DE102012112841B4 - Control method and control device for an electromagnet - Google Patents

Abstract

Voltage-based method for controlling a current profile through an electromagnet (126), in particular for controlling an operating position of an electromagnetic hydraulic valve (100), wherein the electromagnet (126) is used to drive an actuator (122) with current pulses (10) corresponding to a desired actuator position by specifying Voltage pulses (24) are subjected to at least one predeterminable pulse parameter, with superposition pulses (26) being superimposed on the voltage pulses (24), characterized in that the pulse length (30, 34) of the superposition pulses (26) is smaller than the pulse length (20, 22) of the voltage pulses (24) in order to adjust the course of the current pulses (10) assigned to the voltage pulses (24), in particular in order to set a predeterminable edge steepness of the current pulses (10), the pulse length (20, 22, 30, 34) and/or Pulse height (21, 23, 31, 35) of the voltage pulses (24) and/or the superposition pulses (26) from an equality of a time-integrated area under a positive and a negative half-wave of a predeterminable pulse frequency, based on a predeterminable controller voltage (14), be determined.

Description

The present invention relates to a voltage-based method for controlling a current profile through an electromagnet, in particular for controlling an operating position of an electromagnetic hydraulic valve according to the preamble of claim 1. The invention further relates to a method for calculating a duration and height of superposition pulses for use in such a Method and a control device for controlling the operation of an electromagnet, in particular for controlling an electromagnetic hydraulic valve.

STATE OF THE ART

From the EP 0306839 a method and a device for controlling switched electromagnets, in particular in injection valves for internal combustion engines, are known. In order to optimize the control and in particular to reduce the switch-on delay, a short pulse with high voltage is passed through the electromagnet, which is dimensioned so that no thermal overloads occur. Then only a small holding energy, e.g. B. a constant holding current is supplied to the electromagnet. With such a control, the switch-on delay can be noticeably reduced compared to conventional controls; In addition, the switch-off delay is also shorter. The process is optimized for switched electromagnets and only inadequately covers the use of electromagnets, for example in proportional valves or for pressure control, especially in valves with high system friction.

Developments in transmission technology concern electromagnetic hydraulic valves for transmission clutches that can be conveniently coupled with friction, in particular starting/shift clutches or synchronizers, which enable use with little to no transmission oil changes. In addition, such hydraulic valves should be used when poor transmission oil quality is used, for example in developing countries. For this purpose, hydraulic valves with particularly narrow air gaps in the driving electromagnets are usually used in order to reduce the inhibiting influence of possible dirt particles in the oil. Such hydraulic valves have increased friction, which in proportional control operation leads to a high level of effort for the electronic control, which in most cases is carried out in a current-controlled manner. High-quality current control cannot be sufficiently implemented in a motor vehicle because no ideal voltage source is available to be able to specify a desired current curve. Furthermore, current-based control of an electromagnet requires a high level of semiconductor effort with corresponding hardware costs and implies a high susceptibility to errors.

From the US 20020101314 For example, an electromagnetic actuator is known that serves as a drive in a hydraulic valve. The actuator is designed so that the hysteresis of the mechanical positions of a movable iron core as an armature of the electromagnet is small compared to the value of the electric current through the coil of the electromagnet, which can be minimized. The hysteresis behavior of such electromagnetic hydraulic valves can essentially be attributed to three influences: the flow force of hydraulic flows, which depends not only on the type of hydraulic oil but also on its temperature and/or its viscosity, the magnetic hysteresis, which depends on the selected magnetic material, and the friction, which, in addition to the coefficient of friction and the selected material pairings, largely depends on the transverse forces on the anchor. The US 20020101314 describes a magnetic design of an electromagnetic actuator, which is dimensioned such that even with a certain eccentricity of the movable armature of the electromagnet, the lateral force between the housing and the armature can be minimized in order to also be able to minimize the frictional force on the armature. This describes measures that can be taken when designing an electromagnetic actuator in order to facilitate friction-prone operation. Further possible measures for optimizing the operating behavior of such an electromagnetic actuator, in particular with regard to the electrical control of the actuator, are not taken into account.

In the DE 10 2007 006 179 A1 A circuit arrangement and an operating method for an inductive load are described, which achieves a rapid response of the load with simultaneously low electrical power loss. In a first operating phase at the beginning of the energization phase, a boost voltage with a high voltage value is provided. In a second operating phase, a low operating voltage is set. The operating voltage is pulsed to set a desired load current.

The DE 10 2007 026 947 A1 describes a method for operating an injection valve, wherein in a first capture phase an increased voltage value is applied to the valve than in the subsequent hold phase until a maximum current value is reached. By determining a time period until the current value is reached, a diagnosis of the condition of the valve can be carried out.

Finally describes the DE 100 11 924 A1 a control method and a circuit arrangement for controlling a solenoid valve for fuel injection in an internal combustion engine. In a booster phase, a charge stored in a booster capacitor is transferred to a solenoid coil of the solenoid valve at the beginning of control. After the booster phase, the voltage from the supply battery is switched through to the solenoid valve.

Based on the prior art presented above, it is the object of the invention to propose a method for controlling a current profile through an electromagnet, a method for calculating a duration and height of superposition pulses for use in such a method, and a control device for controlling the operation of an electromagnet , wherein the mentioned methods and the control device can be used in particular for stiff electromagnetic hydraulic valves with high friction, e.g. high static or sliding friction, so that safe operation of such hysteresis-afflicted electromagnetic actuators can be guaranteed even with a high system coefficient of friction with minimal maintenance effort and minimal failure rate . A high system friction can be caused, for example, by a tight bearing clearance of the displaceable mechanical parts of the actuator, or by a transverse force with which an armature magnet is pulled onto a wall of the actuator housing. Such frictional forces are increased in particular when an air gap between the armature magnet and a magnetic separating layer of a surrounding pole tube of the actuator is very small, i.e. there is only a small mechanical play.

This task is achieved by a voltage-based method for controlling a current profile through an electromagnet according to the teaching of claim 1, a method for calculating a duration and height of superposition pulses for use in such a method and a control device for controlling the operation of an electromagnet according to the other subordinate ones Claims resolved. The dependent claims suggest advantageous further developments of the invention.

DISCLOSURE OF INVENTION

In a first aspect according to the invention, a voltage-based method for controlling a current profile through an electromagnet, in particular for controlling an operating position of an electromagnetic hydraulic valve, is proposed, wherein the electromagnet is used to drive an actuator with current pulses corresponding to a desired actuator position, or maintaining a desired setting position by means of a specification of voltage pulses is applied with at least one predeterminable pulse parameter. In the method according to the invention, superposition pulses are superimposed on the voltage pulses, the pulse length of which is smaller than the pulse length of the voltage pulses, in order to adjust the course of the current pulses assigned to the voltage pulses, in particular in order to set a predeterminable edge steepness of the current pulses.

As a result, the electrical control of electromagnets, such as those used to operate electromagnetic hydraulic or pressure control valves, can be carried out by regulating the input voltage at the electromagnet. This voltage regulation places lower demands on the hardware of a control device than current intensity regulation and can be carried out with sufficiently high quality even when the supply voltage fluctuates. The control device is therefore cost-effective, but the control properties, such as current pulse shapes, can only be adjusted indirectly, since the inductance and the ohmic resistance of the magnetic coil of the electromagnet influence the current pulse shapes due to their low-pass character and lead to a rounding of an actually desired rectangular shape, as is often the case with pulse width modulation applied, lead. Such a smoothed current curve has certain limitations for precise operation of the electromagnet, for example in a hydraulic or pressure control valve. The proposed invention makes it possible to achieve high-quality behavior of current control using a cost-effective control device with voltage regulation. A voltage control has the excellent advantage over a current control in that it is more similar to a control than a current control because the influence of the feedback is smaller. Controls are much easier to operate than regulations, have no instabilities and are therefore more robust and less prone to errors.

The method according to the invention proposes generating a voltage superimposition (dither) for controlling electromagnets, in particular when used in electromagnetic hydraulic or pressure control valves, with the voltage superimpositions in the form of superposition pulses over a voltage pulse that defines a basic operating state of the electromagnet. In other words, using a voltage-controlled superimposition of superposition pulses over a basic voltage pulse, a current curve that is favorable for driving electromagnets is generated. Through the controlled voltage superposition, a current curve with an adjustable, in particular high edge steepness of the resulting current pulse, for example a rectangular current curve, is achieved. Preferably, a pressure control valve for a clutch transmission can be operated with such a voltage-based control, whereby in the case of a dual clutch, an undesirable switching jerk can be avoided and a clean, smooth gear change can be carried out. Such pressure control valves have a high coefficient of friction, with the control movements of the armature magnet being small, so that precise, fast-acting control is advantageous.

Pulse width modulation is often used to control electromagnets in order to set an average current curve, which can be varied via the so-called duty cycle. The duty cycle at a fixed pulse frequency is usually defined as the ratio of the pulse length at one voltage, for example a reference voltage, to the pulse length at a second voltage, for example zero voltage within the cycle time.

For an improved control of an electromagnet compared to the prior art, an advantageous voltage control has proven to be at least two-stage, in particular four-stage, voltage superposition. In order to favorably influence the course of the rising and/or falling edges, a corresponding control device can emit a high-frequency voltage curve. This leads to a high recharging speed, or a high-frequency current curve within the inductance of the magnetic coil, on the desired steep edges of the current pulses. You can then switch back to a duty cycle that corresponds to an average current pulse for the rest of the voltage half-wave, i.e. a low-frequency voltage curve can be set to generate a constant current level corresponding to a desired magnetic field strength of the electromagnet or position of the proportional valve. Thus, with a multi-stage, in particular four-stage, voltage superposition by means of a voltage control, a desired, in particular rectangular-like current curve can be achieved through the electromagnet. By knowing the frequency characteristics of the electromagnet, a desired current curve can be set using high-frequency controlled voltage excitation. For this purpose, for example, a frequency analysis, in particular an FFT or DFT (Fast or Discrete Fourier Transformation) of the electromagnetic-mechanical system can be carried out in order to find a corresponding voltage signal form for setting a desired current profile through the electromagnet or switching behavior through the electrovalve, and this by combining a voltage pulse and a superposition pulse.

By means of the method according to the invention, a hysteresis property of an electromagnetic actuator caused by high mechanical friction can be mitigated, whereby the required control energy can be significantly reduced and thus the efficiency can be improved and the energy consumption of the actuator can be reduced. The response speed of the actuator is increased and thus higher switching dynamics are achieved. Since the energy consumption can be reduced, the service life is increased, and a high control quality and repeatability of switching processes can be achieved due to the improved dynamic behavior.

According to the invention, the pulse length and/or pulse height of the voltage pulses and/or the superposition pulses are determined from an equality of a time-integrated area under a positive and a negative half-wave of a predeterminable pulse frequency, based on a predeterminable regulator voltage. The equality of the time-integrated areas enables the superimposed voltage signal to behave in a controller-neutral manner. This allows the remanence of the electromagnet to be completely reduced, thus achieving fast switching behavior.

As a parameter for controlling the amplitude, i.e. the pulse height of the superposition pulses, an area can be defined as the setpoint of the amplitude. This represents a suitable measure for the energy content of the superposition pulses and allows its shape-neutral definition. Furthermore, switching effects that result from the multi-stage voltage specification are suppressed. In order to enable frequency-neutral behavior of the area definition, the area can also be normalized to the frequency. It is also possible to conveniently switch to low- or higher-frequency control with the same area.

The calculation of the necessary pulse lengths and pulse heights of the superposition pulses can advantageously be carried out using a multi-step algorithm, whereby the algorithm can generate a multi-stage, in particular four-stage, voltage superposition under the specification of a guaranteed equality of the voltage area between the positive and negative half-wave of the voltage curve.

und $${\text{A}}_2={\text{N}}_{\text{neg\_ges}}*{\text{U}}_{\text{regler}},$$

bestimmt, wobei

Npos_ges

Anzahl von Spannungspulsen der positiven Halbwelle,

Nneg_ges

Anzahl von Spannungspulsen der negativen Halbwelle,

Uref

Referenzspannung eines Stromreglers bei gewünschter Aktuatorstellung,

Uregler

Reglerspannung, maximale Ausgangsspannung des Reglers sind.

The following is an example of a four-stage voltage superposition with four time ranges I, II, III and IV to simulate a Current controller behavior is considered, which defines a voltage overlay that a comparable current controller with a current-based regulated voltage U _regulator would output for a desired actuator position. In a first step, two limiting half-waves (areas I & II or areas III & IV) of the switching cycle are considered, and the sizes of the maximum possible voltage time areas of the positive half-wave of a voltage pulse A ₁ (areas I and II in 2 ) and a negative half-wave A ₂ (areas III and IV in 2 ) determined to simulate the current regulator voltage level U _regulator . The following applies to the maximum voltage time areas: $${\text{A}}_1={\text{N}}_{\text{pos\_ges}}*\left({\text{U}}_{\text{ref}}-{\text{U}}_{\text{regulator}}\right)$$

and $${\text{A}}_2={\text{N}}_{\text{neg\_ges}}*{\text{U}}_{\text{regulator}},$$

determined, whereby

Npos_ges

Number of voltage pulses of the positive half wave,

Nneg_ges

Number of voltage pulses of the negative half wave,

Uref

Reference voltage of a current regulator with the desired actuator position,

Uregulator

Regulator voltage, maximum output voltage of the regulator.

bestimmt werden. Damit wird die limitierende Fläche A_limit im Weiteren als Minimum aus der oben bestimmten, physikalisch maximalen Grenzfläche (A_limit) und einer inertial vorgegebenen Überlagerungsfläche (A_dither) gewählt: $${\text{A}}_{\text{limit}}=\text{Min}\left({\text{A}}_{\text{dither}},{\text{A}}_{\text{limit}}\right)$$

The maximum permitted area can be defined as a minimum from A ₁ and A ₂ $${\text{A}}_{\text{limit}}=\text{Min}\left({\text{A}}_1,{\text{A}}_2\right)$$

be determined. The limiting surface A _limit is then chosen as a minimum from the above-determined, physically maximum interface (A _limit ) and an inertially specified superposition surface (A _dither ): $${\text{A}}_{\text{limit}}=\text{Min}\left({\text{A}}_{\text{dither}},{\text{A}}_{\text{limit}}\right)$$

mit

Np_soll

Soll-Anzahl an positiven Überlagerungspulsen

bestimmt.The next step is to determine the area of the positive half wave. An area for the target number of positive superposition pulses (area I in 2 ) above $${\text{A}}_{\text{1p}}={\text{N}}_{\text{p}\_\text{should}}*\left({\text{U}}_{\text{ref}}-{\text{U}}_{\text{regulator}}\right)$$

with

Np_should

Target number of positive superposition pulses

certainly.

If A _1p lies within the limiting area A _limit , then the actual number of positive superposition pulses can be N _p
N _p = N _{p_should} be set, if not, then will, then will
N _p = integer division (A _limit / (U _ref -V _regulator )) set.

berechnet, sowie die Fläche des „regulären“ Spannungspulses (Bereich II in 2) mit $${\text{A}}_{\text{2p}}={\text{A}}_{\text{dihter}}-{\text{A}}_{1\text{p}}$$

bestimmt.The area used for the positive superposition pulses (area I in.) is then determined 2 ) $${\text{A}}_{1\text{p}}={\text{N}}_{\text{p}}*\left({\text{U}}_{\text{ref}}-{\text{U}}_{\text{regulator}}\right)$$

calculated, as well as the area of the “regular” voltage pulse (area II in 2 ) with $${\text{A}}_{\text{2p}}={\text{A}}_{\text{dither}}-{\text{A}}_{1\text{p}}$$

certainly.

This results in the voltage of the “regular” voltage pulse $${\text{U}}_{\text{dither}}={\text{A}}_{2\text{p}}/\left({\text{N}}_{\text{pos}\_\text{total}}-{\text{N}}_{\text{p}}\right).$$

This means that there is a complete calculation of the positive half-wave, which can be generated within the specifications of a control device.

$${\text{N}}_{\text{n\_soll}}=\text{Soll}-\text{Anzahl an negativen Überlagerungspulsen}$$

ermittelt.The area of the negative half wave is then determined. An area for the target number of negative superposition pulses (area III in 2 ) above $${\text{A}}_{1\text{n}}={\text{N}}_{\text{n\_should}}{\text{*U}}_{\text{regulator}}$$

$${\text{N}}_{\text{n\_should}}=\text{Should}-\text{Number of negative heterodyne pulses}$$

determined.

If A _1n lies within the limiting area A _limit , the actual number of negative superposition pulses becomes N _n
N _n = N _{n_set} , if not, then will
N _n = integer division (A _limit / U _regulator ) set.

berechnet, sowie die Fläche des „regulären“ Spannungspulses (Bereich IV in 2) mit $${\text{A}}_{2\text{n}}={\text{A}}_{\text{limit}}-{\text{A}}_{1\text{n}}$$

bestimmt.The area used for the negative superposition pulses (area III in 2 ) $${\text{A}}_{1\text{n}}={\text{N}}_{\text{n}}*{\text{U}}_{\text{regulator}}$$

calculated, as well as the area of the “regular” voltage pulse (area IV in 2 ) with $${\text{A}}_{2\text{n}}={\text{A}}_{\text{limit}}-{\text{A}}_{1\text{n}}$$

certainly.

This results in the voltage of the “regular” voltage pulse $${\text{U}}_{\text{dither}}={\text{A}}_{2\text{n}}/\left({\text{N}}_{\text{neg\_ges}}-{\text{N}}_{\text{n}}\right).$$

This means that there is a complete calculation of the negative half-wave, which can be generated within the specifications of a control device.

This calculation rule calculates a four-stage voltage superimposition pulse with four time segment ranges, which corresponds to an averaged voltage output U _regulator , whereby a hysteresis-related response behavior of the actuator can be taken into account.

The superposition pulses are not necessarily shorter in time than current pulses from a comparable current-based control. However, they can achieve the same effect at reduced current intensities or reduced duty cycle, especially if the required height of the current pulses is higher than a current control can actually provide achievable amplitudes. The superposition pulses can also be designed in three or two stages or consist only of superpositions, and can also take any intermediate form depending on the calculation rule, characteristic map or data.

The dither pulses can have a typical frequency of 100-300 Hz, although a frequency of 150 Hz can be used when used, for example, to control a pressure control valve in a transmission. As a result, the PWM signals (pulse width modulation signals) for forming the voltage overlays can have a pulse frequency that is approximately 10 to 20 times as high, resulting in PWM pulse frequencies of up to 3kHz to 6kHz, which can be provided cost-effectively with conventional robust electronics.

According to an advantageous further development of the invention, the superposition pulses can be synchronized in time with the voltage pulses and/or with rising and/or falling edges of the voltage pulses. In order to achieve the steepest possible course of the rising and/or falling edges, it is expedient to combine the beginning of the superposition pulse and the voltage pulse or to carry out a fixed correlation of these pulses.

According to an advantageous development of the invention, the voltage pulses can be pulse width modulated, pulse height modulated, pulse frequency modulated and/or pulse phase modulated. These types of pulses can be generated easily and inexpensively using standard components and their parameters can be easily adjusted. The use of superposition pulses to control electromagnets can also be conveniently transferred to other types of modulation.

According to a further advantageous embodiment of the method, the voltage pulses and/or the superposition pulses can represent square-wave pulses; in particular, the total voltage pulse can assume four different voltage levels. A four-stage voltage superposition represents a very favorable embodiment of the method according to the invention, since on the one hand it can favorably influence both rising and falling edges of the current pulses and on the other hand it represents a variant with little complexity in implementation in a technically simple control device.

According to an advantageous development of the invention, a lower limit value of the voltage pulses can be set to be greater than zero and/or an upper limit value of the voltage pulses to be smaller than a reference voltage derived from a voltage source. Such a setting is favorable because the power supply still leaves enough scope for control with superposition pulses.

According to an advantageous development of the invention, the pulse height of the superposition pulses can be varied between zero and the reference voltage, with a maximum influence on the current pulse shapes being given by the maximum possible pulse heights of the superposition pulses.

Various strategies are conceivable to ensure a favorable waveform of the superposition pulses even when the supply voltage is over or under voltage. For example, buffer modules or filters can be used to smooth and stabilize the supply voltage.

Based on one of the two aforementioned exemplary embodiments, when the reference voltage exceeds a predetermined limit voltage, the pulse height and/or the pulse duration and/or the duty cycle of the voltage pulses can be reduced in order to set a current curve through the electromagnet that remains the same for operation at the limit voltage. This makes it possible to compensate for upward fluctuations in the supply voltage for the operation of the electromagnet and to achieve a constant charge transfer rate of the inductance of the electromagnet.

Based on one of the aforementioned exemplary embodiments, if the voltage falls below a predetermined limit, the reference voltage, the pulse height and / or the pulse duration and / or the duty cycle of the voltage pulses can be increased in order to set a current curve through the electromagnet that remains the same for operation at the limit voltage. This makes it possible to compensate for downward fluctuations in the supply voltage for the operation of the electromagnet and to achieve a constant charge transfer rate of the electromagnet's inductance.

According to an advantageous development of the invention, the method can be used to control an electromagnetic hydraulic or pressure control valve with high frictional forces. The method is particularly suitable for controlling a valve in a clutch transmission of a drive train, for example in a dual clutch transmission of a land, sea or aircraft, whereby a clean gear change can be carried out by the two friction clutches by means of pressure control using the valve. The control movements that occur are relatively small, so precise control must be possible. As already explained above, hydraulic valves with high friction forces such as static or sliding friction have particularly large hysteresis values in their response behavior, so that they initially do not respond when energized and show overshoot behavior when a minimum voltage is exceeded, so that a quick and reliable adjustment to one desired opening position is difficult to reach. When used in a dual clutch, this leads to an unpleasant switching jerk, a so-called overlap control from one friction clutch to the other friction clutch. For this reason, current-controlled control methods have been used to control such valves, which require a corresponding amount of hardware and drive up component costs. In this respect, their operation can be made particularly favorable by using the method according to the invention and the resulting positive influence on the edge steepness of the current pulses, without the need for complex current control.

In a secondary aspect of the invention, a method for calculating a duration and height of superposition pulses is proposed for use in a method according to one of the aforementioned exemplary embodiments. In a test bench run with an electromagnetic actuator with hysteresis-related response behavior, in particular with an electromagnetic hydraulic valve with a high system coefficient of friction, at least a first characteristic map for a number of positive and at least a second characteristic map for a number of negative overlay pulses is created by driving with voltage pulses and superposition pulses and current pulses generated therefrom determined, wherein a number and / or an amplitude of the superposition pulses is varied in order to minimize a deviation of the current pulses generated by the voltage pulses and the superposition pulses from a predetermined current pulse curve. The current pulse curve can be obtained from an already known, current-controlled method

With such an optimization algorithm, when operating on a test bench, map parameters can be determined for different operating points, i.e. opening positions of the actuator, which result in the best possible agreement with a desired current curve, for example given in a rectangular shape. The required maps can be generated automatically and the time required to manually enter maps can be reduced or even completely avoided. Another advantage is the independence and non-influence of the test bench operation from use in a real environment, for example a vehicle. This allows automatic parameterization of the characteristic maps for a desired number of reference points.

Here, the first and second maps can advantageously be identical. For certain applications, it may also be beneficial to provide the electromagnetic actuator with a more effective control in the form of a single neutral characteristic field in critical operating situations.

According to an advantageous development of the invention, at least the first and/or the second map can be approximated using a mathematical function and/or a model-based approach can be used to determine the map. This embodiment has the advantage that the use of the possibly memory-intensive maps in a control device can be dispensed with, provided that a more computationally intensive process for function calculation and/or model calculation can be used. Instead of a map, a formula description, a polynomial, spline, Taylor or PWM weighting parameter set or other approach functions can be saved in order to reduce the amount of map data.

According to a further aspect of the invention, a control device for controlling the operation of an electromagnet, in particular for controlling an electromagnetic hydraulic valve, is proposed, wherein the electromagnet is subjected to voltage pulses for driving an actuator. The control device includes a voltage specification device for the predefinable delivery of voltage pulses to the electromagnet. The voltage setting device is set up to emit superposition pulses whose pulse length is smaller than the pulse length of the voltage pulses in order to adjust the course of the current pulses assigned to the voltage pulses, in particular in order to set a predeterminable or desired edge steepness of the current pulses.

According to an advantageous development of the invention, the control device can comprise a memory device for permanently storing the course and height of the voltage pulses and the superposition pulses, preferably an I/O interface device for external programming, i.e. at least for storing but also advantageously for reading out the data from the memory device is provided. For example, the memory device can contain the above-mentioned first and second maps for controlling the electromagnetic actuator or parameter and function descriptions that can emulate the maps or pulse sequences using a computer-based method. Furthermore, it is expedient to have a correction option for changes to the two maps and/or parameter inputs and changes via an I/O interface device.

According to an advantageous development of the invention, the control device can comprise a driver stage for directly controlling an electromagnet of an electromagnetic hydraulic valve and/or a diagnostic device for monitoring the operation of the control device and/or the hydraulic valve. In order to enable a particularly compact design of the control of the electromagnetic actuator, it is advantageous to provide a driver stage in the control device itself, as is often implemented in vehicle control devices. A diagnostic option for monitoring the operation of the control device for maintenance purposes is also very helpful, whereby, for example, the driver stage can be designed to be directly accessible from externally, or the pulse sequences of the control device can be read out externally and the I/O interface device can be contacted. It is also advantageous to arrange a bus coupler device, for example a CAN bus coupler, in the control device in order to provide communication with a higher-level engine control system in order to receive target switching positions of the actuator and to output operating and fault data. In this way, fault cases and/or maintenance requirements for controlled hydraulic valves can be easily determined.

DRAWINGS

Further advantages result from the present drawing description. The drawing shows exemplary embodiments of the invention. The drawing, description and claims contain numerous features in combination.

• 1 einen Spannungs- und Stromverlauf zur Ansteuerung eines Elektromagneten nach dem Stand der Technik;
• 2 einen Spannungs- und Stromverlauf zur Ansteuerung eines Elektromagneten nach einem erfindungsgemäßen Ausführungsbeispiel;
• 3 ein elektromagnetisches Hydraulikventil zur Anwendung des erfindungsgemäßen Verfahrens nach einem weiteren Ausführungsbeispiel;

Show it:

• 1 a voltage and current curve for controlling an electromagnet according to the prior art;
• 2 a voltage and current curve for controlling an electromagnet according to an exemplary embodiment according to the invention;
• 3 an electromagnetic hydraulic valve for using the method according to the invention according to a further exemplary embodiment;

In the figures, identical or similar components are numbered with the same reference numerals.

1 shows a typical voltage and current curve for controlling an electromagnet 126, such as in 3 designed as an electromagnetic hydraulic valve 100, according to the prior art. Shown is a predetermined controller voltage curve U of an input voltage on an electromagnet over time t. The specified voltage curve shows a sequence of square-wave pulses 24 around a mean regulator voltage U _regulator 14, which vary between an upper and a lower limit voltage 13.15. The upper limit voltage 15 is smaller than a reference voltage 16, which is derived from a voltage source, for example an on-board electrical system voltage of a vehicle. The lower limit voltage 13 is greater than zero. The voltage pulses 24 are each characterized by a rising and a falling edge 38, 40, a voltage pulse height 21, 23 and a voltage pulse length 20, 22. A positive half-wave (area I) and a negative half-wave (area II) around the average regulator voltage 14 each form a switching period, the reciprocal of which corresponds to a pulse frequency.

Also shown is the resulting current curve from individual current pulses 10, which results from the voltage-based control of the electromagnet 126 with the voltage pulses 24. Due to the mutual inductance and the resulting low-pass character of the electromagnet 126, the current pulses 10 are strongly rounded or low-pass filtered compared to the applied voltage pulses 24, since the current only slowly reaches its full height after a voltage edge 38,40 has been applied due to the mutual inductance reached and slowly decreases with a binary falling voltage edge as the magnetic energy stored in the magnetic coil is reduced. With such a voltage-controlled control, only imprecise switching positions of an actuator can be achieved with long response times.

2 represents a voltage and current curve for controlling an electromagnet 126 according to an exemplary embodiment according to the invention 1 On the voltage pulse 24 shown, an overlay pulse 26 is superimposed in the time range I, the overlay pulse length 30 of which is shorter than the original voltage pulse length 20, but the overlay pulse height 31 of which is significantly larger, namely equal to the reference voltage U _ref in the example shown. The remaining voltage pulse length 32 in the area of the positive half-wave of time ranges I & II and the superposition pulse length 30 add up to the original voltage pulse length 20 of 1 .

The negative half-wave of the voltage pulse 24 in the time ranges III & IV is superimposed with a negative superposition pulse 26 with the superposition pulse length 34 and the superposition pulse height 35, which is conveniently at zero voltage. Here too, the superposition pulse length 34 and the remaining voltage pulse length 36 add up to the original voltage pulse length 22 1 . The current curve shown shows a significantly faster rise or fall of the current pulses due to the control with superposition pulses in the time ranges I and III, which can be fully controlled between a voltage of zero and the reference voltage, and the reduced voltage levels in the time ranges II and IV 10 as in 1 . This causes the valve 100 to provide a shortened response time, to more accurately set a desired opening position, and to achieve a higher switching frequency.

3 shows an electromagnetic hydraulic valve 100 for using the method according to the invention according to a further exemplary embodiment. This is a volume flow control valve in the basic position, which can be used, for example, to control and regulate hydraulic processes.

The hydraulic valve 100 consists of an electromagnet 126, which is arranged in a housing 112 and, via a plunger 124, drives a hydraulic piston 122, which is located in the same valve housing and represents the actual actuator. The electromagnet 126 comprises a ring-shaped magnetic coil 102, which is firmly connected to the housing 112, for example by a casting compound. Inside the magnetic coil 102 there is a pole tube 104 in which, separated by a thin air gap 106, an armature 108, usually designed as an iron core, can move.

In order to exhibit fail-safe behavior in the case of long transmission oil change intervals - in the extreme case of lifetime filling - the hydraulic valve 100 should advantageously have a high level of robustness. High robustness can be achieved with a large amount of play in the parts to be moved. However, this comes at the expense of the energy balance and leak tightness. The high level of robustness is achieved in that dirt particles in the hydraulic oil cannot lead to jamming of the hydraulic valve 100, since otherwise the anchor 108 has to apply very large axial forces in order to always tear itself free. The hydraulic valve 100 still has a high control quality, which is achieved by means of several design measures. In particular, the transverse forces between the anchor 108 and the pole tube 104 are minimized. One such design feature for reducing transverse forces is a very tight running clearance between the armature 108 and the pole tube 104, which is achieved by means of a very thin separating layer 110 instead of, for example, a sleeve or a thick coating. The thickness of such a thin separating layer 110 can be, for example, a layer thickness of 0.01 mm to 0.06 mm. PTFE layers, but also chemical nickel plating or similar materials are conceivable here.

Such a volume flow control valve 100 is intended, for example, for engaging and disengaging gears in an automatic vehicle transmission. The hydraulic valve 100 has two working ports A and B, as well as a supply port P. In addition, the hydraulic valve 100 also has two tank drains T1 and T2. A hydraulic piston 122 has three circumferential annular grooves 114, 116, 118. By means of the middle annular groove 116, a volume flow of a supply port P arranged axially between the two working ports A, B can be guided to the rear working port B when the hydraulic piston 122 is in the in 3 The basic position shown is with the coil 102 de-energized. In this basic position, the front working connection A is guided via the front annular groove 118 to the rear tank drain T2. However, if a sufficiently large voltage is applied to the coil 102, the hydraulic piston 122 is in a position that is maximally disengaged against the spring force of the helical compression spring 120. In this maximum disengaged position, the hydraulic oil is fed from the supply port P to the front work port B. In return, the rear working connection B is guided via the rear annular groove 114 to the front tank drain T1.

The valve shown has - comparable to a pressure control valve - a narrow spacing and, as a result, high adjustment forces, so that high mixed friction and sliding friction forces result in dynamic operation.

The hydraulic valve 100 shown, as well as a generic pressure control valve for a transmission, in particular a dual clutch transmission, is excellent due to its high coefficient of friction and its hysteresis properties, with an exemplary embodiment of the method according to the invention, for example with a four-stage voltage superimposition 2 to be controlled, the overlay pulse length and the overlay pulse height being determined according to the method described. Furthermore, the hydraulic valve 100 is advantageously controlled using a control device according to the invention for controlling the operation of the electromagnet. The hydraulic valve 100 shown, which has a narrow air gap 106, i.e. high system friction and therefore correspondingly strong hysteresis behavior, can be operated advantageously using the method according to the invention with minimal maintenance effort and minimal failure rate. With a pressure control valve, precise adherence to the control position can be achieved with a reduced reaction time when the setpoint changes using the control method.

Reference symbol list

10

Current pulse

12

Zero tension

13

Lower limit voltage

14

Regulator voltage

15

Upper limit voltage

16

Reference voltage

18

20

Voltage pulse length I

21

Voltage pulse height I

22

Voltage pulse length II

23

Voltage pulse height II

24

Voltage pulse

26

Superposition pulse

30

Superposition pulse length I

31

Superposition pulse height I

32

Voltage pulse length II

33

34

Superposition pulse length III

35

Superposition pulse height III

36

Voltage pulse length IV

37

38

Rising edge

40

Falling edge

100

Hydraulic valve

102

Kitchen sink

104

polar tube

106

air gap

108

anchor

110

Coating

112

Housing

114

Rear ring groove

116

Middle ring groove

118

Front ring groove

120

Helical compression spring

122

Actuator = hydraulic piston

124

Pestle

126

Electromagnet

Claims (15)

Voltage-based method for controlling a current profile through an electromagnet (126), in particular for controlling an operating position of an electromagnetic hydraulic valve (100), wherein the electromagnet (126) is used to drive an actuator (122) with current pulses (10) corresponding to a desired actuator position by specifying Voltage pulses (24) are subjected to at least one predeterminable pulse parameter, with superposition pulses (26) being superimposed on the voltage pulses (24), characterized in that the pulse length (30, 34) of the superposition pulses (26) is smaller than the pulse length (20, 22) of the voltage pulses (24) in order to adjust the course of the current pulses (10) assigned to the voltage pulses (24), in particular in order to set a predeterminable edge steepness of the current pulses (10), the pulse length (20, 22, 30, 34) and/or Pulse height (21, 23, 31, 35) of the voltage pulses (24) and/or the superposition pulses (26) from an equality of a time-integrated area under a positive and a negative half-wave of a predeterminable pulse frequency, based on a predeterminable controller voltage (14), be determined. Procedure according to Claim 1 , characterized in that the superposition pulses (26) are synchronized in time with the voltage pulses (24). are synchronized, and/or that the superposition pulses (26) are synchronized with rising and/or falling edges (38, 40) of the voltage pulses (24). Method according to one of the preceding claims, characterized in that the voltage pulses (24) are pulse width modulated, pulse height modulated, pulse frequency modulated and/or pulse phase modulated. Method according to one of the preceding claims, characterized in that the voltage pulses (24) and/or the superposition pulses (26) represent square-wave pulses, in particular that the total voltage pulse can assume four different voltage levels. Method according to one of the preceding claims, characterized in that a lower limit value of the voltage pulses (24) is set to be greater than zero and/or an upper limit value of the voltage pulses (24) is set to be smaller than a reference voltage (16) derived from a voltage source. Procedure according to Claim 5 , characterized in that the pulse height (31, 35) of the superposition pulses (26) is varied between zero and the reference voltage (16). Procedure according to one of the Claims 5 or 6 , characterized in that when a predetermined limit voltage is exceeded by the reference voltage (16), the pulse height (21, 23) and / or the pulse duration (20, 22) and / or the duty cycle of the voltage pulses (24) is reduced in order to set a to ensure a constant current flow through the electromagnet (126) for operation at the limit voltage. Procedure according to one of the Claims 5 until 7 , characterized in that when the reference voltage (16) falls below a predetermined limit voltage, the pulse height (21, 23) and/or the pulse duration (20, 22) and/or the duty cycle of the voltage pulses (24) is increased in order to set a to ensure a constant current flow through the electromagnet (126) for operation at the limit voltage. Use of a method according to one of the preceding claims, characterized in that the method is used to control an electromagnetic hydraulic valve (100) or a pressure control valve, in particular for use in a clutch transmission, with high system friction. Method for calculating a duration and height of superposition pulses (26) for use in a method according to one of Claims 1 until 8th , characterized in that in a test bench run with an electromagnetic actuator (122), in particular with an electromagnetic hydraulic valve (100) or a pressure control valve with high system friction, by control with voltage pulses (24) and superposition pulses (26) and the resulting current pulses (10) at least a first characteristic map for a number of positive and at least a second characteristic map for a number of negative overlay pulses (26) are determined, a number and/or an amplitude of the overlay pulses (26) being varied in order to avoid a deviation in the voltage pulses (24) and to minimize the current pulses (10) generated by the superposition pulses (26) from a predetermined current pulse curve, the first and the second characteristic maps preferably being identical. Procedure according to Claim 10 , characterized in that at least the first and/or the second map are approximated with a mathematical function and/or a model-based approach is used to determine the maps. Control device for controlling the operation of an electromagnet (126) according to a method according to one of Claims 1 until 8th , in particular for controlling an electromagnetic hydraulic valve (100), the electromagnet (126) being subjected to voltage pulses (24) for driving an actuator (122), comprising a voltage specification device for the predefinable delivery of voltage pulses (24) to the electromagnet (126), wherein the voltage specification device is set up to emit superposition pulses (26), characterized in that the pulse length of the superposition pulses (26) is smaller than the pulse length of the voltage pulses (24) in order to adjust the course of the current pulses (10) assigned to the voltage pulses (24), in particular in order to set a predeterminable edge steepness of the current pulses (10). control device Claim 12 , characterized in that a memory device for permanently storing the course and height of the voltage pulses (24) and the superposition pulses (26) is included, preferably comprising an I/O interface device for external programming of the data of the memory device. control device Claim 12 or 13 , characterized in that a driver stage for direct control of the electromagnet th (126) of an electromagnetic hydraulic valve (100) and/or a diagnostic device for monitoring the operation of the control device and/or the hydraulic valve (100). Control device according to one of the Claims 12 until 14 , characterized in that in the control device at least a first map for a number of positive superimposition pulses and a second map for a number of negative superposition pulses for controlling the operation of an electromagnet, in particular for controlling an electromagnetic hydraulic valve, can be implemented.

Images