JP3758003B2 - In-cylinder injection type spark ignition type internal combustion engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a cylinder injection type spark ignition type internal combustion engine, and more particularly to a fuel injection control technique at the start of the cylinder injection type spark ignition type internal combustion engine.
[0002]
[Related background]
The in-cylinder spark-ignition internal combustion engine includes a fuel injection valve capable of directly injecting fuel into the cylinder at a high pressure, and injects fuel in a compression stroke according to the operating state of the internal combustion engine (engine). The control is switched between a compression stroke injection mode for performing fuel injection and an intake stroke injection mode for performing fuel injection in the intake stroke. Further, both the compression stroke injection mode and the intake stroke injection mode can be operated at a lean air-fuel ratio (lean air-fuel ratio). Thereby, in the cylinder injection type spark ignition type internal combustion engine, it is possible to maintain the engine output properly and improve the fuel efficiency while maintaining the ultra lean air-fuel ratio particularly in the compression stroke injection mode.
[0003]
By the way, normally, when the engine is in a state immediately after starting, the temperature is low and the engine is in a cold state, so that the fuel is difficult to atomize. Thus, if the fuel is difficult to atomize, it is difficult to inject fuel in the compression stroke injection mode in which the time from fuel injection to ignition is extremely short. Therefore, in this case, the intake stroke injection mode in which the atomization time can be maximized can be used. I am trying to select it. Further, in this case, a relatively large amount of fuel is injected so that combustion is reliably performed, so that the air-fuel ratio becomes slightly rich.
[0004]
[Problems to be solved by the invention]
However, if the amount of fuel is increased, the engine temperature is low and the engine speed is low. In other words, under a situation where the amount of intake air is small and the intake air flow is slow, atomization of the fuel is almost accelerated even if fuel is injected during the intake stroke. Instead, the fuel is scattered in the combustion chamber in a relatively large granular form. If the fuel is left in a large granular state, the fuel has a large inertial force due to the action of the high fuel injection pressure, and the penetration force to go straight increases, so that the cylinder wall surface facing the fuel injection valve It will easily adhere to. When the fuel adheres to the cylinder wall surface, the adhering fuel causes incomplete combustion or the like, which is not preferable because it causes smoke.
[0005]
On the other hand, for the purpose of suppressing the generation of smoke, Japanese Patent Laid-Open No. 7-119507 discloses a technique in which fuel is divided into multiple injections and diffused when the engine speed is low and the engine speed is low. Although this technique is disclosed in publications and the like, this technique is intended to control fuel injection in accordance with the engine speed, and in particular, it takes into account the generation of smoke at the time of engine start that is affected by the engine temperature. In addition, it is not intended to prevent the fuel from adhering to the cylinder wall surface.
[0006]
The present invention has been made on the basis of the above-described circumstances, and an object thereof is to provide in-cylinder injection spark ignition that can prevent fuel from adhering to the cylinder wall surface and can reliably suppress the generation of smoke at the time of starting. An object of the present invention is to provide a control device for an internal combustion engine.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, in the control device for a direct injection spark ignition type internal combustion engine, when the internal combustion engine is in a start completed state and the temperature of the internal combustion engine is lower than a predetermined temperature. Since the intake stroke injection mode is selected and the fuel is divided and injected several times in the intake stroke, if the internal combustion engine is immediately after starting and not in a warm-up state, it is in a so-called cold state. Are injected in the intake stroke so that premix combustion is possible, and the fuel is injected intermittently in a plurality of times.
[0008]
Therefore, the amount of fuel injected at one time is reduced and the injected fuel is less likely to be a granular lump, atomization and atomization of the fuel are promoted, and good combustion with good ignitability can be realized.
Also, since the amount of fuel injected at one time is reduced, the inertial force of the injected fuel is reduced, that is, the penetration force is weakened, and the fuel reaches the cylinder wall facing the fuel injection valve. This prevents the fuel from adhering to the wall surface of the cylinder. As a result, the fuel adhering to the wall surface of the cylinder is not incompletely combusted, and smoke is not generated, thereby preventing deterioration of fuel consumption. Furthermore, oil film breakage due to adhesion of hydraulic oil applied to the cylinder wall surface is suppressed, and seizure of the internal combustion engine is also prevented.
[0009]
In the invention of claim 2, the fuel split ratio to be divided into a plurality of times is set according to the temperature of the internal combustion engine, and the fuel injection valve is driven and controlled based on this split ratio. The appropriate amount is set according to the temperature. For example, if the first injected fuel amount is gradually increased in accordance with the temperature rise of the internal combustion engine, even if the internal combustion engine shifts from the cold state to the warm state and completes the divided fuel injection, the combustion is performed. Control can be continued continuously and smoothly, and the combustion state is maintained in a good state.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a longitudinal sectional view of a cylinder injection type spark ignition type internal combustion engine mounted on a vehicle, that is, a cylinder injection gasoline engine, and a schematic configuration diagram showing one embodiment of a control device. A configuration of a control device for a direct injection gasoline engine according to the present invention will be described with reference to FIG.
[0011]
Reference numeral 1 denotes an in-cylinder injection type in-line four-cylinder gasoline engine for automobiles (hereinafter simply referred to as an engine), and the combustion chamber 5 and the intake device are designed exclusively for in-cylinder injection. In the cylinder head 2 of the engine 1, an electromagnetic fuel injection valve 4 is attached obliquely to the cylinder 6 together with a spark plug 3 for each cylinder, so that fuel can be directly injected into the combustion chamber 5. Has been. A hemispherical depression is formed on the top surface of the piston 7 that reciprocates while sliding in the cylinder 6 so that the fuel spray injected from the fuel injection valve 4 in the compression stroke reaches the ignition plug 3 near the top dead center. That is, a cavity 8 is formed.
[0012]
As the valve operating mechanism, a DOHC (double overhead cam) type four-valve type mechanism is employed, and an intake side camshaft 11 and an exhaust are provided above the cylinder head 2 so as to drive the intake and exhaust valves 9 and 10 respectively. The side camshaft 12 is rotatably supported.
An intake port 13 is formed in the cylinder head 2 so as to pass between the camshafts 11 and 12 so as to extend in a substantially upright direction, and the intake air flow passing through the intake port 13 is generated in the combustion chamber 5. It is possible to generate a reverse tumble flow in the reverse direction to normal. About the exhaust port 14, it is formed in the substantially horizontal direction like a normal engine.
[0013]
In the figure, reference numeral 16 denotes a water temperature sensor (temperature detection means) for detecting the cooling water temperature (temperature of the internal combustion engine) Tw, and reference numeral 17 denotes predetermined crank positions of each cylinder (in this embodiment, 5 ° BTDC and 75 ° BTDC). ) Is a crank angle sensor that outputs a crank angle signal SGT, and can detect not only the crank angle but also the engine speed Ne. The camshaft 11 that rotates at half the number of revolutions of the crankshaft is provided with a cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC. It is possible to determine whether or not.
[0014]
An intake pipe provided with an air cleaner, a throttle body, a stepper motor type idle speed control valve, a linear solenoid type large air bypass valve, and the like is connected to the intake port 13 via an intake manifold 21. However, explanation is omitted here.
The exhaust port 14 is connected to an exhaust pipe provided with a three-way catalyst, a muffler, and the like through an exhaust manifold 41 to which an O ₂ sensor 40 is attached.
[0015]
Reference numeral 50 in the figure denotes a fuel supply unit for supplying high-pressure fuel to the fuel injection valve 4, and the fuel supply unit 50 is connected to the fuel injection valve 4 via a pipe, 52. Specifically, a high-pressure fuel pump 54 is interposed in the fuel supply unit 50, and the high-pressure fuel pump 54 is connected to the end of the camshaft 12 so as to be able to rotate synchronously. The high-pressure fuel pump 54 can supply high-pressure (for example, 5 MPa) fuel to the fuel injection valve 4. Although not shown, the fuel supply unit 50 is provided with a pressure regulating valve for regulating the fuel discharged from the high pressure fuel pump 54 to a desired pressure.
[0016]
An electronic control unit (ECU) 70 is installed in the passenger compartment, and an input / output device (not shown), a storage device (ROM, RAM, nonvolatile RAM) for storing a control program, a control map, and the like is provided in the ECU 70. Etc.), a central processing unit (CPU), a timer counter, and the like, and the ECU 70 performs overall control of the engine 1.
[0017]
Various sensors such as the water temperature sensor 16, the crank angle sensor 17, and the O ₂ sensor 40 are electrically connected to the input side of the ECU 70, while the fuel injection valve 4 and the fuel supply are connected to the output side. Various drive devices such as the unit 50 are connected.
Hereinafter, the operation according to the present invention of the control device for the cylinder injection type spark ignition type internal combustion engine configured as described above will be described.
[0018]
Referring to FIG. 2, there is shown a flowchart of a fuel injection control routine executed by the ECU 70. Hereinafter, the control procedure of the fuel injection control according to the present invention will be described along the flowchart.
First, in step S10, it is detected and determined whether or not the engine 1 has been started and is in a start complete state (start completion detecting means). Specifically, it is determined by detecting whether or not the engine 1 is in a complete explosion state from the first explosion and the engine rotation speed Ne is equal to or higher than a predetermined value of extremely low speed. If the determination result is true (Yes), the process proceeds to step S12.
[0019]
In step S12, it is determined whether or not the engine is in an idle operation state. Specifically, here, it is determined whether or not the engine rotational speed Ne is a predetermined idle rotational speed Nid and the throttle body opening, that is, the throttle opening θth is an opening corresponding to idle operation. To do. Alternatively, an idle switch is provided to determine whether the idle switch is in an on state. If the determination result is true (Yes), the process proceeds to step S14.
[0020]
In step S14, based on the information from the water temperature sensor 16, it is determined whether or not the cooling water temperature Tw is lower than a predetermined value Tw0 (for example, 50 ° C.). That is, here, it is determined whether or not the warm-up operation of the engine 1 has been completed and the engine 1 is in a cold state.
If the determination result in step S14 is true (Yes), the coolant temperature Tw is less than the predetermined value Tw0, and the engine 1 is still in the cold state, for example, immediately after starting, the process proceeds to step S15.
[0021]
In step S15, the intake stroke injection mode, that is, the premixed combustion mode is selected as the fuel injection mode. That is, fuel is injected not in the compression stroke but in the intake stroke.
When the intake stroke injection mode is selected, the amount of fuel injected from the fuel injection valve 4 is set in the next step S16. Normally, when the engine is in a cold state, a certain amount of fuel is injected with emphasis on the certainty of ignition so that the air-fuel ratio becomes slightly rich. Accordingly, a relatively large amount of fuel is set here. Specifically, the fuel amount is determined by the discharge pressure of the fuel injection valve 4 and the drive time, and the fuel amount increases in proportion to the drive time of the fuel injection valve 4 under a constant discharge pressure. Therefore, the drive time of the fuel injection valve 4 is set longer here.
[0022]
By the way, when a large amount of fuel is injected at a high pressure in the intake stroke, as described above, when the engine 1 is in the cold fuel state, the intake flow rate is small and the combustion chamber 5 is in a low temperature state. Therefore, the fuel is scattered in the combustion chamber 5 in a relatively large granular form without being atomized. In particular, when the drive time of the fuel injection valve 4, that is, the fuel injection time becomes longer as described above, the kinetic energy of the fuel increases, and the fuel retains a large inertial force, that is, burns with a strong penetrating force. The inside of the chamber 5 goes straight, and most of the fuel adheres to the wall surface of the cylinder 6 facing the fuel injection valve 4. The fuel adhering to the wall surface of the cylinder 6 in this way means that the fuel burns without being atomized, which leads to generation of smoke and is not preferable.
[0023]
Therefore, in the control apparatus for a cylinder injection type spark ignition type internal combustion engine of the present invention, when the engine 1 is in a cold state and a large amount of fuel is injected in the intake stroke, the fuel injection is divided into a plurality of times. Thus, the injection time of the fuel injected in one fuel injection is shortened, the amount of fuel is reduced, and the inertial force is reduced, that is, the penetration force is weakened.
[0024]
Therefore, first, in dividing the fuel injection as described above, in the next step S18, first, the fuel division ratio γ (= first injection amount / total injection amount) of the fuel divided into a plurality of times is set. Here, a case where the number of fuel injections is set to two times of the first injection and the second injection will be described as an example.
The fuel split ratio γ is set in advance as shown in FIG. 3A when the number of fuel injections is, for example, two. That is, the fuel split ratio γ is set to a predetermined value γ0 (for example, 0.5, that is, the ratio between the first injection amount and the second injection amount is 1: 1) regardless of the change in the coolant temperature Tw.
[0025]
More preferably, as shown in FIG. 3B, the fuel split ratio γ is proportional to the cooling water temperature Tw from a predetermined value γ0 (for example, 0.5) after the cooling water temperature Tw rises to a predetermined value or more. It is better to set it to be larger. That is, after the cooling water temperature Tw has reached a predetermined value or more, the first injection amount to be injected first is gradually increased among the total injection amounts, and the second injection amount to be injected later is gradually decreased to continuously It is preferable to gradually shift to normal fuel injection. Thereby, the combustion control of the engine 1 is made smoother.
[0026]
When the fuel split ratio γ is set, an injection interval Int for two fuel injections is set in step S20. As shown in FIG. 4, the injection interval Int is set to a predetermined value Int0 (for example, 2 msec) regardless of the change in the coolant temperature Tw.
In the next step S22, the fuel injection end time Tend is set. This injection end timing Tend means the timing at which the second injection, that is, the second injection is ended, and is actually indicated by the crank position. The injection end timing Tend is a target average effective pressure Pe determined according to the throttle opening θth and the engine speed Ne, or a charging efficiency ηv and an engine speed Ne determined according to the intake air flow rate Qa. Is read from a map set in advance based on the above.
[0027]
When the injection end time Tend is set in this way, the first injection, that is, the start timing of the first injection is obtained from the injection end time Tend by back calculation. That is, since the fuel amount obtained in step S16 is determined based on the discharge pressure and driving time of the fuel injection valve 4 as described above, the driving time of the fuel injection valve 4 is determined once the fuel amount is determined. Therefore, the start timing of the first injection is obtained by calculating back the driving time of the fuel injection valve 4 and the injection interval Int from the injection end timing Tend.
[0028]
When the fuel split ratio γ, the injection interval Int, and the start timing of the first injection are obtained as described above, the split injection is performed in the next step S24. That is, the valve opening control of the fuel injection valve 4 is performed based on the above parameters.
Referring to FIG. 5, the state of fuel spray when fuel injection is divided into two in accordance with the above control in the intake stroke is shown in (a) to (c). The operational effects when the divided injection is performed will be described.
[0029]
As shown in FIG. 5A, when the piston 7 starts to descend from the top dead center, first the first injection is performed and the fuel F1 is injected from the fuel injection valve 4. When a predetermined time (for example, 2 msec) elapses, the second injection is performed and the fuel F2 is injected as shown in FIG. However, as shown in the figure, the fuels F1 and F2 injected separately in this way each have a relatively small amount of fuel, so that the inertial force is small, that is, the penetration force is weak. Therefore, as shown in FIG. 2C, even when the piston 7 reaches the bottom dead center and the intake stroke is completed, unlike the case where all the fuel is injected at once (indicated by a broken line) as in the prior art. The fuels F1 and F2 do not reach the wall surface of the cylinder 6 facing the fuel injection valve 4.
[0030]
That is, by dividing the fuel injection as described above, it is possible to suitably prevent the fuel from inadvertently adhering to the wall surface of the cylinder 6, and the occurrence of smoke can be suppressed satisfactorily. It is.
Further, when the amount of fuel injected at one time is small, that is, when the penetration force is weak, the fuel is unlikely to agglomerate and the fuel is easily atomized. Therefore, dividing the fuel injection has an extremely high effect in terms of promoting fuel atomization. That is, as shown in FIG. 5 (c), the fuel F1 injected by the first injection is promoted to atomize more uniformly than in the state of FIG. To do.
[0031]
By the way, the determination results of step S10, step S12 and step S14 of the fuel injection control in FIG. When Tw is equal to or greater than a predetermined value Tw0 (for example, 50 ° C.), that is, when the engine 1 is not in a cold state, the process proceeds to step S26, and normal fuel injection control is performed without performing the divided injection. Do. That is, normal fuel injection control is performed so that the number of fuel injections is only one.
[0032]
In the normal fuel injection control executed in step S26, the fuel injection mode is also switched in accordance with the engine speed Ne and the target average effective pressure Pe. That is, for example, during low load operation where the engine speed Ne is low and the target average effective pressure Pe is low, the compression stroke injection mode is selected, fuel injection is performed in the compression stroke, and lean air-fuel ratio operation is performed. Further, at the time of medium load operation, the intake stroke injection mode is selected, fuel injection is performed in the intake stroke, and lean air-fuel ratio operation is performed. Further, during high load operation, the intake stroke injection mode is selected, fuel is injected during the intake stroke, and theoretical air-fuel ratio operation is mainly performed.
[0033]
As described above, in the control device for a direct injection spark ignition type internal combustion engine of the present invention, when the engine 1 is in a cold state and the fuel is injected in a large amount in the intake stroke, the fuel injection is performed. It is divided into a plurality of times (for example, two times), and the amount of fuel injected in one fuel injection is reduced so that the inertial force of the fuel is reduced, that is, the penetration force is weakened.
[0034]
Accordingly, the fuel is not inadvertently attached to the wall surface of the cylinder 6 facing the fuel injection valve 4, and at the start of the engine 1, the generation of smoke is suppressed and the deterioration of the fuel consumption is suitably prevented. The Further, by not allowing fuel to adhere to the wall surface of the cylinder 6, it is possible to prevent the oil film from being cut off due to the fuel adhesion of the lubricating oil applied to the wall surface, and to prevent the engine 1 from being seized.
[0035]
In addition, if the amount of fuel injected at one time is small, it is difficult for the fuel to agglomerate. Therefore, fuel atomization is promoted by dividing the fuel injection, so that smoke can be suppressed and combustion with good ignitability is achieved. Good combustion with high efficiency can be realized.
In addition, the cooling water temperature Tw is increased by performing the fuel split injection in the intake stroke injection mode, and the cooling water temperature Tw reaches a temperature at which a lean air-fuel ratio (lean air-fuel ratio) operation can be performed in the compression stroke injection mode. Thereafter, if the fuel injection mode is shifted from the intake stroke injection mode to the compression stroke injection mode, the fuel efficiency is further improved.
[0036]
【The invention's effect】
As described above in detail, according to the control device for a direct injection spark ignition type internal combustion engine of claim 1 according to the present invention, the cold engine in which the internal combustion engine is in a start completed state and is less than a predetermined temperature. In the case of the state, the intake stroke injection mode is selected, and the fuel is divided into a plurality of times in the intake stroke and injected. Therefore, the amount of fuel injected at one time is reduced, and the inertial force of the fuel is reduced, that is, the fuel is thoroughly penetrated. The force can be weakened, and it is possible to suitably prevent the fuel from adhering to the wall surface of the cylinder.
[0037]
Therefore, when starting the internal combustion engine, it is possible to suitably prevent the occurrence of smoke due to incomplete combustion of the fuel adhering to the cylinder wall surface and the deterioration of fuel consumption, and the amount of fuel injected at one time is small and the fuel is granular. Since it does not easily become a lump, atomization and atomization of fuel can be promoted, and good combustion with good ignitability can be realized.
Further, according to the control device for the cylinder injection type spark ignition type internal combustion engine according to claim 2, the divided fuel can be set to an appropriate amount according to the temperature of the internal combustion engine, for example, according to the temperature rise of the internal combustion engine. By gradually increasing the amount of fuel injected for the first time, the combustion control can be continued smoothly and smoothly even when the internal combustion engine transitions from the cold state to the warm state and the fuel split injection ends. The combustion state can be suitably maintained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a direct injection gasoline engine and a schematic configuration diagram showing a control device thereof.
FIG. 2 is a flowchart showing a control routine of fuel injection control according to the present invention.
FIG. 3 is a graph showing the relationship between cooling water temperature Tw and fuel split ratio γ.
FIG. 4 is a graph showing the relationship between cooling water temperature Tw and injection interval Int.
5 is a diagram showing a change in the state of fuel in the combustion chamber, and is a diagram showing an execution result of the flowchart of FIG. 3. FIG.
[Explanation of symbols]
1 engine (internal combustion engine)
4 Fuel Injection Valve 5 Combustion Chamber 6 Cylinder 7 Piston 13 Intake Port 16 Water Temperature Sensor (Temperature Detection Means)
17 Crank angle sensor 50 Fuel supply unit 52 Fuel tank 54 High-pressure fuel pump 70 Electronic control unit (ECU)

Claims (2)

In-cylinder injection spark ignition type internal combustion engine having a fuel injection valve for directly injecting fuel into the combustion chamber and capable of selecting a compression stroke injection mode and an intake stroke injection mode for performing premixed combustion according to the operating state of the internal combustion engine In the engine control device,
Start completion detecting means for detecting a start completion state of the internal combustion engine;
Temperature detecting means for detecting the temperature of the internal combustion engine;
When the start completion state of the internal combustion engine is detected by the start completion detection means and the temperature detected by the temperature detection means is less than a predetermined temperature, the intake stroke injection mode is selected and the fuel is divided into multiple times in the intake stroke. Fuel injection control means for performing drive control of the fuel injection valve so as to inject
A control device for an in-cylinder injection type spark ignition internal combustion engine. The fuel injection control means includes a split ratio setting means for setting a split ratio of the fuel to be divided into a plurality of times according to the temperature of the internal combustion engine, and drive-controls the fuel injection valve based on the split ratio. The control apparatus for a cylinder injection type spark ignition type internal combustion engine according to claim 1, characterized in that:

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