DE102019135209A1 - Method for determining the position of an armature within a solenoid as well as a solenoid actuator - Google Patents

Abstract

A method for determining a position (x) of an armature (16) within a magnet coil (14) of a lifting magnet actuator (10) is described. At least one first pulse-width-modulated voltage pulse is applied to the magnetic coil (14) and a voltage resulting from the voltage pulse is measured across the magnetic coil (14). The position (x) of the armature (16) within the magnetic coil (14) is derived from this. A solenoid actuator (10) is also presented, a position detection unit (24) being provided, by means of which a position (x) of the armature (16) within the magnetic coil (14) can be detected. The position detection unit (24) comprises a voltage pulse source for generating a pulse-width-modulated voltage pulse.

Description

The invention relates to a method for determining a position of an armature within a magnet coil of a lifting magnet actuator.

The invention also relates to a lifting magnet actuator with a magnet coil and an armature, which is movably supported along an actuation axis within the magnet coil, a position detection unit being provided by means of which a position of the armature within the magnet coil can be detected.

Such methods and lifting magnet actuators are known from the prior art.

In this context, position detection units usually include sensors that can detect, in particular, a first end or extreme position and a second end or extreme position of the armature within the magnet coil. It can thus be determined, for example, whether the anchor is in a retracted or in an extended position. This is particularly important when the solenoid actuator is used to lock or fix a component. For example, a valve slide or a hydraulic cylinder can be locked in different positions by means of the solenoid actuator. The hydraulic cylinder can be part of a gear selector or a parking lock. The position detection unit can then be used to distinguish a blocked hold state from an unlocked release state.

The object of the present invention is to further improve a method of the type mentioned at the beginning and at the same time to specify a lifting magnet actuator which has a position detection unit that is simple and inexpensive.

The object is achieved by a method of the type mentioned at the outset, wherein at least one first pulse-width-modulated voltage pulse is applied to the magnet coil, a voltage resulting from the voltage pulse is measured across the magnet coil, and the position of the armature within the magnet coil is derived from the resulting voltage .

In this case, a pulse-width-modulated voltage pulse, in contrast to an alternating voltage pulse, is understood to mean a voltage pulse without negative components. Such a method does not require any sensors to detect the position of the armature. Accordingly, this method can also be used in connection with lifting magnet actuators that are comparatively simple and inexpensive. The method uses the physical effect that an inductance of the magnet coil is proportional to an air gap that varies with the position of the armature within the magnet coil. The smaller the air gap, the higher the inductance. There can be an essentially linear relationship between the inductance and the air gap, so that the position of the armature can easily be deduced from the inductance. The inductance can be determined explicitly or implicitly via the resulting voltage.

A specially designed electrical circuit is preferably used to carry out the method, that is to say to apply the pulse-width-modulated voltage pulse and to detect a resulting voltage. The electrical circuit for determining the position is designed in particular separately from an electrical circuit for actuating the armature.

A fixed number of first pulse-width-modulated voltage pulses is preferably applied to the magnet coil within a measurement cycle and a resulting voltage across the magnet coil is measured for each voltage pulse. An average of all the resulting stresses is used to derive the position of the armature. In this way, the resulting voltage across the magnet coil can be detected with high accuracy. The position of the armature can thus be determined just as precisely. For example, a measurement cycle for this comprises 3 to 20 first pulse-width-modulated voltage pulses. This represents a good compromise between the duration of the measurement cycle and the achievable accuracy of the measurement.

The resulting voltage across the magnet coil can also be measured with a predetermined sampling frequency. Alternatively, the resulting voltage can be determined from a resulting voltage profile across the magnet coil by using a voltage value at a point of maximum voltage drop as the resulting voltage. The sampling frequency is preferably set in such a way that the resulting voltage is recorded as possible in a range of its maximum change over time. The position of the armature can be determined with high accuracy via this voltage value.

According to one variant, the position of the armature is determined as a function of a temperature of the magnet coil. The physical effect is thus taken into account, according to which the inductance is temperature-dependent with a constant air gap. This dependency is essentially linear, the inductance increasing with increasing temperature. Since the method is to lead to precise results with regard to the position of the armature within as large a temperature range as possible, the temperature influence must be compensated. The position of the armature can thus be determined with high accuracy over a wide temperature range of the magnet coil. In this context, the electrical circuit for carrying out the method can be thermally separated from the armature and the magnet coil, that is to say from the actuator, so that the electrical circuit is subject to only slight temperature fluctuations compared to the armature and the magnet coil.

In this context, at least one second pulse width modulated voltage pulse can be applied to the magnet coil, a voltage resulting from the second pulse width modulated voltage pulse can be measured across the magnet coil, a current in the magnet coil resulting from the second pulse width modulated voltage pulse can be determined, and from the resulting voltage and the resulting current a resistance and / or a temperature of the magnet coil can be derived. Alternatively, the determination of the current can also be based on the measured voltage signal and a known, temperature-dependent resistance of the magnet coil. In both variants, a resistance of the magnet coil is calculated. This is temperature dependent. The temperature can thus be determined on the basis of the resistance. For this purpose, the calculated resistance is preferably multiplied by a correction factor. The resulting result is corrected with a correction addend. A temperature coefficient of the material of the magnet coil is preferably taken into account in the correction factor. A temperature of the magnet coil can thus be determined in a simple manner.

In connection with the previously determined voltage, which results from the first voltage pulse, the position of the armature can now be determined by multiplying the resulting voltage with the resistance and a further correction factor. The product of the resulting voltage with an additional correction factor and the product of the resistance of the magnet coil with an additional correction factor are subtracted from this. The result is offset against a correction sum.

A position value obtained in this way can preferably be corrected for quadratic temperature influences. For this, the position value obtained is corrected by a correction summand in which the temperature is entered as a square, a correction summand in which the temperature is entered linearly, and a correction summand without a unit. This results in a corrected position value.

A pulse duration of the first pulse-width-modulated voltage pulse is preferably shorter than a pulse duration of the second pulse-width-modulated voltage pulse. The pulse duration of the first pulse-width-modulated voltage pulse is, for example, 1 to 20 milliseconds. The pulse duration of the second pulse-width-modulated voltage pulse is greater and is preferably at least twice that. When it comes to the pulse duration of the second pulse-width-modulated voltage pulse, it is important that effects caused by the inductance of the magnet coil have largely subsided, so that resulting currents and voltages can be measured that essentially result from an ohmic behavior of the magnet coil. The voltages resulting from the two pulse-width-modulated voltage pulses can thus be recorded separately from one another.

A fixed number of second pulse-width-modulated voltage pulses can be applied to the magnetic coil within a measurement cycle. For each voltage pulse, a resulting voltage across the magnetic coil and / or a resulting current in the magnetic coil is measured, an average of all resulting voltages and / or all resulting currents being used to derive the temperature of the magnetic coil. The mean value can be calculated from the resulting voltages or currents within a measuring cycle. Alternatively, a moving average can be calculated over several measuring cycles. In this way, a temperature can be derived with high accuracy.

In an exemplary embodiment, a measurement cycle comprises 10 first pulse-width-modulated voltage pulses and a second pulse-width-modulated voltage pulse.

A measurement cycle advantageously comprises a fixed number of first pulse-width-modulated voltage pulses and a fixed number of second pulse-width-modulated voltage pulses. For example, eight second pulse-width-modulated voltage pulses and ten first second pulse-width-modulated voltage pulses are provided. A temperature-compensated position of the armature can thus be recorded quickly and easily.

The method is preferably carried out only when the solenoid actuator is not actuated. The voltages and currents necessary to carry out the process do not occur at the same time as current is applied to the magnet coil, which causes a change in position of the Anchor serves. This means that the method can work with comparatively small currents and voltages. These currents and voltages are too small to operate the solenoid actuator. In this way, undesired actuation of the solenoid actuator by a measuring voltage or a measuring current is effectively avoided. Furthermore, the actuation of the solenoid actuator is not disturbed by the method.

The object is additionally achieved by a lifting magnet actuator of the type mentioned at the outset, in which the position detection unit has a voltage pulse source for generating a pulse-width-modulated voltage pulse. The voltage pulse source is electrically coupled to the magnet coil, so that the magnet coil can be acted upon with a first pulse-width-modulated voltage pulse. With such a solenoid actuator, a position of an associated armature can be detected with high accuracy. At the same time, the solenoid actuator has a simple and inexpensive design. In particular, it manages without specific sensors for detecting an anchor position.

A diode is preferably connected between the magnetic coil and the voltage pulse source, a forward direction of the diode being oriented from the voltage pulse source in the direction of the magnetic coil. In this way, the electrical circuit which is used to actuate the solenoid actuator is prevented from having an effect on the electrical circuit for detecting the armature position. In other words, the electrical circuit for position detection is protected from comparatively high voltages from the electrical circuit for actuation. As a result, the electrical circuit for position detection can be constructed in a comparatively simple and inexpensive manner.

A resistor can also be interposed between the magnetic coil and the voltage pulse source. The current acting on the magnet coil by the position detection unit is limited by the resistance.

In one embodiment, the voltage pulse source is designed to generate a plurality of pulse-width-modulated voltage pulses one after the other, in particular wherein the voltage pulse source is designed to generate voltage pulses of different pulse duration. The voltage pulse source can therefore be used to generate first pulse-width-modulated voltage pulses and second pulse-width-modulated voltage pulses which differ in terms of their pulse duration. In this way, as already described above, the position of the armature can be detected while compensating for a temperature influence.

• - 1 einen erfindungsgemäßen Hubmagnetaktor, der an einem Hydraulikzylinder verbaut ist, wobei ein Anker eine erste Position einnimmt,
• - 2 den Hubmagnetaktor aus 1, wobei der Anker eine zweite Position einnimmt,
• - 3 den Hubmagnetaktor aus den 1 und 2, wobei der Anker weiterhin die zweite Position einnimmt,
• - 4 eine Positionserfassungseinheit des Hubmagnetaktors aus den 1 bis 3 in Form einer elektrischen Schaltung,
• - 5 ein Diagramm mit einem resultierenden Spannungsverlauf u(t) über der Zeit und einem resultierenden Stromverlauf i(t) über der Zeit, die mittels der Positionserfassungseinheit detektiert werden, und
• - 6 ein Detail VI der Darstellung aus 5.

The invention is explained below using an exemplary embodiment which is shown in the accompanying drawings. Show it:

• - 1 a solenoid actuator according to the invention, which is installed on a hydraulic cylinder, with an armature occupying a first position,
• - 2 the solenoid actuator 1 with the anchor in a second position,
• - 3 the solenoid actuator from the 1 and 2 with the anchor still in the second position,
• - 4th a position detection unit of the lifting magnet actuator from the 1 to 3 in the form of an electrical circuit,
• - 5 a diagram with a resulting voltage curve u (t) over time and a resulting current curve i (t) over time, which are detected by means of the position detection unit, and
• - 6th a detail VI of the illustration 5 .

The 1 to 3 show a solenoid actuator 10 , which is attached to a hydraulic cylinder for illustration purposes only 12th is installed. Here is the hydraulic cylinder 12th only shown in sections.

The solenoid actuator 10 includes a solenoid 14th and one inside the solenoid 14th recorded anchor 16 .

The anchor 16 is along an actuation axis 18th movably mounted and with a locking element 20th coupled, which is used in the illustrated embodiment, a piston 22nd of the hydraulic cylinder 12th to lock in a predefined position.

In this context, the anchor takes 16 in 1 a first position in which the piston 22nd is locked in a central position.

In the 2 is the piston 22nd in the same position as in 1 , however, are the anchor 16 and thus also the locking element 20th in a second position in which the piston 22nd is unlocked.

In the 3 are the anchor 16 and the locking element 20th still in the unlocked position. However, compared to the representations in the 1 and 2 The piston 22nd postponed.

To a current position of the anchor 16 and thus a locked state of the piston 22nd to be able to detect is a position detection unit 24 intended.

This is in 4th shown in detail.

It includes a voltage pulse source 26th , which is designed to generate several pulse-width-modulated voltage pulses one after the other.

The voltage pulse source can 26th Generate voltage pulses of different pulse duration.

The voltage pulse source is used for this 26th with a voltage source 28 connected, which provides a voltage provided for the logic circuit described below, e.g. B. 5 volts.

The voltage pulse source 26th is with the solenoid 14th electrically connected.

Here is the voltage pulse source 26th and the solenoid 14th a diode 30th interposed, the forward direction of the diode 30th from the voltage pulse source 26th in the direction of the solenoid 14th is oriented.

Furthermore, the solenoid 14th and the voltage pulse source 26th a resistance 32 interposed.

In addition, the position detection unit 24 with a current measuring unit 34 equipped, which is designed to detect a current i (t) as a function of time t through the magnetic coil 14th flows (see also 5 ).

There is also a voltage detection unit 36 provided, which is designed to generate a voltage u (t) across the magnet coil 14th falls, to be recorded as a function of time t (see also 5 ).

There is also a resistance 38 with the solenoid 14th connected in series.

According to an alternative, not shown, is the voltage detection unit 36 wired in such a way that it detects a voltage u (t) across the resistor 38 , the coil 14th and the diode 30th falls off.

Another diode 40 is parallel to the solenoid 14th switched.

In the 4th illustrated electrical circuit of the position detection unit 24 only serves to record the position.

An electrical interface 42 over which the solenoid 14th with an electrical circuit to operate the armature 16 is connected is only shown schematically.

A current position of the anchor 16 is determined as follows.

The solenoid 14th is initially applied with a fixed number of first pulse-width-modulated voltage pulses.

The voltage pulse source is used for this 26th used.

A resulting voltage curve u (t) across the magnet coil 14th and the resistance 38 is by means of the voltage detection unit 36 measured.

A section of such a voltage curve u (t) is shown in 5 shown. There are three voltage peaks resulting from the first pulse-width-modulated voltage pulses 44a , 44b , 44c to see.

A resulting voltage u_pos is determined for each first voltage pulse by using a voltage value u_pos at a point of maximum voltage drop of the resulting voltage profile u (t).

This is for the voltage spike 44a in 6th clearly.

As an alternative to determining the voltage u_pos at the point of the maximum voltage drop, the resulting voltage u_pos can also be recorded with a fixed sampling frequency.

The fixed number of first pulse-width-modulated voltage pulses forms a measurement cycle. After the end of the measuring cycle, an average value of all the resulting voltages u_pos is determined.

About the influence of a temperature T of the solenoid 14th To be able to compensate, the magnetic coil is also used within the measuring cycle 14th applied with a fixed number of second pulse-width modulated voltage pulses.

The pulse duration of the second pulse-width-modulated voltage pulses is significantly greater than the pulse duration of the first pulse-width-modulated voltage pulses.

For every second voltage pulse there is a resulting voltage curve u (t) across the magnet coil 14th by means of the voltage detection unit 36 measured. In this context, in 5 a voltage plateau resulting from a single second voltage pulse 46 to see.

The resulting voltage u_temp corresponds to the voltage value of this voltage plateau 46 .

In addition, a current curve i (t) resulting from the second voltage pulses is determined by means of the current detection unit 34 determined and a resulting current i_temp derived from this (cf. 5 ).

The measurement cycle shown by way of example in the figures thus comprises a single second pulse-width-modulated voltage pulse and three first pulse-width-modulated voltage pulses.

After the measurement cycle has expired, both an average value of all resulting voltages u_temp and all resulting currents i_temp are calculated.

A temperature-dependent resistance R can then be calculated from the quotient of the mean value of the resulting voltages u_temp and the mean value of the resulting currents i_temp.

From this, a correction factor A is then used, which is in particular a temperature coefficient of the material of the magnet coil 14th and the correction summand B calculates a temperature T according to the following formula. A linear relationship between the temperature T and the resistance R is assumed. $$T=\mathrm{A.}\cdot \mathrm{R.}-\mathrm{B.}$$

The correction factor A has the unit ° C / Ω and is in the range from 30 to 200, e.g. B. it is 150. The correction factor A depends in particular on the ohmic resistance R of the magnet coil 14th from.

The correction value B has the unit ° C and is in the range from 200 to 400, e.g. B. 300. The correction value B essentially corresponds to the temperature at which the magnetic coil has a theoretical resistance of 0 Ω.

The correction factor A and the correction value B can be determined experimentally from measurements. The above equation for calculating the temperature T thus corresponds to a linear interpolation of measured values for the temperature T and the associated resistance R.

Alternatively, the temperature can be calculated as a function of the resistance using the following equation: $$T=\left(\frac{\mathrm{R.}}{{\mathrm{R.}}_0}-1\right)/\propto$$

Where Ro is the resistance of the solenoid 14th at 0 ° C and α is the temperature coefficient of the magnet coil 14th . The values of R ₀ and α must therefore be given in order to be able to calculate the temperature T based on R.

The position x of the anchor 16 inside the solenoid 14th can then be calculated using the following formula: $$x=\mathrm{C.}\cdot \mathrm{R.}\cdot u\_pOs-\mathrm{D.}\cdot u\_pOs-\mathrm{E.}\cdot \mathrm{R.}+\mathrm{F.}$$

The values C, D and E represent correction factors.

The correction factor C is in the range from 5 to 8 and is e.g. B. 7.

The correction factor D is in the range from 20 to 40. It is 30, for example.

The correction factor E is in the range from 2 to 7 and is, for example, 4.

The value F is a correction summand and is in the range from 20 to 40. It can be 30.

The correction factors C, D, E and the value F can also be determined experimentally. The above equation for the position x is a plane equation in a space with the axes R, u_pos and x.

The position of the anchor 16 is therefore based on the resulting voltages u_pos and u_temp and as a function of a temperature T of the magnet coil 14th determined.

In order to take non-linear temperature influences into account, the position value x can be corrected using the following formula: $$x_{kOrriGiert}=x_{unkOrriGiert}-G\cdot T^2+H\cdot T+\mathrm{I.}$$

The values G and H are again correction factors. I is a correction group.

G is in the range of 10 ^-4 and H in the range of 10 ^-3 .

I ranges from 0.05 to 0.2.

The aforementioned method for determining the position x of the anchor 16 is only executed if the solenoid actuator 10 is not activated, i.e. the interface 42 is essentially de-energized.

During operation of the solenoid actuator 10 serve the diodes 30th , 40 to do this, the electrical circuit for position detection before the influence of the interface 42 provided currents and voltages for operating the solenoid actuator 10 to protect. The diode can 40 can also be referred to as a freewheeling diode. It protects next to the diode 30th also the interface 42 against impermissibly high voltages.

The resistance 32 is used for the from the voltage pulse source 26th into the solenoid 14th to limit the current introduced.

The lifting magnet actuator explained above 10 and the associated method for determining a position x of the anchor 16 inside the solenoid 14th can be used in conjunction with the hydraulic cylinder 12th be used as part of a parking lock of an automatic transmission or generally as a transmission actuator in a vehicle transmission.

Claims (12)

Method for determining a position (x) of an armature (16) within a magnet coil (14) of a lifting magnet actuator (10), characterized in that the magnet coil (14) is subjected to at least one first pulse-width-modulated voltage pulse, a voltage resulting from the voltage pulse ( u_pos) is measured across the magnetic coil (14), and the position (x) of the armature (16) within the magnetic coil (14) is derived from the resulting voltage (u_pos). Procedure according to Claim 1 , characterized in that the magnetic coil (14) is acted upon with a fixed number of first pulse-width-modulated voltage pulses within a measuring cycle and a resulting voltage (u_pos) is measured across the magnetic coil (14) for each voltage pulse, whereby to derive the position (x) of the armature (16) a mean value of all the resulting voltages (u_pos) is used. Procedure according to Claim 1 or 2 , characterized in that the resulting voltage (u_pos) across the magnet coil (14) is measured with a predetermined sampling frequency or that the resulting voltage (u_pos) is determined from a resulting voltage curve (u (t)) across the magnet coil (14), by using a voltage value at a point of maximum voltage drop as the resulting voltage (u_pos). Method according to one of the preceding claims, characterized in that the position (x) of the armature (16) is determined as a function of a temperature (T) of the magnetic coil (14). Procedure according to Claim 4 , characterized in that the magnetic coil (14) is acted upon by at least one second pulse-width-modulated voltage pulse, a voltage (u_temp) resulting from the second pulse-width-modulated voltage pulse is measured across the magnetic coil (14), a current (i_temp) resulting from the second pulse-width-modulated voltage pulse is determined in the magnetic coil (14), and a resistance (R) and / or a temperature (T) of the magnetic coil (14) can be or will be derived from the resulting voltage (u_temp) and the resulting current (i_temp). Procedure according to Claim 5 , characterized in that a pulse duration of the first pulse-width-modulated voltage pulse is shorter than a pulse duration of the second pulse-width-modulated voltage pulse. Procedure according to Claim 5 or 6th , characterized in that a fixed number of second pulse-width-modulated voltage pulses is applied to the magnetic coil (14) within a measurement cycle and a resulting voltage (u_temp) across the magnetic coil (14) and / or a resulting current (i_temp) in the for each voltage pulse Magnetic coil (14) is measured, a mean value of all resulting voltages (u_temp) and / or all resulting currents (i_temp) being used to derive the temperature (T) of the magnetic coil (14). Method according to one of the preceding claims, characterized in that it is only carried out when the solenoid actuator (10) is not actuated. Lifting magnet actuator (10) with a magnet coil (14) and an armature (16) which is movably mounted along an actuation axis (18) within the magnet coil (14), a position detection unit (24) being provided by means of which a position (x) of the Armature (16) can be detected within the magnetic coil (14), characterized in that the position detection unit (24) has a voltage pulse source (26) for generating a pulse-width-modulated voltage pulse, which is electrically coupled to the magnetic coil (14) so that a first pulse-width-modulated voltage pulse can be applied to the magnetic coil (14). Solenoid actuator (10) Claim 9 , characterized in that a diode (30) is interposed between the magnetic coil (14) and the voltage pulse source (26), a forward direction of the diode (30) being oriented from the voltage pulse source (26) in the direction of the magnetic coil (14). Solenoid actuator (10) Claim 9 or 10 , characterized in that the magnetic coil (14) and the voltage pulse source (26) are interposed with a resistor (32). Solenoid actuator (10) after one of the Claims 9 to 11 , characterized in that the voltage pulse source (26) is designed to generate a plurality of pulse-width-modulated voltage pulses one after the other, in particular wherein the voltage pulse source is designed to generate voltage pulses of different pulse duration.

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