in the variable capacity turbocharger 5 are fixed to the fixed vanes 49 in the actuator 60.
It operates in the direction of increasing the void circulation area between and.

Next, the procedure in the control means C for controlling the solenoid 73 of the solenoid valve 72 will be described with reference to FIG. 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 via the opening / closing valve 72, more precise control becomes possible. This is because the supercharging pressure P ₂ is detected between the variable displacement turbocharger 5 and the intercooler 4, and therefore a slight operation of the throttle valve 74 cannot be sensed, while the intake pressure P _B is lower than the throttle valve 74. This is because it is derived from the side, so that a minute operation of the throttle valve 74 can be detected. That is, 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 operate the entire intake system including the turbocharger 5. It becomes possible to reflect it accurately.

In the first step LL1, 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 vanes 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. This first step L1
When the predetermined time has elapsed, the routine proceeds to the third step L3, where it is judged whether the vehicle speed V exceeds the judgment vehicle speed V _OP3 set with hysteresis, for example, _90/87 km / h, and V> V _OP3 If so, the process proceeds to the fourth step L4, and if V ≦ V _OP3 , the process proceeds to the fifth step L5.

In the fourth step L4, it is determined whether the throttle opening θ _TH is less than the set throttle opening change rate Δθ _THOP2 . This set throttle opening change rate θ
_THOP2 is set with hysteresis, and Δ
When θ _TH <Δθ _THOP2 , the second step L
2, and otherwise 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, for example, 65/63 km /
is set to h. If V <V _OP1 , the seventh step L
7, and when V ≧ V _OP1 , the process proceeds to the sixth step L6 to demagnetize the solenoid 73. In the seventh step L7, it is determined whether the vehicle speed V is _lower than the set vehicle speed V _OP2 . The set vehicle speed V _OP2 has hysteresis and is set to, for example, 4/3 km / h. When V> V _OP2 , 12th step L
12, and if V ≦ V _OP2 , the eighth step L8
Proceed to.

In the eighth step L8, the previous vehicle speed V is the set vehicle speed V
_It is determined whether or not _OP2 is exceeded. When V> V _OP2 , the timer t _OP is reset in the ninth step L9, and then the process proceeds to the tenth step L10. When V ≦ V _OP2 , the process proceeds to the tenth step L10. This tenth
In 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 sixth step L6, and if the state is the excitation state, the eleventh step L11.
Determines whether the timer t _OP exceeds the set timer t _OP0, and if t _OP > t _OP0 , the sixth step L6, and if t _OP ≦ t _OP0 , the second step L6.
Go to step L2.

In the twelfth step L12, it is determined whether the engine speed N _E is less than the set speed N _EOP . The set rotational speed N _EOP has a hysteresis and is set to 2500/2300 rpm, for example. N
_{When E} ≧ N _EOP , the process proceeds to the sixth step L6, and when N _E <N _EOP , the process proceeds to the thirteenth step L13.

In the 13th step L13, the intake pressure P _B is equal to the set intake pressure P
It is determined whether it is less than _BOP . This set intake pressure P _BOP has a hysteresis and is set to, for example, −100 / −150 mmHg. P _B ≧ P
_If it is a _BOP , go to the sixth step L6, and if P _B <
If it is 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 . This set throttle opening θ _THOP is, for example, 2
It is set to 0/15 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 < θ
When it is _THOP1 , the process _proceeds to the second step L2, and otherwise, it proceeds to the sixth step L6.

According to the procedure described above, the variable-capacity turbocharger in the slow acceleration state where 0 <Δθ _TH <Δθ _THOP2 is satisfied at the high vehicle speed exceeding _90/87 km / h as judged by the third step L3 and the fourth step L4. Movable vane 5 of charger 5
4 operates in the direction of increasing the void circulation area between the fixed vane 49. Thereby, pumping loss can be prevented. That is, acceleration is not required in the cruising state at high vehicle speed, and actuating the movable vane 54 to the boost pressure increasing side causes pumping loss due to back pressure increase caused by high engine speed. is there.

Further, in the fifth step L5, the solenoid 73 is demagnetized in the vehicle speed state exceeding 65/63 km / h. However, in such a high vehicle speed state, the control of the electromagnetic control valve 69 shown in FIG. 5 is sufficient. Because. 7th step L7
In the eleventh step L11, at a low vehicle speed of 4/3 km / h or less, that is, when the vehicle is almost stopped, the timer is reset when the previous vehicle speed is almost stopped, and the solenoid 73 is operated while the timer elapses, for example, one minute. Is excited to move the movable vane 54 so that the flow area is increased. This is to prevent the boosting pressure P ₂ from temporarily increasing and the starting gear and the like being overloaded if the movable vane 54 is located on the side where the flow area is reduced at the time of restart. is there. Furthermore, when the movable vane 54 is on the side that reduces the flow area when the vehicle speed is 4/3 km / h or less, by promoting the rotation of the variable displacement turbocharger 5 while rotating due to inertia, In that case, since the throttle opening θ _TH is almost fully closed, the supercharging pressure causes the intake passage internal pressure upstream of the throttle valve to rise. Therefore, by operating the movable vanes 54 in the direction in which the distribution area becomes large, the occurrence of surging due to the boosting is prevented. Moreover, it can also contribute to the temperature rise of the catalyst immediately after starting in cold weather.

Other 12th to 15th steps L12 to L15
V _OP2 <V <V _OP1 , N _E <N
_EOP , P _B <P _BOPT , θ _TH <θ _THOP , 0 <
When all of Δθ _TH <Δθ _THOP1 are satisfied, that is, in the gentle acceleration state under partial load such as 10 mode running, the solenoid 73 is excited to reduce the supercharging pressure P ₂ and thereby prevent pumping loss. be able to.

In the above embodiment, the supercharging pressure P ₂ is detected by the supercharging pressure sensor S _P2 . However, if the supercharging pressure control is performed with the throttle fully opened, it can be detected by the intake pressure sensor S _PB. It is also possible to perform the supercharging pressure control on the assumption that the intake pressure P _B is substantially equal to the supercharging pressure P ₂ .

Further, although the variable capacity turbocharger in which the movable vane 54 is operated to change the capacity is taken up in the above embodiments, the present invention is applicable to the wastegate type and supercharging pressure relief type variable capacity turbocharger. Can also be applied to a so-called supercharger driven by the output power of the engine.

C. As described above, according to the present invention, when it is determined that the feedback control should be performed, the feedback control is started in response to the supercharging pressure exceeding the second predetermined value, and the predetermined value is exceeded. Is changed to a larger value as the rate of change in supercharging pressure is larger, so the timing of transition to feedback control can be optimized according to the change in supercharging pressure. It is possible to accelerate the rising speed of the supercharging pressure while preventing rise and hunting, which can contribute to improvement of acceleration characteristics.
In addition, if it is less than or equal to the first predetermined value lower than the second predetermined value, the basic boost pressure control amount is set to the maximum boost pressure control amount.
The transition to the feedback control can be promptly proceeded, and therefore the transition to the feedback control can be swiftly made stable and less hunting occurs.

Further, according to the second feature, when the supercharging pressure is between the two predetermined values, the basic supercharging pressure control amount is subtracted by the predetermined amount when the supercharging pressure change rate is positive, and the same change rate. Since a predetermined amount is added when is negative, not only can the overshoot at the rise of boost pressure be effectively prevented by subtracting the predetermined amount,
The drop in the supercharging pressure due to the reaction can be covered by the addition of the predetermined amount, and the feedback control can be more swiftly performed while suppressing the occurrence of hunting.

[Brief description of drawings]

1 shows an embodiment of the present invention. FIG. 1 is an overall schematic view showing an intake system and an exhaust system of an internal combustion engine, FIG. 2 is an enlarged vertical 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. 10 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 subroutine for determining the set subtraction duty. 12 is a flowchart showing a routine, FIG. 12 is a diagram showing a map of set subtraction duty, FIG.
Fig is a flowchart showing a subroutine for setting the addition duty determination, Figure 14, Figure 15 and FIG. 16 _{D TRB,} [Delta] P _2ST, shows respectively a setting map of [Delta] P _2FB, Figure 17 is a proportional control term and FIG. 18 is a flowchart showing a subroutine for determining a feedback coefficient relating to the integral control term, FIG. 18 is a diagram showing a change in intake pressure at the time of shift change, and FIG. 19 is a duty and supercharging at the time of transition from open loop control to feedback control. FIG. 20 is a flowchart showing a change in pressure, 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 supercharging pressure control amount, D T _...... set subtraction duty as a predetermined amount, setting the addition duty as D _{TRB ......} predetermined amount, P ₂ ... ... supercharging pressure, ΔP ₂ ... supercharging pressure change rate, P _2ST ... duty control start determination supercharging pressure as a first predetermined value, P _2FB ... feedback control start determination supercharging pressure as a second predetermined value , P _{2REF ・ ・ ・} Target boost pressure, T _{A ・ ・ ・} Intake air temperature

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-60-212625 (JP, A) JP-A-62-26322 (JP, A) JP-A-60-249621 (JP, A)

Claims (2)

[Claims] [Claim 1] In certain operating conditions of the engine, the actual supercharging pressure (P ₂₎ between the target supercharging pressure (P _2ref) supercharging pressure based on the deviation between the (P ₂₎ the target boost pressure ( In the supercharging pressure control method for an internal combustion engine, which performs feedback control so that P _2REF ), the supercharging pressure (P ₂ ) is equal to or lower than the first predetermined value (P _2ST ) when it is determined that the feedback control should be performed. In this case, the basic supercharging pressure control amount (D _M ) is set as the maximum supercharging pressure control amount, and the supercharging pressure (P ₂ ) is higher than the first predetermined value (P _2ST ) by the second predetermined value (P _2ST ).
_2FB ), feedback control is started in response to this, and the second predetermined value (P _2FB ) is the supercharging pressure change rate (ΔP).
_A method for controlling supercharging pressure of an internal combustion engine, wherein the larger value of ₂ ) is changed to a larger value. 2. The supercharging pressure (P ₂ ) is the first predetermined value (P 2
_2ST ) and the second predetermined value (P _2FB )
Is smaller than the above, the basic boost pressure control amount (D _M )
Is subtracted by a predetermined amount (D _T ) when the supercharging pressure change rate (ΔP ₂ ) is positive, and by a predetermined amount (D _T ) when the change rate (ΔP ₂ ) is negative.
_TRB ) addition is performed. The supercharging pressure control method for an internal combustion engine according to the above paragraph.