EP0973178A2 - Method for controlling the motion of an armature of an electromagnetic actuator - Google Patents

Abstract

Following pull-in there is a braking phase in which a voltage is applied to a coil (4a, 4b) up to impact of the armature (4d) upon it. Timing and cyclic course of the voltage applied, are controlled as a function of the desired position (20) of the armature over time.

Description

The invention relates to a method for controlling the movement of an anchor an electromagnetic actuator, in particular for actuating a Gas exchange stroke valves of an internal combustion engine, the armature oscillating between two solenoid coils each against the force at least a return spring by alternating energization of the solenoid coils is moved, and with an approach of the anchor to the first energized coil during the so-called catching process the electrical voltage applied to the armature catching coil is reduced becomes. Regarding the technical environment, reference is made to DE 195 30 121 A1.

A preferred application for an electromagnetic actuator with the features of claim 1 is the electromagnetically actuated valve train of internal combustion engines, i.e. the gas exchange stroke valves of a reciprocating piston internal combustion engine are actuated in such a way by actuators Actuated wise, i.e. oscillatingly opened and closed. At a Such electro-mechanical valve train, the globe valves are individually or also in groups via electromechanical actuators, the so-called actuators moves, the time for opening and closing each Lift valves can be chosen essentially completely freely. This can the valve timing of the internal combustion engine optimally to the current Operating state (this is defined by speed and load) and to the respective requirements with regard to consumption, torque, emissions, Comfort and responsiveness of a driven by the internal combustion engine Be adapted to the vehicle.

The essential components of a known actuator for actuating the lift valves of an internal combustion engine are an armature and two electromagnets for holding the armature in the "lift valve open" or "lift valve closed" position with the associated electromagnetic coils, and also return springs for the movement of the armature between the positions "lift valve open" and "lift valve closed". For this purpose, reference is also made to the attached FIG. 1 , which shows such an actuator with an associated lift valve in the two possible end positions of the lift valve and actuator armature, and the course of the armature stroke between the two shown states or positions of the actuator / lift valve unit z or armature path between the two solenoid coils and also the course of the current flow I in the two solenoid coils each over time t is shown in accordance with a known prior art (compared to DE 195 30 121 A1 mentioned earlier).

As can be seen in Figure 1, the closing process of an internal combustion engine lift valve is shown, which is designated by the reference number 1 and which in this case moves in the direction of its valve seat 30. As usual, a valve closing spring 2a acts on this lifting valve 1, furthermore the actuator designated in its entirety with 4 acts on the stem of the lifting valve 1 - here with the interposition of a (not absolutely necessary) hydraulic valve lash compensation element 3. In addition to two electromagnetic coils 4a, 4b, this consists of a push rod 4c acting on the stem of the lift valve 1, which carries an armature 4d which is guided in an oscillating, longitudinally displaceable manner between the electromagnetic coils 4a, 4b. A valve opening spring 2b also acts on the end of the push rod 4c facing away from the stem of the lifting valve 1.

This is therefore an oscillatory system for which the valve closing spring 2a and the valve opening spring 2b a first and form a second return spring, for which consequently also below the reference numbers 2a, 2b are used. The left-hand side is in FIG first end position of this vibratory system is shown, in which the lift valve 1 is fully open and the armature 4d on the lower one Electromagnet coil 4b is present, which is also referred to below as an opening coil 4b is referred to after this coil 4b, the lift valve 1 in its open Holds position. The second end position of the vibratory system shown in which the lift valve 1 completely is closed and the armature 4d on the upper electromagnet coil 4a is applied, which is also referred to below as a make coil 4a after this coil 4a, the lift valve 1 in its closed position holds.

The closing process of the lift valve 1 will now be briefly described below, ie in FIG. 1 the transition from the left-hand state to the state on the right-hand side; in between, the corresponding courses of the electrical currents I flowing in the coils 4a, 4b and the course of the stroke or the path coordinate z of the armature 4d are respectively plotted against the time t. With regard to the path coordinate z, the value z ₀ corresponds to a fully open globe valve 1, ie the armature 4d bears against the break coil 4b, while at z = z 1 the armature 4d rests on the make coil 4a.

Starting from the left-hand position "lift valve open", the Opener coil 4b energized to the armature 4d in this position against the tensioned To hold valve closing spring 2a (= lower first return spring 2a), the current I in this coil 4b shown in dashed lines in the I-t diagram is. Now the current I of the break coil 4b for a desired transition switched off after "lift valve closed", the armature 4d is released of this coil 4b and the lift valve 1 is by the tensioned valve closing spring 2a accelerated approximately to its central position (upwards), However, due to its inertia, it continues to move and tense the valve opening spring 2b, so that the lifting valve 1 (and the armature 4d) thereby being slowed down. Then the make coil 4a becomes one suitable time (the current I for the coil 4a is in the I-t diagram shown in a solid line), whereby this coil 4a Anchor 4d captures - this is the so-called catching process -, and finally in the position shown on the right "lift valve closed" holds. After the armature 4d is securely caught by the coil 4a in this, moreover, switched to a lower holding current level (see I-t diagram).

Null" initiiert wird. Die notwendige elektrische Energie für den Betrieb jedes Aktuators 4 wird dabei entweder dem Bordnetz des von der zugehörigen Brennkraftmaschine angetriebenen Fahrzeuges entnommen oder über eine separate, dem Ventiltrieb der Brennkraftmaschine angepaßte Energieversorgung bereitgestellt. Dabei wird die elektrische Spannung durch die Energieversorgung konstant gehalten, und der Spulenstrom I der den Brennkraftmaschinen-Hubventilen 1 zugeordneten Aktuatoren 4 durch ein Steuergerät derart gesteuert, daß sich die notwendigen Kräfte für das Öffnen, Schließen und Halten des bzw. der Hubventile 1 in der jeweils gewünschter Position ergeben.The reverse transition from “lift valve closed” to “lift valve open” takes place analogously from the position shown on the right in FIG. 1 by switching off the current I in the make coil 4a and switching on the current for the break coil 4b with a time delay. In general, a sufficient electrical voltage is applied to the coils 4a, 4b while the electrical current I is switched off by reducing the electrical voltage to the value

The electrical energy necessary for the operation of each actuator 4 is either taken from the vehicle electrical system of the vehicle driven by the associated internal combustion engine or is provided via a separate energy supply adapted to the valve train of the internal combustion engine. The electrical voltage is constant through the energy supply and the coil current I of the actuators 4 assigned to the internal combustion engine lift valves 1 is controlled by a control unit such that the forces required for opening, closing and holding the lift valve (s) 1 are obtained in the desired position.

In the prior art just explained, the coil current I during the so-called catching process, in which one of the two coils 4a, 4b seeks to capture anchor 4d from said controller or regulated by a control unit by clocking to a constant value, which is large enough to secure the anchor 4d under all conditions capture. Now the force of the catching electromagnetic coil 4a or 4b on the armature 4d approximately proportional to the current I and vice versa proportional to the distance between the coil and armature. Now - how in the known prior art - a constant current I set, so the magnetic force acting on the armature 4d increases with its approach inversely proportional to the respective coil 4a or 4b capturing it to the remaining gap, causing the armature acceleration and armature speed increase. This results in a high impact speed of the armature 4d on the respective electromagnetic coil 4a or 4b, which for a high level of wear in the actuator 4, but also one results in high noise levels. Another disadvantage is that of the briefly described current control switching losses occurring of the transistors that have increased power consumption and temperature stress of the control unit used and an increased electromagnetic Radiation in the supply lines of the actuators result.

Improvements especially with regard to noise development as well the actuator wear is caused by the above DE 195 30 121 A1 known prior art. Here is a procedure for Reduction of the speed of impact of an anchor on an electromagnetic Actuator proposed, with an approach of the armature to the pole face of the coil capturing the armature, the one lying against it Voltage limited to a predeterminable maximum value (i.e. essentially is reduced) so that the current flowing through the coil during part of the time of the voltage limitation drops. In this said Scripture also speaks of the extent of the voltage limitation or voltage reduction in a map can, it being assumed that the corresponding values and in particular also the respective time at which this voltage reduction should begin to be determined experimentally.

In contrast, it is the object of the present invention to show further improvements, ie a simple, practical and at the same time efficient method for reducing the impact speed of an armature of an electromagnetic actuator is to be demonstrated.
The solution to this problem is characterized in that the braking phase of the catching process is followed by a braking phase in which a clocked electrical voltage is applied to the coil until the armature hits it, the respective switching times and the voltage-pulse ratio of a controller can be determined on the basis of a target trajectory describing the anchor target movement. Advantageous developments and further developments are included in the subclaims, in a preferred embodiment of the invention the controller also determines the sign of the constant voltage value in addition to the voltage-pulse ratio, that is to say clocking either a positive or a negative voltage value or the voltage value Zero "to the coil catching the armature.

In general, according to the present invention, the known one is proposed Current regulation or the also known (to be determined empirically) Voltage reduction during the catching process through regulation to replace which during the so-called braking phase of the catching process shortly before the armature hits the magnet coil catching it electrical voltage is applied to this coil in a controlled manner, namely clocked, the respective switching times for switching off and switching on the electrical voltage (and possibly also its sign) based on a target trajectory that describes the anchor target movement.

The term Trajectory "is known to the person skilled in control engineering and describes a trajectory of an object to be moved controlled by a controller in a state space, in the present case the trajectory of the armature between the two electromagnetic coils. This target trajectory preferably contains over or as a function of of time (as usual with t ") values for the position of the anchor (hereinafter also as Path coordinate ")), for its speed and for the acceleration of the armature, ie it is a quasi a simple table of values that can either be stored in a suitable control device or depending on current boundary conditions in a manner that will be explained in more detail later Tests and calculations have shown that it is sufficient to provide such a target trajectory for the control only in the braking phase mentioned, since at the time the control is activated, the one that is still moving in the capture phase Anchor is always in such a state in which its position (ie the path coordinate), its speed and the acceleration of the anchor are in an essentially constant relationship (at least within the framework of the conditions required for the described application).

In Figure 2 , the corresponding control concept is shown as a block diagram, the controller having the reference number 10, and the control is carried out on the basis of the signals of a target trajectory 20 describing the desired anchor movement, and the controller 10 also processes signals of an observer 11 adjacent to the target trajectory 20 . The output variable of the control concept or of the controller 10 is the electrical voltage U applied or applied to the coil 4a or 4b which catches the armature 4d (see FIG. 1). This voltage U preferably has a constant value and is determined by the Controller 10 is applied to the respective coil 4a or 4b in a timed manner, wherein the controller 10 can also determine the sign of the electrical voltage, ie either a positive or a negative voltage value or the voltage value is clocked Zero "to the coil 4a or 4b catching the armature 4d.

The position of the armature 4d between the coils 4a, 4b corresponding to the stroke profile of the lifting valve 1 or armature 4d by the path coordinate z - this is measured in a suitable manner - is an input variable of the control concept described here, which is further processed by the observer 11. For the sake of simplicity, the position of the anchor will be included in the following z "without the explanatory term Path coordinate "to use.
From this path coordinate or armature position z, the movement speed z ˙ of the armature and the armature acceleration z can be estimated or ascertained by one or two derivations over time t. The value z and the variables z ˙, z ¨ derived therefrom are determined by the observer 11 and communicated to the controller 10 as so-called estimated values 21.

Incidentally, another input variable of the control concept described here is that of the observer 11 when determining the estimated values 21 is processed, which determined in the respective coils 4a, 4b (cf. FIG. 1) Current flow I (as a result of the applied voltage U).

The sequence of figures 3a, 3b, 3c, 3d explained below shows the individual phases of the control according to the invention during the catching process of the armature 4d by one of the two coils 4a, 4b in a system according to FIG. 1:
The voltage U applied to the electromagnetic coil capturing the armature is plotted in each case over the time t in the upper diagram (FIG. 3a), while the associated path coordinate z of the armature 4d (ie the armature position) is plotted in the second diagram (FIG. 3a) z, the values between z = 0 and z = z Max annimt) is shown. The individual phases according to the invention, namely the catching phase FP, the braking phase BP and the holding phase HP following the armature impact on the coil are identified in FIG. 3a.

As far as the start of the catching phase FP at time t ₁ is concerned, at which the coil catching the armature is supplied with electrical voltage U, this switch-on time t _{1 can in} principle be freely selected within certain limits; it only has to be ensured that the anchor 4d can still be caught at all. For the sake of simplicity, it is proposed here that the voltage U is switched on when the armature position z exceeds a certain selectable threshold value. In principle, this threshold value can also be variable, as a result of which additional boundary conditions such as, for example, different external forces acting on the lifting valve 1 to be moved (such as gas forces in particular) can be taken into account at different operating points of the internal combustion engine.

• erstens eine Fangphase FP, und
• zweitens eine sich daran anschließende Bremsphase BP.

An die letzgenannte schließt sich (nach dem Auftreffen des Ankers 4d auf der jeweiligen Spule 4a bzw. 4b) als drittes die übliche Haltephase HP an, in welcher der Anker 4d, nachdem er sicher auf die jeweilige Elektromagnet-Spule 4a bzw. 4b aufgetroffen ist, an dieser gehalten wird. Hierzu wird auf Haltestromregelung umgeschaltet, was wie dargestellt durch eine getaktete Beaufschlagung der jeweiligen Spule 4a, 4b mit der (gleichwertigen) elektrischen Spannung U erfolgt.According to the invention and as shown in FIG. 3a, the controller 10 divides the entire catching process of the armature 4d into two phases, namely:

• firstly, a catch phase FP, and
• secondly, a subsequent braking phase BP.

The latter is followed (after the armature 4d strikes the respective coil 4a or 4b) as the third, the usual holding phase HP, in which the armature 4d, after it has safely hit the respective electromagnetic coil 4a or 4b , is held on this. For this purpose, a switch is made to holding current control, which, as shown, is carried out by clocking the respective coil 4a, 4b with the (equivalent) electrical voltage U.

Returning to the braking phase BP that is essential to the invention, the voltage supply to the respective coil 4a or 4b capturing the armature 4d is first interrupted in this after the known catching phase FP at time t ₂ , whereby this braking phase BP is started, in which the constant electrical voltage U clocked and preferably variable sign applied to the relevant coil 4a, 4b (and thus a current flow I is initiated). The respective points in time for switching off and switching on the voltage U (which is constant in terms of amount) (ie the so-called voltage-pulse ratio) and here in addition the sign of the voltage U (ie the choice between a negative or a positive voltage value) are determined by the controller 10.

The function of the controller 10 can now be described as follows:
In order to achieve a desired reduction in its impact speed on the respective coil 4a or 4b that catches it, the armature 4d (see FIG. 1) must be braked in a controlled manner already in its flight phase, that is to say before the actual impact, namely in the so-called braking phase BP. However, this braking phase BP should not extend the opening and closing times of the internal combustion engine lift valve 1 actuated by the actuator 4 more than necessary.

For the design of a controller 10 that meets these requirements Now suitable state variables for the armature movement have to be selected. In addition to the anchor position z and the anchor speed, preference is given here z ˙, which is fundamentally differentiated by time the armature position z can be determined, the armature acceleration z ¨ as third State size chosen because it is a direct derivative of the anchor speed z ˙ also represents an easily interpretable quantity. In principle can the control can also be set up with other state variables.

During the braking phase BP, the controller 10 can now execute its desired function, namely the anchor 4d as soft and smooth as possible place on the respective electromanet coil 4a, 4b leave, fall back on a so-called target trajectory 20, which is dependent values for position z correlating with time t, contains the speed z ˙ and the acceleration z ¨ of the armature 4d. This target trajectory 20 is therefore nothing other than a value table of target values, which is shown in simplified form in FIG.

If the actual now when operating the electromagnetic actuator 4 Actual values for position z, speed z ˙ and acceleration z ¨ of the armature 4d deviate too much from the target values, so corrected this is the controller 10 by suitably switching the voltage U on or off (including any necessary variation of their sign). The detailed The controller 10 can be designed by various methods of linear and non-linear control theory and should be done here not dealt with in more detail.

As far as the determination of this table of values or the target trajectory 20 is concerned, it is proposed, among other things, from the boundary condition that the acceleration z ¨ of the armature 4d at the time of impact with the respective electromagnetic coil 4a or 4b the value In other words, this means that the armature 4d hits the coil 4a or 4b without jerking. Further boundary conditions are of course the defined position of the armature 4d when it hits (namely z = z Max ), as well as the then valid value of the anchor speed z ˙ = 0 (zero).

For further explanations, reference is now made to FIGS. 3b, 3c, 3d . Again, the position z (Fig.3b), the (desired) anchor speed z ˙ (Fig.3c), and the (desired) anchor acceleration z ¨ (Fig.3d) are in the final phase over time t the armature movement, ie before the armature 4d strikes the coil 4a or 4b which catches it. This essentially shows the time period between t ₂ (this is the end point of the catching phase FP, at which the constant voltage is switched off and the actual control process is started) and the touchdown time t ₄ , ie essentially the braking phase BP is shown.

To the left of t ₂ is the capture phase FP, in which the armature 4d moves towards the coil capturing it, whereby - as can be seen - the acceleration z z in this capture phase FP not only decreases, but even assumes negative values, since with it Approaching movement, for example, the associated return spring 2b (cf. FIG. 1) is tensioned on the coil 4a, ie the armature 4d is already braked in its flight speed z ˙ by this return spring 2b.

The actual control process begins at time t ₂ , ie the braking phase BP is started. This braking phase BP should now be designed in an ideal manner by the controller 10 in such a way that the armature 4d is gently placed on the coil 4a (or 4b), that is to say the acceleration z must again be of the value at the time of placement t ₄ Zero ".

As the z ¨-t diagram of Fig.3d shows, this ideal and thus desired acceleration curve between a point in time t ₃ (this is later than t ₂ ) and the touchdown point in time t _{4 can be} very well defined by a straight line and between the points in time t ₂ and t ₃ approximate by a parabola. The following relationships therefore apply to t ₃ <t ₄ : e.g. (t) = j · (t 4th - t) e.g. (t) = j / 2 · (t 4th - t) 2nd z (t) = j / 6 · (t 4th - t) 3rd + z e The formulas for z ˙ (t) and for z (t) result from a temporal integration of the acceleration z ¨ (t) taking into account the relevant boundary conditions, whereby j "is a constant.

The following relationships are also used for t ₂ <t <t ₃ : e.g. (t) = α 0 + α 1 · T + α 2nd · T 2nd e.g. (t) = e.g. 0 + α 0 · T + α 1 / 2 · t 2nd + α 2nd / 3t 3rd z (t) = z 0 + e.g. 0 · T + α 0 / 2 · t 2nd + α 1 / 6 · t 3rd + α 2nd / 12t 4th The constants z ₀ , z ˙ ₀ , α ₀ , α ₁ and α ₂ are to be determined from the continuity conditions for z ¨, z ˙ and z at time t ₃ , whereby two of these constants can be chosen freely. The values for α ₀ and the position of the vertex of said parabola (at time t _s ) can preferably be chosen as desired within certain limits.

It is expressly pointed out that it is not absolutely necessary is, the said target trajectory as here by one piece each To represent straight lines and a parabola. Others may as well do mathematical-geometric Functions such as polynomials, a sine function or the like can be used.

As can be seen from the previous description, the controller 10 needs for the execution of its function preferred three state variables the anchor position z, the movement speed z ˙ of the anchor 4d and the armature acceleration z ¨. Basically, it is possible to use these state variables to measure using suitable sensors. However, to save sensors or to replace expensive sensors with inexpensive sensors, can at least two of these state variables also by a so-called. Observer 11 can be reconstructed, already in connection with FIG was briefly mentioned.

In this observer 11, the actuator 4 is connected in parallel with an actuator model which is supplied with an actual variable which is essential for the actuator 4, namely with the variable of the current flow I determined in the respective coil 4a, 4b. In this observer 11, the armature position estimated on this basis can be compared with the actual measured armature position z and additionally transmitted to the observer 11 as an input variable, and the difference from this can then be fed back to the variables or so-called state variables of the actuator model via a correction function. In the event of a model error or an incorrect estimate of the initial states, the observer 11, based on the correction function contained therein, compares the estimated values for (here) the armature position z, the movement speed z ˙ of the armature 4d and the armature acceleration z ¨ the actual values therefor on. (It should be pointed out again that, in deviation from the present explanation, as an alternative to the values z, z ˙, z ¨ mentioned, other suitable variables or state variables can also be used to characterize the actuator state.)
The correction function just mentioned can be designed by various methods of linear or non-linear control theory and will not be dealt with in more detail here.

Before advantageous developments of the invention are described, the significant advantages of the method according to the invention, resulting from the use of the controller 10 that uses a target trajectory, are first summarized below:
In principle, the proposed complete state feedback enables the representation of arbitrarily low impingement speeds of the armature 4d on the respective electromagnetic coil 4a or 4b.
In particular, it is possible that the armature 4d is jerk-free (ie with an acceleration z ¨ of the value Zero "strikes the respective coil, so that the noise generated by this impact is minimized at time t ₄ .
Due to the target trajectory calculated in advance or in a suitable control electronics in the background, the real-time computing effort is kept low during the actual control process.
The calculation of the target trajectory in the preferred application mentioned allows adaptation during operation of the internal combustion engine, depending on its current operating state, such as, for example, speed, load torque, temperature, wear and more.
Furthermore, the problem of measuring all the required quantities is solved by using the observer 11 based on the measured quantities valve lift or armature position z and coil current I.

Such a method for motion control will now be described an actuator armature for actuating an internal combustion engine lift valve with a view to achieving further possibilities. As a result, different target trajectories are for different movement sequences the armature and / or the gas exchange valve. The so-called target trajectory becomes visual for the further description simplified simply by the desired sequence of movements of the anchor 4d and designated with the reference number 20 or 20a, 20b, 20c, ....

With such a further development, it is thus possible not only to transfer the armature 4d and the lift valve 1 into their respective end positions in the desired manner, but also that further movements of the elements mentioned can be implemented. Examples of possible further movement sequences are shown in FIGS. 4, 5 in the form of target trajectories 20a, 20b, 20c, which are shown in simplified form as already mentioned, the course of the path coordinate z of the armature 4d over time t being similar to the representation of the target trajectory 20 is shown in Figure 1 .

Thus, in addition to a target trajectory 20a (see FIG. 4 ) leading the lifting valve 1 into its fully open position, at least one target trajectory 20b shown in FIG. 5 and only partially opening the lifting valve 1 can be provided. The representation according to FIG. 5 differs from that of FIGS. 1, 4 in that an opening and a closing movement of the lift valve 1 is shown in FIG. 5 , ie the time axis (t) extends over a longer period of time than in the figures 1, 4 . Preferably, as shown, the lifting valve 1 can be kept near its closed position by the target trajectory 20b which only partially opens it, ie the change in value of the path coordinate z of the armature 4d actuating the lifting valve 1 is relatively small, so that starting from the closed lifting valve 1 or starting from z = z 1 (ie the armature 4d rests on the make coil 4a) only the small armature stroke z = z 3rd or the path coordinate z _{3 is} reached.

With such a target trajectory 20b, the above-mentioned controller can thus set a floating position of the armature 4d in a quasi-fictitious end position, in which the armature 4d remains at least slightly spaced from the normally open coil 4a that previously released it. Thus, for example, when the lifting valve 1 opens , the opening coil 4b (cf. also FIG . 1 ), but a fictitious end position, namely z = z 3rd of the armature 4d in the vicinity of the make coil 4a, which corresponds, for example, to a minimum valve lift of the lift valve 1 of approximately 1 mm to 2 mm. If the armature 4d and thus the lift valve 1 is held in suspension in such a position (for example z ₃ ), this leads to an improved mixture preparation when an internal combustion engine inlet valve is actuated and to optimization when the internal combustion engine exhaust valve is actuated the charge movement, as is generally known to the person skilled in the art for internal combustion engines.

Furthermore, in particular for the closing process of the lifting valve 1, a target trajectory 20c which keeps the armature 4d at least slightly apart from the corresponding electromagnetic coil or closer coil 4a can be provided. As shown in FIG. 4 , it should again start from z = z 0 First of all, a first quasi-end position of the armature 4d is approached by z = z 2nd is defined and in which the armature 4d remains at least slightly spaced from the coil 4a catching it, after which a second armature end position is approached, namely its mechanical end position, namely z = z 1 corresponds. With this, an electronic valve clearance compensation in the lift valve drive of the internal combustion engine is practically possible. Accordingly, when the internal combustion engine lift valve 1 closes, the armature 4d is first moved to the position z ₂ , which corresponds to the placement of the lift valve 1 on its valve seat 30 (see FIG . 1 ). Subsequently, the armature 4d is moved into the position z ₁ , which corresponds to its own mechanical end position, in which it therefore comes to rest on the make coil 4a.
For the rest, when the lift valve 1 is subsequently opened, a first quasi-end position of the armature 4d can then initially correspond to the valve clearance (ie the position again z = z 2nd ) and then a second end position that corresponds to the mechanical end position of the armature 4d on the break coil 4b (namely z = z 0 ), so that the armature 4d strikes the stem of the globe valve ₁ as gently as possible due to or after overcoming the valve clearance in the position z ₂ .

Instead of the mechanical end positions of the armature 4d on the electromagnetic coils 4a, 4b, generally fictitious or so-called quasi-end positions of the armature 4d (lying between z ₀ and z ₁ ) can be approached, that is to say target trajectories (not shown) are provided here move the lift valve 1, for example, into its end positions and keep the armature 4d at a distance from the respective electromagnetic coil 4a or 4b. In this way, a so-called floating position of the armature 4d is set in a fictitious or quasi-end position, in which the armature 4d remains at least slightly spaced from the coil 4a or 4b capturing it. Thus, instead of the mechanical end position of the armature 4d when opening and / or closing the lift valve 1, a fictitious end position is approached in front of the respective electromagnetic coil 4a or 4b, and the armature in this intermediate position by the controller mentioned at the beginning, which processes the corresponding target trajectory pending. Since then the armature 4d does not strike the respective coil 4a or 4b, the noise in the valve train is considerably reduced.

As already explained at the beginning, these different target trajectories 20, 20a, 20b, 20c, .... processed in an electronic controller, the one accordingly applying the respective electromagnetic coil 4a and / or 4b with a suitable voltage-clock ratio. Around everyone will ensure that this controller is extremely robust provided target trajectories 20, ..... as a set of operating states defines in which the regulated system, namely the electromagnetic Valve train for the gas exchange stroke valve 1, which has the desired behavior. Now it must be ensured that this system under consideration the desired target trajectory in the desired operating state brought and this until the conclusion of the respective Movement sequence no longer leaves. This can be done under suitable Requirements due to a discontinuous control signal analogous to a two-point controller can be achieved. Under certain conditions, the desired operating conditions regardless of deviations or faults be selected so that the regulated system is largely independent of deviations and disturbances.

In the following, the significant advantages of this method are summarized, which uses a controller that uses different target trajectories 20, 20a, 20b, 20c, ....:
In principle, the proposed complete state feedback already enables the representation of arbitrarily low impact speeds of the armature 4d on the respective electromagnetic coil 4a or 4b. However, when the armature 4d no longer touches the respective coils 4a, 4b, the touchdown noise associated therewith disappears completely. Furthermore, the signs of wear that are otherwise caused by the touchdown are largely eliminated.
Within certain limits, which are also determined by the return springs 2a, 2b and by the magnetic design as a whole, the stroke of the actuator 4 and thus also of the lift valve 1 can be set as desired and changed for each individual opening and closing process.

Finally, the otherwise in a mechanical internal combustion engine lift valve train hydraulic valve clearance compensation required and the (existing, since always necessary) valve clearance electromagnetic be balanced.

Generally speaking, it has been described so far that the armature of the electromagnetic Actuator controlled in terms of its movement is that the one closer to the anchor and consequently energized Coil applied electrical voltage is regulated clocked and that Voltage-clock ratio of a controller based on the armature target movement descriptive target trajectory is determined. You can the controller and / or the target trajectories to different operating states be adapted to the internal combustion engine. It was also mentioned earlier that the calculation of the target trajectory is an adaptation even during operation the engine allows, depending on their current operating status, such as speed, load torque, temperature, Wear and more. The dynamic behavior actually depends of the actuator in particular due to the gas exchange valve acting gas forces essentially from the load condition and from the speed the internal combustion engine. It can also change component temperatures and especially the temperature of the engine lubricating oil as well as general signs of wear to a change the mechanical properties of the actuator.

The following shows how at least one of the adjustments mentioned can be carried out in a particularly efficient manner. Therefore can in particular adapt to different internal combustion engine operating states in terms of their type in advance using a numerical Optimization algorithm done and in an electronic control unit be filed. Furthermore, an additional adjustment of the controller and / or the target trajectories to changing external boundary conditions Operation of the internal combustion engine in an at least temporarily running Background process.

Adaptation to different internal combustion engine operating conditions should be done in advance, so that the result of this adjustment can be stored in an electronic control unit. Dependent on works from the current operating state of the internal combustion engine then the controller with the corresponding adaptation or accesses one of these Operating state adjusted target trajectory back. The fact of Pre-adaptation means that this adaptation is based on simulations and / or be carried out on the basis of test bench measurements can.

Basically, the use of a numeric for this adjustment Optimization algorithm proposed. In particular, the whole Control process for the armature movement using at least one suitable one Quality criterion can be optimized. An example of such a quality criterion is the speed of impact of the anchor on the one currently catching it Electromagnetic coil, or the armature acceleration at the time of impact.

In particular, the adaptation to changing boundary conditions should when operating the internal combustion engine in an at least temporarily running Background process. It must be ensured that the corresponding electronic control unit has sufficient computing capacity is made available for this so-called ongoing adaptation to enable.

The measures additionally proposed therefore make it an operation the regulation or the movement control method for the actuator ensured even in different operating states of the internal combustion engine. In addition, there will be a change in mechanical properties due to external influences in the regulation. However this and a host of other details can be quite different from the Above description can be designed without the content of the claims leave.

Reference symbol list:

1

Lift valve

2a

Valve closing spring = (first) return spring

2 B

Valve opening spring = (second) return spring

3rd

Valve clearance compensation element

4th

Actuator

4a

Electromagnetic coil = normally open coil

4b

Electromagnetic coil = normally closed coil

4c

Push rod

4d

anchor

10th

Regulator

11

observer

20th

Target trajectory

20a

Target trajectory for 4d, which moves 1 to the closed position

20b

Target trajectory for 4d, which produces only a small stroke at 1

20c

Target trajectory for 4d that takes the valve clearance into account

21

observer

30th

Valve seat (of 1)

BP

Braking phase

FP

Capture phase

HP

Hold phase

I.

Current flow in 4a, 4b

U

electrical voltage at 4a, 4b

t

time

t ₁

FP start phase

t ₂

End time of the catching phase = start time of the braking phase BP

t ₄

The anchor is placed on the coil

e.g.

Position of the anchor 4d = path coordinate of the anchor position

z ˙

Movement speed of the armature 4d

z ¨

Anchor acceleration

Claims (12)

Method for controlling the movement of an armature (4d) of an electromagnetic actuator (4), in particular for actuating a gas exchange stroke valve (1) of an internal combustion engine, the armature (4d) oscillating between two electromagnetic coils (4a, 4b) at least against the force a return spring (2a, 2b) is moved by alternating energization of the solenoid coils (4a, 4b), and with an approach of the armature (4d) to the initially energized coil (4a or 4b) during the so-called catching process which at the Anchor (4d) capturing coil (4a, 4b) applied electrical voltage (U) is reduced
characterized in that the catching phase (FP) of the catching process is followed by a braking phase (BP) in which, until the armature (4d) hits the coil (4a, 4b), clocked electrical voltage (U) is applied to it, whereby the respective switching times and the voltage-pulse ratio are determined by a controller (10) on the basis of a target trajectory (20) describing the armature target movement. Method according to claim 1,
characterized in that clocked either a constant positive or negative voltage value or the voltage value

Zero "is applied to the coil (4a, 4b) catching the armature (4d). The method of claim 1 or 2,
characterized in that the controller (10) compares the estimated values (21) determined parallel to the armature movement for the latter with the target trajectory (20). Method according to one of the preceding claims,
characterized in that the target trajectory (20) contains values for the stroke (z), the speed (z ˙) and the acceleration (z ¨) of the armature (4d) over time. Method according to one of the preceding claims,
characterized in that the target trajectory (20), inter alia, from the boundary condition that the acceleration (z ¨) of the armature (4d) at the time of impact with the electromagnetic coil (4a, 4b) has the value Should have zero "is calculated. Method according to one of the preceding claims,
characterized in that different target trajectories (20a, 20b, 20c, ....) are provided for different movements of the armature (4d) and / or the gas exchange lift valve (1). Method according to claim 6,
characterized in that in addition to a target trajectory (20a) leading the lift valve (1) to its fully open position, at least one target trajectory (20b) which only partially opens the lift valve (1) is provided. Method according to claim 7,
characterized in that the lifting valve (1) is held near its closed position by the target trajectory (20b) which only partially opens it. Method according to one of the preceding claims,
characterized in that a target trajectory (20c) which keeps the armature (4d) at least briefly at a short distance from the corresponding electromagnetic coil (4a) is provided for the closing operation of the lift valve (1). Method according to one of the preceding claims,
characterized in that predetermined trajectories (20) are provided which move the lift valve (1) into its end positions and thereby keep the armature (4d) at a distance from the respective electromagnetic coil (4a or 4b). Method according to one of the preceding claims, wherein the controller (10) and / or the target trajectories (20a, 20b, 20c, ...) is / are adapted to different operating states of the internal combustion engine,
characterized in that the type of adaptation is carried out beforehand using a numerical optimization algorithm and is stored in an electronic control unit. A method according to claim 11,
the controller (10) and / or the target trajectories (20a, 20b, 20c) being / are additionally adapted to changing external boundary conditions,
characterized in that the adaptation takes place during operation of the internal combustion engine in an at least temporarily running background process.

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