DE10240311A1 - Method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to 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 corresponds to the pressure on the other side Injection valve for injecting fuel into the combustion chamber exceeds in particular in a supply line, the combustion chamber pressure in the intake stroke being equated with the intake manifold pressure and in the compression stroke determined via compression, depending on the intake manifold pressure, and the combustion chamber pressure being compared with the pressure on the other side of the injection valve Differential pressure is determined and the injection is terminated when a defined differential pressure is reached, a crank angle being determined as a termination angle if the intake manifold pressure is known and the pressure on the other side of the injection valve is known , at which the injection is stopped at the latest.

Description

The invention relates to a method for operating an internal combustion engine, in particular a motor vehicle, at which a stopping angle of a fuel injection into a Combustion chamber of an internal combustion engine is determined, the break angle no later than corresponds to the crank angle at which the pressure in the combustion chamber Pressure on the other side of an injector to inject Fuel in the combustion chamber, in particular in the rail.

The invention also relates a computer program to carry out of the method and a control unit for the control and regulation an internal combustion engine and an internal combustion engine itself, in particular for a Motor vehicle, with a combustion chamber, injectable into the fuel is, with the injection over a control unit is controllable and / or regulatable.

Such a method and Such internal combustion engines are, for example, from a so-called gasoline direct injection known in motor vehicles. There is fuel in a homogeneous operation while the suction phase or in a shift operation during the compression phase injected into the combustion chamber of the internal combustion engine. The homogeneous operation is preferred for the full load operation of the internal combustion engine is provided during the Shift operation for idle or part-load operation is suitable. For example dependent on of the requested torque in such a direct injection Internal combustion engine switched between the above modes.

For engines with gasoline direct injection Fuel injected directly into the combustion chamber. Usually stands High pressure fuel available as a high pressure pump generated in front of the high pressure injectors (injectors), so that over a pressure drop in the injector towards the combustion chamber. However, in certain operating states must with it be calculated that the pressure of the fuel in the pressure accumulator is lower than the pressure in the combustion chamber.

Especially in the starting phase, in the high-pressure pump has not yet built up sufficient pressure the fuel is particularly in a rail or in general in a fuel supply line with a pressure level that the Pressure level of the electric fuel pump corresponds. Starting the Internal combustion engine is carried out in homogeneous operation. In particular with a cold start it is possible that due to the still small amount of fuel Pressure a relatively long injection period is required to the desired fuel mass inject into the combustion chamber and reliably close the internal combustion engine start. This can cause that the injection continues so long that the internal combustion engine already passes from the intake phase to the compression phase during the injection and that the resulting pressure in the combustion chamber increases than the pressure acting on the fuel in the supply line. in the Combustion chamber pressure increases in the compression stroke with increasing piston stroke on. It can then happen with long injection times that fuel and Gas from the combustion chamber is blown back into the rail, which is in everyone Case must be avoided.

In addition, there are also diagnostic functions lowering the pressure to the level of the electric fuel pump require. And also in shift operation, with the fuel during the compression stroke can be injected operating conditions occur where the combustion chamber pressure is the fuel pressure in the rail or the supply line upstream of the injection valve.

So far, has been to avoid blowback A map is available from gas to rail, which only depends on the given rail pressure specifies a termination angle for the injection.

The corresponding map for the injection termination according to the status the technology can be determined by individual measurements.

For example, from DE 199 13 407 A1 Known 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 having an injection start angle and an injection duration, an injection end angle from the injection start angle and the injection duration is determined and it is checked 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 optimal termination 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 with the pressure on the other side of the injection valve compared 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 the termination angle at which the injection is terminated at the latest.

Through the proposed procedure the stopping angle becomes relative and with additional consideration of the intake manifold pressure determined, resulting in a much more accurate break angle is determinable. From the determination of the combustion chamber pressure and education of the differential pressure above the injection valve can ultimately the necessary crank angle can be calculated to stop the injection. The differential pressure too small, the injection is stopped.

The combustion chamber pressure is in the compression stroke especially about the adiabatic compression depends determined by the intake manifold pressure, whereas the combustion chamber pressure the intake manifold pressure is equated in the suction cycle. In this way, the stopping angle determined more precisely and thus the available injection window be better exploited. This can result in the desired fuel mass be injected and still blow back fuel safely be prevented. The procedure according to the invention is in all operating conditions the internal combustion engine and also applicable to a cold start. On the engine will start safely under all conditions so achieved.

It should be noted that each of the the aforementioned angles as well as each of those described below Angle an associated Time is assigned. All Angles can So be replaced by appropriate times or periods. The conversion depends on the speed of the internal combustion engine.

It can be provided that in the process, the adiabatic compression in the combustion chamber is more specific Engine data and the current crank angle is determined. The specific Motor data can be determined in advance or specified by the manufacturer.

Then becomes the determination equation resolved after the crank angle, results at a given intake manifold pressure and a given rail pressure a crank angle up to which there is a pressure drop towards the combustion chamber is. 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 adiabate Conditions. By Multiplication with the real intake manifold pressure gives the actually necessary one Cut-off angle. The calculation can be done by specifying the values for the adiabatic Compression at ambient pressure in a characteristic curve and subsequent multiplication of the Angle can be simplified with the intake manifold pressure.

It can also be provided that the fuel injection stops at a crank angle takes place by a safety angle before reaching the termination angle lies.

In this case, the difference the pressures different set to such an earlier one To achieve break-off angles and thus further increase the security that no fuel blown back into the rail becomes.

In particular, it can be provided that the procedure during a first operating mode is used in which the injection process while of the suction cycle begins, in particular in homogeneous operation. In this first operating mode of the internal combustion engine is the throttle valve dependent on of the desired one Torque partially opened or closed. The fuel is drawn from the injector during a injected into the combustion chamber by the piston. By over at the same time The throttle valve intake air becomes the injected fuel swirled and thus distributed substantially uniformly in the combustion chamber. Then the fuel / air mixture during the compression phase compressed, then from the spark plug inflamed to become. Due to the expansion of the ignited fuel Piston driven. The resulting torque essentially depends on homogeneous operation from the position of the throttle valve. With regard to a low The fuel / air mixture is as harmful as possible at λ = 1 or λ <1 is set.

In another mode, one the so-called homogeneous lean operation of the internal combustion engine Fuel, as with homogeneous operation, during the intake phase in the Injected combustion chamber. In contrast to homogeneous operation the fuel / air mixture also occur with λ> 1.

There is also a third operating mode known, the so-called shift operation of the internal combustion engine, at where the throttle valve is wide open. The fuel is drawn from the injector during one by the piston caused compression phase injected into the combustion chamber locally in the immediate vicinity of the spark plug, as well as in time suitable distance from the ignition point. Then using the spark plug the fuel ignites, so that the piston in the now following work phase through the Expansion of the inflamed Fuel is driven. The resulting torque largely depends on shift operation on the amount of fuel injected. Essentially, that is Shift operation for the idle operation and the partial load operation of the internal combustion engine intended.

If necessary, other operating modes are also conceivable. Between the described operating modes of the internal combustion engine can now and then switched or switched here.

The previously described homogeneous operation, at which the application of the invention is particularly advantageous lies especially in the start-up phase.

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

It can also be provided that then a change possible at the beginning of the injection angle is, the injection angle are changed especially after "early" can if it is determined that the injection end angle exceeds the stop angle would. It can be achieved that a change in particular of the injection angle possible is when the pressure acting on the fuel is small, e.g. less than a limit pressure and thus a termination, possibly too little fuel for one reliable Operation of the internal combustion engine would be present. at The injection times are a high pressure acting on the fuel so short that it is usually no longer necessary to cancel.

It can be provided that in in this case all the calculations are no longer carried out, to save computing time.

The application in the case of Starting the internal combustion engine, especially when starting, in particular during a cold start the pressure on the fuel is low and corresponds in particular to the pressure in the electric fuel pump. At the same time size Amount of fuel to be injected into the combustion chamber for reliable starting to ensure the internal combustion engine. The injection could therefore be stopped cause the internal combustion engine to die when starting. Out for this reason, it is particularly advantageous when starting the internal combustion engine to prevent the injection from being stopped. By a special optimal use of the injection window, as it is by the Invention possible this can be largely achieved. Furthermore it can be provided that a change in the injection start angle also occurs here is provided, which can further improve that intended fuel mass also completely injected into the combustion chamber becomes. A blow back on the other hand, fuel is prevented.

The invention further relates to a computer program to carry out the method described above when it is on a computer accomplished becomes.

In particular, the computer program can be stored in a memory.

The is of particular importance Realization of the method according to the invention in the form of a control element for a control unit of an internal combustion engine in particular a motor vehicle is provided. It is on the control unit Program that is stored on a microprocessor, in particular executable on a computer and for execution of the method according to the invention suitable is. In this case, the invention is based on the control unit saved program realized so that this with the program provided control unit represents the invention in the same way as the method its execution the program is suitable. In particular, as a storage medium an electrical storage medium can be used, for example a read-only memory or a flash memory. The control device is used for controlling and regulating in particular, the switching or switching back and forth between the operating states to ensure the internal combustion engine. Finally The invention relates to an internal combustion engine, in particular for a motor vehicle with a combustion chamber into which fuel can be injected with a Fuel injector, about which the fuel gets into the combustion chamber, the injection over a control unit is controllable and / or regulatable and can be determined by the control device is whether a stop angle is passed through during injection and the injection has to be stopped.

In particular, the internal combustion engine can control unit to regulate or control in the manner described above.

Other features, possible applications and advantages of the invention will become apparent from the following description of embodiments, which are shown in the figure of the drawing. Thereby everyone described or illustrated features alone or in any combination the subject of the invention regardless of its summary in the claims or their relationship back as well as regardless of their formulation or presentation in the description or in the drawing.

The only figure shows one Block diagram of an embodiment an internal combustion engine according to the invention.

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 done via a fuel feed 12 with fuel from a tank 14 provided. The fuel is supplied by an electric low pressure fuel pump 16 from the tank 14 in the fuel supply 12 promoted. The pressure in the fuel supply 12 is controlled by a control valve.

The high pressure fuel pump 10 delivers via a high pressure line 18 in a rail 20 , which in turn with injectors 22 , which are designed here as high-pressure injection valves, is connected. On the rail 20 is a pressure relief valve 24 and a pressure sensor 26 intended.

The internal combustion engine also includes a control unit 28 , which controls and regulates the injection system.

Not shown in the figure Signal lines, electrical supply lines and more.

Also not shown is the cylinder, which is provided with a combustion chamber which is delimited, among other things, 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. The injection valve protrudes in the area of the intake valve and the exhaust valve 22 and a spark plug in the combustion chamber. Via the injector 22 fuel can be injected into the combustion chamber, not shown. The fuel in the combustion chamber can be ignited with the spark plug.

In the intake pipe, not shown a rotatable throttle valve is housed, through which the intake manifold air supplied is. The amount of feed Air is dependent from the angular position of the throttle valve. There is a in the exhaust pipe Catalyst provided for the purification by combustion of the exhaust gases produced.

One leads from the exhaust pipe Exhaust gas recirculation back to the Intake manifold. In the exhaust gas recirculation pipe an exhaust gas recirculation valve housed with the amount of exhaust gas returned to the intake pipe can be adjusted.

The piston is burned of the fuel in the combustion chamber in a reciprocating motion, which is transmitted to and not on a crankshaft exerts a torque.

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 device 28 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 device 28 with the injectors 22 , the spark plugs and the throttle valve and the like. Connected and generates the necessary signals for their control.

Among other things, the control unit 28 provided to control and / or regulate the operating variables of the internal combustion engine. For example, that of the injector 22 amount of fuel injected into the combustion chamber by the control unit 28 Controlled and / or regulated 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 the so-called homogeneous operation, the so-called homogeneous Lean operation or the so-called shift operation described above were set.

In homogeneous operation, as is the case when the internal combustion engine is started, in particular during a cold start, the pressure in the fuel supply line is high 12 the pressure created by the fuel pump 16 provided. The high pressure pump 10 does not deliver 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 through the injectors during the intake phase of the piston 22 is injected into the piston, there is pressure in the intake manifold during the suction cycle in the combustion chamber. The intake pipe pressure can be between 0, 7 and 1 bar in the starting phase. So far the pressure is on the rail 20 greater than the pressure in the piston. However, in the start-up phase due to the low pressure in the rail 20 the injection duration is relatively long, it may happen that the injection duration begins in the suction stroke, but extends into the compression stroke. In the compression stroke, the pressure in the piston then increases in the course of the adiabatic compression, starting from 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 through the injectors 22 on the rail 20 be blown back. To prevent this, a break-off angle is determined which corresponds to a crank angle at which the compression has progressed so far that the pressure in the piston and 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. The pressure in the rail increases 20 through the high pressure pump 10 at which approx. 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 a 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 a known intake manifold pressure and a known pressure on the other side of the injection valve, i.e. in the rail 20 a crank angle can be determined as a termination angle at which the injection is terminated at the latest.

It can also be provided that if it is determined that the critical angle, i.e. the Termination angle during the injection exceeded is, for which purpose an injection start angle is fixed and an injection duration and over it Injection end angle is determined that then the injection is already earlier uses, and so far that the injection end angle the termination angle does not go through.

In particular, it can also be provided that the termination of the injection by one certain safety angle before the break angle.

By the method according to the invention however, the critical crank angle can be determined more accurately by a better definition of the combustion chamber pressure so that the time window that is available for injection stands, can be better exploited and thus a shift of the Start of injection in many cases can remain.

Claims (12)

Method for operating an internal combustion engine, in which a cut-off angle of a fuel injection into a combustion chamber an internal combustion engine, in particular a motor vehicle, is determined, the break-off angle at the latest corresponds to the crank angle at which the pressure in the combustion chamber Pressure on the other side of an injector for injection of fuel in the combustion chamber in particular in a supply line, the combustion chamber pressure in the suction cycle is equated to the intake manifold pressure and in the compression stroke over the Compression, dependent is determined by the intake manifold pressure and the combustion chamber pressure with the pressure compared on the other side of the injector and a differential pressure is determined and when a defined differential pressure is reached the injection is stopped, with known intake manifold pressure and a known pressure on the other side of the injector a crank angle is determined as a stopping angle at which at the latest the injection is stopped. The method of claim 1, wherein the combustion chamber pressure in the compression stroke over the adiabatic compression is determined. The method of claim 1 or 2, wherein the in particular adiabatic Compression in the combustion chamber specific engine data and the current crank angle is determined. Method according to one of claims 1 to 3, wherein the termination the fuel injection takes place at a crank angle, which is at a safety angle before the stop angle is reached. Method according to one of claims 1 to 4, wherein the method while a first operating mode is used, in particular in so-called homogeneous operation, at which the injection process during the suction cycle begins. Method according to one of the preceding claims, wherein the method is applied when the pressure on the fuel is on the other Side of the injectors in a supply line less than a limit pressure is. Method according to one of the preceding claims, wherein the method in Starting the internal combustion engine is applied. Computer program, the computer program for performing the Method according to one of the preceding claims is suitable if it is based on running on a computer becomes. Computer program according to claim 8, characterized in that it on a memory, in particular on a read-only memory or a flash memory is stored. control unit for the Control and / or regulation for operating an internal combustion engine, especially for a motor vehicle, the control and / or regulating device Memory, on which a computer program according to one of claims 8 or 9 is stored. 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 via Control unit control and / or is controllable and an abort angle by the control device is determinable and can be determined whether a break angle at Injection is run through and the injection is to be stopped. Internal combustion engine according to claim 11, characterized in that that he's a control unit according to claim 10.