STEERING COLUMN FOR A MOTOR VEHICLE

Abstract

A steering column for a motor vehicle may include a casing unit in which a steering spindle is mounted rotatably about a longitudinal axis that extends in a longitudinal direction. The casing unit has at least two casing tubes that have a polygonal cross section and are guided such that they can be adjusted relative to one another in the longitudinal direction. Rolling bodies that have a rolling body radius are arranged between the casing tubes such that the rolling bodies can roll in the longitudinal direction in at least three raceways that are distributed circumferentially. To increase rigidity and improve compactness, center points of the rolling bodies are at a radial spacing that is less than or equal to the rolling body radius from an envelope circle that circumscribes the casing tube, on which the rolling bodies can roll on the outside.

Claims

1.-15. (canceled)

16. A steering column for a motor vehicle, the steering column comprising: a casing unit in which a steering spindle is mounted rotatably about a longitudinal axis that extends in a longitudinal direction, wherein the casing unit includes at least two casing tubes that have a polygonal cross section and are guided such that the at least two casing tubes are adjustable relative to one another in the longitudinal direction; and rolling bodies, which have a rolling body radius, disposed between the at least two casing tubes such that the rolling bodies are configured to roll in the longitudinal direction in at least three raceways distributed circumferentially on an outside of at least one of the at least two casing tubes, wherein center points of the rolling bodies are at a radial spacing that is less than or equal to the rolling body radius from an envelope circle that circumscribes the at least one of the at least two casing tubes on which the rolling bodies are configured to roll.

17. The steering column of claim 16 wherein the center points of the rolling bodies are located outside the envelope circle.

18. The steering column of claim 16 wherein the polygonal cross section has connecting sides that are angled away relative to one another, wherein a first of the at least three raceways is disposed between a first and a second of the connecting sides.

19. The steering column of claim 18 wherein the first raceway is disposed on a raceway side that is located in an angled-away manner between the first and second connecting sides.

20. The steering column of claim 19 wherein at least one of the raceway side or the connecting sides are planar.

21. The steering column of claim 16 wherein the center points of rolling bodies that are disposed in adjacent of the at least three raceways are at a transverse spacing of at least four times the rolling body radius perpendicularly with respect to the longitudinal axis.

22. The steering column of claim 16 wherein a plurality of the rolling bodies are held in a rolling body cage such that the plurality of rolling bodies are rotatable about their respective center points.

23. The steering column of claim 16 wherein the casing unit includes at least three casing tubes that comprise an outer casing tube, an intermediate casing tube, and an inner casing tube, with the intermediate casing tube being disposed in the outer casing tube and the inner casing tube being disposed in the intermediate casing tube, wherein the rolling bodies are configured to roll on outsides of the intermediate casing tube and the inner casing tube.

24. The steering column of claim 23 wherein a first rolling body of the rolling bodies that is disposed on a first casing tube of the at least two casing tubes is at a mean spacing from a second rolling body of the rolling bodies that is disposed on a second casing tube of the at least two casing tubes, wherein the mean spacing is less than or equal to four times the rolling body radius of a largest rolling body of the rolling bodies.

25. The steering column of claim 16 wherein at least one of the at least three raceways is a channel-shaped recess.

26. The steering column of claim 16 wherein a motorized adjusting drive is connected to the at least two casing tubes.

27. A method for producing a steering column that comprises a casing unit in which a steering spindle is mounted rotatably about a longitudinal axis that extends in a longitudinal direction, with the casing unit including an inner casing tube and an outer casing tube that are guided such that the inner and outer casing tubes are adjustable relative to one another in the longitudinal direction by an adjusting travel, wherein the inner and outer casing tubes include raceways that are disposed radially opposite one another, wherein rolling bodies, which have a predefined rolling cross section, are arranged between the inner and outer casing tubes and are configured to roll in the longitudinal direction, wherein an adjusting force required to adjust the casing tubes relative to one another is set to a predefined adjusting force reference value, wherein the method comprises: providing the inner casing tube with an outer raceway and the outer casing tube with an inner raceway, wherein the inner and outer raceways delimit a raceway cross section transversely with respect to the longitudinal axis; providing rolling bodies with a rolling cross section that is greater than the raceway cross section; arranging the rolling bodies in the raceway cross section; applying an axial adjusting force for relative movement of the inner and outer casing tubes in the longitudinal direction over an entirety of the adjusting travel, wherein the rolling bodies deform the raceways plastically, wherein the axial adjusting force that is applied is measured along the adjusting travel; comparing the measured axial adjusting force with the predefined adjusting force reference value to determine if the measured axial adjusting force falls within predefined tolerance limits over the entirety of the adjusting travel; and if the measured axial adjusting force does not fall within the predefined tolerance limits over the entirety of the adjusting travel, repeating the following steps until the measured axial adjusting force does fall within the predefined tolerance limits over the entirety of the adjusting travel: modifying the axial adjusting force, measuring the modified axial adjusting force, and comparing the measured modified axial adjusting force with the predefined adjusting force reference value and the predefined tolerance limits.

28. The method of claim 27 wherein with respect to the step of applying the axial adjusting force, a relative movement of the inner and outer casing tubes occurs in each case over the entirety of the adjusting travel in a forward direction and in an opposed reverse direction.

29. The method of claim 28 comprising: comparing the axial adjusting force that is measured in the forward direction with the axial adjusting force that is measured in the opposed reverse direction; and repeating the step of applying the axial adjusting force until the measured axial adjusting forces in the forward direction and in the opposed reverse direction coincide within the predefined tolerance limits.

30. The method of claim 27 comprising terminating the method if the measured axial adjusting force falls outside the predefined adjusting force reference value after a predefined number of movements.

Description

DESCRIPTION OF THE DRAWINGS

[0054] Advantageous embodiments of the invention will be described in greater detail in the following text on the basis of the drawings, in which, in detail:

[0055] FIG. 1 shows a steering column according to the invention in a diagrammatic perspective view,

[0056] FIG. 2 shows the steering column according to FIG. 1 in a diagrammatic partial interior view,

[0057] FIG. 3 shows a cross section through the steering column according to FIG. 1,

[0058] FIG. 4 shows a cross section through the steering column according to FIG. 1,

[0059] FIG. 5 shows a cross section through a steering column in a further embodiment, and

[0060] FIG. 6 shows a longitudinal section (along the longitudinal axis) through the steering column according to FIG. 1.

EMBODIMENTS OF THE INVENTION

[0061] In the different figures, identical parts are always provided with the same designations, and are therefore as a rule also named or mentioned in each case only once.

[0062] FIG. 1 shows a steering column 1 according to the invention in a view obliquely from the rear with regard to the driving direction, which steering column 1 has an actuating unit 2. The actuating unit 2 comprises a casing unit 3 which has an outer casing tube 31, an intermediate casing tube 32 and an inner casing tube 33. The casing tubes 31, 32 and 33 are arranged coaxially inside one another such that they can be displaced telescopically in the direction of a longitudinal axis L, as indicated by way of a double arrow.

[0063] A steering spindle 4 is mounted in the casing unit 3 such that it can be rotated about the longitudinal axis L, which steering spindle 4 has, at its rear end, a connector section 41 for the attachment of a steering wheel (not shown).

[0064] An adjusting drive 6 has a spindle drive with a spindle nut 61 and a threaded spindle 62 which is screwed therein, which can be driven rotationally relative to one another by an electric motor 63. The threaded spindle 62 extends parallel to the longitudinal axis L and is connected to the inner casing tube 33, and the spindle nut 61 is supported on the outer casing tube 31 in the longitudinal direction which corresponds to the axial direction of the longitudinal axis L. By way of a relative rotation by means of the motor 63, the threaded spindle 62 and the spindle nut 61 are moved together or apart from one another depending on the rotational direction, as a result of which the inner casing tube 33 is retracted into or extended from the outer casing tube 31 in the axial direction, as indicated by way of the double arrow. As a result, a longitudinal adjustment is realized, by way of which a steering wheel which is attached to the connector section 41 can be moved forward into a stowage position, in which the inner casing tube 33 and the intermediate casing tube 32 are retracted into the outer casing tube 31, that is to say are lowered forward.

[0065] As an alternative, the spindle nut 61 can be supported on the inner casing tube 33, and the threaded spindle 62 can be supported on the outer casing tube 31.

[0066] In FIG. 2, the outer casing tube 31 and the intermediate casing tube 32 are cut away and partially omitted. FIGS. 3 and 4 show the same cross section through the casing unit 3.

[0067] First balls 7 which form rolling bodies are received in a first ball cage 71 such that they can be rotated about their ball center points K1. The ball cage 71 is inserted coaxially between the outer casing tube 31 and the intermediate casing tube 32. The balls 7 are arranged such that they can roll between a groove-shaped or channel-shaped raceway 34, which is elongate parallel to the longitudinal axis L and is formed on the outside into the intermediate casing tube 32, and a likewise groove-shaped or channel-shaped raceway 35 which lies radially opposite the former and is configured on the inside in the outer casing tube 31.

[0068] Second balls 8 which form rolling bodies are received in a second ball cage 81 such that they can be rotated about their ball center points K2. The ball cage 81 is inserted coaxially between the intermediate casing tube 32 and the inner casing tube 33. Here, the balls 8 are arranged such that they can roll between a groove-shaped or channel-shaped raceway 36, which is elongate parallel to the longitudinal axis L and is formed on the outside into the inner casing tube 33, and a likewise groove-shaped or channel-shaped raceway 37 which lies radially opposite the former and is configured on the inside in the intermediate casing tube 32.

[0069] In each case a plurality of balls 7, 8 (three are visible in the view of FIG. 2) are arranged in a row in the longitudinal direction, that is to say in the direction of the longitudinal axis L. As can be seen in the cross sections of FIGS. 3 and 4, a total of four rows of balls 7, 8 are arranged distributed around the longitudinal axis L in the example which is shown.

[0070] In the example which is shown, the balls 7 and 8 are of equal size with a ball radius k, that is to say a ball diameter 2k.

[0071] The inner casing tube 33 and the intermediate casing tube 32 have an octagonal cross section. They have connecting sides 321 and 331 which are arranged in each case at a right angle with respect to one another and in each case lie opposite one another in pairs in parallel with regard to the longitudinal axis L. Raceway sides 322 and 332 are arranged in the corner or edge regions between the connecting sides 321 and 331. The raceway sides 332 have the raceways 36, and the raceway sides 322 have the raceways 34. The raceway sides 322 and 332 are inclined in each case with respect to the adjacent connecting sides 321 and 331, and are angled away by approximately 45° in a symmetrical arrangement in the example which is shown.

[0072] The raceways 36 are formed on the outside into the raceway sides 332 in the inner casing tube 33, and the raceways 34 are formed on the outside into the raceway sides 322 of the intermediate casing tube 32.

[0073] The raceway sides 322 of the intermediate casing tube 32 have, on the inside, the raceways 37 which correspond with the raceways 36 and delimit a raceway cross section, in which the balls 8 are received.

[0074] A raceway side 322 of the intermediate casing tube 32 is preferably parallel to a raceway side 332 of the inner casing tube 33.

[0075] The outer casing tube 31 has a rectangular cross section which has four connecting sides 311 which are arranged at a right angle and are connected to one another in the corner or edge regions. The raceways 35 which have a rounded, channel-shaped cross section are situated on the inside in the edge regions.

[0076] In FIG. 3, an envelope circle 90 is illustrated using dashed lines, which envelope circle 90 encloses the inner casing tube 33 and is tangent on the corner regions between the connecting sides 331 and the raceway sides 332. The envelope circle 90 has an envelope circle radius h.

[0077] The circularly annular optimum region according to the invention around said envelope circle 90 is delimited by way of an inner circular limit 91 with the radius (h−k), k being the ball radius, and an outer circular limit 92 with the radius (h+k). The inner and outer circular limits 91, 92 are preferably concentric with respect to the envelope circle 90. In other words, the center points of the envelope circle 90 and of the inner and outer limit 91, 92 coincide and lie on the longitudinal axis L.

[0078] According to the invention, the ball center points K2 of the balls 8 are situated within the optimum region. In the example which is shown, they are spaced apart here by a spacing a radially to the outside from the envelope circle 90, the spacing a being less than or equal to the ball radius k.

[0079] In FIG. 4, an envelope circle 93 is illustrated using dashed lines, which envelope circle 93 encloses the intermediate casing tube 32 and is tangent on the corner regions between the connecting sides 321 and the raceway sides 322. The envelope circle 93 has an envelope circle radius H.

[0080] The circularly annular optimum region according to the invention around said envelope circle 93 is delimited by way of an inner circle 94 with the radius (H−k), k being the ball radius of the balls 7, and an outer circle 95 with the radius (H+k).

[0081] According to the invention, the ball center points K1 of the balls 7 are situated within the optimum region. In the example which is shown, they are spaced apart here by a spacing b radially to the outside from the envelope circle 93, which spacing b is smaller than or equal to the ball radius k.

[0082] FIG. 5 shows a casing unit 3 which comprises only an inner casing tube 33 and an outer casing tube 38. The outer casing tube 38 is of similar construction to the intermediate casing tube 32 of the first embodiment according to FIGS. 3 and 4, and is provided with the same designations, but, in contrast to the latter, does not have any raceways on the outside. Here too, the balls 8 are arranged, as described above, in an optimum region around the envelope circle 90 which circumscribes the inner casing tube 33.

[0083] It can be gathered from the longitudinal section shown in FIG. 6 along the longitudinal axis L that the steering spindle 4 is likewise of telescopic configuration, with an inner shaft 43 which can telescope in the longitudinal direction and engages in a positively locking manner into an outer shaft 42, it being possible for a torque-transmitting linear bearing system which is mounted using plain bearings or anti-friction bearings to be inserted in between.

[0084] The spacing of the ball center points K1 and K2 from one another is smaller than or equal to twice the ball diameter (2 k), that is to say four times the ball radius k.

LIST OF DESIGNATIONS

[0085] 1 Steering column [0086] 2 Actuating unit [0087] 3 Casing unit [0088] 31, 38 Outer casing tube [0089] 32 Intermediate casing tube [0090] 321 Connecting side [0091] 322 Raceway side [0092] 33 Inner casing tube [0093] 331 Connecting side [0094] 332 Raceway side [0095] 34, 35 Raceways [0096] 36, 37 Raceways [0097] 4 Steering spindle [0098] 41 Connector section [0099] 42 Outer shaft [0100] 43 Inner shaft [0101] 5 Supporting unit [0102] 51 Fastening means [0103] 6 Adjusting drive [0104] 61 Spindle nut [0105] 62 Threaded spindle [0106] 63 Motor [0107] 7, 8 Balls [0108] 71, 81 Ball cage [0109] 90, 93 Envelope circle [0110] 91, 92 Limit [0111] 94, 95 Limit [0112] K1, K2 Ball center point [0113] k Ball radius [0114] L Longitudinal axis [0115] H, h Radius [0116] a Spacing [0117] b Spacing