Steering shaft and steering column for a motor vehicle

Abstract

The present invention relates to a linear bearing (6) comprising an outer profile (62) having a cage (63) with a passage (61) which is axially continuous in the longitudinal direction relative to a longitudinal axis (L) and has a non-circular passage cross-section, in which an inner profile (421) is displaceable in the longitudinal direction and rotationally locked with respect to rotation about the longitudinal axis (L), wherein the cage (63) has at least one circulation channel (65) in which rolling elements (66) are received which can roll on the inner profile (421) in the longitudinal direction. In order to enable lower manufacturing and assembly costs, the invention proposes that the outer profile (62) have a first support section (67) in one axial end region and a second support section (68) in the other end region, wherein the first support section (67) has a smaller cross-section than the second support section (68).

Description

State of the art

[0001] The invention relates to a steering shaft, comprising an inner shaft which is telescopically displaceable in the direction of its longitudinal axis in an outer shaft, in which a linear bearing is arranged, in which an inner profile of the inner shaft is linearly roller-mounted, which outer profile comprises a cage with a passage which is axially continuous in the longitudinal direction relative to a longitudinal axis and has a non-circular passage cross-section, in which the inner profile is displaceable in the longitudinal direction and is guided in a rotationally locked manner with respect to rotation about the longitudinal axis, wherein the cage has at least one circulation channel in which rolling elements are received which can roll on the inner profile in the longitudinal direction, and the outer profile has a first support section in one axial end region and a second support section in the other end region, wherein the first support section has a smaller cross-section than the second support section.The invention further relates to a steering column according to the preamble of claim 2.

[0002] To enable longitudinal adjustment of a steering wheel or other manual steering mechanism, it is known to design the steering shaft so that its length can be adjusted. This allows torque to be transmitted between the steering wheel and a functional unit of the steering system that is fixed in the longitudinal direction relative to it. For example, a feedback torque can be coupled into the steering shaft from a motorized feedback actuator and transmitted to the steering wheel, or a manual torque can be introduced from the steering wheel via the steering shaft into a steering gear.

[0003] To achieve longitudinal adjustment, the steering shaft features telescopic steering shaft sections. To enable smooth adjustment and low-backlash torque transmission, it is known to use a linear bearing designed as a linear roller bearing between the steering shaft sections.

[0004] Such a linear bearing is described, for example, in EP 1 070 865 A2. This has an outer profile with a cage that has circulation channels in which balls are accommodated as rolling elements that can rotate endlessly. These balls can roll longitudinally on an inner profile that is accommodated in an axial passage of the cage for longitudinal displacement. The passage has a non-circular cross-section, and the inner profile is correspondingly prism-shaped, so that a positive connection is created with regard to rotation about the longitudinal axis. In this way, a smoothly adjustable, secure rotationally locked connection can be realized, which is suitable, for example, for use in a steer-by-wire steering system with a feedback actuator coupled to the steering shaft, and also for use in a conventional steering system with a mechanical shaft connection between the steering wheel and steering gear.

[0005] The outer profile of the known linear bearing has an axially continuous outer cross-section, i.e., a longitudinally continuous outer cross-section, which can be fixed in a corresponding opening, for example, in a hollow shaft of the steering shaft. This can be achieved, for example, by axially pressing the outer profile into a corresponding bearing opening of a hollow shaft. It must be ensured that the radial holding forces are, on the one hand, large enough to create a secure, force-locking fixation, and, on the other hand, not too high to avoid excessive stress on the rolling bearing. The tight tolerances required for this, however, require a relatively high manufacturing and assembly effort.

[0006] A linear bearing with the features mentioned above is known from US 2011 / 0 088 502 A1 or DE 15 25 197 C.

[0007] In view of the problems explained above, it is an object of the present invention to enable a lower manufacturing and assembly effort. Description of the invention

[0008] This object is achieved according to the invention by the steering shaft having the features of claim 1 and the steering column according to claim 2.

[0009] In a steering shaft comprising an inner shaft which is telescopically displaceable in the direction of its longitudinal axis in an outer shaft, in which a linear bearing is arranged, in which an inner profile of the inner shaft is linearly roller-mounted, which outer profile comprises a cage with a passage which is axially continuous in the longitudinal direction relative to a longitudinal axis and has a non-circular passage cross-section, in which the inner profile is displaceable in the longitudinal direction and is guided in a rotationally locked manner with respect to rotation about the longitudinal axis, wherein the cage has at least one circulation channel in which rolling elements are received which can roll on the inner profile in the longitudinal direction, and the outer profile has a first support section in one axial end region and a second support section in the other end region, wherein the first support section has a smaller cross-section than the second support section, the invention providesthat the outer shaft has a first bearing seat corresponding to the first support section, and a second bearing seat corresponding to the second support section, wherein the support sections are axially pressed into the bearing seats.,

[0010] The smaller cross-section of the first support section is referred to below as the first support cross-section, and the relatively larger cross-section of the second support section is referred to as the second support cross-section. A connecting section can preferably be arranged between the two support sections, the cross-section of which is analogously referred to as the connecting cross-section. The first and second support sections are collectively referred to as the two support sections.

[0011] The smaller, first support cross-section is characterized by the fact that, in a given relative angular orientation of the two support sections with respect to the longitudinal axis, it has a smaller transverse dimension in every radial direction, i.e., measured transversely to the longitudinal axis, than the larger, second support cross-section. Accordingly, the first support cross-section has a smaller cross-sectional area than the second support cross-section.

[0012] The transverse dimensions or the cross-sectional areas of the support cross-sections relative to the connection cross-section are defined analogously.

[0013] Preferably, the two support cross-sections each have a non-circular basic shape, preferably the same basic shape. This can be formed, for example, as a triangle, square, hexagon, or polygon with any number of corners, whereby the corners can be sharp-edged or rounded as desired. This can preferably be equilateral.

[0014] Preferably, the basic shape can be designed and arranged rotationally symmetrically, with the longitudinal axis as the axis of symmetry. This allows for symmetrical torque transmission between the inner profile and the outer profile. Corresponding to the angular basic shape of the cross-section, the inner profile is designed in a prism shape and is guided in the adapted, (rounded or sharp-edged) angular through-section of the outer profile or cage in a rotationally locked manner, i.e., positively locking with respect to rotation about the longitudinal axis, and displaceable in the longitudinal direction.

[0015] In the component relative to which the inner profile is linearly displaceable, in the axial opening of a hollow shaft of the steering shaft, the first support section is pressed into a first bearing seat, and the second support section is pressed into a second bearing seat. The open receiving cross-sections of the bearing seats are adapted to the support cross-sections to create axially joinable press fits.

[0016] The outer profile tapers longitudinally from the larger second support section to the first support section. For installation in the opening of a component, the first, smaller support section is first inserted axially into the relatively larger opening cross-section of the second bearing seat. Insertion is facilitated by the fact that the first support section has continuous radial play with the second bearing seat around its circumference. The first support section can then be guided through the second bearing seat and moved further longitudinally until the first support section reaches the first bearing seat, in which the first support section can be fixed axially by friction by pressing.

[0017] The axial distance between the second bearing seat and the first bearing seat can correspond to the axial distance between the first and second support sections. This allows the two support sections to be fixed simultaneously by axially pressing them into the associated bearing seats.

[0018] It can be provided that the cross section of the first support section (i.e., the first support cross section) is smaller than a connecting cross section of a connecting section arranged between the support sections. The fact that the first support cross section is smaller than the connecting cross section enables easy insertion of the outer profile. It is also advantageous that, during further insertion, the connecting cross section is guided in the larger second bearing seat associated with the second support section until the first support section reaches the associated first bearing seat. This facilitates pressing into a press fit.

[0019] It is possible for the cross-section of the second support section (i.e., the second support cross-section) to be larger than a connecting cross-section of a connecting section arranged between the support sections. In this embodiment, the second bearing seat, adapted to the second support cross-section, is larger than the connecting cross-section, i.e., it has a larger bearing opening. As a result, the connecting section has radial clearance on all sides relative to the second bearing seat, which can simplify the insertion of the outer profile until the first support section reaches the associated first bearing seat.

[0020] It is advantageous that at least one support section is formed on a support ring which is connected to the outer profile.

[0021] A first and / or second support ring can be provided, on which the first and / or second support sections are formed, respectively. A support ring can initially be manufactured and provided as a separate part, which can be connected directly or indirectly to the outer profile using suitable joining methods. This allows for structural adaptation and optimization of the support ring(s) with little effort. The support rings can be optimized independently of the design of the connecting section or the cage, for example, to create a connection to components of a steering column, to fix the cage to the outer profile, and / or with regard to other functional features.

[0022] Furthermore, different types of linear bearings can be realized by using support rings with different shapes and / or dimensions, which can be combined with similar or different designs of outer profiles and / or cages. This allows for a particularly flexible, modular design.

[0023] In the above-mentioned design, it is possible that the cage is fixed between two support rings.

[0024] In this design, the two support rings are arranged axially on both sides of the cage so that the cage can be held and fixed axially between the two support rings.

[0025] It can be provided that the cage has at least one raceway element.

[0026] A raceway element can, for example, have a plate-shaped raceway plate. This can preferably be attached to the outside of the cage so that it covers and closes at least one circulation channel to the outside. This can simplify the manufacturing process of incorporating the circulation channel into the cage. A plurality of individual raceway elements can be attached to the cage and can be distributed around the circumference. For example, raceway elements can be arranged on the side surfaces of the polygonal cross-section. In this case, a raceway element can be plate-shaped or flat, at least in sections in the region of the side surfaces of the connecting section. Alternatively, a continuous raceway element can be provided, which can, for example, be in the shape of a sleeve or tubular section. This can enclose the cage completely or at least partially around the circumference.

[0027] As a further development, it is possible that at least one support ring is connected to a raceway element.

[0028] The cage can be enclosed externally by one or more raceway elements. This can form a kind of outer shell for the outer profile. The two support rings can be attached to this shell, preferably on both axial end faces. In this way, the cage can be axially and radially fixed between the raceway element(s) and the support rings.

[0029] An advantage of this design is that the outer profile can be securely fixed via the two support elements, for example, by pressing them into corresponding bearing seats, whereby the raceway element(s) and the cage are not subjected to any connecting or holding forces. Accordingly, the cage and raceway elements can be optimized with regard to their guiding and bearing functions and designed to be compact and lightweight.

[0030] Another advantage is simplified production and assembly.

[0031] The outer shaft of the steering shaft has a hollow shaft or is designed as a hollow shaft with an axial opening in which the linear bearing is arranged. The inner profile of the inner shaft, which can be displaced linearly relative to the hollow shaft in the longitudinal direction defined by the longitudinal axis, can be inserted into the opening of the hollow shaft.

[0032] The bearing seats correspond to the support sections of the linear bearing, as explained above. The fact that the outer profile, which is tapered in the longitudinal direction according to the invention, first engages the relatively larger bearing seat with the first support section when inserted into the opening of the outer shaft, simplifies assembly.

[0033] It is provided that the outer shaft has a first bearing seat corresponding to the first support section and a second bearing seat corresponding to the second support section.

[0034] The bearing seats are arranged in the opening of the hollow shaft at an axial distance from the support sections. The second bearing seat is arranged in the end region of the outer shaft, preferably in the edge region of the opening. The first bearing seat is arranged at an axial distance from the second bearing seat in the opening, i.e. at a distance from the edge region of the opening. The axial distance between the two bearing seats corresponds to the axial distance between the support sections, so that these can be received in the corresponding bearing seats. The open bearing cross-sections, i.e. the bearing openings of the bearing seats, are adapted to the support cross-sections of the support sections and, like these, are non-circular, preferably polygonal, to create a rotationally locked connection. The support sections can preferably be pressed axially into the bearing seats to create a frictionally locked press fit that is effective in the axial direction.

[0035] In a steering column for a motor vehicle, comprising a steering shaft which is mounted in a casing so as to be rotatable about its longitudinal axis and which is adjustable in the longitudinal direction relative to a support unit, wherein the steering shaft has an inner shaft which is telescopically displaceable in the direction of the longitudinal axis in an outer shaft in which a linear bearing is arranged, in which an inner profile of the inner shaft is linearly roller-mounted, wherein the outer shaft or inner shaft is mounted in the casing so as to be rotatable about the longitudinal axis, according to the invention the steering shaft is designed according to one of the previously described embodiments or combinations thereof.

[0036] The sleeve is held by a support unit attachable to the vehicle body and can be adjustable in the longitudinal direction relative to the feedback actuator to realize a longitudinal adjustment of a steering wheel attached to the steering shaft.

[0037] The change in the distance between the feedback actuator and the casing is compensated for by the telescopic steering shaft. The inner shaft can be coupled to the actuator shaft, and the longitudinally displaceable shaft can be mounted in the casing, or vice versa.

[0038] The steering shaft according to the invention can reduce the manufacturing effort.

[0039] A motorized adjustment drive can preferably be integrated between the support unit and the casing, enabling longitudinal adjustment. The outer shaft and the inner shaft are adjusted longitudinally relative to each other. Description of the drawings

[0040] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Fig. 1 a schematic perspective view of a steering column according to the invention, Fig. 2 a longitudinal section through the steering column according to Fig. 1, Fig. 3 an enlarged detailed view Fig. 2, Fig. 4 is a schematic longitudinally exploded view of the steering shaft of the steering column according to Fig. 1-3, Fig. 5 an enlarged longitudinal section through the linear bearing according to Fig. 4, Fig. 6a,b,c a schematic representation of different phases in the assembly of a linear bearing according to Fig. 4-5, Fig. 7 an enlarged view of Fig. 6b. Embodiments of the invention

[0041] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0042] Fig. 1 shows a steering column 1 in a perspective view, and Fig. 2 in longitudinal section along the longitudinal axis L.

[0043] The steering column 1 has a support unit 2 which can be attached to a vehicle body (not shown here) and by which a casing 3 is held.

[0044] In the casing 3, a steering shaft 4 is mounted so as to be rotatable about its longitudinal axis L. The steering shaft 4 has an outer shaft 41 designed as a hollow shaft, into which an inner shaft 42 with its inner profile 421 is inserted so as to be adjustable in the longitudinal direction, ie axially in the direction of the axis L, as shown in Fig. 2 is indicated by the double arrow.

[0045] The outer shaft 41 has a mounting section 410 for attaching a steering wheel (not shown here). It is rotatably mounted in bearings 411 in the casing 3 and axially fixed.

[0046] The casing 3 is adjustable in the longitudinal direction for the longitudinal adjustment of the steering wheel relative to the support unit 2, as shown in Fig. 1 is indicated by the double arrow.

[0047] A motorized feedback actuator 5 is mounted fixedly in the longitudinal direction relative to the casing 3, for example, by a support (not shown here) on the support unit 2 or the vehicle body. The feedback actuator 5 has a rotatably driven actuator shaft 51, which is arranged coaxially to the axis L and coupled to the inner shaft 42.

[0048] In the axial opening of the outer shaft 41, a linear bearing 6 designed according to the invention is fixed, as in Fig. 3. In this example, the inner profile 421 of the inner shaft 42 is designed as a square profile with a square basic profile cross-section. This is mounted in the linear bearing 6 and is thus longitudinally displaceable relative to the outer shaft 41, as shown in Fig. 3 is marked with the double arrow.

[0049] The inner profile 421 is guided through an axial passage 61 of the linear bearing 6, and thus the inner shaft 42 is also guided axially along the longitudinal axis L and thereby rotationally locked to the linear bearing 6. The linear bearing 6, in turn, has a square cross-sectional basic shape, which is rotationally locked in the opening of the outer shaft 41, as explained below.

[0050] Fig. 5 shows an enlarged longitudinal section through the linear bearing 6. This comprises an outer profile 62, which is composed of a cage 63, which is designed as a ball cage, to which at least one raceway element 64 is attached on the outside, for example a raceway plate.

[0051] The cage 63 has circulation channels 65 in which a plurality of balls 66 are rotatably received. The balls 66 protrude inwardly into the passage 61 in such a way that they can roll longitudinally on the outside of the side surfaces of the square of the inner profile 421. The circulation channels 65 are each closed to the outside by a raceway element 64.

[0052] At one axial end of the linear bearing 6, in Fig. 5 right, a first support ring 67 is attached, and at the other end a second support ring 68. Both support rings 67, 68 can preferably be firmly connected to the raceway element 64. The cage 63 is axially fixed between the support rings 67, 68. The first support ring 67 forms a first support section within the meaning of the invention, and the second support ring 68 forms a second support section, and accordingly, the designations are used analogously below.

[0053] A connecting section 69 extends between the support rings 67, 68.

[0054] The second support ring 68 has a second transverse dimension S2 measured radially between the opposite, parallel side surfaces of the square, and the first support ring 67 has a relatively smaller first transverse dimension S1. Accordingly, the first support section formed on the first support ring 67 has a substantially square cross-section with a first cross-sectional area of approximately (S1). 2 which is smaller than the second support cross-section of the second support section formed on the second support ring 68 with a cross-sectional area of approximately (S2) 2 .

[0055] The connecting section 69 has a connecting cross-section that is smaller than the second support cross-section.

[0056] According to the invention, the linear bearing 6 is tapered from the second support ring 68 in the longitudinal direction to the smaller first support ring 67.

[0057] The assembly of the linear bearing 6 according to Fig. 5 in the outer shaft 41 is shown schematically in longitudinal section in successive phases in Fig. 6a, b and c.

[0058] The opening of the outer shaft 41 has a projection extending from the edge of the opening (in Fig. 6 at the left end of the outer shaft 41), which has a first bearing seat 43 spaced apart from the first bearing seat 43 and has a first bearing dimension B1 adapted to form a press fit with the transverse dimension S1 of the first support ring 67. Between the first bearing seat 43 and the edge of the opening, a second bearing seat 44 is arranged, which has a second bearing dimension B2 adapted to form a press fit with the transverse dimension S2 of the second support ring 68. The second bearing dimension B2 is larger than the first bearing dimension B1 and, accordingly, also larger than the first transverse dimension S1 of the first support ring 67.

[0059] In Fig. 6a, the linear bearing 6 is positioned coaxially from the opening of the outer shaft 41, with the first, smaller support ring 67 facing the opening. The linear bearing 6 is then moved axially, as in Fig. 6a is indicated by the arrow pointing to the right, whereby the linear bearing 6 is axially inserted into the opening, as in Fig. 6b. This is facilitated by first axially pushing the first support ring 67 with radial clearance into the section with the relatively larger second bearing dimension B2. This ensures easy insertion and creates defined guidance. This is followed by the second support ring 68, which is axially pushed into the second bearing seat 44 with a precise fit.

[0060] The axial insertion is continued until the smaller first support ring 67 is pressed axially into the adapted first bearing seat 43. This final assembly state is shown in Fig. 6c shown.

[0061] In Fig. 7 is another enlarged section of Fig.6b. It can be seen that the second bearing seat 44 is larger than the first bearing seat 43. Accordingly, the transverse dimension S1 of the smaller support ring 67 in the second bearing seat 44 with the second (larger) bearing dimension B2 has radial clearance with the inner surface of the opening during insertion of the linear bearing 6. List of reference symbols 1 steering column 2 carrying unit 3 coats 4 Steering shaft 41 Outer shaft 410 fastening section 411 camps 42 inner shaft 421 inner profile 43 first camp location 44 second bearing seat 5 Feedback actuator 51 Actuator shaft 6 linear bearings 61 passage 62 outer profile 63 Cage (ball cage) 64 track element 65 Circulation channel 66 rolling elements (ball) 67 first support section, first support ring 68 second support section, second support ring 69 connecting section L Longitudinal axis S1 first transverse dimension (transverse dimension of the support ring 67) S2 second transverse dimension (transverse dimension of the support ring 68) B1 first bearing dimension (transverse dimension of the first bearing seat 43) B2 second bearing dimension (transverse dimension of the second bearing seat 44)

Claims

[1] Steering shaft (4), comprising an inner shaft (42) which is telescopically displaceable in the direction of its longitudinal axis (L) in an outer shaft (41), in which a linear bearing (6) is arranged, in which an inner profile (421) of the inner shaft (42) is linearly roller-mounted, which outer profile (62) comprises a cage (63) with a passage (61) which is axially continuous in the longitudinal direction relative to a longitudinal axis (L) and has a non-circular passage cross-section, in which the inner profile (421) is displaceable in the longitudinal direction and is guided in a rotationally locked manner with respect to rotation about the longitudinal axis (L), wherein the cage (63) has at least one circulation channel (65) in which rolling elements (66) are received which can roll on the inner profile (421) in the longitudinal direction, and the outer profile (62) has a first support section (67) in one axial end region and a second support section in the other end region (68),wherein the first support section (67) has a smaller cross-section than the second support section (68), , characterized by that the outer shaft (41) has a first bearing seat (43) corresponding to the first support section (67), and a second bearing seat (44) corresponding to the second support section (68), wherein the support sections (67, 68) are pressed axially into the bearing seats (43, 44). [2] Steering column (1) for a motor vehicle, comprising a steering shaft (4) which is rotatably mounted in a casing (3) about its longitudinal axis (L) which is adjustable in the longitudinal direction relative to a support unit (2), wherein the steering shaft (4) has an inner shaft (42) which is telescopically displaceable in the direction of the longitudinal axis (L) in an outer shaft (41), in which a linear bearing (6) is arranged, in which an inner profile (421) of the inner shaft (42) is linearly roller-mounted, wherein the outer shaft (41) or inner shaft (42) is rotatably mounted in the casing (3) about the longitudinal axis (L), characterized by that the steering shaft (4) is designed according to claim 1.

Images