JP5167854B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly to an in-cylinder direct injection internal combustion engine that directly injects fuel into a combustion chamber.

  Conventionally, a so-called in-cylinder direct injection type engine in which fuel is directly injected into a combustion chamber so as to ride on an intake air flow during an intake stroke is known. As such a conventional in-cylinder direct injection engine, for example, a control device for an in-cylinder injection engine described in Patent Document 1 adjusts a fuel pressure and a fuel injection valve that injects fuel into the combustion chamber. A fuel pressure feed pump having a variable fuel pressure feed amount, an EGR device, an EGR valve control means for controlling the EGR valve, an acceleration detection means, and a fuel pressure control means are provided. Then, the control device for the direct injection engine is configured so that the fuel pressure control means increases the fuel injection pressure temporarily in the early stage of acceleration based on detection by the acceleration detection means, and lowers the fuel injection pressure in the middle of acceleration. By controlling the pump, it is possible to suppress the generation of smoke at the initial stage of acceleration when accelerating from a state where exhaust gas recirculation is performed, and to suppress an increase in the external load on the engine, thereby improving the acceleration performance. It is secured. The control device for the in-cylinder injection engine includes injection control means for controlling the fuel injection from the fuel injection valve to be divided into a plurality of times in the same cycle in the early stage of acceleration.

JP 2000-205014 A

  By the way, in the control apparatus for a cylinder injection engine described in Patent Document 1 described above, for example, in order to effectively suppress particulate matter, so-called particulate matter (PM), Even if the split injection period is set to a period in which the fuel can be prevented from adhering to the piston or cylinder bore wall, the particulate matter may not be properly suppressed due to fluctuations in the operating state of the engine.

  Then, an object of this invention is to provide the internal combustion engine which can suppress a particulate matter reliably.

In order to achieve the above object, an internal combustion engine according to a first aspect of the present invention is a combustion chamber in which a mixture of air and fuel can be combusted, and the fuel can be dividedly injected into the combustion chamber in a plurality of times. A fuel injection means; an intake port and an exhaust port communicating with the combustion chamber; an intake valve and an exhaust valve that can freely open and close the intake port and the exhaust port; and Control means for setting a final injection timing of the divided injection during acceleration operation within a homogeneity promotion period that is an injection period of the fuel capable of promoting homogeneity between the air and the fuel, and the control means Indicates that the final injection timing of the divided injection during the steady operation is the fuel injection period during which the fuel can be prevented from adhering to the wall of the combustion chamber during the steady operation. And sets within a period, the period in the vicinity of the maximum lift timing where the lift amount to the combustion chamber side of the intake valve the homogeneity promoting period a period retarded than when the PM suppression period the steady operation is maximum In this case, the lift amount of the intake valve is set to a predetermined period or more .

In the internal combustion engine according to the second aspect of the present invention, the control means sets the first injection timing of the divided injection during the steady operation and the acceleration operation within the steady operation PM suppression period. To do.

An internal combustion engine according to a third aspect of the present invention includes temperature detection means capable of detecting an internal combustion engine temperature, and the control means is configured to perform the acceleration operation when the internal combustion engine temperature is equal to or lower than a predetermined temperature. It is prohibited to set the last injection timing of the divided injection within the homogeneity promotion period.

In an internal combustion engine according to a fourth aspect of the present invention , variable valve operating means capable of opening and closing the intake port and the exhaust port and changing the opening and closing timing using the intake valve and the exhaust valve, and the internal combustion engine temperature Temperature control means capable of detecting the temperature, and the control means sets the final injection timing of the divided injection during the acceleration operation within the homogeneity promotion period, and the internal combustion engine temperature is preset. When the temperature is lower than a predetermined temperature, the variable valve means is controlled to increase the overlap of the valve opening periods of the intake valve and the exhaust valve.

  According to the internal combustion engine of the present invention, the division at the time of acceleration operation is performed within the homogeneity promotion period, which is the fuel injection period that can promote the homogeneity of the air and fuel of the air-fuel mixture from the period of division injection at the time of steady operation. Since the control means for setting the final injection timing of the injection is provided, the control means sets the final injection timing of the divided injection at the time of the acceleration operation within the homogeneity promotion period, so that the homogeneity of the air-fuel mixture at the time of the acceleration operation is set. Property is promoted, and particulate matter can be reliably suppressed.

  Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  1 is a schematic configuration diagram showing an engine according to Embodiment 1 of the present invention, FIG. 2 is a partial cross-sectional view including a combustion chamber of the engine according to Embodiment 1 of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a time chart for explaining a divided injection period of the engine according to the first embodiment of the present invention, FIG. 4 is a diagram illustrating an example of the relationship between the engine speed, the load factor, and the number of divided fuel injections of the engine according to FIG. FIG. 5 is a graph conceptually showing the relationship between the fuel split injection period and the mixture distribution during steady operation in the engine according to the first embodiment of the present invention, and FIG. 6 is the engine according to the first embodiment of the present invention. 7 is a graph conceptually showing the relationship between the fuel split injection period and the air-fuel mixture distribution during acceleration operation in FIG. 7, and FIG. 7 is a flowchart for explaining the injection timing retard control during acceleration operation of the engine according to Embodiment 1 of the present invention. It is.

  An engine 10 as an internal combustion engine according to the first embodiment is mounted on a vehicle such as a passenger car or a truck as shown in FIGS. 1 and 2, and a fuel spray 41 a (see FIG. 2) is injected into a combustion chamber by an injector 41 described later. 18 is a multi-cylinder in-cylinder injection type engine that directly injects fuel into a cylinder 18, and a series of intake strokes, compression strokes, expansion strokes, and exhaust strokes while a piston 14 provided in the cylinder bore 13 is capable of reciprocating twice. This is a so-called four-cycle engine that performs four strokes.

  The engine 10 is a multi-cylinder in-cylinder injection type, and a cylinder head 12 is fastened on a cylinder block 11. A plurality of cylinder bores 13 formed in the cylinder block 11 can move pistons 14 up and down. It is mated. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been. Note that oil supplied to each part of the engine 10 is stored at the bottom of the crankcase 15.

  The combustion chamber 18 is composed of a wall surface of the cylinder bore 13 in the cylinder block 11, an in-cylinder ceiling portion 12 a (see FIG. 2) as a lower surface of the cylinder head 12, and a top surface of the piston 14. That is, it has a pent roof shape that is inclined so that the central portion of the in-cylinder ceiling portion 12a as the lower surface of the cylinder head 12 becomes higher. In the combustion chamber 18, a mixture of fuel and air can be combusted, and an intake port 19 and an exhaust port 20 are formed to face the in-cylinder ceiling portion 12 a that is an upper portion of the combustion chamber 18. The lower end portions of the intake valve 21 and the exhaust valve 22 are positioned with respect to the port 19 and the exhaust port 20, respectively. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction (upward in FIG. 1) for closing the intake port 19 and the exhaust port 20. ing. An intake camshaft 23 and an exhaust camshaft 24 are rotatably supported on the cylinder head 12, and the intake cam 25 and the exhaust cam 26 are in contact with upper ends of the intake valve 21 and the exhaust valve 22.

  Although not shown, the crankshaft sprocket fixed to the crankshaft 16 and the camshaft sprockets respectively fixed to the intake camshaft 23 and the exhaust camshaft 24 are wound with endless timing chains. The crankshaft 16, the intake camshaft 23, and the exhaust camshaft 24 can be interlocked.

  Therefore, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the crankshaft 16, the intake cam 25 and the exhaust cam 26 move up and down the intake valve 21 and the exhaust valve 22 at a predetermined timing. 19 and the exhaust port 20 can be opened and closed so that the intake port 19 and the combustion chamber 18 can communicate with the combustion chamber 18 and the exhaust port 20, respectively. In this case, the intake camshaft 23 and the exhaust camshaft 24 are set to rotate once (360 degrees) while the crankshaft 16 rotates twice (720 degrees). Therefore, the engine 10 executes the four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke while the crankshaft 16 rotates twice. At this time, the intake camshaft 23 and the exhaust camshaft 24 are set to one. It will rotate.

  The valve mechanism of the engine 10 is a variable valve timing mechanism (VVT) 27, 28 that controls the intake valve 21 and the exhaust valve 22 at an optimal opening / closing timing according to the operating state. It has become. The intake / exhaust variable valve mechanisms 27, 28 as variable valve means are configured by providing VVT controllers 29, 30 at the shaft ends of the intake camshaft 23 and the exhaust camshaft 24. 32, the phase of the camshafts 23 and 24 with respect to the cam sprocket is changed by causing the hydraulic pressure from 32 to act on an advance chamber and a retard chamber (not shown) of the VVT controllers 29 and 30, and the opening / closing timing of the intake valve 21 and the exhaust valve 22 is changed. Can be advanced or retarded. In this case, the intake / exhaust variable valve mechanisms 27, 28 advance or retard the opening / closing timing with the operating angle (opening period) of the intake valve 21 and the exhaust valve 22 being constant. In addition, the intake camshaft 23 and the exhaust camshaft 24 are provided with cam position sensors 33 and 34 for detecting the rotational phase thereof.

  A surge tank 36 is connected to the intake port 19 via an intake manifold 35, and an intake pipe 37 is connected to the surge tank 36. An air cleaner 38 is attached to an air intake port of the intake pipe 37. . An electronic throttle device 40 as a load adjusting means having a throttle valve 39 is provided downstream of the air cleaner 38 in the air flow direction. Further, the cylinder head 12 is provided with an injector (fuel injection valve) 41 as fuel injection means for directly injecting fuel into the combustion chamber 18. The injector 41 is located on the intake port 19 side and is inclined at a predetermined angle in the vertical direction. The injector 41 is capable of injecting fuel toward the top surface of the piston 14 so that the fuel gets on the intake air flow generated in the combustion chamber 18. An injector 41 attached to each cylinder is connected to a delivery pipe 42, and a high pressure fuel pump (fuel pump) 44 is connected to the delivery pipe 42 via a high pressure fuel supply pipe 43. Further, the cylinder head 12 is provided with a spark plug 45 that is located above the combustion chamber 18 and ignites the air-fuel mixture.

  On the other hand, an exhaust pipe 47 is connected to the exhaust port 20 via an exhaust manifold 46. The exhaust pipe 47 is a three-way element that purifies harmful substances such as HC, CO, and NOx contained in the exhaust gas. Catalysts 48 and 49 are mounted. Further, the engine 10 is provided with a starter motor 50 that performs cranking. When an unillustrated pinion gear meshes with the ring gear when the engine is started, the rotational force is transmitted from the pinion gear to the ring gear to rotate the crankshaft 16. Can do.

  By the way, the vehicle is equipped with an electronic control unit (ECU) 51 that is configured around a microcomputer and can control each part of the engine 10, and the ECU 51 can control the injector 41, the spark plug 45, and the like. Yes. That is, an air flow sensor 52 and an intake air temperature sensor 53 are mounted on the upstream side of the air flow direction of the intake pipe 37, and an intake pressure sensor 54 is provided in the surge tank 36, and the measured intake air amount and intake air temperature are measured. The intake pressure (intake pipe negative pressure) is output to the ECU 51. In addition, a throttle position sensor 55 is attached to the electronic throttle device 40, and the current throttle opening is output to the ECU 51. Here, the ECU 51 can calculate the engine load (load factor) as the internal combustion engine load based on the detected throttle opening and intake air amount. The accelerator position sensor 56 outputs the current accelerator opening to the ECU 51. Further, a crank angle sensor 57 serving as a crank angle detecting means for detecting the crank angle of the engine 10 outputs the detected crank angle of each cylinder to the ECU 51, and the ECU 51 performs an intake stroke in each cylinder based on the detected crank angle. In addition to determining the compression stroke, the expansion stroke, and the exhaust stroke, the engine speed is calculated. Here, the engine speed corresponds to the rotational speed of the crankshaft 16 in other words. If the rotational speed of the crankshaft 16 increases, the rotational speed of the crankshaft 16, that is, the engine rotational speed of the engine 10 also increases. Get higher.

  The cylinder block 11 is provided with a water temperature sensor 58 that detects the engine cooling water temperature, and outputs the detected engine cooling water temperature to the ECU 51. The delivery pipe 42 communicating with each injector 41 is provided with a fuel pressure sensor 59 that detects the fuel pressure, and outputs the detected fuel pressure to the ECU 51. On the other hand, the exhaust pipe 47 is provided with an A / F sensor 60 that detects the air-fuel ratio of the engine 10 upstream of the three-way catalyst 48 in the exhaust gas flow direction, and an oxygen sensor 61 downstream of the exhaust gas flow direction. The A / F sensor 60 detects the exhaust gas air-fuel ratio of the exhaust gas before being introduced into the three-way catalyst 48, outputs the detected air-fuel ratio to the ECU 51, and the oxygen sensor 61 is discharged from the three-way catalyst 48. Thereafter, the oxygen concentration of the exhaust gas is detected, and the detected oxygen concentration is output to the ECU 51. The air-fuel ratio (estimated air-fuel ratio) detected by the A / F sensor 60 is used for feedback control of the air-fuel ratio (theoretical air-fuel ratio) of the mixed gas composed of intake air and fuel. That is, the A / F sensor 60 detects the exhaust air-fuel ratio from the rich range to the lean range from the oxygen concentration in the exhaust gas and the unburned gas concentration, and feeds this back to the ECU 51 to correct the fuel injection amount. Thus, the combustion can be controlled to an optimum combustion state that matches the operating state.

  Therefore, the ECU 51 drives the high-pressure fuel pump 44 based on the detected fuel pressure so that the fuel pressure becomes a predetermined pressure, and also detects the detected intake air amount, intake air temperature, intake pressure, throttle opening, accelerator opening. The fuel injection amount (fuel injection period), the injection timing, the ignition timing, etc. are determined based on the engine operating state such as the engine speed and the engine cooling water temperature, and the injector 41 and the spark plug 45 are driven to perform the fuel injection and ignition. Run. Further, the ECU 51 feeds back the detected oxygen concentration of the exhaust gas to correct the fuel injection amount so that the air-fuel ratio becomes stoichiometric (theoretical air-fuel ratio).

  The ECU 51 can control the intake / exhaust variable valve mechanisms 27 and 28 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idle, or the load is light, the exhaust gas blows back to the intake port 19 or the combustion chamber 18 by eliminating the overlap between the exhaust valve 22 closing timing and the intake valve 21 opening timing. Reduce the amount to enable stable combustion and improved fuel efficiency. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valve 21 is advanced, thereby reducing the amount of intake air that blows back to the intake port 19 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valve 21 is retarded in accordance with the rotation speed, so that the timing is adjusted to the inertial force of the intake air and the volume efficiency is improved.

  In the engine 10 configured as described above, when the piston 14 descends in the cylinder bore 13, air is sucked into the combustion chamber 18 through the intake port 19 (intake stroke), and the piston 14 falls under the intake stroke. The air is compressed by moving up in the cylinder bore 13 through the dead center (compression stroke). At this time, fuel is injected into the combustion chamber 18 from the injector 41 in the intake stroke or compression stroke, and this fuel and air mix to form an air-fuel mixture. When the piston 14 approaches the top dead center of the compression stroke, the air-fuel mixture is ignited by the spark plug 45, the air-fuel mixture burns, and the piston 14 is lowered by the combustion pressure (expansion stroke). The air-fuel mixture after combustion is discharged as exhaust gas through the exhaust port 20 when the piston 14 rises again toward the top dead center of the intake stroke via the expansion stroke bottom dead center (exhaust stroke). The reciprocating motion of the piston 14 in the cylinder bore 13 is transmitted to the crankshaft 16 through the connecting rod 17, where it is converted into a rotational motion and taken out as an output. When 16 further rotates due to inertial force, the cylinder bore 13 reciprocates as the crankshaft 16 rotates. By rotating the crankshaft 16 twice, the piston 14 reciprocates the cylinder bore 13 twice, during which a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke is performed, and once in the combustion chamber 18. Explosion takes place.

  Note that the engine 10 of the first embodiment uses two combustion modes corresponding to operating conditions. In these two combustion modes, stratified combustion that enables fuel-injection during the compression stroke to concentrate the air-fuel mixture in the vicinity of the spark plug 45 and stratify to realize operation in a lean (oxygen-rich atmosphere) state. By performing fuel injection during the intake stroke and taking a sufficient mixing time, the spray is homogeneously dispersed throughout the combustion chamber, so that the operation with the air-fuel ratio stoichiometric (theoretical air-fuel ratio) can be realized. Here, in the engine 10, a concave cavity 14 a (see FIG. 2) for forming stratified combustion is formed in the intake side portion of the top surface of the piston 14. In the stratified combustion, the engine 10 injects fuel from the injector 41 toward the cavity 14a during the compression stroke, so that the fuel spray is guided along the wall of the cavity 14a of the piston 14, and the jet of the fuel spray The directivity toward the spark plug 45 is added to the spark plug 45, so that the air-fuel mixture can be guided to the spark plug 45 and a stratified air-fuel mixture can be formed in the vicinity of the spark plug 45. The engine 10 of the first embodiment determines the fuel injection mode based on the engine speed and the throttle opening. For example, the stratification is performed in a relatively low load and low rotation operation region in all operation conditions. While performing combustion, homogeneous combustion is performed in a relatively high load and high speed operation region.

  Here, in the engine 10 of the first embodiment, the fuel injection of a necessary amount in one cycle by the injector 41 as the fuel injection means is divided into a plurality of divided injections.

  Specifically, the injector 41 described above can divide and inject fuel into the combustion chamber 18 in a plurality of times. The division number of the divided injection by the injector 41 is set by the ECU 51 based on the engine speed and the load factor. That is, the ECU 51 calculates and sets a required fuel injection amount from the current engine speed and load factor of the engine 10, and sets the number of injection divisions using, for example, a map shown in FIG. Here, FIG. 3 is an example of a map stored in the storage unit of the ECU 51 in order to obtain the number of injection divisions (for example, n1, n2,..., N5) based on the engine speed and the load factor. Yes, it was created in advance by experiments. In FIG. 3, the vertical axis represents the load factor and the horizontal axis represents the engine speed.

  The injector 41 divides the fuel injection into a plurality of times based on the fuel injection amount and the number of divisions set by the ECU 51, and intermittently injects the fuel into the combustion chamber 18 with an injection pause period. Therefore, for example, as compared with the case where the total amount of required fuel injection is injected once, fuel is injected in each short period divided into a plurality of times, and the fuel spray 41a of one injection is injected. The injection amount can be reduced. For this reason, since one fuel spray is injected from the injector 41 within a short period of time, the penetration (penetration force) of the fuel spray can be kept low. That is, in the fuel spray 41a when the fuel is divided and injected by the injector 41, the fuel adheres to the top surface of the piston 14 and the wall surface of the cylinder bore 13 and the like due to the decrease in the spray penetration due to the shortening of each spray period. Can be suppressed. Therefore, when the fuel spray 41a is divided and injected, it is possible to suppress the fuel from adhering to the top surface of the piston 14 or the inner wall surface of the combustion chamber 18 and to generate unburned hydrocarbons (unburned HC). And smoke, particulate matter, so-called particulate matter (PM) can be suppressed. In addition, since the spray penetration force is reduced, the amount of fuel scattered on the piston 14 can be suppressed, and the fuel can be prevented from adhering to the wall surface of the cylinder bore 13. It is possible to suppress the oil flowing into the oil stored at the bottom of the crankcase 15. As a result, it is possible to prevent the oil from diluting and degrading the engine quality, and it is possible to suppress the generation of unburned HC (hydrocarbon) and smoke.

  By the way, when the fuel is divided and injected by the injector 41 as described above, for example, in order to effectively suppress the generation of PM, the fuel divided injection period is a combustion chamber such as the top surface of the piston 14 or the wall surface of the cylinder bore 13. Even if it is set to a period during which the fuel can be prevented from adhering to the 18 wall surfaces, PM may not be properly suppressed due to fluctuations in the operating state of the engine 10.

  That is, the engine 10 can effectively suppress the generation of PM by suppressing the adhesion of fuel to the wall surface of the combustion chamber 18 such as the top surface of the piston 14 and the wall surface of the cylinder bore 13. For this reason, during the steady operation, the engine 10 is a period of fuel split injection by the injector 41 within the steady operation PM suppression period, which is a fuel injection period that can suppress the adhesion of fuel to the wall surface of the combustion chamber 18. By setting (hereinafter, simply referred to as “divided injection period” unless otherwise specified), it is possible to suppress the adhesion of fuel to the wall surface of the combustion chamber 18 and to effectively suppress the generation of PM. it can.

  Here, the PM suppression period during steady operation is a fuel injection period during which PM can be effectively reduced during steady operation of the engine 10. If the engine 10 advances the fuel split injection timing toward the top dead center TDC (TDC: Top Dead Center) side in the first half of the intake stroke, the piston 14 and the injector that move toward the top dead center As a result, the fuel spray 41a injected from the injector 41 directly hits the piston 14 and the fuel easily adheres to the piston 14. As a result, smoke and PM may be increased. On the other hand, if the fuel injection timing is too retarded to the bottom dead center BDC (BDC: Bottom Dead Center) side, the engine 10 causes the fuel spray 41a injected from the injector 41 to protrude toward the combustion chamber 18 and open. As a result, the fuel spray 41a scatters on the intake valve 21, and the scattered fuel adheres to the wall surface of the combustion chamber 18 such as the wall surface of the cylinder bore 13 and PM may be generated. is there. Therefore, in the engine 10, the fuel spray 41a does not directly hit the top surface of the piston 14 on the advance side (first half of the intake stroke), and the fuel spray 41a and the intake valve 21 are unlikely to interfere with each other on the retard side. The PM suppression period during steady operation is set as the period, and the fuel split injection period is set within the PM suppression period during steady operation. That is, in the steady operation, the first injection timing and the final injection timing of fuel split injection are both set within the steady operation PM suppression period.

  On the other hand, during transient operation such as during acceleration operation, the engine 10 temporarily sets the fuel split injection period within the PM suppression period during steady operation, thereby suppressing the adhesion of fuel to the wall surface of the combustion chamber 18. Even if the generation of fuel is suppressed, the mixture of fuel and air injected in a relatively large amount becomes non-uniform compared to that during steady operation, and the homogeneity of the air-fuel mixture during acceleration operation deteriorates. There is a possibility that a rich region where the fuel is excessively generated locally in the mixture distribution in the chamber 18 and a large amount of PM is generated from the fuel-rich region of the mixture. That is, when the engine 10 is configured to set the fuel split injection period to the same steady operation PM suppression period during steady operation and acceleration operation, even if PM can be effectively suppressed during steady operation, There is a risk that a large amount of PM may be generated during acceleration operation.

  Therefore, the engine 10 of the present embodiment performs split injection of the fuel into the combustion chamber 18 in a plurality of times by the injector 41 as described above, and also, as shown in FIG. 4, the air-fuel mixture from the split injection period during steady operation. ECU 51 is provided as a control means for setting the final injection timing of the divided injection during the acceleration operation within the homogeneity promotion period B, which is a fuel injection period that can promote the homogeneity of the air and the fuel. By setting the final injection timing of the divided injection during the acceleration operation within the homogeneity promotion period B, the homogeneity of the air-fuel mixture during the acceleration operation is promoted and the generation of PM is reliably suppressed.

  In FIG. 4, the horizontal axis represents time, the vertical axis represents the intake valve lift amount, the fuel injection period during steady operation, the fuel injection period during acceleration operation, the PM amount and the torque fluctuation due to fuel wall adhesion. Further, in the following description, the case where the number of divisions in the fuel split injection is two will be described, that is, the case where the last fuel injection in the split injection is the second fuel injection will be described. Not limited to this, the number of divisions may be three or more.

  First, the ECU 51 as the control means hardly deteriorates the homogeneity of the air-fuel mixture at the time of steady operation of the engine 10, so that the divided injection by the injector 41 is performed within the range where there is no problem in torque fluctuation as described above. The period is set within the PM suppression period A during steady operation that can effectively suppress the adhesion of fuel to the wall surface of the combustion chamber 18. That is, the ECU 51 does not directly hit the top surface of the piston 14 on the advance side (the first half of the intake stroke) during the PM suppression period A during steady operation, and the intake side of the fuel spray 41a and the intake air on the retard side. The period is set from time t1 to time t3 at which the valve 21 hardly interferes. The engine 10 may cause the fuel spray 41a to hit the top surface of the piston 14 directly when the fuel injection timing of the divided fuel injection is set to the advance angle (TDC side) side from the time t1, but is later than the time t3. If the angle (BDC side) is set, the fuel spray 41a and the intake valve 21 may interfere with each other.

  Here, the ECU 51 prevents the fuel spray 41a from interfering with the intake valve 21 as a period during which the fuel spray 41a can be prevented from adhering to the wall surface of the combustion chamber 18 and the generation of PM can be effectively reduced during steady operation of the engine 10. The PM suppression period A during steady operation is set in a period before the possible interference period, that is, in a period before time t3 when the lift amount of the intake valve 21 becomes equal to or higher than a predetermined value. Then, the ECU 51 performs the first (first) injection timing Ainj1 (start timing of the divided injection period during steady operation) and the second (last) injection timing Ainj2 (in steady operation) during steady operation. The end timing of the divided injection period) is set at time t1 and time t2 within the PM suppression period A during steady operation. Therefore, the injector 41 performs each injection in the split fuel injection at the injection timings Ainj1 and Ainj2 within the PM suppression period A during the steady operation during the steady operation of the engine 10. As a result, during steady operation, the engine 10 can prevent the fuel spray 41a injected from the injector 41 at the injection timing Ainj1 from directly hitting the piston 14 and is injected at the injection timing Ainj2. It is possible to prevent the fuel spray 41a from interfering with the intake valve 21, and to prevent the fuel spray 41a from splashing on the intake valve 21 and attaching the scattered fuel to the wall surface of the combustion chamber 18 such as the cylinder bore 13 wall surface. . Thereby, generation | occurrence | production of PM can be suppressed.

  On the other hand, the ECU 51 sets the homogeneity promotion period B as a fuel injection period that can promote the homogeneity of the air-fuel mixture and the fuel from the PM suppression period A during steady operation. The homogeneity promotion period B is a period in which the homogeneity between the air and the fuel in the air-fuel mixture is promoted more than the PM suppression period A during steady operation by increasing the intake jet generated in the combustion chamber 18. The ECU 51 sets the homogeneity promotion period B to a period delayed from the PM suppression period A during steady operation. In other words, the ECU 51 sets the amount of movement of the intake valve 21 toward the combustion chamber 18 as a period during which the intake jet flow in the combustion chamber 18 increases, that is, a time t3 near the maximum lift timing t4 at which the lift amount is maximum. A period from time t5 to time t5, that is, a period from time t3 to time t5 when the lift amount of the intake valve 21 is equal to or greater than a predetermined value is set as the homogeneity promotion period B. As described above, the homogeneity promotion period B is a period during which the fuel spray 41a and the intake valve 21 can interfere with each other as compared with the PM suppression period A during steady operation. It is also a period during which can be effectively promoted. It should be noted that the interference period between the intake valve 21 and the fuel spray 41a, in other words, the homogeneity promotion period B in which the homogeneity of fuel and air is promoted by the intake jet is substantially the same in both cold and warm conditions. This is a period that is uniquely determined from the specifications of the engine 10 and the like.

  Then, the ECU 51 sets the first (first) injection timing Ainj1 during the acceleration operation to the time t1 within the PM suppression period A during the steady operation as in the steady operation, while the divided injection 2 during the acceleration operation. The second (last) injection timing Ainj2 is set to time t4 within the homogeneity promotion period B. Therefore, the injector 41 performs the first (first) fuel injection at the injection timing Ainj1 (time t1) within the PM suppression period A during the steady operation during the acceleration operation of the engine 10 during the fuel split injection. After that, the second (last) fuel injection is performed at an injection timing Ainj2 (time t4) within the homogeneity promotion period B with an interval.

  As a result, the engine 10 can prevent the fuel spray 41a injected from the injector 41 at the injection timing Ainj1 from directly hitting the piston 14 during acceleration operation. In the acceleration operation, the engine 10 jets the fuel spray 41a injected from the injector 41 at the injection timing Ainj2 within the homogeneity promotion period B into the intake air flow generated in the combustion chamber 18. By utilizing this, the air flow of the fuel spray 41a is increased by the jet effect, the atomization of the fuel and the mixing with the air are promoted, and the homogenization of the fuel spray 41a can be improved. That is, the engine 10 can prevent the mixture of fuel and air from becoming non-uniform during acceleration operation, thereby preventing the homogeneity of the air-fuel mixture from being deteriorated. Generation of a fuel rich region can be prevented. As a result, the engine 10 performs the second (last) fuel injection at the injection timing Ainj2 within the homogeneity promotion period B during the acceleration operation, so that the amount of fuel adhering to the wall surface of the combustion chamber 18 is temporarily reduced. Even if it increases slightly, it is possible to prevent a fuel-rich region that is locally excessive in the mixture distribution in the combustion chamber 18 from occurring, so that a large amount of PM is generated from the fuel-rich region of the mixture. Since it can suppress, generation | occurrence | production of PM can be suppressed by the total amount as a result. That is, the engine 10 appropriately changes each fuel injection timing in the split fuel injection during the steady operation and the acceleration operation, thereby suppressing the PM generation during the steady operation and the PM generation during the acceleration operation. Therefore, even if the operating state of the engine 10 fluctuates, the generation of PM can be suppressed appropriately.

  5 and 6 are graphs conceptually showing the relationship between the fuel split injection period and the mixture distribution in the engine 10, and FIG. 5 shows the mixture distribution during steady operation, while FIG. 6 shows the acceleration operation. The mixture distribution at the time is shown. FIGS. 5 and 6 show the case where the solid line represents the second (last) injection timing Ainj2 in the fuel split injection within the PM suppression period A during steady operation, and the broken line represents the homogeneity promotion period B. Indicates the case of setting.

  When the engine 10 is in steady operation, the second (last) injection timing Ainj2 is set in the steady operation PM suppression period A and in the homogeneity promotion period B as shown in FIG. In any case, the homogeneity of the air-fuel mixture is not extremely deteriorated. For this reason, there is almost no locally fuel-rich fuel-rich region in the air-fuel mixture distribution in the combustion chamber 18, so that PM from the fuel-rich region is reduced. Is rarely generated in large quantities. For this reason, during steady operation, the fuel injection to the wall surface of the combustion chamber 18 is performed by setting the second (last) injection timing Ainj2 to a time within the PM suppression period A during steady operation within a range in which torque fluctuation can be tolerated. Therefore, the generation of PM due to the fuel wall surface adhesion can be effectively suppressed.

  On the other hand, as shown in FIG. 6, the engine 10 is mixed in the combustion chamber 18 when the second (last) injection timing Ainj2 is set to a timing within the PM suppression period A during steady operation, as shown in FIG. As the homogeneity of the air deteriorates, the variation range of the air-fuel ratio of the air-fuel mixture becomes relatively large, and a locally rich fuel rich region is generated in the air-fuel mixture distribution in the combustion chamber 18. There is a possibility that PM is generated from the area. However, as described above, the engine 10 of the present embodiment is mixed by the jet effect of the intake jet by setting the second (last) injection timing Ainj2 to the timing within the homogeneity promotion period B during acceleration operation. The homogeneity of the fuel and the air is promoted, the variation of the air-fuel ratio of the air-fuel mixture is relatively reduced, and the generation of the fuel rich region is suppressed. As a result, PM is generated from the fuel rich region. Therefore, the generation of PM as a total amount can be suppressed.

  Next, with reference to the flowchart of FIG. 7, the acceleration timing retarding control during acceleration operation of the engine 10 according to the present embodiment will be described. This control routine is repeatedly executed at a control cycle of several ms to several tens of ms.

  The ECU 51 reads the engine speed and the load factor (engine load) based on the detection results of the throttle position sensor 55, the crank angle sensor 57, etc. (S100), for example, this engine speed based on the map shown in FIG. Then, the division number of the divided injection by the injector 41 is set from the load factor. Here, as described above, the case where the number of divisions in the divided fuel injection is two will be described.

  Next, the ECU 51 determines the first (first) injection timing Ainj1 and the second (last) injection timing Ainj2 of split fuel injection during steady operation based on the engine speed, load factor, etc. read in S100. Are set (S102). For example, the ECU 51 determines the engine speed and the load factor based on a steady operation time map representing the correspondence between the engine speed and the load factor stored in advance in a storage unit (not shown) and the injection timing Ainj1 and the injection timing Ainj2. From the above, the injection timing Ainj1 and the injection timing Ainj2 during steady operation are read and set. Here, the injection timing Ainj1 and the injection timing Ainj2 are both set to the timing within the steady operation PM suppression period A.

  Next, the ECU 51 reads the intake air amount Ga detected by the airflow sensor 52 and determines whether or not the intake air amount Ga is larger than a value obtained by multiplying the intake air amount Ga0 one cycle before by a predetermined coefficient. (S104). That is, the ECU 51 determines whether or not the current operation state of the engine 10 is an acceleration operation state by determining whether or not the intake air amount Ga is larger than a value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient. Determine.

  When it is determined that the intake air amount Ga is larger than the value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: Yes), that is, when it is determined that the engine 10 is in the acceleration operation, the ECU 51 Based on the engine speed, the load factor, etc., the second (last) injection timing Ainj2 of the fuel split injection during the acceleration operation is set (S106). For example, the ECU 51 accelerates the engine based on the engine speed, the load factor, and the like based on the acceleration operation time map representing the correspondence between the engine speed, the load factor and the injection timing Ainj2 stored in advance in a storage unit (not shown). The injection timing Ainj2 at the time is read and set. Here, the injection timing Ainj1 is set as it is in the steady operation PM suppression period A, while the injection timing Ainj2 is set in the homogeneity promotion period B. Then, the injector 41 performs fuel split injection based on the injection timing Ainj1 and injection timing Ainj2 set in S102 and S106 (S108), and shifts to the next control cycle.

  When it is determined that the intake air amount Ga is equal to or less than a value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: No), that is, when it is determined that the engine 10 is in steady operation, the ECU 51 The intake air amount Ga this time is set to the intake air amount Ga0 one cycle before (S110), and fuel split injection is executed based on the injection timing Ainj1 and injection timing Ainj2 set in S102 (S108). Shift to the control cycle.

  According to the engine 10 according to the embodiment of the present invention described above, the combustion chamber 18 in which a mixture of air and fuel can be combusted, and the injector 41 in which fuel can be dividedly injected into the combustion chamber 18 in a plurality of times. And the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, which is the fuel injection period during which the homogeneity of the air-fuel mixture and the fuel can be promoted from the divided injection period during the steady operation. ECU 51 for setting

  Therefore, the final injection timing Ainj2 of the divided injection in the acceleration operation is set within the homogeneity promotion period B which is the fuel injection period in which the homogeneity of the air-fuel mixture and the fuel can be promoted from the divided injection period in the steady operation. The ECU 51 sets at least the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, so that the homogeneity of the air-fuel mixture during the acceleration operation is promoted and the generation of PM is suppressed. It can be surely suppressed. That is, the engine 10 appropriately changes each fuel injection timing in the split fuel injection during the steady operation and the acceleration operation, thereby suppressing the PM generation during the steady operation and the PM generation during the acceleration operation. Therefore, even if the operating state of the engine 10 fluctuates, the generation of PM can be suppressed appropriately.

  Furthermore, according to the engine 10 according to the embodiment of the present invention described above, the ECU 51 determines the final injection timing Ainj2 of the divided injection at the time of steady operation as the fuel adheres to the wall surface of the combustion chamber 18 at the time of steady operation. Is set within the steady operation PM suppression period A, which is a fuel injection period capable of suppressing the above, and the homogeneity promotion period B is set to a period delayed from the steady operation PM suppression period A. Therefore, since the ECU 51 sets the last injection timing Ainj2 during the steady operation within the PM suppression period A during the steady operation, the fuel spray 41a injected at the injection timing Ainj2 during the steady operation is the combustion chamber 18 such as the wall surface of the cylinder bore 13 or the like. It can suppress adhering to the wall surface of this, and, thereby, generation | occurrence | production of PM can be suppressed. Since the ECU 51 sets the homogeneity promotion period B to a period delayed from the PM suppression period A during steady operation, at least the injection timing Ainj2 during acceleration operation can be set within a period during which the jet effect by the intake jet is high. This makes it possible to promote the homogeneity between the air in the mixture and the fuel.

  Furthermore, according to the engine 10 according to the embodiment of the present invention described above, the ECU 51 sets the first injection timing Ainj1 of the divided injection during the steady operation and the acceleration operation within the PM suppression period A during the steady operation. . Therefore, since the ECU 51 sets the first injection timing Ainj1 of the divided injection within the PM suppression period A during steady operation, the fuel spray 41a injected from the injector 41 at the injection timing Ainj1 during steady operation and acceleration operation. Can be prevented from directly hitting the piston 14, and as a result, generation of PM can be suppressed.

  FIG. 8 is a flowchart illustrating the injection timing retard control during acceleration operation of the engine according to the second embodiment of the present invention. The internal combustion engine according to the second embodiment has substantially the same configuration as the internal combustion engine according to the first embodiment, but prohibits setting the final injection timing of the divided injection within the homogeneity promotion period in a predetermined operation state. This is different from the internal combustion engine according to the first embodiment. In addition, about the structure, effect | action, and effect which are common in the Example mentioned above, while overlapping description is abbreviate | omitted as much as possible, the same code | symbol is attached | subjected. 1 and 2 are referred to for the configuration of the main part.

  The engine 210 as the internal combustion engine of the present embodiment prohibits the ECU 51 as the control means from setting the second (last) injection timing Ainj2 of the divided injection during the acceleration operation in the homogeneity promotion period B when it is cold. By doing so, oil dilution is reduced.

  Specifically, as shown in FIGS. 1, 2, and 8, the engine 210 has a predetermined water temperature Tw0 in which an engine cooling water temperature Tw as an internal combustion engine temperature detected by a water temperature sensor 58 as a temperature detecting means is preset. If higher, that is, when the engine 210 is warm, the ECU 51 sets the second (last) injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B. On the other hand, when the engine cooling water temperature Tw is equal to or lower than a predetermined water temperature Tw0 that is set in advance, that is, when the engine 210 is cold, the engine 210 homogenizes the second (last) injection timing Ainj2 of the divided injection in the acceleration operation. It is prohibited to set it within the acceleration promotion period B, and the control for retarding the second (last) injection timing Ainj2 of the divided injection during the acceleration operation is not performed. Here, the internal combustion engine temperature of the present invention is described as using the engine cooling water temperature Tw detected by the water temperature sensor 58, but is not limited to this, and the engine oil temperature may be used.

  When the second (last) injection timing Ainj2 of the divided injection is set within the homogeneity promotion period B, the engine 210 is injected from the injector 41 during this period because the piston 14 is located on the bottom dead center side. There is a risk that the fuel tends to flow into the oil stored in the bottom of the crankcase 15 through the cylinder bore 13. Here, when the engine 210 is cold, the fuel that has flowed into the oil does not evaporate immediately because the engine temperature is low. As a result, the oil that lubricates each part of the engine 210 is diluted to improve the engine quality. There is a risk of lowering. However, the engine 210 of this embodiment prohibits the ECU 51 from setting the second (last) injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B when the engine 210 is cold. Since control for retarding the second (last) injection timing Ainj2 of the divided injection during the acceleration operation is not performed, oil dilution can be suppressed, and as a result, deterioration in engine quality can be suppressed. On the other hand, when the engine 210 is warm, since the engine temperature is high even if fuel flows into the oil, the engine 51 evaporates immediately. Therefore, the ECU 51 causes the second (last) injection timing of the divided injection during the acceleration operation. Even if Ainj2 is set within the homogeneity promotion period B and control is performed to retard the second (last) injection timing Ainj2 of the divided injection during the acceleration operation, oil dilution does not occur.

  Next, with reference to the flowchart of FIG. 8, the acceleration timing retarding control during the acceleration operation of the engine 210 according to the present embodiment will be described.

  The ECU 51 reads the engine speed and the load factor (engine load) (S100), and sets the number of divided injections by the injector 41.

  Next, the ECU 51 sets the first (first) injection timing Ainj1 and the second (last) injection timing Ainj2 of the split fuel injection in the steady operation (S102).

  Next, the ECU 51 reads the engine cooling water temperature Tw detected by the water temperature sensor 58, and determines whether or not the engine cooling water temperature Tw is higher than a preset predetermined water temperature Tw0 (S203).

  When it is determined that the engine cooling water temperature Tw is higher than a predetermined water temperature Tw0 set in advance (S203: Yes), that is, when it is determined that the engine 210 is warm, the ECU 51 determines that the intake air amount Ga is 1. It is determined whether or not the intake air amount Ga0 before the cycle is larger than a value obtained by multiplying a predetermined coefficient (S104). When it is determined that the intake air amount Ga is larger than the value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: Yes), the ECU 51 performs the second (last) fuel split injection during the acceleration operation. Injection timing Ainj2 is set (S106), fuel split injection is executed based on the set injection timing Ainj1 and injection timing Ainj2 (S108), and the process proceeds to the next control cycle. When it is determined that the intake air amount Ga is equal to or less than the value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: No), the ECU 51 sets the current intake air amount Ga to the intake air amount Ga0 one cycle before. After setting (S110), fuel split injection is executed based on the injection timing Ainj1 and injection timing Ainj2 set in S102 (S108), and the process proceeds to the next control cycle.

  When it is determined that the engine cooling water temperature Tw is equal to or lower than a predetermined water temperature Tw0 set in advance (S203: No), that is, when it is determined that the engine 210 is cold, the ECU 51 performs division during acceleration operation. It is prohibited to set the second (last) injection timing Ainj2 within the homogeneity promotion period B, and control is not performed to retard the second (last) injection timing Ainj2 of divided injection during acceleration operation. Then, the current intake air amount Ga is set to the intake air amount Ga0 one cycle before (S110), and split fuel injection is executed based on the injection timing Ainj1 and injection timing Ainj2 set in S102 (S108). Then, the next control cycle is started.

  According to the engine 210 according to the embodiment of the present invention described above, within the homogeneity promotion period B, which is a fuel injection period that can promote the homogeneity of air and fuel in the air-fuel mixture from the divided injection period during steady operation. Is provided with an ECU 51 for setting the final injection timing Ainj2 of the divided injection during the acceleration operation, and since this ECU 51 sets at least the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, the acceleration operation is performed. The homogeneity of the air-fuel mixture at the time is promoted, and the generation of PM can be reliably suppressed.

  Further, the engine 210 according to the embodiment of the present invention described above includes the water temperature sensor 58 that can detect the engine cooling water temperature Tw, and the ECU 51 is configured to have the engine cooling water temperature Tw equal to or lower than a predetermined water temperature Tw0 that is set in advance. In some cases, it is prohibited to set the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B. Therefore, when the engine 210 is cold, the ECU 51 is prohibited from setting the second (last) injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, and 2 of the divided injection during the acceleration operation is performed. Since control for retarding the second (final) injection timing Ainj2 is not performed, oil dilution can be suppressed.

  FIG. 9 is a flowchart illustrating the injection timing retard control during acceleration operation of the engine according to Embodiment 3 of the present invention. The internal combustion engine according to the third embodiment has substantially the same configuration as the internal combustion engine according to the second embodiment, but the second embodiment is that the overlap between the valve opening periods of the intake valve and the exhaust valve is increased in a predetermined operating state. It differs from the internal combustion engine which concerns on. In addition, about the structure, effect | action, and effect which are common in the Example mentioned above, while overlapping description is abbreviate | omitted as much as possible, the same code | symbol is attached | subjected. 1 and 2 are referred to for the configuration of the main part.

  In the engine 310 as the internal combustion engine of this embodiment, the ECU 51 as the control means controls the intake / exhaust variable valve mechanisms 27 and 28 as variable valve means when the engine 51 is cold so that the intake valve 21 and the exhaust valve 22 are opened. Oil dilution is reduced by increasing the valve period overlap.

  Specifically, as shown in FIGS. 1, 2, and 9, the engine 310 has a predetermined water temperature Tw0 in which an engine cooling water temperature Tw as an internal combustion engine temperature detected by a water temperature sensor 58 as a temperature detecting means is preset. When the engine temperature is higher, that is, when the engine cooling water temperature Tw is equal to or lower than a predetermined water temperature Tw0 that is set in advance, that is, when the engine 310 is cold, the ECU 51 is divided during acceleration operation. The second (last) injection timing Ainj2 of the injection is set within the homogeneity promotion period B.

  When the engine 310 is cold, the ECU 51 controls the intake / exhaust variable valve operating mechanisms 27 and 28 to advance the opening timing of the intake valve 21 so that the intake valve 21 and the exhaust valve 22 The internal EGR rate is increased by increasing the overlap of the valve opening period. As a result, since the in-cylinder temperature rises due to an increase in the internal EGR rate, the engine 310 can immediately evaporate the fuel mixed in the oil even when it is cold, thereby reducing oil dilution. be able to. Moreover, PM can also be suppressed by this. In the engine 310, when the engine cooling water temperature Tw is equal to or lower than a predetermined water temperature Tw0 set in advance, that is, even when the engine 310 is cold, the ECU 51 performs the second (last) injection of the divided injection during the acceleration operation. Since the time Ainj2 can be set within the homogeneity promotion period B, PM can be appropriately reduced even during the cold acceleration operation. That is, it is possible to achieve both reduction of oil dilution and suppression of PM generation.

  Next, with reference to the flowchart of FIG. 9, the acceleration timing retarding control during the acceleration operation of the engine 310 according to the present embodiment will be described.

  The ECU 51 reads the engine speed and the load factor (engine load) (S100), and sets the number of divided injections by the injector 41.

  Next, the ECU 51 sets the first (first) injection timing Ainj1 and the second (last) injection timing Ainj2 of the split fuel injection in the steady operation (S102).

  Next, the ECU 51 determines whether or not the intake air amount Ga is larger than a value obtained by multiplying the intake air amount Ga0 one cycle before by a predetermined coefficient (S104). When it is determined that the intake air amount Ga is larger than the value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: Yes), the ECU 51 performs the second (last) fuel split injection during the acceleration operation. The injection timing Ainj2 is set (S106).

  The ECU 51 determines whether or not the engine cooling water temperature Tw is higher than a predetermined water temperature Tw0 that is set in advance, and if it is determined that the engine cooling water temperature Tw is equal to or lower than the predetermined water temperature Tw0 that is set in advance, the intake valve 21 is set to the valve opening timing advance amount VVTin of the intake valve 21 to increase the overlap between the opening periods of the intake valve 21 and the exhaust valve 22 (S307). If it is determined that the engine cooling water temperature Tw is higher than the predetermined water temperature Tw0 set in advance, fuel split injection is executed based on the injection timing Ainj1 and injection timing Ainj2 set in S102 and S106 as they are (S108). Transition to the next control cycle.

  When it is determined that the intake air amount Ga is equal to or less than the value obtained by multiplying the intake air amount Ga0 by a predetermined coefficient (S104: No), the ECU 51 sets the current intake air amount Ga to the intake air amount Ga0 one cycle before. After setting (S110), fuel split injection is executed based on the injection timing Ainj1 and injection timing Ainj2 set in S102 (S108), and the process proceeds to the next control cycle.

  According to the engine 310 according to the embodiment of the present invention described above, within the homogeneity promotion period B, which is a fuel injection period that can promote the homogeneity of the air and the fuel in the air-fuel mixture from the divided injection period during steady operation. Is provided with an ECU 51 for setting the final injection timing Ainj2 of the divided injection during the acceleration operation, and since this ECU 51 sets at least the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, the acceleration operation is performed. The homogeneity of the air-fuel mixture at the time is promoted, and the generation of PM can be reliably suppressed.

  Further, according to the engine 310 according to the embodiment of the present invention described above, the intake port 19 and the exhaust port 20 communicating with the combustion chamber 18, the intake valve 21 and the exhaust that can freely open and close the intake port 19 and the exhaust port 20. The intake port 19 and the exhaust port 20 can be opened and closed using the valve 22, the intake valve 21 and the exhaust valve 22, and the intake / exhaust variable valve mechanisms 27 and 28 capable of changing the opening / closing timing, and the engine coolant temperature Tw The ECU 51 sets the final injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B, and the engine cooling water temperature Tw is equal to or lower than a predetermined water temperature Tw0 set in advance. In this case, the intake / exhaust variable valve mechanisms 27 and 28 are controlled to increase the overlap of the intake valve 21 and the exhaust valve 22 during the valve opening period. To.

  Therefore, when the engine 310 is cold, the ECU 51 controls the intake / exhaust variable valve mechanisms 27 and 28 to increase the overlap of the valve opening periods of the intake valve 21 and the exhaust valve 22, thereby increasing the internal EGR. The rate can be increased and oil dilution can be reduced. As a result, even when the engine 310 is cold, the ECU 51 sets the second (last) injection timing Ainj2 of the divided injection during the acceleration operation within the homogeneity promotion period B. Since it can be set, PM can be appropriately reduced even during the cold acceleration operation. That is, it is possible to achieve both reduction of oil dilution and suppression of PM generation.

  The internal combustion engine according to the above-described embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the claims.

  As described above, the internal combustion engine according to the present invention is suitable for use in various in-cylinder direct injection internal combustion engines that inject fuel directly into a combustion chamber.

1 is a schematic configuration diagram illustrating an engine according to Embodiment 1 of the present invention. It is a fragmentary sectional view containing the combustion chamber of the engine which concerns on Example 1 of this invention. It is a diagram showing an example of the relationship between the engine speed of the engine which concerns on Example 1 of this invention, a load factor, and the frequency | count of division | segmentation of fuel injection. It is a time chart explaining the division | segmentation injection period of the engine which concerns on Example 1 of this invention. It is a graph which shows notionally the relation between the division injection period of fuel at the time of steady operation in the engine concerning Example 1 of the present invention, and mixture distribution. It is a graph which shows notionally the relationship between the fuel split injection period at the time of the acceleration driving | operation in the engine which concerns on Example 1 of this invention, and mixture distribution. It is a flowchart explaining the injection timing retardation control at the time of acceleration operation of the engine which concerns on Example 1 of this invention. It is a flowchart explaining the injection timing delay angle control at the time of the acceleration operation of the engine which concerns on Example 2 of this invention. It is a flowchart explaining the injection timing retardation control at the time of the acceleration operation of the engine which concerns on Example 3 of this invention.

Explanation of symbols

10, 210, 310 engine (internal combustion engine)
13 Cylinder bore 14 Piston 18 Combustion chamber 19 Intake port 20 Exhaust port 21 Intake valve 22 Exhaust valve 27 Intake variable valve mechanism (variable valve means)
28 Exhaust variable valve mechanism (variable valve mechanism)
41 Injector (fuel injection means)
45 Spark plug 51 ECU (control means)
58 Water temperature sensor (temperature detection means)

Claims (4)

A combustion chamber capable of burning a mixture of air and fuel;
Fuel injection means capable of dividing and injecting the fuel into the combustion chamber a plurality of times;
An intake port and an exhaust port communicating with the combustion chamber;
An intake valve and an exhaust valve that can freely open and close the intake port and the exhaust port;
The last of the split injections in the acceleration operation is within the homogeneity promotion period that is the fuel injection period that can promote the homogeneity of the air and the fuel of the air-fuel mixture from the split injection period in the steady operation. Control means for setting the injection timing,
The control means determines the last injection timing of the divided injection during the steady operation as the fuel injection period during which the fuel can be suppressed from adhering to the wall surface of the combustion chamber during the steady operation. Set within the suppression period, and is a period retarded from the PM suppression period during steady operation, and in the vicinity of the maximum lift timing at which the lift amount to the combustion chamber side of the intake valve is maximum . The period is set to a period in which the lift amount of the intake valve is greater than or equal to a predetermined value ,
Internal combustion engine. The control means sets the initial injection timing of the divided injection during the steady operation and the acceleration operation within the steady operation PM suppression period,
The internal combustion engine according to claim 1. Temperature detecting means capable of detecting the temperature of the internal combustion engine,
The control means prohibits setting the last injection timing of the divided injection during the acceleration operation within the homogeneity promotion period when the internal combustion engine temperature is equal to or lower than a predetermined temperature set in advance. Characterized by the
The internal combustion engine according to claim 1 or 2. Variable valve operating means capable of opening and closing the intake port and the exhaust port using the intake valve and the exhaust valve and capable of changing the opening and closing timing;
Temperature detecting means capable of detecting the internal combustion engine temperature,
The control means sets the final injection timing of the divided injection during the acceleration operation within the homogeneity promotion period, and the variable valve when the internal combustion engine temperature is equal to or lower than a predetermined temperature set in advance. Characterized by controlling the means to increase the overlap of the intake valve and the exhaust valve open period,
The internal combustion engine according to claim 1 or 2.

Images