DE102018219642A1 - Method for determining a remaining operating time of a magnetic coil of an electromagnetic actuator - Google Patents

Abstract

The invention relates to a method for determining a remaining operating time (.DELTA.R ₁ , .DELTA.R ₄ ) of a solenoid coil of an electromagnetic actuator, in particular a valve, with each time the electromagnetic actuator is actuated by means of the solenoid coil, an operating time period (.DELTA.t) as the operating time period and a temperature T) of the magnet coil (131) can be determined during or after the actuation, the temperature (T) of the magnet coil being assigned to one of a plurality of predetermined temperature ranges (ΔT ₁ -ΔT ₇ ), the operating times (Δt) for the actuations respective temperature ranges (ΔT ₁ -ΔT ₇ ) are added separately, a step collective (ΔH ₂ ) for the different temperature ranges (ΔT ₁ -ΔT ₇ ) being formed by the operating times of all temperature ranges for each temperature range (ΔT ₁ -ΔT ₇ ) are added with higher temperature values, and for a certain temperature range ( ΔT ₁ , ΔT ₄ ) a remaining operating time (ΔR ₁ , ΔR ₄ ) of the magnet coil is determined.

Description

The present invention relates to a method for determining a remaining operating time of a magnetic coil of an electromagnetic actuator, in particular a valve, in particular a hydraulic valve.

State of the art

Valves, in particular hydraulic valves, are generally controlled using a computing unit or a corresponding control device. Such a valve has an electromagnetic drive (or actuator) and, in the case of a hydraulic valve, an associated hydraulic actuator, by means of which a predetermined size, such as e.g. a volume flow or a pressure can be set. The current for the magnetic actuator can be predetermined by applying a voltage, also in pulse width modulated form, to a magnetic coil or the corresponding turns of the magnetic actuator.

A magnetic coil is subject to aging due to constant stress and therefore generally only has a limited operating time or service life. When a maximum operating time or service life is reached, a failure of the solenoid and thus of the valve is to be expected.

Disclosure of the invention

According to the invention, a method, a computing unit for carrying it out and a computer program and a machine-readable storage medium with the features of the independent claims are proposed. Advantageous embodiments are the subject of the subclaims and the following description.

A method according to the invention serves to determine a remaining operating time - or a remaining service life or remaining service life - of a magnet coil of an electromagnetic actuator, in particular a valve, in particular a hydraulic valve or a hydraulic valve. Each time the electromagnetic actuator is actuated by means of the magnet coil, an operating period is determined as the duration of the actuation and a temperature of the magnet coil during, or possibly after, the actuation. The temperature of the magnetic coil is determined in particular on the basis of an ohmic resistance of the magnetic coil or its winding. For this purpose, the winding temperature can be calculated or suitable tables or the like can be stored or used to assign a certain temperature to a certain resistance. In particular, the resistance or the temperature can also be determined as an average over the duration of the actuation.

The temperature of the magnetic coil is then assigned to one of several predetermined temperature ranges. These several temperature ranges in particular adjoin one another, i.e. the upper limit of one temperature range also forms the lower limit of the next temperature range. Overall, the temperature ranges should cover the entire range of temperatures that can occur during operation of the magnetic coil. Depending on the specific operating mode, a magnetic coil can heat up to different degrees due to the current flow. The width of a temperature range can be selected depending on the desired accuracy of the proposed method. These can all have the same width, for example.

It is also conceivable, for example in the case of a longer-lasting actuation process in which the temperature changes (greatly), to split such an actuation process into two or more separate actuations or actuation processes in the sense of the aforementioned actuation and to assign them to different temperature ranges in order to obtain a more precise result to obtain.

Furthermore, the operating times for the respective temperature ranges are added separately across the actuations, ie actuation for actuation. In other words, the operating time of a current actuation is added to the already existing operating durations in the temperature range in which the current temperature falls during the current actuation. From this, a so-called step collective for the different temperature ranges is formed by adding the operating times of all temperature ranges with higher temperature values for each temperature range. Thus, a so-called total frequency of the operating times is obtained for each temperature range, which includes the operating times of the higher temperature ranges. For the highest temperature range, this only results in the sum of the operating times in this temperature range. For the second highest temperature range, the total of the operating times in the highest temperature range results, supplemented by the total of the operating times in this second highest temperature range. This principle is also known under the concept of linear damage accumulation, in which it is assumed that a different degree of damage - here the different temperature ranges - causes different degrees of damage. For a descriptive explanation of this, be on at this point also refer to the figures and the associated description.

As a simple example it can be mentioned that the magnetic coil is damaged more at a higher temperature within a certain operating time than at a lower temperature. Accordingly, a shorter maximum operating time or service life is to be expected when operating at a higher temperature than when operating at a lower temperature.

A remaining operating time of the magnetic coil is then determined for a specific temperature range. For this purpose, in particular for the specific temperature range and all temperature ranges with lower temperature values, based on a theoretical maximum operating time of the magnetic coil in the respective temperature range (i.e. for the specific temperature range and all temperature ranges with lower temperature values) and the previous operating time according to the step collective in the respective temperature range Operating time determined in the respective temperature range.

The theoretical maximum operating time of the magnetic coil in the respective temperature range is determined in particular on the basis of a life model of the magnetic coil. This is based on the assumption that the solenoid coil is subjected to different loads at different temperatures, which leads to a different maximum operating time or service life depending on the temperature. Such a model usually results in a smooth course, which has a longer maximum operating time with decreasing temperature. In order to assign such a theoretical, maximum operating time of the magnetic coil to a temperature range, an average temperature value can be selected from the temperature range, for which the theoretical maximum operating time is taken from the model. Constants or parameters for the service life model, in order to be able to determine the theoretical maximum operating time for different temperatures, are generally to be determined for a specific type of magnetic coil or electromagnetic actuator, for example by simulation and / or test measurements.

It should also be considered that a remaining operating time or remaining service life is also determined for the specific temperature range, which can be obtained directly from the model by the associated maximum operating time, but that an even shorter, remaining operating time is available even at lower temperature ranges can be. On the basis of the previously explained procedure for determining the tier collective, the shortest remaining lifespan ascertained must be selected, i.e. the remaining operating time of the temperature ranges which has the lowest value is used as the remaining operating time of the magnetic coil.

The remaining operating time of the magnetic coil (for the specific temperature range) can preferably be determined as a quotient or as a difference from the previous operating time according to the step collective and the theoretical maximum operating time of the magnetic coil in the relevant temperature range. In other words, the remaining operating time is given as a proportion of the theoretical maximum operating time, or as an absolute value, for example as a number of remaining operating hours for this specific temperature range.

In the practical application of the proposed method, the value of the remaining operating time of the magnetic coil determined in this way can then be displayed, for example, on a suitable display, so that a user can estimate when the magnetic coil or the electromagnetic actuator or the component containing this actuator or a Component of the actuator is to be replaced.

The specific temperature range used can be, for example, the temperature range that occurs most recently when actuated, or else the current temperature range. It is of course also conceivable that the remaining service life is determined and possibly displayed for several or even all predetermined temperature ranges in the manner described, for example also in graphic form.

The proposed method thus enables, in particular, a reading of the (previous) stress on the magnetic coil and a prediction of the remaining service life. In addition, status detection is possible without changes to the control of the electromagnetic actuator, and the method can also be implemented in a higher-level, for example also remote computing unit (for example cloud) or in the firmware of a corresponding control unit of the electromagnetic actuator. A warning function and / or an indication of an impending replacement of the magnetic coil or the electromagnetic actuator are also conceivable. An implementation in a model of other damage mechanisms (such as switch-off voltage peaks) is also conceivable. Overall, the field of application of the electromagnetic actuator or the component containing this actuator or a component of the actuator can also be expanded, since a user can use higher ambient temperatures, for example, however, the component containing the electromagnetic actuator, such as the valve, has to be changed more often.

A computing unit according to the invention, e.g. a control device for an electromagnetic actuator or the component containing the actuator is, in particular in terms of programming, set up to carry out a method according to the invention.

The implementation of a method according to the invention in the form of a computer program with program code for carrying out all method steps is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and is therefore present anyway. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories, such as Hard drives, flash memory, EEPROMs, DVDs etc. It is also possible to download a program via computer networks (internet, intranet, etc.).

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

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the present invention.

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

Figure list

• 1 shows schematically a valve with a magnetic coil, in which a method according to the invention can be carried out.
• 2nd shows schematically a diagram with step collective and life model to explain a method according to the invention in a preferred embodiment.

Detailed description of the drawing

In 1 is schematically a valve 100 Shown as a component containing an electromagnetic actuator, in which a method according to the invention can be carried out. The valve 100 is designed as a hydraulic directional control valve and has a slide 110 on, which can be moved in a housing to pressure connections P for a pump, T for a tank and work connections A and B suitable to connect with each other.

The slider 110 is attached to a housing end by means of a spring 120 with a restoring force and at another end of the housing by means of an electromagnet 130 which in turn is a magnetic coil 131 has, with an adjusting force. Slider 110 and electromagnet 130 form the electromagnetic actuator.

On the electromagnet 130 or the solenoid 131 becomes a tension U created the slider 110 depending on the value of the voltage. Furthermore, there is a computing unit designed as a control unit 150 provided to the tension U to the solenoid 131 to create and control the valve.

Furthermore, the through the solenoid 131 flowing current I. to be captured from a quotient of tension U and electricity I. to detect a current ohmic resistance of the magnetic coil. A temperature of the magnetic coil can thus be determined.

In 2nd is a diagram of a step collective and lifetime model for explaining a method according to the invention in a preferred embodiment is shown schematically. There is a temperature for this T plotted over a time t.

As already mentioned, the so-called linear accumulation of damage is used to predict the remaining operating time or lifespan of mechanical components that are subject to an oscillating load. In the present case, this can also be applied to the magnetic coil.

The basic idea behind this damage accumulation is that each vibration amplitude leads to partial damage to the component. All in all, these individual and repetitive stresses eventually lead to component failure. For a valve or hydraulic valve, therefore, as soon as it is actuated electrically, a current flows through the magnet coil, which leads to heating due to the ohmic resistance of the magnet coil or its winding. The temperature changes in turn lead to strains and stresses, which in turn lead to mechanical stress and ultimately to failure, e.g. due to cable breakage, insulation damage and the like.

For each actuation, both the duration of this actuation, and thus an operating duration, and a temperature of the magnetic coil during this actuation are determined. As already mentioned, the temperature can be obtained by determining the ohmic resistance.

Each of these individual periods or operating periods in which 2nd With Δt is then assigned to one of several predetermined temperature ranges. The temperature ranges are in 2nd seven temperature ranges as examples ΔT ₁ to ΔT ₇ shown where ΔT ₁ corresponds to the temperature range with the highest temperature values. Depending on the operation, a different temperature can be set, which in turn means that the operating time is assigned to a different temperature range.

wobei i der Index für den entsprechenden Temperaturbereich ist und im gezeigten Beispiel von 1 bis 7 läuft. Anzumerken ist, dass die einzelnen Betriebsdauern Δt naturgemäß nicht gleich groß sein müssen, vorliegend der Einfachheit halber jedoch nicht näher unterschieden werden.The individual operating times Δt in the respective temperature ranges are then added up separately for the respective temperature ranges. The total operating times for the respective temperature ranges are included Δt ₁ to Δt ₆ shown, it should be noted that there is no temperature range in the example shown ΔT ₇ assigned operating time there. The following applies: $$\Delta t_i={\displaystyle \sum \Delta t\left(\Delta {\text{T}}_i\right)},$$

where i is the index for the corresponding temperature range and runs from 1 to 7 in the example shown. It should be noted that the individual operating times Δt naturally do not have to be the same size, but in the present case, for the sake of simplicity, no further distinction is made.

wobei Δt₀=H₀=0 gilt. In der Figur ist beispielhaft die Betriebsdauer H₂ gemäß Stufenkollektiv für den Temperaturbereich T₂ gezeigt. Wird nun also - anschaulich in Bezug auf das im Diagramm gezeigte Stufenkollektiv gesprochen - bei einem bestimmten Temperaturbereich eine Betriebsdauer hinzugefügt, so verschiebt sich das Stufenkollektiv für diesen bestimmten Temperaturbereich und alle niedrigeren Temperaturbereiche um diese Betriebsdauer nach rechts.The step collective mentioned is now obtained by adding the operating times of all temperature ranges with higher temperature values for each temperature range. An operating time H _i according to the step collective for a specific temperature range T _i thus results according to $$H_i=\Delta t_i+H_{i-1}={\displaystyle \sum _{n=0}^i\Delta t_n},$$

where Δt ₀ = H ₀ = 0 applies. The figure shows, by way of example, the operating time H ₂ according to the step collective for the temperature range T ₂ . So if - clearly speaking with reference to the step collective shown in the diagram - an operating time is added for a certain temperature range, the step collective shifts to the right for this specific temperature range and all lower temperature ranges by this operating time.

Dabei stellen A und B Konstanten dar, die vom konkreten Ventil bzw. der konkreten Magnetspule abhängen und für einen bestimmten Typ von Ventil beispielsweise durch Simulation und/oder Versuche ermittelt bzw. festgelegt werden können. Gleiches gilt für den Beanspruchungsfaktor S. E_a/kT bezeichnet den sog. Arrhenius-Exponenten, bei dem die Temperatur T eingeht, und der im Übrigen auch spezifisch für einen bestimmten Typ von Ventil sein kann. Damit lässt sich also für jede Temperatur eine theoretische, maximale Betriebsdauer für die Magnetspule ermitteln, was in 2 mit der Kurve M eingetragen ist.A service life model such as the Eyring model can now be used to calculate the theoretical maximum service life. According to this model, the theoretical, maximum operating time τ or at least a measure of this can be determined using the following formula: $$\tau =A\cdot \frac{1}{S}\cdot B\cdot \text{exp}\left(\frac{E_a}{k\cdot T}\right).$$

Put it there A and B Constants that depend on the specific valve or the specific solenoid coil and can be determined or determined for a specific type of valve, for example by simulation and / or tests. The same applies to the stress factor S . E _a / kT denotes the so-called Arrhenius exponent at which the temperature T received, and which may also be specific for a certain type of valve. This means that a theoretical, maximum operating time for the solenoid coil can be determined for each temperature 2nd is entered with the curve M.

Based on 2nd it is now also clearly visible that when the step collective is touched - as mentioned, it shifts to the right with each newly added operating time - with curve M the maximum operating time of the solenoid coil has been reached.

Correspondingly, however, a remaining operating time can also be determined for each temperature range in the step collective, which results from the difference between the theoretical, maximum operating time in the temperature range and the total operating time according to the step collective in the temperature range. This is an example for the temperature ranges ΔT ₁ and ΔT ₄ with the remaining operating times Δ _R and ΔR ₄ shown.

As has also already been explained, a remaining operating time of the valve for a specific temperature range can now be determined by using the remaining operating time of the temperature ranges from the remaining operating times of the specific temperature range and all temperature ranges with lower temperature values.

Although a valve in the figures 100 is shown and described as the component containing the electromagnetic actuator, it goes without saying that the invention is advantageous for electromagnetic actuators in any components.

Claims (10)

Method for determining a remaining operating time (ΔR ₁ , ΔR ₄ ) of a magnet coil (131) of an electromagnetic actuator, wherein each time the electromagnetic actuator is actuated by means of the magnet coil (131), an operating time (Δt) as The duration of the actuation and a temperature (T) of the magnet coil (131) are determined during or after the actuation, the temperature (T) of the magnet coil being assigned to one of a plurality of predetermined temperature ranges (ΔT ₁ -ΔT ₇ ), with the actuations being omitted the operating times (Δt) for the respective temperature ranges (ΔT ₁ -ΔT ₇ ) are added separately, a step collective (ΔH ₂ ) for the different temperature ranges (ΔT ₁ -ΔT ₇ ) being formed by (ΔT ₁ -ΔT ₇ ) the operating times of all temperature ranges with higher temperature values are added, and a remaining operating time (ΔR ₁ , ΔR ₄ ) of the magnet coil (131) is determined for a specific temperature range (ΔT ₁ , ΔT ₄ ). Procedure according to Claim 1 Wherein the remaining operating time (.DELTA.R _1, .DELTA.R ₄₎ of the magnetic coil ₍₄ .DELTA.T _1, .DELTA.T) determined for the specific temperature range by ₍₄ .DELTA.T _1, .DELTA.T) and all temperature ranges with lower temperature values in each case based on the specific temperature range, a theoretical , maximum operating time of the magnetic coil (131) in the respective temperature range (ΔT ₁ , ΔT ₄ ) and the previous operating time according to the step collective (ΔH ₂ ) in the respective temperature range (ΔT ₁ , ΔT ₄ ), a remaining operating time (ΔR ₁ , ΔR ₄ ) is determined in the respective temperature range, the remaining operating time (ΔR ₁ , ΔR ₄ ) of the magnetic coil (131) being the remaining operating time of the temperature ranges which has the lowest value. Procedure according to Claim 1 or 2nd , the theoretical, maximum operating time of the magnet coil in the respective temperature range (ΔT ₁ , ΔT ₄ ) being determined on the basis of a life model (M) of the magnet coil. Procedure according to Claim 3 , whereby a model according to Eyring is used as the life model (M). Method according to one of the preceding claims, wherein the remaining operating time (ΔR ₁ , ΔR ₄ ) of the magnetic coil (131) as a quotient or as a difference from the previous operating time according to the step collective (ΔH ₂ ) and the theoretical maximum operating time of the magnetic coil (131) in the relevant temperature range (ΔT ₁ , ΔT ₄ ) is determined. Method according to one of the preceding claims, wherein the temperature (T) of the magnet coil (131) is determined on the basis of an ohmic resistance of the magnet coil (131). Method according to one of the preceding claims, wherein the electromagnetic actuator is used to actuate a valve (100), in particular a hydraulic valve. Computing unit (150) which is set up to carry out a method according to one of the preceding claims. Computer program which causes a computing unit (150) to implement a method according to one of the Claims 1 to 7 to be carried out when it is executed on the computing unit (150). Machine-readable storage medium with a computer program stored on it Claim 9 .

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