JP2007100524A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of improving operability by suppressing the occurrence of knocking even if a trouble lowering an external EGR amount occurs. <P>SOLUTION: This control device 1 for the internal combustion engine 3 comprises an ECU 2. The ECU 2 controls an exhaust gas recirculating mechanism 16, an intake cam phase variable mechanism 50, an exhaust lift variable mechanism 70, and an exhaust cam phase variable mechanism 90 according to the operating conditions of the engine 3 (steps 11, 184 to 191), determines whether a small external EGR trouble occurs or not in the exhaust recirculating mechanism 16 (steps 157 to 163), and sets a target air-fuel ratio KCMD according to the operating conditions of the internal combustion engine 3. When the small external EGR trouble occurs, the ECU 2 sets the target air-fuel ratio KCMD to a target air-fuel ratio KCMDMAP/KEGRCMD in trouble on the leaner side than a map value KCMDMAP (steps 70 to 73). The air-fuel ratio of the mixture is controlled according to the target air-fuel ratio KCMD (steps 24, 26). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls an internal EGR amount, an external EGR amount, and the like in an internal combustion engine in which an internal EGR amount and an external EGR amount can be changed by an internal EGR device and an external EGR device, respectively.

  Conventionally, what was described in patent document 1 is known as a control apparatus of an internal combustion engine. The internal combustion engine is provided with an intake cam phase variable mechanism and an exhaust gas recirculation mechanism. The intake cam phase variable mechanism changes the phase of the intake valve relative to the crankshaft (hereinafter referred to as “cam phase”), thereby The amount of burnt gas remaining in the cylinder (hereinafter referred to as “internal EGR amount”) is changed by changing the valve overlap. Further, the exhaust gas recirculation mechanism includes an EGR passage extending between the exhaust passage and the intake passage, and an EGR control valve that opens and closes the EGR passage. In this exhaust gas recirculation mechanism, the amount of exhaust gas recirculated from the exhaust passage to the intake passage (hereinafter referred to as “external EGR amount”) is changed by changing the opening of the EGR control valve (hereinafter referred to as “EGR opening”). Is done.

  In this control device, the internal EGR amount and the external EGR amount are controlled as described below. That is, according to the operating state of the internal combustion engine, the target cam phase that is the target of the cam phase and the target EGR opening that is the target of the EGR opening are set so that the cam phase becomes the target cam phase. The internal EGR amount is controlled via the intake cam phase variable mechanism, and the external EGR amount is controlled via the EGR control valve so that the EGR opening becomes the target EGR opening. Then, the absolute value of the deviation between the EGR opening and the target EGR opening is compared with a predetermined value. When the absolute value of the deviation is equal to or larger than the predetermined value, a failure occurs in which the EGR control valve is stuck in the opened state. When it is determined that the failure has occurred, the target cam phase is set to a value of 0. Accordingly, the cam phase is controlled to a value that minimizes the valve overlap via the intake cam phase variable mechanism. That is, control is performed so that the internal EGR amount is minimized.

JP 2004-360548 A

  According to the above-described conventional control device for an internal combustion engine, only the failure determination that the EGR control valve is stuck in the opened state, that is, the failure determination that the external EGR amount is excessive is executed, and such a failure occurs. When there is a failure in which the external EGR amount decreases and becomes too small, the total EGR amount is merely controlled to minimize the internal EGR amount via the intake cam phase variable mechanism. When the amount decreases, knocking is likely to occur, and as a result, there is a problem that drivability deteriorates. In particular, this problem may become prominent during high-load operation of the internal combustion engine.

  The present invention has been made in order to solve the above-described problems. Even when a failure that reduces the external EGR amount occurs, the control of the internal combustion engine that can suppress the occurrence of knocking and improve the drivability. An object is to provide an apparatus.

  In order to achieve the above object, the invention according to claim 1 is directed to an external EGR device (exhaust gas recirculation mechanism 16) that recirculates the exhaust gas discharged from the cylinder 3a into the cylinder 3a and changes the recirculation amount of the exhaust gas, An internal EGR device (an intake cam phase variable mechanism 50, an exhaust lift variable mechanism 70) that changes the residual amount of burned gas while causing the burned gas generated in the cylinder 3a to remain in the cylinder 3a as a gas having a temperature higher than that of the exhaust gas. , A control device 1 for an internal combustion engine 3 having an exhaust cam phase variable mechanism 90), which is a first operation state parameter (accelerator opening AP, engine speed NE, fresh air flow rate) representing an operation state of the internal combustion engine 3. EGR control means (ECU2, steps 11, 184 to 191) for controlling the external EGR device and the internal EGR device in accordance with GIN and intake pipe internal pressure PBA), respectively External EGR failure determination means (ECU 2, steps 157 to 163) for determining whether or not a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device, and a second operation state parameter representing the operation state of the internal combustion engine 3 In accordance with (accelerator opening AP, engine speed NE), the target air-fuel ratio KCMD that is the target of the air-fuel ratio of the air-fuel mixture in the internal combustion engine 3 is set, and the EGR failure determination means determines that the external EGR device has failed. When the target air-fuel ratio KCMD is set to the target air-fuel ratio for failure (KCMDMAP · KEGRCMD) leaner than the value set according to the second operating state parameter (map value KCMDMAP). The air-fuel ratio of the air-fuel mixture is set according to the fuel-fuel ratio setting means (ECU 2, steps 70 to 73) and the set target air-fuel ratio KCMD. Air-fuel ratio control means (ECU 2, step 24, 26) which Gosuru and, characterized in that it comprises a.

  According to this control device for an internal combustion engine, the air-fuel ratio of the air-fuel mixture is controlled according to the target air-fuel ratio, and this target air-fuel ratio is normally determined according to the second operating state parameter representing the operating state of the internal combustion engine. And when it is determined that a failure in which the exhaust gas recirculation amount decreases occurs in the external EGR device, the target air-fuel ratio for failure on the lean side than the value set according to the second operating state parameter Set to That is, when the recirculation amount of exhaust gas is reduced due to the failure of the external EGR device, the air-fuel ratio of the air-fuel mixture is controlled to a leaner value than when the external EGR device is normal, and the leaner mixture than when normal By supplying the air, unlike the conventional case, the occurrence of knocking can be suppressed. In particular, the occurrence of knocking can be suppressed even during high-load operation. As a result, the drivability can be improved (in this specification, “remaining burnt gas in the cylinder” means not only remaining burnt gas in the cylinder but also burnt gas). Is recirculated into the cylinder as a gas having a temperature higher than that of the exhaust gas recirculated by the external EGR device via a burned gas supply path in the cylinder head.

  According to a second aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first aspect, the EGR control means determines the amount of exhaust gas recirculated into the cylinder 3a and the inside of the cylinder 3a according to the first operating state parameter. The target EGR rate that is a target of a value that represents the ratio between the total EGR amount that is the sum of the burned gas amount remaining in the engine and the total gas amount that is the sum of the total EGR amount and the amount of fresh air sucked into the cylinder 3a In order to control the external EGR device and the internal EGR device according to the target EGR rate parameter setting means (ECU2, step 60) for setting the parameter (target value KEGCMD of the actual fresh air rate) and the set target EGR rate parameter EGR control value calculation means (ECU2, step 80) for calculating the EGR control value (feedback correction coefficient KEGRFB) of the engine, and third operation representing the operating state of the internal combustion engine 3. In accordance with the state parameters (accelerator opening AP, engine speed NE), the ratio of the exhaust gas amount to be recirculated by the external EGR device to the total EGR amount is set as the external EGR rate EGRDIVEX, and the existing EGR device should be retained by the internal EGR device. EGR ratio setting means (ECU2, steps 61 and 62) for setting a ratio of the fuel gas amount to the total EGR amount as an internal EGR ratio EGRDIVIN, and an external EGR device is set in accordance with the external EGR ratio and the EGR control value. In addition to controlling, the internal EGR device is controlled in accordance with the internal EGR ratio and the EGR control value (steps 63, 64, 81 to 94), and the external EGR failure determination means determines that the EGR control value is not within a predetermined range. (When the determination result of step 157 is YES), the external EGR ratio E When RDIVEX is larger than the internal EGR ratio EGRDIVIN (when the determination result of step 161 is NO), it is determined that a failure in which the exhaust gas recirculation amount decreases occurs in the external EGR device (step 163). To do.

  According to the control device for an internal combustion engine, when the EGR control value is not within the predetermined range and the external EGR ratio is larger than the internal EGR ratio, a failure in which the exhaust gas recirculation amount decreases occurs in the external EGR apparatus. It is determined. This EGR control value is a value for controlling the external EGR device and the internal EGR device. The total EGR amount, which is the sum of the amount of exhaust gas recirculated into the cylinder and the amount of burned gas remaining in the cylinder, The external EGR device is calculated according to the target EGR rate parameter, which is a target value representing the ratio between the EGR amount and the total gas amount that is the sum of the fresh air amount sucked into the cylinder. And the internal EGR device is controlled according to the internal EGR ratio and the EGR control value. Therefore, when the external EGR ratio is larger than the internal EGR ratio, it can be estimated that a failure state in which the EGR control value is not within the predetermined range is caused by a failure on the external EGR device side. By setting, it is possible to accurately determine that a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device.

  According to a third aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first aspect, the EGR control means determines the amount of exhaust gas recirculated into the cylinder 3a and the inside of the cylinder 3a according to the first operating state parameter. The target EGR rate that is a target of a value that represents the ratio between the total EGR amount that is the sum of the burned gas amount remaining in the engine and the total gas amount that is the sum of the total EGR amount and the amount of fresh air sucked into the cylinder 3a It has target EGR rate parameter setting means (ECU2, step 60) for setting a parameter (target value of actual fresh air rate KEGRCMD), and controls the external EGR device and the internal EGR device according to the set target EGR rate parameter. (ECU2, steps 60 to 64, 81 to 94), the target air-fuel ratio setting means determines that the external EGR device has failed by the external EGR failure determination means (step 71). If the other result is YES, the target air-fuel ratio for failure is set according to the target air-fuel ratio and the target EGR rate parameter set according to the second operating state parameter (step 72). It is characterized by.

  According to the control device for an internal combustion engine, when it is determined that the external EGR device and the internal EGR device are controlled according to the target EGR rate parameter, and a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device. The target air-fuel ratio for failure is set according to the target air-fuel ratio set according to the second operating state parameter and the target EGR rate parameter. In this case, the target EGR rate parameter is the sum of the total EGR amount, which is the sum of the exhaust gas amount recirculated into the cylinder and the burned gas amount remaining in the cylinder, and the sum of the total EGR amount and the fresh air amount sucked into the cylinder. Therefore, the target air-fuel ratio at the time of failure is set as the ratio between the total EGR amount and the total gas amount represented by the target EGR rate parameter, By setting according to the target air-fuel ratio set according to the operation state parameter, it is possible to set the value on the lean side so as to reliably cover the shortage of the reflux gas amount due to the failure of the external EGR device. Thus, the occurrence of knocking can be reliably suppressed. As a result, drivability can be further improved.

  According to a fourth aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first aspect, the target air-fuel ratio setting means determines the required output (required torque PMCMD) of the internal combustion engine 3 according to the second operating state parameter. ), And when the external EGR failure determination means determines that the external EGR device has failed, the required output setting means (ECU 2, steps 1 to 3) sets the required output to a predetermined limit value (limit value PMEXEGRLMT). ), The target air-fuel ratio is set according to the set required output, and when it is determined by the external EGR failure determination means that the external EGR device has failed, according to a predetermined limit value, A target air-fuel ratio of a practical value is set (steps 70 to 72).

  According to the control device for an internal combustion engine, when the required output of the internal combustion engine is set according to the second operating state parameter and it is determined that a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device, It is set to a predetermined limit value. The target air-fuel ratio is set in accordance with the required output, and when it is determined that a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device, the failure time value is set in accordance with a predetermined limit value. Since the target air-fuel ratio is set, the target air-fuel ratio of the failure time value can be set to a leaner value that is unlikely to cause knocking by appropriately setting a predetermined limit value. Thereby, even at the time of high load operation, it is possible to more reliably suppress the occurrence of knocking and improve drivability.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, the control device 1 includes an ECU 2. As will be described later, the ECU 2 performs an EGR control process or the like according to the operating state of the internal combustion engine (hereinafter referred to as "engine") 3. Various control processes 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 has a pair of intake valves 4 and 4 (only one is shown) and a pair of exhaust valves 7 and 7 (see FIG. 9), an intake camshaft 5 and an intake cam 6 provided for each cylinder 3a. 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). And a spark plug 11 (see FIG. 2).

  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 so as to rotate integrally therewith. Although not shown, the intake cam 6 is provided for each cylinder 3a and for each cylinder 3a. It consists of one high speed cam with a cam nose higher than the low speed cam.

  Further, the intake side valve mechanism 40 opens and closes the intake valves 4 of the respective cylinders 3a by the rotation of the intake camshaft 5 accompanying the rotation of the crankshaft 3d. And a variable valve mechanism that changes the valve timing of the intake valve 4 steplessly. In the present embodiment, “lift of intake valve 4 (hereinafter referred to as“ intake lift ”)” represents the maximum lift of intake valve 4.

  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. And a variable valve mechanism that changes the valve timing steplessly. In the present embodiment, the “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 cylinder 3a. 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 valve opening time and the valve opening timing are controlled by the ECU 2 based on a fuel injection amount TOUT described later. That is, the fuel injection time and the injection timing are controlled.

  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 combusted at a timing corresponding to the ignition timing.

  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. In the present embodiment, the engine speed NE corresponds to the first, second, and third operating state parameters. 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.

  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 and a throttle valve mechanism 13 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. In the present embodiment, the fresh air flow rate GIN corresponds to the first operating state parameter.

  Furthermore, the throttle valve mechanism 13 includes a throttle valve 13a and a TH actuator 13b for opening and closing the throttle valve 13a. The throttle valve 13a is rotatably provided in the middle of the intake pipe 12, and changes the fresh air flow rate in the intake pipe 12 by changing the opening degree accompanying the rotation. The TH actuator 13b is a combination of a motor connected to the ECU 2 and a gear mechanism (both not shown), and is driven by a TH control input U_TH described later from the ECU 2, thereby opening the throttle valve 13a. To change.

  The throttle valve 13a is provided with two springs (both not shown) for urging the throttle valve 13a in the valve opening direction and the valve closing direction, respectively. Due to the urging force of these two springs, the throttle valve 13a has a predetermined value when the TH control input U_TH is set to a value 0 or when the TH control input U_TH is not input to the TH actuator 13b, as will be described later. The initial opening is maintained. This initial opening is a value close to the fully closed state, and it is possible to appropriately perform idle operation and engine start while stopping, and at the same time secure an intake air amount that can maintain a low-speed driving state during driving. A possible value (for example, 6 °) is set.

  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 13 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. In the present embodiment, the intake pipe internal pressure PBA corresponds to the first operating state parameter.

  On the other hand, the exhaust pipe 14 of the engine 3 is provided with a LAF sensor 25 and a catalyst device 15 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 through the exhaust pipe 14 in a wide range of air-fuel ratios from a rich region richer than the stoichiometric 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. In this case, the detected air-fuel ratio KACT is specifically calculated as an equivalence ratio.

  Further, the engine 3 is provided with an exhaust gas recirculation mechanism 16 (external EGR device). The exhaust gas recirculation mechanism 16 recirculates the exhaust gas in the exhaust pipe 14 to the intake pipe 12 side, and opens and closes the EGR pipe 16a connected between the intake pipe 12 and the exhaust pipe 14 and the EGR pipe 16a. The EGR control valve 16b is configured. One end of the EGR pipe 16a opens to a part upstream of the catalyst device 15 of the exhaust pipe 14, and the other end opens to a part of the intake pipe 12 downstream of the throttle valve mechanism 13.

  The EGR control valve 16b is of a linear solenoid valve type, and its lift (hereinafter referred to as “EGR lift”) is between a maximum value and a minimum value according to an EGR lift control input U_LIFT described later from the ECU 2. It is configured to change linearly, thereby changing the opening of the EGR pipe 16a, that is, the exhaust gas recirculation amount (hereinafter referred to as "external EGR amount").

  An EGR lift sensor 26 is attached to the EGR control valve 16b, and the EGR lift sensor 26 detects an actual EGR lift LACT of the EGR control valve 16b 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 16b so that the EGR lift LACT converges on the target EGR lift LCMD. In the following description, recirculation of exhaust gas by the exhaust gas recirculation mechanism 16 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, an intake lift switching mechanism 41, an intake cam phase variable mechanism 50, and the like.

  The intake lift switching mechanism 41 is configured in the same manner as that already proposed by the present applicant in Japanese Patent Laid-Open No. 2000-227013 and the like, and detailed description thereof will be omitted. Two low-speed rocker arms 43 and 43 (only one is shown) and a high-speed rocker arm (not shown), which are movably attached, and an intake lift electromagnetic valve 44 (see FIG. 2) connected to the ECU 2 are provided.

  In the intake lift switching mechanism 41, the intake lift electromagnetic valve 44 is controlled by the intake lift control input U_VTEC from the ECU 2, whereby the operation mode of the intake lift switching mechanism 41 is switched to the low lift mode or the high lift mode. In this low lift mode, when the intake camshaft 5 rotates, the low-speed rocker arm 43 is driven by the low-speed cam and the high-speed rocker arm is driven by the high-speed cam, but the high-speed rocker arm is independent of the intake valve 4. Rotate around. Thereby, the intake valve 4 is driven to open and close by the low-speed rocker arm 43, and opens and closes with a predetermined lift and a predetermined valve opening time.

  On the other hand, in the high lift mode, when the intake camshaft 5 rotates, it is driven by the high-speed cam, so that the high-speed rocker arm rotates and the low-speed rocker arm 43 rotates together therewith. As a result, the intake valve 4 is driven to open and close by the high speed rocker arm via the low speed rocker arm 43, thereby opening and closing with a higher lift and a longer valve opening time than in the low lift mode. When the engine 3 is operated in a compression ignition combustion mode, which will be described later, the operation mode of the intake lift switching mechanism 41 is set to the low lift mode.

  Next, the intake cam phase varying mechanism 50 will be described. The intake cam phase variable mechanism 50 changes the relative phase of the intake camshaft 5 with respect to the crankshaft 3d (hereinafter referred to as “intake cam phase”) CAIN steplessly to the advance side or the retard side. It is provided at the end of the intake camshaft 5 on the intake sprocket side. As shown in FIG. 5, the intake cam phase varying mechanism 50 includes a housing 51, a three-blade vane 52, a hydraulic pump 53, an intake cam phase electromagnetic valve 54, and the like.

  The housing 51 is configured integrally with an intake sprocket on the intake camshaft 5 and includes three partition walls 51a formed at equal intervals. The vane 52 is coaxially attached to the end of the intake camshaft 5 on the intake sprocket side, extends radially outward from the intake camshaft 5, and is rotatably accommodated in the housing 51. Further, in the housing 51, three advance chambers 55 and three retard chambers 56 are formed between the partition walls 51 a and the vanes 52.

  The hydraulic pump 53 is of a mechanical type connected to the crankshaft 3d. When the crankshaft 3d rotates, along with this, the lubricating oil stored in the oil pan 3e of the engine 3 is supplied to the oil passage 57c. And is supplied to the intake cam phase solenoid valve 54 through the oil passage 57c in a state where the pressure is increased.

  The intake cam phase electromagnetic valve 54 is a combination of a spool valve mechanism 54a and a solenoid 54b, and is connected to the advance chamber 55 and the retard chamber 56 via the advance oil passage 57a and the retard oil passage 57b, respectively. The hydraulic pressure Poil supplied from the hydraulic pump 53 is output to the advance chamber 55 and the retard chamber 56 as the advance hydraulic pressure Pad and the retard hydraulic pressure Prt, respectively. The solenoid 54b of the intake cam phase electromagnetic valve 54 is electrically connected to the ECU 2 and moves the spool valve body of the spool valve mechanism 54a within a predetermined movement range by an intake phase control input U_CAIN described later from the ECU 2. Thus, both the advance hydraulic pressure Pad and the retard hydraulic pressure Prt are changed.

  In the intake cam phase variable mechanism 50 described above, during the operation of the hydraulic pump 53, the intake cam phase electromagnetic valve 54 operates according to the intake phase control input U_CAIN, whereby the advance hydraulic pressure Pad is retarded to the advance chamber 55. The hydraulic pressure Prt is supplied to the retard chamber 56, respectively, whereby the relative phase between the vane 52 and the housing 51 is changed to the advance side or the retard side. As a result, the aforementioned intake cam phase CAIN continuously changes between a predetermined maximum retardation value and a predetermined maximum advance value, whereby the valve timing of the intake valve 4 is indicated by a solid line in FIG. It is steplessly changed between the most retarded angle timing shown and the most advanced angle timing shown by the two-dot chain line in FIG.

  The intake cam phase variable mechanism 50 is provided with a lock mechanism (not shown), and the intake cam phase CAIN is held at a value corresponding to the intake phase control input U_CAIN by the lock mechanism. Furthermore, when the hydraulic pressure supplied from the hydraulic pump 53 is low, the intake phase control input U_CAIN is set to a value 0 as described later, or when U_CAIN is not input to the intake cam phase solenoid valve 54 due to disconnection or the like, the lock is applied. By the mechanism, the change of the intake cam phase CAIN by the intake cam phase variable mechanism 50 is prohibited, and the intake cam phase CAIN is held at a predetermined failure value.

  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. 7, 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. 10). 8 to 9, as shown in FIGS. 8 to 9, the control shaft 71 and the rocker arm shaft 72, the rocker arm mechanism 73 provided for each cylinder 3a on these shafts 71 and 72, and these An exhaust lift actuator 80 for simultaneously driving the rocker arm mechanism 73 is provided.

  The control shaft 71 is an assembly of a rotating shaft portion 71a, a holder portion 71b, and an eccentric shaft portion 71c. The control shaft 71 extends along the exhaust camshaft 8, and the rotating shaft portion 71a is rotatable to the cylinder head 3c. And one end thereof is coupled to the exhaust lift actuator 80.

  On the other hand, each rocker arm mechanism 73 is a combination of upper and lower rocker arms 74, 75. The upper rocker arm 74 includes a pair of links 74a, 74a, a roller shaft 74b, a roller 74c, and a pair of coil springs 74d, 74d. ing. Both ends of the roller shaft 74b are attached to one ends of the links 74a and 74a, respectively, and are rotatably supported by the links 74a and 74a. The roller 74c is rotatably provided on the roller shaft 74b.

  The other end of each link 74a is rotatably attached to an eccentric shaft portion 71c of the control shaft 71, and is connected to the holder portion 71b via a coil spring 74d. In the link 74a, the roller 74c abuts against the cam surface of the exhaust cam 9 by the biasing force of the coil spring 74d. When the roller 74c abuts against the base circle of the cam surface of the exhaust cam 9, the roller shaft 74b Is held at the origin position (position shown in FIG. 7) such that its axis is located on the axis of the rotation shaft portion 71a.

  On the other hand, one end of the lower rocker arm 75 is rotatably supported by the rocker arm shaft 72, and adjustment bolts 75a and 75a are attached to the other end, and these adjustment bolts 75a and 75a are used to It is in contact with the upper end of the exhaust valve 7.

  The lower rocker arm 75 includes a pair of guide portions 75b and 75b protruding upward. Each guide portion 75b has an upper surface serving as a guide surface 75c for guiding the roller shaft 74b of the upper rocker arm 74, and abuts against the roller shaft 74b via the guide surface 75c by the urging force of the valve spring 7e. . The guide surface 75c has a downwardly convex arc shape that coincides with an arc centered on the eccentric shaft portion 71c when the link 74a is in the valve-closing position indicated by the solid line in FIG. Further, in a state where the guide portion 75b and the roller shaft 74b are in contact with each other, the roller 74c is positioned between the guide portions 75b and 75b and contacts only the exhaust cam 9 without contacting the lower rocker arm 75.

  On the other hand, the exhaust lift actuator 80 is a combination of a motor and a reduction gear mechanism (both not shown) and is electrically connected to the ECU 2 and when driven by the ECU 2 as will be described later. The control shaft 71 is rotated around the rotation shaft portion 71a. As the control shaft 71 rotates, the link 74a also rotates about the roller shaft 74b.

  Next, the operation of the variable exhaust lift mechanism 70 configured as described above will be described. In this variable exhaust lift mechanism 70, when the exhaust lift actuator 80 is driven by an exhaust lift control input U_SAAEX described later from the ECU 2, the control shaft 71 rotates. At this time, the rotation angle SAAEX of the control shaft 71 is regulated within a predetermined range by a stopper (not shown), and accordingly, the rotation range of the link 74a is also, for example, when the roller shaft 74b is at the above-described origin position. Are regulated between a zero lift position indicated by a solid line and a maximum lift position indicated by a two-dot chain line in FIG.

  When the link 74a is in the zero lift position as described above, the exhaust cam 9 rotates, and when the roller nose 74c is pushed toward the rocker arm shaft 72 by the cam nose, the link 74a is rotated clockwise in FIG. 7 about the eccentric shaft portion 71c. To turn. At this time, as described above, since the guide surface 75c of the lower rocker arm 75 has a shape that coincides with an arc centered on the eccentric shaft portion 71c, the lower rocker arm 75 is moved by the urging force of the valve spring 7e. The valve is held in the closed position shown in FIG. 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 rotates from the zero lift position to the maximum lift position side and is held at that position, the link 74a is rotated around the eccentric shaft portion 71c by the rotation of the exhaust cam 9, and the timepiece of FIG. When rotating around, the lower rocker arm 75 rotates downward from the valve closing position shown in FIG. 7 while resisting the urging force of the valve spring 7 e, and opens the exhaust valve 7. At that time, the amount of rotation of the lower 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. 10, and the exhaust lift shows 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.

  The exhaust lift variable mechanism 70 is provided with a lock mechanism (not shown). When the exhaust lift control input U_SAAEX is set to a value 0 as will be described later, or due to a disconnection or the like. When the lift control input U_SAAEX is not input to the exhaust lift actuator 80, the rotation angle of the control shaft 71, that is, the exhaust lift is held at a predetermined failure value.

  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 an exhaust phase control input U_CAEX described later, 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.

  The exhaust cam phase variable mechanism 90 is provided with a lock mechanism (not shown). The lock mechanism holds the exhaust cam phase CAEX at a value corresponding to the exhaust phase control input U_CAEX. Further, when the exhaust phase control input U_CAEX is set to a value 0 as will be described later, or when the exhaust phase control input U_CAEX is not input to the exhaust cam phase electromagnetic valve 91 due to disconnection or the like, the exhaust cam phase can be varied by the lock mechanism. The change of the exhaust cam phase CAEX by the mechanism 90 is prohibited, and the exhaust cam phase CAEX is held at a predetermined failure value.

  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 this engine 3, the valve timing of the intake valve 4 can be changed steplessly by the intake cam phase variable mechanism 50, and the exhaust valve 7 is controlled by the exhaust lift variable mechanism 70 and the exhaust cam phase variable mechanism 90. The lift and valve timing can be changed steplessly, so that the amount of burned gas remaining in the cylinder 3a after the combustion stroke (hereinafter referred to as “internal EGR amount”) can be changed by the three variable mechanisms 50, 70, 90. It is configured so that it can be changed freely. In the present embodiment, the three variable mechanisms 50, 70, 90 correspond to the internal EGR device. Further, in the following description, letting the burned gas remain in the cylinder 3a by the three variable mechanisms 50, 70, 90 is referred to as “internal EGR”.

  Further, an atmospheric pressure sensor 30, an accelerator opening sensor 31, a throttle valve opening sensor 32, and an exhaust temperature sensor 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.

  The throttle valve opening sensor 32 is composed of a potentiometer, detects the opening TH of the throttle valve 13b (hereinafter referred to as “throttle valve opening”) TH, and outputs a detection signal representing it to the ECU 2. Further, the exhaust temperature sensor 33 detects the temperature (hereinafter referred to as “exhaust temperature”) TEX of the exhaust gas flowing in the exhaust pipe 14 and outputs a detection signal representing it to the ECU 2.

  On the other hand, the ECU 2 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O interface (all not shown), and the engine 2 according to the detection signals of the various sensors 20 to 33 described above. 3 is determined, and various control processes are executed.

  Specifically, the ECU 2 executes a fuel injection control process, an EGR 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. By these control processes, the engine 3 is operated in the compression ignition combustion mode in which the air-fuel mixture is combusted by the compression self-ignition without spark ignition when the execution condition of the compression ignition combustion described later is satisfied, and the compression ignition combustion. When the execution condition is not satisfied, the operation is performed in the spark ignition combustion mode in which the air-fuel mixture is combusted by spark ignition.

  In the present embodiment, the ECU 2 includes EGR control means, external EGR failure determination means, target air-fuel ratio setting means, air-fuel ratio control means, target EGR rate parameter setting means, EGR control value calculation means, EGR ratio setting means, and This corresponds to request output setting means.

  Hereinafter, a control process executed by the ECU 2 in a control cycle synchronized with the generation of the TDC signal will be described with reference to FIG. In addition, the various values calculated in the following description shall be memorize | stored in RAM of ECU2. In this process, first, in step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), it is determined whether or not an external EGR under-failure flag FS_EXEGRDN described later is “1”.

  When the determination result is NO, the process proceeds to step 2, and the required torque PMCMD is calculated by searching the map shown in FIG. 12 according to the engine speed NE and the accelerator pedal opening AP. Symbols i and j in the figure indicate positive integers, and this is the same in the following description. In this map, the required torque PMCMD is set as the indicated mean effective pressure, and 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.

  On the other hand, if the determination result in step 1 is YES and the external EGR amount is in an excessively small state due to the failure of the exhaust gas recirculation mechanism 16, the process proceeds to step 3 and the required torque PMCMD is set to a predetermined limit value PMEXEGRLMT. This limit value PMEXEGRLMT is set to a value that allows the target air-fuel ratio KCMD to be calculated as a leaner value than normal in the calculation of the target air-fuel ratio KCMD described later. In the present embodiment, the required torque PMCMD corresponds to the required output, and the limit value PMEXEGRLMT corresponds to the predetermined limit value.

  In step 4 following step 2 or 3, it is determined whether or not an EGR normal flag F_EGROK described later is “1”. When the determination result is YES and both the internal EGR and the external EGR are normally performed, the process proceeds to step 5 to determine whether or not the engine water temperature TW is higher than a predetermined temperature TWHCCI.

  When the determination result is YES and TW> TWHCCI, the process proceeds to step 6 to determine whether or not the exhaust gas temperature TEX is higher than the predetermined temperature TEXHCCI. If the determination result is YES and TEX> TEXHCCI, the process proceeds to step 7 where the engine 3 performs compression ignition combustion by searching the map shown in FIG. 13 according to the required torque PMCMD and the engine speed NE. It is determined whether or not it is in the HCCI operating region (region indicated by hatching in the figure).

  If the determination result is YES and the engine 3 is in the HCCI operation region in which compression ignition combustion is to be performed, it is determined that the execution condition for the compression ignition combustion operation is satisfied, and in step 8, the compression ignition combustion flag is used to express it. F_HCCI is set to “1”.

  On the other hand, when the determination result in any of the above steps 4 to 7 is NO, it is determined that the execution condition of the compression ignition combustion operation is not satisfied, and in step 9, the compression ignition combustion flag F_HCCI is set to “ Set to “0”.

  In step 10 following step 8 or 9, fuel injection control processing is executed. This fuel injection 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. To do.

  Next, in step 11, an EGR control process is executed. This EGR control process calculates a target EGR lift LCMD for controlling the external EGR amount via the exhaust gas recirculation mechanism 16, 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 failure determination of these four mechanisms 16, 50, 70, 90 is performed, and details thereof will be described later. .

  Next, the routine proceeds to step 12 where it is determined whether or not the compression ignition combustion flag F_HCCI described above is “1”. When the determination result is YES and the execution condition of the compression ignition combustion operation is satisfied, the ignition process by the spark plug 11 is stopped in step 13 and the present process is terminated. As a result, the engine 3 is operated in the compression ignition combustion mode.

  On the other hand, when the determination result of step 12 is NO, that is, when the execution condition of the compression ignition combustion operation is not established and the operation state is to execute the spark ignition combustion operation, the ignition timing control process is executed in step 14 Then, this process is terminated. Although details of the ignition timing control process are omitted here, the ignition timing is calculated according to the engine load and the like. As a result, the air-fuel mixture is ignited by the ignition plug 11 at the calculated ignition timing, and the engine 3 is operated in the spark ignition combustion mode.

  Hereinafter, the above-described fuel injection control process will be described with reference to FIG. In this process, first, at step 20, the basic fuel injection amount TIM is calculated. This basic fuel injection amount TIM is specifically calculated as shown in FIG.

  That is, first, in step 30, the intake fresh air amount GAIRCYL is calculated. The intake fresh air amount GAIRCYL is a fresh air amount estimated to be sucked into the cylinder 3a, and is calculated based on the fresh air flow rate GIN detected by the air flow sensor 22, the engine speed NE, and the like.

  Next, the routine proceeds to step 31, where the first basic fuel injection amount TIMAFMX is calculated by searching the map shown in FIG. 16 according to the intake fresh air amount GAIRCYL calculated at step 30. In this map, the first basic fuel injection amount TIMAFMX is set to a larger value as the intake fresh air amount GAIRCYL is larger. This is because the output required for the engine 3 increases as the intake fresh air amount GAIRCYL increases.

  Next, the routine proceeds to step 32, where it is determined whether or not the intake lift flag F_VTEC is “1”. The intake lift flag F_VTEC is set to “1” when the operation region of the engine 3 is in the region where the operation mode of the intake lift switching mechanism 41 is to be set to the above-described high lift mode, and is the region to be set to the low lift mode. Is set to “0”. In the drawing, the low lift mode is expressed as “LO.MD”, and the high lift mode is expressed as “HI.MD”.

  If the determination result in step 32 is NO and the operation mode of the intake lift switching mechanism 41 is an operation region in which the operation mode should be set to the low lift mode, the process proceeds to step 33, and is illustrated according to the engine speed NE and the intake cam phase CAIN. The fuel correction coefficient ATI for the low lift mode is calculated by searching the map that does not.

  Next, at step 34, a fuel correction term BTI for the low lift mode is calculated by searching a map (not shown) according to the engine speed NE and the intake cam phase CAIN.

  On the other hand, if the determination result in step 32 is YES and the operation mode of the intake lift switching mechanism 41 is an operation region in which the operation mode should be set to the high lift mode, the process proceeds to step 35, and according to the engine speed NE and the intake cam phase CAIN. The fuel correction coefficient ATI for the high lift mode is calculated by searching a map (not shown).

  Next, at step 36, a fuel correction term BTI for the high lift mode is calculated by searching a map (not shown) according to the engine speed NE and the intake cam phase CAIN.

  In step 37 following step 34 or 36, the sum (PBA · ATI + BTI) of the product of the intake pipe internal pressure and the fuel correction coefficient and the fuel correction term is set as the second basic fuel injection amount TIMBSX.

  Next, the routine proceeds to step 38, where it is determined whether or not the engine start flag F_ENGSTART is “1”. The engine start flag F_ENGSTART is set to “1” during engine start control, that is, during cranking, and is set to “0” otherwise. If the result of this determination is NO and the engine has already been started, the routine proceeds to step 39, where the basic fuel injection amount TIM is set to the second basic fuel injection amount TIMBSX, and then this processing ends.

  On the other hand, if the determination result in step 38 is YES and the engine start control is being performed, the basic fuel injection amount TIMSTX for start-up is calculated in step 40 by searching a map (not shown) according to the engine water temperature TW. To do. Next, in step 41, the basic fuel injection amount TIM is set to the starting basic fuel injection amount TIMSTX, and then the present process is terminated.

  Returning to FIG. 14, after calculating the basic fuel injection amount TIM as described above at step 20, the routine proceeds to step 21, where the actual fresh air rate KEGR is calculated. This actual fresh air rate KEGR corresponds to the ratio of the fresh air amount sucked into the cylinder 3a and the total gas amount (new air amount + internal EGR amount + external EGR amount), and from this value 1.0 A value obtained by subtracting the fresh air rate KEGR (1.0−KEGR) corresponds to a ratio between the total recirculation gas amount (internal EGR amount + external EGR amount) and the total gas amount, that is, the EGR rate. That is, the actual fresh air rate KEGR also represents the EGR rate, and is specifically calculated as shown in FIG.

That is, first, in step 50, the current calculated value KEGRORG of the actual fresh air rate KEGR is calculated by the following equation (1). Here, KTA is an intake air temperature correction coefficient, and is calculated by searching a map (not shown) according to the intake air temperature TA.

  Next, the routine proceeds to step 51, where it is determined whether or not the current calculated value KEGORG is a value of 1.0 or more. When the determination result is NO, the process proceeds to Step 53 described later. On the other hand, when the determination result is YES, in step 52, the current calculated value KEGORG is set to a value of 1.0, and then the process proceeds to step 53.

  In step 53 following step 51 or 52, the buffer value KEGR_TMPn (n = 1 to m) of m (m is a positive integer) number of current calculated values KEGRORG stored in the RAM is updated. Specifically, each buffer value in the RAM is set as a previous calculation value for one control cycle in the fuel injection control (for example, the current value KEGR_TMP1 of the buffer value is shifted to the previous value KEGR_TMP2, and the previous value KEGR_TMP2 Is shifted to the previous value KEGR_TMP3), and the current calculated value KEGRORG calculated in step 51 or 52 is set as the current value KEGR_TMP1 of the buffer value.

Next, the routine proceeds to step 54, where the moving average value KEGR_AVE of the buffer value KEGR_TMPn is calculated by the following equation (2).

  Next, in step 55, the actual fresh air rate KEGR is set to the moving average value KEGR_AVE calculated in step 54, and then this process is terminated.

  Returning to FIG. 14, after calculating the actual fresh air rate KEGR as described above in step 21, the process proceeds to step 22 to calculate the internal EGR target value KEGRCCMDIN and the external EGR target value KEGRCMDEX. These values KEGRCMDIN and KEGRCMDEX are specifically calculated as shown in FIG.

  That is, first, in step 60, a target value KEGCMD of the actual fresh air rate KEGR is calculated by searching a map shown in FIG. 19 according to the required torque PMCMD and the engine speed NE. This target value KEGRCMD is a value set so that 0 <KEGRCMD ≦ 1 is satisfied, and corresponds to a target EGR rate parameter in the present embodiment.

  Next, the routine proceeds to step 61, where an internal EGR ratio EGRDIVIN is calculated by searching a map shown in FIG. 20 according to the required torque PMCMD and the engine speed NE. Thereafter, in step 62, the external EGR ratio EGRDIVEX is set to a value obtained by subtracting the internal EGR ratio EGRDIVIN from the value 1.

Next, in step 63, based on the internal EGR ratio EGRDIVIN and the target value KEGRCMD, the internal EGR target value KEGRCMDIN is calculated by the following equation (3). That is, the internal EGR target value KEGRCMDIN corresponds to a value obtained by subtracting the target value of the ratio of the internal EGR amount in the total EGR amount from the value 1, in other words, it is assumed that the external EGR amount is controlled to the value 0. In this case, the control of the internal EGR amount corresponds to a target value of the ratio of the fresh air amount to be sucked into the cylinder 3a.

Next, in step 64, the external EGR target value KEGRCMDEX is calculated by the following equation (4) based on the external EGR ratio EGRDIVEX and the target value KEGRCMD, and then this process is terminated. That is, the external EGR target value KEGRCMDEX corresponds to a value obtained by subtracting the target value of the ratio of the external EGR amount to the total EGR amount from the value 1, in other words, the internal EGR amount is assumed to be controlled to the value 0. In this case, it corresponds to the target value of the ratio of the fresh air amount to be sucked into the cylinder 3a by controlling the external EGR amount.

  Returning to FIG. 14, after the two target values KEGRCMDIN and KEGRCMDEX are calculated in step 22 as described above, the process proceeds to step 23, where the target air-fuel ratio KCMD is calculated. Specifically, the target air-fuel ratio KCMD is calculated as shown in FIG.

  That is, first, in step 70, the map value KCMDMAP of the target air-fuel ratio is calculated by searching the map shown in FIG. 22 according to the required torque PMCMD and the engine speed NE. This map value KCMDMAP is set as an equivalence ratio.

  Next, the routine proceeds to step 71, where it is determined whether or not the external EGR under fault flag FS_EXEGRDN is “1”. If the determination result is YES and the external EGR amount is in an excessively small state due to a failure of the EGR control valve 16b, the routine proceeds to step 72, where the target air-fuel ratio KCMD is calculated as the product KCMDMAP of the map value and the target value of the actual fresh air rate. -After setting to KEGRCMD, this process is terminated. In this case, as described above, the target value KEGRCMD is set so that 0 <KEGRCMD ≦ 1 is satisfied, and thus the above values KCMDMAP · KEGRCMD are values on the lean side of the map value KCMDMAP.

  On the other hand, when the determination result of step 71 is NO, the process proceeds to step 73, the target air-fuel ratio KCMD is set to the map value KCMDMAP, and this process is terminated. As described above, the target air-fuel ratio KCMD is set to the map value KCMDMAP when the EGR control valve 16b is normal, and the value KCMDMAP · KEGRCMD that is leaner than the map value KCMDMAP when the external EGR amount has an excessively small failure. Set to In the present embodiment, the map value KCMDMAP corresponds to the target air-fuel ratio set according to the second operating state parameter, and the values KCMDMAP · KEGRCMD correspond to the target value for failure of the target air-fuel ratio.

  Returning to FIG. 14, after calculating the target air-fuel ratio KCMD as described above in step 23, the process proceeds to step 24 to calculate the air-fuel ratio correction coefficient KAF. Specifically, the air-fuel ratio correction coefficient KAF is calculated as described below.

  That is, when the execution condition of the air-fuel ratio feedback control is satisfied, the air-fuel ratio correction coefficient KAF causes a predetermined feedback control algorithm (not shown) (for example, PID control) to converge the detected air-fuel ratio KACT to the target air-fuel ratio KCMD. Algorithm or response assignment type control algorithm). On the other hand, when the execution condition of the air-fuel ratio feedback control is not satisfied, the air-fuel ratio correction coefficient KAF is set to a value 1.

  Next, the routine proceeds to step 25, where a total correction coefficient KTOTAL and a battery voltage correction term TIVB are calculated. The total correction coefficient KTOTAL calculates various correction coefficients by searching various maps according to various operation parameters (for example, intake air temperature TA, engine water temperature TW, atmospheric pressure PA, etc.), and It is calculated by multiplying various correction coefficients with each other. The battery voltage correction term TIVB is calculated by searching a map (not shown) according to the battery voltage.

Next, at step 26, the fuel injection amount TOUT is calculated by the following equation (5) based on the various values calculated as described above.

  In step 27 following step 26, it is determined whether or not the compression ignition combustion flag F_HCCI described above is “1”. When the determination result is YES and the execution condition of the compression ignition combustion operation is satisfied, the process proceeds to step 28, and the injection timing calculation process for compression ignition combustion is executed. Although not shown, in this step 28, the fuel injection end timing and the injection time by the fuel injection valve 10 are set to optimum values for compression ignition combustion based on the fuel injection amount TOUT calculated in the above step 26. Calculated. After executing step 28 as described above, the present process is terminated.

  On the other hand, when the determination result of step 27 is NO and the execution condition of the compression ignition combustion operation is not satisfied, the process proceeds to step 29, and the injection timing calculation process for spark ignition combustion is executed. Although not shown, in this step 29, the fuel injection end timing and injection time by the fuel injection valve 10 are set to optimum values for spark ignition combustion based on the fuel injection amount TOUT calculated in step 26 above. Calculated. After executing step 29 as described above, the present process is terminated.

  Hereinafter, the aforementioned EGR control process will be described with reference to FIG. In this process, first, in step 80, a feedback correction coefficient (hereinafter referred to as “FB correction coefficient”) KEGRFB calculation process is executed. The FB correction coefficient KEGRFB is a value for causing the actual fresh air rate KEGR to converge to the target value KEGCMD, and the specific contents of the calculation process will be described later. In the present embodiment, the FB correction coefficient KEGRFB corresponds to an EGR control value.

  Next, in step 81, it is determined whether or not the above-described internal EGR ratio EGRDIVIN is equal to or greater than 0.5. When the determination result is YES, that is, when the internal EGR amount is greater than or equal to the external EGR amount, in step 82, the aforementioned product of the internal EGR target value and the FB correction coefficient KEGRCCMDIN · KEGRRFB is set as the corrected internal EGR rate KEGRMAPIN. .

  On the other hand, when the determination result in step 81 is NO and the internal EGR amount is smaller than the external EGR amount, in step 83, the product KEGRCMDIN · KEGRREFIN between the internal EGR target value and the internal EGR learning value of the FB correction coefficient is corrected. It is set as the rear internal EGR rate KEGRMAPIN.

  In step 84 following step 82 or 83, it is determined whether or not the intake lift flag F_VTEC described above is “1”. When the determination result is NO and the intake lift switching mechanism 41 is set to the low lift mode, in step 85, according to the corrected internal EGR rate KEGRMAPIN calculated in step 82 or 83 and the engine speed NE, The target rotation angle SAAEXCMD for the low lift mode is calculated by searching the map shown in FIG. This target rotation angle SAAEXCMD is used as a target value for the rotation angle SAAEX, as will be described later.

  Next, the routine proceeds to step 86, where a target exhaust cam phase CAEXCMD for the low lift mode is calculated by searching the map shown in FIG. 25 according to the corrected internal EGR rate KEGRMAPIN and the engine speed NE. The target exhaust cam phase CAEXCMD is used as a target value for the exhaust cam phase CAEX, as will be described later.

  Next, at step 87, the target intake cam phase CAINCMD for the low lift mode is calculated by searching the map shown in FIG. 26 according to the corrected internal EGR rate KEGRMAPIN and the engine speed NE. The target intake cam phase CAINCMD is used as a target value for the intake cam phase CAIN, as will be described later.

  On the other hand, when the determination result in step 84 described above is YES and the intake lift switching mechanism 41 is set to the high lift mode, in steps 88 to 90, each predetermined value is determined according to the required torque PMCMD and the engine speed NE. By searching the map (not shown), the target rotation angle SAAEXCMD, the target exhaust cam phase CAEXCMD, and the target intake cam phase CAINCMD for the high lift mode are calculated.

  In step 91 following step 87 or 90 described above, it is determined whether or not the external EGR ratio EGRDIVEX is larger than 0.5. If the determination result is YES and the external EGR amount is larger than the internal EGR amount, the process proceeds to step 92, where the product of the external EGR target value and the FB correction coefficient KEGRCMDEX / KEGRRFB is set as the corrected external EGR rate KEGRMAPEX. .

  On the other hand, when the determination result in step 91 is NO and the external EGR amount is equal to or smaller than the internal EGR amount, the product KEGRCMDEX / KEGRREFEX of the external EGR target value and the external EGR learning value of the FB correction coefficient is corrected in step 93. It is set as the rear external EGR rate KEGRMAPEX.

  Next, after calculating the target EGR lift LCMD in step 94 by searching the map shown in FIG. 27 according to the corrected external EGR rate KEGRMAPEX calculated in step 92 or 93 and the intake pipe gauge pressure HPBGA, The process ends. The intake pipe gauge pressure HPBGA is calculated based on the intake pipe pressure PBA and the atmospheric pressure PA. Further, the target EGR lift LCMD is used as a target value for the EGR lift LACT, as will be described later.

  The processing for calculating the FB correction coefficient KEGRFB in step 80 of FIG. 23 will be described below with reference to FIGS. In this process, in addition to the FB correction coefficient KEGRFB, the internal EGR learning value KEGRREFIN and the external EGR learning value KEGRREFEX are calculated as described below. In this process, first, in step 100, it is determined whether or not the air-fuel ratio feedback flag F_LAFFB = 0 or the target value KEGRCMD = 1.0 of the actual fresh air rate KEGR is established.

  When the determination result is YES, that is, when F_LAFFB = 0 and air-fuel ratio feedback control based on the detected air-fuel ratio KACT of the LAF sensor 25 is not executed, or when KEGRCMD = 1.0, the internal EGR and the external EGR are When both are stopped, it is determined that the actual fresh air rate KEGR is not in the feedback control region, the process proceeds to step 113, the FB correction coefficient KEGRFB is set to a value of 1.0, and then this process ends.

  On the other hand, when the determination result in step 100 is NO, that is, when the air-fuel ratio feedback control is being executed and at least one of the internal EGR and the external EGR is being executed, in the following steps 101 to 106, the FB correction coefficient KEGRFB is calculated by the I-PD control algorithm.

  That is, first, in step 101, a P term gain KEIPDP, an I term gain KEIPDI, and a D term gain KEIPDD are calculated by searching respective maps (not shown) according to the engine speed NE and the required torque PMCMD. To do.

Next, in steps 102 to 104, using the P term gain KEIPDP, the I term gain KEIPDI, and the D term gain KEIPDD calculated in step 101, P terms KEGRFB_P, I terms KEGRFB_I, and D are expressed by the following equations (6) to (8). Each term KEGRFB_D is calculated. Note that KEGRZ1 in the following expressions (6) and (8) represents the previous value of the FB correction coefficient, and KEGRZ2 in the following expression (8) represents the previous value of the FB correction coefficient.

Next, in step 105, the I-PD term KEGRFB_S is calculated by the following equation (9) using the P term KEGRFB_P, the I term KEGRFB_I and the D term KEGRFB_D calculated in steps 102 to 104.

  Next, in step 106, the sum KEGRFB_S + KEGRFB_Z of the I-PD term and the previous value of the FB correction coefficient is set as the FB correction coefficient KEGRFB.

  Thereafter, in steps 107 and 108, the internal EGR learning value KEGRREFIN and the external EGR learning value KEGRREFEX of the FB correction coefficient KEGRFB are calculated, and limit check processing of the FB correction coefficient KEGRFB is performed. These specific processes will be described later.

  Next, proceeding to step 109 in FIG. 29, the external EGR failure flag FS_EXEGRFAIL, the external EGR excessive failure flag FS_EXEGRRO, the external EGR under-failure flag FS_EXEGRDN, and the internal EGR set as described later in the processing of step 107 or 108 above. It is determined whether or not any of the failure flag FS_INEGRFAIL, the internal EGR excessive failure flag FS_INEGRRO, and the internal EGR excessively small flag FS_INEGRDN is “1”.

  If the determination result is NO and all the above six flags are “0”, it is determined that both the internal EGR and the external EGR are normally performed, and in step 110, an EGR normal flag F_EGROK is set to indicate that. Set to “1”.

  On the other hand, when the determination result in step 109 is YES and any of the above six flags is “1”, the internal EGR and / or the external EGR are not performed normally, and in step 111, this is indicated. The EGR normal flag F_EGROK is set to “0”.

  In step 112 following step 110 or 111, the previous value KEGRZ1 of the actual fresh air rate is shifted to the previous value KEGRZ2, the actual fresh air rate KEGR is shifted to the previous value KEGRZ1, and the FB correction coefficient KEGRFB is shifted to the previous value KEGRFB_Z. Thereafter, this process is terminated.

  Hereinafter, the calculation process of the learning value KEGRREFIN for the internal EGR and the learning value KEGRREFEX for the external EGR of the FB correction coefficient KEGRFB in step 107 of FIG. 28 will be described with reference to FIG.

ここで、ＫＥＧＲＲＥＦＩＮＺは、内部ＥＧＲ用学習値ＫＥＧＲＲＥＦＩＮの前回値、ＣＲＥＦＥＧＲＩＮは、値０と値１．０の間に設定される所定の重み係数である。 In this process, first, in step 120, it is determined whether or not the internal EGR ratio EGRDIVIN is a value of 1.0. When the determination result is YES, that is, when only the internal EGR is being executed, the learning value for internal EGR KEGRREFIN is calculated by the following equation (10) at step 121.

Here, KEGRREFINZ is a previous value of the learning value for internal EGR KEGRREFIN, and CREFREFRIN is a predetermined weight coefficient set between a value of 0 and a value of 1.0.

  Next, in steps 122 to 127 below, limit check processing is performed on the internal EGR learning value KEGRREFIN calculated in step 121. That is, first, at step 122, it is determined whether or not the internal EGR learning value KEGRREFIN is equal to or smaller than a predetermined lower limit value KEGRREFINLL. When the determination result is NO, the process proceeds to step 123, where it is determined whether or not the internal EGR learning value KEGRREFIN is equal to or greater than a predetermined upper limit value KEGRREFINLH.

  When the determination result is NO, that is, when KEGRREFINLL <KEGRREFIN <KEGRREFINH is established, it is determined that the internal EGR is normally performed and, in step 124, the internal EGR failure flag FS_INEGRFAIL is set to “0”. Set to. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 123 is YES and KEGRREFIN ≧ KEGRREFINLH, the learning value for internal EGR KEGRREFIN is set to this upper limit value KEGRREFINLH in step 125.

  Next, assuming that the internal EGR is not normally performed, the process proceeds to step 126, and the internal EGR failure flag FS_INEGRFAIL is set to “1” to indicate that. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 122 is YES and KEGRREFIN ≦ KEGRREFINLL, the learning value for internal EGR KEGRREFIN is set to this lower limit value KEGRREFINLL in step 127.

  Next, assuming that the internal EGR is not normally performed, the internal EGR failure flag FS_INEGRFAIL is set to “1” to represent it in step 126 described above, and then the present process is terminated.

ここで、ＫＥＧＲＲＥＦＥＸＺは、外部ＥＧＲ用学習値ＫＥＧＲＲＥＦＥＸの前回値であり、ＣＲＥＦＥＧＲＥＸは、値０と値１．０の間に設定される所定の重み係数である。 On the other hand, when the determination result in step 120 is NO, it is determined in step 128 whether or not the external EGR ratio EGRDIVEX is 1.0. When the determination result is YES and only the external EGR is executed, the process proceeds to step 129, and the external EGR learning value KEGRREFEX is calculated by the following equation (11).

Here, KEGRREFEXZ is the previous value of the external EGR learning value KEGRREFEX, and CREFGREX is a predetermined weight coefficient set between a value of 0 and a value of 1.0.

  Next, in steps 130 to 135, the limit check process for the external EGR learning value KEGRREFEX is performed by the same method as in steps 122 to 127 described above. First, in step 130, it is determined whether or not the external EGR learning value KEGRREFEX is equal to or less than a predetermined lower limit value KEGRREFEXLL. When the determination result is NO, the process proceeds to step 131, where it is determined whether or not the external EGR learning value KEGRREFEX is equal to or greater than a predetermined upper limit value KEGRREFEXLH.

  If this determination result is NO and KEGRREFEXLL <KEGRREFEX <KEGRREFEXLH is established, it is determined that the external EGR is normally performed, and the process proceeds to step 132, and the external EGR failure flag FS_EXEGRFAIL is set to “0” to indicate that. set. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 131 is YES and KEGRREFEX ≧ KEGRREFEXLH, in step 133, the external EGR learning value KEGRREFEX is set to the upper limit value KEGRREFEXLH. Next, assuming that the external EGR is not normally performed, the process proceeds to step 134, and the external EGR failure flag FS_EXEGRFAIL is set to “1” to indicate that. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 130 is YES and KEGRREFEX ≦ KEGRREFEXLL, the routine proceeds to step 135, where the external EGR learning value KEGRREFEX is set to this lower limit value KEGRREFEXLL. Next, assuming that the external EGR is not normally performed, the process proceeds to the above-described step 134, and the external EGR failure flag FS_EXEGRFAIL is set to “1” to indicate that, and then this process is terminated.

  On the other hand, when the determination result of step 128 described above is NO and both the internal EGR and the external EGR are being executed, this processing is ended as it is. That is, in this case, the learning values KEGRREFIN and KEGRREFEX for internal EGR and external EGR are not calculated.

  The limit check process for the FB correction coefficient KEGRFB in step 108 in FIG. 28 will be described below with reference to FIG. In this process, first, in step 150, it is determined whether or not the FB correction coefficient KEGRFB is equal to or greater than a predetermined upper limit value KSTEPEIPDLH. When the determination result is YES, the process proceeds to step 151, and the FB correction coefficient KEGRFB is set to the upper limit value KSTEPIPDLH. Thereafter, in step 152, the counter value C_STEPEPC for determining an excessive failure is incremented.

  Next, the process proceeds to step 153, where it is determined whether or not the counter value C_STEPEPC exceeds a predetermined value STEPEPCONT. When this determination result is NO, this process is terminated as it is. On the other hand, when the determination result is YES, that is, when the number of times that the FB correction coefficient KEGRFB is equal to or greater than the upper limit value KSTEPEDDLH exceeds a predetermined number, an excessive failure stuck with an excessive EGR amount has occurred. Next, the routine proceeds to step 154, where it is determined whether or not the internal EGR ratio EGRDIVIN is larger than 0.5.

  If the determination result is YES and the internal EGR amount is larger than the external EGR amount, it is determined that there is a failure on the internal EGR side, and the process proceeds to step 155 to set the internal EGR excessive failure flag FS_INEGRRO to “1”. After the setting, the process is terminated.

  On the other hand, if the determination result in step 154 is NO and the external EGR amount is equal to or greater than the internal EGR amount, it is determined that the external EGR side is malfunctioning, and the process proceeds to step 156, and an external EGR excessive failure flag is used to indicate this. After FS_EXEGRO is set to “1”, this process ends.

  On the other hand, when the determination result in step 150 is NO, it is determined in step 157 whether or not the FB correction coefficient KEGRFB is equal to or less than a predetermined lower limit value KSTEPIPDLL. When the determination result is YES, the process proceeds to step 158, in which the FB correction coefficient KEGRFB is set to the lower limit value KSTEPEIPDLL. Next, at step 159, the counter value C_STEPEVO for determining an under-failure is incremented.

  Next, the routine proceeds to step 160, where it is determined whether or not the counter value C_STEPEVO has exceeded a predetermined value STEPEVOCONT. When this determination result is NO, this process is terminated as it is. On the other hand, when the determination result is YES, that is, when the number of times that the FB correction coefficient KEGRFB becomes equal to or lower than the lower limit value KSTEPEIPDLL exceeds a predetermined number, it is determined that an under-failure stuck with the EGR amount being too small has occurred Next, the routine proceeds to step 161, where it is determined whether or not the internal EGR ratio EGRDIVIN is larger than 0.5.

  If the determination result is YES and the internal EGR amount is larger than the external EGR amount, it is determined that the internal EGR side is malfunctioning, and in step 162, the internal EGR under-failure flag FS_INEGRDN is set to “1”. Set to. Thereafter, this process is terminated.

  On the other hand, if the determination result in step 161 is NO and the external EGR amount is equal to or greater than the internal EGR amount, it is determined that the external EGR side is a failure, and the process proceeds to step 163 to indicate the external EGR under-malfunction flag. After FS_EXEGRDN is set to “1”, this process ends.

  On the other hand, when the determination result of step 157 is NO, that is, when KSTEPIPDLL <KEGRFB <KSTEPEIPDLH is established, the process proceeds to step 164, and the counter values C_STEPEPC and C_STEPEVO for determining the over / under fault are set to 0 respectively. After resetting, this process ends.

  As described above, in the limit check process for the FB correction coefficient KEGRFB, when KSTEPIPDLH ≦ KEGRRFB and C_STEPEPC> STEPECCONT are both satisfied, it is determined that the internal EGR side is an excessive failure when EGRDIVIN> 0.5. When EGRDIVIN.ltoreq.0.5, it is determined that there is an excessive failure on the external EGR side. Further, in the case where KEGRFB ≦ KSTEPIPIPDLL and C_STEPEVO> STEPEVOCONT are both established, it is determined that the internal EGR side is a minor fault when EGRDIVIN> 0.5, and when EGRDIVIN ≦ 0.5, the external EGR side Is determined to be an under-malfunction.

  Hereinafter, with reference to FIG. 32, the six variable mechanisms of the present embodiment, that is, the throttle valve mechanism 13, the exhaust gas recirculation mechanism 16, the intake lift switching mechanism 41, the intake cam phase variable mechanism 50, the exhaust lift variable mechanism 70, and the exhaust cam. Processing for controlling each of the phase variable mechanisms 90 will be described. Specifically, as described below, this processing calculates six control inputs U_VTEC, U_SAAEX, U_CAEX, U_CAIN, U_LIFT, U_TH for controlling each of the six variable mechanisms. It is executed at a predetermined cycle (for example, 10 msec).

  In this process, first, in step 180, it is determined whether or not the variable mechanism failure flag F_VDNG is “1”. This variable mechanism failure flag F_VDNG is determined when at least one of the six variable mechanisms 13, 16, 41, 50, 70, 90 is failed based on the values of the various failure flags described above. And “1”.

  If the determination result in step 180 is NO and both of these variable mechanisms are normal, the process proceeds to step 181 to determine whether or not the intake lift flag F_VTEC is “1”. When the determination result is NO and the intake lift switching mechanism 41 is set to the low lift mode, the routine proceeds to step 182 where the intake lift control input U_VTEC is set to 0.

  On the other hand, if the determination result in step 181 is YES and the intake lift switching mechanism 41 is set to the high lift mode, the routine proceeds to step 183, where the intake lift control input U_VTEC is set to the predetermined value U_HIVT for the high lift mode.

  In step 184 following step 182 or 183, the target rotation angle SAAEXCMD calculated in step 85 or 88 of FIG. 23 described above is sampled. Thereafter, the process proceeds to step 185, and an exhaust lift control input U_SAAEX for controlling the variable exhaust lift mechanism 70 is calculated based on the target rotation angle SAAEXCMD and the rotation angle SAAEX. Specifically, the exhaust lift control input U_SAAEX is calculated by a predetermined feedback control algorithm (for example, a PID control algorithm or a response designating control algorithm) so that the rotation angle SAAEX converges to the target rotation angle SAAEXCMD.

  Next, at step 186, the target exhaust cam phase CAEXCMD calculated at step 86 or 89 of FIG. 23 is sampled. Thereafter, the process proceeds to step 187, and an exhaust phase control input U_CAEX for controlling the exhaust cam phase variable mechanism 90 is calculated by the same method as in step 185. That is, the exhaust phase control input U_CAEX is calculated by a predetermined feedback control algorithm so that the exhaust cam phase CAEX converges to the target exhaust cam phase CAEXCMD.

  In step 188 following step 187, the target intake cam phase CAINCMD calculated in step 87 or 90 of FIG. 23 is sampled. Thereafter, the process proceeds to step 189, and the intake phase control input U_CAIN for controlling the intake cam phase variable mechanism 50 is calculated by the same method as in steps 185 and 187. That is, the intake phase control input U_CAIN is calculated by a predetermined feedback control algorithm so that the intake cam phase CAIN converges to the target intake cam phase CAINCMD.

  Next, the process proceeds to step 190, and the target EGR lift LCMD calculated in step 94 of FIG. 23 is sampled. Thereafter, in step 191, an EGR lift control input U_LIFT for controlling the exhaust gas recirculation mechanism 16 is calculated by the same method as in steps 185, 187, and 189 described above. That is, the EGR lift control input U_LIFT is calculated by a predetermined feedback control algorithm so that the EGR lift LACT converges to the target EGR lift LCMD.

  Next, the process proceeds to step 192, and a TH control input U_TH for controlling the throttle valve mechanism 13 is calculated by the same method as in steps 185, 187, 189 and 191 described above. That is, a target throttle valve opening THCMD is calculated by map search (not shown) according to the required torque PMCMD and the engine speed NE, and a predetermined value is set so that the throttle valve opening TH converges to the target throttle valve opening THCMD. A TH control input U_TH is calculated by a feedback control algorithm. After calculating the TH control input U_TH as described above at step 192, the present process is terminated.

  On the other hand, if the determination result in step 180 described above is YES and at least one of the six variable mechanisms described above has failed, the process proceeds to step 193 and the six control inputs U_VTEC, U_SAAEX, U_CAEX, U_CAIN, U_LIFT, and U_TH are set. In either case, after setting the value to 0, the present process is terminated. As described above, when all of the six control inputs are set to the value 0, the predetermined intake air amount and the exhaust state are secured, so that the idling operation and the engine starting can be performed while the vehicle is stopped and the vehicle is running. Can continue low speed running.

  As described above, according to the control device 1 of the present embodiment, the target air-fuel ratio KCMD is calculated as the map value KCMDMAP that is searched for the map according to the required torque PMCMD and the engine speed NE during normal operation, When an EGR under-failure occurs, the product KCMDMAP · KEGRCMD of the map value and the target value of the actual fresh air rate is set. Then, the fuel injection amount TOUT is controlled so that the detected air-fuel ratio KACT converges to the target air-fuel ratio KCMD. That is, air-fuel ratio control is executed.

  As described above, when the external EGR amount is in an excessively small state due to the failure of the exhaust gas recirculation mechanism 16, the target air-fuel ratio KCMD is set to a leaner value than when it is normal, and the leaner mixture than when it is normal Unlike the conventional case, the occurrence of knocking can be suppressed by supplying the air into the cylinder 3a. In particular, the occurrence of knocking can be suppressed even during high-load operation.

  In addition to this, when an external EGR under-malfunction occurs, the required torque PMCMD is set to a predetermined limit value PMEXEGRLMT, and this limit value PMEXEGRLMT is a map value of the target air-fuel ratio searched according to this Since KCMDMAP is set to be a value on the lean side, the target air-fuel ratio KCMD when an external EGR under-malfunction has occurred can be reliably set to a value on the lean side that is less likely to cause knocking. it can. As a result, the occurrence of knocking can be more reliably suppressed even during high-load operation.

  Further, when an external EGR under-failure occurs, the target air-fuel ratio KCMD is set to the product KCMDMAP · KEGRCMD of the map value and the target value of the actual fresh air rate, and this target value KEGRCMD is the target of the actual fresh air rate KEGR. Therefore, the target air-fuel ratio KCMD can be set to a lean value that can reliably cover the shortage of the external EGR amount. The occurrence of knocking can be further reliably suppressed. As described above, drivability can be further improved.

  The embodiment is an example in which an intake cam phase variable mechanism 50, an exhaust lift variable mechanism 70, and an exhaust cam phase variable mechanism 90 for changing the amount of burnt gas remaining in the cylinder 3a are used as the internal EGR device. However, the internal EGR device of the present invention is not limited to this, and any device that can change the amount of burnt gas remaining in the cylinder may be used. For example, the burned gas may be left in the cylinder 3a by recirculating the burned gas as exhaust gas having a temperature higher than that of the external EGR through the recirculation path in the cylinder head, and a device capable of changing the remaining amount may be used.

  The embodiment is an example in which the exhaust gas recirculation mechanism 16 is used as an external EGR device. However, the external EGR device of the present invention is not limited to this, and exhaust gas having a temperature lower than that of the internal EGR is recirculated into the cylinder 3a. If it is.

  Furthermore, the embodiment is an example in which the accelerator opening AP, the engine speed NE, the fresh air flow rate GIN, the intake pipe internal pressure PBA, and the like are used as the first operating state parameter. It is not limited to that as long as it represents the operating state of the engine 3. For example, the engine water temperature TW may be used.

  The embodiment is an example in which the accelerator opening AP and the engine speed NE are used as the second and third operating state parameters, but the second and third operating state parameters are not limited to this, and the engine 3 may be used as long as it represents an operation state of 3. For example, an intake fresh air amount GAIRCYL, an intake pipe internal pressure PBA, or the like may be used.

  Further, the embodiment is an example in which the target air-fuel ratio at the time of failure is set to the product KCMDMAP · KEGRCMD of the target air-fuel ratio map value and the target value of the actual fresh air rate. The calculation method of the target air-fuel ratio is not limited to this, and any method may be used as long as it is calculated according to the target air-fuel ratio map value KCMDMAP and the actual fresh air rate target value KEGCMD. For example, the target air-fuel ratio for failure may be calculated by map search according to the target air-fuel ratio map value KCMDMAP and the actual fresh air rate target value KEGRCMD.

  In addition, the embodiment is an example in which the target value KEGRCMD of the actual fresh air rate is used as the target EGR rate parameter, but the target EGR rate parameter is not limited to this, and is a value representing the ratio between the total EGR amount and the total gas amount. Any value can be used as the target. For example, a value obtained by subtracting the target value KEGRCMD of the actual fresh air rate from the value 1 may be used as the target EGR rate parameter.

1 is a schematic diagram showing a schematic configuration of an internal combustion engine to which a control device according to an embodiment of the present invention is applied. It is a block diagram which shows schematic structure of a 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 intake cam phase variable 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 schematic diagram which shows schematic structure of an exhaust side valve operating mechanism. It is a perspective view which shows schematic structure of an exhaust lift variable mechanism. It is a perspective view which shows schematic structure of the link mechanism of an exhaust lift variable mechanism. 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 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 figure which shows an example of the map used for the driving | running | working area | region determination of an internal combustion engine. It is a flowchart which shows a fuel-injection control process. It is a flowchart which shows the calculation process of basic fuel injection amount TIM. It is a figure which shows an example of the map used for calculation of 1st basic fuel injection amount TIMAFMX. It is a flowchart which shows the calculation process of the actual fresh air rate KEGR. It is a flowchart which shows the calculation process of internal and external EGR target value KEGRCMDIN, KEGRCMDEX. It is a figure which shows an example of the map used for calculation of target value KEGRCMD. It is a figure which shows an example of the map used for calculation of internal EGR ratio EGRDIVIN. It is a flowchart which shows the calculation process of the target air fuel ratio KCMD. It is a figure which shows an example of the map used for calculation of the map value KCMDMAP of a target air fuel ratio. It is a flowchart which shows an EGR control process. It is a figure which shows an example of the map used for calculation of the target rotation angle SAAEXCMD for low lift modes. It is a figure which shows an example of the map used for calculation of the target exhaust cam phase CAEXCMD for low lift modes. It is a figure which shows an example of the map used for calculation of the target intake cam phase CAINCMD for low lift modes. It is a figure which shows an example of the map used for calculation of the target EGR lift LCMD. It is a flowchart which shows the calculation process of the feedback correction coefficient KEGRFB. It is a flowchart which shows the continuation of FIG. It is a flowchart which shows the calculation process of the learning value for internal and external EGR KEGRREFIN, KEGRREFEX. It is a flowchart which shows the limit check process of the feedback correction coefficient KEGRFB. It is a flowchart which shows a variable mechanism control process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 ECU (EGR control means, external EGR failure determination means, target air fuel ratio setting means, air fuel ratio control means, target EGR rate parameter setting means, EGR control value calculation means, EG
R ratio setting means, request output setting means)
3 Internal combustion engine 3a Cylinder 16 Exhaust gas recirculation mechanism (external EGR device)
50 Intake cam phase variable mechanism (internal EGR device)
70 Exhaust lift variable mechanism (internal EGR device)
90 Exhaust cam phase variable mechanism (internal EGR device)
NE engine speed (first, second and third operating state parameters
)
AP accelerator opening (first, second and third operating state parameters)
GIN fresh air flow (first operating condition parameter)
PBA intake pipe internal pressure (first operating state parameter)
KCMD Target air-fuel ratio KCMDMAP Target air-fuel ratio map value (set according to the second operating state parameter)
Specified value)
KEGRCMD Target value of actual fresh air rate (target EGR rate parameter)
KEGRFB feedback correction coefficient (value for EGR control)
KSTEPEIPDLL lower limit (value that defines a predetermined range)
EGRDIVEX External EGR ratio EGRDIVIN Internal EGR ratio
PMCMD Required torque (Requested output)
PMEXEGRLMT Predetermined limit value (predetermined limit value)

Claims (4)

The exhaust gas exhausted from the cylinder is recirculated into the cylinder, and the external EGR device that changes the recirculation amount of the exhaust gas, and the burned gas generated in the cylinder as a gas having a temperature higher than that of the exhaust gas are contained in the cylinder. A control device for an internal combustion engine having an internal EGR device for changing the residual amount of the burned gas,
EGR control means for controlling the external EGR device and the internal EGR device, respectively, according to a first operating state parameter representing an operating state of the internal combustion engine;
External EGR failure determination means for determining whether or not a failure in which the exhaust gas recirculation amount is reduced has occurred in the external EGR device;
A target air-fuel ratio that is a target of the air-fuel ratio of the air-fuel mixture in the internal combustion engine is set according to a second operating state parameter that represents the operating state of the internal combustion engine, and the external EGR device is configured by the EGR failure determination means. A target air-fuel ratio setting means for setting the target air-fuel ratio to a target air-fuel ratio for failure that is leaner than a value set according to the second operating state parameter when it is determined that a failure has occurred;
Air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture according to the set target air-fuel ratio;
A control device for an internal combustion engine, comprising: The EGR control means includes
In accordance with the first operating state parameter, a total EGR amount that is a sum of the exhaust gas amount recirculated into the cylinder and the burned gas amount remaining in the cylinder, the total EGR amount, and the cylinder Target EGR rate parameter setting means for setting a target EGR rate parameter that is a target of a value that represents a ratio to the total gas amount that is the sum of the amount of fresh air to be inhaled;
EGR control value calculating means for calculating an EGR control value for controlling the external EGR device and the internal EGR device according to the set target EGR rate parameter;
In accordance with the third operating state parameter representing the operating state of the internal combustion engine, the ratio of the exhaust gas amount to be recirculated by the external EGR device to the total EGR amount is set as the external EGR rate, and the residual by the internal EGR device. EGR ratio setting means for setting, as an internal EGR ratio, a ratio of the amount of burned gas to be made to the total EGR ratio, and controls the external EGR device in accordance with the external EGR ratio and the EGR control value And controlling the internal EGR device according to the internal EGR ratio and the EGR control value,
The external EGR failure determination means is configured such that when the EGR control value is not within a predetermined range and the external EGR rate is larger than the internal EGR rate, a failure in which the exhaust gas recirculation amount decreases is the external EGR device. 2. The control apparatus for an internal combustion engine according to claim 1, wherein it is determined that the engine has occurred. In accordance with the first operating state parameter, the EGR control means includes a total EGR amount that is a sum of the exhaust gas amount recirculated in the cylinder and the burned gas amount remaining in the cylinder, and the total EGR EGR ratio setting means for setting a target EGR rate parameter that is a target of a value representing a ratio between the amount and a total gas amount that is the sum of the fresh air amount sucked into the cylinder, and the set target EGR Controlling the external EGR device and the internal EGR device according to a rate parameter;
The target air-fuel ratio setting means sets the target air-fuel ratio for failure according to the second operating state parameter when the external EGR failure determination means determines that the external EGR device has failed. 2. The control device for an internal combustion engine according to claim 1, wherein the control device is set according to the target air-fuel ratio and the target EGR rate parameter.   The target air-fuel ratio setting means sets the required output of the internal combustion engine according to the second operating state parameter, and when the external EGR failure determination means determines that the external EGR device has failed, There is demand output setting means for setting the demand output to a predetermined limit value, the target air-fuel ratio is set according to the set demand output, and the external EGR device is controlled by the external EGR failure judgment means. 2. The control apparatus for an internal combustion engine according to claim 1, wherein when it is determined that a failure has occurred, a target air-fuel ratio of the failure value is set according to the predetermined limit value.

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