DE102018209236A1 - Steering column with feedback actuator - Google Patents

Abstract

The present invention relates to a steering column (1) with a feedback actuator for a steer-by-wire steering system of a motor vehicle, comprising a steering spindle (3) rotatably mounted in a shell unit (2) about a longitudinal axis (L) and an actuator unit ( 6), which has one of an electric servomotor (62) about a rotor axis (R) rotatably driven actuator shaft (63) which is connected to the steering shaft (3) torque-locking. In order to provide a steering column (1) with an improved feedback actuator, which can be produced with little effort and flexibly adapted, the invention proposes that the actuator shaft (63) via a offset compensating trained decoupling device (7) with the steering shaft (3) torque-locking connected is.

Description

State of the art

The invention relates to a steering column with a feedback actuator for a steer-by-wire steering system of a motor vehicle, comprising a steering shaft rotatably mounted in a shell unit about a longitudinal axis and an actuator unit having an actuator shaft rotatably driven by an electric servomotor about a rotor axis , which is connected to the steering shaft torque-locking.

Steer-by-wire steering systems for motor vehicles counteract manual steering commands of the driver, such as conventional mechanical steering systems, by rotation of a steering wheel which is fastened to the steering column on the steering column on the steering spindle. A steering command introduced into the steering spindle is detected by means of rotational angle or torque sensors, and an electrical control signal generated therefrom is delivered to a steering actuator which adjusts a corresponding steering angle of the wheels by means of an electric actuator.

In steer-by-wire systems, the driver of the steered wheels receives no direct mechanical feedback on the steering line, which in conventional mechanically coupled steering as reaction or restoring torque depending on the road condition, the vehicle speed, the current steering angle and other operating conditions is reported back to the steering wheel. However, a lack of haptic feedback makes it more difficult for the driver to reliably detect current driving situations and to carry out appropriate steering maneuvers, which impairs the vehicle's steering ability and thus the driving safety.

In order to produce a realistic driving feel, it is known in the prior art to detect parameters such as vehicle speed, steering angle, steering reaction torque and the like from an actual instantaneous driving situation or to calculate them in a simulation and to form from these variables a feedback signal which is fed into a feedback actuator. The feedback actuator is integrated into the steering column and has an actuator unit that includes an electric actuator serving as a hand torque or steering wheel actuator. By means of a servomotor, this actuator couples depending on the feedback signal a the real reaction torque corresponding restoring torque (feedback torque) via the steering shaft in the steering wheel. Such "force-feedback" systems give the driver the impression of a real driving situation as in a conventional, mechanically coupled steering, which facilitates an intuitive response.

In the prior art is from the WO 2010/112512 A1 a steering column with a feedback actuator known, which has one of an electric servomotor to rotate about a rotor axis driven actuator shaft. The actuator shaft is formed by the rotor shaft of the servomotor, and is formed integrally with the steering shaft.

The known solution requires by the direct coupling of the rotor shaft with the steering shaft for generating a defined restoring moment a highly accurate and complex motor control. In addition, the integrated design of the steering shaft with the rotor is expensive to manufacture and assemble, and inflexible in terms of adaptation to different types of steer-by-wire steering systems.

In view of the above-explained problem, it is an object of the present invention to provide a steering column with an improved feedback actuator, which can be produced with less effort and flexibly adapted.

Presentation of the invention

This object is achieved by a steering column with the features of claim 1. Advantageous further developments will become apparent from the dependent claims.

In a steering column with a feedback actuator for a steer-by-wire steering system of a motor vehicle, comprising a steering shaft rotatably mounted in a shell unit about a longitudinal axis and an actuator unit, which has one of an electric servomotor about a rotor axis rotatably driven actuator shaft, the is connected torque-lock with the steering shaft, the invention provides that the actuator shaft is connected torque-locking manner via an offset compensating trained decoupling device with the steering shaft.

Characterized in that the steering shaft is formed separately from the actuator shaft, an advantageous, rational production and assembly is possible, similar to a conventional steering column. A bearing of the steering shaft in two bearings, preferably rolling bearings, which are arranged in the shell unit at a distance in the direction of the longitudinal axis, allows an optimization of the rigidity and resonance frequency.

The actuator unit can be structurally designed and dimensioned independently of the space available in the area of the steering spindle become. As a result, a flexible adaptation to differently designed steering columns with relatively little effort is possible. For example, between the servomotor and the actuator shaft driven therefrom, a transmission can be used, so that a smaller constructive actuator can be used. For special applications, a direct drive of the actuator shaft is also conceivable.

Both for the production, as well as for a safe and low-wear continuous operation, it is advantageous that between the actuator shaft and the steering spindle, a displacement compensating trained decoupling device is arranged. By means of the decoupling device, a restoring torque generated by the feedback actuator can be transmitted from the actuator unit to the steering spindle. It is advantageous that a possible axial offset between the rotor axis of the actuator shaft and the longitudinal axis of the steering shaft, which may occur due to tolerances in the assembly of the actuator unit, or even at extremely high loads during operation, for example, a radial and / or angular misalignment of the decoupling device can be compensated. As a result, the actuator shaft and the steering shaft are effectively decoupled from each other with respect to the transmission of potentially damaging radial and axial forces. During operation, friction, noise and wear are reduced.

For the optimized construction of a steering column, it is advantageous that a spatially clearly defined bearing of the steering spindle in two spaced on the longitudinal axis bearings, and also a defined storage of the actuator shaft can be done without an over-defined storage situation occurs, the problematic bearing loads even at low Misalignment or misalignment can result. Thanks to the decoupling according to the invention, the bearing arrangements of the actuator unit and the steering spindle can be optimized largely independently of each other, whereby the vibration behavior, rigidity, wear behavior and reliability can be improved.

The actuator shaft can be accommodated approximately in a middle section in the actuator unit. Furthermore, it is conceivable and possible that the actuator shaft is longer and extends to the edge closer to the rotor axis out or even protrudes from the actuator unit.

The decoupling device can be configured radially and / or angularly and / or axially offset compensating. As a result, the actuator unit can be fastened to the steering column with lower tolerance requirements with regard to the exact coaxial alignment of rotor and longitudinal axis, as a result of which the manufacturing and assembly costs can be reduced. It is particularly advantageous that the decoupling device is designed to compensate for radial and angular misalignment, whereby the main causes of harmful bearing loads are largely avoided.

Preferably, the decoupling device may be attached to an actuator end of the steering shaft. In this embodiment, the steering shaft and the actuator shaft are arranged one behind the other in the axial direction. Except for a possible axial offset, which can be compensated by the decoupling device, the rotor axis and the longitudinal axis are aligned. The actuator end is based on the direction of travel of the vehicle at the front, facing away from the driver end of the steering shaft. There, the actuator is mounted on the vehicle side.

At the actuator-remote, driver-side end, the steering spindle may preferably have fastening means for attaching a steering wheel, for example in the form of a fastening section comprising interlocking and / or force-locking elements.

The decoupling device can have an actuator clutch which can be connected to the actuator shaft and a spindle clutch which can be connected to the steering spindle. The actuator clutch forms the input clutch, via which a restoring torque can be introduced from the actuator shaft into the decoupling device, and the spindle clutch forms the output clutch for transmitting the restoring torque from the decoupling device to the steering shaft. The actuator and spindle clutch can form, force and / or frictionally cooperating coupling elements which cooperate with corresponding coupling elements on the actuator shaft and the steering shaft.

The decoupling device may have an elastic transmission element. The transmission element is used to transmit the restoring torque between the actuator shaft and the steering shaft, wherein it allows a transverse deformation to accommodate a possible radial and / or angular displacement yielding. The transmission element may comprise one or more spring elements or elastomer bodies which are arranged in the torque connection, for example between an actuator coupling and a spindle coupling of the decoupling device. Preferably, the transmission element has a predetermined, relatively high torsional rigidity in order to be able to transmit a restoring moment in a reaction-fast manner and with a low angular distortion. The flexural stiffness can be specified that for a given maximum allowable axis offset over the Transmission element between the actuator shaft and steering shaft transmitted transverse forces remain below a predetermined limit.

A preferred embodiment provides that the transmission element has at least one elastomeric body. The elastomeric body may comprise one or more elastically deformable elements, for example a rubber body or a steel pad, one or more spring elements, which may have a round or non-circular inner cross section, which is mounted as a torque transmitting element between the actuator and spindle coupling. The elasticity and stiffness can be chosen so that the torsional deformation during torque transmission remains within predetermined tolerances, whereby the required compensation of shaft misalignment is ensured. The elastomeric body may be connected to an actuator clutch and a spindle clutch, for example by means of a material and / or positive connection, which is suitable for transmitting the restoring torque, for example a bond or welding.

In an advantageous embodiment, the elastomer element may be tubular, formed with a hollow cylindrical basic shape. The spindle coupling may comprise an inner ring connected to the elastomeric body, to which the steering spindle can be connected in a torque-locking manner. The elastomeric body may be formed between the inner ring and an outer ring. The tubular inner ring may be mounted in the opening, and in turn may have a non-circular inner cross-section, in which the akuatorseitige end of the steering shaft can interlock positively engage the transmission of the restoring moment. As a result, a spindle clutch can be formed. For example, the inner cross section corresponding to the outer cross section of the steering spindle may be polygonal, or may have a so-called trefoil profile, which is formed from a cylindrical or polygonal basic profile, which has arcuate radial and / or recesses. With the elastomeric body, which consists for example of a rubber material, the inner ring can be positively connected, and alternatively or preferably additionally cohesively, for example by gluing, welding or vulcanization. As a result, the transmission element has the spindle coupling.

A tubular spindle coupling with a non-circular opening cross-section described above into which the actuator-side end of the steering spindle can be inserted in a form-fitting axial, in the direction of the longitudinal axis, further has the advantage of easy mounting. The actuator unit can be easily fixed via a suitable connection in the axial direction on the actuator side, in the direction of travel front end of the shell unit, wherein the steering shaft engages positively in the decoupling device according to the invention. Possibly occurring in this connection axial offset between the actuator shaft and the steering shaft is compensated by the decoupling, and the steering shaft is decoupled against unwanted and potentially affecting cross loads. As a result, the manufacturing and assembly costs can be reduced.

Furthermore, an outer ring which can be connected to the actuator coupling can be attached to the elastomer element. For example, on a hollow cylindrical elastomeric element outside a tubular outer ring material and / or positively fixed, which is connectable to a corresponding receiving means of the actuator shaft.

An embodiment may provide that the transmission element has at least one rigid reinforcement element. By means of one or more reinforcing elements, which lie in the force flow of the torque transmission together with the transmission element, the deformability or the rigidity of the decoupling device can be intentionally predetermined or limited. A reinforcing element may preferably be formed of a material having a higher rigidity than the elastomer material, for example, one or more pin-shaped metal or steel elements may be connected to a rubbery elastomeric body, and preferably embedded therein and firmly bonded. The pin-shaped elements can be arranged parallel to the longitudinal axis, whereby the torsional stiffness and the flexural rigidity can be adjusted. It is conceivable and possible that one or more reinforcing elements are formed as ribs or spring elements, such as a plate spring, which are formed parallel to each other and are arranged perpendicular to the longitudinal axis. The reinforcing elements can furthermore be arranged X-shaped or V-shaped. Furthermore, an overload protection can be realized by a reinforcing element, which further allows a torque transmission in case of damage to the elastomeric body.

An advantageous embodiment of the invention provides that the coupling device has an overload clutch with arranged in loose form fit positive locking elements. The overload clutch may be arranged in the torque flow between the actuator shaft and the steering shaft parallel to the transmission element. In normal operation, when the transmission element is twisted by the transmitted restoring torque within predetermined angular tolerances, they have with each other corresponding interlocking elements, the input side rotatably connected to the Akuatorwelle and the output side are connected to the steering shaft, with respect to rotation about the longitudinal axis angular play with each other, and do not contribute to the torque transmission. Only if the transmission element is twisted by overloading or damage beyond the angular tolerance addition, the interlocking elements come into engagement with each other in the circumferential direction and form a form fit between the actuator shaft and the steering shaft effective for torque transmission. For example, a form-fitting element having a connected via an actuator coupling with the actuator shaft flange having a non-round positive connection opening through which the corresponding non-circular steering shaft extends in the axial direction in loose positive engagement, being connected in the course in existing positive connection via a spindle coupling torque-locking with the decoupling device ,

Preferably, it can be provided that the jacket unit has an inner jacket tube telescopically arranged in an outer jacket tube, and the steering spindle has an inner spindle telescopically arranged in an outer spindle. As a result, a known per se, adjustable in the longitudinal direction parallel to the longitudinal axis steering column assembly is realized. The actuator unit can be fixed at the front, actuator end of the lower, body-side axially fixed shell unit.

An advantageous embodiment can provide that the steering spindle is mounted in the shell unit in two spaced bearings in the direction of the longitudinal axis bearings. By the two bearings a spatially defined storage is generated, for example, the steering shaft can be mounted in two rolling bearings in the shell unit, whereby a high rigidity of the steering column is guaranteed. In the case of a longitudinally adjustable steering column, a driver-side, rear steering spindle, which is torque-connected with an actuator-side front steering spindle, can be telescopically mounted in two bearings in a driver-side, rear jacket tube which can be telescoped relative to an actuator-side, front jacket tube. The actuator unit may be connected to the front shell, wherein the actuator shaft according to the invention is connected via the decoupling device with the front steering shaft. The fact that an offset caused by high transverse or bending forces offset axis, an improved transmission of restoring moments and telescoping is guaranteed.

The rear steering spindle may be a tubular outer spindle, on the driver side, a steering wheel is attachable, and in the actuator side, from the front as an inner spindle formed front steering shaft torque-locking and telescoping dips. The front, actuator-side jacket may be formed as an outer jacket tube, in which from the rear formed as an inner jacket tube rear, driver-side jacket dips telescopically. The telescopic arrangements of the steering spindle and the jacket unit can in principle also be designed reversed in each case.

list of figures

• 1 eine erfindungsgemäße Lenksäule in einer schematischen perspektivischen Ansicht,
• 2 die Lenksäule gemäß 1 in einer weiteren perspektivischen Ansicht,
• 3 ein Längsschnitt durch eine Lenksäule gemäß 1,
• 4 eine teilweise perspektivische Ansicht der Lenksäule gemäß 1 in auseinander gezogenem Zustand,
• 5 die Entkopplungseinrichtung in einer vergrößerten Detailansicht von 4,
• 6 eine weitere Ansicht wie in 5 in auseinander gezogenem Zustand,
• 7 eine Explosionsdarstellung der Entkopplungseinrichtung der Lenksäule gemäß der vorangehenden Figuren.

Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail show:

• 1 a steering column according to the invention in a schematic perspective view,
• 2 the steering column according to 1 in a further perspective view,
• 3 a longitudinal section through a steering column according to 1 .
• 4 a partial perspective view of the steering column according to 1 in an extended state,
• 5 the decoupling device in an enlarged detail view of 4 .
• 6 another view like in 5 in an extended state,
• 7 an exploded view of the decoupling device of the steering column according to the preceding figures.

Embodiments of the invention

This object is achieved by a steering column for a motor vehicle having the features of claim 1. Advantageous developments emerge from the subclaims.

In the various figures, the same parts are always provided with the same reference numerals and are therefore usually named or mentioned only once in each case.

1 and 2 show in different perspective views a steering column 1 a steer-by-wire steering system, in 1 from the back left, and in 2 from the back right, in each case based on the direction of travel.

The steering column comprises a jacket unit 2 in which a steering spindle 3 around its longitudinal axis L is rotatably mounted. At its rear, driver-side end, the steering shaft 3 a fixing section 30 for attaching a steering wheel, not shown here.

A carrying unit 4 has mounting holes 41 for attachment to a not shown Vehicle body on, and has two side cheeks facing down 42 , between which the shell unit 2 is included.

A locking device 5 can by turning a locking lever 51 that with a cocking axis 52 is connected, optionally switched to fixing or release position. In fixing position is the shell unit 2 positionally fixed between the side walls 42 clamped. In the release position, the jacket unit 2 for height adjustment of the steering column 1 around a horizontal pivot axis arranged in the front area 53 be pivoted in the height direction H up or down, as indicated by the double arrow.

The shell unit 2 is formed by an outer jacket tube 21 in which an inner jacket tube 22 in the longitudinal direction, ie the direction of the longitudinal axis L is recorded telescopically, as indicated by the double arrow.

The steering spindle 3 has an internal spindle 31 on, which telescopes longitudinally in an outer spindle 32 is used. At the rear, driver-side end has the outer spindle 32 the attachment section 30 on. The outer spindle 32 is in two camps 33 , Rolling bearings preferred, the distance in the direction of the longitudinal axis L have, in the inner jacket tube 22 around the longitudinal axis L rotatably mounted. The arrangement of the bearings 33 is in 3 and 4 recognizable, in 4 for a better overview, the outer jacket tube 21 is omitted.

The inner spindle 31 has a non-circular outer profile, in the example shown a so-called cloverleaf profile, which has a square basic shape with arcuate cross-section, groove-shaped recesses 750 Has. The outer profile is with respect to rotation about the longitudinal axis L positively in the inner profile of the outer spindle 32 used, like 5 is clearly removable.

At the front end of the jacket unit 2 is an actuator unit 6 attached, which has a flange adapter 61 with the front, actuator side end of the outer shell 21 connected is. The actuator unit 6 includes an electric servomotor 62 of which an actuator shaft via a transmission, not shown in detail 63 around a rotor axis R is rotationally driven, as in the longitudinal section of 3 is recognizable.

The actuator shaft 63 is in two rotor bearings 64 , the distance from each other in the direction of the rotor axis R have, in the actuator unit 6 rotatably mounted. The actuator shaft 63 can, as in 3 represented, for example in a central portion in the actuator unit 6 be included. Furthermore, it is conceivable and possible that the actuator shaft 63 is longer and up to the edge closer to the rotor axis R or even from the actuator unit 6 protrudes.

With optimum assembly and without the action of high bending loads is the rotor axis R identical to the longitudinal axis L , tolerances and / or high external forces acting from the outside can cause an axial offset, namely an angular and / or transverse offset.

Between the actuator shaft 63 and the inner spindle 31 is a decoupling device 7 used, based on the representations in the 3 to 7 is explained.

With the actuator shaft 63 is a hollow cylindrical actuator clutch 71 , in the example shown in one piece, formed, the pot-shaped to the steering shaft 3 is open.

In the actuator coupling 71 is a transmission element 72 used rotatably. This has a hollow cylindrical tubular elastomer body 73 on, for example, a rubber body. On the outer circumferential surface is a pipe section-shaped outer ring 74 attached, for example by cohesive connection such as vulcanization, gluing or the like. The outer ring 74 is non-rotatable with the actuator coupling 71 connected.

Inside in the opening of the elastomeric body 73 is an inner ring 75 attached, the one form fit with respect to rotation about the longitudinal axis L with the outer cross section of the inner spindle 31 corresponding, in the example cloverleaf-shaped inner cross-section has. The inner ring 75 can also cohesively with the elastomeric body 73 be connected, and in addition by the non-round cloverleaf, the axially continuous, groove-shaped recesses 750 has to be positively fixed.

In the inner ring 75 can the inner spindle 31 in the longitudinal direction similar to the outer spindle 32 interlock positively. As a result, the inner ring forms a spindle coupling for the torque-locking connection of the elastic transmission element 72 and thereby the decoupling device 7 with the steering spindle 3 ,

With the elastomer body 73 are several pin-shaped reinforcing elements 76 connected, preferably metal pins, such as steel pins, which are parallel to the longitudinal axis L preferably indissolubly embedded in the elastic material. The reinforcing elements 76 can get along the groove-shaped indentations 750 extend, and an increase in the torsional stiffness of the transmission element 72 cause.

It is possible that the reinforcing elements 76 with respect to a torque transmission serve as limiting elements. For this they can with respect to the groove-shaped recesses 750 in loose fit in the circumferential direction elastically in the elastomer body 73 being held. As a result, the torsional rigidity can be increased, and the maximum torsion can be limited by the fact that the reinforcing elements 76 in engagement with the recesses 750 come.

At the actuator clutch 71 is an overload clutch 77 appropriate. This is disc-shaped in the example and has a central coupling opening 770 on. The coupling opening 770 takes in the assembled state, such as in the 3 or 6 shown the non-circular inner shaft 31 with respect to rotation about the longitudinal axis L in loose fit on. By this is meant that the inner shape of the coupling opening 770 with the outer shape of the inner shaft 31 corresponds, for example, how this is clover-shaped, with clearance in normal operation, and no torque is transmitted. Only when the transmission element 72 is twisted by a high torque beyond a predetermined limit, the positive connection between the coupling opening 770 and inner spindle 31 effective, and the torque is from the actuator coupling 71 and the overload clutch 77 on the transmission element 72 past the steering spindle 3 transfer.

Due to its elasticity, the elastomer body 73 an axial offset between the outer ring 74 and the inner ring 75 absorb elastically, whereby an angular and / or transverse offset between the rotor axis R and longitudinal axis L can be compensated, for example, by an extremely high transverse load on the jacket unit 2 and / or tolerances in the assembly of the actuator unit 6 on the jacket unit 2 can occur.

The assembly of the actuator unit 6 is simplified by the fact that when flanging the adapter 61 the inner spindle 31 positively in the inner ring 75 dips, whereby the torque-locking clutch is generated.

Due to the offset compensation of the decoupling device 7 can the steering spindle 3 as shown twice in warehouses 33 in the shell unit 2 be stored, and also the actuator shaft 63 can in the camps 64 be stored twice in the actuator unit, without potentially damaging forces on the steering shaft 3 and / or the jacket unit 2 Act.

LIST OF REFERENCE NUMBERS

1

steering column

2

shell unit

21

Outer casing

22

Inner sheath tube

3

steering shaft

30

attachment section

31

inner spindle

32

outer spindle

33

camp

4

support unit

41

mounting holes

42

Sidewall

5

Locking device

51

Locking lever

52

release axle

53

swivel axis

6

actuator

61

adapter

62

servomotor

63

actuator shaft

64

rotor bearing

7

decoupling device

71

Aktuatorkupplung

72

transmission element

73

elastomer body

74

outer ring

75

Inner ring / spindle coupling

76

reinforcing element

77

Overload clutch

770

coupling opening

L

longitudinal axis

R

rotor axis

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/112512 A1 [0005]

Claims (11)

Steering column (1) with a feedback actuator for a steer-by-wire steering system of a motor vehicle, comprising a steering spindle (3) rotatably mounted in a shell unit (2) about a longitudinal axis (L) and an actuator unit (6) having a of an electric servomotor (62) about a rotor axis (R) rotatably driven actuator shaft (63) which is torque-connected to the steering shaft (3), characterized in that the actuator shaft (63) via an offset compensating trained decoupling device (7) the steering spindle (3) is connected torque-locking. Steering column after Claim 1 , characterized in that decoupling means (7) is formed radially and / or angular and / or axialverschiebungausgleichend. Steering column according to one of the preceding claims, characterized in that the decoupling device (7) is attached to an actuator-side end of the steering spindle (3). Steering column according to one of the preceding claims, characterized in that the decoupling device (7) has an actuator coupling (71) which can be connected to the actuator shaft (63) and a spindle coupling (75) which can be connected to the steering spindle (3). Steering column according to one of the preceding claims, characterized in that the decoupling device (7) has an elastic transmission element (72). Steering column after Claim 5 , characterized in that the transmission element (72) comprises at least one elastomeric body (73). Steering column after Claim 5 or 6 , characterized in that the transmission element (72) comprises at least one rigid reinforcing element (76). Steering column according to one of the Claims 6 or 7 , characterized in that the spindle clutch comprises an elastomeric body (73) connected to the inner ring (75), with which the steering spindle (3) is connected in a torque-locking manner. Steering column according to one of the preceding claims, characterized in that the decoupling device (7) has an overload clutch (77) with the form-locking elements (770, 31) arranged in loose positive engagement. Steering column according to one of the preceding claims, characterized in that the jacket unit (2) has an inner jacket tube (22) telescopically arranged in an outer jacket tube (21), and the steering spindle (3) has an inner spindle (31) telescopically arranged in an outer spindle (32) , Steering column according to one of the preceding claims, characterized in that the steering spindle (3) in the shell unit (2) is mounted in two spaced apart in the direction of the longitudinal axis (L) bearings (33).

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