JP2007255211A - Control device of compression ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively perform intake top dead center injection, by effectively restraining a piston from being damaged by the intake top dead center injection, in a control device of a compression ignition internal combustion engine. <P>SOLUTION: Auxiliary intake top dead center injection is performed besides main injection in the vicinity of the compression top dead center. In the intake top dead center injection, cylinder internal pressure in the vicinity of the intake top dead center is enhanced, by controlling a variable valve train so as to generate a negative valve overlap period when both an intake valve and an exhaust valve close in the vicinity of the intake top dead center. Both the starting timing and the finish timing of the intake top dead center injection are made to fall within the negative valve overlap period. By such the intake top dead center injection, the main injection timing is largely retarded even in idling and a light load area, and the required high exhaust temperature can be set for regenerating an exhaust emission control device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a compression ignition internal combustion engine, and more particularly, to a control device for a compression ignition internal combustion engine suitable as a device for controlling a compression ignition internal combustion engine that performs auxiliary fuel injection near an intake top dead center.

  In recent years, the emission of particulate matter (PM) and nitrogen oxides (NOx), such as soot, to the atmosphere has been further suppressed compared to diesel engines (compression ignition internal combustion engines) mounted on automobiles. Is required to do. In order to meet these requirements, DPF (Diesel Particulate Filter) and DPNR (Diesel Particulate-NOx-Reduction system), NOx occlusion reduction type or NOx selective reduction type NOx catalyst that collects PM in the exhaust system of diesel engines. Exhaust gas purification devices such as these are installed.

  The purification capacity of the NOx catalyst decreases as SOx (sulfur oxide) contained in the exhaust gas is adsorbed. For this reason, it is sometimes necessary to perform a process (S regeneration) for removing the sulfur content accumulated in the NOx catalyst. In order to perform S regeneration, it is necessary to raise the NOx catalyst to a high temperature of about 650 to 700 ° C, for example. Further, in order to perform a process (PM regeneration) for oxidizing and removing PM accumulated in DPF, DPNR, etc., DPF, DPNR, etc. need to be heated to a high temperature of about 600 ° C., for example.

  As described above, when the regeneration process of the exhaust purification device is performed, it is required to raise the exhaust purification device, so that it is necessary to increase the exhaust temperature. For this reason, it is difficult to perform PM regeneration or S regeneration at idling or light load when the exhaust temperature is low. As a method of increasing the exhaust temperature, there is a method of delaying the fuel injection timing (timing retard). However, since the temperature and pressure in the cylinder are low during idling or light load, if the fuel injection timing is delayed, HC in the exhaust gas is likely to increase or misfire may occur. For this reason, sufficient timing retard cannot be performed.

  Japanese Patent Laid-Open No. 2000-291462 discloses an auxiliary fuel injection (hereinafter referred to as “intake top dead center injection” in the vicinity of the intake top dead center so that a large timing retard can be performed even during idling or light load. ) Is disclosed. By performing the intake top dead center injection, the fuel injected by the intake top dead center injection becomes a fire type, and the fuel injected by the main injection becomes easy to burn and can be surely burned. For this reason, it is possible to greatly delay the timing of the main injection.

JP 2000-291462 A JP-A-11-324778 JP 2005-155472 A

  However, when the intake top dead center injection is performed, the following problem occurs. In the vicinity of the intake top dead center, the in-cylinder pressure is significantly lower than that near the compression top dead center. When the in-cylinder pressure is low, the force that fuel injected at a high pressure penetrates through the air in the cylinder increases. For this reason, when the intake top dead center injection is performed, the injected fuel collides with the piston in a large amount with a strong momentum, so that the piston is easily damaged. Further, the fuel that has collided with the piston remains on the piston wall surface as a liquid. For this reason, if much of the fuel injected by intake top dead center adheres to the piston, the effect of intake top dead center injection is diminished. In recent years, as the common rail system has evolved and the like, the fuel injection pressure has been increased, and thus the above problems are more likely to occur.

  The present invention has been made to solve the above-described problems, and can effectively prevent the piston from being damaged by the intake top dead center injection and effectively perform the intake top dead center injection. An object of the present invention is to provide a control device for a compression ignition internal combustion engine that can be performed.

In order to achieve the above object, a first invention is a control device for a compression ignition internal combustion engine,
An injector that injects fuel directly into a cylinder of a compression ignition internal combustion engine;
Main injection means for causing the injector to perform main injection, which is the main fuel injection, near the compression top dead center;
Intake top dead center injection means for causing the injector to perform intake top dead center injection as auxiliary fuel injection near the intake top dead center;
A positive overlap state in which the intake valve and the exhaust valve are driven so that a positive valve overlap period in which both the intake valve and the exhaust valve of the internal combustion engine are open near the intake top dead center occurs; and the intake valve and the exhaust A variable valve mechanism capable of taking a negative overlap state in which the intake valve and the exhaust valve are driven so that a negative valve overlap period in which the valves are closed near the intake top dead center occurs;
When the intake top dead center injection is performed, the variable valve mechanism is set to the negative overlap state so that the start timing and end timing of the intake top dead center injection are both within the negative valve overlap period. Valve control means to control,
It is characterized by providing.

The second invention is the first invention, wherein
When the variable valve mechanism is in the negative overlap state and the intake top dead center injection is executed within the negative valve overlap period, the main injection that delays the timing of the main injection from the normal timing It further has a delay means.

The third invention is the first or second invention, wherein
When the injection amount of the intake top dead center injection is equal to or greater than a predetermined value, the valve control means sets the variable valve mechanism to the negative overlap state, and the injection amount of the intake top dead center injection is the predetermined amount. When the value is smaller than the value, the variable valve mechanism is set to the normal overlap state.

According to a fourth invention, in any one of the first to third inventions,
The intake top dead center injection is performed at the same injection pressure as the main injection.

According to a fifth invention, in any one of the first to fourth inventions,
The intake top dead center injection means starts the intake top dead center injection before the intake top dead center, and ends the intake top dead center injection after the intake top dead center.

  According to the first aspect of the invention, intake top dead center injection that is auxiliary fuel injection can be performed near the intake top dead center. When the intake top dead center injection is performed, the variable valve mechanism is controlled so that a negative valve overlap period occurs in which both the intake valve and the exhaust valve are closed near the intake top dead center. The intake top dead center injection can be started and ended within the valve overlap period. In the negative valve overlap period, since the residual gas is confined in the cylinder and compressed, the in-cylinder pressure can be increased. Therefore, the penetration force of the fuel injected at the intake top dead center can be weakened, and damage to the piston can be effectively suppressed. As a result, a large amount of intake top dead center injection becomes possible. Further, it is possible to suppress the fuel injected at the intake top dead center from adhering to the piston. Furthermore, since the in-cylinder temperature at the time of injection is high, evaporation of the injected fuel can be promoted. For this reason, the intake top dead center injection can be performed very effectively, and the fuel injected by the main injection can be made extremely easy to burn.

  According to the second invention, when the intake top dead center injection is executed within the negative valve overlap period, the timing retard of the main injection can be performed. According to the intake top dead center injection in the negative valve overlap period, the fuel injected in the main injection can be made extremely easy to burn. For this reason, even when the timing retard is performed during idling or in a light load range, adverse effects such as an increase in the concentration of HC in the exhaust gas and misfire are unlikely to occur, and a significant timing retard is possible. Therefore, the exhaust temperature can be made sufficiently high by the timing retard even during idling or in a light load region, and PM regeneration and S regeneration can be performed.

  According to the third aspect of the invention, when the injection amount of the intake top dead center injection is greater than or equal to a predetermined value, the variable valve mechanism is controlled so that a negative valve overlap period occurs, and the intake top dead center injection is performed. When the injection amount is smaller than the predetermined value, the variable valve mechanism can be controlled so that a positive valve overlap period occurs as usual. Therefore, the negative valve overlap period can be generated only when the intake top dead center injection amount is large and the penetration force is large.

  According to the fourth invention, the intake top dead center injection can be performed at the same high injection pressure as the main injection. For this reason, it is not necessary to perform complicated and difficult injection pressure control that lowers the injection pressure only during intake top dead center injection, and the system can be simplified.

  According to the fifth aspect, the intake top dead center injection can be started before the intake top dead center, and the intake top dead center injection can be ended after the intake top dead center. Therefore, intake top dead center injection can be performed at the timing with the highest in-cylinder pressure, damage to the piston can be more reliably suppressed, and the effect of intake top dead center injection can be further enhanced.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a compression ignition type internal combustion engine (diesel engine) 10. An internal combustion engine 10 shown in FIG. 1 includes a cylinder block 4 in which a piston 8 is disposed, and a cylinder head 6 assembled to the cylinder block 4. An intake port 12 and an exhaust port 14 are formed in the cylinder head 6. An intake passage 22 for introducing fresh air into the cylinder is connected to the intake port 12, and an exhaust passage 24 for discharging exhaust gas is connected to the exhaust port 14.

  The intake valve 32 of the internal combustion engine 10 is driven by an intake variable valve mechanism 42. The intake variable valve mechanism 42 changes at least the opening timing of the intake valve 32 continuously or stepwise. The intake variable valve mechanism 42 may further vary the closing timing and lift amount of the intake valve 32. The structure of the intake variable valve mechanism 42 is not particularly limited. For example, in addition to a mechanical variable mechanism, an electromagnetically driven valve or a hydraulically driven valve may be used.

  The exhaust valve 34 of the internal combustion engine 10 is driven by an exhaust variable valve mechanism 44. The exhaust variable valve mechanism 44 changes at least the closing timing of the exhaust valve 34 continuously or stepwise. The exhaust variable valve mechanism 44 may further vary the opening timing and lift amount of the exhaust valve 34. The structure of the exhaust variable valve mechanism 44 is not particularly limited. For example, in addition to a mechanical variable mechanism, an electromagnetically driven valve or a hydraulically driven valve may be used.

  The cylinder head 6 is provided with an injector 30 for directly injecting fuel into the cylinder. The injector 30 is connected to a common rail (not shown), and is supplied with high-pressure fuel from the common rail. The common rail always stores high-pressure fuel compressed by the supply pump. The injector 30 can inject fuel at an arbitrary timing a plurality of times during one cycle.

  A crank angle sensor 56 that detects a rotation angle (crank angle) of the crankshaft 16 is attached in the vicinity of the crankshaft 16 of the internal combustion engine 10.

  An exhaust purification device 28 is disposed in the exhaust passage 24. As the exhaust purification device 28, for example, one of an oxidation catalyst, NOx occlusion reduction type or NOx selective reduction type NOx catalyst, DPF (Diesel Particulate Filter), DPNR (Diesel Particulate-NOx-Reduction system), or these Can be used.

  An intake throttle valve 36 is provided in the intake passage 22. An EGR passage 26 is connected downstream of the intake throttle valve 36 in the intake passage 22. The end on the opposite side of the EGR passage 26 is connected upstream of the exhaust purification device 28 in the exhaust passage 24. A part of exhaust gas (EGR gas) can be introduced into the intake passage 22 through the EGR passage 26. An EGR valve 38 that opens and closes the EGR passage 26 is provided in the middle of the EGR passage 26. Further, an exhaust throttle valve 46 is provided in the exhaust passage 24.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. Various actuators such as the injector 30, the intake throttle valve 36, the EGR valve 38, the intake variable valve mechanism 42, the exhaust variable valve mechanism 44, and the exhaust throttle valve 46 are connected to the output side of the ECU 50. Various sensors such as a crank angle sensor 56 and an accelerator opening sensor 58 are connected to the input side of the ECU 50. The accelerator opening sensor 58 is a sensor that outputs a signal corresponding to the opening of an accelerator pedal (not shown). The ECU 50 drives each actuator according to a predetermined control program based on the output of each sensor.

[Operation of Embodiment 1]
FIG. 2 is a view for explaining intake top dead center injection in the system of the present embodiment. More specifically, FIG. 2 (A) is a lift diagram of the intake valve 32 and the exhaust valve 34, and FIG. 2 (B) is a diagram showing an injection drive pulse for operating the injector 30.

  As shown in FIG. 2B, the internal combustion engine 10 performs fuel injection by the injector 30 in addition to main fuel injection performed near the compression top dead center (hereinafter referred to as “main injection”), as necessary. Pilot injection, post injection, and intake top dead center injection can be performed. The pilot injection is a fuel injection that is performed prior to the main injection, and has the effect of facilitating burning of the fuel of the main injection and preventing noise and the like. The post-injection is a fuel injection that is performed after the completion of combustion, and is a fuel injection that does not contribute to the output of the internal combustion engine 10. By performing post injection, unburned fuel (HC) can be supplied to the exhaust purification device 28, and the exhaust purification device can be heated or reduced. The intake top dead center injection will be described later.

  The internal combustion engine 10 may further perform pre-injection immediately before the main injection, after-injection immediately after the main injection, or the like as necessary.

  In the system of this embodiment, when PM (Particulate Matter) or sulfur content accumulates in the exhaust purification device 28, PM regeneration processing for burning and removing PM, or S regeneration processing for reducing and removing sulfur content. Done. In order to perform PM regeneration and S regeneration, it is necessary to set the exhaust purification device 28 to a high temperature of about 600 to 700 ° C., for example.

  However, when the engine is idling or in a light load region, the exhaust temperature is as low as about 100 to 150 ° C., so even if post injection or the like is performed, the temperature of the exhaust purification device 28 is raised to the temperature required for PM regeneration or S regeneration. Conventionally, it has been difficult to do. The exhaust temperature can be increased as the injection timing of the main injection is delayed (hereinafter also referred to as “timing retard”). However, the more retarded the timing is, the more difficult the fuel burns, so the HC concentration in the exhaust increases and further misfires occur. In the idling or light load range, the temperature and pressure in the cylinder are low, so the HC concentration is increased and misfires are likely to occur due to the timing retard, and a significant timing retard is not possible. For this reason, conventionally, at idle or in a light load range, timing retard cannot be performed until the exhaust temperature necessary for PM regeneration or S regeneration is obtained. It was difficult to perform S regeneration.

  On the other hand, in the present embodiment, the intake top dead center injection is performed in order to enable sufficient timing retard even in idling or in a light load range. In this specification, the intake top dead center injection refers to auxiliary fuel injection performed near the intake top dead center (exhaust stroke end point, intake stroke start point). When the intake top dead center injection is performed, the injected fuel is sufficiently evaporated during the intake stroke and the compression stroke to form an air-fuel mixture that is easy to burn. Then, the air-fuel mixture is ignited, and pilot injection and main injection are performed where the kind of fire is generated. Therefore, the fuel injected by the pilot injection and main injection becomes easy to burn and can be reliably burned.

  If the fuel injected in the main injection can be easily burned by performing the intake top dead center injection, it is possible to prevent the increase in HC concentration and misfire even if the timing of the main injection is retarded. For this reason, sufficient timing retard is possible even during idling or in a light load range. As a result, the exhaust temperature can be made sufficiently high even during idling or in a light load range, and PM regeneration and S regeneration can be performed.

  In the present specification, “near intake top dead center” means that the piston 8 is close to top dead center so that the fuel spray from the injector 30 is contained in the combustion chamber formed on the top surface of the piston 8. This is the crank angle range, and is usually in the range of about 30 ° CA before and after the intake top dead center. Since the intake top dead center injection is performed within such a range, the injected fuel does not hit the cylinder inner wall (bore wall surface). For this reason, problems such as bore flushing in which the oil film on the inner wall of the cylinder is washed away and oil dilution can be prevented.

  Incidentally, in the internal combustion engine 10 of the present embodiment, during normal operation, the intake valve 32 starts to open before the intake top dead center, and the exhaust valve 34 has passed the intake top dead center, as in a general internal combustion engine. It will be completely closed later. The valve lift curves of the intake valve 32 and the exhaust valve 34 at this time are indicated by broken lines in FIG. Thus, during normal operation of the internal combustion engine 10, a period in which both the intake valve 32 and the exhaust valve 34 are open near the intake top dead center (hereinafter referred to as “positive valve overlap period”) occurs. Then, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are controlled. The state in which the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 operate in this way is hereinafter referred to as a “normal overlap state”.

  Thus, in the vicinity of the intake top dead center, the intake valve 32 and the exhaust valve 34 are normally open. For this reason, the in-cylinder pressure in the vicinity of the intake top dead center is normally at a level as low as the intake pipe pressure. When the intake top dead center injection is performed in such a state where the in-cylinder pressure is low, the high-pressure fuel injected from the injector 30 easily penetrates the air in the cylinder and the combustion formed on the top surface of the piston 8 It is easy to collide with the walls of the room vigorously and in large quantities.

  In recent years, the fuel injection pressure has been further increased along with the evolution of the common rail system. For this reason, if the fuel injected from the injector 30 at such a high pressure collides with the piston in a large amount, the piston 8 is easily damaged. Further, the fuel that collides with the piston 8 and adheres to the surface of the piston 8 is likely to remain without being evaporated even after the subsequent intake stroke and compression stroke, and does not contribute to the formation of the air-fuel mixture. For this reason, even if the intake top dead center injection is performed, if the amount of fuel adhering to the piston 8 is large, the effect is diminished.

  If the injection pressure is lowered only during the intake top dead center injection, the above problem can be avoided, but the time interval between the intake top dead center injection and other injection timings such as the main injection is extremely small. Since it is minute, it is extremely difficult to perform such injection pressure control in a short time. For this reason, in the present embodiment, the intake top dead center injection is performed at the same injection pressure (same common rail pressure) as the main injection or the like.

  In the present embodiment, in order to solve the problem associated with the intake top dead center injection as described above, the opening timing of the intake valve 32 and the closing timing of the exhaust valve 34 are changed when the intake top dead center injection is executed. . The solid line in FIG. 2A represents the valve lift curves of the intake valve 32 and the exhaust valve 34 when the intake top dead center injection is executed. At this time, the intake valve 32 and the exhaust valve 34 are dead dead by making the opening timing of the intake valve 32 later than normal (normal overlap state) and closing the exhaust valve 34 earlier than normal. The intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are controlled so that a closed period (hereinafter referred to as a “negative valve overlap period”) occurs near the point. The state in which the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 operate in this way is hereinafter referred to as a “negative overlap state”.

  When the intake top dead center injection is executed, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are in a negative overlap state, and the intake top dead center injection is started within the negative valve overlap period. And finished.

  In the negative valve overlap period, since the intake valve 32 and the exhaust valve 34 are both closed, the intake pipe pressure is not transmitted into the cylinder. Further, when the exhaust valve 34 is closed early, a large amount of the burned gas (residual gas) of the previous cycle remains in the cylinder and becomes trapped. For this reason, in-cylinder pressure in the vicinity of the intake top dead center can be significantly increased as compared with the case where a positive valve overlap period occurs. This high in-cylinder pressure can weaken the penetration force of the fuel injected by the intake top dead center injection. Therefore, it is possible to prevent the fuel injected with the intake top dead center from colliding with the piston 8 vigorously, and the damage to the piston 8 can be effectively suppressed. For this reason, a large amount of intake top dead center injection can be performed. Further, since the penetrating force of the injected fuel is weakened and the amount hitting the piston 8 is reduced, the amount of fuel adhering to the piston 8 can be reduced.

  Further, the cylinder in the negative valve overlap period is not yet filled with fresh air, and is filled with residual gas, that is, burned gas, so that the cylinder temperature is also high. For this reason, since the evaporation of the fuel injected by the intake top dead center injection can be promoted, it is further suppressed that the injected fuel hits the piston 8, and the subsequent air-fuel mixture formation is favorably promoted. be able to.

  For this reason, it is possible to effectively prevent the piston 8 from being damaged by performing the intake top dead center injection during the negative valve overlap period. Further, a large amount of intake top dead center injection is possible, and evaporation of the injected fuel can be promoted, so that intake top dead center injection can be performed more effectively. For this reason, even during idling or in a light load range, an increase in HC concentration or misfire due to timing retard is unlikely to occur, and significant timing retard is possible. Specifically, the timing of main injection can be delayed until after the compression top dead center. As a result, the exhaust temperature can be made sufficiently high even during idling or in a light load range, and PM regeneration and S regeneration can be performed reliably.

  In particular, in the present invention, by making the start timing and end timing of the intake top dead center injection both fall within the negative valve overlap period, the above-described effect can be more reliably exhibited.

  From the viewpoint of increasing the in-cylinder pressure at the time of intake top dead center injection, in the case of a negative overlap state, the variable exhaust valve mechanism 44 is controlled so that the closing timing of the exhaust valve 34 is before the intake top dead center. It is preferable to do. As a result, the amount of residual gas in the cylinder further increases, and the residual gas is compressed by the piston 8 after the exhaust valve 34 is closed, so that the in-cylinder pressure near the intake top dead center can be further increased. it can.

  In the light load region near the idle, it is preferable to close the exhaust valve 34 during the exhaust stroke in order to increase the amount of residual gas. Thereby, the cylinder pressure at the time of intake top dead center injection can be sufficiently increased even in such an operation region.

  In the case of a negative overlap state, it is preferable to control the intake variable valve mechanism 42 so that the opening timing of the intake valve 32 is after the intake top dead center. As a result, the in-cylinder pressure near the intake top dead center can be further increased, and the intake top dead center injection can be performed at the timing when the in-cylinder pressure is highest.

  In addition, the intake top dead center injection may start and end before the intake top dead center, or may start and end after the intake top dead center, during the negative valve overlap period, From the viewpoint of performing the timing at which the in-cylinder pressure is highest, it is preferable to start immediately before the intake top dead center and end immediately after the intake top dead center.

  Next, an example of control during PM regeneration and S regeneration in the present embodiment will be described. FIG. 3 is a diagram for explaining control during PM regeneration and S regeneration, and is a map of the operation region of the internal combustion engine 10 with the engine speed on the horizontal axis and the fuel injection amount (load) on the vertical axis. . As shown in FIG. 3, in the present embodiment, the operating region of the internal combustion engine 10 is divided into regions 1 to 5 in the order of low rotation and light load, and when PM regeneration and S regeneration are performed, the following is performed for each region. Control like this.

  Region 1 is a region near the idle, and is the region of the lowest rotation and light load. When in the region 1 during PM regeneration and S regeneration, as described above, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are set in a negative overlap state, and intake is performed within the negative valve overlap period. While top dead center injection is performed, timing retard of main injection is performed. In this timing retard, it is preferable to delay the start timing of the main injection until after the compression top dead center. Further, in region 1, post injection and exhaust throttling are also performed. By performing exhaust throttling by reducing the opening of the exhaust throttle valve 46, the pumping loss increases and the pumping loss is converted into thermal energy, so that the exhaust temperature can be further increased. As described above, by combining the intake top dead center injection, the timing retard, the post injection, and the exhaust throttling within the negative valve overlap period, the exhaust temperature can be sufficiently increased even in the region 1 of the lowest speed and light load. Therefore, PM regeneration and S regeneration can be performed.

  In region 2, the original exhaust temperature is slightly higher than in region 1, so that the exhaust temperature can be made sufficiently high without exhaust throttling. Therefore, in the region 2 during PM regeneration and S regeneration, exhaust throttling is not performed, but intake top dead center injection, timing retard, and post injection within a negative valve overlap period are performed in combination. The

  In region 3, post injection and exhaust throttling are not performed, and intake top dead center injection in the negative valve overlap period and timing retard are performed in combination. Thereby, the exhaust temperature required for PM regeneration and S regeneration is obtained.

  In the region 4, since the temperature and pressure in the cylinder are relatively high, even if timing retard is performed, the increase in HC concentration and misfire are unlikely to occur. Therefore, it is possible to sufficiently retard the timing without performing the intake top dead center injection. Therefore, when the PM regeneration and the S regeneration are in the region 4, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 remain in the normal positive overlap state, that is, a positive valve overlap period occurs. In this state, the intake top dead center injection is not performed, but only the timing retard of the main injection is performed. Thereby, the exhaust temperature required for PM regeneration and S regeneration is obtained.

  In region 5, since the exhaust temperature is originally high, it is not necessary to take measures to increase the exhaust temperature even when performing PM regeneration and S regeneration. For this reason, when it is in the region 5 at the time of PM regeneration and S regeneration, a state in which a positive valve overlap period is generated is maintained, and main injection is performed at normal timing without performing timing retard.

  When the negative valve overlap period occurs, the length of the negative valve overlap period may be changed according to the load and the exhaust temperature.

  As described above, according to the present invention, an increase in HC concentration and misfire due to timing retard can be avoided by performing the intake top dead center injection even when idling or in a light load range. Timing retard can be performed. As a result, the exhaust temperature can be sufficiently increased even during idling or in a light load range, and PM regeneration and S regeneration can be performed. Further, by performing PM regeneration or S regeneration at idle or in a light load range, it is possible to effectively suppress deterioration in fuel consumption during regeneration.

  Further, according to the present invention, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are operated so that a negative valve overlap period in which both the intake valve 32 and the exhaust valve 34 are closed, and the negative valve overflow is caused. By performing the intake top dead center injection within the lap period, it is possible to effectively suppress the piston 8 from being damaged by the intake top dead center injection. For this reason, a large amount of intake top dead center injection can be performed, and the injected fuel can be prevented from adhering to the piston 8. For this reason, the intake top dead center injection can be effectively performed without causing any harmful effects, and a significant timing retard can be achieved at idle or in a light load range.

  In the first embodiment described above, it has been described that the intake top dead center injection is always performed within the negative valve overlap period. However, in the present invention, the injection amount of the intake top dead center injection is large. The negative valve overlap period may be performed only when the penetrating force is strong. In other words, when it is determined that the intake top dead center injection amount is equal to or greater than the predetermined value and the fuel penetration force is strong, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 are set in a negative overlap state so that the negative valve When the intake top dead center injection is performed within the overlap period, and it can be determined that the intake top dead center injection amount is smaller than the predetermined value and the fuel penetration force is small, the variable intake valve mechanism 42 and the variable exhaust valve mechanism The intake top dead center injection may be performed while the mechanism 44 is in a state in which a positive valve overlap period occurs.

  In the above-described first embodiment, the case where the timing retard of the main injection is performed in combination with the intake top dead center injection has been described. However, the present invention applies to the case where the intake top dead center injection is performed for purposes other than the timing retard. Can also be applied.

  In the first embodiment described above, the intake variable valve mechanism 42 and the exhaust variable valve mechanism 44 correspond to the “variable valve mechanism” according to the first aspect of the present invention. Further, when the ECU 50 issues a signal for performing main injection, the “main injection means” in the first aspect of the invention issues a signal for performing intake top dead center injection. The intake variable top valve mechanism 42 and the variable exhaust valve control mechanism are arranged so that the intake top dead center injection start timing and end timing fall within the negative valve overlap period when the intake top dead center injection is executed. By controlling the valve mechanism 44, the “valve control means” in the first invention performs timing retard of the main injection in the case of the regions 1 to 3 in FIG. "Delay means" are realized respectively.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating intake top dead center injection. It is a figure for demonstrating control at the time of PM reproduction | regeneration and S reproduction | regeneration.

Explanation of symbols

8 piston 10 internal combustion engine 16 crankshaft 22 intake passage 24 exhaust passage 26 EGR passage 28 exhaust purification device 30 injector 32 intake valve 34 exhaust valve 36 intake throttle valve 38 EGR valve 42 intake variable valve mechanism 44 exhaust variable valve mechanism 46 exhaust Throttle valve 50 ECU
56 Crank angle sensor 58 Accelerator opening sensor

Claims (5)

An injector that injects fuel directly into a cylinder of a compression ignition internal combustion engine;
Main injection means for causing the injector to perform main injection, which is the main fuel injection, near the compression top dead center;
Intake top dead center injection means for causing the injector to perform intake top dead center injection as auxiliary fuel injection near the intake top dead center;
A positive overlap state in which the intake valve and the exhaust valve are driven so that a positive valve overlap period in which both the intake valve and the exhaust valve of the internal combustion engine are open near the intake top dead center occurs; and the intake valve and the exhaust A variable valve mechanism capable of taking a negative overlap state in which the intake valve and the exhaust valve are driven so that a negative valve overlap period in which the valves are closed near the intake top dead center occurs;
When the intake top dead center injection is performed, the variable valve mechanism is set to the negative overlap state so that the start timing and end timing of the intake top dead center injection are both within the negative valve overlap period. Valve control means to control,
A control apparatus for a compression ignition internal combustion engine.   When the variable valve mechanism is in the negative overlap state and the intake top dead center injection is executed within the negative valve overlap period, the main injection that delays the timing of the main injection from the normal timing The control apparatus for a compression ignition internal combustion engine according to claim 1, further comprising a delay means.   When the injection amount of the intake top dead center injection is equal to or greater than a predetermined value, the valve control means sets the variable valve mechanism to the negative overlap state, and the injection amount of the intake top dead center injection is the predetermined amount. 3. The control device for a compression ignition internal combustion engine according to claim 1, wherein when the value is smaller than the value, the variable valve mechanism is set to the normal overlap state. 4.   The control apparatus for a compression ignition internal combustion engine according to any one of claims 1 to 3, wherein the intake top dead center injection is performed at the same injection pressure as the main injection.   5. The intake top dead center injection means starts the intake top dead center injection before the intake top dead center, and ends the intake top dead center injection after the intake top dead center. The control apparatus for a compression ignition internal combustion engine according to any one of the preceding claims.

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