inter-axle steering arrangement and method for calibrating a rear axle steering actuator
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2020-06-04
- Publication Date
- 2026-07-23
AI Technical Summary
Existing rear axle steering actuators lack efficient calibration methods and structural optimization, leading to potential position errors and wear-related issues.
A rear axle steering arrangement with a push rod driven by a rotary linear gear, an electric motor, and a rotary angle sensor, coupled with a control unit that uses multi-turn information to determine the push rod's position, allowing for recalibration and error detection, and optionally integrating a planetary roller screw for enhanced positional security.
Enables quick and accurate recalibration, detects wear, and maintains system functionality by adapting reference positions, minimizing position errors and ensuring reliable operation.
Smart Images
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Abstract
Description
[0001] The present invention relates to a rear-axle steering arrangement for a motor vehicle, comprising a rear-axle steering actuator with a housing. An axially displaceable pushrod is arranged within the housing and is driven by a rotary linear drive. The pushrod has a steering fork at each of its two axial ends. Furthermore, an electric motor is provided for driving the rotary linear drive, the motor having a rotation angle sensor (for example, in the form of a rotor position sensor) for detecting the rotational position of the electric motor. The rear-axle steering arrangement also includes a control unit operatively connected to the electric motor. The invention further relates to a method for calibrating a rear-axle steering actuator of a rear-axle steering arrangement.
[0002] German patent application DE 10 2008 032 046 A1 describes a method for calibrating a position determination system of a rear-axle steering actuator for a motor vehicle. The rear-axle steering actuator has an actuator element that can be driven into a translational movement by the rotation of a rotor, and whose geometric center position is determined by means of a reference measurement. The position determination system comprises a linear sensor and a rotary sensor. During the calibration of the position determination system, calibration information is generated, which includes zero-point information from the linear sensor and sector information. The measuring range of the rotary sensor is divided into at least two sectors, and the sector in which the angular position of the rotor, as detected by the rotary sensor, lies when the actuator element is in its geometric center position is identified.The calibration information is stored in the linear sensor.
[0003] The invention is based on the objective of providing a rear axle steering arrangement that is further improved with regard to the calibration of a rear axle steering actuator. Advantageously, the rear axle steering arrangement should also be further optimized with regard to its design. Furthermore, the invention is based on the objective of providing a method for calibrating a rear axle steering actuator that enables recalibration of the rear axle steering actuator using simple means.
[0004] This problem is solved by a rear-axle steering arrangement for a motor vehicle with the features of claim 1 and by a method for calibrating a rear-axle steering actuator with the features of claim 7. A rear-axle steering arrangement according to the invention comprises a rear-axle steering actuator with a housing, a push rod axially displaceable within the housing and driven by a rotary-linear drive, steering forks arranged at the axial ends of the push rod, an electric motor for driving the rotary-linear drive, and a rotary angle sensor for detecting the angular position of the electric motor. Furthermore, the rear-axle steering arrangement comprises a [missing information] operatively connected to the electric motor.to this control unit connected for data communication, wherein the control unit is configured to read the rotation angle signal determined by the rotation angle sensor with regard to the number of full revolutions of the rotor of the electric motor and to store the number of rotor full revolutions, so that after a restart of the ignition of the motor vehicle, the angle signal from the rotation angle sensor and the information about the number of rotor full revolutions from the control unit are provided in the sense of complete multi-turn information.In the context of the invention, multi-turn information refers to position information of the rotor (and consequently also position information of the pushrod), wherein this position information comprises a first part in the sense of the current rotation angle of the rotor and a second part in the sense of the number of full rotations of the rotor completed from a reference position. The control unit is preferably integrated into or attached to the electric motor. Alternatively, the functionality of the control unit, at least partially with regard to the rotation angle sensor, can be implemented by a control unit of the vehicle located outside the rear axle steering actuator.The inventive design of a rear axle steering arrangement provides a rear axle steering arrangement which is improved with regard to the possible safety mechanisms of a system that reads sensor information for determining the position of the pushrod, with a view to fault detection. Furthermore, the advantage is achieved that only one rotation angle sensor (here: the rotor position sensor of the electric motor) is required, which is already present in the system.
[0005] Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined in a technologically meaningful manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are specified and explained in more detail in the description, which also presents further preferred embodiments of the invention.
[0006] According to an advantageous embodiment of the invention, the control unit can be configured to perform a calibration procedure in the event of a loss of the absolute position of the pushrod or the detection of an implausibility in the current position of the pushrod of the rear axle steering actuator. In this procedure, the pushrod is moved to one of its two end positions, the reached end position is compared with a stored end-position reference position, and if the determined end-position position of the pushrod and the stored end-position reference position of the pushrod correspond with sufficient accuracy, the pushrod is moved to the learned and stored center reference position. The advantage of this embodiment lies in the fact that valid information about the actual position of the pushrod can be generated very quickly using simple means.
[0007] According to an alternative embodiment of the invention, to generate valid information about the actual position of the pushrod, the control unit may also be configured to perform a calibration procedure in the event of a loss of the absolute position of the pushrod or the detection of an implausibility of the current position of the pushrod of the rear axle steering actuator, wherein the pushrod is first moved to one end position and then to the other end position and a total travel distance between the two end positions is determined, and starting from the last end position of the pushrod, the pushrod is then moved by half of the previously determined total travel distance to the center position and the new center position is recorded as the new center reference position and stored in a control unit.This allows for the detection and compensation of initial signs of wear in the mechanism – for example, additional wear-related play between the steering forks and the steering fork housing stops. Advantageously, the measured total travel distance is compared with a stored reference travel distance. If there is sufficient agreement – or if the deviation is still tolerable – the system's functionality can be maintained by determining a new center position. Additionally, a warning can be issued to the driver to visit a workshop and have the rear axle steering actuator checked.
[0008] Furthermore, according to another advantageous embodiment of the invention, the rotary linear drive may comprise a planetary roller screw drive with planets arranged in a circumferentially arranged cage, wherein the planets mesh radially inwards with a thread formed on the push rod and radially outwards with a nut, and wherein the cage of the planetary roller screw drive can be driven by the electric motor by means of a wrapping element. The advantageous effect of this embodiment is based on the fact that the positive coupling between the driven part and the push rod further improves the positional stability of the push rod, so that any implausibilities that may occur with regard to the position of the push rod can be minimized.
[0009] According to a further particularly preferred embodiment of the invention, it can be provided that the control unit is a component of the electric motor and, in particular, a component of the motor control unit thereof, thereby reducing possible sources of error in the communication regarding the data on the position of the pushrod - compared to implementing this functionality in a central control unit of the motor vehicle.
[0010] The problem underlying the invention is also solved by a method for calibrating a rear axle steering actuator. In a first embodiment, the method according to the invention works such that, in the event of a loss of the absolute position of the pushrod or the detection of an implausibility in the current position of the pushrod of the rear axle steering actuator, the pushrod is first moved to one end position and then to the other end position, and a total travel distance between the end positions is determined. Then, starting from the last end position, the pushrod is subsequently moved by half the total travel distance between the first and second end positions to the center position, and the new center position is recorded as the new center reference position and stored in a control unit.The advantage that can be achieved through this is that any existing signs of wear can be detected and, if these are within a tolerable range, the system can continue to work in an optimized manner with adjusted reference values and at the same time inform the driver about the current wear situation.
[0011] In a second, alternative embodiment, the method according to the invention operates such that, in the event of a loss of the absolute position of the pushrod or the detection of an implausibility in the current position of the pushrod of the rear axle steering actuator, the pushrod is moved to one of its two end positions. The reached end position is then compared with a stored end-position reference position. If the determined end position of the pushrod and the stored end-position reference position of the pushrod correspond with sufficient accuracy, the pushrod is moved to the learned and stored center reference position. This allows the position of the pushrod to be re-determined or validated very quickly, and the system can continue operating based on the learned and stored reference values.
[0012] According to a further preferred embodiment of the method, the determination of the pushrod's end position can be achieved by evaluating the motor current rise of the electric motor and / or by evaluating a gradient in the position signal. This allows for a reliable conclusion to be drawn about the pushrod reaching its end position using simple means, without the need for additional sensors.
[0013] The invention and its technical context are described below based on the The figures are explained in more detail below. It should be noted that the invention is not intended to be limited by the illustrated embodiment. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained with reference to the figure and combine them with other components and findings from the present description. It should be noted in particular that the figure, and especially the depicted proportions, are only schematic.
[0014] It shows: Fig. 1 a rear axle steering actuator according to the invention in schematic representation.
[0015] Fig. Figure 1 shows a rear axle steering actuator 2 according to the invention in a schematic representation. Fig. Figure 1 illustrates a rear axle steering arrangement 1 for a motor vehicle, comprising a rear axle steering actuator 2 with a case3 Inside the housing 3 A push rod is axially displaceable in this case. 5 arranged via a rotary linear drive 4 e.g., a planetary roller gear unit is driven. At each of the two axial ends of the push rod 5 Each is a steering fork 6 arranged. Furthermore, an electric motor is 7 for driving the rotary linear gear 4 planned. The electric motor 7 It has an internally installed rotor position sensor, which is used as a rotation angle sensor. 8 for recording the rotational angle position of the electric motor 7 It serves this purpose. Furthermore, the rear axle steering actuator shown includes... 2 one with an electric motor 7 connected or data communication-linked control unit 9 The control unit 2Alternatively, its functionality can be fully or partially implemented outside the rear axle steering actuator. 2 be integrated – for example, into a central control unit of the vehicle. In this case, an external control unit (not shown) would connect to the electric motor via an interface. 7 to connect the control unit 9 The system is set up using the rotary angle sensor. 8 Determined rotation angle signal in relation to the number of complete rotor revolutions of the electric motor 7 to read out and store the number of rotor full revolutions in a memory, so that after the ignition of the vehicle is switched on again, the angle signal from the rotary angle sensor is available 8 and the information about the number of rotor full revolutions from the control unit 9 are provided in the sense of complete multi-turn information.
[0016] The control unit 9can be set up in case of a loss of the absolute position (current actual position of the push rod) of the push rod 5 or the recognition of an implausibility in the current position of the push rod 5 of the rear axle steering actuator 2 , to perform a calibration procedure, whereby the push rod 5 into one of the two end positions E1 , E2 The procedure is carried out, the approached final position E1 ; E2 is compared with a stored end position reference position and, in the case of a sufficiently accurate match between the determined end position position of the push rod 5 and stored end position reference position of the push rod 5 , the push rod 5 The process moves to the learned and stored center reference position.
[0017] Alternatively, the control unit 9set up to handle the situation in case of a loss of the absolute position of the push rod 5 or the recognition of an implausibility in the current position of the push rod 5 of the rear axle steering actuator 2 , to perform a calibration procedure, whereby the push rod 5 first into one end position E1 and then into the other end position E2 The procedure is carried out and a position is formed between the two end positions. E1 , E2 The total travel distance is determined, starting from the last reached end position. E2 the push rod 5 the push rod 5 The unit then moves to the center position by half the determined total travel distance, and the new center position is recorded as the new center reference position and stored in a control unit. 9 is deposited.
[0018] The rotary linear gear 4is comprised by a planetary roller screw drive 10 with planets arranged in a circumferentially arranged cage, wherein the planets are radially inward connected to a push rod 5 formed thread and radially outside with a nut, wherein the cage of the planetary roller screw drive 10 through the electric motor 7 It can be driven by means of a wrapping device. The control unit 9 is part of the motor control unit for controlling the electric motor 7 designed and located in or on the engine housing.
[0019] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Insofar as the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy. Reference symbol list 1 Rear axle steering arrangement 2 Rear axle steering actuator 3 cases 4 rotary linear gears 5 push rod 6 steering forks 7 Electric motor 8 Rotary angle sensors 9 Control unit 10 planetary roller screw drives E1 first end position (of the push rod) E2 second end position (of the push rod) QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] DE 102008032046 A1
[0002]
Claims
[1] Rear axle steering arrangement (1) for a motor vehicle, comprising - a rear axle steering actuator (2) with a housing (3), a push rod (5) arranged axially displaceably within the housing (3) and driven by a rotary linear gear (4), steering forks (6) arranged at the axial ends of the push rod (5), an electric motor (7) for driving the rotary linear gear (4), and a rotation angle sensor (8) for detecting the rotation angle position of the electric motor (7), and comprising - a control unit (9) operatively connected to the electric motor (7), characterized by, that the control unit (9) is configured to read the rotation angle signal determined by the rotation angle sensor (8) with respect to the number of rotor full revolutions of the electric motor (7) and to store the number of full revolutions, so that after the ignition of the motor vehicle is switched on again, the angle signal from the rotation angle sensor (8) and the information about the number of rotor full revolutions from the control unit (9) are provided in the sense of complete multi-turn information. [2] Rear axle steering arrangement (1) according to claim 1, characterized by, that the control unit (9) is configured to perform a calibration procedure in the event of a loss of the absolute position of the pushrod (5) or the detection of an implausibility of the current position of the pushrod (5) of the rear axle steering actuator (2), wherein the pushrod (5) is moved to one of the two end positions (E1; E2), the approached end position (E1; E2) is compared with a stored end position reference position, and in the event of a sufficiently accurate match between the determined end position position (E1; E2) of the pushrod (5) and the stored end position reference position of the pushrod (5), the pushrod (5) is moved to the originally learned and stored center reference position. [3] Rear axle steering arrangement (1) according to claim 1, characterized by, that the control unit (9) is configured to perform a calibration procedure in the event of a loss of the absolute position of the push rod (5) or the detection of an implausibility of the current position of the push rod (5) of the rear axle steering actuator (2), wherein the push rod (5) is first moved to one end position (E1) and then to the other end position (E2) and a total travel distance between the two end positions (E1; E2) is determined, and starting from the last end position (E2) the push rod (5) is then moved by half the total travel distance to the center position and the new center position is recorded as the new center reference position and stored in a control unit (9). [4] Rear axle steering arrangement (1) according to any one of the preceding claims, characterized by, that the rotary linear drive (4) comprises a planetary roller screw drive (10) with planets arranged in a circumferentially arranged cage, wherein the planets mesh radially inside with a thread formed on the push rod (5) and radially outside with a nut, and wherein the cage of the planetary roller screw drive (10) can be driven by the electric motor (7) by means of a wrapping means. [5] Rear axle steering arrangement (1) according to any one of the preceding claims, characterized by , that the control unit (9) is part of the electric motor (7). [6] Rear axle steering arrangement (1) according to any one of the preceding claims, characterized by , that the control unit (9) is designed as a motor control unit. [7] Method for calibrating a rear axle steering actuator (2) of a rear axle steering assembly (1), characterized by , that - in the event of a loss of the absolute position of the pushrod (5) or the detection of an implausibility of the current position of the pushrod (5) of the rear axle steering actuator (2), - the push rod (5) is first moved to one end position (E1) and then to the other end position (E2) and a total travel distance between the end positions (E1; E2) is determined, and - starting from the last end position (E2), the push rod (5) is then moved by half the total travel distance between one end position (E1) and the other end position (E2) to the center position, and the new center position is recorded as the new center reference position and stored in a control unit (9). [8] Method for calibrating a rear axle steering actuator (2) of a rear axle steering assembly (1), characterized by, that in the event of a loss of the absolute position of the pushrod (5) or the detection of an implausibility of the present position of the pushrod (5) of the rear axle steering actuator (2), - the push rod (5) is moved to one of the two end positions (E1; E2), the approached end position (E1; E2) is compared with a stored end position reference position, and if there is a sufficiently accurate match between the determined end position position (E1; E2) of the push rod (5) and the stored end position reference position of the push rod (5), the push rod (5) is moved to the learned and stored center reference position. [9] Method according to claim 7 or 8, characterized by , that the determination of an end position of the push rod (5) is carried out by an evaluation of the motor current increase of the electric motor (7). [10] Method according to any one of claims 7-9, characterized by, that the determination of an end position of the push rod (5) is carried out by evaluating a gradient in the position signal.