DE102015211024B4 - A monitoring method for monitoring a leakage balance in an injector assembly, driving method for driving an injector and electronic control unit - Google Patents

Abstract

The invention relates to a monitoring method for monitoring a leakage balance (bl) in an injector arrangement (18), wherein a characteristic field (K) is provided which in each case has a leakage balance gradient (25) for a respective average stroke loss (hm) of an injector needle (24) of the injector arrangement (18). gl) and then a mean stroke loss (hm) of the Injektornadel (24) over several successive injection operations of the injector (18) is determined, and then based on the map (K) of the leakage balance gradient (gl) of the injector (18) is determined. Furthermore, the invention relates to a driving method for driving the injector assembly (18), in which the monitoring method is performed, and an electronic control unit (20), which can perform the monitoring method and the driving method, respectively.

Description

The invention relates to a monitoring method for monitoring a leakage balance in an injector arrangement, to a drive method for actuating an injector arrangement in which the monitoring method is carried out, and to an electronic control unit which is designed to carry out the monitoring method or the activation method.

Fuel injection systems in internal combustion engines are used, a fuel which is subjected to a high pressure - for example, in gasoline internal combustion engines in a pressure range of 250 bar to 400 bar and diesel engines in a pressure range of 2000 bar to 2500 bar - in combustion chambers of Inject internal combustion engine. Fuel injection systems of the new generation often operate according to the so-called common rail principle and have a plurality of arranged on a rail injector arrangements, with which the stored in the rail pressurized fuel can be injected into the combustion chambers of the internal combustion engine. Frequently, one or more injector arrangements, which can be selectively opened and closed, are located at each combustion chamber of the internal combustion engine. During the opening of the injector arrangements, the fuel passes into the interior of the respective combustion chamber and burns there. For combustion and exhaust gas technical view and comfort reasons, a very accurate determination of the amount of fuel injected is advantageous.

The injector arrangements usually have an injector needle, which closes the injection openings of the injector arrangements and then opens when fuel is to be injected into the combustion chambers. The injector needle is driven, for example, in directly operated fuel injection systems by a Stellaktor which exerts a force on the Injektornadel, so that the Injektornadel moves and executes a stroke. Often, the actuating force of the actuating actuator is transmitted to the injector needle via a hydraulic coupling element, so that the stroke of the injector needle hangs on the stroke of the actuating actuator via this hydraulic coupling element. The hydraulic coupling element has essentially the task of compensating for an idle stroke or gap and to realize a translation with path reversal between the stroke of the Stellaktors and the stroke of Injektornadel. A corresponding injector arrangement is for example in the document DE 10 2005 025 638 B4 disclosed. The disclosed one injector has a valve drive and a first and second nozzle needle whose position is adjustable by means of a switching valve. The switching valve is designed as a double servo valve with an outer piston and an inner piston which cooperate. The outer piston and the inner piston each have a contact surface, which are provided so that a valve drive can act on them, to open a control chamber, whereby the nozzle needles influenced in position and the nozzle holes can thereby be opened and closed.

Like, for example, from the document DE 10 2007 052 451 B4 As can be seen, leaks are inherent in the hydraulic system, and in particular the injectors, which is on the one hand a so-called switching leakage and on the other hand a permanent leak. The leakage behavior thereby influences the force balance acting on the nozzle needle and thus the switching behavior of the injection valve. That is why in the DE 10 2007 052 451 B4 a method for determining the current continuous leakage amount of the hydraulic system, in particular the injectors proposed, wherein the leakage amount is determined by means of a balance equation that allows accurate offset control and thus a more precise injection.

document DE 10 2013 212 330 A1 In contrast, proposes a method in which the leakage balance of the internal leakage is already determined or determined in the manufacturing process of the injector. For this purpose, for example, at least two, preferably three, for injection quantities, leakage quantities and / or pressure differences of the injector relevant mechanical games, in particular mating games, matched to each other, in particular paired. The successive adjustment or the pairing of the mechanical plays of the injector can take place such that a leakage inflow to a control chamber of the injector substantially or at least corresponds to a leakage outflow downstream of this control chamber.

Finally, document reveals DE 10 2011 075 124 A1 a method for operating an injector equipped with a servo valve, wherein the fuel pressure is regulated in a pressure accumulator by means of a pressure control. It is distinguished between the Kecagen an old injector and a new injector and varies the control signals of the injector accordingly.

With hydraulically switched injector arrangements, the so-called servo concepts, there is no coupling element, since the injector needle is indirectly driven here. By contrast, in the case of direct-driven concepts, it was previously known to use predominantly vacume-laden systems.

The actuating force of the Stellaktors is in particular via a coupling space of the hydraulic coupling element of the Stellaktor on the Transfer injector needle. The coupling space is fluidly connected via a drainage leakage gap with an actuator chamber in which the Stellaktor is arranged. In addition to the coupling space, the coupling element additionally has a high pressure space, with which the coupling space is also fluidly connected via at least one Zulaufleckagespalt. Due to the effluent leakage gap or the inflow leakage gap, fuel flows into the coupling space from the high-pressure space and out of the coupling space into the actuator space.

The transmission of the actuating force from the Stellaktor via the coupling space is essentially dependent on the gap leakage described above. In this case, it is desired that the same or even more fluid flows into the coupling space via the at least one inlet leakage gap than it drains off via the at least one drainage leakage gap, since otherwise an unintended continuous injection occurs. On the other hand, it is desirable that the inflowing leakage flow through the at least one inlet leakage gap is not too large, otherwise the injector needle accidentally falls during the injection. This means there is an upper and a lower limit of the design and thus the leakage balance.

As long as the leakage balance is within these limits, that is within a predetermined tolerance, the injector assembly is functional as desired. However, if the leakage balance outside the tolerances, this means that the injector, for example, by a life wear, is no longer functional as desired.

The leakage balance is therefore a measure of wear or aging of an injector arrangement and indicates when, for example, maintenance or replacement of the injector arrangement is required.

In the case of injector arrangements which have a coupling element for compensating the idle stroke, the abovementioned systematic effect has either not been considered so far or stored in characteristic diagrams on the basis of a mean assumed behavior, without taking injector individuality or wear into account.

The object of the invention is therefore to provide a monitoring method for monitoring a leakage balance in an injector arrangement.

This object is achieved by a monitoring method having the features of claim 1.

A driving method for driving an injector arrangement in which the monitoring method is performed, and an electronic control unit that can perform the monitoring method and the driving method, respectively, are the subject of the independent claims.

Advantageous embodiments of the invention are the subject of the dependent claims.

• a) Bereitstellen eines Kennfeldes, das einem jeweiligen mittleren Hubverlust der Injektornadel jeweils einen Leckagebilanzgradienten der Injektornadel zuordnet;
• b) Ermitteln eines mittleren Hubverlustes der Injektornadel über mehrere aufeinanderfolgende Einspritzvorgänge der Injektoranordnung;
• c) Ermitteln des Leckagebilanzgradienten aus dem Kennfeld.

A monitoring method for monitoring a leakage balance in an injector assembly, which is designed for injecting fuel into a combustion chamber of an internal combustion engine, and which has the Injektornadel and a Stellaktor in an actuator space, wherein a force from the Stellaktor using a coupling space of a hydraulic coupling element on the Injektornadel is transmitted to generate a stroke of the Injektornadel, wherein the coupling space is fluidly connected via at least one Zulaufleckagespalt with a high-pressure chamber of the injector and at least one Ablaufleckagespalt with the actuator chamber, wherein the transmission of the actuating force is dependent on a leakage balance between inlet leakage gap and drainage leakage gap points the following steps:

• a) providing a map which each assigns a leakage balance gradient of the injector needle to a respective average stroke loss of the injector needle;
• b) determining a mean stroke loss of the Injektornadel over several successive injection operations of the injector;
• c) determining the leakage balance gradient from the map.

A change in the leakage balance in the injector assembly can thus be detected by observing the average lift loss of the injector needle. The mean stroke loss is a change in the stroke of the injector needle over several consecutive injection events. By "several" is meant at least two consecutive injection events, but in particular at least six, preferably seven, successive injection events. This means that in the most preferred case of seven consecutive injection events which are observed, the stroke of the injector needle can be changed and from this a change in the leakage balance in the injector arrangement can be concluded. The map, which brings a respective stroke loss of Injektornadel in connection with a special Leckagebilanzgradienten, is previously determined by measurements and stored for example in an electronic control unit, which is responsible for driving the injector.

Preferably, the average lift loss of the injector needle is determined from a quantity gradient of the fuel quantity injected by the injector arrangement in the case of a plurality of successive injection events. In this case, the injected fuel quantity of the injector arrangement is determined at a plurality of predefined measuring points, and the quantity gradient is determined by fitting a compensation straight line to the plurality of measuring points.

This means that the pre-defined measurement points, for example, advantageously seven predefined measurement points, are used to set a regression line with the least possible error squares, which follows the following equation: F (x) = ax + b

The factor a now describes the individual quantity behavior of the injector arrangement under consideration in a reference range of the predefined measuring points. The factor a represents the slope and thus the gradient of the injected fuel quantity. The change in the injected fuel quantity is dependent on the change in the stroke of the Injektornadel, that is, the lower the stroke of the Injektornadel, the lower the injected fuel amount and vice versa , Here too, the relationship between quantity gradient and stroke loss of the injector needle is advantageously determined externally and then stored, for example, in an electronic control unit, so that it is possible to deduce the loss of lift from the determined quantity gradient and, advantageously, the leakage balance gradient.

Advantageously, in order to determine the injected fuel quantity, the injector arrangement is actuated at the predefined measuring points in each case with the same control parameters. As a result, a change in the injected fuel quantity or the stroke of the injector needle can be detected particularly reliably, since influences due to different activation parameters are eliminated.

Advantageously, the injector arrangement is controlled at the respectively predefined measuring points so that an injection quantity of approximately 4 mg to 5 mg can be achieved. This is done via a predetermined energy which is supplied to the Stellaktor, and a predetermined time, which is to be opened the Injektornadel. Essentially, therefore, the drive parameters are advantageously the energy supplied to the actuator and the time at which the actuator is driven.

In advantageous Injektoranordnungen the Stellaktor is provided by a piezoelectric actuator. The supplied energy to such a special piezoelectric actuator corresponds to the voltage with which the piezoelectric actuator is driven.

The determination of the injected fuel quantity is preferably carried out at a maximum system pressure of the fuel in the injector arrangement. For diesel fuel, the maximum system pressure is in the range of about 2500 bar, while for gasoline fuel, the range is about 400 bar. These pressures are then present as the maximum system pressures in the injector assembly since the injector assembly fluidly communicates with the rail, i. H. the high-pressure accumulator, is connected.

In the determination of the injected fuel quantity, the actually injected fuel quantity is preferably measured. This is possible, for example, after production of the injector assembly at one end of the production line, where each injector assembly can be subjected to a test. The injected fuel quantities are then measured exactly at the predefined measuring points. Each injector arrangement has due to different component scattering a characteristic volume behavior and thus also an individual volume gradient, which can be advantageously detected in determining the amount of fuel actually injected.

Alternatively, however, it is also possible to determine a needle opening duration of the injector needle after a triggering time of the injector arrangement when determining the injected fuel quantity. There are situations, namely when the injector arrangement is already installed in, for example, a vehicle, where the quantity gradient can not be determined via the actually injected fuel quantity. Therefore, it is proposed to use an advantageous substitute quantity, namely the needle opening period. This results from a time duration between the activation time of the injector arrangement, which is predetermined by, for example, the electronic control unit, and the closing time of the injector needle, which can be determined online by the electronic control unit for each injection process. A change in the needle opening time duration, which can thus be detected online, corresponds to a change in the injected fuel quantity, so that it is possible to calculate back from a determined needle opening time-duration gradient to a volume gradient.

Such an indirect determination of the injected fuel quantity can be carried out, for example, during cyclic service appointments, but it is also possible to carry out this determination continuously online in the vehicle.

It is advantageous by averaging a plurality of individual quantity gradients of a plurality determined by individual injector arrangements a standard quantity gradient of a theoretical Norminjektoranordnung.

By evaluating a larger number of injector arrangements, for example of at least about 100 injector arrangements, the rate gradient and thus also the leakage balance gradient can be determined, which is generally to be expected for an injector arrangement. This mean assumed behavior of a theoretical Norminjektoranordnung has already deposited without Injektorindividualität in corresponding maps in electronic control units that controls the injector arrangements.

Preferably, however, an individual correction factor is now determined in each case since each injector arrangement has individual component scatters which are not mapped by the standard quantity gradient.

To determine an individual correction factor for at least one activation parameter of an individual injector arrangement for equalizing an individual leakage balance gradient of the individual injector arrangement, an individual quantity gradient of the individual injector arrangement is normalized to the value of the standard quantity gradient with the aid of a normalization factor. Advantageously, a map is provided that associates each normalization factor with a respective correction factor for correcting the at least one driver parameter.

So far, only a general correction factor has been deposited, with which the at least one control parameter has been corrected in the same way for each injector arrangement. However, the individual leakage balance gradient assigned to this individual injector arrangement is determined by the steps described above for each individual injector arrangement. By normalizing to the general norm quantity gradient, which is deposited anyway, a factor results which reflects the difference between the behavior of the standard injector arrangement and the considered individual injector arrangement. The individual correction factor for this individual injector arrangement can then be calculated from this normalization factor, so as to correct the at least one actuation parameter adapted to the individual injector arrangement.

Preferably, the determination of the individual correction factor for each individual injector assembly is made after fabrication of the individual injector assembly and prior to installation of the individual injector assembly into a fuel injection system. Alternatively or additionally, the determination of the individual correction factor for each individual injector arrangement is carried out during a cyclical check of the fuel injection system. This makes it possible to adjust the correction factor after a certain period of the individual injector arrangement.

Advantageously, a limit value for an amount of the leakage balance gradient is defined, wherein an error signal is generated when the leakage balance gradient exceeds the limit value.

In the case in which the amount of the leakage balance gradient still moves below the predetermined limit value, the leakage balance can be kept within the desired tolerances by the individual injector arrangement or the cyclically determined correction factor. If, however, the amount of the leakage balance gradient exceeds the predefined limit value, it can be assumed that the correction factor can no longer guarantee the required injection accuracy of the respective injector arrangement, and therefore maintenance of the injector arrangement or even replacement is required. For this purpose, an error signal is output when the limit value is exceeded.

• i) Bereitstellen wenigstens eines vordefinierten Ansteuerungsparameters zum Ansteuern der individuellen Injektoranordnung;
• ii) Ermitteln eines Leckagebilanzgradienten der individuellen Injektoranordnung wie oben beschrieben, wobei ein individueller Korrekturfaktor zum Korrigieren des wenigstens einen Ansteuerungsparameters ermittelt wird;
• iii) Korrigieren des wenigstens einen Ansteuerungsparameters mit dem Korrekturfaktor;
• iv) Ansteuern der Injektoranordnung unter Verwendung des korrigierten Ansteuerungsparameters.

In a driving method for driving an individual injector assembly in a fuel injection system having multiple injector assemblies, the following steps are performed:

• i) providing at least one predefined drive parameter for driving the individual injector arrangement;
• ii) determining a leakage balance gradient of the individual injector assembly as described above, wherein an individual correction factor for correcting the at least one driver parameter is determined;
• iii) correcting the at least one drive parameter with the correction factor;
• iv) driving the injector assembly using the corrected drive parameter.

With the monitoring method described above, it is therefore possible to determine the individual correction factor for each individual injector arrangement at least directly after production of the injector arrangement, but also cyclically, for example during service appointments or even permanently in the vehicle, and then use this to individually associate the injector arrangement to drive the correct drive parameters, so as to achieve a correct injection of the injector.

An electronic control unit for controlling functions in an internal combustion engine, in particular for controlling functions of a fuel injection system, is designed to carry out the monitoring method described above or the drive method described above.

For this purpose, the electronic control unit has at least one detection device with which an injected fuel quantity of each individual injector arrangement can be detected at predefined measuring points at least indirectly. In addition, the electronic control unit comprises a memory device in which various maps and predefined general control parameters for all injector arrangements are stored. It is also advantageous if the electronic control unit has additionally deposited a limit value for an amount of a leakage balance gradient and / or a standard quantity gradient. The electronic control unit additionally has a processing device which processes data supplied to it by the detection device or the memory device, so that the electronic control unit, since it additionally advantageously has an output device, outputs control parameters for driving each individual injector arrangement and / or error signals may indicate a fault of an individual injector arrangement.

An embodiment of the invention will be explained in more detail with reference to the accompanying drawings. It shows:

1 a section of a schematically illustrated fuel injection system for injecting fuel into a combustion chamber of an internal combustion engine having a plurality of injector assemblies, which are arranged on a high-pressure accumulator, and an electronic control unit;

2 a schematic longitudinal sectional view of one of the injector arrangements 1 ;

3 a schematic detail of the electronic control unit 1 ;

4 Diagrams, the activation parameters and the behavior of the injector arrangement 1 represent at six consecutive injection events;

5 Diagrams for four individual injector arrangements representing the respective injection behavior during seven consecutive injection events;

6 a schematic representation of steps of a monitoring method for monitoring a leakage balance in a in 1 shown injector arrangement;

7 Charts showing a correlation between a needle opening period of an injector needle of one of the injector assemblies 1 to an injected amount of fuel of the respective injector arrangement; and

8th a schematic representation of steps of a driving method for driving an individual injector from 1 ,

1 shows a portion of a fuel injection system 10 with which a fuel 12 can be injected into combustion chambers of an internal combustion engine. In the subsection of the fuel injection system 10 are a high pressure pump 14 , an accumulator 16 in the form of a so-called Rails, as well as injector arrangements 18 provided over that in the high-pressure pump 14 pressurized and in the accumulator 16 stored fuel 12 ultimately injected into the combustion chambers of the internal combustion engine.

The elements of the fuel injection system 10 be via an electronic control unit 20 , which will be described in more detail later, driven.

2 shows a schematic sectional view of an injector 18 out 1 that a Stellaktor 22 and an injector needle 24 which has one of the Stellaktor 22 applied force F _{s is} moved. The Stellaktor 22 is in an actor room 26 the injector arrangement 18 arranged and may be formed for example by a piezoelectric actuator. The power transmission from the Stellaktor 22 on the injector needle 24 is not done by a direct contact, but via a hydraulically intermediate coupling element 28 , which for this purpose a coupling room 30 as well as a high pressure room 32 having. The coupling room 30 is with the injector needle 24 on a first injector needle side 34 coupled such that a force in the coupling space 30 prevails, for example, a compressive force in the entire injector 18 arranged fuel 12 , on this first Injektornadelseite 34 can be transferred. The high pressure room 32 is like that with the injector needle 24 on a second Injektornadelseite 36 coupled to a force in the high-pressure space 32 prevails, for example, a compressive force in the existing fuel there 12 , on this second Injektornadelseite 36 can be transferred. The forces of the high-pressure chamber 32 on the injector needle 24 and from the coupling room 30 on the injector needle 24 therefore act opposite to each other on the Injektornadel 24 ,

The Stellaktor 22 is over a pestle 38 with a piston 40 connected to the coupling room 30 and the high pressure room 32 separates. coupling space 30 and high pressure room 32 are about inlet leak column 42 to the piston 40 and at the injector needle 24 both in an injector housing 44 are guided fluidly connected to each other. Next is the coupling room 30 fluidly via a drainage leakage gap 46 on the plunger 38 also in the injector housing 44 is guided, with the actuator room 26 fluidly connected.

The high pressure room 32 is with the accumulator 16 hydraulically connected, so that a fuel pressure in the accumulator 16 one in the high pressure room 32 prevailing fuel pressure, if this with fuel 12 is filled.

In the high pressure room 32 Therefore, a significantly higher pressure acts as in the coupling space 30 as well as in the actuator room 26 , This flows over the inlet leak column 42 from the high pressure room 32 Fuel 12 in the paddock 30 , Increases the pressure in the coupling space by this inflow 30 , fuel flows 12 over the drainage leakage gap 46 from the coupling room 30 in the actuator room 26 ,

By the force F _{s ,} the Stellaktor 22 over the pestle 38 on the piston 40 applies, this piston moves 40 inside the injector housing 44 and increases or decreases the volume of the coupling space 30 , By this volume change in the coupling space 30 There is also a pressure change in the coupling space 30 , thereby fuel 12 over the drainage leakage gap 46 in the actuator room 26 is pressed.

The Stellaktor 22 is designed such that it the piston 40 displaced by an elongation, for example, in the case of a piezoelectric actuator, an energy in the form of voltage V to the Stellaktor 22 is created. If the voltage V is withdrawn again, the piston returns 40 back to its original position, as a piston spring 48 in the high pressure room 32 is provided, on the one hand to the injector 44 and on the other hand on a piston surface 50 supported. Through this piston spring 48 becomes inactivity of the Stellaktors 22 hence the piston 40 in the direction of the pestle 38 moved back to its original position.

The injector needle 24 is for closing and releasing multiple injection ports 52 intended. At rest, a tip closes 54 the injector needle 24 the injection openings 52 What a needle spring 56 is provided, on the one hand to the injector 40 and on the other hand on an injector needle surface 58 which supports the injection opening 52 is arranged opposite. This needle spring 56 tenses the injector needle 24 towards a closed position.

The power transmission from the Stellaktor 22 on the injector needle 24 is essentially from the gap leaks in the inlet leak gaps 42 or the drainage leakage gap 46 dependent. A leakage balance b ₁ between inlet leak and drainage leakage should preferably be between an upper and a lower limit range in order to ensure that, on the one hand, an unintended continuous injection of the injector arrangement 18 is avoided, on the other hand, but the Injektornadel 24 does not accidently fall during an injection process.

In order to monitor the leakage balance b _l , therefore, a monitoring method is proposed, with which the leakage balance b _l in the injector arrangement 18 can be monitored. Further, a driving method for the injector arrangement 18 described with the correction of control parameters, the leakage balance b _l can be kept within the tolerances. The two methods will be described later in detail.

The activation of the injector arrangement 18 via the electronic control unit 20 , which below with reference to 3 , which is a schematic representation of the electronic control unit 20 shows, is described in detail.

The electronic control unit 20 has a detection device 60 on, with the data obtained from the fuel injection system 10 , therefore also from the injector arrangement 18 , can be recorded. For example, via the detection device 16 an injected amount of fuel m _e are detected indirectly, for example by detecting a needle opening period t _d . Next, the electronic control unit 20 a storage device 62 in which various maps K are stored, the values related to each other. For example, a map K can be stored, which has a mean stroke loss h _{m of} the injector needle 24 associated with the leakage balance b _l . Furthermore, a map K can also be stored which contains an injected fuel quantity m _e in connection with a mean stroke loss h _{m of} the injector needle 24 puts. In addition, it is also possible that in the storage device 62 a map K is stored which relates a _norm quantity gradient g _norm with correction factors f _k . Next, in the storage device 62 Also be stored control parameters that are predefined, and with which, for example, the injector 18 can be controlled. In addition, it is also possible in the storage device 62 the standard quantity gradient g _norm save itself as well as a threshold value G for an amount of a Leckagebilanzgradienten g _l.

Next, the electronic control unit 20 a processing device 64 on, with the data and parameters that the processing device 64 for example, the detection device 60 or the storage device 62 be supplied, can be processed. Finally, the electronic control unit 20 an output device 66 on, with the signals, such as drive signals for driving the injector 18 , about a desired needle opening period t _d or a voltage V, can be output. In addition, it is also possible with the output device 66 to issue a warning signal, for example, when the leakage balance gradient g _l exceeds the limit G in its amount.

The processing device 64 Therefore, for example, has a quantity gradient calculation unit 68 which calculates a quantity gradient g _m from the indirectly detected fuel quantities m _e at various predetermined measuring points. Next, the processing device 64 a normalization unit 70 , which normalizes the calculated quantity gradient g _m with the addition of the _norm quantity gradient g _norm . From this normalization results the correction factor f _k with the aid of the characteristic field K, which sets the standard quantity gradient g _norm , with a correction factor f _k . The correction therefore takes place in a correction device 72 , Next is a parameter calculator 74 provided on the basis of the determined correction factor f _k and the predefined control parameters stored in the memory device 62 are actually stored for the individual injector arrangement 18 required control parameters and then to the output device 66 passes.

In addition, the processing device 64 a comparison device 76 which compares the magnitude of the actually existing leakage balance gradient g _l with the limit value G in order to determine whether the leakage balance gradient g _{l is} still within a predetermined tolerance or already outside, and therefore whether a warning signal must be output.

4 shows the change of work results of three different injector arrangements on the basis of four diagrams 18 with different Leckagebilanzen- b _l (b _l₁ <b _l₂ <b _l₃ ). In diagram a), the charge is applied for six consecutive injection cycles EZ, with which the Stellaktor 22 is controlled. The diagram b) represents the actuating force F _s for the corresponding six injection cycles EZ, which at the Stellaktor 22 , which is designed as a piezoelectric actuator act. In diagram c) is a stroke H of Stellaktors 22 for each of the six injection cycles EZ and diagram d) shows the respective of the three considered injector arrangements 18 at the respective injection cycle EZ injected amount of fuel m _e . In diagram d) it can be seen that the smaller the leakage balance b _l in the injector arrangement 18 is, ie the more fuel 12 in the actuator room 26 flows, a gradient of the amount of fuel m _e , which has been injected in the six consecutive injection cycles EZ, the greater. This gradient corresponds to a stroke loss of the injector needle 24 and thus also a leakage balance gradient g _l , of the respectively considered injector arrangement 18 ,

In 5 is for four different injector arrangements 18 ( 18a . 18b . 18c . 18d ) for six consecutive injection cycles EZ (represented by the triangles above the graph) represent the injected fuel quantity m _e for each injection cycle. As can be seen, the injected fuel quantity m _e decreases continuously over the seven injection events. The injected fuel quantity m _e is therefore detected at seven predefined measuring points p _m . At the measuring points p _m become the four injector arrangements 18a - 18d each with the same drive parameters from the electronic control unit 20 activated, ie it is in each case a same voltage V to the Stellaktor 22 created for an equal period of time t _d . Preferably, the drive parameters are selected such that an injected fuel quantity m _e of approximately 4 mg to 5 mg is aimed for in the successive injections.

As from the diagrams in 5 As can be seen, each of the injector arrangements has 18a - 18d Different components scattering and thus a characteristic quantity behavior. The first injection process has a special role and is influenced by a superimposed effect and therefore can not be considered in the evaluation. Through the measuring points p _{m of} the other injection processes, a balancing line with the least possible error squares is set, which satisfies the equation F (x) = ax + b, where the factor a is the individual quantity behavior of the respectively considered injector arrangement 18 describes. That is, it will be for each individual injector assembly 18 an individual quantity gradient g _{m is determined} via the factor a. For this purpose, this factor a is normalized to a _norm quantity gradient g _norm using a normalization factor. The standard quantity gradient g _norm represents the quantity gradient g _{m of} a theoretical standard injector arrangement 18 By evaluating a larger number of individual injector arrangements 18 is determined. This standard quantity gradient g _norm is in the electronic control unit 20 deposited and forms the usual correction factor f _k , with all the injector arrangements 18 Generally always be corrected. However, this correction factor f _k is not individual for each injector arrangement 18 , first by normalizing to the actual quantity gradient g _{m of} each individual injector arrangement under consideration 18 will be the correct correction factor f _k for each individual injector arrangement 18 determined. This injector-individual correction factor f _k can then be determined for the individual injector arrangement 18 be coded and then in the engine control in the electronic control unit 20 be used for the control.

In the electronic control unit 20 (Engine control) continue to be the other dependencies of the effect, such as the injection quantity, the fuel pressure, the distance between the individual injections, the fuel temperature, either conventionally in maps K for the theoretical Norminjektoranordnung 18 or in a model-based approach using physical equations as a description. In the processing facility 64 Therefore, the correction of the driving time of the energy, that is, the voltage V can be calculated by the desired injection quantity, the existing fuel pressure, the distance between the injection events, the current fuel temperature, the amount gradient g _m and the _norm quantity gradient g _norm are offset against each other.

The monitoring method with which the leakage balance b _{l of} an individual injector arrangement 18 can be monitored below using the schematic representation of the individual steps in 6 explained. After the start, the respectively injected fuel quantity m _e is first determined for a number n of successive injection processes, in particular indirectly via the detection of a needle opening time period t _d . Thereafter, a compensation straight line is laid through the measuring points p _m and fitted to the measured values, wherein the slope of the straight line is determined, which determines the quantity gradient g _{m of} the respectively considered injector arrangement 18 represents. After that, due to the in the electrical control unit 20 stored maps K, the leakage balance gradient g _l individually considered injector arrangement 18 be calculated and compared, whether the amount of this leakage balance gradient g _l exceeds a predetermined limit G. If this is the case, the electronic control unit 20 issued a warning signal, the replacement or maintenance of the individual injector arrangement 18 displays. However, if the magnitude of the leakage balance gradient g _l is within the tolerances, ie below the predetermined limit value G, then a correction factor f _k can be determined with which the individual leakage balance gradient g _l can be compensated. The determination of the correction factor f _k can also already take place parallel to the evaluation as to whether the leakage balance gradient g _l exceeds the limit value G. First, the quantity gradient g _{m is} normalized and then, with the aid of a characteristic map K which relates a normalization factor to the correction factor f _k , the correction factor f _{k is determined} individually for the injector arrangement under consideration 18 determined. This correction factor f _k is then stored in the memory device 62 the electronic control unit 20 saved.

With the determined correction factor f _k , each individual injector arrangement can then be designed in accordance with a driving method described later 18 be controlled correctly.

The correction factor f _k can be determined, on the one hand, when the injector arrangement 18 is just finished, that is at the end of the tape, where it is possible here to use the actually injected fuel quantity m _e to determine the correction factor f _k .

But also built-in injector arrangements 18 should be monitored for safety-related reasons to exclude any wear-related malfunction. Since it is not possible in the vehicle to directly measure the quantity gradient g _m as a measure of the leakage balance gradient g _l , a substitute variable is used, which results as follows.

7 shows on the basis of diagrams, as from a needle opening period t _d indirectly the quantity gradient g _m can be determined. The illustrations a) and b) each show three different individual injector arrangements 18 at seven consecutive injections (represented by the triangles). The diagram a) shows the quantity gradient g _m , which is due to the stroke loss of the respective Injektornadel 24 and in graph b) is the associated detected needle closing timing to the ballistic injection, which reflects the needle opening period t _d . The needle closing time and thus the needle opening period t _d is in the electronic control unit 20 evaluated during operation anyway via the piezoelectric signals and determined online for each injection process. As described above, compensation straight lines are laid through the measuring points p _{m of} the fuel quantity m _e injected in each case and the needle closing times and the respective gradient of the compensation straight line is considered. Diagram c) shows a correlation between the two gradients for the injected fuel quantity m _e and the needle opening time period t _d . Applying the two gradients on top of each other results in a very good correlation with a coefficient of determination of advantageously 0.9991, which can be used as a basis.

For the cyclic monitoring of the limit wear on the functionally relevant guides of the piston 40 , the pestle 38 and the injector needle 24 in the injector housing 44 For example, at the service intervals on the vehicle at idle, the point is set cyclically at a sevenfold injection and the needle opening time duration gradient is determined by the method described above. The determined gradient is calculated back on the basis of the correlation on the quantity gradient g _m and with the in the electronic control unit 20 stored maximum and minimum allowable gradient, that is, the limit G, plausibility for a secure function. If the thus indirectly determined quantity gradient g _m and thus the leakage balance gradient g _{l is} outside the tolerances, the respective individual injector arrangement 18 marked and replaced with a service note. If the respective gradients of the individual injector arrangements 18 However, within the permissible tolerances, the injector-individual correction factor f _k for the aged component is determined again via the normalization described above and the value stored directly after production is adjusted.

In 8th is shown schematically how the electronic control unit 20 then the individual injector arrangement 18 controls. In this case, initially generally in the memory device 62 deposited control parameters used for each injector 18 generally apply. Then, for each individual injector arrangement 18 As described above, the correction factor f _{k is} determined and then the generally valid drive _parameters corrected with this correction factor f _k . Thereafter, with the individual control parameters, which have been determined so, the individual injector arrangement 18 driven.

Claims (11)

Monitoring method for monitoring a leakage balance (b _l ) in an injector arrangement ( 18 ), which are used for injecting fuel ( 12 ) is formed in a combustion chamber of an internal combustion engine, and which an injector needle ( 24 ) and a Stellaktor ( 22 ) in an actuator room ( 26 ), wherein a force (f _s ) of the Stellaktor ( 22 ) by means of a coupling space ( 30 ) of a hydraulic coupling element ( 28 ) on the injector needle ( 24 ) for generating a stroke of the injector needle ( 24 ), wherein the coupling space ( 30 ) fluidly via at least one inlet leakage gap ( 42 ) with a high-pressure chamber ( 32 ) of the injector assembly ( 18 ) and at least one drainage leakage gap ( 46 ) with the actuator space ( 26 ), wherein the transmission of the actuating force (F _s ) is dependent on a leakage balance (b _l ) between inflow leakage gap ( 42 ) and drainage leakage gap ( 46 ), wherein the monitoring method comprises the following steps: a) provision of a characteristic diagram (K) corresponding to a respective average stroke loss (h _m ) of the injector needle ( 24 ) each have a leakage balance gradient (g _l ) of the injector needle ( 24 ) assigns; b) determining an average stroke loss (h _m ) of the injector needle ( 24 ) over several successive injections of the injector assembly ( 18 ); c) determining the leakage balance gradient (g _l ) from the characteristic field (K). Monitoring method according to claim 1, characterized in that the average stroke loss (h _m ) of the injector needle ( 24 ) from a quantity gradient (g _m ) of the through the injector arrangement ( 18 ) injected fuel quantity (m _e ) is determined in a plurality of successive injection events, wherein the injected fuel quantity (m _e ) of the injector arrangement ( 18 ) is determined at a plurality of predefined measuring points (p _m ), and wherein the quantity gradient (g _m ) is determined by fitting a compensation straight line to the plurality of measuring points (p _m ). Monitoring method according to claim 2, characterized in that for determining the injected fuel quantity (m _e ) the injector arrangement ( 18 ) at the predefined measuring points (p _m ) in each case with the same control parameters, wherein the determination of the injected fuel quantity (m _e ), in particular at a maximum system pressure of the fuel ( 12 ) in the injector assembly ( 18 ) he follows. Monitoring method according to one of claims 2 or 3, characterized in that in the determination of the injected fuel quantity (m _e ), the actually injected fuel quantity (m _e ) is measured. Monitoring method according to one of claims 2 or 3, characterized in that in the determination of the injected fuel quantity (m _e ) a needle opening period (t _d ) of the injector needle ( 24 ) after a triggering time of the injector arrangement ( 18 ) is determined. Monitoring method according to one of claims 2 to 5, characterized in that by averaging a plurality of individual quantity gradients (g _m ) of a plurality of individual injector arrangements ( 18 ) a standard quantity gradient (g _norm ) of a theoretical Norminjektoranordnung is determined. Monitoring method according to claim 6, characterized in that for determining an individual correction factor (f _k ) for at least one control parameter of an individual Injector arrangement ( 18 ) for balancing an individual leakage balance gradient (g _l ) of the individual injector arrangement ( 18 ) an individual quantity gradient (g _m ) of the individual injector arrangement ( 18 ) is normalized with the aid of a normalization factor to the value of the standard quantity gradient (g _norm ), wherein in particular a characteristic map (K) is provided which assigns to each normalization factor a respective correction factor (f _k ) for correcting the at least one activation parameter. Monitoring method according to claim 7, characterized in that the determination of the individual correction factor (f _k ) for each individual injector arrangement ( 18 ) after production of the individual injector arrangement ( 18 ) and before installation of the individual injector arrangement ( 18 ) in a fuel injection system ( 10 ) and / or that the determination of the individual correction factor (f _k ) for each individual injector arrangement ( 18 ) during a cyclical check of the fuel injection system ( 10 ) he follows. Monitoring method according to one of claims 1 to 8, characterized in that a limit value (G) for an amount of the leakage balance gradient (g _l ) is defined, wherein an error signal is generated when the leakage balance gradient (g _l ) exceeds the limit value (G). Driving method for driving an individual injector assembly ( 18 ) in a fuel injection system ( 10 ), which has several injector arrangements ( 18 ), wherein the activation method comprises the following steps: i) providing at least one predefined activation parameter for actuating the individual injector arrangement ( 18 ); ii) determining a leakage balance gradient (g _l ) of the individual injector arrangement ( 18 ) according to one of claims 1 to 9, wherein an individual correction factor (f _k ) for correcting the at least one driving parameter is determined; iii) correcting the at least one drive parameter with the correction factor (f _k ); iv) driving the injector assembly ( 18 ) using the corrected drive parameter. Electronic control unit ( 20 ) for controlling functions in an internal combustion engine, in particular functions of a fuel injection system ( 10 ) configured to perform the monitoring method according to any one of claims 1 to 9 and / or the driving method according to claim 10.

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