DE102016217985A1 - Control unit and method for monitoring the operation of an electromagnetic actuator - Google Patents

Abstract

The present invention relates to a method and a control unit for monitoring the function of an electromagnetic actuator, for. B. a switching valve, which may be blocked. In the electromagnetic actuator, a magnetic core is displaceable by energizing an electric coil. In one step of the method, a measurement of a time-varying current flowing through the coil takes place, wherein the measured current rises during a current increase phase (21) during which the magnetic core is initially idling. In a further step, a logarithm function of the current measured in the current increase phase (21) is formed. In a further step, the logarithmic function representing an early temporal segment of the idling is approximated by a linear function. There is a continuous determination of a difference between the logarithmic function and the linear function over the early temporal portion of the idle time. In a further step, a time of departure (46) is determined based on when the difference reaches a predefined difference measure. According to the invention, a malfunction of the electromagnetic actuator is detected when the determined deviation time (46) is earlier than a predefined deviation point in time.

Description

The present invention initially relates to a method for monitoring the function of an electromagnetic actuator. The electromagnetic actuator may be, for example, a switching valve. The function of the electromagnetic actuator may be disturbed in particular by the fact that the electromagnetic actuator is blocked. The invention further relates to a control unit for controlling and monitoring an electromagnetic actuator.

The US 2011/0163769 A1 shows a method for detecting at least one middle stroke position of a load driven by an active material element. In this middle stroke position, the material element undergoes a load change.

From the US 2005/0146408 A1 a method for detecting the achievement of a closure position of an electromagnetic switching valve is known, in which the current flowing after a deactivation of the switching valve current is evaluated.

The DE 10 2013 213 329 A1 teaches a method for detecting the operation of a switching valve, which comprises a coil running in a magnetic core and a valve body which is moved by means of the magnetic core and the energized coil in the axial direction. In this method, a current flow induced in the non-energized coil by the magnetic core is detected. The induced current profile is evaluated with regard to the waveform or height of the induced current.

Starting from the state of the art, the object of the present invention is to be able to monitor the function of an electromagnetic actuator more precisely, in order in particular to be able to more reliably detect blockages of the electromagnetic actuator.

Said object is achieved by an electromagnetic actuator according to the appended claim 1 and by a control unit according to the appended independent claim 10.

The method according to the invention serves to monitor the function of an electromagnetic actuator. The electromagnetic actuator is preferably a switching valve which is used, for example, in an automobile, in a chemical plant, in an energy-technical plant, in a machine or in a medical-technical plant. The switching valve may be designed in particular for an internal combustion engine of a motor vehicle. The electromagnetic actuator may also be a lifting magnet, for example. With the method according to the invention, the correct functioning of the electromagnetic actuator is monitored, so that possible errors and / or defects of the actuator and possible errors and / or defects of an element driven by the actuator can be detected. In particular, with the method according to the invention mechanical blockages of the actuator can be seen.

The electromagnetic actuator comprises a magnetic core and an electrical coil, inside which the magnetic core is preferably arranged. The magnetic core is displaceable by energizing the electric coil, so that electrical energy is converted into mechanical energy and the electromagnetic actuator drives the element to be moved by it. The magnetic core is preferably displaceable in the electrical coil in the axial direction of the electrical coil. At the magnetic core, an actuator element is mounted, which is displaced by the magnetic core. The actuator element is preferably a valve body when the actuator is formed by a switching valve.

In one step of the method according to the invention, a measurement of a time-varying current flowing through the electrical coil takes place. This measurement takes place in particular during the energization of the electric coil. The measured current increases during a current increase phase. The current increase phase is in an early phase of the energization. In the course of the current increase phase, the magnetic core is initially idle. The time portion of the idle is followed by a temporal portion of the magnetic saturation, which is also in the current increase phase. The current increase phase preferably lasts between 0.1 ms and 10 ms; more preferably between 1 ms and 3 ms.

In a further step of the method according to the invention, a logarithm function of the current measured in the current increase phase is formed. Thus, the argument of the logarithm function includes the temporally variable current. Accordingly, the logarithm function depends on the time.

In a further step of the method according to the invention, an approximation of the logarithmic function representing an early temporal segment of the idling is performed by a linear function. This approximation is possible because the current in the current increase phase increases nearly logarithmically as long as the magnetic core is idle. As a result of this step lies the Linear function, which represents the time course of the logarithmic function of the measured current during the early part of the period of idle with great accuracy.

In addition, there is an ongoing determination of a difference between the logarithm function and the linear function beyond the early time segment of the idling and, if appropriate, until the end of the current increase phase. The difference may already be determined during the early part of the idling period. The difference is very small during the early part of the idle phase because the logarithm function in this section is almost linear.

After the early part of the time interval of idling, the difference becomes increasingly larger and increases significantly in particular towards the end of the time interval of idling. Therefore, in a further step of the method according to the invention, a determination of a time of departure is based on when the difference reaches or exceeds a predefined difference measure. The time of departure describes the time from when the time course of the measured current is no longer logarithmic, which is due to an incipient magnetic saturation.

According to the invention, a detection of a malfunction of the electromagnetic actuator takes place when the determined time of departure is earlier than a predefined deviation of the standard deviation. The malfunction of the electromagnetic actuator is particularly given by a blockage of the electromagnetic actuator in which the magnetic core is prevented from being displaced. The invention is based on the surprising finding that the time profile of the measured current leaves its logarithmic course at an earlier point in time when the actuator is blocked.

The detected malfunction is preferably output, for example by a control unit for controlling and monitoring the actuator in the form of a switching valve, which reports the malfunction to a higher-level system for controlling an internal combustion engine.

A particular advantage of the method according to the invention is that it allows safe monitoring of electromagnetic actuators during their operation and thereby damage due to a blocked actuator can be avoided. For example, considerable damage can be caused by electromagnetic actuators in the form of switching valves in an internal combustion engine of a motor vehicle, if one of the switching valves is blocked because of a defect. In particular, an inadvertent deceleration of the motor vehicle, a sub-optimal fuel-air ratio, damage to unburned fuel in the internal combustion engine or total damage to the internal combustion engine due to non-closed valves in the combustion chamber may occur. Such damage can be prevented by the method according to the invention.

The blocking of a switching valve is a typical error. Such a blockage can be due to various causes; For example, a production error, low quality workmanship, inadequate lubrication during operation, to extreme temperature conditions, to a faulty energization or wear and tear.

In the electromagnetic actuator electrical energy is converted into mechanical energy. The current flowing through the electrical coil results from a balancing of various energies, namely an electrical energy, a magnetic energy, a kinetic energy, a work against a spring acting in the actuator and thermal losses. The present invention utilizes the balance between the electrical energy and the magnetic energy to detect blockage of the actuator.

The current increase phase described above begins in preferred embodiments of the method according to the invention, after an operating voltage has been applied to the electrical coil in order to energize the electrical coil. After the operating voltage has been applied to the electrical coil, the current increase phase begins with or without a short time delay.

The current flowing through the electrical coil preferably increases during the current increase phase from a minimum current value to a maximum current value. This rise in the current can be superimposed on a small alternating current component. Upon reaching the maximum current value, a magnetic saturation of the electromagnetic actuator has taken place.

In preferred embodiments of the method of the invention, the current rise phase is followed by a peak current phase in which the current decreases from a peak current phasing value to a peak current phase intermediate and increases from the peak current phaseshifter to a peak current phaseshift. This sinking and rising of the current can be superimposed on a small alternating current component.

In preferred embodiments of the method according to the invention, a holding current phase adjoins the peak current phase, in which the measured current drops to a holding current value range and remains there.

In preferred embodiments of the method according to the invention, there is a phase-out phase after the peak current phase, which phase follows in particular the holding current phase. The time start of the phase-out is given by the fact that the operating voltage has been taken back from the electric coil; d. H. that the electromagnetic actuator has been switched off. During the coast down phase, the measured current rises from a coast down phase current value to a coast phase intermediate current value, after which it decreases from the coast phase intermediate current value to a coast phase end current value. The phasing end current value is preferably zero.

The magnetic core is preferably during the current increase phase, a predominant part of the current increase phase at idle; at least when the electromagnetic actuator is working properly.

The early period of idling is preferably at least half the duration of idling; at least when the electromagnetic actuator is working properly.

In preferred embodiments of the method according to the invention, the measured current has a negative sign in the argument of the logarithm function. Consequently, the logarithm function decreases with time.

In preferred embodiments of the method according to the invention, the measured current in the argument of the logarithm function is subtracted from the maximum current value. In this case, the argument of the logarithm function preferably comprises a positive constant as a summand in order to guarantee that the argument is greater than zero.

The logarithmic function is preferably a decadic logarithm, whereby the logarithm function can also have a different basis.

The logarithm function, which is _denoted below by the formula symbol f _{i_log} (t), is preferably defined by the following formula: f _{i_log} (t) = log [I _max - i (t) + c] In this formula, i (t) stands for the measured current in the current increase phase. I _max stands for the maximum current value. The symbol c stands for the positive constant.

In preferred embodiments of the method according to the invention, the approximation is performed by a linear approximation of the logarithm function representing the early time interval of idling. Various methods for linear approximation are known and established.

The end of the early period of idling may be predefined by measurements. Preferably, however, the end of the early time portion of the idle is defined when an approximation error of the linear approximation exceeds a predetermined maximum approximation error measure.

In simple preferred embodiments of the method according to the invention, the determination of the time of departure takes place in that the time at which the difference reaches the predefined difference measure is used as the time of departure.

In preferred embodiments of the method according to the invention, the determination of the time of departure is effected in that the time at which the difference reaches the predefined difference measure is reduced by one calibration period and is used as the time of departure. The calibration period is preferably determined in advance by measurements on the electromagnetic actuator.

In preferred embodiments of the method according to the invention, the definition of the deviation from the norm takes place in that the departure time for a plurality of correctly functioning electromagnetic actuators of the same type as the electromagnetic actuator to be monitored is determined. Preferably, the earliest of the determined departure times is reduced by a tolerance measure and used as the standard deviation time.

In further preferred embodiments of the method according to the invention, a further criterion is additionally used to detect a malfunction of the electromagnetic actuator. In these embodiments, the time-varying, flowing through the coil current during energization and possibly also after the energization of the electric coil is measured.

In a particular class of preferred embodiments, an evaluation product is additionally used as a further criterion for a malfunction of the electromagnetic actuator to recognize. In this class of preferred embodiments, the measurement of the time-varying, flowing through the electric coil current takes place in particular during the energization of the electric coil and / or after the energization of the electric coil. There is a selection of a temporal evaluation section of the course of the measured current. In this evaluation section, the current changes from a section start current value I _a to a section end current value I _b , which change is monotonous. The monotonic change can be formed by a monotonous slope or by a monotonous drop. The monotone change can be interrupted by negligible fluctuations of the current. The time evaluation section takes a section of time _t. Preferably, the current in the evaluation section monotonically changes from the section start current value I _a via a section intermediate current value I _d to the section end current value I _b . Until the occurrence of the section intermediate current value I _d, an intermediate section period t _ad passes. The evaluation product is formed from factors which comprise at least on the one hand the section start current value I _a and the section end current _value I _b and on the other hand the section time duration t _ab . Consequently, at least one of the factors comprises the portion of initial current value I _a and / or the end portion current value I _b and at least one other of the factors, the section time period _t. Both the section start current value I _a and the section end current _value I _b enter the product. The product may include partial products as summands. In any case, the evaluation product has electricity as a first dimension and time as a second dimension. The evaluation product is preferably formed from factors which comprise, at least on the one hand, the section start current value I _a , the section intermediate current _value I _d and the section end current _value I _b and, on the other hand, the section period t _ab and the intermediate section time t _ad . In addition, a malfunction of the actuator is detected by comparing the evaluation product with a valuation product boundary. The malfunction of the electromagnetic actuator is particularly given by a blockage of the electromagnetic actuator in which the magnetic core is prevented from being displaced.

In preferred embodiments of the particular class of preferred embodiments, the evaluation product represents an area of an area on a function graph of the time-varying current. The function graph is arranged in a Cartesian coordinate system. The surface is bounded at least in two points by the function graph. The area is bounded at least by a point of the function graph assigned to the section start current value and by a point of the function graph assigned to the section end current value.

The area described is preferably limited by a first straight line running through the point of the function graph associated with the section start current value. The first straight line runs parallel to an axis assigned to the time of the coordinate system or to an axis of the coordinate system assigned to the current.

The described area is preferably delimited by a second straight line running through the point of the function graph associated with the section end current value. The second straight line runs parallel to the axis of the coordinate system assigned to the time or to the axis of the coordinate system assigned to the current.

The first straight line and the second straight line are preferably aligned perpendicular to one another. Preferably, one of the two straight lines is aligned parallel to the time-associated axis of the coordinate system, while the other of the two straight lines is aligned with the axis of the coordinate system assigned to the current. Depending on which of the two straight lines is aligned parallel to the axis of the coordinate system assigned to the time, the surface is above or below the function graph shown in the coordinate system.

In preferred embodiments of the particular class of preferred embodiments, a part of the function graph associated with the evaluation section is approximated in a first evaluation section by a third straight line, while in a second evaluation section it is approximated by a fourth straight line. The first evaluation subsection and the second evaluation subsection follow each other directly. The first evaluation section commences simultaneously with the evaluation section, while the second evaluation section ends simultaneously with the evaluation section. The approximation of the part of the function graph associated with the evaluation section by two straight lines reduces the computational outlay for determining the evaluation product. The two straight lines represent a good approximation for typical evaluation sections of the course of the current flowing through the coil of the actuator current.

The surface described above is preferably formed by a quadrilateral whose four sides are formed by the first straight line, by the second straight line, by the third straight line and by the fourth straight line. The quadrilateral preferably has a right angle, that of the first straight line and the second straight line Just being stretched. The surface area of this quadrilateral can be determined with little effort.

The surface described above is preferably formed by a right triangle with a non-straight hypotenuse. The triangle is preferably formed concave by its hypotenuse. The catheters of the triangle are formed by the first straight line and by the second straight line. The hypotenuse is preferably formed by the part of the function graph assigned to the evaluation section. Alternatively, the hypotenuse is preferably formed jointly by the third and fourth straight lines. Accordingly, the evaluation product is conceivable as a triangle operator Δ. The triangle operator Δ is an indicator of an energetic balance between electrical energy, magnetic energy and kinetic energy in the evaluation section, which is recognizable by the current flowing through the electrical coil.

In preferred embodiments of the specific class of preferred embodiments is represented by the lying on the function graph intersection point between the third line and the fourth straight section of the intermediate current value I _d.

In preferred embodiments of the particular class of preferred embodiments, the evaluation product comprises, as a further factor, a voltage value of an operating voltage applied to the electric coil for energizing the electrical coil. This factor can be dispensed with in particular if the voltage V is constant.

In a first group of preferred embodiments of the particular class of preferred embodiments, the evaluation section is within the current increase phase.

In this first group of preferred embodiments, the section start current value is preferably given at the time of departure. In this first group of preferred embodiments, the section end current value I _{b is} smaller than the maximum current value and thus lies temporally before the end of the current increase phase.

In the first group of preferred embodiments, the evaluation product is preferably formed by the following triangular Δ expansion _phase : Δ _rise phase = 0.5V · ((I _ab + I _ad ) · t _ab - I _ab · t _ad )

In this case, I _ab = I _b -I _a and I _ad = I _d -I _a .

In the first group of preferred embodiments, the malfunction of the actuator is preferably additionally identified when the triangular operator Δ _{increase phase is} at least as large as the evaluation _product limit predefined for the triangular operator Δ _rise phase.

If the triangle operator Δ _{rise phase is} large, this indicates that the current i (t) is increasing very rapidly, so that less electrical energy is converted into other forms of energy. If the triangle operator Δ _{increase phase is} smaller, this indicates that more electrical energy is being converted into kinetic energy for the movement of the magnetic core. Reducing the triangle operator Δ _rise phase also indicates changing magnetic properties, such as narrowing an air gap, which converts more electrical energy.

In the first group of preferred embodiments, the current difference value I _ab is preferably used as a further criterion for detecting a malfunction of the actuator.

In the first group of preferred embodiments, a measure of the slope of the current i (t) after reaching I _ab is preferably used as a further criterion for detecting a malfunction of the actuator.

In the first group of preferred embodiments, a duration from reaching the current rise phase initial value to reaching the current increase phase end value is preferably used as another criterion for detecting a malfunction of the actuator.

In the first group of preferred embodiments, a center of gravity of the area representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator.

In the first group of preferred embodiments, a center of the surface representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator.

In a second group of preferred embodiments of the particular class of preferred embodiments, the evaluation portion is within the peak current phase.

In the second group of preferred embodiments, the section start current value is preferably formed by the maximum current value.

In the second group of preferred embodiments, the section end current value is preferably greater than the peak current phase intermediate value and is achieved prior to the peak current phase intermediate value.

In the second group of preferred embodiments, the evaluation product is preferably formed by the following triangle operator Δ _peak current _phase : Δ _peak current phase = 0.5V · (I _ab * t _ad + I _bd * t _ab )

In this case, I _ab = I _{a -I b} and I _bd = I _{d -I b} .

The malfunction of the actuator is preferably recognized when the triangle operator Δ _peak current _{phase is} at most as large as the evaluation _product limit predefined for the triangle operator Δ _peak current phase.

If the triangular operator Δ _peak current _{phase is} small, this indicates a rapid discharge by the current i (t) and a low energy conversion between kinetic energy and magnetic energy. If the triangular operator Δ _peak current _{phase is} larger, this indicates a slow movement of the magnetic core and a low kinetic energy. An increase in the triangle operator Δ _{peak current} phase also indicates changing magnetic properties, such as a reduction in an air gap, resulting in less magnetic energy.

In the second group of preferred embodiments, the current difference value I _ab is preferably used as a further criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a current difference value I _{min formed} by the difference between the peak current phase initial value and the peak current phase intermediate value is preferably used as another criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a duration t _min from reaching the peak current phase initial value to reaching the peak current phase intermediate value is preferably used as a further criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, an operator A _peak current phase is preferably used as another criterion for detecting a malfunction of the actuator. The operator A _{peak current phase} is defined as follows: A _peak current phase = 0.5V · [I _ab * t _ab - (I _ab * t _ad + I _bd * t _ab )]

In the second group of preferred embodiments, a ratio of the triangular Δ _peak current phase to the A _peak current phase is preferably used as another criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a center of gravity of the surface representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a center of the surface representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a ratio of the current difference value _from I to time is preferably _from t is used as a further criterion for detecting a malfunction of the actuator.

In the second group of preferred embodiments, a length of the function graph from the peak current phase intermediate value to the peak current phase final value is preferably used as another criterion for detecting a malfunction of the actuator.

In a third group of preferred embodiments of the particular class of preferred embodiments, the evaluation section is within the phasing-out phase.

In the third group of preferred embodiments of the method according to the invention, the phasing initial value is used as the section preamble current value.

In the third group of preferred embodiments, the section tail current value is less than the coast phase intermediate value and is timed prior to the coast phase intermediate value.

In the third group of preferred embodiments, the evaluation product is preferably formed by the following triangle operator Δ _{phase-out phase} : Δ _{phase-out phase} = 0.5V · ((I _ab - I _ad ) · t _ab + I _ab · t _ad )

In this case, I _ab = I _b -I _a and I _ad = I _d -I _a .

In the third group of preferred embodiments, the malfunction of the actuator is preferably recognized when the Triangle operator Δ _{phase-out phase} at most as large as the evaluation _product limit predefined for the triangle operator Δ _{phase-out phase} .

If the triangle operator Δ _{phase-out phase is} small, this indicates small current values. This also indicates a rapid increase in the current i (t) and that less electrical energy is converted into other forms of energy. This also indicates a slight movement of the magnetic core and a lack of kinetic energy. An enlargement of the triangle operator Δ _{phase-out phase} indicates an increased conversion of electrical energy into magnetic energy, which is caused, for example, by an enlargement of an air gap.

In the third group of preferred embodiments, the current difference value I _ab is preferably used as a further criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments, a ratio of the current difference value I _ab to the duration t _ab is preferably used as a further criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments, a length of the function graph from the start-of-run phase value to the idle-phase intermediate value is preferably used as another criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments of the method according to the invention, a triangular operator Δ _{phase-out phase} A is preferably used as a further criterion for detecting a malfunction of the actuator. The operator triangle operator Δ _phase-outA is defined as follows: Δ _{phase-out phase A} = 0.5V · ((I _ab + I _ad ) · t _ab - I _ab · t _ad )

In the third group of preferred embodiments, it is preferable to use the phasing-out intermediate value and the time duration until it is reached as further criteria for detecting a malfunction of the actuator.

In the third group of preferred embodiments, it is preferable to use another of the evaluation sections which is in the later part of the outflow phase, ie, after reaching the outflow phase intermediate value. The outflow phase intermediate value is preferably used as the section start current value I _a . The section end flow value I _b is preferably smaller than the outflow phase intermediate value and is reached in time prior to the phase out end value.

In the third group of preferred embodiments, a triangular operator Δ _{phase-out phase B} is preferably used for the later part of the phase _{-out phase} as a further criterion for detecting a malfunction of the actuator. The triangle operator Δ _{phase-out B} is defined as follows: Δ leakage _phase B = 0.5V · ((I _ab + I _ad ) · t _ab - I _ab · t _ad )

In this case, I _ab = I _a -I _b and I _ad = I _a -I _d .

In the third group of preferred embodiments, a triangular operator Δ _{phase-out phase C} is preferably used for the later part of the phase _{-out phase} as a further criterion for detecting a malfunction of the actuator. The triangle operator Δ _{phase-out C} is defined as follows: Δ _phase-out C = 0.5V · ((I _ab - I _ad ) · t _ab + I _ab · t _ad )

In this case, I _ab = I _a -I _b and I _ad = I _a -I _d .

In the third group of preferred embodiments, a sum of the triangular operators Δ _{outflow phase} , Δ _{outflow phase A} , Δ _{outflow phase B} and Δ _{outflow phase C} is preferably used as another criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments, a center of gravity of the surface representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments, a center of the area representing the evaluation product is preferably used as another criterion for detecting a malfunction of the actuator. The midpoint is a time center and possibly an average value of the measured current in the evaluation section.

In the third group of preferred embodiments, the intermediate section period is preferably used as another criterion for detecting a malfunction of the actuator.

In the third group of preferred embodiments, at least one ratio between the triangular operators is preferably used as another criterion for detecting a malfunction of the actuator. At least one of the following conditions is preferably formed: Δ _{phase-out phase} / Δ _{phase-out phase A} , Δ _{phase-out phase} / Δ _{phase-out phase B} , Δ _{phase-out phase} / Δ _{phase-out phase C} , Δ _{phase-out phase A} / Δ _{phase-out phase B} and Δ _{phase-out phase C} / Δ _{phase-out phaseB} .

The preferred criteria for detecting a malfunction of the actuator mentioned for the three groups of preferred embodiments are preferably also used in combination. Preferably, the criteria mentioned for the three groups of preferred embodiments for detecting a malfunction of the actuator are also applied across groups in combination, ie, that a plurality of the criteria mentioned for the three groups of preferred embodiments for detecting a malfunction of the actuator are used together in combination.

The control unit according to the invention serves to control and monitor an electromagnetic actuator and is configured to carry out the method according to the invention. The control unit according to the invention is preferably configured to carry out preferred embodiments of the method according to the invention.

Further details, advantages and developments of the invention will become apparent from the following description of preferred embodiments of the invention, with reference to the drawing. Show it:

1 a according to a preferred embodiment of a method according to the invention to be monitored switching valve in a schematic diagram;

2 a temporal course of a current for energizing the in 1 shown switching valves;

3 a temporal course of a movement of an in 1 shown magnetic core and one in 1 shown valve body when energizing the switching valve;

4 a section of the in 2 shown course of the current in detail with an inventively to be determined deviation time;

5 a current increase phase of in 4 shown course of the current with a determined according to a preferred embodiment of the method according to the invention surface area;

6 a peak current phase of the in 2 shown course of the current with a determined according to a preferred embodiment of the method according to the invention surface area;

7 in the 6 shown peak current phase with a to be determined according to a further preferred embodiment of the method according to the invention surface area;

8th a phase-out of the in 2 shown course of the current with a determined according to a preferred embodiment of the method according to the invention surface area; and

9 in the 8th shown outlet phase with further to be determined according to further preferred embodiments of the method according to the invention surface contents.

1 shows a switching valve to be monitored according to a preferred embodiment of a method according to the invention in a schematic diagram. It represents an electromagnetic actuator and includes a movable magnetic core 01 in an electric coil 02 is displaceable. The sink 02 sits on a fixed magnetic core 03 in which the movable magnetic core 01 is displaceable. Between the movable magnetic core 01 and the fixed magnetic core 03 is an air gap 04 educated.

At the movable magnetic core 01 is a valve body 06 attached, which forms part of a valve, not shown. The displacement movement of the movable magnetic core 01 with the valve body 06 gets through a first stop 07 and by a second stop 08 limited. The displacement movement of the movable magnetic core 01 with the valve body 06 is by a first spring 09 and by a second spring 11 sprung.

To the electric coil 02 is a control unit 12 electrically connected, with which the coil 02 the switching valve can be energized. This is the coil 02 through the control unit 12 applied with an operating voltage V, whereupon a time dependent current i (t) through the coil 02 flows. The control unit 12 is configured to carry out the method according to the invention, which will be explained below.

2 shows a time course of with respect to the 1 described current i (t). The current i (t) increases after the application of the operating voltage V during a current increase phase 21 and goes through a peak current phase 22 , whereupon he is in a holding current phase until the end of the application of the operating voltage V 23 remains. After the application of the operating voltage V, a phase-out phase closes 24 at.

3 shows a time course of a movement of the in 1 shown magnetic core 01 and of in 1 shown valve body 06 at a current supply of the switching valve. The temporal course of the movement of the in 1 shown magnetic core 01 is by a solid line 31 shown in the diagram. The temporal course of the movement of the in 1 shown valve body 06 is by a dashed line 32 shown in the diagram.

4 shows a section of the in 2 shown course of the current i (t) in detail. This course is a solid line 41 shown in the case that the switching valve is working properly. This course is with a dashed line 42 illustrated in the case that the switching valve is blocked. A dotted line 43 illustrates the case when the switching valve and its energization would be dimensioned so that it does not come to the magnetic saturation in the switching valve, and also the switching valve is blocked. However, switching valves are usually sized to operate near or in electromagnetic saturation. The current i (t) initially increases exponentially, but due to the electromagnetic saturation, a steeper increase occurs. In a faultlessly functioning switching valve part of the electrical energy is converted into kinetic energy. In a blocked switching valve, the electrical energy leads to a higher degree of electromagnetic saturation, so that the exponential profile of the current i (t) is left earlier.

During an idling phase 44 is the movable magnetic core 01 (shown in 1 ) still idle. In the idle phase 44 the current i (t) is logarithmic. After the idling phase 44 it comes to the magnetic saturation of the switching valve, so that the current i (t) increases more than according to the logarithmic curve. The onset of this stronger slope of the current i (t) sets at a point of departure 46 one. If the switching valve is blocked, it comes as described above earlier to the magnetic saturation of the switching valve, so that the deviation point 46 earlier in time. According to the invention, the time of departure 46 determined during energization of the switching valve. If it lies ahead of a predefined deviation point in time, a blocking of the switching valve is detected according to the invention and an error message is output.

5 shows in particular the current increase phase 21 of in 4 shown course of the current i (t), wherein the determination of the time of departure 46 is illustrated. First, a logarithmic function f _{i - log} (t) of the time course of the measured current i (t) is determined, which is indicated by a dashed line 51 is shown. For the formation of the logarithm function f _{i - log} (t), a maximum current value I _{max is} taken into account in addition to the current i (t). A positive constant c as a summand in the argument of the logarithm function f _{i_log} (t) guarantees that the argument is always positive. The logarithm function f _{i_log} (t) is determined as follows: f _{i_log} (t) = log [i (t) _{-I max} + c]

The logarithm function f _{i_log} (t) initially runs linear. In an early temporal section 52 In the idling _phase , a linear approximation of the logarithm function f _{i - log} (t) is carried out, in the result of which a linear function f _lin (t) is obtained, which is indicated by a thin solid line 53 is shown. At a difference measure time 54 The logarithm function f _{i_log} (t) and the linear function f _lin (t) differ from each other by a predetermined difference measure. From this difference measure time 54 a calibration period is subtracted, whereby the time of departure 46 is obtained.

During the current increase phase 21 the course of the current i (t) is further determined according to a preferred embodiment of the method according to the invention, an area containing a triangle operator Δ represents. The triangle operator Δ is determined in a judgment section which is in one with the deviation point 46 coincident point a begins and rises to a point b almost to the peak current I _max . The evaluation section takes a period of time _t. The current i (t) increases during the evaluation section _from a current difference value I. Between the point a and the point b, a point d is selected on the function graph of the current i (t). The temporal section from the point a to the point d represents a judging section which lasts a time t _ad . At point d, the current i (t) is greater by a current difference value I _ad than at point a. Through the point a, a first straight line runs 61 , which is aligned parallel to the axis of time t. Through the point b, a second straight line runs 62 , which is aligned parallel to the axis of the current i (t). The first straight 61 and the second straight line 62 intersect at a point c. A third straight line 63 passes through the points a and d. A fourth straight line 64 passes through the points d and b. The first straight 61 , the second straight line 62 , the third straight line 63 and the fourth straight line 64 span a quadrangle, which can also be understood as a right-angled triangle with an odd hypotenuse coming from the third straight line 63 and the fourth straight line 64 is formed. The third straight 63 and the fourth straight line 64 formed Hypotenuse represents an approximation to the function of the current i (t) in the evaluation section. The area of the rectangular triangle with the odd hypotenuse forms the triangle operator Δ. According to the invention, a blocking of the switching valve is recognized if the triangular operator Δ formed for the current increase phase is at least as large as a predefined evaluation product limit.

6 shows the in 2 shown peak current phase 22 the course of the current i (t) with a surface area to be determined according to a preferred embodiment of the method according to the invention, which represents a further triangular operator Δ. The triangle operator Δ is determined in a further evaluation section in which the current i (t) at a point a from a peak current phase initial value to a point b decreases to almost a peak current phase intermediate value. The peak current phase initial value is the peak current I _max . Again, the evaluation section takes a period of time _t. The current i (t) decreases during the evaluation section by a current difference value I _from . Between the point a and the point b, again a point d on the function graph of the current i (t) is selected. The temporal section from the point a to the point d represents a judging section which lasts a time t _ad . At point d, the current i (t) is greater by a current difference value I _bd than at point b. By the point a in turn runs a first straight line 61 which, however, is aligned parallel to the axis of the current i (t). By the point b in turn runs a second straight line 62 , which, however, is aligned parallel to the axis of time t. The first straight 61 and the second straight line 62 intersect again at a point c. A third straight line 63 again passes through the points a and d. A fourth straight line 64 again passes through the points d and b. The first straight 61 , the second straight line 62 , the third straight line 63 and the fourth straight line 64 span a quadrangle, which can also be understood as a right-angled triangle with an odd hypotenuse coming from the third straight line 63 and the fourth straight line 64 is formed. The third straight 63 and the fourth straight line 64 The formed hypotenuse represents an approximation to the functional course of the current i (t) in the evaluation section. The area of the rectangular triangle with the odd hypotenuse in turn forms the triangle operator Δ. According to the invention, a blocking of the switching valve is detected when the triangular operator Δ formed for the peak current phase is at most as large as a previously defined evaluation product limit.

7 shows the in 6 shown peak current phase 22 with an area to be determined according to a further preferred embodiment of the method according to the invention. A different scoring section is determined in which the current i (t) decreases from the peak current phaseshift to fully at the peak current phaseshifter. This evaluation section lasts a period t _min . During this evaluation section, the current i (t) decreases by a current difference value I _min . By the time of Spitzenstromphasenanfangswertes again runs a first straight line 61 , which is aligned parallel to the axis of the current i (t). The peak current phase intermediate value again leads to a second straight line 62 , which is aligned parallel to the axis of time t. According to an alternative preferred embodiment, the area of a surface is determined, which of the first straight line 61 , the second straight 62 and the function graph of the current i (t) is limited. This area represents an alternatively preferred triangle operator Δ. The peak current phase initial value is followed by a fifth straight line 65 , which is aligned parallel to the axis of time t. By the time of the peak current phase intermediate value runs a sixth straight line 66 , which is aligned parallel to the axis of the current i (t). According to an alternative preferred embodiment, the area of a surface is determined, which of the fifth straight line 65 , the sixth straight line 66 and the function graph of the current i (t) is limited. This area represents an operator A, which according to an alternative preferred embodiment is used as a criterion for detecting a malfunction of the actuator.

8th shows the in 2 shown phase-out 24 the course of the current i (t) with a surface area to be determined according to a preferred embodiment of the method according to the invention, which represents a further triangular operator Δ. The triangle operator Δ is determined in a further evaluation section in which the current i (t) at a point a from an outflow phaseline initial current value to a point b increases to almost a maximum phased out phasic current value. Again, the evaluation section takes a period of time _t. The current i (t) increases during the evaluation section _from a current difference value I. Between the point a and the point b, again a point d on the function graph of the current i (t) is selected. The temporal section from the point a to the point d represents a judging section which lasts a time t _ad . At point d, the current i (t) is greater by a current difference value I _ad than at point a. By the point a in turn runs a first straight line 61 , which is aligned parallel to the axis of the current i (t). By the point b in turn runs a second straight line 62 , which is aligned parallel to the axis of time t. The first straight 61 and the second straight line 62 intersect again at a point c. A third straight line 63 again passes through the points a and d. A fourth straight line 64 again passes through the points d and b. The first straight 61 , the second straight line 62 , the third straight line 63 and the fourth straight line 64 span a quadrangle, which can also be understood as a right-angled triangle with an odd hypotenuse coming from the third straight line 63 and the fourth straight line 64 is formed. The third straight 63 and the fourth straight line 64 The formed hypotenuse represents an approximation to the functional course of the current i (t) in the evaluation section. The area of the rectangular triangle with the odd hypotenuse in turn forms the triangle operator Δ. According to the invention, a blockage of the switching valve is detected when the one formed for the peak current phase Triangular operator Δ is at most as large as a predefined evaluation product limit.

9 shows the in 8th shown peak current phase 24 with further surface areas to be determined for further preferred embodiments of the method according to the invention. A different evaluation section is determined in which the current i (t) increases from the phased-out initial phase current value to fully at the maximum phased-out intermediate current value. This evaluation section lasts a time t _max . During this evaluation section, the current i (t) increases by a current difference value I _max . The outflow phase initial flow value is followed by a fifth straight line 65 , which is aligned parallel to the axis of time t. By the time of the maximum phase-out intermediate current value, a sixth straight line runs 66 , which is aligned parallel to the axis of the current i (t). According to an alternative preferred embodiment, the area of an area A is determined, which of the fifth straight line 65 , the sixth straight line 66 and the function graph of the current i (t) is limited. This area is a triangle Δ operator _A, which is used as a criterion for detecting a malfunction of the actuator according to an alternative preferred embodiment.

Alternatively or additionally, a deviating evaluation section is determined in which the current i (t) decreases from the maximum outflow phase intermediate current value to an outflow phase end current value. Due to the phase-out phase end current value, a seventh straight line runs 67 , which is aligned parallel to the axis of the current i (t). According to an alternatively preferred embodiment, the surface area of a surface B is determined, which of the fifth straight line 65 , the sixth straight line 66 , the seventh straight 67 and the function graph of the current i (t) is limited. This surface area represents an alternatively preferred triangular operator Δ _B. According to a further alternatively preferred embodiment, the area of a surface C is determined, which of the second straight line 62 , the seventh straight 67 and the function graph of the current i (t) is limited. This area represents an alternatively preferred triangular operator Δ _C. According to the invention, the various triangular operators and further operators can be used individually or in combination as criteria for detecting a malfunction of the actuator.

LIST OF REFERENCE NUMBERS

01

 movable magnetic core

02

 electric coil

03

 solid magnetic core

04

 air gap

05

06

 valve body

07

 first stop

08

 second stop

09

 first spring

10

11

 second spring

12

 control unit

20

21

 Current rise phase

22

 Peak current phase

23

 Holding current phase

24

 phasing

30

31

 Movement of the magnetic core (solid line)

32

 Movement of the valve body (dashed line)

40

41

 Course of the current i (t) (solid line)

42

 Course of the current i (t) with blocked switching valve (dashed line)

43

 Course of the current i (t) without magnetic saturation (dotted line)

44

 Idle phase

45

46

 Time of departure

50

51

Logarithm function f _{i_log} (t) (dashed line)

52

 early part of the idle phase

53

linear function f _lin (t) (thin solid line)

54

 Differenzmaßzeitpunkt

60

61

 first straight

62

 second straight line

63

 third straight line

64

 fourth straight

65

 fifth straight line

66

 sixth straight line

67

 seventh straight line

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• US 2011/0163769 A1 [0002]
• US 2005/0146408 A1 [0003]
• DE 102013213329 A1 [0004]

Claims (10)

Method for monitoring the function of an electromagnetic actuator, wherein in the electromagnetic actuator a magnetic core ( 01 ) by energizing an electric coil ( 02 ) is displaceable; and wherein the method comprises the steps of: measuring a time-varying current through the electrical coil ( 02 ) current, the measured current during a current increase phase ( 21 ), during which the magnetic core ( 01 ) is initially idle; - forming a logarithm function of the in the current increase phase ( 21 ) measured current; Approximating the logarithmic function representing an early temporal segment of idling by a linear function; - continuously determining a difference between the logarithm function and the linear function over the early portion of the idle time; - Determining a time of departure ( 46 ) based on when the difference reaches a predefined difference measure; and detecting a malfunction of the electromagnetic actuator when the determined time of departure ( 46 ) is earlier than a predefined deviation point in time. Method according to claim 1, characterized in that the current increase phase ( 21 ) begins after an operating voltage to the electric coil ( 02 ) was created. A method according to claim 1 or 2, characterized in that by the electrical coil ( 02 ) flowing electricity during the current increase phase ( 21 ) rises from a minimum current value up to a maximum current value, with a magnetic saturation of the electromagnetic actuator having taken place when the maximum current value is reached. Method according to one of claims 1 to 3, characterized in that the magnetic core ( 01 ) with a correct function of the electromagnetic actuator during the current increase phase ( 21 ) in a major part of the current increase phase ( 21 ) is idle. Method according to one of claims 1 to 4, characterized in that the measured current in the argument of the logarithmic function has a negative sign. A method according to claim 5, characterized in that the measured current is subtracted in the argument of the logarithm function of the maximum current value. Method according to one of claims 1 to 6, characterized in that the determination of the time of departure ( 46 ) takes place in that the time at which the difference reaches the predefined difference measure is reduced by one calibration time period and as the time of departure ( 46 ) is used. Method according to one of claims 1 to 7, characterized in that the definition of the standard deviation time point takes place in that the time of departure ( 46 ) is determined for several correctly functioning electromagnetic actuators of the same type as the electromagnetic actuator to be monitored. Method according to one of claims 1 to 8, characterized in that it comprises the following further steps: - selecting a temporal evaluation section of the course of the measured current in which the current changes from a section start current value to a section end current value, wherein the time evaluation section lasts a section time period ; Forming an evaluation product from factors which comprise, at least on the one hand, the section start current value and the section end current value and, on the other hand, the section time duration; and detecting a malfunction of the electromagnetic actuator by comparing the evaluation product with an evaluation product boundary. Control unit ( 12 ) for controlling and monitoring an electromagnetic actuator configured to carry out a method according to any one of claims 1 to 9.

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