EP2470769B1 - Method and controller for operating an electromagnetic actuator - Google Patents

Description

State of the art

The invention relates to a method for operating an electromagnetic actuator, in particular a fuel injection valve of an internal combustion engine of a motor vehicle, in which the electromagnetic actuator is activated during an activation process in order to influence an operating state of the actuator.

The invention also relates to a control device for carrying out such an operating method.

A method of the type mentioned is already from the DE 101 38 483 A1 known. To increase the precision in the control of the electromagnetic actuator, the known method provides for applying a current pulse to the electromagnetic actuator before it is activated, and for correcting the control based on a variable that characterizes the duration of the current pulse. This ensures that a control duration for several control processes with different supply voltages is constant.

The disadvantage of the known method is the requirement to have to provide a separate current pulse before the actual control of the electromagnetic actuator. This results in particular restrictions with regard to the minimum time intervals between successive actuation processes. In addition, the current pulses that are not themselves part of the control increase the electrical energy requirement of a corresponding circuit.

The DE 101 34 332 A1 discloses a device and a method for controlling a consumer, in particular for metering fuel in an internal combustion engine. At least a first control and a second control of the consumer take place. The beginning of the second activation is at a minimum distance from the end of the first activation. In certain states, a variable is recorded that characterizes the flow of current in the consumer after the consumer has been activated. The minimum distance is determined on the basis of this size.

Disclosure of the invention

Accordingly, it is the object of the present invention to improve a method and a control device of the type mentioned at the outset in such a way that there is increased precision in the control of the electromagnetic actuator without requiring additional current pulses that are not part of the control processes.

This object is achieved with a method according to claim 1.

In this way, according to the invention, particularly precise control of the electromagnetic actuator is advantageously possible because a residual magnetic field influencing the operating behavior of the electromagnetic actuator, which results for example from previous control processes, can be taken into account and, in particular, its effects on future control can be compensated for.

According to the invention, it has been recognized that, in particular, a magnetizing current that flows through a primary inductance of the magnetic circuit of the electromagnetic actuator at the start of the control process has a significant influence on the operating behavior of the electromagnetic actuator. According to the invention, it is therefore proposed that the electromagnetic actuator be controlled as a function of a magnetization parameter that characterizes the magnetization current.

According to the invention, the magnetization parameter can be determined, for example, as a function of a time profile of a coil current flowing through a magnet coil of the electromagnetic actuator. In particular, it is advantageously possible to set a time interval between the start of the control process and to determine the point in time at which the coil current reaches a predeterminable setpoint value, and to form the magnetization parameter as a function of the determined time interval. This variant of the invention is distinguished by its low complexity and allows the magnetization parameter considered according to the invention to be determined by a simple time measurement.

According to the invention, both the activation duration for the current activation process and / or an activation start can be specified as a function of the state of the magnetic circuit and / or the magnetization parameter.

Another very advantageous embodiment of the method according to the invention provides that a coil voltage applied to the magnet coil is determined at a defined point in time before the start of the control process, and that the magnetization parameter is formed as a function of this determined voltage value. A formation of the magnetization parameter as a function of several of the aforementioned variables (coil current, time interval, coil voltage) is also conceivable.

According to the invention, it is provided that the state of the magnetic circuit is determined based on a model as a function of at least one control variable for the electromagnetic actuator.

By using a model representing the electromagnetic actuator, a state of the magnetic circuit of the electromagnetic actuator can be determined particularly precisely as a function of at least one control variable for the electromagnetic actuator. In particular, using the model according to the invention, the state of the magnetic circuit of the electromagnetic actuator can be determined not only at the beginning of a respective control process, but also at further operating times of the electromagnetic actuator.

Using the model according to the invention, the state of the magnetic circuit can be particularly advantageous as a function of one or several previous control processes can be determined, resulting in increased precision with regard to the information characterizing the state of the magnetic circuit.

A control device according to patent claim 7 is specified as a further solution to the object of the present invention.

The implementation of the operating method according to the invention in the form of a computer program according to claim 8, which can be stored on an electronic or optical storage medium and which can be executed by a control and / or regulating device, e.g. for an internal combustion engine, is of particular importance.

Further advantages, features and details emerge from the following description, in which various exemplary embodiments of the invention are shown with reference to the drawing. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

Figur 1

Schematisch ein Kraftstoffeinspritzventil einer Brennkraftmaschine eines Kraftfahrzeugs mit einem erfindungsgemäß betriebenen elektromagnetischen Aktor,

Figur 2

ein vereinfachtes Ersatzschaltbild eines magnetischen Kreises des elektromagnetischen Aktors aus Figur 1,

Figur 3 und 4

jeweils einen zeitlichen Verlauf verschiedener Betriebsgrößen des elektromagnetischen Aktors, und

Figur 5

ein Funktionsdiagramm einer weiteren Ausführungsform des erfindungsgemäßen Betriebsverfahrens.

Figur 1

zeigt schematisch ein Kraftstoffeinspritzventil 100 einer

In the drawing shows:

Figure 1

Schematically, a fuel injection valve of an internal combustion engine of a motor vehicle with an electromagnetic actuator operated according to the invention,

Figure 2

a simplified equivalent circuit diagram of a magnetic circuit of the electromagnetic actuator Figure 1 ,

Figures 3 and 4

in each case a time profile of various operating variables of the electromagnetic actuator, and

Figure 5

a functional diagram of a further embodiment of the operating method according to the invention.

Figure 1

shows schematically a fuel injection valve 100 of a

Internal combustion engine of a motor vehicle. The fuel injector 100 has an electromagnetic actuator 10, which drives at least one component of the fuel injection valve 100, not shown here, for example a valve needle, in order to effect fuel injections. The electromagnetic actuator 10 is controlled by a control device 20 assigned to it. In a manner known per se, the control device 20 has a computing unit such as a microcontroller or a digital signal processor (DSP), which are suitable for executing a computer program representing the method according to the invention.

Figure 2 shows a simplified equivalent circuit diagram of a magnetic circuit 11 of a typical electromagnetic actuator 10 ( Figure 1 ).

The equivalent circuit has a resistor R_c, which represents the ohmic resistance of a primary coil of the electromagnetic actuator 10. A main inductance L_h, which represents an inductance of the magnet coil of the electromagnetic actuator 10, is connected in series with the ohmic resistance R_c.

In parallel with the main inductance L_h, a series circuit is provided which has a leakage inductance L_σ and a further ohmic resistance R_w *.

The further ohmic resistance R_w * is an eddy current resistance of the electromagnetic actuator 10 translated to the side of the magnet coil.

When the electromagnetic actuator 10 or the magnetic circuit 11 implemented by it is subjected to a control voltage u, a coil current i_c results in accordance with the circuit topology described above.

The coil current i_c branches out as if Figure 2 visible between the main inductance L_h and the leakage inductance L_σ to a magnetizing current i_m and an eddy current i_w * according to the knot rule: i_c + i_w * = i_m.

Of the currents described above, only the magnetizing current i_m is decisive for the generation of a magnetic force of the electromagnetic Actuator 10, which is used to move the valve needle of the fuel injector 100. The eddy current i_w * contributes in a manner known per se to the electrical power loss of the electromagnetic actuator 10.

Overall, in the equivalent circuit according to Figure 2 a distinction can be made between a main current path l_1 and an eddy current path l_w, the eddy current path l_w extending over the leakage inductance L_σ.

Figure 3 FIG. 13 shows a time profile of the currents described above through the magnetic circuit according to FIG Figure 2 .

This is based on an operating state of the electromagnetic actuator 10 which is characterized in that at the beginning t_0 of a control process no energy in the form of magnetic fields is stored in the inductances L_h, L_σ. This statement is synonymous with the fact that both the magnetizing current i_m and the eddy current i_w * have a value of zero at the time t_0, compare Figure 3 .

At the beginning t_0 of the control according to Figure 3 is controlled by the control unit 20 ( Figure 1 ) a constant control voltage u ( Figure 2 ), which can be a so-called boost voltage u = u_boost, for example, is applied to the terminals of the electromagnetic actuator 10 until the coil current i_c has reached a predeterminable setpoint value l_boos. The control voltage u is then set to a lower value.

With the control pattern described above by the control voltage u, the time profiles of the currents i_c, i_m, i_w * result as shown in FIG Figure 3 are shown.

However, as soon as - in accordance with a further possible operating scenario - non-vanishing values for the magnetizing current i_m occur at the start of actuation t_0, one of the values above with reference to FIG Figure 3 explained scenario deviating course.

The occurrence of magnetizing currents i_m that do not vanish at the beginning t_0 of the control can, for example, result from the fact that a the previous control process was ended so shortly before the beginning t_0 that the entire magnetic field of the leakage inductance L_σ has not already decayed.

In this case, there is a non-vanishing eddy current i_w * in the eddy current path l_w and a corresponding, likewise non-vanishing, magnetizing current i_m through the main inductance L_h ( Figure 2 ), which has a magnetic force.

In the Figure 4 The current curves i_c1, i_m1, i_w * 1 shown here result in an operating scenario of the electromagnetic actuator 10 that corresponds to the in Figure 3 is comparable to the operating scenario illustrated. This means that the current curves i_c1, i_m1, i_w * 1 are set when, at time t_0, a static electromagnetic actuator 10 is subjected to a constant control voltage u until the coil current i_c1 reaches the predefinable setpoint l_boos. As already described, the relevant currents then decay.

The first of a total of three in Figure 4 As already described above, the operating scenarios illustrated is characterized in that no magnetizing current i_m1 flows at time t_0, that is to say i_m1 = 0.

However, if - following a further operating scenario - a non-vanishing magnetization current through the main inductance L_h ( Figure 2 ) flows, compare the current profile i_m2, according to investigations by the applicant, it can be determined that the corresponding coil current profile i_c2 already reaches the predefinable setpoint l_boos at an earlier point in time t <t_1 compared to the coil current profile i_c1.

The eddy current curve i_w * 2 that is established here is also in Figure 4 illustrated.

According to a further possible operating scenario, the magnetizing current i_m3 can also have an even greater value at the activation start time t_0 than is the case with the magnetizing current profile i_m2 is the case. The reason for this can be, for example, a particularly short pause between two successive control processes of the electromagnetic actuator 10, so that at the control start time t_0 of the control process under consideration, a relatively large amount of energy is still stored in the magnetic field of the leakage inductance L_σ.

In this operating scenario, the coil current i_c3 accordingly reaches the specifiable setpoint value l_boos the earliest.

The corresponding eddy current curve is illustrated by the reference symbol i_w * 3.

According to the invention, a state of the magnetic circuit 11 ( Figure 2 ) of the electromagnetic actuator 10 to be taken into account in the control of the electromagnetic actuator 10, whereby a precise control of the electromagnetic actuator 10 is possible especially in those operating states in which at the control start time t_0 a non-vanishing magnetization current i_m2, i_m3 ( Figure 4 ) prevails.

According to the invention, a particularly simple and efficient way of obtaining information about the state of the magnetic circuit 11 of the electromagnetic actuator 10 is to determine a magnetization parameter that characterizes a magnetization current i_m that flows through the primary inductance L_h at the beginning t_0 of the control process. According to the invention, this magnetization parameter can advantageously be used directly to modify the control of the electromagnetic actuator 10, that is to say in particular the control voltage u. For example, the temporal course of the control voltage u can be modified as a function of the magnetization parameter in such a way that, regardless of the actual value of the magnetization current i_m at the time t_0, the same operating behavior of the electromagnetic actuator 10 and thus, for example, the same injection quantity when the fuel injection valve 100 is operated ( Figure 1 ) results.

The magnetization parameter can be determined particularly efficiently as a function of a time profile of the coil current i_c flowing through the magnet coil of the electromagnetic actuator 10.

This can be achieved particularly easily by determining a time interval t_mess between the start t_0 of the control process and the point in time t_1 at which the coil current i_c1 reaches the predeterminable setpoint value l_mess. The magnetization parameter used to modify the control variable u can finally be formed as a function of the determined time interval t_mess. It is particularly advantageous to select the setpoint l_mess equal to the setpoint l_boos, since the end of the boost phase with constant voltage u-boos then also marks the point in time t_1.

According to the above with reference to Figure 4 The dependencies described between the point in time t_1 when the target value l_boos for the coil current i_c is reached and the associated value of the magnetizing current i_m at the point in time t_0 are for the various operating scenarios according to Figure 4 get different time intervals t_mess. For example, the coil current i_c3 reaches the specifiable setpoint value l_boos at the earliest from the activation time t_0, because a relatively large magnetizing current i_m3 has already flowed at the time t_0. The smallest time interval results accordingly for this third operating scenario.

From the above-described time behavior of the coil current i_c, which is generated, for example, by the control unit 20 ( Figure 1 ) can be recorded in a known manner by measurement, according to the invention a default value for the control duration for the current control process and / or a control start, for example a future control, can be specified depending on the state of the magnetic circuit.

Another advantageous method of determining the state of the magnetic circuit at the beginning of the activation consists in determining the voltage u immediately before the boost voltage is applied. This works particularly well when the coil current i_c = 0 before the start of control is. In this case, according to Kirchhoff's law, i_m = i_w * applies. But it immediately follows that: $$\frac{\mathrm{di}\_\mathrm{m}}{\mathrm{German}}=-\mathrm{R.}\_\mathrm{w}*\cdot \mathrm{i}\_\mathrm{m}\cdot \frac{1}{\mathrm{L.}\_\mathrm{\sigma }+\mathrm{L.}\_\mathrm{H}}$$

u ist also proportional zu i_m.The following then applies to the voltage u: $$\mathrm{u}=\mathrm{L.}\_\mathrm{H}\cdot \frac{\mathrm{di}\_\mathrm{m}}{\mathrm{German}}+\mathrm{R.}\_\mathrm{c}\cdot \mathrm{i}\_\mathrm{c}\stackrel{\mathrm{i}\_\mathrm{c}=0}{=}\mathrm{L.}\_\mathrm{H}\cdot \frac{\mathrm{di}\_\mathrm{m}}{\mathrm{German}}=-\mathrm{R.}\_\mathrm{w}*\cdot \mathrm{i}\_\mathrm{m}\cdot \frac{\mathrm{L.}\_\mathrm{H}}{\mathrm{L.}\_\mathrm{\sigma }+\mathrm{L.}\_\mathrm{H}},$$

So u is proportional to i_m.

In a further very advantageous embodiment of the operating method according to the invention, the state of the magnetic circuit 11 is determined based on a model as a function of at least one control variable for the electromagnetic actuator 10.

This can be done in Figure 5 The model 200 shown can be used, which can be used, for example, by a corresponding computer program in a processing unit of the control unit 20 Figure 1 ) is implemented.

According to the invention, input variables E1, E2 are fed to the model 200. The input variables E1, E2 can, for example, be parameters of the last fuel injection that are present in the control unit 20. Furthermore, the input variables E1, E2 can also include desired properties of the subsequent injection.

The model 200 according to the invention uses this to determine parameters for the control of the subsequent injection, which are, for example, a time profile of the control voltage u ( Figure 2 ) can act. The model 200 according to the invention can be made available by making metrologically recorded operating parameters of the electromagnetic actuator 10 available, which are shown in FIG Figure 5 are symbolized by the reference symbol M, can be adapted during its operation. The model 200 individually to the special fuel injection valve 100 ( Figure 1 ) be adjusted.

The metrologically recorded variables M can be, for example, the control voltage u, the control current I, from which further variables can be determined, for example an opening time and / or a closing time and / or a flight duration of a movable component of the fuel injection valve 100, which during the activation of the fuel injection valve performs a ballistic trajectory.

From the input variables E1, E2, M supplied to it, the model 200 according to the invention forms output variables A for controlling the electromagnetic actuator 10, which can be, for example, the time profile of the control voltage u.

By considering the magnetizing current at the beginning t_0 of the control process according to the invention, a particularly precise control of the electromagnetic actuator 10 can be realized. For example, an activation of the electromagnetic actuator 10 can thereby advantageously be realized in which various activation processes are carried out in quick succession. The pause times between the adjacent control processes are so short that the magnetic field of the leakage inductance L_σ has not already completely broken down again until a subsequent control process begins. Accordingly, a non-vanishing magnetization current I_m results at the point in time t_0, which according to the invention is advantageously taken into account in the formation of the control variables for the subsequent control process.

Claims (9)

1. Method for operating an electromagnetic actuator (10), in particular of a fuel injection valve (100) of an internal combustion engine of a motor vehicle, in which the electromagnetic actuator (10) is actuated during an actuation process in order to influence an operating state of the actuator (10), wherein a residual magnetic field which is present at the start of the actuation process, of a magnetic circuit (11) of the electromagnetic actuator (10) is taken into account during the actuation of the electromagnetic actuator (10), wherein the actuation is carried out as a function of a magnetization characteristic variable which characterizes a magnetization current (i_m) which flows through a primary inductance (L_h) of the magnetic circuit (11) of the electromagnetic actuator (10) at the start (t_0) of the actuation process, wherein the magnetization characteristic variable is determined in a model-based fashion, characterized in that the magnetic circuit (11) of the electromagnetic actuator (10) is modelled with a resistance (R_c) which represents the ohmic resistance of the primary coil of the electromagnetic actuator (10), in series with a main inductance (L_h) which represents an inductance of the magnetic coil of the electromagnetic actuator (10), wherein a series circuit which has a leakage inductance (L_σ) and a further ohmic resistance (R_w*) is provided parallel to the main inductance (L_h).
2. Method according to Claim 1, characterized in that the magnetization characteristic variable is determined as a function of a time profile of a coil current (i_c) which flows through a solenoid of the electromagnetic actuator (10).
3. Method according to Claim 2, characterized in that a time interval (t_mess) is determined between the start (t_0) of the actuation process and the time (t_1) at which the coil current (i_c) reaches a specifiable setpoint value (l_mess), and in that the magnetization characteristic variable is formed as a function of the determined time interval (t_mess).
4. Method according to one of the preceding claims, characterized in that an actuation period for the current actuation process and/or a start of actuation is specified as a function of the state of the magnetic circuit (11) and/or of the magnetization characterization variable.
5. Method according to one of the preceding claims, characterized in that the state of the magnetic circuit (11) is determined in a model-based fashion as a function of at least one actuation variable for the electromagnetic actuator (10).
6. Method according to Claim 5, characterized in that the state of the magnetic circuit (11) at the start of a future actuation process is determined as a function of one or more preceding actuation processes.
7. Control unit (20) for operating an electromagnetic actuator (10), in particular a fuel injection valve (100) of an internal combustion engine of a motor vehicle, in which the electromagnetic actuator (10) can be actuated during an actuation process in order to influence an operating state of the actuator (10), wherein a residual magnetic field which is present at the start of the actuation process, of a magnetic circuit (11) of the electromagnetic actuator (10) is taken into account during the actuation of the electromagnetic actuator (10), wherein the actuation is carried out as a function of a magnetization characteristic variable which characterizes a magnetization current (i_m) which flows through a primary inductance (L_h) of the magnetic circuit (11) of the electromagnetic actuator (10) at the start (t_0) of the actuation process, wherein the magnetization characteristic variable is determined in a model-based fashion, characterized in that the magnetic circuit (11) of the electromagnetic actuator (10) is modelled with a resistance (R_c) which represents the ohmic resistance of the primary coil of the electromagnetic actuator (10), in series with a main inductance (L_h) which represents an inductance of the magnetic coil of the electromagnetic actuator (10), wherein a series circuit which has a leakage inductance (L_σ) and a further ohmic resistance (R_w*) is provided parallel to the main inductance (L_h).
8. Computer program with program code means for carrying out all the steps of the method according to one of Claims 1 to 6, when the computer program is run on a computer or a corresponding computing unit in a control unit (20) according to Claim 7.
9. Computer program product with program code means which are stored on a computer-readable data carrier in order to carry out all the steps of the method according to one of Claims 1 to 6, when the computer program is run on a computer or a corresponding computing unit in a control unit (20) according to Claim 7.

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