Method for monitoring a belt drive of a steering system and steering system of a motor vehicle

Abstract

The invention relates to a method for monitoring a belt drive (5) of a steering system (1) of a motor vehicle, which has a toothed belt (53) which runs in a driving manner around a drive pulley (51) and a driven pulley (52), wherein the drive pulley (51) is coupled to a motor shaft of a motor (41) and the driven pulley (52) is operatively connected to a steering actuator (4), and the rotational position of at least one of the pulleys (51, 52) is detected by means of a rotational sensor (8) of a monitoring device (8, 9) and is analyzed in a control device (9). In order to achieve reliable functional monitoring with low outlay, it is proposed that a defined reference position (R) of the steering actuator (4) is generated, and a current measurement of the rotational position of the drive pulley (51) detected by means of the rotational sensor (8) is compared with a predefined reference value in order to detect deviations.

Description

Technical Field

[0001] This invention relates to a method for monitoring a belt drive mechanism of a motor vehicle's steering system. The belt drive mechanism has a toothed belt that rotates drivably around a driving pulley and a driven pulley. The driving pulley is connected to a motor shaft, and the driven pulley is effectively connected to a steering actuator. The rotational position of at least one pulley is detected by means of a rotation sensor in a monitoring device and analyzed in a control device. The steering system used to perform this method is also the subject of this invention. Background Technology

[0002] A known steering system for a motor vehicle has one or more electric steering actuators with toothed belt drives. In a steering system with in-line steering, the steering actuator can be configured as a steering drive or wheel actuator to generate steering rotation of one or more steerable wheels. Furthermore, the steering actuator can be used as a feedback actuator to couple feedback torque via the steering column's steering spindle to a manually rotatable steering wheel mounted thereon, thereby simulating a realistic driving feel.

[0003] To reliably ensure steering capability, especially in steering systems with wire steering, the proper functioning of the toothed belt drive is crucial. The required synchronized torque transmission from the driving pulley mounted on the motor shaft to the driven pulley connected to the adjustable actuator element can be affected by slippage, for example, through tooth skipping. This occurs when a tooth of the toothed belt fails to engage properly with the pulley teeth, skipping a tooth pitch in the direction of force transmission. This failure can be caused by factors such as wear and insufficient belt tension, and can lead to steering system misalignment.

[0004] DE 10 2017 214 649 A1 proposes a method that uses a first rotation sensor to detect the rotation angle of the driving pulley mounted on the rotor shaft of a motor. This measurement is then compared to a measurement from a second rotation sensor, configured as an index sensor to detect the rotation angle of the driven pulley. The deviation between the measurements from the two rotation sensors can identify skipped teeth. This enables monitoring of the operating status of the toothed belt drive and ensures reliable operation. However, a drawback is the complex structure, which requires two rotation sensors under all circumstances. Summary of the Invention

[0005] In view of the aforementioned problems, the object of the present invention is to achieve reliable functional monitoring with minimal cost.

[0006] According to the invention, this objective is achieved by the method according to claim 1 and the steering system having the features of claim 6. Advantageous improvements are derived from the dependent claims.

[0007] In a method for monitoring a belt drive for a steering system of a motor vehicle, the belt drive has a toothed belt that drives around a driving pulley and a driven pulley, wherein the driving pulley is connected to a motor shaft of a motor and the driven pulley is effectively connected to a steering actuator, and the rotational position of at least one pulley is detected by means of a rotation sensor of a monitoring device and analyzed in a control device. According to the method of the invention, a defined reference position for the steering actuator is generated, and the current measurement of the rotational position of the driving pulley detected by the rotation sensor is compared with a preset reference value to detect deviations.

[0008] The adjustment position of the steering actuator is associated with the rotational position of the driven pulley via a belt drive. Through a form-fitting connection between the driving and driven pulleys (hereinafter collectively referred to as pulleys) achieved by means of a toothed belt, the steering actuator's preset reference position according to the invention is associated with the corresponding current rotational position of the driving pulley. In trouble-free operation, the connection is slip-free, or at least substantially slip-free within a preset tolerance, so that the rotational position of the driven pulley in the reference position corresponds to the clearly defined current rotational position of the driving pulley. A reference value corresponding to the measured value of the driving pulley in that rotational position is stored in the control device.

[0009] According to the present invention, the measurement value corresponding to the current rotational position of the drive pulley can be detected at a defined reference position of the steering actuator by means of a single rotation sensor. To perform a functional check on the belt drive, this current measurement value is compared with a stored reference value. If the comparison shows that the current measurement value is consistent with the reference value within a preset tolerance, this corresponds to a fault-free operating state of the belt drive. However, if the comparison shows that the deviation between the current measurement value and the reference value exceeds a preset limit value beyond the acceptable tolerance, it indicates that an angular misalignment has occurred between the drive pulley and the driven pulley, caused, for example, by skipped teeth or a faulty toothed belt. In this case, a fault exists, and preferably a warning signal can be issued and / or safe operation can be activated.

[0010] The advantage of the method according to the invention is that faults in the drive mechanism of the steering actuator can be reliably detected by means of a single rotation sensor that works in conjunction with the driving wheel. This allows for a simpler design for operation and functional monitoring than in the prior art, which requires at least one second rotation sensor on the driven wheel.

[0011] In practice, another advantage can be achieved by activating the redundant backup operation according to the invention in a given system used to monitor the steering actuator, in the event of failure of the rotation sensor that interacts with the driven wheel. This allows for reliable monitoring of the belt drive with the sole remaining intact rotation sensor. This, in turn, improves the level of safety with minimal cost.

[0012] Advantageously, the reference position can be generated by a mechanical stop. The stop defines the mechanical end position of the steering actuator driven by the belt drive, i.e., an end stop. Thus, a robust, accurate, and well-defined reference position can be provided with minimal effort, which is clearly related to the rotational position of the driven wheel.

[0013] Typically, steering actuators have a defined, preset adjustment range, preferably defined by mechanical end stops that can be arranged in the movement path of functional elements that can be adjusted relative to each other. For example, the steering actuator can have a linear drive mechanism driven by a belt drive, such as a screw drive, rack and pinion drive, or similar mechanism, which can achieve maximum linear movement between the end stops. Such a linear steering actuator can, for example, be used as a steering adjuster in a steering drive system. Alternatively, the steering actuator can be designed to preferably couple torque for rotary drive to the steering shaft via a transmission mechanism. Thus, for example, torque can be introduced into the steering spindle or steering shaft of the steering column by a steering actuator designed as a power assist drive or feedback actuator, the rotation angle of which is limited by mechanical stops.

[0014] Similarly, the maximum possible rotation of the driven wheel can be limited by at least one stop. This stop can be configured to release a preset rotation angle between a portion of one or more rotations. Thus, a reference position for the steering actuator can also be preset.

[0015] Alternatively, the reference position can be generated by adjusting the steering actuator. Here, the reference position of the steering actuator and the corresponding defined angular position of the driven wheel can be preset by an externally applied adjusting force or torque. During vehicle operation, the reference position can be defined, for example, by the straight-line travel of the vehicle, which can be achieved by adjusting the steering actuator to an externally adjustable intermediate position.

[0016] It may be possible, but is not mandatory, to determine the adjustment state corresponding to the reference position through external parameters. These external parameters may be determined, for example, in continuous operation to monitor the vehicle's driving dynamics, and thus, for example, the vehicle's straight-line driving or defined steering can be identified based on detailed navigation coordinates from a GPS navigation system, without the need for additional sensors.

[0017] Another possibility is to determine, for example, the reference position of the steering actuator connected to the steerable wheels by detecting the vehicle's yaw rate.

[0018] In any situation, monitoring can be achieved at a lower cost than existing technologies.

[0019] Preferably, the reference position can be set by means of a belt drive. The reference position can be generated by means of a motor, for example, by mechanically moving a steering actuator onto a stop, wherein the steering actuator moves to an end position against a stop that mechanically limits the possible adjustment range. Advantageously, at least one end stop is usually already present, and the detection of the stop can be achieved simply and especially without an additional rotation sensor. For example, it can practically be achieved without additional cost by detecting the stop through an increase in the current supplied to the motor when the adjustment movement mechanically stops at the stop. Thus, the reference position can be achieved through simple manipulation of the steering actuator.

[0020] The use of a belt-driven motor provides an additional advantage: the ability to automatically execute monitoring programs, such as the steering actuator moving to the stop before or after vehicle operation begins.

[0021] The reference position can be preset via external settings on the steering actuator. These external settings can, for example, correspond to the vehicle's straight-line driving, with the steering actuator in a neutral position. The external force used to adjust the steering actuator can be provided, for example, through manually input hand force, reaction force acting from the lane onto the steerable wheels, or other external forces acting on the steering actuator.

[0022] A steering system for a motor vehicle includes: a belt drive having a toothed belt that rotates drivably around a driving pulley and a driven pulley, wherein the driving pulley is connected to a motor shaft of a motor and the driven pulley is effectively connected to a steering actuator; and a monitoring device having a rotation sensor connected to a control device for detecting the rotational position of at least one of the pulleys, wherein the steering system is configured to perform the aforementioned method according to the invention.

[0023] The steering system according to the invention may have all the features and designs described above, explicitly or implicitly in conjunction with the method according to the invention.

[0024] Preferably, a single rotation sensor can be provided, configured to detect the rotation of the drive wheel, the steering actuator can be placed at a defined reference position, and the control device is configured to store the reference value for comparison with the current measurement value of the rotation sensor at the reference position.

[0025] Unlike existing technologies that require at least one additional rotation sensor, such as one for detecting the rotation of the driven wheel, the steering actuator according to the invention requires only a single rotation sensor on the driving wheel. This rotation sensor can be an electrical sensor in a manner known per se, capable of detecting and outputting a current measurement of the rotational or angular position of the driving wheel using suitable measurement methods, such as magnetic, capacitive, optical, and / or other measurement methods.

[0026] The steering actuator has at least one (e.g., exactly one) reference position corresponding to a specific adjustment state. This can preferably be achieved via an end position in a mechanical stop, as described above for the method. Alternatively, the adjustment state can be determined by external parameters, which do not require sensors on the steering actuator.

[0027] The control device may preferably include a storage device in which reference values ​​are stored electronically. To implement the method according to the invention, the steering actuator is positioned at a reference position. Preferably, the steering system may be implemented such that the reference position is automatically identified by the control device, for example, by an increase in motor current when the end stop of the mechanism is engaged. Here, the current measurement value is detected by a rotation sensor, preferably automatically by a corresponding design of the control device. According to the invention, the control device has a comparison device. This comparison device is configured to compare the current measurement value of the rotation sensor with the stored reference value and detect a deviation. The comparison device may preferably be connected to an output device. The output device is preferably configured to provide an alarm signal when a deviation is detected outside a preset tolerance range, indicating a fault in the drive unit, and / or automatically activating emergency operation of the steering system. If no deviation is detected, a positive response signal can be provided, confirming a non-defective function.

[0028] Advantageously, the steering system is constructed as a steer-by-wire system. A steer-by-wire system in a motor vehicle is similar to a conventional mechanical steering system, receiving manual steering commands from the driver via the rotation of a steering wheel, which is attached to a steering spindle rotatably mounted in the steering column. However, this steering spindle is not mechanically connected to the steerable wheels via a steering transmission as in a conventional steering system. Instead, it works in conjunction with an angle sensor or torque sensor, which detects the introduced steering command and outputs the resulting electrical control signal to a steering adjuster, which adjusts the corresponding steering rotation of the wheels by means of an electric servo drive.

[0029] It is possible that the reference position for the method according to the invention is provided by the rotational position of the steering column of the steer-by-wire type.

[0030] The steering actuator may include a feedback actuator. To generate a realistic driving feel, it is known to detect or calculate parameters, such as vehicle speed, steering angle, and steering reaction torque, from actual instantaneous driving conditions, and to generate feedback signals from these parameters, which are then input to the feedback actuator. The driven wheel may preferably be connected to the steering spindle, with the steering wheel mounted on the steering spindle as a manual steering input.

[0031] During vehicle operation, the motor is controlled by a control unit to couple a return torque (feedback torque) corresponding to the actual reaction torque of the steerable wheels to the steering wheel via the steering spindle. This "force feedback" system gives the driver the impression of real driving conditions, just like in traditional steering, making intuitive responses easier.

[0032] A steering actuator can have a wheel actuator that is effectively connected to a steerable wheel. The wheel actuator, which may be referred to as a steering adjuster or steering drive, may, for example, have an actuator rod movable in its longitudinal direction within a housing, which is connected to the steering knuckle of the steerable wheel via a steering tie rod. For adjusting the actuator rod, a linear drive, such as a screw drive or rack and pinion drive, can be provided, driven by an electric motor via a belt drive. Alternatively, a belt drive can be coupled to the steering knuckle for rotational drive. Attached Figure Description

[0033] Advantageous embodiments of the invention will now be explained in detail with reference to the accompanying drawings. The drawings show in detail: Figure 1 A schematic diagram of the steer-by-wire system according to the present invention is shown. Figure 2 A schematic axial view of the drive pulley of the belt drive according to the present invention is shown. Figure 3 It shows according to Figure 1 A schematic diagram of the steering actuator of the steering system. Detailed Implementation

[0034] In different accompanying drawings, the same parts are always given the same reference numerals, and therefore are usually named or mentioned only once each.

[0035] Figure 1A steering system 1 according to the invention, configured as a steer-by-wire system, is schematically shown. The steering system includes a steering column 2. The steering column has a support unit 21 that can be mounted on a vehicle body (not shown), and a steering spindle 22 is supported by the support unit 21 in a manner rotatable about its longitudinal axis L. At its driver-side end, relative to the direction of travel, a steering wheel 23 is torsionally mounted on the steering spindle 22 for inputting manual steering commands.

[0036] The steering column 2 houses rotation angle and torque detection sensors (not shown in detail), which convert steering commands introduced into the steering spindle 22 as rotation of the steering wheel 23 into electrical control signals, i.e., steering signals.

[0037] The control signal is transmitted through the electrical control line 3 to the electric steering actuator 4 according to the invention, which can be designed according to the invention.

[0038] The steering actuator 4 has a belt drive 5, which is configured as a toothed belt drive and has a driving pulley 51 as a first pulley, a driven pulley 52 as a second pulley, and a toothed belt 53 that runs around the two pulleys 51 and 52 as a traction mechanism.

[0039] The driving wheel 51 is mounted on the motor shaft of the electric motor 41 and is rotatably driven about the motor axis M. The driven wheel 52 is effectively connected to the screw drive and is rotatably driven about the screw axis A, which is parallel to the motor axis M.

[0040] The screw drive has, in a manner known per se, a screw nut, which is axially supported in the housing of the steering actuator 4 and rotatably supported about the screw axis A, and connected to the driven wheel 52. A threaded spindle engages in the screw nut and is non-rotatably, but longitudinally movable about the spindle axis A, within the steering actuator 4, as indicated by the double arrows.

[0041] The screw drive is hinged to the steerable wheel 61 in a manner known per se via the steering tie rod 6.

[0042] The schematically illustrated rotation sensor 8 is configured to detect the rotational position of the drive wheel 51. To implement the method according to the invention, this rotation sensor 8 is required as the sole rotation sensor, and correspondingly, it can be the sole rotation sensor for the steering actuator 4.

[0043] The rotation sensor 8 is connected to the control device 9 via control line 81. The rotation sensor is preferably configured as an absolute sensor to detect and output the current measurement value X for the current rotational position of the drive wheel 51.

[0044] Figure 2 A schematic axial view of the drive wheel 51 in the direction of the motor axis M is shown. Figure 3 A schematic side view of the steering actuator 4, viewed transversely to the main shaft axis A, is shown.

[0045] According to the method of the invention, the steering actuator 4 is brought to a reference position R, for example, at the mechanical end stop at the end of the maximum possible linear adjustment stroke of the screw in the screw drive. The reference position R corresponds to a defined rotational position of the drive wheel 51. This is in Figure 2 In Chinese, it is also represented by "R".

[0046] The reference value corresponding to the reference position R is stored in the control device 9.

[0047] With the aid of rotation sensor 8, the current measurement value X is measured in the end stop of steering actuator 4 for the rotational position of drive wheel 51 in reference position R, in this example.

[0048] If the measured value X matches the reference value of the stored reference position R, then there is no interference.

[0049] However, if the comparison of the measured value X with R gives a deviation, such as Figure 2 As exemplified in the example, this clearly indicates a misalignment between the driving wheel 51 and the driven wheel 52, for example, due to tooth skipping. Consequently, a linear offset occurs in the adjustment of the steering actuator 4, as shown in... Figure 3 As illustrated in the diagram.

[0050] In this case, the deviation can be automatically analyzed by the control device 9, and if the deviation exceeds the preset limit value indicating a fault, a warning signal can be output and / or emergency operation can be activated.

[0051] Explanation of reference numerals in the attached figures

[0052] 1. Steering System

[0053] 2 steering columns

[0054] 21 bearing units

[0055] 22 steering spindle

[0056] 23 steering wheel

[0057] 3 control circuits

[0058] 4 steering actuators

[0059] 41 motors

[0060] 5. Belt drive device

[0061] 51 drive wheel

[0062] 52 driven wheel

[0063] 53-tooth belt

[0064] 6-Steering tie rod

[0065] 61 wheels

[0066] 8 sensors

[0067] 81 control circuit

[0068] 82 Measurement Sensor

[0069] 9 control devices

[0070] L-axis

[0071] A. Main spindle axis

[0072] M motor axis

[0073] R reference position

[0074] X measurement value

Claims

1. A method for monitoring a belt drive (5) of a steering system (1) of a motor vehicle, the belt drive having a toothed belt (53) that drives about a driving pulley (51) and a driven pulley (52), wherein, The drive pulley (51) is connected to the motor shaft of the motor (41) and the driven pulley (52) is effectively connected to the steering actuator (4). The rotational position of at least one of the pulleys (51, 52) is detected by means of the rotation sensor (8) of the monitoring device (8, 9) and analyzed in the control device (9). The characteristic feature is that a defined reference position (R) of the steering actuator (4) is generated, and the current measured value of the rotational position of the drive pulley (51) detected by the rotation sensor (8) is compared with a preset reference value to detect deviation.

2. The method according to claim 1, characterized in that, The reference position (R) is generated by a mechanical stop.

3. The method according to any one of the preceding claims, characterized in that, The reference position (R) is generated by the adjustment state of the steering actuator (4).

4. The method according to any one of the preceding claims, characterized in that, The reference position is set by means of a belt drive (5).

5. The method according to any one of the preceding claims, characterized in that, The reference position (R) is preset by external settings of the steering actuator.

6. A steering system (1) for a motor vehicle, comprising a belt drive (5) and equipped with monitoring devices (8, 9), said belt drive having a toothed belt (53) that rotates in drive about a driving pulley (51) and a driven pulley (52), wherein, The driving wheel (51) is connected to the motor shaft of the motor (41) and the driven wheel (52) is effectively connected to the steering actuator (4). The monitoring device has a rotation sensor (8) connected to the control device (9) for detecting the rotational position of at least one of the pulleys (51, 52). The steering system (1) is characterized in that it is configured to implement the method according to any one of claims 1 to 5.

7. The steering system according to claim 6, characterized in that, A unique rotation sensor (8) is provided, the rotation sensor being configured to detect the rotation of the drive wheel (51), the steering actuator (4) being able to be placed in a defined reference position (R), and the control device (9) being configured to store, so as to compare the reference value with the current measurement value (M) of the rotation sensor (8) in the reference position (R).

8. The steering system according to any one of the preceding claims, characterized in that, The steering system is configured as a steer-by-wire system.

9. The steering system according to any one of the preceding claims, characterized in that, The steering actuator (4) has a feedback actuator.

10. The steering system according to any one of the preceding claims, characterized in that, The steering actuator (4) has a wheel actuator (4) that is effectively connected to a steerable wheel (61).

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