JP4207013B2 - Supercharger control device - Google Patents

Description

  The present invention relates to a control device for a supercharger that variably controls a supercharging pressure.

  An exhaust-driven supercharger provided in an exhaust passage of an internal combustion engine forcibly introduces air in an intake passage into a combustion chamber using the flow force of exhaust flowing in the exhaust passage, that is, supercharges intake air. Thus, the filling rate of the intake air amount is improved.

  Further, in recent years, a supercharger capable of variably controlling the supercharging pressure in accordance with the engine operating state has been put into practical use. For example, in the supercharger described in Patent Document 1, nozzle vanes that change the flow passage area of the exhaust are provided in the exhaust introduction portion to the turbine wheel. The supercharging pressure is controlled through adjustment of the opening degree of the nozzle vane.

  On the other hand, an exhaust purification catalyst is disposed in the exhaust passage of the internal combustion engine. As is well known, this exhaust purification catalyst exhibits a purification function only when its temperature reaches a certain level. Therefore, there is a possibility that exhaust gas cannot be sufficiently purified when the exhaust gas temperature is low, such as during low-load operation. Therefore, during such a low load operation, the combustion mode of the engine is switched from the mode for normal operation to the mode for temperature increase control for increasing the temperature of the exhaust gas. In this combustion mode for temperature rise control, the intake air amount is reduced or the exhaust gas recirculation amount (so-called EGR) is reduced by reducing the opening of the throttle valve. The exhaust purification function at the time is maintained.

  Further, in some exhaust passages of the internal combustion engine, a NOx purification catalyst (for example, a NOx occlusion reduction type catalyst) for purifying NOx (nitrogen oxide) in the exhaust is provided. This NOx purification catalyst is poisoned by sulfur components in the fuel, and when the degree of poisoning becomes large, the NOx purification function deteriorates. Therefore, when the sulfur component accumulates to some extent in the NOx purification catalyst, control for releasing the sulfur component from the catalyst, so-called sulfur poisoning recovery control is executed. In this sulfur poisoning recovery control, the combustion mode of the engine is switched from the mode for normal operation to the mode for sulfur poisoning recovery control. In this combustion mode for sulfur poisoning recovery control, the air-fuel ratio is enriched by reducing the intake air amount by reducing the opening of the throttle valve, controlling the exhaust gas recirculation amount, etc., and controlling the temperature rise of the NOx purification catalyst As a result, the sulfur component is released from the NOx purification catalyst. That is, sulfur poisoning of the catalyst is recovered, and its NOx purification function is recovered and maintained.

Thus, in an internal combustion engine equipped with an exhaust purification catalyst, the combustion mode may be switched in order to maintain the function of the catalyst.
JP-A-10-77856

  By the way, when adjusting the supercharging pressure by changing the exhaust passage area in the exhaust introduction part of the supercharger, it is desirable to feedback-control the exhaust passage area according to the supercharging pressure. For example, the basic opening of the nozzle vane is set based on the target supercharging pressure, and the basic opening is corrected by a feedback correction amount calculated according to the deviation between the actual supercharging pressure and the target supercharging pressure. It is desirable to perform such feedback control.

  Here, in the case where the internal combustion engine in which the combustion mode is switched as described above is provided with the supercharger having a variable supercharging pressure, and the drive of the variable mechanism such as the nozzle vane is feedback-controlled according to the supercharging pressure. May cause the following inconveniences.

For example, when the combustion mode is switched from the normal operation mode to the temperature increase control mode, the following inconvenience may occur.
When switching to the combustion mode for temperature increase control, the engine load state is low and the boost pressure itself is low. Further, the intake air intake amount is also reduced, and the supercharging effect is not so much obtained. Therefore, in such a case, even if the exhaust passage area is changed, the supercharging pressure does not change so much, and the control sensitivity of the supercharging pressure is low. Thus, in the situation where the control sensitivity of the supercharging pressure is low, erroneous learning of the feedback correction amount is likely to occur, and in some cases, the supercharging pressure may increase excessively.

When the combustion mode is switched from the normal operation mode to the sulfur poisoning recovery control mode, the following inconvenience may occur.
When switched to the combustion mode for sulfur poisoning recovery control, the air-fuel ratio is enriched. At this time, the intake air amount, the exhaust gas recirculation amount, etc. are set so that the air-fuel ratio is suitable for sulfur poisoning recovery. Is adjusted. Here, when the variable mechanism such as the nozzle vane is feedback-controlled, the exhaust passage area changes variously and the back pressure in the exhaust passage fluctuates. As a result, the controllability of the exhaust gas recirculation amount deteriorates.

  On the other hand, when the engine load changes from a high load to a low load, the exhaust passage area is reduced so that the supercharging pressure is reduced. In such a case, the intake air amount is reduced, that is, the combustion mode (the combustion mode for temperature increase control, the combustion mode for sulfur poisoning recovery control, etc.) in which the opening of the throttle valve is reduced can be switched. In some cases, a surge may occur in the intake passage at the time of transition of the supercharging pressure.

  That is, since the supercharger is driven using the exhaust discharged from the engine combustion chamber, the decrease in the supercharging pressure tends to be delayed with respect to the decrease in the engine load. If the combustion mode is switched to each of the above combustion modes in the state where the decrease in the supercharging pressure occurs, the throttle valve opening is reduced, so that the supercharged intake air is not easily introduced into the combustion chamber. The pressure difference between the intake air intake side and the intake air discharge side of the supercharger increases. When such an increase in pressure difference occurs, the air in the intake passage flows backward from the discharge side to the suction side, and a pulsation phenomenon of intake air, a so-called surge, is generated, causing abnormal noise.

  In particular, when the variable control of the exhaust flow passage area is performed by the feedback control as described above, the reduction time of the exhaust flow passage area tends to be longer than when the control is performed by the open control. The generation time of the pressure difference is also increased, and a surge is likely to occur.

  Incidentally, in the turbocharger described in the above-mentioned Patent Document 1, a throttle is provided in the operating pressure input path to the actuator that drives the nozzle vane, and the opening / closing response of the nozzle vane is changed through a variable setting of the throttle amount, whereby the surge I try to suppress the occurrence of. However, if the opening / closing response is adjusted by the aperture in this way, the response and controllability of the feedback control may be adversely affected when the nozzle vane is opened / closed.

  As described above, when a supercharger having a variable mechanism for changing the exhaust passage area of the exhaust introduction portion is provided in the internal combustion engine in which the combustion mode is switched in order to maintain the function of the exhaust purification catalyst, Inconvenience may occur.

  The present invention has been made in view of such circumstances, and an object thereof is to appropriately perform drive control of a variable mechanism provided in a supercharger even when the combustion mode of an internal combustion engine is switched. It is an object of the present invention to provide a supercharger control device that can perform the above-described operation.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is applied to an internal combustion engine in which the combustion mode is switched in order to maintain the function of the exhaust purification catalyst, and is provided with a variable mechanism that can change the exhaust flow passage area of the exhaust inflow portion. In the control device for controlling the drive of the variable mechanism so that the supercharging pressure of the charger becomes the target supercharging pressure, the combustion mode is reduced from the mode for normal operation to the reduction of the exhaust gas recirculation amount and the reduction of the intake air amount. The gist of the invention is that the change means reduces the feedback correction amount when the mode is switched to a temperature increase control mode in which the temperature of the exhaust gas is increased .

In this configuration, the drive of the variable mechanism that changes the exhaust passage area in the exhaust inflow portion of the supercharger is feedback controlled, and the basic drive amount of the variable mechanism that is set based on the target supercharging pressure is The correction is made with a feedback correction amount calculated based on the deviation between the actual boost pressure and the target boost pressure. Here, according to the same configuration, the feedback correction amount is changed in accordance with the switching of the combustion mode of the engine, so that the drive mode of the variable mechanism is changed in accordance with the switching of the combustion mode. Therefore, even when the combustion mode of the internal combustion engine is switched, the drive control of the variable mechanism provided in the supercharger can be appropriately performed.
When the combustion mode is switched from the normal operation mode to the temperature increase control mode, the control sensitivity of the supercharging pressure is low, so that erroneous learning of the feedback correction amount is likely to occur. May rise excessively.
In this regard, in this configuration, when the combustion mode is switched from the mode for normal operation to the mode for temperature increase control, the feedback correction amount is reduced, so that the erroneous learning that causes excessive increase of the supercharging pressure occurs. Can be suppressed.
In addition, if the intake air intake amount is reduced due to the switching to the combustion mode for temperature increase control during the transition of the supercharging pressure drop, the pressure difference between the suction side and the discharge side of the supercharger increases. Although the surge is likely to occur, the feedback correction amount is reduced when the intake air amount is reduced. Accordingly, when setting the drive amount of the variable mechanism, the set amount based on the basic drive amount increases, while the correction amount based on the feedback control decreases. Therefore, the drive control of the variable mechanism approaches so-called open control, the exhaust passage area is reduced more rapidly, and the supercharging pressure is also rapidly reduced. Therefore, the pressure difference can be reduced at an early stage, and the occurrence of surge can be suitably suppressed.

Invention according to claim 2, in the control system of a turbo-machine according to claim 1, when weight loss of the feedback correction amount, the proportional term that constitute the feedback correction amount, the integral term, and the by differential term The gist is that the correction of the basic driving amount is prohibited.

  PID control is known as one aspect of the feedback control. In this PID control, the feedback correction amount for correcting the manipulated variable to be controlled is composed of a proportional term (P), an integral term (I), and a derivative term (D). The proportional term is a value corresponding to the correction amount according to the deviation between the target value to be controlled and the actual value, and the integral term is a value corresponding to the correction amount according to the accumulated value of the deviation. The differential term is a value corresponding to a correction amount corresponding to the change rate of the deviation.

  In the same configuration, when such PID control is adopted for the drive control of the variable mechanism, when the feedback correction amount is reduced, the basic drive amount is corrected by the proportional term, the integral term, and the derivative term. It is forbidden. That is, since the feedback correction amount is substantially “0”, the feedback correction amount can be reliably reduced. Further, since the drive control of the variable mechanism when the feedback correction amount is set to “0” is open control based on the basic drive amount, it is possible to sufficiently suppress the occurrence of erroneous learning and surge. it can.

According to a third aspect of the present invention, in the supercharger control device according to the first or second aspect , the combustion mode is emptied from the normal operation mode through control of the exhaust gas recirculation amount and reduction of the intake air amount. The gist is that the change means reduces the feedback correction amount when the mode is switched to the sulfur poisoning recovery control mode for enriching the fuel ratio.
The invention according to claim 4 is applied to an internal combustion engine in which the combustion mode is switched in order to maintain the function of the exhaust purification catalyst, and is provided with a variable mechanism that can change the exhaust flow passage area of the exhaust inflow portion. In a control device for controlling the driving of the variable mechanism so as to make the supercharging pressure the target supercharging pressure, a setting unit that sets a basic driving amount of the variable mechanism based on the target supercharging pressure; Feedback control means for correcting the basic drive amount by a feedback correction amount calculated based on a deviation between the supercharging pressure of the engine and the target supercharging pressure, and switching of the combustion mode
And a sulfur poisoning recovery control that enriches the air-fuel ratio through the control of the exhaust gas recirculation amount and the reduction of the intake air amount from the normal operation mode. The gist of the present invention is that the change means reduces the feedback correction amount when the mode is switched to the normal mode .

  When the combustion mode is switched from the mode for normal operation to the combustion mode for sulfur poisoning recovery control, the air-fuel ratio is enriched. At this time, the air-fuel ratio suitable for sulfur poisoning recovery is set. The intake air amount and exhaust gas recirculation amount are adjusted. Here, when the variable mechanism is feedback-controlled, the exhaust passage area changes variously and the back pressure in the exhaust passage varies, so the controllability of the exhaust gas recirculation amount deteriorates.

  In this regard, in the same configuration, the feedback correction amount is reduced when the combustion mode is switched from the mode for normal operation to the mode for sulfur poisoning recovery control. Accordingly, when setting the drive amount of the variable mechanism, the set amount based on the basic drive amount increases, while the correction amount based on the feedback control decreases, so that the drive control of the variable mechanism approaches the open control. Therefore, the fluctuation of the exhaust passage area due to the feedback control can be suppressed, and thereby the fluctuation of the back pressure can also be suppressed. Therefore, it becomes possible to suitably suppress the deterioration of the controllability of the exhaust gas recirculation amount.

  In addition, if the intake air intake amount is reduced due to switching to the combustion mode for sulfur poisoning recovery control during the transient transition of the supercharging pressure, the pressure difference between the suction side and the discharge side of the supercharger increases. Thus, the surge is likely to occur. In this regard, in the same configuration, the feedback correction amount is reduced when the intake air amount is reduced, so that the drive control of the variable mechanism comes closer to open control, so the exhaust passage area is reduced more quickly. As a result, the supercharging pressure also decreases quickly. Therefore, the pressure difference can be reduced at an early stage, and the occurrence of surge can be suitably suppressed.

According to a fifth aspect of the present invention, in the supercharger control device according to the third or fourth aspect , when the feedback correction amount is reduced, a proportional term, an integral term, and a differential term constituting the feedback correction amount. The essential point is that the correction of the basic driving amount by the integral term and the differential term is prohibited.

  In this configuration, when the PID control as described above is adopted for the drive control of the variable mechanism, the correction of the basic drive amount by the integral term and the differential term is prohibited when the feedback correction amount is reduced. . That is, since the integral term and the differential term constituting the feedback correction amount are substantially “0”, the feedback correction amount can be reliably reduced. Further, since the drive control of the variable mechanism when the integral term and the differential term are set to “0” in this way becomes closer to the open control based on the basic drive amount, the controllability of the exhaust gas recirculation amount is improved. Deterioration and occurrence of surge can be sufficiently suppressed.

  By the way, while the temperature increase control is executed in a region where the engine load is low, the sulfur poisoning recovery control may be executed even in a higher engine load region, and in such a region where the engine load is high. The supercharging pressure is increased to some extent. Here, variations in supercharging characteristics, etc. in individual turbochargers are compensated by the proportional term. However, if the variable mechanism drive control is performed only by open control, variation compensation by the proportional term is not performed. For this reason, there is an adverse effect that it is difficult to appropriately control the supercharging pressure. In this regard, in the same configuration, even when the feedback correction amount is reduced, the basic drive amount is corrected by the proportional term. For this reason, it is possible to suitably suppress an adverse effect due to the above-described variation when adjusting the supercharging pressure.

  The adverse effect due to the above-described variation becomes smaller as the supercharging pressure (the target supercharging pressure or the actual supercharging pressure adjusted toward the target supercharging pressure) becomes lower. Therefore, according to the invention described in claim 6, when the feedback correction amount is reduced, the basic drive by the integral term and the differential term of the proportional term, the integral term, and the differential term constituting the feedback correction amount. It is also possible to adopt a configuration in which the correction of the amount is prohibited and the proportional term is reduced according to the supercharging pressure.

  Then, when variably setting the proportional term in accordance with the supercharging pressure, a configuration is adopted in which the proportional term is made smaller as the supercharging pressure is lowered, as in the seventh aspect of the invention. Thus, the proportional term can be set appropriately.

Hereinafter, an embodiment in which a supercharger control device according to the present invention is applied to a supercharger control device provided in a diesel engine will be described.
FIG. 1 is a schematic configuration diagram illustrating a control device for a supercharger according to the present embodiment.

  The engine 1 that is a diesel engine is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 a to 4 d are attached to the cylinder head 2. These fuel injection valves 4a to 4d inject fuel into the combustion chambers of the cylinders # 1 to # 4. In addition, the cylinder head 2 is provided with intake ports for introducing outside air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. ing.

  The fuel injection valves 4a to 4d are connected to a common rail 9 that accumulates high-pressure fuel. The common rail 9 is connected to the supply pump 10. The supply pump 10 sucks fuel in the fuel tank and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is injected into the cylinder from the fuel injection valves 4a to 4d when the fuel injection valves 4a to 4d are opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3 via a surge tank 12. A throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, a turbocharger (supercharger) 60 is provided for supercharging the intake air introduced into the cylinder using the exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the outlet of the compressor wheel 64 of the turbocharger 60 and the throttle valve 16. The intake air whose temperature has risen due to supercharging of the turbocharger 60 is cooled by the intercooler 18.

  An exhaust purification device 30 that purifies exhaust components is provided in the middle of the exhaust passage 26 and on the outlet side of the turbine wheel 61 of the turbocharger 60. Inside the exhaust purification device 30, two catalysts are arranged in series.

  Of these two catalysts, the first catalyst provided upstream of the exhaust carries a NOx storage-reduction catalyst (hereinafter referred to as NSR (NOx storage-reduction) catalyst) that purifies NOx in the exhaust. This is the NSR catalyst 31.

  The second catalyst provided downstream of the NSR catalyst 31 is a NOx purification catalyst with a filter function that collects PM (particulate matter) in the exhaust, so-called DPNR (Diesel Particulate-NOx Reduction). system) catalyst 32. The DPNR catalyst 32 is a porous ceramic structure carrying an NSR catalyst, and PM in the exhaust gas is collected when passing through the porous wall. Further, when the air-fuel ratio of the exhaust is lean, NOx in the exhaust is stored in the NSR catalyst, and when the air-fuel ratio becomes rich, the NOx stored in the NSR catalyst is reduced and released by HC, CO, and the like.

  In addition, the engine 1 is provided with an exhaust gas recirculation device (hereinafter referred to as an EGR device). This EGR device is a device that reduces the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air, thereby reducing the amount of NOx generated. This device includes an EGR passage 13 that connects an intake passage (surge tank 12) and an exhaust passage (exhaust manifold 8), an EGR valve 15 provided in the EGR passage 13, an EGR cooler 14, and the like. The EGR valve 15 adjusts the exhaust gas recirculation amount introduced from the exhaust passage into the intake passage, that is, the EGR amount by adjusting the opening degree. The EGR cooler 14 reduces the temperature of the exhaust gas flowing in the EGR passage 13. The EGR valve 15 is provided with an EGR valve opening sensor 22, and the EGR valve opening sensor 22 detects the opening of the EGR valve 15 (EGR valve opening EA).

Next, the turbocharger 60 will be further described.
The turbocharger 60 is a turbine wheel 61 that is rotated by exhaust gas flowing through the exhaust passage 26, and a compressor wheel (impeller) that is disposed in the intake passage 3 and is connected to the turbine wheel 61 via the rotor shaft 62 so as to be integrally rotatable. 64. In the turbocharger 60, exhaust is blown to the turbine wheel 61 and the wheel 61 rotates. This rotation is transmitted to the compressor wheel 64 via the rotor shaft 62. As a result, in the engine 1, not only is air fed into the combustion chamber due to the negative pressure generated in the combustion chamber as the piston moves, but the air is forcibly forced by the rotation of the compressor wheel 64 of the turbocharger 60. Is sent (supercharged). In this way, the efficiency of filling the combustion chamber with air is increased.

  Further, an exhaust passage is formed in the turbocharger 60 along the rotational direction of the turbine wheel 61 so as to surround the outer periphery of the turbine wheel 61. For this reason, the exhaust passes through the exhaust passage and is blown toward the turbine wheel 61. The exhaust passage is provided with a variable nozzle mechanism 71 capable of changing the exhaust passage area at the exhaust inflow portion of the turbocharger 60. By the opening / closing operation of the variable nozzle mechanism 71, the exhaust passage area in the exhaust passage is changed, and the flow velocity of the exhaust blown to the turbine wheel 61 is changed. By making the flow rate of the exhaust gas variable in this way, the rotational speed of the turbine wheel 61 is adjusted, and consequently the amount of air forcedly fed into the combustion chamber is adjusted.

FIG. 2 shows a schematic structure of the variable nozzle mechanism 71.
2A shows a side sectional structure of the variable nozzle mechanism 71, and FIG. 2B shows a front structure of the variable nozzle mechanism 71. As shown in FIG. As shown in FIG. 2A, the variable nozzle mechanism 71 includes a ring-shaped nozzle back plate 72. In the nozzle back plate 72, a plurality of shafts 73 are provided at equal angles around the center of the nozzle back plate 72. These shafts 73 are rotatably supported through the nozzle back plate 72 in the thickness direction. In addition, a nozzle vane 74 is fixed to one end of these shafts 73 (the left end in FIG. 2A). An opening / closing lever 75 is provided at the other end of the shaft 73 and extends in the direction of the outer edge of the nozzle back plate 72 at right angles to the same axis. A pair of sandwiching portions 75a branched into two forks is formed at the tip of the opening / closing lever 75.

  An annular ring plate 76 is provided so as to be sandwiched between each open / close lever 75 and the nozzle back plate 72. The ring plate 76 is rotatable around a circular center. Further, the ring plate 76 is provided with a plurality of pins 77 at equal angles around the center of the circle. These pins 77 are sandwiched between the holding portions 75a of the opening / closing lever 75, and support the opening / closing lever 75 in a rotatable manner.

  When the ring plate 76 is rotated around the center of the circle by the actuator 68 shown in FIG. 1, each pin 77 pushes the holding portion 75a in the rotation direction. As a result, the opening / closing lever 75 rotates the shaft 73. As the shaft 73 rotates, each nozzle vane 74 also rotates about the axis line of the coaxial 73. With such a mechanism, each nozzle vane 74 can be rotated in a synchronized state. Further, the size of the gap between the adjacent nozzle vanes 74 is adjusted by the rotation of the nozzle vanes 74.

  For example, the narrower the gap between the nozzle vanes 74, that is, the smaller the vane opening of the nozzle vane is set, the smaller the exhaust passage area is and the higher the flow rate of the exhaust blown to the turbine wheel 61. The higher the flow rate of the exhaust gas blown to the turbine wheel 61, the higher the rotational speed of the turbine wheel 61 and the higher the supercharging pressure of the turbocharger 60. Further, for example, as the gap between the nozzle vanes 74 is enlarged, that is, as the vane opening is set larger, the exhaust passage area is enlarged, and the flow velocity of the exhaust blown to the turbine wheel 61 becomes lower. The lower the flow rate of the exhaust gas blown to the turbine wheel 61, the lower the rotational speed of the turbine wheel 61 and the lower the supercharging pressure of the turbocharger 60. Thus, the variable nozzle mechanism 71 functions as a variable mechanism for adjusting / changing the supercharging pressure of the turbocharger 60.

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the air flow meter 19 provided on the intake upstream side of the compressor wheel 64 detects the intake air amount GA in the intake passage 3. The throttle opening sensor 20 detects the opening of the throttle valve 16 (throttle opening TA). A first exhaust temperature sensor 33 provided on the exhaust downstream side of the NSR catalyst 31 measures a first exhaust temperature Ta that is the temperature of the exhaust immediately after passing through the NSR catalyst 31. A second exhaust temperature sensor 34 provided on the exhaust downstream side of the DPNR catalyst 32 detects a second exhaust temperature Tb that is the temperature of the exhaust immediately after passing through the DPNR catalyst 32. The engine rotation speed sensor 23 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE. The accelerator sensor 24 detects an accelerator pedal depression amount, that is, an accelerator operation amount ACCP. The air-fuel ratio sensor 21 provided on the exhaust upstream side of the NSR catalyst 31 detects the air-fuel ratio λ of the exhaust. The intake pressure sensor 50 provided in the surge tank 12 detects the supercharging pressure of the supercharger.

  The outputs of these various sensors are input to the control device 25. The control device 25 includes a central processing control device (CPU), a read only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface, an output interface, and the like.

  The control device 25 executes, for example, fuel injection amount control and fuel injection timing control of the fuel injection valves 4a to 4d, discharge pressure control of the supply pump 10, and drive amount control of the actuator 17 that opens and closes the throttle valve 16. Further, control of the EGR device, supercharging pressure control through drive control of the actuator 68, and the like are also executed.

  For example, for the EGR device, control for adjusting the actual EGR amount to the target EGR amount set based on the engine load (or fuel injection amount) and the engine speed is performed. Further, control for adjusting the EGR amount so as to obtain a target intake air amount set based on the engine load (or fuel injection amount) and the engine rotation speed, or the EGR amount so that the air-fuel ratio becomes a desired air-fuel ratio. Control for adjusting the value is also performed. In controlling these EGR amounts, the opening degree of the EGR valve 15 is adjusted according to the target EGR amount.

  The actuator 68 is feedback-controlled so as to adjust the actual boost pressure to the target boost pressure set based on the engine load (or fuel injection amount) and the engine speed. That is, the opening degree of the nozzle vane 74 is feedback-controlled so that the exhaust passage area becomes an area corresponding to the target supercharging pressure.

  And the control apparatus 25 also performs fuel addition control from the injection nozzle 5 demonstrated below. The injection nozzle 5 is provided in the cylinder head 2 and supplies fuel as an additive to the exhaust purification device 30, that is, the NSR catalyst 31 and the DPNR catalyst 32. The injection nozzle 5 and the supply pump 10 are connected by a fuel supply pipe 27, and fuel is injected from the injection nozzle 5 into the exhaust port 6d of the fourth cylinder # 4. The injected fuel reaches the NSR catalyst 31 and the DPNR catalyst 32 together with the exhaust gas. The position of the injection nozzle 5 can be changed as appropriate as long as it is in the exhaust passage and upstream of the exhaust purification device 30.

The reason why the fuel is added toward the NSR catalyst 31 and the DPNR catalyst 32 will be described below with reference to (A) to (C).
(A) In the case of a diesel engine, the air-fuel ratio of the exhaust gas is normally lean. It is necessary to reduce and release the NOx stored in the catalyst 32. Therefore, when the NOx occlusion amount estimated based on the engine operating state or the like reaches a predetermined limit value, the control device 25 executes the NOx reduction process through the fuel addition by the injection nozzle 5. When the fuel injected at this time reaches the NSR catalyst 31 or the DPNR catalyst 32, it acts as a NOx reducing agent. Further, when the fuel is burned by the NSR catalyst 31 and the DPNR catalyst 32, oxygen is consumed, and the air-fuel ratio of the exhaust gas becomes rich. By such NOx reduction treatment, the NOx purification function of the NSR catalyst 31 and the DPNR catalyst 32 is maintained.

  (B) When the amount of PM trapped in the DPNR catalyst 32 increases, the pressure loss in the DPNR catalyst 32 increases. Therefore, it is necessary to perform a so-called DPNR catalyst regeneration process that reduces the accumulated PM before the pressure loss increases so as to adversely affect the engine operating state and the like. Therefore, when the PM accumulation amount estimated based on the engine operating state, the difference between the upstream exhaust pressure and the downstream exhaust pressure of the DPNR catalyst 32, etc. reaches a predetermined limit value, the control nozzle 25 The DPNR catalyst regeneration process is performed through the fuel addition according to the above. The fuel injected at this time is combusted when it reaches the DPNR catalyst 32, whereby PM is ignited and finally burned off. That is, this injected fuel acts as a PM combustion accelerator. By such a regeneration process of the DPNR catalyst, the amount of PM deposited on the DPNR catalyst 32 is reduced.

  (C) The NOx occlusion reduction type catalyst has a property of absorbing sulfur components derived from fuel and lubricating oil. Here, since the storage amount of the NOx storage reduction catalyst is limited, when the sulfur absorption amount is increased, the NOx amount that can be stored is decreased, and a phenomenon of lowering the NOx purification function due to so-called sulfur poisoning occurs. On the other hand, it is known that the sulfur component absorbed by the NOx occlusion reduction type catalyst is released in a reduced state from the catalyst in a reducing atmosphere at a high temperature close to 600 degrees. The amount of the sulfur component absorbed by the storage reduction catalyst can be reduced. Therefore, when the sulfur absorption amount estimated based on the engine operating state or the like reaches a predetermined limit value, the control device 25 executes sulfur poisoning recovery control through fuel addition by the injection nozzle 5. The fuel injected at this time is burned in the NSR catalyst 31 and the DPNR catalyst 32, and the temperature of each catalyst is raised by the heat. In addition, the oxygen around each catalyst is consumed by the combustion of the fuel, the oxygen concentration around the NSR catalyst 31 and the DPNR catalyst 32 is lowered, the conditions such as high temperature and reducing atmosphere are satisfied, and the sulfur component absorbed in each catalyst Is reduced and released. This fuel also functions as a sulfur component reducing agent.

For the reasons (A) to (C) above, fuel is added to the NSR catalyst 31 and the DPNR catalyst 32.
By the way, as is well known, the exhaust purification catalyst such as the NSR catalyst 31 and the DPNR catalyst 32 exhibits an exhaust purification function only when the temperature thereof reaches a certain level. Therefore, there is a possibility that exhaust gas cannot be sufficiently purified when the exhaust gas temperature is low, such as during low-load operation. Therefore, during such a low load operation, the combustion mode of the engine is switched from the mode for normal operation to the mode for temperature increase control for increasing the temperature of the exhaust gas. In this temperature increase control combustion mode, the intake air amount is reduced by reducing the opening of the throttle valve 16, the EGR amount is reduced, etc., and thereby the exhaust temperature rises and the exhaust purification function during low load operation is achieved. Is maintained. It should be noted that as a mode of reducing the EGR amount, it is desirable to perform the EGR cut so that the exhaust introduction amount to the intake air is set to “0”.

  Further, when the sulfur poisoning recovery control is executed, the combustion mode of the engine is switched from the normal operation mode to the sulfur poisoning recovery control mode. In this combustion mode for sulfur poisoning recovery control, the air-fuel ratio is enriched through the reduction of the intake air amount due to the decrease in the opening of the throttle valve 16 and the control of the EGR amount. Sulfur components are released from the NSR catalyst 31 and the DPNR catalyst 32 by forming a reducing atmosphere by enriching the air-fuel ratio and controlling the temperature rise of the exhaust purification catalyst. That is, sulfur poisoning of each catalyst is recovered, and its NOx purification function is recovered and maintained.

Thus, in the engine 1 including the NSR catalyst 31 and the DPNR catalyst 32, the combustion mode is switched in order to maintain the function of each catalyst.
Next, the control of the turbocharger 60 performed by the control device 25, more specifically, the variable nozzle mechanism 71 that is implemented to adjust the actual supercharging pressure detected by the intake pressure sensor 50 to the target supercharging pressure. The nozzle vane opening degree control will be described.

In FIG. 3, the process sequence concerning the vane opening degree setting of the nozzle vane 74 is shown. This process is repeatedly executed by the control device 25 every predetermined period.
When this process is started, first, the base opening BVN of the nozzle vane 74 is calculated based on the engine speed NE and the fuel injection amount Q (S100). This base opening degree BVN is a value corresponding to the exhaust passage area assumed to be necessary for setting the actual supercharging pressure to the set target supercharging pressure, and is variable based on the target supercharging pressure. This is a value corresponding to the basic drive amount of the nozzle mechanism 71.

  Next, a feedback correction amount F for the base opening degree BVN is calculated based on the deviation between the target boost pressure and the actual boost pressure (S110). Here, since PID control is assumed as the feedback control, the proportional term P, the integral term I, and the differential term D are calculated based on the deviation, and the added value of each value is set as the feedback correction amount F. The The proportional term is a value corresponding to the correction amount according to the deviation between the target value to be controlled and the actual value, and the integral term is a value corresponding to the correction amount according to the accumulated value of the deviation. The differential term is a value corresponding to a correction amount corresponding to the change speed of the deviation. The detailed calculation mode of the feedback correction amount F will be described later.

When the feedback correction amount F is calculated in this way, the value is added to the base opening BVN to calculate the vane opening FVN of the nozzle vane 74 (S120).
Next, the calculated vane opening degree FVN is limited by the upper limit value and the lower limit value (S130), so that the vane opening degree FVN can be allowed from the viewpoint of the reliability of the engine 1 and the engine output. Set to a value within the range. Here, when the vane opening degree FVN is larger than the upper limit value set as appropriate, the value of the vane opening degree FVN is replaced with the upper limit value. When the vane opening degree FVN is smaller than the lower limit value set as appropriate, the value of the vane opening degree FVN is replaced with the lower limit value.

  When the final vane opening degree FVN is calculated in this way, the present process is temporarily terminated. The drive of the actuator 68 is controlled so that the opening degree of the nozzle vane 74 becomes the calculated vane opening degree FVN.

Next, calculation of the feedback correction amount F will be described.
FIG. 4 shows a processing procedure for calculating the feedback correction amount F. This process is also repeatedly executed by the control device 25 at predetermined intervals.

  When this process is started, it is first determined whether or not the feedback correction amount correction flag FF is “ON” (S200). This feedback correction amount correction flag FF is a flag that is set to “ON” when the combustion mode of the engine is in the temperature increase control mode or in the sulfur poisoning recovery control mode. In other modes, that is, the mode for normal operation, it is set to “OFF”.

  When the feedback correction amount correction flag FF is “OFF” (S200: NO), the feedback correction amount F is calculated based on the following equation (1) (S210).

Feedback correction amount F = proportional term P + integral term I + differential term D (1)

On the other hand, when the feedback correction amount correction flag FF is “ON” (S200: YES), the feedback correction amount F is calculated based on the following equation (2) (S220). The proportional term correction coefficient PK and the integral term correction coefficient IK will be described later. Further, as shown in Expression (2), when the feedback correction amount correction flag FF is “ON”, the differential term D is substantially set to “0”.

Feedback correction amount F = proportional term P × proportional term correction coefficient PK
+ Integral term I × Integral term correction coefficient IK (2)

When the feedback correction amount F is calculated in step S210 or step S220, the calculated feedback correction amount F is limited by the upper limit value and the lower limit value (S230). The value is set within the allowable range from the viewpoint of the reliability of the engine 1, the engine output, the response of feedback control, and the like. Here, when the feedback correction amount F is larger than the upper limit value set as appropriate, the value of the feedback correction amount F is replaced with the value of the upper limit value. When the feedback correction amount F is smaller than a lower limit value set as appropriate, the value of the feedback correction amount F is replaced with the lower limit value.

When the final feedback correction amount F is calculated in this way, this process is once terminated.
Next, setting of the proportional term correction coefficient PK and the integral term correction coefficient IK will be described.
FIG. 5 shows a processing procedure for setting correction coefficients such as a proportional term correction coefficient PK and an integral term correction coefficient IK. This process is also repeatedly executed by the control device 25 at predetermined intervals.

When this process is started, it is first determined whether the combustion mode of the engine is the combustion mode for temperature increase control or the combustion mode for sulfur poisoning recovery control (S300).
If the combustion mode is not the temperature increase control mode or the sulfur poisoning recovery control mode, that is, if it is the normal operation combustion mode (S300: NO), this process is temporarily terminated.

  On the other hand, if the combustion mode is for temperature increase control or the combustion mode for sulfur poisoning recovery control (S300: YES), the feedback correction amount correction flag FF is set to “ON” (S310).

  Next, it is determined whether the combustion mode is a combustion mode for temperature increase control (S320). If the combustion mode is for temperature increase control (S320: YES), both the proportional term correction coefficient PK and the integral term correction coefficient IK are set to “0” (S330), and this process is temporarily terminated. The

  When the proportional term correction coefficient PK and the integral term correction coefficient IK are both set to “0” in this way, the right side of the above equation (2) becomes “0” and is calculated from the equation (2). The feedback correction amount F is reduced from the feedback correction amount F calculated from the above equation (1). Further, when the feedback correction amount F becomes “0”, the correction of the base opening BVN by the proportional term P, the integral term I, and the differential term D is prohibited, that is, the correction of the base opening BVN by the feedback correction amount F is prohibited. The base opening degree BVN becomes the vane opening degree FVN as it is. That is, the opening degree control of the nozzle vane 74 is substantially open control.

  On the other hand, when the combustion mode is not the temperature increase control mode, that is, when the combustion mode is the sulfur poisoning recovery control mode (S320: NO), the proportional term correction coefficient PK is set to “1” and the integral term. The correction coefficient IK is set to “0” (S340), and this process is temporarily terminated.

  In this way, when the proportional term correction coefficient PK is set to “1” and the integral term correction coefficient IK is set to “0”, the right side of the above equation (2) is only the proportional term P. The feedback correction amount F calculated from (1) is less than the feedback correction amount F calculated from the above equation (1). Further, since the proportional term P is set to the feedback correction amount F as it is and the correction of the base opening BVN by the integral term I and the differential term D is prohibited, the opening control of the nozzle vane 74 approaches the open control. become.

Next, the effects of executing the vane opening setting process, the feedback correction amount calculation process, and the correction coefficient setting process will be described.
When the combustion mode is switched from the normal operation mode to the temperature increase control mode, the engine load state is low and the supercharging pressure itself is low. Further, the intake air intake amount is also reduced, and the supercharging effect is not so much obtained. Therefore, in such a case, even if the exhaust passage area is changed, the supercharging pressure does not change so much, and the control sensitivity of the supercharging pressure is low. Thus, in the situation where the control sensitivity of the supercharging pressure is low, erroneous learning of the feedback correction amount F is likely to occur, and in some cases, the supercharging pressure may increase excessively.

  In this regard, in the present embodiment, by executing the feedback correction amount calculation process and the correction coefficient setting process, the feedback correction amount F is changed according to the switching of the combustion mode, and the variable nozzle is changed according to the switching of the combustion mode. The driving mode of the mechanism 71 is changed. Therefore, even when the combustion mode of the engine 1 is switched, the drive control of the variable nozzle mechanism 71 provided in the turbocharger 60 can be appropriately performed.

  More specifically, when the combustion mode is switched from the normal operation mode to the temperature increase control mode, the feedback correction amount F is decreased. Accordingly, it is possible to suppress the occurrence of erroneous learning of the feedback correction amount F that is likely to occur when the combustion mode is switched to the temperature increase control mode.

  Further, when the feedback correction amount F is reduced in this way, the correction of the base opening BVN by the proportional term P, the integral term I, and the differential term D constituting the feedback correction amount F is prohibited. That is, since the feedback correction amount F is set to “0”, the feedback correction amount F can be reliably reduced. Furthermore, since the drive control of the variable nozzle mechanism 71 when the feedback correction amount is set to “0” is open control based on the base opening BVN, the erroneous learning of the feedback correction amount F can be sufficiently suppressed. become able to.

  On the other hand, when the combustion mode is switched from the normal operation mode to the combustion mode for sulfur poisoning recovery control, the air-fuel ratio is enriched. At this time, the air-fuel ratio is suitable for sulfur poisoning recovery. As described above, the intake air amount, the EGR amount, and the like are adjusted. Here, when the opening degree of the nozzle vane 74 is feedback-controlled, the exhaust passage area changes variously and the back pressure in the exhaust passage fluctuates. Therefore, the fluctuation in the back pressure becomes a disturbance to the adjustment of the EGR amount. As a result, the controllability of the EGR amount may be deteriorated.

  In this regard, in the present embodiment, by executing the feedback correction amount calculation process and the correction coefficient setting process, the feedback correction amount F is changed according to the switching of the combustion mode, and the variable nozzle is changed according to the switching of the combustion mode. The driving mode of the mechanism 71 is changed. Therefore, even when the combustion mode of the engine 1 is switched, the drive control of the variable nozzle mechanism 71 provided in the turbocharger 60 can be appropriately performed.

  More specifically, when the combustion mode is switched from the normal operation mode to the sulfur poisoning recovery control mode, the feedback correction amount F is decreased. Accordingly, when the drive amount of the variable nozzle mechanism 71 is set, the set amount based on the base opening BVN increases, while the correction amount based on the feedback control decreases, and the drive control mode of the variable nozzle mechanism 71 is changed from the feedback control. Get closer to open control. Therefore, the fluctuation of the exhaust passage area due to the feedback control can be suppressed, and thereby the fluctuation of the back pressure can also be suppressed. Therefore, it becomes possible to suppress the deterioration of the controllability of the EGR amount as described above.

  When the feedback correction amount F is reduced when the combustion mode is switched to the sulfur poisoning recovery control, among the proportional term P, integral term I, and differential term D constituting the feedback correction amount F Correction of the base opening BVN by the integral term I and the differential term D is prohibited. That is, since the integral term I and the differential term D constituting the feedback correction amount F are set to “0”, the feedback correction amount F can be reliably reduced. Further, when the integral term I and the differential term D are set to “0” in this way, the integral term I and the differential term D are set to values larger than “0” and smaller than “1”. In comparison, the drive control of the variable nozzle mechanism 71 can be made closer to the open control based on the base opening BVN. Accordingly, it becomes possible to sufficiently suppress the controllability deterioration of the EGR amount.

  Here, the temperature increase control is executed in a region where the engine load is low, whereas the sulfur poisoning recovery control may be executed even in a higher engine load region, and thus the region where the engine load is high. Then, the supercharging pressure is increased to some extent. By the way, the dispersion of the supercharging characteristics or the like in each supercharger is compensated by the proportional term P. However, when the drive control of the variable nozzle mechanism 71 is performed only by the open control, the dispersion compensation by the proportional term P is performed. Therefore, there is an adverse effect that it is difficult to appropriately control the supercharging pressure. In this regard, in the present embodiment, when the feedback correction amount F is decreased when the combustion mode is switched to the sulfur poisoning recovery control, the base opening degree BVN is corrected by the proportional term P. For this reason, it is possible to suppress an adverse effect due to the above-described variation when adjusting the supercharging pressure.

  On the other hand, when the engine load changes from a high load to a low load, the exhaust passage area is reduced so that the supercharging pressure is reduced. In such a case, the intake air amount is reduced, that is, the combustion mode (the combustion mode for temperature increase control or the combustion mode for sulfur poisoning recovery control) in which the opening of the throttle valve 16 is reduced is switched. In some cases, a surge may occur in the intake passage at the time of transition of the supercharging pressure.

  That is, since the turbocharger 60 is driven using the exhaust discharged from the engine combustion chamber, the decrease in the supercharging pressure tends to be delayed with respect to the decrease in the engine load. When the combustion mode is switched to each of the above combustion modes in the state where the decrease in the supercharging pressure occurs, the opening of the throttle valve 16 is reduced, so that the supercharged intake air is introduced into the combustion chamber. The pressure difference between the inlet side (intake and intake side) and the outlet side (intake and discharge side) of the compressor wheel 64 increases. When such a pressure difference increases, the air in the intake passage flows backward from the outlet side of the compressor wheel 64 to the inlet side, and a pulsation phenomenon of the intake air, a so-called surge, is generated, causing abnormal noise. It becomes.

  In particular, when the variable control of the exhaust flow passage area is performed by the feedback control as described above, the reduction time of the exhaust flow passage area tends to be longer than when the control is performed by the open control. The generation time of the pressure difference is also increased, and a surge is likely to occur.

  In this regard, in the present embodiment, as described above, the feedback correction amount F is changed in accordance with the switching of the combustion mode, and the driving mode of the variable nozzle mechanism 71 is changed in accordance with the switching of the combustion mode. Therefore, even when the combustion mode of the engine 1 is switched, the drive control of the variable nozzle mechanism 71 provided in the turbocharger 60 can be appropriately performed.

  More specifically, when the combustion mode for normal operation is switched to the combustion mode for temperature increase control or the combustion mode for sulfur poisoning recovery control, the feedback correction amount F is reduced as described above. The drive control mode of the variable nozzle mechanism 71 approaches the open control from the feedback control. As a result, the exhaust passage area can be reduced more quickly, and the supercharging pressure can be quickly reduced. Therefore, the pressure difference can be reduced at an early stage, and the occurrence of surge can be suitably suppressed.

  As described above, when the combustion mode for normal operation is switched to the combustion mode for temperature increase control, the base opening degree based on the proportional term P, the integral term I, and the differential term D constituting the feedback correction amount F BVN correction is prohibited, and the drive control of the variable nozzle mechanism 71 at this time is open control based on the base opening BVN. Therefore, the occurrence of the surge can be sufficiently suppressed. When the combustion mode for normal operation is switched to the combustion mode for sulfur poisoning recovery control, correction of the base opening BVN by the integral term I and the differential term D constituting the feedback correction amount F is prohibited. Therefore, the drive control of the variable nozzle mechanism 71 at this time comes closer to the open control based on the base opening BVN from the feedback control, and the occurrence of the surge can be sufficiently suppressed.

  As described above, in the present embodiment, the drive control of the variable nozzle mechanism 71 is appropriately performed through the execution of the above processes. For this reason, it is possible to suppress the occurrence of various inconveniences that are likely to occur by providing the turbocharger 60 including the variable nozzle mechanism 71 in the engine 1 in which the combustion mode is switched in order to maintain the function of the exhaust purification catalyst.

As described above, according to the present embodiment, the following effects can be obtained.
(1) In the engine 1 in which the combustion mode is switched in order to maintain the exhaust purification function of the exhaust purification device 30, the variable nozzle mechanism is used to control the supercharging pressure of the turbocharger 60 including the variable nozzle mechanism 71. When performing feedback control of the drive of 71, the feedback correction amount F is changed in accordance with switching of the combustion mode. Therefore, even when the combustion mode of the engine 1 is switched, the drive control of the variable nozzle mechanism 71 can be appropriately performed.

  (2) The feedback correction amount F is decreased when the combustion mode is switched from the normal operation mode to the temperature increase control mode for raising the temperature of the exhaust gas by reducing the EGR amount and the intake air amount. ing. Accordingly, it is possible to suppress the occurrence of erroneous learning of the feedback correction amount F that causes an excessive increase in the supercharging pressure. In addition, when the intake air intake amount is reduced due to switching to the combustion mode for temperature increase control at the time of transition of the boost pressure drop, a surge is likely to occur in the intake passage. Such a surge can be suitably suppressed.

  (3) When the feedback correction amount F is reduced when the mode is switched to the temperature increase control mode, the base opening BVN based on the proportional term P, the integral term I and the differential term D constituting the feedback correction amount F is changed. The correction is prohibited. Therefore, the feedback correction amount F can be reliably reduced. In addition, since the drive control of the variable nozzle mechanism 71 in this case is open control based on the base opening degree BVN, it is possible to sufficiently suppress the occurrence of erroneous learning and surge.

  (4) When the combustion mode is switched from the normal operation mode to the sulfur poisoning recovery control mode that enriches the air-fuel ratio through the control of the EGR amount and the reduction of the intake air amount, the feedback correction amount F is changed. I try to lose weight. Therefore, the fluctuation of the exhaust passage area due to the feedback control can be suppressed, so that the deterioration of the controllability of the EGR amount can be suitably suppressed. In addition, when the intake air intake amount is reduced due to switching to the combustion mode for sulfur poisoning recovery control at the time of transition of the boost pressure drop, surge is likely to occur in the intake passage. Therefore, the occurrence of such a surge can be suitably suppressed.

  (5) When the feedback correction amount F is reduced when the mode is switched to the sulfur poisoning recovery control mode, the integral term of the proportional term P, the integral term I, and the differential term D constituting the feedback correction amount F The correction of the base opening BVN by I and the differential term D is prohibited. Therefore, the feedback correction amount F can be reliably reduced. Further, since the drive control of the variable nozzle mechanism 71 in this case comes closer to the open control based on the base opening BVN, it is possible to sufficiently suppress the deterioration of the controllability of the EGR amount and the occurrence of a surge. Further, even when the feedback correction amount F is reduced, the base opening degree BVN is corrected by the proportional term P. For this reason, it is possible to suitably suppress the adverse effect of variations in the supercharging characteristics or the like in the individual superchargers on the supercharging pressure adjustment.

In addition, the said embodiment can also be changed and implemented as follows.
Correction of the proportional term P when the feedback correction amount F is reduced when switching from the combustion mode for normal operation to the combustion mode for temperature increase control or when switching to the combustion mode for sulfur poisoning recovery control At least one of the coefficient, the correction coefficient of the integral term I, and the correction coefficient of the differential term D may be variably set.

  For example, in the above embodiment, by setting the proportional term correction coefficient PK when switching to the combustion mode for sulfur poisoning recovery control to “1”, supercharging in each supercharger during supercharging pressure control is performed. It compensated for variations in characteristics. Here, as described above and as shown in FIG. 6, the temperature increase control is executed in a region where the engine load is low, whereas the sulfur poisoning recovery control is executed even in a higher engine load region. In such a region where the engine load is high, the supercharging pressure is increased to some extent. On the other hand, adverse effects due to variations in the supercharging characteristics and the like become smaller as the supercharging pressure (the target supercharging pressure or the actual supercharging pressure adjusted toward the target supercharging pressure) becomes lower. Therefore, when the feedback correction amount F is reduced when the combustion mode for normal operation is switched to the combustion mode for sulfur poisoning recovery control, the proportional term P, the integral term I, and the differential term constituting the feedback correction amount F are used. The correction of the base opening BVN by the integral term I and the differential term D of D may be prohibited, and the proportional term P may be reduced according to the supercharging pressure. In this case, the proportional term correction coefficient PK decreases as the boost pressure decreases, for example, as shown in FIG. 6, so that the proportional term P decreases as the boost pressure decreases as the engine load decreases. By variably setting the proportional term correction coefficient PK so as to decrease, the proportional term P can be set appropriately.

  The process of reducing the feedback correction amount F accompanying the switching of the combustion mode is not limited to the above aspect, and can be changed as appropriate. For example, when the combustion mode is switched from the normal operation mode to each of the combustion modes, the feedback correction amount F calculated from the equation (1) may be directly corrected with a predetermined reduction coefficient.

  The feedback correction amount F may be reduced only when the combustion mode for normal operation is switched to the combustion mode for temperature increase control. Further, the feedback correction amount F may be reduced only when the combustion mode for normal operation is switched to the combustion mode for sulfur poisoning recovery control.

-Although the said additive was the fuel of the engine 1, what kind of thing may be sufficient as long as the effect | action similar to this is acquired.
The turbocharger 60 is a variable control of the supercharging pressure through the adjustment of the opening degree of the nozzle vane 74. In addition, the present invention can be similarly applied to a supercharger in which the supercharging pressure is variably controlled by changing the exhaust passage area by a method other than the adjustment of the opening degree of the nozzle vane 74.

  In the above embodiment, the exhaust purification device 30 is provided with two catalysts. In addition, the present invention can be similarly applied to an exhaust purification device in which one catalyst is disposed, or an exhaust purification device in which three or more catalysts are disposed.

  The NSR catalyst 31 is not limited to the NOx storage reduction catalyst as described above. In short, any catalyst that can purify NOx may be used. In each embodiment, the catalyst disposed in the exhaust purification device is the NSR catalyst 31 or the DPNR catalyst 32, and is a catalyst to which an additive is supplied. It is not limited to such a thing. That is, the present invention can be similarly applied to any catalyst that can maintain its exhaust purification function by switching the combustion mode of the engine.

  The internal combustion engine to which the present invention is applied is not limited to a diesel engine. For example, the present invention can be similarly applied to a gasoline engine including a NOx purification catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the structure in the one Embodiment about the control apparatus of the supercharger concerning this invention. (A) is the schematic which shows the side cross-section structure of a variable nozzle mechanism. (B) is the schematic which shows the front structure of a variable nozzle mechanism. The flowchart which shows the procedure of the vane opening degree setting process in the embodiment. 5 is a flowchart showing a procedure of feedback correction amount calculation processing in the embodiment. 6 is a flowchart showing a procedure of correction coefficient setting processing in the embodiment. The schematic diagram which shows the variable setting aspect of a proportional term correction coefficient in the modification of the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4a-4d ... Fuel injection valve, 5 ... Injection nozzle, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, 10 ... Supply pump, 12 ... surge tank, 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... throttle valve, 17 ... actuator, 18 ... intercooler, 19 ... air flow meter, 20 ... throttle opening sensor, 21 ... Air-fuel ratio sensor, 22 ... EGR valve opening sensor, 23 ... Engine speed sensor, 24 ... Accelerator sensor, 25 ... Control device (setting means, feedback control means, changing means), 26 ... Exhaust passage, 27 ... Fuel supply Pipe, 30 ... exhaust purification device, 31 ... NSR catalyst, 32 ... DPNR catalyst, 33 ... first exhaust temperature sensor 34, second exhaust temperature sensor, 50 ... intake pressure sensor, 60 ... turbocharger, 61 ... turbine wheel, 62 ... rotor shaft, 64 ... compressor wheel, 68 ... actuator, 71 ... variable nozzle mechanism, 72 ... nozzle back Plate 73 ... Shaft 74 ... Nozzle vane 75 ... Open / close lever 75a ... Nipping part 76 ... Ring plate 77 ... Pin

Claims (7)

  Applied to internal combustion engines where the combustion mode is switched in order to maintain the function of the exhaust purification catalyst, and for the supercharger having a variable mechanism capable of changing the exhaust passage area of the exhaust inflow portion, the supercharging pressure is targeted In a control device for controlling the driving of the variable mechanism to obtain a supercharging pressure,
  Setting means for setting a basic drive amount of the variable mechanism based on the target boost pressure;
  Feedback control means for correcting the basic drive amount with a feedback correction amount calculated based on a deviation between an actual supercharging pressure and the target supercharging pressure;
  Changing means for changing the feedback correction amount in accordance with the switching of the combustion mode,
  When the combustion mode is switched from the mode for normal operation to the mode for temperature increase control that raises the temperature of the exhaust gas through the reduction of the exhaust gas recirculation amount and the reduction of the intake air amount, the changing means changes the feedback correction amount. To lose weight
  A supercharger control device.   In the supercharger control device according to claim 1,
  When reducing the feedback correction amount, correction of the basic drive amount by the proportional term, integral term, and derivative term constituting the feedback correction amount is prohibited.
  A supercharger control device.   In the supercharger control device according to claim 1 or 2,
  When the combustion mode is switched from the normal operation mode to the sulfur poisoning recovery control mode that enriches the air-fuel ratio through the control of the exhaust gas recirculation amount and the reduction of the intake air amount, the changing means Decrease feedback correction amount
  A supercharger control device.   Applied to internal combustion engines where the combustion mode is switched in order to maintain the function of the exhaust purification catalyst, and for the supercharger having a variable mechanism capable of changing the exhaust passage area of the exhaust inflow portion, the supercharging pressure is targeted In a control device for controlling the driving of the variable mechanism to obtain a supercharging pressure,
  Setting means for setting a basic drive amount of the variable mechanism based on the target boost pressure;
  Feedback control means for correcting the basic drive amount with a feedback correction amount calculated based on a deviation between an actual supercharging pressure and the target supercharging pressure;
  Changing means for changing the feedback correction amount in accordance with the switching of the combustion mode,
  When the combustion mode is switched from the normal operation mode to the sulfur poisoning recovery control mode that enriches the air-fuel ratio through the control of the exhaust gas recirculation amount and the reduction of the intake air amount, the changing means Decrease feedback correction amount
  A supercharger control device.   In the supercharger control device according to claim 3 or 4,
  When reducing the feedback correction amount, correction of the basic drive amount by the integral term and the differential term of the proportional term, the integral term, and the differential term constituting the feedback correction amount is prohibited.
  A supercharger control device.   In the supercharger control device according to claim 3 or 4,
  When the feedback correction amount is reduced, correction of the basic drive amount by the integral term and the differential term of the proportional term, the integral term, and the differential term constituting the feedback correction amount is prohibited, and the proportional term is Decreasing according to the supercharging pressure
  A supercharger control device. The supercharger control device according to claim 6,
The control unit for a supercharger, wherein the proportional term is made smaller as the supercharging pressure becomes lower.

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