Length-adjustable control unit and steer-by-wire system

Abstract

Length-adjustable control unit (1) for influencing the driving direction of a motor vehicle (2) by a user, comprising a telescopic extension device (4) that can be coupled to a steering means (33) and has an outer guide tube (5) in which an inner extension tube (6) is arranged and is guided translationally relative to the outer guide tube (5) via a linear roller bearing (7), wherein the linear roller bearing (7) has a cage (8) in which a plurality of rolling elements (9) are rotatably guided, wherein the rolling elements (9) roll on a plurality of inner rolling tracks (10) of the inner extension tube (6) and a plurality of outer rolling tracks (11), wherein the outer rolling tracks (11) each extend axially on separate outer track elements (12) and the cage (8) as well as the inner extension tube (6) are essentially square-shaped, characterized in thatthat the outer track elements (12) each have a radially inwardly pointing tab (19) at their two axial ends, so that the outer track elements (12) engage the cage (8), the outer track elements (12) being fixed to the outer guide tube (5).

Description

[0001] The present invention relates to a length-adjustable control unit for influencing the direction of travel of a motor vehicle by a user, comprising a telescopic extension device that can be coupled to a steering means and has an outer guide tube in which an inner extension tube is arranged and guided translationally relative to the outer guide tube via a linear rolling bearing. The linear rolling bearing has a cage in which a plurality of rolling elements are rotatably guided, the rolling elements rolling on a plurality of inner rolling tracks of the inner extension tube and a plurality of outer rolling tracks. The invention further relates to a steer-by-wire system.

[0002] Electric steering systems are used, among other things, in motor vehicles to receive a driver's directional command and translate it into the corresponding movement of one or more wheels. In contrast to purely mechanical steering systems, a distinction is made between electrically assisted steering systems and fully electric steering systems, so-called "steer-by-wire" steering systems. These steer-by-wire steering systems in particular have the advantage that the control unit can be positioned relatively freely within the vehicle, independent of mechanical connecting components. This not only saves costs when differentiating between, for example, right- and left-hand drive vehicles, but also improves accident behavior due to the lack of a direct connection between the steering gear and the steering column. Furthermore, the control unit can be moved into a stowed position, which, for example,is also used for fully automatic steering.

[0003] A steer-by-wire steering system, as defined in the present invention, is a steering system that essentially consists of a so-called handwheel actuator (HWA), for example, the actuator system around the commanding vehicle steering wheel, and a roadwheel actuator (RWA), i.e., the actuator system acting on the steering mechanism connected to the vehicle wheels. The steering signal is transmitted from the HWA to the RWA via a cable ("by wire").

[0004] Such systems are generally known from the prior art. DE 10 2015 224 602 A1 discloses an adjustable steering column for a steer-by-wire steering system of a motor vehicle, comprising an actuating unit that includes a steering spindle mounted in a casing unit for rotation about a longitudinal axis. The casing unit has a first casing tube in which at least one second casing tube is arranged in a rotationally fixed manner with respect to the longitudinal axis and mounted in a telescopically axially displaceable manner. An actuating drive is connected to the first and second casing tubes, by which the second casing tube can be axially retracted and extended relative to the first casing tube. The actuating drive comprises a spindle drive with a threaded spindle arranged parallel to the longitudinal axis and rotatably driven by an electric actuator. The spindle is supported on one casing tube and is screwed into a spindle nut that is rotationally fixedly attached to the other casing tube.wherein the threaded spindle extends within the first casing tube, and the spindle nut is attached to the second casing tube,

[0005] With regard to the further development towards autonomous driving, the aim is to give the driver of the vehicle the option of retracting the steering wheel almost completely towards the dashboard during autonomous driving in order to achieve an improved comfort zone without a steering wheel that could potentially be perceived as annoying, which also allows for completely new design concepts for the passenger compartment.

[0006] Such new designs of the passenger compartment in autonomously driving vehicles often result in special requirements for the retractable steering wheel, in particular with regard to the required travel distance, which is usually considerably greater than the travel distance for an extendable steering column in a non-autonomously driving vehicle.

[0007] It has become apparent that existing drives for adjusting the position of the steering wheel in steering columns are only partially suitable for steer-by-wire steering columns with greatly extended travel ranges and increased adjustment speeds. As already explained in the introduction, this type of adjustment typically involves an electric motor coupled to a gear (spur gear, planetary gear, crown gear, or worm gear). This gear drives an axially mounted spindle, the rotation of which causes a non-rotatable spindle nut to move axially. This displacement then causes, for example, a steering column extension along with the steering wheel to be moved longitudinally.

[0008] The longitudinal adjustment range of the steering wheel will tend to become increasingly larger in future vehicles - as already explained above - so that, for example, the steering wheel can be completely stowed away during autonomous driving, or so that the steering wheel can be moved far away from the driver to make getting in and out easier and increase the space for movement when getting out.

[0009] In such steer-by-wire steering systems, in addition to the requirement for a very large adjustment range of the steering wheel, the requirement for a low displacement force of the steering wheel is now increasingly becoming the focus of development, since this allows the motor that adjusts the steering wheel to be designed as small as possible.

[0010] To achieve particularly low-friction linear displacement, state-of-the-art linear ball bearings are known. These are special ball bearings with multiple ball circuits. Instead of an outer ring, various linear ball bearings in the lightweight series have several raceway plates on the outer diameter of the bearing, on which the balls roll in the linear bearing. Shafts made of precisely machined steel, for example, serve as counter-raceways for such linear ball bearings. Such linear roller bearings are known, for example, from EP 1 629 212 B1.

[0011] In applications with telescopically variable-length shafts, such as a telescopic steering column, such a bearing must also transmit the torque transmitted through the shaft. Telescopically variable-length shafts are used, for example, as steering shafts in modern motor vehicles. These bearings are equipped with one or more recirculating ball systems, in which the balls successively pass through a loaded zone and then a load-free return zone and are guided back to the loaded zone. Such a linear rolling bearing is described, for example, in DE 33 03 831 A1. A sleeve is provided with rolling element raceways on the inside and outside and is enclosed inside and outside by cage halves. The rolling elements roll from the loaded inner zone on the inner diameter of the sleeve and the outer contour of the sliding shaft, guided by a cage, into the unloaded zone, over the outer contour of the sleeve, and from there back into the loaded zone.

[0012] The generic US 2005 / 0 215 329 A1 discloses a bearing for the longitudinally movable mounting of an inner profile and an outer profile, which are movable relative to each other along a longitudinal axis. The bearing transmits torques between the profiles and elastically compensates for a bearing play directed transversely to the longitudinal axis in order to preload the profiles against each other without play. It comprises an outer sleeve, ball guides with orbital ball raceways, spring-elastic elements, and an overload protection device. The ball guide is designed in one piece with at least one orbital ball raceway and is arranged between the outer sleeve and the inner profile.

[0013] US 6,350,203 B1 discloses a torque-transmitting linear rolling bearing comprising ball races formed in a cage between an inner and an outer profile element. The rolling elements move along a first guideway and are elastically preloaded by a spring plate. The inner rolling element profile has a non-circular cross-section and at least two torque-transmitting, outwardly directed outer wall sections that interact with inner wall sections of the outer rolling element profile. The rolling elements are guided in at least one rolling element circuit, which guides the rolling elements in the longitudinal direction of the linear rolling element bearing through a loaded and a load-free zone.

[0014] US 2013 / 0 143 678 A1 discloses a sliding joint comprising a female part with four axially extending segments that together form an outer boundary. Each segment has its own ball tracks that extend substantially the length of the female part. A unitary male part with an outer surface defined by a plurality of axially extending ball tracks is arranged radially inward of the female part. A cage with ball openings and balls allows selective movement of the male part relative to the female part, while a tubular element is in direct radial outward contact with the female part.

[0015] The object of the invention is to provide a length-adjustable control unit for influencing the driving direction of a motor vehicle by a user, which enables particularly low-friction length adjustment, a compact design, and cost-effective production. Furthermore, the object of the invention is to implement an optimized steer-by-wire system.

[0016] This object is achieved by a length-adjustable operating unit for influencing a direction of travel of a motor vehicle by a user, comprising a telescopic extension device which can be coupled to a steering means and has an outer guide tube in which an inner extension tube is arranged and is guided translationally relative to the outer guide tube via a linear rolling bearing, wherein the linear rolling bearing has a cage in which a plurality of rolling elements are rotatably guided, wherein the rolling elements roll on a plurality of inner rolling tracks of the inner extension tube and a plurality of outer rolling tracks, wherein the outer rolling tracks are each formed on separate outer track elements extending in the axial direction and the cage and the inner extension tube are substantially square-shaped.

[0017] This offers the advantage of creating a particularly compact radial control unit that is also cost-effective to manufacture. This allows for the design of a particularly low-friction, yet still economically attractive telescopic extension device, which also allows for the use of more compact and reduced-power adjustment motors.

[0018] The separate outer track elements are preferably strip-shaped. Preferably, there is no connection between the separate outer track elements in the circumferential direction.

[0019] According to a further preferred development of the invention, the cage can also be made of a plastic. The cage can be constructed in one piece or in multiple pieces.

[0020] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the linear rolling bearing has a number of separate outer track elements which corresponds to the number of edges of the cage and / or the inner extension tube.

[0021] According to a further particularly preferred embodiment of the invention, it can be provided that the outer track elements are connected to the cage in a frictional and / or positively locking manner, so that a modular construction of the linear rolling bearing is enabled.

[0022] Furthermore, the invention can also be further developed in such a way that the outer track elements are formed from a sheet metal, in particular a spring sheet, which on the one hand allows cost-effective production and on the other hand can provide sufficiently high wear resistance.

[0023] It is further preferred that the outer track elements are shaped substantially identically, which has a positive influence on the manufacturing costs due to the high degree of uniformity.

[0024] In a likewise preferred embodiment of the invention, it can also be provided that the outer track elements have a first radially inwardly offset raceway section and a second radially inwardly offset raceway section and the rolling elements roll in a load-transmitting manner between the respective inner rolling track and the respective raceway section, and the outer track elements further have a radially outwardly offset raceway section which, together with the cage, forms a first return channel and a second return channel for the rolling elements.

[0025] According to the invention, the outer track elements each have a radially inwardly pointing tab at their two axial ends, so that the outer track elements encompass the cage.

[0026] According to the invention, the outer track elements are fixed to the outer guide tube.

[0027] Preferably, the pull-out device can be pulled in and out by means of a motor drive unit.

[0028] Finally, the object of the invention can also be achieved by a steer-by-wire system comprising a length-adjustable control unit according to one of claims 1-9.

[0029] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0030] It shows: Fig. 1 a steer-by-wire system of a motor vehicle in a schematic block diagram, Fig. 2 a length-adjustable operating unit with a linear roller bearing in a cross-sectional view, Fig. 3 a length-adjustable control unit with a linear roller bearing in a front view, Fig. 4 a length-adjustable control unit with a linear roller bearing in an axial section view, Fig. 5 a cage of the linear rolling bearing in a perspective view.

[0031] The Fig. 1 shows a steer-by-wire system 20 comprising a length-adjustable control unit 1, which is Fig. 2-4 is explained in more detail.

[0032] The Fig. 2-4 each show a length-adjustable operating unit 1 for influencing a driving direction of a motor vehicle 2 by a user, comprising a telescopic extension device 4 which can be coupled to a steering means 33 and has an outer guide tube 5 in which an inner extension tube 6 is arranged and is guided translationally relative to the outer guide tube 5 via a linear roller bearing 7.

[0033] The linear roller bearing 7 has a cage 8 in which a plurality of rolling elements 9 are rotatably guided. The rolling elements 9 roll on a plurality of inner rolling tracks 10 of the inner extension tube 6 and a plurality of outer rolling tracks 11. The outer rolling tracks 11 are each formed on separate outer track elements 12 extending in the axial direction. These outer track elements 12 are fixed to the outer guide tube 5, for example, by means of a press fit.

[0034] The cage 8, made of plastic, and the inner extension tube 6 are essentially square-shaped. In the embodiment shown, the linear roller bearing 7 thus has a number of separate outer track elements 12, which corresponds to the number of edges 13 of the cage 8 and the inner extension tube 6.

[0035] The outer track elements 12 are formed from a spring sheet and are frictionally and / or positively connected to the cage 8.

[0036] The outer track elements 12 each have a first radially inwardly offset raceway section 14 and a second radially inwardly offset raceway section 15, wherein the rolling elements 9 roll in a load-transmitting manner between the respective inner rolling track 10 and the respective raceway section 14, 15.

[0037] The outer track elements 12 further have a radially outwardly offset raceway section 16, which together with the cage 8 forms a first return channel 17 and a second return channel 18 for the rolling elements 9. The rolling elements 9 can thus circulate endlessly in a first and a second endless circulation channel 22, 23, wherein the circulation channel 22, 23 has a load channel 24, 25 parallel to the longitudinal axis, a return channel 17, 18 parallel to the longitudinal axis and two deflection channels endlessly connecting the load channel 24, 25 and the return channel 17, 18, which can be clearly seen from the synopsis of Fig. 5, Fig. 4 and Fig. 2 can be recognized.

[0038] The outer track elements 12 each have a radially inwardly pointing tab 19 at their two axial ends, so that the outer track elements 12 encompass the cage 8, which can be clearly seen from the illustration of the Fig. 3 can be understood.

[0039] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols 1 control unit 2 motor vehicles 4 pull-out device 5 Guide tube 6 Extension tube 7 linear roller bearings 8 cage 9 rolling elements 10 inner roller track 11 Outer roller track 12 outer track elements 13 edges 14 Career Stage 15 career stages 16 career stages 17 Return channel 18 Return channel 19 Tab 20 Steer-by-wire system 22 Circulation channel 23 Circulation channel 24 load channels 25 load channel 33 steering devices

Claims

[1] Length-adjustable operating unit (1) for influencing a driving direction of a motor vehicle (2) by a user, comprising a telescopic extension device (4) which can be coupled to a steering means (33) and has an outer guide tube (5) in which an inner extension tube (6) is arranged and is guided translationally relative to the outer guide tube (5) via a linear rolling bearing (7), wherein the linear rolling bearing (7) has a cage (8) in which a plurality of rolling elements (9) are rotatably guided, wherein the rolling elements (9) roll on a plurality of inner rolling tracks (10) of the inner extension tube (6) and a plurality of outer rolling tracks (11), wherein the outer rolling tracks (11) are each formed on separate outer track elements (12) extending in the axial direction, and the cage (8) and the inner extension tube (6) are substantially square-shaped, characterized bythat the outer track elements (12) each have a radially inwardly pointing tab (19) at their two axial ends, so that the outer track elements (12) engage around the cage (8), wherein the outer track elements (12) are fixed to the outer guide tube (5). [2] Control unit (1) according to claim 1, characterized by that the cage (8) is made of a plastic. [3] Control unit (1) according to one of the preceding claims, characterized by that the linear rolling bearing (7) has a number of separate outer track elements (12) which corresponds to the number of edges (13) of the cage (8) and / or the inner extension tube (6). [4] Control unit (1) according to one of the preceding claims, characterized by that the outer track elements (12) are frictionally and / or positively connected to the cage (8). [5] Control unit (1) according to one of the preceding claims, characterized bythat the outer track elements (12) are formed from a sheet metal, in particular a spring sheet. [6] Control unit (1) according to one of the preceding claims, characterized by that the outer track elements (12) have a first radially inwardly offset raceway section (14) and a second radially inwardly offset raceway section (15) and the rolling elements (9) roll in a load-transmitting manner between the respective inner rolling track (10) and the respective raceway section (14, 15), and the outer track elements (12) further have a radially outwardly offset raceway section (16) which, together with the cage (8), forms a first return channel (17) and a second return channel (18) for the rolling elements (9). [7] Steer-by-wire system (20) comprising a length-adjustable operating unit (1) according to one of the preceding claims.

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