EP0995025B1 - Method for operating an internal combustion engine mainly intended for a motor vehicle - Google Patents

Description

State of the art

The invention relates to a method for operating a Internal combustion engine, in particular of a motor vehicle, at the fuel either in a first mode of operation a compression phase or in a second operating mode directly into a combustion chamber during an intake phase is injected, in which the supplied to the combustion chamber Air mass is determined, and in which in the combustion chamber injected fuel mass in the two operating modes is controlled and / or regulated differently. Of the invention further relates to an internal combustion engine especially for a motor vehicle, with a Injector, with fuel in either one first operating mode during an intake phase or in a second operating mode directly during a compression phase is injectable into a combustion chamber, and with a Control unit for determining the supply to the combustion chamber Air mass and for different control and / or Regulation of the injected into the combustion chamber Fuel mass in the two operating modes, according to the DE-A-197 37 375.

Such systems for the direct injection of fuel in the combustion chamber of an internal combustion engine are general known. It is the first operating mode so-called shift operation and as a second operating mode so-called homogeneous operation. The Shift operation is particularly important for smaller loads used during the homogeneous operation at larger, at the Internal loads applied to the internal combustion engine.

In shift operation, the fuel is used during the Compression phase of the internal combustion engine in the combustion chamber injected in such a way that a Cloud of fuel in the immediate vicinity of a spark plug located. This injection can be different Way. So it is possible that the injected Fuel cloud is already during or immediately after the injection is at the spark plug and from this is ignited. It is also possible that the injected cloud of fuel through a charge movement the spark plug is led and then ignited. at the two combustion processes are not uniform Fuel distribution before, but a stratified charge.

The advantage of shift operation is that there a very small amount of fuel smaller loads carried out by the internal combustion engine can be. However, larger loads cannot the shift operation can be fulfilled.

In homogeneous operation intended for such larger loads the fuel is during the intake phase of the Internal combustion engine injected so that a swirl and thus a distribution of the fuel in the combustion chamber can still be done easily. To that extent corresponds to Homogeneous operation such as the operation of Internal combustion engines in the conventional way Fuel is injected into the intake pipe. If necessary can operate even with smaller loads be used.

In shift operation, the throttle valve becomes the Combustion chamber leading intake pipe wide open and the Combustion is essentially only through the Fuel mass to be injected controlled and / or regulated. In homogeneous operation, the throttle valve is in Dependent on the requested moment opened or closed and the fuel mass to be injected is in Controlled depending on the intake air mass and / or regulated.

In both operating modes, i.e. in shift operation and in Homogeneous operation, the fuel mass to be injected in Dependence on a number of others Input variables on one with regard to Saving fuel, reducing emissions and the like optimal value controlled and / or regulated. The control and / or regulation is in the two operating modes differently.

It is necessary to remove the internal combustion engine from the Shift operation in homogeneous operation and back again switch. The throttle valve is in shift operation is wide open and thus largely dethrones the air is supplied, the throttle valve is only in homogeneous operation partially opened, reducing the intake of Air. Especially when switching from shift operation to homogeneous operation must be the ability of the Combustion chamber leading intake pipe are taken into account, air save. If this is not taken into account, it can Switching to an increase in that of the internal combustion engine given moments.

The object of the invention is a method for operating to create an internal combustion engine with which an optimal Switching between the operating modes is possible.

This task is initiated in a procedure mentioned type or in an internal combustion engine of initially mentioned type solved according to the invention in that depending on the air mass supplied to the combustion chamber between the first mode and the second mode is switched.

The air mass supplied to the combustion chamber provides an accurate one and reliable criterion on the basis of which the Switching process from the first to the second operating mode or from the second to the first operating mode can. Furthermore, the one supplied to the combustion chamber Air mass either from the controller using Model calculations can be determined or it is in the Intake pipe of the internal combustion engine a pressure sensor or Air mass meter to determine the combustion chamber supplied air mass available. Both options are simple and with little design effort feasible.

In an advantageous embodiment of the invention switched from the first to the second operating mode if the air mass supplied to the combustion chamber a maximum Air mass falls below for homogeneous operation. In the Switching from shift operation to homogeneous operation takes the air mass supplied to the combustion chamber. Reaches that Air mass the specified maximum value for the Homogeneous operation, the system switches to homogeneous operation. This transition is thus easy to control and implement.

It when the supply of the Air mass in the combustion chamber before switching to the second Operating mode is reduced. This is due to the previous one Close the throttle valve before actually switching reached.

In an advantageous development of the invention, in the second operating mode, the supplied air / fuel mixture to a given, in particular stoichiometric value controlled and / or regulated. The The fuel / air mixture therefore has a defined one specified value, for example 1. This becomes a particularly low-pollution operation of the internal combustion engine reached.

It is particularly expedient if the one to be injected Fuel mass after switching to the second Operating mode is determined from the supplied air mass. In this way it can be ensured that the predetermined or stoichiometric value of the fuel / air mixture preserved.

Furthermore, it is particularly useful if the Firing angle after switching to the second operating mode is determined from the requested moment. With the help of Firing angles can therefore be particularly short-term Torque changes can be achieved without the given or to change stoichiometric value.

In an advantageous embodiment of the invention switched from the second to the first operating mode if the air mass supplied to the combustion chamber is minimal Air mass for shift operation exceeds. In the Switching from homogeneous to shift operation takes the air mass supplied to the combustion chamber. Reaches that Air mass the specified minimum value for the Shift operation, the system switches to shift operation.

This transition is thus easy to control and implement.

It when the supply of the Air mass in the combustion chamber before switching to the first Operating mode is increased. This is done by opening the Throttle valve reached before switching.

It is particularly expedient if the one to be injected Fuel mass before switching to the first operating mode is increased. Furthermore, it is particularly useful if the ignition angle before switching to the first operating mode is adjusted after late.

Figur 1

zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels einer erfindungsgemäßen Brennkraftmaschine eines Kraftfahrzeugs,

Figur 2

zeigt ein schematisches Ablaufdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens zum Betreiben der Brennkraftmaschine der Figur 1,

Figur 3

zeigt ein schematisches Zeitdiagramm von Signalen der Brennkraftmaschine der Figur 1 bei Durchführung des Verfahrens nach der Figur 2, und

Figur 4

zeigt ein schematisches Zeitdiagramm von Signalen der Brennkraftmaschine der Figur 1 bei Durchführung eines dem Verfahren der Figur 1 entgegengerichteten Verfahrens.

Of particular importance is the implementation of the method according to the invention in the form of a control element which is provided for a control unit of an internal combustion engine, in particular a motor vehicle. A program is stored on the control element, which is executable on a computing device, in particular on a microprocessor, and is suitable for executing the method according to the invention. In this case, the invention is thus implemented by a program stored on the control element, so that this control element provided with the program represents the invention in the same way as the method for the execution of which the program is suitable. In particular, an electrical storage medium, for example a read-only memory, can be used as the control element.

Figure 1

1 shows a schematic block diagram of an exemplary embodiment of an internal combustion engine of a motor vehicle according to the invention,

Figure 2

1 shows a schematic flow diagram of an exemplary embodiment of a method according to the invention for operating the internal combustion engine of FIG. 1,

Figure 3

shows a schematic time diagram of signals of the internal combustion engine of Figure 1 when performing the method of Figure 2, and

Figure 4

shows a schematic time diagram of signals of the internal combustion engine of Figure 1 when performing a method opposite to the method of Figure 1.

1 shows an internal combustion engine 1, in which a piston 2 in a cylinder 3 back and forth is movable. The cylinder 3 has a combustion chamber 4 provided, on the valves 5, an intake pipe 6 and a Exhaust pipe 7 are connected. Furthermore are the Combustion chamber 4 can be controlled with a signal TI Injector 8 and a controllable with a signal ZW Associated with spark plug 9.

The intake pipe 6 is with an air mass sensor 10 and that Exhaust pipe 7 can be provided with a lambda sensor 11. The air mass sensor 10 measures the air mass of the Intake pipe 6 supplied fresh air and generated in Depending on this, a signal LM. The lambda sensor 11 measures the oxygen content of the exhaust gas in the exhaust pipe 7 and generates a signal λ depending on this.

A throttle valve 12 is in the intake pipe 6 housed, whose rotational position by means of a signal DK is adjustable.

In a first operating mode, the shift operation of the Internal combustion engine 1, the throttle valve 12 becomes wide open. The fuel is supplied from the injection valve 8 during one caused by the piston 2 Compression phase injected into the combustion chamber 4 locally in the immediate vicinity of the spark plug 9 and at a suitable distance before the ignition point. Then the fuel is ignited using the spark plug 9, so that the piston 2 in the now following working phase by the expansion of the ignited fuel is driven.

In a second operating mode, the homogeneous operation of the Internal combustion engine 1, the throttle valve 12 in Dependence on the desired air mass supplied partially opened or closed. The fuel will from the injector 8 during one through the piston 2 induced suction phase in the combustion chamber 4 injected. The air sucked in at the same time the injected fuel swirls and thus in the Combustion chamber 4 is distributed substantially uniformly. After that the fuel / air mixture during the Compression phase compressed to then from the spark plug 9 to be ignited. By the expansion of the inflamed The piston 2 is driven by fuel.

In shift operation as well as in homogeneous operation, the driven pistons a crankshaft 14 in a Rotational movement over which ultimately the wheels of the Motor vehicle are driven. The crankshaft 14 is assigned a speed sensor 15 which is a function of the rotational movement of the crankshaft 14 generates a signal N.

The in the shift operation and in the homogeneous operation of the Injection valve 8 injected into the combustion chamber 4 Fuel mass is in particular from a control unit 16 with a view to low fuel consumption and / or controlled low pollutant development and / or regulated. For this purpose, the control unit 16 is equipped with a Microprocessor provided in a storage medium, a program in particular in a read-only memory has saved, which is suitable for the named Control and / or regulation to perform.

The control unit 16 is acted upon by input signals, the operating variables measured by sensors Represent internal combustion engine. For example, that is Control unit 16 with the air mass sensor 10, the lambda sensor 11 and the speed sensor 15 connected. Furthermore is the control unit 16 with an accelerator pedal sensor 17 connected, which generates a signal FP, the position indicates an accelerator pedal which can be actuated by a driver. The Control unit 16 generates output signals with which over Actuators the behavior of the internal combustion engine accordingly the desired control and / or regulation influenced can be. For example, the control unit 16 with the Injector 8, the spark plug 9 and the throttle valve 12 connected and generates the for their control required signals TI, ZW and DK.

The control unit 16 subsequently uses the Figures 2 and 3 described method for switching from carried out a shift operation in a homogeneous operation. The blocks shown in FIG. 2 represent Functions of the method, for example in the Form of software modules or the like in the Control device 16 are realized.

In FIG. 2, it is assumed in a block 21 that that the internal combustion engine 1 in a stationary Shift operation is located. Then in a block 22 for example, based on a driver's request Acceleration of the motor vehicle a transition into one Homogeneous operation requested. The time of the request of the homogeneous operation can also be seen from FIG. 3.

This is followed by debouncing using blocks 23, 24, with the a short successive switching back and forth prevented between stratified and homogeneous operation becomes. If homogeneous operation is enabled, then the transition from shift operation to homogeneous operation started by a block 25. The time when the Switching process begins, is in Figure 3 with the Reference numeral 40 marked.

At the aforementioned time 40, the throttle valve 12 by means of a block 26 from it in shift operation fully opened wdksch in at least one partially open or closed state wdkhom for controlled homogeneous operation. The rotational position of the Throttle valve 12 in homogeneous operation is on stoichiometric fuel / air mixture, i.e. to λ = 1 aligned and also depends on e.g. the requested torque and / or the speed N of the Internal combustion engine 1 and the like.

By adjusting the throttle valve 12 is the Internal combustion engine 1 from the stationary stratified operation in unsteady shift operation. In this Operating state drops the supplied to the combustion chamber 4 Air mass from a filling rlsch during the Shift work slowly towards smaller fillings. This can be seen from Figure 3. The combustion chamber 4 supplied air mass rl or its filling is from the control unit 16, inter alia, from the signal LM of the Air mass sensor 10 determined. According to a block 27 the internal combustion engine 1 continues to operate in shifts operated.

In a block 28 of Figure 2 it is checked whether the Combustion chamber 4 supplied air mass a certain value has reached, namely whether the filling rl has become smaller is as a maximum air mass or a maximum filling for homogeneous operation rlmaxhom. So it is checked whether rl <rlmaxhom is. The filling rlmaxhom is such predetermined that that is delivered by the internal combustion engine 1 Moment at λ = 1 remains approximately constant.

If rl <rlmaxhom is not fulfilled, it is looped waited further via block 26. However, if this is the case Case, what in Figure 3 in one with the reference numeral 41 marked time is given in this Time from the unsteady shift operation in one non-stationary homogeneous operation switched. According to the figure 2, the switching is done by means of a block 29 carried out. The fuel / air mixture will continue at λ = 1 kept.

According to a block 30, the in the Combustion chamber 4 injected fuel mass rk in Dependence on the air mass supplied to the combustion chamber 4 rl controlled and / or regulated so that a stoichiometric fuel / air mixture occurs that so λ = 1.

The fuel mass rk influenced in this way has Consequence that - at least for a certain period of time - the torque Md output by the internal combustion engine 1 would increase. This is compensated for by the fact that Event 41, i.e. with the switchover to Homogeneous operation, the ignition angle ZW, based on the value is adjusted so that the torque Md maintains the value mdsoll and thus remains approximately constant.

This is achieved in FIG. 2 via a block 30. There the fuel mass rk from the combustion chamber 4th supplied air mass rl on the basis of a stoichiometric fuel / air mixture determined. Of further the ignition angle ZW is dependent on the The moment to be released must be towards a late ignition adjusted. With regard to this late adjustment lies thus a certain deviation from the normal Homogeneous operation, with which temporarily too much supplied air mass and the resulting too much generated torque of the internal combustion engine 1 is destroyed.

A block 31 checks whether the combustion chamber 4 supplied air mass rl finally to that filling which has fallen to a stationary homogeneous operation belongs to a stoichiometric fuel / air mixture. is if this is not yet the case, it will loop over waiting for block 30 further. However, if this is the case, so the internal combustion engine 1 in the stationary Homogeneous operation without an ignition angle adjustment using the Blocks 32 continued to operate. In Figure 3, this is in one the point in time marked with the reference number 42 Case.

This corresponds to that in this stationary homogeneous operation Combustion chamber 4 supplied air mass of the filling rlhom for the Homogeneous operation and the ignition angle zwhom for the spark plug 9 also corresponds to that for homogeneous operation. The same applies to the rotary position wdkhom Throttle valve 12.

FIG. 4 shows a switchover from homogeneous operation represented in a shift operation. It is from one stationary homogeneous operation in which for example, due to the size of the company Internal combustion engine 1 in a stationary shift operation should be transferred.

The switch to shift operation is carried out by the Control unit 16 initiated by the requirement of Homogeneous operation is withdrawn. After a debouncing the switch to shift operation is released and it turns the throttle valve 12 into that rotational position controlled, which is intended for shift operation. there it is a rotary position in which the Throttle valve 12 is largely open. This is through the transition from wdkhom to wdksch in FIG. 4 shown.

The opening of the throttle valve 12 has the consequence that the Combustion chamber 4 supplied air mass rl increases. This goes in 4 from the course of rlhom. exceeds the air mass rl a minimum value for the Shift operation rlminsch, so the switchover from Homogeneous operation in shift operation. This is in the figure 4 the case at time 43.

Before switching to shift operation, the increasing air mass supplied to the combustion chamber 4 compensates that the injected fuel mass rk increased and the ignition angle ZW is retarded. This results from the course of rkhom and zwhom.

After switching to shift operation, the injected fuel mass rk to the value rksch for the Shift operation set. The same applies to the Ignition angle ZW, which is between the values for the Shift operation is set.

Claims (13)

1. Method for operating an internal combustion engine (1), in particular of a motor vehicle, in which fuel is injected directly into a combustion chamber (4), either, in a first operating mode, during a compression phase or, in a second operating mode, during an induction phase, in which the air mass (rl) supplied to the combustion chamber (4) is determined, and in which the mass of fuel injected into the combustion chamber (4) is controlled differently in the two operating modes, characterized in that the engine is switched (41, 43) between the first operating mode and the second operating mode as a function of the air mass (rl) supplied to the combustion chamber (4).
2. Method according to Claim 1, characterized in that the engine is switched (41) from the first operating mode to the second operating mode when the air mass (rl) supplied to the combustion chamber (4) drops below (28) a maximum air mass for homogeneous operation (rlmaxhom).
3. Method according to Claim 2, characterized in that the supply of the air mass (rl) into the combustion chamber (4) is reduced (26) before the engine is switched (41) to the second operating mode.
4. Method according to one of Claims 1 to 3, characterized in that in the second operating mode the fuel/air mixture supplied is controlled to a predetermined, in particular stoichiometric value (λ = 1).
5. Method according to Claim 4, characterized in that the fuel mass (rk) to be injected is determined (30) from the air mass (rl) supplied after the engine has been switched (41) to the second operating mode.
6. Method according to one of Claims 4 or 5, characterized in that the ignition angle (ZW) is determined (30) from the demanded torque (mdsoll) after the engine has been switched (41) to the second operating mode.
7. Method according to Claim 6, characterized in that the ignition angle (ZW) is shifted to a late position.
8. Method according to one of the preceding claims, characterized in that the engine is switched (43) from the second operating mode to the first operating mode when the air mass (rl) supplied to the combustion chamber (4) exceeds a minimum air mass for stratified operation (rlminsch).
9. Method according to Claim 8, characterized in that the supply of the air mass (rl) to the combustion chamber (4) is increased before the engine is switched (43) to the first operating mode.
10. Method according to one of Claims 8 or 9, characterized in that the fuel mass (rk) to be injected is increased before the engine is switched (43) to the first operating mode.
11. Method according to one of Claims 8 to 10, characterized in that the ignition angle (ZW) is adjusted to a late position before the engine is switched (43) to the first operating mode.
12. Control element, in particular read only memory, for implementation in a method according to one of Claims 1 to 11, for use in a control unit (16) of an internal combustion engine (1), in particular of a motor vehicle, at which a program which can run on a computer, in particular on a microprocessor, is stored.
13. Internal combustion engine (1) in particular for a motor vehicle, having an injection valve (8), by means of which fuel can be injected directly into a combustion chamber (4) either, in a first operating mode, during a compression phase or, in a second operating mode, during an induction phase, and having a control unit (16) for determining the air mass (rl) supplied to the combustion chamber (4) and for differently controlling the mass of fuel injected into the combustion chamber (4) in the two operating modes, characterized in that the control unit (16) is used to switch (41, 43) the engine between the first operating mode and the second operating mode as a function of the air mass (rl) supplied to the combustion chamber (4).

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