Force feedback actuator of a steering column

Abstract

Force feedback actuator of a steering column of a vehicle with an electromagnetic braking device (1), wherein the electromagnetic braking device (1) has a shaft arranged along an axis of rotation, a stator (4, 16, 20) and a rotor (3, 17, 19) and with at least one housing element arranged around the shaft (2), wherein the stator (4, 16, 20) has a coil carrier (6) with at least one coil (5), wherein the coil carrier (6) has a friction surface (7) and wherein at least one magnetizable, annular elastic spring sheet (10, 21) is arranged between the friction surface (7) and the rotor (3, 17, 19), characterized in that the annular elastic spring sheet (10) has at least one slot (12) which extends completely through the spring sheet (10) in the axial direction and thus defines two free arc-shaped legs,which are elastically deflectable in the radial direction and which, when the coil (5) is energized, bear against the friction surface (7), and the spring sheet furthermore has a fastening zone (13) opposite the slot (12) for a connecting element (11), which is arranged such that it connects the spring sheet (10, 21) to a rotating component and / or the rotor (3, 17, 19).

Description

Field of invention

[0001] The present invention relates to a force feedback actuator of a steering column of a vehicle and a steer-by-wire steering system with such a force feedback actuator. Background of the invention

[0002] Modern steering systems allow the steering wheel to be adjusted in height and reach, i.e., its axial position. In such systems, the steering column or shaft components are movable relative to each other, for example, in a telescopic configuration. This allows the steering wheel to be positioned optimally for the driver.

[0003] Furthermore, steer-by-wire steering systems are also known, in which the mechanical connection between the steering wheel and the axle to be steered via the steering column is omitted, and the steering of the wheels is controlled by corresponding signals. Two types of steer-by-wire steering systems can be distinguished in particular: steer-by-wire steering systems with a force feedback actuator located far from the steering wheel and steer-by-wire steering systems with a force feedback actuator located near the steering wheel.

[0004] Steer-by-wire systems with a force feedback actuator located far from the steering wheel utilize familiar crash elements, such as metal strips that deform plastically when a defined force is exceeded. Plastic sleeves on the telescopic steering shaft, which are destroyed by a predetermined force, are also known. Steer-by-wire systems with a force feedback actuator located near the steering wheel eliminate the need for the telescopic steering shaft.

[0005] Furthermore, it is known that such force-feedback actuators incorporate electric motors, spring mechanisms, and braking devices that enable targeted feedback and deceleration, even to the point of locking the steering wheel, for example, at virtual stops. Magnetorheological braking devices can be used in this context.

[0006] DE 10 2011 013 957 A1 shows a brake of a steering wheel lock in an EPSc system and reveals a spring element which is actuated by means of a magnetic force.

[0007] US Patent 2002 / 0108804 A1 discloses a powder brake in which the rotor and the stator are equipped with an excitation coil whose magnetic flux leads to powder-filled gaps, causing the iron powder contained therein to form adhering, braking “threads” or “chains”.

[0008] EP 2 130 742 A1 discloses a speed superposition device for a motor vehicle steering system, comprising an output shaft and a drive shaft aligned axially and rotatably mounted on a body-fixed support structure. The device includes an auxiliary drive with a rotor connected to a gearbox, as well as an adjustable locking device for selectively coupling the shafts in a rotationally fixed manner. The rotor is arranged coaxially with the shafts and is rotationally fixed to a ferromagnetic or permanent magnet first contact element, the coupling being effected by frictional engagement with a second contact element that is rotationally fixed to the support structure. The required contact force for the frictional force is generated magnetically, and the first contact element is designed as a resiliently bendable disk that is movable in the axial direction.

[0009] DE 199 06 703 A1 discloses an actuator for superimposed steering intervention in a vehicle steering device, comprising an input shaft, an output shaft, an electric motor, and an electromagnetic brake. The electric motor is designed such that the rotor is permanently magnet excited and the motor housing is fixed in a non-rotatable position. The electromagnetic brake is designed to block relative movement between the input and output shafts when closed. A particular feature is that the electromagnet of the brake is attached to the motor housing and has a magnetic yoke divided into a fixed and a rotatable yoke part, one of which is non-rotatably connected to the rotor shaft and the other to the output shaft.

[0010] DE 10 2015 224 602 A1 discloses an adjustable steering column for a steer-by-wire steering system of a motor vehicle. This column comprises an actuating unit with a steering spindle rotatably mounted about a longitudinal axis in a sleeve. The sleeve consists of a first sleeve tube in which a second sleeve tube is mounted so as to be rotationally fixed and axially displaceable by telescoping. An actuating drive enables the axial extension and retraction of the second sleeve tube relative to the first sleeve tube, wherein a threaded spindle runs inside the first sleeve tube and a spindle nut is attached to the second sleeve tube.

[0011] DE 10 2010 002 892 A1 discloses a power steering system, in particular an electric power steering system for a vehicle. This system comprises a drive screw driven by a servo motor, consisting of a nut mounted axially immovably in a frame and an axially displaceable component whose thread engages with a thread on the nut. A rolling bearing for axially and radially supporting the nut in the frame is also described, wherein at least the inner ring or the outer ring of the rolling bearing is divided into two ring parts along a parting plane. These ring parts are installed in the frame with an axial distance from each other and are spring-loaded against each other by at least one spring element to minimize operating noise and maintain the operating clearance within a predetermined range. Summary of the invention

[0012] It is therefore an object of the present invention to provide a force feedback actuator with an improved powderless, sealless electromagnetic braking device.

[0013] According to the invention, this problem is solved by a force feedback actuator of a steering column of a vehicle with an electromagnetic braking device, wherein the electromagnetic braking device has a shaft arranged along an axis of rotation, a stator and a rotor and with at least one housing element arranged around the shaft, wherein the stator has a coil carrier with at least one coil, wherein the coil carrier has a friction surface and wherein at least one magnetizable, annular elastic spring sheet is arranged between the friction surface and the rotor.

[0014] This design, using a spring-loaded sheet, allows for improved tactile feedback and increased frictional force. This occurs because, when the coils are energized, the spring-loaded sheet is drawn directly onto the coil carrier, creating numerous small friction contacts that, on average, produce a uniform frictional force. This effect can be further enhanced by applying an additional friction layer to the spring-loaded sheet, such as friction lacquer, friction paper, a sliding layer, Teflon, and / or by applying additional grease.

[0015] Preferably, two or more coils are provided. Each coil is wound from the outside and can additionally be axially inserted into a thin plastic or steel casing. The coils can be inserted into the stator's central section from either side. The rotor is a band carrier and can be made of aluminum, metal, or plastic. Preferably, the rotor or band carrier is made of a non-magnetizable material so that the magnetizable spring lamination is attracted to the stator in the magnetic field and not to the rotor.

[0016] According to one embodiment of the invention, the stator is arranged around the outer circumference of the rotor. This entire unit forms an internal rotor. Such a design is particularly advantageous when a steering shaft is present and the rotor is arranged directly around it.

[0017] According to one embodiment of the invention, the rotor is arranged around the outer circumference of the stator. This entire unit forms an external rotor. With this arrangement, the coils can be wound particularly easily into corresponding recesses in the stator and, if necessary, potted. An advantage of such an arrangement is that the friction radius is located very far outwards, thus enabling a high frictional torque. In particular, the use of several coils in separate, machined coil grooves with additional pole and friction surfaces in between is especially easy to implement in this design and also increases the frictional torque.

[0018] Preferably, a gap is provided between the friction surface and the rotor, in which the spring plate is arranged, and the gap has a width of less than 1 mm. Furthermore, the gap also serves to protect the spring plate against deformations, such as buckling.

[0019] According to the invention, the annular elastic spring sheet has at least one slot. This serves to achieve a spring effect of the spring sheet, since the spring sheet, during radial movement, exhibits a larger or smaller circumferential angle and thus "breathes" in the slot. Advantageously, the thickness of the spring sheet can be 0.2–0.5 mm, and the width 5–50 mm, so that the cross-sectional area can transmit a sufficient amount of axial force (i.e., braking force).

[0020] The spring plate can be pre-tensioned so that it rests against the rotor, thus having an air gap (typically 0.5 mm) to the friction surfaces. Advantageously, however, the spring plate is shaped in such a way that it contacts the friction surfaces with minimal force in localized areas. This results in a precisely controllable brake response, because when energized, the spring plate does not first move through the gap and then snap onto the friction surface, but instead simply increases its contact force with the friction surface without actually moving.

[0021] Due to its magnetizability, the spring steel acts like an exceptionally thin armature, closing the open magnetic circuit of the stator. Although the spring steel is thin, it has a significantly higher permeability than the powder in magnetrheological brakes, resulting in strong attraction and enabling a high braking torque.

[0022] According to one embodiment of the invention, the annular elastic spring sheet has at least one guide contour. The guide contour can be axially oriented and formed, for example, by means of lateral grooves, partially or fully circumferentially, possibly also by means of several small tabs, or by means of a slight convexity or longitudinal grooves. Furthermore, a friction zone of the spring sheet and / or the coil carrier can have a surface modification, which is formed, for example, by affixed paper / friction paper, particularly with fibers, greasing (also in combination with paper), coating (galvanic, Teflon spray, dry film lubricant, etc.), or corrosion protection.

[0023] According to the invention, a connecting element is provided which is arranged such that it connects the spring sheet to a rotating component and / or rotor. This serves to clamp the spring sheet to the rotor. The connecting element can be screwed or otherwise connected to the external component and / or rotor. Uniform clamping (over a large area) has the advantage over other fastening techniques that the very thin spring sheet is not subjected to locally high, damaging force transmission.

[0024] According to an alternative embodiment of the invention, the annular elastic spring sheet has at least one wing element, wherein the at least one wing element contacts the stator at the friction surfaces and may optionally encompass it.

[0025] Further aspects of the invention relate to an adjustment unit and a steer-by-wire steering system with the use of a force feedback actuator according to the invention. Brief description of the drawing

[0026] Four exemplary embodiments of the invention are illustrated below with reference to ten figures. These show: Fig. 1 a longitudinal section of an electromagnetic braking device of a force feedback actuator according to a first embodiment (not shown in detail), Fig. 2 a detailed view of the electromagnetic braking device Fig. 1, Fig. 3 a representation of a rotor of the electromagnetic braking device Fig. 1, Fig. 4 a representation of a spring sheet electromagnetic braking device Fig. 1, Fig. 5 a representation of the coils of the unenergized electromagnetic braking device Fig. 1, Fig. 6 a representation of the coils energized electromagnetic braking device from Fig. 1, Fig. 7 a representation of the coil with spring steel, Fig. 8 a longitudinal section of an electromagnetic braking device of a force feedback actuator according to a second embodiment (not shown in detail), Fig. 9 a longitudinal section of an electromagnetic braking device of a force feedback actuator according to a third embodiment (not shown in detail), and Fig. 10 a longitudinal section of an electromagnetic braking device of a force feedback actuator according to a fourth embodiment and not shown in detail. Detailed description of the drawings

[0027] Fig. Figures 1 to 4 show different representations of a force feedback actuator according to the invention (not shown in detail) with an electromagnetic braking device 1 according to a first embodiment.

[0028] The electromagnetic braking device 1 has a shaft 2 arranged along an axis of rotation, which is formed integrally with a rotor 3. Furthermore, a stator 4 is formed around the outer circumference of the rotor 3. The stator 4 itself is designed such that it forms a three-part coil carrier 6, in which, in this embodiment, two coils 5 are arranged. The coils 5 are wound externally, optionally in a thin plastic or steel sheath, and are inserted axially into the coil carrier 6.

[0029] The coil carrier 6 has at least two (N-pole and S-pole of the electromagnet), and in the illustrated example three, friction surfaces 7, which are arranged opposite the outer circumference of the rotor 3. A gap 9 is formed between the friction surface 7 and the rotor 3, extending around the circumference. At least one annular elastic spring sheet 10 is arranged in this gap 9. "Annular" here means that the spring sheet extends around the outer or inner circumference of the rotor / stator. The gap 9 has a width of 1 mm and the spring sheet is 0.2 mm thick.

[0030] Furthermore, a connecting element 11 is provided, which is screwed against the rotor 3 in order to clamp the spring plate 10 in between. (see Fig. 3)

[0031] Fig. Figure 4 shows the spring plate 10, which has a slot 12 and a fastening zone 13 for the connecting element 11. The fastening zone 13 is provided here by means of two holes for screwing.

[0032] The Fig. 5 and Fig. Figures 6 each show a representation of the coils 5 in an unenergized and an energized state.

[0033] In Fig. 5 the coils 5 are unenergized, i.e. the spring plate 10 is in contact with the rotor 3 and both elements can rotate. Fig. Figure 6 shows the coils 5 in a energized state. Here, the spring plate 10 is pulled onto the coil carrier 6 (except for the clamped area of ​​the spring plate 10 with the connecting element 11). This creates friction between the rotor 3 and the spring plate 10 when the rotor rotates.

[0034] Fig. Figure 7 shows a representation of the coil 5 with different versions of the spring sheet 10. The spring sheet 10 has at least one guide contour 14, which is axially provided and is formed, for example, by means of lateral grooves, partially or fully circumferentially, by means of a slight convexity or by longitudinal grooves.

[0035] The Fig. Figures 8 to 10 show further embodiments of the invention. To simplify the description, identical components are named with the same reference numerals. The following description therefore focuses on the differences.

[0036] Fig. Figure 8 shows a second embodiment. As can be seen, the rotor 17 is formed along an axially extending side surface 15 of the stator 16 and around its outer circumference. In this embodiment as well, the stator 16 has a coil carrier 6 in which two coils 5 are arranged. The spring plate 10 is clamped to the rotor 17 by the connecting element 11.

[0037] Fig. Figure 9 shows another embodiment. Here, the spring plate 10 is clamped to a rotating outer part 18 by means of the connecting element 11. The coil carrier 6 with a coil 5 is arranged internally, as in the previous example. This is an external rotor.

[0038] Fig.Figure 10 shows another embodiment. Here, the rotor 19, e.g., made of iron, is formed around the stator 20. The stator 20 has the coil 5. A spring plate 21 is arranged between the rotor 19 and the stator 20, which has wings 22 bent towards the stator 20. The spring plate 21 is connected to the rotor 19 by forming (in section, it looks as if the spring plate 19 is split – but in section, it only has a hole through which a formed pin of the rotor 19 protrudes). Reference symbol list 1 Electromagnetic braking device 2nd wave 3 Rotor 4 Stator 5 coils 6 coil carriers 7 friction surface 9 columns 10 spring plates 11 Connecting element 12 slots 13 Mounting zone 14 Leadership contour 15 side surface 16 Stator 17 Rotor 18 Outdoor part 19 Rotor 20 Stator 21 Spring sheet 22 wings

Claims

[1] Force feedback actuator of a steering column of a vehicle with an electromagnetic braking device (1), wherein the electromagnetic braking device (1) has a shaft arranged along an axis of rotation, a stator (4, 16, 20) and a rotor (3, 17, 19) and with at least one housing element arranged around the shaft (2), wherein the stator (4, 16, 20) has a coil carrier (6) with at least one coil (5) wherein the coil carrier (6) has a friction surface (7) and wherein at least one magnetizable, annular elastic spring sheet (10, 21) is arranged between the friction surface (7) and the rotor (3, 17, 19), characterized by, that the annular elastic spring sheet (10) has at least one slot (12) which extends completely through the spring sheet (10) in the axial direction and thus defines two free arc-shaped legs which are elastically deflectable in the radial direction and which, when the coil (5) is energized, bear against the friction surface (7) and the spring sheet furthermore has a fastening zone (13) opposite the slot (12) for a connecting element (11) which is arranged in such a way that it connects the spring sheet (10, 21) to a rotating component and / or the rotor (3,17,19). [2] Force feedback actuator according to claim 1, wherein the stator (4, 16, 20) is arranged around the outer circumference of the rotor (3, 17, 19). [3] Force feedback actuator according to claim 1, wherein the rotor (3, 17, 19) is arranged around the outer circumference of the stator (4, 16, 20). [4] Force feedback actuator according to one of the preceding claims, wherein a gap (9) is provided between the friction surface (7) and the rotor (3, 17, 19) in which the spring plate (10) is arranged and wherein the gap (9) has a width of less than 1 mm. [5] Force feedback actuator according to one of the preceding claims, wherein the annular elastic spring sheet (10) has at least one guide contour. [6] Adjustment unit of a steering column of a vehicle comprising a force feedback actuator according to one of the preceding claims. [7] Steer-by-wire steering system comprising a force feedback actuator according to any one of claims 1-5 or an adjustment unit according to claim 6.

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