DE102010014825A1 - Method for operating an injection system and an injection system, which has an injection valve and a control device - Google Patents

Abstract

A method for operating an injection system has an injection valve and a control device, the injection valve having a valve needle and a valve seat. A determination of a value of a guide parameter, which is indicative of a closing behavior of the injection valve, and a regulation of a counterforce applied to the valve needle by means of the control device based on the value of the guide parameter are carried out, the counterforce being regulated in such a way that the valve needle bounces is reduced on the valve seat.

Description

The invention relates to a method for operating an injection system. Furthermore, the invention relates to an injection system, which has an injection valve and a control device.

An injection system, in particular the injection system for a motor vehicle with an internal combustion engine, may have an injection valve and a control device. When closing the injection valve, a valve needle may bounce off a valve seat or perform a bounce, whereby a functioning of the injection system and in particular of the injection valve may be impaired.

By means of a hydraulic damping by the fuel located in the injection valve (injector, injector), the undesired bouncing of the valve needle (injector needle) can be reduced or prevented. A fuel path in the injector can be dimensioned via throttle points so that bouncing occurring is hydraulically damped.

Furthermore, by means of mechanical decoupling of magnet armature and valve needle, the mass accelerated in the closing process and impacting on the valve seat can be reduced. This can be achieved by the positive connection between the armature and valve needle is replaced by a clearance fit that allows axial movement between two armature between armature and valve needle.

It is an object of the invention to provide a method of operating an injection system and an injection system with which a technical process, which is fundamental for a movement cycle of an injection valve, is improved.

The object may be achieved by the subject matter of the independent claims. Advantageous embodiments are described in the dependent claims.

In one aspect, there is provided a method of operating an injection system that includes an injector and a controller, the injector having a valve needle and a valve seat. The method includes: opening the injector by moving the valve needle away from the valve seat by an opening force, closing the injector by moving the valve needle toward the valve seat by a closing force, determining a value of a pilot parameter that is indicative for a closing behavior of the injection valve, and regulating a counterforce applied to the valve needle by means of the control device based on the value of the guide parameter, wherein the counterforce is controlled so that a bouncing of the valve needle is reduced on the valve seat.

According to a further aspect, an injection system is provided, which has an injection valve and a control device, wherein the injection valve has a valve needle and a valve seat. The injection system is configured such that the injection valve can be opened by means of an opening force by the valve pin being movable away from the valve seat by means of the opening force and the injection valve being closable by means of a closing force by the valve needle being movable toward the valve seat by means of the closing force. Furthermore, the injection valve is set up so that a value of a guidance parameter can be determined for the injection valve, which is indicative of a closing behavior of the injection valve, and that a counterforce applied to the valve needle can be regulated. The counterforce can be regulated by means of the control device based on the value of the guidance parameter, wherein the counterforce can be regulated in such a way that bouncing of the valve needle on the valve seat is reduced.

The term "injection system" may refer to a device with which an injection quantity of a fluid can be generated and controlled. In particular, the injection system may represent a fuel injection system which may be construed as part of an internal combustion engine and which may serve the purpose of determining or changing the injection quantity of a fuel injected into a combustion chamber of the internal combustion engine. As a result, may be changeable with the injection system, a power output of the internal combustion engine. The injection system may further comprise supply lines for fuel and electrical leads for the transmission of signals and electrical power. Furthermore, the injection system may have a fuel pump with which a fuel pressure may be generated in the injection system.

The term "injector" may refer to a part of the injection system. In particular, the injection valve may have a valve needle movable in the injection valve and a fluid supply line or fuel supply line. Furthermore, the injection valve may have a valve seat, wherein the valve needle and the valve seat may be brought into a mutual positive engagement, that injection or escape of fuel from a nozzle of the injection valve may be suppressed at a given fuel pressure. A state in which the positive connection is given, may be referred to as a closed state of the injection valve. In contrast, may indicate an open state of the injector that, for example, fuel in one such amount may enter via a nozzle in a combustion chamber of the internal combustion engine, that after ignition of the fuel, a desired power stroke may take place. Furthermore, the injection valve may have a spring, which causes a closing of the injection valve by the spring force according to the open state of the injection valve.

The term "control device" may refer to another part of the injection system which allows control of movement of the valve needle. In particular, controlling the control device may be done electronically. In particular, the controller may be software based, hardware based, or based on a hybrid design. The controller may be part of an electronic engine controller or identical to the engine controller. The control device may be located in the region of an engine compartment or located in another region of a motor vehicle.

The term "opening the injector" may refer to any process in which the valve needle moves away from the valve seat. In particular, for the opening of the injection valve, a force, for example, an inertial force due to movement of the valve needle may be the cause. At a time end of the opening, the injection valve may be in the open state. In particular, the opened state of the injection valve may indicate a state of the injection valve at which the fuel reaches a maximum flow rate for a given cycle.

The term "opening force" may refer to a force which, for example, against a force of a fuel pressure and the closing spring acting, may cause the opening of the injector. The opening force may be caused by technical measures in the injection valve. In particular, the opening force may be generated by means of a coil. The coil which applies the opening force may be referred to as an injector coil. However, the opening force may also be generated in another way, such as mechanically, by means of a cam. The opening force may be controllable in particular by means of the control device.

The term "closing the injector" may refer to any operation where the valve needle and valve seat approach each other. In particular, for the closing of the injection valve, a force, for example also partially an inertial force due to a movement of the valve needle, be the cause. At a time end of closing, the injector may be in a closed state. The closed state of the injection valve may designate a state of the injection valve in which the valve needle and the valve seat reach a positive connection or are in mutual positive engagement or a positive connection is substantially achieved, so that hardly more fuel can be injected.

The term "closing force" may refer to a force that may cause closing of the injector. The closing force may be partly based on a force which is also partially generated by means of the fuel pressure. Furthermore, the closing force may be caused by technical measures in the injection valve. In particular, the closing force may be generated by means of a spring.

The term "closing behavior" or closing process may refer to a process which begins in an open state of the injector, which has the closing of the injector and at the end of which the injection valve may be permanently closed, before subsequently the injection valve again, for example, targeted may be brought to an open state. Thus, the term "closing behavior" may not capture only the period in the cycle in which the injection valve enters an open state. In particular, the period of closing behavior may include motions in the injector which may have a partial opening of the valve which may occur due to rebound of the valve needle from the valve seat. By describing the bounce, therefore, a part of the closing behavior may be describable.

The term "value of a guidance parameter" may be a compilation, for example a multidimensional matrix, of magnitude values and / or of numerical values which can be determined from magnitude values. The size values may be determinable from measured values. The value of the guide parameter may be indicative of the closing behavior of the injection valve, wherein the guide parameter may have one or more reference variables. The reference variables may likewise be indicative of the closing behavior, for example individually or together. A reference variable may be, for example, the speed at which the valve needle strikes the valve seat when closing. The higher the speed of the valve needle when hitting the valve seat, the more bouncing may occur. Another reference variable may be, for example, the closing time, d. H. the time it takes the valve needle to reach the valve seat when closing.

The term "counterforce" may refer to a force acting on the valve needle and which is controllable. In particular, the counterforce does not like to be dependent on the Fuel pressure resulting force. The counterforce may thus be regulated independently of the fuel pressure. The counterforce may be generated within and / or by means of the injection valve. In particular, the counterforce may be applied in a direction opposite to a direction of closing during the closing of the injection valve.

In particular, the counterforce may be applied before or during a bounce. In particular, the counterforce may be applied during an open state of the injector. Furthermore, the counterforce may be applied after an open state and before closing the valve needle. Furthermore, the opposing force may be created at the beginning of a closing.

The term "bouncing" may refer to a process in which the valve needle performs a movement that occurs due to closing of the injector, wherein the valve needle with the valve seat at least twice reaches a positive connection before the valve is brought back by means of the opening force an open state with which a new cycle may begin. Between the two or more times reaching the positive connection may therefore remove the valve needle from the valve seat. In particular, the bouncing may occur as a result of an elastic shock between the valve needle and the valve seat after closing the valve needle from the open state.

According to the aspect, a method of operating an injector may be provided whereby bouncing may be reduced, suppressed or prevented. The closing of the injection valve may be detected by means of physical value measurements. In particular, the measured values may be based on measurements of electrical quantities, such as, for example, a measurement of the current, the voltage, the capacitance and / or the inductance. Furthermore, the measurements may be based on an optical, magnetic, magneto-optical measurement.

From the measurements which describe the closing behavior, a reference variable may be determinable by means of which the closing behavior of the injection valve can be determined and / or predicted. Also, several reference variables may be determinable from the measurements which determine and / or predict the closing behavior of the injection valve. The value of the guide parameter may have one or more values of reference values. From the value of the guide parameter, the counterforce may be determined by means of which the bouncing of the valve needle is prevented. Depending on the knowledge of the injection valve based on one or more measured values of one or more physical variables, the counterforce may be adjustable so that bouncing is completely prevented.

Furthermore, the fuel pressure and the injector temperature may have an influence on the closing behavior of the injection valve. The regulation of the counterforce may be based on one or more experimentally determined maps, which have a dependence of the closing behavior of the fuel pressure and / or the injector temperature. The guidance parameter may be determined based on a map, the map representing a dependence of the guidance parameter on fuel pressure and / or injector temperature. In particular, the reference variable may be determined based on a characteristic map, wherein the characteristic field reproduces a dependence of the reference variable on the fuel pressure and / or the injector temperature.

According to an exemplary embodiment, a method is provided, wherein the injection valve has a coil and wherein the guide parameter has a voltage-value-based reference variable whose value can be determined based on a measured value of an induced voltage at the coil.

In the following, an exemplary determination of the voltage value-based reference variable may be discussed. By analyzing the variation in the measured self-induction voltage versus a calculated reference model describing the same voltage response but without the influence of motion, it may be found that a local voltage maximum may be reached when the valve needle strikes the valve seat when closing. In this case, the speed of the valve needle and the positively connected magnet armature, for example as a result of closing the closing spring and the fuel pressure may be maximum. Thus, the closing time by means of determining a local maximum voltage in the coil from a voltage measurement and the calculation of a reference model can be subsequently determined. In particular, the closing time may be determinable from the measurement of the self-induction voltage.

Determining a plurality of command values, which may be determined based on the voltage value-based command variable, is given in conjunction with the description of the figures.

According to one embodiment, a method is provided, wherein the guidance parameter has a current-value-based reference variable, the value of which can be determined based on a measured value of a current through the coil.

A hold phase in which the injector may be maintained in an open state is followed by a turn-off phase, which may be characterized in that a voltage applied to hold the armature and valve needle to the injector coil is turned off. This time at which the injector coil is de-energized may be referred to as zero time. Before the zero time, ie before switching off the applied voltage, a stable state may have set in the injector coil. The value of the current flowing in the injector coil may therefore be determinable shortly before the zero time point or at the zero time point, that is to say in particular before the current value drops appreciably by switching off the voltage. From the measured value of the current at zero time or shortly before, in particular, the closing behavior for the injection valve may be predictable. The value for the current may allow determining a state of the magnetic circuit. In particular, a period of time may be predictable that the valve needle requires from zero time to hit the valve seat. The closing time may be the time duration which starts with the zero time and ends with the first time of the impact of the valve needle on the valve seat.

Conversely, with a close knowledge of the mutual relationship of the self-induction voltage and the current in the coil, the closing time may also be predictable from the course of the self-induction voltage. Furthermore, the closing time from the analysis of the current profile may be subsequently determined by a measurement. A knowledge of said mutual relationship between the self-induction voltage and the current in the injector coil may include a simple relationship between current, voltage and resistance. In particular, however, may be necessary for this purpose the knowledge of other relationships, which may require in particular a precise knowledge of the magnetic circuit.

According to one embodiment, a method is provided wherein the counter force is applied in a direction which is opposite to a direction of closing, and / or wherein the counter force is applied in a direction which is opposite to the direction of opening.

The counterforce may be applied against the direction of closing, so that when closing the injection valve, the valve needle is decelerated. As a result, a bouncing of the valve needle on the valve seat may be reduced or completely suppressed, since the speed of the valve needle is limited. Furthermore, in the case of a positive connection of the valve needle with the valve seat, the counterforce may be applied against the direction of opening, so that opening of the injection valve may be reduced or completely suppressed. The counterforce applied against the direction of opening may, for example, be applied by a coil which is not an injector coil.

If the counterforce is applied for a certain period of time may thus be transmitted to the valve needle impulse.

According to one embodiment, a method is provided wherein the coil is an injector coil and wherein the counterforce is a braking force generated by applying a braking voltage to the injector coil.

The term "injector coil" may refer to a coil with which the valve needle may be brought to an open state of the injector. Also may be held in an open state with the injector coil, the injection valve. Thus, the force applied by means of the injector coil may act against the direction of movement when closing the valve needle and thus slow the movement of the valve needle. Limiting the speed of the valve needle associated with the braking of the valve needle may reduce or completely prevent bouncing.

According to one embodiment, there is provided a method wherein the controlling comprises determining a value of a system size determined based on the value of the guidance parameter.

The term "value of a system quantity" may denote values of physical quantities on which the counterforce or the braking force may be controlled based. For example, based on a boost voltage which is applied at a certain time and for a certain duration, a current and thus a magnetic field in the injector coil may be caused, which causes the braking force. The system size may thus have the boost voltage or an applied voltage curve, the time of application of the voltage and the time duration for which the voltage is applied.

According to one embodiment, the method comprises: determining a value of the system size based on the voltage-based command variable, wherein the voltage-based command variable is determined from the measured value of the induced voltage during a cycle, and determining a value of the system magnitude based on the current-based command variable, wherein the current-based command variable is determined from the measured value of the current during a further cycle.

A cycle may designate a period of a periodic process in which the injector is first opened and then closed. It may be advantageous to determine different reference variables at different cycles. For example, a reference value indicating a measured closing time may be determined in one cycle. In a further cycle, the reference variable may be determined, on which basis an expected closing time may be determined. The cycle and the further cycle may be arbitrary in their order. In particular, it may be directly consecutive cycles. Alternatively, it may be cycles that do not directly follow each other.

According to an exemplary embodiment, a method is provided which comprises determining a value of the system variable, which in particular determines a time duration for applying the counterforce, by means of a control difference in a control loop, the control difference being determined from a difference of the voltage-value-based command variable resulting in a control loop second time in a cycle and the current value-based command variable, which is determined at a first time in the cycle, the second time in the cycle following the first time in the cycle.

At the beginning of a cycle, ie at a first point in the cycle, in particular in the open state of the injection valve, the current-value-based reference variable may be determined with which the closing behavior for this cycle may be predicted. In particular, the determination of the current-value-based reference variable may be based on the measurement of the current in the coil, the measurement of the fuel pressure and the measurement of the injector temperature. From the value for the current, the value for the fuel pressure and the value of the injector temperature, the current-value-based reference variable may be determinable in particular by means of a predetermined characteristic diagram. The current-value-based reference variable may thus enter into the control difference, in particular as a reference value for the reference variable. Starting from a measurement of the current in the coil, which may represent an influencing variable, the closing behavior may be predictable by means of the current-value-based reference variable. Thereafter, the injection valve may close. Based on the voltage value-based reference variable, the closing time may be determinable at a second time in the cycle, which lies after the first time in the cycle. From the determined by the voltage-based command variable measured command variable and the means of the setpoint of the current-based command variable may be determined by subtraction a control difference, which may be processed in the control loop. In particular, the control loop may be based on a software, hardware or hybrid application. Based on the control difference may be determined by means of the controller, a controller output variable, in particular the time duration for which the boost voltage is applied. The time duration for which the boost voltage is applied as well as the time at which the boost voltage is applied may cause a current in the injector coil, which may be considered as a manipulated variable.

According to one embodiment, a method is provided wherein the control loop is a PID control loop.

In particular, a PID loop may be suitable for providing control to the injector because the PID controller may merge beneficial characteristics of other regulators.

It may also be noted in particular that, due to the eddy currents in the magnetic circuit of the injector, it may take time to decelerate after the braking current pulse has been applied to build up a magnetic force with a braking effect. In order to accelerate the dynamics of the magnetic force buildup, the magnetic circuit of the injector may be constructed of magnetic materials which may have the highest possible electrical resistance.

Finally, it may be stated that by means of the subject matter of the independent claims from characteristic parameters of the derived motion induction voltage in the case of an injector closure, it is possible to derive a measure of an intensity of an injector bounce and thus a suitable reference variable for a control loop. Starting from the deviation of the reference variable from a nominal value, after switching off the injector current at the end of the holding phase, a brake current pulse can be applied via a control circuit. The brake current pulse may generate a magnetic field in the injector which may slow down the speed of the armature and associated valve needle in the closing operation and thus reduce the bounce of the injector.

Furthermore, it may be stated, in particular with reference to the description of the figures, that a measure of the closing speed of the valve needle and the correlated intensity of the injector bouncing can be derived from a separated movement-induced voltage during an injector closing may be derived. The derived measure may serve as a reference variable for an electronic anti-bounce control. Starting from a deviation of the reference variable from the respective desired value, a braking current pulse may be impressed as a manipulated variable after switching off the injector current at the end of the holding phase via a control loop. The brake current pulse may generate a magnetic field in the injector, which may slow down the speed of the armature and the connected valve needle during the closing operation, since the built-up magnetic force may counteract the acting in the closing direction spring and hydraulic force. In this way, the bounce of the injector may be reduced or completely suppressed.

An indicated algorithm for electronic anti-bounce control may be used in the engine control unit. The regulation may be made individually for each injector installed on the engine.

It should be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments of the invention are described with method claims. However, it will be readily apparent to those skilled in the art upon reading this application that, unless explicitly stated otherwise, in addition to a combination of features associated with a type of subject matter, any combination of features may be contemplated Types of inventions include.

Further advantages and features of the present invention will become apparent from the following exemplary description of an embodiment which presents a variety of variations. The figures of this application are merely schematic. Also, the embodiments underlying the figures may be modifiable. In particular, the embodiments underlying the figures may be combinable.

1 shows a typical current control profile and the corresponding voltage curve for a direct injection valve with a coil drive.

2 shows a detection of the closing time based on a time derivative of the induced voltage in the coil.

3 Figure 11 shows a detection of the closing timing using a reference voltage waveform which characterizes the induction effect in the coil due to the decay of eddy currents in the magnet armature.

4 shows an intended for driving a valve output stage, which has a reference generator for generating the reference voltage waveform.

5 shows an extension for the in 4 illustrated reference generator for generating reference voltage waveforms of higher order.

6 shows a differential amplifier for forming the difference between an induced coil voltage and a reference voltage waveform.

7 shows the time courses of an induced coil voltage, a reference voltage and the difference between the induced coil voltage and the reference voltage.

8th shows a current control profile and the corresponding voltage curve of the coil with impressed counter voltage.

It should be noted that features or components of different embodiments, which are the same or at least functionally identical with the corresponding features or components of the embodiments, are provided with the same reference numerals. In order to avoid unnecessary repetitions, features or components already explained on the basis of a previously described exemplary embodiment will not be explained in detail later.

It should also be noted that the embodiments described below represent only a limited selection of possible embodiments of the invention. In particular, it is possible to combine the features of individual embodiments in a suitable manner with one another, so that a multiplicity of different embodiments are to be regarded as obviously disclosed to the person skilled in the art with the embodiment variants shown explicitly here.

Introductory to 1 may be considered on the basic technical and physical conditions in the operation of injection systems or in the operation of injectors.

For the operation of modern internal combustion engines and the observance of strict emission limit values, the engine control predicts via the cylinder filling model the air mass enclosed in the cylinder per working cycle. In accordance with the modeled air mass and the desired air-fuel ratio (lambda), the corresponding fuel quantity setpoint (MFF_SP) is injected via the injection valve. The main requirement for the injection valve is in addition to tightness against uncontrolled fuel outflow, the jet preparation, the time and quantity exact metering of the pilot injection quantity. By means of the injection valve, the fuel quantity to be injected is so dimensioned that an optimum lambda for exhaust gas aftertreatment in the catalytic converter is set. For the direct injection gasoline engines with internal mixture formation, which are the focus here, the fuel is injected directly into the combustion chamber at a pressure in the range of 40-200 bar.

The injector consists of the main components linear actuator with coil and the valve group. The drive converts an applied electrical voltage via a current flow into a magnetic field, which exerts a magnetic force on the armature and the positively connected valve needle. If the magnetic force acting axially on the armature exceeds the sum of the spring force of the closing spring acting on the valve needle, the friction force and the hydraulic closing force as well as the inertial force of the moving mass, the armature and valve needle are raised.

The valve group consists of the armature and the positively connected valve needle, the valve seat body and the nozzle plate. With sufficient magnitude of the magnetic force, the valve needle is raised about 80 microns from the valve seat body and the nozzle plate via the armature, whereby a free cross section is released in the nozzle plate, so that fuel can escape from the injection valve.

To close the injector occurs after switching off the electrical voltage on the drop in the current when the spring force and hydraulic force exceed the inertial forces of the masses and the decreasing magnetic force. There is a resulting axial force, which accelerate the valve needle and the connected armature in the direction of the valve seat body. By striking the valve needle on the valve seat body, there is a central inelastic impact, with the result that the valve needle is deflected by the elastic forces again in the opening direction and thus again escapes fuel through the free cross section in the nozzle plate. This unwanted process is called bouncing the injection valve. Depending on the elasticity of valve needle and valve seat body, the height of the fuel pressure, the spring constant of the closing spring and the stroke of the valve needle may result in one or more bounce operations.

The bouncing process injects an additional amount of fuel, which results in a deviation from the nominal injection quantity set by the pilot control. In addition, the mixture preparation of the amount of fuel injected in the bouncing process is insufficient, as it comes to throttling effects in the valve seat due to the small valve needle and thus the responsible for the mixture formation fuel pressure at the nozzle plate is greatly reduced.

The method for operating an injection valve may be based on a determination of the closing time of a solenoid-operated fuel injection valve (injector coil drive) based on an evaluation of the drive voltage, which is a method for detecting the mechanical closing time of a valve needle, which must be positively connected to the armature of the injector, may correspond. The method may thus be based on the effect that after switching off the drive current, the closing movement of armature and connected valve needle leads to a speed-dependent influence on the injector voltage. The coil-driven injection valve, after switching off the injector current to a reduction in the magnetic force. By spring preload and hydraulic force, resulting in a resultant force which accelerates armature and valve needle in the direction of the valve seat. Immediately before the impact on the valve seat anchor and valve needle reach their maximum speed. At this speed, the air gap between the coil core and the armature increases. Due to the movement of the magnet armature and the associated Luftspaltehöhung, the remanent magnetism of the magnet armature leads to a voltage induction in the injector coil. The maximum occurring movement induction voltage characterizes the maximum speed of the magnetic needle and thus the timing of the mechanical closing of the valve needle.

On the basis of this knowledge in particular, it may be possible to derive a measure of the intensity of the injector bounce from characteristic characteristics of the derived movement induction voltage at the injector closure and thus to derive a suitable reference variable for a control loop. Starting from the deviation of the reference variable from a nominal value mag, after switching off the injector current at the end of the holding phase, a brake current pulse can be applied via a control circuit. The brake current pulse may generate a magnetic field in the injector which may slow down the speed of the armature and associated valve needle in the closing operation and thus reduce the bounce of the injector.

In the following, technical and physical fundamentals may be discussed which show that values for reference variables can ultimately be determined from measured values for an injection valve, which can be used to determine the Guiding parameters and thus suitable for determining the controlled variable. Thus, based on the controlled variable, the applied counterforce may be controllable in such a way that bouncing is reduced.

The electrical control of a direct injection valve usually takes place via current-controlled full-bridge output stages of the engine control. A full-bridge output stage makes it possible to supply the injection valve with an onboard supply voltage of the motor vehicle and, alternatively, with an amplification voltage. The boost voltage is often referred to as boost voltage (U_boost) and may be, for example, about 60V.

• A) Pre-Charge-Phase: Während dieser Phase der Dauer t_pch mag durch die Brückenschaltung der Endstufe die Batteriespannung U_bat, welche der Bordnetzspannung des Kraftfahrzeugs entsprechen mag, an den Spulenantrieb des Einspritzventils anliegen. Bei Erreichen eines Stromsollwertes I_pch mag die Batteriespannung U_bat durch einen Zweipunktregler abgeschaltet werden und nach Unterschreiten einer weiteren Stromschwelle mag U_bat wieder eingeschaltet werden.
• B) Boost-Phase: An die Pre-Charge Phase mag sich die Boost-Phase anschließen. Dazu mag von der Endstufe die Verstärkungsspannung U_boost solange an den Spulenantrieb angelegt werden, bis ein Maximalstrom I_peak erreicht sein mag. Durch den schnellen Stromaufbau mag das Einspritzventil beschleunigt öffnen. Nach Erreichen von I_peak mag sich bis zum Ablauf von t_1 eine Freilaufphase anschließen, während dieser wiederum die Batteriespannung U_bat an den Spulenantrieb angelegt werden mag. Die Zeitdauer Ti der elektrischen Ansteuerung mag ab dem Beginn der Boost-Phase gemessen werden. Dies mag bedeuten, dass der Übergang in die Freilaufphase durch das Erreichen des vorgegebenen Maximalstroms I_peak getriggert werden mag. Die Dauer t_1 der Boost-Phase mag in Abhängigkeit des Kraftstoffdrucks fest vorgegeben sein.
• C) Abkommutierungs-Phase: Nach Ablauf von t_1 mag eine Abkommutierungs-Phase folgen. Durch Abschalten der Spannung mag hier eine Selbstinduktionsspannung entstehen, welche im Wesentlichen auf die Boostspannung U_boost begrenzt sein mag. Die Spannungsbegrenzung während der Selbstinduktion mag sich zusammensetzen aus der Summe von U_boost, sowie den Vorwärtsspannungen einer Rekuperationsdiode und einer sog. Freilaufdiode. Die Summe dieser Spannungen mag im Weiteren als Rekuperationsspannung bezeichnet werden. Aufgrund einer differentiellen Spannungsmessung, welche der 1 zugrunde liegen mag, ist die Rekuperationsspannung in der Abkommutierungs-Phase negativ dargestellt.

1 shows a typical current drive profile I (thick solid line) for a direct injection valve with a coil drive. 1 also shows the corresponding voltage U (thin solid line) that may be applied to the direct injection valve. The control may be divided into the following phases:

• A) Pre-charge phase: During this phase of the duration t_pch, the battery voltage U_bat, which may correspond to the vehicle electrical system voltage of the motor vehicle, may be applied to the coil drive of the injection valve by the bridge circuit of the output stage. When a current setpoint I_pch is reached, the battery voltage U_bat may be switched off by a two-point controller, and U_bat may be switched on again once the current threshold has fallen below another.
• B) Boost phase: The pre-charge phase may be followed by the boost phase. For this purpose, the boost voltage U_boost may be applied to the coil drive by the output stage until a maximum current I_peak may have been reached. Due to the rapid current build-up, the injection valve may open at an accelerated rate. After reaching I_peak, a freewheeling phase may follow until the end of t_1, during which time the battery voltage U_bat may in turn be applied to the coil drive. The duration Ti of the electrical control may be measured from the beginning of the boost phase. This may mean that the transition to the freewheeling phase may be triggered by reaching the predetermined maximum current I_peak. The duration t_1 of the boost phase may be fixed as a function of the fuel pressure.
• C) Abkommutierungs-Phase: After lapse of t_1 a Abkommutierungs-phase may follow. By switching off the voltage, a self-induction voltage may arise here, which may be essentially limited to the boost voltage U_boost. The voltage limitation during self-induction may be composed of the sum of U_boost, as well as the forward voltages of a recuperation diode and a so-called freewheeling diode. The sum of these voltages may be referred to below as the recuperation voltage. Due to a differential voltage measurement, which the 1 may be underlying, the recuperation in the Abkommutierungs phase is shown negative.

• D) Halte-Phase: An die Abkommutierungs-Phase mag sich die sog. Haltephase anschließen. Hier mag wiederum über einen Zweipunktregler der Sollwert für den Haltestromsoll I_hold über die Batteriespannung U_bat eingeregelt werden.
• E) Abschalt-Phase: Durch Abschalten der Spannung mag eine Selbstinduktionsspannung entstehen, welche, wie oben erläutert, auf die Rekuperationsspannung begrenzt sein mag. Dadurch mag ein Stromfluss durch die Spule entstehen, welcher nun das Magnetfeld abbauen mag. Nach Überschreiten der hier negativ dargestellten Rekuperationsspannung fließt kein Strom mehr. Dieser Zustand mag auch als ”open coil” bezeichnet werden. Aufgrund der ohmschen Widerstände des magnetischen Materials mögen die beim Feldabbau der Spule induzierten Wirbelströme abklingen. Die Abnahme der Wirbelströme mag wiederum zu einer Feldänderung in der Magnetspule und somit zu einer Spannungsinduktion führen. Dieser Induktionseffekt mag dazu führen, dass der Spannungswert am Injektor ausgehend vom Niveau der Rekuperationsspannung nach dem Verlauf einer Exponentialfunktion auf Null ansteigen mag. Der Injektor mag nach Abbau der Magnetkraft über die Federkraft und die durch den Kraftstoffdruck verursachte hydraulische Kraft schließen.

The recuperation voltage may cause a current to flow through the coil, which may reduce the magnetic field. The abkommutierungs phase may be timed and may depend on the battery voltage U_bat and on the duration t_1 of the boost phase. The Abkommutierungs phase may end after a further period of time t_2.

• D) holding phase: The so-called holding phase may follow the commutation phase. Here, in turn, the desired value for the holding current setpoint I_hold can be adjusted via the battery voltage U_bat via a two-point controller.
• E) Shutdown Phase: By switching off the voltage may arise a self-induction voltage, which, as explained above, may be limited to the recuperation voltage. This may cause a current flow through the coil, which may now degrade the magnetic field. After exceeding the negative recuperation voltage shown here no current flows. This condition may also be called "open coil". Due to the ohmic resistances of the magnetic material, the eddy currents induced during the field breakdown of the coil may decay. The decrease of the eddy currents in turn may lead to a field change in the magnetic coil and thus to a voltage induction. This induction effect may cause the voltage value at the injector to increase to zero starting from the level of the recuperation voltage after the course of an exponential function. The injector may close upon release of the magnetic force via the spring force and the hydraulic force caused by the fuel pressure.

• – Zunächst mag das Abschalten der Spannung an der Spule des Einspritzventils zu einer Selbstinduktionsspannung führen, welche durch die Rekuperationsspannung begrenzt werden mag. Die Rekuperationsspannung mag typischerweise dem Betrag nach etwas größer als die Boostspannung sein. Solange die Selbstinduktionsspannung die Rekuperationsspannung übersteigt, mag es zu einem Stromfluss in der Spule kommen und das Magnetfeld in der Spule mag abgebaut werden. Die zeitliche Lage dieses Effektes ist in 1 mit ”I” gekennzeichnet.
• – Bereits während des Abklingens des Spulenstromes mag es zu einer Verminderung der Magnetkraft kommen. Sobald die Federvorspannung und die hydraulische Kraft aufgrund des Druckes des einzuspritzenden Kraftstoffs die abnehmende Magnetkraft übersteigen, mag sich eine resultierende Kraft ergeben, welche den Magnetanker zusammen mit der Ventilnadel in Richtung des Ventilsitzes beschleunigen mag.
• – Übersteigt die Selbstinduktionsspannung die Rekuperationsspannung nicht mehr, so fließt kein Strom mehr durch die Spule. Die Spule mag elektrisch im sogenannten ”open coil” Betrieb sein. Aufgrund der ohmschen Widerstände des magnetischen Materials des Magnetankers mögen die beim Feldabbau der Spule induzierten Wirbelströme exponentiell abklingen. Die Abnahme der Wirbelströme mag wiederum zu einer Feldänderung in der Spule und somit zu der Induktion einer Spannung führen. Dieser Induktionseffekt mag dazu führen, dass der Spannungswert an der Spule ausgehend vom Niveau der Rekuperationsspannung nach dem Verlauf einer Exponentialfunktion bis auf Null Volt ansteigen mag. Die zeitliche Lage dieses Effektes ist in 1 mit ”III” gekennzeichnet.
• – Unmittelbar vor dem Aufschlag der Ventilnadel in den Ventilsitzes mögen Magnetanker und Ventilnadel ihre maximale Geschwindigkeit erreichen. Mit dieser Geschwindigkeit mag sich der Luftspalt zwischen Spulenkern und Magnetanker vergrößern. Aufgrund der Bewegung des Magnetankers und der damit einhergehenden Luftspalterhöhung, mag der remanente Magnetismus des Magnetankers zu einer Spannungsinduktion in der Spule führen. Die auftretende maximale Induktionsspannung mag die maximale Geschwindigkeit des Magnetankers (und auch der verbundenen Ventilnadel) und damit den Zeitpunkt des mechanischen Schließens der Ventilnadel kennzeichnen. Dieser von Magnetanker und der damit verbundenen Ventilnadel-Geschwindigkeit verursachte Induktionseffekt mag dem Induktionseffekt aufgrund des Abklingens der Wirbelströme überlagert sein. Die zeitliche Lage dieses Effektes ist in 1 mit ”IV” gekennzeichnet.
• – Nach dem mechanischen Schließen der Ventilnadel mag typischerweise ein Prellvorgang erfolgen, bei dem die Ventilnadel noch einmal kurzzeitig aus der Schließposition ausgelenkt werden mag. Infolge der Federspannung und des anliegenden Kraftstoffdrucks mag die Ventilnadel jedoch wieder in den Ventilsitz gedrückt werden. Das Schließen des Ventils nach dem Prellvorgang ist in 1 mit ”V” gekennzeichnet.

The described closing time detection method may appear on the following physical effects that may occur in the shutdown phase of an injector:

• - First, the switching off of the voltage across the coil of the injection valve may lead to a self-induction voltage, which may be limited by the Rekuperationsspannung. The recuperation voltage may typically be slightly larger than the boost voltage in magnitude. As long as the self-induction voltage exceeds the recuperation voltage, there may be a current flow in the coil and the magnetic field in the coil may be degraded. The timing of this effect is in 1 marked with "I".
• - Already during the decay of the coil current may cause a reduction in the magnetic force. As soon as the spring preload and the hydraulic force due to the pressure of the fuel to be injected exceed the decreasing magnetic force, a resulting force may arise, which may accelerate the armature together with the valve needle in the direction of the valve seat.
• If the self-induction voltage no longer exceeds the recuperation voltage, then no current flows through the coil. The coil may be electrically in the so-called "open coil" operation. Due to the ohmic resistances of the magnetic material of the magnet armature, the eddy currents induced during the field breakdown of the coil may decay exponentially. The decrease of the eddy currents in turn may lead to a field change in the coil and thus to the induction of a voltage. This induction effect may lead to the voltage value at the coil starting from the level of the recuperation voltage after the course of an exponential function rising to zero volts. The timing of this effect is in 1 marked with "III".
• - Immediately before the impact of the valve needle in the valve seat magnet armature and valve needle may reach their maximum speed. At this speed, the air gap between the coil core and the magnet armature may increase. Due to the movement of the magnet armature and the associated Luftspaltehöhung, the remanent magnetism of the magnet armature may lead to a voltage induction in the coil. The occurring maximum induction voltage may indicate the maximum speed of the armature (and also the connected valve needle) and thus the timing of the mechanical closing of the valve needle. This induced by magnet armature and the associated valve needle speed induction effect may be superimposed on the induction effect due to the decay of the eddy currents. The timing of this effect is in 1 marked with "IV".
• - After the mechanical closing of the valve needle may typically occur a bounce, in which the valve needle may be briefly deflected out of the closed position again. As a result of the spring tension and the applied fuel pressure, however, the valve needle may again be pressed into the valve seat. The closing of the valve after the bouncing process is in 1 marked with "V".

The method may be based on detecting the closing time of the injection valve from the induced voltage curve in the switch-off phase. As explained in detail below, this detection may be performed by different methods.

2 shows different waveforms at the end of the hold phase and in the shutdown phase. The transition between the hold phase and the turn-off phase may occur at the turn-off time, represented by a vertical dashed line. The current through the coil may be indicated by the reference numeral 100 provided curve in the unit ampere. In the turn-off phase, an induced voltage signal may arise from a superposition of the induction effect due to magnet armature and valve needle speed and the induction effect due to the decay of the eddy currents 110 result. The voltage signal 110 is in unity 10 Volt shown. You can see the voltage signal 110 in that the speed of the voltage increase in the region of the closing time decreases sharply before the speed of the voltage increase due to the rebounding of valve needle and armature increases again. The with the reference number 120 provided curve represents the time derivative of the voltage signal 110 in this derivation 120 like the closing time at a local minimum 121 be recognizable. After the rebound process, another closing time may be at a further minimum 122 to be recognized.

Furthermore, in 2 a curve 150 which shows the fuel flow in units of grams per second. It can be seen that the measured fuel flow through the injection valve drops very rapidly shortly after the detected closing time from above. The time offset between - on the basis of the evaluation of the drive voltage - detected closing time and the time at which the measured fuel flow rate reaches zero for the first time, resulting from the limited measurement dynamics in the determination of the fuel flow. From a time of about 3.1 ms, the corresponding measurement signal may seem like 150 level to zero.

To reduce the computational power required to perform the described closure timing detection technique, the determination of the derivative may be helpful 120 also be carried out only within a limited time interval, which contains the expected closing time.

For example, if one defines a time interval I with the width 2Δt around the expected closing time t _{Close_Expected} , the following applies for the actual closing time t _Close : I = {t _{Close_Expected} - Δt, t _{Close_Expected} + Δt] U _min = min {dU (t) / dt | t ε I} t _close = {t ε I | U (t) = U _min } (1)

As already indicated above, this approach may be extended to detect the re-closing of the valve due to a bouncing valve needle at a time t _{Close_Bounce} . For this purpose one defines a time interval with the width 2Δt _bounce around the time t _{Close_Bounce_Expected of} the expected closing after the first bouncing process. The time t _{Close_Bounce_Expected} may be set relative to the closing time t _close via t _{Close_Bounce_Expected} . I _Bounce = [t _close + t _{Close_Bounce_Expected} - Δt _Bounce , t _close + t _{Close_Bounce_Expected} + Δt _Bounce ] U _{min_Bounce} = min (dU (t) / dt | t ε I _bounce } t _{close_Bounce} = {t ε I _Bounce | U ( t) = U _{min_Bounce} } (2)

3 Figure 11 shows a detection of the closing timing using a reference voltage waveform which characterizes the induction effect in the coil due to the decay of eddy currents in the magnet armature. In 3 are as well as in 2 the end of the hold phase and the shutdown phase are shown. The measured voltage curve 110 , which may result from a superposition of the induction effect due to air gap and the identical valve needle speed and the induction effect due to the decay of the eddy currents, is the same as in 2 , Also the coil current 100 is compared to 2 unchanged.

Idea is now the share of the voltage signal 110 , which may be caused solely by the induction effect due to the decay of the eddy currents, to be calculated by a reference model. A corresponding reference voltage signal may be indicated by the reference numeral 215 be shown. By determining the voltage difference between the measured voltage curve 110 and the reference voltage signal 215 one may eliminate the induction effect due to decaying eddy currents. The differential voltage signal 230 may thus characterize the motion-related induction effect and may be a direct measure of the speed of the armature and valve needle. The maximum 231 the differential voltage signal 230 may characterize the maximum armature or valve needle speed which may be achieved just prior to the needle impacting the valve seat. Thus, the maximum likes 231 of the differential _{voltage signal} to be used to determine the actual closing time t _{close_} .

As an example, a simple phenomenological reference model may be cited below. The reference model may be calculated online in the electronic engine control. However, other physical model approaches are also conceivable.

The reference model may be started (t = 0) as soon as or after the self-induction _voltage no longer exceeds the recuperation _voltage , but before reaching t _{Close_Expected} , and thus no current flows through the coil. The coil may then be in electrical "open coil" mode. The reference voltage curve 215 may be measured for a reference injector on the injection test bench at a fuel pressure greater than the maximum opening pressure. The injector may be clamped hydraulically in a closed position despite electrical control. The voltage curve measured in the switch-off phase may therefore characterize exclusively the voltage component induced by exponentially decaying eddy currents.

The model parameter (s) of the reference model may then be optimized in offline mode so that the best possible agreement with the measured voltage profile is achieved 215 is achieved. This may be achieved in a known manner via the minimization of a quality measure by means of a gradient search method.

In general, the modeled reference _voltage U _{INJ_MDL results in} a time-dependent model with the parameters of a measured voltage _start value U _Start from shutdown phase, the electrical resistance and the temperature _{behavior of} the magnetic material R _{MAG_Material} (θ) in which the eddy currents flow and the current value I _hold in the _hold phase at the time of shutdown. This may be mathematically described by the following equation: U _{INJ_MDL} (t) = f (U _start , R _{MAG_material} (θ), I _hold ) (3)

A simple realization may be achieved by the following model. The time constant with the dependencies injector temperature and I _hold may be stored according to the embodiment shown here by a map. U _{INJ_MDL} (t) = U _start · [1 - exp {t / τ (θ, I _hold )}] (4)

The closing time may be as above from the determination of the local maximum of the voltage difference 230 between the reference model 215 and the measured induction voltage 110 result. This evaluation in turn may take place in the time interval I with the width 2Δt _bounce around the expected closing time t _{Close_Expected} . I = [t _{Close_Expected} - Δt, t _{Close_Expected} + Δt] U _{diff_max} = max {U _{INJ_MDL} (t) - U _{INJ_MES} (t) | t ε I} t _close = {t ε I | [U _{INJ_MDL} (t) - U _{INJ_MES} (t)] = U _{diff_max} } (5)

Where U _{INJ_MES} (t) stands for the measured voltage signal 110 ,

As already shown above, the algorithm may be expanded by defining a suitable observation time interval to detect the re-closing of the injector at time t _{Close_Bounce} due to a bouncing injector needle.

• a) Eine Generatorschaltung zum Erzeugen des Referenzspannungssignals 215, welches die durch die Wirbelströme induzierte, exponentiell abklingende Spulenspannung zeitsynchron zum Anschaltvorgang nachbildet. Die Generatorschaltung wird nachfolgend auch als Referenzgenerator bezeichnet.
• b) Eine Subtraktionsschaltung zur Differenzbildung von Spulenspannung 110 und Referenzspannungssignals 215, um den durch die Wirbelströme induzierten Spannungsanteil des Spannungssignals 110 zu eliminieren. Dadurch verbleibt im Wesentlichen der bewegungsinduzierte Anteil der Spulenspannung.
• c) Eine Auswerteschaltung zum Erkennen des Maximums 231 des bewegungsinduzierten Anteils der Spulenspannung, welches den Schließzeitpunkt des Injektors indiziert.

The course of the reference voltage signal 215 can not only be calculated by means of a suitably programmed arithmetic unit but can also be simulated with an electronic circuit, ie in hardware. Such a circuit for detecting the closing time may advantageously consist of three functional groups:

• a) A generator circuit for generating the reference voltage signal 215 , which simulates the exponentially decaying coil voltage induced by the eddy currents in synchronism with the startup process. The generator circuit is also referred to below as a reference generator.
• b) A subtraction circuit for subtracting coil voltage 110 and reference voltage signal 215 to the voltage component of the voltage signal induced by the eddy currents 110 to eliminate. This essentially leaves the motion-induced portion of the coil voltage.
• c) An evaluation circuit for detecting the maximum 231 the movement-induced portion of the coil voltage, which indicates the closing time of the injector.

4 shows an intended for driving a valve output stage, which is such a reference generator 360 may have to generate the reference voltage waveform.

During the turn-off phase, the transistors T1, T2 and T3 are switched off by means of the control signals Control1, Control2 and Control3. The voltage generated by the magnetic flux in the injector coil L_inj may cause the voltage at the recuperation diode D1 to increase until the recuperation diode D1 and a freewheeling diode D3 become conductive and a current flow arises between the boost voltage V_boost and ground (GND).

It should be noted that the coil voltage in the 2 and 3 is shown as a differential voltage. Accordingly, the turn-off voltage has negative values. In the real circuit, however, here the left side of the coil L_inj may be approximately at ground, whereas the right side of the coil L_inj may be at a positive voltage value.

In the reference generator 360 For example, the coil voltage V_Spule may be fed via a diode D12 to the emitter of an NPN transistor T10. Its base potential is determined by means of a voltage divider, which may have the diodes D10 and D11 and the resistor R10, to a value of about 1.4 V below the voltage of V_boost. As long as the coil voltage V_spool is substantially smaller than V_boost, T10 may be de-energized because of the reverse-biased diode D12, so that the voltage across the resistor R11 is 0V. During the turn-off switching phase, the coil voltage V_spool may increase to V_boost plus the flux voltage from the diode D1. As a result, the transistor T10 may be turned on and charges a capacitor C11, so that the voltage V_Reference may quickly increase to the value of V_boost. The charging current through the transistor T10 may be much greater than the discharge current through the resistor R11. If the coil is discharged so far that its voltage drops below V_boost, T10 blocks and the capacitor C11 may now be discharged through the resistor R11. With a suitable choice of the component values, the discharge curve has the desired exponentially decaying course, which may take place synchronously in time with the course of the coil voltage V_spule.

5 shows an extension for the in 4 illustrated reference generator for generating reference voltage waveforms of higher exponential order. In doing so, the in 4 represented components R11 and C11, which are both connected between V_Reference and ground, by the in 4 illustrated supplementary circuit 470 replaced. The supplementary circuit 470 has a capacitor C11, two parallel connected in series resistors R11a and R11b and a parallel to R11b switched capacitor C12.

The difference between the coil signal and the reference signal may be used as a differential amplifier 580 wired operational amplifier 582 respectively. Such a differential amplifier 580 is in 6 shown. The differential amplifier 580 has four resistors R20, R21, R22 and R23, each with the positive or the negative input of the operational amplifier 582 are contacted. At the output of the differential amplifier is the motion-induced coil voltage V_BEMF, which in the 2 with the reference number 230 is featured, available.

7 shows the time courses of the induced coil voltage 610 (V_spool), the reference voltage 615 (V_Reference) and the differential voltage 630 (V_BEMF) between the induced coil voltage 610 and the motion-induced reference voltage 610 ,

The difference voltage 630 (V_BEMF) may be evaluated, for example, with a circuit disclosed in German Offenlegungsschrift DE 10 2005 044 886 A1 (please refer 6 and 7 ) is explained in detail. Around the differential voltage generated here 630 (V_BEMF) may like this directly to the base of the transistor T1 of the known in the 6 and 7 DE 10 2005 044 886 A1 described electronic evaluation circuit are created. In the present application, the resistors R1-R4, as well as C1 and D3 accounts for this known evaluation circuit. Further changes to this known evaluation circuit are not required.

It should be noted that the circuits described in this document are only possible embodiments to explain the operation. Of course, other circuit variants are conceivable.

The method described in this document may also be used to detect the closing of the control valve in a coil-type diesel injector. In addition, the described method may also be used for detecting the closing of the valve needle in a direct-drive spool drive diesel injection valve.

It may therefore be noted that the induction voltage, which is caused by the armature movement, can be separated from the voltage curve in the turn-off phase. The time at which the maximum induction voltage may occur describes the mechanical closing of the valve needle.

• 1) Detektion Schließzeitpunkt über Ableitung des Spannungsverlaufes in der Abschaltphase
• 2) Detektion Schließzeitpunkt über Referenzspannungsmodell
• 3) Detektion Schließzeitpunkt über Erzeugung der Referenzspannung über eine Hardware-Schaltung

The closing time of the injector may be determinable, in particular, by three different methods:

• 1) Detection closing time via derivation of the voltage curve in the shutdown phase
• 2) Detection closing time via reference voltage model
• 3) Detection closing time via generation of the reference voltage via a hardware circuit

From the separated motion-induced voltage at injector closing may be derived a measure of the closing speed of the valve needle and the correlating intensity of the injector bounce. The derived measure may serve as a reference variable for an electronic anti-bounce control.

The closing time of the injector may be determined in particular via the reference voltage model. In this case, the voltage curve after switching off the injector current (current in the injector coil), which is caused by the induction effect due to the decay of the eddy currents, may be calculated by a reference model. This reference voltage curve U _{INJ_MDL} may occur at an injector, which may experience no movement of armature and valve needle when energized, due to an excessive hydraulic force (too high fuel pressure). The voltage difference between the course U _{INJ_MES} and the reference model measured at the injector with moved magnet armature and valve needle may separate the motion- _{induced stress effect} . The maximum of the motion-induced stress may characterize the maximum armature or valve needle speed change at the time of impact of the valve needle on the valve seat body. Thus, over the time at which the local maximum of the motion-induced voltage occurs, the injector closing time t _Close can be determined.

The evaluation may take place in an observation time interval I with the width 2Δt around the expected injector closing time t _{Close_Expected} . By definition, t _close = 0 may be the time at which the injector current is turned off at the end of the hold phase. t _close mag, represented in a slightly different manner, thus describing the time difference between the end of the holding phase and the closing of the valve needle. I = [t _{Close_Expected} - Δt, t _{Close_Expected} + Δt] U _{diff_max} = max {U _{INJ_MDL} (t) - U _{INJ_MES} (t) | t ε I} t _close = {t ε I | [U _{INJ_MDL} (t) - U _{INJ_MES} (t)] = U _{diff_max} } (6)

Measurements may indicate that t _close may correlate with the closing speed of the valve needle. For example, when increasing the fuel pressure, t _{close may} decrease monotonically. The reason for this may be that increasing the fuel pressure may increase the hydraulic closing force, and thus the valve needle and armature may be more accelerated to impact the valve seat body.

To increase the robustness against system tolerances (injector, injector output stage, temperature, ...), the relative change of this time with respect to the measured value without activated electronic anti-bounce control may be used as a reference variable as an alternative to the absolute value t _close . t _{close_rel} = t _close / t _{close_no_control} (7)

Measurements may also indicate that the maximum stress U _{diff_max of} the separated motion- _induced stress defined in equation 6) for the observation time interval I correlates with the closing speed of the valve needle. For example, with an increase in the Fuel _pressure U _{diff_max} monotonously increase. The reason for this may be that an increase in the fuel pressure increases the hydraulic closing force and thus the valve needle and armature are more accelerated to impact on the valve seat body and thus may increase the movement induced stress on the occurring greater speed change.

In order to increase the robustness against system tolerances (injector, injector _{output stage} , temperature,...), The relative change of this voltage with respect to the measured value without activated electronic anti-bounce control may be used as a reference variable as an alternative to the absolute _value U _{diff_max} . U _{diff_max_rel} = U _{diff_max} / U _{diff_max_no_control} (8)

If the evaluation of the motion- _induced voltage signal in the observation time interval I _{_bounce} with the width 2Δt _{_bounce is performed} around the expected injector closing time for the bouncing t _{Close_Expected_bounce} , one may obtain a definition for closing time t _{close_bounce} . The introduced sizes like through 1 be explained. I _{_bounce} = [t _{Close_Expected_bounce} - Δt _{_bounce} , t _{Close_Expected_bounce} + Δt _{_bounce} ] U _{diff_max_bounce} = max {U _{INJ_MDL} (t) - U _{INJ_MES} (t) | t ε I _{_bounce} } t _{close_bounce} = {t ε I _{_bounce} | [U _{INJ_MDL} (t) - U _{INJ_MES} (t)] = U _{diff_max_bounce} ) - t _close (9)

The time t _{close_bounce} may _correlate with the stroke of the valve needle due to the bounce process and thus with the additionally injected fuel quantity. The additional amount of fuel injected may increase monotonically with an increase of t _{close_bounce} .

To increase the robustness against system tolerances (injector, injector _{output stage} , temperature, ...), the relative change of this time in relation to the measured value without activated electronic anti-bounce control may be used as a reference variable as an alternative to the absolute _value t _{close_bounce} . t _{close_bounce_rel} = t _{close_bounce} / t _{close_bounce_no_control} (10)

In the following, a regulated anti-bounce operation with a control value for the brake current pulse may be explained. In particular, a pre-control of the time for the activation of the brake current pulse may take place.

Due to the eddy currents in the magnetic circuit of the injector, it may come after a time delay after impressing the brake current pulse to build up a magnetic force with a braking effect on the armature and the associated valve needle. To achieve the desired braking effect, the structure of the braking magnetic force may occur shortly before or at the beginning of the armature and needle movement in the direction of valve closing. In order to ensure the required temporal correlation between the beginning of the armature movement and the development of the magnetic force with a braking effect, the time for the activation of the current pulse (t _{break_delay} ) _{may depend} on the injector closing time t _close . Since the dynamics of the armature and valve needle during the closing process may depend significantly on the fuel pressure (FUP), this factor may also be taken into account when determining t _{break_delay} . The mentioned dependencies may be realized via a map which may be determined experimentally. t _{break_delay} = f (t _close , FBD) (11)

In particular, a setpoint specification for the reference variables may take place. The quantities defined in (6), (7), (8), (9) and (10) may be used as control variables w for the control. wε {t _close , t _{close_rel} , U _{diff_max} , U _{diff_max_rel} , t _{close_bounce} , t _{close_bounce_rel} } (12)

The desired value w _{sp of} a reference variable may be described as a function of the relevant influencing variables, such as fuel pressure FUP, injector current at the time of switching off the voltage at the end of the injection pulse and the injector temperature. The mentioned dependencies may be realized or represented via a map or a set of maps which may be determined experimentally. w _{sp_N} = f (FUP, I (t = 0), θ _INJ ) (13)

Furthermore, the controller and the manipulated variable may be more accurately describable. For example, the controller output y _N can be determined via a control difference e _N via a PID controller. The controller output may correspond to the controlled variable. Since the measurement of feedback variable W _{measured_N} only at discrete times t _N - closing the injector - happens may take place a discrete-time control. The return value may also correspond to a reference variable. e _N = w _{sp_N -w measured_N} (14)

The controller output y _N may determine the time duration for the impressed brake current pulse t _break as a manipulated variable. Due to the discrete-time control, the manipulated variable for the N + 1th injection pulse (next pulse) may be calculated on the basis of the controller output of the Nth pulse (current pulse).

For the N + 1-th injection pulse, the voltage U_boost may be applied to the injector coil for the duration t _{break_N + 1} at the time t _{break_delay_N + 1} via the final stage, which may lead to the application of the brake current pulse required for bounce-free injector operation.

Controller parameters K _P , K _I , K _D may be stored as a function of the influencing variables in characteristic diagrams. The determination of the controller parameters may be done experimentally. K _P = f (FUP, I (t = 0), θ _INJ ) K _I = f (FBD, I (t = 0), θ _INJ ) K _D = f (FBD, I (t = 0), θ _INJ ) (15)

8th shows a current control profile and the corresponding voltage curve of the coil with impressed counter voltage. The current course ( 810 ) and the voltage curve ( 820 ) may initially have a similar characteristic course, as he already from the 1 may be known. After a zero time (t = 0) ( 831 ), which corresponds to the time of switching off the applied voltage, which keeps the injection valve in an open state, may subsequently increase in the sequence of an induced voltage in the manner already described. At a time t _{break_delay} after the zero time, a boost voltage V_boost ( 822 ), which may be maintained for a period t _break . The boost voltage V_boost ( 822 ) may thus generate a counterforce, which may be contrary to the closing of the injection valve. By impressing the boost voltage V_boost ( 822 ) may have a current in the coil ( 812. ), which causes a magnetic field and thus the counterforce on the coupled with the valve needle armature. With the counterforce may thus be reduced bouncing of the valve needle on the valve seat or completely suppressed.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005044886 A1 [0096]

Claims (10)

A method of operating an injection system having an injector and a controller, the injector having a valve needle and a valve seat, the method comprising: Opening the injection valve by moving the valve needle away from the valve seat by means of an opening force, Closing the injection valve by moving the valve needle towards the valve seat by means of a closing force, Determining a value of a guidance parameter which is indicative of a closing behavior of the injection valve, Controlling an opposing force applied to the valve needle by means of the control device based on the value of the guidance parameter, wherein the counterforce is controlled such that a bouncing of the valve needle is reduced on the valve seat. Method according to claim 1, wherein the injection valve has a coil, wherein the guidance parameter comprises a voltage-value-based reference variable whose value can be determined based on a measured value of an induced voltage at the coil. The method of claim 1 or 2, wherein the guide parameter has a current value-based reference variable whose value can be determined based on a measured value of a current through the coil. Method according to one of claims 1 to 3, wherein the counterforce is applied in a direction which is opposite to a direction of closing, and / or wherein the counterforce is applied in a direction opposite to the direction of opening. Method according to one of claims 1 to 4, wherein the coil is an injector coil and wherein the counterforce is a braking force generated by applying a braking voltage to the injector coil. The method of claim 1, wherein the controlling comprises determining a value of a system size determined based on the value of the guidance parameter. The method of claim 6, wherein the method further comprises: Determining a value of the system size based on the voltage-based command variable, wherein the voltage-based command variable is determined from the measured value of the induced voltage during a cycle, Determining a value of the system size based on the current-based command variable, wherein the current-based command variable is determined from the measured value of the current during a further cycle. Method according to claim 6 or 7, Determining a value of the system size, which in particular determines a time period for the application of the counterforce, by means of a control difference in a control loop, wherein the control difference is determined from a difference the voltage-based reference variable, which is determined at a second time in a cycle, and the current-value-based reference variable, which is determined at a first time in the cycle, the second time in the cycle following the first time in the cycle. The method of claim 8, wherein the control loop is a PID control loop. Injection system, which has an injection valve and a control device, wherein the injection valve has a valve needle and a valve seat, wherein the injection system is set up such that the injection valve can be opened by means of an opening force, in that the valve needle can be moved away from the valve seat by means of the opening force, the injection valve is closable by means of a closing force, in that the valve needle is movable toward the valve seat by means of the closing force, a value of a guidance parameter can be determined for the injection valve, which is indicative of a closing behavior of the injection valve, a voltage applied to the valve needle counterforce is adjustable, the counterforce is controllable by means of the control device based on the value of the guidance parameter, wherein the counterforce is adjustable so that a bouncing of the valve needle is reduced to the valve seat.

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