STEERING COLUMN FOR A MOTOR VEHICLE

Abstract

An adjustment drive for a motor-adjustable steering column for a motor vehicle, includes a spindle drive having a threaded spindle which engages in a spindle nut which, so as to be able to be driven in a rotating manner about the spindle axis relative to the threaded spindle, is coupled to the rotor shaft of a drive motor which has a rotor and a stator. In order to enable a compact design with minor complexity, the rotor shaft of the drive motor is configured as a hollow shaft which is disposed so as to be coaxial with the spindle axis and in which the threaded spindle is coaxially disposed.

Claims

1.-13. (canceled)

14. An adjustment drive for a motor-adjustable steering column for a motor vehicle, comprising: a spindle drive, comprising: a drive motor having a rotor having a rotor shaft and a stator; a spindle nut coupled to the rotor shaft such that rotation of the rotor shaft drives the spindle nut in a rotating manner; and a threaded spindle having a spindle axis, the threaded spindle engaged with the spindle nut, wherein the rotor shaft of the drive motor is a hollow shaft disposed so as to be coaxial with the spindle axis and in which the threaded spindle is coaxially disposed.

15. The adjustment drive of claim 14 wherein the spindle nut is received in the hollow shaft.

16. The adjustment drive of claim 14 wherein the spindle nut has one or more of a force-fitting, a form-fitting or a substance-to-substance connection to the hollow shaft.

17. The adjustment drive of claim 16 wherein the connection is configured at least on a sub-portion of the external circumference of the spindle nut.

18. The adjustment drive of claim 16 wherein the connection is configured so as to be releasable by breaking when exceeding a predefined limit force which, in the direction of the spindle axis, acts on the spindle nut relative to the hollow shaft.

19. The adjustment drive of claim 14 wherein an energy absorbing element is disposed between the spindle nut and the hollow shaft.

20. The adjustment drive of claim 19 wherein the energy absorbing element has one or both of a friction installation or a deformation installation interacting with the spindle nut and the hollow shaft.

21. The adjustment drive of claim 20 wherein the deformation installation has at least one deformation element which is disposed in a passage opening of the hollow shaft and by which the spindle nut in an axial movement relative to the hollow shaft is plastically deformable.

22. The adjustment drive of claim 14 wherein the spindle nut is made of a material that is softer than that of the hollow shaft.

23. The adjustment drive of claim 14 wherein the drive motor has a motor housing in which the hollow shaft is mounted.

24. The adjustment drive of claim 23 wherein the hollow shaft has at least two axially spaced-apart bearings.

25. The adjustment drive of claim 14 wherein the drive motor is a servomotor.

26. A motor-adjustable steering column for a motor vehicle comprising the adjustment drive of claim 14, the spindle drive of said adjustment drive being disposed between a support unit that is configured to connect to the bodywork and a casing unit that rotatably receives a steering spindle, and/or between casing tubes of a casing unit that are mutually adjustable in a telescopic axial manner and mount the steering spindle.

Description

DESCRIPTION OF THE DRAWINGS

[0029] Advantageous embodiments of the invention will be explained in more detail hereunder by means of the drawings in which:

[0030] FIG. 1 shows a schematic perspective view of a steering column according to the invention;

[0031] FIG. 2 shows a further perspective view of the steering column according to the invention, according to FIG. 1, from another point of view;

[0032] FIG. 3 shows a longitudinal section along the spindle axis of the adjustment drive of the steering column according to FIG. 1;

[0033] FIG. 4 shows an enlarged sectional view through the drive unit of an adjustment drive from FIG. 3 in the normal operating position;

[0034] FIG. 5 shows the adjustment drive from FIG. 3 after the event of a crash;

[0035] FIG. 6 shows a second embodiment of an adjustment drive in a view as in FIG. 4;

[0036] FIG. 7 shows a longitudinal section along the spindle axis of the adjustment drive in a third embodiment of a steering column;

[0037] FIG. 8 shows a cross-section A-A through the steering column according to FIG. 7;

[0038] FIG. 9 shows a schematic, partially sectional, perspective detailed view of the adjustment drive;

[0039] FIG. 10 shows a drive motor in a second embodiment, in a cross-sectional view as in FIG. 8; and

[0040] FIG. 11 shows an exploded perspective view of the drive motor according to FIG. 10.

EMBODIMENTS OF THE INVENTION

[0041] Identical parts are at all times provided with the same reference signs in the different figures, and are therefore typically also referred to or mentioned only once, respectively.

[0042] FIG. 1 shows a steering column 1 according to the invention in a schematic perspective view from obliquely above onto the rear end in terms of the travel direction of a vehicle (not illustrated), a steering wheel (not illustrated) here being held in the operating region. FIG. 2 shows a view onto the front end.

[0043] The steering column 1 comprises a support unit 2 which is configured as a console which has fastening means 21 in the form of fastening bores for attaching to a vehicle bodywork (not illustrated). A casing unit 4, also referred to as a guide box or a swingarm box, is held by the support unit 2, said casing unit 4 comprising an external casing 40, also referred to as the external casing tube 40, in which an actuator unit 3 having an internal casing 31, also referred to as an internal casing tube 31, is received.

[0044] A steering spindle 32 is mounted so as to be rotatable about the longitudinal axis L thereof in the casing tube 31 is, said steering spindle 32 extending axially in the longitudinal direction, that is to say in the direction of the longitudinal axis L. A fastening portion 33 to which a steering wheel (not illustrated) is able to be attached is configured at the rear end on the steering spindle 32. The steering spindle 32 at the front end is connected in a torque-fitting manner to a yoke 35 of a universal joint.

[0045] The internal casing tube 31 of the actuator unit 3 for implementing a longitudinal adjustment in the external casing tube 40 of the casing unit 4 is received so as to be telescopically displaceable in the direction of the longitudinal axis L, so as to be able to position the steering wheel connected to the steering spindle 32 back and forth in the longitudinal direction relative to the support unit 2, as is indicated by the double arrow parallel to the longitudinal axis L.

[0046] The casing unit 4 at the front end region thereof is mounted in a pivot bearing 22 on the support unit 2 so as to be pivotable about a horizontal pivot axis 24 which is transverse to the longitudinal axis L. The casing unit 4 in the rear region is connected to the support unit 2 by way of a rotatable actuator lever 41. On account of a rotating movement of the actuator lever 41, the casing unit 4 can be pivoted about the pivot axis 24 relative to the support unit 2, said pivot axis 24 in the installed state being horizontal, on account of which an adjustment of a steering wheel attached to the fastening portion 33 can be performed in the height direction H, this being indicated by the double arrow.

[0047] An adjustment drive 5 according to the invention for the longitudinal adjustment of the actuator unit 3 in the direction of the longitudinal axis L relative to the casing unit 4 has a spindle drive having a spindle nut 51 having an internal thread in which a threaded spindle 52 that extends along a spindle axis S engages, said threaded spindle 52 by way of the external thread thereof thus being screwed into the spindle nut 51. This arrangement can be readily seen in FIGS. 3 to 6. The spindle axis S runs so as to be substantially parallel to the longitudinal axis L.

[0048] The threaded spindle 52 by way of a fastening element 54 configured at the rear end of said threaded spindle 52 is connected to the internal casing tube 31 by way of a transmission element 34, and specifically so as to be fixed in the direction of the spindle axis S and also so as to be stationary in terms of a rotation about the spindle axis S. On account of the rotatingly drivable spindle nut 51 which in the direction of the spindle axis S is supported on the external casing tube 40, and the threaded spindle 52 which in terms of rotation is stationary relative to said spindle nut 51, a so-called plunger spindle drive is implemented.

[0049] The transmission element 34 from the actuator unit 3 extends through a slot-shaped passage opening 42 in the casing unit 4. In order for the steering column 1 to be adjusted in the longitudinal direction, the transmission element 34 can be freely moved along in the longitudinal direction in the passage opening 42.

[0050] The adjustment drive 5 has a drive unit having an electric drive motor 6, said drive unit being illustrated in detail in FIGS. 3 to 6. The drive motor 6 has a stator 61 which is disposed in a stator housing 62. A rotor 63 which has a rotor shaft 64 is mounted in roller bearings 65a, 65b in the stator 61 so as to be rotatable about the spindle axis S, said roller bearings 65a, 65b being inserted in the stator housing 62. The stator housing 62 in the direction of the spindle axis S is supported on the external casing tube 40.

[0051] According to the invention, the rotor shaft 64 is configured as a tubular hollow shaft which has a passage opening which is continuous in the direction of the spindle axis S and which in the example illustrated in FIGS. 4 and 5 is circular having an internal diameter D.

[0052] The spindle nut 51 in the example illustrated is configured so as to be externally cylindrical and dimensioned such that said spindle nut 51, while forming an interference fit for generating the assembly illustrated in FIG. 4, can be pressed into the rotor shaft 64 in the axial direction. The interference fit generates a force-fitting or friction-fitting, respectively, connection between the internal face of the passage opening of the rotor shaft 64 and the external face of the spindle nut 51 that in the radial direction lies in a friction-fitting manner on said internal face. The spindle nut 51 in this embodiment illustrated is disposed in the rear end region of the passage opening that faces the driver.

[0053] In an embodiment not illustrated, the spindle nut in the direction of the spindle axis S is disposed so as to be centric in the rotor shaft.

[0054] The friction-fitting connection forms a rotary or rotating connection which serves for transmitting the motor torque from the rotor shaft 64 to the spindle nut 51 which is consequently driven directly at the rotating speed of the motor, on the one hand. On the other hand, said friction-fitting connection acts as a translatory or longitudinal connection by way of which the adjustment force from the threaded spindle 52 is transmitted by way of the spindle nut 51 in the direction of the spindle axis S.

[0055] The spindle nut 51 is coaxial with the spindle axis S and herein, as shown in the example, is preferably disposed completely within the rotor shaft 64.

[0056] The threaded spindle 52 which engages in the spindle nut 51 likewise extends so as to be coaxial with the spindle axis S, wherein said threaded spindle 52 in each potential state of adjustment at least partially plunges into the passage opening and is thus disposed within the rotor shaft 64.

[0057] The stator housing 62 has fastening means 66, for example a flange or pin-type protrusions, which are connected to a support console 43 which, for example by means of screws 44 or other fastening means, is fixedly attached to the external casing tube 40. On account thereof, the drive motor 6 is fixed to the casing tube 40 and supported in the direction of the spindle axis S.

[0058] For the longitudinal adjustment of the internal casing tube 31 of the steering column 1, the rotor 63 by a suitable electrical actuation can be driven in a rotating manner about the spindle axis S relative to the stator 61. On account thereof, the spindle nut 51 that is attached in a rotationally fixed manner in the rotor shaft 64 is directly driven in a rotating manner relative to the stationary threaded spindle 52 at the rotating speed of the rotor 63. Depending on the rotating direction of the drive 6, the threaded spindle 52 in the direction of the spindle axis S is repositioned in a translatory manner relative to the spindle nut 51 such that the internal casing tube 31 that is connected to the threaded spindle 52 in the direction of the longitudinal axis L is correspondingly adjusted in a telescopic manner relative to the casing tube 40 that supports the drive motor 6.

[0059] On account of the described disposal of the spindle nut 51 in the rotor shaft 64, an energy absorbing installation in a first embodiment is implemented in the embodiment shown in FIG. 4. In the event of a crash, for example in the event of a frontal collision, a high force F in the direction of the longitudinal axis L on account of a body impacting the steering wheel is introduced by way of the steering spindle 32 into the internal casing tube 31, and by way of the transmission element 34 is transmitted to the threaded spindle 52. This force F, also referred to as the crash force, in the direction of the spindle axis S is directed by way of the spindle nut 51 into the rotor shaft 64, and by way of the bearing 65a, b and the stator housing 62 on the support console 43 is finally absorbed on the external casing tube 40. Consequently, as is plotted in FIG. 4, the crash force F acts in the axial direction on the connection between the spindle nut 51 and the rotor shaft 64.

[0060] When the crash force F is so high that the limit force of the axial retention effect, this being the retention force of the friction-fit of the interference fit, is exceeded, the spindle nut 51 in the direction of the spindle axis S is displaced relative to the rotor shaft 64 on account of the crash force F herein acting from the right, as is indicated by the arrows in FIG. 5. The kinetic crash energy is absorbed on account of the friction arising in the relative movement between the external side of the spindle nut 51 and the rotor shaft 64.

[0061] The crash path, this being the path in the direction of the spindle axis S, along which kinetic energy can be dissipated by the relative movement between the spindle nut 51 and the rotor shaft 64 in the event of a crash, can extend across the length of the rotor shaft 64.

[0062] The embodiment of the rotor shaft 64 illustrated in FIG. 4 has an internal diameter D which is consistent across the length of said rotor shaft 64. On account of the internal diameter D in the normal operating state being the same size at the seat of the spindle nut 51 as in the profile of the entire crash path, the absorption of energy takes place substantially by friction.

[0063] A refinement of the energy absorbing installation is shown in FIG. 6. The difference in comparison to the embodiment shown in FIG. 6 is that the internal diameter D in the normal operating state at the seat of the spindle nut 51 on account of inwardly projecting deformation elements 68 is constricted in the direction of the crash path, from right to left in FIGS. 4, 5, and 6. This can be implemented, for example, by a passage opening which conically tapers down to the deformation internal diameter d, the latter being smaller than the initial diameter D. The absorption of energy is influenced in various ways on account thereof. On the one hand, the friction when pressing the spindle nut 51 between the deformation elements 68 is increased such that the absorption of energy by friction increases. On the other hand, the energy absorbing elements 68 deform the spindle nut 51 such that additional deformation work is performed, the energy absorbing capability being additionally increased on account thereof.

[0064] Diverse energy absorbing characteristics can be flexibly implemented by measures which in terms of production technology can be implemented with little complexity, for example the design embodiment of the contact faces of the force-fit, the ratio of dimensions of the interference fit, the shaping of the energy absorbing elements 68, the material pairings between the rotor shaft 64 and the spindle nut 51, and combinations thereof. For example, the threaded spindle 52 and the rotor shaft 64 can be made from steel, and the spindle nut 51 can be made from plastics material or non-ferrous metal. The behavior in terms of friction and deformation when the spindle nut 51 passes through the rotor shaft 64 in the event of a crash can be influenced by the choice of the material pairing, and the energy absorbing characteristic can be predefined on account thereof.

[0065] The bearings 65a and 65b are of identical construction, specifically as angular-contact ball bearings which have in each case one bearing inner ring 651 that is fixedly attached to the rotor shaft 64, one bearing outer ring 652 that is fixedly inserted in the stator housing, and therebetween balls 653 which are disposed so as to be able to roll as rolling members. The bearings 65a and 65b are mutually preloaded in the direction of the spindle axis S. The extensions of the imaginary connecting lines between the bearing inner ring 651 and the bearing outer ring 652, through the ball contact faces (pressure points) of the two bearings 65a and 65b are schematically plotted withlines and provided with the reference sign X. Said connecting lines intersect in the shape of an X on the spindle axis S in the region of the hollow shaft 64, between the bearings 65a and 65b, on account of which a so-called X mounting is implemented.

[0066] A second adjustment drive which, for example by way of the actuator lever 41, engages in the height direction H between the support unit 2 and the casing unit 4 and which is only schematically indicated is identified by the reference sign 7. The actuator drive 7 can be configured in a construction mode known from the prior art, as a plunger spindle drive or a rotating spindle drive, or so as to be configured according to the present invention, depending on the installation space available in the motor vehicle.

[0067] A third embodiment is illustrated in FIGS. 7 to 9, wherein the steering column 1 of FIGS. 7 to 9 has a construction which is identical to that of the steering column from FIGS. 1 to 5, wherein the difference lies in the space-saving and compact configuration of the adjustment drive 5 which can be seen in the cross-sectional view of FIG. 8, which shows a section A-A from FIG. 7, as well as in the schematic perspective view of FIG. 8, the stator housing 62 having been omitted for improved clarity in the latter. A particularity of the illustrated drive motor 6 in comparison to the drive motor 6 illustrated in FIGS. 1 to 5 is the asymmetrically shaped stator 61 which on the circumference thereof that faces the casing unit 4, or the longitudinal axis L, respectively, has a radial concavity 67 which enables a relatively large stator diameter for a high motor torque to be predefined and to nevertheless keep the spacing between the spindle axis S and the longitudinal axis L relatively small so as to implement a compact construction mode. The concavity 67 is implemented in that the stator 6 in the cross-sectional profile has a recess in the shape of a segment of a circle. With the exception of the configuration of the stator 61, the further construction of the adjustment drive 5 is identical to that of FIGS. 1 to 5 such that a spindle drive having a threaded spindle 52 which engages in the spindle nut 51 which, so as to be able to be driven in a rotating manner about the spindle axis S relative to the threaded spindle 52, is coupled to the rotor shaft 64 of a drive motor 6 which has a rotor 63 and a stator 62, wherein the rotor shaft 64 of the drive motor 6 is configured according to the invention as a hollow shaft 64 which is disposed so as to be coaxial with the spindle axis S and in which the threaded spindle 51 is coaxially disposed. The drive motor 6 illustrated in FIGS. 7 to 9 can be operated in a particularly uniform manner, preferably by means of a pulse width modulated actuation system.

[0068] A drive motor 6 in a second embodiment is separately illustrated in FIG. 10 in a cross-sectional view as in FIG. 8, and in FIG. 11 in an exploded illustration exploded in the direction of the spindle axis S, wherein the actuator unit has been omitted for improved clarity. The individual parts having identical functions herein are provided with the same reference signs.

[0069] In a refinement of the first embodiment, the drive motor 6 has two radial concavities 67 which in terms of the spindle axis S are formed so as to be opposite in the circumference of the stator housing 62. As in the first embodiment, said concavities 67 in the cross-sectional profile form recesses in the shape of segments of a circle. The concavities 67 can in each case have the same cross section, as is illustrated, and be disposed so as to be symmetrical in terms of the spindle axis S. The quiet running can be improved on account thereof. Moreover, asymmetrical arrangements as well as, additionally or alternatively, different cross sections of the concavities 67, and/or additional concavities 67 are conceivable. The running properties can be adapted, or special installation situations can be taken into account on account thereof.

LIST OF REFERENCE SIGNS

[0070] 1 Steering column

[0071] 2 Support unit

[0072] 21 Fastening means

[0073] 22, 23 Pivot bearing

[0074] 24 Pivot axis

[0075] 3 Actuator unit

[0076] 31 Internal casing/internal casing tube

[0077] 32 Steering spindle

[0078] 33 Fastening portion

[0079] 34 Transmission element

[0080] 35 Yoke

[0081] 4 Casing unit

[0082] 40 External casing/external casing tube

[0083] 41 Actuator lever

[0084] 42 Passage opening

[0085] 43 Support console

[0086] 44 Screws

[0087] 5 Adjustment drive

[0088] 51 Spindle nut

[0089] 52 Threaded spindle

[0090] 54 Fastening element

[0091] 6 Drive motor

[0092] 61 Stator

[0093] 62 Stator housing

[0094] 63 Rotor

[0095] 64 Rotor shaft

[0096] 65a,b Roller bearing

[0097] 651 Bearing inner ring

[0098] 652 Bearing outer ring

[0099] 653 Ball

[0100] 66 Fastening means

[0101] 67 Concavity

[0102] 68 Deformation element

[0103] 7 Adjustment drive

[0104] L Longitudinal axis

[0105] H Height direction

[0106] S Spindle axis

[0107] V Adjustment

[0108] D, d Internal diameter