Steering system for a motor vehicle and method for determining the steering rod force in a steering system

Abstract

A steering system (1; 100) for a motor vehicle comprises a first toothed belt pulley (23.1; 123.1), a second toothed belt pulley (23.2; 123.2), a toothed belt (23.3; 123.3) which drive-couples the first toothed belt pulley (23.1; 123.1) and the second toothed belt pulley (23.2; 123.2), a first sensing device (25; 125) for generating a signal which represents the rotational angle position of the first toothed belt pulley (23.1; 123.1), and a second sensing device (26; 126) for generating a signal which represents the rotational angle position of the second toothed belt pulley (23.2; 123.2). Furthermore, an evaluation device (27; 127) is provided, to which the signals of the first and second sensing devices (25, 26; 125, 126) are applied, and which is configured to generate a value representing the belt force of the toothed belt (23.3; 123.3) from the signals of both sensing devices (25, 26; 125, 126).Furthermore, a method for determining the steering rod force in a steering system is specified.

Description

[0001] The invention relates to a steering system for a motor vehicle and further to a method for determining the steering rod force in a steering system.

[0002] In a steer-by-wire steering system for a motor vehicle, unlike conventional vehicle steering systems with mechanical override, the mechanical coupling typically found between a steering handle, such as a steering wheel, on the one hand, and a wheel actuator, such as a steering gear with a steering rod leading to the vehicle wheels, on the other hand, is eliminated. To apply the steering forces, the wheel actuator comprises an electric motor, which is coupled to the steering rod via a toothed belt drive. The necessary information between the steering handle and the wheel actuator is transmitted solely electrically or, if necessary, wirelessly.

[0003] By eliminating the mechanical coupling, the steering handle could move virtually without feedback and without any additional measures. However, a steering wheel that always turns equally easily with almost no resistance would take a lot of getting used to for a driver familiar with a conventional steering system with mechanical coupling, especially since any feedback from the road surface at the steering wheel would be lost. For this reason, an actuator is coupled to the steering handle. This actuator generates artificial feedback at the steering handle, thus adjusting the haptic feel of the steering that the driver can perceive. Such an actuator, which usually comprises an electric motor, is therefore also referred to as a haptic actuator or force feedback actuator.

[0004] The control of the haptic actuator and the determination of a control variable for it can not only be carried out as a function of a steering wheel angle, but can also take into account the steering angle of the vehicle wheels as additional feedback, as described, for example, in DE 103 38 427 A1, EP 1 273 501 A2 and EP 1 433 691 A2.

[0005] Another approach involves determining a rack force as feedback for the haptic actuator's manipulated variable. However, with regard to steer-by-wire steering systems, the term "steering rack force" is more generally used here, since toothing in the sense of a rack is no longer absolutely necessary. Accordingly, the term "steering rack" is used below instead of the term "rack."

[0006] In addition to being used for a haptic actuator, such a steering rod force can also be considered for other control and / or regulation purposes on the vehicle, for example, in the context of steering and / or driving dynamics. Precise determination of the steering rod force could, for example, enable control strategies with expanded functional scopes.

[0007] A wide variety of approaches are known for determining such a steering rod force. A basic distinction can be made between sensor-based approaches and estimation methods.

[0008] However, estimation methods usually suffer from relatively high inaccuracies and require appropriate plausibility checks. Sensor-based approaches offer higher accuracy but are generally more costly due to the additional components and assembly steps required.

[0009] For example, in DE 10 2011 055 339 A1, the steering rod force is estimated from the lateral force of the relevant steering axis. This also includes filtering using a signal processing element with proportional-differential transmission characteristics to create a more comfortable steering feel. The lateral force is calculated using a vehicle model from the vehicle's speed, yaw rate, and lateral acceleration. However, such an estimation is often only possible with the steering rod moving. Once the steering is in the range of static friction, precise values ​​can no longer be determined.

[0010] DE 10 2017 105 370 A1 describes controlling a haptic actuator based on an estimated steering rod force. A vehicle model and a steering gear model are used to estimate the steering rod force. Their combination is intended to result in a more accurate determination of the steering rod force and thus an improved steering feel for the driver.

[0011] Further strategies for non-sensor-based steering rod force estimation are described in WO 2022 / 069146 A1 and DE 10 2019 118 831A1.

[0012] Sensor-based approaches are mentioned, for example, in EP 2 383 167 A1. In particular, force sensors are mentioned therein, which are arranged between the tie rods and the steering rod. These sensors can provide a signal that directly represents the axial force on the steering rod. Another type of sensor can be provided near a pressure piece that forces the steering rod into close contact with a steering pinion. The load on a thrust element is representative of the force acting between the meshing teeth of the steering pinion and the steering rod. A third type of sensor, according to EP 2 383 167 A1, can detect the axial force on the steering pinion, which arises from the inclination of the teeth on the steering rod and the steering pinion. Due to this inclination, any force or load in the axial direction of the steering rod leads to an axial force component on the steering pinion, which can be measured.

[0013] From EP 0 194 003 A1 it is known to detect an axially acting force of a steering pinion by means of piezoelectric transducers, wherein the piezoelectric transducers are associated with a ball bearing and directly measure the forces acting in the axial direction of the pinion.

[0014] DE 10 2022 203 322 A1 discloses an indirect sensory detection of the handlebar force by detecting, for example, on a pressure piece, a pressure force component directed radially to the longitudinal axis of the handlebar.

[0015] However, with steer-by-wire steering systems, such solutions are obsolete due to the lack of a steering pinion.

[0016] Against this background, the invention is based on the object of demonstrating alternative possibilities which allow a sensor-supported determination of a steering rod force on a steering system for a motor vehicle with little effort.

[0017] This object is achieved by a steering system for a motor vehicle having the features of patent claim 1. The steering system comprises a first toothed belt pulley, a second toothed belt pulley, a toothed belt that drive-couples the first toothed belt pulley and the second toothed belt pulley, a first sensing device for generating a signal representing the angular position of the first toothed belt pulley, a second sensing device for generating a signal representing the angular position of the second toothed belt pulley, and an evaluation device to which the signals from the first and second sensing devices are applied. The evaluation device is configured to generate a variable representing the belt force from the signals of both sensing devices.

[0018] The belt force represents the force applied to the steering rod, which can be obtained with little effort in this way, since the sensors used for this purpose are usually present on the vehicle for other purposes. This takes advantage of the fact that the belt's elongation is largely insensitive to temperature fluctuations within the relevant operating temperature range, to service life, and to other fluctuations, and is also generally almost proportional to the torque applied to the timing belt drive.

[0019] In the simplest case, the torque can be determined from the signal comparison, since the stretching behavior of the timing belt is known.

[0020] Particular embodiments of the invention are the subject of further patent claims.

[0021] In order to improve the accuracy, a difference can be formed from the angles of rotation of both toothed belt pulleys to obtain the value representing the belt force by means of the said signals of the first and second sensing device, said difference being normalized to the angle of rotation of one of the toothed belt pulleys, taking into account the transmission ratio of the toothed belt drive.

[0022] Furthermore, when obtaining the value representing the belt force, the difference can be related to a reference value for the difference for a minimum value of the belt force. The minimum value can be specified as a fixed value or continuously updated during driving. Ideally, the minimum value can be zero.

[0023] Optionally, it is also possible to relate the difference to the angle of rotation of one of the two sensing devices. In this context, a reference position for the minimum value of the belt force can also be specified for at least one of the signals from the two sensing devices. This makes it possible to take into account any dependencies of the belt force on the angle of rotation of the timing belt pulleys.

[0024] According to a particular embodiment of the invention, the first sensing device comprises or is an absolute angle sensor. Using an absolute angle sensor, a signal can be generated that provides a unique signal for each angle within an angular range of 0° to 360° (single-turn sensor) or for angular ranges greater than 360° (multi-turn sensor or single-turn sensor in combination with detection of the number of complete revolutions). In an electromechanical steering system, at least one such sensor is generally present.

[0025] According to another particular embodiment of the invention, the second sensing device comprises or is an index angle sensor. An index angle sensor is an incremental encoder that delivers a specific number of step pulses per revolution. The value is calculated by counting the pulses. An absolute angle can only be determined after processing a reference mark or detecting the marking of a zero point. Index angle sensors offer high angular resolutions, but their frequency depends on the steering speed. In the context of the present invention, this allows for greater accuracy than with an absolute measuring sensor, since the angle value is very precise when detecting an index.Furthermore, the index angle sensor can be used as a back-biased sensor, which means that no magnet is required, but rather only a more cost-effective ferromagnetic structure such as a stamped sheet on the large pulley.

[0026] However, it is also possible that the second sensing device, like the first sensing device, has or is an absolute value angle sensor.

[0027] The second sensing device can also be provided via at least one haptic reference mark, over which a significant change in the motor current of an electric motor driving the first toothed belt pulley occurs. In this case, the motor current is evaluated as a signal from the second sensing device.

[0028] The haptic reference mark changes the steering resistance, which is noticeable in the electric motor's current. As long as there is no belt jump during driving, a significant change in the electric motor's current will always occur at a specific rotor position of the electric motor and will shift slightly as the timing belt stretches. This shift corresponds to the belt force and thus ultimately to the steering rod force.

[0029] Relevant reference information can be kept on the vehicle. Timing belt stretching will generally develop more slowly than belt jumps, which can be used to differentiate between the latter. A corresponding test routine can be provided for this purpose.

[0030] This eliminates the need for any dedicated sensors on the handlebar. By creating a haptic reference mark, for example, on the handlebar or on a component connected to it on the handlebar side of the timing belt drive (as opposed to the electric motor side of the timing belt drive), appropriate information regarding timing belt stretching or belt jumping can be provided using the components already present for controlling the electric motor.

[0031] According to another particular embodiment of the invention, the first sensing device is a rotor position sensor of an electric motor that is rotationally fixedly coupled to the first toothed belt pulley. The rotor position sensor of the electric motor can be scanned at a very high frequency.

[0032] However, the detection of the angle of rotation of the first toothed belt pulley on the drive side can also take place at another location, for example directly on the first toothed belt pulley or on a component coupled to it, such as a drive shaft of the electric motor or an auxiliary shaft coupled to it or the first toothed belt pulley.

[0033] The evaluation of the rotation angle difference based on the difference between the signals from the two sensor devices can be implemented in a steering control unit. However, the evaluation device can also be implemented as a separate component that is not part of the steering control unit.

[0034] The steering system with toothed belt drive described above enables a new, cost-effective and accurate method for determining the steering rod force, in which a value representing the belt force is generated from the signals of both sensing devices, which is considered as the steering rod force.

[0035] Taking into account the fixed transmission ratio of the toothed belt drive, the rotational angle position of the first toothed belt pulley corresponds to a specific rotational angle position of the second toothed belt pulley at a minimum value of the belt force.

[0036] If the belt force increases due to a steering rod force, the toothed belt elastically stretches. As a result, the original relationship between the rotational angle position of the first toothed belt pulley and the rotational angle position of the second toothed belt pulley changes. This results in an offset. This can be detected by the rotational angle sensor described above and used to determine the steering rod force.

[0037] In the following, ways of implementing the invention are explained in more detail using exemplary embodiments illustrated in the drawing. The drawing shows: Fig. 1 is a schematic representation of a steering system for a motor vehicle in the form of a steer-by-wire steering system according to a first embodiment of the invention, Fig. 2 a schematic representation of the steering gear or wheel actuator of the Fig. 1 shown steering, Fig. 3 a detailed view of the steering from the Fig. 1 and Fig. 2, Fig. 4 a diagram illustrating the dependence of the belt force on a standardized rotation angle offset, Fig. 5 is a schematic view of an electromechanical steering system according to a second embodiment of the invention, and in Fig. 6 a detailed view of a steering rod of the steering according to Fig. 5.

[0038] Fig. 1 shows a schematic representation of a possible example of a steering system 1 for a motor vehicle, in particular for a passenger car or light commercial vehicle.

[0039] The steering system 1 of the first exemplary embodiment is embodied here as a steer-by-wire steering system. It can be divided into a steering column module 10 for inputting a driver-side steering command and a steering gear module (also wheel actuator) 20, which are mechanically decoupled from each other.

[0040] The steering column module 10 includes a steering handle 11 for inputting the steering command by a driver of the motor vehicle. The steering handle 11 is, for example, a steering wheel as shown, but can also be another input device such as a joystick or the like. In the case of a steering wheel, the steering command is a steering wheel angle. Furthermore, the steering command can optionally take into account the steering wheel angular velocity and / or steering wheel angular acceleration.

[0041] Furthermore, the steering column module 10 of the steering system 1 includes a haptic actuator (also known as a force feedback actuator) 12, which is mechanically coupled to the steering handle 11. The haptic actuator 12 serves to simulate a steering reaction for the driver on the steering handle 11. This is expressed in resistance when steering and, if necessary, in an active return of the steering handle 11 to a neutral position corresponding to straight-ahead driving on level ground.

[0042] The haptic actuator 12 comprises a motor 13, which is mechanically coupled to the steering handle 11 by means of a shaft 14. In addition, a Fig. 1 control unit 3a, not shown in detail, is provided for controlling the motor 13 of the haptic actuator 12.

[0043] The steering gear module 20 of the steering system 1 forms a wheel actuator for adjusting a steering angle on steerable vehicle wheels 2 of the motor vehicle and has an electric motor 21, which drives a steering rod 22 coupled to the vehicle wheels 2. A further control unit 3b can be provided on the steering gear module 20.

[0044] Characteristic of a steer-by-wire steering system 1, there is no mechanical coupling between the steering gear module 20 and the steering handle 11 and the haptic actuator 12. To link the steering gear module 20 to the steering handle 11 and the haptic actuator 12, the steering system 1 comprises a control device 3 configured to, depending on a driver-side steering command, cause the steering gear module 20 to effect a steering actuation of the vehicle wheels 2 and to cause the haptic actuator 12 to generate a steering reaction on the steering handle 11. The connection can be electrically wired or wireless.

[0045] The control device 3 of the steering system 1 can be concentrated in a central control unit or, as shown here by way of example, distributed over various control units 3a and 3b on the haptic actuator 12 and on the steering gear module 20 or arranged in another way.

[0046] The steering gear module 20 of the steering 1 is in Fig. 2. In addition to the aforementioned electric motor 21 and the steering rod 22, this further comprises a gear 23 for translating a rotary movement of the electric motor 21 into a translational movement of the steering rod 22.

[0047] The transmission 23 comprises a toothed belt drive, as shown in Fig. 2 is shown as an example. A first toothed belt pulley 23.1 on the transmission input side is non-rotatably coupled to a drive shaft 21.1 of the electric motor 21, while a second toothed belt pulley 23.2 on the output side is drivingly coupled to the steering rod 22, for example via a ball screw drive 24. Said toothed belt pulleys 23.1 and 23.2 are in turn drivingly coupled to one another via a toothed belt 23.3, so that a torque applied by the electric motor 21 can be applied as a longitudinal force on the steering rod 22.

[0048] The steering system 1 has a first sensing device 25, by means of which a signal is generated that represents the rotational angle position of the first toothed belt wheel 23.1.

[0049] Furthermore, the steering system 1 has a second sensing device 26, by means of which a signal is generated that represents the rotational angle position of the second toothed belt wheel 23.2.

[0050] The angle of rotation can be detected directly on the respective toothed belt pulley 23.1, 23.2 or on a component connected to it in a rotationally fixed manner.

[0051] The signals of the first and second sensing devices 25 and 26 are connected to an evaluation device 27, which is integrated, for example, in the control unit 3b of the steering gear module 20, but can also be provided at another location and, if necessary, also as a separate component.

[0052] The evaluation device 27 is configured to generate a value representing the belt force from the signals of both sensing devices 25, 26.

[0053] The belt force correlates strongly with the handlebar force, which can therefore be determined very precisely.

[0054] This is based on the consideration that the stretching behavior of the timing belt 23.3 is proportional to the torque applied to the timing belt drive, as shown in Fig. 4. Furthermore, this expansion behavior is insensitive to temperature fluctuations within the relevant operating temperature range of the steering system 1 and changes only imperceptibly over its service life. Therefore, the steering rod force can be determined very easily and reliably from the angular offset between the toothed belt pulleys 23.1 and 23.2, taking into account the gear ratio of the toothed belt drive.

[0055] For this purpose, the angle of rotation of one toothed belt pulley 23.1 or 23.2 can be conveniently standardized to the angle of rotation of the other toothed belt pulley 23.2 or 23.1 using the gear ratio. The standardization can also be performed to a different angular value.

[0056] In particular, in order to obtain the value representing the belt force, a difference can be formed from the standardized angles of rotation of both toothed belt wheels from 23.1 and 23.2 by means of said signals of the first and second sensing devices 25 and 26.

[0057] The difference can be related to a reference value for a minimum value of the belt force. We in Fig. As shown in Figure 4, the angular misalignment increases linearly with increasing transmitted torque of the timing belt drive due to an elastic stretching of the timing belt 23.3.

[0058] In principle, it is possible to use sensors for the second sensing device 25 that detect the position of a steering component on the transmission output side of the toothed belt drive, i.e., toward or on the steering rod 22. However, nonlinearities in the power transmission become increasingly noticeable here, which must be taken into account when evaluating the signal from the second sensing device 25. Therefore, positioning the sensors as close as possible to the toothed belt 23 is preferable.

[0059] In one possible embodiment, the angle of rotation of the first toothed belt pulley 23.1 on the transmission input side can be provided via a first sensing device 25 in the form of a rotor position sensor of the electric motor 21, which is scanned at a very high frequency.

[0060] The angle of rotation of the second toothed belt pulley 23.2 on the output side is not detected by an absolute angle sensor, but rather by an index angle sensor or incremental encoder. Such an incremental encoder offers high angular resolution. The evaluation preferably takes place directly on the control unit 3b of the steering gear module 20.

[0061] In a modification of this, however, the second sensing device 26 can also comprise an absolute value angle sensor or be designed as such.

[0062] Furthermore, as explained below in the context of a second exemplary embodiment, the second sensing device 26 can have at least one haptic reference mark, which, when passed over, causes a significant change in the motor current of the electric motor 21. In this case, the motor current can be evaluated as a signal from the second sensing device 26.

[0063] The configuration explained above enables the precise determination of a steering rod force of a steering system 1 using components that are usually present on such a steering system 1 in a simple and cost-effective manner.

[0064] In particular, it enables a method for determining the steering rod force in a steering system 1, in which a value representing the belt force, which is considered the steering rod force, is generated from the signals of both sensing devices 25 and 26. The signal difference corresponds to a rotational angle offset between the first toothed belt pulley 23.1 and the second toothed belt pulley 23.2 of the toothed belt drive, via which the torque of the electric motor 21 is applied to the steering rod 22.

[0065] The principle for determining the steering rod force explained above in the context of a steer-by-wire steering system can also be used in other steering configurations, especially those with mechanical through-reach. Fig. 5 and Fig. 6 shows a second embodiment which shows an electromechanical steering system 100 for a passenger car or light commercial vehicle.

[0066] The electromechanical steering 100 in the Fig. 5 and Fig. 6 has a steering gear housing 120 through which a steering rod 122 extends. The steering rod 122 is coupled at its axial ends to a steerable vehicle wheel 2 via tie rod joints 101 and tie rods 102.

[0067] A steering pinion 110 can engage the steering rod 122 in order to transmit a steering command applied by the driver to a steering handle 111 to the vehicle wheels 2 via the steering rod 122. For this purpose, a corresponding toothed section 122a can be formed on the steering rod 122, which engages with the steering pinion 110.

[0068] Furthermore, the electromechanical steering 100 in Fig. 5 has an electric drive unit for generating a steering torque, which comprises an electric motor 121. The electric motor 121 is drivingly coupled to the handlebar 122 via a gear in order to translate a rotational movement of the electric motor 121 into a translational movement of the handlebar 122 in the longitudinal direction A thereof.

[0069] The transmission comprises at least one toothed belt drive 123 and, in this case, by way of example, also a ball screw drive 124. The toothed belt drive 123 ensures a defined assignment of the position of the rotor of the electric motor 121 to the position of the steering rod 122.

[0070] The toothed belt drive 123 has a first toothed belt pulley 123.1, which is preferably arranged in a rotationally fixed manner on a drive shaft 121a of the electric motor 121. Furthermore, the toothed belt drive 123 has a second toothed belt pulley 123.2, which is drivingly coupled to the first toothed belt pulley 123.1 by means of a toothed belt 123.3. The second toothed belt pulley 123.2 is here connected in a rotationally fixed manner to a ball screw nut 124a of the ball screw drive 124. The ball screw nut 124a, in turn, is threadably engaged via balls with a spindle portion 122b formed on the handlebar 122.

[0071] In the illustrated embodiment, the electric motor 121 is arranged axially parallel to the handlebar 122. However, such an arrangement can also be deviated from by interposing one or more suitable gear stages.

[0072] As already explained in connection with the first exemplary embodiment, the steering system 100 of the second exemplary embodiment also has a first sensing device 125 for detecting the angular position of the first toothed belt pulley 123.1, in this case in the form of a rotor position sensor of the electric motor 121. Such a first sensing device 125 is required, among other things, for providing steering assistance by the electric motor 121 and is accordingly usually present in an electromechanical steering system 1. A signal is available via the first sensing device 125, which represents the absolute position of the rotor position of the electric motor 121 as well as the angular position of the first toothed belt pulley 123.1.

[0073] As part of a second sensing device 126 for generating a signal which represents the rotational angle position of the second toothed belt wheel 123.2, at least one haptic reference mark 126a is provided on the handlebar 122 or, if appropriate, also on a component coupled thereto, which, with respect to the toothed belt drive 123, is located on the side of the handlebar 122 and not on the side of the electric motor 1219.

[0074] The at least one haptic reference mark 126a is designed such that, when the vehicle passes over it, a significant change in the motor current i of the electric motor 121 occurs. The reason for this is that, when the vehicle passes over the at least one haptic reference mark 126a, the resistance in the steering changes slightly, which can be read off in the signal of the motor current i, which changes significantly in this case.

[0075] The at least one haptic reference mark 126a can be formed, for example, by an elevation on a contact surface or by a depression in a contact surface of the handlebar 121.

[0076] A haptic reference mark 126a can be applied, for example, using a laser through additive embossing to create a raised area. Play is reduced in this area, thus slightly increasing steering resistance. Suitable raised areas are in the range of 0.01 to 0.2 mm in height. Applying a haptic reference mark 126a using laser marking is a cost-effective and precise process.

[0077] Instead of a laser marking, a haptic reference mark 126a can also be provided in other ways. For example, it can be applied using machining processes, engraving, or the introduction of wave patterns and / or chatter marks. Furthermore, it is possible to increase resistance by intentionally omitting surface finishing, such as finishing, in certain areas of the contact surfaces.

[0078] In the Fig. In the embodiment shown in Figure 6, two haptic reference marks 126a are arranged on the spindle section 122b of the handlebar 122. However, the number of haptic reference marks 126a and their positioning may vary from the illustrated arrangement.

[0079] When the ball screw nut 124a of the ball screw drive 124 engages the relevant area of ​​the spindle section 122b, the haptic reference marks 126a reduce the play of the balls of the ball screw drive 124, causing it to briefly become somewhat stiffer. However, the stiffness created by this does not impair the handling of the steering, but rather occurs in an area close to or within the driver's perception threshold. If necessary, the crossing of the haptic reference marks 126a can be designed in such a way that it normally goes unnoticed by the driver.

[0080] Furthermore, the expected time of crossing the at least one haptic reference mark 126 in relation to the rotational angle position of the first toothed belt pulley 123.1, for example at minimal belt force, is known. If the toothed belt 123.3 elongates as a result of the transmitted torque, the occurrence of the significant change in the motor current i shifts relative to the rotor position of the electric motor 121 and thus also to the rotational angle position of the first toothed belt pulley 123.1. In this respect, the motor current i can be considered as a signal from the second sensing device 126 and used to determine the steering rod force in the manner demonstrated in the first exemplary embodiment. By appropriately interpreting the signal of the motor current i, such a torque-related elastic and temporary elongation of the toothed belt 123.3 can be distinguished from belt jumping.

[0081] As already mentioned, the haptic reference marks 126 do not necessarily have to be arranged on the spindle section 122b of the handlebar 122 in order to cause a significant change in the motor current i, but can also be provided elsewhere where they increase or decrease the resistance in the steering 100.

[0082] By using haptic reference marks 126a, additional components within the electromechanical steering system 100 can be dispensed with for determining the steering rod force. Instead, this is achieved using components already required on the vehicle in conjunction with a routine that can be implemented purely in software. In particular, no additional external sensors or cables are required for determining the steering rod force. Accordingly, a corresponding ECU connection for generating the signal of the second sensing device 126 is omitted.

[0083] In a modification of this, however, a sensor device for detecting structure-borne noise can optionally be provided and arranged in such a way as to acoustically detect the passing of a haptic reference mark 126. This can replace or verify the information obtained via the motor current i, but at the expense of additional sensor technology.

[0084] The invention has been explained in more detail above using exemplary embodiments and further modifications. The exemplary embodiments and modifications serve to demonstrate the feasibility of the invention. Technical features explained above in the context of further features can also be implemented independently of these and in combination with further features, even if this is not expressly described, as long as this is technically possible. The invention is therefore expressly not limited to the specifically described exemplary embodiments, but encompasses all configurations defined by the patent claims. List of reference symbols 1 steering 2 vehicle wheel 3 Control unit 3a Control unit on the steering column module side 3b Control unit on the steering gear module side 10 Steering column module 11 Steering handle 12 Haptic actuator 13 Engine 14 Wave 20 Steering gear module 21 Electric motor 22 Handlebar 23 gearboxes 23.1 first toothed belt wheel of the gearbox 23 23.2 second toothed belt wheel of the gearbox 23 23.3 Timing belt 24 ball screw 25 first sensing device 26 second sensing device 27 Evaluation device 100 Steering 101 Tie rod end 102 Tie rod 110 steering pinion 111 Steering handle (steering wheel) 120 steering gear housing 121 electric motor 121a drive shaft 122 handlebar 122a Gear section 122b spindle section 123 Toothed belt drive 123.1 first toothed belt wheel 123.2 second toothed belt pulley 123.3 Timing belt 124 Ball screw 124a ball screw nut 125 first sensing device 126 second sensing device 126a haptic reference mark 127 Evaluation device A Longitudinal direction of the handlebar QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 103 38 427 A1

[0004] EP 1 273 501 A2

[0004] EP 1 433 691 A2

[0004] DE 10 2011 055 339 A1

[0009] DE 10 2017 105 370 A1

[0010] WO 2022 / 069146 A1

[0011] DE 10 2019 118 831A1

[0011] EP 2 383 167 A1

[0012] EP 0 194 003 A1

[0013] DE 10 2022 203 322 A1

[0014]

Claims

[1] Steering (1; 100) for a motor vehicle, comprising a first toothed belt wheel (23.1; 123.1), a second toothed belt wheel (23.2; 123.2), a toothed belt (23.3; 123.3) which couples the first toothed belt wheel (23.1; 123.1) and the second toothed belt wheel (23.2; 123.2) in a driving manner, a first sensing device (25; 125) for generating a signal representing the rotational angle position of the first toothed belt wheel (23.1; 123.1), a second sensing device (26; 126) for generating a signal representing the angular position of the second toothed belt wheel (23.2; 123.2), and an evaluation device (27; 127) to which the signals of the first and second sensing devices (25, 26; 125, 126) are applied, wherein the evaluation device (27; 127) is configured to generate a variable representing the belt force of the toothed belt (23.3; 123.3) from the signals of both sensing devices (25, 26; 125, 126). [2] Steering system for a motor vehicle according to claim 1, characterized by in that, in order to obtain the value representing the belt force, a difference is formed from the angles of rotation of both toothed belt wheels (23.1, 23.2; 123.1, 123.2) standardized to the angle of rotation of one of the toothed belt wheels, taking into account the transmission ratio of the toothed belt drive, by means of said signals from the first and second sensing devices (25, 26; 125, 126). [3] Steering system for a motor vehicle according to claim 2, characterized by that the difference is related to a reference value for a minimum value of the belt force. [4] Steering system for a motor vehicle according to one of claims 1 to 3, characterized bythat the first sensing device (25; 125) comprises or is an absolute value angle sensor. [5] Steering system for a motor vehicle according to one of claims 1 to 4, characterized by that the second sensing device (26; 126) comprises or is an index angle sensor. [6] Steering system for a motor vehicle according to one of claims 1 to 4, characterized by that the second sensing device (26; 126) comprises or is an absolute value angle sensor. [7] Steering system for a motor vehicle according to one of claims 1 to 4, characterized by in that the second sensing device (26; 126) has at least one haptic reference mark (126a) which, when passed over, causes a significant change in a motor current of an electric motor (21; 121) which drives the first toothed belt wheel (23.1; 123.1), wherein the motor current is evaluated as a signal of the second sensing device (26; 126). [8] Steering system for a motor vehicle according to one of claims 1 to 7, characterized by that the first sensing device (25; 125) is a rotor position sensor of an electric motor (121) which is non-rotatably coupled to the first toothed belt wheel (23.1; 123.1). [9] Method for determining the steering rod force in a steering system according to one of the preceding claims, in which a variable representing the belt force is generated from the signals of both sensing devices (25, 26; 125, 126), which is regarded as the steering rod force. [10] Method according to claim 9, characterized by that a signal difference is generated from the signal representing the angular position of the first toothed belt wheel (23.1; 123.1) and the signal representing the angular position of the second toothed belt wheel (23.2; 123.2), such that the signal difference corresponds to a angular offset between the first toothed belt wheel (23.1; 123.1) and the second toothed belt wheel (23.2; 123.2).

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