EP2819552B1 - Electromotive furniture drive for a piece of furniture, method for monitoring a pulse-width ratio of an electromotive furniture drive, and a corresponding piece of furniture - Google Patents

Description

The invention relates to an electromotive furniture drive for furniture according to the preamble of claim 1. The invention also relates to a method for monitoring a pulse width ratio of an electromotive furniture drive. The invention also relates to a corresponding piece of furniture.

Furniture with several support surfaces for supporting a person in the furniture are widely used and known, for example as beds, sofas, armchairs and the like. They have at least one movable support surface which is movably mounted relative to at least one further support surface. The movable support surface is, for example, a back part and / or a leg part, which is adjustable with at least one electromotive furniture drive. For this purpose, the movable support surface can be pivotable, displaceable or both by means of a suitable fitting. It is also possible for a basic element, e.g. a bed frame, to be designed to be height-adjustable with one or more furniture drives.

An electromotive furniture drive comprises at least one electric motor, which is often designed as a brushed DC motor. A gear is connected downstream of the motor, a direct current gear motor usually being used. Furthermore, the electromotive furniture drive comprises an operating unit and a control device. The operating unit can be wired or wireless and has a number of pushbuttons, when actuated, via the signal transmission, a control signal for the electrical control of the respective motor takes place in the respective direction of rotation.

Various solutions have been given for positioning an output member of the electromotive furniture drive. In one example, the controller has a counter for counting pulse signals from a respective motor. The pulses are added in a first direction of rotation and subtracted in a second direction of rotation. So-called memory controls are used to repeatedly set a previously definable position. The previously determinable position can be saved by the user and called up again and again, ie adjusted.

Motors with Hall sensors / reed contacts / light barriers as pulse generators are known. Hall sensors are expensive and complex to assemble, e.g. their signal transmitters (magnets) have to be installed separately from the Hall sensors, which are arranged on their own circuit boards. Two Hall sensors are required for reliable detection of the direction of rotation. Cabling with multi-core cables, e.g. 5-core motor cable, is necessary. The control requires the use of a microprocessor or microcomputer. Existing furniture without memory control cannot be retrofitted, or only with great effort.

The document DE 10 2009 059 267 A1 describes a method and a device for positioning an output member of an electric motor drive, in particular for a piece of furniture. Pulses of a back EMF of a respective electric motor are recorded and evaluated.

The object of the present invention is to create an improved electromotive drive.

Another object is to provide an improved method.

Yet another object is to provide improved furniture.

This object is achieved by an electric motor drive with the feature of claim 1.

The object is also achieved by a method having the features of claim 16 and by a piece of furniture having the features of claim 21.

An electromotive furniture drive is created, the control device of which has a digital potentiometer in a simple design for memory control and synchronous controls.

An electromotive furniture drive according to the invention for adjusting a movable part of a piece of furniture by means of an output member comprises a) at least one adjustment drive, each with at least one electric motor, a speed reduction gear coupled therewith, with which the output member is drive-coupled and linearly movable and / or rotatable, wherein the output member actuates a limit switch and / or a reference switch and / or a switching device when a predetermined position is reached, b) at least one control device, and c) at least one operating unit, the control device has a positioning device for the output member with a control block with a counter and a memory device for evaluating pulses of a back EMF of the at least one electric motor. At least one monitoring device is provided for monitoring a pulse width ratio of a detected back EMF of the at least one electric motor.

With such a monitoring device, the reliability of the electromotive furniture drive is increased in a simple manner.

In one embodiment, it is provided that the monitoring device comprises at least one filter unit with a pulse shaper, and a load monitoring device with a pulse width ratio detector, a comparator and a signal generator. It has been found that with high loads on the_Elektromotors_das pulse width ratio, the ripple of the back EMF changes in a certain way. These changes can advantageously be recognized by the monitoring device. Countermeasures can be taken which increase reliability and reduce an error rate.

It is advantageous if the pulse shaper is a square-wave pulse shaper, so that there is always a defined pulse.

In a further embodiment, the pulse width ratio detector is designed to detect the pulse width ratio of the detected back EMF of the at least one electric motor. This can be done, for example, by means of simple electronic components that are available on the market at low cost and in high quality.

In yet another embodiment, the comparator is designed to compare the detected pulse width ratio with a value that can be determined beforehand. According to measurements and investigations carried out, a critical value is a pulse width ratio of 10/90. It is therefore advantageous if the previously definable value corresponds to a pulse width ratio of 10/90.

It is also provided that the signal generator is designed to generate a signal for controlling the engine in order to throttle the engine. A simple and effective countermeasure can thus be taken in that less energy is supplied to the respective motor when a critical value of the pulse width ratio is reached. In addition, the throttling protects the engine under high loads.

In yet another embodiment, the monitoring device has at least one return monitoring device which is coupled to the output of the filter unit. This means that the same measuring arrangement can be used to determine whether the motor may be twisted under an external mechanical load when it is switched off, short-circuited.

For this purpose, it is provided that the return monitoring device is designed to detect a rotation of a motor shaft of the motor when the motor is short-circuited and switched off and to signal such a detection. This makes it possible in a simple manner to detect a rotation of the motor shaft and thus a change in positioning due to external mechanical influences. Corresponding corrections can be carried out, e.g. resetting the output link to a specific, defined position.

In yet another embodiment, it is provided that the monitoring device is equipped and connected to at least one energy store, preferably an accumulator or a capacitor of high capacity. In this way, the part of the electrical circuit of the positioning device for detecting, evaluating and counting the ripples in the currentless state can be operated at least for a certain period of time with the aid of the energy store.

For this purpose, it is advantageous that a storage capacity of the energy store is designed in such a way that the part of the electrical circuit of the positioning device for detecting, evaluating and counting the ripples in the currentless state can be operated at least for a certain period of time with the aid of the energy store.

In another embodiment, the at least one electric motor is equipped with at least one bridgeable series resistor for a soft start. As a result, possible disturbances in the detection of the back EMF by a PWM control in other embodiments according to the prior art are easily excluded. It is particularly advantageous if this resistor (or a part of it) is used at the same time as a measuring resistor for the back EMF.

In a further embodiment, the control device can have a digital potentiometer which outputs an electrical value proportional to the position of the output member as an output value.

It is particularly advantageous that a standard motor cable (2-wire) with a standard plug connection (2-pin) can be used on the controller. In principle, no changes to the standard motors are necessary.

In one embodiment, the digital potentiometer has at least one buffer and at least one digital-to-analog converter, the buffer being provided for buffering the counter readings of the counter, and the digital-to-analog converter converting the counter reading buffered in the buffer into an analog Converts output value. This allows a simple structure of the digital potentiometer. Existing free storage capacities of a storage device can be used as intermediate storage. It may also be possible to build the digital-to-analog converter in software with the existing microprocessor (s), which allows space to be saved.

The analog output value converted by the digital-to-analog converter is a voltage value and / or a current value that is easy to process further. In an advantageous manner, furniture drives can thus be replaced with a potentiometer built in as a displacement sensor, which is reflected, for example, in a very simple assembly. The output signal of the digital-to-analog converter is practically identical to the analog voltage output of a potentiometer in furniture drives of the prior art.

In addition, the analog output value converted by the digital-to-analog converter can be within a predetermined voltage or current interval, e.g. 0-5 V or 5-20 mA. wherein a minimum value corresponds to a first end position state of the output member and a maximum value corresponds to a second end position state of the output member.

The buffer memory can be designed as a volatile or non-volatile memory that can be overwritten. Many types of buffer storage can be used.

In another embodiment, at least one of the limit switches is provided in an end position of the output member to control the interruption of the power supply to the motor, to control the short-circuiting of the motor and to control the resetting of a reference point for the control or positioning of the output member. Thus, on the one hand, there is a reliable shutdown and on the other hand, a defined state of the motor, namely with regenerative braking, is possible in the off state.

In yet another embodiment, at least one limit switch is arranged as a reference switch in the range of motion of the output member at a predetermined location and is provided to control the resetting of a reference point for the control or positioning of the output member. This can significantly reduce an error rate in the repeatability

At this point, the essential difference to furniture drives of the prior art with pulse generators such as motors with Hall sensors is shown, whereby motors with Hall sensors are used for very precise positioning, for example in high-quality height-adjustable tables with synchronization of several motors with one another. Such furniture drives with synchronizers are very complex and expensive. The embodiment according to the present invention lays the foundation for an alternative of synchronizations and positioning accuracies with high quality, but is very simple in structure and only has a similar quality of the positioning accuracy. In tests, however, the embodiment and the method of the present invention have proven to be very reliable, with a very high degree of positioning quality being achieved, which can be regarded as completely sufficient for the furniture described.

• (V1) Erfassen von Impulsen einer Gegen-EMK des zumindest einen elektrischen Motors (M1) des elektromotorischen Möbelantriebs durch Messen eines Spannungsabfalls an einem Widerstand oder einem Eigenwiderstand eines Transistors;
• (V2) Erfassen eines Pulsweitenverhältnisses von Ripple der so erfassten Gegen-EMK des zumindest einen elektrischen Motors;
• (V3) Vergleichen des so erfassten Pulsweitenverhältnisses mit einem vorher festlegbaren Wert; und
• (V4) Überwachen des Pulsweitenverhältnisses durch Bewerten des so erhaltenen Vergleichens.

A method according to the invention for monitoring a pulse width ratio of the electromotive furniture drive described above has the method steps:

• (V1) detecting pulses of a back EMF of the at least one electric motor (M1) of the electromotive furniture drive by measuring a voltage drop across a resistor or an intrinsic resistance of a transistor;
• (V2) detecting a pulse width ratio of ripple of the back EMF of the at least one electric motor thus detected;
• (V3) comparing the pulse width ratio detected in this way with a value that can be set in advance; and
• (V4) Monitoring the pulse width ratio by evaluating the comparison thus obtained.

In this way it is advantageously possible to monitor the pulse width ratio in a simple manner, with parts (measuring resistor, filter unit) of the positioning device which are present at the same time being usable.

It is advantageous if, in method step (V1), the detected pulses are converted into rectangular pulses, since these have a defined shape and can be easily processed.

According to the examinations and measured values carried out, it is advantageous if the previously definable value for comparison in method step (V3) corresponds to a pulse width ratio of 10/90.

In one embodiment, it is provided that in method step (V4), when the value falls below a critical comparison value, the at least one electric motor is throttled during operation. This is possible through simple measures, e.g. appropriate control signals, by intervening in the motor control, for example by connecting at least one series resistor as mentioned above in series with the motor.

It is also provided that in method step (V3) a frequency of the ripple is monitored and in method step (V4) a signal is generated that there is a trapping or overload. Additional monitoring can thus take place.

A piece of furniture (1) according to the invention with
a) with at least one base element for coupling the piece of furniture to an installation location, and b) with at least one support element which has at least one part that is movably arranged relative to the support element or relative to a further support element or relative to the base element, c) the at least a movably arranged part is designed to be displaceable and / or pivotable, d) wherein the furniture has at least one electromechanical furniture drive, e) the at least one movably arranged part is coupled to the at least one electromechanical furniture drive, has the electromotive furniture drive described above.

In a further embodiment, the control device has a memory control. The use of the electromotive furniture drive with the digital potentiometer enables simple retrofitting and simple assembly with conventional adjustment drives.

In this way it is also advantageously easily possible for the control device to have a synchronous control, the adjustment speeds of at least two electromotive furniture drives adapted to each other, in particular equated.

This creates both a memory control and a synchronous control which can be used in any piece of furniture and which can be connected to any electromotive furniture drive used in the piece of furniture.

Figur 1

eine schematische Perspektivansicht eines beispielhaften erfindungsgemäßen Möbels;

Figur 2-2a

schematische Perspektivansichten einer Bedienungseinheit;

Figur 3

ein schematisches Blockschaltbild eines Ausführungsbeispiels eines erfindungsgemäßen elektromotorischen Möbelantriebs;

Figur 4-4a

schematische Schaltpläne von Schaltkontaktkonfigurationen;

Figur 5

einen schematischen Schaltplan einer H-Brückenschaltung;

Figur 6

ein schematisches Blockschaltbild eines Verstellantriebs mit Abtriebsglied und Endschaltern bzw. mit Referenzschaltern;

Figur 7

ein schematisches Blockschaltbild einer erfindungsgemäßen Überwachungsvorrichtung; und

Figur 8

ein schematisches Flussdiagramm eines erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to the accompanying drawings. Show it:

Figure 1

a schematic perspective view of an exemplary piece of furniture according to the invention;

Figure 2-2a

schematic perspective views of an operating unit;

Figure 3

a schematic block diagram of an embodiment of an electromotive furniture drive according to the invention;

Figure 4-4a

schematic circuit diagrams of switch contact configurations;

Figure 5

a schematic circuit diagram of an H-bridge circuit;

Figure 6

a schematic block diagram of an adjustment drive with output member and limit switches or with reference switches;

Figure 7

a schematic block diagram of a monitoring device according to the invention; and

Figure 8

a schematic flow diagram of a method according to the invention.

Fig. 1 shows an embodiment of a piece of furniture 1 according to the invention. FIGS. 2 and 2a show schematic perspective views of an operating unit 10, 10 '. In Fig. 3 a schematic block diagram of an exemplary embodiment of an electromotive furniture drive 100 according to the invention is shown.

The furniture 1 is shown here as a bed and has at least one support element 3 for receiving objects, upholstery, a mattress M and / or a person. The support element 3 is for example as a slatted frame, or as a flat support surface the like formed and attached to a base element 2, here a frame with feet, for coupling the piece of furniture 1 to an installation location, for example the floor.

The support element 3 here has a back part 4 and a leg part 5, which are arranged so as to be moveable relative to the support element 3 and / or a further support element or relative to the base element 2. This movable arrangement is implemented here by means of what is known as a movement fitting 6. The movement is designed to be displaceable and / or pivotable.

The piece of furniture 1 also has an electromotive furniture drive 100, which here comprises two adjustment drives 7 and 8, a control device 9 and an operating unit 10.

The movably mounted back part 4 and the leg part 5 are each coupled to an adjustment drive 7, 8. The back part 4 is coupled to the adjustment drive 7. The adjustment drive 8 is provided for moving or adjusting the leg part 5.

The adjusting drives 7, 8 are designed here as linear drives. The linear drives have one or a number of electric motors, each motor being followed by a speed reducing gear with at least one gear stage. The speed reduction gear can be followed by a further gear, for example in the form of a threaded spindle gear, which converts the rotary movement of the motor into a linear movement of an output member 19 ( Fig. 3 ) generated. The last gear element or a further element connected to it forms the output element 19. The output element 19 of the respective adjustment drive is connected to the respective furniture component (back part 4, leg part 5) or, alternatively, to a component connected to the base frame 2, so that during operation of the electric motor of the respective adjustment drive 7, 8, the movable furniture components 4, 5 are adjusted relative to one another or relative to the base frame 2.

The adjusting drives 7, 8 are each connected to a control device 9 via a drive line 100a, as in FIG Fig. 3 is shown. This drive line 100a can for example be designed as a pluggable cable connection. The control device 9 has an electrical supply unit 9a, which provides the electrical energy, for example from the network, for the adjustment drives 7, 8. For this purpose, the control device 9 in this example can be connected to a mains connection via mains cable 9d with a mains plug 9e. The mains plug 9e conducts the mains voltage on the input side to the electrical supply unit 9a of the control device via the mains cable 9d 9, which on the secondary side emits a low voltage in the form of a direct voltage and forwards this to a motor controller with control switches 9b.

As an alternative to this, the control device 9 is preceded by a network-dependent voltage supply (not shown in detail) with a network input and a secondary-side low-voltage output, which supplies the low-voltage in the form of a direct voltage via the line 9d.

A control unit 10, 10 'is also assigned to the piece of furniture 1, with its control elements 12, 13 (see FIG Fig. 2 ) the adjustment drives 7, 8 can be controlled via the control device 9.

The operating unit 10 according to Fig. 2 is provided with a transmitter or transmitter / receiver for wireless transmission. The wireless transmission can be a radio transmission path, optical transmission path (for example infrared) and / or an ultrasonic transmission path, the control device 9 being equipped with a respective corresponding receiving device.

In another embodiment, the operating unit 10 'is designed with an operating line 18 in wired form, what Fig. 2a shows. The operating line 18 can be connected to the control device 9, for example plugged in.

The operating unit 10, 10 'is provided with operating elements 12, 13, which are provided for operating a respective adjustment drive 7, 8. The operating elements 12, 13 are designed as buttons, for example. For example, the operating elements 12 are used to raise and the operating elements 13 to lower the respective movable furniture part. In Figures 2 and 2a operating units 10, 10 'for six adjustment drives are shown.

Furthermore, the operating unit 10, 10 'is equipped with a signaling element 14, for example a light-emitting diode. The signaling element 14 is used, for example, for function display or feedback, error display, etc.

An additional operating element 15, which can also consist of a plurality of operating elements and / or a combination operating element, serves for a so-called memory function of the adjustment drives 7, 8.

In addition, additional functions, such as reading lamps and / or heating, can be operated using additional operating elements 16, 17.

The additional operating elements 15, 16, 17 can be designed as buttons and / or switches.

When an operating element 12, 13 is actuated, a control signal for controlling the respective adjusting drive 7, 8 is transmitted to the control device 9 wirelessly or by wire via the transmission path. The control device 9 has control switches 9b with switching elements which convert the control signals of the transmission path into switching signals for switching the respective adjusting drive 7, 8. The switching elements can be, for example, relay switches and / or semiconductor switches. The manually operable operating elements 12, 13 of the operating unit 10 generate control signals which are here converted by a receiver 9c of the control device 9 into control currents for the switching elements. In the wired operating unit 10 ', the operating elements 12, 13 switch the control current of the relay switches or the semiconductor switches. In both cases, the circuit breakers of the relay switches or the semiconductor switches switch the high motor current of the respective adjusting drive 7, 8.

The adjusting drives 7, 8 are designed as brushed DC motors or have them.

The control device 9 of the electromotive furniture drive 100 also includes a positioning device 200 for positioning the respective output member 19 of the respective adjustment drive 7, 8. The positioning device 200 is according to the one in the document DE 10 2009 059 267 A1 Positioning device described and formed with the in the DE 10 2009 059 267 A1 equipped control block 110 described, which is shown here with a counter 117 and a storage device 118.

For a so-called memory control and / or synchronous controls for a plurality of adjusting drives 7, 8, a back EMF of the respective motor M1 is detected, with so-called ripples of the back EMF being evaluated. A procedure for this is also in the DE 10 2009 059 267 A1 described in detail, which is fully incorporated herein by reference.

The electromotive furniture drive 100 according to the invention, in contrast to the positioning device of DE 10 2009 059 267 A1 additionally a monitoring device 20 for monitoring a pulse width ratio of ripple of the detected back EMF of the motor M1 and both furthermore and beyond a digital potentiometer 120. The monitoring device 20 is described in detail below.

The digital potentiometer 120 has at least one intermediate memory 121 and at least one digital-to-analog converter 122. The intermediate memory 122, which is designed, for example, as an overwritable volatile or non-volatile memory, is connected to the counter 117 of the control block 110 and is provided for the intermediate storage of counter readings of the counter 117. The digital-to-analog converter 121 converts the counter reading temporarily stored in the buffer memory 121 into an analog output value and makes it available at an analog output.

The analog output value is e.g. a voltage value and / or a current value. For example, it can be within a predetermined voltage or current interval. A minimum value corresponds to a first end position of the output member 19 and a maximum value to a second end position of the output member 19. This interval can range, for example, from 0 V to 5 V, with 0 V corresponding to a first end position of the output member 19 and 5 V to a second End position of the output member 19 corresponds. This simulates a potentiometer which is coupled to the output member 19 of the respective adjusting drive 7, 8.

The control device 9 also has an energy store 130. The energy store is preferably an accumulator or a capacitor of high capacity. A storage capacity of the energy store 130 is designed in such a way that the part of the electrical circuit for detecting, evaluating and counting the ripples of the positioning device 200 can be operated at least for a certain period of time with the aid of the energy store 130 in the currentless state.

Figures 4 and 4a show schematic circuit diagrams of switch contact configurations.

In Fig. 4 the motor M1 is connected to a connection 1 of a changeover contact S1 via a first connection line. The second connection line of the motor M1 is connected to a connection 1 of a second changeover contact S2 via a resistor R1. The changeover contacts S1 and S2 are, for example, switching contacts each of a relay.

In another embodiment, not shown in detail, the operating unit 10 has at least two switchover contacts S1 and S2 which are actuated by the operating elements 12, 13.

Fig. 4 shows the motor M1 in a non-switched on state. NC connections 2 of the changeover contacts S1 and S2 are connected to one another and to a positive line of the supply unit (not shown) of the control device 9. Normally open contacts 3 of the changeover contacts S1 and S2 are also connected to one another and connected to a minus / ground line of the supply unit (not shown) of the control device 9. Fig. 4 shows the non-switched-on state of the motor M1. The motor M1 is short-circuited via the break contacts 2 of the changeover contacts S1 and S2 and the resistor R1. This state is also known as a regenerative brake.

To detect the back EMF of the motor M1, a voltage which drops across the resistor R1 due to the motor current flowing through the resistor R1 when the motor M1 is operating is measured at the terminals A and B of the resistor R1.

In the configuration according to Fig. 4 If the motor M1 is short-circuited, it is also possible to detect the motor current that is generated by the rotation of the motor shaft of the motor M1 due to high load despite the short circuit. Such a rotation can occur if, for example, a self-locking of the mechanical gear, which is interposed between the motor shaft and the introduction of force, is overcome by applying a great deal of force. It is also possible that a braking device still allows the motor shaft to rotate if the overload torque is not provided. Such cases can be recorded and appropriate countermeasures initiated.

In an alternative implementation, the Figure 4a shows, the back EMF of the motor M1 can also be detected in the power supply line. In this case, a resistor R2 is arranged in the minus / ground line to the normally open contacts 3 of the changeover contacts S1 and S2. The motor lines of the motor M1 are each connected directly to the connections 1 of the changeover contacts S1, S2. The back EMF of the motor M1 can be detected as a function of its motor current at the connections A 'and B' of the resistor R2. In this case, only one motor can be moved at a time if the resistor R2 is in a common supply line for all motors.

The further resistor R3 in the minus / ground line fulfills further functions for certain versions, which are explained in more detail below.

This resistor R3 can be switched into the line for a so-called soft start function. This is done, for example, in that the resistor R3 can be bridged by a contact. This bridging is opened during the soft start so that the motor current has to flow through the resistor R3. After a corresponding start-up time, the bridge is closed again and the resistor R3 is bridged for normal operation of the motor M1.

Alternatively or additionally, it is possible to connect several resistors in series or in parallel, whereby these are then automatically bridged, e.g. via relay contacts or semiconductor switches. The resistor R3 can also be an NTC with additional bridging.

Instead of the resistor R3, an adjustable resistor, e.g. a transistor, can of course also be used. The transistor can be controlled more or less via a ramp function. The ramp function is e.g. current-controlled and / or temperature-controlled. A high current leads to a brief ramp.

Alternatively, the resistor R2 and R3 can also be designed in one embodiment or combination, so that two functions, namely soft start and detection of the back EMF, can be carried out with one resistor. After the soft start, a bridging takes place in such a way that a residual resistance remains, above which the back EMF can drop for detection.

By using the resistor R3 and the alternatives or additions described above, a significant advantage over PWM control of the motor M1 for obtaining a soft start in connection with the evaluation of the back EMF is possible. A PWM control would interfere with an evaluation of the so-called ripple of the back EMF.

Furthermore, the soft start can also be understood as the throttling described at the outset, since the moment the electric motor is switched on and at the same time when high loads are moving, the pulse width ratio can be in the critical range, which affects the evaluation and counting of the ripples. In an inventive way, the soft start or the throttling acts like a resistor. In the simplest way, a resistor is used as described above. Another resistance also has an imaginary component and can have an inductance or a capacitance. The resistor R3 could thus also be an inductance or have an inductance.

The evaluation of the back EMF is carried out in an analog and discrete manner using filters, as in FIG DE 10 2009 059 267 A1 is specified, and takes place after digitization by means of a microprocessor which is present in the control device 9 and is designed with a correspondingly high sampling rate.

The motor M1 of each adjustment drive 7, 8 can also be switched and controlled with semiconductor switches. To do this shows Fig. 5 a schematic circuit diagram of a so-called H-bridge circuit.

The motor M1 is connected in the bridge branch between two series-connected transistors T1, T2 and T3, T4. Here a resistor R1 is connected in series with the motor M1. The transistors T1 ... T4 can be designed as MOS-FETs, for example, whereby they are partly conductive or non-conductive in the idle state.

There are several possibilities for detecting the back EMF of the motor M1, which are briefly given here in tabular form. Table 1: Measuring points No. Port 1 Connection 2 1 A. B. 2 C. Dimensions 3 D. Dimensions 4th C. D. 5 E. F. 6th C. Positive pole 7th D. Positive pole

A measurement according to No. 1 is preferably carried out at the connections A and B via the resistor R1, since a rotation of the motor M1 in the short-circuited state can thus also be detected.

A measurement according to No. 4 enables fluctuations in the collector current to be recorded.

Since the transistors T1 ... T4 themselves each have an inherent resistance in the conductive state, a measurement can be made, for example, via the transistor T2 according to No. 5 (of course also via any other of the transistors T1 ... T4). The inherent resistance of the respective transistor T1 ... T4 can thus be used in the simplest possible way.

In the switched-off state of the motor M1, in which the motor M1 is to be short-circuited to generate the generator brake, the transistors T2 and T4 are switched to earth in this example.

Fig. 6 shows a schematic block diagram of an adjusting drive 7, 8 with an output member 19 and limit switches S3, S4, S5. The output member 19 is adjustable by the adjusting drive 7, 8 along an adjusting path 19b in the directions of the arrows. When the end positions are reached, a cam 19a interacts with a limit switch S3 or S5. For a detailed description, see the document DE 10 2009 059 267 A1 referenced, only the differences are explained here in the following.

The first difference is that when one of the limit switches S3 or S5 is actuated in the associated end positions of the output member 19, the motor circuit of the adjustment drive 7, 8 does not open, but the energy supply is switched off, the motor M1 is short-circuited and a reference point for the control or positioning of the output member 19 is reset.

The limit switches S3 and S5 are integrated in a manner not shown in a control circuit of a transistor T1 ... T4 or a changeover contact S1, S2. In an alternative version and also not shown in detail, the limit switches S3 and S5 are designed as changeover contacts, interrupt the motor current when actuated by a switching cam and short-circuit the motor when the contact is switched, so that the regenerative braking properties of the motor unfold.

The second difference is formed by at least one third limit switch S4, which is arranged within the adjustment path 19a at a predetermined location, for example in the middle. If this at least one third limit switch S4 is actuated while the output member 19 is being adjusted by the cam 19b, the reference point for the control or positioning of the output member 19 is correspondingly reset.

In other words, the limit switches S3 and S5 switch off the motor M1 by switching off the power supply, short-circuit it and reset the reference point. Limit switch S3 only resets the reference point. As a result, an error rate when positioning the output member 19 is reduced.

In this in Fig. 6 In the example shown, the limit switches S3, S4 and S5 are designed with break contacts, the connections 1 of the break contacts being connected to one another and to a common limit switch connection EG. The respective connections 2 of the normally closed contacts of the limit switches S3, S4 and S5 are each connected separately to a limit switch connection E5, E6, E7. The limit switch connections EG, E5, E6, E7 are connected to the control device 9.

It has also been found that when evaluating the back EMF, the occurrence of the pulses or ripples to be counted can be problematic if the respective adjustment drive 7, 8 is under high load. This can have various causes, the effects on the ripple are that, on the one hand, after the filtering (see document DE 10 2009 059 267 A1 ) a pulse width ratio of the ripple changes and, on the other hand, the amplitudes of the ripple decrease. Either no more ripples can be counted, or too many ripples are counted. After detailed investigations, it turned out that a certain pulse width ratio, for example of 10/90, forms a critical point.

Fig. 7 represents a schematic block diagram of a monitoring device 20 according to the invention.

The monitoring device 20 comprises a filter unit 21 with a pulse shaper 21a, and a load monitoring device 22 with a pulse width ratio detector 23, a comparator 24 and a signal generator 25.

The filter unit 21 has, for example, two filters as in FIG DE 10 2009 059 267 A1 described on. The back EMF of the relevant motor M1 is, as already explained above, measured via a resistor R1, R2 and / and R3 as a voltage drop at the connections of this resistor due to the motor current flowing through and fed to the filter unit 21. The filter unit 21 preferably has two filters. For a description of their function, see the document DE 10 2009 059 267 A1 referenced.

The output signals of the filter unit 21 are here formed into a square-wave signal by the pulse shaper 21a. If the associated motor M1 is overloaded, the pulse width ratio of the square-wave signal is reduced considerably, with the frequency also decreasing since the speed of the motor M1 decreases. Furthermore, a square-wave signal or a slightly distorted square-wave signal can also result, but which can be evaluated as a square-wave signal.

The pulse width ratio detector 23 detects the pulse width ratio of the square-wave signal formed in this way and supplies it to the comparator 24, which compares it with a predetermined value, for example the critical value 10/90. As soon as the recorded pulse width ratio falls below or exceeds the previously definable value in this comparison, this is signaled to the signal generator 25 in a corresponding manner.

The signal generator 25 then generates corresponding output signals, which it provides at an output 25a for further processing for the associated motor M1.

The further processing of these generated output signals takes place by the control device 9 in such a way that the energy supply of the associated motor M1 is throttled. This is realized, for example, by PWM control of motor M1 for throttling or a series resistor being connected upstream of motor M1. This can be, for example, the resistor R3 described above or the inductance described above with a resistor component R3 with the options specified.

In addition, in this example the monitoring device 20 comprises a return monitoring device 26 with a return detection unit 27, which is coupled on the input side to the output of the filter unit 21. As already mentioned above, the motor current in the short-circuited state of the motor M1 - for example according to Fig. 4 - can also be recorded. For this purpose, the return detection unit 27 is activated by the control device 9 via a control input 28 when the associated motor M1 is in the short-circuited state. If the return detection unit 27 then detects a rotation of the motor shaft of the motor M1 on the basis of detected back EMF, it generates a signal which it provides at an output 29 for further processing, for example for registration or warning messages. The return detection unit 27 is equipped with a high gain amplifier in order to detect even small back EMF amounts.

The monitoring device 20 can be in the positioning device 200 of DE 10 2009 059 267 A1 can be integrated to be provided as an additional unit, having its own filter unit 21. The monitoring device 20 can, however, also be coupled in a corresponding manner to the output of the filter already present in the positioning device 200, the pulse shaper 21a being added.

Finally shows Fig. 8 a schematic flow diagram of a method according to the invention for monitoring a pulse width ratio of an electromotive furniture drive 100.

In a first method step V1, a back EMF of the relevant motor M1 of the electromotive furniture drive 100 is detected. This is done by measuring a voltage drop across a resistor R1, R2, R3 or an internal resistance of a transistor T1, T2, T3, T4. The respective voltage drop is generated by the motor current of the associated motor M1. The pulses or ripples that occur are converted into square-wave pulses by the pulse shaper 21a.

A pulse width ratio of the ripple detected and reshaped in this way is detected by the pulse width ratio detector 23 in a second method step V2. For this purpose, the pulse width detector 23 generates a corresponding signal, which it supplies to the comparator 24 in a form that can be determined beforehand.

In a further method step V3, the comparator 24 compares the signal supplied to it with a previously determinable value, e.g. the critical value 10/90. This previously definable value is provided in such a way that it can be compared in a simple and reliable manner with the signal supplied by the pulse width ratio detector 23 by means of the comparator 24.

As soon as the detected pulse width ratio in this comparison with the comparator 24 falls below or exceeds the previously definable value, this is correspondingly signaled to the signal generator 25 by the comparator 24 in a fourth method step V4 for monitoring the pulse width ratio of the electromotive furniture drive 100. The signal generator 25 then generates corresponding output signals as described above.

Load monitoring can also detect jamming or overload if a frequency of the ripple falls below a certain value. This can be done with the comparator 24.

The invention is not restricted to the exemplary embodiments described above. It can be modified within the scope of the attached claims.

For example, it is conceivable that the motor M1 is completely switched off when the critical pulse width ratio is present. Documentation of these occurrences can be stored in a memory (not shown) and read out later. At the same time, an acoustic / optical / haptic message is also possible through appropriate reporting devices.

• ∘ fällt die Ripple-Frequenz und ändert sich ein weiterer Parameter (z.B. steigt Motorstrom, sinkt die Spannung am Motor) so liegt ein Einklemmfall oder eine Überlast vor
• ∘ Lernfahrt bei Erstinbetriebnahme: Dabei wird über dem gesamten Verstellweg 19b (Fig. 6) permanent wenigstens ein Parameter detektiert (die Ripple-Frequenz und/oder der Motorstrom und/oder die Motorspannung). Eine Software schreibt eine Tabelle "Verfahrweg in Abhängigkeit der Parameter". Somit können Verstellbereiche mit höherem Kraftbedarf / leichtgängigere Bereiche erfasst werden.
• ∘ Im regulären Betrieb des Motors bildet die Tabelle einen Richtwert. Weicht der aktuell ermittelte Parameter wesentlich von dem Tabellenwert ab, liegt wohlmöglich eine Überlast oder ein Einklemmfall vor.
• ∘ Die Tabelle kann auch vorprogrammiert und für ein bestimmtes Möbel charakteristisch sein.

The load monitoring with the monitoring device 20 can form what is known as an intelligent ÜSA (ÜSA = overcurrent shutdown) of the respective motor M1.

• If the ripple frequency falls and another parameter changes (eg if the motor current increases, the voltage on the motor decreases), there is a trapping or overload
• ∘ Learning run during initial start-up: This is done over the entire adjustment path 19b ( Fig. 6 ) at least one parameter is permanently detected (the ripple frequency and / or the motor current and / or the motor voltage). Software writes a table "Travel depending on the parameters". Adjustment areas with a higher force requirement / easier-to-move areas can thus be recorded.
• ∘ The table is a guide value for normal engine operation. If the currently determined parameter deviates significantly from the table value, there is probably an overload or trapping.
• ∘ The table can also be preprogrammed and characteristic of a particular piece of furniture.

Unless otherwise described, all or individual features and functions of an electrical and electronic nature described at the beginning can be used as a discrete circuit. As an alternative or in addition to this, the subject matter of the invention is also to design individual functions and features as a program or as individual program sections which interact as a computing method with a computing device, for example in the form of a microcontroller.

For this purpose, the respective connections A to H, EG, E4 to E7 are connected to an input of the microcontroller. The following program sections come into consideration: corresponding to the pulse width ratio detector 23 described at the beginning with detection and evaluation of the pulse width ratio and comparison with a critical value 10/90 here now as a program section for monitoring a pulse width ratio and / or as a program section for load monitoring; corresponding to the filter unit 21 described at the beginning, here now as an image of a computation routine with at least one mean value calculation; corresponding to the return monitoring device 26 described above with a return detection unit 27, here now with a computation routine with a further counting of the ripple signals with the motor M1 switched off; in accordance with the load monitoring described at the beginning for the detection of a jamming or an overload, here now as a computation routine with a comparison of predetermined memory values; corresponding to the signal generator 25 described at the outset, here now as a computation routine for switching a switching or control output of the microcontroller.

Reference number

1

Furniture

2

Basic element

3

Support element

4th

Back part

5

Leg part

6th

Movement fitting

7, 8

Adjustment drive

9

Control device

9a

Supply unit

9b

Control switch

9c

receiver

9d

Power cord

9e

Power plug

10, 10 '

Control unit

11

casing

12, 13

Control element

14th

Reporting element

15, 16, 17

Additional control element

18th

Operating management

19th

Output link

19a

Cam

19b

Adjustment path

20th

Monitoring device

21st

Filter unit

21a

Pulse shaper

22nd

Load monitoring device

23

Pulse width ratio detector

24

Comparator

25th

Signal generator

25a

exit

26th

Return monitoring device

27

Return detection unit

28

Control input

29

exit

100

Electromotive furniture drive

100a

Drive line

110

Control block

117

counter

118

Storage facility

120

Digital potentiometer

120a

Analog output

121

Cache

122

Digital-to-analog converter

130

Energy storage

200

Positioning device

A ... H, A ', B'

connection

EG, E4 ... 7

Limit switch connection

M.

mattress

M1

engine

R1 ... 3

resistance

S1 ... 2

Changeover contact

S3 ... 5

Limit switch

T1 ... 4

transistor

V1 ... 4

Process step

Claims (23)

1. An electromotive furniture drive (100) for adjusting a movable part (4, 5) of a piece of furniture (1) by means of an output element (19), comprising

   a) at least one adjusting drive (7, 8) with respectively at least one electric motor (M1), a revolution speed reducing gear mechanism which is coupled thereto and which ensures that the output element (19) is drivingly coupled and can be linearly displaced and/or rotatably moved, wherein the output element (19), upon reaching a predetermined position, actuates an end switch (S3, S4, S5) and/or a reference switch and/or a switching means;

   b) at least one control device (9), and

   c) at least one operating unit (10),
   wherein the control device (9) comprises a positioning apparatus (200) for the output element (19) with a control block (110) with a counter (117) and a memory device (118) for evaluating pulses of a back-EMF of the at least one electric motor (M1),
   characterized in that

   d) at least one monitoring apparatus (20) is provided for monitoring a pulse-width ratio of a detected back-EMF of the at least one electric motor (M1).
2. An electromotive furniture drive (100) according to claim 2, characterized in that the monitoring apparatus (20) comprises at least one filter unit (21) with a pulse former (21a) and a load monitoring device (22) with a pulse-width ratio detector (23), a comparator (24) and a signal generator (25).
3. An electromotive furniture drive (100) according to claim 3, characterized in that the pulse former (21a) is a square-wave pulse former.
4. An electromotive furniture drive (100) according to claim 2 or 3, characterized in that the pulse-width ratio detector (23) is arranged for detecting the pulse-width ratio of the detected back-EMF of the at least one electric motor (M1).
5. An electromotive furniture drive (100) according to one of the claims 2 to 4, characterized in that the comparator (24) is arranged for comparing the detected pulse-width ratio with a previously determinable value.
6. An electromotive furniture drive (100) according to claim 5, characterized in that the previously determinable value corresponds to a pulse-width ratio of 10/90.
7. An electromotive furniture drive (100) according to one of the claims 2 to 6, characterized in that the signal generator (25) is arranged for generating a signal for the control of the motor (M1) for throttling the motor (M1).
8. An electromotive furniture drive (100) according to one of the claims 2 to 7, characterized in that the monitoring apparatus (20) comprises at least one return-motion monitoring device (26) which is coupled to the output of the filter unit (21), wherein the return-motion monitoring device (26) is arranged for recognizing a rotation of a motor shaft of the motor (M1) in the short-circuited and deactivated state of the motor (M1) and for signaling such recognition.
9. An electromotive furniture drive (100) according to one of the claims 2 to 8, characterized in that the monitoring apparatus (20) is equipped with and connected to at least one energy storage unit (130), preferably a rechargeable battery or a capacitor of high capacitance, wherein a storage capacity of the energy storage unit (130) is arranged in such a way that the part of the electric circuit of the positioning apparatus (200) for detecting, evaluating and counting the ripples in the currentless state can be operated at least for a specific time interval by means of the energy storage unit (130).
10. An electromotive furniture drive (100) according to one of the preceding claims, characterized in that the control device (9) comprises a digital potentiometer (120) which outputs an electric value as an output value which is proportional to the position of the output element (19).
11. An electromotive furniture drive (100) according to claim 10, characterized in that the digital potentiometer comprises at least one buffer memory unit (121) and at least one digital-to-analog converter (122), wherein the buffer memory unit (121) is provided for the intermediate storage of counts of the counter (117), and wherein the digital-to-analog converter (122) converts the count which is intermediately stored in the buffer memory unit (121) into an analog output value, wherein the analog output value which was converted by the digital-to-analog converter (122) is a voltage value and/or a current value and wherein the buffer memory unit (121) is arranged as a rewritable volatile or non-volatile memory.
12. An electromotive furniture drive (100) according to claim 11, characterized in that the analog output value which was converted by the digital-to-analog converter (122) lies within a predetermined voltage or current interval, wherein a minimum value corresponds to a first end position state of the output element (19) and a maximum value corresponds to a second end position state of the output element (19).
13. An electromotive furniture drive (100) according to one of the preceding claims, characterized in that at least one of the end switches (S3, S5), upon actuation in an end position of the output element (19), is provided for controlling the interruption in the power supply to the motor (M1), for controlling the short-circuiting of the motor (M1) and for controlling the new setting of a reference point for the control or positioning of the output element (19).
14. An electromotive furniture drive (100) according to one of the preceding claims, characterized in that at least one end switch (S4) is arranged at a previously determined location and is provided for controlling the new setting of a reference point for the control or positioning of the output element (19).
15. An electromotive furniture drive (100) according to one of the preceding claims, characterized in that the at least one electric motor (M1) is equipped for soft start-up with at least one bridgeable series resistor (R3).
16. A method for monitoring a pulse-width ratio of an electromotive furniture drive (100) according to one of the claims 1 to 15, characterized by the method steps:

    (V1) detection of pulses of a back-EMF of the at least one electric motor (M1) of the electromotive furniture drive (100) by measuring a voltage drop in a resistor (R1, R2, R3) or a specific resistance of a transistor (T1, T2, T3, T4);

    (V2) detection of a pulse-width ratio of ripples of the thus detected back-EMF of the at least one electric motor (M1);

    (V3) comparison of the thus detected pulse-width ratio with a previously determinable value, and

    (V4) monitoring of the pulse-width ratio by evaluating the comparison obtained in this manner.
17. A method according to claim 16, characterized in that the detected pulses are converted into square-wave pulses in the method step (V1).
18. A method according to claim 16 or 17, characterized in that the previously determinable value for comparison in the method step (V3) corresponds to a pulse-width ratio of 10/90.
19. A method according to one of the claims 16 to 18, characterized in that in the method step (V4) a throttling of the at least one electric motor (M1) occurs in operation when the value drops below a critical comparative value.
20. A method according to one of the claims 16 to 19, characterized in that a frequency of the ripples is monitored in the method step (V3) and a signal is generated in the method step (V4) that there is a case of jamming or an overload.
21. A piece of furniture (1), comprising

    a) at least one base element (2) for coupling the piece of furniture (1) to an installation site, and

    b) at least one support element (3) which comprises a part (4, 5) which is movably arranged relative to the support element (3) or relative to a further support element (3) or relative to the base element (2),

    c) wherein the at least one movably arranged part (4, 5) is arranged to be displaceable and/or pivotable,

    d) wherein the piece of furniture (1) comprises at least one electromechanical furniture drive (100),

    e) wherein the at least one movably arranged part (4, 5) is coupled to the at least one electromechanical furniture drive (100),
    characterized in that

    f) the at least one electromotive furniture drive (100) is arranged according to one of the claims 1 to 15.
22. A piece of furniture (1) according to claim 21, characterized in that the control device (9) comprises a memory control unit.
23. A piece of furniture (1) according to claim 21 or 22, further comprising at least two electromotive furniture drives (100), characterized in that the control device (9) comprises a synchronous control unit, wherein the adjusting speeds of the at least two electromotive furniture drives (100) are adjusted with respect to each other, especially put equally with respect to each other.

Images