JP4534403B2 - Compression ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine mounted on a vehicle or the like, and more particularly to a compression ignition internal combustion engine having a variable valve mechanism.
[0002]
[Prior art]
In general, in a compression ignition type internal combustion engine (diesel engine), in order to prevent a reduction in the excess air ratio at high load, in other words, to improve intake charging efficiency at high load, the closing timing of the intake valve is set to intake air. The compression ratio is set to be high for the purpose of improving the startability and improving the combustion efficiency at the time of low load, while being largely retarded after the stroke bottom dead center.
[0003]
By the way, in an internal combustion engine having a high compression ratio, it is necessary to increase the strength and rigidity of the cylinder head and the cylinder block. Therefore, the mass per displacement tends to be larger than that of an ignition type internal combustion engine (gasoline engine). As a result, an increase in weight when mounted on a vehicle may be disadvantageous in improving fuel consumption.
[0004]
On the other hand, a method of reducing the compression ratio of the internal combustion engine is conceivable. However, the in-cylinder atmosphere temperature at the fuel injection timing (in the vicinity of the top dead center of the compression stroke), so-called compression end temperature, decreases, so at the time of starting or at low load Incomplete combustion tends to occur, and there is a risk that white smoke and particulate matter (Particulate Matter: PM) emissions will increase and the fuel consumption rate will deteriorate.
[0005]
Therefore, conventionally, a compression ignition type internal combustion engine in which a variable valve mechanism is incorporated at the same time as the compression ratio is lowered has been developed.
[0006]
Such a compression ignition type internal combustion engine with a low compression ratio, for example, retards the intake valve opening timing until the intake stroke top dead center after a low load and closes the intake valve closing timing to the vicinity of the intake stroke bottom dead center. The intake valve opening timing is advanced to just before the intake stroke top dead center and the intake valve closing timing is retarded to the intake stroke bottom dead center or later at medium and high loads.
[0007]
Here, when the load is low, it is difficult to obtain the inertia effect of the intake air, which may reduce the charging efficiency of the intake air. However, by delaying the intake valve opening timing after the top dead center of the intake stroke, As a result, the intake valve is opened while the inside is in a negative pressure. As a result, the intake air flows into the cylinder vigorously, and the charging efficiency of the intake air is improved.
[0008]
Furthermore, in an internal combustion engine with a low compression ratio, the compression end temperature tends to be low at low loads, but the effective compression stroke length is sufficiently secured by setting the intake valve closing timing in the vicinity of the bottom dead center of the intake stroke. It becomes possible.
[0009]
Therefore, if the intake valve opening timing is retarded until after the intake stroke top dead center at the time of low load and the intake valve closing timing is set in the vicinity of the intake stroke bottom dead center, intake charging efficiency is improved at the same time. Since the effective compression stroke length increases, the compression end temperature can be increased, and hence the generation amount of PM and the deterioration of the fuel consumption rate are suppressed.
[0010]
On the other hand, since it is easy to obtain the inertial effect of intake during medium and high loads, setting the intake valve opening timing near the top dead center of the intake stroke makes it possible to reduce the intake pumping loss and reduce the intake charge efficiency. Can be improved.
[0011]
In addition, at medium and high loads, the compression end temperature tends to become excessively high due to the improvement in intake charging efficiency, but the effective compression stroke length is shortened by retarding the intake valve closing timing after the bottom dead center of the intake stroke. It becomes possible.
[0012]
Therefore, if the intake valve opening timing is set in the vicinity of the intake stroke top dead center at medium and high loads, and the intake valve closing timing is delayed until after the intake stroke bottom dead center, the intake charging efficiency is reduced. Therefore, since the effective compression stroke length is shortened, it is possible to suppress an excessive increase in the compression end temperature, thereby preventing pre-ignition of the fuel.
[0013]
In recent compression ignition internal combustion engines, a technology has been proposed in which a small amount of fuel injection (pilot injection) is performed multiple times prior to normal fuel injection (main injection) for the purpose of reducing combustion noise and improving exhaust emissions. Has been.
[0014]
Thus, when pilot injection is performed a plurality of times prior to the main injection, it is possible to generate a combustible atmosphere in the cylinder while preventing bore flushing or the like in which the injected fuel reaches the cylinder wall surface and adheres.
[0015]
If a combustible atmosphere is generated in the cylinder before the main injection is performed, the premixed combustion is performed at an early stage after the main injection is started, so the ignition delay period is shortened and the premixed combustion is performed. It is possible to reduce the amount of fuel supplied to the fuel cell.
[0016]
As a result, combustion noise can be reduced and the amount of soot and nitrogen oxides (NOx) generated can be suppressed.
[0017]
[Problems to be solved by the invention]
By the way, when pilot injection control is applied to an internal combustion engine with a low compression ratio as described above, the in-cylinder pressure changes in accordance with the control state of the variable valve mechanism, so the control state of the variable valve mechanism It is necessary to perform pilot injection control according to the above.
[0018]
For example, when the variable valve mechanism is controlled to increase the in-cylinder pressure, the pilot-injected fuel forms a combustible mixture in a relatively short period of time. There are cases where ignition occurs or ignition occurs immediately after the start of main injection. In such a case, since the period during which the main injected fuel is mixed with air (ignition delay period) is shortened, there is a risk that the amount of soot generated will increase.
[0019]
On the other hand, when the variable valve mechanism is controlled to reduce the in-cylinder pressure, it takes time for the pilot-injected fuel to form a combustible mixture. You may not be able to form your mind. In such a case, since the ignition delay period becomes longer, the amount of fuel supplied to the premixed combustion increases, and the generation amount of nitrogen oxide (NOx) may increase.
[0020]
Therefore, if the pilot injection control is executed without considering the control state of the variable valve mechanism, exhaust emission may be deteriorated.
[0021]
Further, the compression ignition type internal combustion engine may include an EGR mechanism that suppresses the generation amount of nitrogen oxides (NOx) by recirculating a part of the exhaust gas to the internal combustion engine. At that time, the EGR mechanism is controlled by using the fuel amount contributing to torque generation of the internal combustion engine and the engine speed as main parameters.
[0022]
By the way, in a situation where the in-cylinder pressure is increased by the variable valve mechanism, all of the fuel from the pilot injection and the main injection is easily reflected in the torque of the internal combustion engine, but in a situation where the in-cylinder pressure is lowered by the variable valve mechanism. Pilot injected fuel is less likely to be reflected in the torque of the internal combustion engine.
[0023]
For this reason, in EGR control using the fuel amount reflected in the torque of the internal combustion engine as a parameter, it is necessary to perform control in consideration of the control state of the variable valve mechanism. In other words, when EGR control is performed using the total fuel injection amount of the pilot injection and the main injection as a parameter when the fuel injected by the pilot is not reflected in the torque of the internal combustion engine, the amount of nitrogen oxide (NOx) generated is reduced. On the other hand, the exhaust gas recirculation amount is excessively increased, and there is a risk that deterioration of combustibility and exhaust emission may be induced.
[0024]
The present invention has been made in view of the various circumstances as described above, and in the case where pilot injection control is applied to a low compression ratio compression ignition internal combustion engine having a variable valve mechanism, the variable valve An object of the present invention is to provide a technique capable of realizing fuel injection control, EGR control, and the like suitable for the control state of a mechanism, and to prevent deterioration of combustibility and exhaust emission of an internal combustion engine.
[0025]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems.
That is, the first invention for solving the above-described problem is
A variable valve mechanism that changes the opening / closing timing and / or lift amount of the intake valve of the compression ignition internal combustion engine;
A valve mechanism control means for controlling the variable valve mechanism so that the pressure in the cylinder is higher when the load of the internal combustion engine is low than when it is high;
Main injection means for injecting fuel into the cylinder;
Pilot injection means for performing pilot injection a plurality of times prior to fuel injection by the main injection means;
When the variable valve mechanism is controlled to increase the in-cylinder pressure, pilot injection control means for prohibiting the execution of pilot injection set within a predetermined period from the execution timing of the first pilot injection;
Is a compression ignition type internal combustion engine.
[0026]
Prior to normal fuel injection (main injection), a variable valve mechanism that changes the opening / closing timing and / or lift amount of the intake valve so that the in-cylinder pressure is high at low loads and the in-cylinder pressure is low at high loads. In a compression ignition type internal combustion engine provided with pilot injection means for performing a plurality of pilot injections, when the variable valve mechanism is controlled so as to increase the in-cylinder pressure, it is predetermined from the execution timing of the first pilot injection. The greatest feature is that the execution of pilot injection set within the period is prohibited.
[0027]
In such a compression ignition type internal combustion engine, the valve mechanism control means controls the variable valve mechanism so that the in-cylinder pressure becomes high when the load of the internal combustion engine is low, and the in-cylinder pressure becomes low when the load of the internal combustion engine is high. The variable valve mechanism is controlled so that
[0028]
Here, if the in-cylinder pressure is increased when the load of the internal combustion engine is low, the in-cylinder pressure at the top dead center of the compression stroke (so-called compression end temperature) is increased, so that the ignitability and combustion stability of the fuel are improved, As a result, an increase in particulate matter (PM) emissions and a deterioration in fuel consumption rate are prevented.
[0029]
On the other hand, if the in-cylinder pressure is lowered when the load of the internal combustion engine is high, the compression end temperature is lowered, so that the combustion temperature does not become excessively high. As a result, the nitrogen oxide (NOx) at the time of high load is reduced. The generation amount is suppressed.
[0030]
By the way, when the in-cylinder pressure is increased by the variable valve mechanism, the pilot-injected fuel is vaporized relatively early to form a combustible mixture, so that the combustible mixture is ignited before the main injection is performed. Alternatively, ignition may occur immediately after the start of the main injection, and the period during which the main injected fuel is mixed with air (ignition delay period) may become excessively short.
[0031]
On the other hand, in the compression ignition type internal combustion engine according to the present invention, when the in-cylinder pressure is increased by the variable valve mechanism, the pilot injection control means is a pilot set within a predetermined period from the execution timing of the first pilot injection. The execution of injection was prohibited.
[0032]
In this case, since the pilot injection is executed for the first time after a predetermined period has elapsed from the execution time of the first pilot injection, the time when the execution of the main injection is started from the time when the first pilot injection is actually executed The period until is shortened.
[0033]
As a result, the period during which the pilot-injected fuel is exposed to a high in-cylinder pressure is shortened, and the pilot-injected fuel is not pre-ignited before the start of the main injection or immediately after the start of the main injection.
[0034]
If the execution of pilot injection set within a predetermined period from the start timing of the first pilot injection execution is prohibited, the fuel injection amount decreases by the amount of pilot injection set within the predetermined period. You may make it add the fuel-injection amount of the minute to the pilot injection after a predetermined period.
[0035]
In the compression ignition internal combustion engine according to the present invention, the variable valve mechanism includes a first opening / closing timing and / or lift amount at which the in-cylinder pressure increases, and a second opening / closing timing and / or lift amount at which the cylinder pressure decreases. Any one of these may be configured to be selectable, or configured to be continuously changeable from the first opening / closing timing and / or lift amount to the second opening / closing timing and / or lift amount. It may be.
[0036]
In this case, the valve mechanism control means selects the first opening / closing timing and / or lift amount when the load on the internal combustion engine is low, and selects the second opening / closing timing and / or lift amount when the load on the internal combustion engine is high. Control the variable valve mechanism to select.
[0037]
The pilot injection control means increases the total amount and / or number of pilot injections when the variable valve mechanism is switched from the first opening / closing timing and / or lift amount to the second opening / closing timing and / or lift amount. You may make it make it.
[0038]
This is because when the variable valve mechanism is switched from the first opening / closing timing and / or the lift amount to the second opening / closing timing and / or the lift amount, the in-cylinder pressure decreases, and the pilot-injected fuel forms a combustible mixture. This is because it becomes difficult to be reflected in the torque of the internal combustion engine.
[0039]
Next, the second invention for solving the above-described problems is as follows.
A variable valve mechanism for changing the opening / closing timing and / or lift amount of the intake valve of the compression ignition internal combustion engine;
A valve mechanism control means for controlling the variable valve mechanism so that the pressure in the cylinder is higher when the load of the internal combustion engine is low than when it is high;
Main injection means for injecting fuel into the cylinder;
Pilot injection means for performing pilot injection a plurality of times prior to fuel injection by the main injection means;
Exhaust gas recirculation means for recirculating part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system;
Exhaust gas recirculation control means for controlling the exhaust gas recirculation amount by the exhaust gas recirculation means with the total fuel injection quantity by the main injection means and the pilot injection means as parameters.
When the variable valve mechanism is controlled to reduce the in-cylinder pressure, the total fuel injection amount used for the exhaust gas recirculation control is reduced and corrected as compared to when the variable valve mechanism is controlled to increase the in-cylinder pressure. Parameter correction means;
A compression ignition type internal combustion engine.
[0040]
The present invention provides a variable valve mechanism that changes the opening / closing timing and / or lift amount of an intake valve so that the in-cylinder pressure is high at low loads and low at high loads, and multiple pilot injections are performed prior to main injection. In a compression ignition type internal combustion engine having a pilot injection means to be executed and an exhaust gas recirculation mechanism controlled by using the total fuel injection amount of the main injection and the pilot injection as a parameter, a variable valve mechanism is provided so as to reduce the in-cylinder pressure. When controlled, the greatest feature is that the total fuel injection amount used for exhaust gas recirculation control is reduced and corrected compared to when the variable valve mechanism is controlled so that the in-cylinder pressure is increased. .
[0041]
In such a compression ignition type internal combustion engine, the valve mechanism control means controls the variable valve mechanism so that the in-cylinder pressure becomes high when the load of the internal combustion engine is low, and the in-cylinder pressure becomes low when the load of the internal combustion engine is high. The variable valve mechanism is controlled so that
[0042]
By the way, when the in-cylinder pressure is increased by the variable valve mechanism, all of the fuel injected by the pilot injection and the main injected fuel are easily reflected in the torque of the internal combustion engine. There is no problem if the exhaust gas recirculation mechanism is controlled using the injection amount as a parameter. However, when the cylinder is lowered by the variable valve mechanism, a part of the fuel injected by the pilot is not easily reflected in the torque of the internal combustion engine. Therefore, when the exhaust gas recirculation mechanism is controlled using the total fuel injection amount by the pilot injection and the main injection as a parameter, the exhaust gas recirculation amount may increase with respect to the generation amount of nitrogen oxides (NOx).
[0043]
On the other hand, in the compression ignition type internal combustion engine according to the present invention, when the in-cylinder pressure is lowered by the variable valve mechanism, the exhaust gas recirculation control is performed compared to when the in-cylinder pressure is raised by the variable valve mechanism. The total fuel injection amount used for the is corrected to decrease.
[0044]
When the total fuel injection amount used for control of the exhaust gas recirculation mechanism is corrected to decrease when the cylinder pressure is reduced by the variable valve mechanism, the exhaust gas is regenerated relative to the generated amount of nitrogen oxides (NOx). The circulation amount does not increase excessively, and the combustibility and exhaust emission of the internal combustion engine do not deteriorate.
[0045]
In the compression ignition type internal combustion engine according to the present invention, the parameter correction means may change the reduction correction amount of the total fuel injection amount in accordance with the execution timing of each pilot injection. This is because the pilot-injected fuel is less likely to be reflected in the torque of the internal combustion engine as the pilot injection timing becomes earlier.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of a compression ignition type internal combustion engine according to the present invention will be described with reference to the drawings.
[0047]
<Embodiment 1>
First, a first embodiment of a compression ignition type internal combustion engine according to the present invention will be described with reference to FIGS.
[0048]
FIG. 1 is a diagram showing a schematic configuration of a compression ignition type internal combustion engine according to the present invention.
The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-stroke cycle diesel engine having four cylinders 2 and has a relatively low compression ratio.
[0049]
Each cylinder 2 of the internal combustion engine 1 is provided with two intake valves 20 and two exhaust valves 21 and a fuel injection valve 3 that directly injects fuel into a combustion chamber (not shown). Furthermore, each cylinder 2 is provided with an in-cylinder pressure sensor 4 that outputs an electrical signal corresponding to the pressure in the cylinder.
[0050]
Each fuel injection valve 3 described above communicates with a pressure accumulation chamber (common rail) 5 that accumulates fuel to a predetermined pressure. A common rail pressure sensor 5 a that outputs an electrical signal corresponding to the pressure of the fuel in the common rail 5 (common rail pressure) is attached to the common rail 5.
[0051]
The common rail 5 communicates with a fuel pump 7 through a fuel supply pipe 6. The fuel pump 7 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source, and a pump pulley 7a attached to the input shaft of the fuel pump 7 is connected to the output shaft of the internal combustion engine 1 ( And a crank pulley 1a attached to the crankshaft) via a belt 8.
[0052]
In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 7, the fuel pump 7 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 7. The fuel is discharged at a pressure according to the pressure.
[0053]
The fuel discharged from the fuel pump 7 is supplied to the common rail 5 through the fuel supply pipe 6, accumulated to a predetermined pressure in the common rail 5, and distributed to the fuel injection valves 3 of each cylinder 2. When a predetermined drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0054]
Next, an intake branch pipe 9 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 9 communicates with a combustion chamber of each cylinder 2 through an intake port (not shown). The intake branch pipe 9 is connected to an intake pipe 10, and the intake pipe 10 is connected upstream to an air cleaner box and an air duct (not shown).
[0055]
An intake throttle valve 60 for restricting the flow rate of the intake air flowing through the intake pipe 10 is attached in the middle of the intake pipe 10. The intake throttle valve 60 is composed of a step motor or the like according to the magnitude of applied power. An intake throttle actuator 61 that opens and closes the intake throttle valve 60 is attached.
[0056]
In the intake system configured as described above, the intake air that has flowed into the air cleaner box is guided to the intake pipe 10 after dust or dust in the intake air is removed by the air cleaner in the air cleaner box. The intake air guided to the intake pipe 10 is throttled as necessary by the intake throttle valve 60 and then flows into the intake branch pipe 9, and then the intake air of each cylinder 2 through each branch pipe of the intake branch pipe 9. Distributed to the port. The intake air distributed to the intake port is drawn into the combustion chamber of each cylinder 2 when the intake valve 20 is opened.
[0057]
On the other hand, an exhaust branch pipe 11 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 11 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch pipe 11 is connected to an exhaust pipe 12, and the exhaust pipe 12 is connected downstream to an exhaust purification catalyst.
[0058]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 11 through the exhaust port, and then from the exhaust branch pipe 11 to the exhaust pipe. 12 is discharged. Exhaust gas flowing into the exhaust pipe 12 is purified by an exhaust purification catalyst downstream of the exhaust pipe 12 and then discharged into the atmosphere.
[0059]
The intake branch pipe 9 and the exhaust branch pipe 11 communicate with each other via an exhaust gas recirculation passage (EGR passage) 13 that guides a part of the exhaust gas flowing through the exhaust branch pipe 11 to the intake branch pipe 9. A flow rate adjusting valve (EGR) that is constituted by an electromagnetic valve or the like in the middle of the EGR passage 13 and changes the flow rate of exhaust gas (hereinafter referred to as EGR gas) that flows in the EGR passage 13 in accordance with the magnitude of applied power. Valve) 14 is provided.
[0060]
An EGR cooler 15 that cools the EGR gas flowing in the EGR passage 13 is provided at a position upstream of the EGR valve 14 in the EGR passage 13.
[0061]
In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 14 is opened, the EGR passage 13 becomes conductive, and a part of the exhaust gas flowing through the exhaust branch pipe 11 flows into the EGR passage 13. It is guided to the intake branch pipe 9 through the EGR cooler 15.
[0062]
At that time, in the EGR cooler 15, heat exchange is performed between the EGR gas flowing in the EGR passage 13 and a predetermined refrigerant, and the EGR gas is cooled.
[0063]
The EGR gas recirculated from the exhaust branch pipe 11 to the intake branch pipe 9 via the EGR passage 13 is guided to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 9. The fuel injected from the injection valve 3 is burned using an ignition source.
[0064]
Here, the EGR gas contains water (H ₂ O) and carbon dioxide (CO ₂ ) And the like, and an inert gas component having endothermic properties is contained in the mixture, so if EGR gas is contained in the mixture, the combustion temperature of the mixture is lowered. Therefore, the amount of nitrogen oxide (NOx) generated is suppressed.
[0065]
Further, when the EGR gas is cooled in the EGR cooler 15, the temperature of the EGR gas itself is reduced and the volume of the EGR gas is reduced. Therefore, when the EGR gas is supplied into the combustion chamber, the atmospheric temperature in the combustion chamber is reduced. Is not increased unnecessarily, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber is not unnecessarily reduced.
[0066]
In addition, the internal combustion engine 1 according to the present embodiment is provided with a variable valve mechanism 100 that changes the lift amount and operating angle of the intake valve 20.
[0067]
The variable valve mechanism 100 is provided to improve both the operability and exhaust emission of the internal combustion engine 1 at the time of engine start and low load, and the improvement of operability and exhaust emission of the internal combustion engine 1 at medium and high loads. It is a mechanism provided.
[0068]
This is because the compression ignition type diesel engine with a low compression ratio suppresses an excessive increase in the compression end temperature and suppresses the nitrogen oxide (NOx) in the middle and high load operation region where the inertia effect of the intake is easily obtained and the charging efficiency of the intake is easily increased. ) And the amount of soot can be suppressed while ensuring combustion stability, but it is difficult to obtain the inertia effect of the intake air, and the compression end temperature is increased in a low load operation region where the intake charging efficiency is likely to be reduced. This is because it may be difficult to reduce operability and exhaust emission due to poor ignitability and combustion stability.
[0069]
As shown in FIG. 2, the variable valve mechanism 100 includes an intake camshaft 30 that is rotatably supported by the cylinder head of the internal combustion engine 1, and a rocker shaft 33 that is fixed to the cylinder head in parallel with the intake camshaft 30. A rocker arm 34 rotatably supported by the rocker shaft 33, an intake valve 20 that is driven to open and close by the rotation of the rocker arm 34, and a valve spring 200 that urges the intake valve 20 in the valve closing direction. I have.
[0070]
The intake camshaft 30 is provided with two types of cams 31 and 32 having different cam profiles as many as the number of cylinders (four in this embodiment). These two types of cams 31 and 32 are formed such that the profile of one cam 31 is larger in lift amount and operating angle than the profile of the other cam 32. Hereinafter, the cam 31 is referred to as a high lift cam 31 and the cam 32 is referred to as a low lift cam 32.
[0071]
The rocker shaft 33 described above is disposed obliquely below the intake camshaft 30, and the rocker shaft 33 rotatably supports the base end portion of the rocker arm 34. At this time, it is assumed that the same number of rocker arms 34 as the number of cylinders are attached to the rocker shaft 33.
[0072]
An arm 35 projects from the tip of each rocker arm 34 described above. The distal end of the arm 35 is bifurcated, and the two branched distal ends are in contact with the proximal ends of the two intake valves 20 of each cylinder 2.
[0073]
As shown in FIG. 3, a movable cam follower 36 that can come into contact with the high lift cam 31 and a roller cam follower 37 that can come into contact with the low lift cam 32 are disposed on the surface of each rocker arm 34.
[0074]
The roller cam follower 37 is rotatably supported by the rocker arm 34 and is configured to transmit the pressing force of the low lift cam 32 to the rocker arm 34 while being in rolling contact with the low lift cam 32.
[0075]
The movable cam follower 36 is disposed so as to be slidable in the vertical direction with respect to the rocker arm 34. A coil spring 38 that biases the movable cam follower 36 toward the high lift cam 31 is interposed between the movable cam follower 36 and the rocker arm 34.
[0076]
Here, the rocker arm 34 is provided with a lock mechanism 39 that selectively permits or restricts (locks) relative sliding of the movable cam follower 36 with respect to the rocker arm 34.
[0077]
As shown in FIG. 4, the locking mechanism 39 includes a sliding hole 40 penetrating the rocker arm 34 in the vertical direction and slidably supporting the movable cam follower 36, and the rocker arm 34 so as to intersect the sliding hole 40. A cylinder hole 41 formed in the cylinder hole 41, a lock pin 42 loosely fitted in the cylinder hole 41, and a cylinder pin 41. The lock pin 42 is separated from the slide hole 40. A coil spring 43 biasing in the direction.
[0078]
A stopper 44 projects from the end of the lock pin 42 on the sliding hole 40 side. When the lock pin 42 is positioned at the base end of the cylinder hole 41, the stopper 44 is mostly accommodated in the cylinder hole 41 as shown in FIG. 4, and the lock pin 42 is positioned at the tip of the cylinder hole 41. 5, most of the stopper 44 projects into the sliding hole 40 as shown in FIG. 5.
[0079]
Further, a base end side space 45 defined by the lock pin 42 in the cylinder hole 41 is a hydraulic chamber into which hydraulic oil for sliding the lock pin 42 is introduced. A rocker arm oil passage 46 formed in the rocker arm 34 communicates with the hydraulic chamber 45. The rocker arm oil passage 46 communicates with a rocker shaft oil passage 47 (see FIGS. 1 and 2) formed in the rocker shaft 33.
[0080]
As shown in FIG. 3, the rocker shaft oil passage 47 communicates with an oil control valve (OCV) 50 via an oil passage 48. An oil supply passage 51 and an oil return passage 52 are connected to the OCV 50.
[0081]
The oil supply passage 51 is connected to an oil pump 53 for forcibly circulating the lubricating oil of the internal combustion engine 1, and the oil return passage 52 is connected to an oil pan 54 for storing the lubricating oil of the internal combustion engine 1. ing.
[0082]
The OCV 50 described above selectively connects one of the oil supply passage 51 and the oil return passage 52 with the oil passage 48. The OCV 50 is constituted by, for example, a solenoid valve. When the drive current is not applied, the OCV 50 is electrically connected to the oil return passage 52 and the oil passage 48. When the drive current is applied, the OCV 50 is connected to the oil supply passage 51 and the oil passage 48. Conduct.
[0083]
In the lock mechanism 39 configured as described above, when the drive current is not applied to the OCV 50, the oil passage 48 and the oil return passage 52 are electrically connected, so that the hydraulic oil in the hydraulic chamber 45 is transferred to the rocker arm oil passage 46 → The oil is discharged to the oil pan 54 through the rocker shaft oil passage 47 → the oil passage 48 → the oil return passage 52.
[0084]
When the hydraulic oil in the hydraulic chamber 45 is discharged to the oil pan 54, the hydraulic pressure in the hydraulic chamber 45 decreases, so that the lock pin 42 receives the urging force of the coil spring 43 and moves to the base end of the cylinder hole 41. (Refer to FIG. 4) Accordingly, the stopper 44 is accommodated in the cylinder hole 41.
[0085]
In this case, the movable cam follower 36 can slide in the sliding hole 40. That is, relative sliding of the movable cam follower 36 with respect to the rocker arm 34 is allowed.
[0086]
When relative sliding of the movable cam follower 36 with respect to the rocker arm 34 is permitted, the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is transmitted to the rocker arm 34 via the coil spring 38.
[0087]
At that time, since the urging force of the coil spring 38 is set sufficiently smaller than the urging force of the valve spring 200, the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is expanded and contracted by the coil spring 38 ( In other words, it is absorbed by the sliding motion of the movable cam follower 36). In other words, a force larger than the urging force of the valve spring 200 is not transmitted from the high lift cam 31 to the rocker arm 34.
[0088]
As a result, the rocker arm 34 is swung by the pressing force transmitted from the low lift cam 32 to the roller cam follower 37, and the intake valve 20 is driven to open and close as the rocker arm 34 swings. That is, the intake valve 20 is driven to open and close according to the cam profile shape of the low lift cam 32.
[0089]
On the other hand, when the drive current is applied to the OCV 50, the oil passage 48 and the oil supply passage 51 are electrically connected, so that the hydraulic oil discharged from the oil pump 53 is oil supply passage 51 → oil passage 48 → rocker shaft oil. The oil is supplied to the hydraulic chamber 45 through the passage 47 → the rocker arm oil passage 46.
[0090]
When hydraulic oil is supplied from the oil pump 53 to the hydraulic chamber 45, the hydraulic pressure in the hydraulic chamber 45 increases, so that the lock pin 42 moves to the tip of the cylinder hole 41 against the biasing force of the coil spring 43. However, the stopper 44 protrudes into the sliding hole 40 along with this (see FIG. 5).
[0091]
In this case, since the bottom surface of the movable cam follower 36 contacts the stopper 44 with the movable cam follower 36 displaced to the uppermost position, the relative sliding of the movable cam follower 36 with respect to the rocker arm 34 is restricted (locked).
[0092]
When the relative sliding of the movable cam follower 36 with respect to the rocker arm 34 is restricted (locked), the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is transmitted to the rocker arm 34 via the stopper 44 and the lock pin 42. It becomes like this.
[0093]
As a result, the rocker arm 34 is swung by the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 and the lock pin 42, and the intake valve 20 is driven to open and close as the rocker arm 34 swings. . That is, the intake valve 20 is driven to open and close according to the cam profile shape of the high lift cam 31.
[0094]
Here, the cam profile of the high lift cam 31 is, for example, as shown by the solid line in FIG. 6, the opening timing of the intake valve 20 is 2 ° earlier than the intake stroke top dead center (TDC: TOP DEAD CENTER). The timing (BTDC 2 °, BTDC: BEFORE TOP DEAD CENTER) and the closing timing of the intake valve 20 is 30 ° later than the intake stroke bottom dead center (BDC: BOTTOM DEAD CENTER) (ABDC 30 °, ABDC: AFTER BOTTOM DEAD CENTER).
[0095]
When the high lift cam 31 formed in this way is selected, the intake valve 20 opens immediately before the intake stroke top dead center, so that the pumping loss of intake air is reduced and the intake valve is dead under the intake stroke. Since the valve is closed much later than the point, the effective compression stroke length is shortened, and the pressure in the cylinder 2 is relatively low.
[0096]
In this case, the compression end temperature of each cylinder 2 does not become excessively high, and accordingly, the combustion temperature of the air-fuel mixture also becomes relatively low. Therefore, if the high lift cam 31 is selected in the medium and high load operation region where the inertia effect of the intake air can be easily obtained and the charging efficiency of the intake air tends to be high, it is possible to prevent the engine output from being reduced due to the reduction of the pumping loss. By shortening the effective compression stroke length, it is possible to prevent an excessive increase in the compression end temperature and the combustion temperature.
[0097]
On the other hand, the cam profile of the low lift cam 32 is, for example, as shown by the broken line in FIG. 6, the opening timing of the intake valve 20 is 60 ° later than the top dead center of the intake stroke (ATDC 60 °), and It is assumed that the closing timing of the intake valve 20 is 20 ° later than the bottom dead center of the intake stroke (ABDC 20 °).
[0098]
When the low lift cam 32 formed in this way is selected, the intake valve 20 is opened in the middle of the intake stroke, so that the cylinder 2 has a negative pressure when the intake valve 20 is opened, and the intake air Vigorously flows into the cylinder 2. Further, since the intake valve 20 is closed at a relatively early time after the bottom dead center of the intake stroke, the effective compression stroke length is increased, and the pressure in the cylinder 2 can be increased.
[0099]
In this case, the compression end temperature of each cylinder 2 rises, and the combustion temperature of the air-fuel mixture becomes relatively high accordingly. Therefore, if the low lift cam 32 is selected in a low load operation region where it is difficult to obtain the inertia effect of intake and the intake charge efficiency tends to be low, the intake charge efficiency is increased by increasing the momentum of the intake air flowing into the cylinder 2. It is possible to increase the compression end temperature by increasing the effective compression stroke length.
[0100]
Returning to FIG. 1, the internal combustion engine 1 is provided with an electronic control unit (ECU) 18 for controlling the operating state of the internal combustion engine 1. The ECU 18 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the driver's request, and is configured as an arithmetic logic operation circuit including a CPU, ROM, RAM, backup RAM, and the like. Has been.
[0101]
In addition to the in-cylinder pressure sensor 4 and the common rail pressure sensor 5a, the ECU 18 includes a crank position sensor 16 that outputs a pulse signal every time the crankshaft of the internal combustion engine 1 rotates by a predetermined angle (for example, 10 °), and the internal combustion engine 1. A water temperature sensor 17 for outputting an electric signal corresponding to the temperature of the cooling water circulating in the water jacket of the vehicle, an accelerator opening sensor 19 for outputting an electric signal corresponding to the operation amount of the accelerator pedal, and the like are electrically connected to each other. Are output to the ECU 18.
[0102]
The ECU 18 is electrically connected to the fuel injection valve 3, the EGR valve 14, and the OCV 50 of the variable valve mechanism 100, and the output signal of the ECU 18 is the above-described fuel injection valve 3, EGR valve 14, and variable valve mechanism. It is input to the mechanism 100.
[0103]
The ECU 18 configured as described above executes fuel injection control, which is the gist of the present invention, in addition to EGR control and variable valve control in accordance with various application programs stored in advance in the ROM.
[0104]
In the EGR control, the ECU 18 first inputs an output signal (cooling water temperature) of the crank position sensor 16, the water temperature sensor 17, and an output signal (accelerator opening) of the accelerator opening sensor 19. The ECU 18 calculates the engine speed based on the output signal of the crank position sensor 16, and determines the load (engine load) of the internal combustion engine 1 from the engine speed and the accelerator opening.
[0105]
Next, the ECU 18 determines whether or not an EGR control execution condition is satisfied from the engine load, the coolant temperature, and the accelerator opening. Examples of EGR control execution conditions include conditions such as the cooling water temperature being equal to or higher than a predetermined temperature, the operation state of the internal combustion engine 1 not in the high load operation region, and the operation state of the internal combustion engine 1 not in the deceleration operation region. be able to. These conditions are conditions for ensuring drivability during cold and reducing black smoke emission during high load operation.
[0106]
When it is determined that the EGR control execution condition as described above is satisfied, the ECU 18 calculates the target opening of the EGR valve 14 using the engine speed and the total fuel injection amount per cycle as parameters. The EGR valve 14 is controlled so that the opening degree of the EGR valve 14 matches the target opening degree.
[0107]
Further, the ECU 18 may feedback control the opening degree of the EGR valve 14 so that the intake air amount of the internal combustion engine 1 becomes a predetermined target intake air amount. For example, when the actual intake air amount of the internal combustion engine 1 is smaller than the target intake air amount, the ECU 18 closes the EGR valve 14 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 9 from the EGR passage 13 decreases, and the amount of EGR gas sucked into each cylinder 2 of the internal combustion engine 1 decreases accordingly. As a result, the amount of air taken into the cylinder 2 of the internal combustion engine 1 increases by the amount that the EGR gas has decreased.
[0108]
On the other hand, when the actual intake air amount of the internal combustion engine 1 is larger than the target intake air amount, the ECU 18 opens the EGR valve 14 by a predetermined amount. In this case, the amount of EGR gas flowing into the intake branch pipe 9 from the EGR passage 13 increases, and the amount of EGR gas sucked into each cylinder 2 of the internal combustion engine 1 increases accordingly. As a result, the amount of air taken into the cylinder 2 of the internal combustion engine 1 decreases by the amount of EGR gas increased.
[0109]
Next, in the variable valve control, the ECU 18 determines the engine load from the accelerator opening and the engine speed. When the engine load is in the low load region, the ECU 18 stops applying the drive current to the OCV 50 to open and close the intake valve 20 by the low lift cam 32. Further, when the engine load is in the middle and high load region, the ECU 18 applies a drive current to the OCV 50 so as to open and close the intake valve 20 by the high lift cam 31.
[0110]
As described above, when the high lift cam 31 is selected in the medium and high load operation region of the internal combustion engine 1, the decrease in the engine output due to the pumping loss and the excessive increase in the compression end temperature are prevented. It is possible to lower the combustion temperature without reducing the output of the internal combustion engine 1. As a result, it is possible to suppress the generation amount of nitrogen oxide (NOx) and soot while ensuring the operability of the internal combustion engine 1.
[0111]
Further, when the low lift cam 32 is selected at the time of starting the internal combustion engine 1 or in a low load operation region, the compression end temperature can be suitably increased, so that the ignitability and combustion stability of the fuel can be improved. It becomes possible. As a result, the amount of unburned fuel components emitted can be reduced while ensuring the operability of the internal combustion engine 1.
[0112]
Next, in the fuel injection control, the ECU 18 first calculates a basic injection amount: Qbase using the engine speed and the accelerator opening as parameters. At that time, the relationship between the engine speed, the accelerator opening, and the basic injection amount: Qbase may be mapped in advance and stored in the ROM.
[0113]
Further, the ECU 18 calculates the maximum value of the fuel amount that can theoretically be combusted in each cylinder 2 at the current engine speed (hereinafter referred to as the basic maximum injection amount). Next, the ECU 18 calculates the maximum injection amount: Qfull by correcting the basic maximum injection amount according to various parameters (for example, intake pressure, intake air temperature, fuel temperature, cooling water temperature, etc.).
[0114]
After calculating the basic injection amount: Qbase and the maximum injection amount: Qfull as described above, the ECU 18 compares these two injection amounts and determines the smaller one as the final target fuel injection amount.
[0115]
When the target fuel injection amount is determined in this way, the ECU 18 divides the final target fuel injection amount into a total pilot injection amount and a main injection amount. At that time, the ECU 18 determines the total pilot injection amount according to the parameter indicating the engine operating state such as the engine speed and the accelerator opening and the target fuel injection amount, and subtracts the total pilot injection amount from the target fuel injection amount. The main injection amount is determined.
[0116]
Subsequently, the ECU 18 determines the number of pilot injections and the injection amount of each pilot injection according to the total pilot injection amount and the parameter indicating the engine operating state.
[0117]
When the main injection amount and the individual pilot injection amounts are determined in this manner, the ECU 18 performs basic main injection execution timing (basic main injection timing) and each of the engine rotation speed and accelerator opening as parameters. The pilot injection execution timing (basic pilot injection timing) is calculated, and the basic main injection timing and basic pilot injection timing are corrected according to various parameters (for example, intake pressure, cooling water temperature, common rail pressure, etc.) A target main injection timing and a target pilot injection timing are calculated.
[0118]
When the target main injection timing and the target pilot injection timing are determined, the ECU 18 obtains the crank position of each cylinder 2 from the output signal of the crank position sensor 16, and the target pilot injection timing matches the crank position of each cylinder 2. A drive current is applied to the fuel injection valve 3 of each cylinder 2 at the time and when the target main injection timing coincides with the crank position of each cylinder 2.
[0119]
Here, the combustion of the compression ignition type internal combustion engine includes an ignition delay period from the start of fuel injection until a combustible mixture is formed by evaporation and diffusion of fuel, a premixed combustion period in which the combustible mixture self-ignites and burns. The diffusion combustion period in which the flame diffuses into the fuel continuously injected from the fuel injection valve and the post-combustion period in which the fuel existing in the cylinder after the fuel injection ends burns. In normal fuel injection control, the target main injection timing is set so that the above-described premixed combustion period is near the top dead center of the compression stroke, and the target pilot injection timing is changed from the latter half of the intake stroke to the compression stroke. It is set appropriately within the period up to the second half.
[0120]
By the way, when the high lift cam 31 is selected in the variable valve mechanism 100, the pressure in the cylinder 2 (in-cylinder pressure) is relatively low, so that the fuel injected by the pilot forms a combustible atmosphere in the cylinder 2. However, when the low lift cam 32 is selected in the variable valve mechanism 100, the in-cylinder pressure increases, so that the fuel injected by the pilot forms a combustible atmosphere in a relatively short time. become.
[0121]
Therefore, when the low lift cam 32 is selected in the variable valve mechanism 100 and the target pilot injection timing is set at the same time as when the high lift cam 31 is selected in the variable valve mechanism 100, It is assumed that the pilot-injected fuel is prematurely ignited before the main injection is performed, or is immediately ignited after the main injection is started, and the ignition delay period is excessively shortened.
[0122]
If the ignition delay period becomes excessively short, the main injected fuel is used for combustion in a state of air shortage, and there is a possibility that a large amount of particulate matter (PM) such as soot is generated.
[0123]
Therefore, in the present embodiment, when the low lift cam 32 is selected in the variable valve mechanism 100, the ECU 18 within a predetermined period from the target pilot injection timing of the first pilot injection among a plurality of pilot injections. Execution of the pilot injection with the target pilot injection timing set is prohibited, and the fuel injection amount of the prohibited pilot injection is added to the pilot injection with the target pilot injection timing set after the predetermined period.
[0124]
Specifically, as shown in FIG. 7, when five pilot injections: Qsub1 to Qsub5 are set before the main injection: Qmain, the ECU 18 starts execution of the first pilot injection: Qsub1. To a predetermined period (hereinafter referred to as a pilot injection prohibition period): pilot injection set during Δt: execution of Qsub1 to Qsub2 is prohibited, and the pilot injection amount: Qsub1 + Qsub2 is set to the pilot injection prohibition period: Δ Pilot injection set after t: First pilot injection among Qsub3 to Qsub5: Qsub3 is added (Qsub3 = Qsub1 + Qsub2 + Qsub3).
[0125]
In this case, since the period from the execution start timing of Qsub3, which is substantially the first pilot injection, to the start of execution of main injection: Qmain is shortened, the pilot injected fuel is exposed to a high in-cylinder pressure. The time is shortened, so that the fuel that has been pilot-injected does not ignite prematurely before or after the start of the main injection.
[0126]
As a result, the ignition delay period for the fuel of main injection: Qmain to mix with air is not excessively shortened, and it is possible to prevent a large amount of PM such as soot from being generated.
[0127]
The pilot injection prohibition period: Δt may be a fixed value obtained experimentally in advance. However, even when the low lift cam 32 is selected, the pilot injection prohibition period: Δt actually depends on the operating state of the internal combustion engine 1. Therefore, it is preferable to determine the predetermined period based on the output signal value of the in-cylinder pressure sensor 4 provided in each cylinder 2.
[0128]
Therefore, in the present embodiment, a basic pilot injection prohibition period (hereinafter referred to as a basic pilot pilot injection prohibition period): Δtbase is experimentally obtained in advance when the low lift cam 32 is selected, and the basic pilot injection prohibition is performed. Period: Δtbase is corrected based on the output signal value of the in-cylinder pressure sensor 4 to calculate the pilot injection prohibited period: Δt.
[0129]
Hereinafter, the fuel injection control according to the present embodiment will be described along the flowchart of FIG.
[0130]
The flowchart shown in FIG. 8 is a flowchart showing a fuel injection control routine. This fuel injection control routine is a routine stored in the ROM in advance, and is repeatedly executed by the ECU 18 every predetermined time (for example, every time the crank position sensor 16 outputs a pulse signal).
[0131]
In the fuel injection control routine, first, in step S801, the ECU 18 calculates the target main injection amount and the target total pilot injection amount using the engine speed, the accelerator opening, the intake pressure, the intake air temperature, the fuel temperature, the coolant temperature, and the like as parameters. calculate.
[0132]
In step S802, the ECU 18 calculates the number of pilot injections and the target pilot injection amount of each pilot injection, using the target total pilot injection amount, the engine speed, and the accelerator opening as parameters.
[0133]
In S803, the ECU 18 calculates the target main injection timing and the target pilot injection timing of each pilot injection using the engine speed and the accelerator opening as parameters.
[0134]
In step S <b> 804, the ECU 18 determines whether or not the low lift cam 32 is selected in the variable valve mechanism 100, specifically, whether or not the drive current is applied to the OCV 50.
[0135]
If it is determined in S804 that the low lift cam 32 is not selected, in other words, if the high lift cam 31 is selected, the ECU 18 proceeds to S812, and the target pilot injection amount calculated in S802 is calculated. Pilot injection is executed in accordance with the target pilot injection timing calculated in S803.
[0136]
Subsequently, the ECU 18 proceeds to S811, executes main injection according to the target main injection amount calculated in S801 and the target main injection timing calculated in S803, and temporarily ends the execution of this routine.
[0137]
On the other hand, if it is determined in S804 that the low lift cam 32 is selected, the ECU 18 proceeds to S805, and reads the basic pilot injection inhibition period: Δtbase from the ROM.
[0138]
In S806, the ECU 18 inputs the output signal value (in-cylinder pressure) of the in-cylinder pressure sensor 4.
[0139]
In S807, the ECU 18 accesses a map as shown in FIG. 9 using the in-cylinder pressure input in S806 as a parameter, and calculates an in-cylinder pressure correction coefficient kvvt corresponding to the in-cylinder pressure.
[0140]
Here, the in-cylinder pressure correction coefficient: kvvt is the first predetermined in-cylinder pressure as shown in FIG.
When the pressure in the range is equal to or higher than the pressure and equal to or lower than the second predetermined pressure (> first predetermined pressure), the larger the in-cylinder pressure is within a positive number range (0 <kvvt <1), the larger the value is. Is set. Further, the in-cylinder pressure correction coefficient: kvvt is set to “0” when the in-cylinder pressure is less than the first predetermined pressure, and is set to “1” when the in-cylinder pressure is higher than the first predetermined pressure. The
[0141]
When the in-cylinder pressure correction coefficient kvvt is calculated by the method as described above, the ECU 18 proceeds to S808, where the basic pilot injection inhibition period read out in S805: Δtbase and the in-cylinder pressure correction calculated in S807. The coefficient: kvvt is integrated to calculate the pilot injection prohibition period: Δt.
[0142]
In S809, the ECU 18 corrects the target pilot injection amount calculated in S802 and the target pilot injection timing calculated in S803 according to the pilot injection prohibition period: Δt calculated in S808.
[0143]
Specifically, the ECU 18 performs the pilot injection in which the target pilot injection timing is set within the pilot injection prohibition period: Δt from the first target pilot injection timing among the plurality of pilot injections set in S803. Execution is prohibited, and the fuel injection amount of the pilot injection that is prohibited is added to the target pilot injection amount of the first pilot injection after the pilot injection prohibition period: Δt.
[0144]
In S810, the ECU 18 executes pilot injection according to the target pilot injection timing and the target pilot injection amount corrected in S809.
[0145]
In S811, the ECU 18 executes main injection according to the target main injection amount calculated in S801 and the target main injection timing calculated in S803, and temporarily ends the execution of this routine.
[0146]
Thus, when the low lift cam 32 is selected in the variable valve mechanism 100 by the ECU 18 executing the fuel injection control routine, a predetermined period from the execution timing of the first pilot injection among the plurality of pilot injections: Δ Since execution of the pilot injection set within t is prohibited, the start timing of the pilot injection is substantially delayed, and the period from the start timing of the first pilot injection to the execution start timing of the main injection Will be shortened.
[0147]
As a result, pilot-injected fuel does not ignite prematurely before or immediately after execution of main injection, so that excessive reduction in the ignition delay period can be prevented and soot generation can be suppressed. .
[0148]
Therefore, according to the present embodiment, when the variable valve mechanism 100 is applied to a compression ignition internal combustion engine in which pilot injection control is performed, the pilot injection control suitable for the control state of the variable valve mechanism 100 is executed. Thus, the amount of PM generated can be suppressed.
[0149]
In the compression ignition internal combustion engine according to the present embodiment, when the variable valve mechanism 100 shifts from the low lift cam 32 selected state to the high lift cam 31 selected state, the ECU 18 determines the number of executions of pilot injection and the target total It is preferable to increase the pilot injection amount.
[0150]
Specifically, the ECU 18 actually sets the cam from the time when the switching control from the low lift cam 32 to the high lift cam 31 is started in the variable valve mechanism 100 (that is, when the switching signal is transmitted from the ECU 18 to the OCV 50). In the period up to the time when the switching is completed, the number of pilot injections is increased and the target total pilot injection amount is increased.
[0151]
This is because when the variable valve mechanism 100 is switched from the low lift cam 32 to the high lift cam 31, the in-cylinder pressure decreases and the amount of fuel reflected in the torque of the internal combustion engine 1 decreases. This is because there is a risk of sudden fluctuation.
[0152]
However, if the number of pilot injections and the target total pilot injection amount are increased in a situation where the in-cylinder pressure of the internal combustion engine 1 is excessively high, there is a risk of causing an excessive increase in the combustion pressure (combustion temperature) or premature ignition of fuel. Therefore, it is preferable not to perform the above control when the output signal value of the in-cylinder pressure sensor 4 is equal to or higher than a predetermined pressure.
[0153]
In the present embodiment, the pilot injection prohibition period: Δt is determined in consideration of the pressure in the cylinder 2 when the low lift cam 32 is selected, but the fuel ignitability in the cylinder 2 is determined in the cylinder 2. Since the temperature difference between the compressed air and the fuel injected from the fuel injection valve 3 becomes higher, the compressed air and the fuel are set with parameters such as cooling water temperature, intake air temperature, lubricating oil temperature, intake air pressure, and fuel temperature. And the pilot injection prohibited period: Δt may be determined in consideration of the estimated value and the pressure in the cylinder 2.
[0154]
In this embodiment, a variable valve mechanism that switches between a high lift cam and a low lift cam by hydraulic pressure is described as an example. However, even if a cam is switched using electromagnetic force or negative pressure. Good.
[0155]
In the present embodiment, as the variable valve mechanism according to the present invention, a two-stage switching type variable valve mechanism 100 that switches two cams of the high lift cam 31 and the low lift cam 32 according to the operating state of the internal combustion engine. The cam profile can be continuously changed from the cam profile (high lift cam profile) similar to the high lift cam 31 to the cam profile (low lift cam profile) similar to the low lift cam 32. A variable valve mechanism having a three-dimensional cam may be used.
[0156]
In this case, the pilot injection prohibition period: Δt is set to “0” when the high lift cam profile is selected, and may be set longer as the selected cam profile is closer to the low lift cam profile. .
[0157]
<Embodiment 2>
Next, a second embodiment of the compression ignition type internal combustion engine according to the present invention will be described with reference to FIGS. Here, a configuration different from the first embodiment described above will be described, and the description of the same configuration will be omitted.
[0158]
In the first embodiment described above, the example in which the control method of pilot injection is changed according to the control state of the variable valve mechanism 100 has been described. However, in the present embodiment, the control state of the variable valve mechanism 100 is changed. An example in which the control method of the EGR valve 14 is changed accordingly will be described.
[0159]
In normal EGR control, the opening degree of the EGR valve 14 is controlled using the engine speed and the fuel injection amount as parameters, and the fuel injection amount reflected in the torque of the internal combustion engine 1 is the fuel injection amount at that time. Used.
[0160]
By the way, when the low lift cam 32 is selected in the variable valve mechanism 100, the in-cylinder pressure becomes high, so that all the fuel injection amounts (total fuel injection amount) by the pilot injection and the main injection become the torque of the internal combustion engine 1. Although it is easy to reflect, when the high lift cam 31 is selected in the variable valve mechanism 100, the in-cylinder pressure becomes low, so that pilot injection occurs during a part of the total fuel injection amount, particularly during the intake stroke or during the compression stroke. It is difficult for the fuel thus produced to be reflected in the torque of the internal combustion engine 1.
[0161]
Therefore, when the low lift cam 32 is selected in the variable valve mechanism 100, there is no problem even if the EGR valve 14 is controlled using the total fuel injection amount of the pilot injection and the main injection and the engine speed as parameters. When the high lift cam 31 is selected in the variable valve mechanism 100, when the EGR valve 14 is controlled using the total fuel injection amount of the pilot injection and the main injection and the engine speed as parameters, the nitrogen oxide (NOx) There is a possibility that the amount of EGR gas is excessive with respect to the generated amount, the combustion stability of the internal combustion engine 1 is reduced, and the amount of particulate matter (PM) such as soot is excessively increased.
[0162]
Therefore, in the present embodiment, the amount of fuel reflected in the torque of the internal combustion engine 1 (hereinafter referred to as torque reflected fuel amount): Qtrq is estimated using the control state of the variable valve mechanism 100 as a parameter, and the torque reflected fuel amount is estimated. : The EGR valve 14 is controlled according to Qtrq.
[0163]
Hereinafter, the EGR control according to the present embodiment will be described with reference to the flowchart of FIG.
[0164]
The flowchart shown in FIG. 10 is a flowchart showing an EGR control routine. This EGR control routine is a routine stored in the ROM in advance, and is repeatedly executed by the ECU 18 every predetermined time (for example, every time the crank position sensor 16 outputs a pulse signal).
[0165]
In the EGR control routine, first in step S1001, the ECU 18 obtains various data such as the accelerator opening, the engine speed: Ne, the coolant temperature, the target main injection amount, the target pilot injection amount, the target main injection timing, and the target pilot injection timing. Read from RAM.
[0166]
In S1002, the ECU 18 determines whether or not an EGR control execution condition is satisfied based on the data read in S1001.
[0167]
If it is determined in S1002 that the EGR control execution condition is not satisfied, the ECU 18 once ends the execution of this routine.
[0168]
On the other hand, when it is determined in S1002 that the EGR control execution condition is satisfied, the ECU 18 proceeds to S1003 and determines whether or not the low lift cam 32 is selected in the variable valve mechanism 100.
[0169]
If it is determined in S1003 that the low lift cam 32 has been selected, the ECU 18 proceeds to S1004, calculates the total fuel injection amount: Qfin by adding the target main injection amount and all the target pilot injection amounts, The total fuel injection amount: Qfin is stored in the RAM as the torque reflected fuel amount: Qtrq.
[0170]
In S1005, the EGR calculates a target EGR opening degree: θ using the torque reflected fuel amount: Qtrq calculated in S1004 and the engine speed: Ne read in S1001 as parameters. At that time, the relationship between the torque reflected fuel amount: Qtrq, the engine speed: Ne, and the target EGR opening degree: θ may be previously mapped and stored in the ROM.
[0171]
In S1006, the ECU 18 controls the EGR valve 14 in accordance with the target EGR opening calculated in S1005, and temporarily ends the execution of this routine.
[0172]
On the other hand, if it is determined in S1003 that the low lift cam 32 is not selected, in other words, if it is determined that the high lift cam 31 is selected in the variable valve mechanism 100, the ECU 18 performs the target main injection. The total fuel injection amount: Qfin, which is the sum of the amount and all target pilot injection amounts, is corrected to decrease, and the torque reflected fuel amount: Qtrq is calculated.
[0173]
Specifically, the ECU 18 first reads out a basic reduction correction coefficient: kf1 from the ROM. This reduction correction coefficient: kf1 is a positive number less than 1 set in advance.
[0174]
Subsequently, the ECU 18 calculates a reduction correction coefficient: kf2 corresponding to the target pilot injection timing of each pilot injection based on a map as shown in FIG. 11 and a reduction correction coefficient corresponding to the injection timing of the main injection: kf2 is calculated.
[0175]
The ECU 18 multiplies the target main injection amount of main injection by the above-described reduction correction coefficient: kf1 and kf2, and calculates the fuel amount reflected in the torque of the internal combustion engine 1 out of the main injected fuel. Further, by multiplying the target pilot injection amount of each pilot injection by the above-described reduction correction coefficient: kf1 and kf2, the fuel amount reflected in the torque of the internal combustion engine 1 among the fuel injected by each pilot injection is calculated. .
[0176]
The ECU 18 adds the main injection amount after the reduction correction and all the pilot injection amounts to calculate the torque reflected fuel amount: Qtrq.
[0177]
When the torque reflected fuel amount: Qtrq is calculated in this way, the ECU 18 proceeds to S1005, and the torque reflected fuel amount: Qtrq calculated in S1007 and the engine speed: Ne calculated in S1001 are parameters. The target EGR opening degree: θ is calculated as follows.
[0178]
Subsequently, the ECU 18 proceeds to S1006 and controls the EGR valve 14 according to the target EGR valve opening degree θ calculated in S1005.
[0179]
As described above, since the ECU 18 executes the EGR control routine, the fuel injection amount used as the EGR control parameter can be optimized according to the control state of the variable valve mechanism 100. The amount of EGR gas does not increase excessively with respect to the amount of generated substances (NOx), and therefore, the amount of PM emission can be suppressed while suppressing the amount of nitrogen oxide (NOx) generated.
[0180]
【The invention's effect】
According to the present invention, when a variable valve mechanism is applied to a compression ignition internal combustion engine in which pilot injection control is performed, it is possible to perform fuel injection control, EGR control, etc. suitable for the control state of the variable valve mechanism Thus, it becomes possible to suppress the deterioration of the combustibility of the internal combustion engine and the deterioration of the exhaust emission.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a compression ignition type internal combustion engine according to the present embodiment.
FIG. 2 shows the configuration of a variable valve mechanism (1)
FIG. 3 is a diagram showing the configuration of a variable valve mechanism (2)
FIG. 4 is a diagram showing a configuration of a lock mechanism
FIG. 5 is a diagram for explaining the operation of the locking mechanism.
FIG. 6 is a view showing cam profiles of a high lift cam and a low lift cam.
FIG. 7 is a diagram showing a method for correcting pilot injection timing and pilot injection amount
FIG. 8 is a flowchart showing a fuel injection control routine.
FIG. 9 is a graph showing the relationship between in-cylinder pressure and in-cylinder pressure correction coefficient.
FIG. 10 is a flowchart showing an EGR control routine.
FIG. 11 is a diagram showing a relationship between fuel injection timing and a reduction correction coefficient.
[Explanation of symbols]
1 ... Internal combustion engine
2. Cylinder
3. Fuel injection valve
4 .... In-cylinder pressure sensor
13 ... EGR passage
14 ... EGR passage
18 ... ECU
20 ... Intake valve
100 ... Variable valve mechanism

Claims (2)

A variable valve mechanism that changes the opening / closing timing and / or lift amount of the intake valve of the compression ignition internal combustion engine;
A valve mechanism control means for controlling the variable valve mechanism so that the pressure in the cylinder is higher when the load of the internal combustion engine is low than when it is high;
Main injection means for injecting fuel into the cylinder;
Pilot injection means for performing pilot injection a plurality of times prior to fuel injection by the main injection means;
Exhaust gas recirculation means for recirculating part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system;
Exhaust gas recirculation control means for controlling the exhaust gas recirculation amount by the exhaust gas recirculation means with the total fuel injection quantity by the main injection means and the pilot injection means as parameters.
When the variable valve mechanism is controlled to reduce the in-cylinder pressure, the total fuel injection amount used for the exhaust gas recirculation control is reduced and corrected as compared to when the variable valve mechanism is controlled to increase the in-cylinder pressure. Parameter correction means;
A compression ignition type internal combustion engine comprising: 2. The compression ignition internal combustion engine according to claim 1, wherein the parameter correction means changes a reduction correction amount of the total fuel injection amount in accordance with an execution timing of each pilot injection.

Images