DE10160311A1 - Internal combustion engine operation method, involves delivering fuel by fuel pump connected to pressure area and determining actual pressure for driving pump - Google Patents

Abstract

The method involves delivering fuel by an electric driven fuel pump (36), which is connected to a fuel container on the input side and to a pressure area. The actual pressure (pist) is determined in the pressure area by a pressure sensor (44) and the pump is driven at least temporarily dependent on the actual pressure. Independent claims are also provided for: (a) Computer program for carrying out the internal combustion engine operation method (b) Control and/or actuation apparatus for operating the internal combustion engine (c) Internal combustion engine

Description

State of the art

The invention initially relates to a method for operating an internal combustion engine in which the fuel comes from a electrically driven fuel pump is promoted which on the inlet side with a fuel tank and is connected to a pressure area on the outlet side.

Such a method is used, for example, by internal combustion engines Intake manifold injection known. With these the Fuel from an electric fuel pump from one Fuel tank in a pressure range to which again a fuel injector is connected. This is in an intake manifold of the internal combustion engine arranged. In this way, the fuel can Fuel injector into the intake manifold and from there in reach the combustion chambers of the internal combustion engine.

Another method of the type mentioned is from Internal combustion engines are known, which with Direct fuel injection work. With these Internal combustion engines run out of fuel electric fuel pump, which also as Prefeed pump is referred to from the fuel tank promoted in a pressure range, from which he to an im general mechanically driven high pressure Fuel pump (main feed pump) arrives. This promotes the fuel further into a fuel rail ("rail") to which several injectors are connected and in which the fuel is stored under high pressure is. The injectors inject the fuel directly into corresponding combustion chambers of the internal combustion engine.

In both cases, the electric fuel pump and the downstream pressure range as so-called "constant pressure system" designed. With this is the Pressure range via a mechanical pressure regulator with the Fuel tank connected. In normal operation, the electrically powered fuel pump the fuel continuously and with maximum conveying capacity. Those Amount of fuel, which in systems with Intake manifold injection from the injector not into that Intake pipe is injected, and which in systems with Direct fuel injection not from the high pressure pump is promoted, flows with the known Internal combustion engines or the known methods on the mechanical pressure regulator back into the fuel tank.

Because the electrically driven fuel pump is always with maximum conveying capacity is running, it is ensured that the pressure in the pressure area even when from the injector or the injectors the maximum possible amount of fuel is requested, always remains at the desired level.

Demand-controlled fuel systems are also known. at these are also constant pressure systems, at those by controlling a mechanical Pressure regulator the pressure in the pressure range on one constant value is set. This runs the Fuel pump no longer constantly at maximum Funding, but will meet the current needs of Internal combustion engine controlled accordingly. excess Fuel continues to flow through the mechanical one Pressure regulator back into the tank. The adjustment of the Delivery rate of the fuel pump to the current Operating point of the engine causes due to possible reduction in performance of the fuel pump Fuel economy of the internal combustion engine.

The object of the present invention is a method of the type mentioned at the beginning so that in Operation of the internal combustion engine again fuel saved and the life of the fuel pump increased can be.

This task is initiated in a procedure mentioned type solved in that an actual pressure in Pressure range detected by a pressure sensor and the Fuel pump at least temporarily depending on the actual pressure is controlled.

Advantages of the invention

With the inventive method, the delivery rate the electrically driven fuel pump each Adjusted as needed. Then when from the injector or Only a little fuel is required for injectors electrically driven fuel pump with accordingly low performance work. This will make the Power consumption of the electrically driven Fuel pump in normal operation of the internal combustion engine lowered. Usually from one with the internal combustion engine connected generator must therefore be less electrical What will ultimately be made available to energy Fuel consumption of the internal combustion engine is reduced.

It was also found that the known Procedure from the pressure range via the pressure control valve in fuel returned to the fuel tank due to compression and heat loss from the fuel pump is warmed up and so it heats up over time of the fuel in the fuel tank comes. However, this warming is stronger Evaporation rate of the one present in the fuel tank Fuel, which also the Fuel consumption increased in the known systems. This is reduced in the method according to the invention since at this, if any, only a small amount Fuel via a pressure control Overflow or pressure relief valve in the Fuel tank flows back.

Yet another advantage is that a appropriate control of the electrically driven Fuel pump the pressure in the pressure area upstream from the electrically driven fuel pump very quickly to the different operating points of the Internal combustion engine can be adjusted. Thus, in each operating point of the internal combustion engine for this optimal fuel pressure can be provided. at Internal combustion engines in which the intake air through a Compressor is pre-compressed, for example by a variable pressure in the pressure range of the metering range Injectors to be expanded. In addition, under so-called "Hot fuel conditions" the fuel pressure increases become.

Furthermore, the pressure in the pressure range can be set in this way that the pressure difference across the injectors is minimal. This leads to minimal system pressure and thereby reducing fuel consumption. Also enables accurate pressure detection to be taken into account the actual pressure in the pressure range during the calculation the injection time through the fuel injectors. This can be especially in the case of a delayed, so slow pressure build-up, be advantageous. Through the Detection of the actual pressure in the pressure range can Injection times to be corrected accordingly inject the necessary amount of fuel and so start to enable the internal combustion engine or to go out Avoid internal combustion engine. By measuring the Actual pressure in the pressure range can also diagnose the Fuel system.

At this point it should be noted that the Method according to the invention in internal combustion engines Intake manifold injection is just as advantageous as with Internal combustion engines with gasoline direct injection. there With direct petrol injection, the fuel pre-pressure according to the temperature boundary conditions (temperature of the Fuel and / or the high pressure fuel pump) can be varied.

Overall, the power consumption by the invention the electrical fuel pump minimizes the vehicle electrical system relieves the life of the electric fuel pump increases, and their operating noise decreases.

Advantageous developments of the invention are in Subclaims specified.

In a first particularly advantageous development suggested that a target pressure for fuel pressure is formed in the pressure range and the actual pressure in Pressure range through a closed control loop, especially by a PI controller, according to the target pressure is regulated. A regulation of the fuel pressure in the Print area has the particular advantage that Manufacturing tolerances for the electrical used driven fuel pumps, which at the same Control performance at different funding levels lead identical fuel pumps, compensated can be. The pressure in the pressure area can be caused by this The measure according to the invention is therefore set particularly precisely become.

This is done in a particularly preferred further development suggested that in a feedforward control at least one input power dependent on the target pressure for the electrically driven fuel pump is determined. Such feedforward control makes a particular one possible rapid adjustment of benchmarks and Disturbance variable. By using a Pre-control is the scope of the control interventions minimized so that, for example, changes in the target pressure under and / or caused by the regulation Overshoots are smaller or even entirely remain under. The setting of the desired pressure in the With this method, the pressure range is still included better precision possible. One is also possible Determination of input tax performance also depends on Operating point (e.g. speed, load) of the Internal combustion engine.

In an advantageous embodiment, it is proposed that that the input tax payment includes a share which in particular by means of a map, from the target pressure and one dependent on the operating point of the internal combustion engine Fuel volume flow is determined. The advantage of one Kennfelds is that it is easy to use in terms of software is to be realized. The use of the target pressure on the one hand and on the other hand one dependent on the operating point Fuel volume flow enables a very precise Illustration of the electric fuel pump too providing funding. The fuel volume flow can easily from the speed and the relative Fuel mass, which for the desired performance of the Internal combustion engine is required to be determined.

It is possible that the fuel volume flow includes a portion that corresponds to the volume flow, that of a fuel injector in the Comes into the combustion chamber, and one that depends on the set pressure Portion that corresponds to the volume flow that via a pressure relief valve from the pressure range to Fuel tank flows. Such one Pressure relief valve is generally available to a pressure relief of the fuel system, for example in the operating phases of the internal combustion engine Thrust shutdown, maintaining the Fuel pressure when the internal combustion engine is switched off, and a base load for the electrically powered To create or provide fuel pump. Possibly. can with that overflowing from the pressure relief valve Amount of fuel is a flow of fuel to the fuel tank be created back by a suction jet pump is driven, which is arranged in the fuel tank. With the method according to the invention, this is Fuel flow takes into account what the precision at Determination of input tax performance improved again.

The continuing education of the inventive method, in which the proportion of Volume flow, which corresponds to the volume flow that over a pressure relief valve from the pressure range to Fuel tank flows, is zeroed when the Pressure in the pressure range is less than the opening pressure of the Pressure relief valve is. The opening pressure is there of the pressure relief valve with intake manifold injection in Generally below normal system pressure, whereas with direct fuel injection mostly above the normal system pressure. In the latter case it is Overflow quantity of the pressure load valve in the normal case always zero, so no fuel flows out of the Pressure range via the pressure relief valve to Fuel tank back.

It is also envisaged that the fuel volume flow will be one Portion that corresponds to a volume flow that from a temporal pressure gradient in a fuel Manifold and the volume of the fuel manifold and the modulus of elasticity of the fuel. In In this case, the method according to the invention is used Internal combustion engines with direct fuel injection used. To in the low pressure range of the corresponding Minimize pressure overshoot or undershoot in the fuel system or to be able to avoid (this is especially the case with small ones Fuel quantities advantageous), the pilot control Mass balance between the high pressure and low pressure range of the Fuel system considered. This will make the Precision in determining input tax performance improved.

In a particularly preferred embodiment of the The inventive method is also proposed that the input tax includes a portion that only from the change in the current load, in particular the change the currently injected fuel mass. This "load dynamic adjustment" of the pilot control power enables extremely rapid adjustment of the conveying capacity the electrically driven fuel pump at one rapid change of the engine by the user desired power of the internal combustion engine. Over or Undershoot of the actual pressure in the pressure range, which at such a rapid change in performance through the regulation of the pressure in the print area could be caused are thereby reduced.

This "load dynamics adjustment" can be done easily be realized that the current load in one Low pass filter fed and the difference between the current load and the output of the low-pass filter and that from the difference, especially by means of a characteristic curve, the share of the input tax which only depends on the current change in the load.

Analogously, it is also proposed that the Input tax includes a portion of only one current change of the target pressure depends. This "Adjustment of the target pressure" of the pilot control power enables rapid adjustment of the electrical output driven fuel pump in a rapid change of the target pressure. This can e.g. B. with a rapid change the operating point (e.g. speed, load, etc.) of the Enter the internal combustion engine. The advantages correspond those of the above "Last Dynamic Range Adjustment".

Analog to the "load dynamics adjustment" the current one Set pressure fed into a low pass filter and the Difference between the current target pressure and the output of the low pass filter, and it can be made from the Difference, in particular by means of a characteristic curve, the proportion of the input tax payment, which is made only by the current change of the target pressure depends. This too is easy to implement and enables a very accurate Determination of input tax.

It is also proposed that the input tax payment be a That includes the portion at the start of the startup process Internal combustion engine the difference between the maximum permissible control power of the electrical Fuel pump and from the volume flow of the electric fuel pump and the target pressure formed Input tax performance corresponds and then becomes smaller, and the is set to zero at the end of the start process. hereby the electrically powered fuel pump will during the starting process of the internal combustion engine with maximum Power controlled so that the pressure in the printing area so is set up as quickly as possible. This will make the Start quality increased, exhaust emissions reduced and the Starting process of the internal combustion engine is shortened and ultimately the fuel consumption of the internal combustion engine is reduced.

In terms of software, such a method is easy to do realize if from the difference between the actual pressure and the target pressure, in particular by means of a characteristic curve, a time constant of a low-pass filter is formed, and if the low pass filter with the difference between the maximum permissible control power of the electrical Fuel pump and the share of the drive power is initialized, which is determined from the volume flow that is from the pressure relief valve Pressure range flows to the fuel tank.

To save fuel, modern Internal combustion engines injecting fuel into the Combustion chambers in overrun operation of the internal combustion engine interrupted. In this case, if there is no flow Pressure relief valve (opening pressure of the Pressure relief valve greater than the system pressure) one inadmissible increase in fuel pressure in the pressure range to prevent and, when reinstalling the Fuel injection into the combustion chambers, one to prevent regulatory undershoots of pressure it is proposed that the Internal combustion engine at least when activated Thrust shutdown of the integrator of the PI controller reset or stopped, the output of the PI controller set to zero or the integrator stopped and the electrically driven fuel pump not or with constant power is driven such that it essentially does not deliver fuel.

No injection takes place when the overrun fuel cut-off is activated of fuel into the combustion chambers and, in the case of Direct fuel injection, no fuel delivery through the high pressure pump. The one in the print area Fuel heats up and subsequently expands. As a result, the pressure can be up to the opening pressure of the Pressure relief valve rise. When reinstalling the normal operation, it may take a few seconds for the predetermined target pressure is reached again, because the pressure in the system is only broken down by the injections.

That pressure increase, which is caused by the heating of the Fuel is unavoidable. The integrator of the controller is activated when Thrust cutout reset or stopped and the Control power reduced or set to zero because otherwise the pressure in the pressure area as a result of thermal expansion of fuel rise and try the regulator would counteract this condition for as long as until the control power of the electric fuel pump Is zero.

The integrator of the controller would have been in such a case integrated up to a very large negative value, so that when the fuel cut-off is deactivated, it becomes a large undershoot in the pressure signal. By the Reset or stop the controller and by the Do not activate the electric fuel pump activated overrun cutoff becomes an undershoot of the Actual pressure after deactivation of the fuel cut-off avoided. Furthermore, the time until the Target pressure is shortened.

It is particularly advantageous if the above measures can only be carried out if the actual pressure is also present is equal to or greater than a certain value. This means that if there is a fuel cut-off and the Actual pressure has reached a certain value at least (and when the pressure relief valve is closed), the Control is switched off. The regulation starts again, as soon as the actual pressure has a (different) certain value below.

Overall, it is advantageous if the target pressure of Operating parameters of the internal combustion engine, in particular of an operating temperature and / or the speed of the Crankshaft and / or a relative air filling, depends. The consideration of the operating temperature enables the Setting a target pressure, which, for example, when hot Internal combustion engine and / or hot fuel the start the same relieved.

In an advantageous embodiment of the invention The procedure is an adaptation of the pre-control Input tax on the individually used electric fuel pump performed. This adaptation is preferably done within certain Plausibility limits. The input tax is thus on the delivery capacity of the individual electrical Fuel pump adapted at the appropriate system pressure. The differences from a copy of an electrical Fuel pump to another copy are in the Delivery rate and are due to component and Manufacturing tolerances. The adaptation increases the precision of the Feedforward and improves the dynamics and the Diagnostic options for the fuel supply system.

The invention also relates to a computer program which is suitable for performing the above method if it is running on a computer. It becomes special preferred if the computer program is on a memory, especially on a flash memory or a ferrite RAM, is saved.

Furthermore, the invention relates to a control and / or Control device for operating an internal combustion engine. To im Operation of the internal combustion engine will save fuel proposed that the control and regulating device one Includes memory on which a computer program of the above Type is stored.

The invention also relates to an internal combustion engine a fuel system, with a fuel tank, with an electrically driven fuel pump, which on the inlet side with the fuel tank and on the outlet side is connected to a print area.

To fuel in such an internal combustion engine To save, it is proposed that a pressure sensor is present, which of the electrically driven Fuel pump detected in the pressure range generated pressure, and that the fuel pump is dependent at least temporarily is controlled by the signal of the pressure sensor. Especially such an internal combustion engine is preferred, which a Control and / or regulating device of the above type includes.

drawing

Below is a particularly preferred one Embodiment of the invention with reference to the enclosed drawing explained in detail. In the drawing demonstrate:

Figure 1 is a schematic diagram of an internal combustion engine with an electric fuel pump.

FIG. 2 is a flowchart illustrating a method for operating the electric fuel pump of the internal combustion engine of FIG. 1, the method comprising a pilot control and a PI controller;

FIG. 3 is a flowchart which shows the sequence of the precontrol of the method from FIG. 2;

FIG. 4 is a flowchart which shows the precontrol of the electric fuel pump in accordance with the method illustrated in FIGS. 2 and 3;

FIG. 5 is a flowchart showing the initialization of a low-pass filter which is used in the method shown in FIG. 4;

FIG. 6 is a flowchart showing the PI control of the method shown in FIG. 2;

Fig. 7 is a graph in which a possible course of the relative fuel mass is shown over time;

Fig. 8 is a diagram in which a fuel flow is shown over time;

Fig. 9 is a diagram in which a load-dependent ratio of a pilot power is shown over time;

Fig. 10 is a graph showing total pilot power versus time;

FIG. 11 is a diagram in which a rotation speed of the electric fuel pump is shown over time; and

Fig. 12 is a diagram showing a controller performance over time.

Description of the embodiment

In Fig. 1, an internal combustion engine is identified overall by reference numeral 10. It comprises several combustion chambers, only one of which is shown in FIG. 1 with reference number 12 . The combustion chamber 12 can be connected to an intake manifold 16 via an inlet valve 14 . A fuel injection device 18 is arranged in the intake manifold 16 . Upstream of the fuel injection device 18 there are also a throttle valve 20 and an air mass meter 22 designed as a hot film sensor (“HFM sensor”) in the intake manifold. The combustion chamber 12 can be connected to an exhaust pipe 26 via an exhaust valve 24 . A fuel-air mixture located in the combustion chamber 12 is ignited by a spark plug 28 . This is controlled by an ignition system 30 .

The fuel injection device 18 is part of a fuel system 32 . This comprises a fuel tank 34 , from which an electrically driven fuel pump 36 delivers the fuel into a fuel line 38 , which leads to the fuel injection device 18 . Downstream from the electrically driven fuel pump 36 , the fuel line 38 is connected to a pressure relief valve 40 . From this line (without reference numerals) leads to a suction jet pump 42 , which is arranged in the area of the fuel tank 34 . The electrically driven fuel pump 36 , the overflow valve 40 and the suction jet pump 42 can also be designed as a common module in the fuel tank 34 .

The fuel pressure prevailing in the fuel line 38 is detected by a pressure sensor 44 , which can also be part of the above common module. It delivers corresponding signals to a control and regulating device 46 . This also receives signals from the HFM sensor 22 and from a speed sensor 48 , which taps the speed of a crankshaft 50 of the internal combustion engine 10 . Furthermore, the control and regulating device 46 is supplied with signals from a temperature sensor 52 , which detects the temperature of an engine block (not shown) of the internal combustion engine 10 . A position transmitter 54 , which detects the position of an accelerator pedal 56 , is also connected to the control and regulating device 46 .

On the output side, the control and regulating device 46 controls, among other things, the ignition system 30 , the throttle valve 20 and the fuel injection device 18 . Furthermore, the control output of the electric fuel pump 36 is set by the control and regulating device 46 . This is done by driving a clock module 58 , which outputs a pulse duty factor. The control power of the electrically driven fuel pump 36 is therefore varied by pulse width modulation (PWM).

In the internal combustion engine shown in FIG. 1, the fuel pressure in the fuel line 38 is regulated according to a setpoint. The setpoint value in turn depends on the current operating parameters of the internal combustion engine 10 , in particular on the temperature detected by the temperature sensor 52 , the speed of the crankshaft 50 detected by the speed sensor 58 and the air charge detected by the HFM sensor 22 . The pressure in the fuel line 38 is regulated by a corresponding variation in the voltage (and thus ultimately the speed or the torque) of the electric fuel pump 36 . The control principle will now be explained in detail with reference to FIGS. 2 to 6:
In FIG. 2, the actual pressure is pist in the fuel line 38 detected in a block 60. The corresponding signal is provided by the pressure sensor 44 . In the actual pressure detection 60 , the voltage signal supplied by the pressure sensor 44 is averaged over, for example, ten measured values and this averaged voltage value is converted into a raw pressure value via a voltage-pressure line of the pressure sensor 44 . In a block 62 , the raw pressure value is filtered, which generates an actual pressure pist, and is fed to a PI controller (block 64 ).

The signals from the HFM sensor 22 , the speed sensor 48 , the temperature sensor 42 , and the position transmitter 54 are used in a block 66 to calculate a set pressure psoll. This is also fed to the PI controller 64 . A controller power rgl is determined in PI controller 64 in accordance with the difference between setpoint pressure psoll and actual pressure pist. As already explained above, this takes the form of a specific duty cycle. The setpoint pressure psoll and the signals from the sensors 22 , 48 , 52 and 54 are also used in block 68 to generate a pilot control power vsl. Both are fed into a software block 57 "control clock module", which controls the clock module 58 , which is present as hardware, via a PWM output stage of the control unit 46 .

The individual functions within block 68 are recorded in greater detail in FIG. 3:
In a block 70 , a fuel volume flow vol is determined. This fuel volume flow vol is the volume flow which is to be promoted overall by the electric fuel pump 36 . The input variables in block 70 are the rotational speed nmot, which is provided by the rotational speed sensor 48 , a relative fuel mass rk, which is determined in a block 72 as a function of the air filling rl, which in turn depends on the desired torque or on the position of the position sensor 54 Accelerator pedal 56 depends and is detected by the HFM sensor 22 , and a constant C1, which is provided in block 74 .

The setpoint pressure calculation in block 66 is essentially based on the rotational speed nmot, which is provided by the rotational speed sensor 48 , on a relative air filling, rl, which is determined by the HFM sensor 22 , and the temperature tmot of the internal combustion engine, which is provided by the temperature sensor 52 . It is noted that the pressure set point used in block 70 may be gradient limited to avoid large changes in the set point. Such a gradient limitation depends on the maximum dynamics of the system and improves the quality of the control. The fuel volume flow vol and the target pressure psoll are fed into a map (block 76 ) in which a pilot control power vslroh is determined.

For this purpose, a pilot control power vslrk, which was determined in block 80 , is added in 78. As explained in detail below, this pilot control power vslrk is used to adjust the pilot control power at high load dynamics. In 82, a pilot control power vslpsoll is added, which was determined in block 84 . This pilot control power vslpsoll is an adjustment of the pilot control power with strong setpoint pressure dynamics. This will also be discussed in more detail below. It is pointed out that instead of the target pressure dynamics adjustment in block 84 , a differential component can also be provided in controller 64 . Finally, a portion vslstart is added in 86, which was determined in block 88 . This pilot control power vslstart plays a role when starting the internal combustion engine or when the electric fuel pump is advanced.

The functions of the pilot control block 68 are shown in more detail in FIG. 4. First, the functions of block 70 , in which the fuel volume flow vol is determined, are explained in detail:
A first portion of the fuel volume flow vol is determined by multiplying the speed nmot by the constant C1 and the relative fuel mass rk in the multiplier 90 . The portion full is the fuel volume flow that reaches the combustion chamber 12 of the internal combustion engine 10 through the fuel injection device 18 . A second portion vol2 is added to this in 92. This is in turn determined from a characteristic curve 94 which is addressed with the target pressure psoll. The fuel volume flow vol2 is the volume flow that flows from the fuel line 38 via the pressure relief valve 40 to the suction jet pump 42 or back into the fuel tank 34 . In a non-illustrated embodiment (internal combustion engine with direct fuel injection), a third volume flow is added. This corresponds to the volume flow that depends on a pressure gradient over time in a fuel rail, the volume of the fuel rail and an elastic modulus of the fuel. The pilot control also takes into account the mass balance between a high-pressure and a low-pressure area of the fuel system.

However, since fuel flows through the pressure relief valve 40 only when the pressure in the fuel line 38 is greater than the opening pressure of the pressure relief valve 40 , a switch 96 is present between the characteristic curve 94 and the addition block 92 . Its switching position depends on a "code word" (not shown in FIG. 4), which in turn depends on whether the pressure relief valve 40 is overflowed or not. If the opening pressure of the pressure relief valve 40 is above the maximum system pressure, the pressure relief valve 40 is not overflowed. The volume flow vol2 is therefore set to zero by switch 96 . Otherwise vol2 is the output of the characteristic curve 94 , into which the target pressure psoll is fed. The overflow volume vol2 then depends on the set pressure psoll. The sum of the parts full and vol2 (as well as the third part mentioned above in the case of an internal combustion engine with direct fuel injection) gives the total volume of fuel vol to be delivered by the electrically driven fuel pump 36 .

The functions of block 80 will now be explained, in which that portion vslrk is determined by which a strong dynamic of the load can be taken into account in the pilot control power vsl. For this purpose, the relative fuel mass rk is fed into a low-pass filter 98 . The output of the low-pass filter 98 is subtracted from the relative fuel mass rk in 100. This difference is fed into a characteristic curve 102 , which outputs the portion vslrk of the drive power.

The effect of block 80 is as follows: if, for example, due to a sudden performance request by the user, there is a jump in the value of the relative fuel mass rk, there is initially a relatively large difference in 100, which, according to the time constant of the low-pass filter 98 , exponentially gets smaller. A sudden increase or decrease in the fuel mass rk to be injected thus immediately leads to an increase or decrease in the pilot control output, which then gradually subsides again. The advantage of this procedure in connection with the control in the PI controller 64 is discussed in more detail below in the explanation of FIGS. 7 to 12.

Analogously to block 80 , the set pressure psoll is fed into a low-pass filter 104 in block 84 . The difference between the output of the low-pass filter 104 and the target pressure psoll is formed in 106. The result is fed into a characteristic curve 108 , which converts the difference into a portion vslpsoll of the input tax performance. The function of block 84 is analogous to that of block 80 .

The function of block 88 , in which the proportion vslstart of the pilot control power for starting the internal combustion engine 10 is determined, is now explained in detail in connection with FIGS. 4 and 5: Thereafter, the difference between the target pressure psoll and the actual pressure is explained in 110 pist formed in the fuel line 38 . The difference is fed into a characteristic curve 112 . This converts the difference into a time constant T of a low-pass filter 114 .

The addressing of the low-pass filter 114 is shown in FIG. 5: The setpoint pressure psoll is then fed into the characteristic curve 94 already known from FIG. 4 in connection with block 70 . The result vol2 is the volume flow that flows back from the fuel line 38 to the fuel tank 34 via the pressure relief valve 40 . Since the rotational speed nmot is only very low when the internal combustion engine is started, the fuel volume flow vol2 corresponds to the total fuel volume flow vol which reaches the combustion chambers 12 of the internal combustion engine 10 via the fuel injection device 18 .

This fuel volume flow vol, like the set pressure psoll, is fed into the characteristic map 76 known from FIGS . 3 and 4, which outputs a raw pilot control power vslroh. The difference between this raw pilot control power vslroh and a maximum permissible control power aslmax for the electric fuel pump 36 is now formed in 116. The maximum permissible drive power aslmax (which is expressed by a pulse duty factor) depends on the characteristic of the clock module 58 used and is stored in a memory 118 . The low-pass filter 114 is now initialized with the difference formed in 116.

The presence of a starting process is recognized by the fact that a corresponding condition B1, which indicates the end of the starting process, has not yet been met (the condition E1 can be expressed in software terms, for example, by the status of a specific bit or flag). However, there is a starting process, corresponds to the pilot power vslstart due to the initialization in Fig. 5, first the difference between the maximum permissible aslmax drive power and the pilot power determined in the characteristic field 76 vslroh. Since the two pilot control powers vslroh and vslstart are added in 86, the pilot control power vsl initially corresponds to the maximum permissible control power aslmax of the electric fuel pump 36 in the start case . This therefore rotates at maximum speed, so that the pressure in the fuel line 38 is built up at maximum speed.

The share vslstart of the input tax benefit vsl reduced down to zero according to an exponential function. The The time in which this happens depends on the Difference between the actual pressure pist and the target pressure psoll from. As soon as the actual pressure pist and the target pressure psoll are roughly equal, the vslstart share becomes zero. The the same also applies to the case that the starting process has ended, which is recognized by condition B1.

The functions of the PI controller in block 64 are now explained with reference to FIG. 6: The difference between the target pressure psoll and the actual pressure pist is then formed in 120. This difference dp is fed into a proportional controller 122 and an integral controller 124 . The proportional controller 122 supplies a proportional component dpp, the integral controller 124 an integral component dpi. The two parts dpp and dpi are added in 126 and converted into a controller power rgl in block 128 . This is fed to the hardware clock module 58 via the control 57 implemented in software.

The integral controller 124 has some special features: For example, the integral part dpi is determined by limit values max and min. which are provided in memories 130 and 132 are limited. Furthermore, the integral controller 124 is stopped when a condition B2 (block 134 ) is fulfilled. If a condition B3 (block 136 ) is met, the integral controller 124 is reset. Condition B3 is fulfilled when a fuel cut-off of internal combustion engine 10 is activated or such activation is to be expected. In this case, no fuel is introduced into the combustion chambers 12 of the internal combustion engine by the fuel injection device 18 . Normally, therefore, no fuel should be delivered by the electrically driven fuel pump 36 . Conditions B2 and B3 can each consist of a specific combination of the states of bits and / or flags and / or code words.

If the opening pressure of the pressure relief valve 40 is above the maximum system pressure, that is to say the pressure relief valve 40 is not overflowed, it can happen at the same time that the actual pressure pist in the fuel line 38 rises above the set pressure psoll when the fuel is cut off. One reason for this may be heat conduction, which originates from the warm engine block and heats up the fuel present in the fuel line 38 , so that it expands. If the integral controller 124 were not reset or stopped, it would attempt to counteract this deviation of the actual value pist from the setpoint psoll, and specifically until the controller output rgl is equal to zero. In this case, the integral controller 124 would have integrated itself up to a very large negative value. When reinstalled, there would then be a significant undershoot of the actual pressure pist.

Condition 138 sets switch 138 in such a way that the controller power rgl becomes zero. In the case of the overrun fuel cut-off, the electric fuel pump 36 is driven as constant power only in a manner not shown in the figure, and in such a way that it just runs at a certain speed but does not deliver any fuel (in another exemplary embodiment they just turned off completely). By resetting or stopping the integral controller 124 and activating the electric fuel pump 36 with constant output without delivery, the reaching of a target pressure after the overrun fuel cut-off is accelerated and it is avoided that an undershoot of the actual pressure pist occurs after the end of the fuel cut-off.

In normal operation of the internal combustion engine 10 , the control power is composed of the pilot control power vsl and the controller power rgl. These are brought together in the control block 57 for the clock module 58 . An example of an operating situation is shown in FIGS. 7 to 12: It is assumed that the internal combustion engine is initially operated at constant power and speed. At a time t1, the accelerator pedal 56 is suddenly depressed by the user. Due to a corresponding resistance torque on the crankshaft, the rotational speed nmot of the internal combustion engine 10 remains constant. The sudden increase in the driver's desired torque results in a sudden increase in the relative fuel mass rk to be injected ( FIG. 7).

This results in an immediate increase in the fuel volume flow vol ( FIG. 8), which was determined in block 70 in FIG. 4. The effected thereby increasing the pilot power of the fuel pump 36 would be the moving parts of the fuel pump 36 lead due to the mass inertia, only a gradual increase in the delivery rate of the electric fuel line 36th For this reason, the load dynamics correction of block 80 is present: This causes a portion vslrk for the pilot control power, which is shown in FIG. 9. The total pilot power vsl then has the course shown in FIG. 10.

The excessive pilot control power vsl causes a rapid increase in the speed nekp of the electric fuel pump 36 ( FIG. 11). By means of the pilot control in block 68 , the delivery capacity of the electric fuel pump 36 is already very well adapted to the increased fuel requirement. The deviation of the actual pressure pist from the target pressure psoll is thus kept so small even in the event of a sudden change in the fuel mass rk to be injected that the controller output rgl to be output by the PI controller 64 is only very low ( FIG. 12).

It should be pointed out at this point that the control and regulating device shown above can be used not only in the internal combustion engine 10 with intake manifold injection shown in FIG. 1, but also in an internal combustion engine with direct petrol injection. In this case, the above control concept would be used to control or regulate the pressure in the low-pressure range, that is, between the pre-feed pump and the high-pressure pump.

As stated above, the driving performance of the electric fuel pump is expressed by a duty cycle. Although this is not shown in the drawing, a battery voltage correction is therefore carried out in the control block 57 for the clock module 58 , with which the pulse width is adapted to the current battery voltage. Furthermore, in the control block 57 for the clock module 58, the total duty cycle is limited to a minimum and a maximum value. In the event of a crash, the duty cycle to be output in the clock module 58 is set to zero as a safety fuel cut-off when an airbag has been triggered.

Claims (23)

1. A method for operating an internal combustion engine ( 10 ), in which the fuel is conveyed by an electrically driven fuel pump ( 36 ), which is connected on the inlet side to a fuel tank ( 34 ) and on the outlet side to a pressure region ( 38 ), characterized in that a Actual pressure (pist) in the pressure range ( 38 ) is detected by a pressure sensor ( 44 ) and the fuel pump ( 36 ) is activated at least temporarily depending on the actual pressure (pist). 2. The method according to claim 1, characterized in that a target pressure (psoll) for the fuel pressure in the pressure area ( 38 ) is formed and the actual pressure (pist) in the pressure area ( 38 ) by a closed control loop, in particular by a PI controller ( 64 ), is regulated according to the target pressure (psoll). 3. The method according to claim 2, characterized in that in a pilot control ( 68 ) an at least on the target pressure (psoll) dependent pilot control power (vsl) for the electrically driven fuel pump ( 36 ) is determined. 4. The method according to claim 3, characterized in that the pilot control power (vsl) comprises a portion (vslroh) which, in particular by means of a map ( 76 ), from the target pressure (psoll) and one from the operating point (nmot, rk) of the internal combustion engine ( 10 ) dependent fuel volume flow (vol) is determined. 5. The method according to claim 4, characterized in that the fuel volume flow (vol) comprises at least a portion (full), which corresponds to the volume flow that enters the combustion chamber ( 12 ) from a fuel injection device ( 18 ), and one of the set pressure (psoll) dependent portion (vol2), which corresponds to the volume flow that flows via a pressure relief valve ( 40 ) from the pressure area ( 38 ) to the fuel tank ( 34 ). 6. The method according to claim 5, characterized in that the proportion (full) of the fuel volume flow (vol), which corresponds to the volume flow that comes from the fuel injection device ( 18 ) into the combustion chamber ( 12 ), at least from a speed (nmot) of a crankshaft ( 50 ) and a current load of the internal combustion engine ( 10 ), in particular a fuel mass (rk) to be injected. 7. The method according to any one of claims 5 or 6, characterized in that the portion (vol2) of the volume flow, which corresponds to the volume flow that flows via a pressure relief valve ( 40 ) from the pressure region ( 38 ) to the fuel tank ( 34 ) to zero is set when the pressure (pist) in the pressure region ( 38 ) is less than the opening pressure of the pressure relief valve ( 40 ). 8. The method according to any one of claims 5 to 7, characterized characterized that the fuel volume flow a Portion that corresponds to a volume flow that from a temporal pressure gradient in a fuel Manifold and / or the volume of fuel Manifold and / or the modulus of elasticity of the Fuel depends. 9. The method according to any one of claims 3 to 8, characterized characterized that the input tax payment (vsl) a Share (vslrk) includes only the current change the load, especially the current change in fuel mass to be injected (rk). 10. The method according to claim 9, characterized in that the current load (rk) is fed into a low-pass filter ( 98 ) and the difference between the current load (rk) and the output of the low-pass filter ( 98 ) is formed, and that from the difference , in particular by means of a characteristic curve ( 102 ), the portion (vslrk) of the pilot control power (vsl) is formed, which only depends on the current change in the load (rk). 11. The method according to any one of claims 3 to 10, characterized characterized that the input tax payment (vsl) a Percentage (vslpsoll) that only includes the current Change of the target pressure (psoll) depends. 12. The method according to claim 11, characterized in that the current target pressure (psoll) is fed into a low-pass filter ( 104 ) and the difference between the current target pressure (psoll) and the output of the low-pass filter ( 104 ) is formed, and that from the difference , in particular by means of a characteristic curve ( 104 ), the portion (vslpsoll) of the pilot control power (vsl) is formed, which only depends on the current change in the target pressure (psoll). 13. The method according to any one of claims 3 to 12, characterized in that the pilot control power (vsl) comprises a portion (vslstart) which, at the beginning of the starting process of the internal combustion engine ( 10 ), the difference between the maximum permissible control power (aslmax) of the electric fuel pump ( 36 ) and the control power (vslroh) formed from the target volume flow (vol) of the electric fuel pump ( 36 ) and the target pressure (psoll) and then becomes smaller, and which is set to zero at the end of the starting process. 14. The method according to claim 13, characterized in that the portion (vslstart) is formed by a time constant (T) from the difference between the actual pressure (pist) and the target pressure (psoll), in particular by means of a characteristic curve ( 112 ). a low-pass filter ( 114 ) is formed, and the low-pass filter ( 114 ) is initialized with the difference between the maximum permissible actuation power (aslmax) of the electric fuel pump ( 36 ) and the proportion (vslroh) of the actuation power (vsl), which is derived from the volume flow ( vol2) is determined, which flows via the pressure relief valve ( 40 ) from the pressure area ( 38 ) to the fuel tank ( 34 ). 15. The method according to any one of claims 2 to 14, characterized in that in an overrun mode of the internal combustion engine ( 10 ) at least when the overrun fuel cutoff is activated, the integrator ( 124 ) of the PI controller ( 64 ) is reset or stopped, the output of the PI controller ( 64 ) is set to zero ( 138 ) and the electrically driven fuel pump ( 36 ) is not driven or is driven at a constant power such that it essentially does not deliver any fuel. 16. The method according to claim 15, characterized in that the measures specified in claim 14 only be carried out if the actual pressure (pist) is equal to or greater than a certain value. 17. The method according to any one of claims 2 to 16, characterized in that the target pressure (psoll) of operating parameters of the internal combustion engine, in particular of an operating temperature (tmot) and / or the speed (nmot) of the crankshaft ( 50 ) and / or a relative Air filling (rl), depends. 18. The method according to any one of claims 3 to 17, characterized characterized in that an adaptation of the Input tax on the individually used electric fuel pump is performed. 19. Computer program, characterized in that it is used for Carrying out the method according to one of the preceding Claims is appropriate when it is on a computer is performed. 20. Computer program according to claim 19, characterized characterized it on a store, in particular stored on a flash memory or a ferrite RAM is. 21. Control and / or regulating device ( 46 ) for operating an internal combustion engine ( 10 ), characterized in that it comprises a memory on which a computer program according to one of claims 19 or 20 is stored. 22. Internal combustion engine ( 10 ) with a fuel system ( 32 ), with a fuel tank ( 34 ), with an electrically driven fuel pump ( 36 ), which is connected on the inlet side to the fuel tank ( 34 ) and on the outlet side to a pressure region ( 38 ), characterized that a pressure sensor ( 44 ) is present, which detects the pressure (pist) generated by the electrically driven fuel pump ( 36 ) in the pressure area ( 38 ), and that the fuel pump ( 36 ) is controlled at least temporarily depending on the signal of the pressure sensor ( 44 ) becomes. 23. Internal combustion engine ( 10 ) according to claim 22, characterized in that it comprises a control and / or regulating device ( 46 ) according to claim 21.