DE102012209967A1 - Method of operating solenoid valve, involves comparing time integral with threshold value such that to judge state of solenoid valve - Google Patents

Abstract

The method involves placing a valve element (22) of a solenoid valve (10) by a biasing force in a first position (11) and magnetic force into a second position (29). The current flowing through a magnetic coil (14) of the solenoid valve is determined during a period without supplying current. The time integral is compared with the threshold value such that to judge the state of the solenoid valve. Independent claims are included for the following: (1) a control and/or regulating device; and (2) a computer program of operating solenoid valve.

Description

State of the art

The invention relates to a method according to the preamble of claim 1, and a control and / or regulating device and a computer program according to the independent claims.

Are known from the market, solenoid valves in which a valve element, in particular a valve needle, is moved to allow an opening operation and a closing operation of the solenoid valve. For example, such a solenoid valve may be used to meter a urea aqueous solution into an exhaust aftertreatment system of an internal combustion engine. The exhaust aftertreatment system includes, for example, an SCR (SCR) catalyst. In this case, a reliable function of the solenoid valve is of particular importance. For example, the valve element may be blocked in the event of a fault, as a result of which the solenoid valve may have a permanently open or permanently closed state. Both are undesirable.

A patent publication in this field is, for example, the DE 102 32 358 A1 ,

Disclosure of the invention

The problem underlying the invention is achieved by a method according to claim 1, and by a control and / or regulating device and a computer program according to the independent claims. Advantageous developments are specified in subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

The invention has the advantage that a solenoid valve, for example, for injecting a reducing agent in an exhaust aftertreatment system of an internal combustion engine, can be monitored for its function particularly reliable. For this purpose, a valve element, such as a valve needle of the solenoid valve, checked for its movement. In particular, blocked states of the solenoid valve can be determined comparatively safely. The method according to the invention requires little or no additional elements and can be carried out with relatively little software effort. A supplementation of existing software structures by the method according to the invention ("functional integration") is comparatively simple.

Furthermore, it is advantageous that a detection of the movement of the valve needle can be carried out regardless of the exact time of movement. The method has a comparatively high degree of robustness in that a current flowing via a magnetic coil of the magnetic valve is evaluated over a relatively long period of time after the end of a current supply. The method comprises a temporal integration of the current, which can be carried out easily and with little effort. Because of the integration, additional filtering of the current requires little effort or is even unnecessary. Because the method according to the invention is carried out after the end of the energization, there are correspondingly no disturbing pulse-like drive signals (PWM) in the current or a variable characterizing the current. The method works particularly well when the solenoid valve has a comparatively strong biasing device, for example. In the form of a spring which can bring the valve needle in the de-energized state of the solenoid in a defined position.

The invention relates to a method for operating a solenoid valve, wherein a valve element of the solenoid valve can be brought by a biasing force in a first position and by magnetic force in a second position. According to the invention, a time integral (sum of the values over time) is determined during a period of time without (active) current supply, for example by triggering an output stage, using a current flowing through a magnetic coil of the solenoid valve or a variable characterizing the current. The variable characterizing the current may be, for example, a voltage which drops across a measuring resistor connected in series with the magnet coil. The time integral determined in this way is compared with at least one threshold value, and it is concluded from the comparison with the at least one threshold value on a state of the solenoid valve.

In particular, a blocked state of the solenoid valve, that is, for example, a mechanical blocking of the valve element, are determined. It is possible according to the invention - For example, by means of a second threshold - even to distinguish between an open-blocked and a closed-locked state of the solenoid valve. In the "open-blocked" state, the solenoid valve is substantially open and in the "closed-blocked" state, the solenoid valve is substantially closed. In addition, the solenoid valve may be blocked in an intermediate state between "open" and "closed". This can likewise be recognized by means of the method according to the invention. The use of a time integral makes it possible to determine and evaluate the current flowing through the magnetic coil over a longer time interval, wherein any interference signals are filtered by the integration. The inventive method corresponds to a so-called "detection function" to determine the state of the solenoid valve.

The method is performed using the voltage induced by movement of the valve member in the solenoid and a resultant change in the current flowing through the solenoid coil. In particular, a part of the stored energy can be converted into electrical energy by means of the magnetic coil after the end of the energization due to the expansion of the biasing means. At the same time, the inductance of the magnetic coil is changed, that is, generally reduced, with the

Energy storage capacity of the solenoid reduced accordingly. As a result, the magnetic coil can store less energy at the same current.

Generally, the energy stored in a solenoid is: W = 1/2 · L · I ²

A portion of the energy released by the expansion of the biasing means is thermally translated in an electrical circuit associated with the solenoid coil. In this case, the current flowing through the magnetic coil is at least temporarily increased. The course of the current over time can be integrated, resulting in a corresponding amount of charge ΔQ according to the following formula: ΔQ = ∫i (t) · dt

Integration over the square of the current waveform is proportional to the energy converted, according to the formula:

E α ∫i ² (t) · dt , where the symbol "α" denotes a proportionality.

The movement of the valve element generally occurs during and / or after the above-described at least temporary increase of the current. As a result, the current may even increase even further. Therefore, the amount of charge ΔQ is greater for a normally functioning solenoid valve than for a blocked solenoid valve. This difference can be further increased by using a current _threshold - referred to in the following formula as I _grenz - as will be described below.

ΔQ = ∫ _tεT i (t) · dt , where or as long as i (t)> I _limit .

The total integration time T corresponds to a predefinable time window after the end of the current supply ("EIP window").

Δt

= Zeitabstand zwischen jeweils zwei Abtastungen; und

i_dv(k)

= mittels eines Offsetwertes I_OFFSET korrigierter Stromwert in der Magnetspule, entsprechend der Formel:

i_dv(k)

= i_dv,MESS(k) – I_OFFSET, mit k = 1, 2, ..., 60; wobei

i_dv,MESS(k)

= Messwert des noch nicht durch I_OFFSET korrigierten Stroms in der Magnetspule.

The latter formula is shown as a molecular formula:

.delta.t

= Time interval between every two scans; and

i _dv (k)

= corrected current value in the magnet coil by means of an offset value I _OFFSET , according to the formula:

i _dv (k)

= i _{dv, MESS} (k) - I _OFFSET , _where k = 1, 2, ..., 60; in which

i _{dv, MESS} (k)

= Measured value of the current in the solenoid that has not yet been corrected by I _OFFSET .

The charge quantity ΔQ determined by the integration or summation is then compared with a threshold ΔQ _LIMIT . If the determined charge quantity ΔQ exceeds the threshold value ΔQ _LIMIT , then a correct movement of the valve element is presumed and thus closed to a normally functioning solenoid valve. However, if the determined amount of charge ΔQ _falls below the threshold value ΔQ _LIMIT , that becomes

Valve element suspected as blocked and closed accordingly to a blocked solenoid valve. The method according to the invention thus has two threshold values which are required for determining the state of the solenoid valve, namely the current threshold I _limit and the threshold value ΔQ _LIMIT for determining and evaluating the integral or the sum.

Preferably, the threshold _{.DELTA.Q LIMIT is set} such that it corresponds approximately to an average of the integrals or sums for the normally functioning and for the blocked solenoid valve. This allows a particularly secure distinction between the two states. Expressed as a formula: ΔQ _LIMIT = 1/2 · (ΔQ _{MIN, GUT} + ΔQ _{MAX, BLCK} ), in which
the index "MIN, GOOD" corresponds to a minimum charge amount ΔQ determined in the experiment for a normally functioning solenoid valve; and
the index "MAX, BLCK" corresponds to a maximum charge quantity ΔQ determined in the experiment for a blocked solenoid valve.

An embodiment of the method provides that the time integral is determined substantially immediately after the end of an energization of the magnetic coil. As a result, drive pulses of the magnetic coil, by means of which the magnetic coil was previously energized (active), do not disturb the method. The accuracy is thus increased.

A further embodiment of the method provides that the time integral is determined immediately after the end of a rapid quenching of the magnetic coil. In this state of the solenoid valve, the current flowing in the magnetic coil is comparatively small, so that changes in the residual current can be well determined and evaluated. This additionally increases the accuracy of the method.

In particular, it is provided that a contribution to the time integral occurs only when the current exceeds a current threshold. Preferably, the current threshold is set in such a way that a first time current course, which corresponds to a normally functioning state of the solenoid valve, is substantially above the current threshold, and a second time current course, which corresponds to a blocked state of the solenoid valve, is substantially below the current threshold. This improves the distinctness of the states.

The accuracy of the method is further improved if the time integral is determined by subtracting an offset value from the current flowing through the solenoid coil. The offset value corresponds, for example, to an averaged quiescent current in the magnet coil after a certain period of time has elapsed after the end of the active energization.

The method is particularly easy to use when the first position is a closed position and the second position is an open position of the solenoid valve.

When the solenoid coil is energized, an armature of the solenoid valve can attract and thus open the solenoid valve. If the solenoid coil is not energized (more), the valve needle can be actuated by spring force and thus close the solenoid valve. In de-energized state of the - normally functioning - solenoid valve thus an undesirable flow of a medium is prevented.

A further embodiment of the method provides that, in addition to an evaluation of a current profile before and / or during energization of the solenoid takes place. In particular, the method according to the invention can also be combined with another method, which is not described here, and which can detect an opening process of the solenoid valve during the energization. By applying the method according to the invention after the end of the current supply, these other methods, which are carried out before and / or during the energization, are not hindered. Thus, you can additional variables characterizing the solenoid valve are detected, thereby improving diagnosis.

The method is particularly useful when monitoring actuation of the solenoid valve for injecting a reductant into an exhaust aftertreatment system of an internal combustion engine. This can be a blocking of the solenoid valve ("metering") detected and thus a deterioration of emissions can be prevented early.

The method according to the invention is preferably carried out by means of a control and / or regulating device for an internal combustion engine or for an exhaust gas aftertreatment system. The required method steps can be carried out particularly easily by means of a computer program. It is understood that the determination of the time integral described above can be made to arbitrary parts by means of analog and / or digital signal processing.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

1 a simplified schematic representation of a solenoid valve in a closed state;

2 the solenoid valve of 1 in an open state;

3 a table with different states of the solenoid valve;

4 an energy balance of the solenoid valve;

5 a first illustration of a current flowing through a solenoid of the solenoid valve stream;

6 a second representation of the current flowing through the magnetic coil; and

7 a flowchart of a method for operating the solenoid valve.

The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

1 shows in a simplified schematic representation of some elements of a solenoid valve 10 for introducing a reducing agent into an exhaust gas aftertreatment system, not shown, of an internal combustion engine (also not shown). The solenoid valve 10 of the 1 is in a first position 11 What is present in a closed position of the solenoid valve 10 equivalent. An electromagnetic actuator 12 of the solenoid valve 10 in the present case comprises a magnetic coil 14 and an anchor 16 , which when energized in the solenoid 14 can be pulled. The possible movements of the anchor 16 are through a retirement home 18 as well as a stroke stop 20 limited. The 1 shows a position of the solenoid valve 10 when the solenoid is not energized 14 ,

In the present case is the anchor 16 rigid with a valve needle 22 ("Valve element") coupled, which at its lower end in the drawing against a valve seat 24 is struck. On the anchor 16 acts in the drawing from above a stressed on compression coil spring 26 and acts on the valve needle 22 thus in the closing direction. An outlet opening 28 of the solenoid valve 10 is on the valve seat 24 resting valve needle 22 closed and with the valve needle lifted 22 open. Other elements of the solenoid valve 10 , such as fluid channels are not shown. All movements happen in one on the 1 related vertical direction.

2 shows the solenoid valve 10 of the 1 in an energized state of the solenoid 14 , Here is the anchor 16 medium magnetic force from the retirement seat 18 lifted off and on the stroke stop 20 dressed. The one with the anchor 16 rigidly coupled valve needle 22 is also from the valve seat 24 lifted. The solenoid valve 10 of the 2 is in a second position 29 What is present in an open position of the solenoid valve 10 equivalent. This is a spray 30 deposited the reducing agent.

It is understood that the solenoid valve 10 also - unlike in the 1 and 2 shown - may have a so-called anchor path, wherein the armature 16 by means of a driver with the valve needle 22 is coupled. Furthermore, it is understood that the invention is not limited to that in the 1 and 2 shown solenoid valve 10 is limited to the introduction of the reducing agent in the exhaust aftertreatment system. Rather, the method described in more detail below together with a plurality of embodiments of the solenoid valve 10 and be done in a variety of applications.

3 shows a table with different states of the solenoid valve 10 , In a column left in the drawing, a total of six different elements or sizes of the solenoid valve 10 listed. In the three further columns shown to the right of it a respective behavior of the element or a respective state of the size is described in keywords. These three other columns describe in the drawing from left to right each one state of the solenoid valve 10 in normal operation, in an open state and in a closed state.

The abbreviation "EIP" (English "end of injection pulse") used in the table in this case means an end of a current supply to the magnetic coil 14 , This causes a normally functioning solenoid valve 10 a transition from that in the 2 illustrated opened state in the in the 1 illustrated closed state. The in the table of the 3 The six lines shown thus describe the behavior of the respective elements or the state of the respective variables in connection with an end of the current supply of the magnetic coil 14 ,

The coil spring 26 changed with normal function of the solenoid valve 10 their state of "compressed" in "comparatively little compressed". By contrast, the coil spring remains 26 in the open-blocked state continuously compressed and in the closed-locked state constantly slightly compressed.

The in the coil spring 26 stored energy is at normal working solenoid valve 10 smaller at the transition from the open to the closed state. In contrast, the points in the coil spring 26 stored energy in the open-blocked state or in the closed-locked state to a respective unchanged value.

Furthermore, with normally functioning solenoid valve 10 a movement of the valve needle 22 , whereas in the open-blocked and the closed-locked state of the solenoid valve 10 no such movement of the valve needle 22 he follows.

Furthermore, an inductance of the magnetic coil 14 before the end of the energization of the solenoid 14 comparatively large, because as a result of the stroke stop 20 attracted anchor 16 a magnetic circuit of the solenoid valve 10 essentially "closed". This also results in the open-blocked state of the solenoid valve 10 , In contrast, in the closed-locked state of the solenoid valve 10 the inductance of the magnetic coil 14 constantly comparatively small.

Accordingly, the inductance of the magnetic coil 14 with a normally functioning solenoid valve 10 as a result of the movement of the anchor 16 smaller at the transition from the energized to the de-energized state. In contrast, takes place in the open-blocked and in the closed-blocked state of the solenoid valve 10 essentially no such change in inductance.

4 shows in a simplified schematic representation of a coordinate system with an energy balance of the solenoid valve 10 or the magnetic coil 14 , This energy balance relates to a transition from an energized to a de-energized state of the solenoid 14 , In this case, a movement of the valve needle takes place 22 or the anchor 16 from the open to the closed state of the solenoid valve 10 ,

In the drawing, three columns (a) to (c) are drawn from left to right, each of which has a normally functioning solenoid valve 10 , as well as an open-blocked solenoid valve 10 and a closed-blocked solenoid valve 10 characterize. An ordinate of the coordinate system describes a respective energy 32 of the solenoid valve 10 or the magnetic coil 14 ,

• – eine Restenergie in der Magnetspule 14, die somit einer elektrischen Energiequelle entspricht, entsprechend dem Bezugszeichen 34;
• – einer aufgrund der Induktivitätsänderung bewirkten Energieänderung in der Magnetspule 14, entsprechend dem Bezugszeichen 36; und
• – ein Teil der von der Schraubenfeder 26 abgegebenen Energie, wegen der Induktion während der Bewegung der Ventilnadel 22 bzw. des Ankers 16, entsprechend dem Bezugszeichen 38.

Simplified can be said that after the end of - caused by an electrical drive circuit - energization of the solenoid 14 then in the solenoid 14 flowing electricity 40 (see the 5 ) as a result of movement of the valve needle 22 or the anchor 16 essentially determined by three causes:

• - A residual energy in the solenoid 14 , which thus corresponds to an electrical energy source, corresponding to the reference numeral 34 ;
• - A caused due to the inductance change energy change in the magnetic coil 14 , corresponding to the reference numeral 36 ; and
• - Part of the coil spring 26 given energy, because of the induction during the movement of the valve needle 22 or the anchor 16 , corresponding to the reference numeral 38 ,

Compared to a normally functioning solenoid valve 10 carries with an open-blocked or a closed-blocked solenoid valve 10 essentially only the first of the three energy balance terms mentioned. This connection is made in the 4 characterized by said columns (a), (b) and (c). In particular, in the closed-locked solenoid valve 10 by the reference numeral 34 The energy content of the column (c) is slightly smaller than that of the column (b). The difference arises from the fact that when the solenoid valve is closed 10 according to the 1 the anchor 16 not at the stroke stop 20 is struck and thus the inductance of the solenoid 14 smaller than in the open state of the solenoid valve 10 after 2 is.

5 shows a first diagram with two different time courses of the by the magnetic coil 14 flowing electricity 40 , Shown is a coordinate system whose abscissa with time t and its ordinate with the current 40 are dimensioned. In each case a time course of a current is shown 40a a normally functioning solenoid valve 10 and a stream 40b a blocked solenoid valve 10 , A current level in the upper left area of the diagram corresponds to a holding current 41 of the solenoid valve 10 ,

The current 40 respectively. 40a respectively. 40b For example, by means of a to the magnetic coil 14 in series - and in general comparatively low impedance - shunt (shunt) are determined. For example, a voltage at the measuring resistor can be detected by means of a so-called "delta-sigma converter", the voltage then being filtered in an analog low-pass filter and subsequently fed to an analog-to-digital converter in order to allow further processing. The analog-to-digital converter is, for example, a direct conversion analog-to-digital converter ("FADC", "flash-analog-to-digital-converter").

A first time range shown on the left in the drawing 42 between a time t0 and a time t1 corresponds to energization of the magnetic coil 14 , An immediately following second time range 44 between the time t1 and a time t2 corresponds to a so-called quick erasure, wherein a substantial part of the magnetic coil 14 during the energization supplied electrical energy is dissipated again. The first deletion is completed by a first window 46 ("EIP window", English "end of injection pulse") between the time t2 and a time t3, in which present the respective time course of the current 40a respectively. 40b determined and then evaluated. The window 46 Thus, it essentially comprises an area immediately after the end of the energization or the rapid quenching and is characterized by the times t2 and t3 and additionally by an expected amplitude range 47 characterized.

In one embodiment of the method, a total of 60 samples of the current 40 between times t2 and t3 of the first window 46 determined. In this case, a time interval between each two samples is 20 μs, and the total measurement time comprises 1.2 ms. Preferably, the 60 samples are buffered in a data buffer prior to further processing.

In the drawing on the right there is a second window in the coordinate system 48 ("Offset window") between a time t4 and a time t5. In the second window 48 are the streams 40a and 40b essentially settled to a constant value, so that an offset value 50 ("Quiescent current") of the stream 40a respectively. 40b can be determined. The offset value 50 corresponds to an averaged value of the quiescent current in the second window 48 , In general, it is sufficient to set the offset value 50 only occasionally to determine.

The current 40a Characterizes a normally functioning solenoid valve 10 and the stream 40b characterizes a blocked solenoid valve 10 , The change of energy in the solenoid 14 is for the normally functioning solenoid valve 10 greater than for the blocked solenoid valve 10 , compare to the above description to the 4 , The current is corresponding 40a in the first window 46 - and beyond - greater than the current 40b , This allows the two states of the solenoid valve 10 be well differentiated from each other, as in the following 6 will be explained in more detail.

6 shows a second and to the 5 similar diagram with practically determined time courses of the magnetic coil 14 flowing streams 40 , The Indian 6 shown time range corresponds approximately to the time range of 5 between times t1 and t4. In addition, in the diagram of the 6 a current threshold 52 entered as well as a time interval 54 in which the electricity 40 the current threshold 52 each exceeds. The current threshold 52 corresponds to the current _threshold I _limit described above.

The streams 40 are divided into different individual time courses as a result of statistically distributed irregularities in a plurality of measurements. Three cases are distinguishable: First, flows 40a for a normally functioning solenoid valve 10 second, streams 40b1 for an open-blocked solenoid valve 10 , and third, streams 40b2 for a closed-locked solenoid valve 10 ,

In the following, a method for operating the solenoid valve 10 carried out as follows:

It becomes the electricity 40 in a period without energization - ie during the first window 46 - determined on an ongoing basis. As long as the electricity 40 the current threshold 52 exceeds, a difference between the current 40 and the current threshold 52 by means of a time integral 80 (please refer 7 ) added up. This is in the drawing by the time interval 54 characterized. As long as the electricity 40 the current threshold 52 does not exceed, there is no contribution to the time integral 80 that is, a respective value of the time integral 80 stay constant. The summation thus takes place nonlinearly as a function of the current threshold 52 ,

It can be seen that with a normally functioning solenoid valve 10 the time integral thus determined 80 has a comparatively large positive value. By contrast, the time integral 80 with a blocked solenoid valve 10 the value zero, because the currents 40b1 respectively. 40b2 the current threshold 52 during the first window 46 do not exceed.

In addition to the current threshold 52 For example, another current threshold (not shown) may be used to indicate the state of an open-blocked solenoid valve 10 from the state of a closed-locked solenoid valve 10 to distinguish. This further current threshold is in the 6 but not shown.

7 shows a flowchart for performing the method for operating the solenoid valve 10 , Preferably, the flowchart is executed by means of a computer program which is stored, for example, on a control and / or regulating device of an internal combustion engine or of an exhaust gas aftertreatment system. In a starting block 60 starts in the 7 illustrated procedure ("detection function" to the state of the solenoid valve 10 close).

A count variable "k" is taken from the start block 60 set to an initial value of k = 1. In a following query block 62 it is checked whether this count variable k has exceeded a limit of k = 60. If so, it becomes a block 64 branched lower in the drawing. If not, it becomes a following block 66 branches, in which a buffer ("EIP buffer"), at least during the first window 46 continuously determined values of the current 40 stores, with each new value of the count variable k is read out.

In a following subtractor 68 is from each of the value of the current determined by the count variable k 40 the offset value 50 subtracts and thus a corrected current value 70 determined. The corrected current value 70 corresponds to the above-described corrected current value i _dv (k). In a following query block 72 becomes the corrected current value 70 with the current threshold 52 compared. If the corrected current value 70 the current threshold 52 exceeds, then becomes a following block 74 branched. Otherwise it will be in a block 76 the count variable k is increased by the value "1" and then again to the query block 62 branched.

In the block 74 become values of the corrected current value 70 numerically integrated according to the counting variable k. It is at the time t2, so at the beginning of the first window 46 , by means of an initial condition 78 a time integral to be formed 80 set to zero. The time integral 80 integrates the corrected current values 70 over time t and thus has a dimension "current times time" corresponding to a charge Q. The value of the time integral 80 or the value of the charge Q is to the following block 64 transmitted.

The block 64 is from the query block 62 triggered when the count variable k has exceeded the limit of k = 60. Then the block transmits 64 the value of the charge Q to a query block 82 in which it is checked whether the charge Q has a predefinable threshold value 84 has exceeded. If so, so it is concluded that a movement of the anchor 16 or the valve needle 22 has been discovered. The solenoid valve 10 can therefore be rated as "normally functioning", compare to the description 6 , Then it becomes a first endblock 86 branched. The threshold 84 corresponds to the above-described threshold value ΔQ _LIMIT .

If the charge Q is the threshold 84 but has not exceeded, it is concluded that no (sufficient) movement of the anchor 16 or the valve needle 22 took place. The solenoid valve 10 can be rated as "blocked" in this case. Then it becomes a second endblock 88 branched. In the end blocks 86 respectively. 88 ends in the 7 presented procedure. The result of the method thus determined can subsequently be transmitted to a diagnostic device (OBD, "on board diagnosis"), so that when the solenoid valve is blocked 10 possible countermeasures can be carried out.

That in the 1 to 7 described method and in particular the determination of the time integral 80 essentially take place after the end of the active energization of the magnetic coil 14 , This makes it possible, the method in addition to an evaluation of a current waveform before and / or during energization of the magnetic coil 14 perform. Thus, additional information about the state of the solenoid valve 14 be determined.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 10232358 A1 [0003]

Claims (10)

Method for operating a solenoid valve ( 10 ), wherein a valve element ( 22 ) of the solenoid valve ( 10 ) by a biasing force in a first position ( 11 ) and by magnetic force in a second position ( 29 ), characterized in that during a period without energization a time integral ( 80 ) using a magnetic coil ( 14 ) of the solenoid valve ( 10 ) flowing stream ( 40 ) or one the stream ( 40 ) characterizing variable, and that the time integral ( 80 ) with at least one threshold ( 84 ) and that from the comparison with the at least one threshold ( 84 ) to a state of the solenoid valve ( 10 ) is closed. Method according to Claim 1, characterized in that the time integral ( 80 ) substantially immediately after the end of energization of the magnetic coil ( 14 ) is determined. Method according to claim 1 or 2, characterized in that the time integral ( 80 ) immediately after the end of a rapid quenching of the magnetic coil ( 14 ) is determined. Method according to at least one of the preceding claims, characterized in that a contribution to the time integral ( 80 ) only occurs when the stream ( 40 ) a current threshold ( 52 ) exceeds. Method according to at least one of the preceding claims, characterized in that the time integral ( 80 ) is determined by an offset value ( 50 ) of which by the magnetic coil ( 14 ) flowing stream ( 40 ) is subtracted. Method according to at least one of the preceding claims, characterized in that the first position ( 11 ) a closed position and the second position ( 29 ) an open position of the solenoid valve ( 10 ). Method according to at least one of the preceding claims, characterized in that in addition to an evaluation of a current profile before and / or during an energization of the magnetic coil ( 14 ) he follows. Method according to at least one of the preceding claims, characterized in that an actuation of the solenoid valve ( 10 ) is monitored for an injection of a reducing agent in an exhaust aftertreatment system of an internal combustion engine. Control and / or regulating device, characterized in that it is designed to perform a method according to at least one of the preceding claims 1 to 8. Computer program, characterized in that it is programmed to perform a method according to at least one of the preceding claims 1 to 8.

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