EP3458638B1 - Dynamic control of a door-opening device of a domestic appliance, in particular by means of dc supply voltage - Google Patents

Description

The invention relates to a method for controlling a door opening device of a household appliance and a door opening device in a household appliance according to the preambles of the independent claims. In addition, the invention relates to a household appliance with such a door opening device.

Household appliances for the care of laundry items which have an interior which can be closed by means of a door, for example a washing machine, a tumble dryer or a washer-dryer combination, usually have a locking device which holds the door in a closed position by means of a force fit. Modern household appliances can be equipped with an electromechanical door opening device for exerting a pressing force on the inside of the household appliance door in order to overcome the frictional connection exerted by the locking device. A household appliance with such a door opening device is from the DE 10 2013 223 431 B3 as well as from the DE 10 2014 201 924 A1 known. Finally the document reveals JP 2008-032323 A , which is considered the closest prior art, a refrigerator with a door opening device, and the document DE 10 2012 010 929 A1 discloses a locking device for a door of a domestic washing machine.

However, such an automatic opening process must meet the specified requirements for the safety and comfort of the opening process.

It is therefore an object of the present invention to provide a method, a door opening device and a household appliance, which provide greater security and improved comfort when the door is opened.

This object is achieved by a method and by a door opening device and by a household appliance in accordance with the independent claims. Advantageous embodiments of the present invention are the subject of the dependent claims.

The invention is based on a method for actuating a door opening device comprising an electromechanical actuator of a household appliance comprising a door during an opening process, the actuator comprising two actuator connections for electrical actuation. The method comprises providing an electrical supply voltage between an electrical supply connection and an electrical reference connection of the door opening device, which has a voltage form specified in an intended operating state of the household appliance, providing an electrical coupling device for coupling, if necessary, a first of the two actuator connections to the supply connection and / or a second of the two actuator connections to the reference connection. Furthermore, the method comprises coupling the supply voltage and the two actuator connections by means of the coupling device as a function of a pulse-shaped coupling signal for the electrical control of the actuator and generating a pressing force for acting on the door as a function of the electrical control of the actuator. The electromechanical actuator can be an actuator with a magnetic coil connected between the two actuator connections, preferably with a solenoid, which can be controlled such that a magnetic force can be exerted on a movable actuator element. The movable actuator element is preferably a magnetizable material, in particular a ferromagnetic material. The movable actuator element can be arranged in such a way that in a rest position it is mounted at least partially outside an inner region of the magnet coil and is pulled in the direction of the magnet coil when the actuator is electrically actuated.

When using a magnetizable material as a movable actuator element, the attraction is based on the reluctance force, which is based on the change in the magnetic resistance. The resulting force is proportional to the square of the current that flows through the magnetic coil and generates the magnetic field. The force acting on the movable actuator element is therefore independent of the sign of the current through the magnetic coil, which makes such an embodiment of the electromechanical actuator usable for direct control with an alternating signal (AC). Alternatively, the use of a permanent magnetic material for the movable actuator element can be provided, which is the case when using an electrical Supply voltage in the form of an AC voltage requires an additional rectification for electrical control of the solenoid.

According to the invention, the method is developed further by generating the pulse-shaped coupling signal as a function of the predetermined voltage form and / or as a function of the coupling device provided in order to achieve a time profile of the pressing force, which has an increasing envelope. Envelope is understood here to mean a curve that touches the graph of the temporal course of the pressing force in each case close to a local minimum. In the simplest case, the envelope is a sequence of straight lines. To simplify matters, the envelope curve can also be determined by connecting the respective local maxima by the straight line segments. In this case it can happen that the envelope does not touch the graph of the temporal course of the pressing force in the vicinity of the local maxima, but intersects, the deviation from an "ideal envelope" being negligibly small. To simplify matters, the envelope curve can thus be described by an interpolated, in particular linearly interpolated, course of the local maxima with a positive sign of the graph of the time course of the pressing force.

The invention is based on the finding that, with controls which are usually used for such door opening devices and which are based on an electrical alternating voltage and which allow a very simple implementation of a control circuit on the basis of a triac or a relay, restrictions with regard to the adjustable time characteristic of the pressing force subject to.

A current implementation of a door opening device uses an extra pin to push / push the door from its closed position. This pin is guided by the control of a magnetic coil. The pin and the magnetic coil require a certain force to overcome the holding force of a door locking device. Nevertheless, when using an AC control for the solenoid, the energy required to open the door must be made available within half a period (10 milliseconds at 50 Hertz). This means that enough energy must be available within approximately 10 milliseconds. After that, the energy in the magnetic coil does not continue to rise.

This short time leads to some disadvantages. The operating time of a shock has a greater dependence on the frequency. In the event of a longer operating period during which the magnet coil is activated, vibrations can occur due to the zero crossings, in which the current through the magnet coil becomes zero. The door, the household appliance and the door holding mechanism are mechanical parts which are assembled. Therefore, they may absorb a rapid shock from the door opening device by forming a mechanical filter for a shock lasting up to 10 milliseconds. Furthermore, a large current pulse is required to control the actuator. Furthermore, voltage fluctuations can lead to different impact forces due to the different energy that is provided to the magnet coil within the 10 milliseconds. A fine adjustment for voltages between 170 volts and 260 volts is therefore not possible. In return, to ensure that the door opens in any case, even at a low voltage of 170 volts AC, an oversized shock at 260 volts AC can be expected.

By actuating the actuator in such a way that the time course of the pressing force has an increasing envelope curve, greater security and improved comfort of the door opening device can be achieved. In particular, this can prevent the door from being violently pushed against a user and injuring the user.

Furthermore, the electrical coupling device has a resistance element with a variable electrical resistance that is electrically connected in series with the actuator. In particular, the variable electrical resistance is a temperature-dependent resistance, preferably a thermistor (NTC), the resistance value of which has a negative temperature coefficient. Such a resistance element can be used both with an electrical supply voltage in the form of a DC voltage and with an electrical supply voltage in the form of an AC voltage. Starting from an idle state of the door opening device, in which the resistance element is at ambient temperature and has a high resistance value, a current flow through the resistance element leads to self-heating of the resistance element and thus to it a decrease in the electrical resistance value. This leads to an increase in the current through the actuator, for example through a magnetic coil of the actuator, which is connected between the two actuator connections, and in the case of operation with an alternating voltage as the supply voltage, an increase in the amplitude of the current is correctly mentioned instead of an increase in the current should to avoid misunderstandings regarding a decrease in the current time value due to the voltage curve shape. A suitable selection of the resistance element with parameters adapted to the solenoid of the actuator, taking into account the operating voltage provided as the electrical supply voltage, can thus achieve a time profile of the pressing force, which has an increasing envelope curve as soon as the coupling signal puts the electrical coupling device into a coupling state ( On) controls.

According to an advantageous development of the method, the provision of the coupling device and the generation of the pulse-shaped coupling signal are carried out in such a way that the time course of the pressing force during an active pulse phase of the coupling signal has a sequence of at least two local maxima, which are in each case on or near the increasing envelope , a second local maximum of the at least two local maxima following a first local maximum of the at least two local maxima later in time having a higher value than the first local maximum. In this way, the maximum force exerted on the door can be increased successively. Particularly preferably, the provision of the coupling device and the generation of the pulse-shaped coupling signal are carried out in such a way that the sequence of the at least two local maxima has a third local maximum that follows the second local maximum and has a higher value than the second local maximum. This allows the graduated exertion of the opening force on the door to be further refined.

According to an advantageous embodiment of the method, the electrical supply voltage is provided by a DC voltage source. This results in greater flexibility in the type of actuation of the electromechanical actuator; in particular, the effects of the zero crossings that are inherent when using an AC voltage are eliminated.

Alternatively, it can be provided that the electrical supply voltage is provided by an AC voltage source. In this case, a rectifier is preferably connected between the supply voltage and the electromechanical actuator. The use of a rectifier when fed from an AC voltage source thus also enables the use of a permanent magnetic material as a movable actuator element. Furthermore, an electrical filter element can be provided behind the rectifier, that is to say on the rectified side to which the actuator is connected, which reduces a reduction in the drops in the time course of the pressing force caused by the zero crossings of the AC voltage.

According to a further advantageous embodiment of the method, the coupling signal is generated during the opening process with a sequence of a plurality of individual pulses spaced apart in time. As a result, the course of the pressing force, which has an increasing envelope curve, can be optimized in accordance with the requirements with regard to a safe and convenient opening process of the door.

Alternatively, the coupling signal can be generated with a single single pulse during the opening process. The shape of the time course of the pressing force and the increasing envelope curve is determined by the electrical coupling element itself. By selecting an appropriate, suitable electrical coupling element, which is provided according to the method according to the invention, the desired time profile of the pressing force can thus be achieved.

According to a further advantageous embodiment of the method, the coupling signal is generated as a function of a first signal, which signals an open state of the door, and / or as a function of a second signal, which signals a locked state of the door. This enables the door opening device to open the door gently while checking whether the door is already open. In the event that the door is already open, the door opening device would interrupt the actuation of the actuator in order to avoid an additional impact on the door, which could possibly hit a user of the household appliance. In addition, household appliances can be equipped with a door locking system, which also provides locking of the door, which is of considerable importance in particular in the case of a washing machine in the form of a front loader with a loading opening provided on the front. This can cause water damage if the door is opened while a critical water level in the drum has been exceeded. In the case of a door lock, the door opening mechanism is also expediently blocked in order to prevent damage to components of the household appliance, in particular the locking device or the door opening device.

The invention is also based on a door opening device in a household appliance comprising a door, the door opening device comprising an electrical supply connection and an electrical reference connection, between which an electrical supply voltage, which has a voltage form that is predetermined in an intended operating state of the household appliance, can be provided. Furthermore, the door opening device comprises an electromechanical actuator for generating a pressing force for acting on the door as a function of an electrical control of the actuator, which comprises two actuator connections for electrical control, and an electrical coupling device, which is designed for electrical control of the actuator in Depending on a pulse-shaped coupling signal to couple a first of the two actuator connections to the supply connection and / or a second of the two actuator connections to the reference connection. The pulse-shaped coupling signal is in particular a binary signal, which can assume two states, namely coupled (on) and not coupled (off).

Furthermore, the electrical coupling device has a resistance element with a variable electrical resistance that is electrically connected in series with the actuator. In particular, the variable electrical resistance is a temperature-dependent resistance, preferably a thermistor (NTC), the resistance value of which has a negative temperature coefficient. Such a resistance element can be used both with an electrical supply voltage in the form of a DC voltage and with an electrical supply voltage in the form of an AC voltage. Starting from an idle state of the door opening device, in which the resistance element is at ambient temperature is located and has a high resistance value, a current flow through the resistance element leads to self-heating of the resistance element and thus to a decrease in the electrical resistance value. This leads to an increase in the current through the actuator, for example through a magnetic coil of the actuator, which is connected between the two actuator connections, and in the case of operation with an alternating voltage as the supply voltage, an increase in the amplitude of the current is correctly mentioned instead of an increase in the current should to avoid misunderstandings regarding a decrease in the current time value due to the voltage curve shape. A suitable selection of the resistance element with parameters adapted to the solenoid of the actuator, taking into account the operating voltage provided as the electrical supply voltage, can thus achieve a time profile of the pressing force, which has an increasing envelope curve as soon as the coupling signal puts the electrical coupling device into a coupling state ( On) controls.

According to a further advantageous embodiment of the door opening device, the electrical coupling device has a first electronic switching element which is electrically connected in series with the actuator. In the case of a direct voltage (DC) as an electrical supply voltage, the electronic switching element is preferably designed as a transistor, in particular as a bipolar transistor or field-effect transistor, particularly preferably as a field-effect transistor with an insulated gate (MOSFET or IGFET). In the case of an alternating voltage (AC) as the supply voltage, the first electronic switching element is preferably designed as a bidirectional thyristor triode (triac) or as a relay, in particular as a semiconductor relay. In this case, galvanically isolated control can preferably take place via an optical connection, for example via an optical fiber.

According to an advantageous development of the door opening device, the electrical coupling device has a second electronic switching element which is electrically connected in series with the first electronic switching element. The actuator, which can be electrically represented by a magnet coil connected between the two actuator connections, and the first electronic switching element and the second electronic switching element are thus electrically connected to one another in series. The second electronic switching element can be used to implement a safety circuit which is designed to cause the electrical activation of the actuator to be interrupted if the first electronic switching element is actuated incorrectly by the pulse-shaped coupling signal. For example, the signal generation unit can be implemented by a program-controlled computing unit, in particular by a microcontroller / microprocessor, which provides the coupling signal to the first electronic switching element. In this case, the second electronic switching element can preferably be controlled by an independent analog circuit, which thus takes over the function of an electronic fuse. In this way, for example, an overload of the actuator can be prevented even if the program-controlled computing unit crashes.

According to an advantageous development of the door opening device, the signal generation unit is designed to generate the coupling signal as a function of an electrical current through the actuator. As a result, the current through the actuator can be regulated in such a way that a desired time profile results in accordance with a predefined setpoint profile of the pressing force. In particular, influences caused by voltage fluctuations can be compensated for.

According to an advantageous development of the door opening device, the signal generation unit is designed to generate the coupling signal as a pulse width modulation signal. This means that the coupling signal is generated with a constant, predefinable pulse period, namely the reciprocal of a pulse width modulation frequency (PWM frequency), a variable pulse width being set. The ratio of the pulse width to the pulse period is determined by the so-called duty cycle. Alternatively, a pulse sequence control can be provided, in which a constant, predefinable switch-on time is set, and the duty cycle by controlling the respective switch-off time is realized. A constant switch-off time can also be provided and the switch-on time can be varied accordingly.

The duty cycle can preferably be implemented for each clock cycle according to a so-called cycle-by-cycle control. It can also be provided to generate the coupling signal based on a two-point controller method in that the coupling signal is switched on when the current through the actuator has fallen below a predeterminable minimum value and the coupling signal is switched off when the current through the actuator exceeds a predefinable maximum value. The respectively valid minimum value and / or the respectively valid maximum value can be time-dependent. In this way, a particularly simple control procedure can be implemented.

A household appliance, in particular for the care of laundry, can preferably have a door opening device according to the invention and a door which can be pushed out of a closed position by the door opening device, which results in a household appliance according to the invention. The door of the household appliance can be pushed open by the door opening device with better time controllability and a gentle rise behavior. Improved compensation for a possible fluctuation in the input voltage, which is used as the supply voltage for the household appliance, is also possible. In addition, the use of a feedback can be provided, which is used to avoid a much stronger impact on the door when the door is already open. However, such an additional shock does not occur at all if the rise is slow enough. In addition, an absorption effect, which is generated by the mechanical parts of the household appliance, can be overcome. Longer pulses, for example when using an entire pulse train, also mean less noise from the door opening device. In particular, when using a DC voltage as the internal supply voltage of the door opening device, independence from the mains frequency and mains voltage of a supply network on which the household appliance is operated can be achieved.

Further features of the invention result from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, and those mentioned below in the description of the figures and / or features and combinations of features shown in the figures alone can be used not only in the combination indicated in each case, but also in other combinations without departing from the scope of the invention. Embodiments of the invention are thus also to be regarded as encompassed and disclosed, which are not explicitly shown and explained in the figures, but which emerge from the explanations explained and can be generated by separate combinations of features.

Further advantages and features result from the following description of exemplary embodiments, taking into account the attached figures. In the figures, the same reference symbols denote the same features and functions.

Fig. 1

in vereinfachter schematischer Frontansicht ein Haushaltsgerät gemäß der Erfindung;

Fig. 2

in vereinfachter schematischer Darstellung eine zum Betrieb einer Türöffnungsvorrichtung, wie sie in dem Haushaltsgerät gemäß Fig. 1 angeordnet ist, verwendete Schaltungsanordnung;

Fig. 3

in vereinfachter schematischer Darstellung eine Modifikation der in der Fig. 2 dargestellten Schaltungsanordnung zur Verwendung in einer erfindungsgemäßen Türöffnungsvorrichtung gemäß einer erfindungsgemäßen ersten Ausführungsform; und

Fig. 4

in vereinfachter schematischer Darstellung eine zweite Ausführungsform einer nichterfindungsgemäßen Türöffnungsvorrichtung.

Show it:

Fig. 1

in a simplified schematic front view of a household appliance according to the invention;

Fig. 2

in a simplified schematic representation one for operating a door opening device, as in the household appliance according to Fig. 1 is arranged, circuitry used;

Fig. 3

in a simplified schematic representation a modification of the in Fig. 2 Circuit arrangement shown for use in a door opening device according to the invention according to a first embodiment of the invention; and

Fig. 4

in a simplified schematic representation, a second embodiment of a door opening device according to the invention.

A household appliance 1 for the care of laundry is in the Fig. 1 shown. This can be a washing machine, a tumble dryer or a combination device consisting of a washing machine and tumble dryer. In the illustrated embodiment, it is a so-called front loader, which has a door 2 opening to the front, which is used to close a loading opening 3, which is circular, for example. The household appliance 1 comprises a housing 4, in which a drum 5 for holding laundry items is arranged. The loading opening 3 is a front opening of the drum 5. The household appliance 1 furthermore comprises an operating device 6, which is to be understood only in an exemplary and non-limiting manner in configuration and position and which has at least one operating element 7 and a display unit 8. In addition, a drawer-like induction bowl 9 is shown.

The pivotably arranged and in particular porthole-shaped door 2 is in mechanical contact with a door opening device 10 arranged within the household appliance 1. In the exemplary embodiment, this door opening device 10 is arranged such that it can act on the inside of an edge piece of the door 2. This edge piece is opposite another edge piece of the door 2, on which the door 2 by means of a Fig. 1 Hinge, not shown, is pivotally mounted on the household appliance 1.

The door opening device 10 comprises an electromechanical actuator 11, which has a magnetic coil and an actuator element made of a magnetic or magnetizable material, preferably made of a ferromagnetic material, which is movably mounted in the effective range of a magnetic field that can be generated by the magnetic coil. The door opening device 10 further comprises a signal generation unit 12, which is designed to provide a pulse-shaped coupling signal to an electrical coupling device 13, which effects the electrical activation of the electromechanical actuator 11.

The door 2 can be opened automatically by means of the door opening device 10 at the end of a washing or drying process if a correspondingly set program for treating laundry items has expired. Alternatively or additionally, it can be provided that the door 2 of the household appliance 1 is opened by the door opening device 10 when a user of the household appliance 1 opens one Corresponding operating action via the operating device, for example by pressing a button on the operating device 6 or by means of an input element on a touch screen, for example the display unit 8.

Fig. 2 shows the electrical part of a door opening device 10, which in a household appliance 1 as shown in FIG Fig. 1 can be used. The door opening device 10 comprises a supply connection 16 and a reference connection 17. The reference connection 17 can be electrically connected to a neutral conductor connection (N) of a supplying AC or three-phase network. The supply connection 16 can be electrically connected to an outer conductor connection (L) of the supplying alternating voltage or three-phase network. Such an arrangement can be fed with a voltage of 230 volts and a frequency of 50 Hertz. A first actuator connection 14 of two actuator connections 14, 15 is electrically conductively connected to the supply connection 16. A second actuator connection 15 of the two actuator connections 14, 15 is electrically coupled to the reference connection 17 via an electrical coupling device 13 in the form of a first switching element 21, which is designed as a reusable thyristor triode (triac).

A supply voltage 18, which has a sinusoidal shape, is present between the supply connection 16 and the reference connection 17. In particular, it is a voltage of 230 volts with a mains frequency of 50 Hertz. An electrical control of the actuator 11 takes place by means of a pulse-shaped coupling signal 19 Fig. 2 is represented by its solenoid. The current through the magnetic actuator is shown schematically as actuator current 20. The actuator current 20 has both positive and negative half-waves, the amplitude of which is the same in each case. When using an actuator element in the form of a ferromagnetic element, the attraction force of which is based on the reluctance force, an attraction force results which is proportional to the square of the actuator current 20. For this reason, there is an unsigned course of the pressing force transmitted from the actuator element to the door 2 by means of a tappet, regardless of a momentary flow direction of the actuator current 20. Relative to the representations in FIG Fig. 2 this results in only successive positive half-waves for the course of the pressing force.

The electrical actuation of the magnetic coil of the actuator 11 with an alternating current (AC), which is shown in the figure by way of example with three half-periods, must therefore already have the force required for opening within the first half period, that is to say at a mains frequency of 50 Deploy Hertz within 10 milliseconds. In other words, within a half-period, that is to say within 10 milliseconds, the total energy (W) resulting from half the inductance (L) of the coil, which in turn depends on the position of the movable actuator element in relation to the magnet coil of the actuator 11 depends, times the square of the current (I) through the actuator 11 results (W = ½ · L · I ² ). After that, the energy in the magnetic coil does not increase any further, so that no further increase in force for the push-out force can be achieved from this.

This short time has several disadvantages. On the one hand, the effective pulse duration depends on the frequency. If the solenoid remains activated for a longer period of time, vibrations can occur due to the zero crossings of the actuator current 20 at a phase position of 0 degrees and 180 degrees. The door 2, the household appliance 1 and a door holding mechanism are mechanical parts which are connected to one another. Under certain circumstances, they can largely absorb the effect of a rapid impact by the door opening device 10 with a duration of less than or equal to 10 milliseconds, since they act as a mechanical filter. A large pulse is therefore required. Furthermore, voltage fluctuations can lead to different press-on forces, since different energy is supplied to the solenoid within the 10 milliseconds, so fine adjustment for voltages between 170 volts and 260 volts is not possible. To ensure that door 2 opens at 170 volts AC at all times, a stronger impact at 260 volts AC must be permitted. The pulse width of the control of the pulse-shaped coupling signal 19, which is used to control the first switching element 21 in the form of the triac, is shown in FIG Fig. 2 to be understood only as representative and not restrictive.

To achieve a time profile of the pressing force, which has an increasing envelope, according to a first exemplary embodiment of the invention, which is shown in FIG Fig. 3 a resistance element 22 in electrically connected in series with the actuator 11 is further shown in the electrical part of the door opening device 10 Form of a thermistor, which has a temperature-dependent resistance value with a negative temperature coefficient, supplemented. The resistance element 22 is thus connected between the first actuator connection 14 and the supply connection 16 and takes the place of the direct electrical connection between the first actuator connection 14 and the supply connection 16 as shown in FIG Fig. 2 .

In principle, a door opening device 10 as shown in FIG Fig. 3 If the actuator is activated for a longer period of time, vibration occurs depending on the system frequency and the mechanical characteristics. Such a tendency to oscillate can be reduced by coupling the magnet coil of the actuator 11 via a full-wave rectifier (bridge rectifier). In this case, it is also possible to integrate a smoothing element, for example a capacitor, behind the rectifier in order to achieve filtering of network-frequency components from the excitation signal.

An NTC takes some time to cool down again, which leads to the system not working so efficiently in the event that door 2 is to be opened twice within a short time. In this case, a second embodiment shown below provides a more effective way to control the door opening device 12 by means of a DC-powered circuit arrangement.

According to the second embodiment of the door opening device, which does not represent the present invention, as shown in FIG Fig. 4 a DC voltage is connected to the supply connection 16 and the reference connection 17 as a supply voltage 18. The supply voltage 18 can preferably be 175 volts DC to 400 volts DC. These values are not to be understood as restrictive, rather any voltage level, in particular also less than 175 volts DC, can be provided. The coupling device 13, which is coupled in series with the electromechanical actuator 11 in a known manner, has, in the second exemplary embodiment shown, a first switching element 21 and a second switching element 24, which are connected in series with one another. The first switching element 21 and / or the second switching element 24 can be implemented as bipolar transistors. A freewheeling diode 23 is coupled to the first actuator connection 14 and the second actuator connection 15 parallel to the magnetic coil of the actuator 11.

The free-wheeling diode 23 serves to prevent overvoltage peaks which can otherwise occur when the first switching element 21 and / or the second switching element 24 are switched off. The first switching element 21, which in the present case is designed as a bipolar transistor, receives the pulse-shaped coupling signal 19 at its base connection. In the second embodiment, the pulse-shaped coupling signal 19 is designed as a pulse width modulation signal (PWM signal). The coupling signal 19 in a subsequent clock cycle each has a larger pulse width than in the previous clock cycle. This results in an actuator current 20 which has an increasing envelope. From the functional relationship according to which the pressing force is correlated with the actuator current 20, for example, as shown above, a proportionality to the square of the actuator current 20, an increasing envelope curve also results for the course of the pressing force over time.

The second switching element 24 represents a safety circuit (PEC). The type of implementation of this second switching element 24 is not important for the invention.

The relationship between the actuator current 20 and the time course of the pressing force generated therefrom can have a very different characteristic depending on the type of electromechanical actuator 11 used. According to the second exemplary embodiment, the use of a pulse-shaped coupling signal 19 as a curve consisting of a plurality of individual pulses thus allows the curve shape of the actuator current 20 to be freely adjustable in accordance with the requirements for a pressure force curve to be set. As a result, the dynamic behavior of the opening process can be optimized in terms of a safe and comfortable process.

The circuit arrangement shown has several advantages in the door opening process. A pulse sequence with increasing pulse width can be provided to the coupling device 13, for example with a continuous increase from 0 percent to 100 percent duty cycle. Different rise curves can be generated depending on the circuit arrangement and the mechanical properties of the actuator 11, for example with a slight overshoot towards the end of the door opening process.

Likewise, the increase in the duty cycle can be adapted to the level of the available DC voltage, which is obtained, for example, for the electrical supply of further components of the household appliance 1, such as a drive motor or a heating device, from the supplying AC or three-phase network. A better compensation of possible input voltage fluctuations is also possible.

A slow rise behavior serves to reduce the impression of an abrupt door impact and also to reduce the noise. If the climb is slow enough, this additional shock will not occur.

If the rise is carried out so slowly that an additional door opening signal (feedback signal) can be recognized, the door opening device can be deactivated immediately in order to avoid a much stronger additional impact on the door already released by the door holding mechanism.

While the first embodiment of the invention can be implemented with very simple means, the second embodiment not according to the invention offers a significantly higher degree of flexibility and in particular also allows independence from the network frequency and the network input voltage.

The exemplary embodiments merely serve to explain the invention and are not restrictive for it. In particular, the specific configuration of the circuitry means by means of which the invention is implemented can be designed in any way without departing from the spirit of the invention.

It has thus been shown above how a door opening device 10, in particular a door opening device 10 controlled by means of direct voltage, as shown in the second embodiment, can be designed to improve safety and comfort in a door opening process carried out by the household appliance. In addition to a DC-based activation of the door opening device 10, an improved AC-based activation of the door opening device 10 has also been proposed.

Reference symbol list

1

Home appliance

2nd

door

3rd

Loading opening

4th

casing

5

drum

6

Operating device

7

Control element

8th

Display unit

9

Induction bowl

10th

Door opening device

11

electromechanical actuator

12

Signal generation unit

13

electrical coupling device

14

first actuator connection

15

second actuator connection

16

Supply connection

17th

Reference connection

18th

Supply voltage

19th

pulse-shaped coupling signal

20th

Actuator current

21st

first switching element

22

Resistor element, variable

23

Free-wheeling diode

24th

second switching element

Claims (14)

1. Method for activating a door opening device (10), comprising an electromechanical actuator (11), of a household appliance (1) comprising a door (2) during an opening process, wherein the actuator (11) comprises two actuator connections (14, 15) for electrical activation, by:

   - providing an electrical supply voltage (18) between an electrical supply connection (16) and an electrical reference connection (17) of the door opening device (10), which has a predefined voltage waveshape in an intended operating state of the household appliance (1),

   - providing an electrical coupling device (13) for coupling, if necessary, a first of the two actuator connections (14, 15) to the supply connection (16) and/or a second of the two actuator connections (14, 15) to the reference connection (17),

   - coupling the supply voltage (18) and the two actuator connections (14, 15) by means of the coupling device (13) as a function of a pulse-shaped coupling signal (19) for the electrical activation of the actuator (11), and

   - generating a pressing force for acting on the door (2) as a function of the electrical activation of the actuator (11),

   - generating the pulse-shaped coupling signal (19) as a function of the predefined voltage waveshape and/or as a function of the coupling device (13) provided in order to achieve a time characteristic of the pressing force, which has a rising envelope,

   characterised in that

   - the electrical coupling device (13) has a resistance element (22) with a variable electrical resistance which is electrically connected in series to the actuator (11).
2. Method according to claim 1, characterised in that the provision of the coupling device (13) and the generation of the pulse-shaped coupling signal (19) is carried out such that the time characteristic of the pressing force during an active pulse phase of the coupling signal (19) has a sequence of at least two local maxima, which are respectively on or near the rising envelope, wherein a second local maximum of the at least two local maxima which follows a first local maximum of the at least two local maxima later in time has a higher value than the first local maximum.
3. Method according to claim 2, characterised in that the provision of the coupling device (13) and the generation of the pulse-shaped coupling signal (19) is carried out such that the sequence of the at least two local maxima has a third local maximum which follows the second local maximum later in time, said third local maximum having a higher value than the second local maximum.
4. Method according to one of the preceding claims, characterised in that the electrical supply voltage (18) is provided by a DC voltage source.
5. Method according to one of claims 1 to 3, characterised in that the electrical supply voltage (18) is provided by an AC voltage source.
6. Method according to one of the preceding claims, characterised in that the coupling signal (19) is generated during the opening process with a sequence of a plurality of individual pulses spaced apart in time.
7. Method according to claim 5, characterised in that the coupling signal (19) is generated during the opening process with a single individual pulse.
8. Method according to one of the preceding claims, characterised in that the coupling signal (19) is generated as a function of a first signal which signals an opening state of the door (2), and/or as a function of a second signal which signals a locking state of the door (2).
9. Door opening device (10) for a household appliance (1) comprising a door (2), wherein the door opening device (10) comprises:

   - an electrical supply connection (16) and an electrical reference connection (17), between which an electrical supply voltage (18), which has a predefined voltage waveshape in an intended operating state of the household appliance (1), can be provided,

   - an electromechanical actuator (11) for generating a pressing force for acting on the door (2) as a function of an electrical activation of the actuator (11), which comprises two actuator connections (14, 15) for electrical activation, and

   - an electrical coupling device (13) which is designed for the electrical activation of the actuator (11) as a function of a pulse-shaped coupling signal (19) to couple a first of the two actuator connections (14, 15) to the supply connection (16) and/or a second of the two actuator connections (14, 15) to the reference connection (17),

   - a signal generation unit (12) which is designed to generate the coupling signal (19) as a function of the predefined voltage waveshape and/or as a function of the coupling device (13) to achieve a time characteristic of the pressing force, which has a rising envelope,

   characterised in that

   - the electrical coupling device (13) has a resistance element (22) with a variable electrical resistance which is electrically connected in series to the actuator (11).
10. Door opening device (10) according to claim 9, characterised in that the electrical coupling device (13) has a first electronic switching element (21) which is electrically connected in series to the actuator (11).
11. Door opening device (10) according to claim 10, characterised in that the electrical coupling device (13) has a second electronic switching element (24) which is electrically connected in series to the first electronic switching element (21).
12. Door opening device (10) according to one of claims 9 to 11, characterised in that the signal generation unit (12) is designed to generate the coupling signal (19) as a function of an electrical current through the actuator (11).
13. Door opening device (10) according to one of claims 9 to 12, characterised in that the signal generation unit (12) is designed to generate the coupling signal (19) as a pulse width modulation signal.
14. Household appliance (1), in particular for the care of laundry, having a door opening device (10) according to one of claims 9 to 13, and having a door (2) which can be pushed out of a closed position by the door opening device (10).

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