DE102020118949A1 - Monitoring a state of an actuator in a system for variable valve control of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for monitoring the state of an actuator (1) in a system for variable valve control of an internal combustion engine, the actuator (1) having an electromagnet (2) with a coil (3) and an armature which can be moved by means of the electromagnet (2). (4) which is coupled to an actuator pin (9) movable between a fully retracted position and a fully extended position, wherein a pulsed current (I) flowing in the coil (3) of the electromagnet (2) is measured, and a Switch-on time (TON) and a switch-off time (TOFF) of the pulses of the pulsed current (I) are determined, with a characteristic (K) being determined as a function of the switch-on time (TON) and the switch-off time (TOFF), with a time profile of the characteristic (K) is observed to monitor movement of the actuator pin (9), particularly towards the fully retracted position. In addition, the invention includes a corresponding system for variable valve control of an internal combustion engine.

Description

The invention relates to a method for monitoring a state of an actuator in a system for variable valve control of an internal combustion engine, the actuator comprising an electromagnet with a coil and an armature which can be moved by means of the electromagnet and which has a position between a fully retracted position and a fully extended position movable actuator pin is coupled. Furthermore, the invention relates to a system for variable valve control with an actuator which includes an electromagnet with a coil and an armature which can be moved by means of the electromagnet and which is coupled to an actuator pin which can be moved between a fully retracted position and a fully extended position.

Such actuators are used in systems for variable valve control, for example, to move cam pieces with several different cam contours axially on a shaft. Such cam pieces are also referred to as sliding cams. A curved groove is provided on the cam piece, into which a movable actuator pin of the actuator can selectively engage. In its retracted position, the actuator pin does not engage the groove, so the cam piece remains in its current axial position. In the extended position of the actuator pin, on the other hand, it engages in the curved groove and can thereby bring about an axial displacement of the cam piece. Such actuators often have a number of actuator pins, so that a number of displacement steps can be controlled. Such an actuator is, for example, from DE 10 2013 210 871 A1 known.

In such actuators, it is desirable to monitor movement of the actuator pin to enable control of the actuator pin and/or to provide early detection of damage to the actuator. For this purpose, however, it is necessary to provide additional sensors which detect the position of the actuator pin, as a result of which an increased outlay in terms of equipment is created.

Against this background, the task arises of enabling cost-effective monitoring of the movements of the actuator pin.

The object is achieved by a method for monitoring the state of an actuator in a system for variable valve control of an internal combustion engine,
wherein the actuator comprises an electromagnet with a coil and an armature which can be moved by means of the electromagnet and which is coupled to an actuator pin which can be moved between a fully retracted position and a fully extended position,
where a pulsed current flowing in the coil of the electromagnet is measured,
and a switch-on time and a switch-off time of the pulses of the pulsed current are determined,
a parameter is determined as a function of the switch-on time and the switch-off time,
a time profile of the parameter being observed in order to monitor a movement of the actuator pin, in particular in the direction of the fully retracted position.

In the method according to the invention, the pulsed current flowing in the coil of the electromagnet is measured and evaluated. The switch-on time and the switch-off time are determined for the pulses of the pulsed current. Depending on the switch-on time and the switch-off time, a parameter is determined and its progression over time is observed. Conclusions about the movement of the actuator pin, in particular in the direction of the fully retracted position—that is, the retraction movement—can be drawn from the course of this parameter over time. This is due to the fact that the moving actuator pin causes the armature to move and the movement of the armature in the magnetic field of the electromagnet induces a voltage in the coil of the electromagnet which counteracts the voltage present on the coil and is also known as the counter electromotive force (EMF). ) referred to as. The induced voltage results in measurable on-time and off-time changes in the pulsed current of the coil. The method according to the invention has the advantage that motion sensors for detecting the movement of the actuator pin can be dispensed with. This enables cost-effective monitoring of the movement of the actuator pin.

The on-time is preferably defined as the period of time during which the current increases in the course of a pulse. Alternatively, the on-time can be defined as the period of time during which the pulsed current increases monotonically between a lower threshold and a higher threshold.

The turn-off time is preferably defined as the period of time during which the current falls in the course of a pulse. Alternatively, the turn-off time can be defined as the period of time during which the pulsed current falls monotonically between a higher threshold and a lower threshold

ermittelt werden, wobei k₁, k₂, m, n vorgegebene Parameter sind. Beispielsweise kann $$k_1=-\mathrm{1,}m=\mathrm{1,}{k}_2=\mathrm{1,}n=1$$

gelten. Insofern kann die Kenngröße die Summe von Einschaltzeit und Ausschaltzeit sein oder die Differenz zwischen Einschaltzeit und Ausschaltzeit bzw. Ausschaltzeit und Einschaltzeit. Bevorzugt ist vorgesehen, dass ein oder mehrere der vorgegebenen Parameter während der Überwachung des Aktors geändert werden, beispielsweise dann, wenn die Kenngröße einen vorgegebenen Schwellenwert unterschreitet. Hierdurch könne Situationen vermieden werden, in denen die Kenngröße so klein wird, dass sie anfällig gegenüber Rauschen wird. Wenn die vorgegebenen Parameter zu $$k_1=-\mathrm{1,}m=\mathrm{1,}{k}_2=\mathrm{1,}n=1$$

gewählt sind, kann beispielsweise bei einem Unterschreiten des vorgegebenen Schwellenwerts $$k_1=\mathrm{0,}m=\mathrm{1,}{k}_2=\mathrm{1,}n=1$$

gesetzt werden, um eine zu geringe Kenngröße zu vermeiden.The parameter can be a function, for example, which is dependent on both the switch-on time and the switch-off time. examples such functions are the ratio of on-time to off-time, or the ratio of off-time to on-time, or the ratio of on-time to the sum of on-time and off-time, or the ratio of the sum of on-time and off-time to on-time. Alternatively, the parameter as a function f (t _on , t _off ) according to the equation $$ƒ\left(t_{On},t_{Off}\right)=k_1\cdot t_{On}^m+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\cdot t_{Off}^n$$

are determined, where k ₁ , k ₂ , m, n are predetermined parameters. For example, can $$k_1=-\mathrm{1,}m=\mathrm{1,}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2=\mathrm{1,}n=1$$

be valid. In this respect, the parameter can be the sum of the switch-on time and switch-off time or the difference between switch-on time and switch-off time or switch-off time and switch-on time. Provision is preferably made for one or more of the predefined parameters to be changed while the actuator is being monitored, for example when the parameter falls below a predefined threshold value. In this way, situations can be avoided in which the parameter becomes so small that it becomes susceptible to noise. If the default parameters $$k_{}$$$${}_1=-\mathrm{1,}m=\mathrm{1,}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2=\mathrm{1,}n=1$$

are selected, for example, when the predetermined threshold value is not reached $${\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="DE102020118949A1\_0011.png,DE102020118949A1\_0012.png"\; state="\{\{state\}\}">k</figure-callout>}}_1=\mathrm{0,}m=\mathrm{1,}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2=\mathrm{1,}n=1$$

be set in order to avoid a parameter that is too low.

Provision is preferably made for the electromagnet to be driven with a pulsed voltage or a pulsed current, for example with a voltage or a current which is provided by pulse width modulation (PWM). The pulsed voltage or the pulsed current is particularly preferably regulated in such a way that the pulsed current rises to a specified, higher threshold value when it falls below a specified, lower threshold value and falls to the specified, lower threshold value when the specified, higher threshold value is exceeded. With such a pulsed current, the switch-on time and the switch-off time are variable and can be influenced by the movement of the armature.

According to an advantageous embodiment, it is provided that a chronological derivation of the parameter is determined. Based on the time derivation of the parameter, it is possible to evaluate the time profile of the parameter with increased accuracy. For example, abrupt changes in the parameter as well as maxima and minima of the parameter can be detected with great reliability.

An embodiment of the invention is advantageous in which a starting point in time is determined at which a movement of the actuator pin begins in the direction of the retracted position. Due to the voltage induced in the coil by the movement of the armature, an abrupt change in the characteristic occurs at the start time, which can be detected.

In this context, it is particularly advantageous if a time derivative of the parameter is determined and a maximum of the time derivative of the parameter is determined to determine the start time. The time derivation of the parameter assumes a local or absolute maximum at the start time, which can be detected.

According to an advantageous embodiment, it is alternatively or additionally provided that a maximum point in time is determined at which the parameter assumes a maximum. With the maximum point in time, it becomes possible to monitor the stroke of the actuator pin. A maximum of the parameter is preferably determined to determine the maximum point in time.

wobei re t_on, t_off) die Kenngröße ist, CurrMin(ft_on, t_off)) das aktuelle Minimum der Kenngröße bis zum aktuellen Zeitpunkt ist und FactorMax einen Kalibrierungsfaktor bezeichnet, der es ermöglicht, die starke Variation der Kenngröße bei Beginn der mechanischen Bewegung des Aktorstifts zu erkennen.A preferred embodiment of the method provides that both a start time is determined at which a movement of the actuator pin begins in the direction of the retracted position and a maximum time is determined at which the parameter assumes a maximum and a time interval between the start time and the maximum time is determined. Preferably, at the end of a current pulse or voltage pulse, it is checked whether the following condition is met: $$ƒ\left(t_{On},t_{Off}\right)=C\mathrm{and}\mathrm{right}\mathrm{right}Min\left(ƒ\left(t_{On},t_{Off}\right)\right)\cdot \left(1+facktO\mathrm{right}Max\right)$$

where re t _on , t _off ) is the parameter, CurrMin(ft _on , t _off) ) is the current minimum of the parameter up to the current point in time and FactorMax designates a calibration factor that enables the strong variation of the parameter at the beginning of the mechanical to detect movement of the actuator pin.

wobei h die Länge des Aktorstifts, Δt der zeitliche Abstand zwischen dem Start-Zeitpunkt und dem Maximum-Zeitpunkt und t die Zeit ist. In der vollständig ausgefahrenen Stellung, insbesondere zum Start-Zeitpunkt, ist x = h, in der vollständig eingefahrenen Stellung gilt x = 0. Der zeitliche Abstand zwischen dem Start-Zeitpunkt und dem Maximum-Zeitpunkt ist abhängig von der Temperatur und/oder der Drehzahl des Verbrennungsmotors. Es ist daher möglich, den zeitlichen Abstand zwischen dem Start-Zeitpunkt und dem Maximum-Zeitpunkt für unterschiedliche Werte von Temperatur und/oder Drehzahl des Verbrennungsmotors zu erfassen und für Diagnosezwecke während des Betriebs des Aktors abzuspeichern.It is advantageous in this context if, as a function of the distance between the start time and the maximum time, an estimate of the time profile of the position of the Aktorstifts is calculated. The position x(t) of the actuator pin from the start time can be specified as an approximation $$x\left(t\right)=H-\left(H\cdot \frac{1}{2\cdot \mathrm{\Delta }t}\cdot t\right)$$

where h is the length of the actuator pin, Δt is the time interval between the start time and the maximum time, and t is the time. In the fully extended position, in particular at the start time, x=h, in the fully retracted position x=0. The time interval between the start time and the maximum time depends on the temperature and/or the speed of the combustion engine. It is therefore possible to record the time interval between the start time and the maximum time for different values of temperature and/or speed of the internal combustion engine and to store it for diagnostic purposes during operation of the actuator.

According to an advantageous embodiment, it is provided that a calculated speed is determined on the basis of the start time and the maximum time and is compared with an actual speed of the internal combustion engine. For example, based on the start time and the maximum time, the time interval between the two points in time can be calculated and a calculated rotational speed determined in advance for the time interval, for example from a memory, can be provided. A possible malfunction of the actuator can be detected by comparing the calculated speed with the actual speed of the combustion engine. For this purpose, it can be checked whether a deviation of the calculated speed from the actual speed is less than a predetermined threshold value.

A configuration is advantageous in which the distance between the start time and the maximum time is determined, and if the determined distance deviates from a predefined theoretical value, an error signal is generated which indicates that the actuator is faulty is. To determine the deviation, the difference between the theoretical value and the determined distance can be formed and this difference can be compared with a predetermined deviation threshold value. In the event that the difference is greater than the deviation threshold, the error signal may be generated. The theoretical value can be determined depending on the speed.

A constructively advantageous embodiment provides that the actuator additionally has a pivoting lever, via which the armature is coupled to the actuator pin. A lever ratio or transmission ratio between a movement of the armature and a movement of the actuator pin can be set via the pivoted lever. The armature is preferably coupled to the actuator pin via the pivoted lever in such a way that a smaller stroke of the armature causes a larger stroke of the actuator pin, so that the actuator, in particular the electromagnet, can be designed to be compact. This means that the stroke of the armature is less than the stroke of the actuator pin.

Another subject of the invention is a system for variable valve control of an internal combustion engine with an actuator, which includes an electromagnet with a coil and an armature that can be moved by means of the electromagnet and that is coupled to an actuator pin that can be moved between a retracted position and an extended position, and with a control and evaluation unit that is set up to
to measure a pulsed current flowing in the coil of the electromagnet,
to determine a switch-on time and a switch-off time of the pulses of the pulsed current,
to determine a parameter as a function of the switch-on time and the switch-off time and
to observe a time course of the parameter in order to monitor a movement of the actuator pin, in particular in the direction of the fully retracted position.

The same advantages can be achieved with the system as have already been described in connection with the method according to the invention for monitoring a state of an actuator in a system for variable valve control of an internal combustion engine.

Furthermore, the advantageous configurations and features described in connection with the method can also be used alone or in combination in the system.

• 1 ein Ausführungsbeispiel eines Aktors für ein System zur variablen Ventilsteuerung eines Verbrennungsmotors in einer schematischen Schnittdarstellung, wobei sich der Aktorstift in einer vollständig ausgefahrenen Stellung befindet;
• 2 der Aktor gemäß 1, wobei sich der Aktorstift in einer vollständig eingefahrenen Stellung befindet;
• 3 einen zeitlichen Verlauf der an der Spule des Elektromagnets anliegenden Spannung sowie des in der Spule fließenden Stroms;
• 4 eine beispielhafter gepulster Stromverlauf;
• 5 einen zeitlichen Verlauf der Bewegung des Ankers bei einlaufendem Aktorstift;
• 6 einen zeitlichen Verlauf einer von der Einschaltzeit und dem Ausschaltzeit abhängigen Kenngröße sowie deren zeitlicher Ableitung bei einlaufendem Aktorstift; und
• 7-9 zeitliche Verläufe der Kenngröße bei unterschiedlichen Drehzahlen des Verbrennungsmotors sowie eine geschätzte und eine tatsächliche Stellung des Aktorstifts.

Further details and advantages of the invention will be explained below with reference to the embodiment shown in the drawings. Herein shows:

• 1 an embodiment of an actuator for a system for variable valve control of an internal combustion engine in a schematic sectional view, wherein the actuator pin is in a fully extended position;
• 2 the actor according to 1 , wherein the actuator pin is in a fully retracted position;
• 3 a time course of the voltage applied to the coil of the electromagnet and of the current flowing in the coil;
• 4 an exemplary pulsed current curve;
• 5 a time course of the movement of the armature with an incoming actuator pin;
• 6 a time profile of a parameter that is dependent on the switch-on time and the switch-off time, and its derivative over time when the actuator pin arrives; and
• 7-9 time courses of the parameter at different speeds of the internal combustion engine as well as an estimated and an actual position of the actuator pin.

In 1 and 2 an exemplary embodiment of an actuator 1 is shown, which can be used in a system for variable valve control of an internal combustion engine. The actuator 1 includes an electromagnet 2 with a coil 3 and a movable means of the electromagnet 2 armature 4. The armature 4 is between the in 1 shown extended position and in 2 shown retracted position along a parallel to a longitudinal axis of the coil 3 direction R movable. The armature 4 comprises an armature ram 4.1 and an armature sleeve 4.2 with a receptacle in which the armature ram 4.1 is accommodated. The armature tappet 4.1 is guided in a sleeve 6, which seals an interior space of the electromagnet 2, in which the armature 4 can be moved. This seal makes it possible to fill the interior with a lubricant, such as an oil.

The actuator 1 also includes an actuator pin 9, which is located between an in 2 fully retracted position shown and a 1 shown fully extended position is movable. The actuator pin 9 is coupled to the armature 4 via a pivoted lever 7 which is pivotably mounted at a bearing point 8 . For this purpose, a free end of the armature tappet 4.1 is in contact with the pivoted lever 7. The pivoted lever 7 in turn makes contact with one end of the anchor pin 9. The anchor pin 9 is pretensioned by a spring element 10 in the direction of its retracted position. In the system for variable valve timing, the actuator 1 is used together with a cam piece which is axially slidably mounted on the camshaft. This cam piece includes a curved groove in which the actuator pin 9 can engage. The groove of the cam piece also includes a ramp-shaped area which, starting from its fully extended position, pushes the actuator pin 9 in the direction of its fully retracted position.

In a modification of the in 1 and 2 shown embodiment, the actuator can include two actuator pins, which are each controlled by a separate electromagnet.

A pulsed voltage is applied to the coil of the electromagnet 2 in order to extend the actuator pin 9 and to hold the actuator pin 9 in its fully extended position. To this end, the system includes a control and evaluation unit. This is set up to drive the coil with a pulsed voltage, for example with a voltage that is provided by pulse width modulation (PWM). The representation in 3 shows the voltage U applied to the coil 3, which is provided in pulsed form in a first phase PI, in which the actuator pin 9 is extended. In a second phase PII, in which the actuator pin 9 is in its fully extended position and is held there, the voltage U is also provided in pulsed form. The pulsed voltage is regulated in such a way that the pulsed current rises to a predetermined, higher threshold value when it falls below a predetermined, lower threshold value and falls to the predetermined, lower threshold value when the predetermined, higher threshold value is exceeded. With such a pulsed current, the switch-on time and the switch-off time are variable and can be influenced by the movement of the armature. In this case, the lower threshold value and the higher threshold value are both constant.

The representation in 4 shows an exemplary pulsed current curve, the switch-on time t _{ON being} the time span during which the current I increases over the course of a pulse and the switch-off time T _{OFF being} the time span during which the current I falls over the course of a pulse. The sum of T _ON and T _OFF is the period of the pulsed current.

The effects of the movement of the armature 4 on the pulsed current I of the coil 3 are explained below using the illustration in 5 are explained, which shows the measured deflection of the armature 4 in the upper area and the pulsed current I in the coil 3 in the lower area. Initially, ie at time t ₀ , the armature 4 is in its extended position. At time t ₁ the movement of the armature 4 begins in the direction of its retracted position. It can be seen that the switch-on time and the switch-off time of the individual pulses change from time t ₁ compared to the area before time t ₁ . This change is due to the fact that the movement of the armature 4 in the magnetic field of the electromagnet 2 generates a voltage in the coil 3 of the electromagnet 2 induced, which counteracted the voltage U applied to the coil 2.

At time t ₂ the pulsed current I is switched off. The result of this is that the movement of the armature 4 in the direction of its retracted position is no longer counteracted by a magnetic force and the armature 4 overshoots its end position—several times here. At time t ₃ the armature has then assumed its retracted position.

, wobei k₁, k₂, m, n vorgegebene Parameter sind. Beispielsweise kann $$k_1=-\mathrm{1,}m=\mathrm{1,}{k}_2=\mathrm{1,}n=1$$

gelten.In order to monitor the state of the actuator 1, in particular the movement of the actuator pin 9, the pulsed current I in the coil 3 is therefore measured in the system for variable valve control according to the invention and the switch-on time and switch-off time of the pulses of the pulsed current are determined. A parameter K is then determined as a function of the switch-on time and the switch-off time, and its progress over time is observed in order to monitor the movement of the actuator pin 9, in particular in the direction of the fully retracted position. Such a course of the parameter K and its time derivative K' and the corresponding pulsed voltage U at the coil 3 is shown in 6 shown. According to the exemplary embodiment, the parameter K is a function f(t _on , t _off ) according to the equation $$ƒ\left(t_{On},t_{Off}\right)={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="DE102020118949A1\_0011.png,DE102020118949A1\_0012.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\cdot t_{On}^m+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\cdot t_{Off}^n$$

, where k ₁ , k ₂ , m, n are predetermined parameters. For example, can $$k_1=-\mathrm{1,}m=\mathrm{1,}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102020118949A1\_0010.png,DE102020118949A1\_0011.png"\; state="\{\{state\}\}">k</figure-callout>}}_2=\mathrm{1,}n=1$$

be valid.

In the method according to the exemplary embodiment, it is also provided that a starting point in time t _{S is} determined, at which a movement of the actuator pin begins in the direction of the fully retracted position. In order to determine this start time t _S , the time derivative K′ of the parameter K is first formed and then a maximum of the time derivative K′ of the parameter K is determined.

wobei h die Länge des Aktorstifts und t die Zeit ist. Im Betrieb des Verbrennungsmotors kann anhand des Start-Zeitpunkts t_S und des Maximum-Zeitpunkts t_M eine rechnerische Drehzahl ermittelt und mit einer tatsächlichen Drehzahl des Verbrennungsmotos verglichen werden. Die rechnerische Drehzahl kann dabei als Funktion von Start-Zeitpunkt t_S und dem Maximum-Zeitpunkt t_M und ggf. der Temperatur aus der Speichereinheit ausgelesen werden.The method also provides that a maximum point in time t _{M is} determined, at which the parameter assumes a maximum. Furthermore, the time interval Δt between the start time t _S and the maximum time t _{M is} determined, which is characteristic of the instantaneous speed of the internal combustion engine and also the prevailing temperature. As part of the production of the internal combustion engine, preferably at the end of production, the time interval Δt is recorded for different values of temperature and speed of the internal combustion engine and stored in a memory unit of the system for variable valve control for diagnostic purposes. These stored values can be used during operation in order to check the functionality of the system, in particular of the actuator 1. Because the position x (t) of the actuator pin 9 from the start time t _S can be approximately specified as $$x\left(t\right)=H-\left(H\cdot \frac{1}{2\cdot \mathrm{\Delta }t}\cdot t\right)$$

where h is the length of the actuator pin and t is the time. During operation of the internal combustion engine, _{a calculated speed can be determined using the start time t S} and the maximum time t _M and compared with an actual speed of the internal combustion engine. The calculated speed can be read from the memory unit as a function of the start time t _S and the maximum time t _{M and possibly the temperature.}

The representation in 7 shows a time course of the parameter K for a speed of 2000 rpm at a temperature of 60 °C. Also shown are the approximate course of the position x̃(t) of the actuator pin 9 and the actual position x(t) of the actuator pin 9 measured by means of a laser measuring device.

In the representation in 8th is a time course of the parameter K for a speed of 1300 rpm at a temperature of 60 °C. Also shown are the approximate course of the position x̃(t) of the actuator pin 9 and the actual position x(t) of the actuator pin 9 measured by means of a laser measuring device.

The representation in 9 shows a time course of the parameter K for a speed of 500 rpm at a temperature of 60 °C. Also shown are the approximate course of the position x̃(t) of the actuator pin 9 and the actual position x(t) of the actuator pin 9 measured by means of a laser measuring device.

The method described above can be applied to variable valve timing systems that include sliding cams, as well as to electrohydraulic variable valve timing systems or electromechanical variable valve timing systems.

Reference List

1

actuator

2

electromagnet

3

Kitchen sink

4

anchor

4.1

anchor tappet

5

actuator housing

6

sleeve

7

swing lever

8th

storage place

9

actuator pin

10

spring element

I

electricity

K

parameter

K'

Derivation of the parameter

u

voltage

tS

start time

tm

maximum time

Δt

temporal distance

VOLUME

on time

TOFF

off time

x(t)

Position of the actuator pin

x̃(t)

approximate position of the actuator pin

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102013210871 A1 [0002]

Claims (10)

Method for monitoring the state of an actuator (1) in a system for variable valve control of an internal combustion engine, the actuator (1) comprising an electromagnet (2) with a coil (3) and an armature (4) which can be moved by means of the electromagnet (2). , which is coupled to an actuator pin (9) that can be moved between a fully retracted position and a fully extended position, a pulsed current (I) flowing in the coil (3) of the electromagnet (2) being measured, and a switch-on time (T _ON ) and a switch-off time (T _OFF ) of the pulses of the pulsed current (I) are determined, with a parameter (K) being determined as a _{function of the switch-on time (T ON} ) and the switch-off time (T _{OFF ), with a time profile of the parameter} (K) is observed to monitor movement of the actuator pin (9), particularly towards the fully retracted position. procedure after claim 1 , characterized in that a time derivative (K') of the parameter (K) is determined. Method according to one of the preceding claims, characterized in that a start time (t _s ) is determined at which a movement of the actuator pin (9) begins in the direction of the fully retracted position. procedure after claim 3 , characterized in that a time derivative (K') of the parameter (K) is determined and to determine the start time (ts) a maximum of the time derivative (K') of the parameter (K) is determined. Method according to one of the preceding claims, characterized in that a maximum point in time (t _M ) is determined at which the parameter (K) assumes a maximum. procedure after claim 3 , characterized in that a maximum time (t _M ) is determined at which the parameter (K) assumes a maximum and a time interval (Δt) between the start time (ts) and the maximum time (t _M ) is determined. procedure after claim 6 , characterized in that as a function of the distance (Δt) between the start time (ts) and the maximum time (t _M ), an estimate of the time profile of the Position of the actuator pin (9) is calculated. Method according to one of the preceding claims, characterized in that a calculated speed is determined on the basis of the start time (ts) and the maximum time (t _M ) and is compared with an actual speed of the internal combustion engine. Method according to one of the preceding claims, characterized in that the actuator (1) additionally has a pivoted lever (7) via which the armature (4) is coupled to the actuator pin (9). System for variable valve control of an internal combustion engine with an actuator (1) which comprises an electromagnet (2) with a coil (3) and an armature which can be moved by means of the electromagnet (2) and which has a position between a fully retracted position and a fully extended position movable actuator pin (9), and with a control and evaluation unit which is set up to measure a pulsed current (I) flowing in the coil of the electromagnet (2), a switch-on time (T _ON ) and a switch-off time (T _OFF ) of the pulses of the pulsed current (I), to determine _{a parameter (K) as a function of the switch-on time (T ON} ) and the switch-off time (T _OFF ) and to observe a time profile of the parameter (K) in order to To monitor movement of the actuator pin (9), especially in the direction of the fully retracted position.

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