WO2004022958A1

WO2004022958A1 - Method for operating an internal combustion engine

Info

Publication number: WO2004022958A1
Application number: PCT/DE2003/002230
Authority: WO
Inventors: Markus Amler; Thomas Wenzler; Thomas Frenz
Original assignee: Robert Bosch Gmbh
Priority date: 2002-08-31
Filing date: 2003-07-03
Publication date: 2004-03-18
Also published as: EP1537319A1; DE10240311A1; JP2005537430A

Abstract

The invention relates to a method for operating an internal combustion engine, whereby an interruption angle for a fuel injection into a combustion chamber of an internal combustion engine, in particular, in a motor vehicle is determined. The latest interruption angle corresponds to the crankshaft angle at which the pressure in the combustion chamber exceeds the pressure on the other side of an injection valve for the injection of fuel into the combustion chamber, in particular in a supply line. The combustion chamber pressure during the inlet stroke is set equal to the pressure in the inlet manifold and the pressure during the compression stroke is determined from the inlet manifold pressure by means of the compression ratio, the combustion chamber pressure is compared with the pressure on the other side of the injection valve and a differential pressure is determined. When a fixed differential pressure is achieved the injection is interrupted, whereby for known inlet manifold pressures and a known pressure on the other side of the injection valve a crankshaft angle is determined as the interruption angle, which represents the latest interruption of the injection.

Description

Method for operating a pulp engine

State of the art

The invention relates to a method for operating an internal combustion engine, in particular a motor vehicle, in which a termination angle of a fuel injection into a combustion chamber of an internal combustion engine is determined, the termination angle corresponding at the latest to the crank angle at which the pressure in the combustion chamber corresponds to the pressure on the other side of an injection valve for injecting fuel into the combustion chamber, in particular in the rail. The invention also relates to a computer program for carrying out the method, as well as a control device for the control and regulation of an internal combustion engine, and a

Internal combustion engine itself, in particular for a motor vehicle, with a combustion chamber in the

Fuel can be injected, the injection being controllable and / or regulatable via a control unit.

Such a method and such an internal combustion engine are known, for example, from a so-called gasoline direct injection in motor vehicles. There is fuel in one

Homogeneous operation is injected into the brake chamber of the internal combustion engine during the intake phase or in a stratified operation during the ner seal phase. Homogeneous operation is preferably provided for full-load operation of the internal combustion engine, while stratified operation is suitable for idle or part-load operation. For example, depending on the requested torque, such a direct-injection internal combustion engine switches between the aforementioned operating modes.

In engines with gasoline direct injection, fuel is injected directly into the combustion chamber. Fuel with high pressure is normally available because a high-pressure pump generates this upstream of the high-pressure injectors (injectors), so that there is a pressure drop in the direction of the combustion chamber above the injectors. However, in certain operating states must be expected that the pressure of the fuel in the pressure accumulator is lower than the pressure in the combustion chamber.

In particular in the starting phase, in which the high-pressure pump has not yet built up sufficient pressure, the fuel is present in particular in a rail or generally in a fuel feed line with a pressure level that corresponds to the pressure level of the electric fuel pump. The internal combustion engine is started in homogeneous operation. In particular during a cold start, it is possible that, due to the still low pressure acting on the fuel, a relatively long injection period is required in order to inject the desired fuel mass into the combustion chamber and to start the internal combustion engine reliably. This can lead to the fact that the injection lasts so long that the internal combustion engine already changes from the intake phase to the compression phase during the injection and that the pressure that then arises in the combustion chamber becomes greater than the pressure acting on the fuel in the supply line. In the combustion chamber, the pressure rises in the compression cycle with increasing piston stroke. With long injection times it can then happen that fuel and gas are blown back into the rail from the combustion chamber, which must be avoided in any case.

There are also diagnostic functions that require lowering the pressure to the level of the electric fuel pump. And also in shift operation, in which fuel is injected during the compression stroke, operating states can occur in which the combustion chamber pressure exceeds the fuel pressure in the rail or the feed line upstream of the injection valve.

To prevent gas being blown back into the rail, a map has so far been available which only specifies a termination angle for the injection depending on the rail pressure present.

The corresponding map for the injection termination must be determined by individual measurements according to the prior art.

For example, it is known from DE 199 13 407 AI to provide a method for operating an internal combustion engine and an internal combustion engine itself, which is operated in particular in two operating modes, in which fuel is injected into a combustion chamber, the

Injection has an injection start angle and an injection duration, an injection end angle being determined from the injection start angle and the injection duration and a check being carried out to determine whether an injection termination angle is exceeded by the injection end angle. If this is the case, then the injection start angle is shifted to "early". The object of the invention is to provide a method for operating an internal combustion engine, with which the optimum stopping angle can be described in all operating points and, moreover, the data determination is considerably simplified. This should ensure an improved utilization of the time window available for the injection.

This object is achieved according to the invention in a method of the type mentioned at the outset in that the combustion chamber pressure in the intake stroke is set equal to the intake manifold pressure and in the compression stroke is determined via the compression depending on the intake manifold pressure and the combustion chamber pressure is compared with the pressure on the other side of the injection valve and a differential pressure is determined and the injection is stopped when a defined differential pressure is reached, with a known intake manifold pressure and a known pressure on the other side of the injection valve determining a crank angle as a termination angle at which the injection is stopped at the latest. By means of the proposed method, the break angle is determined relatively and with additional consideration of the intake manifold pressure, whereby a much more precise break angle can be determined. From the determination of the combustion chamber pressure and the formation of the differential pressure across the injection valve, the crank angle required to terminate the injection can ultimately be calculated. If the differential pressure is too low, the injection is stopped. In the compression stroke, the combustion chamber pressure is determined in particular via the adiabatic compression as a function of the intake manifold pressure, whereas the combustion chamber pressure is equated to the intake manifold pressure in the intake cycle. In this way, the

Stop angle determined more precisely and thus the available injection window can be better used. As a result, the desired fuel mass can be injected and fuel blowing back can nevertheless be reliably prevented. The invention

The procedure can be used for all operating conditions of the internal combustion engine and also for a cold start. This ensures that the internal combustion engine is started safely under all conditions. It should be noted that an associated time is assigned to each of the angles mentioned above and also to each of the angles described below. All angles can therefore be replaced by corresponding times or periods. The conversion depends on the speed of the internal combustion engine. It can be provided that in the method the in particular adiabatic compression in the combustion chamber is determined via specific engine data and the current crank angle. The specific engine data can be determined in advance or specified by the manufacturer. If the equation of determination is then resolved according to the crank angle, a crank angle results up to the given intake manifold pressure and given rail pressure, up to which there is a pressure drop in the direction of the combustion chamber. A theoretical termination angle at ambient pressure can e.g. B. at an intake manifold pressure equal to ambient pressure and a current rail pressure can be determined using the equation for adiabatic conditions. Multiplying by the real intake manifold pressure results in the actually required break-off angle. The calculation can be done by specifying the values for the adiabatic compression

Ambient pressure in a characteristic curve and subsequent multiplication of the angle with the intake manifold pressure can be simplified.

It can further be provided that the fuel injection is stopped at a crank angle that is a safety angle before the stop angle is reached.

In this case, the difference in pressures is set differently in order to achieve an earlier termination angle and thus further increase the certainty that no fuel is blown back into the rail. In particular, it can be provided that the method is used during a first operating mode in which the injection process begins during the suction cycle, that is to say in particular in homogeneous operation. In this first operating mode of the internal combustion engine, the throttle valve is partially opened or closed depending on the desired torque. The fuel is injected into the combustion chamber by the injection valve during an induction phase caused by the piston. The air that is simultaneously sucked in via the throttle valve swirls the injected fuel and thus distributes it substantially uniformly in the combustion chamber. The fuel / air mixture is then compressed during the compression phase in order to then be ignited by the spark plug. The piston is driven by the expansion of the ignited fuel. In homogeneous operation, the resulting torque essentially depends on the position of the throttle valve. In view of a low pollutant development, the fuel / air mixture is set at λ = 1 or λ <1 if possible.

In another operating mode, a so-called homogeneous lean operation of the internal combustion engine, the fuel is, as in homogeneous operation, during the intake phase in the Injected brake room. In contrast to homogeneous operation, the fuel / air mixture can also occur with λ> 1.

Furthermore, a third operating mode is known, the so-called stratified operation of the internal combustion engine, in which the throttle valve is opened wide. The fuel is injected from the injection valve into the combustion chamber during a compression phase caused by the piston, locally in the immediate vicinity of the spark plug, and at a suitable time from the ignition point. Then the fuel is ignited with the aid of the spark plug, so that the piston is driven in the now following working phase by the expansion of the ignited fuel. The resulting torque largely depends on the amount of fuel injected in shift operation. The stratified operation is essentially intended for the idle operation and the partial load operation of the slurry engine. If necessary, other operating modes are also conceivable. It is possible to switch back and forth between the described operating modes of the internal combustion engine. The homogeneous operation described above, in which the application of the invention is particularly advantageous, is present in particular in the starting phase.

It is also particularly advantageous if the invention is applied at a pressure acting on the fuel that is less than a limit pressure.

It can also be provided that it is then possible to change the start of the injection angle, the injection angle being able to be changed, in particular after “early”, if it is determined that the

Injection end angle would exceed the stopping angle. It can thus be achieved that, in particular, a change in the injection angle is possible if the pressure acting on the fuel is small, for example less than a limit pressure, and thus an interruption, possibly too little fuel, would be present for reliable operation of the internal combustion engine - de. When the pressure acting on the fuel is high, the injection times are so short that it is usually no longer necessary to stop.

In this case, it can be provided that the entire calculations are no longer carried out in order to save computing time.

The application when starting the internal combustion engine is particularly advantageous, since the pressure on the fuel is low, in particular when starting, in particular during a cold start, and in particular corresponds to the pressure in the electric fuel pump. At the same time, a large amount of fuel must be injected into the combustion chamber in order to ensure that the internal combustion engine starts reliably. An interruption of the injection could therefore cause the internal combustion engine to die when starting. That is why it is special advantageous to prevent a termination of the injection when starting the internal combustion engine. This can be largely achieved by using the injection time window in a particularly optimal manner, as is possible with the invention. In addition, it can be provided that a change in the injection start angle is also provided here, whereby it can be further improved that the intended fuel mass is also completely in the

Combustion chamber is injected. A blow back of fuel is prevented on the other hand. The invention further relates to a computer program for performing the method described above when it is executed on a computer. In particular, the computer program can be stored on a memory.

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. In this case, a program is stored on the control device that can be run on a microprocessor, in particular on a computer, 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 device, so that this control device 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 can be used as the storage medium, for example a read-only memory or a flash memory. The control device for controlling and regulating is used in particular to ensure the switching or switching back and forth between the operating states of the internal combustion engine. Finally, the invention relates to an internal combustion engine, in particular for a Kraftfal rzeug with a combustion chamber, in which fuel can be injected with a fuel injection device, via which the fuel enters the combustion chamber, the injection being controlled and / or regulated by a control unit and by the Control device can be determined whether a break angle at

Injection is run through and the injection is to be stopped.

In particular, the internal combustion engine can include a control device for regulating or controlling in the manner described above. Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments which are shown in the figure of the drawing. All of the features described or illustrated, individually or in any combination, form the subject matter of the invention regardless of their summary in the patent claims or their relationship and regardless of their wording or representation in the description or in the drawing.

The single figure shows a block diagram of an embodiment of an internal combustion engine according to the invention. FIG. 1 shows a block diagram of an internal combustion engine according to the invention with an injection insert for internal combustion engines. A high-pressure fuel pump 10 is supplied with fuel from a tank 14 via a fuel inlet 12. The fuel is conveyed from the tank 14 into the K fuel inlet 12 by an electric low pressure fuel pump 16. The pressure in the fuel inlet 12 is regulated via a control valve. The high-pressure fuel pump 10 feeds via a high-pressure line 18 into a rail 20, which in turn is connected to injection valves 22, which are designed here as high-pressure injection valves. A pressure limiting valve 24 and a pressure sensor 26 are provided on the rail 20. Furthermore, the internal combustion engine comprises a control unit 28, which takes over the control and regulation of the injection system.

Signal lines, electrical supply lines and other items are not shown in the figure.

Also not shown is the cylinder, which is provided with a combustion chamber, which i.a. is limited by the piston, an inlet valve and an outlet valve. An intake pipe is coupled to the intake valve and an exhaust pipe is coupled to the exhaust valve. In the area of the intake valve and the exhaust valve, the injection valve 22 and a spark plug protrude into the combustion chamber. Fuel can be injected into the combustion chamber (not shown) via the injection valve 22. The fuel in the combustion chamber can be ignited with the spark plug. In the intake pipe, not shown, a rotatable throttle valve is accommodated, via which air can be supplied to the intake pipe. The amount of air supplied depends on the angular position of the throttle valve. A catalytic converter is provided in the exhaust pipe and serves to purify the exhaust gases resulting from the combustion of the fuel. Exhaust gas recirculation leads from the exhaust pipe back to the intake pipe. An exhaust gas recirculation valve is housed in the exhaust gas recirculation valve, with which the amount of exhaust gas recirculated into the intake pipe can be adjusted.

The piston is reciprocated by the combustion of the fuel in the combustion chamber

Movement moved, which is transmitted to a crankshaft, not shown, and exerts a torque on this. The control unit 28 is acted upon by input signals which represent operating variables of the internal combustion engine measured by means of sensors. For example, the control unit 28 is connected to an air mass sensor, a lambda sensor, a speed sensor and the like. Furthermore, the control unit is connected to an accelerator pedal sensor that generates a signal that indicates the position of an accelerator pedal that can be actuated by a driver and thus the requested torque. The control unit 28 generates output signals with which the behavior of the internal combustion engine can be influenced via actuators or actuators. For example, the control unit 28 is connected to the injection valves 22, the spark plugs and the throttle valve and the like and generates the necessary signals for their control. Among other things, the control unit 28 is provided to control and / or regulate the operating variables of the internal combustion engine. For example, the amount of fuel injected into the combustion chamber by the injection valve 22 is controlled and / or regulated by the control unit 28, in particular with regard to low fuel consumption and / or low pollutant development. For this purpose, the control device is provided with a microprocessor, in particular a computer, which is provided with a storage medium on which a program is stored which is suitable for carrying out the control and / or regulation mentioned and thus for operating the method according to the invention. In this way, different operating modes, such as, for example, the so-called homogeneous operation, the so-called homogeneous lean operation or the so-called shift operation, which have been described above, can be set.

In homogeneous operation, as is present during the start of the internal combustion engine, in particular during a cold start, the pressure in the fuel supply line 12 is the pressure that is provided by the fuel pump 16. The high-pressure pump 10 does not yet provide an increase in pressure at this time. The pressure is then between 4 and 8 bar in the fuel supply line 12.

In homogeneous operation, in which the fuel is injected into the piston through the injection valves 22 during the intake phase of the piston, the pressure in the intake pipe prevails in the brake chamber during the suction cycle. The intake pipe pressure can be between 0, 7 and 1 bar in the starting phase. In this respect, the pressure in the rail 20 is greater than the pressure in the piston. However, since the injection duration is relatively long in the starting phase due to the low pressure in the rail 20, it may happen that the injection duration begins in the suction cycle, but extends into the compression cycle. In the compression stroke, the pressure in the piston then increases in the course of the adiabatic compression based on the intake manifold pressure, so that it can become greater than the pressure in the fuel supply line and in the rail. In this case it is possible that Fuel and gas are blown back into the rail 20 through the injection valves 22. To prevent this, a break-off angle is determined which corresponds to a crank angle at which the compression has progressed to such an extent that the pressure in the piston exceeds the pressure in the rail 20 in the start-up phase. It can further be provided that a limit pressure is defined on the rail side and that the termination crank angle is only determined if the pressure in the rail 22 is less than this limit pressure. If the pressure in the rail 20 rises due to the high-pressure pump 10, and approximately 1000 bar can be reached, there can no longer be a blow back. A limit pressure can therefore be set, after which a blow back can no longer occur.

It is therefore provided that the combustion chamber pressure is determined by means of the adiabatic compression depending on the intake manifold pressure, which is compared with the pressure on the rail side and the injection is stopped when a defined differential pressure is reached, with known intake manifold pressure and a known pressure on the other side of the injection valve, that is to say a crank angle can be determined as a termination angle in the rail 20, at which the

Injection is canceled.

Furthermore, it can be provided that if it is determined that the critical angle, that is to say the termination angle, is exceeded during the injection, an injection start angle being defined for this purpose and an injection duration and an injection end angle being determined via this, so that the injection then occurs earlier is used, to the extent that the injection end angle does not pass through the termination angle.

In particular, provision can also be made here for the injection to be terminated by a certain safety angle before the termination angle. However, the critical crank angle can be determined more precisely by the method according to the invention, by better determining the combustion chamber pressure, so that the time window that is available for injection can be better utilized and, in many cases, there can thus be no shift in the start of injection.

Claims

Expectations

1. A method for operating an internal combustion engine in which a termination angle of a fuel injection into a combustion chamber of an internal combustion engine, in particular a motor vehicle, is determined, the termination angle corresponding at the latest to the crank angle at which the pressure in the combustion chamber is the pressure on the other side of an injection valve for injection zen of fuel in the combustion chamber exceeds in particular in a feed line, the combustion chamber pressure in the intake stroke being equated with the intake manifold pressure and in the compression stroke over the

Compression is determined depending on the intake manifold pressure and the combustion chamber pressure is compared with the pressure on the other side of the injection valve and a differential pressure is determined and the injection is stopped when a defined differential pressure is reached, with known intake manifold pressure and a known pressure on the other side of the injection valve a crank angle is determined as the termination angle at which the injection is terminated at the latest.

2. The method according to claim 1, wherein the combustion chamber pressure is determined in the compression stroke via the adiabatic compression.

3. The method of claim 1 or 2, wherein the particularly adiabatic compression in the combustion chamber is determined via specific engine data and the current crank angle.

4. The method according to any one of claims 1 to 3, wherein the termination of the fuel injection already takes place at a crank angle which is a safety angle before reaching the termination angle.

5. The method according to any one of claims 1 to 4, wherein the method during a first mode of operation ^'is used, in particular in so-called homogeneous operation, in which the injection process during the suction stroke begins.

6. The method according to any one of the preceding claims, wherein the method is used when the pressure acting on the fuel on the other side of the injection valves in a supply line is less than a limit pressure.

7. The method according to any one of the preceding claims, wherein the method is applied when starting the internal combustion engine.

8. Computer program, wherein the computer program is suitable for performing the method according to one of the preceding claims when it is executed on a computer.

9. Computer program according to claim 8, characterized in that it is in a memory, in particular is stored on a read-only memory or a flash memory.

10. Control device for the control and / or regulation for operating an internal combustion engine, in particular for a motor vehicle, the control and / or regulating device comprising a memory on which a computer program according to one of claims 8 or 9 is stored.

11. Internal combustion engine, in particular for a motor vehicle with a combustion chamber into which fuel can be injected, with a fuel injection device, via which fuel enters the fuel chamber, the injection being controllable and / or regulatable via a control unit and an abort angle determined by the control device is and can be determined whether a break-off angle is passed through during injection and the injection is to be stopped.

12. Internal combustion engine according to claim 11, characterized in that it comprises a control device according to claim 10.