EP3394866B1 - Determination of armature stroke by measurement of hysteresis characteristics - Google Patents

Description

The present invention relates to a method for determining the armature stroke on an electromagnetically actuated valve and a method for determining a hysteresis curve of such a valve.

State of the art

With modern, fast-switching electromagnetic valves, such as those used in diesel injection valves, for example, precise knowledge or setting of the armature stroke is necessary for optimal functionality of the valve. The anchor stroke should be between a lower threshold and an upper threshold. If the armature stroke is too small, the valve will throttle. If the armature stroke is too large, closer bouncing can occur.

From the DE 10 2012 206 484 A1 and from the DE 10 2013 223 121 A1 electromagnetic fuel injectors with measuring systems for the armature stroke are known. These measuring systems transmit the lifting movement of the armature with additional transmission elements to a measuring device.

DE 10 2010 063 009 A1 discloses a method for determining the point in time of the start of a movement of a fuel injector having a coil drive for an internal combustion engine of a motor vehicle, the method including detecting a current curve through a coil of the coil drive, detecting a voltage curve of a voltage applied to the coil, determining a magnetic hysteresis curve based on the recorded current curve and the recorded voltage curve, comparing the determined magnetic hysteresis curve with a first predetermined magnetic hysteresis curve, which is characteristic of a fuel injector fixed in a first end position, and determining the point in time of the start of the movement based on the comparison of the determined magnetic hysteresis curve with the first specified magnetic hysteresis curve.

Disclosure of the invention

The present invention consists in a method for determining a hysteresis curve of an electromagnetically actuated valve according to claim 1 and in a method for determining the armature stroke of an electromagnetically actuated valve according to claim 13. Preferred method features are specified in the dependent claims. These methods are to be considered with a view to the production of an electromagnetically actuatable valve from an electromagnet, an armature that can be moved by the electromagnet and a valve body. The valve body contains means for converting a movement of the armature into a Open or close the valve. The electromagnet and the armature are inserted into the valve body.

According to the invention, before the electromagnet is inserted into the valve body, a magnetic hysteresis curve of a combination of the electromagnet with a test armature resting on this electromagnet is recorded. The slope m _{1 of} a first, essentially linear curve section of the hysteresis curve in the unsaturated state is determined. The test armature preferably has the same dimensions and the same magnetic properties as the armature of the valve.

From the slope m ₁ , the slope m ₁ ^{* of} a curve section corresponding to the first curve section of a hysteresis curve of the fully assembled valve with the armature permanently in contact with the electromagnet is determined.

The electromagnet and the armature jointly form a magnetic circuit with a magnetic flux Ψ that can be determined, for example, directly via an additional measuring coil or indirectly by integrating the voltage U _ind = U _K -I · R induced in the electromagnet over time. Here U _{K is} the terminal voltage across the electromagnet, I the current through the electromagnet and R the ohmic resistance of the electromagnet. The ohmic resistance R of the electromagnet can for example be determined in a phase of constant current I according to R = U _K / I.

The dependence Ψ (I) of the magnetic flux Ψ on the current I through the electromagnet shows a typical ferromagnetic hysteresis loop, since magnetic energy is stored at least in the ferromagnetic core of the electromagnet and in the ferromagnetic armature. If an air gap is formed between the armature and the electromagnet as a result of the armature falling from the electromagnet to a rest position, this air gap also contains a magnetic energy amount ΔE, which depends on the width of the air gap and thus on the armature stroke AH sought. This energy contribution ΔE is reflected in a change in the ferromagnetic hysteresis curve and can therefore be evaluated from the comparison of hysteresis curves that were measured with and without an air gap.

However, once the valve has been fully assembled, a complete hysteresis curve of the magnetic circuit with the armature permanently in contact with the electromagnet can no longer be measured. Especially in the curve section of the hysteresis curve, which represents the unsaturated state of the electromagnet and in which the flux Ψ depends essentially linearly on the current I, the restoring force of the valve, which can be a spring force, outweighs the magnetic force that the armature on the Attracts electromagnet. The armature returns to its rest position, and the actual state to be examined, in which the armature is in contact with the electromagnet, is lost. In order to record a hysteresis curve in this state, it would be necessary to hold the armature mechanically on the electromagnet against the restoring force. For this purpose, the armature is no longer accessible in the fully assembled state of the valve.

The inventors have recognized that the curve section of the hysteresis curve with the armature permanently attached to the electromagnet, which represents the unsaturated state of the electromagnet and in which the flux Ψ depends essentially linearly on the current I, can be obtained at least approximately by the electromagnet before assembly is placed in the valve on a test anchor and the hysteresis curve is measured with this. This curve section is essentially characterized by its gradient m ₁ . From this, the slope m ₁ ^{* of} the corresponding curve section of a hysteresis curve of the fully assembled valve with the armature permanently attached to the electromagnet, which is no longer accessible for direct measurement, can be determined in various ways. In this respect, the slope m ₁ obtained before the assembly of the valve is a very important reference value which, after the assembly of the valve, enables the armature stroke AH of the valve to be measured in a particularly simple and transparent manner.

und hieraus ergibt sich der Ankerhub AH als $$\mathrm{AH}=\frac{2\cdot \mathrm{\Delta }E\cdot n^2\cdot {\mu }_0}{{\mathrm{\Psi }}^2\cdot \left(\frac{1}{A_1}+\frac{1}{A_2}\right)}=\frac{n^2\cdot {\mu }_0}{\left(\frac{1}{A_1}+\frac{1}{A_2}\right)}\cdot \left(\frac{1}{m_0}-\frac{1}{m_1^{\ast }}\right).$$

If a curve section of the hysteresis curve representing the unsaturated state of the electromagnet is traversed in the fully assembled state of the valve, the valve has a slope m ₀ which is less than the slope m ₁ ^* . The reason for this is that an air gap has formed due to the armature falling away from the electromagnet and the amount of energy ΔE is stored in this air gap has been. From the area between corresponding curve sections with gradients m ₀ or m ₁ ^* , the amount of energy ΔE, and thus ultimately the armature stroke AH sought, can be evaluated. The amount of energy ΔE is given by $$\mathrm{\Delta }\mathrm{E.}=\frac{{\mathrm{<figure-callout\; id="2"\; label="\Psi "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\Psi </figure-callout>}}^2}{2}\cdot \left(\frac{1}{m_0}-\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">m</figure-callout>}}_1^{\ast }}\right),$$

and this results in the armature stroke AH as $$\mathrm{AH}=\frac{2\cdot \mathrm{\Delta }\mathrm{E.}\cdot {\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}^2\cdot {\mathrm{<figure-callout\; id="0"\; label="\mu "\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_0}{{\mathrm{<figure-callout\; id="2"\; label="\Psi "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\Psi </figure-callout>}}^2\cdot \left(\frac{1}{{\mathrm{A.}}_1}+\frac{1}{{\mathrm{A.}}_2}\right)}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}^2\cdot {\mathrm{<figure-callout\; id="0"\; label="\mu "\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_0}{\left(\frac{1}{{\mathrm{A.}}_1}+\frac{1}{{\mathrm{A.}}_2}\right)}\cdot \left(\frac{1}{m_0}-\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">m</figure-callout>}}_1^{\ast }}\right).$$

Here n is the number of turns of the coil of the electromagnet. µ ₀ is the magnetic permeability of the vacuum. A ₁ and A ₂ are cross-sectional areas of the air gap that are independent of its width, that is, of the armature stroke AH.

Thus, the preservation of m ₁ as a reference value before the valve is installed and the subsequent determination of m ₁ ^* from m ₁ enables the armature stroke AH to be determined on the finished valve by determining m ₀ from a further hysteresis curve. For the sake of clarity, a hysteresis curve of the magnetic circuit, which is recorded in the fully assembled state of the valve, is referred to below as the "hysteresis curve of the valve".

In a particularly advantageous embodiment of the invention, the slope m ₁ ^{* is} determined from the slope m ₁ via a predetermined first functional relationship. In the simplest approximation, it can be assumed, for example, that m ₁ ^{* is} identical to m ₁ . This approximation is already accurate enough for many applications. If, for example, the valve body and / or the means for converting a movement of the armature to opening or closing the valve contain ferromagnetic materials, then these materials influence the magnetic flux Ψ of the magnetic circuit, and thus also m ₁ ^* . The first functional relationship can advantageously be refined in such a way that this influence is taken into account. The more precisely m ₁ ^{* is} determined, the more precisely the armature stroke AH can be determined from this.

In a particularly advantageous embodiment of the invention, to determine the first functional relationship, at least one completely assembled The armature of the solenoid valve was determined and the hysteresis curve was recorded in this state. This valve is a special test or data entry copy which differs from the series-produced valves in that the armature stroke AH is always zero and the valve cannot switch. Apart from this difference, the valve behaves magnetically exactly like the series-produced valves. Ideally, the first hysteresis curve is recorded on the magnetic circuit of a valve before assembly and m _{1 is} determined from this, and after this magnetic circuit has been assembled in the valve, the second hysteresis curve is recorded and m ₁ ^{* is} determined from this.

The slope m ₁ ^* can also be obtained, for example, from the slope m ₁ by using numerical methods, such as the finite element method, to calculate the influence of other ferromagnetic materials in the valve on the magnetic circuit formed by the electromagnet and armature.

Alternatively or in combination with this, m ₁ ^{* can} also be refined by comparing reference values of further variables determined before the valve was installed with values of these variables determined after the valve was installed.

Therefore, in a further particularly advantageous embodiment of the invention, the slope m _{2 of} a second linear curve section of the hysteresis curve, which is recorded on the combination of the electromagnet with the test armature, is determined in the saturated state before the electromagnet is inserted into the valve body. Furthermore, the current value I ₀ is advantageously also determined, at which a linear continuation of the second curve section to the current axis I intersects the current axis I.

Both variables are also accessible for measurement on the fully assembled valve, because when the electromagnet is saturated, the armature is attracted to the electromagnet, so that the magnetic circuit is in the same state as during the reference measurement on the combination of the electromagnet and the test armature.

In order to obtain a comparison value corresponding to m ₂ after the valve has been installed, a further magnetic hysteresis curve of the valve is advantageously recorded after the valve has been installed. The slope m _{3 of} a second, essentially linear curve section of the further magnetic hysteresis curve, which represents the saturated state, is determined. This second curve section corresponds to the second curve section of the magnetic hysteresis curve measured before the assembly of the valve on the combination of electromagnet and test armature.

In order to continue to obtain a comparison value corresponding to I ₀ after the valve has been installed, the current value I ₁ is also advantageously determined at which a linear continuation of the second curve section to the current axis I intersects the current axis I. The inventors have recognized that the comparison of the current value I ₁ with the current value I ₀ offers an additional possibility of quality control for the magnetic properties of the components used in the valve. In particular, it can be monitored whether the armature and / or a residual air gap disc (RLSS) arranged between the armature and the electromagnet corresponds to the desired specification. A large deviation of the current value I ₁ from the current value I ₀ can indicate a relevant standard deviation or also an undesirable particle formation on the contact surfaces of the residual air gap disc to the armature and / or to the electromagnet.

Therefore, in a further particularly advantageous embodiment of the invention, the absolute difference Δl between the current value I ₁ and the current value I _{0 is} determined and the valve is classified as faulty if this absolute difference exceeds a predetermined threshold value.

mit zwei Parametern ko und k₁ aufgestellt werden.In a further particularly advantageous embodiment of the invention is formed from the slopes m ₁ and m ₂ is a correlation and / or a second functional relationship between the slopes m ₁ and m ₂ obtained. The second functional relationship advantageously places the ratio m ₂ / m ₁ in a linear relationship with the current value I ₀ . For example, a parameterized approach to the form $${\mathrm{I.}}_0={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\cdot \frac{m_2}{{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">m</figure-callout>}}_1}+{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">k</figure-callout>}}_0$$

can be set up with two parameters ko and k ₁ .

During series examinations of electromagnets, the inventors have recognized that m ₁ , m ₂ and I ₀ , taken in and of themselves, are subject to specimen scatter. However, within a batch of electromagnets with nominally identical geometry, which were manufactured in a nominally identical manner, the correlation between m ₁ , m ₂ and I ₀ according to equation (3) with the same parameters k ₀ and k _{1 is} valid to a good approximation. The most important production parameters that have an influence on the parameters k ₀ and k ₁ are the magnetic powder used for the production of the magnet core of the electromagnet, the pressed density and any heat treatment of the magnet core.

One approach for a refinement of the original approximation that the reference value m ₁ determined before the assembly of the valve can also be used unchanged as the gradient m ₁ ^* after the assembly of the valve is to use it in the evaluation of the amount of energy ΔE and the armature stroke AH according to not to use the reference value m ₁ directly in accordance with equations (1) and (2), but rather to determine m ₁ ^* with the aid of the second functional relationship between m ₁ and m ₂ and optionally also l ₀ . If, for example, the approach according to equation (3) is made for this, the functional relationship is characterized by the parameters k ₀ and k ₁ .

ist dann ein verfeinerter Näherungswert für m₁ ^* im fertig montierten Zustand des Ventils erhältlich, der näher an dem der Messung nicht mehr unmittelbar zugänglichen Wert ist als der an der Kombination aus Elektromagnet und Prüfanker vor der Montage des Ventils ermittelte Referenzwert m₁.The parameters k ₀ and k ₁ obtained before the valve was assembled can be used, for example, by determining the slope m _{3 of} a curve section of the hysteresis curve representing the saturated state on the fully assembled valve and using it as m ₂ in equation (3) . According to $${\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">m</figure-callout>}}_1^{\ast }=\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="imgf0003.png,imgf0005.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\cdot {\mathrm{<figure-callout\; id="3"\; label="m"\; filenames="imgf0001.png,imgf0005.png"\; state="\{\{state\}\}">m</figure-callout>}}_3}{{\mathrm{I.}}_0-k_0}$$

a refined approximate value for m ₁ ^* in the fully assembled state of the valve is then available, which is closer to the value that is no longer directly accessible for the measurement than the reference value m ₁ determined on the combination of electromagnet and test armature prior to assembly of the valve.

Together with the value for m ₀ obtained when the armature has fallen on the fully assembled valve, the refined approximate value for m ₁ ^* can be used to evaluate the amount of energy ΔE and finally the armature stroke AH according to equations (1) and (2).

In a further particularly advantageous embodiment of the invention, the slope m ₁ , the slope m ₂ , the slope m ₁ ^* , and / or the first functional relationship, and / or the second functional relationship, and / or the correlation between the slopes m ₁ and m ₂ , noted on the electromagnet, and / or on a machine-readable information carrier connected to the electromagnet, and / or clearly linked to the electromagnet in a database. In particular, the functional relationship according to equation (3) can be represented by the parameters k ₀ and k ₁ . The mass production of the electromagnets can then be decoupled in a particularly simple manner from the mass production of the electromagnetically actuated valves. For example, a plant can pre-produce electromagnets for several other plants, which use them to manufacture various types of electromagnetically actuated valves. The machine-readable information carrier can for example contain a data matrix code, for example a QR code.

The decoupling of the production of electromagnets on the one hand and valves on the other hand can be simplified in a further particularly advantageous embodiment of the invention by adding a large number of electromagnets according to the value of the slopes m ₁ and / or m ₂ , and / or according to the functional relationship and / or the correlation between the slopes m ₁ and m ₂ , is classified. The functional relationship can, for example, be classified using the parameters k ₀ and k ₁ in equation (3). The classification discretizes the accuracy of the reference values for the electromagnet, but speeds up mass production, since electromagnets from one class can be processed in an identical form and no longer have to go into magnet-specific reference values. Furthermore, conspicuous electromagnets that cannot be assigned to any class according to the specification can be sorted out as scrap from the start.

According to what has been said above, the invention also relates to a method for determining the armature stroke AH on an electromagnetically actuated valve. This valve comprises an electromagnet, an armature that can be moved by the electromagnet and preferably a valve body, within which the electromagnet, the armature and means for converting a movement of the armature into opening or closing of the valve are arranged. To determine the armature stroke AH, a magnetic hysteresis curve of the valve is recorded and a first slope m _{0 of} a first linear curve section of the hysteresis curve of the valve in the unsaturated state is determined. In this state, the armature has fallen away from the electromagnet due to the restoring force effective in the valve, so that an air gap exists between the armature and the electromagnet.

According to the invention, to determine the armature stroke AH, the magnetic energy ΔE in the air gap is derived from the difference between the first slope m ₀ and a second slope m ₁ ^* of the first, essentially linear curve section, which corresponds to the first curve section of the hysteresis curve, of a further magnetic hysteresis curve which the valve would have evaluated with the armature held on the electromagnet. To determine the second slope m ₁ ^* , at least one reference value m ₁ for this slope m ₁ ^* determined before the electromagnet is inserted into the valve body can be used. The reference value m ₁ can in particular have been obtained in the context of the production method described above.

The methods disclosed in connection with the method for determining the hysteresis curve are available for determining m ₁ ^* using the reference value m ₁ .

In a further particularly advantageous embodiment of the invention, the second slope m ₁ ^{* is} derived from the slope m _{3 of} a second linear curve section of the magnetic hysteresis curve of the valve in the saturated state in connection with a functional relationship and / or a correlation between the slopes m ₁ , m _{2 of} the curve sections of the further hysteresis curve are determined. The correlation or the functional relationship can also be determined before the electromagnet is inserted into the valve body and preserved as a reference value.

For example, the functional relationship according to equation (3) can have been preserved in the form of the parameters k ₀ and k ₁ .

The method for determining the hysteresis curve, with which one or more reference values on the electromagnet are obtained and preserved before the assembly of the valve, and the method for determining the armature stroke, with which after assembly of the valve, advantageously using these reference values via the magnetic energy ΔE The armature stroke AH is evaluated in the air gap between the armature and the electromagnet, work synergistically hand in hand in order to ultimately enable an exact determination of the armature stroke AH. Through the advantageously complete measurement of hysteresis curves on all electromagnets (magnet assemblies) used and the preservation of the reference values obtained during this measurement, the influence of batch fluctuations of the components used on the accuracy of the specific armature stroke AH is minimized. The armature stroke AH determined according to the invention can particularly advantageously be used as a feedback in order to precisely set the armature stroke in the factory during the production of electromagnetically operated valves for fuel injectors and to monitor it during operation.

Further measures improving the invention are shown in more detail below together with the description of the preferred exemplary embodiments of the invention with reference to figures.

Embodiments

• Figur 1 Schematische Darstellung eines elektromagnetisch betätigbaren Ventils 1 (Figur 1a) und einer Kombination 6 aus Elektromagnet 2, 2a, 2b und Prüfanker 3a (Figur 1b);
• Figur 2 Ausschnitt der an der Kombination 6 gemessenen Hysteresekurve 10.
• Figur 3 Ausschnitt der am fertig montierten Ventil 1 gemessenen Hysteresekurve 20.
• Figur 4 In einer Reihenuntersuchung von Elektromagneten 2 ermittelter funktionaler Zusammenhang 8 zwischen dem Steigungsverhältnis m₂/m₁ und dem Stromwert I₀.
• Figur 5 Vollständige Hysteresekurve 20 des Ventils 1.
• Figur 6 Beispielhafte Einflüsse der Exemplarstreuung zwischen Elektromagneten 2 auf die Hysteresekurve 10 der Kombination 6 aus Elektromagnet 2 und Prüfanker 3a.

It shows:

• Figure 1 Schematic representation of an electromagnetically actuated valve 1 ( Figure 1a ) and a combination 6 of electromagnet 2, 2a, 2b and test anchor 3a ( Figure 1b );
• Figure 2 Section of the hysteresis curve 10 measured on combination 6.
• Figure 3 Section of the hysteresis curve 20 measured on the fully assembled valve 1.
• Figure 4 Functional relationship 8 determined in a series examination of electromagnets 2 between the slope ratio m ₂ / m ₁ and the current value I ₀ .
• Figure 5 Complete hysteresis curve 20 of valve 1.
• Figure 6 Exemplary influences of the sample variance between electromagnets 2 on the hysteresis curve 10 of the combination 6 of electromagnet 2 and test anchor 3a.

To Figure 1a the valve 1 shown here by way of example as a 2/2-way valve comprises a valve body 5 with an inlet 1a and an outlet 1b. The valve 1 switches the flow of a medium between the inlet 1a and the outlet 1b. For this purpose, an electromagnet 2 is arranged within the valve body 5 and consists of a ferromagnetic magnetic core 2a and a coil 2b wound onto the ferromagnetic magnetic core 2a. A machine-readable information carrier 7 which contains a barcode with reference values is attached to the electromagnet 2. These reference values were measured on a combination 6 of the electromagnet 2 with a test anchor 3 a before the electromagnet 2 was inserted into the valve body 5.

In the valve 1, an armature 3 is arranged relative to the electromagnet 2 in such a way that the electromagnet 2 can attract the armature 3. Via a coupling mechanism 4a, the actuator 4c of the valve 1 is then counteracted by the return force exerted by the valve spring 4b from the in Figure 1a switching position shown in which the valve 1 is closed, into the in Figure 1a switching position, not shown, in which the valve 1 is open, transferred. The coupling mechanism 4a, the valve spring 4b and the actuator 4c together form the means 4 which convert the movement of the armature 3 into opening or closing of the valve 1.

In the in Figure 1a There is an air gap 9 between the armature 3 and the electromagnet 2 shown in the closed switching position of the valve 1. If, however, the armature 3 is attracted to the electromagnet 2, this air gap 9 disappears. The width of the air gap 9 in the closed switching position in which the armature 3 has fallen from the electromagnet 2, corresponds to the armature stroke AH of the valve 1.

The electromagnet 2 and the armature 3 together form a magnetic circuit through which a magnetic flux Ψ passes. From this magnetic flux Ψ are in Figure 1a two flow lines drawn as an example.

Figure 1b shows the combination 6 of the electromagnet 2 and the test anchor 3a, on which at least the slope m _{1 of} a curve section 11 of a hysteresis curve 10 in the unsaturated state is determined as a reference value. The test anchor 3a is in Figure 1b Means not shown also kept in contact with the magnetic core 2a of the electromagnet 2 when the coil 2b of the electromagnet 2 is not energized.

Figure 2 shows a section of the hysteresis curve 10, which was recorded on the combination 6 of the electromagnet 2 and the test anchor 3a. The magnetic flux Ψ is plotted against the current I through the coil 2b of the electromagnet 2. In a first curve section 11, which represents the unsaturated state of the electromagnet 2, the hysteresis curve 10 runs essentially linearly with a gradient m ₁ , so that in this curve section 11 approximately Ψ (l) = m ₁ · l + c ₁ with a constant c ₁ applies. In a second curve section 12, which represents the saturated state of the electromagnet 2, the hysteresis curve 10 also runs essentially linearly with a slope m ₂ , so that in this curve section 12 approximately Ψ (l) = m ₂ · l + c ₂ with a Constant c ₂ holds. A linear continuation 13 of this second curve section 12 with the same slope m ₂ to the current axis I intersects the current axis I at the current value I ₀ . The in Figure 2 The section of the hysteresis curve 10 shown was recorded on the basis of the saturated state of the electromagnet 2. Starting from the highest current I through the coil 2b of the electromagnet 2, the current I was successively reduced.

Figure 3 shows a section of the hysteresis curve 20 that was recorded on the fully assembled valve 1. Analogous to Figure 1 the magnetic flux Ψ in the magnetic circuit of the valve 1 formed from the electromagnet 2 and armature 3 is plotted against the current I through the coil 2b of the electromagnet 2. Analogous to Figure 1 the highest value of the current I in the saturated state of the electromagnet 2 was assumed and the current I was successively reduced.

In the unsaturated state, the hysteresis curve 20 also has a first curve section 21 in which it runs essentially linearly with a gradient m ₀ . In this curve section 21, approximately Ψ (l) = m ₀ · l + c ₀ with a constant c ₀ applies. In a second curve section 22, which represents the saturated state, the hysteresis curve 20 also runs essentially linearly with a gradient m3. In this curve section 22, approximately Ψ (l) = m ₃ · l + c ₃ with a constant c ₃ applies. The linear continuation 23 of the curve section 22 with the same gradient m ₃ to the current axis I intersects the current axis I at the current value l ₁ .

For comparison, in Figure 3 additionally the curve section 31 of the in Figure 2 hysteresis curve 30 shown, which the fully assembled valve would have with the armature permanently in contact with the electromagnet. In this curve section 31, approximately Ψ (l) = m ₁ ^* · l + c ₁ ^* with a constant c ₁ ^* applies.

From the course of the hysteresis curve 20 starting from the second curve section 22 towards lower current values I it can be clearly seen that the falling of the armature 3 from the electromagnet 2 discontinuously reduces the magnetic flux Ψ. The reason for this is that the fall of the armature 3 forms the air gap 9 between the armature 3 and the electromagnet 2 and a magnetic energy ΔE is deposited in the air gap 9. This energy ΔE corresponds to the area between the first curve segment 21 of the hysteresis curve 20 and the first curve segment 31 of the hysteresis curve 30. The armature stroke AH sought can be determined from the energy ΔE.

Figure 4 shows the second functional relationship 8 between the slope ratio m ₂ / m ₁ and the current value l ₀ , which in a Serial examination of electromagnet 2 was determined. The second functional relationship 8 corresponds to equation (3). Each measuring point marked with a rhombus as a symbol represents an electromagnet 2 to which the second functional relationship 8 applies approximately. Each measuring point marked with a circle as a symbol represents an electromagnet 2 that deviates significantly from the second functional relationship 8. In Figure 4 two groups 8a and 8b of such outliers can be seen. Electromagnets 2 that are conspicuous in this way are preferably sorted out as rejects.

Figure 5 shows, for a better understanding, a complete hysteresis curve 20 of the valve 1 with symmetrical control. Starting from the highest current value I in the saturated state, branch 28 is first traversed towards lower current values I. First of all, the second curve section 21, which runs essentially linearly, is passed. Following this second curve section 21, the magnetic flux Ψ in the sloping curve section 24 decreases faster than linearly, before the armature 3 drops off the electromagnet 2 at point 27a due to the restoring force exerted by the valve spring 4b of the valve 1 and the air gap 9 between the armature 3 and the electromagnet 2 is formed. This can be seen in a discontinuous decrease in the magnetic flux Ψ. The branch 28 of the hysteresis curve 20 then changes over to the first curve section 21 in the unsaturated state. Here the magnetic flux Ψ runs essentially linearly with the current l.

In the lower left quadrant of Figure 5 the branch 28 of the hysteresis curve 20 changes into an increasing curve section. At point 26b the armature 3 is attracted to the electromagnet 2, which is shown by a small discontinuity in the curve.

If the current I is then increased again in the saturated state, the branch 29 of the hysteresis curve 20 is traversed. Here the hysteresis curve 20 changes again into a falling curve section 24 in which the armature 3 drops from the electromagnet 2 at point 27b. When the branch 29 of the hysteresis curve 29 crosses into the right upper quadrant, the next attractive one begins Curve section 25. At point 26a, armature 3 is again attracted to electromagnet 2.

Analogous to Figure 3 are in Figure 5 the linear continuation 23 of the second curve section 21 to the current axis I and the current value l ₁ at which the continuation 23 intersects the current axis I are also shown.

Figure 6 uses a few examples to illustrate how the specimen variance between different electromagnets 2 can influence the course of the hysteresis curve 10 of a combination 6 of the respective electromagnet 2 with the test armature 3a.

In Figure 6a deviations between a first hysteresis curve 10 and a second hysteresis curve 10a are shown of a type that can be caused, for example, by differences in the heat treatment of the magnetic cores 2a of different electromagnets 2, or by a different chemical composition of the magnetic powder used for both magnetic cores 2a . In the saturated state, which is represented by the second curve section 12, the course of the two hysteresis curves 10 and 10a is identical. Thus, the deviation in the composition of the magnetic cores 2a does not change the slope m ₂ in the second curve section 12 and also not the current value I ₀ at which the linear continuation 13 of the second curve section 12 intersects the current axis I. The courses of the first curve sections 11 and 11a in the unsaturated state are, however, different and in particular also have different slopes m ₁ .

Figure 6b shows the opposite case, that within a series of five electromagnets 2 the hysteresis curves 10, 10a-10d measured in the combination 6 with a test anchor 3a only differ significantly in the saturated state, while the hysteresis curves 10, 10a-10d practically in the unsaturated state run parallel to each other. For example, the second curve sections 12 and 12a of the hysteresis curves 10 and 10a have different slopes m ₂ in the saturated state, and the linear continuations 13 and 13a of these second curve sections 12 and 12a for The current axis I intersect the current axis I at different current values l ₀ . In contrast, the slope m ₁ in the unsaturated state is almost identical for all hysteresis curves 10, 10a-10d.

Figure 6c In contrast, shows the case that within a series of three electromagnets 2, the hysteresis curves 10, 10a, 10b measured in combination 6 with a test anchor 3a are both in their slopes m ₁ in the unsaturated area and in their slopes m ₂ in the second Clearly distinguish curve sections 12, 12a in the saturated area. Correspondingly, the linear continuations 13, 13a of the second curve sections 12, 12a for the current axis I also intersect the current axis l at different current values l ₀ .

If the specimen variance between electromagnets 2 is only shown in changes in the hysteresis curve 10 which change m ₁ , m ₂ and l ₀ in a correlated manner, the manufacturing method can be used in a simplified form. There is then no need to record a hysteresis curve 10 on each individual electromagnet 2. Instead, it is sufficient to measure a random sample of a few electromagnets 2 of a batch of nominally identically dimensioned and manufactured electromagnets 2 and from this to determine the functional relationship 8 according to equation (3). For example, reference valves in which the armature 3 is fixed as a test armature 3a on the electromagnet 2 can be used for this random sample. m ₁ can then be evaluated for all further electromagnets 2 from the batch according to equation (4).

Claims (15)

1. Method for determining a hysteresis curve of an electromagnetically driveable valve (1) made of an electromagnet (2, 2a, 2b), an armature (3) which is movable by the electromagnet (2, 2a, 2b) and a valve body (5) with means (4, 4a, 4b, 4c) for converting a movement of the armature (3) into an opening or closing of the valve (1), wherein the electromagnet (2, 2a, 2b) and the armature (3) are inserted into the valve body (5), wherein a magnetic hysteresis curve (10) of a combination (6) of the electromagnet (2, 2a, 2b) with a test armature (3a) resting against said electromagnet (2, 2a, 2b) is recorded before the electromagnet (2, 2a, 2b) is inserted into the valve body (5),
   characterized in that
   the gradient m₁ of a first, substantially linear curve section (11) of the hysteresis curve (10) is determined in the unsaturated state and in that the gradient m₁ ^* of a curve section (31) of a hysteresis curve (30), corresponding to the first curve section (11), of the fully assembled valve (1) with an armature (3) permanently resting against the electromagnet (2, 2a, 2b) is determined from the gradient m₁.
2. Method according to Claim 1, characterized in that the gradient m₁ ^* is determined from the gradient m₁ by way of a specified first functional relationship.
3. Method according to Claim 2, characterized in that, for the purposes of determining the first functional relationship on at least one fully assembled valve (1), the armature (3) is secured to the electromagnet (2, 2a, 2b) and a hysteresis curve (30) is recorded in this state.
4. Method according to any one of Claims 1 to 3, characterized in that the gradient m₂ of a second, substantially linear curve section (12) of the hysteresis curve (10) of the combination (6) is additionally determined in the saturated state, before the electromagnet (2, 2a, 2b) is inserted into the valve body (5).
5. Method according to Claim 4, characterized in that the current value I₀ at which a linear continuation (13) of the second curve section (12) towards the current axis I intersects the current axis I is additionally determined.
6. Method according to either of Claims 4 and 5, characterized in that a further magnetic hysteresis curve (20) of the valve (1) is recorded after the assembly of the valve (1) and in that the gradient m₃ of a second, substantially linear curve section (22) of the further magnetic hysteresis curve (20) in the saturated state, corresponding to the second curve section (12) of the magnetic hysteresis curve (10), is determined.
7. Method according to Claim 6, characterized in that the current value I₁ at which a linear continuation (23) of the second curve section (22) of the further hysteresis curve (20) towards the current axis I intersects the current axis I is additionally determined.
8. Method according to Claim 7 depending on Claim 5, characterized in that the absolute value of the difference ΔI between the current value I₁ and the current value I₀ is determined and the valve (1) is classified as faulty if the absolute value of the difference ΔI exceeds a specified threshold.
9. Method according to any one of Claims 4 to 8, characterized in that a correlation and/or a second functional relationship (8) between the gradients m₁ and m₂ is determined from the gradients m₁ and m₂.
10. Method according to Claim 9 depending on Claim 5, characterized in that the second functional relationship (8) establishes a linear relationship between the ratio m_2/m₁ and the current value I₀.
11. Method according to any one of Claims 1 to 10, characterized in that the gradient m₁, the gradient m₂, the gradient m₁ ^* and/or the first functional relationship and/or the second functional relationship (8) and/or the correlation between the gradients m₁ and m₂ are recorded on the electromagnet (2, 2a, 2b) and/or on a machine-readable information medium (7) connected to the electromagnet (2, 2a, 2b) and/or are clearly linked to the electromagnet (2, 2a, 2b) in a database.
12. Method according to any one of Claims 1 to 11, characterized in that a multiplicity of electromagnets (2, 2a, 2b) are classified according to the value of the gradients m₁ and/or m₂ and/or according to the second functional relationship (8) and/or the correlation between the gradients m₁ and m₂.
13. Method for determining the armature stroke (AH) in an electromagnetically driveable valve (1) which comprises an electromagnet (2, 2a, 2b) and an armature which is movable by the electromagnet (2, 2a, 2b),
    characterized in that
    a magnetic hysteresis curve (20) of the valve (1) is recorded and a first gradient m₀ of a first, substantially linear curve section (21) of the hysteresis curve (20) of the valve (1) is determined in the unsaturated state,
    wherein the magnetic energy ΔE in an air gap (9) formed between the armature (3) and the electromagnet (2, 2a, 2b), and hence the armature stroke (AH) to be determined, is evaluated from the difference between the first gradient m₀ and a second gradient m₁* of the first, substantially linear curve section (31) of a further magnetic hysteresis curve (30), which corresponds to the first curve section (21) of the hysteresis curve (20) and which the valve (1) would have if the electromagnet (2, 2a, 2b) were to be secured to the armature (3).
14. Method according to Claim 13, wherein the valve (1) comprises a valve body (5) and wherein the electromagnet (2, 2a, 2b), the armature (3) and means (4, 4a, 4b, 4c) for converting a movement of the armature (3) into an opening or closing of the valve (1) are arranged within the valve body (5), characterized in that at least one reference value m₁ for this gradient m₁*, which reference value was determined before the electromagnet (2, 2a, 2b) was inserted into the valve body (5), is used for the purposes of determining the second gradient m₁*.
15. Method according to either of Claims 13 and 14, characterized in that the second gradient m₁* is determined from the gradient m₃ of a second linear curve section (22) of the magnetic hysteresis curve (20) of the valve (1) in the saturated state in conjunction with a second functional relationship (8) and/or a correlation between the gradients m₁, m₂ of curve sections (11, 12) of a further hysteresis curve (10), which was recorded using a test armature resting against the electromagnet before the electromagnet was inserted into the valve body, where m₁ represents the gradient of a first, substantially linear curve section of this hysteresis curve in the unsaturated state and m₂ represents the gradient of a second, substantially linear curve section of this hysteresis curve in the saturated state.

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