Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
  • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
  • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/30—Controlling fuel injection
  • F02D41/38—Controlling fuel injection of the high pressure type
  • F02D41/3809—Common rail control systems
  • F02D41/3836—Controlling the fuel pressure

Definitions

• the present invention relates to a method for operating an internal combustion engine, in particular a motor vehicle.
• the invention also relates to an associated internal combustion engine.
• Modern internal combustion engines have a fuel injection system with at least one injector per combustion chamber of the internal combustion engine.
• the respective injector is usually a needle valve, which is characterized by a needle-shaped valve member for controlling injection holes.
• the fuel injection can be influenced.
• Small hole cross sections are advantageous, since this improves the atomization effect during the injection process and produces smaller, faster evaporating fuel droplets.
• the smaller the hole cross-sections the greater the risk of coking the injection holes.
• the flow-through cross section of the injection holes decreases, which influences the amount of injected fuel per injection process, namely reduced.
• the combustion process changes, which affects the operating state of the internal combustion engine.
• the internal combustion engine in particular in the idling range, can run restlessly.
• the energy efficiency changes
• DE 10 2005 034 449 A1 discloses a method and a device for detecting coking at injection nozzles in combustion chambers of internal combustion engines.
• a prescribable operating point of the injection of fuel into an unpolluted injection nozzle at least one cylinder pressure gradient criterion or at least one thermodynamic criterion in an origin is measured at a predeterminable time (original time of origin) and in the same Operating point, the at least one measured criterion of the cylinder pressure curve or the thermodynamic profile of the same injector to a predetermined
• Time is measured for diagnostic purposes (diagnosis time point), wherein the value measured at the time of diagnosis for the detection of coking with the in
• a suitable cylinder pressure gradient criterion is, for example, a maximum
• Another cylinder pressure gradient criterion is, for example, an average pressure that can be calculated per working cycle from the cylinder pressure curve.
• a suitable thermodynamic criterion is, for example, a level of a plateau of an integral heating course per working cycle between the combustion of a pre-injection and main injection.
• Another thermodynamic criterion is, for example, an angular position of the 5% energy conversion point per working cycle or alternatively an angular position of a minimum of the heating profile per working cycle.
• Detection of coking should be carried out as part of an on-board diagnosis and generate a corresponding error signal in the case of a detected coking and possibly be signaled via a warning device. This makes it possible, for example, to allow the injectors to be cleaned in the event of coking in order to enable proper operation for the internal combustion engine.
• the present invention is concerned with the problem of providing an improved embodiment for a method or for an internal combustion engine of the aforementioned type, which is characterized in particular by the fact that the effects of coking of the respective injector on the operating behavior of the internal combustion engine are reduced.
• the invention is based on the general idea, the presence of a
• Injectors are monitored and the fuel injection system is adapted depending on the determined coking so that the adverse consequences of coking are eliminated or at least reduced.
• the invention proposes this in particular during a
• Combustion chamber to determine an actual conversion rate of injected with the respective injector in this combustion chamber fuel during a combustion process.
• this actual conversion rate can be compared with a target conversion rate, which is predetermined for the predetermined operating state of the internal combustion engine. If a setpoint-actual deviation occurs, at least one injection parameter of the fuel injection system can now be adapted to reduce the actual-to-actual deviation as a function of this setpoint-actual deviation. This means that the adaptation of the fuel injection system
• Combustion process occurring target-actual deviation of the conversion rate is reduced at a later combustion process and at best eliminated, that is within tolerable limits.
• This process can be realized, for example, in the manner of a closed-loop control or in the manner of a closed loop.
• the target conversion rate which is used for the target / actual comparison, can be determined, for example, in the context of a reference measurement with new injectors.
• the invention utilizes the knowledge that the conversion rate of the fuel converted in the combustion chamber during a combustion process at least in the
• the injected fuel quantity is specified comparatively exactly for the predetermined operating state, namely by the relevant for this
• Injection parameters such. B. hole cross-section, number of holes, injection pressure and
• the invention now also makes use of the consideration that by coking at the respective injector essentially only the effective hole cross section, that is to say the cross section present for the throughflow, can change, while the other injection parameters are essentially unaffected by coking. Consequently, a reduced amount of fuel suggests a coking of the injection holes.
• a decreasing coking can be adapted by the target-actual comparison of the conversion rate and adaptation of the respective injection parameter.
• a decreasing coking can occur, for example, when coking residues detach from the injection holes, for example due to thermal expansion effects, vibrations and the like. Since the coking of
• Injection holes can be compensated due to the procedure according to the invention, even very small and smallest nozzle hole geometries can be used. As a result, for example, the raw emission of the internal combustion engine can be improved. Furthermore, an exhaust gas aftertreatment can thereby be improved. Also, it comes then to a reduced oil dilution by lower fuel accumulation on combustion chamber walls.
• a full-load operation of the internal combustion engine can be used as the predetermined operating state of the internal combustion engine.
• This embodiment is based on the consideration that, especially in full load operation, there is a direct correlation between the conversion rate and the fuel quantity per combustion process. For example. are in full load disturbing influences, such. As a high exhaust gas recirculation rate and / or a stoichiometric air supply, reduced.
• an operating point in the partial load can be used as a predetermined operating condition.
• the actual conversion rate can be determined during a predetermined crankshaft angle range.
• Embodiment is based on the consideration that it is not absolutely necessary to determine the conversion rate, the entire crankshaft angle range of the
• the actual conversion rate can be determined on the basis of a pressure curve which is present in the respective combustion chamber during the course of the combustion process
• the internal combustion engine can be equipped with a corresponding, suitable pressure-measuring sensor, with which it is possible, in particular, to measure the pressure within the respective combustion chamber.
• the pressure curve in the combustion chamber correlates with the chemical energy released during the combustion process, ie the conversion or the conversion rate of the injected fuel. This in turn correlates with the injected one
• the injected fuel quantity can be determined via the time-resolved pressure curve.
• An embodiment in which an injection pressure provided to the respective injector is adapted as an injection parameter is particularly expedient.
• Embodiment is based on the finding that the injected amount of fuel substantially the product of the available, permeable
• Fuel quantity corresponds to reduce the effect of coking, thus increasing the injection pressure.
• the reduced through the coking flow-through cross section of the injection holes can be compensated.
• the injection duration remains constant.
• Pressure supply line so-called “common rail” operates, to which a plurality of injectors are connected, the injection pressure can be varied by varying the fuel pressure in this pressure supply line, in other words, at a
• the rail pressure is varied to achieve the desired adaptation of the fuel injection system.
• the rail pressure that is to say the fuel pressure in the respective common pressure supply line, can, for example, be preceded by a corresponding activation of one of the respective pressure supply lines
• High-pressure fuel pump can be realized.
• Fuel pump per injector works, so-called. "Pump-nozzle system", the injection pressure can be varied by varying a pump pressure generated by the respective fuel pump.
• a splash duration map which assigns injection durations to all operating states of the internal combustion engine, can be adapted depending on the changed injection pressure.
• Such a splash duration map assigns all the operating conditions of the internal combustion engine the respectively required
• Parameters for the calculation or design of the splash duration map namely the injection pressure.
• Injection pressure for example, by taking into account a dependent of the changed injection pressure correction factor, it is possible for all operating conditions of the
• a plurality of actual conversion rates can be detected during the predetermined operating state, wherein for determining the target-actual deviation then a mean actual conversion rate is compared with the predetermined target conversion rate. This can either for all injectors
• average actual turnover rate can be determined or for each individual injector an average actual turnover rate can be determined.
• the determined actual turnover rates then have a higher reliability.
• Injection parameters are performed globally for all injectors of the internal combustion engine.
• coking is considered to occur substantially equally with all injectors.
• the realization of such an embodiment is comparatively simple. In this case, the actual conversion rate can also be averaged for all injectors.
• Injection parameters locally for the respective injector so be performed individually.
• individual coking per injector is taken into account.
• the actual sales rate is also recorded individually for the respective injector.
• An internal combustion engine according to the invention which is used, for example, in a motor vehicle, comprises a fuel injection system which has at least one injector for each combustion chamber of the internal combustion engine. Furthermore, the Internal combustion engine equipped with a control device that is configured or programmed so that they can perform the method described above for operating the internal combustion engine. For this purpose, the control device can be suitably coupled to the injectors or with suitable pressure sensors or with at least one fuel pump.
• FIGURE 1 shows a greatly simplified schematic diagram of an internal combustion engine.
• an internal combustion engine 1 which, for example, can be arranged in a motor vehicle, comprises a plurality of cylinders 2, each of which encloses a combustion chamber 3.
• a piston not recognizable here, is arranged such that it can be adjusted in terms of stroke.
• the internal combustion engine 1 is equipped with a fuel injection system 4, which is configured in the illustrated preferred example as a common rail system.
• the fuel injection system 4 has, for each combustion chamber 3, an injector 5, which projects into the respective associated combustion chamber 3 with an injector end 6 which has a plurality of injection holes (not shown here). All injectors 5 are connected to a common pressure supply line 7, so-called "rail" or "common rail".
• a high-pressure fuel pump 8 is the pressure side connected to the pressure supply line 7 and generates a fuel pressure in the pressure supply line 7, which may correspond to the injection pressure of the injectors 5.
• the individual injectors 5 can also contain so-called pressure translators which convert the fuel pressure provided via the pressure supply line 7 into a significantly higher input. can translate injection pressure. Since the pressure booster act only a relative pressure gain, a variation of the fuel pressure in the pressure supply line 7 to a proportional variation of the injection pressure at the respective injector 5. For simplicity, injectors 5 are considered without such pressure booster, so that the fuel pressure in the pressure supply line 7 the injection pressure of the injector 5 corresponds.
• Fuel not required by the injectors 5 is supplied via a throttle 9 and a return line 10 to a fuel tank 11, from which, in the example, a feed line 12 leads to the high-pressure pump 8.
• a throttle 9 and a return line 10 to a fuel tank 11, from which, in the example, a feed line 12 leads to the high-pressure pump 8.
• additional pumps, valve means, and the like may be present.
• the internal combustion engine 1 is equipped with a plurality of cylinder pressure sensors 13, wherein each cylinder 2, such a cylinder pressure sensor 13 is provided, with the aid of which the pressure in the combustion chamber 3 of the respective cylinder 2 can be measured.
• a line pressure sensor 14 is also provided, by means of which the pressure in the pressure supply line 7 can be measured.
• the internal combustion engine 1 is also equipped with a control device 15. This is electrically connected via control lines 16 to the injectors 5, via a control line 17 to the high-pressure pump 8, via signal lines 18 to the cylinder pressure sensors 13 and via a signal line 19 to the line pressure sensor 14.
• the control device 15 can thus control the injectors 5 and the high-pressure pump 8. Furthermore, it receives the pressure measurement signals of the cylinder pressure sensors 13 and of the line pressure sensor 14. Furthermore, the controller 15 knows the current operating state of the internal combustion engine 1.
• the control device 15 can be coupled to a corresponding engine control unit. Likewise, it is possible to integrate the control device 15 at least partially in terms of hardware in the engine control unit and / or at least partially implement software in the engine control unit.
• the internal combustion engine 1 presented here can be operated with the aid of the control device 15 as follows:
• a predetermined operating state of the internal combustion engine 1 preferably at full load operation of the internal combustion engine 1, with the aid of the cylinder pressure sensors 13 the temporal pressure curve within the combustion chambers 3 are determined during the respective combustion process. From the pressure curve in the respective combustion chamber 3 during a predetermined crankshaft angle range, an actual conversion rate of the fuel injected with the respective injector 5 into the respective combustion chamber 3 during the combustion process can be determined. The actual conversion rate determined in this way can now be compared with a desired conversion rate, which is predetermined or known for the predetermined operating state of the internal combustion engine 1. This desired conversion rate can be determined, for example, during the predetermined operating state in the context of a reference measurement, which is expediently carried out with new injectors 5.
• a desired-actual deviation can now be determined.
• at least one injection parameter of the fuel injection system 4 can now be adapted such that a reduction of the nominal / actual deviation occurs.
• the controller 15 may adapt the injection pressure available to the injectors 5 for performing the fuel injection.
• the control device 15 can for this purpose control the high-pressure pump 8 to generate an increased fuel pressure. In this way, the desired-actual deviation of the conversion rate can be minimized, so that in the best case over the entire life of the internal combustion engine 1 almost constant combustion properties can be ensured.
• the control device 15 expediently has access to a spray duration characteristic map 20 which assigns injection periods to all operating states of the internal combustion engine 1. If the control device 15 now due to a target-actual comparison of the conversion rate a
• the controller 15 may additionally perform a corresponding adaptation of the injection duration map 20 to the changed injection pressure.
• the adapted injection duration characteristic map 20 can be used as before in all operating states of the internal combustion engine 1, although the target actual deviation of the conversion rate has been determined only for a single, predetermined operating state, namely preferably full load operation.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

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Citations (5)

Family Cites Families (4)

• 2012
  • 2012-05-05 DE DE102012009008A patent/DE102012009008A1/de not_active Withdrawn
• 2013
  • 2013-04-26 WO PCT/EP2013/001262 patent/WO2013167242A1/fr not_active Ceased

Patent Citations (5)

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