Vacuum cleaner, preferably hand vacuum cleaner

Abstract

The invention relates to a vacuum cleaner (1), preferably a handheld vacuum cleaner (1), with a blower (12) with an impeller for generating an airflow, with a first electric motor (12a) for driving the impeller of the blower (12), with a suction nozzle (14) with a rotatable brush (15), with a second electric motor (15a) for driving the rotatable brush (15) and with a control unit (17) which is designed and configured to operate at least the first electric motor (12a) and / or the second electric motor (15a).The vacuum cleaner (1) is characterized in that the control unit (17) is designed and configured to cause a movement (B) of the rotor (15c) of the second electric motor (15a) relative to the stator (15b) of the second electric motor (15a) from a first orientation (A1) to a second orientation (A2), to detect a value of an electrical quantity which is influenced by the movement (B) from the first orientation (A1) to the second orientation (A2), and to determine from the value of the electrical quantity whether the initiated movement (B) has taken place or not.

Description

[0001] The invention relates to a vacuum cleaner, preferably a handheld vacuum cleaner. Such a vacuum cleaner is known from EP 2245974.

[0002] Vacuum cleaners are cleaning devices that suck in air and dirt from a surface and then expel the air, at least largely purified of dirt, back outside. Such vacuum cleaners can be connected to a power outlet via a cable for operation. However, it can be more convenient for the user not to have to worry about the cable while vacuuming, which is why cordless vacuum cleaners are also well-known and widespread. These use a battery or accumulator as a rechargeable electrical energy storage device. In particular, the comparatively compact and lightweight handheld vacuum cleaners are often battery-operated to make them quicker and easier for the user to use.

[0003] A vacuum cleaner has a fan that can generate the airflow. This can create a negative pressure on the intake side of the fan, which can cause air to flow inward; this section of the vacuum cleaner can also be referred to as the vacuum zone.

[0004] On the side opposite the fan, towards which the airflow is directed, there is usually at least one filter or filter system through which the airflow is passed. This section of the vacuum cleaner can also be referred to as the vacuum cleaner's overpressure zone. The filter can trap dirt such as dust, particularly house dust, as well as other smaller particles from the airflow and thereby filter the airflow, which then leaves the vacuum cleaner cleaner than when it was sucked in. This allows the dirt to be cleaned from the surface. The surface can be any surface, such as a floor or its floor covering.

[0005] Depending on the design of the vacuum cleaner, the airflow and dirt can be directed directly via a suction nozzle, which acts as an intake opening and is a component of the vacuum cleaner itself. The suction nozzle, which can also be referred to as a floor nozzle, can also be connected to the vacuum cleaner via a suction hose and, if necessary, an additional telescopic tube. In this case, the vacuum cleaner and the other components, such as the suction nozzle, suction hose, and, if necessary, the telescopic tube, can be referred to as a vacuum cleaner system. In either case, the suction nozzle can be guided by a user over a surface to collect dirt with the sucked-in air.

[0006] To improve the cleaning effect, a brush can be installed near the suction nozzle. This brush can be driven in a rotating manner to brush the surface to be cleaned, loosening dirt from the fibers of a carpet, for example, so that the loosened dirt can be more effectively carried away by the airflow. This can improve the cleaning effect of the vacuum cleaner. This brush can also be called a floor brush or a brush roller.

[0007] The fan of such vacuum cleaners is typically powered by a first electric motor. Brushless electric motors are often used for this purpose, as they do not have slip rings or commutators and brushes between the rotor and stator, which can wear out. Therefore, brushless electric motors typically have a longer service life than brushed motors. This can have a correspondingly positive effect on the service life of the vacuum cleaner. Brushless electric motors also typically have higher performance than brushed motors.

[0008] The floor brush can also be operated with a second electric motor, which, however, is usually designed with brushes, i.e. as a brushed electric motor, for cost reasons.

[0009] To optimally operate and control the floor brush and achieve the best possible cleaning results, it can be helpful to know the surface or floor covering to be cleaned. On a hard floor or smooth surface, a very low speed is beneficial, or it is even advantageous if the floor brush does not rotate at all, so that dirt on a hard floor is not "shot away." On a carpet, on the other hand, better cleaning results are usually achieved when the floor brush is operated, especially at a comparatively high speed.

[0010] Appropriate sensors can be used to detect the surface or floor covering to be cleaned. However, this increases costs due to the purchase and installation of the sensor, as well as its connection and evaluation by the vacuum cleaner's control unit. The sensor and its wiring also require additional installation space. Furthermore, this increases electrical consumption, which can be undesirable, especially with a battery-operated vacuum cleaner.

[0011] DE 10 2007 021 299 A1 describes a method for controlling the speed of at least one electric motor in a mobile device during movement of this device across a surface area depending on its respective surface characteristics by generating detection signals corresponding to the respective surface characteristics for the formation of corresponding control signals for the mobile device. Current values ​​of at least one current consumed by an electric motor of the mobile device are determined as detection signals, which correlate with a movement of the mobile device in the respective surface area with regard to at least one parameter, in particular its magnitude. The respective current values ​​are evaluated based on at least one current setpoint corresponding to a specific surface characteristic.The electric motor is operated at a speed that can be set based on an evaluation result between the respective determined current value and at least one current setpoint.

[0012] A disadvantage of the method of DE 10 2007 021 299 A1 is that the floor covering is detected via the motor current of an already rotating floor brush, and thus a rotating movement of the floor brush must already be present in order to apply this method. However, since the floor brush should not rotate at all on a hard floor to be cleaned in order to avoid "shooting" dirt onto the hard floor, detection of the floor covering without rotation of the floor brush would be desirable. In particular, the floor covering should be detected immediately upon start-up of the device, i.e., without a time delay, in order to operate or regulate the floor brush accordingly, or even to prevent it from being started at all. Operating the floor brush on a hard floor also requires electrical energy, which in this case does not contribute to the cleaning and is therefore wasted, which can be undesirable, particularly with battery-operated vacuum cleaners.

[0013] The invention therefore addresses the problem of providing a vacuum cleaner with a rotating floor brush that can detect the surface or floor covering to be cleaned directly from the start of operation, i.e., without the use of a corresponding sensor, without prior operation of the floor brush. This should preferably be achieved in a way that is as simple, cost-effective, space-saving, and / or energy-efficient as possible. This should preferably be implemented for battery-operated vacuum cleaners. At the very least, an alternative to known vacuum cleaners of this type should be created.

[0014] According to the invention, this problem is solved by a vacuum cleaner having the features of independent claim 1. Advantageous embodiments and further developments of the invention emerge from the following subclaims.

[0015] The invention thus relates to a vacuum cleaner according to the preamble of claim 1. The above-mentioned object is solved by the features of the preamble and the characterising part of independent claim 1.

[0016] In other words, according to the invention, a defined movement of the rotor of the second electric motor of the vacuum cleaner's floor brush is initiated with respect to its starting and ending points, which differs from a cleaning operation of the vacuum cleaner using the floor brush. An electrical value is measured during the initiated or attempted movement, and it is examined whether or not this electrical value can be used to determine whether the actual implementation of this movement has been achieved. From this, conclusions can be drawn about the surface that the floor brush is intended to clean or even about a blockage in the floor brush.

[0017] The present invention is based on the finding that the surface to be cleaned by a vacuum cleaner's floor brush presents varying levels of resistance to the floor brush or its second electric motor or rotor, depending on the type of surface, such as a hard floor or a carpet. Carpets of different textures, such as different lengths, can also exhibit different levels of resistance. This also applies to a blockage of the floor brush, for example, due to objects being sucked in.

[0018] In any case, the manner or the driving force with which the movement from the first orientation to the second orientation of the rotor of the floor brush is initiated can be specified in order to infer from the movement that has occurred or not occurred whether a certain surface is present or whether at least a certain surface can be ruled out. This can enable sensorless floor type detection without the floor brush having to be operated for this purpose. Preferably, the rotor of the second electric motor can be moved beforehand into the first orientation relative to the stator of the second electric motor in order to have a defined starting position or to assume the first orientation. This can be regarded as initialization. However, the first orientation can also be the orientation the rotor has, in particular randomly, at the start of operation. This can simplify the procedure.

[0019] According to a further aspect of the invention, the control unit is designed and configured such that the rotatable brush is not driven by the second electric motor once the instructed movement has occurred. This can prevent operation, for example, on a hard floor, for the reasons mentioned above if the rotor has actually moved, thus indicating a surface with comparatively low resistance, such as a hard floor.

[0020] According to a further aspect of the invention, the control unit is designed and configured such that the movement into the second orientation is initiated again by means of a higher drive force than before if the initiated movement has not occurred. In this way, an iterative or successive procedure can be initiated or carried out in order to test, so to speak, floor types with low resistance by increasing the drive force once or repeatedly and to exclude or identify these floor types based on the reaction of a movement that has occurred or has not occurred. According to a further aspect of the invention, the control unit is designed and configured such that the rotatable brush is operated by means of the second electric motor if the initiated movement has occurred by means of the higher drive force and if the higher drive force is below a threshold value for detecting a blocked rotatable brush.This allows the floor brush to operate to clean the detected surface, which is not a hard floor. At the same time, blockage of the floor brush can be prevented.

[0021] According to a further aspect of the invention, the control unit is designed and configured such that the rotatable brush is driven by the second electric motor at a predetermined speed corresponding to a surface that corresponds to the driving force with which the initiated movement occurred. In this case, the surface can be determined from the driving force at which the initiated movement actually occurred. Different surfaces, at least hard floors and non-hard floors, but possibly also different types of carpet, can be differentiated from one another and, depending on the surface, a corresponding operating behavior for cleaning precisely this type of surface can be stored, for example, in the control unit. This cleaning operation, tailored to the detected surface, can then be implemented in order to optimize the cleaning of the surface.

[0022] According to a further aspect of the invention, the control unit is designed and configured such that the rotating brush is not operated by the second electric motor if the higher drive force reaches a threshold for detecting a blockage of the rotating brush. This also allows detection of a blockage of the floor brush, for example, due to objects being sucked in, and the floor brush is then not operated to prevent damage.

[0023] According to a further aspect of the invention, the control unit is designed and configured to initiate a further movement of the rotor of the second electric motor into a third orientation relative to the stator of the second electric motor. This allows for repeated or continuous detection, since the surface may ultimately change during use, and this should be detected accordingly according to the invention. This can occur at sufficiently short intervals throughout the entire duration of use to be able to immediately detect and respond to each surface or change in surface.

[0024] According to a further aspect of the invention, the control unit is designed and configured to initiate the further movement into the third orientation in the same direction as the movement into the second orientation. Thus, a circular movement sequence can be realized, which may represent one possible implementation.

[0025] According to a further aspect of the invention, the control unit is designed and configured to initiate the further movement into the third orientation in the opposite direction to the movement into the second orientation. In this case, a back-and-forth movement sequence can be realized, which may represent another possible implementation.

[0026] According to a further aspect of the invention, the electrical quantity is an induced voltage or a resulting current. These can represent possible implementations for utilizing a measurable electrical quantity.

[0027] According to a further aspect of the invention, the driving force is generated by means of an electrical voltage or an electrical current. These can represent possible ways of generating the driving force.

[0028] According to a further aspect of the invention, the first electric motor and / or the second electric motor are brushless. This can increase the performance and / or longevity of the first electric motor of the blower and / or the second electric motor of the rotating floor brush.

[0029] According to a further aspect of the invention, the vacuum cleaner has a rechargeable electrical energy storage device, which is designed and configured to supply electrical power to at least the first electric motor, the second electric motor, and the control unit. The rechargeable electrical energy storage device can, in particular, be an accumulator or battery. This can allow the user to use the vacuum cleaner without the inconvenience of a cable for the electrical power supply.

[0030] The vacuum cleaner according to the invention can utilize the approach of field-oriented control or space vector modulation. In this case, specific voltage space vectors can be applied to the motor stator by suitable modulation of the B6 bridge. As already mentioned, the motor rotor contains at least one pole pair. For example, the motor can be connected in a star configuration, although a delta connection is also possible. If, for example, a voltage with the predetermined vector is applied to the motor, the rotor aligns itself in a first orientation relative to a stator. This can be regarded as the initial orientation. If a further voltage vector, rotated by 90°, for example, is subsequently applied to the motor, the rotor aligns itself in a second orientation relative to the stator, also rotated by 90°, provided the electrical torque is sufficient. A movement takes place.

[0031] The movement of the rotor induces a voltage that can be measured. This allows the controller on the control electronics, i.e., a control unit, to detect whether the rotor has moved or not. It is irrelevant how many pole pairs the motor has and whether it is an internal or external rotor. With a higher number of pole pairs, the mechanical angle of rotation decreases by a factor of the number of pole pairs.

[0032] The generated torque can be influenced, for example, by adjusting the amplitude of the voltage space vector. For example, it's conceivable that during the initial rotor alignment, a relatively high voltage is applied to the motor, resulting in a relatively high torque, so that the rotor aligns itself, provided it isn't blocked.

[0033] In the next step, a space vector, electrically rotated by 90°, can be applied to the motor with a relatively small amplitude. If the floor brush is now on a hard floor, the mechanical counter-torque is relatively low, and the rotor would move, which can be detected via the induced voltage. The motor remains off because a hard floor has been detected.

[0034] If the rotor, and thus the roller, isn't rotating, the roller is either blocked or is resting on a carpet, causing the counter-torque to be too high and thus no movement. Therefore, in the next steps, the amplitude of the space vector could be gradually increased until movement occurs. Based on the amplitude, it may be possible to distinguish between different carpets and / or a blockage.

[0035] If a carpet is detected, the floor brush can be switched on. Using the previously described method of detecting the floor covering via the motor current, it may be possible to detect when the floor covering has changed to a hard floor, and the brush can then be switched off.

[0036] Various detection configurations are conceivable on a hard floor. For example, the rotor could continuously oscillate back and forth between the two rotor positions of the two orientations until a carpet is detected. It is also possible to rotate the electrical angle of the voltage space vector by 90° in each step. This would cause the rotor to rotate by the electrical angle divided by the number of pole pairs.

[0037] The detection itself can be achieved by measuring the induced voltage if the B6 bridge is switched off again after the voltage space vector is switched on. It is also conceivable to measure the detection via the resulting current. If the rotor is stationary, the electrical circuit consists only of an inductance and a series-connected resistor. The step response of the current to the voltage space vector would therefore result in a PT-1 behavior. However, if the rotor is set in motion, the induced voltage also has an effect, and the step response of the current would have a different behavior than the PT-1 behavior.

[0038] Furthermore, it is conceivable to regulate the current with a specific space vector instead of specifying the voltage.

[0039] An embodiment of the invention is shown purely schematically in the drawings and is described in more detail below. It shows Figure 1 shows a schematic side view of a vacuum cleaner according to the invention in the form of a handheld vacuum cleaner according to the invention; Figure 2 shows a B6 bridge for operating a second electric motor of a rotatable floor brush of the handheld vacuum cleaner according to the invention; Figure 3 shows a star connection of the stator windings of the second electric motor; Figure 4 shows a rotor of the second electric motor in a first orientation relative to the stator of the second electric motor; Figure 5 shows a movement of the rotor into a second orientation; Figure 6 shows the rotor in the second orientation; and Figure 7 shows a flowchart of a method according to the invention.

[0040] The Figure 1is viewed in Cartesian coordinates. A longitudinal direction X extends, which can also be referred to as depth X or length X. Perpendicular to the longitudinal direction X extends a transverse direction (not shown), which can also be referred to as width. Perpendicular to both the longitudinal direction X and the transverse direction extends a vertical direction Z, which can also be referred to as height Z.

[0041] The Figure 1 shows a schematic side view of a vacuum cleaner 1 according to the invention in the form of a handheld vacuum cleaner 1. The handheld vacuum cleaner 1 has a housing 10, which can be held and guided by a user by means of a handle 11. A fan 12 including a first electric motor 12a for driving the fan 12 is arranged in the housing 10. The first electric motor 12a is brushless. Furthermore, at least one filter and one exhaust opening are provided (not shown).

[0042] Opposite the handle 11, a suction tube 13 is arranged on the housing 10. At the end of the suction tube 13 applied to the housing 10, a suction nozzle 14 is provided, which can also be referred to as a floor nozzle 14 or a brush head 14. The suction nozzle 14 has an interior which is open downwards in the vertical direction Z by means of an opening 16, which can also be referred to as a suction opening 16. Arranged within the interior of the suction nozzle 14 is a rotatable brush 15 which can be driven in rotation by a second electric motor 15a. The second electric motor 15a is designed as a brushless, permanently excited DC motor.

[0043] The handheld vacuum cleaner 1 further comprises a control unit 17, which can operate both the first electric motor 12a and the second electric motor 15a. This can be done, in particular, via pulse-width-modeled signals. The first electric motor 12a, the second electric motor 15a, and the control unit 17 can be electrically supplied by a rechargeable electrical energy storage device 18.

[0044] The rotatable brush 15 has a stator 15b or stator windings 15b, a rotor 15c, and a roller 15d, which can be rotated by the second electric motor 15a in a first direction of rotation and in an opposite second direction of rotation. The roller 15d has a plurality of bristles or combs pointing radially outward, which serve to clean the surface 2.

[0045] If the handheld vacuum cleaner 1 according to the invention is now operated by the user by means of the two electric motors 12a, 15a, an air flow can be generated by the blower 12 by means of the first electric motor 12a and the surface 2 can be additionally cleaned by means of the rotating brush 15 by means of the second electric motor 15a.

[0046] However, operation of the floor brush 15 on a hard surface 2, such as tiles 2, may be undesirable because the dirt is more likely to be distributed by the rotating brush 2 or moved away from the suction nozzle 14, which reduces the cleaning effect. Thus, the second electric motor 15a of the floor brush 15 should not be operated if a hard surface 2 is being cleaned. On a soft surface 2, such as carpets 2, the second electric motor 15a should indeed drive the floor brush 15, in particular with a drive power or speed suitable for the respective carpet 2 in order to improve cleaning. However, the user should be spared the task of constantly switching the second electric motor 15a on and off or changing it during operation when changing the surface 2, as this could be perceived as cumbersome and annoying.However, using additional sensors would incur costs.

[0047] According to the invention, the second electric motor 15a is therefore operated by the control unit 17 in such a way that when the vacuum cleaner 1 starts operating, no cleaning operation or no brushing operation of the second electric motor 15a takes place, but instead a floor detection is carried out which is based on the induced voltage of the stator 15b of the second electric motor 15a.

[0048] Thus, firstly, a movement 100 of the rotor 15c of the second electric motor 15a into a first orientation A1 relative to the stator 15b of the second electric motor 15a takes place, see Figure 4 This can be seen as the starting position or initialization.

[0049] Now, a movement B of the rotor 15c of the second electric motor 15a is initiated 200 into a second orientation A2 relative to the stator 15b of the second electric motor 15a, see Figure 5 For this purpose, the rotor 15c of the second electric motor 15a is first driven with such a low drive force that the desired or initiated movement B only actually occurs if the ground 2 offers no or no noticeable resistance to this movement B. Such a ground 2 can be a hard floor 2 or a smooth floor 2.

[0050] A value of an electrical quantity influenced by the movement B from the first orientation A1 to the second orientation A2 is then detected 300. This can be a voltage induced in the stator 15b of the second electric motor 15a, which is actually induced in the case of the movement B occurring or then has a value other than zero. However, if the desired or initiated movement B is not implemented, no voltage is induced either.

[0051] Then, from the value of the electrical quantity, ie from the induced or non-induced voltage, a determination 400 is made as to whether the induced movement B has occurred or not. If the movement B has actually occurred, see Figure 6, it can be concluded that a smooth floor 2 is the subsurface 2. In response to this, the cleaning operation of the floor brush 14 can be omitted in order not to disturb the cleaning of the smooth floor 2 by the rotation of the floor brush 14.

[0052] If the initiated movement B has not occurred, it can be concluded that the floor 2 is not smooth and that the operation of the floor brush 14 would be helpful in assisting in cleaning the surface 2. Thus, in this case, the floor brush 14 could in principle be operated.

[0053] However, in this case, the floor detection as described above can also be continued by increasing the driving force with which the desired movement B from the first orientation A1 to the second orientation A2 is initiated. For example, a driving force can now be generated so that, analogously to the previous procedure, a distinction can be made between a short-pile carpet 2 and a long-pile carpet 2. If the movement B is now actually initiated, it can be concluded that a short-pile carpet 2 is the underlying surface 2, the resistance of which could be overcome with the increased driving force of the second electric motor 15a.

[0054] If no movement B occurs, it can be concluded that the floor 2 is a long-pile carpet, since its resistance could not be overcome even with the increased drive force of the second electric motor 15a, or that the floor brush 14 is blocked. These two cases can also be distinguished, as previously described, by a further corresponding increase in the drive force. If a blockage of the floor brush 14 is detected, operation can be completely stopped for safety reasons. Furthermore, depending on the type of carpet detected as the floor 2, the cleaning operation can be adapted accordingly.

[0055] If a smooth surface 2 has been detected as described above, this procedure can be continued or repeated during the operation of the vacuum cleaner 1 in order to be able to detect a possible change in surface away from a smooth surface 2 and to react to this as described above. List of reference symbols (part of the description)

[0056] A1First alignment or first orientation of the rotor 15c A2Second alignment or second orientation of the rotor 15c BMovement or direction of movement of the rotor 15c UPhase U of the stator 15b or the stator windings 15b VPhase V of the stator 15b or the stator windings 15b WPhase W of the stator 15b or the stator windings 15b XLongitudinal direction; depth; length Zvertical direction; height 1 Vacuum cleaner; handheld vacuum cleaner 10 Housing 11 Handle of the housing 10 12 Blower 12a First (brushless) electric motor of the blower 12 13 Suction tube 14 Suction nozzle; floor nozzle; brush head 15 Rotatable (floor) brush; rotatable bristle roller 15a Second (brushless) electric motor of the rotatable (floor) brush 15 15b Stator or stator windings of the second (brushless) electric motor 15a 15c Rotor of the second (brushless) electric motor 15a 15d Roller of the rotatable (floor) brush 15 16 (Suction) opening 17 Control unit 18 Rechargeable electrical energy storage device; accumulator; battery 2Subsurface; floor; floor covering; surface to be cleaned; tiles; hard floor; carpet; short-pile carpet; long-pile carpet 100Moving the rotor 15c into a first orientation A1 relative to a stator 15b 200Initiating a movement B of the rotor 15c into a second orientation A2 300Detecting a value of an electrical quantity 400Determining whether the initiated movement B has occurred or not 500Initiating a further movement of the rotor 15c into a third orientation

Claims

1. Vacuum cleaner (1), preferably a handheld vacuum cleaner (1), comprising a fan (12) having an impeller for generating an air flow, a first electric motor (12a) for driving the impeller of the fan (12), a suction nozzle (14) having a rotatable brush (15), a second electric motor (15a) for driving the rotatable brush (15), and a control unit (17) which is designed and configured to operate at least the first electric motor (12a) and / or the second electric motor (15a), wherein the control unit (17) is designed and configured to initiate a movement (B) of a rotor (15c) of the second electric motor (15a) relative to the stator (15b) of the second electric motor (15a) from a first orientation (A1) into a second orientation (A2), to detect a value of an electrical quantity which is influenced by the movement (B) from the first orientation (A1) into the second orientation (A2), and to determine from the value of the electrical quantity whether the initiated movement (B) has occurred or not, characterised in that the control unit (17) is designed and configured such that the movement (B) is initiated by means of a driving force, which is sufficient for the movement (B) to be carried out on a hard floor as a surface (2), but is too low for the movement (B) to be carried out on a different surface (2).

2. Vacuum cleaner (1) according to claim 1, wherein the control unit (17) is designed and configured such that the rotatable brush (15) is not driven by means of the second electric motor (15a) if the initiated movement (B) has occurred.

3. Vacuum cleaner (1) according to either of the preceding claims, wherein the control unit (17) is designed and configured such that the movement (B) into the second orientation (A2) is initiated again by means of a higher driving force than before if the initiated movement (B) has not occurred.

4. Vacuum cleaner (1) according to claim 3, wherein the control unit (17) is designed and configured such that the rotatable brush (15) is operated by means of the second electric motor (15a), if the movement (B) was initiated by the higher driving force and if the higher driving force is below a limit value for detecting a blocked rotatable brush (15).

5. Vacuum cleaner (1) according to claim 4, wherein the control unit (17) is designed and configured such that the rotatable brush (15) is driven by means of the second electric motor (15a) at a predetermined rotational speed which corresponds to a surface (2) which corresponds to the driving force by means of which the initiated movement (B) has occurred.

6. Vacuum cleaner (1) according to claim 5, wherein the control unit (17) is designed and configured such that the rotatable brush (15) is not operated by means of the second electric motor (15a) if the higher driving force reaches a limit value for detecting a blockage of the rotatable brush (15).

7. Vacuum cleaner (1) according to any of the preceding claims, wherein the control unit (17) is designed and configured to initiate a further movement of the rotor (15c) of the second electric motor (15a) into a third orientation relative to the stator (15b) of the second electric motor (15a).

8. Vacuum cleaner (1) according to claim 7, wherein the control unit (17) is designed and configured to initiate the further movement into the third orientation in the same direction as the movement (B) into the second orientation (A2).

9. Vacuum cleaner (1) according to claim 7, wherein the control unit (17) is designed and configured to initiate the further movement into the third orientation in the opposite direction to the movement (B) into the second orientation (A2).

10. Vacuum cleaner (1) according to any of the preceding claims, wherein the electrical quantity is an induced voltage or an adjusting current.

11. Vacuum cleaner (1) according to any of the preceding claims, wherein the driving force is caused by means of an electrical voltage or by means of an electric current.

12. Vacuum cleaner (1) according to any of the preceding claims, wherein the second electric motor (15a) and / or the first electric motor (12a) is / are brushless.

13. Vacuum cleaner (1) according to any of the preceding claims, further comprising a rechargeable electrical energy store (18) which is designed and configured to electrically supply at least the first electric motor (12a), the second electric motor (15a) and the control unit (17).

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