JP5482483B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine mounted on an automobile or the like. In particular, the present invention relates to measures for optimizing the fuel injection timing of the fuel injection valve.

  Conventionally, as an engine (internal combustion engine) mounted on an automobile, for example, as disclosed in Patent Document 1 and Patent Document 2 below, an in-cylinder direct injection injector that directly injects fuel into a cylinder The one with is known. The in-cylinder direct injection injector is configured such that fuel whose pressure has been increased by a high-pressure fuel pump is supplied via a delivery pipe, and high-pressure fuel is directly injected into the cylinder at a predetermined fuel injection timing.

  This in-cylinder direct injection injector is often used in combination with a port injection injector that injects fuel into an intake passage (intake port) of an engine as disclosed in Patent Document 1. There are various usage forms of these in-cylinder direct injection injectors and port injection injectors. For example, when the engine load is low, fuel is injected from the direct injection injector in the cylinder and stratified combustion of the air-fuel mixture is performed in the combustion chamber. When the engine load is high, fuel injection is performed from the port injector and the air-fuel mixture is homogeneous in the combustion chamber. For example, combustion is performed. Also, when the engine load is high, fuel is injected from the in-cylinder direct injection injector, and the in-cylinder temperature is lowered by increasing the heat of vaporization of the fuel in the cylinder (intake air cooling effect). It is also possible to increase the charging efficiency by increasing the density or to advance the ignition timing of the spark plug.

  Further, in Patent Document 1, when the combustion in the combustion chamber deteriorates, the fuel injection from the in-cylinder direct injection injector is divided into two, the first fuel injection is performed in the first stage of the intake stroke, and the second fuel is injected. It is disclosed that the injection is performed in the late stage of the intake stroke.

  Further, Patent Document 2 discloses that the required fuel amount after the increase injected from the in-cylinder direct injection injector is divided and injected for a set period from when the required fuel amount is increased.

JP 2006-194098 A JP 2008-240551 A

  However, in the configuration of each patent document described above, the injection mode (split ratio, etc.) in each split injection is fixed, and it is improved in order to optimize the split mode of fuel injection from the in-cylinder direct injection injector. There was room for. For example, there is still room for improvement in order to optimize engine performance, oil dilution (oil (lubricating oil) dilution due to fuel adhering to the cylinder inner wall surface), exhaust emission, etc., depending on the fuel injection division mode. there were.

  The present invention has been made in view of the above points, and an object of the present invention is to optimize the division ratio when dividing and executing fuel injection from the in-cylinder direct injection injector. An object of the present invention is to provide a control device for an internal combustion engine.

-Principle of solving the problem-
The solution principle of the present invention devised to achieve the above object is that the intake stroke top dead center side and the intake stroke bottom dead center are as fuel injection forms from the in-cylinder direct injection injector (in-cylinder injection fuel injection valve). In this case, the division ratio is corrected in accordance with the operating state of the internal combustion engine.

-Solution-
Specifically, the present invention includes an in-cylinder injection fuel injection valve that directly injects fuel into the combustion chamber, and the fuel injection from the in-cylinder injection fuel injection valve in the intake stroke is divided into a top dead center side divided injection and a lower injection. A control device for an internal combustion engine that can be divided into dead-split divided injection and executed is assumed. With respect to the control device for the internal combustion engine, the split injection and the bottom dead side on the top dead center side according to the oil dilution rate caused by the fuel injected from the in-cylinder fuel injection valve adhering to the cylinder wall surface. a dividing ratio correction means for compensation a division ratio between split injection point side, to set the fuel injection pressure from said cylinder injection fuel injection valve based on the division ratio corrected by the dividing ratio correction means Fuel injection pressure setting means .

  By this specific matter, for example, the division ratio for optimizing the combustion state in the combustion chamber, the exhaust emission, the fuel consumption rate, the WOT (Wide Open Throttle) performance, the oil dilution rate, etc. can be obtained. It is possible to realize an optimal fuel injection mode when performing split injection from the fuel injection valve.

In this case, the fuel injection from the in-cylinder fuel injection valve is based on the top dead center side split ratio, which is the ratio of the top dead center split injection amount to the bottom dead center split injection amount. Set the pressure. Specifically, the fuel injection pressure from the in-cylinder injection fuel injection valve is set higher as the top dead center side division ratio is higher.

  This is because when the top dead center side split ratio is high, the fuel injection amount in the top dead center side split injection is large and the fuel injection period tends to be long, so the fuel injection pressure of the in-cylinder fuel injection valve is increased. By setting and shortening the fuel injection period until the required amount of fuel injection is completed, the interval can be secured long, which contributes to improving the mixing property between air and fuel.

Also, the fuel injection pressure from the fuel injection valve for in-cylinder injection is set based on the bottom dead center side split ratio that is the injection amount in the bottom dead center side split injection to the injection amount in the top dead center side split injection To do. Specifically, the fuel injection pressure from the in-cylinder injection fuel injection valve is set higher as the above-described bottom dead center side split ratio is higher. Since the injection period tends to be long, the fuel injection period until the fuel injection pressure of the in-cylinder fuel injection valve is set high and the required amount of fuel injection is completed (the injection period in the split injection on the bottom dead center side) By shortening, it is possible to secure a long interval and contribute to improving the mixing property between air and fuel.

  In the present invention, when the fuel injection form from the in-cylinder fuel injection valve is divided into the intake stroke top dead center side and the intake stroke bottom dead center side, these division ratios are corrected according to the operating state of the internal combustion engine. Like to do. As a result, it is possible to realize an optimum fuel injection mode in the case of performing the divided injection.

1 is a schematic configuration diagram of an interior of an engine when a V-type engine according to an embodiment is viewed from a direction along an axis of a crankshaft. It is a system configuration diagram showing an outline of an engine and intake and exhaust systems. It is a figure which shows typically the structure of a fuel supply system. It is a block diagram which shows the control system of an engine. It is a figure for demonstrating the change range of the fuel-injection period in each in-cylinder direct injection injector and a port injection injector. It is a figure which shows the division ratio setting map utilized when setting a top dead center side division ratio according to an oil dilution rate. It is a figure which shows the direct injection timing setting map utilized when setting the direct injection timing according to a top dead center side division | segmentation ratio. It is a figure which shows the direct injection fuel pressure setting map utilized when setting the direct injection fuel pressure according to a top dead center side division | segmentation ratio. It is a figure which shows the injection ratio setting map utilized when setting the injection ratio of port injection and in-cylinder direct injection according to a top dead center side division ratio. It is a figure which shows the port injection timing setting map utilized when setting a port injection timing according to a top dead center side division | segmentation ratio. It is a figure which shows the direct injection timing setting map utilized when setting the direct injection timing according to a bottom dead center side division | segmentation ratio. It is a figure which shows the direct injection fuel pressure setting map utilized when setting a direct injection fuel pressure according to a bottom dead center side division | segmentation ratio.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the case where the present invention is applied to a V-type 8-cylinder gasoline engine (internal combustion engine) for automobiles will be described.

-Description of overall engine configuration-
First, the overall configuration of the engine according to the present embodiment will be described.

  FIG. 1 is a diagram showing a schematic configuration inside an engine when a V-type engine E according to the present embodiment is viewed from a direction along the axis of a crankshaft C. FIG. 2 is a system configuration diagram showing an outline of the engine E and the intake / exhaust system.

  As shown in these drawings, the V-type engine E has a pair of banks 2L and 2R protruding in a V-shape at the upper part of the cylinder block 1. Each bank 2L, 2R includes a cylinder head 3L, 3R installed at the upper end of the cylinder block 1 and a head cover 4L, 4R attached to the upper end thereof. The cylinder block 1 is provided with a plurality of cylinders 5L, 5R,... (For example, four in each bank 2L, 2R) with a predetermined sandwich angle (for example, 90 °). The pistons 51L, 51R,... The pistons 51L, 51R,... Are connected to the crankshaft C through connecting rods 52L, 52R,. Further, a crankcase 6 is attached to the lower side of the cylinder block 1, and a space extending from the lower part in the cylinder block 1 to the inside of the crankcase 6 is a crank chamber 61. An oil pan 62 serving as an oil reservoir is disposed further below the crankcase 6.

  The cylinder heads 3L and 3R are respectively assembled with intake valves 32L and 32R for opening and closing the intake ports 31L and 31R and exhaust valves 34L and 34R for opening and closing the exhaust ports 33L and 33R. The valves 32L, 32R, 34L, and 34R are opened and closed by the rotation of the cam shafts 35L, 35R, 36L, and 36R disposed in the cam chambers 41L and 41R formed between the head covers 4L and 4R. To be done.

  Further, the cylinder heads 3L and 3R of the engine E according to the present embodiment have a divided structure. Specifically, the cylinder heads 3L and 3R are constituted by cylinder head bodies 37L and 37R attached to the upper surface of the cylinder block 1 and camshaft housings 38L and 38R assembled on the upper side of the cylinder head bodies 37L and 37R.

  On the other hand, intake manifolds 7L and 7R corresponding to the banks 2L and 2R are disposed on the inner side (between banks) of the banks 2L and 2R, and the downstream ends of the intake manifolds 7L and 7R correspond to the respective banks. It communicates with the intake ports 31L, 31R,. The intake manifolds 7L and 7R are connected to an intake pipe 73 having a surge tank 71 (see FIG. 2) common to each bank and a throttle valve 72, and an air cleaner 74 is provided upstream of the intake pipe 73. Is provided. Thereby, the air introduced into the intake pipe 73 from the air cleaner 74 is introduced into the intake manifolds 7L and 7R through the surge tank 71.

  Port injection injectors (fuel injection valves for intake passages) 75L and 75R are provided in the intake ports 31L and 31R of the cylinder heads 3L and 3R, respectively. During fuel injection from the port injection injectors 75L and 75R, The air introduced into the intake manifolds 7L and 7R and the fuel injected from the port injectors 75L and 75R are mixed to form an air-fuel mixture, and this air-fuel mixture is accompanied by the opening of the intake valves 32L and 32R. It will be introduced into the combustion chambers 76L, 76R. The fuel injection timing from the port injectors 75L and 75R includes synchronous injection that performs fuel injection in conjunction with the valve opening operation of the intake valves 32L and 32R, and valve opening operation of the intake valves 32L and 32R. In other words, there is asynchronous injection that executes fuel injection even when the intake valves 32L and 32R are closed, and these can be switched.

  The engine E according to the present embodiment also includes in-cylinder direct injection injectors (in-cylinder injection fuel injection valves) 78L and 78R. During fuel injection from the in-cylinder direct injection injectors 78L and 78R, The fuel is directly injected into the combustion chambers 76L and 76R.

  As an example of the fuel injection form of the port injectors 75L and 75R and the in-cylinder direct injection injectors 78L and 78R, fuel injection from both the injectors 75L, 75R, 78L, and 78R is performed when the engine E is operated at low and medium loads. A homogeneous air-fuel mixture is generated to improve the fuel consumption rate and exhaust emission. Further, during high load operation of the engine E, fuel injection from only the in-cylinder direct injection injectors 78L and 78R is performed to improve intake charging efficiency and suppress knocking by the intake air cooling effect. The fuel injection mode of these injectors 75L, 75R, 78L, 78R is not limited to this.

  A fuel supply system for supplying fuel to the port injectors 75L and 75R and the in-cylinder direct injectors 78L and 78R will be described later.

  Spark plugs 77L and 77R (see FIG. 2) are disposed at the tops of the combustion chambers 76L and 76R. In the combustion chambers 76L and 76R, the combustion pressure of the air-fuel mixture accompanying the ignition of the spark plugs 77L and 77R is transmitted to the pistons 51L and 51R, causing the pistons 51L and 51R to reciprocate. The reciprocating motion of the pistons 51L and 51R is transmitted to the crankshaft C via the connecting rods 52L and 52R, converted into rotational motion, and taken out as the output of the engine E. The camshafts 35L, 35R, 36L, and 36R are driven to rotate by the power extracted from the crankshaft C being transmitted by the timing chain, and by this rotation, the valves 32L, 32R, 34L, and 34R are opened and closed. Let it be done.

  The air-fuel mixture after combustion becomes exhaust gas and is discharged to the exhaust manifolds 8L and 8R when the exhaust valves 34L and 34R are opened. Exhaust pipes 81L and 81R are connected to the exhaust manifolds 8L and 8R, respectively, and catalytic converters 82L and 82R incorporating a three-way catalyst or the like are attached to the exhaust pipes 81L and 81R. By passing the exhaust gas through the catalytic converters 82L and 82R, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxide components (NOx) contained in the exhaust gas are purified. Yes. Further, the downstream ends of the exhaust pipes 81L and 81R are joined and connected to the muffler 83.

  In addition, as a lubricating structure for lubricating between the inner wall surfaces of the cylinders 5L and 5R and the outer peripheral surfaces of the pistons 51L and 51R in the engine E, an oil pump, an oil filter, an oil jet mechanism, and the like (not shown) are provided. . The lubricating oil stored in the oil pan 62 is sucked by the oil pump through the filter and supplied to the oil jet mechanism. The lubricating oil supplied to the oil jet mechanism is supplied to the inner wall surfaces of the cylinders 5L and 5R, so that the space between the inner wall surfaces of the cylinders 5L and 5R and the outer peripheral surfaces of the pistons 51L and 51R is lubricated. . Thereafter, as the pistons 51L and 51R reciprocate, the lubricating oil is scraped off from the inner wall surfaces of the cylinders 5L and 5R and returned to the oil pan 62.

  Further, when lubrication with the lubricating oil is performed in this way, a part of the fuel injected from the in-cylinder direct injection injectors 78L and 78R adheres to the inner wall surfaces of the cylinders 5L and 5R. Lubricating oil is diluted by the adhered fuel. That is, the lubricating oil and the fuel are mixed and collected in the oil pan 62, and the lubricating oil stored in the oil pan 62 is diluted with the fuel. The fuel flowing into the oil pan 62 is then evaporated and introduced into the intake system of the engine E by a PCV device (not shown).

-Fuel supply system-
Next, a fuel supply system for supplying fuel to the port injectors 75L and 75R and the in-cylinder direct injectors 78L and 78R will be described with reference to FIG. FIG. 3 is a diagram schematically showing the structure of the fuel supply system 100 provided in one bank of the engine E according to the present embodiment. That is, in the engine E, the same fuel supply system 100 is provided in each of the banks 2L and 2R. Here, the fuel supply system 100 provided in the right bank 2R will be described as a representative.

  The fuel supply system 100 includes a feed pump 102 that feeds fuel from a fuel tank 101. A low-pressure fuel pipe 103 connected to the discharge side of the feed pump 102 is directed toward the low-pressure fuel system LF and the high-pressure fuel system HF. Each branching.

  The low pressure fuel system LF is provided with a low pressure fuel system delivery pipe 104 connected to one branch side of the low pressure fuel pipe 103. The low pressure fuel delivery pipe 104 is connected to the port injectors 75R, 75R,... Of each cylinder (four cylinders), and suppresses fuel pressure pulsation in the low pressure fuel delivery pipe 104. A pulsation damper 105 is provided.

  On the other hand, the high pressure fuel system HF is pressurized by the fuel pumped out by the feed pump 102 and sucked through the other branch side of the low pressure fuel pipe 103, and the in-cylinder direct injection injector 78R of each cylinder (four cylinders). , 78R, a high pressure fuel pump 110 is provided.

  As a schematic configuration of the high-pressure fuel pump 110, a cylinder 111, a plunger 112, a pressurizing chamber 113, and an electromagnetic spill valve 114 are provided. The plunger 112 has a lifter 112a attached to its lower end. A drive cam 115 is integrally attached to the intake camshaft 35R. The drive cam 115 is formed with two cam peaks (cam noses) 116 and 116 at an angular interval of 180 ° around the rotation axis of the intake camshaft 35R. Thereby, the rotation of the drive cam 115 accompanying the rotation of the intake camshaft 35R causes the plunger 112 to be pushed up by the cam noses 116, 116 via the lifter 112a. The volume of the is increased or reduced.

  Since the engine E according to the present embodiment has four cylinders in one bank, the injector (the port injection injector 75R described above) provided for each cylinder during one cycle of the engine E, that is, while the crankshaft C rotates twice. And one or both of the in-cylinder direct injection injectors 78R). Further, in the engine E, the intake camshaft 35R rotates once every time the crankshaft C rotates twice. Therefore, the fuel discharge operation from the high-pressure fuel pump 110 is performed twice for each cycle of the engine E.

  The pressurizing chamber 113 is partitioned by a plunger 112 and a cylinder 111. The pressurizing chamber 113 communicates with the feed pump 102 via a low-pressure fuel pipe 103, and communicates with a high-pressure fuel delivery pipe (pressure accumulation container) 107 via a high-pressure fuel pipe 106.

  The in-cylinder direct injection injectors 78R, 78R,... Are connected to the high-pressure fuel delivery pipe 107, and a return pipe 108 is connected via a relief valve 107a. The relief valve 107a is opened when the fuel pressure in the high-pressure fuel system delivery pipe 107 exceeds a predetermined pressure (for example, 15 MPa). By opening the valve, a part of the fuel stored in the high-pressure fuel system delivery pipe 107 is returned to the fuel tank 101 via the return pipe 108. As a result, an excessive increase in fuel pressure in the high-pressure fuel delivery pipe 107 is prevented. The return pipe 108 and the high-pressure fuel pump 110 are connected by a fuel discharge pipe 109, and the fuel leaked from the gap between the plunger 112 and the cylinder 111 enters the fuel storage chamber 118 at the upper part of the seal unit 117. Then, the fuel is accumulated and then returned to the fuel tank 101 through the fuel discharge pipe 109 and the return pipe 108 connected to the fuel storage chamber 118.

  The low-pressure fuel pipe 103 is provided with a filter 103a and a pressure regulator 103b. The pressure regulator 103b returns the fuel in the low-pressure fuel pipe 103 to the fuel tank 101 when the fuel pressure in the low-pressure fuel pipe 103 exceeds a predetermined pressure (for example, 0.4 MPa). The fuel pressure is maintained below a predetermined pressure. Further, a pulsation damper 119 is provided on the suction side of the high-pressure fuel pump 110, and the pulsation damper 119 suppresses fuel pressure pulsation in the low-pressure fuel pipe 103 when the high-pressure fuel pump 110 is operated. It has become. The high-pressure fuel pipe 106 is provided with a check valve 120 for preventing the fuel discharged from the high-pressure fuel pump 110 from flowing backward.

  The high-pressure fuel pump 110 is provided with the electromagnetic spill valve 114 for communicating or blocking between the low-pressure fuel pipe 103 and the pressurizing chamber 113. The electromagnetic spill valve 114 includes an electromagnetic solenoid 114a, and opens and closes by controlling energization to the electromagnetic solenoid 114a. The electromagnetic spill valve 114 is opened by the biasing force of the coil spring 114b when energization to the electromagnetic solenoid 114a is stopped. Hereinafter, the opening / closing operation of the electromagnetic spill valve 114 will be described.

  First, when the energization of the electromagnetic solenoid 114a is stopped, the electromagnetic spill valve 114 is opened by the biasing force of the coil spring 114b, and the low pressure fuel pipe 103 and the pressurizing chamber 113 are in communication with each other. In this state, when the plunger 112 moves in the direction in which the volume of the pressurizing chamber 113 increases (intake stroke), the fuel sent from the feed pump 102 is sucked into the pressurizing chamber 113 through the low-pressure fuel pipe 103. Is done.

  On the other hand, when the plunger 112 moves in the direction in which the volume of the pressurizing chamber 113 contracts (pressurization stroke), the electromagnetic spill valve 114 closes against the urging force of the coil spring 114b by energizing the electromagnetic solenoid 114a. Then, the low-pressure fuel pipe 103 and the pressurizing chamber 113 are disconnected from each other, and the check valve 121 is opened when the fuel pressure in the pressurizing chamber 113 reaches a predetermined value. And is discharged toward the high-pressure fuel system delivery pipe 107.

  The fuel discharge amount in the high-pressure fuel pump 110 is adjusted by controlling the valve closing period of the electromagnetic spill valve 114 in the pressurization stroke. That is, if the closing time of the electromagnetic spill valve 114 is advanced and the closing period is lengthened, the fuel discharge amount increases. If the closing start time is delayed by delaying the closing time of the electromagnetic spill valve 114, the fuel discharge amount decreases. To come. In this way, the fuel pressure in the high-pressure fuel delivery pipe 107 is controlled by adjusting the fuel discharge amount of the high-pressure fuel pump 110.

  The above is the structure of the fuel supply system 100 provided in the right bank 2R, and the same fuel supply system 100 is provided in the left bank 2L.

-Description of control block-
The operating state of the engine E configured as described above is controlled by an engine ECU (Electronic Control Unit) 9. As shown in FIG. 4, the engine ECU 9 includes a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, a backup RAM 94, and the like.

  The ROM 92 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 91 executes arithmetic processing based on various control programs and maps stored in the ROM 92. The RAM 93 is a memory that temporarily stores calculation results in the CPU 91, data input from each sensor, and the like. The backup RAM 94 is a non-volatile memory that stores data to be saved when the engine E is stopped.

  The ROM 92, CPU 91, RAM 93, and backup RAM 94 are connected to each other via a bus 97, and are connected to an external input circuit 95 and an external output circuit 96.

The external input circuit 95 includes a water temperature sensor 201, an air flow meter 202, an intake air temperature sensor 203, A / F sensors 204L and 204R, O ₂ sensors 205L and 205R, a throttle position sensor 206, a crank angle sensor 207, a cam angle sensor 208L, 208R, knock sensors 209L and 209R, an intake pressure sensor 210, an accelerator opening sensor 211, and the like are connected. Of the above sensors, the A / F sensors 204L and 204R, the O ₂ sensors 205L and 205R, the cam angle sensors 208L and 208R, and the knock sensors 209L and 209R are provided corresponding to the banks 2L and 2R, respectively. ing.

  On the other hand, the external output circuit 96 performs the ignition operation of the port injectors 75L and 75R, the in-cylinder direct injectors 78L and 78R, the throttle motor 72a for driving the throttle valve 72, and the spark plugs 77L and 77R. The igniters 220L and 220R are connected.

  The water temperature sensor 201 detects the temperature of the cooling water flowing in the water jacket 11 (see FIG. 2) formed in the cylinder block 1 and transmits the cooling water temperature signal to the engine ECU 9. Further, the temperature of the lubricating oil stored in the oil pan 62 is estimated based on the coolant temperature signal from the water temperature sensor 201. The temperature of the lubricating oil may be directly detected by providing an oil temperature sensor in the oil pan 62.

  The air flow meter 202 is disposed on the downstream side of the air cleaner 74, detects the intake air amount, and transmits the intake air amount signal to the engine ECU 9.

  The intake air temperature sensor 203 is disposed on the downstream side of the air cleaner 74, detects the intake air temperature, and transmits the intake air temperature signal to the engine ECU 9.

  The A / F sensors 204L and 204R are respectively arranged upstream of the catalytic converters 82L and 82R, and, for example, a limiting current type oxygen concentration sensor is applied. The A / F sensors 204L and 204R generate an output voltage corresponding to the air-fuel ratio over a wide air-fuel ratio region, and transmit the voltage signal to the engine ECU 9.

The O ₂ sensors 205L and 205R are respectively arranged downstream of the catalytic converters 82L and 82R, and for example, an electromotive force type (concentration cell type) oxygen concentration sensor is applied. The O ₂ sensors 205L and 205R determine whether or not the air-fuel ratio in the exhaust gas is the stoichiometric air-fuel ratio, and transmit a determination signal to the engine ECU 9.

  The throttle position sensor 206 detects the opening of the throttle valve 72 and transmits a throttle opening detection signal to the engine ECU 9.

  The crank angle sensor 207 is disposed in the vicinity of the crankshaft C and detects the rotation angle (crank angle CA) and the rotation speed (engine rotation speed NE) of the crankshaft C. Specifically, the crank angle sensor 207 outputs a pulse signal every predetermined crank angle (for example, 30 °). As an example of the crank angle detection method by the crank angle sensor 207, external teeth are formed at intervals of 30 ° on the outer peripheral surface of the rotor (NE rotor) integrally rotated with the crankshaft C, and are opposed to the external teeth. The crank angle sensor 207 formed of an electromagnetic pickup is disposed. When the external teeth pass near the crank angle sensor 207 as the crankshaft C rotates, the crank angle sensor 207 generates an output pulse.

  The cam angle sensors 208L and 208R are disposed in the vicinity of the intake camshafts 35L and 35R, respectively. For example, compression between the first cylinder located in the left bank 2L and the second cylinder located in the right bank 2R is performed. It is used as a cylinder discrimination sensor by outputting a pulse signal corresponding to each of the top dead center (TDC). That is, the cam angle sensors 208L and 208R output a pulse signal for each rotation of the intake camshafts 35L and 35R. As an example of a cam angle detection method using the cam angle sensors 208L and 208R, external teeth are formed at one location on the outer peripheral surface of the rotor integrally formed with the intake camshafts 35L and 35R, and the external teeth face each other. The cam angle sensors 208L and 208R, which are electromagnetic pickups, are arranged, and when the external teeth pass near the cam angle sensors 208L and 208R as the intake cam shafts 35L and 35R rotate, 208R generates an output pulse. Since the rotor rotates at half the rotational speed of the crankshaft C, an output pulse is generated every time the crankshaft C rotates 720 °. In other words, when a certain cylinder has the same stroke (for example, in the cam angle sensor 208L of the left bank 2L, the piston 51L of the first cylinder reaches the compression top dead center, the cam angle sensor 208R of the right bank 2R In this case, the output pulse is generated every time the piston 51R of the second cylinder reaches the compression top dead center.

  The knock sensors 209L and 209R are vibration sensors that detect the vibration of the engine transmitted to the cylinder block 1 by a piezoelectric element type (piezo element type) or an electromagnetic type (magnet, coil), and the like. An output signal corresponding to the above is transmitted to the engine ECU 9.

  The intake pressure sensor 210 is attached to the surge tank 71, detects the pressure in the intake pipe 73 (intake pipe pressure), and transmits the intake pressure signal to the engine ECU 9.

  The accelerator opening sensor 211 outputs a detection signal corresponding to the accelerator pedal depression amount (accelerator opening), and recognizes the operation speed of the accelerator by recognizing the amount of change in the accelerator opening per unit time. It can be done.

  And engine ECU9 controls each part, such as port injection injectors 75L and 75R, in-cylinder direct injection injectors 78L and 78R, throttle motor 72a, igniters 220L and 220R, based on the output signals of various sensors 201-211. Thus, various controls such as fuel injection control are executed.

  As an example, in the basic control of the ignition timing of the ignition plugs 77L and 77R by the igniters 220L and 220R, the ignition timing is advanced so that the ignition timing approaches MBT (Minimum Spark Advance for Best Torque). In the meantime, when knocking is detected by the knock sensors 209L and 209R, control is performed such that the knocking is eliminated by correcting the retard of the ignition timing.

In addition, as basic control of fuel injection of each of the injectors 75L, 75R, 78L, 78R, a target air-fuel ratio is calculated based on the engine load, engine speed, etc., and based on the intake air amount detected by the air flow meter 202, Control of the fuel injection amount (control of the valve opening time of the injectors 75L, 75R, 78L, 78R) is performed so that the target air-fuel ratio is obtained. At this time, the oxygen concentration in the exhaust gas is calculated based on the outputs of the A / F sensors 204L and 204R and the O ₂ sensors 205L and 205R, and the actual air-fuel ratio obtained from the calculated oxygen concentration is determined as the target air-fuel ratio. Air-fuel ratio feedback control is performed such that the fuel injection amount by the injectors 75L, 75R, 78L, 78R is controlled so as to match (for example, the theoretical air-fuel ratio). Further, as described above, when the engine E is operated at a low and medium load, fuel is injected from both the injectors 75L, 75R, 78L, 78R to generate a homogeneous air-fuel mixture, thereby improving the fuel consumption rate and reducing the emission. . Further, during high load operation of the engine E, fuel injection from only the in-cylinder direct injection injectors 78L and 78R is performed to improve the charging efficiency by the intake air cooling effect and suppress knocking. The fuel injection mode of these injectors 75L, 75R, 78L, 78R is not limited to this. In addition, the fuel injection form of each injector 75L, 75R, 78L, 78R, which is a feature of the present embodiment (the split ratio of split injection as the injection form from the in-cylinder direct injection injectors 78L, 78R, the in-cylinder direct injection injector 78L) , 78R and the injection ratio between the fuel injection amounts from the port injectors 75L and 75R, etc.) will be described later.

  Further, as the drive control of the throttle motor 72a, the opening degree of the throttle valve 72 which is the intake air amount for obtaining the requested engine output is obtained based on the opening degree of the accelerator pedal operated by the driver. In addition, the drive amount of the throttle motor 72a is controlled.

-Oil dilution rate judgment operation-
As described above, when a part of the fuel injected from the injector (mainly in-cylinder direct injection injectors 78L and 78R) adheres to the inner wall surfaces of the cylinders 5L and 5R, the fuel is lubricated in the liquid phase (cylinder 5L , 5R and the engine oil contributing to lubrication between the piston 51L and the outer peripheral surface of the piston 51L. The fuel mixed with the lubricating oil is scraped off from the cylinder inner wall surface and flows into the oil pan 62 as the pistons 51L and 51R reciprocate. If such a situation continues, the oil dilution in the oil pan 62 proceeds, leading to deterioration of the lubricating performance.

  In the present embodiment, in order to prevent the oil dilution from proceeding, the fuel injection mode in the in-cylinder direct injection injectors 78L and 78R and the port injection injectors 75L and 75R is changed according to the state of occurrence of oil dilution. Like to do.

  In order to change the fuel injection mode as described above, it is necessary to accurately recognize the degree of oil dilution (hereinafter referred to as “oil dilution rate”), so that an oil dilution rate determination operation is performed. It has become. Various methods have already been proposed for this oil dilution rate determination operation. In the following description, a typical operation for determining the oil dilution rate will be described, but the operation for determining the oil dilution rate is not limited to this.

The oil dilution rate is obtained by using a known fuel injection amount feedback correction amount FAF and a learning value of the feedback correction amount FAF (a value representing a constant deviation amount of the fuel injection amount) FGAF. That is, the exhaust air / fuel ratio is obtained based on the outputs of the A / F sensors 204L and 204R and the O ₂ sensors 205L and 205R, and the feedback correction amount FAF and the learning value are calculated from the deviation amount of the exhaust air / fuel ratio with respect to the target air / fuel ratio. FGAF is calculated.

  When the actual air-fuel ratio is lean (when leaner than the theoretical air-fuel ratio), the feedback correction amount FAF is calculated so that the actual air-fuel ratio shifts to the rich side. When the air-fuel ratio is rich (when richer than the theoretical air-fuel ratio), the feedback correction amount FAF is calculated so that the actual air-fuel ratio shifts to the lean side. Note that since the calculation method of the feedback correction amount FAF is known, description thereof is omitted here. Further, the learning value FGAF is calculated by adding or subtracting the update amount determined based on the map to the previously calculated learning value FGAF when a predetermined learning condition is satisfied. The learning value FGAF is calculated as a smaller value as the fuel injection amount is excessive (the actual fuel injection amount is larger than the target fuel injection amount). On the other hand, the smaller the fuel injection amount (the smaller the actual fuel injection amount than the target fuel injection amount), the larger the learning value FGAF is calculated. In addition, since the calculation method of learning value FGAF is also well-known, description here is abbreviate | omitted.

  In accordance with the feedback correction amount FAF and the learning value FGAF calculated in this way, the oil dilution rate Δqd by the fuel is calculated according to the following equation (1) (the oil dilution rate by the oil dilution rate recognition means in the present invention). Calculation operation).

Δqd = (FAF + FGAF) / constant (1)
As another oil dilution rate determination operation, a fuel correction amount that is a sum of the feedback correction amount FAF and the learning value FGAF is calculated, and the fuel correction amount during engine high load operation and during the engine low load operation are calculated. For example, the oil dilution rate Δqd is calculated from the deviation from the fuel correction amount.

-Variable range of fuel injection period-
Next, the change range of the fuel injection period in each of the in-cylinder direct injection injectors 78L and 78R and the port injection injectors 75L and 75R will be described. FIG. 5 is a diagram showing a change range of the fuel injection period in each of the injectors 78L, 78R, 75L, 75R (a diagram showing a rotation angle position of the crankshaft C). This will be specifically described below.

  As shown in FIG. 5, the valve opening period IVP of the intake valves 32L, 32R and the valve opening period EVP of the exhaust valves 34L, 34R are set by valve timing control executed by the engine ECU 9.

  In general, in the valve opening period IVP of the intake valves 32L and 32R, the valve opening start is set at a timing advanced from the suction top dead center (TDC), and the valve opening end is set from the suction bottom dead center (BDC). The timing is retarded. On the other hand, in the valve opening period EVP of the exhaust valves 34L and 34R, the valve opening start is set at a timing more advanced than the exhaust bottom dead center (BDC), and the valve opening end is the exhaust top dead center (TDC = suction top dead center). ), The timing is on the retard side.

  The change range of the fuel injection period from the in-cylinder direct injection injectors 78L and 78R is divided into two, that is, an intake stroke top dead center side injection range DIP1 and an intake stroke bottom dead center side injection range DIP2. Specifically, the intake stroke top dead center side injection range DIP1 is set to be advanced from the position 90 ° after the intake stroke top dead center (ATDC) of the pistons 51L and 51R at the rotation angle of the crankshaft C. Yes. For example, it is set in the range of 20 ° to 70 ° after the top dead center (ATDC) of the intake stroke. On the other hand, the suction stroke bottom dead center side injection range DIP2 is set to be retarded from the position 90 ° after the suction stroke top dead center (ATDC) of the pistons 51L and 51R in the rotation angle of the crankshaft C. For example, the suction stroke is set in a range of 110 ° to 160 ° after top dead center (ATDC).

  Further, as the fuel injection range (port fuel injection range) PIP from the port injectors 75L and 75R, when the port injectors 75L and 75R execute the asynchronous injection, the pistons 51L and 51R at the rotation angle of the crankshaft C are used. The suction stroke is set to the retard side from the position 90 ° before the top dead center (BTDC) and to the advance side from the suction top dead center (TDC). For example, the suction stroke is set in a range of 80 ° to 30 ° before top dead center (BTDC).

  Fuel injection from the in-cylinder direct injection injectors 78L and 78R and the port injection injectors 75L and 75R is executed during a part of the change range of the fuel injection period. The specific fuel injection execution period and fuel injection amount in each change range will be described later.

-Fuel injection mode-
Next, the fuel injection form from each injector 78L, 78R, 75L, 75R which is the feature of this embodiment is demonstrated. The control parameters in this fuel injection mode include the following.

  (1) Ratio between the fuel injection amount in the intake stroke top dead center side injection range DIP1 and the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 in the in-cylinder direct injection injectors 78L and 78R (hereinafter referred to as “division ratio”). ").

  In the following, the ratio of the fuel injection amount in the intake stroke top dead center side injection range DIP1 to the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 (DIP1 / DIP2) is expressed as “top dead center side division ratio ( Kh) ”, and the ratio of the fuel injection amount in the intake stroke bottom dead center injection range DIP2 to the fuel injection amount in the intake stroke top dead center injection range DIP1 (DIP2 / DIP1) (Kl) ".

  (2) Fuel injection timing (direct injection timing ainjd) of the in-cylinder direct injection injectors 78L and 78R set according to the top dead center side division ratio Kh.

  (3) Fuel injection pressure (direct injection fuel pressure epr) from the in-cylinder direct injection injectors 78L and 78R according to the top dead center side division ratio Kh.

  (4) Injection ratio (kpfi) between the fuel injection amount from the port injectors 75L and 75R and the fuel injection amount from the in-cylinder direct injection injectors 78L and 78R according to the top dead center side division ratio Kh.

  (5) Fuel injection timing (port injection timing ainjp) from the port injectors 75L and 75R according to the top dead center side division ratio Kh.

  (6) Fuel injection timing (direct injection timing ainjd) from the in-cylinder direct injection injectors 78L and 78R according to the bottom dead center side division ratio Kl.

  (7) Fuel injection pressure (direct injection fuel pressure epr) from the in-cylinder direct injection injectors 78L and 78R according to the bottom dead center side division ratio Kl.

  Next, the setting operation of each control parameter described above will be specifically described.

(1) Division ratio setting operation First, the fuel injection amount in the intake stroke top dead center side injection range DIP1 and the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 in the in-cylinder direct injection injectors 78L and 78R. The setting operation of the ratio (division ratio) will be described.

  When fuel is injected from the direct injection injectors 78L and 78R in the intake stroke top dead center side injection range DIP1, from the time when the fuel is injected to the ignition timing (combustion stroke start timing) of the spark plugs 77L and 77R. This period is relatively long (because it is obtained longer than when fuel is injected in the intake stroke bottom dead center side injection range DIP2), so that the homogeneity of the mixture in the cylinder at the start of the combustion stroke is high. can get. For this reason, stable combustion can be realized. Further, in the intake stroke top dead center side injection range DIP1, since the pistons 51L and 51R are located close to the top dead center, the in-cylinder pressure is relatively high and the fuel penetration force (penetration) is relatively low. The areas of the inner wall surfaces of the cylinders 5L and 5R exposed in the cylinder are relatively small. For this reason, the amount of fuel adhering to the inner wall surfaces of the cylinders 5L and 5R tends to decrease. That is, the oil dilution is unlikely to occur.

  On the other hand, when fuel is injected from the in-cylinder direct injection injectors 78L and 78R in the suction stroke bottom dead center side injection range DIP2, the lowering speed of the pistons 51L and 51R (the speed of movement from the top dead center toward the bottom dead center) ) Passes through the fastest period (around ATDC 90 °) and the fuel injection is performed with the intake air flow rate being high. Therefore, the fuel injection is performed with a large disturbance of the intake air in the cylinder. For this reason, stirring of the fuel is promoted, and weak stratified combustion is performed during the combustion stroke. As a result, the combustion speed is increased, and the engine output and the fuel consumption rate can be improved. However, in the suction stroke bottom dead center side injection range DIP2, since the pistons 51L and 51R are close to bottom dead center, the pressure in the cylinder is relatively low (the suction stroke top dead center side). (It is lower than the pressure in the cylinder in the injection range DIP1) The penetration force (penetration) of the fuel is relatively high, and the areas of the inner wall surfaces of the cylinders 5L and 5R exposed in the cylinder are relatively large . For this reason, the amount of fuel adhering to the inner wall surfaces of the cylinders 5L and 5R tends to increase. That is, the oil dilution is likely to occur.

  Therefore, in the present embodiment, the higher the oil dilution rate Δqd determined by the above-described oil dilution rate determination operation, the higher the top dead center side division ratio Kh is set (division ratio correction means in the present invention). (Division ratio correction operation). As a result, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 in which oil dilution is likely to occur is corrected to be reduced, and oil dilution can be suppressed.

  FIG. 6 is a division ratio setting map used when the top dead center side division ratio Kh is set according to the oil dilution ratio Δqd. By applying the oil dilution rate Δqd obtained by the oil dilution rate determination operation to this division ratio setting map, the top dead center side division ratio Kh is read out, and the intake stroke is performed so that the top dead center side division ratio Kh is obtained. The fuel injection amount in the top dead center side injection range DIP1 and the fuel injection amount in the intake stroke lower dead center side injection range DIP2 are set. This division ratio setting map is created in advance by experiments, simulations, or the like, and is stored in the ROM 92. The total fuel injection amount in the intake stroke top dead center side injection range DIP1 and the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 are based on the engine load, engine speed, etc. It is set according to the injection amount setting map.

  Further, the calculation formula when the top dead center side division ratio Kh is set by calculation is as shown in the following formula (2).

Kh = Kh ₀ × (1 + Δqd) (2)
Kh: Top dead center side division ratio to be set Kh ₀ : Top dead center side division ratio when oil dilution ratio Δqd is “0” (top dead center side division ratio set in advance by experiment, simulation, etc.)
Δqd: Oil dilution ratio As a specific example, when the oil dilution ratio Δqd is “0 (no oil dilution)”, the top dead center side division ratio is set to “1”. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 and the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 are made the same. When the oil dilution rate Δqd is “0.1 (10% dilution)”, the top dead center side division ratio is set to “1.1”. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is set to be 10% larger than the fuel injection amount in the intake stroke bottom dead center side injection range DIP2. These numerical values are not limited to this, and are appropriately set by experiment, simulation, or the like.

  Thus, by setting the top dead center side division ratio Kh according to the oil dilution rate Δqd, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 is a range in which oil dilution can be suppressed or prevented. Can be set to the maximum. That is, it is possible to set a division ratio that can achieve both ensuring of engine performance, improvement of fuel consumption rate, and suppression of oil dilution.

  In the above description, the case where the top dead center side division ratio Kh is set according to the oil dilution ratio Δqd has been described. However, since the top dead center side division ratio Kh and the bottom dead center side division ratio Kl are correlated, The bottom dead center division ratio Kl may be set according to the oil dilution rate Δqd. That is, as the oil dilution rate Δqd is higher, the bottom dead center side division ratio Kl is set lower. As described above, when the bottom dead center side division ratio Kl is set according to the oil dilution rate Δqd as described above, the division ratio setting map prepared in advance (in this case, the lower the oil dilution rate Δqd, the lower the dead The map is such that the point-side division ratio Kl is reduced), and the bottom dead center-side division ratio Kl is obtained by calculation.

(2) Fuel Injection Timing Setting Operation of In-Cylinder Direct Injection Injectors 78L and 78R Next, the setting operation of the start timing of fuel injection from in-cylinder direct injection injectors 78L and 78R will be described.

  When the top dead center side division ratio Kh is set as described above, the fuel injection amount in the intake stroke top dead center side injection range DIP1 changes according to the top dead center side division ratio Kh. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 increases as the top dead center side division ratio Kh is set higher. Along with this, the injection period also changes (when the fuel injection pressure is constant). For this reason, it is necessary to optimize the injection period. In other words, when the injection period deviates from the optimum period, there is a concern that combustion, exhaust emission, fuel consumption rate, WOT (Wide Open Throttle) performance, and oil dilution are all deteriorated.

  In view of this point, the fuel injection timing (hereinafter referred to as the direct injection timing ainjd) in the intake stroke top dead center side injection range DIP1 is set according to the top dead center side division ratio Kh.

  Specifically, according to each purpose such as (A) improvement of mixing characteristics of air and fuel, (B) suppression of oil dilution, and (C) improvement of air filling efficiency, it depends on the top dead center side division ratio Kh. Thus, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set (the fuel injection timing setting operation by the in-cylinder fuel injection timing setting means in the present invention). Hereinafter, the setting of the direct injection timing ainjd corresponding to each purpose will be individually described.

(A) Improvement of mixing property between air and fuel In order to improve the mixing property between air and fuel, the ignition timing of the spark plugs 77L and 77R after the fuel injection of the in-cylinder direct injection injectors 78L and 78R is completed. It is effective to secure a long period (interval). Therefore, as the top dead center side division ratio Kh is higher, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set to the advance side. That is, when the top dead center side division ratio Kh is high, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is large and the fuel injection period is also long, so the direct injection of the in-cylinder direct injection injectors 78L and 78R. By setting the injection timing ainjd to the advance side and obtaining the fuel injection end timing in the intake stroke top dead center side injection range DIP1 at an early stage, the above interval is secured long and the mixing property of air and fuel is improved. I am doing so.

  FIG. 7 is a direct injection timing setting map used when the direct injection timing ainjd is set according to the top dead center side division ratio Kh. The direct injection timing ainjd is read by applying the top dead center side division ratio Kh set as described above to this direct injection timing setting map, and the direct injection timing ainjd is obtained so that the direct injection timing ainjd is obtained. The fuel injection of 78L and 78R is controlled. The direct injection timing setting map is created in advance by experiments, simulations, and the like, and is stored in the ROM 92. The direct injection timing ainjd before being corrected according to the direct injection timing setting map is set in advance based on the engine load, the engine speed, and the like.

  Further, an arithmetic expression when the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set by calculation is as the following expression (3).

ainjd = ainjd ₀ + Kh × Kainjd (3)
ainjd: set direct injection timing ainjd ₀ : direct injection timing when top dead center side division ratio Kh is “0” (direct injection timing set in advance by experiment, simulation, etc.)
Kainjd: Conversion coefficient to direct injection timing In this way, by setting the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 in accordance with the top dead center side division ratio Kh, the in-cylinder direct injection injector It is possible to ensure a long period from the end of the fuel injection of 78L and 78R to the time when the ignition timing of the spark plugs 77L and 77R is reached, improving the mixing property of air and fuel, and combustion, exhaust emission, Fuel consumption rate, WOT performance, and oil dilution can be improved.

  In addition, as the top dead center side division ratio Kh targeted by the setting operation of the direct injection timing ainjd for improving the mixing property between air and fuel, for example, the top dead center side division ratio Kh is “0.5”. If it exceeds, the direct injection timing ainjd may be set according to the top dead center side division ratio Kh. That is, when the top dead center side division ratio Kh exceeds a predetermined value set in advance, the higher the top dead center side division ratio Kh, the more advanced the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1. Set to the side. This is to cope with a situation in which improvement of the mixing performance is required when the fuel injection amount in the intake stroke top dead center side injection range DIP1 is relatively large.

  In the above description, the case where the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set according to the top dead center side division ratio Kh has been described, but the top dead center side division ratio Kh and the bottom dead center are set. Since there is a correlation with the side division ratio Kl, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 may be set according to the bottom dead center side division ratio Kl. That is, as the bottom dead center side division ratio Kl is lower, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set to the advance side. As described above, when the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set according to the bottom dead center side division ratio Kl as described above, a direct injection timing setting map ( In this case, as the bottom dead center side division ratio Kl is lower, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is set to the advance side) and the direct injection timing ainjd is obtained by calculation. Like that.

(B) Suppression of oil dilution In order to suppress the oil dilution described above, fuel injection is performed with a relatively high in-cylinder pressure to reduce the penetration of the fuel, and it is exposed to the cylinder. It is effective to perform fuel injection in a state where the inner wall surfaces of the cylinders 5L and 5R are relatively small. Therefore, the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the advance side as the oil dilution rate Δqd obtained by the oil dilution rate determination operation is higher. That is, when the top dead center side division ratio Kh is high, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is large and the fuel injection period is also long, so the fuel injection of the in-cylinder direct injection injectors 78L and 78R. The timing is set to the advance side, fuel injection is performed with the cylinder pressure being relatively high, and the penetration of the fuel (penetration) is lowered, and the cylinders 5L and 5R exposed in the cylinder Fuel injection is performed with the wall surface having a relatively small area.

  Thus, oil dilution can be suppressed by setting the direct injection timing ainjd in the suction stroke top dead center side injection range DIP1 in accordance with the oil dilution rate Δqd.

(C) Improvement of air charging efficiency In order to improve the air charging efficiency ηv, the injected fuel must not be blocked from flowing air into the cylinder, and the latent heat of vaporization can be maximized. It is effective to effectively utilize the intake air cooling effect of the fuel. Therefore, the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the advance side as the top dead center side division ratio Kh is lower. That is, when the top dead center side division ratio Kh is low, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is small and the fuel injection period is also short, so the direct injection of the in-cylinder direct injection injectors 78L and 78R. The injection timing ainjd is set to the advance side so that fuel injection can be stopped in a period in which the intake air amount per unit time is large. Specifically, fuel injection is performed during a period (for example, 60 ° to 120 ° after the top dead center) in which the descending speed of the pistons 51L and 51R (speed moving from the top dead center toward the bottom dead center) is the fastest in the intake stroke. In other words, at 60 ° after the top dead center, the direct injection timing ainjd is advanced so that the injection of a required amount of fuel in the intake stroke top dead center side injection range DIP1 is completed. Set to the side.

  Thus, by setting the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 in accordance with the top dead center side division ratio Kh, the air charging efficiency ηv can be increased, and combustion and exhaust emissions can be achieved. , Fuel consumption rate, WOT performance can be improved.

  As the top dead center side division ratio Kh targeted for the setting operation of the direct injection timing ainjd for improving the air charging efficiency ηv, for example, the top dead center side division ratio Kh is less than “0.3”. In this case, the direct injection timing ainjd may be set according to the top dead center side division ratio Kh. That is, when the top dead center side division ratio Kh falls below a predetermined value, the direct injection timing ainjd in the intake stroke top dead center side injection range DIP1 is advanced as the top dead center side division ratio Kh decreases. Set to the side. This is because a relatively small amount of fuel can be stopped during the period when the descending speed of the pistons 51L and 51R (the speed of movement from the top dead center toward the bottom dead center) is the fastest in the intake stroke. This is because the above-described effect can be achieved when the fuel injection amount is injected. In other words, when the top dead center side division ratio Kh is relatively high, even if the direct injection timing ainjd is set to the advance side, it may not be possible to obtain the effect of improving the air charging efficiency ηv. The range of the top dead center side division ratio Kh targeted by the above operation is specified.

(3) Fuel injection pressure setting operation from in-cylinder direct injection injectors 78L and 78R Next, the setting operation of fuel injection pressure from in-cylinder direct injection injectors 78L and 78R (hereinafter referred to as direct injection fuel pressure epr) will be described. To do.

  When the top dead center side division ratio Kh is set as described above, the fuel injection amount in the intake stroke top dead center side injection range DIP1 changes according to the top dead center side division ratio Kh. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 increases as the top dead center side division ratio Kh is set higher. Along with this, an appropriate fuel injection pressure for appropriately obtaining the injection period also changes. In other words, when the fuel injection pressure deviates from an appropriate value, there is a concern that combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution are all deteriorated.

  In view of this point, the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set according to the top dead center side division ratio Kh.

  Specifically, from the direct injection injectors 78L and 78R in accordance with the top dead center side division ratio Kh, according to the respective objectives (A) improvement of mixing characteristics of air and fuel, and (B) suppression of oil dilution. The direct injection fuel pressure epr is set (setting operation of the fuel injection pressure by the fuel injection pressure setting means in the present invention). Hereinafter, the setting of the direct injection fuel pressure epr corresponding to each purpose will be described individually.

(A) Improvement of mixing property between air and fuel As described above, in order to improve the mixing property between air and fuel, the spark plug 77L, after the fuel injection of in-cylinder direct injection injectors 78L, 78R is completed. It is effective to ensure a long period (interval) until the ignition timing of 77R. Therefore, the direct injection fuel pressure epr is set to the high pressure side so that the fuel injection period in the intake stroke top dead center side injection range DIP1 can be shortened as the top dead center side division ratio Kh increases. That is, when the top dead center side division ratio Kh is high, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is large and the fuel injection period tends to be long, so that the direct injection of the in-cylinder direct injection injectors 78L and 78R The fuel injection pressure epr is set high, and the fuel injection period until the required amount of fuel injection is completed is shortened, so that the interval can be secured long, and the mixing property between air and fuel is improved. .

  FIG. 8 is a direct injection fuel pressure setting map used when the direct injection fuel pressure epr is set according to the top dead center side division ratio Kh. By applying the top dead center side division ratio Kh set as described above to the direct fuel pressure setting map, the direct fuel pressure epr is read out, and the high pressure fuel pump 110 ( The electromagnetic spill valve 114) is controlled. This direct injection fuel pressure setting map is created in advance by experiments, simulations, etc., and is stored in the ROM 92.

  Further, an arithmetic expression when the direct fuel injection pressure epr from the in-cylinder direct injection injectors 78L and 78R is set by calculation is as the following expression (4).

epr = epr ₀ + Kh × Kepr (4)
epr: Direct injection fuel pressure to be set epr ₀ : Direct injection fuel pressure when the top dead center side division ratio Kh is “0” (direct injection fuel pressure set in advance by experiment, simulation, etc.)
Kepr: Conversion coefficient to direct injection fuel pressure In this way, by setting the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R according to the top dead center side division ratio Kh, the necessary amount can be obtained in a short time. Fuel injection can be completed, and it is possible to ensure a long period from the end of fuel injection of the in-cylinder direct injection injectors 78L and 78R until the ignition timing of the spark plugs 77L and 77R is reached. Mixability with fuel can be improved, and combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution can be improved.

  Further, in this case, since the fuel pressure in the intake stroke bottom dead center side injection range DIP2 also increases, the injection period is set short and the top dead center side division ratio Kh is maintained.

  In the above description, the direct injection fuel pressure epr is set according to the top dead center side split ratio Kh. However, the top dead center side split ratio Kh and the bottom dead center side split ratio Kl are correlated. The direct injection fuel pressure epr may be set according to the bottom dead center side division ratio Kl. That is, the direct injection fuel pressure epr is set to the higher pressure side as the bottom dead center side division ratio Kl is lower. Even when the direct injection fuel pressure epr is set in accordance with the bottom dead center division ratio Kl as described above, a direct injection fuel pressure setting map (in this case, the bottom dead center division ratio Kl prepared in advance as described above) is used. The lower the value is, the more the direct injection fuel pressure epr becomes a map for setting the high pressure side), or the direct injection fuel pressure epr is obtained by calculation.

(B) Suppression of oil dilution In order to suppress the oil dilution, it is effective to reduce the penetration force (penetration) of the fuel injected from the in-cylinder direct injection injectors 78L and 78R. Therefore, the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set to the lower pressure side as the oil dilution rate Δqd obtained by the oil dilution rate determination operation is higher. Thereby, the penetration force (penetration) of the fuel is set low.

  Thus, oil dilution can be suppressed by setting the direct injection fuel pressure epr in accordance with the oil dilution rate Δqd.

  If the direct injection fuel pressure epr is set to the low pressure side in this way, the fuel injection period tends to become longer. In this case, the fuel injection periods of the in-cylinder direct injection injectors 78L and 78R are set to the advance side. It is preferable to shift to.

(4) Injection ratio setting operation Next, an injection ratio (sharing ratio in the present invention) kpfi between the fuel injection amount from the port injectors 75L and 75R and the fuel injection amount from the in-cylinder direct injection injectors 78L and 78R. The setting operation will be described.

  When the top dead center side division ratio Kh is set as described above, the fuel injection amount in the intake stroke top dead center side injection range DIP1 changes according to the top dead center side division ratio Kh. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 increases as the top dead center side division ratio Kh is set higher. And in order to further improve the combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution when the top dead center side division ratio Kh is set in this way, it is necessary to optimize the above-mentioned injection division ratio It is.

  In view of this point, the ejection division rate kpfi is set according to the top dead center side division ratio Kh.

  Specifically, the top dead center side split ratio Kh is set according to the purposes such as (A) improvement of air / fuel mixing, (B) suppression of oil dilution, and (C) optimization of air charging efficiency. Accordingly, the injection division ratio kpfi is set (setting operation of the sharing ratio by the fuel injection sharing ratio setting means in the present invention). Hereinafter, the setting of the injection ratio kpfi according to each purpose will be described individually.

(A) Improvement of mixing property between air and fuel As described above, in order to improve the mixing property between air and fuel, the spark plug 77L is used after the fuel injection from the injectors 75L, 75R, 78L, 78R is completed. , 77R is effective to ensure a long period (interval) until the ignition timing. Therefore, the fuel injection amount from the port injectors 75L and 75R is increased as the top dead center side division ratio Kh is higher. That is, the in-cylinder direct injection injectors 78L and 78R are set to have low injection ratios, and the port injection injectors 75L and 75R are set to have high injection ratios. As a result, among the total amount of fuel injected from each of the injectors 75L, 75R, 78L, 78R, a large amount of fuel (the amount of fuel from the port injectors 75L, 75R) obtained with a long interval is secured, and air and The mixing with the fuel is improved. That is, when the top dead center side division ratio Kh is set high, it is assumed that fuel injection control that requires a mixing improvement of air and fuel is being performed, so the port injectors 75L and 75R side The fuel injection mode that can further improve the mixing property between the air and the fuel is realized by setting the injection ratio of the fuel to be high.

  FIG. 9 is an injection ratio setting map used when the injection ratio (port injection ratio on the port injectors 75L and 75R side) kpfi is set in accordance with the top dead center side division ratio Kh. By applying the top dead center side division ratio Kh set as described above to this injection ratio setting map, the injection ratio kpfi is read out, and each of the injectors 75L, 75R, 78L, so as to obtain this injection ratio kpfi. The fuel injection amount (valve opening period) from 78R is controlled. This injection ratio setting map is created in advance by experiments, simulations, or the like, and is stored in the ROM 92.

  Further, an equation for setting the injection ratio kpfi by calculation is as the following equation (5).

kpfi = kpfi ₀ + Kh × Kkpfi (5)
kpfi: set injection ratio kpfi ₀ : injection ratio when the top dead center side division ratio Kh is “0” (an injection ratio set in advance by experiments, simulations, etc.)
Kkpfi: Conversion coefficient to injection ratio By setting the injection ratio kpfi according to the top dead center side split ratio Kh in this way, the total amount of fuel injected from each injector 75L, 75R, 78L, 78R Among them, it is possible to secure a large amount of fuel that can be obtained with a long interval, improve the mixing characteristics of air and fuel, and improve combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution. it can.

  In the above description, the case where the ejection division rate kpfi is set according to the top dead center side division ratio Kh has been described. However, the top dead center side division ratio Kh and the bottom dead center side division ratio Kl have a correlation. The spray division rate kpfi may be set according to the bottom dead center side division ratio Kl. That is, the lower the bottom dead center split ratio Kl, the higher the jet split ratio on the port injectors 75L, 75R side. In this way, also in the case of setting the injection division rate kpfi according to the bottom dead center side division ratio Kl, the injection division rate setting map prepared in advance as described above (in this case, the bottom dead center side division ratio Kl is low). The map is such that the injection ratio on the port injectors 75L and 75R side is set higher), and the injection ratio kpfi is obtained by calculation.

(B) Suppression of oil dilution In order to suppress the oil dilution, it is effective to lower the penetration force (penetration) of the fuel supplied into the cylinder. Therefore, the higher the oil dilution rate Δqd obtained by the oil dilution rate determination operation, the larger the fuel injection amount from the port injectors 75L and 75R. That is, the in-cylinder direct injection injectors 78L and 78R are set to have low injection ratios, and the port injection injectors 75L and 75R are set to have high injection ratios. The port injection injectors 75L and 75R are disposed in the intake ports 31L and 31R and have a relatively large distance from the inner wall surface of the cylinders 5L and 5R (the inner wall surfaces of the in-cylinder direct injection injectors 78L and 78R and the cylinders 5L and 5R). Further, the pressure of the fuel injected from the port injectors 75L and 75R is about the discharge pressure from the feed pump 102 and is relatively low (the discharge pressure from the high-pressure fuel pump 110 is received). This is lower than the fuel injection pressure of the in-cylinder direct injection injectors 78L and 78R). For this reason, by setting a high injection ratio on the side of the port injectors 75L and 75R, it becomes possible to reduce the penetration force (penetration) of the fuel directly injected into the cylinder. The amount of fuel adhering to the wall surface can be reduced.

  Thus, oil dilution can be suppressed by setting the spray distribution rate kpfi according to the oil dilution rate Δqd.

(C) Optimization of air filling efficiency When the air filling efficiency ηv is too high, the amount of fuel injection is increased accordingly, and there is a concern about the occurrence of knocking. That is, when the top dead center side division ratio Kh is high, the fuel injection amount in the intake stroke top dead center side injection range DIP1 in which the intake air cooling effect is greatly generated increases, so the air charging efficiency ηv becomes too high. There is a possibility that knocking may occur.

  Therefore, as the top dead center side division ratio Kh is higher, that is, as the fuel injection amount in the intake stroke top dead center side injection range DIP1 is larger, the fuel injection amounts from the port injectors 75L and 75R are set larger. That is, the in-cylinder direct injection injectors 78L and 78R are set to have low injection ratios, and the port injection injectors 75L and 75R are set to have high injection ratios.

  As a result, the total fuel injection amount from the in-cylinder direct injection injectors 78L and 78R is reduced, and as a result, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is also reduced (the division ratio is changed). Without this, the fuel injection amount in the intake stroke top dead center side injection range DIP1 is reduced).

  Thus, by setting the injection ratio kpfi according to the top dead center side division ratio Kh, the air filling efficiency ηv can be optimized and knocking can be suppressed.

(5) Fuel Injection Timing Setting Operation for Port Injectors 75L and 75R Next, the fuel injection timing setting operation from the port injectors 75L and 75R will be described.

  When the top dead center side division ratio Kh is set as described above, the fuel injection amount in the intake stroke top dead center side injection range DIP1 changes according to the top dead center side division ratio Kh. That is, the fuel injection amount in the intake stroke top dead center side injection range DIP1 increases as the top dead center side division ratio Kh is set higher. In order to further improve the combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution when the top dead center side division ratio Kh is set in this way, the port injection injectors 75L and 75R It is necessary to optimize the fuel injection timing.

  In view of this point, the fuel injection timing from the port injectors 75L and 75R (hereinafter referred to as port injection timing ainjp) is set according to the top dead center side division ratio Kh.

  Specifically, the port injection timing is determined according to the top dead center side split ratio Kh according to the respective objectives of (A) improving air charging efficiency and suppressing knocking, and (B) suppressing oil dilution and ensuring engine performance. ainjp is set (fuel injection timing setting operation by the intake passage fuel injection timing setting means in the present invention). Hereinafter, the setting of the port injection timing ainjp according to each purpose will be individually described.

  As described above, the port injection timing ainjp is not synchronized with the synchronous injection in which the fuel injection is performed in conjunction with the opening operation of the intake valves 32L and 32R and the opening operation of the intake valves 32L and 32R. In other words, there is asynchronous injection that performs fuel injection even when the intake valves 32L and 32R are closed, and these can be switched, or the ratio between the injection amount in the synchronous injection and the injection amount in the asynchronous injection can be changed. It has become. In general, asynchronous injection is performed during normal operation of the engine E, and synchronous injection is performed during cold operation.

(A) Improvement of air charging efficiency and suppression of knocking When the top dead center side division ratio Kh is higher than a predetermined value, synchronous injection is performed as the port injection timing ainjp from the port injection injectors 75L and 75R. Alternatively, the port injection timing ainjp from the port injection injectors 75L and 75R is set so that the injection amount in the synchronous injection is larger than the injection amount in the asynchronous injection as the top dead center side division ratio Kh is higher.

  In the synchronous injection, the same effect as the fuel injection in the in-cylinder direct injection injectors 78L and 78R is exhibited, and the fuel injection pressure is relatively low, so the amount of fuel adhering to the inner wall surfaces of the cylinders 5L and 5R is Few. For this reason, oil dilution can be suppressed, engine E performance can be secured, and knocking can be suppressed.

  FIG. 10 is a port injection timing setting map used when the port injection timing ainjp is set according to the top dead center side division ratio Kh. By applying the top dead center side division ratio Kh set as described above to this port injection timing setting map, the port injection timing ainjp is read, and the fuel of the port injection injectors 75L and 75R is obtained so as to obtain this port injection timing ainjp. The injection is controlled. In FIG. 10, the upper side of the port injection timing ainjp, which is the vertical axis, is the side on which the synchronous injection amount is increased. This port injection timing setting map is created in advance by experiments, simulations, etc., and is stored in the ROM 92.

  An arithmetic expression when the port injection timing ainjp is set by calculation is as shown in the following expression (6).

ainjp = ainjp ₀ + Kh × Kainjp (6)
ainjp: Port injection timing to be set ainjp ₀ : Port injection timing when top dead center side division ratio Kh is “0” (port injection timing set in advance by experiment, simulation, etc.)
Kainjp: Conversion coefficient to port injection timing In this way, by setting the port injection timing ainjp according to the top dead center side division ratio Kh, oil dilution is suppressed, engine E performance is secured, and knocking is suppressed. Is possible.

  In the above description, the port injection timing ainjp is set according to the top dead center side division ratio Kh. However, the top dead center side division ratio Kh and the bottom dead center side division ratio Kl have a correlation. The port injection timing ainjp may be set according to the bottom dead center side division ratio Kl. That is, when the bottom dead center side division ratio Kl is equal to or less than the predetermined value, the synchronous injection is executed as the port injection timing ainjp, or the lower the bottom dead center side division ratio Kl is, the port injection injectors 75L and 75R are. Is set so that the injection amount in the synchronous injection is larger than the injection amount in the asynchronous injection. Even when the port injection timing ainjp is set according to the bottom dead center division ratio Kl as described above, the port injection timing ainjp is obtained by a port injection timing setting map prepared in advance as described above or by calculation. .

(B) Suppression of oil dilution and securing of engine performance When the top dead center side division ratio Kh is lower than a predetermined value, asynchronous injection is performed as the port injection timing ainjp. Or it sets so that the injection quantity in asynchronous injection may become larger than the injection quantity in synchronous injection, so that the top dead center side division ratio Kh is low.

  In the asynchronous injection, as described above, the fuel injection is performed when the intake valves 32L and 32R are closed. Therefore, the fuel and air are mixed in the intake ports 31L and 31R, and the intake valves 32L and 32R are mixed. When the valve is opened, the premixed air-fuel mixture is introduced into the cylinder. For this reason, it is possible to suppress oil dilution and ensure the performance of the engine E.

(6) Fuel injection timing setting operation in the intake stroke bottom dead center side injection range DIP2 Next, the fuel injection start timing setting operation in the intake stroke bottom dead center side injection range DIP2 of the in-cylinder direct injection injectors 78L and 78R Will be described.

  When the bottom dead center side division ratio Kl is set as described above, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 changes according to the bottom dead center side division ratio Kl. That is, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 increases as the bottom dead center side division ratio Kl is set higher. Along with this, the injection period also changes (when the fuel injection pressure is constant). For this reason, it is necessary to optimize the injection period. In other words, when the injection period deviates from the optimum period, there is a concern that combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution are all deteriorated.

  In view of this point, the fuel injection timing (hereinafter referred to as the direct injection timing ainjd) in the intake stroke bottom dead center side injection range DIP2 is set according to the bottom dead center side division ratio Kl.

  Specifically, according to the objectives such as (A) improvement of mixing characteristics of air and fuel, (B) suppression of oil dilution, (C) improvement of air filling efficiency, and (D) suppression of smoke generation, The direct injection timing ainjd in the suction stroke bottom dead center side injection range DIP2 is set according to the dead point side division ratio Kl. Hereinafter, the setting of the direct injection timing ainjd corresponding to each purpose will be individually described.

(A) Improvement of mixing property between air and fuel In order to improve the mixing property between air and fuel, the ignition timing of the spark plugs 77L and 77R after the fuel injection of the in-cylinder direct injection injectors 78L and 78R is completed. It is effective to secure a long period (interval). Therefore, the direct injection timing ainjd in the intake stroke bottom dead center side injection range DIP2 is set to the advance side as the bottom dead center side division ratio Kl is higher. That is, when the bottom dead center side division ratio Kl is high, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 is large and the fuel injection period is also long, so the direct injection of the in-cylinder direct injection injectors 78L and 78R. The injection timing ainjd is set to the advance side to ensure a long interval and improve the mixing performance of air and fuel.

  FIG. 11 is a direct injection timing setting map used when the direct injection timing ainjd is set according to the bottom dead center side division ratio Kl. The direct injection timing ainjd is read by applying the bottom dead center side division ratio Kl set as described above to the direct injection timing setting map, and the direct injection timing ainjd is obtained so that the direct injection timing ainjd is obtained. The fuel injection of 78L and 78R is controlled. The direct injection timing setting map is created in advance by experiments, simulations, and the like, and is stored in the ROM 92. The direct injection timing ainjd before being corrected according to the direct injection timing setting map is set in advance based on the engine load, the engine speed, and the like.

  Further, an arithmetic expression when the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set by calculation is as the following expression (7).

ainjd = ainjd ₀ + Kl × Kainjd (7)
ainjd ₀ : direct injection timing when the bottom dead center side split ratio Kl is “0” (fuel injection timing set in advance by experiment, simulation, etc.)
In this way, by setting the direct injection timing ainjd in the intake stroke bottom dead center side injection range DIP2 in accordance with the bottom dead center side division ratio Kl, fuel injection from the in-cylinder direct injection injectors 78L and 78R is completed. It is possible to ensure a long period from the ignition timing to the ignition timing of the spark plugs 77L, 77R, improve the mixing characteristics of air and fuel, and improve combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution be able to.

  In the above description, the case where the direct injection timing ainjd in the intake stroke bottom dead center side injection range DIP2 is set according to the bottom dead center side split ratio Kl has been described. However, the bottom dead center side split ratio Kl and the top dead center are set. Since there is a correlation with the side division ratio Kh, the direct injection timing ainjd in the intake stroke lower dead center side injection range DIP2 may be set according to the top dead center side division ratio Kh. That is, as the top dead center side division ratio Kh is lower, the direct injection timing ainjd in the intake stroke lower dead center side injection range DIP2 is set to the advance side. Thus, also when the direct injection timing ainjd in the intake stroke lower dead center side injection range DIP2 is set according to the top dead center side division ratio Kh, a direct injection timing setting map ( In this case, the lower the top dead center side division ratio Kh is, the map becomes such that the direct injection timing ainjd in the intake stroke lower dead center side injection range DIP2 is set to the advance side) and the direct injection timing ainjd is obtained by calculation. Like that.

(B) Suppression of oil dilution In order to suppress the oil dilution described above, fuel injection is performed with a relatively high in-cylinder pressure to reduce the penetration of the fuel, and it is exposed to the cylinder. It is effective to perform fuel injection in a state where the inner wall surfaces of the cylinders 5L and 5R are relatively small. Therefore, the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the advance side as the oil dilution rate Δqd obtained by the oil dilution rate determination operation is higher. That is, when the bottom dead center side division ratio Kl is high, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 is large and the fuel injection period is also long, so that the fuel injection of the in-cylinder direct injection injectors 78L and 78R. The timing is set to the advance side, fuel injection is performed with the cylinder pressure being relatively high, and the penetration of the fuel (penetration) is lowered, and the cylinders 5L and 5R exposed in the cylinder Fuel injection is performed with the wall surface having a relatively small area.

  Thus, oil dilution can be suppressed by setting the direct injection timing ainjd in the intake stroke bottom dead center side injection range DIP2 in accordance with the oil dilution rate Δqd.

(C) Improvement of air charging efficiency In order to improve the air charging efficiency ηv, the injected fuel must not be blocked from flowing air into the cylinder, and the latent heat of vaporization can be maximized. It is effective to effectively utilize the intake air cooling effect of the fuel. Therefore, the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the retarded side as the bottom dead center side division ratio Kl is lower. That is, when the bottom dead center side split ratio Kl is low, the fuel injection amount in the suction stroke bottom dead center side injection range DIP2 is small and the fuel injection period is also shortened, so the direct injection of the in-cylinder direct injection injectors 78L and 78R. The injection timing ainjd is set to the retarded angle side so that fuel injection is started after a period when the intake air amount per unit time is large. Specifically, fuel injection is performed during a period (for example, 60 ° to 120 ° after the top dead center) in which the descending speed of the pistons 51L and 51R (speed moving from the top dead center toward the bottom dead center) is the fastest in the intake stroke. In other words, the direct injection timing ainjd is set to the retarded side so that the fuel injection in the intake stroke bottom dead center side injection range DIP2 is started after passing through 120 ° after the top dead center.

  Thus, by setting the direct injection timing ainjd in the intake stroke bottom dead center side injection range DIP2 in accordance with the bottom dead center side division ratio Kl, the air charging efficiency ηv can be increased, and the exhaust emission, fuel The consumption rate and WOT performance can be improved.

(D) Smoke generation suppression In order to suppress the generation of smoke, it is effective to suppress the adhesion of the liquid phase fuel to the top surfaces of the pistons 51L and 51R. That is, it is necessary to avoid the generation of smoke due to the lack of oxygen around the top surfaces of the pistons 51L and 51R.

  Therefore, the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the advance side as the bottom dead center division ratio Kl is higher. That is, in order to suppress adhesion of liquid phase fuel to the top surfaces of the pistons 51L and 51R, the fuel injection in the intake stroke bottom dead center side injection range DIP2 is changed from the top dead center to the bottom dead center. It is effective to complete while moving toward. In other words, when the pistons 51L and 51R are moving from the bottom dead center toward the top dead center, the pistons 51L and 51R approach the in-cylinder direct injection injectors 78L and 78R. When injection is performed, there is a concern that liquid phase fuel may adhere to the top surfaces of the pistons 51L and 51R. Therefore, the higher the bottom dead center split ratio Kl is, the more the direct injection timing ainjd of the in-cylinder direct injection injectors 78L and 78R is set to the advance side, and the pistons 51L and 51R are farther away from the in-cylinder direct injection injectors 78L and 78R. During this period, fuel injection is completed, and adhesion of liquid phase fuel to the top surfaces of the pistons 51L and 51R is suppressed, thereby suppressing the occurrence of smoke.

(7) Fuel injection pressure setting operation according to bottom dead center side split ratio Kl Next, fuel injection pressures (direct fuel pressure epr) from in-cylinder direct injection injectors 78L and 78R according to bottom dead center side split ratio Kl ) Setting operation will be described.

  When the bottom dead center side division ratio Kl is set as described above, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 changes according to the bottom dead center side division ratio Kl. That is, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 increases as the bottom dead center side division ratio Kl is set higher. Along with this, an appropriate fuel injection pressure for appropriately obtaining the injection period also changes. In other words, when the fuel injection pressure deviates from an appropriate value, there is a concern that combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution are all deteriorated.

  In view of this point, the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set according to the bottom dead center side division ratio Kl.

  Specifically, the bottom dead center side division is performed in accordance with each purpose such as (A) improvement of mixing characteristics of air and fuel, (B) suppression of oil dilution, and (C) optimization of the mixture state in the cylinder. The direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set in accordance with the ratio Kl. Hereinafter, the setting of the direct injection fuel pressure epr corresponding to each purpose will be described individually.

(A) Improvement of mixing property between air and fuel As described above, in order to improve the mixing property between air and fuel, the spark plug 77L, after the fuel injection of in-cylinder direct injection injectors 78L, 78R is completed. It is effective to ensure a long period (interval) until the ignition timing of 77R. Therefore, the direct injection fuel pressure epr is set to the high pressure side so that the intake stroke bottom dead center side injection range DIP2 can be shortened as the bottom dead center side division ratio Kl increases. That is, when the bottom dead center side split ratio Kl is high, the fuel injection amount in the intake stroke bottom dead center side injection range DIP2 is large and the fuel injection period tends to be long, so that the direct injection of the in-cylinder direct injection injectors 78L and 78R. The fuel injection pressure epr is set high, and the fuel injection period until the required amount of fuel injection is completed is shortened, so that the interval can be secured long, and the mixing property between air and fuel is improved. .

  FIG. 12 is a direct injection fuel pressure setting map used when the direct injection fuel pressure epr in the intake stroke bottom dead center side injection range DIP2 is set according to the bottom dead center side division ratio Kl. The direct injection fuel pressure epr is read by fitting the bottom dead center side division ratio Kl set as described above to this direct injection fuel pressure setting map, and the high pressure fuel pump 110 ( The electromagnetic spill valve 114) is controlled. This direct injection fuel pressure setting map is created in advance by experiments, simulations, etc., and is stored in the ROM 92.

  In addition, the calculation formula for setting the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R by calculation is as shown in the following formula (8).

epr = epr ₀ + Kl × Kepr (8)
epr ₀ : direct injection fuel pressure when the bottom dead center side division ratio Kl is “0” (direct injection fuel pressure set in advance by experiment, simulation, etc.)
In this way, by setting the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R according to the bottom dead center side division ratio Kl, a required amount of fuel injection can be completed in a short time, It is possible to ensure a long period from the end of fuel injection from the in-cylinder direct injection injectors 78L and 78R to the ignition timing of the spark plugs 77L and 77R, improving the mixing property between air and fuel, and exhaust emission. , Fuel consumption rate, WOT performance, oil dilution can be improved.

(B) Suppression of oil dilution In order to suppress the oil dilution, it is effective to reduce the penetration force (penetration) of the fuel injected from the in-cylinder direct injection injectors 78L and 78R. Therefore, the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set to the lower pressure side as the oil dilution rate Δqd obtained by the oil dilution rate determination operation is higher. Thereby, the penetration force (penetration) of the fuel is set low.

  Thus, oil dilution can be suppressed by setting the direct injection fuel pressure epr in accordance with the oil dilution rate Δqd.

(C) Optimization of the air-fuel mixture state in the cylinder In order to optimize the air-fuel mixture state in the cylinder, the mixing property of air and fuel is effective so that the air-fuel mixture can be effectively stirred in the cylinder. Need to improve. For this reason, the higher the bottom dead center split ratio Kl, the higher the direct injection fuel pressure epr from the in-cylinder direct injection injectors 78L and 78R is set to the higher pressure side, thereby promoting the generation of turbulent flow in the cylinder and increasing the combustion speed. It is designed to improve combustion efficiency.

  Any one of the setting operations of the control parameters (1) to (7) described above may be executed during operation of the engine E, or a plurality of them may be executed simultaneously. Or you may make it perform all simultaneously. By setting these control parameters, the fuel injection mode can be optimized, and combustion, exhaust emission, fuel consumption rate, WOT performance, and oil dilution can be improved.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to the V-type 8-cylinder gasoline engine E for automobiles has been described. The present invention is not limited to this, and can also be applied to an in-line engine for automobiles, a horizontally opposed engine for automobiles, and the like. Further, the present invention is not limited to automobiles but can be applied to other engines. Further, the number of cylinders, the angle between the V banks in the V-type engine E, and other specifications of the engine E are not particularly limited.

  Further, the present invention can be applied to any of FF (front engine / front drive) type vehicles, FR (front engine / rear drive) type vehicles, and four-wheel drive vehicles.

  Of the control parameters (1) to (7) in the fuel injection mode described above, only in-cylinder direct injection injectors 78L and 78R are used as fuel injection valves for (1) to (3), (6), and (7). It can also be applied to an engine equipped with

  The present invention suppresses oil dilution by setting a split ratio between fuel injection on the suction top dead center side and fuel injection on the suction bottom dead center side in an automotive engine equipped with an in-cylinder direct injection injector. The present invention is applicable to fuel injection control.

5L, 5R Cylinder 31L, 31R Intake port 75L, 75R Port injection injector (fuel injection valve for intake passage)
76L, 76R Combustion chambers 78L, 78R In-cylinder direct injection injector (fuel injection valve for in-cylinder injection)
9 Engine ECU
E engine (internal combustion engine)
DIP1 Suction stroke top dead center side injection range DIP2 Suction stroke bottom dead center side injection range KL Top dead center side division ratio Kl Bottom dead center side division ratio Δqd Oil dilution rate

Claims (5)

A fuel injection valve for in-cylinder injection that directly injects fuel into the combustion chamber is provided, and fuel injection from the fuel injection valve for in-cylinder injection in the intake stroke is divided into top dead center side split injection and bottom dead center side split injection. In a control device for an internal combustion engine that can be divided and executed,
The split ratio between the top dead center side split injection and the bottom dead center side split injection according to the oil dilution rate caused by the fuel injected from the cylinder fuel injection valve adhering to the cylinder wall surface and compensation for the dividing ratio correction means,
And a fuel injection pressure setting means for setting a fuel injection pressure from the in-cylinder injection fuel injection valve based on the division ratio corrected by the division ratio correction means. apparatus. The control apparatus for an internal combustion engine according to claim 1,
The fuel injection pressure setting means is configured to perform fuel injection for in-cylinder injection based on a top dead center side split ratio that is a ratio of an injection amount in the top dead center side split injection to an injection amount in the bottom dead center side split injection. A control apparatus for an internal combustion engine, characterized in that a fuel injection pressure from a valve is set. The control apparatus for an internal combustion engine according to claim 2,
The control apparatus for an internal combustion engine, wherein the fuel injection pressure setting means is configured to set the fuel injection pressure from the in-cylinder fuel injection valve higher as the top dead center side division ratio is higher. The control apparatus for an internal combustion engine according to claim 1,
The fuel injection pressure setting means is configured so that the fuel injection valve for in-cylinder injection is based on a bottom dead center side split ratio that is an injection amount in the bottom dead center side split injection with respect to an injection amount in the top dead center side split injection. A control apparatus for an internal combustion engine, characterized in that the fuel injection pressure is set. The control apparatus for an internal combustion engine according to claim 4,
The control device for an internal combustion engine, wherein the fuel injection pressure setting means is configured to set the fuel injection pressure from the in-cylinder fuel injection valve higher as the lower dead center side division ratio is higher.

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