JP4274966B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls the ignition timing and the air-fuel ratio of the air-fuel mixture in accordance with the air-fuel ratio of the air-fuel mixture in the vicinity of an ignition plug in the combustion chamber of the internal combustion engine.

  Conventionally, as a control device for an internal combustion engine that controls the ignition timing and the air-fuel ratio, for example, the one described in Patent Document 1 is known. This control device includes an air-fuel ratio sensor for detecting the air-fuel ratio of the air-fuel mixture in the vicinity of the spark plug in the combustion chamber, and a control unit to which the air-fuel ratio sensor is connected.

  In this control apparatus, the target air-fuel ratio and ignition timing in the combustion cycle are determined by the control unit according to the operating state of the internal combustion engine, and the ignition timing in the combustion cycle is determined by the air-fuel ratio sensor. During the predetermined detection period, the air-fuel ratio of the air-fuel mixture near the spark plug is detected. Then, the minimum air-fuel ratio that is the richest value in the detected value of the air-fuel ratio of the air-fuel mixture is compared with the target air-fuel ratio, and when the minimum air-fuel ratio is a value that is richer than the target air-fuel ratio, In the fuel injection control in the next combustion cycle, the fuel injection timing is corrected so that the ignition timing coincides with the detection timing of the minimum air-fuel ratio. On the other hand, when the minimum air-fuel ratio is a value leaner than the target air-fuel ratio, in fuel injection control in the next combustion cycle, the deviation between the target air-fuel ratio and the average value of the air-fuel ratio during the detection period Based on this, the fuel injection amount is corrected.

Japanese Patent No. 2932887 (6 pages, FIG. 17)

  According to the conventional control device for an internal combustion engine, in the fuel injection control in the next combustion cycle, the fuel injection timing or the fuel is determined based on the comparison result between the detected value of the air-fuel ratio of the air-fuel mixture in the combustion cycle and the target air-fuel ratio. Since only the injection amount is corrected, in the combustion cycle, the ignition operation is forcibly executed at the ignition timing determined by the control unit regardless of the state of the air-fuel ratio of the air-fuel mixture. That is, since the air-fuel ratio state of the air-fuel mixture in the vicinity of the spark plug cannot be appropriately reflected in the ignition timing control in the combustion cycle, for example, when the operation state such as the transient operation state is not stable, Even when the air-fuel mixture at the ignition timing of the combustion cycle is too thin, the ignition operation may be executed. In such a case, good ignitability cannot be ensured, and the combustion efficiency may be deteriorated. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can improve the ignitability of an air-fuel mixture and thereby improve the combustion efficiency. And

In order to achieve the above object, the invention according to claim 1 is directed to a stratified combustion mode in which fuel is directly injected into the combustion chamber 3d and the air-fuel mixture in the combustion chamber 3d is stratified combustion, and a uniform combustion in which uniform combustion is performed. A control device 1 for an in-cylinder injection internal combustion engine 3 that can be operated by switching to a mode, which is an air-fuel ratio detection means (for example, an implementation) that detects an air-fuel ratio AF of an air-fuel mixture near a spark plug 10 in a combustion chamber 3d ECU 2, air-fuel ratio sensor 20), rotation angle position parameter detection means (ECU 2, crank angle sensor 40) for detecting a rotation angle position parameter representing the rotation angle position θCRK of the crankshaft 3 e of the internal combustion engine 3, and the internal combustion engine according to the three operating condition parameter indicative of an operating condition of the (engine speed N E), sets the ignition timing (final ignition timing ShitaIGCMD) ignition Determination means (ECU2, step 34) for determining whether the air-fuel mixture is in an ignitable state based on the detection result of the period setting means (ECU2, steps 22, 25, 27, 30) and the air-fuel ratio detection means And after the detected rotational angle position parameter has reached the ignition timing, the determination means determines that the air-fuel mixture is in an ignitable state (the determination result in step 33 is NO and the determination result in step 34) And an ignition control means (ECU2, step 35) for executing an ignition operation by the spark plug 10 when the internal combustion engine 3 is operated in the uniform combustion mode. When (when step 21 is NO), the ignition timing is set according to the required torque PMCMD required for the internal combustion engine 3 in addition to the operating state parameter ( Steps 22 to 25) .

According to this control apparatus for an internal combustion engine, the ignition timing is set by the ignition timing setting means according to the operating state of the internal combustion engine, and the determination means is used for mixing based on the detection result of the air-fuel ratio in the vicinity of the spark plug. It is determined whether or not the gas is in an ignitable state, and when it is determined that the air-fuel mixture is in an ignitable state after the rotation angle position parameter reaches the ignition timing, the ignition control means An ignition operation by the spark plug is executed. As described above, after the rotation angle position parameter reaches the ignition timing in the combustion cycle, the ignition operation is suspended and the mixture can be ignited until it is determined that the mixture is in an ignitable state. The ignition operation in the combustion cycle is executed when it is determined that the combustion state is in a state, so that the ignition operation is forcibly executed even when the air-fuel mixture at the ignition timing of the combustion cycle is too thin. Unlike those, good ignitability can be ensured, and thereby combustion efficiency can be improved. (In this specification, “detection of air-fuel ratio” means that the air-fuel ratio is directly detected by a sensor. And the air-fuel ratio is calculated by a program). Further, when the internal combustion engine is operated in the uniform combustion mode, the ignition timing is set according to the required torque required for the internal combustion engine in addition to the operation state parameter.

The invention according to claim 2 is the control device 1 for the internal combustion engine 3 according to claim 1, wherein the ignition timing setting means is operated when the internal combustion engine is operated in the stratified combustion mode (when step 21 is YES). Is characterized in that the ignition timing is set in accordance with the fuel injection timing (fuel injection end timing IJLOGD for the stratified combustion mode) into the combustion chamber 3d in addition to the operation state parameter (steps 27 to 30). .
According to the control device for an internal combustion engine, when the internal combustion engine is operated in the stratified combustion mode, the ignition timing is set according to the fuel injection timing into the combustion chamber in addition to the operation state parameter.

According to a third aspect of the present invention, in the control device 1 for the internal combustion engine 3 according to the first or second aspect, a value on the most retarded side that can ignite the air-fuel mixture is determined based on the ignition timing (final ignition timing θIGCMD). Threshold calculation means (ECU2, steps 26, 31) for calculating the threshold value θIGLMT is further provided, and the ignition control means can ignite the air-fuel mixture after the rotation angle position parameter reaches the ignition timing and by the determination means. If it is determined that the rotation angle position parameter has reached the threshold value θIGLMT (when steps 34 and 37 are NO), the ignition operation is executed (step 35). And
According to this control device for an internal combustion engine, after the rotation angle position parameter has reached the ignition timing, and when it is determined by the determination means that the air-fuel mixture is not in an ignitable state, the rotation angle position parameter is set. When the threshold is reached, an ignition operation is performed.

1 is a diagram illustrating a schematic configuration of a control device according to an embodiment of the present invention and an internal combustion engine to which the control device is applied. It is sectional drawing which shows schematic structure of an air fuel ratio sensor and a spark plug. It is (a) sectional drawing and (b) front view which show schematic structure of the front-end | tip part vicinity of an air fuel ratio sensor. It is a figure which shows an example of the relationship between the air fuel ratio of the air-fuel mixture detected by the air fuel ratio sensor, and the air fuel ratio of the exhaust gas detected by the exhaust gas analyzer. It is a flowchart which shows the calculation process of the air fuel ratio AF of the air-fuel mixture in the vicinity of the spark plug. It is a flowchart which shows an ignition timing control process. It is a figure which shows an example of the map used for calculation of basic ignition timing (theta) IGBASE for uniform combustion modes. It is a flowchart which shows the calculation process of request | requirement torque PMCMD. 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 calculation of the basic ignition timing (theta) IGBASE for stratified combustion modes. It is a flowchart which shows a fuel-injection control process. It is a flowchart which shows a swirl control process. It is a flowchart which shows an EGR control process.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. As will be described below, the control device 1 controls the ignition timing and the like according to the air-fuel ratio of the air-fuel mixture in the vicinity of the spark plug 10 of the internal combustion engine (hereinafter referred to as “engine”) 3. As shown, an ECU 2 is provided. The ECU 2 will be described later.

  The engine 3 is an in-line multi-cylinder gasoline engine mounted on a vehicle (not shown), and includes a plurality of sets of cylinders 3a and pistons 3b (only one set is shown). A combustion chamber 3d is formed in the cylinder head 3c of the cylinder 3a. The engine 3 is of a four-valve type, and the cylinder head 3c is provided with two intake valves 4 and two exhaust valves 6 for each cylinder 3a (only one is provided for each). (Illustrated).

  Each intake valve 4 opens and closes the intake port of the intake passage 5 with the rotation of a camshaft (not shown). When the intake valve 4 is opened, air is sucked into the combustion chamber 3d through the intake passage 5. Is done. Each exhaust valve 6 opens and closes the exhaust port of the exhaust passage 7 with the rotation of a camshaft (not shown). When the exhaust valve 6 is opened, the combustion gas in the combustion chamber 3d is moved to the exhaust passage 7 side. To be discharged.

  The cylinder head 3c is provided with a variable intake valve mechanism 13. This variable intake valve mechanism 13 changes the valve lift of one of the two intake valves 4 in each cylinder 3a (hereinafter referred to as “swirl control intake valve”) in a stepless manner. The configuration is the same as that proposed by the present applicant in Japanese Patent Application No. 2003-154286. The ECU 2 controls the swirl flow and the tumble flow in the combustion chamber 3d as will be described later by controlling the valve lift of the swirl control intake valve 4 via the variable intake valve mechanism 13. In the following description, both swirl flow control and tumble flow control are collectively referred to as “swirl control”.

  Furthermore, a fuel injection valve 8 and a spark plug 10 are attached to the cylinder head 3c so as to face the combustion chamber 3d. In the engine 3, fuel (gasoline) is directly injected into the combustion chamber 3 d by opening the fuel injection valve 8. That is, the engine 3 is configured as a so-called direct injection engine. The fuel injection valve 8 is connected to the ECU 2, and a drive signal from the ECU 2 is supplied to the fuel injection valve 8 during operation of the engine 3. Thereby, the fuel injection amount of the fuel injection valve 8 is controlled.

  The spark plug 10 is connected to the ECU 2 via an ignition coil 9 and includes a center electrode 11 and a ground electrode 12 at the lower end thereof as shown in FIG. The center electrode 11 and the ground electrode 12 are provided with a predetermined gap between them. During operation of the engine 3, the center electrode 11 of the spark plug 10 is discharged when an ignition control signal (voltage signal) from the ECU 2 is applied via the ignition coil 9, and generates a spark between the center electrode 11 and the ground electrode 12. Thereby, the air-fuel mixture in the combustion chamber 3d is combusted.

  Further, the spark plug 10 is provided with an air-fuel ratio sensor 20 as air-fuel ratio detection means. As shown in FIGS. 2 and 3 (a) and 3 (b), the air-fuel ratio sensor 20 includes a hollow cylindrical cable case 21 extending through the spark plug 10 in the vertical direction, and the cable case 21. The optical fiber cable 22 accommodated and the holder 26 etc. which were attached to the lower end part of the cable case 21 so that attachment or detachment were possible were provided. In FIG. 2 and FIG. 3A, the cross-sectional hatching is omitted as appropriate for easy understanding.

  The cable case 21 is made of a heat-resistant metal (for example, stainless steel) and is housed in the spark plug 10 in an airtight state. The cable case 21 includes a main portion 21a having a constant diameter and a mounting portion 21b extending downward from the lower end thereof. I have. The inner diameter and outer diameter of the mounting portion 21b are formed to be smaller than the main portion 21a.

  The optical fiber cable 22 is housed in an airtight state in the main portion 21a of the cable case 21, and extends over the entire main portion 21a. The portion extending outward from the spark plug 10 includes two optical fiber cables 22a, Branches to 22b. The tip ends of these optical fiber cables 22a and 22b are connected to a light emitter 31 and a light receiver 32, which will be described later.

  The optical fiber cable 22 includes a protective layer 23 and light-emitting and light-receiving optical fibers 24 and 25 built in the center thereof. The protective layer 23 is for protecting the optical fibers 24 and 25 on the light emitting side and the light receiving side, and is made of a heat-resistant material (for example, stainless steel or zirconia ceramics). The optical fibers 24 and 25 on the light emitting side and the light receiving side are made of silica-based fibers having heat resistance.

  The light-emitting side optical fiber 24 extends in the optical fiber cables 22 and 22 a, and an end portion (hereinafter referred to as “light-emitting end portion”) 24 a on the combustion chamber 3 d side is an inner hole of the attachment portion 21 b of the cable case 21. The end opposite to the light emitting end 24 a is connected to the light emitter 31. The optical fiber 25 on the light receiving side extends in the optical fiber cables 22 and 22b, and is disposed in the optical fiber cable 22 so as to be adjacent to the optical fiber 24 on the light emitting side. Further, the optical fiber 25 on the light receiving side has a mounting portion 21b in a state where an end portion (hereinafter referred to as “light receiving end portion”) 25a on the combustion chamber 3d side is adjacent to the light emitting end portion 24a of the light emitting side optical fiber 24. The end opposite to the light receiving end 25 a is connected to the light receiver 32.

  On the other hand, the holder 26 is a bottomed one formed in a hollow cylindrical shape, and its upper half is a sapphire holder 26a that holds the sapphire 27 inside, and its lower half is sapphire. A reflecting mirror holder 26b that holds the reflecting mirror 28 inside is integrated with the holder 26a.

  A fitting portion 21b of the cable case 21 is fitted into the inner hole of the sapphire holder 26a, and two female screw holes are formed in the fitting portion of the fitting portion 21b. Screws 29, 29 are screwed into these female screw holes in a state of passing through the sapphire holder 26a and tightened. Thereby, the sapphire holder 26a is detachably attached to the attachment portion 21b via the screws 29, 29, and the holder 26 is detached from the cable case 21 by removing the screws 29, 29 during maintenance. It is. An annular step 26c is formed at the lower end of the inner wall of the sapphire holder 26a so as to protrude inward.

  The sapphire 27 is for protecting the light emitting end 24a and the light receiving end 25a of the two optical fibers 24, 25, and is formed in a cylindrical shape. Washers 30 and 30 are accommodated in a state compressed in the vertical direction between the upper end surface of the sapphire 27 and the lower end surface of the attachment portion 21b and between the lower end surface of the sapphire 27 and the upper surface of the step portion 26c. Has been. These washers 30 and 30 are made of a heat-resistant material (for example, copper), and the inside of the optical fiber cable 22, sapphire 27, and sapphire holder 26 a is formed by the sealing properties of these washers 30 and 30. The space is kept airtight with respect to the combustion chamber 3d. That is, the light emitting end 24a and the light receiving end 25a of the two optical fibers 24 and 25 are configured not to be directly exposed to the air-fuel mixture in the combustion chamber 3d.

  On the other hand, the reflector holder 26b has a detection hole 26d that opens toward the electrodes 11 and 12 side. The detection hole 26d is formed in a substantially semi-cylindrical shape, and the air-fuel mixture near the electrodes 11 and 12 in the combustion chamber 3d is introduced into the reflector holder 26b through the detection hole 26d. The reflecting mirror 28 is disc-shaped and is accommodated in the lower half of the reflecting mirror holder 26b, and is positioned at a position facing the light emitting end 24a and the light receiving end 25a of the optical fibers 24 and 25. Are arranged at predetermined intervals. The reflecting mirror 28 has a substantially spherical reflecting surface 28a whose upper surface is concave downward, and the infrared laser beam emitted from the light emitting end 24a is transmitted to the light receiving end 25a by the reflecting surface 28a. The light is reflected at a very small predetermined reflection angle (≈0 °).

The light emitter 31 described above is composed of a He—Ne laser and is electrically connected to the ECU 2. When driven by a drive signal from the ECU 2, the light emitter 31 emits an infrared laser beam having a wavelength of 3.39 μm to a predetermined intensity. The light is emitted to the optical fiber 24 on the light emission side at I ₀ .

  Further, the light receiver 32 includes a photoelectric conversion circuit and a band-pass filter (both not shown) and is electrically connected to the ECU 2 and receives an infrared laser beam from the optical fiber 25 on the light receiving side. Then, a detection signal indicating the intensity I of the received infrared laser beam is output to the ECU 2.

Next, the detection operation and the detection principle of the air-fuel ratio sensor 20 as described above will be described. When the air-fuel mixture is generated in the combustion chamber 3d by opening the intake valve 4 and the fuel injection valve 8 while the engine 3 is in operation, the ECU 2 drives the light emitter 31 and has a predetermined intensity I ₀ at a wavelength of 3.39 μm. The infrared laser beam is emitted from the light emitter 31 to the optical fiber 24 side of the light emission side.

  This infrared laser beam is emitted from the light emitting end 24a of the light-emitting optical fiber 24 toward the reflecting mirror 28 in the combustion chamber 3d, passes through the sapphire 27, and reaches the reflecting surface 28a of the reflecting mirror 28. At this time, since the air-fuel mixture in the combustion chamber 3d enters the detection hole 26d between the sapphire 27 and the reflecting mirror 28, the infrared laser beam passes through the air-fuel mixture. Next, the infrared laser beam is reflected by the reflecting surface 28a toward the optical fiber 25 on the light receiving side, passes through the mixture again, and then enters the optical fiber 25 from the light receiving end 25a of the optical fiber 25 on the light receiving side. And reaches the light receiver 32 through this. The light receiver 32 outputs a detection signal indicating the intensity I of the received infrared laser beam to the ECU 2.

The ECU 2 uses the following formulas (1) and (2) based on the ratio (that is, transmittance) I / I ₀ of the received infrared laser beam intensity I to the predetermined intensity I ₀ of the infrared laser beam when the light emitter 31 emits light. ) To calculate the air-fuel ratio AF of the air-fuel mixture near the spark plug 10.
log (I / I ₀ ) = − ε · L · C (1)
AF = [(2 · Q) / (NE · Ncy)] / (C · Vs · Mf) (2)
In Expression (1), ε represents the molar absorption coefficient, L represents the transmission distance of the mixture of the infrared laser beam, and C represents the gasoline concentration of the mixture. In Expression (2), Q is the intake pipe flow rate (mass flow rate) calculated from the intake pipe absolute pressure PBA, NE is the number of revolutions of the engine 3, Ncy is the number of cylinders of the engine 3, and Vs is the cylinder 3a. , Mf represents gasoline mass. In the case of the air-fuel ratio sensor 20 of the present embodiment, the transmission distance L is a value that is approximately twice the distance Lc between the lower end surface of the sapphire 27 and the central portion of the reflecting surface 28a shown in FIG. This corresponds to (2 · Lc≈L).

  FIG. 4 shows the vicinity of the spark plug 10 detected by using the air-fuel ratio sensor 20 as described above when the engine 3 is in a predetermined operating state (the rotation speed is 1500 rpm and the intake pipe internal pressure is −400 hPa). It shows the relationship between the air-fuel ratio of the air-fuel mixture and the air-fuel ratio of the exhaust gas detected by the exhaust gas analyzer. As can be seen from the figure, the air-fuel ratio of the air-fuel mixture shows substantially the same value as the air-fuel ratio of the exhaust gas, and the air-fuel ratio sensor 20 of this embodiment uses the actual air-fuel mixture in the combustion chamber 3d. It can be seen that the air-fuel ratio AF is accurately detected. That is, it was demonstrated that the air-fuel ratio sensor 20 has high detection accuracy.

  The engine 3 includes an EGR control valve 14 and a throttle valve mechanism 15. The EGR control valve 14 opens and closes an EGR passage (not shown) extending between the exhaust passage 7 and the intake passage 5 to perform an EGR operation for returning the exhaust gas from the exhaust passage 7 to the intake passage 5 side. Is. The EGR control valve 14 is composed of a linear electromagnetic valve and is connected to the ECU 2, and its valve lift changes linearly in response to a drive signal from the ECU 2. The ECU 2 controls the EGR amount by controlling the valve lift of the EGR control valve 14 as will be described later.

  On the other hand, the throttle valve mechanism 15 includes a throttle valve and a motor (both not shown). The throttle valve is rotatably provided in the intake passage 5 and changes the amount of intake air flowing through the intake passage 5 by a change in opening degree associated with the rotation. The motor is connected to the ECU 2 and is controlled by a drive signal from the ECU 2 to change the opening of the throttle valve.

  Further, the ECU 2 includes a crank angle sensor 40, an accelerator opening sensor 41, a water temperature sensor 42, an intake air temperature sensor 43, an intake pipe absolute pressure sensor 44, an air flow sensor 45, an intake valve lift sensor 46, and an EGR valve lift sensor 47, respectively. It is connected.

  The crank angle sensor 40 (rotation angle position parameter detection means) outputs a CRK signal and a TDC signal, both of which are pulse signals, to the ECU 2 as the crankshaft 3e of the engine 3 rotates. One pulse of the CRK signal is output every predetermined crank angle (for example, 1 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. This engine speed NE corresponds to an operating state parameter.

  The TDC signal is a signal indicating that the piston 3b of each cylinder 3a is at a predetermined crank angle position slightly before the TDC position of the intake stroke, and one pulse is output for each predetermined crank angle. The ECU 2 calculates a rotational angle position (hereinafter referred to as “crank angle position”) θCRK of the crankshaft 3e based on the TDC signal and the CRK signal. The crank angle position θCRK (rotational angle position parameter) is calculated using the position when the TDC signal is generated at the start of the combustion cycle as a reference (0 °).

  The accelerator opening sensor 41, the water temperature sensor 42, and the intake air temperature sensor 43 are respectively a depression amount (hereinafter referred to as “accelerator opening”) AP of the accelerator pedal (not shown) of the vehicle, and the temperature of the cooling water circulating in the cylinder block of the engine 3. Detection signals representing the engine water temperature TW and the intake air temperature TA are output to the ECU 2.

  The intake pipe absolute pressure sensor 44 outputs a detection signal representing the absolute pressure in the intake passage 5, that is, the absolute pressure in the intake pipe (not shown) PBA (hereinafter referred to as "absolute pressure in the intake pipe") to the ECU 2, and the air flow sensor 45 Outputs a detection signal representing the amount of intake air passing through the throttle valve (hereinafter referred to as “TH passage intake air amount”) GTH to the ECU 2.

  Further, the intake valve lift sensor 46 outputs a detection signal representing the actual valve lift (hereinafter referred to as “intake valve lift”) LIN of the intake valve 4 for swirl control to the ECU 2, and the EGR valve lift sensor 47 performs EGR control. A detection signal indicating the actual valve lift (hereinafter referred to as “EGR valve lift”) LEGR of the valve 14 is output to the ECU 2.

  On the other hand, the ECU 2 is composed of a microcomputer including an I / O interface, a CPU, a RAM, and a ROM (all not shown), and a ROM according to the detection signals of the various sensors 20, 40 to 47 described above. Various arithmetic processes and control processes are executed based on the control program stored in the program.

  Specifically, as will be described later, the air-fuel ratio AF of the air-fuel mixture near the spark plug 10 is calculated based on the detection signal of the air-fuel ratio sensor 20. Further, the operating state of the engine 3 is determined based on the above various detection signals, and based on the determination result, the combustion mode of the engine 3 is changed to the stratified combustion mode at the extremely low load operation, and the uniform combustion at the other operation. Switch to each mode. Further, fuel injection control, ignition timing control, swirl control, EGR control, and the like are executed according to the combustion mode.

  In this stratified combustion mode, fuel is injected from the fuel injection valve 8 into the combustion chamber 3d during the compression stroke, and a fuel jet is formed by causing most of the injected fuel to collide with the recess 3f at the upper end of the piston 3b. The The fuel jet flow, swirl flow and tumble flow by swirl control generate a stratified mixture, and the piston 3b is located near the top dead center of the compression stroke, so that the surroundings of the stratified mixture However, a portion having a high gasoline concentration is burned while being unevenly distributed in the vicinity of the spark plug 10. As a result, combustion is performed at an air / fuel ratio (for example, 65) that is extremely leaner than the stoichiometric air / fuel ratio. Further, in the stratified combustion mode, the opening degree of the throttle valve is controlled to be almost fully open.

  Further, in the uniform combustion mode, fuel is injected into the combustion chamber 3d during the intake stroke, and an air-fuel mixture is generated by the fuel jet and the swirl flow and tumble flow by the swirl control, and is uniformly dispersed in the combustion chamber 3d. In this case, the combustion is performed at a richer air-fuel ratio (for example, 12 to 22) than in the stratified combustion mode.

In the present embodiment, the ECU 2 comprises air-fuel ratio detection means, rotation angle position parameter detection means, ignition timing setting means, determination means, ignition control means , air- fuel ratio control means, and threshold value calculation means .

  Next, a process executed by the ECU 2 to calculate the air-fuel ratio (hereinafter simply referred to as “air-fuel ratio”) AF of the air-fuel mixture near the spark plug 10 will be described with reference to FIG. This process is interrupted at a predetermined cycle (for example, 10 msec) according to the setting of the program timer.

  In this process, first, in step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), it is determined whether or not the stratified combustion permission flag F_DISCOK is “1”. The stratified combustion permission flag F_DISCOK is set to “1” when the engine 3 is in an operation state in which the stratified combustion mode is to be executed, and is set to “0” when in an operation state in which the uniform combustion mode is to be executed.

  When the determination result of step 1 is NO and the engine 3 is in an operation state in which the uniform combustion mode should be executed, the process proceeds to step 2 and whether or not the crank angle position θCRK is smaller than the detection start angle position θSTART1 for the uniform combustion mode. Is determined. The detection start angle position θSTART1 for the uniform combustion mode is set to a predetermined crank angle position during the intake stroke in accordance with a fuel injection timing for the uniform combustion mode described later. If the result of this determination is YES and the crank angle position θCRK has not reached the detection start angle position θSTART1 for the uniform combustion mode, it is determined that the air-fuel ratio AF should not be calculated, and the present process is terminated.

  On the other hand, if the determination result in step 2 is NO and the crank angle position θCRK has reached the detection start angle position θSTART1 for the uniform combustion mode, the process proceeds to step 3 where the crank angle position θCRK is the detection end angle for the uniform combustion mode. It is determined whether or not the position is smaller than θEND1. The detection end angle position θEND1 for the uniform combustion mode is set to a predetermined crank angle position during the compression stroke according to the fuel injection timing for the uniform combustion mode.

  When the determination result in step 3 is YES and the crank angle position θCRK has not reached the detection end angle position θEND1 for the uniform combustion mode, the process proceeds to step 4 and based on the detection signal of the air-fuel ratio sensor 20, the above-described formula (1 ) And (2), the air-fuel ratio AF is calculated.

  Next, in step 5, the buffer values AFBUFF1 for m uniform combustion modes stored in the RAM are updated. These buffer values AFBUFF1 for the uniform combustion mode represent the sampling values of the air-fuel ratio AF respectively sampled in m loops before the previous time in synchronization with the execution of this processing in the uniform combustion mode. The value m is such that the m buffer values AFBUFF1 include the sampling values of all the air-fuel ratios AF in the combustion cycle and the sampling values of all the air-fuel ratios AF in a plurality of previous combustion cycles. It is set to a predetermined integer.

  In the update process of the buffer value AFBUFF1 in step 5, each value in the RAM is set as an old value for one control cycle. For example, the air / fuel ratio AF sampled this time is set as the current value AFBUFF1 (k) of the buffer value for the uniform combustion mode, the current value AFBUFF1 (k) is set as the previous value AFBUFF1 (k−1), and the previous value AFBUFF1 (k-1) is set as the previous value AFBUFF1 (k-2). As described above, after updating the buffer value AFBUFF1 for the uniform combustion mode, the present process is terminated.

  On the other hand, if the determination result in step 3 is NO and the crank angle position θCRK has reached the detection end angle position θEND1 for the uniform combustion mode, it is determined that the air-fuel ratio AF should not be calculated, and this process ends.

  On the other hand, if the determination result in step 1 is YES and the engine 3 is in the operating state where the stratified combustion mode should be executed, the process proceeds to step 6 where the crank angle position θCRK is smaller than the detection start angle position θSTART2 for the stratified combustion mode. It is determined whether or not. The detection start angle position θSTART2 for the stratified combustion mode is set to a predetermined crank angle position during the compression stroke according to the fuel injection timing for the stratified combustion mode described later. If the determination result is YES and the crank angle position θCRK has not reached the detection start angle position θSTART2 for the stratified combustion mode, it is determined that the air-fuel ratio AF should not be calculated, and the present process is terminated.

  On the other hand, if the determination result in step 6 is NO and the crank angle position θCRK has reached the detection start angle position θSTART2 for the stratified combustion mode, the process proceeds to step 7 where the crank angle position θCRK is the detection end angle for the stratified combustion mode. It is determined whether or not the position is smaller than θEND2. The detection end angle position θEND2 for the stratified combustion mode is a predetermined crank angle during the compression stroke on the combustion stroke side with respect to the detection start angle position θSTART2 for the stratified combustion mode according to the fuel injection timing for the stratified combustion mode. Set to position.

  When the determination result in step 7 is YES and the crank angle position θCRK has not reached the detection end angle position θEND2 for the stratified combustion mode, the process proceeds to step 8, and based on the detection signal of the air-fuel ratio sensor 20, the above-described formula (1 ) And (2), the air-fuel ratio AF is calculated.

  Next, in step 9, the buffer value AFBUFF2 for n stratified combustion modes stored in the RAM is updated. This update process is executed in the same manner as in Step 5 described above. Further, these buffer values AFBUFF2 for the stratified combustion mode represent the sampling values of the air-fuel ratio AF sampled in the previous n loops in synchronization with the execution of this processing in the stratified combustion mode. . Further, the value n is such that the n buffer values AFBUFF2 include sampling values of all air-fuel ratios AF in the combustion cycle and sampling values of all air-fuel ratios AF in a plurality of previous combustion cycles. It is set to a predetermined integer. As described above, after updating the buffer value AFBUFF2 for the stratified combustion mode, the present process is terminated.

  On the other hand, if the determination result in step 7 is NO and the crank angle position θCRK has reached the detection end angle position θEND2 for the stratified combustion mode, it is determined that the air-fuel ratio AF should not be calculated, and this process ends.

  Next, an ignition timing control process executed by the ECU 2 will be described with reference to FIG. This process is interrupted at a predetermined cycle (for example, 10 msec) after the fuel injection timing is calculated in the fuel injection control process described later. In this process, first, in step 20, it is determined whether or not a calculated flag F_CAL described later is “1”.

  When the determination result is NO, the process proceeds to step 21 to determine whether or not the stratified combustion permission flag F_DISCOK described above is “1”. When the determination result is NO and the engine 3 is in the operation state in which the uniform combustion mode should be executed, the process proceeds to step 22 and the map shown in FIG. 7 is searched according to the engine speed NE and the required torque PMCMD. The basic ignition timing θIGBASE is calculated. The required torque PMCMD (operating state parameter) is calculated by searching the map shown in FIG. 9 according to the engine speed NE and the accelerator pedal opening AP in step 40 of FIG.

  Next, the routine proceeds to step 23, where the average air-fuel ratio AFAVE1 for the uniform combustion mode is calculated. The average air-fuel ratio AFAVE1 for the uniform combustion mode is calculated as an arithmetic average value of m buffer values AFBUFF1 for the uniform combustion mode stored in the RAM.

  Next, the process proceeds to step 24, where a correction term θAF1 for the uniform combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE1 for the uniform combustion mode calculated in step 23.

In step 25 following step 24, the final ignition timing θIGCMD is calculated by the following equation (3).
θIGCMD = θIGBASE + θIGCR + θAF1 (3)
Here, θIGCR is a total correction term, and a plurality of correction terms are searched according to a plurality of parameters such as intake air temperature TA, engine water temperature TW, and EGR amount, and these correction terms are added to each other. Calculated.

  Next, the routine proceeds to step 26, where the ignition timing threshold value θIGLMT is calculated based on the final ignition timing θIGCMD. This threshold value θIGLMT is set to the most retarded value that is assumed to allow the air-fuel mixture to be ignited.

  On the other hand, when the determination result in step 21 is YES and the engine 3 is in the operation state in which the stratified combustion mode should be executed, the process proceeds to step 27, and according to the engine speed NE and the fuel injection end timing IJLOGD for the stratified combustion mode, The basic ignition timing θIGBASE is calculated by searching the map shown in FIG. The fuel injection end timing IJLOGD (operating state parameter) for the stratified combustion mode is calculated by a fuel injection control process described later.

  Next, the process proceeds to step 28, and the average air-fuel ratio AFAVE2 for the stratified combustion mode is calculated by the same method as in step 23 described above. That is, the average air-fuel ratio AFAVE2 for the stratified combustion mode is calculated as an arithmetic average value of the n buffer values AFBUFF2 for the stratified combustion mode stored in the RAM.

  Next, the process proceeds to step 29, and a correction term θAF2 for the stratified combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE2 for the stratified combustion mode calculated in step 28.

In step 30 following step 29, the final ignition timing θIGCMD is calculated by the following equation (4).
θIGCMD = θIGBASE + θIGCR + θAF2 (4)

  Next, the routine proceeds to step 31, where the ignition timing threshold θIGLMT is calculated based on the final ignition timing θIGCMD as in step 26.

  In step 32 following step 26 or step 31, the calculated flag F_CAL is set to “1” to indicate that the final ignition timing θIGCMD and the ignition timing threshold value θIGLMT have been calculated. Thereby, in the loop after the next time, the determination result of step 20 becomes YES, and in that case, the process proceeds to step 33.

  In step 33 following step 20 or step 32, it is determined whether or not the crank angle position θCRK is smaller than the final ignition timing θIGCMD. If the determination result is YES and the crank angle position θCRK has not reached the final ignition timing θIGCMD, it is determined that the ignition operation should not be performed, and the present process is terminated.

  On the other hand, if the determination result in step 33 is NO and the crank angle position θCRK has reached the final ignition timing θIGCMD, the process proceeds to step 34 to determine whether the air-fuel ratio AF is equal to or less than a predetermined value AFREF. The predetermined value AFREF is set to the most lean value that can ignite the air-fuel mixture.

  When the determination result is YES and the air-fuel ratio AF of the air-fuel mixture is a value that can be ignited, the routine proceeds to step 35, where an ignition control signal is output to the spark plug 10 via the ignition coil 9. Thereby, the air-fuel mixture in the combustion chamber 3d is ignited. Next, in step 36, the calculated flag F_CAL is set to “0”, and then this process is terminated.

  On the other hand, when the determination result in step 34 is NO, that is, when the air-fuel mixture is thin and ignition is difficult, the routine proceeds to step 37, and whether or not the crank angle position θCRK is smaller than the ignition timing threshold θIGLMT. Is determined. If the determination result is YES and the crank angle position θCRK has not reached the ignition timing threshold value θIGLMT, it is determined that the ignition operation should not be performed, and the present process is terminated.

  On the other hand, when the determination result in step 37 is NO and the crank angle position θCRK has reached the ignition timing threshold value θIGLMT, the aforementioned steps 35 and 36 are executed to forcibly execute the ignition operation. Thereafter, this process is terminated.

  As described above, in this ignition timing control process, after the crank angle position θCRK reaches the final ignition timing θIGCMD and until the threshold θIGLMT is reached, the air-fuel ratio AF shows a value that can be ignited. The ignition operation is executed, and at other times, the ignition operation is suspended. This ensures better ignitability compared to the conventional case where the ignition operation is forcibly executed even when the air-fuel mixture at the ignition timing of the combustion cycle is too thin, thereby improving the combustion efficiency. Can be improved. In particular, in the case of a direct injection engine such as the engine 3 of the present embodiment, during the stratified combustion mode, the portion of the stratified air-fuel mixture is controlled so as to be unevenly distributed in the vicinity of the spark plug 10 than the surroundings. Therefore, as described above, by performing the ignition operation while monitoring whether or not the air-fuel ratio AF of the air-fuel mixture in the vicinity of the spark plug 10 is in an ignitable state, the ignitability of the air-fuel mixture can be more effectively improved. Can be improved.

  During the uniform combustion mode, the correction term θAF1 for the uniform combustion mode is calculated according to the average air-fuel ratio AFAVE1 for the uniform combustion mode, and the final ignition timing θIGCMD is obtained as a value corrected by the correction term θAF1. Is calculated. Further, during the stratified combustion mode, the correction term θAF2 for the stratified combustion mode is calculated according to the average air-fuel ratio AFAVE2 for the stratified combustion mode, and the final ignition timing θIGCMD is calculated as a value corrected by the correction term θAF2. Is done. Therefore, it is possible to perform ignition timing control in the current combustion cycle while reflecting the state of the air-fuel ratio AF detected in a plurality of combustion cycles before the current combustion cycle, thereby The ignitability can be further improved.

  Next, the fuel injection control process will be described with reference to FIG. This process is interrupted in synchronization with the generation timing of the TDC signal. In this process, first, in step 50, it is determined whether or not the above-described stratified combustion permission flag F_DISCOK is “1”.

When the determination result is NO and the engine 3 is in an operation state in which the uniform combustion mode should be executed, the process proceeds to step 51, and as described below, the engine 3 is uniformly according to the TH passing intake air amount GTH and the intake pipe absolute pressure PBA. A basic fuel injection amount TIBASE1 for the combustion mode is calculated. That is, first, the actual intake air amount GCYL estimated to be actually sucked into the cylinder 3a is calculated by the following equation (5).
GCYL = GTH-VB. (PBA-PBAZ) / (R.TB) (5)
Here, VB represents the volume in the intake pipe, R represents a predetermined gas constant, TB represents the temperature in the intake pipe, and PBAZ represents the previous value of the absolute pressure PBA in the intake pipe.

  Next, a basic fuel injection amount TIBASE1 for the uniform combustion mode is calculated by searching a table (not shown) according to the actual intake air amount GCYL calculated as described above.

  In step 52 following step 51, the average air-fuel ratio AFAVE1 for the uniform combustion mode is calculated as in step 23 described above.

  Next, the process proceeds to step 53, and a correction coefficient KAVE1 for the uniform combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE1 for the uniform combustion mode calculated in step 52.

Next, at step 54, the required fuel injection amount TCYL is calculated by the following equation (6).
TCYL = TIBASE1, KAVE1, KTOTAL, KCMD, KSTR
...... (6)
Here, KTOTAL is a total correction coefficient, and is calculated by performing a table search for various correction coefficients such as the engine water temperature TW and the intake air temperature TA, and multiplying them together. KCMD is a target air-fuel ratio calculated according to the operating state of the engine 3 by a predetermined control algorithm, and KSTR is a feedback coefficient calculated by a predetermined feedback control algorithm.

  Next, the routine proceeds to step 55, where the final fuel injection amount TOUT is calculated by subjecting the required fuel injection amount TCYL calculated at step 54 to a predetermined adhesion correction process.

  Next, at step 56, the fuel injection timing for the uniform combustion mode is calculated. Specifically, first, a map value of the fuel injection end timing is calculated by searching a map (not shown) according to the final fuel injection amount TOUT and the engine speed NE, and this is corrected according to the engine water temperature TW. Thus, the fuel injection end timing for the uniform combustion mode is calculated. Further, the fuel injection start timing for the uniform combustion mode is calculated based on the fuel injection end timing for the uniform combustion mode and the final fuel injection amount TOUT. As described above, after calculating the fuel injection timing for the uniform combustion mode, the present process is terminated.

  On the other hand, when the determination result in step 50 is YES and the engine 3 is in the operating state in which the stratified combustion mode should be executed, in step 57, the same method as the calculation method of the basic fuel injection amount TIBASE1 for the uniform combustion mode described above is used. Then, the basic fuel injection amount TIBASE2 for the stratified combustion mode is calculated. That is, the actual intake air amount GCYL is calculated by the above-described equation (5), and the basic fuel injection amount TIBASE2 for the stratified combustion mode is calculated by searching a table (not shown) according to the actual intake air amount GCYL. .

  Next, in step 58, the average air-fuel ratio AFAVE2 for the stratified combustion mode is calculated as in step 28 described above.

  Next, the routine proceeds to step 59, where a correction coefficient KAVE2 for the stratified combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE2 for the stratified combustion mode calculated at step 58 above.

Next, at step 60, the required fuel injection amount TCYL is calculated by the following equation (7).
TCYL = TIBASE2 / KAVE2 / KTOTAL / KCMD / KSTR
...... (7)

  Next, the process proceeds to step 61, and similarly to step 55 described above, the final fuel injection amount TOUT is calculated by subjecting the required fuel injection amount TCYL calculated in step 60 to an adhesion correction process.

  Next, at step 62, the fuel injection timing for the stratified combustion mode is calculated. Specifically, first, a fuel injection end timing IJLOGD for the stratified combustion mode is calculated by searching a map (not shown) according to the final fuel injection amount TOUT and the engine speed NE. Further, the fuel injection start timing for the stratified combustion mode is calculated based on the fuel injection end timing IJLOGD for the stratified combustion mode and the final fuel injection amount TOUT. After calculating the fuel injection timing for the stratified combustion mode in this way, the present process is terminated.

  As described above, according to this fuel injection control process, during the uniform combustion mode, the correction coefficient KAVE1 for the uniform combustion mode is calculated according to the average air-fuel ratio AFAVE1 for the uniform combustion mode, and this correction coefficient The final fuel injection amount TOUT is calculated as a value corrected by KAVE1. Further, during the stratified combustion mode, the correction coefficient KAVE2 for the stratified combustion mode is calculated according to the average air-fuel ratio AFAVE2 for the stratified combustion mode, and the final fuel injection amount TOUT is calculated as a value corrected by this correction coefficient KAVE2. Calculated. Accordingly, it is possible to perform the fuel injection control in the current combustion cycle while reflecting the state of the air-fuel ratio AF detected in a plurality of combustion cycles before the current combustion cycle. Can be accurately controlled to a value that can be ignited.

  Next, the swirl control process will be described with reference to FIG. As described below, this process controls the swirl flow and tumble flow generated in the combustion chamber 3d by controlling the valve lift LIN of the intake valve 4 for swirl control via the variable intake valve mechanism 13. The control is performed, and the interrupt is executed in synchronization with the generation timing of the TDC signal. In this process, first, in step 70, it is determined whether or not the stratified combustion permission flag F_DISCOK described above is “1”.

  When the determination result is NO and the engine 3 is in an operation state in which the uniform combustion mode should be executed, the process proceeds to step 71, and a uniform combustion is performed by searching a map (not shown) according to the engine speed NE and the required torque PMCMD. The basic intake valve lift LINBASE1 for the mode is calculated.

  Next, the routine proceeds to step 72, where the average air-fuel ratio AFAVE1 for the uniform combustion mode is calculated in the same manner as in steps 23 and 52 described above. Thereafter, in step 73, a correction lift DLIN1 for uniform combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE1 for uniform combustion mode calculated in step 72.

In step 74 following step 73, the target intake valve lift LINCMD is calculated by the following equation (8).
LINCMD = LINBASE1 + DLIN1 (8)

  Next, the routine proceeds to step 75, where the intake valve lift control process is executed. In this intake valve lift control process, the value of the control signal to the variable intake valve mechanism 13 is calculated by a predetermined feedback control algorithm so that the intake valve lift LIN converges to the target intake valve lift LINCMD. Thereafter, this process is terminated.

  On the other hand, when the determination result in step 70 is YES and the engine 3 is in the operating state in which the stratified combustion mode should be executed, in step 76, a map (not shown) is searched according to the engine speed NE and the required torque PMCMD. The basic intake valve lift LINBASE2 for the stratified combustion mode is calculated.

  Next, in step 77, the average air-fuel ratio AFAVE2 for the stratified combustion mode is calculated in the same manner as in steps 28 and 58 described above. Thereafter, in step 78, a correction lift DLIN2 for the stratified combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE2 for the stratified combustion mode calculated in step 77.

In step 79 following step 78, the target intake valve lift LINCMD is calculated by the following equation (9).
LINCMD = LINBASE2 + DLIN2 (9)

  Next, after executing step 75 as described above, the present process is terminated.

  As described above, according to this swirl control process, during the uniform combustion mode, the correction lift DLIN1 for the uniform combustion mode is calculated according to the average air-fuel ratio AFAVE1 for the uniform combustion mode, and this correction lift DLIN1. The target intake valve lift LINCMD is calculated as the value corrected by. Further, during the stratified combustion mode, the correction lift DLIN2 for the stratified combustion mode is calculated according to the average air-fuel ratio AFAVE2 for the stratified combustion mode, and the target intake valve lift LINCMD is calculated as a value corrected by the corrected lift DLIN2. Calculated. Therefore, it is possible to perform the swirl control in the current combustion cycle while reflecting the state of the air-fuel ratio AF detected in a plurality of combustion cycles before the current combustion cycle. It can be accurately controlled to a value that can be ignited. In particular, in the stratified combustion mode, a portion having a higher gasoline concentration than the surroundings of the stratified mixture needs to be unevenly distributed in the vicinity of the spark plug 10 by swirl control. Can be improved more effectively.

  Next, the EGR control process will be described with reference to FIG. As will be described below, this process controls the amount of exhaust gas reduced to the intake side, that is, the amount of EGR by controlling the valve lift LEGR of the EGR control valve 14, and is synchronized with the generation timing of the TDC signal. Interrupted. In this process, first, in step 90, it is determined whether or not the above-described stratified combustion permission flag F_DISCOK is “1”.

  When the determination result is NO and the engine 3 is in an operation state in which the uniform combustion mode should be executed, the process proceeds to step 91, where a uniform combustion is performed by searching a map (not shown) according to the engine speed NE and the required torque PMCMD. A basic EGR valve lift LEGRBASE1 for the mode is calculated.

  Next, the routine proceeds to step 92, where the average air-fuel ratio AFAVE1 for the uniform combustion mode is calculated in the same manner as in steps 23, 52, 72 described above. Thereafter, in step 93, the correction lift DLEGR1 for the uniform combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE1 for the uniform combustion mode calculated in step 92.

In step 94 following step 93, the target EGR valve lift LEGRCMD is calculated by the following equation (10).
LEGRCMD = LEGRBASE1 + DLEGR1 (10)

  Next, the routine proceeds to step 95, where EGR valve lift control processing is executed. In this EGR valve lift control process, the value of the control signal to the EGR control valve 14 is calculated by a predetermined feedback control algorithm so that the EGR valve lift LEGR converges to the target EGR valve lift LEGRCMD. Thereafter, this process is terminated.

  On the other hand, when the determination result in step 90 is YES and the engine 3 is in the operating state in which the stratified combustion mode should be executed, in step 96, similarly to step 91 described above, according to the engine speed NE and the required torque PMCMD, By searching a map (not shown), a basic EGR valve lift LEGRBASE2 for the stratified combustion mode is calculated.

  Next, in step 97, the average air-fuel ratio AFAVE2 for the stratified combustion mode is calculated in the same manner as in steps 28, 58 and 77 described above. Thereafter, in step 98, a correction lift DLEGR2 for the stratified combustion mode is calculated by searching a table (not shown) according to the average air-fuel ratio AFAVE2 for the stratified combustion mode calculated in step 97.

In step 99 following step 98, the target EGR valve lift LEGRCMD is calculated by the following equation (11).
LEGRCMD = LEGRBASE2 + DLEGR2 (11)

  Next, after executing step 95 as described above, the present process is terminated.

  As described above, according to the EGR control process, during the uniform combustion mode, the correction lift DLEGR1 for the uniform combustion mode is calculated according to the average air-fuel ratio AFAVE1 for the uniform combustion mode, and the correction lift DLEGR1 The target EGR valve lift LEGRCMD is calculated as the value corrected by. Further, during the stratified combustion mode, the correction lift DLEGR2 for the stratified combustion mode is calculated in accordance with the average air-fuel ratio AFAVE2 for the stratified combustion mode. Calculated. Therefore, the EGR control in the current combustion cycle can be performed while reflecting the state of the air-fuel ratio AF detected in a plurality of combustion cycles before the current combustion cycle. It can be accurately controlled to a value that can be ignited.

  The embodiment is an example in which the crank angle sensor 20 is used as the rotation angle position parameter detection means, but the rotation angle position parameter detection means of the present invention is not limited to this, and the rotation representing the rotation angle position of the crankshaft 3e. What is necessary is just to detect an angular position parameter. For example, a cam angle sensor that detects the rotation angle position of the camshaft may be used, and the rotation angle position of the camshaft that rotates as the crankshaft rotates may be detected as the rotation angle position parameter.

  The embodiment is an example in which the correction terms θAF1, θAF2, correction coefficients KAVE1, KAVE2, correction lifts DLIN1, DLIN2, correction lifts DLEGR1, DLEGR2 are calculated according to the average air-fuel ratios AFAVE1, AFAVE2, respectively. The parameters used for the calculation are not limited to the average air-fuel ratio AFAVE1, AFAVE2, but may be any parameter that represents the state of the air-fuel ratio AF. For example, a weighted average value of the buffer values AFBUFF1 and AFBUFF2 may be used instead of the average air-fuel ratios AFAVE1 and AFAVE2 which are arithmetic average values.

Further, the embodiment is an example using the expressions (1) and (2) as the calculation formula of the air-fuel ratio AF, but the calculation formula of the air-fuel ratio AF is not limited to these, and is calculated by the expression (1). Any device that can calculate the air-fuel ratio AF using the gasoline concentration C may be used. For example, the air-fuel ratio AF may be calculated by the following equation (12) using the gasoline concentration C calculated by the equation (1).
AF = (1-C) / C (12)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 ECU (Air-fuel ratio detection means, rotation angle position parameter detection means, ignition timing setting means, determination means, ignition control means, air-fuel ratio control means, threshold value calculation means )
3 Internal combustion engine 3d Combustion chamber 3e Crankshaft 10 Spark plug 20 Air-fuel ratio sensor (air-fuel ratio detection means)
40 Crank angle sensor (rotation angle position parameter detection means)
AF Air-fuel ratio of air-fuel mixture near spark plug θCRK Crankshaft rotation angle position (rotation angle parameter)
NE Engine speed (operating condition parameter)
PMCMD request torque IJLOGD end of the fuel injection for stratified combustion mode timing θIGCMD final ignition timing (ignition timing)
θIGLMT threshold

Claims (3)

A control device for an in-cylinder injection internal combustion engine that can be operated by switching between a stratified combustion mode in which the fuel-air mixture in the combustion chamber is stratified combustion and a uniform combustion mode in which uniform combustion is performed while fuel is directly injected into the combustion chamber There,
And air-fuel ratio detecting means for detecting an air-fuel ratio of the mixture around the spark plug in the combustion chamber,
Rotation angle position parameter detecting means for detecting a rotation angle position parameter representing a rotation angle position of a crankshaft of the internal combustion engine;
Ignition timing setting means for setting an ignition timing according to an operating state parameter representing an operating state of the internal combustion engine;
Determination means for determining whether the air-fuel mixture is in an ignitable state based on a detection result of the air-fuel ratio detection means;
Ignition control for performing an ignition operation by the spark plug when the determination unit determines that the air-fuel mixture is in an ignitable state after the detected rotation angle position parameter reaches the ignition timing. Means,
Equipped with a,
The ignition timing setting means sets the ignition timing according to a required torque required for the internal combustion engine in addition to the operation state parameter when the internal combustion engine is operated in the uniform combustion mode. A control device for an internal combustion engine. When the internal combustion engine is operated in the stratified combustion mode, the ignition timing setting means sets the ignition timing according to the fuel injection timing into the combustion chamber in addition to the operation state parameter. The control apparatus for an internal combustion engine according to claim 1, wherein the control apparatus is an internal combustion engine. Threshold calculation means for calculating, as a threshold value, a value on the most retarded side that can ignite the air-fuel mixture based on the ignition timing,
The ignition control means, after the rotation angle position parameter reaches the ignition timing, and when the determination means determines that the mixture is not in an ignitable state, the rotation angle position parameter is The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the ignition operation is executed when the threshold value is reached.

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