DE102015218497A1 - Method for determining a predetermined position of an actuator and actuator - Google Patents

Abstract

The invention relates to a method for determining a predetermined position of an actuator, in particular for actuating a clutch of a vehicle, in which an actuating element (6) by an electric motor (4, 5) is driven, wherein the rotational movement of the electric motor (4, 5) is converted by a transmission (3) in an axial disengagement of a unit to be actuated. In a method in which a particularly reliable detection of the release travel of the clutch actuator is possible, a sensor (22, 28, 34, 35) detects the positions of two targets (18, 19, 20, 21), each with one, from The carrier element (16, 17) driven by the electric motor (4, 5) revolves, and recognizes the predetermined position of the actuator (1) when the detected positions of the targets (18, 19, 20, 21) overlap.

Description

The invention relates to a method for determining a predetermined position of an actuator, in particular for the actuation of a clutch of a vehicle, in which an actuating element is driven by an electric motor, wherein the rotational movement of the electric motor is converted by a gear in an axial disengagement of a unit to be actuated and an actuator for carrying out the method.

Actuator arrangements are used in clutch actuation systems which have an electric motor serving for the drive and a rotary linear drive for converting the rotational movement of the electric motor into a linear movement for actuating the clutch. This actuator arrangement comprises a transmission system which is connected to the rotor of the electric motor. The actuator comprises a mechanical stop to limit its movement.

There is known an actuator in which on a threaded spindle of the rotary-linear gear a fixed in relation to the threaded spindle in the axial direction and fixed in position stop disc is arranged. Between stop disc and thrust bearing of planetary rollers designed as planetary gear transmission rotary linear gear is located in relation to the threaded spindle in the axial direction movable needle bearing and a likewise movable in the axial direction of the stop spring. Serially to the stop spring also a biasing spring is arranged. By the introduction of a drive torque by the electric motor, the planetary rollers of the planetary gear with its sleeve move to the left, ie in the direction of opening and allow a pressure reduction in the clutch. As soon as the needle bearing comes into contact with the stop disc, the stop spring is deformed. The stop spring is thereby deformed until a balance is established between the introduced drive torque and the resistance moment caused by the deformation of the stop spring. If, at this point of equilibrium, the angle of the threaded spindle detected by an angle sensor attached to the threaded spindle end is registered as plausible, then a referencing point is found which can be used as a stop position.

From the DE 10 2009 048 389 A1 is an arrangement for detecting more than one revolution by means of magnets known as locators, in which two gears mesh with each other, each sitting on a shaft, of which the shaft of the one gear is driven from the outside to rotate about the axis of rotation, while the other gear means a shaft journal is only rotatably mounted. The juxtaposed gears have a different number of teeth. The rotational position of shaft and shaft journal are detected by a magnet unit is rotatably mounted on each of the gears. These magnet units are detected by an oppositely disposed angle sensor element. Such an arrangement is very complex and has only a lack of accuracy in the determination of the angular position.

The invention has for its object to provide a method for determining a predetermined position of an actuator and an actuator, in which its position during operation is clearly visible.

According to the invention, the object is achieved in that a sensor detects the positions of two targets, each of which rotates with one, driven by the electric motor support member, and the overlapping of the detected positions of the targets, the predetermined position of the actuator is detected. This has the advantage that can be dispensed with mechanical stops. The predetermined position is thereby virtually determined and calculated, which simplifies the structure of the actuator.

A development of the invention relates to an actuator, in particular for the actuation of a clutch of a vehicle, which comprises a Planetenwälzgewindsspindeltrieb for converting a rotational movement of an electric motor into an axial disengagement movement of a threaded spindle. In an actuator in which the actuator position is reliably detectable, a motor shaft is connected to a gear unit comprising two carrier elements driven by the motor shaft, a target being positioned in or on each carrier element, both targets being overlapped by a sensor for detection of a sensor be sampled predetermined position of the actuator. With this configuration, the overlap of the targets can be measured simply without contact. Since the sensor is stationarily positioned, information is provided as to whether no, one or both targets are at the measured position.

Advantageously, a first and a second toothing with different numbers of teeth are axially axially successively formed on the motor shaft, in which two coaxially arranged, the carrier elements of the transmission unit forming secondary gears, which also have a different number of teeth, engage, wherein the lying in a plane toothing and secondary gear itself comb and form different translations. This has the advantage that a virtual operating point of the actuator is detected by means of a very robust device which is determined with reliable accuracy.

In one embodiment, the targets are formed as continuous openings in the support elements. By using the window-like openings, an optical sensor can be used, which can uniquely determine when the two targets of the two support elements are directly above each other over him. If this is the case, it is ensured that the actuator is always at the same position, which is characterized by this position of the targets. The window-like openings are preferably arranged one above the other at or near the end of Aktorweges.

In one embodiment, the targets are arranged on a radially extending surface of the carrier elements, wherein the surfaces carrying the targets are arranged opposite, wherein each target is formed in particular by an interruption of a layer applied to the surface of the carrier elements. By means of such layers can be realized particularly close distances between the two coaxially arranged carrier elements, which leads to an accurate detection of the overlap of the targets and reduces the space of the gear unit.

In one embodiment, the first target is rotationally coupled to the second support member, while the second target is rotationally connected to the first support member, wherein the second target bearing layer is formed as a bearing of the first support member. As a result, the two layers carrying the targets can lie directly against one another and at the same time be positioned directly above the sensor.

In order to make the storage of the first support element particularly simple, the, the second target-bearing layer is designed as a rotary feedthrough having a radial, directed to the axis of rotation of the support element bend, wherein the bend opposite the second support member, while the rotary feedthrough with the first support member is firmly connected.

In one embodiment, the targets are each formed by a permanent magnet, which is integrated in each carrier element, wherein an inductive sensor has a, comprising two carrier elements Flußleitkörper which is provided with a coil.

In one alternative, each target comprises a flux guide, which are formed so that when a superposition of the targets, a magnetic flux with the inductive sensor, which is horseshoe-shaped, is closed. Since in this embodiment, the Flußleitkörper are also integrated into the target, can be dispensed with an external core, which reduces the cost.

In an advantageous embodiment, the first and the second toothing are mounted on a holder, preferably a housing of an angle magnet of the electrically commutated electric motor, which is seated on the motor shaft. The use of existing in the actuator components for the teeth costs for the determination of the reference position can be saved.

In one variant, the target is formed on the first carrier element as a fixed elevation, while on the second carrier element, an elastically suspended elevation is positioned, wherein the sensor detects a deflection of the elastically suspended elevation and at the largest deflection, the predetermined position of the actuator is detected. During the movement of the support elements, the elastically suspended elevation of the fixedly positioned elevation yields. The sensor is designed as a distance sensor and only has to detect the deflection of the elastic survey. This provides the information as to whether the target passes at normal distance or comes very close to this.

A development of the invention relates to an actuator, in particular for the actuation of a clutch of a vehicle, which comprises a Planetenwälzgewindsspindeltrieb for converting a rotational movement of an electric motor into an axial disengagement movement of a threaded spindle. In an actuator whose position is reliably detected, a motor shaft is connected to a gear unit comprising two support members driven by the motor shaft, wherein in each of the support member and a target is positioned and each target for sensing a rotational position, a sensor is associated with are connected to an AND logic to determine the overlap of the target positions. Since the carrier elements are not arranged coaxially, a crosstalk between the various sensors and targets can be excluded. The AND logic can be implemented in software. This variant offers the advantage that the absolute position of the actuator can be calculated by means of the sensor information in combination with a threaded spindle angle signal even after a short travel.

The invention allows numerous embodiments. Several of these will be explained in more detail with reference to the figures shown in the drawing.

Show it:

1 : an embodiment of a hydrostatic clutch actuator,

2 FIG. 1 shows a first view of a first embodiment of a transmission unit of the hydrostatic clutch actuator, FIG.

3 FIG. 2 is a second view of the first embodiment of the transmission unit of the hydrostatic clutch actuator, FIG.

4 a second embodiment of the transmission unit of the hydrostatic clutch actuator,

5 a third embodiment of the transmission unit of the hydrostatic clutch actuator,

6 FIG. 1 shows an exemplary embodiment of the position of the targets over a threaded spindle angle over 40 revolutions, FIG.

7 : an enlarged view of the position of the individual targets according to 6 .

8th a fourth embodiment of the transmission unit of the hydrostatic clutch actuator,

9 A fifth embodiment of the transmission unit of the hydrostatic clutch actuator,

10 a sixth embodiment of the transmission unit of the hydrostatic clutch actuator,

11 a seventh embodiment of the transmission unit of the hydrostatic clutch actuator,

12 An eighth embodiment of the transmission unit of the hydrostatic clutch actuator.

In 1 is an embodiment of a hydrostatic clutch actuator 1 illustrated how it is used in a clutch actuation system of a vehicle. The hydrostatic clutch actuator 1 includes a housing 2 which is a rotary linear gear 3 encloses, in turn, by a rotor 4 an electrically commutated electric motor is surrounded, wherein a stator 5 the rotor 4 the electric motor is arranged opposite.

The rotary linear gear 3 includes a threaded spindle 6 whose axial force is transmitted to a clutch, not shown, of the motor vehicle and actuates this. The electric motor 4 . 5 axially opposite one another, radially expanding, a carrier plate 7 arranged on which an electronics 8th and a sensor for detecting a rotation angle of the threaded spindle 6 is arranged. The threaded spindle 6 stands with several planetary roles 9 engaged with one of the planetary rollers 9 surrounding ring gear 10 combing, with the planetary roles 9 in a planet roll container 11 are positioned rotatably about their own longitudinal axis. This encloses a gear unit 12 the threaded spindle 6 ,

The gear unit 12 has a holder in a first embodiment 13 on which the threaded spindle 6 encloses and at the same time as a bearing of an angle magnet for commutation of the electric motor 4 . 5 is provided. How out 1 and 2 can be seen, is at its outer diameter a first toothing 14 and an axially displaced second toothing 15 arranged. The gears 14 and 15 have different numbers of teeth. In the teeth 14 engages a first secondary gear 16 one, while the gearing 15 a second secondary gear 17 leads. Also the secondary gears 16 . 17 have different numbers of teeth, wherein the smaller number of teeth having first secondary gear 16 in the, the larger number of teeth having teeth 14 and the second secondary gear having the larger number of teeth 17 in the, the smaller number of teeth having teeth 15 , While the bracket 13 is guided on the motor shaft and is driven by this, are the coaxially arranged slave gears 16 and 17 rotatably mounted on a pin.

Each secondary gear 16 . 17 has a trained as a target continuous opening 18 . 19 on. Because the two secondary gears 16 . 17 and the gears 14 . 15 different translations to the threaded spindle 6 can realize the position of the hydrostatic clutch actuator with a sensor 1 can be detected easily. This is done when the below the coaxially arranged slave gears 16 . 17 positioned, not shown sensor overlap of the openings 18 . 19 detected directly above. The secondary gears 16 . 17 form the carrier elements as openings 18 . 19 trained targets.

In 4 is a second embodiment of the transmission unit 12 shown. In each case an interrupt serves as a target 20 . 21 , which is formed in each of a metal or plastic existing layer, which on the opposite surfaces of the secondary gears 16 and 17 are arranged. An overlap of interruptions 20 . 21 is from a sensor 22 , which is below the secondary gears 16 . 17 is arranged detected.

In 4 an initial state is shown in which the two interruptions 20 . 21 exactly on top of each other. This ideally corresponds to the absolute end position of the hydrostatic clutch actuator 1 , The sensor 22 looks from below at the secondary gears 16 . 17 and registered when the two breaks 20 . 21 lie over him. Alternatively, the sensor 22 but also above or laterally on the secondary gears 16 . 17 watch.

In 5 is another embodiment of the transmission unit 12 shown in which the metal or plastic layer with the interruption 20 which is connected to the secondary gear 16 is arranged and below the interruption 21 that of the secondary gear 17 is worn, is arranged. Here it is, the interruption 16 supporting metal or plastic layer as a rotary feedthrough 23 formed with the first secondary gear 16 connected is. The rotary feedthrough 23 has an angled radially outward bending 24 on, in which the interruption 20 is trained.

The sensor 22 In the various embodiments, it is able to detect when targets 18 . 19 according to 2 . 3 or the targets 20 . 21 according to 4 . 5 stand simultaneously at the sensor position. The targets 18 . 19 respectively. 20 . 21 are arranged so that they are at or near the end of the Aktorweges the Kupplungsaktors 1 stand. This arrangement allows the targets 18 . 19 respectively. 20 . 21 also have more overlaps. Two overlaps are particularly advantageous, with an overlap at the absolute end of the Aktorweges the hydrostatic clutch actuator 1 is used for emergencies, while a second overlap, which is about the coasting distance of the hydrostatic clutch actuator 1 remote from it is used for normal referencing. For normal referencing, the hydrostatic clutch actuator should be used 1 be turned off in the normal state before switching off.

In 6 is an embodiment of the location of the individual targets 18 . 19 respectively. 20 . 21 in a signal from the sensor 22 and a threaded spindle angle 40 Turns shown while 7 an enlargement of 6 shows over the first five turns. It shows 6a the first target 18 . 20 about the turn while 6b the second target 19 . 21 represents. In 6c are two overlaps of the targets 18 . 19 respectively. 20 . 21 to recognize. These are due to the fact that, due to the different translations between the gears 14 . 15 and the secondary gears 16 . 17 , the targets 18 . 19 respectively. 20 . 21 to each other. In 6d is the rotational movement of the angle over the threaded spindle 6 shown.

This embodiment is based on the following configuration: toothing 14 on the bracket 13 has 17 Teeth, while at the secondary gear 16 31 teeth are present. The gearing 15 on the bracket 13 includes 20 Teeth, while that in this gearing 15 engaging auxiliary gear 17 35 teeth. The targets 14 . 15 respectively. 20 . 21 are 30 ° wide.

How out 7 Obviously, there are two areas where the two targets 14 . 15 respectively. 20 . 21 overlap and for the sensor 22 are open. The left-hand area serves as the absolute end stop E. The right-hand area is the area R, which is referenced in the normal range. Here is the clutch actuator 1 also be parked when turning off the vehicle. The distance between the two areas E and R is just under two revolutions of the secondary gears 16 . 17 and thus corresponds approximately to a Ausrollweg the hydrostatic clutch actuator 1 , This distance can be adjusted very flexibly via the tooth ratios.

If a fault occurs on the hydrostatic clutch actuator, which can happen, for example, during a power failure, it is not known at which position the hydrostatic clutch actuator will be 1 located. For this purpose, it is driven at reduced speed in the direction of the region E to the end stop (to the left) until either one of the two targets 14 . 15 respectively. 20 . 21 is detected or at least the distance between the two targets 14 . 15 respectively. 20 . 21 was covered. This is done by the electronics 8th controlled as the distance between the two targets 14 . 15 respectively. 20 . 21 is known. The size of the reduced speed is based on the Ausrollweg the hydrostatic clutch actuator 1 , Will be within the distance traveled by the two targets to the left 14 . 15 respectively. 20 . 21 no target 14 . 15 respectively. 20 . 21 detected, it is ensured that the hydrostatic clutch actuator 1 above the two targets 14 . 15 respectively. 20 . 21 located. It can therefore be driven at full speed in the direction of the area E (end stop) until the first target 14 respectively. 20 is recognized. The distinction as to which overlap is currently positioned, is also based on the width of the overlap as a function of the threaded spindle angle or on the beginning and end of the overlap also related to the threaded spindle angle.

In the event of an error may then for the distance of the two targets 14 . 15 respectively. 20 . 21 only with reduced speed toward the end stop, which represents a virtual stop, be driven so that the width of the emergency window is sufficient, the hydrostatic clutch actuator 1 to stop. This will ensure that even if a following error occurs, damage to the clutch actuator 1 is prevented.

An embodiment with only one overlap is conceivable, especially if this is very wide, to allow a rolling out of the hydrostatic clutch actuator in case of failure.

In 8th is another embodiment of the transmission unit 12 shown in which a mechanical implementation of the targets 25 . 26 is shown in an exploded view. This is located on the secondary gear 16 a survey 25 which is stationarily positioned. On the other side gear 17 , which is located underneath, is also a survey 26 , This survey 26 is elastic on a suspension 27 attached and so can when touched by the first survey 25 give in. The two secondary gears 16 . 17 are also arranged coaxially here. By the movement of the secondary gear 16 will the survey 25 on the elastic suspension 27 , which is formed in a circular arc and at the free end of the second survey 26 is arranged, pressed down, so that the distance of the second survey 26 to the sensor not shown 22 changed. The sensor 22 is designed as a distance sensor and provides information whether the survey 26 passing him by in his normal state or being particularly close to him.

In 9 is shown a further embodiment in which in the coaxially arranged secondary gears 16 . 17 not shown further permanent magnets are arranged. As a sensor that senses the superimposition of the permanent magnets, an inductive sensor 28 used. This inductive sensor 28 consists of a horseshoe-shaped iron core 29 , the two secondary gears 16 . 17 encloses axially. To the iron core 29 is a coil 30 wound in which the permanent magnets in reaching a position in which they overlap and at the same time from the outside through the iron core 29 be covered, inducing a magnetic field, resulting from the inductive sensor 28 is detected. The iron core 29 can also be designed as a ferrite core. By means of the inductive sensor 28 The inductance is at the location of the two secondary gears 16 . 17 measured. By this inductance, the information is supplied, whether just no, one or both designed as a permanent magnet targets 14 . 15 respectively. 20 . 21 occur at the measured location. Ideally, the horseshoe-shaped iron core 28 consist of several parts, which facilitates the assembly.

In 10 another embodiment is shown in which the idea of inductance measurement is further developed. This is on an external iron core 28 waived. The magnetic flux is generated by a suitable shaping of the target iron cores 31 . 32 . 33 passed in the secondary gears 16 . 17 are integrated and if both secondary gears 16 . 17 in a position over each other. In the secondary gear 16 is the iron core 31 horseshoe-shaped integrated, while in the secondary gear 17 two iron cores extending axially next to each other 32 . 33 are arranged. The distance between the two iron cores 32 . 33 is chosen so that they lie on top of each other with the iron core 30 of the first secondary gear 16 complete with this directly. The inductive sensor 28 , which is arranged outside, is also provided with an arcuate iron core, around which in turn the coil is wound. This inductive sensor 28 becomes the second secondary gear from below 17 created and measures an inductance when the iron core 30 of the first secondary gear 16 and the iron cores 31 . 32 of the slave gear 17 directly above the inductive sensor 28 stand.

A variant with a separate sensor for each slave gear 16 . 17 is in 11 shown. The secondary gears 16 . 17 are each on a different side of the bracket 13 arranged and engage in the teeth 14 respectively. 15 one. The secondary gear 16 is a sensor 34 and the slave gear 17 another sensor 35 arranged opposite. The sensor 34 detects the position of the target 36 while the sensor 35 that at the second secondary gear 17 arranged targets 37 scans. A crosstalk between the various sensors and targets is thus excluded. The sensors 34 . 35 are with the electronics 8th connected, which has an AND logic, which is formed in a software. By means of this AND logic, the overlaps of the targets 36 . 37 detected. This variant offers the advantage that the absolute position of the hydrostatic clutch actuator can already be determined after a short travel via the additional sensor information in combination with a threaded spindle angle signal 1 can be calculated.

12 shows a further embodiment of the transmission unit 12 in which the drive element, for example the threaded spindle 6 , a planetary gear 38 drives on which a target 39 is arranged. The planet wheel 38 is on the planet cage 9 the planetary gear 3 arranged and from the ring gear 10 limited. In this embodiment, an interference pattern only with a target 39 receive. The target 39 is on the planet 38 so attached it between the threaded spindle 6 as a sun and a ring gear 10 circulates. This describes the target 39 a hypocycloid that can be made to travel the path of the hydrostatic clutch actuator 1 once or n times by a sensor, not shown, is detected. Likewise, multiple sensors may be used to securely detect particular discrete locations of the hydrostatic clutch actuator. In addition, another optional target 38 with its own sensor on the planet cage 9 be attached for more information.

The proposed principle can also be implemented with three or more secondary gears. Likewise, other types of gears, such as a bevel gear and internal gears or toothed belt can be used.

LIST OF REFERENCE NUMBERS

1

 Hydrostatic clutch actuator

2

 casing

3

 Rotation-linear transmission

4

 rotor

5

 stator

6

 screw

7

 support plate

8th

 electronics unit

9

 planetary roller

10

 ring gear

11

 Planetary roller cage

12

 gear unit

13

 bracket

14

 gearing

15

 gearing

16

 Besides gear

17

 Besides gear

18

 opening

19

 opening

20

 interruption

21

 interruption

22

 sensor

23

 Rotary union

24

 angling

25

 survey

26

 survey

27

 suspension

28

 Inductive sensor

29

 iron core

30

 Kitchen sink

31

 iron core

32

 iron core

33

 iron core

34

 sensor

35

 sensor

36

 target

37

 target

38

 planet

39

 target

40

 target

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009048389 A1 [0004]

Claims (10)

Method for determining a predetermined position of an actuator, in particular for actuating a clutch of a vehicle, in which an actuating element ( 6 ) by an electric motor ( 4 . 5 ), wherein the rotational movement of the electric motor ( 4 . 5 ) by a transmission ( 3 ) is converted into an axial disengagement movement of a unit to be actuated, characterized in that a sensor ( 22 . 28 . 34 . 35 ) the positions of two targets ( 18 . 19 ; 20 . 21 ), each with one, by the electric motor ( 4 . 5 ) driven carrier element ( 16 . 17 ), detected and overlapping the detected positions of the targets ( 18 . 19 ; 20 . 21 ) the predetermined position of the actuator ( 1 ) is recognized. Actuator, in particular for actuating a clutch of a vehicle, which has a planetary roller screw drive ( 3 ) for converting a rotary motion of an electric motor ( 4 . 5 ) in an axial disengagement movement of a threaded spindle ( 6 ), characterized in that a motor shaft with a gear unit ( 12 ), which two, driven by the motor shaft carrier elements ( 16 . 17 ), wherein in or on each support element ( 16 . 17 ) a target ( 18 . 19 ; 20 . 21 ) and both targets ( 18 . 19 ; 20 . 21 ) from a sensor ( 22 ) to overlap for detecting a predetermined position of the actuator ( 1 ) are scanned. Actuator according to claim 2, characterized in that on the motor shaft axially one behind the other a first and a second toothing ( 14 . 15 ) are formed with different numbers of teeth, in which two coaxially arranged, the support elements ( 16 . 17 ) of the transmission unit ( 12 ) forming secondary gears, which also have different numbers of teeth, intervene, wherein the lying in a plane toothing ( 14 . 15 ) and secondary gear ( 16 . 17 ) comb each other and form different translations. Actuator according to Claim 1, 2 or 3, characterized in that the targets ( 18 . 19 ) as continuous openings in the carrier elements ( 16 . 17 ) are formed. Actuator according to Claim 1 or 2, characterized in that the targets ( 20 . 21 ) on a radially extending surface of the carrier elements ( 16 . 17 ), wherein the, the targets ( 20 . 21 ) bearing surfaces are arranged opposite each other and each target ( 20 . 21 ) in particular by an interruption of a on the surface of the support elements ( 16 . 17 ) applied layer is formed. Actuator according to Claim 5, characterized in that the first target ( 20 ) rotationally to the second carrier element ( 19 ), while the second target ( 21 ) rotationally to the first support element ( 17 ), wherein the layer forming the second target acts as a bearing for the first carrier element ( 16 ) is trained. Actuator according to claim 6, characterized in that the, the second target ( 21 ) supporting layer as rotary feedthrough ( 23 ) is formed, which has a radial, to the axis of rotation of the carrier element ( 17 ) directed bend ( 24 ), wherein the bend ( 24 ) the second carrier element ( 17 ) while the rotary union ( 23 ) with the first carrier element ( 16 ) is firmly connected. Actuator according to claim 1 or 2, characterized in that the targets are each formed by a permanent magnet, which in each carrier element ( 16 . 17 ) and the inductive sensor ( 28 ) one, the two support elements ( 16 . 17 ) flux guide body ( 29 ) provided with a coil ( 30 ) is provided. Actuator according to claim 1, characterized in that the target on the first support element ( 16 ) as a fixed survey ( 25 ) is formed, while on the second carrier element ( 17 ) an elastically suspended survey ( 26 ), the sensor ( 22 ) a deflection of the elastically suspended survey ( 26 ) and at the largest deflection the predetermined position of the actuator ( 1 ) is recognized. Actuator, in particular for actuating a clutch of a vehicle, which has a planetary roller screw drive ( 3 ) for converting a rotary motion of an electric motor ( 4 . 5 ) in an axial disengagement movement of a threaded spindle ( 6 ), characterized in that a motor shaft with a gear unit ( 12 ), which two, driven by the motor shaft carrier elements ( 16 . 17 ), wherein in or on each support element ( 16 . 17 ) a target ( 36 . 37 ), and each target ( 36 . 37 ) for sensing a rotational position, a sensor ( 34 . 35 ) associated with an AND logic for determining the overlap of the target position.

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