EP1464819A2 - Method for operating a combustion engine - Google Patents

Abstract

Method for operating a combustion engine in which when the fuel pump is on balance transporting fuel, the number of transporting phases (48) of the pump per rotation of the drive shaft is dependent on at least one operating parameter of the combustion engine. Independent claims are included for (1) a corresponding computer program, (2) electronic storage medium, (3) engine control unit (4) combustion engine.

Description

State of the art

The invention initially relates to a method for operating an internal combustion engine in which a drive shaft Fuel pump powered by the engine and the fuel from the fuel pump in at least one Fuel manifold is promoted, from which he is over at least one fuel injector in at least one combustion chamber, and in which the amount from the fuel pump to the fuel rail delivered fuel by means of a valve device which is an outlet side of the Fuel pump with at least occasionally Connect low pressure area (control phase) and from this can separate (funding phase).

The invention further relates to a computer program electrical storage medium, a control and / or Control device and an internal combustion engine.

A method of the type mentioned at the outset is from DE 195 39 885 A1 known. In this one Fuel supply system for an internal combustion engine with Direct fuel injection described. A first electrically driven fuel pump promotes the Fuel from a fuel tank through a Fuel connection to a second, from the Internal combustion engine mechanically driven high pressure fuel pump. This second fuel pump in turn delivers the fuel via a fuel manifold ("Rail") to several fuel injection valves. This inject the fuel directly into them assigned combustion chambers.

The high pressure fuel pump is mechanical with a Output shaft of the internal combustion engine coupled. she works in proportion to the speed of the output shaft the internal combustion engine. This speed can be very be different. The output shaft can for example a crankshaft or a camshaft act the internal combustion engine.

To from the second fuel pump to the fuel rail amount of fuel delivered regardless of To be able to set the speed of the internal combustion engine an electromagnetic flow control valve is provided. With This can be an outlet side of the second fuel pump with a low pressure side of the second fuel pump get connected. In another switch position of the Flow control valve this connection is interrupted. is opened the connection, the second fuel pump rolls the fuel from its high pressure side to the Low pressure side. A promotion in the fuel manifold therefore does not take place.

From DE 197 31 102 A1 is known during a Overrun operation of the internal combustion engine, a changeover valve, which is similar to the volume control valve mentioned above is arranged to open. During the overrun operation of the Internal combustion engine is therefore no fuel from the High pressure fuel pump promoted.

The object of the present invention is a method of the type mentioned in such a way that the Fuel with the highest possible precision in the combustion chambers the internal combustion engine can be introduced at at the same time long life and as short as possible Power consumption of the fuel pump.

This task is initiated in a procedure mentioned kind in that if the Fuel pump total fuel promotes the number the delivery phases of the fuel pump per revolution of Drive shaft (delivery rate) of at least one Operating parameters of the internal combustion engine depends.

In the case of a computer program, the one mentioned at the beginning Task solved by using this computer program Programming the procedure of the above type and programmed is stored on a storage medium.

With an electrical storage medium, the task solved by having a computer program on it above type is stored.

With a control and regulating device, the task is thereby solved that it is for use in a method of the above Type is programmed.

In the case of an internal combustion engine, this accomplishes the above task solved that it includes a control and / or regulating device, which is to be used in a method of the above art is programmed.

Advantages of the invention

In the method according to the invention, the advantages an operating concept in which the fuel pump only a small number of funding phases (e.g. only one) per revolution of the drive shaft, and of such an operating concept in which the fuel pump a larger number (for example three) of funding phases has per revolution of the drive shaft, with each other be combined.

An advantage of funding with few funding phases per Revolution of the drive shaft lies in the slight thermal load on the fuel pump. In the Compression of the fuel in the fuel pump this is heated. Is the outlet side of the Fuel pump only comparatively rarely with that Low pressure area connected, is only a comparative small amount of this heated fuel to Low pressure area promoted back so that the Fuel pump heated less overall.

It also has a small number of funding phases per Revolution of the drive shaft is less Power consumption of the fuel pump as a result Dead volume has to be compressed less frequently. at A smaller number of funding phases can be found under Under certain circumstances, a larger maximum amount per revolution the drive shaft are promoted. The reason for this is the Fact that the number of opening and closing phases the valve device and the compression phases as a whole is less and therefore more time for the actual funding remains.

A larger number of fuel pump delivery phases however, per revolution of the drive shaft has advantages in With regard to the uniformity of the delivery pressure curve. There is therefore less fluctuation in the Fuel pressure in the fuel rail what the Accuracy in the metering of the fuel in the Improved combustion chambers. Due to the uniformity of the Pressure history in the fuel rail will be too the corresponding components are less stressed, what positive on the life of the corresponding Components.

Advantageous developments of the invention are in Subclaims specified.

In a first advantageous development of the The method according to the invention proposes that the Delivery rate from an operating temperature of Internal combustion engine, and / or from the injected Amount of fuel depends. Is little fuel a low delivery rate can be selected with the corresponding advantages. Are because of low taken from the fuel rail Fuel quantities are the pressure differences in the fuel rail between individual injections comparatively low, so that the corresponding components are not excessively loaded and the Accuracy of metering the injected Amount of fuel is not significantly affected.

Even at a high operating temperature Internal combustion engine can choose a low delivery rate to prevent the fuel pump from overheating avoid. At a normal operating temperature the Internal combustion engine and / or a large one In contrast, the amount of fuel to be injected is a comparatively high funding rate to be chosen to achieve corresponding advantages. With this procedure can the advantages of the invention by evaluating operating parameters of the internal combustion engine recorded anyway be achieved.

It is also proposed that a distance of a first Funding phase of a funding interval with a specific Delivery rate (delivery rate interval) from the last one Funding phase of a previous funding rate interval and / or a duration of the first funding phase of a new one Delivery rate interval before changing the delivery rate can be determined. This will Pressure overshoot while changing from one Delivery rate to another delivery rate avoided.

The method according to the invention is particularly advantageous when the middle of a last delivery phase of a certain delivery rate interval is at least approximately apart from the middle of the first delivery phase of another delivery rate interval by a waiting angle (W) of a crankshaft of the internal combustion engine, which is calculated according to the following formula: W = 720 * X + Y 2 * X * Y where X = delivery rate before switching and Y = delivery rate after switching.

This causes a deviation in the actual pressure in the fuel rail from the target pressure at a Change to a higher funding rate avoided. By the namely said angle ensures that the actual pressure about halfway through the first Funding phase after the change approximately at the level of Target pressure is.

It is also proposed that a reduction in Delivery rate is only allowed if at an angular position the crankshaft, which plus the current angular position corresponds to the waiting angle, a funding phase is permitted. This takes into account the fact that for Simplify control and regulation funding phases only at certain crank angles of the crankshaft Internal combustion engine may be permissible. So it is with one Single funding, i.e. only one funding phase per revolution the drive shaft usually only a subsidy an angle of the crankshaft at which a Injection into the first cylinder of the internal combustion engine he follows.

drawing

Figur 1

eine schematische Darstellung einer Brennkraftmaschine mit Kraftstoff-Direkteinspritzung, mit einer Hochdruck-Kraftstoffpumpe, einem Mengensteuerventil, und einer Kraftstoff-Sammelleitung;

Figur 2

ein Diagramm, in dem der Kraftstoffdruck in der Kraftstoff-Sammelleitung, eine Förderphase des Mengensteuerventils, und Einspritzphasen über einem Kurbelwinkel in einem ersten Betriebszustand der Brennkraftmaschine von Figur 1 aufgetragen sind;

Figur 3

ein Diagramm ähnlich Figur 2, für einen zweiten Betriebszustand der Brennkraftmaschine von Figur 1;

Figur 4

ein Diagramm ähnlich Figur 2, für einen dritten Betriebszustand der Brennkraftmaschine von Figur 1;

Figur 5

ein Diagramm ähnlich Figur 2, welches eine Erhöhung einer Förderrate der Kraftstoffpumpe von Figur 1 zeigt;

Figur 6

ein Diagramm ähnlich Figur 2, welches eine Verringerung der Förderrate der Kraftstoffpumpe von Figur 1 zeigt; und

Figur 7

ein Flussdiagramm, welches ein Verfahren zum Betreiben der Brennkraftmaschine von Figur 1 zeigt.

Particularly preferred exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1

a schematic representation of an internal combustion engine with direct fuel injection, with a high-pressure fuel pump, a quantity control valve, and a fuel manifold;

Figure 2

a diagram in which the fuel pressure in the fuel rail, a delivery phase of the quantity control valve, and injection phases are plotted against a crank angle in a first operating state of the internal combustion engine of FIG. 1;

Figure 3

a diagram similar to Figure 2, for a second operating state of the internal combustion engine of Figure 1;

Figure 4

a diagram similar to Figure 2, for a third operating state of the internal combustion engine of Figure 1;

Figure 5

a diagram similar to Figure 2, showing an increase in a delivery rate of the fuel pump of Figure 1;

Figure 6

a diagram similar to Figure 2, showing a reduction in the delivery rate of the fuel pump of Figure 1; and

Figure 7

a flowchart showing a method for operating the internal combustion engine of Figure 1.

Description of the embodiments

In Figure 1 carries a four-stroke internal combustion engine overall reference number 10. It drives a motor vehicle, which is not shown in Figure 1.

A fuel system belongs to the internal combustion engine 10 12. This includes a fuel tank 14 from which an electric fuel pump 16 promotes. The Electric fuel pump 16 delivers to a high pressure fuel pump 18, which is indicated by a dash-dotted line Line is indicated. On the inlet side is in the high pressure fuel pump 18 first a check valve 20 and then the actual conveyor unit 22 is arranged. On the outlet side of the conveyor unit 22 is again Check valve 24 arranged. With the high pressure fuel pump 18 in the present case it is a Three-cylinder radial piston pump, but only that Components of a cylinder are shown.

The pumped by the high pressure fuel pump 18 Amount of fuel is controlled by a quantity control valve 26 set. It is open and in its rest position connects the outlet side of the conveyor unit 22 with the Inlet side. Is in a closed switch position this connection is broken. The switch positions are changed by means of an electromagnet 27.

The high-pressure fuel pump 18 delivers to Fuel manifold 28, which is also called a "rail" referred to as. In total there are six fuel injectors 30 connected, for reasons the clarity in Figure 1 only one of the fuel injection devices provided with a reference number is. The fuel injectors 30 inject the Fuel directly in their respective combustion chambers 32 a. Here too, only one of the combustion chambers is included Provide reference numerals. In operation of the internal combustion engine 10, a crankshaft 34 is rotated. This drives in a manner not shown in the figure a drive shaft 36 of the delivery unit 22 of the high pressure fuel pump 18 on, with two crankshaft revolutions cause one rotation of the drive shaft.

The angular position of the crankshaft 34 is determined by a sensor 38, the temperature of one in Figure 1 not in detail shown cylinder head of the internal combustion engine 10 of a sensor 40, and the pressure in the fuel rail 28 detected by a sensor 42. The signals of sensors 38, 40 and 42 become a control and Control device 44 supplied, which in turn the electromagnet 27 of the quantity control valve 26 drives and a quantity MI of the fuel to be injected. The control takes place according to a method which as Computer program on a memory 46 of the control and Control device 44 is stored.

The amount of fuel from the high pressure fuel pump 18 to Fuel manifold 28 is fuel delivered adjusted with the aid of the quantity control valve 26. Is this Quantity control valve 26 closed, the fuel is Fuel manifold 28 promoted. This phase will also referred to as the "funding phase". Is this Quantity control valve 26, however, open, no fuel promoted to fuel manifold 28. Instead it will the fuel is largely depressurized to the inlet side conveyed back. This phase is also called the "tax phase" designated.

In the high-pressure fuel pump shown in Figure 1 18 can per revolution of the drive shaft 36 of the Conveyor unit 22 several funding phases or just one Funding phase should be provided. This will depend on the Signals from sensors 38, 40 and 42 and from Injection quantity MI fixed. The number of funding phases the high pressure fuel pump 18 per revolution of the Drive shaft 36 is also called a "delivery rate" or "Driving frequency" referred to.

A first operating situation is shown in FIG Internal combustion engine 10 shown. This is only one Delivery phase 48 per revolution of the drive shaft 36 provided (that in Figure 2 and the subsequent diagrams specified angles refer to the Crank angle of crankshaft 34; the drive shaft 36 of the High pressure fuel pump 18 rotates at half Rotational speed of the crankshaft 34; on Crank angle range of 720 ° corresponds to one Rotation of the drive shaft 36 of the high pressure fuel pump 18).

The funding phase 48 in FIG. 2 is comparatively long and extends from a crank angle of approximately 10 ° to to a crank angle of approximately 240 °. The injections through one of the fuel injectors 30 are in Figure 2 labeled 50. From the breadth of the Injection pulses 50 can be seen that a rather large one Fuel quantity MI is to be injected. The history of the pressure PR in the fuel rail 28 carries this Reference number 52. It can be seen that - a constant Required pressure in the fuel rail 28 provided - With a funding rate of only one funding phase 48 per Revolution of the drive shaft 36 the entire of the Fuel injectors 30 during one Fuel quantity injected MI during the working cycle a delivery phase 48 into the fuel rail 28 must be promoted.

After the end of the funding phase 48, there is initially a comparatively high fuel pressure in the fuel rail 28, which is then due to the injections 50 clearly on the initial pressure at the beginning of the funding phase 48 drops. A funding rate with a single funding phase 48 per revolution of the drive shaft 36, at large Fuel quantities MI to be injected, for example only then be selected when the sensor 40 is a relatively high one Temperature of the cylinder head of the internal combustion engine 10 detected. The reason is as follows:

During a compression phase in the conveyor unit 22 the fuel is compressed in the delivery unit 22. at a control phase is that which is warmed by the compression Fuel returned to the inlet side and back in directed the pump. This heats up the fuel even more and also the high pressure fuel pump 18 is heated yourself. The high pressure fuel pump 18 is typically in arranged in close proximity to the cylinder head. It is too whose temperature T is relatively high, can easily be a critical temperature at which the High pressure fuel pump 18 can be damaged.

Adding warm fuel can also cause it to an inadmissible increase in temperature in the fuel rail 28, the fuel injectors 30 and ultimately come in the cylinder head. this will avoided if at high cylinder head temperatures T a low funding rate with only one funding phase 48 and thus even only one control phase per revolution of the Drive shaft 36 is selected.

It can also be seen from FIG. 2 that the pressure in the Fuel rail 28 during a work cycle of Internal combustion engine 10 fluctuates significantly, so that in the individual fuel injections into the combustion chambers 32 different pressures in the fuel rail 28 rule. This reduces the accuracy of the Measuring the desired amount of fuel in the combustion chambers 32nd

Another operating situation is shown in FIG Internal combustion engine 10 shown: This is how from the width of the injection phases 50 can be seen, only one comparatively small amount of fuel MI in the Combustion chambers 32 injected. Accordingly, with the single funding phase 48, which is also in this Operating situation of the internal combustion engine 10 per revolution the drive shaft 36 of the conveyor unit 22 is provided, only comparatively little fuel is delivered. The Funding phase 48 of Figure 3 is therefore significantly shorter than the funding phase 48 of FIG. 2 falls correspondingly less also the pressure drop of the pressure PR in the fuel rail 28 during one work cycle, i.e. two Revolutions of the crankshaft 34.

The accuracy in metering the amount of fuel in the combustion chambers 32 is therefore in the operating situation of Figure 3 significantly better than in the operating situation of Figure 2. A single delivery phase 48 per revolution of Drive shaft 36 could therefore, regardless of that of the sensor 40 recorded temperature, should be selected whenever only a comparatively small amount of fuel MI from the Fuel injectors 30 into combustion chambers 32 to be injected. In many use cases a single delivery phase 48 per revolution of the drive shaft 36 only used if, for example, a Overheating of the pump and fuel can be avoided and normally the funding rate is chosen so that a good over the entire injection range Metering accuracy is possible.

Another operating situation is shown in FIG. 4 shown:

A comparatively large amount of fuel is said to be in this MI from the fuel injectors into the Fuel manifold 28 are injected, the Temperature T detected by sensor 40 is normal. In this In this case, "triple funding" is provided, ie one Funding rate at which three funding phases 48a, 48b and 48c each Rotation of the drive shaft 36 are provided. The Funding phases 48a, 48b and 48c are even within one working cycle of the internal combustion engine 10 distributed. You can see that despite the large injected Fuel quantity MI the pressure PR in the fuel rail 28 is comparatively stable.

FIG. 5 shows a change from a delivery rate to a Conveying phase 48 to one per revolution of the drive shaft 36 Funding rate with three funding phases 48a, 48b and 48c each Rotation of the drive shaft 36 shown. Are there a total of four work cycles, ie eight revolutions of the Crankshaft 34 of the internal combustion engine 10, applied. Out For reasons of clarity, there is only one injection pulse designated by the reference numeral 50. The injection pulses 50 themselves are for illustration purposes only as a line drawn, although in reality they are roughly one correspond to acute-angled triangular pulse.

The high-pressure fuel pump 18 initially works with a delivery rate of one delivery phase 48 per revolution of the Drive shaft 36. Therefore, the pressure PR increases in the Fuel manifold 28 initially steep, then again in steps with every injection pulse 50 decrease.

At a crank angle of approximately 450 ° (dash-dotted line 54), the control and regulating device 44 determines on the basis of the signals from the sensors 40, 42 and 44 that the delivery rate is to be increased to three delivery phases 48a, 48b and 48c per revolution of the drive shaft 36 , However, this changeover request 54 is not implemented immediately, but it is waited until the middle of the next funding phase 48 is reached. This is indicated in FIG. 5 by a dash-dotted line 56. A predetermined waiting angle W is then added to the current crank angle. This was according to the formula W = 720 * X + Y 2 * X * Y determined, where X = delivery rate before switching and Y = delivery rate after switching. In the present six-cylinder internal combustion engine, the waiting angle W is therefore 480 °. The first delivery phase 48a of the delivery rate with three delivery phases 48a, 48b and 48c is now set so that its center lies at a crank angle of 480 ° after the middle of the last delivery phase 48 of the delivery rate with only one delivery phase.

In Figure 6 it is shown how with a delivery rate three conveying phases per revolution of the drive shaft 36 a delivery rate with only one delivery phase 48 per revolution the drive shaft 36 is switched. The Injection pulses 50 are additionally by the number of the corresponding cylinder of the internal combustion engine 10 characterized. The in the present embodiment assumed injection or ignition sequence is therefore 1-5-3-6-2-4. The switchover is basically analog to the method explained in connection with FIG. 5, it must also be taken into account that a individual delivery phase 48 per revolution of the drive shaft 36 only permissible at such an angle of the crankshaft 34 is one in each of the cylinders with the number 1 Injection is carried out by an injection pulse 50. The Injecting pulses 50, of which for the sake of clarity only one has a reference number are off For illustration purposes only drawn as a line, even though it is in Reality in about an acute-angled triangular pulse correspond.

Although a switch request 54 has already occurred during the last delivery phase 48c (injection pulse 50 into the cylinder Number 2) has been recorded, the actual Switching (reference numeral 56) only during the the next but one funding phase 48b of the following Working cycle (injection pulse 50 in the cylinder number 3); because only then is it ensured that under Consideration of the waiting angle W of 480 ° crank angle the individual funding phases 48 of the subsequent lower ones Delivery rate at a crank angle of the crankshaft 34 in the cylinder with the number 1 is injected. This angular position of the individual Funding phases 48 is for control reasons required.

FIG. 7 shows a method by which the in Figure 6 shown switching can take place. After one Start block 58 is first queried in a block 60 whether a change in the funding rate is desired. Is the answer in block 60 "yes" (this corresponds to that in FIG. 6 with 54 designated switch request), is in block 62 checked whether at an angular position of the crankshaft 34, which the current angular position plus the waiting angle W a single funding phase is permitted. First if the query in block 62 is answered with "yes" can be changed in block 56 from the higher to the lower Delivery rate switched (this corresponds to the dash-dotted line 56 in Figure 6). Now with bigger ones Fluctuations in the fuel pressure in the fuel rail 28 is to be expected in block 66 Regulator with which the actual fuel pressure in the fuel rail 28 tracked a target fuel pressure is reset. The actual regulation takes place in Block 68. The method ends in block 70.

Claims (9)

Method for operating an internal combustion engine (10), in which a drive shaft (36) of a fuel pump (18) is driven by the internal combustion engine (10) and the fuel is conveyed by the fuel pump (18) into at least one fuel collecting line (28) from which it reaches via at least one fuel injection device (30) in at least one combustion chamber (32), and in which the amount of fuel delivered by the fuel pump (18) into the fuel collecting line (28) is adjusted by means of a valve device (26) , which can connect an outlet side of the fuel pump (18) at least temporarily to a low-pressure area (control phase) and separate from it (delivery phase) (48), characterized in that when the fuel pump (18) delivers fuel as a whole, the number of delivery phases (48) of the fuel pump (18) per revolution of the drive shaft (36) (delivery rate) of at least one operating parameter (T, MI) of the internal combustion engine machine (10) depends. A method according to claim 1, characterized in that the delivery rate depends on an operating temperature (T) of the internal combustion engine (10) and / or on the fuel quantity (MI) to be injected, and / or on a speed of the internal combustion engine. Method according to one of the preceding claims, characterized in that a distance (W) of a first funding phase (48) of a funding interval with a specific funding rate (funding rate interval) from the last funding phase (48) of a previous funding rate interval and / or a duration of the first funding phase new delivery rate interval before the change (56) in the delivery rate is or will be (62). Method according to one of the preceding claims, characterized in that the middle of a last delivery phase (48) of a certain delivery rate interval to the middle of the first delivery phase (48) of another delivery rate interval at least approximately by a waiting angle (W) of a crankshaft (34) of the internal combustion engine (10), which is calculated using the following formula (62): W = 720 * X + Y 2 * X * Y where X = delivery rate before switching and Y = delivery rate after switching. Method according to Claim 4, characterized in that a change (56) in the delivery rate is only permitted if a delivery phase (48) is permissible for an angular position of the crankshaft (34) which corresponds to the current angular position plus the waiting angle (W). Computer program, characterized in that it is programmed to carry out the method according to one of the preceding claims and is stored on a storage medium (46). Electrical storage medium (46) for a control and / or regulating device (44) of an internal combustion engine (10), characterized in that a computer program according to claim 6 is stored on it. Control and / or regulating device (44) for an internal combustion engine (10), characterized in that it is programmed for use in a method according to one of claims 1 to 5. Internal combustion engine (10), in particular for a Motor vehicle, with a control and / or regulating device (44), which is for use in a method according to one of the Claims 1 to 5 is programmed.

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