ADJUSTABLE STEERING COLUMN HAVING AT LEAST ONE MRF ACTUATOR

Abstract

A steering column may include a steering spindle that is surrounded by a casing tube and is connected to a steering wheel, a guide clamp in which the casing tube is guided displaceably along a longitudinal axis of the steering spindle. The guide clamp may be mounted pivotably about a pivot axis in a holding part that is connectable to a chassis of the motor vehicle. The position of the casing tube may be adjustable relative to the holding part, and a blocking device may be arranged between the casing tube and the holding part. The blocking device may comprise a threaded rod engaged with a spindle nut. The spindle nut may be mounted in a rolling bearing. Rolling bodies of the rolling bearing may be at least partially surrounded by a magnetorheological fluid, and the blocking device may comprise an electromagnet.

Claims

1.-10. (canceled)

11. A steering column for a motor vehicle, the steering column comprising: a steering spindle that is surrounded by a casing tube and connected to a steering wheel; a guide clamp in which the casing tube is guided displaceably along a longitudinal axis of the steering spindle, wherein the guide clamp is mounted pivotably about a pivot axis in a holding part that is connectable to a chassis of the motor vehicle, wherein a position of the casing tube is adjustable relative to the holding part; and a blocking device disposed between the casing tube and the holding part, wherein the blocking device comprises a threaded rod engaged with a spindle nut, wherein the spindle nut is mounted in a rolling bearing, wherein the rolling bodies of the rolling bearing are at least partially surrounded by magnetorheological fluid, wherein the blocking device comprises an electromagnet.

12. The steering column of claim 11 wherein the spindle nut is mounted in a transmission housing so as to be rotatable and positionally fixed relative to the guide clamp, wherein axial movement of the threaded rod relative to the spindle nut leads to rotation of the spindle nut.

13. The steering column of claim 11 wherein the threaded rod is movable without self-locking.

14. The steering column of claim 11 wherein the blocking device is a first blocking device, the steering column comprising a second blocking device, wherein a length of the steering column is configured to be fixed by the first blocking device and a height of the steering column is configured to be fixed by the second blocking device.

15. The steering column of claim 11 wherein the rolling bodies comprise a magnetizable material, wherein the electromagnet is configured to magnetize or to demagnetize the rolling bodies.

16. A method for controlling an adjustable steering column of a motor vehicle, the adjustable steering column comprising a steering spindle that is surrounded by a casing tube and is connected to a steering wheel, a guide clamp in which the casing tube is guided displaceably along a longitudinal axis of the steering spindle, wherein the guide clamp is mounted pivotably about a pivot axis in a holding part that is connectable to a chassis of the motor vehicle, wherein a position of the casing tube is adjustable relative to the holding part, wherein a blocking device is disposed between the casing tube and the holding part, the blocking device comprising a threaded rod that is engaged with a spindle nut, wherein the blocking device is switchable between a fixing position and a release position, wherein in the fixing position adjustment of the steering column is blocked and in the release position adjustment of the steering column is unblocked, the method comprising: providing a rolling bearing that supports the spindle nut, wherein rolling bodies of the rolling bearing are at least partially surrounded by magnetorheological fluid; while switching the blocking device into the fixing position, magnetizing the rolling bodies by way of an electromagnet to increase a viscosity of the magnetorheological fluid such that rotation of the spindle nut is blocked; and while switching the blocking device into the release position, demagnetizing the rolling bodies by way of the electromagnet to reduce the viscosity of the magnetorheological fluid such that rotation of the spindle nut is unblocked.

17. The method of claim 16 wherein the spindle nut is mounted in a transmission housing so as to be rotatable and positionally fixed relative to the guide clamp, wherein an axial movement of the threaded rod relative to the spindle nut leads to a rotation of the spindle nut.

18. The method of claim 16 wherein the threaded rod is movable without self-locking.

19. The method of claim 16 wherein the blocking device is a first blocking device, wherein the steering column comprises a second blocking device, the method comprising fixing a length of the steering column with the first blocking device and fixing a height of the steering column with the second blocking device.

20. The method of claim 16 comprising energizing the electromagnet such that in a crash event the spindle nut is rotatable with a predefined braking moment.

21. A method for controlling a steering column comprising: while switching a blocking device into a fixing position where adjustment of the steering column is prevented, magnetizing rolling bodies of a rolling bearing that are at least partially surrounded by magnetorheological fluid by way of an electromagnet to increase a viscosity of the magnetorheological fluid such that rotation of a spindle nut supported by the rolling bearing is blocked; and while switching the blocking device into a release position where adjustment of the steering column is permitted, demagnetizing the rolling bodies by way of the electromagnet to reduce the viscosity of the magnetorheological fluid such that rotation of the spindle nut is unblocked.

22. The method of claim 21 wherein the spindle nut is mounted in a transmission housing so as to be rotatable and positionally fixed relative to a guide clamp, wherein an axial movement of a threaded rod relative to the spindle nut leads to a rotation of the spindle nut.

23. The method of claim 21 wherein the threaded rod is movable without self-locking.

24. The method of claim 21 wherein the blocking device is a first blocking device, the method comprising fixing a length of the steering column with the first blocking device and fixing a height of the steering column with a second blocking device.

25. The method of claim 21 comprising energizing the electromagnet such that in a crash event the spindle nut is rotatable with a predefined braking moment.

Description

[0024] Preferred embodiments of the invention will be explained in more detail below with reference to the drawings. Components which are identical or act in an identical manner will be referred to by the same reference signs in the figures, in which:

[0025] FIG. 1 shows a first three-dimensional illustration of a steering column with a blocking device for the longitudinal adjustment direction and a blocking device for the height adjustment direction,

[0026] FIG. 2 shows a second three-dimensional illustration of a steering column according to FIG. 1 with a blocking device for the longitudinal adjustment direction and a blocking device for the height adjustment direction,

[0027] FIG. 3 shows a detailed longitudinal section through a blocking device of the steering column,

[0028] FIG. 4 shows a three-dimensional illustration of the steering column of FIG. 1 without covering the blocking device,

[0029] FIG. 5 shows a cross section through the steering column according to FIGS. 1 and 2, and

[0030] FIG. 6 shows a detailed illustration of a rolling bearing of a blocking device in cross section;

[0031] FIG. 7 shows a three-dimensional illustration of a steering column in a second embodiment with a blocking device for the longitudinal adjustment direction and a blocking device for the height adjustment direction and with motorized adjustment drives.

[0032] FIG. 1 and FIG. 2 illustrate a steering column 1 of a motor vehicle, which comprises a steering spindle 2 which is mounted rotatably about its axis of rotation in a steering spindle bearing unit 3, comprising a casing tube 4. The casing tube 4 is guided displaceably along the longitudinal axis L of the steering spindle 2 in a guide clamp 5, which may also be referred to as outer casing tube or box-section swing arm. The guide clamp 5 is mounted pivotably about a pivot axis 100 in a holding part 6. The holding part 6 can be fastened to the body (not illustrated) at fastening points 7. The rotational movement introduced into the steering spindle 2 by a driver via a steering wheel (not illustrated) is introduced into the steering mechanism (not illustrated). In order to increase the comfort for the driver, the height of the steering column 1 can be adjusted in the height adjustment direction 101 and the length in the longitudinal adjustment direction 102. In order to realize the adjustment in the height adjustment direction 101, the casing tube 4 is pivotable together with the guide clamp 5 about the pivot axis 100.

[0033] A first blocking device 22 for fixing the casing tube 4 in relation to the guide clamp 5 in the longitudinal adjustment direction 101 and therefore for fixing the casing tube 4 in relation to the holding part 6 is provided, wherein the first blocking device 22 comprises a threaded rod 12 and a spindle nut 13.

[0034] The threaded rod 12 is connected to the casing tube 4 via a coupling lever 14, and therefore a displacement of the casing tube 4 in relation to the guide clamp 5 leads to a displacement of the coupling lever 14 in relation to the guide clamp 5.

[0035] The threaded rod 12 is held on the coupling lever 14 and extends in the longitudinal adjustment direction 102 and therefore in the direction of the longitudinal axis L.

[0036] A second blocking device 122 for fixing the casing tube 4 and the guide clamp 5 in the height adjustment direction 102 in relation to the holding part 6 is provided, wherein the second blocking device 122 comprises a threaded rod 12 and a spindle nut 13.

[0037] The spindle nut 13 is set into rotation by displacement of the threaded rod 12 in the axial direction. The threaded rod 12 of the second blocking device 122 is connected to an adjustment lever 16 via a joint 15. The adjustment lever 16 is held pivotably on the holding part 6 in a joint axis 18 and on the guide clamp 5 in a joint axis 17. The effect achieved by this is that the guide clamp 5 is pivoted in relation to the holding part 6 via the spindle nut 113 and the threaded rod 112 if the casing tube 4 is pivoted about the pivot axis 100 in relation to the holding part 6.

[0038] FIG. 3 shows the design of the first blocking device 22 in detail. The design of the second blocking device 122 corresponds to the design of the first blocking device 22. The threaded rod 12 engages by means of an external thread 19 into an internal thread 20 of a spindle nut 13, 113. The thread is configured in such a manner that no self-locking is present. The spindle nut 13 is mounted in a transmission housing 21 in a rotatable, but positionally fixed, manner, and therefore an axial movement of the threaded rod 12 leads to a rotation of the spindle nut 13 relative to the threaded rod 12.

[0039] The blocking device 22, 122 can be switched over between a fixing position and a release position. In the release position, the longitudinal and/or height adjustment of the steering column can take place. In the fixing position, the blocking device 22, 122 prevents an adjustment of the threaded rod 12.

[0040] As FIGS. 3 to 6 show, the blocking device 22, 122 comprises a rolling bearing 23 which supports the spindle nut 13, wherein the rolling bodies 24 are at least partially surrounded by a magnetorheological fluid 25. Furthermore, an electromagnet 26 (electric coil) is provided on an end side of the rolling bearing 23 level with the rolling bodies 24. The rolling bodies 24, which are designed as a permanent magnet, are magnetized or demagnetized via temporary and correspondingly strong magnetic pulses of the electric coil 26. The existing magnetic field of the magnetized rolling bodies 24 leads to linking of the magnetorheological particles of the magnetorheological fluid 25, said particles being located between the rolling bodies 24. Linking of the magnetorheological particles increases the viscosity, which leads to the adjustment device being fixed since the rotation of the spindle nut 13 is blocked. The blocking device 22, 122 can therefore be switched over between a fixing position and a release position. In the release position, the longitudinal and/or height adjustment of the steering column can take place. In the fixing position, the blocking device 22, 122 prevents an adjustment of the threaded rod 12 since the viscosity is increased by the linking of the magnetorheological particles, which leads to the blocking device being fixed since the rotation of the spindle nut 13 is blocked. If the rolling bodies 24 designed as a permanent magnet are demagnetized by the electromagnet 26, the blocking device is transferred into the release position and the casing tube 4 can be adjusted in relation to the holding part.

[0041] The magnetorheological fluid refers to a suspension of small magnetically polarizable particles which are finely distributed in a carrier fluid. If a magnetic field acts on the fluid, the particles are polarized and form chains in the direction of the field lines. By means of the orientation of the particles, the suspension becomes more viscous as the field strength increases. A magnetorheological fluid (MRF) in a magnetic field can therefore be drastically, rapidly and reversibly changed. In order to avoid negative properties, such as abrasion, sedimentation and aging, the fluids are stabilized with additives.

[0042] The first and second blocking devices 22, 122 also serve as an energy absorption device. Since the blocking device 22, 122 or the rolling bearing 23 has a basic friction with an adjustable basic torque it already incorporates obstruction of the steering column. In the event of a crash, the blocking device 22, 122 can be used as a pure controlled system. In this case, the electromagnet 26 is energized in such a manner that the spindle nut 13, 113 can be rotated with a certain braking moment, and therefore the components of the steering column can be shifted in relation to one another and, in the process, energy is absorbed. Different forces can be realized depending on the voltage applied.

[0043] FIG. 7 shows a three-dimensional illustration of a steering column in a second embodiment with a first blocking device 22 for the longitudinal adjustment direction and a second blocking device 122 for the height adjustment direction and with motorized adjustment drives for the longitudinal adjustment and a motorized adjustment drive for the height adjustment. The motorized adjustment drive makes it possible to adjust the casing tube 4 in relation to the holding part 6 by means of an electric motor 300 when the blocking device 22 is in the release position. It is an advantage of the invention that both the blocking device and the energy absorption device are formed compactly and in a manner saving on construction space as one unit.

[0044] The present steering column with one or two blocking device(s) can be used in electromechanical motor vehicle servo steering systems, but also in steer-by-wire steering systems of a motor vehicle.