JP4778879B2 - Supercharging pressure control device for internal combustion engine - Google Patents

Description

  The present invention relates to a supercharging pressure control device for an internal combustion engine that controls supercharging pressure in an internal combustion engine with a turbocharger that burns an air-fuel mixture by self-ignition and spark ignition.

  Conventionally, what was described in patent document 1 is known as a control apparatus of an internal combustion engine. This internal combustion engine can be operated by switching between a self-ignition combustion mode in which the air-fuel mixture is combusted by self-ignition and a spark ignition combustion mode in which the air-fuel mixture is combusted by spark ignition. In the example shown in FIG. A throttle valve mechanism for changing the amount of intake air and a variable valve mechanism for changing the lift and valve timing of the intake and exhaust valves are provided. In addition, the control device detects an air flow sensor, an accelerator opening sensor, a brake pedal force sensor, a vehicle speed sensor, a crank angle sensor, a cooling water temperature sensor, an exhaust gas temperature sensor for detecting a driver's intention, a running state of the vehicle, and an engine operating condition. And various sensors such as an air-fuel ratio sensor and an intake air temperature sensor, and an ECU to which these various sensors are connected.

  The ECU calculates the engine speed and the accelerator opening based on the detection signals of the crank angle sensor and the accelerator opening sensor, determines the output torque of the internal combustion engine based on the calculated values, and performs fuel injection. The amount and the intake air amount are determined, and the variable valve mechanism and the throttle valve mechanism are controlled based on the determined intake air amount (lines 24 to 29 on page 7). In the control process of FIG. 2, one of the self-ignition combustion mode and the spark ignition combustion mode is selected as the combustion mode in accordance with the detection signals of the various sensors described above. When the self-ignition combustion mode is selected, the control method shown in FIG. 4 is used in order to reduce the exhaust opening area and allow the burned gas to remain in the combustion chamber in order to ensure the amount of heat necessary for self-ignition. Then, the lift of the exhaust valve is controlled to a value smaller than that in the spark ignition combustion mode based on detection signals of the air flow sensor and the air-fuel ratio sensor. Hereinafter, in this specification, the combustion gas remaining in the combustion chamber is referred to as “internal EGR”, the residual amount is referred to as “internal EGR amount”, and the ratio of the internal EGR amount to the total gas amount in the combustion chamber is represented by This is called “internal EGR rate”. Further, in the control method shown in FIG. 5, as in the method of FIG. 4, in order to ensure the internal EGR, the opening time of the exhaust valve is determined based on the detection signals of the air flow sensor and the air-fuel ratio sensor. The value is controlled to be smaller than that in the mode.

  Further, in the internal combustion engine shown in FIG. 29 of Patent Document 1, a supercharger is provided upstream of the throttle valve mechanism in the intake passage. In this control device, the ECU detects the driver intention, the running state of the vehicle, and the engine operating condition based on the detection signals of the various sensors described above, and controls the driver intention, the vehicle in order to control the intake air amount. The supercharger and the throttle valve mechanism are controlled in accordance with the traveling state and the engine operating condition. As described above, the turbocharger is used in addition to the throttle valve mechanism when the temperature of the mixture in the combustion chamber is controlled by the internal EGR under the engine operating condition of high load and high rotation. This is to avoid such a state because the necessary amount of intake air cannot be secured and the mixture temperature may not be appropriately controlled.

International Publication No. 02/14665 Pamphlet

  In general, in the case of an internal combustion engine that is operated by self-ignition combustion, the amount of heat necessary to self-ignite the air-fuel mixture in the combustion chamber must be adequately secured without excess or deficiency. Need to be controlled accurately. Here, in the case of an internal combustion engine equipped with a turbocharger as a supercharger, when a turbocharging operation is performed by the turbocharger, the exhaust turbine becomes a flow path resistance, and the exhaust pressure in the exhaust passage rises. As a result, the internal EGR amount or the internal EGR rate changes to the increasing side. For example, in the case of a turbocharger with a wastegate valve, the internal EGR amount or the internal EGR rate in accordance with the change in the opening degree of the wastegate valve, and in the case of a variable nozzle type turbocharger, in accordance with the change in the opening degree of the nozzle vane. Changes. On the other hand, in the example shown in FIG. 29 of the conventional control device, since the change in the internal EGR amount or the internal EGR rate during the supercharging operation as described above is not taken into consideration, the turbocharger is used as the supercharger. When the is used, the control accuracy of the internal EGR is lowered, so that the combustion state becomes unstable, and the exhaust gas characteristics and the drivability may be deteriorated. This problem becomes more prominent in the self-ignition combustion mode than in the spark ignition combustion mode for the reason for securing the heat quantity in the combustion chamber as described above.

  The present invention has been made in order to solve the above-described problems. In an internal combustion engine with a turbocharger that can change the internal EGR degree and can be operated in a plurality of combustion modes including a self-ignition combustion mode, a plurality of combustion modes are provided. In any case, an object of the present invention is to provide a control device for an internal combustion engine that can ensure a good combustion state.

In order to achieve the above object, the invention according to claim 1 is capable of freely changing the residual amount of burned gas generated in the cylinder 3a in the cylinder 3a and burning the stratified mixture by self-ignition. The stratified self-ignition combustion mode, the stratified flame propagation combustion mode in which the stratified mixture is burned by spark ignition, and the mixture including both the stratified mixture and the homogeneous mixture are formed, and the stratified mixture is burned by spark ignition. In addition, it switches between multiple combustion modes including a self-ignition combustion mode in which a homogeneous mixture is self-ignited and combusted using a stratified mixture to be combusted, and a homogeneous flame propagation combustion mode in which the homogeneous mixture is combusted by spark ignition. In the internal combustion engine 3 with the turbocharger 13 that can be operated in a row, the supercharging pressure control device 1 of the internal combustion engine 3 that controls the supercharging pressure by the turbocharger 13 is provided. Thus, a variable mechanism (variable nozzle mechanism 14) for changing the kinetic energy received from the exhaust gas by the turbocharger 13 and an operating state parameter (engine speed NE, accelerator opening AP) representing the operating state of the internal combustion engine 3 are detected. Operation state parameter detection means (ECU2, crank angle sensor 20, accelerator opening sensor 31) and combustion mode selection means (ECU2, ECU2) for selecting one of a plurality of combustion modes according to the detected operation state parameter Step 4) and the boost pressure control means (ECU 2, step 5, which controls the boost pressure by determining the operating amount of the variable mechanism (nozzle opening command value LVNT_CMD) according to the selected combustion mode). and 7,12～14,30～40), equipped with a boost pressure control means (ECU 2) is spark ignition combustion mode is selected When the stratified self-ignition combustion mode is selected, the operating amount of the variable mechanism (variable nozzle mechanism 14) (nozzle opening command value LVNT_CMD) is set so that the residual degree of burned gas in the cylinder becomes smaller than when the stratified self-ignition combustion mode is selected. ) (Steps 14, 30 to 32, 36 to 38), and after the internal combustion engine 3 is started, the heat capacity of the exhaust gas supplied to the exhaust gas purification catalyst (catalyst device 17) is increased. Is operated (when the determination result in step 11 is YES), the operating amount of the variable mechanism (variable nozzle mechanism 14) (nozzle opening) is set so that the kinetic energy received by the turbocharger 13 from the exhaust gas is minimized. Degree command value LVNT_CMD) is determined (step 18) .

According to the supercharging pressure control device for an internal combustion engine, the stratified self-ignition combustion mode, the stratified flame propagation combustion mode, the fire type self-ignition combustion mode, and the homogeneous flame propagation combustion mode are selected in accordance with the operation state parameter representing the operation state of the internal combustion engine. Are selected, and the operation amount of the variable mechanism is determined according to the selected combustion mode, whereby the supercharging pressure is controlled. Since this variable mechanism changes the kinetic energy that the turbocharger receives from the exhaust gas, the exhaust pressure in the exhaust passage changes according to the amount of operation of the variable mechanism, resulting in the internal EGR. The quantity or internal EGR rate will change. That is, according to this supercharging pressure control device, it is possible to control the exhaust pressure according to the selected combustion mode, and thereby, according to the combustion mode, the amount of exhaust gas discharged from the combustion chamber, in other words, The internal EGR amount or the internal EGR rate can be controlled. As a result, in an internal combustion engine with a turbocharger, in any of a plurality of combustion modes, in addition to the intake air amount, the internal EGR amount or the internal EGR rate can be appropriately secured without excess or deficiency. A good combustion state and good exhaust gas characteristics and operability.

Further, when the ignition type self-ignition combustion mode is selected, the operation amount of the variable mechanism is determined so that the residual degree of burned gas in the cylinder becomes smaller than when the stratified self-ignition combustion mode is selected. . Comparing these stratified self-ignition combustion mode and fire type self-ignition combustion mode, in the fire type self-ignition combustion mode, the stratified mixture is burned by spark ignition and the homogeneous mixture is self-ignited using the combusted stratified mixture as a fire type. Compared with the stratified self-ignition combustion mode in which only the stratified mixture is self-ignited and combusted, the thermal energy generated by the combustion of the mixture becomes higher, and as a result, it is necessary to secure the thermal energy in the combustion chamber. The amount of internal EGR can be reduced. Therefore, according to this supercharging pressure control device, the operating amount of the variable mechanism can be appropriately determined according to the difference in thermal energy between the two combustion modes, so that the stratified self-ignition combustion mode and the fire type self-ignition In both of the combustion modes, the internal EGR amount can be appropriately secured without excess or deficiency. Further, after the internal combustion engine is started, when the internal combustion engine is operated so that the heat capacity of the exhaust gas supplied to the exhaust gas purification catalyst is increased, the kinetic energy received from the exhaust gas by the turbocharger is variable. Since the operating amount of the mechanism is determined, the exhaust gas can be supplied to the catalyst while minimizing its heat energy loss, and thus the catalyst can be activated quickly.

The invention according to claim 2 is the supercharging pressure control device for an internal combustion engine according to claim 1, the supercharging pressure control means (ECU 2), one of the stratified self-ignition combustion mode and stratified flame propagation combustion mode When selected, the operating amount (nozzle opening command) of the variable mechanism (variable nozzle mechanism 14) is set so that the residual degree of burned gas in the cylinder 3a becomes larger than when the homogeneous flame propagation combustion mode is selected. The value LVNT_CMD) is determined (steps 14, 30 to 36, 39, 40).

  In this case, in the stratified self-ignition combustion mode and the stratified flame propagation combustion mode, the amount of internal EGR necessary for securing thermal energy in the combustion chamber is larger than in the homogeneous flame propagation combustion mode. On the other hand, according to the supercharging pressure control apparatus for an internal combustion engine, when the stratified self-ignition combustion mode or the stratified flame propagation combustion mode is selected, the internal combustion engine has a higher pressure in the cylinder than when the homogeneous flame propagation combustion mode is selected. Since the amount of operation of the variable mechanism is determined so that the degree of residual burned gas remains, the internal EGR amount is adequately secured in both the stratified self-ignition combustion mode and the stratified flame propagation combustion mode. be able to.

  Hereinafter, an internal combustion engine supercharging pressure control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, the supercharging pressure control device 1 includes an ECU 2, which is supercharged according to the operating state of an internal combustion engine (hereinafter referred to as “engine”) 3 as will be described later. Various control processes such as a pressure control process are executed.

  As shown in FIGS. 1 and 3, the engine 3 is an in-line four-cylinder gasoline engine having four cylinders 3a and pistons 3b (only one set is shown). A combustion chamber 3g is formed between the piston 3b of 3a and the cylinder head 3c.

  The engine 3 includes a pair of intake valves 4 and 4 (only one is shown) and a pair of exhaust valves 7 and 7 (only one is shown), an intake camshaft 5 and an intake cam 6 provided for each cylinder 3a. In addition, an intake side valve mechanism 40 that opens and closes each intake valve 4, an exhaust side valve mechanism 60 that includes the exhaust camshaft 8 and the exhaust cam 9 and drives each exhaust valve 7 to open and close, and the fuel injection valve 10 (FIG. 2), a spark plug 11 (see FIG. 2), and the like.

  The intake valve 4 has a stem 4a slidably fitted to a guide 4b, and the guide 4b is fixed to the cylinder head 3c. Further, the intake valve 4 is biased in the valve closing direction by upper and lower spring seats 4c and 4d and a valve spring 4e provided therebetween.

  Each of the intake camshaft 5 and the exhaust camshaft 8 is rotatably attached to the cylinder head 3c via a holder (not shown) and extends along the arrangement direction of the cylinders 3a. An intake sprocket (not shown) is coaxially disposed on one end of the intake camshaft 5 and is rotatably provided.

  The intake sprocket is connected to the crankshaft 3d via a timing chain (not shown), and is connected to the intake camshaft 5 via an intake cam phase variable mechanism 50 described later. With the above configuration, the intake camshaft 5 rotates once every time the crankshaft 3d rotates twice. The intake cam 6 is provided on the intake camshaft 5 for each cylinder 3a so as to rotate integrally therewith.

  Further, the intake side valve mechanism 40 is configured to open and close the intake valves 4 of the respective cylinders 3a by the rotation of the intake camshaft 5 accompanying the rotation of the crankshaft 3d. It consists of a variable valve mechanism that changes the timing steplessly.

  On the other hand, the exhaust valve 7 has a stem 7a slidably fitted to a guide 7b, and the guide 7b is fixed to the cylinder head 3c. Further, the exhaust valve 7 is urged in the valve closing direction by upper and lower spring seats 7c and 7d and a valve spring 7e provided therebetween.

  An exhaust sprocket (not shown) is coaxially disposed on one end of the exhaust camshaft 8 and is rotatably provided. The exhaust sprocket is connected to the crankshaft 3d via a timing chain (not shown), and is connected to the exhaust camshaft 8 via an exhaust cam phase varying mechanism 90 described later. With the above configuration, the exhaust camshaft 8 rotates once every time the crankshaft 3d rotates twice. Further, the exhaust cam 9 is provided for each cylinder 3a on the exhaust camshaft 8 so as to rotate integrally therewith.

  Further, the exhaust side valve mechanism 60 drives the exhaust valve 7 of each cylinder 3a to open and close by the rotation of the exhaust camshaft 8 accompanying the rotation of the crankshaft 3d. It consists of a variable valve mechanism that changes the lift and valve timing steplessly. In the present embodiment, “the maximum lift of the exhaust valve 7 (hereinafter referred to as“ exhaust lift ”)” represents the maximum lift of the exhaust valve 7.

  On the other hand, the fuel injection valve 10 is provided for each cylinder 3a, and is attached to the cylinder head 3c so as to inject fuel directly into the combustion chamber 3g. That is, the engine 3 is configured as a direct injection engine. The fuel injection valve 10 is electrically connected to the ECU 2, and the ECU 2 controls the opening / closing timing based on the fuel injection timing described later.

  A spark plug 11 is also provided for each cylinder 3a and attached to the cylinder head 3c. The spark plug 11 is electrically connected to the ECU 2, and the discharge state is controlled by the ECU 2 so that the air-fuel mixture in the combustion chamber 3 g is sparked at a timing according to an ignition timing IG_LOG described later.

  On the other hand, the engine 3 is provided with a crank angle sensor 20 and a water temperature sensor 21. The crank angle sensor 20 includes a magnet rotor and an MRE pickup, and outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3d rotates.

  The CRK signal is output at one pulse every predetermined crank angle (for example, 10 °), and the ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b of each cylinder 3a is at a predetermined crank angle position slightly ahead of the TDC position of the intake stroke, and one pulse is output for each predetermined crank angle. In the present embodiment, the crank angle sensor 20 corresponds to the driving state parameter detecting means, and the engine speed NE corresponds to the driving state parameter.

  Further, the water temperature sensor 21 detects the engine water temperature TW, which is the temperature of the cooling water circulating in the cylinder block 3e of the engine 3, and outputs a detection signal representing it to the ECU 2.

  On the other hand, an air flow sensor 22, a turbocharger 13, and a throttle valve mechanism 14 are provided in the intake pipe 12 of the engine 3 in order from the upstream side. The air flow sensor 22 is constituted by a hot-wire air flow meter, detects a flow rate of fresh air flowing through the intake pipe 12 (hereinafter referred to as “fresh air flow rate”) GIN, and outputs a detection signal representing it to the ECU 2. To do.

  The turbocharger 13 is of a variable capacity type, and is provided in the middle of the compressor blade 13a and the exhaust pipe 16 provided on the downstream side of the air flow sensor 22 of the intake pipe 12, and integrated with the compressor blade 13a. A rotating turbine blade 13b, a variable nozzle mechanism 14, and a housing for housing them are provided.

  In the turbocharger 13, when the turbine blade 13 b is rotationally driven by the exhaust gas flowing in the exhaust pipe 16, the compressor blade 13 a integrated therewith also rotates at the same time, so that the air in the intake pipe 12 is pressurized. That is, the supercharging operation is executed.

  The variable nozzle mechanism 14 (variable mechanism) is for changing the supercharging pressure generated by the turbocharger 13, and includes a plurality of variable nozzle vanes 14a (only two are shown) and vanes that drive the variable nozzle vanes 14a. An actuator 14b and the like are provided. The variable nozzle vane 14a is rotatably attached to the wall of the portion that houses the turbine blade 13b of the housing. The vane actuator 14b is electrically connected to the ECU 2 and mechanically connected to the variable nozzle vane 14a.

  The ECU 2 changes the opening (hereinafter referred to as “nozzle opening”) LVNT of the variable nozzle vane 14a via the vane actuator 14b and changes the amount of exhaust gas blown to the turbine blade 13b, whereby the turbine blade 13b receives from the exhaust gas. Change kinetic energy. Thereby, the supercharging pressure is changed by changing the rotational speed of the turbine blade 13b, that is, the rotational speed of the compressor blade 13a.

  Further, the throttle valve mechanism 15 includes a throttle valve 15a and a TH actuator 15b that opens and closes the throttle valve 15a. The throttle valve 15a is rotatably provided in the middle of the intake pipe 12, and changes the fresh air flow rate in the intake pipe 12 by the change in the opening degree accompanying the rotation. The TH actuator 15b is a combination of a motor connected to the ECU 2 and a gear mechanism (both not shown), and is driven by a control input signal from the ECU 2 to change the opening of the throttle valve 15a. .

  Further, an intake air temperature sensor 23 and an intake pipe internal pressure sensor 24 (both of which are shown in FIG. 2) are provided downstream of the throttle valve mechanism 15 of the intake pipe 12. The intake air temperature sensor 23 detects the temperature (hereinafter referred to as “intake air temperature”) TA of the air flowing through the intake pipe 12 and outputs a detection signal indicating the detected temperature to the ECU 2.

  The intake pipe internal pressure sensor 24 is constituted by, for example, a semiconductor pressure sensor, and detects a pressure (hereinafter referred to as “intake pipe internal pressure”) PBA in the intake pipe 12 and outputs a detection signal representing the detected pressure to the ECU 2. This intake pipe internal pressure PBA is detected as an absolute pressure.

  On the other hand, the exhaust pipe 16 of the engine 3 is provided with a LAF sensor 25 and a catalyst device 17 (catalyst) in order from the upstream side. The LAF sensor 25 is composed of zirconia, a platinum electrode, and the like, and linearly adjusts the oxygen concentration in the exhaust gas flowing in the exhaust pipe 16 in a wide range of air-fuel ratios from a rich region richer than the theoretical air-fuel ratio to an extremely lean region. And a detection signal representing it is output to the ECU 2. The ECU 2 calculates a detected air-fuel ratio KACT representing the air-fuel ratio in the exhaust gas based on the value of the detection signal of the LAF sensor 25.

  The engine 3 is provided with an exhaust gas recirculation mechanism 18. The exhaust gas recirculation mechanism 18 recirculates exhaust gas in the exhaust pipe 16 to the intake pipe 12 side, and opens and closes the EGR pipe 18a connected between the intake pipe 12 and the exhaust pipe 16 and the EGR pipe 18a. The EGR control valve 18b is configured. One end of the EGR pipe 18a opens to a portion upstream of the catalyst device 15 of the exhaust pipe 16, and the other end opens to a portion downstream of the throttle valve mechanism 13 of the intake pipe 12.

  The EGR control valve 18b is of a linear electromagnetic valve type, and its lift (hereinafter referred to as “EGR lift”) linearly changes between a maximum value and a minimum value in accordance with a control input signal from the ECU 2. Thus, the opening degree of the EGR pipe 18a, that is, the exhaust gas recirculation amount (hereinafter referred to as “external EGR amount”) is changed.

  An EGR lift sensor 26 is attached to the EGR control valve 18b, and the EGR lift sensor 26 detects an actual EGR lift LACT of the EGR control valve 18b and outputs a detection signal representing it to the ECU 2. As will be described later, the ECU 2 controls the external EGR amount via the EGR control valve 18b so that the EGR lift LACT converges to the target EGR lift LCMD. In the following description, recirculation of exhaust gas by the exhaust gas recirculation mechanism 18 is referred to as “external EGR”.

  Next, the intake side valve mechanism 40 described above will be described. As shown in FIG. 4, the intake side valve mechanism 40 includes an intake camshaft 5, an intake cam 6, a rocker arm shaft 42, two rocker arms 43 and 43, an intake cam phase variable mechanism 50, and the like. In the intake valve side valve operating mechanism 40, when the intake camshaft 5 rotates, the two rocker arms 43, 43 rotate around the rocker arm shaft 42, thereby opening and closing the intake valve 4.

  The intake cam phase variable mechanism 50 changes the relative phase of the intake camshaft 5 relative to the crankshaft 3d (hereinafter referred to as “intake cam phase”) CAIN steplessly or forwardly. Since the present applicant has the same configuration as that already proposed in Japanese Patent Application Laid-Open No. 2005-315161, the outline will be briefly described below.

  The intake cam phase variable mechanism 50 is provided at the end of the intake camshaft 5 on the intake sprocket side, and includes an intake cam phase electromagnetic valve 51 and an advance chamber and a retard chamber to which hydraulic pressure is supplied via the intake cam phase electromagnetic valve 51. Etc. The intake cam phase solenoid valve 51 is connected to the ECU 2 and changes the hydraulic pressure supplied to the advance chamber and the retard chamber in accordance with a control input signal from the ECU 2, thereby changing the intake cam phase CAIN to a predetermined value. It is continuously changed steplessly between the most retarded angle value and a predetermined most advanced angle value. Thereby, the valve timing of the intake valve 4 is changed steplessly between the most retarded timing shown by the solid line in FIG. 6 and the most advanced timing shown by the two-dot chain line in FIG.

  On the other hand, an intake cam angle sensor 27 (see FIG. 2) is provided at the end of the intake camshaft 5 opposite to the intake cam phase varying mechanism 50. The intake cam angle sensor 27 includes, for example, a magnet rotor and an MRE pickup, and outputs an INCAM signal, which is a pulse signal, to the ECU 2 every predetermined cam angle (for example, 1 °) as the intake cam shaft 5 rotates. To do. The ECU 2 calculates the intake cam phase CAIN based on this INCAM signal and the aforementioned CRK signal.

  Next, the exhaust side valve mechanism 60 described above will be described. As shown in FIG. 5, the exhaust side valve mechanism 60 includes an exhaust camshaft 8, an exhaust cam 9, an exhaust lift variable mechanism 70, an exhaust cam phase variable mechanism 90, and the like.

  The variable exhaust lift mechanism 70 opens and closes the exhaust valve 7 by the rotation of the exhaust camshaft 8 accompanying the rotation of the crankshaft 3d, and the exhaust lift is between a value 0 and a predetermined maximum value LEXMAX (see FIG. 7). Therefore, the outline is briefly described below because it is configured in the same manner as already proposed in Japanese Patent Application No. 2005-288057.

  The variable exhaust lift mechanism 70 includes a control shaft 71 and a rocker arm shaft 72, a rocker arm mechanism 73 provided on the shafts 71 and 72 for each cylinder 3a, and an exhaust lift actuator 80 for simultaneously driving the rocker arm mechanisms 73. (Refer to FIG. 2).

  The rocker arm mechanism 73 includes a link 74a, a roller shaft 74b, a roller 74c, a rocker arm 75, and the like. The exhaust lift actuator 80 is a combination of a motor, a reduction gear mechanism (both not shown), etc., and is electrically connected to the ECU 2, and when driven by a control input signal from the ECU 2, The control shaft 71 is rotated, thereby rotating the link 74a about the roller shaft 74b.

  When the link 74a is in the zero lift position indicated by the solid line in FIG. 5, when the exhaust cam 9 rotates and the roller nose 74c is pushed toward the rocker arm shaft 72 by the cam nose, the link 74a is centered on the control shaft 71 as shown in FIG. Rotate clockwise. At this time, since the guide surface 75a of the rocker arm 75 has a shape that coincides with the arc centered on the control shaft 71, the rocker arm 75 is moved to the closed position shown in FIG. 5 by the urging force of the valve spring 7e. Retained. As a result, the exhaust lift is maintained at the value 0, and the exhaust valve 7 is maintained in the closed state.

  On the other hand, when the link 74a is rotated from the zero lift position to the position on the maximum lift position (the position indicated by the broken line in FIG. 5) and held at that position, the link 74a is controlled by the rotation of the exhaust cam 9. When pivoting clockwise in FIG. 5 around 71, the rocker arm 75 pivots downward from the valve closing position shown in FIG. 5 while opening the exhaust valve 7 against the urging force of the valve spring 7e. At this time, the amount of rotation of the rocker arm 75, that is, the exhaust lift becomes larger as the link 74a is closer to the maximum lift position.

  For the above reasons, the exhaust valve 7 is opened with a larger lift as the link 74a is closer to the maximum lift position side. Specifically, the exhaust valve 7 is connected to the link while the exhaust cam 9 is rotating. When 74a is at the maximum lift position, the valve is opened according to the valve lift curve shown by the solid line in FIG. 7, and the exhaust lift indicates its maximum value LEXMAX. Therefore, in the variable exhaust lift mechanism 70, the exhaust lift is set between the value 0 and the predetermined maximum value LEXMAX by rotating the link 74a between the zero lift position and the maximum lift position via the exhaust lift actuator 80. Can be changed steplessly between.

  Further, the exhaust lift variable mechanism 70 is provided with a rotation angle sensor 28 (see FIG. 2). The rotation angle sensor 28 detects the rotation angle SAAEX of the control shaft 71 and represents it. A detection signal is output to the ECU 2.

  Next, the exhaust cam phase varying mechanism 90 will be described. The exhaust cam phase variable mechanism 90 changes the relative phase of the exhaust camshaft 8 relative to the crankshaft 3d (hereinafter referred to as “exhaust cam phase”) CAEX steplessly or forwardly. It is provided at the end of the exhaust camshaft 8 on the exhaust sprocket side.

  Since the exhaust cam phase variable mechanism 90 is configured in the same manner as the intake cam phase variable mechanism 50 described above, the exhaust cam phase electromagnetic valve 91 and the like are provided. When the exhaust cam phase solenoid valve 91 is driven by the control input signal, the exhaust cam phase CAEX is continuously changed between a predetermined maximum retardation value and a predetermined maximum advance value. Thereby, the valve timing of the exhaust valve 7 is changed steplessly between the most retarded timing shown by the solid line in FIG. 6 and the most advanced timing shown by the two-dot chain line in FIG.

  On the other hand, an exhaust cam angle sensor 29 (see FIG. 2) is provided at the end of the exhaust camshaft 8 opposite to the exhaust cam phase varying mechanism 90. The exhaust cam angle sensor 29 includes, for example, a magnet rotor and an MRE pickup, and outputs an EXCAM signal, which is a pulse signal, to the ECU 2 at predetermined cam angles (for example, 1 °) as the exhaust camshaft 8 rotates. To do. The ECU 2 calculates the exhaust cam phase CAEX based on the EXCAM signal and the above-described CRK signal.

  As described above, in the engine 3, the valve timing of the intake valve 4 can be changed steplessly by the intake side valve mechanism 40, and the lift and valve timing of the exhaust valve 7 are not changed by the exhaust side valve mechanism 60. The amount of burned gas remaining in the cylinder 3a, that is, the amount of internal EGR can be freely changed by the two valve mechanisms 40 and 60. This burned gas exhibits a higher temperature than the exhaust gas recirculated by the exhaust gas recirculation mechanism 16.

  In the following description, the intake cam phase variable mechanism 50, the exhaust lift variable mechanism 70, and the exhaust cam phase variable mechanism 90 are collectively referred to as “three variable mechanisms 50, 70, 90”.

  Further, an atmospheric pressure sensor 30, an accelerator opening sensor 31, a throttle valve opening sensor 32, and an ignition switch (hereinafter referred to as “IG · SW”) 33 are connected to the ECU 2. The atmospheric pressure sensor 30 is composed of a semiconductor pressure sensor, detects the atmospheric pressure PA, and outputs a detection signal representing it to the ECU 2. The accelerator opening sensor 31 detects an accelerator opening AP, which is an operation amount of an accelerator pedal (not shown), and outputs a detection signal representing the detected value to the ECU 2. In the present embodiment, the accelerator opening sensor 31 corresponds to the driving state parameter detecting means, and the accelerator opening AP corresponds to the driving state parameter.

  The throttle valve opening sensor 32 is composed of a potentiometer, detects the opening TH of the throttle valve 14b (hereinafter referred to as “throttle valve opening”) TH, and outputs a detection signal indicating the detected value to the ECU 2. Further, the IG / SW 33 is turned ON / OFF by operating an ignition key (not shown), and outputs a signal indicating the ON / OFF state to the ECU 2.

  On the other hand, the ECU 2 is composed of a microcomputer including a CPU, RAM, ROM, and I / O interface (all not shown), and the detection signals of the various sensors 20 to 32 described above and the IG / SW 33 are turned on. In accordance with the / OFF signal or the like, the operating state of the engine 3 is determined and various control processes are executed.

  Specifically, the ECU 2 executes a fuel injection control process, a boost pressure control process, an ignition timing control process, a variable mechanism control process, and the like, as will be described later, according to the operating state of the engine 3. With these control processes, the engine 3 operates in any one of the stratified self-ignition combustion mode, the stratified flame propagation combustion mode, the fire type self-ignition combustion mode, and the homogeneous flame propagation combustion mode in accordance with a combustion mode value STS_BURNCMD described later. Driven.

  In this stratified self-ignition combustion mode, a stratified mixture is generated by injecting fuel only in the compression stroke, and this is self-ignited and combusted. When the operating state of the engine 3 is in a predetermined first operating region More specifically, it is executed when the engine speed NE is in a predetermined low speed range and a later-described required torque PMCMD is in a predetermined low load range. In this stratified self-ignition combustion mode, the stratified mixture is generated in a state where self-ignition combustion occurs, so spark ignition is essentially unnecessary, but misfire prevention and proper self-ignition combustion timing are adequate. For the purpose of control, spark ignition by the spark plug 11 is executed even in the stratified self-ignition combustion mode in the ignition timing control process described later in the present embodiment.

  In the stratified flame propagation combustion mode, a stratified mixture is generated by injecting fuel only in the compression stroke, and this is subjected to flame propagation combustion by spark ignition. The operation state of the engine 3 is a predetermined second operation. It is executed when the engine is in a region (a region where the stratified mixture does not self-ignite and combust in a low-medium rotational region and a region on the lower load side than the first operating region).

  Furthermore, the self-ignition combustion mode includes both a homogeneous mixture and a stratified mixture by injecting fuel in the intake stroke to generate a homogeneous mixture and then injecting a very small amount of fuel in the compression stroke. An air-fuel mixture is generated, and the stratified air-fuel mixture is subjected to flame propagation combustion by spark ignition, and the homogeneous air-fuel mixture is self-ignited and combusted using this as a fire type. This fire type self-ignition combustion mode is executed when the operating state of the engine 3 is in a predetermined third operating region (a region on the high load side of the first operating region in the low and medium rotation region).

  On the other hand, in the homogeneous flame propagation combustion mode, a homogeneous mixture is generated by injecting fuel in the intake stroke, and this is subjected to flame propagation combustion by spark ignition. It is executed when the vehicle is in a predetermined fourth operation region other than the three operation regions.

  In the present embodiment, the ECU 2 corresponds to an operating state parameter detection unit, a combustion mode selection unit, and a supercharging pressure control unit.

  Hereinafter, the control process executed in the ECU 2 at a predetermined cycle (for example, 10 msec) by setting the timer will be described with reference to FIG. Various values calculated or set in the following control process are stored in the RAM of the ECU 2.

  In this process, first, in Step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the engine speed NE, the required torque PMCMD, the combustion mode value STS_BURNCMD, a target intake cam phase CAINCMD described later, and a target rotation angle described later. Various data such as SAAEXCMD and a target exhaust cam phase CAEXCMD described later are read.

  Next, the process proceeds to step 2, and an engine start flag F_ENGSTART setting process is executed. The engine start flag F_ENGSTART is set based on the engine speed NE and the ON / OFF state of the IG / SW 33 to determine whether or not the engine start control is being performed, that is, cranking, and is executed based on the determination result. Is done. Specifically, the engine start flag F_ENGSTART is set to “1” when the engine start control is being performed, and is set to “0” otherwise.

  In step 3 following step 2, the setting process of the catalyst warm-up flag F_FIREON is executed. The catalyst warm-up flag F_FIREON is set based on the catalyst warm-up control for rapidly activating the catalyst in the catalyst device 17 after the engine is started based on the elapsed time after the engine is started, the engine water temperature TW, the accelerator pedal opening AP, and the like. It is determined whether or not an execution condition is satisfied, and the process is executed based on the determination result. Specifically, the catalyst warm-up flag F_FIREON is set to “1” when the catalyst warm-up control execution condition is satisfied, and is set to “0” when the catalyst warm-up control is executed. Is set.

  Next, in step 4, a setting process for the combustion mode value STS_BURNCMD is executed. This combustion mode value STS_BURNCMD represents which of the four combustion modes described above is selected as the combustion mode of the engine 3 as described above, and depends on the engine speed NE and the required torque PMCMD. This is set by searching a map (not shown).

  More specifically, the combustion mode value STS_BURNCMD is obtained when the stratified self-ignition combustion mode is selected as the combustion mode of the engine 3 because the engine speed NE and the required torque PMCMD are in the predetermined first operating range described above. The engine speed NE and the required torque PMCMD are set to “1”, and are set to “2” when the stratified flame propagation combustion mode is selected. Further, the combustion mode value STS_BURNCMD is set to “3” when the ignition type self-ignition combustion mode is selected because the engine speed NE and the required torque PMCMD are in the predetermined third operating region described above, and the engine speed The NE and the required torque PMCMD are in the predetermined fourth operating range described above, so that “4” is set when the homogeneous flame propagation combustion mode is selected.

  In step 5 following step 4, a supercharging pressure control process is executed. This supercharging pressure control process calculates a nozzle opening command value LVNT_CMD (amount of operation of the variable mechanism), and details thereof will be described later.

  Next, at step 6, the target throttle valve opening THCMD is calculated by searching a map (not shown) according to the accelerator opening AP and the required torque PMCMD.

  Next, it progresses to step 7 and a variable mechanism control process is performed. This variable mechanism process controls the variable nozzle mechanism 14, the throttle valve mechanism 15, the exhaust gas recirculation mechanism 18, the intake cam phase variable mechanism 50, the exhaust lift variable mechanism 70, and the exhaust cam phase variable mechanism 90, as described below. For this purpose, the value of the control input signal is calculated.

  In this process, first, the value of the control input signal to the variable nozzle mechanism 14 is calculated based on the nozzle opening command value LVNT_CMD described above, and the calculated control input signal is used as the vane actuator of the variable nozzle mechanism 14. The nozzle opening degree LVNT is feedforward controlled by being supplied to 14b. As a result, the supercharging pressure is controlled. In this case, the larger the nozzle opening command value LVNT_CMD, the smaller the kinetic energy that the turbine blade 13b of the turbocharger 13 receives from the exhaust gas, thereby controlling the supercharging pressure to be smaller.

  Further, the value of the control input signal to the throttle valve mechanism 15 is calculated by a predetermined feedback control algorithm so that the throttle valve opening TH converges to the target throttle valve opening THCMD, and the control input thus calculated is calculated. By supplying a signal to the TH actuator 15b of the throttle valve mechanism 15, the throttle valve opening TH is feedback-controlled. As a result, the intake air amount is controlled.

  Further, the value of the control input signal to the exhaust gas recirculation mechanism 18 is calculated by a predetermined feedback control algorithm so that the EGR lift LACT converges to the target EGR lift LCMD, and the calculated control input signal is the exhaust gas recirculation. The external EGR is controlled by being supplied to the EGR control valve 18b of the mechanism 18. As a result, the external EGR ratio is controlled to be a calculated value EGRDIVEX described later.

  On the other hand, the value of the control input signal to the intake cam phase variable mechanism 50 is calculated by a predetermined feedback control algorithm so that the intake cam phase CAIN converges to the target intake cam phase CAINCMD, and the control input thus calculated is calculated. By supplying a signal to the intake cam phase electromagnetic valve 51 of the intake cam phase varying mechanism 50, the intake cam phase CAIN is feedback-controlled.

  Further, the value of the control input signal to the variable exhaust lift mechanism 70 is calculated by a predetermined feedback control algorithm so that the rotation angle SAAEX converges to the target rotation angle SAAEXCMD, and the control input signal thus calculated is calculated. Is supplied to the exhaust lift actuator 80 of the variable exhaust lift mechanism 70 so that the exhaust lift is feedback-controlled.

  Further, the value of the control input signal to the exhaust cam phase variable mechanism 90 is calculated by a predetermined feedback control algorithm so that the exhaust cam phase CAEX converges to the target exhaust cam phase CAEXCMD, and the control thus calculated is calculated. By supplying the input signal to the exhaust cam phase electromagnetic valve 91 of the exhaust cam phase variable mechanism 90, the exhaust cam phase CAEX is feedback-controlled. As described above, by controlling the intake cam phase CAIN, the exhaust lift and the exhaust cam phase CAEX, the internal EGR is controlled, and as a result, the internal EGR ratio is controlled to a calculated value EGRDIVIN described later. .

  After executing the variable mechanism control process of step 7 as described above, the present process is terminated.

  Next, the above-described supercharging pressure control process will be described with reference to FIG. In this process, first, in step 10, it is determined whether or not the engine start flag F_ENGSTART described above is “1”.

  If the determination result is YES and the engine start control is being performed, the process proceeds to step 18 where the nozzle opening command value LVNT_CMD is set to a predetermined maximum value LVNT_LMTH (for example, 100%), and then this process is terminated. As described above, when the nozzle opening command value LVNT_CMD is set to the predetermined maximum value LVNT_LMTH, the kinetic energy received from the exhaust gas by the turbine blade 13b of the turbocharger 13 is minimized, so that supercharging is hardly performed. It becomes.

  On the other hand, when the determination result of step 10 is NO, the process proceeds to step 11 to determine whether or not the catalyst warm-up flag F_FIREON described above is “1”. When the determination result is YES and the catalyst warm-up control is being performed, as described above, after executing step 18, the present process is terminated.

  On the other hand, when the determination result of step 11 is NO, the process proceeds to step 12 to calculate the basic value LVNT_BASE of the nozzle opening command value. The basic value LVNT_BASE is specifically calculated as shown in FIG. First, in step 30, it is determined whether or not the combustion mode value STS_BURNCMD is “1”.

  If the determination result is YES and the stratified self-ignition combustion mode is selected as the combustion mode of the engine 3, the process proceeds to step 31 and the map shown in FIG. 11 is searched according to the engine speed NE and the required torque PMCMD. Thus, the value LVNT_HCCI for the stratified self-ignition combustion of the nozzle opening command value is calculated. Symbols i and j in the figure indicate positive integers, and this is the same in the following description.

  Next, the routine proceeds to step 32, where the basic value LVNT_BASE is set to the stratified self-ignition combustion value LVNT_HCCI, and then this processing is terminated.

  On the other hand, when the determination result of step 30 is NO, the process proceeds to step 33 to determine whether or not the combustion mode value STS_BURNCMD is “2”. When the determination result is YES and the stratified flame propagation combustion mode is selected, the routine proceeds to step 34, where the nozzle opening degree is searched by searching the map shown in FIG. 12 according to the engine speed NE and the required torque PMCMD. The value LVNT_DISC for stratified flame propagation combustion of the command value is calculated.

  Next, the routine proceeds to step 35, where the basic value LVNT_BASE is set to the stratified flame propagation combustion value LVNT_DISC, and then this processing is terminated.

  On the other hand, when the determination result of step 33 is NO, the process proceeds to step 36 to determine whether or not the combustion mode value STS_BURNCMD is “3”. When the determination result is YES and the fire type self-ignition combustion mode is selected, the routine proceeds to step 37, where the nozzle opening degree is searched by searching the map shown in FIG. 13 according to the engine speed NE and the required torque PMCMD. A value LVNT_CC for fire type self-ignition combustion of the command value is calculated.

  Next, the routine proceeds to step 38, where the basic value LVNT_BASE is set to the value LVNT_CC for fire type self-ignition combustion, and then this process is terminated.

  On the other hand, when the determination result in step 33 is NO and the homogeneous flame propagation combustion mode is selected, the routine proceeds to step 39, where the map shown in FIG. 14 is searched according to the engine speed NE and the required torque PMCMD. Then, a homogeneous flame propagation combustion value LVNT_STK of the nozzle opening command value is calculated.

  Next, the routine proceeds to step 40, where the basic value LVNT_BASE is set to the homogeneous flame propagation combustion value LVNT_STK, and then this processing is terminated.

  In each of the maps of FIGS. 11 to 14 described above, the three types of values LVNT_HCCI, LVNT_CC, and LVNT_STK of the nozzle opening command value are set to have a relationship as shown in FIG. Although the stratified flame propagation combustion value LVNT_DISC is not shown in FIG. 15, it is set to substantially the same value as the stratified self-ignition combustion value LVNT_HCCI.

  This figure shows the relationship between the three types of values LVNT_HCCI, LVNT_CC, and LVNT_STK with respect to the required torque PMCMD when the engine speed NE is at a predetermined value NEX (for example, 2000 rpm) in the low speed range, and the value LVNT_LMTL in the figure. Represents a predetermined minimum value (for example, 0%).

  As shown in the figure, the homogeneous flame propagation combustion value LVNT_STK is set to the maximum value LVNT_MAX regardless of the magnitude of the required torque PMCMD. This is because, in the homogeneous flame propagation combustion mode, the combustion state becomes unstable when the internal EGR amount is large in the low rotation range, so the nozzle opening LVNT is controlled to a value as large as possible to suppress the increase in exhaust pressure. This is to avoid an increase in the amount of internal EGR and to ensure the stability of the combustion state.

  Further, the stratified self-ignition combustion value LVNT_HCCI is set to the minimum value LVNT_LMTL in the low load region. This is because, in the low load region, the exhaust pressure is increased and the internal EGR amount is increased, so that the temperature in the combustion chamber is raised to a value at which the stratified mixture appropriately performs self-ignition combustion. In addition, the stratified self-ignition combustion value LVNT_HCCI is set to a larger value as the required torque PMCMD is larger in the middle and high load range. This is because, in the middle and high load range, as the required torque PMCMD is larger, it is necessary to increase the supercharging pressure in order to ensure a larger engine output.

  Further, the value LVNT_CC for the ignition type self-ignition combustion is set to the same value as the value LVNT_HCCI for the stratified self-ignition combustion in the extremely low load region and the extremely high load region, and the stratified self-ignition combustion in the other load regions. It has the same tendency as the utility value LVNT_HCCI, and is set to a value slightly larger than this. This is because, in the self-ignition combustion mode, compared with the stratified self-ignition combustion mode, thermal energy is generated with the combustion of the stratified mixture that becomes the fire species, and the temperature in the combustion chamber rises, so the exhaust pressure decreases. This is to reduce the internal EGR amount by the temperature rise.

  Returning to FIG. 9, after calculating the basic value LVNT_BASE in step 12 as described above, the process proceeds to step 13 where the feedback correction term LVNT_FB is calculated as described below. First, the target value PBA_CMD of the intake pipe internal pressure PBA (that is, the supercharging pressure) is calculated by searching a table (not shown) according to the engine speed NE. Then, the feedback correction term LVNT_FB is calculated by a predetermined feedback control algorithm so that the intake pipe internal pressure PBA converges to the target value PBA_CMD.

  Next, in step 14, the nozzle opening command value LVNT_CMD is set to the sum LVNT_BASE + LVNT_FB of the basic value and the feedback correction term. After that, in steps 15 to 18, limit processing of the nozzle opening command value LVNT_CMD is executed.

  That is, in step 15, it is determined whether or not the nozzle opening command value LVNT_CMD is less than or equal to the minimum value LVNT_LMTL. When the determination result is YES, in step 17, the nozzle opening command value LVNT_CMD is set to the minimum value LVNT_LMTL, and then the present process is terminated.

  On the other hand, when the determination result of step 15 is NO, the process proceeds to step 16 to determine whether the nozzle opening command value LVNT_CMD is equal to or greater than the maximum value LVNT_LMTH. When the determination result is YES, as described above, the nozzle opening command value LVNT_CMD is set to the maximum value LVNT_LMTH in Step 18, and then the present process is terminated.

  On the other hand, when the determination result of step 16 is NO and LVNT_LMTL <LVNT_CMD <LVNT_LMTH, this process is terminated as it is.

  Hereinafter, with reference to FIG. 16, a control process that is executed in the ECU 2 in a control cycle synchronized with the generation of the TDC signal will be described. In this process, first, in step 50, various data such as the engine speed NE, the accelerator pedal opening AP, the engine start flag F_ENGSTART, the catalyst warm-up flag F_FIREON, and the combustion mode value STS_BURNCMD are read.

  Next, at step 51, the required torque PMCMD is calculated by searching the map shown in FIG. 17 according to the engine speed NE and the accelerator pedal opening AP. In this map, the required torque PMCMD is set to a larger value as the engine speed NE is higher or the accelerator pedal opening AP is larger. This is because the engine load becomes larger as the engine speed NE is higher or the accelerator pedal opening AP is larger, and this is to cope with it.

  In step 52 following step 51, fuel injection control processing is executed. This control process calculates a fuel amount (hereinafter referred to as “fuel injection amount”) TOUT to be injected into the cylinder 3a via the fuel injection valve 10 and its injection timing, and the details thereof will be described later.

  Next, in step 53, an EGR control process is executed. This control process calculates the target EGR lift LCMD for controlling the external EGR amount via the exhaust gas recirculation mechanism 18, and controls the internal EGR amount via the three variable mechanisms 50, 70, 90. The target rotation angle SAAEXCMD, the target exhaust cam phase CAEXCMD, and the target intake cam phase CAINCMD are calculated, and details thereof will be described later.

  Next, at step 54, as will be described later, after executing the ignition timing control process, this process is terminated.

  Next, the above-described fuel injection control process will be described with reference to FIG. As shown in the figure, in this process, first, in step 60, it is determined whether or not the engine start flag F_ENGSTART described above is “1”. If the determination result is YES and the engine start control is being performed, the routine proceeds to step 61, where a fuel injection control process for engine start is executed. In this process, the fuel injection amount TOUT is calculated based on various operating state parameters such as the engine coolant temperature TW, and the opening / closing timing of the fuel injection valve 10, that is, the fuel injection timing is calculated based on the calculated value. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 60 is NO, the process proceeds to step 62 to determine whether or not the catalyst warm-up flag F_FIREON is “1”. If the determination result is YES and the catalyst warm-up control is being performed, the routine proceeds to step 63, where fuel injection control processing for catalyst warm-up control is executed. In this process, the fuel injection amount TOUT is calculated based on various operating state parameters such as the engine coolant temperature TW, and the fuel injection timing is calculated based on the calculated value. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 62 is NO, the process proceeds to step 64, and after executing the normal fuel injection control process, this process is terminated. Specifically, the normal fuel injection control process is executed as shown in FIG.

  First, in step 70, a map search is performed using various operating state parameters such as fresh air flow rate GIN, engine speed NE, intake cam phase CAIN, engine water temperature TW, intake air temperature TA, detected air-fuel ratio KACT, and required torque PMCMD. The fuel injection amount TOUT is calculated by a predetermined calculation method including

  Next, the routine proceeds to step 71, where it is determined whether or not the combustion mode value STS_BURNCMD is “1”. If the determination result is YES and the stratified self-ignition combustion mode is selected, the routine proceeds to step 72, where a stratified self-ignition combustion is performed by searching a map (not shown) according to the fuel injection amount TOUT and the engine speed NE. The fuel injection timing is calculated. The fuel injection timing for stratified self-ignition combustion is calculated as the timing during the compression stroke. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 71 is NO, the process proceeds to step 73 to determine whether or not the combustion mode value STS_BURNCMD is “2”. If the determination result is YES and the stratified flame propagation combustion mode is selected, the routine proceeds to step 74, where a stratified flame propagation combustion is performed by searching a map (not shown) according to the fuel injection amount TOUT and the engine speed NE. The fuel injection timing is calculated. The fuel injection timing for stratified flame propagation combustion is also calculated as the timing during the compression stroke, similarly to the fuel injection timing for stratified self-ignition combustion. Thereafter, this process is terminated.

  On the other hand, when the determination result of step 73 is NO, the process proceeds to step 75 to determine whether or not the combustion mode value STS_BURNCMD is “3”. If the determination result is YES and the fire type self-ignition combustion mode is selected, the routine proceeds to step 76 where a map (not shown) is searched according to the fuel injection amount TOUT and the engine speed NE and the search value is used. The fuel injection timing for the ignition type self-ignition combustion is calculated by the predetermined arithmetic expression. The fuel injection timing for this kind of self-ignition combustion is calculated as two timings during the intake stroke and the compression stroke. Thereafter, this process is terminated.

  On the other hand, when the determination result in step 75 is NO and the homogeneous flame propagation combustion mode is selected, the routine proceeds to step 77, where a map (not shown) is searched according to the fuel injection amount TOUT and the engine speed NE. The fuel injection timing for homogeneous flame propagation combustion is calculated. The fuel injection timing for homogeneous flame propagation combustion is calculated as the timing during the intake stroke. Thereafter, this process is terminated.

  Next, the EGR control process described above will be described with reference to FIG. As shown in the figure, in this process, first, in step 80, a target fresh air rate KEGRCMD is calculated by searching a map (not shown) according to the required torque PMCMD and the engine speed NE.

  Next, the routine proceeds to step 81, where the internal EGR ratio EGRDIVIN is calculated. Specifically, the internal EGR ratio EGRDIVIN is calculated as shown in FIG. That is, first, at step 90, it is determined whether or not the combustion mode value STS_BURNCMD is “1”.

  If the determination result is YES and the stratified self-ignition combustion mode is selected as the combustion mode of the engine 3, the process proceeds to step 91, and a map shown in FIG. 22 is searched according to the engine speed NE and the required torque PMCMD. Thus, the value EGRDIVIN_HCCI for the stratified self-ignition combustion of the internal EGR ratio is calculated.

  Next, the routine proceeds to step 92, where the internal EGR ratio EGRDIVIN is set to the value for stratified self-ignition combustion EGRDIVIN_HCCI, and then this processing is terminated.

  On the other hand, when the determination result of step 90 is NO, the process proceeds to step 93 to determine whether or not the combustion mode value STS_BURNCMD is “2”. If the determination result is YES and the stratified flame propagation combustion mode is selected, the routine proceeds to step 94, and the internal EGR ratio is searched by searching the map shown in FIG. 23 according to the engine speed NE and the required torque PMCMD. The value for stratified flame propagation combustion EGRDIVIN_DISC is calculated.

  Next, the routine proceeds to step 95, where the internal EGR ratio EGRDIVIN is set to the stratified flame propagation combustion value EGRDIVIN_DISC, and then this processing is terminated.

  On the other hand, when the determination result of step 93 is NO, the process proceeds to step 96 to determine whether or not the combustion mode value STS_BURNCMD is “3”. If the determination result is YES and the fire type self-ignition combustion mode is selected, the routine proceeds to step 97, where the internal EGR ratio is searched by searching the map shown in FIG. 24 according to the engine speed NE and the required torque PMCMD. The value EGRDIVIN_CC for self-ignition combustion is calculated.

  Next, the routine proceeds to step 98, where the internal EGR ratio EGRDIVIN is set to the value for ignition type self-ignition combustion EGRDIVIN_CC, and then this processing is terminated.

  On the other hand, when the determination result in step 96 is NO and the homogeneous flame propagation combustion mode is selected, the process proceeds to step 99, and the map shown in FIG. 25 is searched according to the engine speed NE and the required torque PMCMD. Then, a value EGRDIVIN_STK for homogeneous flame propagation combustion of the internal EGR ratio is calculated.

  Next, the routine proceeds to step 100 where the internal EGR ratio EGRDIVIN is set to the homogeneous flame propagation combustion value EGRDIVIN_STK, and then the present process is terminated.

  22 to 25, the four types of values EGRDIVIN_HCCI, EGRDIVIN_DISC, EGRDIVIN_CC, and EGRDIVIN_STK of the internal EGR ratio are set as follows. That is, in the predetermined low rotation range, the stratified self-ignition combustion value EGRDIVIN_HCCI and the stratified flame propagation combustion value EGRDIVIN_DISC are set to substantially the same value, and the fire type self-ignition combustion value EGRDIVIN_CC is the difference in the thermal energy described above. Therefore, the value is set to be smaller than the value for stratified self-ignition combustion EGRDIVIN_HCCI. Further, as described above, the homogeneous flame propagation combustion value EGRDIVIN_STK is set to a small value so that the internal EGR amount becomes substantially 0 in order to ensure the stability of combustion.

  Returning to FIG. 20, after calculating the internal EGR ratio EGRDIVIN as described above in step 81, the process proceeds to step 82 where the external EGR ratio EGRDIVEX is set to a value obtained by subtracting the internal EGR ratio EGRDIVIN from 1.

Next, the routine proceeds to step 83, where the internal EGR target value KEGRCMDIN is calculated by the following equation (1) based on the internal EGR ratio EGRDIVIN and the target fresh air rate KEGRCMD.
EGRDIVIN = 1- (1-KEGRCMD) · EGRDIVIN (1)

In step 84 following step 83, the external EGR target value KEGRCMDEX is calculated by the following equation (2) based on the external EGR ratio EGRDIVEX and the target fresh air rate KEGCMDM.
EGRDIVEX = 1- (1-KEGRCMD) · EGRDIVEX (2)

  Next, in step 85, a target rotation angle SAAEXCMD is calculated by searching a map (not shown) according to the internal EGR target value KEGCMDIN and the engine speed NE. Thereafter, at step 86, a target exhaust cam phase CAEXCMD is calculated by searching a map (not shown) according to the internal EGR target value KEGCMDIN and the engine speed NE.

  In step 87 subsequent to step 86, a target intake cam phase CAINCMD is calculated by searching a map (not shown) according to the internal EGR target value KEGRCMDIN and the engine speed NE.

  Next, at step 88, a target EGR lift LCMD is calculated by searching a map (not shown) according to the external EGR ratio EGRDIVEX and the intake pipe gauge pressure HPBGA, and then the present process is terminated. The intake pipe gauge pressure HPBGA is calculated based on the intake pipe pressure PBA and the atmospheric pressure PA.

  Next, the ignition timing control process described above will be described with reference to FIG. As shown in the figure, in this process, first, in step 110, it is determined whether or not an engine start flag F_ENGSTART is “1”. If the determination result is YES and the engine start control is being performed, the routine proceeds to step 111, where the ignition timing IG_LOG is set to a predetermined engine start value IG_CRK, and then this process is terminated.

  On the other hand, when the determination result of step 110 is NO, the process proceeds to step 112 to determine whether or not the catalyst warm-up flag F_FIREON is “1”. If the determination result is YES and the catalyst warm-up control is being performed, the routine proceeds to step 113, where the catalyst warm-up control value IG_FIRE at the ignition timing is calculated. This catalyst warm-up control value IG_FIRE is determined on the retard side so that the engine speed NE is maintained at a predetermined catalyst warm-up control speed and the heat capacity of the exhaust gas is increased by a calculation formula including a predetermined feedback control algorithm. Is calculated as the value of.

  Next, in step 114, the ignition timing IG_LOG is set to the catalyst warm-up control value IG_FIRE, and then this process is terminated.

  On the other hand, when the determination result in step 112 is NO, the process proceeds to step 115, the normal ignition timing control process is executed, and the present process is terminated. Specifically, the normal ignition timing control process is executed as shown in FIG.

  First, in step 120, it is determined whether or not the combustion mode value STS_BURNCMD is “1”. When the determination result is YES and the stratified self-ignition combustion mode is selected as the combustion mode of the engine 3, the routine proceeds to step 121, where a predetermined injection is performed based on the fuel injection timing for stratified self-ignition combustion, the engine speed NE, and the like. A stratified self-ignition combustion value IG_HCCI of the ignition timing is calculated by a calculation method. As described above, the stratified self-ignition combustion value IG_HCCI is calculated to a value that can prevent misfire in the stratified self-ignition combustion mode and appropriately control the self-ignition combustion timing.

  Next, the routine proceeds to step 122, where the ignition timing IG_LOG is set to the stratified self-ignition combustion value IG_HCCI, and then this processing is terminated.

  On the other hand, when the determination result of step 120 is NO, the process proceeds to step 123 to determine whether or not the combustion mode value STS_BURNCMD is “2”. If the determination result is YES and the stratified flame propagation combustion mode is selected, the routine proceeds to step 124, where the ignition timing is determined by a predetermined calculation method based on the fuel injection timing for stratified flame propagation combustion, the engine speed NE, and the like. The IG_DISC value for stratified flame propagation combustion is calculated.

  Next, the routine proceeds to step 125, where the ignition timing IG_LOG is set to the stratified flame propagation combustion value IG_DISC, and then this processing is terminated.

  On the other hand, when the determination result of step 123 is NO, the process proceeds to step 126 to determine whether or not the combustion mode value STS_BURNCMD is “3”. When the determination result is YES and the fire type self-ignition combustion mode is selected, the routine proceeds to step 127, and a predetermined calculation method is performed based on the fuel injection timing in the compression stroke for the fire type self-ignition combustion, the engine speed NE, and the like. Thus, the ignition type self-ignition combustion value IG_CC at the ignition timing is calculated.

  Next, the routine proceeds to step 128, where the ignition timing IG_LOG is set to the ignition type self-ignition combustion value IG_CC, and then this process is terminated.

  On the other hand, if the determination result in step 126 is NO and the homogeneous flame propagation combustion mode is selected, the process proceeds to step 129, and according to various operating state parameters such as the engine speed NE, the required torque PMCMD, and the engine water temperature TW. Then, the homogeneous flame propagation combustion value IG_STK of the ignition timing is calculated by a predetermined calculation method such as map search.

  Next, the routine proceeds to step 130, where the ignition timing IG_LOG is set to the homogeneous flame propagation combustion value IG_STK, and then this processing is terminated.

  As described above, in the present embodiment, the ECU 2 sets the value of the combustion mode value STS_BURNCMD according to the engine speed NE and the required torque PMCMD, and according to the value of the combustion mode value STS_BURNCMD set as such. Any one of the stratified self-ignition combustion mode, the stratified flame propagation combustion mode, the fire type self-ignition combustion mode and the homogeneous flame propagation combustion mode is selected, and the engine 3 is operated in the selected combustion mode. Various control processes are executed.

  At that time, in the supercharging pressure control process, the basic value LVNT_BASE of the nozzle opening command value of the variable nozzle mechanism 14 is set to one of the four values LVNT_HCCI, LVNT_DISC, LVNT_CC, and LVNT_STK according to the selected combustion mode. The nozzle opening command value LVNT_CMD is calculated by adding the feedback correction term LVNT_FB to the basic value LVNT_BASE. Since the variable nozzle mechanism 14 changes the kinetic energy received by the turbocharger 13 from the exhaust gas, the exhaust pressure in the exhaust pipe 16 changes according to the nozzle opening command value LVNT_CMD. As a result, the internal EGR amount or the internal EGR rate changes.

  That is, according to the supercharging pressure control device 1, the exhaust pressure can be controlled according to the selected combustion mode, whereby the amount of exhaust gas discharged from the combustion chamber 3g according to the combustion mode, In other words, the internal EGR amount or the internal EGR rate can be controlled. As a result, in the internal combustion engine 3 with the turbocharger 13, in any of the four combustion modes, the internal EGR amount or the internal EGR rate can be appropriately secured in addition to the intake air amount, and accordingly, Thus, it is possible to ensure a good combustion state and to ensure good exhaust gas characteristics and operability.

  Further, when the fire type self-ignition combustion mode is selected, the nozzle opening command value LVNT_CMD of the variable nozzle mechanism 14 is set to a smaller value than when the stratified self-ignition combustion mode is selected. In this case, in the ignition type self-ignition combustion mode, the stratified mixture is burned by spark ignition, and the homogeneous mixture is self-ignited and burned using the stratified mixture to be fired. Compared with the ignition combustion mode, the heat energy generated by the combustion of the air-fuel mixture becomes higher. As a result, the amount of internal EGR necessary to secure the heat energy in the combustion chamber 3g can be reduced. Accordingly, by setting the nozzle opening command value LVNT_CMD as described above, the nozzle opening command value of the variable nozzle mechanism 14 is set in accordance with the difference in thermal energy generated by the combustion of the air-fuel mixture between the two combustion modes. LVNT_CMD can be set appropriately, whereby the internal EGR amount can be appropriately ensured in both the stratified self-ignition combustion mode and the fire type self-ignition combustion mode.

  Furthermore, when the stratified self-ignition combustion mode or the stratified flame propagation combustion mode is selected, the basic value LVNT_BASE of the nozzle opening command value LVNT_CMD is set to a smaller value than when the homogeneous flame propagation combustion mode is selected. That is, the nozzle opening degree command value LVNT_CMD is set so that the degree of residual burned gas in the cylinder 3a becomes larger. In this case, since the in-cylinder temperature needs to be increased in order to generate self-ignition, the amount of internal EGR required to secure thermal energy in the combustion chamber is increased as compared with the homogeneous flame propagation combustion mode. Therefore, by setting the nozzle opening command value LVNT_CMD as described above, when the stratified self-ignition combustion mode or the stratified flame propagation combustion mode is selected, the cylinder is more effective than when the homogeneous flame propagation combustion mode is selected. Since the supercharging pressure can be controlled so that the degree of residual burned gas in the chamber increases, the internal EGR amount must be appropriately secured in both stratified self-ignition combustion mode and stratified flame propagation combustion mode. Can do.

  In addition, according to the supercharging pressure control device 1, after the engine 3 is started, the catalyst warm-up control process is executed so that the heat capacity of the exhaust gas supplied to the catalyst device 17 for exhaust gas purification is increased. 3 is operating, the nozzle opening command value LVNT_CMD is set to its maximum value LVNT_LMTH so that the kinetic energy received by the turbocharger 13 from the exhaust gas is minimized, so that the heat energy loss of the exhaust gas is minimized. The catalyst device 17 can be supplied while being suppressed, whereby the catalyst of the catalyst device 17 can be activated quickly.

  The embodiment is an example in which the variable nozzle mechanism 14 is used as the variable mechanism. However, the variable mechanism of the present invention is not limited to this, and any kinetic energy that the turbocharger can receive from the exhaust gas can be changed. Good. For example, a waste gate valve may be used as the variable mechanism.

  The embodiment is an example in which three variable mechanisms 50, 70, 90 are used as a mechanism for changing the internal EGR ratio EGRDIVIN, that is, the internal EGR amount. However, the mechanism for changing the internal EGR amount is not limited to these. Any device that can freely change the internal EGR amount can be used.

1 is a schematic diagram showing a schematic configuration of an internal combustion engine to which a supercharging pressure control device according to an embodiment of the present invention is applied. It is a block diagram which shows schematic structure of a supercharging pressure control apparatus. It is sectional drawing which shows schematic structure of the intake side valve mechanism and the exhaust side valve mechanism of an internal combustion engine. It is a schematic diagram which shows schematic structure of an intake side valve mechanism. It is a schematic diagram which shows schematic structure of an exhaust side valve operating mechanism. The valve lift curve of the intake valve when the intake cam phase is set to the most retarded value (solid line) and the most advanced value (two-dot chain line) by the intake cam phase variable mechanism, and the exhaust cam by the exhaust cam phase variable mechanism It is a figure which respectively shows the valve lift curve of an exhaust valve when a phase is set to the most retarded angle value (solid line) and the most advanced angle value (two-dot chain line). It is a figure which shows the change state of the exhaust lift by an exhaust lift variable mechanism. It is a flowchart which shows the control processing performed with a predetermined period by a timer setting. It is a flowchart which shows a supercharging control process. It is a flowchart which shows the calculation process of the basic value LVNT_BASE of a nozzle opening degree command value. It is a figure which shows an example of the map used for calculation of the value LVNT_HCCI for stratified self-ignition combustion of a nozzle opening degree command value. It is a figure which shows an example of the map used for calculation of the value LVNT_DISC for stratified flame propagation combustion of a nozzle opening degree command value. It is a figure which shows an example of the map used for calculation of the value LVNT_CC for fire type self-ignition combustion of a nozzle opening degree command value. It is a figure which shows an example of the map used for calculation of the value LVNT_STK for homogeneous flame propagation combustion of a nozzle opening degree command value. It is a figure which shows the relationship of three types of value LVNT_HCCI, LVNT_CC, and LVNT_STK with respect to request | requirement torque PMCMD in the case of NE = NEx. It is a flowchart which shows the control processing performed with the control period synchronized with generation | occurrence | production of a TDC signal. It is a figure which shows an example of the map used for calculation of request | requirement torque PMCMD. It is a flowchart which shows a fuel-injection control process. It is a flowchart which shows the fuel injection control process for normal use. It is a flowchart which shows an EGR control process. It is a flowchart which shows the calculation process of internal EGR ratio EGRDIVIN. It is a figure which shows an example of the map used for calculation of the value EGRDIVIN_HCCI for stratified self-ignition combustion of an internal EGR ratio. It is a figure which shows an example of the map used for calculation of the value EGRDIVIN_DISC for stratified flame propagation combustion of an internal EGR ratio. It is a figure which shows an example of the map used for calculation of the value EGRDIVIN_CC for the ignition type self-ignition combustion of an internal EGR ratio. It is a figure which shows an example of the map used for calculation of the value EGRDIVIN_STK for homogeneous flame propagation combustion of an internal EGR ratio. It is a flowchart which shows an ignition timing control process. It is a flowchart which shows a normal ignition timing control process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supercharging pressure control apparatus 2 ECU (Operating state parameter detection means, combustion mode selection means, supercharging pressure control means)
3 Internal combustion engine 3a Cylinder 13 Turbocharger 14 Variable nozzle mechanism (variable mechanism)
17 Catalytic device (catalyst)
20 Crank angle sensor (operating state parameter detecting means)
31 Accelerator opening sensor (operating state parameter detection means)
NE Engine speed (operating condition parameter)
AP accelerator opening (operating condition parameter)
LVNT_CMD Nozzle opening command value (operation amount of variable mechanism)
EGRDIVIN Internal EGR ratio (Ratio of residual amount of burned gas)

Claims (2)

The residual amount of burned gas generated in the cylinder can be changed freely, and the stratified self-ignition combustion mode in which the stratified mixture is burned by self-ignition and the stratified mixture is burned by spark ignition. A stratified flame propagating combustion mode, and an air-fuel mixture including both a stratified mixture and a homogeneous mixture , and the stratified mixture is burned by spark ignition, and the homogeneous mixture is burned using the combusted stratified mixture as a fire type. In an internal combustion engine with a turbocharger that can be operated by switching between a plurality of combustion modes including a self-ignition combustion mode for self-ignition combustion and a homogeneous flame propagation combustion mode for combusting a homogeneous mixture by spark ignition, A supercharging pressure control device for an internal combustion engine for controlling a supercharging pressure by a turbocharger,
A variable mechanism for changing the kinetic energy received by the turbocharger from the exhaust gas;
An operating state parameter detecting means for detecting an operating state parameter representing an operating state of the internal combustion engine;
Combustion mode selection means for selecting one of the plurality of combustion modes according to the detected operating state parameter;
A supercharging pressure control means for controlling the supercharging pressure by determining an operation amount of the variable mechanism in accordance with the selected combustion mode;
Equipped with a,
The supercharging pressure control means is configured such that when the fire type self-ignition combustion mode is selected, the residual degree of the burned gas in the cylinder is smaller than when the stratified self-ignition combustion mode is selected. Determining the amount of operation of the variable mechanism, and after the internal combustion engine is started, when the internal combustion engine is operated so that the heat capacity of the exhaust gas supplied to the exhaust gas purification catalyst is increased, the turbocharger is A boost pressure control device for an internal combustion engine , wherein an operation amount of the variable mechanism is determined so that kinetic energy received from exhaust gas is minimized . The supercharging pressure control means is configured such that when one of the stratified self-ignition combustion mode and the stratified flame propagation combustion mode is selected, the burned fuel in the cylinder is more than when the homogeneous flame propagation combustion mode is selected. 2. The supercharging pressure control device for an internal combustion engine according to claim 1 , wherein an operation amount of the variable mechanism is determined so that a residual degree of gas becomes large .

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