TURN ANGLE SENSOR ARRAY AND STEERING SYSTEM FOR A VEHICLE

Description

[0001] The present invention relates to a steering system for a vehicle of the type mentioned in the preamble of claim 1.

[0002] Such steering systems for vehicles are already known in the art in numerous embodiments. The known rotary angle sensor arrangements for determining the angle of rotation of a shaft when the shaft rotates about an axis of rotation include, among other things, a rotation encoder connected to the shaft in force transmission and a rotation sensor for detecting movement of the rotation encoder. The known steering systems for vehicles comprise a rigid steering column, a control unit, and a steering wheel rotatably mounted on the steering column by means of a shaft, wherein the aforementioned rotary angle sensor arrangement, which is connected to the control unit via signal transmission, is designed to determine the angle of rotation of the shaft when the shaft rotates about an axis of rotation.wherein the rotary angle sensor arrangement comprises a rotation encoder connected to the shaft in power transmission connection and a rotation sensor for detecting movement of the rotation encoder, and wherein a rotationally fixed first gear part of a gear unit of the rotary angle sensor arrangement is arranged on the shaft, the rotation encoder is designed as a second gear part of the gear unit engaging with the first gear part, and the gear unit simultaneously forms a fixed mechanical stop of the shaft at a first end of a rotational angular range of the shaft when the shaft is rotated counterclockwise and at a second end of the rotational angular range of the shaft when the shaft is rotated clockwise.

[0003] See, for example, JP H11 211 456 A and KR 100 802 664 B1 from which such steering systems with rotary angle sensor arrangements according to the preamble of claim 1 are known.

[0004] Furthermore, reference should be made to the following publications: DE 103 48 914 A1, US 8 004 277 B2, DE 10 2014 212 498 A1, DE 10 2015 202 733 A1, US 2020 070 871 A1 and DE 10 2008 045 195 A1.

[0005] This is where the present invention comes in.

[0006] The present invention is based on the objective of improving a steering system for a vehicle equipped with a rotary angle sensor arrangement.

[0007] This problem is solved by a steering system with the features of claim 1, characterized in that the steering wheel (4) is rotatably arranged on the steering column by means of a steering wheel actuator and the shaft (8), wherein the steering wheel actuator, which is connected to the control system for signal transmission and has an external rotor electric motor, is rigidly attached to the steering column and is connected to the steering wheel (4) for torque transmission by means of the shaft (8).and wherein the rotary angle sensor arrangement (6), which is connected to the control unit for signal transmission, further comprises a rotary angle encoder (20) connected to the steering wheel (4) in a rotationally fixed manner and connected to the steering wheel actuator in a torque-transmitting manner for determining a rotational angle of the shaft (8) when the shaft (8) is rotated about an axis of rotation (10) of the shaft (8), and a rotary angle sensor corresponding to the rotary angle encoder (20) for detecting rotations of the shaft (8) about the axis of rotation (10) in a rotational angle range of less than + / - 360°, wherein the rotary angle encoder (20) and the rotary angle sensor are additionally designed to detect the rotational position of the outer rotor of the electric motor relative to the rigid steering column. The dependent claims relate to advantageous embodiments of the invention.

[0008] A significant advantage of the invention lies particularly in the fact that a steering system for a vehicle equipped with a rotation angle sensor arrangement is improved. Due to the inventive design of the steering system for a vehicle, its construction is considerably simplified. In the steering angle system according to the invention, the gearbox serves, firstly, as a fixed mechanical stop for the shaft when it rotates counterclockwise and clockwise around its axis of rotation, thus effectively and reliably preventing over-rotation of the shaft, for example, over-steering of the steering wheel. Secondly, the gearbox simultaneously serves to detect partial, complete, and / or multiple rotations of the shaft and thus of the steering wheel.This enables a space-saving, component-saving, and design- and manufacturing-friendly construction of the steering system for a vehicle, equipped with a rotary angle sensor arrangement.

[0009] This also enhances the functionality of the rotary encoder and rotary angle sensor. Detecting the rotational position of the electric motor's outer rotor relative to the rigid steering column is necessary, for example, when asymmetries in the motor or sensor system need to be compensated for over a rotational angle range of more than + / - 360°. Such compensation is conveniently performed in the control system using a lookup table. Angles between the support points of the aforementioned table are calculated mathematically, for example, by interpolation.

[0010] Compensation across the full ±360° is important because many mechanical tolerance effects and asymmetries can only be detected and thus compensated for over the full ±360° range. Of course, asymmetries with a period of ±180° or smaller divisions of ±360° can also develop, and these must be corrected using the same procedure.

[0011] In principle, the rotary angle sensor arrangement of the steering system according to the invention can be freely selected within wide suitable limits with regard to type, function, material and dimensions.

[0012] An advantageous embodiment of the steering system according to the invention provides that the angle sensor arrangement is designed to determine multiple 360° rotations of a shaft, wherein the shaft is rotatable about its axis of rotation within a rotational angle range of -n*360° to +n*360°, and the transmission simultaneously engages one of the shaft's fixed mechanical stops at both a rotational angle of -n*360° and a rotational angle of +n*360°. This significantly expands the application range of the angle sensor arrangement. For example, this is advantageous for commercial vehicles such as trucks or the like, where multiple rotations of the steering wheel are typically required to control the vehicle. n can be a natural number, but this is not mandatory.Accordingly, rotation angle ranges could also be conceivable in which the rotation angle range ends with an incomplete revolution in each case when rotating the shaft counterclockwise and clockwise, starting from 0°.

[0013] A further advantageous embodiment of the rotary angle sensor arrangement of the steering system according to the invention provides that the first gear part is designed as an integral component of the shaft, preferably that the first gear part is designed as a threaded groove in the shaft and the second gear part as a T-nut guided in the threaded groove. This allows the gear to be implemented in a particularly simple and robust manner from a design and manufacturing perspective. This applies especially to the preferred embodiment of this embodiment.

[0014] A particularly advantageous embodiment of the rotary angle sensor arrangement of the steering system according to the invention provides that the rotary angle sensor is arranged on a free end face of the shaft, preferably that the rotary angle sensor is formed as an integral part of the shaft. In this way, for example, a so-called coarse-fine tracking method is possible using the rotation encoder and the rotation sensor on one side and using the rotary angle encoder and the rotary angle sensor on the other side. The application of the so-called vernier method is also conceivable.

[0015] An advantageous further development of the aforementioned embodiment of the rotary angle sensor arrangement of the steering system according to the invention provides that the rotary angle encoder and the rotary angle sensor are additionally designed to detect rotations of the shaft about the axis of rotation within a rotation angle range greater than ≥ 360°, preferably ≥ n*360°. This makes it sufficient, for example, if the rotation angle range of the steering wheel in a vehicle is reduced to less than two revolutions, to detect only two switching states using the rotary encoder and the rotary angle sensor.

[0016] Accordingly, in this or similar cases, it is not necessary for the rotation encoder and rotation sensor to detect the angle of rotation with high resolution. Instead, the rotation encoder and rotation sensor can simply function as a counter with a limited and manageable number of switching positions. The rotation sensor can be implemented, for example, capacitively, inductively, or optically (e.g., as a light barrier). Such systems are also known as proximity switches.

[0017] For example, in a steering system with a rotation angle range of -350° to +350°, such a counter can be designed so that a metal surface (a darkening or reflective surface in the case of optical sensors) is active under / in front of the proximity switch for a nominal range of -350° to 0°, while no such effect is present in the nominal range of 0° to +350°. In other words, such a switch is implemented that activates at 0°, which corresponds to the vehicle traveling straight ahead. Turning the steering wheel to the left or right, i.e., rotating the shaft counterclockwise or clockwise, is clearly distinguishable by the switching state.

[0018] Depending on the choice of switch and the underlying physical principle used (capacitive, inductive, optical), a safety improvement can be achieved by employing a diverse range of physical principles. This means that different physical principles are generally not affected simultaneously by the same fault or disturbance.

[0019] Another aspect to consider when choosing a diverse design can be the minimization of crosstalk, if integration into the building space in a confined area is desired or necessary.

[0020] These considerations regarding the choice of diverse basic principles apply equally to rotary encoders and rotary sensors and / or rotary angle encoders and rotary angle sensors, each with higher resolutions than is the case when designed as a switch or the like.

[0021] The functionality remains the same, regardless of whether the rotation encoder and the rotation sensor are designed as high-resolution or as a switch, possibly as a multi-stage switch, in combination with the rotary angle encoder and the rotary angle sensor, whereupon the choice in each individual case must be made based on commercial and installation space integration considerations as well as on considerations of functional safety.

[0022] Another advantageous embodiment of the rotary angle sensor arrangement of the steering system according to the invention provides that the rotation sensor and / or the rotary angle sensor are each designed as an inductive sensor, preferably that the rotation sensor and / or the rotary angle sensor each have a measuring frequency greater than 1 MHz. Inductive sensors are robust and very reliable even under harsh operating conditions, such as in vehicles. This applies particularly to the preferred embodiment of this embodiment. Due to the preferred embodiment, parasitic crosstalk of the motor currents or from permanent magnets is effectively prevented. Without further shielding measures of the rotation sensor and / or the rotary angle sensor, it is thus possible to comply with the electromagnetic compatibility (EMC) tests known in the automotive environment with regard to incoming and outgoing radiation.

[0023] In principle, the steering system according to the invention can be freely selected for a vehicle within wide suitable limits with regard to type, function, material and dimensions. In particular, the steering system according to the invention can be used to advantage in so-called steer-by-wire vehicles.

[0024] A further advantageous embodiment of the steering system according to the invention provides that the detection of the rotational position is designed and configured to correspond to a pole pair pitch of the electric motor. In this way, the increase in the functionality of the rotary encoder and the rotary angle sensor according to the invention is achieved particularly advantageously.

[0025] Another advantageous embodiment of the steering system according to the invention provides that the angle sensor is arranged on a circuit board attached to the steering column, and the shaft with the angle sensor projects through an opening in the circuit board. This makes it possible, for example, to arrange the angle sensor in a very space-saving manner relative to the external rotor electric motor, since a ring- or segment-shaped sensor can be accommodated very efficiently in external rotor electric motors. Such angle sensors are, for example, constructed as a ring or as a segment of a ring.

[0026] The invention is explained in more detail below with reference to the attached, roughly schematic drawing. The single figure shows: Fig. 1 shows an embodiment of the steering system according to the invention for a vehicle with the rotation angle sensor arrangement in a partial perspective view.

[0027] In theFig. 1 An embodiment of the steering system according to the invention for a vehicle with the rotation angle sensor arrangement is shown purely by way of example.

[0028] The vehicle is in the Fig. 1 The steering system 2 is designed as a so-called steer-by-wire system and comprises a rigid steering column, a control unit, and a steering wheel 4 rotatably mounted on the steering column by means of a steering wheel actuator and a shaft 8. The steering wheel actuator, which is connected to the control unit for signal transmission and has an external rotor electric motor, is rigidly attached to the steering column and connected to the steering wheel 4 for torque transmission via the shaft 8. Furthermore, the steering system 2 comprises a rotary angle sensor arrangement 6, which is connected to the control unit for signal transmission, for determining the angle of rotation of the shaft 8, which is non-rotatably connected to the steering wheel 4 and connected to the steering wheel actuator for torque transmission, when the shaft 8 is rotated about an axis of rotation 10 of the shaft 8. The steering column, the control unit, and the steering wheel actuator with the external rotor electric motor are arranged in the Fig. 1 Not shown. The control unit is arranged on a circuit board of the steering system 2 in a manner known to those skilled in the art.

[0029] The rotary angle sensor arrangement 6 for determining the angle of rotation of the shaft 8 during a rotation of the shaft 8 about the axis of rotation 10 of the shaft 8 comprises a rotation encoder 12 connected to the shaft 8 by force transmission and a rotation sensor 14 for detecting a movement of the rotation encoder 12, wherein, according to the invention, a first gear part 16 of a gear unit 18 of the rotary angle sensor arrangement 6 is arranged on the shaft 8 in a rotationally fixed manner, and the rotation encoder 12 is designed as a second gear part of the gear unit 18 which engages with the first gear part 16, and wherein the gear unit 18 simultaneously forms a fixed mechanical stop of the shaft 8 at a first end of a rotation angle range of the shaft 8 when the shaft 8 is rotated counterclockwise and at a second end of the rotation angle range of the shaft 8 when the shaft 8 is rotated clockwise.

[0030] In the present embodiment, the rotary angle sensor arrangement 6 is configured to determine a plurality of 360° rotations of the shaft 8, wherein the shaft 8 is rotatable about its axis of rotation 10 within a rotational angle range of -n*360° to +n*360°, and the gearbox 18 simultaneously forms one of the fixed mechanical stops of the shaft 8 at a rotational angle of -n*360° and at a rotational angle of +n*360°. The signs "-" and "+" in the application text refer only to a possible counterclockwise and clockwise rotation of the shaft 8 about its axis of rotation 10.

[0031] The first gear part 16 is designed here as an integral part of the shaft 8, namely in such a way that the first gear part 16 is designed as a threaded groove in the shaft 8 and the second gear part 12 is designed as a T-nut guided in the threaded groove 16.

[0032] In the present embodiment, the rotary angle sensor arrangement 6 further comprises a rotary angle encoder 20, which is non-rotatably connected to the shaft 8, and a rotary angle sensor corresponding to the rotary angle encoder 20 for detecting rotations of the shaft 8 about the axis of rotation 10 within a rotational angle range of less than +360°. The rotary angle encoder 20 is arranged on a free end face of the shaft 8, such that it is formed as an integral part of the shaft 8. The rotary angle sensor is not shown and has conductive traces arranged on the circuit board of the steering system 2, which is also not shown.

[0033] In other embodiments of the invention, the rotary encoder and the rotary angle sensor can additionally be configured to detect rotations of the shaft about the axis of rotation within a rotation angle range greater than + / - 360°, preferably + / - n*360°. See also the relevant details in the introductory description.

[0034] In the present embodiment, the rotation sensor 14 and the angle sensor are each designed as inductive sensors, each having a measuring frequency greater than 1 MHz. However, other sensor principles, such as capacitive or optical sensors, are also conceivable. See also the corresponding explanations in the introductory section.

[0035] In the present embodiment, the rotary encoder 20 and the rotary angle sensor are further designed to detect the rotational position of the outer rotor of the electric motor relative to the rigid steering column, specifically such that the detection of the rotational position is configured and adapted to a pole pair pitch of the electric motor. Further details on this can be found in the introductory description.

[0036] The following describes the functioning of the steering system according to the invention for a vehicle with the rotation angle sensor arrangement according to the invention, as illustrated in the present embodiment. Fig. 1 briefly explained.

[0037] As soon as a driver (not shown) turns the steering wheel 4 of the steering system 2, the shaft 8 is also rotated about its axis of rotation 10. Since the rotation encoder 12, designed as a cam follower, is engaged with the first gear part 16 of the gearbox 18, which is designed as a thread, the rotation encoder 12 is moved in the plane of the image by means of the rotation of the shaft 8 about its axis of rotation 10. Fig. 1 Depending on the direction of rotation, the shaft 8 moves from left to right or from right to left. In this embodiment, the rotational movement of the shaft 8 is thus converted into a translational movement of the rotation encoder 12. Since this changes the relative position of the rotation encoder 12 to the rotation sensor 14, the change in the angle of rotation can be detected by the rotation sensor 14 and forwarded to the control system for further processing.

[0038] With the aforementioned rotation of shaft 8 about its axis of rotation 10, the [missing text] also [missing text] into the [missing text] from the Fig. 1 The integrated rotary encoder 20 on the visible front face is rotated about the axis of rotation 10. Its relative position to the rotary angle sensor changes accordingly, so that the change in the rotation angle can also be detected by the rotary angle sensor and forwarded to the controller for further processing.

[0039] Output signals generated in the aforementioned manner by the rotation sensor 12 and the rotation angle sensor can, for example, be converted in the control system into a rotation angle of the shaft 8 and thus of the steering wheel 4 of the steering system 2 using one of the methods mentioned in the introductory description.

[0040] Due to the design of the steering system 2 according to the invention, the construction of the steering system 2 is significantly simplified. This is particularly true because, on the one hand, the gearbox 18 in the rotary angle sensor arrangement 6 serves as a fixed mechanical stop for the shaft 8 when the shaft 8 rotates counterclockwise and clockwise around its axis of rotation 10, thus effectively and reliably preventing over-rotation of the shaft 8, i.e., over-steering of the steering wheel 4 of the steering system 2. On the other hand, the gearbox 18 simultaneously serves to detect partial and / or complete and / or multiple rotations of the shaft 8 and thus, for example, of the steering wheel 4 of the steering system 2. This enables a space-saving and component-saving design of the rotary angle sensor arrangement 6 and the steering system 2 equipped with it, which is easy to design and manufacture.

[0041] The invention is not limited to the present embodiment. For example, the steering system and the rotary angle sensor arrangement according to the invention can also be advantageously used in other types of vehicles.

[0042] In particular, the invention is not limited to the aforementioned design and manufacturing details.

[0043] For example, instead of the thread-like first threaded part, the rotation encoder designed as a second threaded part, for example the T-nut from the exemplary embodiment, can be guided on the shaft by means of the first threaded part in such a way that the rotation encoder does not move translationally, but rotationally, when the shaft is rotated about its axis of rotation, with respect to the axis of rotation.

[0044] In contrast to the rotary angle encoder 20 designed as a so-called end-of-shaft encoder in the present embodiment, the rotary angle encoder in other embodiments of the invention can be designed as a so-called through-hole encoder. Accordingly, the rotary angle sensor could be arranged on a circuit board attached to the steering column, with the shaft in this case protruding through an opening in the circuit board along with the rotary angle encoder. Reference symbol list

[0045] 2 Steering system 4 Steering wheel 6 Rotation angle sensor assembly 8 Shaft 10 Shaft axis 8 12 Rotation encoder 14 Rotation sensor 16 First gear part of the transmission 18 18 Transmission 20 Rotation angle encoder

Claims

1. Steering system (2) for a motor vehicle, comprising a rigid steering column, a controller, a steering wheel (4) arranged rotatably on the steering column by means of a shaft (8), and a rotation angle sensor arrangement (6) connected to the controller in a signal-transmitting manner for determining a rotation angle of the shaft (8) when the shaft (8) rotates about a rotation axis (10) of the shaft (8), wherein the rotation angle sensor arrangement (6) comprises a rotation encoder (12) connected to the shaft (8) in a force-transmitting connection and a rotation sensor (14) for detecting a movement of the rotation encoder (12), wherein a first gear part (16) of a gear (18) of the rotation angle sensor arrangement (6) is arranged on the shaft (8) in a rotationally rigid manner and the rotation encoder (12) is designed as a second gear part of the gear (18) which is in engagement with the first gear part (16), wherein the gear (18) simultaneously forms a fixed mechanical stop of the shaft (8) at a first end of a rotation angle range of the shaft (8) when the shaft (8) rotates in anti-clockwise direction and at a second end of the rotation angle range of the shaft (8) when the shaft (8) rotates in clockwise direction, characterised in that the steering wheel (4) is arranged rotatably on the steering column by means of a steering wheel actuator and the shaft (8), wherein the steering wheel actuator that is connected to the controller in a signal-transmitting manner and has an external rotor electric motor, is rigidly fixed to the steering column and connected to the steering wheel (4) in a torque-transmitting manner by means of the shaft (8), wherein the rotation angle sensor arrangement (6) that is connected to the controller in a signal-transmitting manner is used to determine an angle of rotation of the shaft (8) that is connected to the steering wheel (4) in a rotationally rigid manner and to the steering wheel actuator in a torque-transmitting manner when the shaft (8) is rotated about an axis of rotation (10) of the shaft (8), and further comprises a rotation angle encoder (20) connected to the shaft (8) in a rotationally rigid manner and a rotation angle sensor corresponding to the rotation angle encoder (20) for detecting rotations of the shaft (8) about the axis of rotation (10) in a rotation angle range of less than - / + 360°, said rotation angle encoder (20) and said rotation angle sensor additionally being designed to detect the rotational position of the external rotor of the electric motor relative to the rigid steering column.

2. Steering system (2) according to claim 1, characterised in that the rotation angle sensor arrangement (6) is designed to determine a plurality of 360° rotations of a shaft (8), said shaft (8) being rotatable about the axis of rotation (10) of the shaft (8) in a rotation angle range from -n*360° to +n*360°, and the gear (18) simultaneously forming one of the fixed mechanical stops of the shaft (8) at a rotation angle of -n*360° and at a rotation angle of +n*360°.

3. Steering system (2) according to claim 1 or 2, characterised in that the first gear part (16) is designed as an integral component of the shaft (8), preferably such that the first gear part (16) is designed as a thread-like groove in the shaft (8) and the second gear part (12) is designed as a sliding block guided in the thread-like groove.

4. Steering system (2) according to one of claims 1 to 3, characterised in that the rotation angle sensor (20) is arranged on a free end face of the shaft (8), preferably such that the rotation angle sensor (20) is designed as an integral component of the shaft (8).

5. Steering system (2) according to claim 4, characterised in that the rotation angle encoder and the rotation angle sensor are additionally suitably designed to detect rotations of the shaft about the axis of rotation in a rotation angle range of greater than - / + 360°, preferably of - / + n*360°.

6. Steering system (2) according to one of claims 1 to 5, characterised in that the rotation sensor (14) and / or the rotation angle sensor is / are each designed as an inductive sensor, preferably such that the rotation sensor (14) and / or rotation angle sensor each has / have a measuring frequency of greater than 1 MHz.

7. Steering system (2) according to one of claims 1 to 6, characterised in that the detection of the rotational position is designed and set up to match the pitch of a pole pair of the electric motor.

8. Steering system according to any one of claims 1 to 7, characterised in that the rotation angle sensor is arranged on a printed circuit board attached to the steering column and the shaft with the rotation angle encoder protrudes through an opening in the printed circuit board.