STEERING COLUMN FOR A MOTOR VEHICLE

Description

State of the art

[0001] The invention relates to a motor-adjustable steering column for a motor vehicle, comprising a casing unit in which a steering spindle can be mounted so as to rotate about a longitudinal axis, and which has an inner casing arranged in the outer casing and which can be telescoped relative to an outer casing in the direction of the longitudinal axis, and a motor-driven adjustment drive which is coupled to the inner casing and the outer casing, wherein a pretensioning device is provided which has a pressure piece supported on the outer casing and can be braced against the inner casing, wherein the pretensioning device has a guide device which cooperates with the pressure piece and for linearly guiding the inner casing relative to the outer casing in the direction of the longitudinal axis, wherein the guide device has form-locking elements which act in the circumferential direction, wherein the guide elements comprise a slide rail and a slide piece which is guided so as to slide therein.

[0002] A motor-adjustable steering column for a motor vehicle has a steering spindle mounted in a housing unit for rotation about its longitudinal axis. A steering wheel is attached to the rear end of the spindle, facing the driver. The housing unit is held by a support unit attached to the vehicle body, and the steering wheel position relative to the driver's position is adjusted by motorized adjustment of the housing unit relative to the support unit.

[0003] In a steering column of this type, a motorized longitudinal adjustment, in which the steering wheel can be adjusted backwards or forwards in the longitudinal direction, i.e., in the direction of the longitudinal axis relative to the driver's position, is made possible by a telescopically adjustable design of the steering column and the steering spindle. Furthermore, the steering column can be collapsed longitudinally in the event of a crash, effectively preventing the steering column from penetrating the interior of the passenger compartment and causing injuries to the occupants.

[0004] The telescopic casing unit comprises at least one outer casing, also referred to as an outer casing tube or outer casing tube, into which an inner casing, also referred to as an inner casing tube or inner casing tube, is inserted coaxially and can be adjusted longitudinally. Multiple telescopic arrangements can also be formed, in which at least one further intermediate casing is arranged coaxially between the outer and inner casings. In order to enable the quietest possible longitudinal adjustment with a uniform adjustment force and at the same time ensure the highest possible rigidity of the casing unit, it is known to define the radial play and the friction force between the casings. For this purpose, EP 3 299 253 A1 specifies the provision of a pretensioning device acting between the outer and inner casings. This pretensioning device has a pressure piece supported on the outer casing radially with respect to the longitudinal axis and clamped radially inward against the inner casing transversely to the longitudinal axis.The thrust piece rests against an outer surface of the inner casing with a friction or sliding surface, with a preload force that can be specified by adjusting the preload device. This allows the radial play to be optimized for sufficiently smooth adjustment while maintaining the highest possible rigidity.

[0005] It is also necessary to secure the inner casing against twisting relative to the outer casing. In the current state of the art, this requires additional measures in addition to the aforementioned pre-tensioning device, which increases the manufacturing and assembly effort.

[0006] A steering column of the type mentioned above is known, for example, from JP 4 433561 B2 or JP 2013 129322 A. The guide device has flattened portions as positive-locking elements. The disadvantage of this is the relatively low load capacity, rigidity, and natural frequency.

[0007] In view of the problems explained above, it is an object of the present invention to enable a functionally optimized longitudinally adjustable steering column with less effort. Description of the invention

[0008] This object is achieved according to the invention by the steering column having the features of claim 1. Advantageous further developments emerge from the subclaims.

[0009] In a motor-adjustable steering column for a motor vehicle, comprising a casing unit in which a steering spindle can be mounted so as to rotate about a longitudinal axis, and which has an inner casing arranged in the outer casing which is telescopic relative to an outer casing in the direction of the longitudinal axis, and a motor-driven adjustment drive which is coupled to the inner casing and the outer casing, wherein a pretensioning device is provided which has a pressure piece supported on the outer casing and which can be braced against the inner casing, wherein the pretensioning device has a guide device which cooperates with the pressure piece, for the linear guidance of the inner casing relative to the outer casing in the direction of the longitudinal axis, wherein the guide device has form-locking elements which act in the circumferential direction, wherein the guide elements comprise a slide rail and a slide piece which is guided so as to slide therein, the invention providesthat the guide elements comprise a guide groove formed in one piece by plastic deformation into the inner casing or the outer casing, designed as a bead-shaped depression, and a guide projection engaging therein.

[0010] The guide device has form-locking elements that act in the circumferential direction. For this purpose, the pretensioning device can have corresponding form-locking elements that can preferably be brought into form-locking engagement with one another in the radial direction to form a form-locking engagement that acts in the circumferential direction. The form-locking elements are arranged correspondingly on the inner and outer casings and enable protection against rotation. It is advantageous that such form-locking elements can be provided with little effort and enable simple assembly. Thanks to the inventive integration into the pretensioning device, a separate anti-rotation device is no longer required, and it is possible to exert the pretensioning force on the form-locking elements in order to hold them in form-locking engagement with a defined play or defined force.

[0011] The guide elements comprise a guide groove and a guide projection engaging therein. The guide groove has a radially open groove cross-section and extends longitudinally, for example on the outside of the inner casing or on the inside of the pressure piece facing the inner casing. The guide groove can extend over a longer section in the longitudinal direction, for example in a guide rail, or with a relatively short dimension in the longitudinal direction, for example on a sliding piece. The guide projection preferably has a cross-section that is matched to the groove cross-section in such a way that a positive connection effective in the circumferential direction is formed. A guide projection can comprise a longitudinally elongated web or a short, cam-like extension. A guide groove can be arranged on the inner casing and a corresponding guide projection on the pressure piece, or vice versa.Combinations of guide grooves and / or guide projections on the inner casing and the pressure piece are also possible. With the arrangement according to the invention, the guide projection can be pressed radially into the open groove cross-section by the preload force exerted by the preload device, thereby clamping it in the guide groove.

[0012] According to the invention, a guide element is formed integrally into the inner shell or the outer shell by plastic forming. For example, a guide groove can be formed integrally into the outer circumference of the inner shell parallel to the longitudinal axis, for example by non-cutting plastic forming processes such as pressing or rolling. A guide groove can be efficiently introduced into a metallic inner shell, which can preferably be made from a sheet steel profile, by cold forming. The guide groove is accordingly designed as a bead-shaped depression. It is particularly advantageous that the guide groove, in particular the bead-shaped depression, is continuous and that the inner shell or the outer shell has no perforations, openings, holes or the like in the region of the depression.In other words, the wall of the inner or outer casing is continuous in the circumferential direction in the area of ​​the bead-shaped recess. This increases the rigidity and stability of the assembly. A guide projection or web can also be formed as a single piece. This single-piece design reduces the number of parts, optimizes rigidity, and simplifies production and assembly. A single-piece design of a guide element with the pressure piece is also possible.

[0013] In the invention, a linear guide device is integrated with the preloading device. This can be achieved by providing the pressure piece, which in the prior art is purely a clamping element, with an additional guide function. This guide function allows the relative movement of the inner and outer shells to be defined in a positive guide manner, allowing linear, telescopic adjustment in the longitudinal direction, while limiting or largely eliminating any undesirable relative rotation between the inner and outer shells to a maximum acceptable angular play.

[0014] An advantage of the invention is that the preloading device can be configured with the inventive guide function with minimal effort, requiring only an adaptation of the pressure piece to a cooperating linear guide, which can also be provided with minimal manufacturing effort. The linear guide forms a type of forced guide, which essentially limits the relative movement of the pressure piece relative to the inner casing to the longitudinal direction.

[0015] A further advantage is that the effort required to assemble and adjust the steering column is no higher than with the pretensioning device known in the prior art, but is lower than if an additional guide device were provided.

[0016] The simplified integration of preload and guide functions according to the invention also allows weight and costs to be saved.

[0017] The combination of the preloading and guiding functions according to the invention also makes it possible to achieve a higher rigidity of the casing unit, in particular with regard to high torsional rigidity.

[0018] The motorized adjustment drive is connected to the inner and outer casings. To adjust the steering column, a motorized adjustment drive is provided which is coupled to the inner and outer casings in order to adjust them relative to one another in the direction of the longitudinal axis, i.e. to extend or retract the steering column telescopically. The adjustment drive can comprise a spindle drive with a spindle nut arranged on a threaded spindle and a drive motor by which the threaded spindle and spindle nut can be driven in rotation relative to one another. The spindle nut is attached to the inner or outer casing so that it cannot be moved in the direction of the longitudinal axis, and the threaded spindle is attached to the other casing, i.e. the outer or inner casing, which can be telescoped relative to it.The spindle nut or the threaded spindle is driven in rotation by an electric servo motor via a suitable gear, for example a worm or belt gear, whereby the threaded spindle or spindle nut, which is fixed relative to it with regard to rotation, is moved translationally in the direction of the spindle's longitudinal axis, and depending on the relative direction of rotation, the inner casing moves in or out in the longitudinal direction relative to the outer casing.

[0019] The embodiment according to the invention is particularly well suited for a motor-adjustable steering column, since the adjustment force to be overcome by the adjustment drive during adjustment can be precisely and permanently specified, and at the same time a particularly compact and structurally simple design is enabled.

[0020] It can advantageously be provided that the guide device has a first guide element on the inner casing, and a corresponding second guide element on the pressure piece, which is guided on the first guide element so as to be movable in the direction of the longitudinal axis. One of the guide elements can extend in the longitudinal direction, for example as an elongated form-fitting element on the inner casing. The other guide element is arranged on the pressure piece so that it is in guiding engagement with said first guide element. The guide elements preferably comprise mutually corresponding form-fitting elements on the pressure piece and on the inner casing, which enable a linearly guided relative movement in the longitudinal direction and block a relative rotation through the form-fitting engagement in the circumferential direction.Through the inventive integration into the preloading device, the guide elements can be subjected to the preload force and thus clamped together in a form-locking engagement. This gives the form-locking elements an advantageous dual function, namely preloading and guiding.

[0021] An advantageous embodiment is that the guide elements comprise a slide rail and a sliding piece slidably guided therein. A slide rail is elongated in the direction of the longitudinal axis, for example, as a guide element on the inner casing. The slide rail has a cross-section transverse to the longitudinal axis that corresponds in a form-fitting manner to the cross-section of the sliding piece, which can be designed as a guide element on the pressure piece. The slide rail and the sliding piece form form-fitting elements that can slide relative to one another in the longitudinal direction, as described above. These can be provided by molding processes with low manufacturing effort, are easy to assemble, and enable long-lasting, reliable, and low-maintenance operation.

[0022] An advantageous further development is that the guide elements have corresponding side flanks that converge in a wedge shape transverse to the longitudinal axis. The pretensioning device pretensions the guide elements against one another in the direction of the converging wedge surfaces, i.e. in the wedge direction. This makes it possible to create a wedge guide that enables secure and low-play or play-free adjustment of the guide device via the wedge surfaces even with a relatively low pretensioning force. Preferably, the side flanks can be formed in a guide groove with an essentially V-shaped or trapezoidal cross-section. These limit the angular play of a guide projection that engages therein in a form-fitting manner in the circumferential direction. The guide projection can also have a V-shaped or trapezoidal cross-section adapted to the groove cross-section.Alternatively, the guide projection can have an arcuate, rounded cross-section that rests in line contact with the wedge-shaped side flanks. In this way, optimized sliding guidance can be achieved through the design of the cross-sections. A further advantage of the wedge-shaped side flanks is that the pressure piece can be independently aligned and positioned in the guide device when it is preloaded and pressed against the corresponding guide element with the preload force in the direction of the converging wedge surfaces. In an advantageous further development, the groove cross-section can be provided with a Gothic profile. This can reduce the effective surface pressure, and thus wear, particularly with a rounded cross-section of the guide projection.

[0023] The optimized frictional connection of the wedge surfaces advantageously allows a high torsional rigidity of the shell unit to be achieved.

[0024] Wedge-shaped side flanks can also be efficiently produced in one piece by means of plastic forming, for example by cold forming a guide groove into an inner shell, preferably made of steel.

[0025] The shape and relative dimensions of the guide elements—for example, a guide groove and a guide projection engaging therein—can define the angular play by which the inner casing can be rotated relative to the outer casing. The angular play is preferably less than 10°, particularly preferably less than 2°, or it can be set to zero, corresponding to 0° angular play.

[0026] It can be provided that the guide device is designed to be at least partially friction-reducing. In a sliding guide of the guide device, at least the sliding surfaces that slide on one another, for example of the sliding piece and / or slide rail, can preferably have a good sliding, low-friction material pairing. This ensures relatively smooth adjustment even with a higher preload force, which enables greater rigidity. For example, at least one sliding surface can be formed at least partially from a plastic such as polytetrafluoroethylene (PTFE) or have a coating. The friction-reducing design can also be achieved by means of rolling elements that are arranged between the at least one guide element and the pressure piece. The rolling elements are preferably held on the pressure piece and roll on the at least one guide element.

[0027] In an advantageous further development, it can be provided that the pressure piece is formed from a plastic or comprises such a plastic.

[0028] In one embodiment, the pressure piece can be made of or comprise a metallic material such as steel, an aluminum alloy, a brass alloy, or a zamak alloy. In a particularly preferred embodiment, the surface of the pressure piece in contact with the at least one guide element can be overmolded with a plastic or provided with a sliding film. This can further improve the tribological properties.

[0029] The preload device may be adjustable. To adjust the force or play between the guide elements, an adjustable preload element can be provided, for example, with an adjusting screw or the like. This allows the pressure piece to be radially adjusted relative to the outer casing in the direction of the preload force in order to adjust the play between the guide elements and / or the preload force exerted on the guide elements via the pressure piece. The adjustability enables the adjustment and matching of the preload force and thus the adjustment force of the steering column.

[0030] An advantageous embodiment can provide for the preload device to be fixed in a predetermined setting position. This allows for an optimal, permanent, and subsequently unchangeable factory setting of the adjustment force during production, in the sense of a one-time calibration within a predetermined tolerance. For example, an adjustment element such as an adjustment screw can be permanently fixed by partial plastic deformation and / or a material bond at a predetermined, set play or preload force.

[0031] It is possible for the preloading device to comprise a spring element. The spring element can be preloaded against the thrust piece, so that its elasticity permanently maintains the preload force. For this purpose, the spring element can be arranged between the thrust piece and the outer casing to elastically load the thrust piece radially from the outside against the inner casing. This allows tolerances to be compensated, even those caused by changing operating conditions such as temperature fluctuations or the like. A spring element can preferably be combined with an adjustable preloading device.

[0032] It may be advantageous for the inner casing to be radially supported in the outer casing at the preloading device by the thrust piece and at two additional circumferential regions spaced apart from each other in the circumferential direction. For this purpose, two radially inwardly projecting sliding surfaces can be formed within the outer casing on the inner circumference, spaced apart from the thrust piece in the circumferential direction. These sliding surfaces are spaced apart from each other in the circumferential direction and are opposite the thrust piece with respect to the longitudinal axis. This creates a defined, stable three-point bearing in cross-section, which enables optimized, play-free mounting of the inner casing.

[0033] The casing unit, together with the steering spindle mounted therein, forms an actuating unit. This actuating unit can be mounted in a support unit that can be connected to a vehicle body. The actuating unit can be mounted on the support unit so that it can be vertically pivoted about a pivot axis that is horizontal and transverse to the longitudinal axis. By pivoting about such a pivot axis, a height adjustment can be achieved, allowing the steering wheel, which is mounted at the rear end of the steering spindle, to be adjusted relative to the driver's position.

[0034] The height adjustment can be done manually. Especially for automated stowing of the steering column during autonomous driving, it is advantageous to have an electric height adjustment drive connected to the support unit and the actuating unit, which allows the actuating unit to be moved relative to the support unit about the pivot axis. The height adjustment drive is also known per se and can be implemented, for example, as an electric motor-driven spindle drive, as described above for the longitudinal adjustment. Description of the drawings

[0035] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Figure 1 shows a steering column according to the invention in a schematic perspective view obliquely from above, Figure 2 shows the steering column according to Figure 1 in a view obliquely from below, Figure 3 a longitudinal section through the steering column according to Figures 1 to 2, Figure 4 a cross section through the steering column according to Figures 1 to 3 , Figure 5 a partial view of a cross section as in Figure 4 a second embodiment, Figure 6 a partial view of a cross section as in Figure 4 a third embodiment. Embodiments of the invention

[0036] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0037] A steering column 1 according to the invention is shown schematically in a perspective view from the rear (relative to the direction of travel of a motor vehicle not shown) in Figure 1 from above and in Figure 2 shown from below.

[0038] The steering column 1 can be attached to the body of a motor vehicle (not shown) by means of a support unit 2, also referred to as a bracket. The support unit 2 comprises fastening means 21 for connection to the body, for example, fastening openings through which fastening elements (not shown), such as screws, can be passed.

[0039] In a casing unit 3, a steering spindle 30 is rotatably mounted in an inner casing 31, also referred to as the inner casing tube, upper or inner casing tube, about its longitudinal axis L, which extends forward in the longitudinal direction. A fastening section 32 for attaching a steering wheel (not shown) is formed at the rear of the steering spindle 30.

[0040] The inner casing 31 is held in an outer casing 33, also referred to as outer casing tube, outer or lower casing tube, in the longitudinal direction, ie in the direction of the longitudinal axis L, in a telescopically displaceable manner, as indicated by the double arrow.

[0041] An energy absorption device comprising at least one deformation element that is plastically deformed in the event of a vehicle crash can be effectively provided between the inner shell 31 and the outer shell 33. Such devices are well known to those skilled in the art.

[0042] For height adjustment, the casing unit 3 is pivotable about a horizontal height adjustment axis 22 located in the lower or front area with respect to the direction of travel, so that a steering wheel attached to the rear or top of the fastening section 32 can be adjusted upwards or downwards in the height direction H, as shown in Figure 1 indicated by the double arrow.

[0043] A height adjustment lever 4 is mounted on the support unit 2 for rotation about a lever axis 23 located horizontally and transversely to the longitudinal axis L. A motorized adjustment drive 5, designed as a rotary spindle drive, engages an input-side lever arm 41 with a spindle nut 51 connected to the free end of the lever arm 41 by a connecting bolt 54. A threaded spindle 52, which is rotatably driven by an electric motor drive unit 53, engages the spindle nut 51. The drive unit 53 is supported on the casing unit 33 in the direction of the longitudinal axis L. A motor-driven rotation of the threaded spindle 52 moves the spindle nut 51 translationally relative to the casing unit 33, as indicated by the double arrow, whereby the height adjustment lever 4 is pivoted about the height adjustment axis 23.

[0044] For longitudinal adjustment, a motorized adjustment drive 6 is provided, which in the example shown is designed as a rotary spindle drive, with a spindle nut 61 into which a threaded spindle 62 is screwed, which can be driven in rotation relative to the spindle nut 61 by a motorized drive unit 63. Because the threaded spindle 62 is supported in the direction of the longitudinal axis L, i.e. in the longitudinal direction, on the outer casing 33, and the spindle nut 61 on the inner casing 31, the latter can be adjusted telescopically in the longitudinal direction relative to the casing unit 33 by appropriately controlling the drive unit 63.

[0045] In the view of Figure 2 a pretensioning device 7 according to the invention can be seen, which is arranged in the area of ​​the underside of the outer casing 33. The pretensioning device 7 is shown in detail in longitudinal section along the longitudinal axis L in Figure 3 shown, as well as in the cross section AA from Figure 3 , which in Figure 4is shown enlarged.

[0046] As in Figure 3 As can be seen, two pretensioning devices 7 are arranged at a distance from one another in the longitudinal direction on the casing unit 3, which are essentially of the same construction, so that the features described below apply to each pretensioning device 7.

[0047] The pretensioning device 7 has an adjusting screw 71 as an adjustable pretensioning element, which is screwed into an internal thread 34 in a radial bore 35 directed toward the longitudinal axis L. A pressure piece 72 is arranged on the adjusting screw 71 on the radially inwardly directed end face. The pressure piece 72 is movable in the bore 35 in the radial direction, toward the outside of the inner casing 31, and is supported in a form-fitting manner on the outer casing 33 in the circumferential and longitudinal directions.

[0048] A spring element 73, namely a compression spring elastically deformable in the radial direction, such as a conical or corrugated spring washer, is arranged between the adjusting screw 71 and the pressure piece 72. It is also conceivable and possible to use other spring designs, such as disc springs or spiral springs.

[0049] The pressure piece 72 has, on its inner side facing inwardly away from the adjusting screw 71, a guide projection with two radially inwardly converging side flanks 721 and 722. The side flanks 721 and 722 each run parallel to the longitudinal axis L and delimit a prism-shaped cross-section converging at a wedge angle, which is oriented transversely to the longitudinal axis L; in other words, the tip of the wedge points radially inward.

[0050] An elongated guide groove 36 extending parallel to the longitudinal axis L is formed into the inner casing 31, preferably by cold forming, and is thus pressed into the inner casing 31, which is preferably made of steel, and is thus bead-shaped. The pressure piece 72, with its wedge-shaped cross section, radially penetrates the guide groove 36.

[0051] The guide groove 36 has a V-shaped groove cross-section to which the pressure piece 72 is adapted, so that its side flanks 721 and 722 rest on the V-shaped converging inner sides of the guide groove 36, as in Figure 4 is recognizable.

[0052] By screwing in, the adjusting screw 71 can be moved radially in the direction of the longitudinal axis L, whereby the pressure piece 72 is pressed radially from the outside into the guide groove 36 via the spring element 73 with a preload force F.

[0053] The pressure piece 72 engages positively in the guide groove 36, with the wedge-shaped side flanks 721 and 722 being guided in a sliding manner in the longitudinal direction on the inner sides of the guide groove 36. The guide groove 36 thus functions as an elongated slide rail in which the pressure piece 72 can slide as a guided slide piece.

[0054] Because the side flanks 721 and 722 rest in the guide groove 36, spring-loaded by the spring element 73, without play, a circumferentially effective positive engagement is formed between the thrust piece 72 and the inner casing 31, the angular play of which can be set to zero by the elastic preload. The thrust piece 72, supported circumferentially on the outer casing 33, thus provides a virtually play-free anti-rotation lock of the inner casing 31 in the outer casing 33.

[0055] By screwing or unscrewing the adjusting screw 71, the radial preload force F with which the pressure piece 72 is preloaded in the guide groove 36 can be adjusted. This allows the frictional force to be adjusted and specified with small tolerances, which must be overcome as an adjustment force by the adjustment drive 6 for the telescopic length adjustment of the inner casing 31 relative to the outer casing 33. The positive locking according to the invention acting in the circumferential direction creates a linear guide device in the longitudinal direction, which prevents rotation between the inner casing 31 and the outer casing 33. In other words, the invention creates an integrated preload-guide device that combines the two functions of preload and guidance.

[0056] The surfaces of the side flanks 721 and 722, which are in sliding contact with one another, and / or the inner sides of the guide groove 36, can preferably be designed to reduce friction, for example by being at least partially coated, at least on one side, with a plastic with good sliding properties, such as polytetrafluoroethylene (PTFE) or the like. As a result, the preload force F can be set relatively high without impairing adjustment, and the rigidity of the casing unit 3 can be advantageously increased. It is further advantageous that the inventive combination of preload and guidance also increases, in particular, the torsional rigidity of the casing unit 33.

[0057] Within the outer casing 33, radially inwardly projecting sliding surfaces 37 and 38 can be formed on the inner circumference, spaced from the pressure piece 72 in the circumferential direction, which are spaced relative to one another in the circumferential direction and are opposite the pressure piece 72 with respect to the longitudinal axis L. The inner casing 31 is clamped in a defined three-point bearing between the sliding surfaces 37 and 38 and the pressure piece 72.

[0058] As in Figure 3 As can be seen, two prestressing devices 7 are preferably arranged at a distance in the longitudinal direction. This allows an advantageously high bending stiffness and natural frequency of the shell unit to be achieved.

[0059] In Figure 5 is in cross-sectional view as in Figure 4A second embodiment is shown enlarged. This differs only in the design of the pressure piece 72. Instead of the two angled, flat side flanks 721, 722, this has a bearing surface 723 with a convex, rounded cross-section, which acts as a guide projection and extends into the cross-section of the guide groove 36. The rounded bearing surface 723 rests in two line contacts 724 in the guide groove 36, which also creates a positive connection in the circumferential direction.

[0060] Figure 6 shows in the same view as Figure 5 A third embodiment, wherein the pressure piece 72 and the guide groove are modified. The pressure piece 72 has a guide groove 725, into which a radially outwardly projecting guide web 361 engages in a form-fitting manner, which is formed in the cross-section of the guide groove 36. This creates the form-fitting connection effective in the circumferential direction. List of reference symbols

[0061] 1Steering column 2Support unit 21Fasteners 22Height adjustment axis 23Lever axis 3Shell unit 30Steering spindle 31Inner shell 32Fastening section 33Outer shell 34Internal thread 35Bore 36Guide groove 361Guide web 37, 38Sliding surface 5, 6Adjustment drive 51, 61Spindle nut 52, 62Threaded spindle 53, 63Drive unit 7Pretensioning device 71Adjusting screw 72Thrust piece 721Side flank 722Side flank 723Bearing surface 724Line contacts 725Guide groove 73Spring element LLongitudinal axis FPreload force

Claims

1. Motor-adjustable steering column (1) for a motor vehicle, comprising a casing unit (3) in which a steering spindle (30) can be mounted so as to rotate about a longitudinal axis (L), and which has an inner casing (31) which can be telescoped relative to an outer casing (33) in the direction of the longitudinal axis (L) and is arranged in the outer casing (33), and a motor-adjustment drive (6) which is coupled to the inner casing (31) and the outer casing (33) wherein a pretensioning device (7) is provided, which has a pressure piece (72) supported on the outer casing (33) and braceable against the inner casing (31), wherein the pretensioning device (7) has a guide device cooperating with the pressure piece (72) for linear guidance of the inner casing (31) relative to the outer casing (33) in the direction of the longitudinal axis (L), wherein the guide device has positive-locking elements (36, 721, 722, 723), the guide device having a first guide element (36) on the inner casing (31), and a second guide element (72, 721, 722, 723) corresponding thereto on the pressure piece (72), which is guided on the first guide element (36) so as to be movable in the direction of the longitudinal axis (L) characterized in in that the guide elements comprise a guide groove (36) formed in one piece by plastic deformation into the inner casing (31) or the outer casing (33) and designed as a bead-shaped depression, and a guide projection (72, 721, 722, 723) engaging therein.

2. Steering column according to claim 1, characterized in that the guide elements comprise a slide rail (36) and a slide piece (72, 721, 722, 723) slidingly guided therein.

3. Steering column according to claim 1 or 2, characterized in that the guide elements have wedge-shaped converging side flanks (721, 722) transverse to the longitudinal axis (L).

4. Steering column according to one of the preceding claims, characterized in that the guide device is at least partially designed to reduce friction.

5. Steering column according to one of the preceding claims, characterized in that the pretensioning device (7) is adjustable.

6. Steering column according to claim 5, characterized in that the pretensioning device (7) can be fixed in a predetermined setting position.

7. Steering column according to one of the preceding claims, characterized in that the pretensioning device (7) has a spring element (73).