JP4691822B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an internal combustion engine for an automobile, for example, an in-cylinder type that directly injects fuel into a combustion chamber is known.
[0003]
In such an internal combustion engine, when the temperature of the combustion chamber is low, such as when starting from a cold state (during cold start), the fuel injected into the combustion chamber is difficult to atomize and remains liquid fuel. Fuel combustion may be performed in a state where liquid fuel is present in the combustion chamber. In this case, the liquid fuel in the combustion chamber may be scorched by heat during combustion, and black smoke may be contained in the exhaust from the internal combustion engine.
[0004]
Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-324778, exhaust of the internal combustion engine is present in the combustion chamber during fuel combustion, thereby reducing the combustion temperature during fuel combustion and suppressing the burning of the liquid fuel. At the same time, the temperature of the combustion chamber may be increased by the heat of the exhaust to promote atomization of the liquid fuel. Thus, by suppressing the burning of the liquid fuel in the combustion chamber and promoting the atomization of the fuel, the generation of black smoke can be suppressed.
[0005]
[Problems to be solved by the invention]
However, the presence of exhaust from the internal combustion engine in the combustion chamber during fuel combustion means that there is a gas (exhaust gas) that does not contribute to the combustion in the combustion chamber during fuel combustion. It cannot be denied that it tends to be unstable. Therefore, unless appropriate measures are taken to prevent the combustion state from becoming unstable in this way, the generation of black smoke can be suppressed by allowing the exhaust of the internal combustion engine to exist in the combustion chamber during fuel combustion. However, the fuel combustion state may become unstable due to exhaust in the combustion chamber.
[0006]
The present invention has been made in view of such circumstances, and its purpose is to suppress the combustion of fuel when the exhaust of the internal combustion engine is present in the combustion chamber during fuel combustion in order to suppress the generation of black smoke. An object of the present invention is to provide a control device for an internal combustion engine that can prevent the state from becoming unstable.
[0007]
[Means for Solving the Problems]
  In the following, means for achieving the above object and its effects are described.
  In order to achieve the above object, in the first aspect of the present invention, an in-cylinder injection type equipped with adjusting means for adjusting the amount of exhaust gas contained in the combustion chamber gas during fuel combustion by changing the valve timing of the engine valve. In a control device for an internal combustion engine, which is applied to an internal combustion engine and controls the adjusting means to increase the exhaust amount in the gas when it is determined that the engine state includes black smoke in the exhaust from the engine. The control of the adjustment means to the exhaust amount increase side is performed at the time of cold start of the internal combustion engine, and monitoring means for monitoring the combustion state of the fuel;By the monitoring meansThe combustion stateofunstableDetectedWhenInStabilization means for controlling a predetermined control system used for operation control of the internal combustion engine in a direction in which the combustion state is stabilized;With,further,When the control of the adjusting means to the exhaust amount increasing side at the time of cold start of the internal combustion engine is performed,In the process of changing the displacement of the gas,Of a control system used for operation control of the internal combustion engine based on the actual driving amount of the adjusting means and the estimated temperature of the combustion chamber, a control system related to the combustion of fuel different from the control of the valve timing is selected. ControlThis suppresses instability of the combustion state in the process of changing the displacementControl meansThePrepared.
[0008]
  According to the above configuration, by changing the valve overlap amount by changing at least one of the engine valves such as the intake valve and the exhaust valve of the internal combustion engine, the exhaust gas existing in the combustion chamber during fuel combustion is changed. The amount is adjusted, thereby suppressing the generation of black smoke.
  In addition, when the internal combustion engine is started from a cold state, it is possible to suppress the generation of black smoke by controlling the adjustment means to the exhaust amount increase side, and exhaust exists in the combustion chamber during fuel combustion. Accordingly, it is possible to suppress the combustion state from becoming unstable.
  Also, when the adjustment means is controlled to the exhaust increase side and the combustion state becomes unstable due to the exhaust of the internal combustion engine existing in the combustion chamber during fuel combustion, the predetermined control system of the internal combustion engine stabilizes the combustion state. It is controlled in the direction to make. Thereby, it can suppress that a combustion state becomes unstable with exhaust existing in the combustion chamber at the time of fuel combustion.
  In addition, when the adjustment unit is controlled to increase the displacement, the controlIn the process of changing the displacement of the gas,A control system related to the combustion of fuel different from the valve timing control based on the actual drive amount of the adjusting means, that is, the actual amount of exhaust gas existing in the combustion chamber during fuel combustion and the estimated temperature of the combustion chamber Is controlledThis suppresses instability of the combustion state in the process of changing the displacement.. Therefore, when controlling the adjusting means, a response delay or the like occurs in the driving of the adjusting means by the control, and the amount of exhaust existing in the combustion chamber at the time of fuel combustion changes to a predetermined value based on the control. Even if a response delay occurs, the control of the control system related to the combustion of the fuel is different from the control of the valve timing and is suitable for the actual amount of exhaust existing in the combustion chamber at the time of fuel combustion. In this manner, the combustion state is prevented from becoming unstable due to the response delay.
[0009]
  Existence of exhaust in the combustion chamber during fuel combustion can be realized by recirculating the exhaust of the internal combustion engine to the intake system or by leaving exhaust after combustion of fuel in the combustion chamber.
  Further, the combustion state of the fuel can be known from the rotational speed of the internal combustion engine and fluctuations in the rotational speed. And abovePredeterminedThe control system control includes control of the adjustment means to the exhaust amount reduction side, control of increase of intake air amount, combustion mode switching control to a combustion mode in which combustion is likely to be stable, retard control of fuel injection timing, and ignition timing Advance angle control and the like.
Further, examples of the control of the control system related to the combustion include intake air amount control, air-fuel ratio control, combustion mode switching control, fuel injection timing control, and ignition timing control.
[0010]
  In invention of Claim 2,In the first aspect of the present invention, the stabilizing means may include prohibiting means for prohibiting the adjustment means from controlling the exhaust amount increasing side.Prepared.
[0011]
According to the above configuration, the adjustment means is controlled to the exhaust increase side, and when the combustion state becomes unstable due to the exhaust of the internal combustion engine existing in the combustion chamber at the time of fuel combustion, the adjustment means to the exhaust increase side. Is prohibited, and the combustion state is stabilized. Therefore, it is possible to suppress the combustion state from becoming unstable due to the presence of exhaust in the combustion chamber during fuel combustion.
[0017]
  Claim3In the described invention,In the invention according to claim 1 or 2,On the condition that the internal combustion engine is in an idling operation state, a permitting means for permitting the control of the adjusting means to the exhaust amount increasing side is provided.
[0018]
According to the above configuration, when the internal combustion engine is in an idle operation state, that is, when the vehicle on which the engine is mounted is stopped, the control of the adjusting means to the exhaust gas increase side is performed. Therefore, it is possible to prevent the combustion state from becoming unstable due to the exhaust that exists in the combustion chamber during fuel combustion while the vehicle is running. Therefore, it is possible to prevent the combustion state from becoming unstable while the vehicle is running and deteriorating the drivability of the vehicle.
[0019]
  Claim4In the described invention,In the invention according to claim 1 or 2,In order to change the flow state of the gas in the combustion chamber, the intake passage of the internal combustion engine is provided so as to be openable and closable. When the adjustment means is controlled to increase the displacement, the gas flow in the combustion chamber is disturbed. An airflow control valve that is controlled to be opened and closed, and a permission unit that permits control of the adjustment unit to the exhaust amount increase side on the condition that the opening and closing control of the airflow control valve is completed. .
[0020]
Before the opening / closing control of the airflow control valve for increasing the turbulence of the gas flow in the combustion chamber is completed, the adjustment means is controlled to increase the exhaust amount, and the turbulence of the gas flow in the combustion chamber is small. Sometimes, when a large amount of exhaust gas is included in the combustion chamber gas during fuel combustion, the exhaust gas is unevenly distributed in the combustion chamber. In this state, there is a possibility that the fuel is burned in the rich exhaust portion in the combustion chamber. In such a case, the combustion state becomes unstable. However, according to the above configuration, the control to the exhaust amount increase side of the adjusting means is executed after completion of the opening / closing control of the airflow control valve, and accordingly, due to the uneven distribution of exhaust existing in the combustion chamber at the time of fuel combustion It can suppress that a combustion state becomes unstable.
[0021]
  In invention of Claim 5, in invention of any one of Claims 1-4,in frontAnd setting means for setting a target value for controlling the adjusting means to the exhaust amount increasing side based on the estimated temperature.
  The higher the temperature in the combustion chamber, the smaller the amount of exhaust in the combustion chamber required for suppressing the generation of black smoke during fuel combustion. According to the said structure, the target value at the time of controlling an adjustment means can be set so that the quantity of the said exhaust gas may become so small that the estimated temperature of a combustion chamber becomes high. Then, by setting the target value in this way and adjusting the amount of exhaust existing in the combustion chamber during fuel combustion, the amount of exhaust is limited to the amount necessary to suppress the generation of black smoke. And can prevent the combustion state from becoming unstable due to the exhaust..
[0023]
  Claim6In the described invention,In any one of Claims 1-5In the invention described above, the adjusting means is driven and controlled by hydraulic pressure, and the adjusting means is first moved to the exhaust after the start of the internal combustion engine.Volume increaseWhen controlling to the side, the driving force for the control was made larger than usual.
[0024]
  When the internal combustion engine is started in a cold state, the viscosity of the hydraulic oil for driving the adjusting means becomes high, and it becomes difficult to drive and control the adjusting means. However, according to the above configuration, the adjustment means is exhausted even in such a case.Volume increaseSince the driving force for controlling to the side is made larger than usual, the control of the adjusting means can be executed accurately.
[0025]
  Note that the adjusting means is exhausted.Volume increaseThe driving force for controlling to the side may be maximized instead of being larger than usual. In this case, the exhaust of the adjusting means when the viscosity of the hydraulic oil is highVolume increaseThis is more preferable in that the control to the side is accurately performed.
[0026]
  Claim7In the described invention, the claimsAny one of 1-6In the described invention, the exhaust of the adjusting means at the start of the internal combustion engineVolume increaseThe gist is that control to the side is not performed at extremely low temperatures.
[0027]
  According to the above configuration, the exhaust of the adjusting means is exhausted at an extremely low temperature at which the operating oil for driving the adjusting means becomes too viscous to drive the adjusting means.Volume increaseThe control to the side can be prevented from being carried out wastefully.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an in-cylinder injection spark ignition engine for an automobile will be described with reference to FIGS.
[0034]
In the engine 1 shown in FIG. 1, air is sucked into the combustion chamber 3 from the intake passage 2 in a bifurcated state, and the fuel injected from the fuel injection valve 4 into the combustion chamber 3 and the air Ignition by the spark plug 5 is performed on the air-fuel mixture comprising The ignition timing of the spark plug 5 is adjusted by an igniter 5a. When the air-fuel mixture in the combustion chamber 3 is combusted by this ignition, the piston 6 reciprocates due to the combustion energy at that time, and the air-fuel mixture after combustion is sent to the exhaust passage 7 as exhaust gas.
[0035]
The combustion mode of the air-fuel mixture in the combustion chamber 3 of the engine 1 is switched between stratified combustion, weakly stratified combustion, and homogeneous combustion shown in the following [1] to [3] according to the operating state of the engine 1. It is done.
[0036]
[1] In stratified combustion, a stratified mixture in which a combustible mixture exists only around the spark plug 5 is formed by fuel injection in the compression stroke, and the stratified mixture is burned by ignition by the spark plug 5 in that state. Is called.
[0037]
[2] In the homogeneous combustion, a homogeneous mixture in which fuel is evenly mixed with air is formed by fuel injection in the intake stroke, and the homogeneous mixture is burned by ignition with the spark plug 5 in that state.
[0038]
[3] In weakly stratified combustion, the state of the air-fuel mixture in the combustion chamber 3 is brought into an intermediate state between the stratified air-fuel mixture and the homogeneous air-fuel mixture by fuel injection in both the intake stroke and the compression stroke. The mixture in the intermediate state is burned by ignition by the spark plug 5 in the state.
[0039]
By executing any one of these combustion modes, the piston 6 reciprocates. This reciprocating movement of the piston 6 is converted into rotation of the crankshaft 9 that is the output shaft of the engine 1 by the connecting rod 8. When the crankshaft 9 rotates, a signal corresponding to the rotation is output from the crank position sensor 10, and the rotation is transmitted to the tire of the automobile via a transmission or the like. When the engine 1 is driven as described above, the engine 1 is cooled by the cooling water, and the temperature of the cooling water is detected by the water temperature sensor 36.
[0040]
In the intake passage 2, a throttle valve 11 that opens and closes to adjust the amount of air sucked into the combustion chamber 3 (intake air amount) is provided at an upstream portion thereof, and the intake passage 2 is disposed downstream of the throttle valve 11. A vacuum sensor 12 for detecting the internal pressure (intake pressure) is provided. The opening degree of the throttle valve 11 (throttle opening degree) is adjusted according to the depression amount (accelerator depression amount) of the accelerator pedal 13 operated by the driver of the automobile. The accelerator depression amount is detected by the accelerator position sensor 14, and the throttle opening is detected by the throttle position sensor 15.
[0041]
An airflow control valve 16 that changes the flow state of the gas in the combustion chamber 3 is provided at one of the two branches of the intake passage 2 so that good combustion of the air-fuel mixture is obtained. The air flow control valve 16 is driven to open and close by an actuator 17 that operates based on the pressure difference between the pressure (negative pressure) in the intake passage 2 and the atmospheric pressure. When the differential pressure reaches a value at which the actuator 17 can be operated, the air flow control valve 16 can be closed by operating the actuator 17.
[0042]
When the airflow control valve 16 is closed, air is sucked into the combustion chamber 3 from only one of the two branched intake passages 2. In this state, the gas sucked into the combustion chamber 3 As a result, the gas flow in the combustion chamber 3 becomes more turbulent and gas mixing in the combustion chamber 3 is promoted. On the other hand, when the airflow control valve 16 is open, the turbulence of the gas flow in the combustion chamber 3 is small, but the intake resistance of the engine 1 is reduced at high loads and high revolutions. Can do.
[0043]
On the other hand, an EGR passage 18 for allowing a part of the exhaust to flow into the intake passage 2 is connected to the exhaust passage 7 into which the exhaust from the combustion chamber 3 is sent. The amount of exhaust gas (EGR amount) recirculated from the exhaust passage 7 to the intake passage 2 through the EGR passage 18 is adjusted by controlling the opening degree of the EGR valve 19 provided in the EGR passage 18. Such exhaust gas recirculation is executed for the purpose of, for example, reducing the combustion temperature of the fuel to suppress the generation of nitrogen oxides (NOx) and reducing the NOx emission of the engine 1.
[0044]
In the engine 1, the intake passage 2 and the combustion chamber 3 are connected and cut off by the opening / closing operation of the intake valve 20, and the exhaust passage 7 and the combustion chamber 3 are connected and cut off by the opening / closing operation of the exhaust valve 21. . The intake valve 20 and the exhaust valve 21 are opened and closed in accordance with the rotation of the intake camshaft 22 and the exhaust camshaft 23 to which the rotation of the crankshaft 9 is transmitted. In the vicinity of the intake camshaft 22, a cam position sensor 24 for detecting the rotational position of the shaft 22 is provided.
[0045]
The intake camshaft 22 is provided with a variable valve timing mechanism 25 that changes the valve timing (opening / closing timing) of the intake valve 20 by changing the relative rotation phase of the intake camshaft 22 with respect to the rotation of the crankshaft 9. ing. An advance angle side oil passage 26 and a retard angle side oil passage 27 are connected to the variable valve timing mechanism 25. These oil passages 26 and 27 are connected to the oil pan 31 of the engine 1 through an oil control valve (OCV) 28, a supply passage 29 and a discharge passage 30.
[0046]
The supply passage 29 is provided with an oil pump 32 that is driven as the crankshaft 9 rotates. The OCV 28 is switched by the urging forces of the coil spring 33 and the electromagnetic solenoid 34 acting in opposite directions to connect the supply passage 29 and the discharge passage 30 to the advance side oil passage 26 and the retard side oil passage 27. Change state.
[0047]
That is, when the electromagnetic solenoid 34 is demagnetized, the OCV 28 communicates the retard angle side oil passage 27 and the supply passage 29 and communicates the advance angle side oil passage 26 and the discharge passage 30. In this case, the oil (operating oil) in the oil pan 31 is sent out to the retard side oil passage 27 by the oil pump 32, and the oil (operating oil) in the advance side oil passage 26 enters the oil pan 31. Returned. At this time, oil is supplied to the variable valve timing mechanism 25 through the retard side oil passage 27. As a result, the variable valve timing mechanism 25 is hydraulically driven so as to retard the relative rotational phase of the intake camshaft 22 with respect to the crankshaft 9. As a result, the valve timing of the intake valve 20 changes to the retard side.
[0048]
When the electromagnetic solenoid 34 is excited, the retard angle side oil passage 27 and the discharge passage 30 communicate with each other, and the advance angle side oil passage 26 and the supply passage 29 communicate with each other. In this case, the oil in the oil pan 31 is sent out to the advance side oil passage 26 by the oil pump 32 and the oil in the retard side oil passage 27 is returned to the oil pan 31. At this time, oil is supplied to the variable valve timing mechanism 25 through the advance side oil passage 26. As a result, the variable valve timing mechanism 25 is hydraulically driven to advance the relative rotational phase of the intake camshaft 22 with respect to the crankshaft 9. As a result, the valve timing of the intake valve 20 changes to the advance side.
[0049]
Next, the electrical configuration of the engine control apparatus of this embodiment will be described.
This control device is provided with an electronic control device 35 mounted on the automobile to control the operation of the engine 1. The electronic control device 35 controls the drive of the igniter 5a, the fuel injection valve 4, the throttle valve 11, the actuator 17, the EGR valve 19, and the OCV 28. The electronic control unit 35 receives detection signals from various sensors such as the crank position sensor 10, the vacuum sensor 12, the accelerator position sensor 14, the throttle position sensor 15, the cam position sensor 24, and the water temperature sensor 36.
[0050]
Based on detection signals from the crank position sensor 10, the throttle position sensor 15, the vacuum sensor 12, and the accelerator position sensor 14, the electronic control unit 35 determines the engine speed NE, the intake pressure PM, the accelerator depression amount ACCP, and the throttle opening TA. Ask for. Then, the electronic control unit 35 sets the load factor KL, which is a value indicating the current load ratio with respect to the maximum engine load, to the engine speed NE, the throttle opening degree TA, the accelerator depression amount ACCP, the intake pressure PM, and the like of the engine 1. It is calculated based on parameters related to the intake air amount.
[0051]
The electronic control unit 35 performs ignition timing control, fuel injection amount control, fuel injection timing control, intake air amount control, and air flow control valve 16 opening / closing control in accordance with the operating state of the engine 1 such as the engine speed NE and the load factor KL. Then, various operation controls of the engine 1 such as the opening degree control of the EGR valve 19, the valve timing control of the intake valve 20, and the combustion mode switching control are executed.
[0052]
Next, a procedure for suppressing the generation of black smoke when the engine 1 is in an engine state where black smoke is contained in the exhaust gas, such as when the engine 1 is cold started, will be described with reference to FIG.
FIG. 2 controls the valve timing of the intake valve 20 to adjust the amount of exhaust gas contained in the gas in the combustion chamber 3 at the time of fuel combustion, thereby suppressing the generation of the black smoke and the fuel combustion as described above. 7 is a flowchart showing a black smoke suppression routine for suppressing the combustion state from becoming unstable due to the presence of exhaust gas in the combustion chamber 3 at the time. This black smoke suppression routine is periodically executed through the electronic control unit 35, for example, with an angle interruption for each predetermined crank angle.
[0053]
At the start of starting the engine 1, importance is attached to the stable combustion of the air-fuel mixture, and the combustion mode of the engine 1 is selected to be homogeneous combustion that combusts the homogeneous air-fuel mixture. Further, in consideration of starting the engine 1 with homogeneous combustion, the actuator 17 is closed so that the air flow control valve 16 is closed in order to increase the gas flow turbulence in the combustion chamber 3 and promote the mixing of the air-fuel mixture. Be controlled. However, since the actuator 17 is operated by the differential pressure between the intake pressure PM and the atmospheric pressure to close the airflow control valve 16, the intake pressure PM is used to operate the actuator 17 after the engine 1 is started. A predetermined time is required to change to the vacuum side to the required value. Therefore, the airflow control valve 16 remains open even if the actuator 17 attempts to close the valve until the predetermined time elapses after the start of the engine 1 starts.
[0054]
In the black smoke suppression routine, first, it is determined whether or not the engine 1 has been started, for example, whether or not the engine speed NE is equal to or higher than a preset idle speed (S101).
[0055]
If a negative determination is made in step S101, it is determined that the engine 1 has not been started, and the duty ratio D used for drive control of the OCV 28 is set to “0%” (S111). This duty ratio D is used for duty control of the applied voltage to the electromagnetic solenoid 34 of the OCV 28 performed through the electronic control unit 35. By such duty control, the oil supply to the variable valve timing mechanism 25 is controlled, and the valve timing of the intake valve 20 is adjusted based on the driving of the variable valve timing mechanism 25.
[0056]
As described above, when the duty ratio D is “0%”, oil is supplied to the variable valve timing mechanism 25 through the retard angle side oil passage 27, whereby the valve timing of the intake valve 20 is the most retarded. Kept in a state. In this state, the valve overlap amount between the intake valve 20 and the exhaust valve 21 becomes “0”, and the amount of exhaust gas existing in the combustion chamber 3 during fuel combustion is minimized to stabilize the combustion state. Thus, the startability of the engine 1 is good.
[0057]
On the other hand, if an affirmative determination is made in step S101, an estimated temperature T, which is a value obtained by estimating the temperature of the combustion chamber 3, is calculated (S102).
The actual temperature of the combustion chamber 3 rises for each combustion cycle of the engine 1 by an amount corresponding to the amount of fuel consumed in the combustion cycle (fuel injection amount Qfin). Therefore, in the process of step S102, the temperature rise of the combustion chamber 3 in the current combustion cycle is calculated by multiplying the fuel injection amount Qfin by the conversion coefficient K, and this value “Qfin · K” is calculated in the previous step S102. By adding to the estimated temperature T calculated in the process, the current estimated temperature T is calculated.
[0058]
As the fuel injection amount Qfin, for example, a command value of the fuel injection amount used when the fuel injection amount control of the engine 1 is performed, that is, a command value of the fuel injection amount obtained from the load factor KL, the engine speed NE, etc. is adopted. The The conversion coefficient K multiplied by the fuel injection amount Qfin is the amount of fuel consumed (combusted) in one combustion cycle of the engine 1 (fuel injection amount Qfin), and the temperature of the combustion chamber 3 is increased by the combustion. It is for converting to the unit of quantity.
[0059]
When the process of step S102 is first executed after the start of the engine 1, the initial temperature calculated from the cooling water temperature of the engine 1 is adopted as the previous estimated temperature T used for calculating the estimated temperature T. . This initial temperature is calculated so as to increase as the cooling water temperature of the engine 1 obtained from the detection signal of the water temperature sensor 36 increases.
[0060]
After the estimated temperature of the combustion chamber 3 is calculated in this way, it is determined whether or not it is a situation where the generation of black smoke should be suppressed by the exhaust gas contained in the gas in the combustion chamber 3 during fuel combustion. These decisions are
Whether or not the estimated temperature T is higher than the predetermined value a1 (S103), that is, the engine low temperature state (extremely low temperature state) in which the oil viscosity becomes so high as to hinder the driving of the variable valve timing mechanism 25. Whether or not
Whether the estimated temperature T is equal to or lower than a predetermined value a2 (a2> a1) (S104), that is, whether the temperature of the combustion chamber 3 is equal to or lower than a value at which black smoke may be generated,
Whether or not the vehicle is in an idle operation state (S105), that is, whether or not the vehicle is stopped;
This is done based on such a judgment.
[0061]
If all the determinations in steps S103 to S105 are affirmative, it is determined that black smoke should be suppressed, and the valve timing advance processing of the intake valve 20 is executed (S106). In this process, exhaust of the engine 1 contained in the gas in the combustion chamber 3 at the time of fuel combustion is generated by controlling the valve timing of the intake valve 20 to the advance side rather than the most retarded state to cause valve overlap. Adjust the amount to increase.
[0062]
When the temperature of the combustion chamber 3 is raised by the exhaust, the fuel injected and supplied into the combustion chamber 3 is suppressed from being atomized without being atomized. Furthermore, since the combustion temperature of the fuel is lowered by the exhaust gas existing in the combustion chamber 3 at the time of fuel combustion, the liquid fuel in the combustion chamber 3 is also suppressed from being burned by the combustion heat. In this way, the generation of black smoke due to the burning of the liquid fuel can be suppressed by reducing the combustion temperature when the fuel burns while reducing the liquid fuel in the combustion chamber 3. .
[0063]
In the valve timing advance control (S106) of the intake valve 20 for suppressing the generation of such black smoke, it is determined that the estimated temperature of the combustion chamber 3 is equal to or less than a value at which black smoke may be generated ( (S104: YES) Therefore, the adjustment of the amount of exhaust gas contained in the gas in the combustion chamber 3 at the time of fuel combustion described above is limited to only when it is really necessary to suppress the generation of black smoke, such as when the engine 1 is cold started. Will be executed. For this reason, it is possible to shorten the state in which the combustion state in which there is a large amount of exhaust from the engine 1 in the combustion chamber 3 during fuel combustion, which may cause the combustion state to become unstable, as much as possible. It is possible to prevent the combustion state from becoming unstable due to the presence of exhaust gas.
[0064]
Further, the valve timing advance control (S106) of the intake valve 20 is executed on the condition that it is determined that the engine is in the idle operation state (S105: YES). Therefore, the adjustment of the exhaust gas existing in the combustion chamber 3 during fuel combustion is not performed while the vehicle is running, and the adjustment of the combustion causes the combustion state to become unstable and the drivability of the vehicle to deteriorate. Can be suppressed.
[0065]
On the other hand, if a negative determination is made in any of steps S103 to S105, it is determined that the above-described suppression of black smoke generation is not to be executed, and the intake valve 20 for suppressing black smoke generation is determined. The valve timing advance control (S106) is not executed.
[0066]
That is, when a negative determination is made in either step S103 or step S105, the process of step S111 described above is executed without executing the process of step S106. Accordingly, when the estimated temperature T is equal to or lower than the predetermined value a1 (S103: NO), the valve timing advance control (S106) of the intake valve 20 for suppressing the generation of black smoke is not executed. It is. For this reason, it is possible to prevent the valve timing advance control from being performed unnecessarily at an extremely low temperature at which the oil viscosity becomes so high that the variable valve timing mechanism 25 cannot be driven.
[0067]
Further, if a negative determination is made in step S104, it is determined that the temperature in the combustion chamber 3 is higher than a value that may cause black smoke, and normal valve timing control is executed (S112). ). In other words, the normal valve timing control is executed when the engine 1 leaves the cold start time.
[0068]
In this normal valve timing control, the advance amount of the valve timing of the intake valve 20 is adjusted according to the operating state of the engine 1 such as the load factor KL and the engine speed NE. The advance amount is a value indicating how much the valve timing is advanced with reference to the time when the valve timing is in the most retarded state. The valve timing advance amount is adjusted with respect to the target advance angle amount θt set according to the load factor KL and the engine speed NE, and the actual advance angle amount θr obtained from the detection signal of the cam position sensor 24. Is performed by changing the duty ratio D so as to approach.
[0069]
When the duty ratio D is set to “0%”, oil is supplied to the variable valve timing mechanism 25 through the retarded oil passage 27, whereby the valve timing of the intake valve 20 is in the most retarded state. The variable valve timing mechanism 25 is driven as described above. On the other hand, when the duty ratio D is set to “100%”, the oil is supplied to the valve timing variable mechanism 25 through the advance side oil passage 26, whereby the valve timing of the intake valve 20 is maximized. The variable valve timing mechanism 25 is driven so as to be in the advanced state.
[0070]
Therefore, the duty ratio D in the normal valve timing control is set to a value closer to “0%” when the actual advance angle amount θr is a value closer to the valve timing advance angle than the target advance angle amount θt. When the amount θr is a value on the retard side with respect to the target advance amount θt, it is set to a value closer to “100%”. In this way, by changing the duty ratio D based on the actual advance amount θr and the target advance amount θt, the actual advance amount θr can be brought close to the target advance amount θt, and the valve timing of the intake valve 20 is set to the engine 1. The optimal timing for driving.
[0071]
Next, with respect to the process of step S106 in the black smoke suppression routine, that is, the process of adjusting the valve timing of the intake valve 20 to the advance side from the most retarded state, refer to the flowchart of FIG. 3 showing the valve timing advance routine. Will be described in detail. This valve timing advance routine is executed through the electronic control device 35 every time the process proceeds to step S106 of the black smoke suppression routine (FIG. 2).
[0072]
In the valve timing advance routine, it is first determined whether or not the valve timing of the intake valve 20 has never reached the most advanced angle state after the start of the engine 1 is completed (S201). If the determination is affirmative, it is determined whether or not the airflow control valve 16 has been closed based on, for example, whether or not the intake pressure PM has changed to the vacuum side to a value necessary for the operation of the actuator 17. (S101). If the determination is affirmative, the duty ratio D is set to “100%” (S203).
[0073]
Therefore, after the start of the engine 1 is completed, until the valve timing of the intake valve 20 first reaches the most advanced angle state, the duty ratio D is “on the condition that the airflow control valve 16 has been closed. 100% ". Thus, when the duty ratio D is set to “100%”, the driving force when driving the valve timing variable mechanism 25 is maximized so that the valve timing of the intake valve 20 changes to the advance side. Become.
[0074]
Immediately after starting the engine 1, the oil for driving the variable valve timing mechanism 25 is in a low temperature state, so that the viscosity of the oil becomes high and it becomes difficult to drive the variable valve timing mechanism 25. Therefore, it is difficult to execute the valve timing advance control of the intake valve 20 for suppressing the generation of black smoke. However, since the control is performed with the maximum driving force as described above, the control should be accurately executed. Will be able to.
[0075]
By setting the duty ratio D to “100%” as described above, the valve timing of the intake valve 20 is set to the most advanced state in the shortest time even in a situation where the valve timing variable mechanism 25 is difficult to drive as described above. Is done. As a result, the valve overlap amount is quickly maximized, and the amount of exhaust existing in the combustion chamber 3 during fuel combustion is quickly maximized.
[0076]
Further, setting the duty ratio D to “100%” and setting the valve timing of the intake valve 20 to the most advanced angle state is performed under the condition that the airflow control valve 16 is completely closed. Is executed after the air flow control valve 16 is closed. For this reason, when the airflow control valve 16 is not closed and the turbulence of the gas flow in the combustion chamber 3 is small, the presence of a large amount of exhaust gas in the combustion chamber 3 during fuel combustion is avoided. .
[0077]
If this happens, the gas flow in the combustion chamber 3 is less disturbed, so that the large amount of exhaust gas is unevenly distributed in the combustion chamber 3. For this reason, there is a possibility that the air-fuel mixture is ignited by the spark plug 5 when the exhaust gas rich portion in the combustion chamber 3 is around the spark plug 5. In such a case, the combustion state becomes unstable. However, a large amount of exhaust gas is present in the combustion chamber 3 during fuel combustion after the airflow control valve 16 is closed and the gas flow in the combustion chamber 3 becomes large. Therefore, it is possible to suppress the combustion state from becoming unstable as the exhaust gas is unevenly distributed in the combustion chamber 3.
[0078]
When the valve timing of the intake valve 20 is set to the most advanced angle state as described above, a negative determination is made in the process of step S201. In this case, the target advance amount θt is calculated based on the estimated temperature T (S204), and the duty ratio D is calculated so that the actual advance amount θr approaches the target advance amount θt (S205).
[0079]
Here, the target advance amount θt calculated in step S204 becomes smaller as the estimated temperature T becomes larger as shown in FIG. Further, the duty ratio D calculated in step S205 becomes a value close to “0%” when the actual advance amount θr is a value on the advance side with respect to the target advance amount θt, and the target advance amount θt. On the other hand, when the actual advance amount θr is a value on the retard side, the value approaches “100%”. By calculating the duty ratio D, the actual advance amount θr is brought closer to the target advance amount θt, and the valve timing of the intake valve 20 changes to the retard side as the estimated temperature T increases.
[0080]
By the way, as the estimated temperature T becomes higher, the fuel injected into the combustion chamber 3 is less atomized and becomes liquid fuel, and the fuel is adjusted by adjusting the valve timing of the intake valve 20 to the advance side. The generation of black smoke can be suppressed without increasing the amount of exhaust present in the combustion chamber 3 during combustion. That is, the higher the estimated temperature T, the smaller the amount of exhaust gas in the combustion chamber 3 at the time of fuel combustion necessary to suppress the generation of black smoke.
[0081]
Therefore, as the estimated temperature T becomes higher as described above, the target advance amount θt is set to the retard side value, and the amount of exhaust existing in the combustion chamber 3 at the time of fuel combustion is reduced, thereby reducing the amount of exhaust. Only the amount necessary for suppressing the generation of black smoke can be used, and the exhaust state can be prevented from becoming unstable due to this exhaust gas.
[0082]
When one of the processes in step S203 and step S205 is executed, the control system related to the combustion of fuel among the control systems that control the operation of the engine 1 is based on the estimated temperature T and the actual advance angle θr. It is controlled (S206). As control of the control system performed based on the estimated temperature T and the actual advance amount θr in this way, intake air amount control, air-fuel ratio control, combustion mode switching control, fuel injection timing control, ignition timing control, and the like are given. be able to.
[0083]
Here, based on the duty ratio D calculated in step S203 or step S205, when the valve timing variable mechanism 25 is driven, the combustion state is prevented from becoming unstable due to the response delay of the drive. I have to. That is, even if a response delay occurs when the response delay occurs and the amount of exhaust gas existing in the combustion chamber 3 at the time of fuel combustion changes to a predetermined amount, the above is performed based on the actual advance angle θr. Each control is performed in a mode suitable for the amount of exhaust that actually exists in the combustion chamber 3 during fuel combustion. Therefore, even if a response delay occurs in the drive of the variable valve timing mechanism 25, it is possible to suppress the combustion state from becoming unstable along with this.
[0084]
Hereinafter, the outline of each control based on the estimated temperature T and the actual advance angle amount θr will be individually described.
[Intake air volume control]
The throttle valve 11 is driven and controlled such that the throttle opening TA increases as the estimated temperature T decreases and the actual advance angle θr increases. Thus, the intake air amount of the engine 1 is controlled to a value suitable for the temperature of the combustion chamber 3 and the amount of exhaust gas actually present in the combustion chamber 3 during fuel combustion. FIG. 5 shows the relationship between the estimated temperature T, the actual advance amount θr, and the intake air amount when such intake air amount control is executed. As can be seen from the figure, the intake air amount increases as the actual advance angle amount θr increases, and increases as the estimated temperature T decreases. When the amount of intake air increases in this way, the amount of oxygen present in the combustion chamber 3 at the time of fuel combustion increases, and combustion of fuel is promoted to stabilize the combustion state. Therefore, as the estimated temperature T becomes lower and the actual advance angle θr becomes larger (the exhaust amount in the combustion chamber 3 at the time of fuel combustion) becomes larger, the intake air amount becomes larger as the combustion state tends to become unstable. As a result, the combustion state is stabilized.
[0085]
[Air-fuel ratio control]
As shown in FIG. 6, the fuel injection amount is increased through the drive control of the fuel injection valve 4 so that the air-fuel ratio of the engine 1 becomes richer as the estimated temperature T becomes lower and the actual advance amount θr becomes larger. Is done. As a result, the air-fuel ratio of the engine 1 is controlled to a value suitable for the temperature of the combustion chamber 3 and the amount of exhaust gas actually present in the combustion chamber 3 during fuel combustion. The optimum air-fuel ratio for the combustion state of the fuel tends to shift to the rich side as the temperature of the combustion chamber 3 increases and the amount of the exhaust gas increases. However, the air-fuel ratio control is performed to obtain such an optimum air-fuel ratio. This is executed to stabilize the combustion state.
[0086]
[Combustion mode switching control]
As shown in FIG. 7, when the actual advance amount θr is large, the combustion mode is switched from homogeneous combustion to weakly stratified combustion. Then, the value of the actual advance amount θr at which the combustion mode is switched is set to a smaller value (a retarded value) as the estimated temperature T becomes lower. When the weak stratified combustion is executed, ignition is performed when the fuel injected in the compression stroke reaches around the spark plug 5, and the fuel concentration of the air-fuel mixture existing around the spark plug 5 at the time of ignition is increased. Therefore, it is possible to stabilize the combustion state with good ignition of the fuel. Further, since the air-fuel ratio is made leaner during weak stratified combustion than in homogeneous combustion, the amount of oxygen present in the combustion chamber 3 during fuel combustion increases, and the combustion of the fuel is promoted to improve the combustion state. Become stable. Therefore, as the estimated temperature T becomes lower and the combustion state in which the actual advance amount θr becomes larger is more likely to be unstable, switching from homogeneous combustion to weak stratified combustion becomes easier. This stabilizes the combustion state.
[0087]
[Fuel injection timing control]
This fuel injection timing control is performed in conjunction with the weak stratified combustion based on the combustion mode switching control. As shown in FIG. 8, as the estimated temperature T decreases and the actual advance angle θr increases, the compression stroke fuel The fuel injection valve 4 is driven and controlled so that the fuel injection timing at the time of injection is retarded. When the fuel injection timing is retarded in this way, the injected fuel does not diffuse so much in the combustion chamber 3 and reaches around the spark plug 5, and ignition is performed in this state. Therefore, the fuel concentration of the air-fuel mixture existing around the spark plug 5 at the time of ignition can be accurately increased, and the combustion state can be stabilized with good ignition of the fuel. Accordingly, as the estimated temperature T becomes lower and the combustion state in which the actual advance amount θr becomes larger is likely to become unstable, the fuel injection timing in the compression stroke is retarded and the combustion state is stabilized. Be able to.
[0088]
[Ignition timing control]
As shown in FIG. 9, the igniter 5a is driven and controlled so that the ignition timing is advanced as the estimated temperature T is lowered and the actual advance amount θr is increased. During homogeneous combustion, if there is exhaust in the combustion chamber 3 during fuel combustion, the combustion speed of the fuel decreases. However, as described above, the ignition timing is advanced and ignition is performed earlier, so that the combustion speed is reduced. It can suppress that a combustion state becomes unstable with a fall. Further, at the time of weak stratified combustion, the ignition timing is advanced so that the fuel injected in the compression stroke reaches around the spark plug and is ignited in a state where the fuel is not diffused much. Therefore, the fuel concentration of the air-fuel mixture existing around the spark plug 5 at the time of ignition can be increased, and the combustion state can be stabilized with good ignition of the fuel. Therefore, the ignition timing is advanced and the combustion state is stabilized as the estimated temperature T becomes lower and the combustion state in which the actual advance amount θr becomes larger becomes more unstable.
[0089]
The outline of each control performed based on the estimated temperature T and the actual advance amount θr has been described above. In the process of step S206 in the valve timing advance routine (FIG. 3), at least one of the above controls is executed. Is done. When this valve timing advance routine ends, the process returns to the black smoke suppression routine (FIG. 2).
[0090]
After the process of step S106 (valve timing advance routine) in the black smoke suppression routine is executed, the rotation fluctuation dln of the engine 1 (crankshaft 9) is calculated (S107). That is, for example, the time required for the crankshaft 9 to pass 180 ° CA in the current expansion stroke is subtracted from the time required for the crankshaft 9 to pass 180 ° CA in the previous expansion stroke. A value obtained by filtering the subtracted value is defined as a rotation fluctuation dln.
[0091]
Subsequently, it is determined whether or not the combustion state has become unstable by the process of step S106. These decisions are
Whether or not the rotational fluctuation dln is larger than the predetermined value A (S108), that is, whether or not the rotational fluctuation dln is uncomfortable for the driver,
Whether or not the engine speed NE is less than a predetermined value B that is smaller than the idle speed (S109), that is, whether or not the engine speed NE has been reduced;
It is performed based on such a judgment.
[0092]
If an affirmative determination is made in any one of steps S108 and S109, it is determined that the combustion state has become unstable due to the process in step S106, and combustion stabilization is performed to stabilize this combustion state. Processing is executed (S110). For such combustion stabilization processing, for example, valve timing retardation control of the intake valve, intake air amount increase control, switching control of the combustion mode to weakly stratified combustion, fuel injection timing retardation control, and ignition timing advancement It is conceivable to perform various controls such as control. Below, the outline | summary of the said various control is demonstrated separately.
[0093]
[Valve timing delay control of intake valve]
By changing the duty ratio D to a value close to “0%” and controlling the valve timing of the intake valve 20 to the retard side to reduce the valve overlap amount, the combustion chamber 3 at the time of fuel combustion is brought into the combustion chamber 3. The amount of exhaust that exists is reduced, and the combustion state is prevented from becoming unstable due to the exhaust. By performing the valve timing retardation control in this way, the combustion state can be stabilized. Note that the change of the duty ratio D to a value close to “0%” may be realized, for example, by setting the duty ratio D to “0%”, or the duty ratio D may be changed as shown in FIG. You may implement | achieve by variably setting so that it may become a value near "0%", so that the rotation fluctuation dln becomes large.
[0094]
[Increase control of intake air volume]
The throttle valve 11 is driven and controlled so that the throttle opening degree TA becomes an open side value as the rotational fluctuation dln increases. Thus, as shown in FIG. 11, the intake air amount increases as the rotational fluctuation dln increases. When the amount of intake air increases, the amount of oxygen present in the combustion chamber 3 during fuel combustion increases, fuel combustion is promoted, and the combustion state is stabilized. Therefore, by increasing the intake air amount in accordance with the rotational fluctuation dln as described above, the combustion state can be appropriately stabilized.
[0095]
[Switching control of combustion mode to weakly stratified combustion]
When the combustion mode is switched from homogeneous combustion to weak stratified combustion, ignition is performed when the fuel injected in the compression stroke reaches around the spark plug 5, and the fuel of the air-fuel mixture existing around the spark plug 5 at the time of ignition Since the concentration is increased, the combustion state can be stabilized with good ignition of the fuel. Also, at the time of weak stratified combustion, since the air-fuel ratio is leaner than at the time of homogeneous combustion, the amount of oxygen present in the combustion chamber 3 at the time of fuel combustion increases, and the combustion of the fuel is promoted and the combustion state is improved. Stabilize. Therefore, the combustion state can be stabilized by switching the combustion mode to weak stratified combustion as described above.
[0096]
[Delay control of fuel injection timing]
This retard control of the fuel injection timing is performed in conjunction with the switching control to the weakly stratified combustion of the above-described combustion mode, and as shown in FIG. 12, the compression stroke fuel injection is increased as the rotational fluctuation dln becomes larger. This is realized by controlling the fuel injection valve 4 so that the fuel injection timing is delayed. When the fuel injection timing is retarded in this way, the injected fuel does not diffuse so much in the combustion chamber 3 and reaches around the spark plug 5, and ignition is performed in this state. Therefore, the fuel concentration of the air-fuel mixture existing around the spark plug 5 at the time of ignition can be accurately increased, and the combustion state can be stabilized with good ignition of the fuel. Therefore, the combustion state is appropriately stabilized by retarding the fuel injection timing in accordance with the rotational fluctuation dln as described above.
[0097]
[Advance control of ignition timing]
In this advance control of the ignition timing, the igniter 5a is driven and controlled so that the ignition timing is advanced as the rotational fluctuation dln increases as shown in FIG. During homogeneous combustion, even if the combustion speed decreases due to the presence of exhaust in the combustion chamber 3 during fuel combustion, the ignition speed is advanced and ignition is performed earlier, thereby reducing the combustion speed. Accordingly, it is possible to suppress the combustion state from becoming unstable. Further, at the time of weak stratified combustion, the ignition timing is advanced so that the fuel injected in the compression stroke reaches around the spark plug and is ignited in a state where the fuel is not diffused much. Therefore, the fuel concentration of the air-fuel mixture existing around the spark plug 5 at the time of ignition can be increased, and the combustion state can be stabilized with good ignition of the fuel. As described above, the ignition timing is advanced in accordance with the rotational fluctuation dln, so that the combustion state can be stabilized appropriately.
[0098]
As described above, the outline of various controls for stabilizing the combustion state when the combustion state becomes unstable by the process of step S106 has been described. In the process of step S110 in the black smoke suppression routine (FIG. 2), At least one of the various controls is executed.
[0099]
Next, when the generation of black smoke is suppressed after the start of the engine 1, the open / close state of the air flow control valve 16, the duty ratio D, the actual advance angle θr, and the estimated temperature T are changed as time elapses. Will be described with reference to the time chart of FIG.
[0100]
Immediately after the start of the engine 1, even if the air flow control valve 16 is closed by the operation of the actuator 17, the air pressure control is not performed because the intake pressure PM has not decreased to the value required for the operation of the actuator 17. The valve 16 remains open. Then, calculation of the estimated temperature T is started when the engine 1 is started, and when the intake pressure PM reaches a value necessary for the operation of the actuator 17 after the start is completed and the airflow control valve 16 is closed,
The estimated temperature T is not less than the predetermined value a1,
The estimated temperature T is not greater than the predetermined value a2,
・ Idle operation
As long as all the conditions are satisfied, the duty ratio D is changed from “0%” to “100%”.
[0101]
As a result, the valve timing variable mechanism 25 is driven and controlled so that the valve timing of the intake valve 20 is changed from the most retarded state to the most advanced angle state. Then, when the actual advance angle amount θr reaches the maximum value and the valve timing of the intake valve 20 reaches the most advanced angle state for the first time after starting the engine 1, the actual advance angle amount θr is set according to the estimated temperature T thereafter. The duty ratio D is calculated so as to approach the target advance amount θt. The valve timing variable mechanism 25 is driven and controlled based on the duty ratio D, whereby the valve timing of the intake valve 20 is set to a timing corresponding to the target advance amount θt.
[0102]
As described above, after the start of the engine 1 is started, the valve timing of the intake valve 20 is controlled to the advance side with respect to the most retarded state, so that it is included in the gas in the combustion chamber 3 during fuel combustion due to valve overlap. The amount of exhausted air is adjusted to the increase side, and the generation of black smoke is suppressed. Further, in the advance control of the valve timing, a response delay occurs in the variable valve timing mechanism 25, and there is a response delay as the amount of exhaust existing in the combustion chamber 3 during fuel combustion changes to a predetermined value. Even if it occurs, the control of the control system related to the combustion of the fuel is performed based on the actual advance amount θr which is a value corresponding to the actual value of the exhaust amount, and the combustion state becomes unstable. It is suppressed.
[0103]
On the other hand, even if there is no response delay as described above, the presence of exhaust from the engine 1 in the combustion chamber 3 at the time of fuel combustion means that gas (not contributing to the combustion) in the combustion chamber 3 at the time of fuel combustion ( Exhaust) is present, and it cannot be denied that the combustion state tends to become unstable. However, when the combustion state becomes unstable, the predetermined control system for controlling the operation of the engine 1 is controlled in a direction to stabilize the combustion state, and the combustion state is stabilized. Therefore, it is suppressed that the combustion state becomes unstable due to the presence of exhaust in the combustion chamber 3 during fuel combustion.
[0104]
Even when the valve timing advance control is performed, the estimated temperature T gradually increases with time. When the estimated temperature T becomes higher than the predetermined value a2, normal valve timing control is performed instead of the valve timing advance control.
[0105]
According to the embodiment described in detail above, the following effects can be obtained.
(1) When the engine 1 is cold started, the valve timing of the intake valve 20 is controlled from the most retarded state to the advanced side, that is, the side that increases the amount of exhaust gas existing in the combustion chamber 3 during fuel combustion. This is performed (S106) when it is determined that the estimated temperature T of the combustion chamber 3 is equal to or less than a value (predetermined value a2) that may cause black smoke (S104: YES). For this reason, in order to suppress the generation of black smoke, the amount of exhaust gas existing in the combustion chamber 3 at the time of fuel combustion is adjusted by the valve timing advance angle control when it is truly necessary. It becomes only. Therefore, the state in which the combustion state in which there is a large amount of exhaust gas in the combustion chamber 3 at the time of fuel combustion can be unstable can be shortened as much as possible, and the exhaust gas exists in the combustion chamber 3 at the time of fuel combustion. In connection with it, it can suppress that a combustion state becomes unstable.
[0106]
(2) When the combustion state becomes unstable due to the valve timing advance control (S106) of the intake valve 20, the duty ratio D is set to “0%” to prohibit the valve timing advance control and It is possible to stabilize the combustion state by reducing the amount of exhaust gas present in the combustion chamber 3 during combustion (S110). Therefore, even if the amount of exhaust gas in the combustion chamber 3 at the time of fuel combustion is adjusted to the increase side in order to suppress the generation of black smoke, it is possible to suppress the combustion state from becoming unstable accordingly.
[0107]
(3) Also, instead of setting the duty ratio D to “0%” as described above,
The duty ratio D is set to a retarded value according to the rotation fluctuation dln, and the amount of exhaust existing in the combustion chamber 3 during fuel combustion is reduced.
・ Increase intake air volume
・ Switch combustion mode to weak stratified combustion and retard fuel injection timing for compression stroke fuel injection
・ Advance ignition timing
It is also possible to perform at least one of various controls for stabilizing the combustion state (S110). In this case as well, when the amount of exhaust gas in the combustion chamber 3 at the time of fuel combustion is adjusted to the increase side in order to suppress the generation of black smoke, the combustion state is prevented from becoming unstable accordingly. it can.
[0108]
(4) After the start of the engine 1 is completed, after the valve timing of the intake valve 20 reaches the most advanced angle state, the actual advance angle is set to the target advance angle θt set according to the estimated temperature of the combustion chamber 3. The duty ratio D is calculated so that the amount θr approaches, and the valve timing variable mechanism 25 is driven and controlled based on the duty ratio D. Thereby, the valve timing of the intake valve 20 is changed to the retard side as the estimated temperature T becomes higher, and the amount of exhaust existing in the combustion chamber 3 during fuel combustion is reduced. As the estimated temperature T of the combustion chamber 3 increases, black smoke is less likely to be generated. Therefore, the amount of exhaust gas present in the combustion chamber 3 during fuel combustion is reduced by changing the valve timing as described above. Only the amount necessary to suppress the generation can be achieved, and the exhaust state can suppress the combustion state from becoming unstable.
[0109]
(5) The valve timing advance control (S106) of the intake valve 20 is executed when the vehicle is in an idling state, that is, while the vehicle is stopped. As a result, the amount of exhaust gas present in the combustion chamber 3 during fuel combustion is adjusted in order to suppress the generation of black smoke while the automobile is running, and the combustion state becomes unstable, and the drivability of the automobile deteriorates accordingly. Can be suppressed.
[0110]
(6) The valve timing advance control (S106) of the intake valve 20 is executed on condition that the airflow control valve 16 is closed after the start of the engine 1 is completed. If the valve timing advance control is executed with the airflow control valve 16 opened, the gas flow in the combustion chamber 3 during fuel combustion is small when the turbulence of the gas flow in the combustion chamber 3 is small. Since the gas contains a large amount of exhaust gas, the exhaust gas is unevenly distributed in the combustion chamber 3. In this state, there is a possibility that the air-fuel mixture is ignited by the spark plug 5 when the dark exhaust portion in the combustion chamber 3 is around the spark plug 5. In such a case, the combustion state becomes unstable. However, a large amount of exhaust gas is present in the combustion chamber 3 during fuel combustion after the airflow control valve 16 is closed and the gas flow in the combustion chamber 3 becomes large. Therefore, it is possible to suppress the combustion state from becoming unstable as the exhaust gas is unevenly distributed in the combustion chamber 3.
[0111]
(7) After the start of the engine 1, when the valve timing of the intake valve 20 is first controlled toward the most advanced state, the duty ratio D is set to “100%” (S203), and the valve timing is set to The driving force of the variable valve timing mechanism 25 for achieving the most advanced angle state is maximized. Immediately after the start of the engine 1, the oil for driving the variable valve timing mechanism 25 is in a low temperature state, so that the viscosity of the oil becomes high and it becomes difficult to drive the variable valve timing mechanism 25. Therefore, it is difficult to execute the valve timing advance control for suppressing the generation of black smoke. However, since the control is performed with the maximum driving force as described above, the control can be accurately executed. become.
[0112]
(8) The valve timing advance control (S106) of the intake valve 20 is not executed when it is determined that the temperature is extremely low (S103: NO). Therefore, when the viscosity of the oil becomes so high that the valve timing variable mechanism 25 cannot be driven at a very low temperature, the valve timing advance control can be prevented from being performed wastefully.
[0113]
(9) When the valve timing advance control is performed, the control is related to the combustion of the fuel based on the actual advance amount θr that is a value corresponding to the actual amount of exhaust existing in the combustion chamber 3 at the time of fuel combustion. At least one of the control system controls, that is, the intake air amount control, the air-fuel ratio control, the combustion mode switching control, the fuel injection timing control of the compression stroke fuel injection in weak stratified combustion, and the ignition timing control is performed. (S206). Therefore, in the advance control of the valve timing, a response delay occurs in the variable valve timing mechanism 25, and there is a response delay as the amount of exhaust existing in the combustion chamber 3 during fuel combustion changes to a predetermined value. Even if it occurs, the control of the control system is performed in a mode suitable for the actual value of the displacement, and this can suppress the combustion state from becoming unstable due to the response delay.
[0114]
In addition, this embodiment can also be changed as follows, for example.
-Fuel combustion by adjusting the valve overlap amount by controlling the valve timing of the exhaust valve 21 or by adjusting the valve overlap amount by controlling the valve timing of both the exhaust valve 21 and the intake valve 20 The exhaust amount existing in the combustion chamber 3 at the time may be adjusted. ,
Instead of adjusting the valve overlap amount by controlling the valve timing of the intake valve 20 and adjusting the amount of exhaust existing in the combustion chamber 3 during fuel combustion, the exhaust passage 7 is adjusted by adjusting the opening of the EGR valve 19. By adjusting the amount of exhaust gas recirculated to the intake passage 2, the amount of exhaust gas existing in the combustion chamber 3 during fuel combustion can also be adjusted.
[0115]
When the valve timing advance control (S106) of the intake valve 20 is executed, it is not always necessary to perform control of the control system related to fuel combustion in accordance with the actual advance amount θr.
[0116]
-After the start of the engine 1, until the valve timing of the intake valve 20 first reaches the most advanced angle state, the duty ratio D is set to "100%", and the valve timing is variable to make the above valve timing the most advanced angle state. Although the driving force for driving the mechanism 25 is maximized, the present invention is not limited to this. For example, the duty ratio D may be set to a value other than “100%” such as “80%” and the valve timing can be controlled to the advance side.
[0117]
The valve timing of the intake valve 20 is set to the most advanced angle state once after the start of the engine 1, but the present invention is not limited to this. For example, the target advance angle amount θt is calculated based on the estimated temperature T as in the process of step S204 even during the period from the start of the engine 1 until the valve timing of the intake valve 20 reaches the most advanced angle state first. On the other hand, when the target advance amount θt is equal to or less than the value at the most advanced valve timing, the duty ratio D is not forcibly set to 100% (S203), but as in the process in step S205. The duty ratio D may be calculated so that the advance amount θr becomes the target advance amount θt. Further, the duty ratio D may be calculated so that the actual advance amount θr approaches the target advance amount θt calculated based on the estimated temperature T from the beginning after the start of the engine 1. Even in this case, after the cold start of the engine 1 is started, the duty ratio D is first set to “100%”, and then the estimated temperature T rises and the target advance angle θt becomes the most advanced valve timing. When the angle is equal to or less than the value at the time of an angle, the duty ratio D is changed between “0%” and “100%” so that the actual advance amount θr approaches the target advance amount θt.
[0118]
The valve timing advance control is performed when the estimated temperature T is higher than the predetermined value a1, the estimated temperature T is lower than the predetermined value a2, the idling operation state, the airflow control valve 16 is closed. It is executed when various conditions such as being present are satisfied, but it is not always necessary to provide all of these conditions.
[0119]
・ As a result of the above valve timing advance control, when the combustion state becomes unstable, the predetermined control system is controlled to stabilize the combustion state. However, it is not always necessary to execute such control. Absent.
[0120]
Instead of calculating the estimated temperature T from the fuel injection amount Qfin, for example, the estimated temperature T may be calculated based on the elapsed time since the start of the engine 1 is completed.
The estimated temperature T may not be calculated after the start of the engine 1 is completed, but may be calculated from the start start time of the engine 1.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an entire engine to which a control device of an embodiment is applied.
FIG. 2 is a flowchart showing a procedure for suppressing generation of black smoke.
FIG. 3 is a flowchart showing a procedure for controlling the valve timing of the intake valve from the most retarded state to the advanced side in order to suppress the generation of black smoke.
FIG. 4 is a graph showing a trend of a target advance amount relative to a change in estimated temperature when calculating a target advance amount based on the estimated temperature.
FIG. 5 is an explanatory diagram used to explain the relationship between the actual advance angle amount, the estimated temperature, and the intake air amount when the intake air amount control is executed in anticipation of a response delay of the variable valve timing mechanism.
FIG. 6 is an explanatory diagram used to explain the relationship between an actual advance angle amount, an estimated temperature, and an air-fuel ratio when air-fuel ratio control is executed in anticipation of a response delay of the valve timing variable mechanism.
FIG. 7 is an explanatory diagram for explaining a combustion mode switching mode when combustion mode switching control is executed in anticipation of a response delay of the valve timing variable mechanism.
FIG. 8 is an explanatory diagram used to explain the relationship between the actual advance angle amount, the estimated temperature, and the fuel injection timing when the fuel injection timing control is executed in anticipation of a response delay of the variable valve timing mechanism.
FIG. 9 is an explanatory diagram used to explain the relationship between the actual advance amount, the estimated temperature, and the ignition timing when the ignition timing control is executed in anticipation of a response delay of the variable valve timing mechanism.
FIG. 10 shows how the duty ratio is changed in response to a change in the rotation fluctuation when the duty ratio is made variable in accordance with the rotation fluctuation in the valve timing retardation control for stabilizing the combustion state. Graph.
FIG. 11 is a graph showing how the intake air amount is changed in response to a change in rotational fluctuation during the increase control of the intake air amount for stabilizing the combustion state.
FIG. 12 is a graph showing how the fuel injection timing is retarded with respect to a change in rotational fluctuation during the retard control of the fuel injection timing for stabilizing the combustion state.
FIG. 13 is a graph showing how the ignition timing is advanced with respect to a change in rotation fluctuation during the ignition timing advance control for stabilizing the combustion state;
FIG. 14 shows how the airflow control valve opening / closing state, duty ratio, actual advance angle amount, and estimated temperature change over time when black smoke generation is suppressed after the engine starts. A time chart showing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Combustion chamber, 4 ... Fuel injection valve, 5 ... Spark plug, 5a ... Igniter, 10 ... Crank position sensor, 11 ... Throttle valve, 12 ... Vacuum sensor, 13 ... Accelerator pedal, 14 ... Accelerator position sensor , 15 ... Throttle position sensor, 16 ... Airflow control valve, 17 ... Actuator, 18 ... EGR passage, 19 ... EGR valve, 20 ... Intake valve, 21 ... Exhaust valve, 22 ... Intake camshaft, 23 ... Exhaust camshaft, 24 ... cam position sensor, 25 ... variable valve timing mechanism, 26 ... advance angle side oil passage, 27 ... retard angle side oil passage, 28 ... oil control valve (OCV), 29 ... supply passage, 30 ... discharge passage, 31 ... oil Pan, 32 ... Oil pump, 35 ... Electronic control unit, 36 ... Water temperature sensor.

Claims (7)

This is applied to an in-cylinder injection internal combustion engine having an adjusting means for adjusting the amount of exhaust gas contained in the gas in the combustion chamber at the time of fuel combustion by changing the valve timing of the engine valve. In a control device for an internal combustion engine that controls the adjusting means to increase the exhaust amount in the gas when it is determined that the engine state is included,
The control of the adjustment means to the exhaust amount increase side is executed at the time of cold start of the internal combustion engine,
Monitoring means for monitoring the combustion state of the fuel;
Wherein when the destabilization of the combustion state is detected by the monitoring means includes a stabilizing means for controlling the predetermined control system used for operation control of the internal combustion engine in the direction in which the combustion state is stable,
Further, the internal combustion engine when the control to the exhaust amount increase side of the adjusting means at the time of cold start is performed, in the course of the exhaust amount of the gas Ri by its control is changed, the actual of said adjusting means Based on the drive amount and the estimated temperature of the combustion chamber, among the control systems used for operation control of the internal combustion engine, the exhaust system is controlled by controlling a control system related to fuel combustion different from the valve timing control. Control means for suppressing instability of the combustion state in the process of changing the amount
Control apparatus for an internal combustion engine, wherein a call. The control device for an internal combustion engine according to claim 1, wherein the stabilization unit includes a prohibiting unit that prohibits the control of the adjusting unit to increase the displacement. 3. The control device for an internal combustion engine according to claim 1, further comprising permission means for permitting control of the adjustment means to the exhaust amount increase side on condition that the internal combustion engine is in an idle operation state. In order to change the flow state of the gas in the combustion chamber, the intake passage of the internal combustion engine is provided so as to be openable and closable. An air flow control valve that is controlled to open and close,
3. The control device for an internal combustion engine according to claim 1, further comprising permission means for permitting the control of the adjustment means to the exhaust amount increase side on the condition that the opening / closing control of the airflow control valve is completed. Before Symbol Based on the estimated temperature, the control apparatus for an internal combustion engine according to the adjustment means in any one of claims 1 to 4, and a setting means for setting a target value in controlling to the exhaust amount increase side. The adjusting means is driven and controlled by hydraulic pressure. When the adjusting means is first controlled to the exhaust amount increasing side after the start of the internal combustion engine, the driving force for the control is more than usual. The control device for an internal combustion engine according to any one of claims 1 to 5 . The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the control of the adjustment means to the exhaust amount increase side at a cold start of the internal combustion engine is not executed at an extremely low temperature.

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