Abstract:
A suspension actuator ( 1 ) for positioning a movably mounted component of a motor vehicle suspension, including a first actuator component ( 4 ), which is to be connected to the movably mounted component, and a second actuator component ( 3 ), which is to be connected to a fixed suspension component, wherein both actuator components can be axially adjusted relative to one another via a ball-type linear drive ( 5 ), which includes a threaded spindle ( 6 ) and a nut ( 7 ) running thereon. Either the nut can be driven via a drive motor ( 10 ) for the axial adjustment of the threaded spindle or the spindle can be driven via a drive motor for axial adjustment of the nut. A brake unit ( 14, 28 ), which can be actuated by an external force on the suspension side and acts on the nut ( 7 ) or the spindle and rotates them, and which builds up a friction torque opposing a nut rotation or the spindle rotation, which acts between the nut ( 7 ) or the spindle ( 6 ) and a fixed actuator element ( 22, 35 ) or between a drive shaft of the drive motor ( 10 ) and a fixed actuator element ( 45 ) associated therewith, is provided.

Description:
BACKGROUND 
       [0001]    The invention relates to a suspension actuator for positioning a movably mounted component of a vehicle suspension, with the actuator comprising a first actuator component for connecting to the movably mounted component and a second actuator component for connecting to a fixed suspension component, wherein both actuator components can be adjusted relative to each other in the axial direction by a ball-type screw drive comprising a threaded spindle and a nut running on this spindle, wherein either the nut can be driven by a drive motor for the axial adjustment of the threaded spindle or the spindle can be driven by the drive motor for the axial adjustment of the nut. 
         [0002]    Such a suspension actuator is used in suspensions of vehicles, for example, on a wheel suspension of a vehicle wheel. By use of the suspension actuator that can be driven independently, a desired adjustment of the suspension-side, movably mounted component, such as, for example, of a wheel carrier or the like, is possible. A suspension actuator suitable for this purpose, as is known, for example, from DE 10 2005 023 250 A1, has available two actuator components, wherein a first actuator component is connected to the suspension component to be adjusted and a second actuator component is connected to a fixed suspension component, thus it is supported there on the vehicle body. Both actuator components could be adjusted relative to each other in the axial direction, with a ball-type screw drive being used for this purpose. This drive comprises a threaded spindle by which both actuator components are connected, as well as a nut running on this spindle, with the nut running on the spindle via balls located in-between. For the axial adjustment of the spindle and thus for moving the actuator components away from or toward each other for the desired suspension adjustment, a drive motor is used that rotates the fixed nut, which leads to the axial movement of the spindle relative to the fixed nut. A different construction provides a fixed spindle rotationally driven by the drive motor, while the nut that is connected to the suspension part for positioning is moved axially. Such suspension actuators—typically an independent suspension actuator that can be driven separately is allocated to each wheel—take over safety-relevant tasks, which is why, in principle, there is the requirement that the linked suspension components do not carry out undesired positioning movements, for example, when there is the loss of an actuator, but instead are held in the last set position. Likewise it must be guaranteed that external forces that are introduced in the reverse direction into the actuator via the suspension are absorbed reliably, without the actuator carrying out undesired positioning movements due to these external forces. 
         [0003]    For this purpose, in the suspension actuator according to DE 10 2005 023 250 A1, a locking mechanism in the form of a mechanical ramp catch is provided that has a switchable construction. This locking mechanism blocks the driven part, that is, the nut, when the driving force of the actuator is less than an external force acting on the nut, wherein this force is applied either by the drive motor or is 0 for an adjustment that has not yet been performed. For example, if the suspension actuator described there is used for active adjustment of the wheel camber of a wheel of a motor vehicle, for example, shocks introduced into the wheel from the outside are forwarded only up to the driven part, that is, the nut of the actuator. An introduction of these shock forces into the actuator up to the motor is ruled out, because the driven part, that is, the nut, is blocked by the locking mechanism. The shock forces are introduced into the fixed suspension itself by the locking mechanism. The locking mechanism itself is constructed in the known suspension actuator as a clamping-roller locking mechanism and comprises a clamping ring provided with clamping ramps and a hollow-cylindrical part with a cylindrical clamping track that forms, together with the clamping ramp part, the clamping gap in which the clamping rollers are arranged that can be switched into and out of clamping engagement with the clamping ramps. The clamping rollers themselves are constantly ready for clamping, for which purpose they are biased with springs. 
         [0004]    Such a clamping-roller locking mechanism could indeed realize the desired actuator locking that satisfies the requirements named above. However, such clamping locking with clamping ramps knows, in principle, only two positions, namely the locked position or the unlocked position. From this situation, problems can result when the spindle is to be adjusted in the loading direction, i.e., an external force is applied that acts in the positioning direction. This leads to so-called “locking jerking movements.” These are generated because the load constantly overtakes the drive, i.e., the clamping rollers are constantly brought into the clamping position by the external load. When the drive motor has somewhat “caught up” to the load again, the motor opens the clamping locking mechanism again, whereupon the load overtakes the drive again, resulting again in the locking of the locking mechanism, and so on. This, however, is disadvantageous or not permissible in many applications. 
       SUMMARY 
       [0005]    Thus, the objective forming the basis of the invention is to provide a suspension actuator that avoids the occurrence of locking jerking movements and allows a jerking-movement-free positioning also for an externally applied load. 
         [0006]    For meeting this objective, in the suspension actuator of the type noted above it is provided according to the invention that a brake unit is provided that can be activated by an external, suspension-side force acting on the nut or the spindle and rotating these parts, wherein this brake unit builds up a friction moment acting against a nut rotation or a spindle rotation and acting between the nut or the spindle and a fixed actuator element or between a drive shaft of the drive motor and a fixed actuator element allocated to this motor. 
         [0007]    By use of the brake unit provided according to the invention, it is possible to build up a friction moment that is dependent on the degree of loading of the brake unit, that is, on the magnitude of the external, suspension-side force, wherein this moment counteracts a nut rotation or the spindle rotation—according to which element is loaded with the external force and would adjust itself undesirably. Finally, this friction moment could be so large that the brake unit is completely blocked, consequently it acts as a locking unit. By use of this variable friction moment, it is possible to also realize a jerking-movement-free positioning movement for an adjustment in the direction of an external load, after which a braking effect is indeed achieved by the building friction moment, but despite all of this, finally a braked positioning movement is possible. True locking is used only when the drive motor itself is not activated, consequently no positioning movement is to be performed. The brake unit then builds up to such a high friction moment that a nut rotation or a spindle rotation is completely prevented. For the case that a positioning movement is to be performed and an external force is being applied, the brake unit generates a counteracting friction moment that is, however, somewhat “over-rotated” by the positioning drive motor that actively rotates the nut or the spindle according to the embodiment itself, so that it results merely in a braked nut rotation that is, however, not completely blocked. 
         [0008]    Thus, with such an integrated brake unit that is somewhat variable with respect to the “braking force,” the locking jerking movements that occur in actuators of the prior art using clamping-roller locking are advantageously avoided, so that such a suspension actuator according to the invention is suitable especially for safety-related positioning tasks as given in the field of suspensions, in particular, in the field of wheel adjustment with respect to wheel steering. 
         [0009]    Here it is conceivable to integrate the brake unit directly in the area of the nut or spindle, that is, to arrange it somewhat axially. Alternatively, however, the brake unit could also be provided in the area of the drive motor that is provided offset to this unit and that is connected to the nut or the spindle, e.g., by a belt or a gear mechanism, where it acts on the connection of the motor driven shaft for the belt or gear mechanism operation. 
         [0010]    The brake unit itself advantageously comprises a helical wrap-spring that wraps around the fixed, cylindrical actuator element for building up the friction moment and that is coupled with the drive motor for loosening the spring wrap and to the nut or the spindle for closing the spring wrap. Here it involves a coil-spring locking mechanism under the use of a helical wrap-spring or a coil band that interacts with the fixed, cylindrical actuator element, for example, in the form of a sleeve or a housing component. 
         [0011]    For activating the helical wrap-spring, an opening element and a closing element are provided, wherein the opening element can be rotated by the drive motor and attaches to one of the two angled spring ends of the helical wrap-spring according to the rotational direction of the drive motor or the opening element. In this way, the helical wrap-spring is opened, i.e., it is detached from its friction contact on the fixed, cylindrical actuator element, so that a low-friction-moment rotation of the nut or the spindle is possible. For closing, a closing element is provided that is locked in rotation with the nut or the spindle and that likewise attaches to one of the two angled spring ends by the action of an external force leading to a nut or spindle rotation; the helical wrap-spring, however, either contracts or expands according to the functional principle, so that it results in friction contact on the actuator element and thus to the generation of friction or brake moment. Both the opening element and also the helical wrap-spring, just like also the closing element, are arranged on the side of the nut, that is, rotate in the regular positioning operation, driven by the drive motor, with the nut or the spindle. The rotationally locked connection could be realized somewhat directly with an axial configuration; alternatively, an indirect, rotationally fixed connection between the nut/spindle and the motor-side brake unit by the belt or the gear mechanism is also possible. 
         [0012]    The opening element and closing element each have two advantageously circular-arc-shaped catches that are offset opposite each other by 180°, wherein the catches of both elements engage with each other with a slight peripheral distance, wherein the two spring elements are each positioned between two catches. The opening and the closing elements are thus rotated about the longitudinal axis of the spindle, so that the corresponding catches likewise rotate and are moved, according to the rotational direction, against one end or the other of the spring element, which results in that the helical wrap-spring is either opened or closed, but in each case it is deformed. The configuration with engaging catches is useful with respect to a compact form of the brake unit (that could also be addressed as a combination brake and locking unit). The spring ends themselves advantageously project inward in the radial direction, thus are angled inward in the radial direction, which allows the gear mechanism of a higher force via the catches than for an outwardly angled section. It remains to be said, however, that obviously a construction with outwardly angled spring elements and correspondingly formed opening and closing elements is also conceivable with respect to correspondingly positioned catches. 
         [0013]    The fixed actuator element itself is preferably wrapped around its outer face, i.e., such that the helical wrap-spring is pulled tight for locking, consequently is reduced in its inner diameter, so that the helical wrap-spring forms a planar and friction contact with its inner side on the outer side of the actuator element that is constructed as a sleeve or the like. For opening, the helical wrap-spring is expanded, that is, bent open. Here, it is naturally also conceivable to realize a kinematically inverted construction in which the fixed actuator element, for example, as a cylindrical housing component, interacts with its cylindrical inner wall with the helical wrap-spring that is then expanded for generating the braking moment, that is, for closing, so that its outer diameter increases and the spring outer side forms a contact on the element inner side. For opening, that is, for releasing the friction-fit connection, the spring is then contracted, that is, reduced in diameter again. 
         [0014]    The drive motor is preferably arranged laterally on a housing of the suspension actuator and coupled with the nut or the spindle by a traction mechanism, in particular, a belt, or a gear mechanism. Through the use of this belt or the gear mechanism, the drive motor, in principle, an electric motor, can actively drive the nut or the spindle for the desired positioning movement. Alternatively, however, it is also conceivable to arrange the drive motor axially if the configuration of the suspension actuator allows this with respect to the existing suspension-side space for installation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0015]    An embodiment of the invention is shown in the drawings and is described in more detail below. Shown are: 
           [0016]      FIG. 1  a block diagram of a suspension actuator according to the invention in cross-section, 
           [0017]      FIG. 2  a perspective view of the brake unit with helical wrap-spring, 
           [0018]      FIG. 3  a cross-sectional view through the brake unit from  FIG. 2 , 
           [0019]      FIG. 4  a longitudinal section view through the brake unit from  FIG. 2 , 
           [0020]      FIG. 5  a block diagram, partially in section, of an assembled example of a suspension actuator, 
           [0021]      FIG. 6  an exploded view of another embodiment of a brake unit, 
           [0022]      FIG. 7  a cross-sectional view through the assembled brake unit from  FIG. 6 , 
           [0023]      FIG. 8  a longitudinal section view through the brake unit, 
           [0024]      FIG. 9  a block diagram of a second embodiment of a suspension actuator according to the invention in cross-section, 
           [0025]      FIG. 10  the suspension actuator from  FIG. 9  in another operating position, 
           [0026]      FIG. 11  an exploded view of another embodiment of a brake unit, and 
           [0027]      FIG. 12  a section view through the assembled brake unit from  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  shows a suspension actuator  1  according to the invention, comprising a housing  2  with a first actuator component  3 , as well as a second actuator component  4  moving axially relative to the first actuator component  3 . The first actuator component  3  is to be connected, in the scope of the assembly, to a fixed suspension component, for example, a suspension carrier or the like, while the second actuator component  4  is to be connected to a moving suspension component, for example, a part of the wheel suspension for positioning the wheel camber or the like. For this purpose, in a known way, corresponding fastening elements are provided with respect to bearing receptacles. 
         [0029]    For the axial adjustment of the two actuator components  3 ,  4  relative to each other, a ball-type screw drive  5  is provided, comprising a threaded spindle  6  that is part of the second actuator component  4  or is connected to this component. A threaded nut  7  is guided over a plurality of balls  8  and runs on the threaded spindle  6  which is sealed outward by an expansion bellows  27  and extends into the interior of the housing  2 . The threaded nut  7  is rotationally mounted by a bearing  9  so that it can rotate, but is fixed in the housing  2 . For the axial adjustment of the threaded spindle  6  that is moved in this way into the housing  2  or out from this housing is a drive motor  10  not described in more detail here, for example, a simple, small electric motor that is coupled with the nut  7  by toothed belt  11  shown only partially here. For this purpose, on the electric motor  10  there is a belt pulley  12  over which the belt  11  runs and the nut  7  likewise has a belt pulley  13  over which the belt  11  runs. This belt pulley  13  is connected to a brake unit still to be described below with respect to the part itself. According to the direction in which the electric motor  10  rotates, the nut  7  rotates on the threaded spindle  6  that is here moved either into the housing  2  or out from the housing  2 , so that the axial position of the two actuator components  3 ,  4  changes relative to each other. 
         [0030]    In order to avoid locking jerking movements for an axial adjustment of the actuator component  4  in the direction of a load acting on this actuator component  4 , in the illustrated example, a brake unit  14  is provided that can be activated as a function of the suspension-side force acting externally and is built up by the friction moment that counteracts the nut rotation and acts between the nut  7  and a fixed actuator element. In this way, a friction-damped axial movement can be realized somewhat, wherein the friction moment is suppressed by the electric motor  10  for a desired adjustment in the direction of the acting external load. For an undesired positioning movement, that is, when the electric motor  10  is stationary, the friction moment is so large that it results in a complete locking and consequently the nut  7  is moved by the external force only by a small, possible rotational angle until the complete locking of the brake unit and any further movement is then blocked. 
         [0031]    The brake unit  14  is shown in detail in  FIGS. 2-4 . It involves a coil-spring brake comprising a helical wrap-spring  15  whose two ends  16 ,  17  are angled and project outward in the radial direction in the illustrated embodiment. The helical wrap-spring  15  is held between an opening element  18  and a closing element  19 ; the two elements each have two catches  20  on the opening element  18  and  21  on the closing element  19 , respectively, which have a circular-arc-shaped construction and engage one in the other, see  FIG. 3 . The two spring ends  16 ,  17  each lie between a catch  20  and a catch  21 . The opening element  18  and the closing element  19  can move separately relative to each other. The opening element  18  has the belt pulley  13  by which the nut  7  is rotated by the electric motor  10 . The closing element  19  is rotated by the externally applied load, if one is given. 
         [0032]    The brake unit  14  further comprises a stationary ring that forms the stationary actuator element  22  that is connected fixed to the bearing housing  2 . This ring is cylindrical and is wrapped around on the outside by the cylindrical helical wrap-spring  15 . 
         [0033]    During operation, should the second actuator component  4  be moved axially, then the motor  10  actively drives the nut via the belt  11 . For this purpose, initially the closing element  18  is rotated, which has the result that the catch  20  located between the two spring ends  16 ,  17  runs according to the rotational direction either against the spring end  16  or the spring end  17 . This has the result that the helical wrap-spring  15  is expanded, that is, its inner diameter is increased, so that it definitely does not contact the outer face of the actuator element  22 , consequently, no friction moment is also built up there. After rotation by a defined angle increment, the torque is transferred completely to the nut  7 , so that this is rotated and it results in an axial displacement of the threaded spindle  6 . The opposite catch  20  is likewise rotated, but it has no opening function, it is merely provided for reasons of weight symmetry. 
         [0034]    If an external load acts on the suspension actuator  1 —assuming the electric motor  10  is not in operation—then this load has the effect that the nut  7  is driven by the loaded threaded spindle  6 , leading to an axial displacement of the threaded spindle  6  relative to the fixed nut  7  in the loading direction. This is prevented, however, by the integrated brake unit  14  according to the invention. If an external load acts on the brake unit  14 , then this has the result that, for an unmoved opening element  18 , the closing element  19  connected to the nut  7  is moved. According to in which direction this rotation takes place, one of the catches  21  engages either on the spring end  16  or on the spring end  17 , which has the result that, when the rotational movement continues, the helical wrap-spring  15  is tightened, consequently the inner diameter is reduced and it forms a friction-fit connection with its inner side on the outer side of the stationary actuator element  22 . When a defined rotational angle is reached, the friction moment is so large that further nut movement is completely stopped. This rotational angle equals only a few degrees, so that a significant undesired positioning movement in the axial direction is immediately prevented. 
         [0035]    For an active axial adjustment, that is, when the electric motor  10  is actively driving the nut  7 , such an external load is applied, so this results in the electric motor  10  continuously opening the opening element  18 , that is, expands the helical wrap-spring  15 . The external force counteracts this in that the nut rotates by this force likewise actively in the same direction as driven by the electric motor  10 . This has the result that the catches  21  of the closing element  19  retract the helical wrap-spring  15  again, consequently build up a friction moment. Due to the active rotation by the electric motor  10 , however, this leads to no jerking movement, but instead only a certain friction moment is built up continuously by the closing element  19 , wherein, however, this friction moment is “over-rotated” by the active electric-motor rotation. This friction moment has merely a damping, but not blocking effect, so that a jerking movement is not applied. That is, it results in a braked or damped axial positioning movement, that is, a braked lowering or raising under a rectified load. 
         [0036]    The friction moment that can be achieved is adjustable, on one hand, by a corresponding adaptation of the diameter of the helical wrap-spring  15 , on the other hand by a suitable selection of materials. Finally it should be very low, because it is to be overcome by the motor  10 . 
         [0037]      FIG. 5  shows an assembled example of a suspension actuator  1  according to the invention that is connected by the first actuator component to a stationary suspension component  23 , while the second actuator component  4  is connected to a moving suspension component  24 , here a part of the wheel bearing  25 . For an axial movement of the second actuator component  4 , the wheel bearing  25  could be pivoted and thus the wheel camber of the wheel  26  could be adjusted. However, this is only one example for a possible application of the suspension actuator; other possible applications on the side of the suspension are also conceivable for carrying out positioning movements of a moving suspension component relative to a fixed suspension component. 
         [0038]      FIGS. 6-8  show another embodiment of a brake unit  28  that could be used in a suspension actuator as shown in  FIG. 1  or that could be integrated in this actuator. This unit comprises a housing  29  in which a helical wrap-spring  30  as well as a closing element  31  and an opening element  32  are held. The closing element  31  here also has two catches  33 , while the opening element  32  shows two catches  34 . Both catch pairs lie opposite each other; in the assembled position they also engage in each other, cf.  FIG. 7 . The spring ends  36  and  37  of the helical wrap-spring  30  are here bent inward and are also held between a catch  33  and a catch  34 . The housing  29  here forms the stationary actuator element  35  against whose inner face the helical wrap-spring contacts for generating the brake moment. In the assembled state, here the closing element  31  is also connected to the nut  7  (cf.  FIG. 1 ), while the opening element  32  is connected to the electric motor  10  (cf.  FIG. 1 ) by a belt or the like. For carrying out the positioning movement, the electric motor  10  also rotates the opening element  32  that runs with its catch  34  against one of the spring ends  36 ,  37  and contracts the helical wrap-spring  30  for further rotation, so that its outer diameter is reduced. Thus, the helical wrap-spring  30  is not in friction-fit connection with the cylindrical inner face of the housing  29 , so that the positioning movement can be carried out without friction. 
         [0039]    If an external load is applied, then this rotates the nut  7 , by which the closing element  31  connected to the nut  7  is rotated. One of its catches  33  engages on one of the spring ends  36 ,  37 , which has the result that the helical wrap-spring  30  is bent and it forms a friction contact with its outer side on the inner face of the housing  29 . This leads to the build-up of a braking moment that is so large when the electric motor  10  is turned off that the rotation of the nut  7  is completed blocked and there is no undesired positioning movement. 
         [0040]    When a load is applied, if the electric motor is operating for a positioning movement performed in the load direction, then it here results in a simultaneous build-up of a friction moment damping the positioning movement and dependent in its height on the height of the external force, but the positioning movement is always possible due to the motor drive “over-forcing” the braking effect. Also, this does not result in locking jerking movements. The construction of the brake unit shown here is advantageous to the extent that the spring ends directed inward allow the introduction of higher forces. 
         [0041]      FIGS. 9-12  show another embodiment of a suspension actuator along with the brake unit. The suspension actuator  1  is here constructed as an electromechanical level regulation. It has a first actuator component  3  and a second actuator component  4 , wherein the actuator component  3 , see  FIG. 10 , is constructed as a piston rod that can be extended out from the cylinder-like actuator component  4 . The actuator component  3  is thus the moving component that is connected to the suspension part to be regulated. 
         [0042]    Here, a ball-type screw drive  5  is also provided, comprising a nut  7  and a spindle  6 , wherein the fixed spindle  6  viewed in the axial direction is, in this embodiment, the component driven by the drive motor  10 , while due to the spindle rotation, the nut  5  is moved in the axial direction along the spindle  6 , in order to shift the actuator component  3 , here, the rod, in the axial direction, see  FIGS. 9 and 10 . 
         [0043]    Here, a brake unit  14  is also provided, wherein, however, this is not provided like in the construction according to  FIG. 1  somewhat axially with respect to the two actuator components  3 ,  4 , but instead offset laterally. It is located in the axial extension to the motor  10  and is coupled with the motor, which will be discussed below. By use of the gear mechanism  38 , the motion of the motor  10  is coupled with the spindle  6 , for which the gear mechanism  38  has a pinion  39  that meshes with a corresponding teeth section  40  on the spindle  6 . Accordingly, in this embodiment, the spindle  6  is the driven part of the ball-type screw drive  5 , so the locking is realized here against an externally acting load for preventing an undesired lowering or raising motion by the gear mechanism  38  and the spindle  6 , and not, as in the previously described embodiment, by the nut. 
         [0044]      FIGS. 11 and 12  show an enlarged diagram of the brake unit  14 . This comprises an adapter plate  41  by which the unit is fastened to the drive motor  10 . A helical wrap-spring  42  is also further provided here that also has here spring ends angled inward. It interacts, in turn, with a closer  43  and an opener  44  that, according to the operating situation, retract the helical wrap-spring  42  from its friction contact on the inner side of a sleeve  45 , in order to open it, or, in order to close it, bring it into the friction contact. An angular contact ball bearing  46 , as well as a housing  47 , is further provided on which the already described  39  is arranged on one side. 
         [0045]    During operation, if an active adjustment of the level regulation is to be performed, the motor drives the opener  42  by its driven shaft, wherein this opener is connected to the driven shaft by a coupling journal  48 . The opener  42  engages on the corresponding spring end  50  by its corresponding catch  49 , takes along the helical wrap-spring  42  that takes along on its side, in turn, the closer  43  that is coupled with the gear mechanism  38  with respect to the pinion  39  as part of this gear mechanism, wherein this pinion then meshes with the teeth  40  of the spindle  6 , so that this is then rotated in the desired direction defined by the motor rotational direction and consequently the nut  7  is moved in the desired axial adjustment direction. 
         [0046]    If an external force is applied by the actuator component, then the spindle rotation is to be locked, which is realized by the gear mechanism  38  or the pinion  39  coupled with the spindle  6  in connection with the brake unit  14  or the helical wrap-spring  42 . If a back-rotating force is applied to the spindle  6  due to an external force applied to the nut  7 , then this has the result that a rotational movement is given to the closer  43  immediately and directly by the teeth  40  and the pinion  39 . This closer now engages with its corresponding catch  51  on the corresponding spring end  50  of the helical wrap-spring and closes this, that is, brings it into a friction-fit, fixed contact with the sleeve  45  that forms the actuator element that is fixed in position and against which it is braked. Through this, a direct locking of the back-rotational movement is realized, according to which any rotational movement of the spindle  6  is blocked by the brake unit  14 . 
         [0047]    The invention is not limited to the shown constructions. The suspension actuators could instead take on any positioning tasks, that is, they could be used, e.g., for track adjustment, for camber adjustment, or for level regulation. 
       LIST OF REFERENCE SYMBOLS  
       [0048]      1  Suspension actuator 
         [0049]      2  Housing 
         [0050]      3  Actuator component 
         [0051]      4  Actuator component 
         [0052]      5  Ball-type screw drive 
         [0053]      6  Threaded spindle 
         [0054]      7  Nut 
         [0055]      8  Ball 
         [0056]      9  Bearing 
         [0057]      10  Drive motor 
         [0058]      11  Toothed belt 
         [0059]      12  Belt pulley 
         [0060]      13  Belt pulley 
         [0061]      14  Brake unit 
         [0062]      15  Helical wrap-spring 
         [0063]      16  Spring end 
         [0064]      17  Spring end 
         [0065]      18  Opening element 
         [0066]      19  Closing element 
         [0067]      20  Catch 
         [0068]      21  Catch 
         [0069]      22  Actuator element 
         [0070]      23  Suspension component 
         [0071]      24  Suspension component 
         [0072]      25  Wheel bearing 
         [0073]      26  Wheel 
         [0074]      27  Expansion bellows 
         [0075]      28  Brake unit 
         [0076]      29  Housing 
         [0077]      30  Helical wrap-spring 
         [0078]      31  Closing element 
         [0079]      32  Opening element 
         [0080]      33  Catch 
         [0081]      34  Catch 
         [0082]      35  Actuator element 
         [0083]      36  Spring end 
         [0084]      37  Spring end 
         [0085]      38  Gear mechanism 
         [0086]      39  Pinion 
         [0087]      40  Teeth section 
         [0088]      41  Adapter plate 
         [0089]      42  Helical wrap-spring 
         [0090]      43  Closer 
         [0091]      44  Opener 
         [0092]      45  Sleeve 
         [0093]      46  Angular contact ball bearing 
         [0094]      47  Housing 
         [0095]      48  Coupling journal 
         [0096]      49  Catch 
         [0097]      50  Spring end 
         [0098]      51  Catch