DE102021214003A1 - Method for determining a parameter in a circuit of a coil - Google Patents

Abstract

The invention relates to a method for determining at least one parameter in an electric circuit of a coil, the coil being controlled with at least one type of recurring control phases (L, E), the durations (ΔtL, ΔtE) of the control phases (L, E) being determined , and wherein the at least one parameter is determined based on the durations and/or based on fluctuations in the durations (ΔtL, ΔtE), in particular within a type of control phases (L, E), and in particular whether an electrical fault is present.

Description

The present invention relates to a method for determining at least one parameter in an electric circuit of a coil, on the basis of which conclusions can be drawn, e.g.

Background of the Invention

Coils can be used, for example, in suction valves or electric suction valves with a freely movable valve piston, which in turn can be used in combination with piston pumps as high-pressure pumps to compress fuel to a desired pressure value, the so-called rail pressure, and pump it into a high-pressure accumulator (so-called . Common Rail). The suction valve opens in the suction stroke of the pump piston and allows fuel to continue to flow and can be controlled in the compression stroke of the pump piston in such a way that it closes so that the fuel does not flow out into the low pressure.

Loose contacts or other electrical faults can lead to incorrect actuation in such an electrical suction valve—but also in the case of other uses of coils. From the DE 10 2008 002 131 A1 For example, there is a known way of detecting a loose contact in a piezo actuator by measuring the duration of the discharge of the piezo actuator.

Disclosure of Invention

According to the invention, a method for determining at least one parameter in a circuit of a coil as well as a computing unit and a computer program for its implementation with the features of the independent patent claims are proposed. Advantageous configurations are the subject of the dependent claims and the following description.

The invention deals with the operation or control of coils and there in particular with the determination of parameters, e.g. technical parameters such as electrical, magnetic or mechanical parameters. Technical parameters can generally be understood to mean, for example, technical properties such as electrical and/or magnetic resistance, inductance or the operating voltage, the value or change of which allows conclusions to be drawn about operating situations or errors in the component or components connected to it. Based on this, electrical faults in their circuit (or supply circuit), e.g. in the supply lines, contact points or even the wires of the coil itself, can be detected.

An electrical fault is to be understood in particular as a fault that causes an at least temporary change in at least one technical parameter or physical variable, in particular an electrical resistance and/or magnetic resistance and/or an inductance, in the circuit, e.g. a loose contact . Changing electrical resistance values can also be due, for example, to oxidation or wear of the contact material at contact points or changes in the cross-section of electrical conductors, for example due to fraying and partially or completely breaking conductors in the aforementioned circuit, e.g. due to the ingress of water or mechanical vibration as well as to temperature influences ( e.g. externally introduced).

A preferred application in which such a coil can be used is, for example, an electromagnetic actuator, in particular in the case of a solenoid valve, which, for example, includes a magnet armature that can be moved by controlling the coil. In principle, however, the invention can be used with all electromagnetic actuators, for example with electrical contactors, mechanical locking/unlocking (moving bolts, pins), electromagnets for holding loads, e.g. for holding doors open, etc.

In order to explain the invention, an electric suction valve, already mentioned at the outset, is to be dealt with in particular here, which is assigned to a conveying system of a high-pressure pump of an internal combustion engine. In this way, fuel can be conveyed, in particular from a low-pressure area, via a conveying chamber of the conveying system into a high-pressure accumulator. In the case of the electric suction valve, a magnetic armature is typically provided, which serves in particular as a travel limiter for a valve piston which can close a flow opening between the low-pressure area and the pumping chamber. By means of an electromagnet (with the coil), the magnet armature can then be adjusted by appropriate control between a first position in which the valve piston cannot close the flow opening and a second position in which the valve piston can close the flow opening.

To deliver a certain amount of fuel, the electric suction valve is generally energized, i.e. the coil there in particular, so that when the coil is energized or activated, the magnet armature is raised at the desired time and the electric suction valve can thereby close. A target delivery rate can be set in that, for example, the pump piston pushes the fuel out of the delivery chamber (pump chamber) during the upward movement and the electric suction valve closes when the magnet armature is raised, with the required delivery quantity remaining in the delivery chamber, being compressed and pushed out into the high-pressure accumulator.

The electrical suction valve is controlled, for example, via an electrical output stage in a control unit (e.g. engine control unit). In general, the so-called two-point control can be used to control the current of an electromagnetic actuator, in addition to other methods, in which the circuit is interrupted when a predetermined upper limit of the target current is reached and the circuit is closed again when a lower limit of the target current is reached.

With such a two-point control, self-adjusting control frequencies and duty cycles result.

There are also other ways of controlling or setting the current. With a PWM control (i.e. a pulse width modulated control), there is a constant control frequency and a variable duty cycle, by means of which the target current is set via a controller. Control by means of (non-pulsed) direct current with the required amperage is also possible, for example.

Within the scope of the invention, the coil is controlled with at least one type of recurring control phase. A charging phase (or charging process) and a discharging phase (or discharging process) of the coil can be considered as types of control phases, i.e. phases in which a magnetic field is built up and dissipated, as is the case, for example, within the framework of the two-point control mentioned . It is irrelevant whether the build-up or dissipation of the magnetic field is complete in each case. Rather, alternating between different magnetic field strengths is sufficient for the proposed method.

Time durations of the control phases are also determined, that is to say of several of the recurring control phases. Based on the durations (i.e. in particular their absolute values) and/or fluctuations in the durations, in particular within a type of control phase, i.e. e.g. during the charging phases or the discharging phases, one or more (technical) parameters of the coil or the connected elements are then determined determined in the circuit, in particular via exponential relationships. Based on this, one or more operating states and/or one or more errors (or error states) can then be inferred, for example, based on absolute and/or dynamic changes in the parameters. In particular, based on the absolute changes, it is also possible to draw conclusions about environmental conditions, for example. The absolute values, i.e. the durations themselves, can be used in particular for plausibility checks or the calculation of limiting envelope curves, etc.

Although an electric suction valve and its special features are discussed here and below to explain the invention in more detail, the invention, as already mentioned, can also be used with coils that are used in other ways.

In normal operation, the high-pressure pump delivers fuel to the high-pressure accumulator. To deliver fuel, the electric suction valve is closed (by an armature movement directed towards the pole core). As a rule, in operation without a shortened pull-in phase (in so-called non-ballistic operation), the armature movement is completed when the holding phase begins, so that mechanically almost constant conditions prevail at the pole core at this point in time.

Within the scope of the present invention, these relationships are now considered in particular in combination with a new type of analysis of the duration (duration), e.g. of the charging or discharging phase in two-point control. One connection is that, for example, a loose contact causes a certain proportion of dynamic changes in the system, especially the overall electrical resistance. This dynamic change in the total resistance is expressed in the dynamics of the durations, e.g. of the charging and discharging phases in two-point control. A charging phase lasts longer than usual, e.g. due to an electrical connection that is temporarily interrupted and/or has an increased electrical resistance and the associated, temporarily reduced current flow (due to the loose contact). It is possible that the system is still within the limits of stable operation. However, preventive detection of errors due to system changes is possible.

The spectrum of variables that can be diagnosed is not limited to changes in resistance. For example, short turns (reduction in inductance and electrical resistance) in the coil can also be detected.

und in der Entladephase der Formel $$iL\left(t\right)=I_0\text{exp}\left(-t/\tau \right),$$

jeweils mit τ=L/R, einer Exponentialfunktion.The duration of the charging and discharging phases is determined by electrical properties (including inductive ity, electrical resistance, operating voltage, etc.) and mechanical properties (e.g. armature movement) of the system are determined. In principle, the current curve i _L (t) in the charging phase follows the formula $$i_L\left(t\right)=I_0\left(1-\text{ex}\left(-t/\tau \right)\right),$$

and in the discharge phase of the formula $$iL\left(t\right)={\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="DE102021214003A1\_0004.png"\; state="\{\{state\}\}">I</figure-callout>}}_0\text{ex}\left(-t/\tau \right),$$

each with τ=L/R, an exponential function.

Changes in operating conditions, in particular mechanical, magnetic and/or electrical operating conditions, are reflected in changes in the charging and discharging durations. The current levels that determine the beginning and end of a charging/discharging phase can usually be freely selected. They should only be (at least almost) constant over the period under consideration. This consideration generally refers to charging and discharging phases, so that these can not only be within the current control around a constant current level, but also at the beginning or end of current control phases in order to reach the desired (new) current levels (e.g. initial rise time, current settling time). in the freewheeling phase between two current control phases with different current levels, etc.).

In order to hide undesired effects (e.g. reversal processes), it is particularly advantageous to consider only a part of the entire energization range, i.e. only a specific operating phase of the coil (e.g. the holding phase mentioned or only a part there).

During operation, for example, the dynamics, i.e. the change, scatter or fluctuation within an operating phase under consideration, the aforementioned durations of the charging and discharging phases or the control phases in general are evaluated, e.g. within the holding phase. This can then be compared with an expected dynamic (or an expected or permissible maximum fluctuation). The expected dynamics are preferably determined by those (usually known) operating conditions (i.e. process engineering conditions) or specified or selected depending on them, which have a significant impact on the durations of the process during normal operation of the technical process (in which the coil-operated actuator is located). have charging and discharging phases. Electrical component parameters (e.g. electrical, magnetic resistances, inductance) may be included as constants or dependent values. In particular, this means that the dynamics become indeterminate (and thus deviate) if an unconsidered variable (e.g. total electrical resistance) exerts an additional influence (as a disturbance variable) in the process. These operating conditions can be, for example, one or more of the following: An armature position and/or armature movement (including the hydraulic support, which includes a dependence on the operating point of the internal combustion engine), an ambient, fuel, and/or coil temperature, and operating voltage fluctuations.

The lower the dynamics to be expected (or fluctuation of the time durations relative to one another), the greater the selectivity or recognition sensitivity of the proposed method. Ideally, a measurement section is selected in which, with an intact system, the time durations considered (of the control phases) have no or very little dynamics. A combination of different measurement sections in the evaluation is also advantageous.

Any additional dynamics or variation in time durations - in the measurement results, in addition to an expected dynamic - is a sign of a deviation from normal. The cause can be narrowed down by quantifying or categorizing the (additional) dynamics.

It is particularly advantageous to use one or more of the following variables for this: an absolute fluctuation in the durations, e.g. of the charging or discharging phases relative to one another, including the measured maximum/minimum values; an absolute fluctuation in the period lengths calculated from the rise and fall times (duration of the charging or discharging phase) or the resulting control frequency of the current or two-point control in the holding phase; Fluctuations in the specified time durations related to a period of time, e.g. for hiding slower processes (e.g. temperature influences); a frequency of dynamic boundary crossings per time; and a distribution of the dynamics, e.g. across operating points of the high-pressure pump and/or the internal combustion engine. Furthermore, the absolute (static) values of the durations of the charging and/or discharging phases can also be used for calculations of technical parameters or can be derived from this diagnostic information. For example, the evaluation can be staged: First, dynamic components are evaluated in order to rule out contact and/or cable problems or interturn faults. If this analysis can be completed without findings, a calculation of operating variables (e.g. temperature, operating voltage, etc.) is conceivable.

The durations and/or the fluctuations in the durations can also be determined using methods based on artificial intelligence or machine learning (eg using artificial neural networks), and the parameters can be determined based thereon and errors can be inferred. In this case, no direct comparison with thresholds or expected values is necessary; instead, characteristic features of signal patterns can be recognized.

The accuracy of the proposed method can be increased in particular by the fact that influencing factors are modeled more precisely, that influencing factors are masked out by a specific selection of the measurement section to be evaluated because their effect is not relevant in the measurement section in question, and/or that a measurement duration is selected in which certain, slowly changing influencing factors can be assumed to be constant.

In the case of an electromagnetic actuator, for example, it is advantageous to consider the charging and discharging times in the holding phase of the energization. In this measurement section, the armature is fixed in its upper end position in an advantageous configuration of the control and does not move, so that an almost constant inductance and no counter-induction due to an armature movement can be assumed.

In a further advantageous embodiment, the influence of the operating voltage can be minimized by analyzing the duration of the discharge phase. A discharging process usually follows immediately after a charging phase ended by a (known) current threshold, which thus determines the initial conditions of this discharging phase. It is possible that these initial conditions (current threshold) differ slightly, which may be due to signal propagation times within the hardware or software. In this case, a correction depending on e.g. the current increase at the switch-off point of the charging process is advantageous.

The measurement sections considered can move within one or also over several current application phases. It can be advantageous to dimension the measuring sections sufficiently large compared to the dynamics of the effects of loose contacts or short turns, for example, but sufficiently small compared to slow influencing variables (e.g. temperature) that are to be factored out, so that their change in the measuring section is not significant affect the result. If slow influencing variables are the focus of the recording, correspondingly large measurement sections must be defined. As mentioned, static values can also be evaluated.

In summary, an evaluation of measured current supply parameters such as charging and discharging phases (switch-on and switch-off times) is possible with e.g. two-point control. Ideally, a measurement section with little process-related influence (e.g. no armature movement) is used for the evaluation. For example, it can be determined without additional hardware (e.g. sensors) whether the electrical resistances of all components in the relevant circuit of the coil have a constant value within limits (i.e. with fluctuations within certain limits). In addition to loose contacts, changing electrical resistance values can indicate oxidation or wear of the contact material at contact points or changes in the cross-section of electrical conductors, for example due to fraying and partially or completely breaking conductors in the aforementioned circuit, e.g. due to the ingress of water or mechanical vibration. This information or derivations or conclusions from it can be made available to an executing control unit as diagnostic information (e.g. status of loose contact) for further processing. Reliable detection of unstable contact conditions makes it possible to take preventive measures before a complete failure or unstable operating conditions.

A computing unit according to the invention, e.g. a control unit of a motor vehicle, is set up, in particular in terms of programming, to carry out a method according to the invention. A suitable circuit such as an ASIC can also be used.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is advantageous because this causes particularly low costs, especially if an executing control device is also used for other tasks and is therefore available anyway. Finally, a machine-readable storage medium is provided with a computer program stored thereon as described above. Suitable storage media or data carriers for providing the computer program are in particular magnetic, optical and electrical storage devices such as hard drives, flash memories, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.). Such a download can be wired or wired or wireless (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).

Further advantages and refinements of the invention result from the description and the attached drawing.

The invention is shown schematically in the drawing using an exemplary embodiment and is described below with reference to the drawing.

character list

• 1 shows schematically an electromagnetic actuator in which a method according to the invention can be carried out.
• 2 shows schematically a current flow in a coil of an electromagnetic actuator.
• 3 shows a part of the current flow diagram 2 for a more detailed explanation of a method according to the invention in a preferred embodiment.
• 4 shows schematically a sequence of a method according to the invention in a preferred embodiment.

embodiment(s) of the invention

In 1 An exemplary electromagnetic actuator 10 is shown schematically, which can be used, for example, in or as an electric suction valve for a high-pressure pump in a fuel injection system. The electromagnetic actuator 10 includes an electromagnet 20 with a coil 30 that can be energized. A magnet armature or armature 40 can be moved by the energization in order, for example, to open or close a valve opening or to move an electrical contact.

In addition, a computing unit 80 is shown, e.g. a control unit for the fuel injection system mentioned or an internal combustion engine, by means of which (among other things) the electromagnetic actuator 10 can be controlled.

In 2 is a schematic of a current flow in a coil of an electromagnetic actuator (eg an electric suction valve), such as that of 21 shown. For this purpose, a current I in the electromagnet or in the coil is plotted against a time t. In this case, an actuation is shown which initially takes place with an inrush current I _A , as a result of which the magnet armature is raised.

Activation with the inrush current is then terminated at a certain point in time (which is no longer relevant here), with the current dropping in a freewheeling phase and then at point in time t ₀ merging into a holding phase with holding current I _H . It can be seen that the current is not constant for both the pull-in phase and the holding phase, but fluctuates between two limits. This is due to the two-point current control used.

In 3 is a schematic of part of the current curve 2 for a more detailed explanation of a method according to the invention in a preferred embodiment, in particular from the point in time t ₀ at which the holding phase begins. In addition to the current I, a voltage or control voltage U applied to the coil is also plotted over time.

In particular, an upper current or limit value I _O and a lower current or limit value I _U are shown here, upon reaching which the voltage is switched off (when exceeded I _O ) or switched on (below Iu); this can be recognized by the change in voltage between a value U ₀ and 0. This results, for example, in a (very short) charging phase L (shown here) and a (longer shown here) discharging phase E, in which the coil is charged and discharged so that the current rises and falls again. Basically, this is done according to the formulas mentioned above. Such a current control method is referred to as two-point current control.

As can also be seen, these two phases, charging and discharging, alternate; these are two different types of control phases. The current I is thus adjusted to an average value, the holding current I _H . A charging phase forms a period T together with the subsequent discharging phase. The durations of the charging or discharging phase are denoted by Δt _L (charging or rise time) or Δt _E (discharging or fall time).

The durations ΔtL or ΔtE of the charging or discharging phase are now determined, for example by corresponding current or voltage measurement or by time measurement of state changes of comparators based on analog comparisons with respective (analog) reference variables. However, some charging or discharging phases (or periods T, here two periods T as an example) can be disregarded when measuring or determining the durations, since there is still a certain dynamic after the free-running phase or its effects are expected. In the present case, a measurement window M should only start at time t ₁ from which the durations of the charging and discharging phase are determined. It is also important to ensure that, if possible, only full control phases, i.e. full charging or discharging phases, are taken into account; for example, the last The period that is no longer completely in the measurement window M is no longer taken into account, since a transition to a phase other than the holding phase is already taking place there. The number of charging and discharging phases can preferably be selected to be the same in each case, but it is also possible, for example, to select one charging phase more than discharging phases.

In 4 a sequence of a method according to the invention is shown schematically in a preferred embodiment. For this purpose, several (only two in the example) durations Δt _L of charging phases are shown, which are determined in a step 400, for example. These will not be identical but will differ to some extent. Such a fluctuation is denoted by Δt, for example, which can be determined accordingly in a step 410 . For this purpose, for example, the (absolute) difference between the smallest or largest value of a mean value can be selected, or also the (absolute) difference between the smallest and the largest value. This fluctuation Δt is then compared, for example, with an expected or permissible maximum fluctuation Δt _R , ie a reference value for this. If the fluctuation Δt is greater than the expected fluctuation Δt _R , for example, an error F can be assumed in a step 420 . This can be output with a note for a repair, for example. In principle, various filter mechanisms, as are customary in digital signal processing, can be used and are advantageous for eliminating interference variables in the measurement signals.

This can be done in the same way for the discharge phases and their durations. It is also conceivable that a fluctuation is determined jointly for charging and discharging phases; a relative value can then be used here in order to take into account the different lengths of the charging and discharging phases.

Changes in various parameters typically have different effects on the charging and discharging times. For example, increases in resistance in the coil circuit increase the charging times and decrease the discharging times. A winding short circuit (reduction in the inductance as well as the electrical coil resistance) leads to reduced charging and discharging times. Increasing the operating voltage reduces the charging time, but does not affect the discharging time. From the ratios of charging and discharging times (or their changes) it is possible to estimate the current level at which the charging/discharging process took place. This can be used, for example, for plausibility checks. An evaluation of these relationships, which are only mentioned here as examples, and their chronological categorization enables a separation of temporary and/or fast (e.g. unstable contacts, interturn shorts, etc.) from slow and continuous processes (e.g. thermal). This also allows a distinction to be made according to the type of error.

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 102008002131 A1 [0003]

Claims (14)

Method for determining at least one parameter in an electric circuit of a coil (30), the coil (30) being controlled with at least one type of recurring control phases (L, E), the durations (Δt _L , Δt _E ) of the control phases (L, E) are determined, and the at least one parameter is determined based on the time periods and/or based on fluctuations (Δt) in the time periods (Δt _L , Δt _E ), in particular within a type of control phase (L, E). procedure after claim 1 , wherein an electrical fault or fault condition is determined based on absolute and/or dynamic changes in the at least one parameter. procedure after claim 2 , wherein the electrical error (F) causes an at least temporary change in at least one technical parameter in the circuit, and in particular includes a loose contact in the circuit, or wherein the electrical error (F) includes a shorted turn in the coil. Method according to one of the preceding claims, wherein physical operating variables, in particular an operating voltage, are determined based on absolute and/or dynamic changes in the at least one parameter. Method according to one of the preceding claims, in which the coil (30) is controlled as part of a current control, in particular a two-point control, for adjusting a predetermined current (I) through the coil (30). Method according to one of the preceding claims, wherein the durations and / or the fluctuations (Δt) of the durations (Δt _L , Δt _E ) are compared with expected durations and / or fluctuations (Δt _R ) and based thereon the at least one parameter is determined, and in particular whether there is an electrical fault. procedure after claim 6 , where the expected fluctuations are predetermined or selected as a function of known operating conditions. Procedure according to one of Claims 1 until 5 , wherein the durations and/or the fluctuations (Δt) of the durations (Δt _L , Δt _E ) are determined using methods based on artificial intelligence and the at least one parameter is determined based thereon, and in particular whether an electrical fault is present. Method according to one of the preceding claims, wherein the at least one type of recurring activation phase comprises charging phases (L) and/or discharging phases (E). Method according to one of the preceding claims, wherein a coil of an electromagnetic actuator (10) is used as the coil (30). procedure after claim 10 , An electromagnetic actuator of a magnet valve being used as the electromagnetic actuator (10), which in particular comprises a magnet armature (40) which can be moved by actuating the coil (30). Arithmetic unit (80) which is set up to carry out all method steps of a method according to one of the preceding claims. Computer program that causes a computing unit (80) to all method steps of a method according to one of Claims 1 until 11 to be performed when it is executed on the computing unit (80). Machine-readable storage medium with a computer program stored on it Claim 13 .

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