Patent Publication Number: US-2023150467-A1

Title: Actuator assembly for a vehicle brake and method for activating an actuator assembly for a vehicle brake

Description:
TECHNICAL FIELD 
     The invention relates to an actuator assembly for a vehicle brake, having a carrier assembly on which an activating carriage for a brake lining is guided linearly, an electric motor fastened to the carrier assembly and which is coupled drivingly to the activating carriage via a gear unit and a spindle drive such that the activating carriage can be displaced selectively between a retracted position and an extended position, and a locking assembly for selectively immobilizing in rotation an output shaft of the electric motor. 
     BACKGROUND 
     The invention moreover concerns a method for activating an actuator assembly for a vehicle brake. 
     Such actuator assemblies are known from the prior art. They are also referred to as electromechanical actuator assemblies. The locking assembly is here usually used to perform the function of a parking brake. In this connection, the activating carriage is first transferred into its extended position. The output shaft of the electric motor is then immobilized by means of the locking assembly. The activating carriage is thus fixed in the extended position. 
     In this connection, an activating carriage should be understood to mean a component which is mounted so that it can move essentially linearly and which is designed to move another component, in this case a brake lining of the vehicle brake. With reference to the vehicle brake, the extended position of the activating carriage is thus associated with activation of the vehicle brake. The retracted position of the activating carriage is accordingly associated with an unactivated state of the vehicle brake. 
     In this connection, the vehicle brake is configured, for example, as a disc brake. 
     SUMMARY 
     It is furthermore known that actuator assemblies for vehicle brakes must be installed in very narrow structural spaces. 
     Against this background, the object of the invention is to improve an actuator assembly of the type mentioned at the beginning. It is in particular intended to produce a compact actuator assembly. 
     The object is achieved by an actuator assembly of the type mentioned at the beginning, in which the locking assembly comprises a locking lever which at a first end is mounted rotatably on the carrier assembly and at a second opposite end is coupled to a locking actuator, wherein a locking tooth, which can be selectively brought into engagement with a locking contour provided on the output shaft, is positioned in the direction in which the locking lever extends longitudinally between the first end and the second end. This configuration ensures a compact structure of the actuator assembly such that the latter can be easily integrated into a relatively small structural space on a vehicle. Such an actuator assembly is additionally reliable when in operation. 
     The gear unit of the actuator assembly can here comprise a gear train and/or a planetary gear stage. The planetary gear stage is preferably arranged behind the gear train in a flow of power from the electric motor to the spindle drive. In this way, drive power from the electric motor can be reliably geared down. 
     The locking actuator is preferably a linear actuator. It engages, for example, on an opening at the second end of the locking lever which can be configured as a slot. The locking lever can thus be reliably activated. 
     According to an embodiment, the locking contour is formed by a toothing of an output gear wheel coupled fixedly to the output shaft. In this way, the output shaft can be effectively prevented from rotating. Furthermore, an output gear wheel of this type can also be used as an input element for the gear unit. The output gear wheel therefore performs two functions such that there is no need to provide a separate locking contour. A simpler and more compact structure of the actuator assembly thus results. 
     The gear unit, the spindle drive and associated drive couplings are preferably configured so that they are not self-locking. This means that the activating carriage can be relocated by the application of an axial force when in an operating situation in which it is not driven by means of the electric motor. As a result, when the actuator assembly is in operation, the activating carriage does not need to be actively withdrawn from its extended position. Instead, it is also possible with such a configuration that the activating carriage is, owing to elasticities inherent in the system, shifted from its extended position in the direction of the retracted position, as long as the electric motor is not activated. A vehicle brake equipped with an actuator assembly of this type is therefore open at all times when it is not activated, i.e. in particular even if the supply of current has failed. The actuator assembly and the vehicle brake equipped therewith thus always assume a defined state. 
     An axis of rotation of the output shaft can also be arranged essentially parallel to a centre axis of the spindle drive. A compact structure of the actuator assembly results. 
     In an alternative, the first end of the locking lever is fork-shaped and receives a bearing bolt fastened to the carrier assembly in order to rotatably mount the locking lever. In this connection, fork-shaped means that the receiving space for the bearing bolt is open on one side. The bearing bolt is therefore enclosed  180 ° by the first end. As a result, the locking lever can be mounted relatively quickly and simply inside the actuator assembly. 
     The locking actuator can comprise a solenoid. The solenoid can here preferably be turned on electrically. The locking lever can thus be activated simply and reliably. 
     The locking actuator can here be bistable. This means that the locking actuator is held in two positions without any current. These are thus preferably a retracted position and an extended position. They are further preferably associated with a locking position and a release position of the locking assembly. The locking position can here also be referred to as the locking state, and the release position as the release state. The locking assembly can thus be operated in a reliable and energy-efficient fashion. 
     In the event that the locking actuator is a solenoid, the latter can be configured to be bistable such that two permanent magnets, integrated into the solenoid, are each designed to hold the armature of the solenoid in the retracted position and the extended position. It is also conceivable to equip the solenoid with mechanical fixing devices which are likewise designed to hold the armature of the solenoid in the retracted position and the extended position. 
     According to an alternative embodiment, a supporting contour for supporting a force component acting essentially radially with respect to the rotatable mounting of the locking lever is provided between the first end and the second end in the direction in which the locking lever extends longitudinally, wherein the supporting contour interacts with a bearing contour provided on the carrier assembly. Such a supporting contour and an associated bearing contour are, in particular in combination with a locking lever which has a fork-shaped end, advantageous. No tensile forces can namely be transmitted from the locking lever to the bearing bolt at such a fork-shaped end. Forces of this type are consequently supported by means of the supporting contour and the bearing contour and result, for example, in the locked state from a torque present at the output shaft of the electric motor. The supporting contour and the bearing contour thus cause the output shaft to be reliably prevented from rotating. 
     The supporting contour and/or the bearing contour can here comprise a cylindrical surface portion of a circular cylinder, the centre axis of which coincides with an axis of rotation associated with the rotatable mounting of the locking lever. Such a design of the supporting contour and/or the bearing contour ensures reliable support of forces acting radially with respect to the bearing bolt. At the same time, the locking lever possesses the required degree of freedom of movement. In the event that both the supporting contour and the bearing contour comprise cylindrical surface portions, the forces acting radially with respect to the bearing bolt are supported over a large area and reliably. 
     In an embodiment, the supporting contour is formed on a flank of a supporting projection. The supporting projection can here have a toothed design. Moreover, the supporting projection is preferably arranged on a side of the locking lever opposite the locking tooth. More preferably, the supporting projection is provided as an integral part of the locking lever. Overall, the supporting contour can in this way be provided in a simple and cost-effective manner. At the same time, it functions with a high degree of reliability. 
     The bearing contour can be formed on an arc-shaped wall section of the carrier assembly. Such a wall section can be produced simply and cost-effectively. Furthermore, forces supported by means of the bearing contour can in this way be reliably transmitted into the carrier assembly. 
     According to an alternative embodiment, the locking lever has two sections in the direction in which it extends longitudinally, the sections being offset relative to each other in a direction which corresponds to the direction in which the output shaft extends longitudinally. The locking lever can also be described as cranked. A locking lever of this type can be integrated easily into narrow and cramped structural spaces. It is in particular thus possible that the locking lever, on the one hand, interacts with an output gear wheel on the output shaft of the electric motor and, on the other hand, leaves a large enough structural space for the gear unit which must be coupled drivingly likewise with the output shaft. As a result, at least one section of the locking lever can advantageously be positioned behind the gear unit in a direction corresponding to the direction in which the output shaft extends longitudinally. 
     The object is additionally achieved by a method of the type mentioned at the beginning, wherein the actuator assembly comprises an electric motor which is coupled drivingly, via a gear unit and a spindle drive, to an activating carriage for a brake lining such that the activating carriage can be displaced selectively between a retracted position and an extended position. A locking assembly which can be activated by a locking actuator is moreover provided for selectively immobilizing in rotation an output shaft of the electric motor. Thus, in order to activate a parking brake mode, 
     the activating carriage is transferred into the extended position by means of the electric motor, and 
     the locking assembly is then transferred into a locking state by means of the locking actuator whilst the activating carriage is held in the extended position by means of the electric motor. 
     Alternatively, in order to deactivate the parking brake mode, the electric motor is operated in a direction associated with the extended position of the activating carriage and/or the locking actuator is operated in a direction associated with the release state. 
     When the parking brake mode is activated, the supply of current to the electric motor is therefore not stopped until the locking assembly has securely reached the locking state. In the event that the locking actuator has a bistable design, supply of current to it can then also be stopped. The parking brake mode can consequently be activated with a high degree of reliability. There are several alternatives for deactivating the parking brake mode. In a preferred alternative, the electric motor is first operated in a direction associated with the extended position of the activating carriage. As a result, the force on the locking lever is relaxed. The locking actuator is then operated in a direction associated with the release state such that the locking lever, in particular the locking tooth, is removed from the locking contour. However, it is of course also possible just to operate the locking actuator in a direction associated with the release state in order to deactivate the parking brake mode. In this alternative embodiment too, the parking brake mode is reliably deactivated. However, the locking lever may here be shifted under load. In a second alternative embodiment, just the electric motor is operated in a direction associated with the extended position of the activating carriage in order to deactivate the parking brake mode. In this way, the locking lever is forced into its release position via the locking tooth. The locking actuator thus snaps over by virtue of the application of an external force. 
     The actuator assembly is further preferably configured so that they are not self-locking such that an associated vehicle brake is released by virtue of elasticities inherent in the system as soon as the locking assembly is in the release state and the electric motor is not activated. 
     The actuator assembly used in the method according to the invention is in particular an actuator assembly according to the invention. 
     When the parking brake mode is deactivated, the electric motor can be operated after the locking assembly has been moved in a direction associated with the retracted position of the activating carriage. In this alternative embodiment, the activating carriage is therefore transferred actively into its retracted position by means of the electric motor. A vehicle brake associated with the actuator assembly is consequently opened with a high degree of reliability. 
     It is moreover possible that the locking assembly assumes a release state in a service brake mode. The locking assembly is therefore not used in a service brake mode in which the actuator assembly serves to perform the function of a service brake. 
     In other words, the locking lever is held constantly in the release position and just the electric motor is used to activate the vehicle brake. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained below with the aid of an exemplary embodiment which is shown in the attached drawings, in which: 
         FIG.  1    shows an actuator assembly according to the invention which can be operated by means of a method according to the invention in a perspective exploded view, 
         FIG.  2    shows a drive assembly of the actuator assembly from  FIG.  1    in an isolated, partially cut-away view, 
         FIG.  3    shows the actuator assembly from  FIG.  1    in a view in section in the plane III in  FIG.  1   , wherein a brake caliper assembly is attached to the actuator assembly, 
         FIG.  4    shows the actuator assembly from  FIG.  3    in a view along the line of section IV-IV, wherein a spindle drive of the actuator assembly is not illustrated, 
         FIG.  5    shows a carrier assembly of the drive assembly from  FIG.  2    in a perspective exploded view, 
         FIG.  6    shows the drive assembly from  FIG.  2    in a rear view, wherein a spindle drive is not illustrated, 
         FIG.  7    shows a detailed view of a locking assembly of the actuator assembly from  FIGS.  1  to  6   , wherein the locking assembly assumes a locking state, 
         FIG.  8    shows a detailed view corresponding to  FIG.  7    of the locking assembly, wherein the locking assembly assumes a release state, 
         FIG.  9    shows a control assembly of the actuator assembly from  FIG.  1    in a perspective exploded view, and 
         FIG.  10    shows the control assembly from  FIG.  9    in a view in the direction X in  FIG.  9   . 
     
    
    
     DESCRIPTION 
       FIG.  1    shows an actuator assembly  10  for a vehicle brake. 
     The actuator assembly  10  comprises a control assembly  12  which can be mounted as a separate subunit, and a drive assembly  14  which can be mounted as a separate subunit. 
     The control assembly  12  and the drive assembly  14  are arranged in a common housing  16 . 
     The housing  16  comprises an essentially shell-shaped housing base part  18  and a housing cover  20  by means of which the housing base part  18  is closed leaktightly in the mounted state. 
     In the embodiment illustrated, the housing cover  20  is also essentially shell-shaped. 
     Both the housing base part  18  and the housing cover  20  are produced from a plastic material. The housing  16  as a whole is thus made from plastic material. 
     The drive assembly  14  can be seen in detail in  FIGS.  2  to  6   . 
     The drive assembly  14  comprises a carrier assembly  22  which has a plate-like frame part  24  (see in particular  FIGS.  2  and  5   ). 
     A first fastening interface  26 , on which an electric motor is fastened in the exemplary embodiment illustrated, is provided on the plate-like frame part  24 . 
     To be more precise, the electric motor  28  is connected captively to the frame part  24  via the first fastening interface  26 . For this purpose, a bore  30  via which the electric motor  28  can be fastened on the frame part  24  by means of a screw is provided on the frame part  24  (see  FIGS.  4  and  5   ). 
     A centring device  32  in the form of a centring surface is furthermore arranged on the frame part  24 . The electric motor  28  can therefore be fastened on the frame part  24  so that it is centred with respect to a centre axis  34  of the first fastening interface  26 . 
     In addition, an anti-rotation device  36  in the form of an anti-rotation depression is provided which is designed so as to prevent the electric motor  28  from rotating relative to the frame part  24 . 
     An output gear wheel  40  is arranged on an output shaft  38  of the electric motor  28  in order to impart torque to the drive assembly  14 . 
     Furthermore, a bearing pin  42 , on which, in the embodiment illustrated, a gear wheel  44  is mounted which meshes with the output gear wheel  40 , is provided on the frame part  24 . 
     A receiving space  46  for a planetary gear stage  48  is provided on the frame part  24 . In the embodiment illustrated, the receiving space  46  is essentially bell-shaped (see in particular  FIG.  5   ). 
     A centre axis  50  of the receiving space  46  is here arranged essentially parallel to the centre axis  34  of the first fastening interface  26 . 
     A reinforcing part  52  is moreover fastened on the frame part  24  in such a way that it spans the receiving space  46  at an axial end with respect to the centre axis  50 . 
     In the embodiment illustrated, the reinforcing part  52  is essentially cross-shaped. 
     In addition, a bearing point  54  for a gear wheel  56  arranged coaxially with respect to the planetary gear stage  48  is provided on the reinforcing part  52 . 
     The gear wheel  56  meshes with the gear wheel  44 . 
     A gear train  58 , the input element of which is embodied by the output gear wheel  40 , is consequently formed by the gear wheel  44  and the gear wheel  56 . 
     The gear wheel  56  is moreover formed integrally with a sun wheel  60  of the planetary gear stage  48 . In this way, the gear train  58  and the planetary gear stage  48  are coupled drivingly. 
     The planetary gear stage  48  moreover comprises a ring gear  62  which runs essentially along an inner periphery of the receiving space  46  (see in particular  FIG.  5   ). 
     In the embodiment illustrated, a total of three planetary gears  64  are provided drivingly between the sun wheel  60  and the ring gear  62 . They are mounted rotatably on a planet carrier  66 . 
     The planet carrier  66  here represents an output element of the planetary gear stage  48 . 
     The gear train  58  and the planetary gear stage  48  are also together referred to a gear unit  67 . 
     The frame part  24  furthermore has a second fastening interface  68  which is designed to fasten a bearing sleeve  70  for a spindle drive  72 . 
     A centre axis of the second fastening interface  68  here coincides with the centre axis  50  of the receiving space  46  and for this reason is provided with the same reference numeral. 
     The second fastening interface  68  has an anti-rotation geometry  74 , which is formed by a plurality of radial projections  76  and radial depressions  78  arranged alternately around the periphery, running peripherally around the centre axis  50 . For the sake of greater clarity, only one exemplary radial projection  76  and one exemplary radial depression  78  are in each case provided with a reference numeral in  FIGS.  5  and  6   . 
     The radial projections  76  and the radial depressions  78  are provided with a constant spacing. This means that the radial depressions  78  are each of the same length peripherally. The radial projections  76  are also each of the same length peripherally. A radial height of the radial projections  76  is furthermore constant. 
     In this way, an anti-rotation device  80  of the second fastening interface  68  is formed. 
     A complementary geometry  82  is provided at the end of the bearing sleeve  70  which is to be coupled to the second fastening interface  68  such that the bearing sleeve  70  can be pushed along the centre axis  50  into the anti-rotation geometry  74  of the second fastening interface  68  and held there, fixed in rotation. 
     The spindle drive  72  is received inside the bearing sleeve  70 . 
     It comprises a spindle  84  which in the present case is configured as a ball screw (see in particular  FIG.  2   ). 
     The spindle  84  is here connected to the planet carrier  66  via the toothed section  86  so that it is fixed in rotation. 
     The spindle drive  72  can thus be driven by means of the electric motor  28 . In detail, the electric motor  28  is coupled drivingly to the spindle drive  72  via the gear train  58  and the planetary gear stage  48 . 
     A spindle nut  88  with a piston-like design is mounted on the spindle  84 . Rotation of the spindle  84  here causes the spindle nut  88  to be shifted axially along the centre axis  50 . 
     The spindle nut  88  is here guided on the bearing sleeve  70  along the centre axis  50  by a linear guide geometry  90 . The linear guide geometry  90  corresponds essentially to a cylindrical surface forming the inner periphery of the bearing sleeve  70 . 
     The spindle nut  88  is moreover prevented from relative rotation about the centre axis  50  by means of an anti-rotation device  92  which is formed as a slot on the bearing sleeve  70 . For this purpose, a radial protrusion  94 , which engages in the slot, is attached to the spindle nut  88  (see  FIG.  3   ). 
     The spindle nut  88  furthermore serves as an activating carriage for a first brake lining  96  of a brake caliper assembly  98  (see  FIG.  3   ). Because the spindle nut  88  and the activating carriage are formed by the same component, they have been provided with the same reference numeral. 
     The first brake lining  96  can thus be moved by means of the actuator assembly  10  onto a brake rotor  100  which takes the form of a brake disc in the embodiment illustrated. 
     In detail, the activating carriage  88  is transferred selectively into an extended position which is associated with the application of the first brake lining  96  to the brake rotor  100  by means of the electric motor  28  via the gear train  58 , the planetary gear stage  48  and the spindle drive  72 . 
     A second brake lining  102  is also applied to the brake rotor  100  by virtue of the reaction forces acting within the actuator assembly  10  and the brake caliper assembly  98  (see also  FIG.  3   ). 
     It should be understood that the activating carriage  88  can in the same way be displaced into a retracted position which is associated with lifting the first brake lining  96  and the second brake lining  102  off from the brake rotor  100  by operating the electric motor  28 . 
     However, in the present case the actuator assembly  10  is configured so that it is not self-locking such that the activating carriage  88  is also automatically shifted back into the retracted position by virtue of the elasticities inherent in the system when it is no longer actively forced into the extended position by means of the electric motor  28 . 
     A third fastening interface  104  is furthermore provided on the frame part  24  (see in particular  FIG.  6   ). 
     It is designed to fasten a locking assembly  106 , wherein the locking assembly  106  is in turn provided to immobilize the output shaft  38  of the electric motor  28  selectively in terms of rotation. 
     In this connection, the third fastening interface  104  comprises a bearing bolt  108  fastened on the frame part  24  and a fastening interface  110  for a locking actuator  112 . 
     The locking assembly  106  is equipped with a locking lever  114  which has a first fork-shaped end  116  which receives the bearing bolt  108  for rotatably mounting the locking lever  114 . 
     The locking lever  114  is therefore rotated at its first end  116  so that it can rotate on the carrier assembly  22 , to be more precise on the frame part  24 . 
     At a second opposite end  118  of the locking lever  114 , the latter is coupled to the locking actuator  112  via a slot  120 . 
     In the embodiment illustrated, the locking actuator  112  is designed as a bistable solenoid. 
     This means that an armature  122  of the locking actuator  112  can be held both in its extended position and in its retracted position without any current (see  FIGS.  7  and  8   ). The locking actuator  112  needs to be supplied with current only to shift the armature  122  between these two positions. 
     A locking tooth  124  is moreover positioned between the first end  116  and the second end  118  in the direction in which the locking lever  114  extends longitudinally. 
     It is formed integrally with the locking lever  114 . 
     The toothing of the output gear wheel  40  additionally acts as a locking contour. 
     The locking tooth  124  can thus be brought into engagement with the locking contour selectively by activating the locking actuator  112 . 
     In the event that the locking tooth  124  is thus engaged in the output gear wheel  40 , the electric motor  28  is immobilized in terms of rotation (see  FIG.  7   ). Such a position of the locking assembly  106  is also referred to as a locking position or locking state. 
     When the locking tooth  124  lies outside the toothing of the output gear wheel  40 , the latter can be freely rotated. Such a position of the locking assembly  106  is referred to as the release position (see  FIG.  8   ). 
     The locking lever  114  moreover has a support projection  126 , the flank  128  of which forms a supporting contour  129 , between the first end  116  and the second end  118  in the direction in which it extends longitudinally. 
     The support projection  126  is also formed integrally on the locking lever  114 . 
     The flank  128  thus bears against a bearing contour  132  formed as an arc-shaped wall section  130  of the frame part  24 , i.e. of the carrier assembly  22 , in an essentially radial direction with respect to the bearing bolt  108 . 
     A side face, facing the flank  128 , of the arc-shaped wall section  130  here takes the form of a cylindrical surface portion of a circular cylinder, the centre axis of which coincides with a centre axis of the bearing bolt  108 . 
     The flank  128  likewise takes the form of a cylindrical surface portion of such a circular cylinder. 
     The locking lever  114  is therefore supported via the supporting projection  126  and the bearing contour  132  on the frame part  24 , i.e. on the carrier assembly  22 , with respect to such force components which act essentially radially in terms of the rotational mounting of the latter about the bearing bolt  108 . 
     Such force components result, in the locking state, from a torque which is present at the output gear wheel  40 . 
     The bearing contour  132  can thus also be seen as a constituent part of the third fastening interface  104 . 
     In order to be able to engage in the output gear wheel  40  for the purpose of immobilizing rotational movement of the electric motor  28 , but at the same time not obstruct meshing of the output gear wheel  40  with the gear wheel  44 , the locking lever  114  has, in the direction in which it extends longitudinally, a first section  114   a  which comprises the first end  116 . A second section  114   b  comprises the second end  118 . 
     The second section  114   b  is here offset along the centre axis  34  relative to the first section  114   a  in the direction of the electric motor  28 . It is also possible to describe the locking lever  114  as having a cranked design. 
     It is thus possible that the second section  114   b  runs behind the gear wheel  44 , viewed in the axial direction. 
       FIGS.  9  and  10    show the control assembly  12  in detail. 
     It comprises a bulkhead wall  134  which is provided in the embodiment illustrated with a peripheral rim  136  which runs essentially completely around the outer periphery of the bulkhead wall  134 . 
     The bulkhead wall  134  can thus also be referred to as a bulkhead tray. 
     The control assembly  12  moreover comprises a printed circuit board  138  on which electrical and electronic components designated as a whole by  140  are arranged and are connected to one another electrically via traces. 
     The electrical and electronic components  140  here form a speed-regulating unit for regulating the speed of the electric motor  28 . 
     A current measuring unit for measuring a current received by the electric motor  28  is moreover constructed from the electrical and electronic components  140 . 
     The electrical and electronic components  140  furthermore represent a current supply unit for supplying electrical energy to the electric motor  28 . In this connection, the electrical and electronic components  140  can also be referred to as a power electronic system. 
     The electrical and electronic components  140  moreover form a temperature measuring unit for measuring a temperature within the actuator assembly  10 . 
     A force measuring unit for measuring a brake actuating force supplied by means of the actuator assembly is also provided by the electrical and electronic components  140 . 
     The electrical and electronic components  140  moreover represent a control unit for the locking assembly  106 . 
     A rotational position detection unit for identifying a rotational position of the electric motor  28  is additionally formed from the electrical and electronic components  140  and is explained in more detail below. 
     In order to fasten the bulkhead wall  134  and the printed circuit board  138  against each other in a predetermined relative position, means  142  for positioning and fastening the printed circuit board  138  are provided on the bulkhead wall  134 . 
     In the embodiment illustrated in  FIG.  9   , the means  142  for positioning and fastening are formed by fastening domes arranged on the bulkhead wall  134  and into which screws are screwed which extend through the printed circuit board  138 . 
     The bulkhead wall  134  and the printed circuit board  138  are furthermore connected to each other via a sealing material  146  illustrated only schematically in an exemplary region. An intermediate space present between the bulkhead wall  134  and the printed circuit board  138  is here preferably filled essentially completely by the sealing material  146 . In this way, the electrical and electronic components  140  are protected from undesired external influences, in particular from vibrations and moisture. 
     The bulkhead wall  134  and the printed circuit board  138  are arranged relative to the electric motor  28  such that the output shaft  38  of the electric motor  28  is oriented perpendicular to the bulkhead wall  134  and to the printed circuit board  138 . 
     A magnet  148  is here arranged at an end, facing the control assembly  12 , of the output shaft  38  of the electric motor  28  (see in particular  FIGS.  2  and  4   ). 
     An associated sensor  150  is positioned on the printed circuit board  138  at a location situated opposite the magnet  148  (see in particular  FIG.  4   ). 
     The sensor  150  takes the form of a Hall effect sensor in the embodiment illustrated. In this way, a rotational position of the output shaft  38  of the electric motor  28  can be detected. Revolutions of the output shaft  38  can also be determined when evaluating the rotational position signals over time. 
     In order to supply the control assembly  12  and in particular the electrical and electronic components  140  with electrical energy, a plug connector half  152  is provided integrally on the housing  16 , to be more precise on the housing base part  18  (see  FIGS.  1  and  4   ). 
     The plug connector half  152  is here electrically connected to the printed circuit board  138  via a plurality of lines which are referred to collectively as a first electrical line  154 . 
     Starting from the plug connector half  152 , the first electrical line  154  runs initially inside the housing base part  18 . In this connection, the first electrical line  154  can be integrated into the housing base part  18  when the latter is produced. 
     A section  154   a  , on the printed circuit board side, of the first electrical line  154  is here designed as dimensionally stable and protrudes from the housing base part  18  in a direction which is oriented essentially parallel to the centre axes  34  and  50 . 
     Contact openings  16  associated with the first electrical line  154  are provided on the printed circuit board  138 . 
     A passage is moreover formed on the bulkhead wall  134  such that it is ensured that the section  154   a , on the printed circuit board side, reaches the printed circuit board  138  without contacting the bulkhead wall  134 . 
     The passage  158  is additionally provided with a rim  160  such that the passage  158  is kept free of sealing material  146 . 
     When the control assembly  12  is mounted on the housing base part  18 , the first electrical line  154 , to be more precise its section  154   a  on the printed circuit board side, is consequently plugged into the associated contact openings  156 . They thus form an electrical press contact. 
     In the embodiment illustrated, the plug connector half  152  serves not only to supply current but also to connect the actuator assembly  10  to a bus system which is, for example, a CAN bus system. 
     Wheel speed sensors can moreover be connected to the actuator assembly  10  via the plug connector half  152 . 
     The electric motor  28  is also electrically connected to the printed circuit board  138 . 
     For this purpose, dimensionally stable contacts essentially parallel to the centre axis  34  protrude from the electric motor  28  and are referred to collectively as the second electrical line  162 . 
     Contact openings  164  on the printed circuit board  138  are likewise associated with the second electrical line  162 . 
     A passage  166  is moreover provided on the bulkhead wall  134 , through which the second electrical line  162  can come into engagement with the contact openings  164 . 
     The passage  166  is again equipped with a rim  168  such that it is ensured that the passage  166  is kept free of sealing material  146 . 
     As already explained with regard to the first electrical line  154 , when the control assembly  12  is mounted, the second electrical line  162  also enters the associated contact openings  164  and forms an electrical press contact. 
     The locking actuator  112  is electrically connected to the printed circuit board  138  via a third electrical line  170  (see  FIGS.  1  and  2   ). 
     The third electrical line  170  is here also again formed from dimensionally stable contacts which protrude from the locking actuator  112  along the centre axes  34  and  50 . 
     Contact openings  172  in the printed circuit board  138  are again associated with the third electrical line  170  (see  FIG.  9   ). 
     So that the third electrical line  170  can be plugged into the contact openings  172 , a passage  174  is additionally provided on the bulkhead wall  134 . It is equipped with a rim  176  such that the passage  174  is also kept free of sealing material  146 . 
     As already explained with regard to the first electrical line  154  and the second electrical line  162 , the third electrical line  170  is also pushed into the associated contact openings  172  and forms an electrical press contact when the control assembly  12  is mounted. 
     In summary, the printed circuit board  138  is therefore coupled electrically both to the plug connector half  152  and to the electric motor  28  and the locking actuator  112 . 
     On a side, facing the drive assembly  14 , of the bulkhead wall  134 , retaining ribs  178  are additionally provided in the region of the output gear wheel  40  and the gear wheel  44  which essentially form an envelope around a gear stage formed by the output gear wheel  40  and the gear wheel  44 . 
     Retaining ribs  180  are also provided in the region of the planetary gear stage  48 . 
     The retaining ribs  178 ,  180  here serve to ensure that a lubricating medium is held in the region of the gear wheels to be lubricated even when the output gear wheel  40 , the gear wheel  44  and the planetary gear wheel  48  rotate. 
     A function of a service brake can be provided by means of the actuator assembly  10  if the actuator assembly  10  is coupled to the brake caliper assembly  98 . The actuator assembly  10  is then operated in a service brake mode. The electric motor  28  is thus controlled by means of the control assembly  12  in such a way that it effects a desired shifting of the spindle nut  88 , i.e. of the activating carriage  88 , along the centre axis  50  via the gear train  58 , the planetary gear stage  48  and the spindle drive  72 . 
     The electric motor  28  can here in principle be activated in both directions of rotation such that the activating carriage  88  can also be shifted actively in both directions. 
     It is likewise conceivable to use the electric motor  28  only to displace the activating carriage  88  into an extended position, i.e. to apply the brake lining  96  to the brake motor  100 . 
     The activating carriage  88  can be restored to a retracted position and the pressure on the brake lining  96  can therefore be relaxed in this connection by virtue of elasticities which are inherent in the system, on the one hand, and the design of the actuator assembly  10  as not self-locking, on the other hand. 
     In such a service brake mode, the locking assembly  106  at all times assumes the release state (see  FIG.  8   ). 
     A function of a parking brake can moreover be provided by means of the actuator assembly  10 . 
     In this connection, a parking brake mode can be activated by the spindle nut  88  which forms the activating carriage  88  being transferred into its extended position by means of the electric motor  28  and the brake lining  96  thus being applied to the brake rotor  100 . The brake lining  102  is thus applied to the brake rotor  100  by virtue of the reaction forces acting inside the actuator assembly  10 . 
     The locking assembly  106  is then transferred into the locking state by means of the locking actuator  112  (see  FIG.  7   ). 
     Up to the point at which the locking tooth  124  actually engages in the toothing of the output gear wheel  40  and rotation of the output shaft  38  is thus blocked, the spindle nut  88  which forms the activating carriage  88  is held actively in the extended position by means of the electric motor  28 , i.e. the electric motor  28  is correspondingly supplied with current. 
     The delivery of current to the electric motor  28  is interrupted only if the locking tooth  124  engages securely in the locking contour formed by the toothing of the output gear wheel  40 . 
     There are several alternatives for deactivating the parking brake mode. 
     In a preferred alternative, to do this the electric motor  28  is activated in a direction in which it stresses the spindle nut  88  which forms the activating carriage  88  into the extended position, i.e. shifts it in the direction of the brake lining  96 . 
     In this way, the force on the locking lever  114  is relaxed. 
     The locking lever  114  can thus be easily transferred from the locking position into the release position by means of the locking actuator  112  (see  FIGS.  7  and  8   ). 
     Supply of current to the electric motor  28  can then be stopped such that the spindle nut  88  moves back automatically into the retracted position owing to the lack of any self-locking effect. 
     It is alternatively conceivable that the locking lever  114  is transferred into the release position not by activation of the locking actuator  112  but by the electric motor  28  being activated in a direction corresponding to the extended position of the spindle nut  88  in such a way that the locking lever  114  is forced into its release position by means of the electric motor  28 . 
     The electric motor  28  can then be operated in a direction associated with the retracted position of the spindle nut  88  such that the parking brake mode is deactivated. 
     It is of course also conceivable to deactivate the parking brake mode only by activating the locking lever  114  by means of the locking actuator  112 . In this alternative, the electric motor  28  is not used to deactivate the parking brake mode. It may therefore not be necessary to shift the locking lever  114  under load. 
     The actuator assembly  10  can be produced as follows. 
     First, the housing base part  18  is supplied. 
     Then, the already premounted drive assembly  14  is inserted into the housing base part  18 . 
     As already explained, the drive assembly  14  comprises the carrier assembly  22  on which are mounted the electric motor  28 , the spindle drive  72  and the gear unit  67  coupling the electric motor  28  and the spindle drive  72  drivingly  22  and which comprises the gear train  58  and the planetary gear stage  48 . 
     The control assembly  12  is then inserted into the housing base part  18 . 
     As already explained, the control assembly  12  comprises the bulkhead wall  134  and the printed circuit board  138 . 
     The electric motor  28  is additionally connected electrically to the printed circuit board via the second electrical line  162  by the insertion of the control assembly  12  into the housing base part  18 . 
     The plug connector half  152  is moreover connected electrically to the printed circuit board  138  via the first electrical line  154 . 
     The locking actuator  112  is also connected to the printed circuit board  138  via the third electrical line  170  when the control assembly  12  is inserted. 
     The electrical connections are here in each case created by the electrical lines  154 ,  162 ,  170  being plugged into the respective associated contact openings  156 ,  164 ,  172  to form a press contact. 
     Lastly, the housing base part  18  is closed by the housing cover  20  being placed on top.