EP1046803B1 - Method for the operation of an internal-combustion engine - Google Patents

Description

State of the art

The invention relates to a method for operating an internal combustion engine, in particular a motor vehicle, in which a fuel mass is injected in a first mode during a compression phase and in a second mode during a suction directly into a combustion chamber in which the injected fuel mass from a spark plug at a firing angle is ignited, and in which the fuel mass and the ignition angle as a function of an enterable via an accelerator pedal driver request and as a function of the speed of the internal combustion engine are controlled and / or regulated. Also, the invention relates to an associated compuzerprogramm, a corresponding control device and an internal combustion engine, in particular for a motor vehicle.

Such a method and such an internal combustion engine are known for example from a so-called gasoline direct injection in motor vehicles. There, fuel is injected in a homogeneous operation during the intake phase or in a shift operation during the compression phase in the combustion chamber of the internal combustion engine. The homogeneous operation is preferably provided for the full-load operation of the internal combustion engine, while the stratified operation is suitable for idling and part-load operation. For example, depending on the driver's request, the fuel mass and the ignition angle is influenced by the control unit in such a direct-injection internal combustion engine.

From DE 44 00 260 A1 a so-called intake manifold injection for an internal combustion engine is known. There, the speed of the internal combustion engine is influenced by means of an adjustment of the ignition angle.

Due to hardware and / or software errors, there is the possibility that the fuel mass and / or the ignition angle are erroneously controlled and / or regulated by the control unit, so that the internal combustion engine emits a torque that is greater than the torque requested by the driver. This can lead to an undesirable acceleration of the motor vehicle just when the driver has taken his foot off the accelerator pedal and thus desires no further acceleration.

The object of the invention is to provide a method for operating an internal combustion engine, with which the generation of an undesirable torque is avoided.

This object is achieved according to the invention in a method of the type mentioned by the features of the characterizing part of claim 1. In a computer program, a control unit and an internal combustion engine of the type mentioned, the object is achieved according to the invention.

Due to the retardation of the ignition angle, fuel that has erroneously entered the combustion chamber of the internal combustion engine is burned on the one hand. On the other hand, however, the combustion is such that it provides substantially no contribution to moment generation. Despite the existing too much fuel is thus no unwanted acceleration of the motor vehicle. Due to the retardation of the ignition angle, the fuel resulting from the excess fuel is destroyed.

In an advantageous development of the invention, no fuel mass is injected at the driver's request, which is smaller than the predetermined threshold, and at the rotational speed which exceeds the predetermined threshold in the direction of greater values. The possibility that too much fuel due to a malfunction of the controller is present, thereby reduced or even avoided.

In a further advantageous embodiment of the invention, no fuel mass is injected more first, and then the ignition angle is retarded. In this case, the ignition angle is adjusted so late that no more torque is emitted by the internal combustion engine. This represents a particularly simple and nevertheless effective procedure for avoiding unwanted acceleration of the motor vehicle.

In an advantageous embodiment of the invention, an error is detected when at a driver's request that is smaller than the predetermined threshold, and at a speed that exceeds the predetermined threshold towards greater values, the firing angle is not retarded afterwards. It is therefore monitored whether under the specified conditions, the retardation of the ignition angle is performed. If this is not the case, then a software error is concluded. In this case, it is particularly advantageous if the control and / or regulation of the fuel mass and the ignition angle is restarted.

Of particular importance is the realization of the method according to the invention in the form of a computer program which is provided for a control unit of an internal combustion engine, in particular of a motor vehicle. In this case, the computer program is on a computing device, in particular on a microprocessor, executable and suitable for carrying out the method according to the invention. The computer program can be stored on an electrical storage medium, for example on a read-only memory.

Figur 1

zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels einer erfindungsgemäßen Brennkraftmaschine,

Figur 2

zeigt vier schematische Zeitdiagramme eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens zum Betreiben der Brennkraftmaschine der Figur 1, und

Figur 3

zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels des Verfahrens der Figur 2.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing.

FIG. 1

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

FIG. 2

shows four schematic timing diagrams of an embodiment of a method according to the invention for operating the internal combustion engine of Figure 1, and

FIG. 3

shows a schematic block diagram of an embodiment of the method of Figure 2.

1 shows an internal combustion engine 1 of a motor vehicle is shown, in which a piston 2 in a cylinder 3 back and forth. The cylinder 3 is provided with a combustion chamber 4, which is limited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the intake valve 5 is an intake pipe 7 and with the exhaust valve 6, an exhaust pipe 8 is coupled.

In the region of the intake valve 5 and the exhaust valve 6, an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4. Fuel can be injected into the combustion chamber 4 via the injection valve 9. With the spark plug 10, the fuel in the combustion chamber 4 can be ignited.

In the intake pipe 7, a rotatable throttle valve 11 is housed, via which the intake pipe 7 air can be supplied. The amount of air supplied is dependent on the angular position of the throttle valve 11. In the exhaust pipe 8, a catalyst 12 is housed, which serves to purify the exhaust gases resulting from the combustion of the fuel.

From the exhaust pipe 8, an exhaust gas recirculation pipe 13 leads back to the intake pipe 7. In the exhaust gas recirculation pipe 13, an exhaust gas recirculation valve 14 is housed, with which the amount of recirculated into the intake pipe 7 exhaust gas can be adjusted.

From a fuel tank 15, a tank vent line 16 leads to the intake pipe 7. In the tank vent line 16, a tank vent valve 17 is housed, with which the amount of fuel vapor supplied to the intake pipe 7 from the fuel tank 15 is adjustable.

The piston 2 is set by the combustion of the fuel in the combustion chamber 4 in a reciprocating motion, which is transmitted to a non-illustrated crankshaft and exerts on this torque.

A control unit 18 is acted upon by input signals 19, which represent operating variables of the internal combustion engine 1 measured by means of sensors. For example, the controller 18 is connected to an air mass sensor, a lambda sensor, a speed sensor, and the like. Furthermore, the control unit 18 is connected to an accelerator pedal sensor which generates a signal indicative of the position of an accelerator pedal which can be actuated by a driver and thus the driver's request or its requested torque. The control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the controller 18 is connected to the injection valve 9, the spark plug 10 and the throttle valve 11 and the like, and generates the signals required for driving them.

Among other things, the control unit 18 is provided to control the operating variables of the internal combustion engine 1 and / or to regulate. For example, the fuel mass injected by the injection valve 9 into the combustion chamber 4 is controlled and / or regulated by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant development. To For this purpose, the control unit 18 is provided with a microprocessor which has stored in a storage medium, in particular in a read-only memory, a program which is suitable for carrying out said control and / or regulation.

In a first operating mode, a so-called homogeneous operation of the internal combustion engine 1, the throttle valve 11 is partially opened or closed depending on the desired torque. The fuel is injected from the injection valve 9 during a suction phase caused by the piston 2 into the combustion chamber 4. By simultaneously sucked through the throttle valve 11 air, the injected fuel is swirled and thus distributed in the combustion chamber 4 substantially uniformly. Thereafter, the fuel-air mixture is compressed during the compression phase to be ignited by the spark plug 10. Due to the expansion of the ignited fuel, the piston 2 is driven. The resulting torque depends in homogeneous operation, inter alia, on the position of the throttle valve 11. With a view to low pollutant development, the fuel / air mixture is adjusted as far as possible to lambda = 1.

In a second operating mode, a so-called homogeneous lean operation of the internal combustion engine 1, the fuel is injected into the combustion chamber 4 as in the homogeneous operation during the intake phase. In contrast to the homogeneous operation, however, the fuel / air mixture can also occur with lambda> 1.

In a third operating mode, a so-called shift operation of the internal combustion engine 1, the throttle valve 11 is opened wide. The fuel is supplied from the injection valve 9 during a through the piston. 2 caused compression phase injected into the combustion chamber 4, locally in the immediate vicinity of the spark plug 10 and at a suitable time before the ignition timing. Then, the fuel is ignited by means of the spark plug 10, so that the piston 2 is driven in the now following working phase by the expansion of the ignited fuel. The resulting torque largely depends on the injected fuel mass during shift operation. Essentially, the stratified operation is provided for the idling operation and the partial load operation of the internal combustion engine 1.

FIG. 2 shows in the first time diagram a profile of the accelerator pedal position fp, which drops from an approximately constant value to a minimum value. This course occurs, for example, when a driver takes his foot off the accelerator pedal and thus signals that the engine 1 no more moment should be delivered. The driver's request is therefore "zero".

The course of the accelerator pedal signal fp has the consequence that a fuel mass mk plotted in the second time diagram also drops to a low value. This low fuel mass is on the one hand sufficient to apply the required for the operation of the internal combustion engine 1 and possibly for the operation of consumers of the motor vehicle, "inner" moment. On the other hand, this fuel mass is dimensioned such that the internal combustion engine 1 no moment "out", ie in particular emits to the wheels of the motor vehicle. The motor vehicle is thus not accelerated by the internal combustion engine 1. Also, the internal combustion engine 1 is operated at no high speed more.

A speed n of the internal combustion engine 1 plotted in the third time diagram likewise falls to low values from. Usually, the speed n drops approximately to the idling speed, which is selected such that the internal combustion engine 1 can apply the said "internal" moment just.

At a time t1, the accelerator pedal position fp falls below a threshold value fp1, which is slightly greater than the minimum value of the accelerator pedal position fp. It can be seen that the accelerator pedal has reached its minimum position and the driver's request is "zero". At a time t2, the speed n falls below a threshold value n1, which is slightly larger than the idle speed. It can be seen that the internal combustion engine 1 has now reached its idle speed substantially.

It is assumed that a fault occurs at a time ts. As can be seen from the second timing diagram of FIG. 2, the disturbance has the consequence that more fuel mass mk enters the combustion chamber 4 of the internal combustion engine 1.

The fault may be a hardware or software fault of the controller 18 that results in an incorrect increase in fuel mass mk. It is also possible that at least one of the injectors 9 is dirty or defective, so that more fuel is injected in this way. It is also possible that over the tank vent, for example, due to a not completely closing tank vent valve 17, too much fuel enters the combustion chamber 4. Without further ado, other possibilities are also conceivable which lead to an undesirable increase in the fuel mass mk, as shown in the second timing diagram of FIG. 2 after time ts.

The increase in the fuel mass mk after the time ts leads to an increase in the speed n of the internal combustion engine according to the third timing diagram of Figure 2. This speed increase also leads to an increase of the torque generated by the internal combustion engine 1. This has the consequence that the internal combustion engine 1 also outputs a moment "outwards" and thus accelerates the motor vehicle. Such, issued by the internal combustion engine 1 to the wheels of the motor vehicle torque is in contrast to the driver's request "zero" corresponding to the accelerator pedal position fp.

According to the third timing diagram, the rotational speed n at a time t3 exceeds the threshold n1 toward larger values. This is detected by the controller 18. It is now the conditions are met that the accelerator pedal position fp is smaller than the threshold fp1, and that the speed n is greater than the threshold n1.

Due to the fulfillment of the aforementioned conditions, the control unit 18 first switches off the injection immediately after the time t3. Thus, there is no more injection of fuel into the combustion chambers 4 of the internal combustion engine 1. This is shown in the second timing diagram of Figure 2, in which the fuel mass mk is reduced to zero after the time t3.

Furthermore, after the fulfillment of the aforementioned conditions, either approximately simultaneously or in particular after switching off the injection, in addition the ignition angle zw for the ignition of the fuel is retarded. This is shown in the fourth timing diagram of Figure 2, in which shortly after the time t3, the ignition angle zw is set to a very late value. The ignition angle values before time t3 are not important and therefore not shown.

Even if, after the time t3, fuel still undesirably passes into the combustion chamber 4 of the internal combustion engine 1 via a defective injection valve 9 or via the tank ventilation valve 17, this fuel is ignited and burnt with the ignition angle retarded. Due to the late ignition angle zw, however, essentially no torque is generated by the internal combustion engine 1 as a result of these burns. This has the consequence that, in particular due to the late ignition angle zw no increase in the speed n takes place or the speed n is reduced again. This is shown in the third time diagram after time t3.

Due to the falling speed and in turn, in particular due to the late ignition angle zw, no additional torque is generated by the internal combustion engine 1, so that no torque is emitted "to the outside". An acceleration of the motor vehicle is thus omitted. This corresponds to the driver's request "zero" according to the first timing diagram.

In the figure 3, the internal combustion engine 1 with the throttle valve 11, the injection valve 9 and the spark plug 10 is shown again schematically. Also shown is a block 21, which is intended to represent a preselected by a driver on the accelerator pedal driver's request, and a block 22, which should represent the speed of the internal combustion engine 1.

With a block 23 controls and / or controls the control unit 18, the throttle valve 11, the injection valve 9 and the spark plug 10 in the manner described with reference to FIG 2.

A block 24 is used to monitor the said control and / or regulation. For the purpose of this monitoring, the control unit 18 checks again and again whether a driver request is present, which is smaller than the predetermined threshold fp1, and whether at the same time there is a speed which is greater than the predetermined threshold n1. If this is the case, then the control unit continues to check whether the ignition angle is subsequently retarded. If this is the case, then there is no error and the control and / or regulation continues unchanged. However, if this is not the case, that is, the ignition angle is not delayed despite the fulfillment of the conditions mentioned, it is concluded that there is an error.

In this case, the procedure continues with a block 25 containing an error routine. In it the driver can be made aware of the error or other fault-indicating measures can be taken. It is also possible to restart the control unit 18, ie to perform a "reset" of the control unit 18. Thereafter, the control and / or regulation of the internal combustion engine 1 is restarted or reinitialized, so that any existing software error may no longer be present.

Claims (10)

1. Method for operating an internal combustion engine (1) in particular of a motor vehicle, in which method a mass of fuel (mk) is sprayed directly into a combustion chamber (4) during a compression phase in a first operating mode and during an induction phase in a second operating mode, in which method the injected mass of fuel (mk) is ignited by a spark plug (10) at an ignition angle (zw), and in which method the mass of fuel (mk) and the ignition angle (zw) are controlled in an open-loop and/or closed-loop fashion as a function of a driver demand (fp), which can be input by means of an accelerator pedal, and as a function of the speed (n) of the internal combustion engine (1), characterized in that the ignition angle (zw) is adjusted in the retarded direction in the event of a driver demand (fp) being smaller than a predefined threshold (fp1), and if it is determined that the speed (n) crosses a predefined threshold (n1) initially in the direction of relatively small values and subsequently in the direction of relatively large values, wherein the predefined threshold (n1) for the speed (n) is greater than an idle speed of the internal combustion engine (1).
2. Method according to Claim 1, characterized in that, when the driver demand (fp) is smaller than the predefined threshold (fp1) and when the speed (n) crosses the predefined threshold (n1) in the direction of relatively large values, no more mass of fuel (mk) is injected thereafter.
3. Method according to Claim 2, characterized in that no more mass of fuel (mk) is injected initially, and in that the ignition angle (zw) is then adjusted in the retarded direction.
4. Method according to one of Claims 1 to 3, characterized in that the ignition angle (zw) is adjusted in the retarded direction in such a way that torque is no longer output by the internal combustion engine (1).
5. Method according to one of Claims 1 to 4, characterized in that a fault is detected (25) if, when a driver demand (fp) is smaller than the predefined threshold (fp1) and when a speed (n) crosses the predefined threshold (n1) in the direction of relatively large values, the ignition angle (zw) is not adjusted in the retarded direction thereafter.
6. Method according to Claim 5, characterized in that the open-loop and/or closed-loop control of the mass of fuel (mk) and of the ignition angle (zw) is started again.
7. Computer program for a control unit (18), characterized in that it is programmed for use in a method according to one of Claims 1 to 6.
8. Computer program according to Claim 7,
   characterized in that it is stored on an electric storage medium.
9. Control unit (18) for an internal combustion engine (1), characterized in that it is set up for use in a method according to one of Claims 1 to 6.
10. Internal combustion engine (1) in particular for a motor vehicle, having a control unit (18), characterized in that the control unit (18) is set up for use in a method according to one of Claims 1 to 6.

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