DE102015218047A1 - Method and device for operating an internal combustion engine, in particular a motor vehicle with dual fuel injection - Google Patents

Abstract

The present invention relates to a method and a device for operating an internal combustion engine, in particular of a motor vehicle with a dual suction tube-based fuel metering (SRE) and a direct fuel metering (BDE), wherein the intake-pipe-based fuel metering and the direct metering of fuel in a variable blending operation by means of a division (415 ), and wherein provision is made in particular for exhaust gas recirculation of the internal combustion engine to take place with a predefined exhaust gas recirculation rate (405) in said variable mixing mode and for the said distribution (415) to be adapted to the predetermined exhaust gas recirculation rate (405).

Description

The invention relates to a method and a device for operating an internal combustion engine, in particular of a motor vehicle with dual fuel metering, according to the preambles of the respective independent claims. The present invention also relates to a computer program, a machine-readable data carrier for storing the computer program and an electronic control unit, by means of which the method according to the invention can be carried out.

State of the art

From practice it is known that an internal combustion engine in an injection pure operation, in which a cylinder of the internal combustion engine during a working stroke of the cylinder exclusively with an injector of a port injection (SRE) or with a direct injection injector (BDE) can be fueled , or can be operated in a mixed injection mode, in which a cylinder of the internal combustion engine can be fueled during its working cycle with both the SRE injector and the BDE injector with fuel. A ratio or a division between an injection quantity of the fuel by means of the SRE injector and an injection quantity of the fuel by means of the BDE injector can be set as a function of engine-specific properties for different load points. The engine-specific characteristics must be set and controlled as accurately as possible and in consideration of boundary conditions, such as emission regulations (for example California Air Resources Board (CARB) legislation), performance, starting behavior and also diagnoses for functions of the internal combustion engine.

In a said mixing operation, the extent of said division of the fuel mass is known to be dependent on operating conditions of the internal combustion engine. Thus, as an operating function, a component protection function or an emergency function of the internal combustion engine can be implemented to perform a dynamic compensation, to provide a heating of the catalyst after a cold start, or to perform a mixture adaptation, a tank ventilation and / or various diagnoses.

A method for determining a said degree of division in here affected internal combustion engine goes out DE 10 2010 039 434 A1 out. In this case, an operating point-dependent division measure is determined, wherein a plurality of special operating functions, which are assigned to specific operating conditions, each assigned a priority. It is determined which particular operating function (s) exist and one or more operating functions selected depending on the respective priority. Possible restrictions on the permissible ranges of the selected operating functions, eg, a component protection operation function, adapting to dynamic behavior, and / or heating a catalyst, will determine a suitable amount of division. In this way, even in the presence of operating conditions, which are assigned to a plurality of operating functions, an optimal operation of the internal combustion engine can be ensured.

Disclosure of the invention

The invention is based on a dual fuel metering device which is operated here and which is operated in a mixed operation, in particular in a variable mixing operation, in which a variable fuel distribution takes place with a certain distribution ratio between a named intake-pipe-based fuel metering and a said direct fuel metering.

Such a variable mixing operation allows the advantages of both types of fuel for optimal mixture formation of a fuel-air mixture and the combustion of this mixture in a combustion chamber of the internal combustion engine to use equally. Thus, a direct fuel metering in a dynamic or full-load operation of the internal combustion engine is more advantageous, and in particular uncontrolled combustion or spontaneous combustion of the metered fuel (so-called "knocking") is effectively prevented. On the other hand, suction pipe-based fuel metering in a partial load operation of the internal combustion engine is more advantageous because it is more effective in reducing particulates and nitrogen oxides in the exhaust gas.

The invention is based on the idea, in an internal combustion engine with a so-called exhaust gas recirculation (EGR) serving to reduce exhaust emissions with a certain, i. predetermined or predefinable exhaust gas recirculation rate to adapt said mixed operation to the respective or current exhaust gas recirculation rate or to correlate with this.

The invention proposes a method which is improved over the prior art and a corresponding device in which said relative split of intake manifold-based fuel metering (SRE) and direct fuel metering (BDE) is the result of the overall variable mixing operation of a person concerned Dualsystems depending on a specified exhaust gas recirculation rate (EGR rate) takes place.

The exhaust gas recirculation (EGR) is preferably a so-called internal EGR. Compared with a so-called external EGR, in which the regulation of the exhaust gas recirculation takes place by means of an exhaust gas recirculation valve arranged outside the internal combustion engine, the advantage of internal EGR is lower throttle losses and resulting fuel consumption advantages as well as a reduction of nitrogen oxides in the combustion exhaust gases. In addition, an internal EGR in transient engine operation, e.g. during fast load changes, faster controllable or adjustable and therefore more accurate than an external EGR. In addition, the disadvantage typically occurring with an external EGR of an unequal filling of the cylinder of the internal combustion engine with recirculated exhaust gas does not exist.

The method according to the invention is based, in particular, on the recognition and the technical effect that the internal EGR rate and a remaining amount of residual gas in a cylinder of the internal combustion engine caused thereby overlap the activation times of inlet and / or outlet valves arranged in an inlet channel and an outlet channel of the respective cylinder is determined. These activation times relate in particular to the opening of these valves as well as the pressure conditions prevailing at these times in the cylinder. It should also be ensured that there is a sufficient pressure gradient between the inlet side and the outlet side, so that the combustion in the respective combustion chamber of the cylinder is better and more stable controllable and thus required for the operating comfort of the motor vehicle smoothness of the internal combustion engine is achieved.

In addition, too large a proportion of suction pipe-based metered amount of fuel caused by the corresponding introduced fuel vapor displacement of air in the intake manifold. This reduces the pressure gradient between a named intake valve and exhaust valve, which in turn leads to an unstable amount of residual gas.

In the case of the method according to the invention, it can therefore be provided that in the case of a change, in particular an increase in the internal EGR rate, a certain level of the pressure gradient or the differential pressure between a given inlet channel, a respective cylinder and an outlet channel is maintained as far as possible To be able to set the EGR rate in the combustion chamber reliably and reproducibly. If it is determined that a corresponding minimum pressure gradient is not maintained or guaranteed, the said distribution of the fuel quantity to be injected via the SRE and the BDE injection path can lead to a (relatively) reduced proportion of the SRE contribution and a (relatively) increased Proportion of the BDE contribution.

In the method according to the invention, it can further be provided that, for a given relative distribution between a given SRE and BDE fuel metering, an activation of the intake valve and / or the exhaust valve takes place, as a result of this actuation it is checked whether there is a sufficient pressure gradient during activation between the inlet channel, the cylinder and the outlet channel, it is ensured that if this condition is not met, a changed division is determined, and that the inlet valve and / or the outlet valve are controlled for the changed division.

The method and the device according to the invention make possible an improved, in particular safer, more comfortable, lower-emission and at the same time more stable combustion mode of an internal combustion engine with dual fuel metering, in particular during driving operation of the motor vehicle and also while maintaining it, operated in a named variable mixing operation the required by the aforementioned legislation exhaust emissions of the internal combustion engine.

It should be emphasized that a named variable mixing operation comprises exclusively intake-pipe-based metering of fuel, exclusively direct fuel metering and any variable division between the two operating modes. In addition, such a mixed operation can be applied in the starting phase of the internal combustion engine and thereby enable different start types.

The invention can be used in particular in a dual fuel injection system of an internal combustion engine of a motor vehicle which is affected here. In addition, an application in the industrial field, e.g. In internal combustion engine used in chemical engineering with such a dual fuel injection possible.

The computer program according to the invention is set up to carry out each step of the method, in particular if it runs on a computing device or a control device. It allows the implementation of the method according to the invention on an electronic control unit, without having to make structural changes to this. For this is the machine-readable Data carrier provided on which the computer program according to the invention is stored. By loading the computer program according to the invention onto an electronic control unit, the electronic control unit according to the invention is obtained, which is set up to control a dual fuel metering device affected here by means of the method according to the invention.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a schematic representation of a dual fuel injection device for a four-cylinder internal combustion engine, according to the prior art.

2 schematically shows the timing of fuel injections in a fuel port injection, according to the prior art.

3 schematically shows the timing of fuel injections in a direct fuel injection, according to the prior art.

4 shows an embodiment of the method according to the invention with reference to a combined block / flow diagram.

5 schematically shows a pressure gradient between a cylinder, an inlet channel and an outlet channel of an internal combustion engine concerned here.

Description of exemplary embodiments

In the 1 shown internal combustion engine has four cylinders 11 on top of a cylinder head 12 are covered. The cylinder head 12 limited in each cylinder 11 together with a cylinder, not shown here 11 guided reciprocating a combustion chamber 13 , which has an inlet opening, which is also not shown, and which is controlled by an inlet valve (not shown here). The inlet opening forms the mouth of a cylinder head 12 penetrating, also not shown here inlet channel.

The illustrated fuel injector includes an air flow path 18 for supplying combustion air to the combustion chambers 13 the cylinder 11 , which are end-to-end, to the individual inlet channels 16 leading flow channels 17 having. In addition, a first group of fuel injection valves 19 that inject fuel directly into each combustion chamber 13 the cylinder 11 inject as well as a second group of fuel injectors 20 , the fuel in the flow channels 17 inject, arranged. It should be noted that alternatively every cylinder 11 a separate fuel injection valve 20 can be assigned.

The first group of fuel injection valves 19 which directly into the cylinder 11 Injecting is by a high-pressure fuel pump 21 supplied while the second group of fuel injectors 20 , which flows into the flow channels 17 inject, from a low-pressure fuel pump 22 be supplied. A usually in a fuel tank 23 arranged low-pressure fuel pump thereby promotes fuel from the fuel tank 23 on the one hand to the second group of fuel injection valves 20 and on the other hand to the high-pressure fuel pump 21 , The injection timing and the injection duration of the fuel injection valves 19 . 20 are controlled by an integrated in an engine control unit electronic control unit, depending on operating points of the internal combustion engine, wherein substantially the fuel injection via the fuel injection valves 19 the first group takes place and the fuel injectors 20 The second group can only be used in addition to shortcomings of the direct fuel injection by the fuel injection valves 19 Improve the first group in certain operating areas and to use additional degrees of freedom or injection strategies.

The fuel injectors 20 The second group are designed as multi-jet injection valves, the at least two separate, mutually angularly offset fuel jets at the same time and inject and in the air flow path 18 are arranged so that the injected fuel jets 24 . 25 , which usually have the shape of a spray cone, get into different flow channels. In this internal combustion engine are two double-jet injectors 26 . 27 provided in the air flow path 18 are placed so that the one two-jet injector 26 in the first and second cylinders 11 leading flow channels 17 and the second dual-jet injection valve 27 in the third and fourth cylinders 11 leading flow channels 17 inject. These are the flow channels 17 designed so that between two directly adjacent flow channels 17 one Installation point for the two-jet injection valve 26 respectively. 27 is available.

It is also known that, in the case of a named fuel intake manifold injection of an internal combustion engine affected here, the air-fuel mixture arises outside the combustion chamber in the intake manifold. The respective injection valve injects the fuel before an inlet valve, wherein the mixture flows in the intake stroke through the open inlet valve into the combustion chamber. The fuel is supplied by means of a fuel delivery module, which promotes the required amount of fuel with a defined pressure from the tank to the injectors. An air control ensures that the engine is the right air mass available at each operating point. The injectors arranged on a fuel feeder precisely meter the desired amount of fuel into the airflow. Said engine control unit regulates based on the torque as a central reference the required air-fuel mixture. An effective exhaust gas purification is achieved with a lambda control, by means of which always a stoichiometric air-fuel ratio (λ = 1) is adjusted.

In contrast, in a direct fuel injection, the air-fuel mixture is formed directly in the combustion chamber. Fresh air flows in via a designated inlet valve, the fuel being injected into this air stream at high pressure (up to 200 bar). This allows optimal turbulence of the air-fuel mixture and improved cooling of the combustion chamber.

It is also known that in a four-stroke internal combustion engine (gasoline engine) the working cycle includes the processes suction, compression, working and ejection, each cylinder moves up and down twice and thereby in two top dead centers (TDC) and two bottom dead centers (UT ) comes to a standstill. The crankshaft thus executes two revolutions in a working cycle, the camshaft one revolution. The ignition of the spent in a cylinder gas-fuel mixture takes place at a top dead center, in which the mixture is just compressed. This is called the ignition TDC (ZOT). On the other hand, there is an overlap OT (ÜOT) where both the intake and exhaust valves are open at the transition from exhaust to intake.

Accordingly, ignition is carried out at all top dead centers (TDC) immediately after starting, at least in one cylinder, wherein at certain top dead centers, in particular every second TDC, at crankshaft angles of 720 ° there is a shift in the ignition time. Depending on whether at the top dead center (TDC), in which the ignition timing is performed, or at a shifted by 360 crankshaft angle, the air-fuel mixture is actually ignited, a reduction of the physical work done in each cylinder is observed.

In 2 the y-direction at different speeds of the internal combustion engine taking place Saugrohreinspritzungen over the crankshaft angle (KW) measured in the unit [degrees] are shown. The four-stroke combustion cycle according to the gasoline engine principle comprises, as is known, crankshaft angles between a first bottom dead center (UT1), a first top dead center (TDC), another bottom dead center (UT2) and another top dead center (ZOT), in which the air present in the combustion chamber Fuel mixture is ignited.

The mentioned time reference marks are given very differently for the two injection paths. This is the case with intake manifold injection (SRE), as in 2 shown schematically, at only four examples shown four different speeds n = 1000, 2000, 4000 and 7000 U / min taking place injections 200 one before the end 210 of the injection cycle 225 to be provided, constant temporal delay share 205 considered, since the injection valves are arranged at a SRE outside of the respective combustion chamber of the internal combustion engine and the fuel therefore must first reach the combustion chamber from the injection site. This extra time is changing, as in 2 to see, not with changing or increasing speed of the internal combustion engine. Therefore, the injections are controlled accordingly earlier, eg at 7000 U / min even before the time behind the previous ZOT 220 Ignition UT1, so at all speeds of the constant time required 205 provided. The entire time injection window for the injection cycle shown corresponds, as already mentioned, the marked bracket 225 , The one on the previous ZOT 220 subsequent next ZOT is with 215 designated.

In contrast, in a direct gasoline injection (BDE) at the respective injections 300 given as reference marks (concrete) angle marks empirically, as in 3 is shown schematically. In other words, in contrast to the SRE, the BDE does not take into account any constant time shares, such as those from the course 305 the respective injection ends can be seen. Therefore, the injections can be closer to the ignition event of the ZOT 315 and are therefore calculated accordingly at later times. In the present example, the end follows 310 of the injection cycle shown here 325 an ignition on following ZOT 315 , The ZOT 315 previous ignition timing takes place on a preceding ZOT 320 ,

In a dual system mentioned above, the described two components are known to be combined in the form of systems or system components. In particular, a correct distribution of the available or to be metered total fuel mass is required. The total fuel mass KM _ges for a cylinder is composed as in the following equation (1): KM _tot = KM _SRE + KM _BDE , (1) where KM _{SRE is} the relative fuel mass of the SRE path and KM _{BDE is} the relative mass of fuel of the BDE path.

• – Temperatur der Brennkraftmaschine bzw. des/der jeweiligen Brennraums/-räume
• – Hochdruck im BDE-Betrieb einer hier betroffenen dualen Kraftstoffzumessvorrichtung
• – Vorliegender Fehlerfall
• – Ergebnis einer On-Board-Diagnose
• – Etwa durchgeführte Adaptionen bei der Kraftstoffzumessung bzw. -einspritzung
• – Besondere Fahrsituationen, z.B. fahrerseitige Aktivierung eines „Kick-down“ an einem Fahrpedal oder fahrerseitiges Zurückschalten eines Zwischengangs

As described below, the calculation of a suitable for a present operating situation of the internal combustion engine distribution factor between SRE and BDE operation takes place. In this case, first of all possible operating states and / or currently existing operating requirements of an internal combustion engine affected here or of a motor vehicle having such an internal combustion engine are detected. The operating conditions or requirements recorded in this way are first assigned to the following exemplary categories:

• - Temperature of the internal combustion engine or the / the respective combustion chamber / spaces
• - High pressure in the BDE operation of a dual fuel metering device concerned here
• - Present error case
• - Result of an on-board diagnosis
• - Approximately carried out adaptations in the fuel metering or injection
• - Special driving situations, eg driver-side activation of a "kick-down" on an accelerator pedal or driver-side downshift of an intermediate gear

Thus, depending on the temperature of the internal combustion engine, an optimum operating range may be at the start of an internal combustion engine having a dual fuel meter, e.g. with regard to speed, particle formation or response, by means of which a named prioritization can be carried out. Other detection options for the mentioned different types of start are, in addition to the temperature, the high pressure required for a high-pressure start or a start / stop operation with rapid restart in a named BDE mode.

Due to the mentioned plurality of possibilities for the distribution factor, which are physically equivalent but are preferable under the mentioned, different operational aspects in real driving, an appropriate prioritization is required, so that an unambiguous determination or determination of a distribution factor is made possible constantly between different distribution factors must be changed. Such frequent changes are therefore to be avoided, since a change in the distribution factor on the one hand is associated with an increased applicative effort in order to adjust the change in real operation as possible torque and mixture neutral.

An embodiment of the method according to the invention is described below with reference to an in 4 described combined block / flow diagram. In this case, valve timing of a specified intake valve and of an exhaust valve is initially dependent on a desired, ie predetermined, EGR rate 405 , pilot-controlled 400 , By the pilot control 400 In particular, the said time overlap of the two valves is controllable. By means of a suitable sensing of the closing of the intake and exhaust valves, for example in a manner known per se by means of structure-borne noise detection or from existing characteristic maps or characteristic curves for the respective valve lift course, the opening and closing of the intake and exhaust valves is precisely determined.

In step 410 Now, a control of the intake valve and the exhaust valve, based on a predetermined in the manner described division factor 415 between SRE and BDE injection. As a result of this activation 410 will be in a subsequent test step 420 checked, whether with this control 410 a sufficient pressure gradient is ensured between the inlet channel, the cylinder and the outlet channel. Is this condition 420 fulfilled, becomes again to step 410 jumped back to a re-actuation of the intake valve and the exhaust valve, based on a possibly adjusted in the meantime distribution factor 415 to perform. Is the condition 420 not satisfied, then a changed distribution factor 415 determined and there is a renewed control 410 of the intake valve and the exhaust valve based on the so-changed division factor.

An underlying cylinder 500 an internal combustion engine affected here is schematically in 5 shown. In particular, one between the cylinder 500 , an inlet channel 505 and an exhaust duct 510 illustrates a pressure gradient occurring in a given internal combustion engine. The cylinder 500 is known to comprise a piston 515 and one with the piston 515 frictionally connected, arranged in a crankcase, not shown here crankshaft 520 , In the cylinder area of the inlet channel 505 is an inlet valve 525 arranged, whereas in the cylinder region of the outlet channel 510 is an exhaust valve 530 is arranged. From a fuel pump 540 subsidized fuel is via an injection valve 535 in the inlet channel 505 injected by way of a named intake manifold injection (SRE). In addition, a direct (BDE) injection of fuel via a likewise with the fuel pump 540 connected high-pressure injection valve 545 respectively.

With an increase in the internal EGR rate, it is required a certain level of the pressure drop and the differential pressure Ap = p _in - _a p between the inlet channel 505 , the cylinder 500 and the outlet channel 510 maintain, so that the EGR rate in the combustion chamber can be set reliably and reproducibly. In the cylinder 500 while a pressure p _{zyl is applied} . The significance of the corresponding _a pressure variables p, p is p _cyl and _out of 5 to see. If a corresponding minimum pressure gradient is not ensured, the aforementioned division of the fuel quantity to be injected in each case via the SRE and the BDE injection path is adjusted to a (relatively) reduced share of the SRE contribution and a (relatively) increased share of the BDE contribution.

It should be noted here that the pressure conditions generated by said actuation of the intake and exhaust valves acting as gas exchange valves are achieved in a manner known per se during the relevant periods of time, e.g. during a specified load change of the internal combustion engine, measurements performed can be detected or can be determined via corresponding model values.

• – Interne AGR-Rate;
• – Drehzahl;
• – Last;
• – Luftmassenstrom;
• – Drosselklappenstellung;
• – Druck im Ansaugkanal.

Said change of the division or the division factor for the above-mentioned purpose can be made dependent on the following operating parameters of the internal combustion engine:

• - Internal EGR rate;
• - Rotation speed;
• - Load;
• - air mass flow;
• - Throttle position;
• - Pressure in the intake duct.

An increase in the EGR rate is known to result in a slower burn through behavior of the fuel / air mixture in the combustion chamber. However, an increased EGR rate, in turn, leads to an increase in the noise of the internal combustion engine negatively affecting the comfort.

Due to the increase in the amount of fuel injected via the BDE path, increased turbulence and corresponding thorough mixing of the fuel / air mixture in the combustion chamber occur due to the kinetic energy supplied by the injection pulse of the fuel. This in turn leads to an improved, faster combustion or a faster burnout of the fuel / air mixture and thereby to an improved stability of the total mixture conversion through the combustion.

The described method can be used particularly advantageously in fuel metering systems in which the valve drive is not or only gradually adjustable, both with regard to corresponding opening times, opening times and variable valve lifts.

The method described can be implemented in the form of a control program for an electronic control unit for controlling an internal combustion engine or in the form of one or more corresponding electronic control units (ECUs).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010039434 A1 [0004]

Claims (9)

Method for operating an internal combustion engine, in particular of a motor vehicle with a dual fuel metering device, in which a suction pipe-based fuel metering (SRE) and a direct metering of fuel (BDE) in a variable mixing operation are based on a division ( 415 ), characterized in that in said variable mixing mode an exhaust gas recirculation of the internal combustion engine with a predetermined exhaust gas recirculation rate ( 405 ) and that the said allocation ( 415 ) to the predetermined exhaust gas recirculation rate ( 405 ) is adjusted. Method according to claim 1, characterized in that a control ( 410 ) one in an inlet channel ( 505 ) of a cylinder ( 500 ) of the internal combustion engine arranged inlet valve ( 525 ) and / or one in an outlet channel ( 510 ) of the cylinder ( 500 ) of the internal combustion engine arranged exhaust valve ( 530 ) on the basis of the to the predetermined exhaust gas recirculation rate ( 405 ) adapted breakdown ( 415 ) he follows. A method according to claim 1 or 2, characterized in that the exhaust gas recirculation with the predetermined exhaust gas recirculation rate ( 405 ) is realized by an internal exhaust gas recirculation. Method according to claim 2 or 3, characterized in that when the exhaust gas recirculation rate ( 405 ) a certain pressure difference between an inlet channel ( 505 ) of the cylinder ( 500 ) and an outlet channel ( 510 ) of the cylinder ( 500 ) is maintained. A method according to claim 4, characterized in that it is detected whether a minimum differential pressure between the inlet channel ( 505 ) and the outlet channel ( 510 ) of the cylinder ( 500 ), that in the absence of this differential pressure, a modified distribution ( 415 ) is determined, and that a control of the inlet valve ( 525 ) and / or the exhaust valve ( 530 ) for the modified breakdown ( 415 ) he follows. A method according to claim 5, characterized in that in the absence of this differential pressure, said division ( 415 ) is adjusted to a reduced proportion of intake manifold based metering and to an increased proportion of direct fuel metering. A computer program configured to perform each step of a method according to any one of claims 1 to 6. Machine-readable data carrier on which a computer program according to claim 7 is stored. Electronic control unit which is set up to control an internal combustion engine or a fuel metering device by means of a method according to one of claims 1 to 6.

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