Road wheel steering actuator for a steer-by-wire steering system for a motor vehicle, and steer-by-wire steering system

Abstract

A road wheel steering actuator for a steer-by-wire steering system for a motor vehicle, and a steer-by-wire steering system are provided. [Solution] A road wheel steering actuator (4) for a steer-by-wire steering system (1) is designed to receive a control signal from a vehicle operation controller (9) to convert a steering command into a steering operation of at least one steerable wheel (7) of a motor vehicle, and the road wheel steering actuator comprises an electric motor (41), a deactivation device, and a control device, the deactivation device being switchable between a deactivation state and an activation state, and in the deactivation state of the deactivation device, the electric motor is switchable to a generator operation mode by a damping signal, and the control device is configured to send a deactivation control signal to the deactivation device to switch the deactivation device to the deactivation state.

Description

[Technical Field]

[0001] The present invention relates to a road wheel steering actuator for a steer-by-wire steering system for a motor vehicle, and to a steer-by-wire steering system for a motor vehicle. [Background technology]

[0002] In a steer-by-wire steering system, the steered road wheels of a motor vehicle are not connected to a steering wheel via a mechanical connection. Instead, steering commands are detected by sensors and converted into electrical signals that are transmitted via hardwire to road wheel steering actuators. The road wheel steering actuators cause the rotation of the steerable road wheels in response to the steering commands via electric motors.

[0003] Because there is no mechanical connection between the steering wheel and the road wheels, if a steer-by-wire steering system fails, the driver can no longer steer the vehicle. However, if the steer-by-wire steering system fails, it must be possible to safely stop the motor vehicle on the side of the road. To this end, the vehicle's drive and braking systems can be used to distribute torque to affect the yaw angle of the motor vehicle (torque vectoring).

[0004] DE 102024104136 A1 relates to a method for performing a "limp-aside" maneuver by selective acceleration and / or deceleration of individual wheels in order to move a vehicle into a safe parking position.

[0005] It is particularly important that the steering angle of the steerable wheels cannot be changed arbitrarily and freely, as this can lead to safety-critical driving situations.

[0006] To this end, EP 4273025 A1 relates to a steer-by-wire steering system that can switch the electric motor of a steering actuator into generator mode when a predetermined serious emergency condition is detected. To this end, the steer-by-wire steering system includes circuitry with switching elements operable to connect phases of the electric motor to each other so that the electric motor can operate in generator mode. As a result, the electric motor operates as an electric motor-driven brake, so that externally applied steering movement of the steerable wheels of the motor vehicle is limited, damped, or blocked.

[0007] For safe operation of a steer-by-wire steering system, it must be ensured that the externally applied steering motion is damped or blocked only when interference with the steer-by-wire steering system actually exists. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Application Publication No. 102024104136 [Patent Document 2] European Patent Application Publication No. 4273025 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem addressed by the present invention is to provide a road wheel steering actuator and steer-by-wire steering system that allows safe actuation of the damping or blocking of steering motion. [Means for solving the problem]

[0010] According to the present invention, the aforementioned problem is solved by a road wheel steering actuator for a steer-by-wire steering system for a motor vehicle. The road wheel steering actuator is designed to receive a control signal from a vehicle motion controller, in particular a steering wheel controller and / or an automatic steering controller, in order to convert a steering command into a steering movement of at least one steerable wheel of the motor vehicle, and preferably convert the received control signal into, in particular, a mechanical movement of a steering pinion. For this purpose, the road wheel steering actuator comprises an electric motor, a deactivation device, and a control device. The deactivation device is switchable between a deactivation state and an activation state, and in the deactivation state of the deactivation device, the electric motor can be switched into a generator operation mode by a damping signal. According to the present invention, the control device is configured to send a deactivation control signal to the deactivation device in order to switch the deactivation device into the deactivation state.

[0011] The deactivation device is preferably designed to establish an electrical connection between the damping signal input of the road wheel steering actuator and the operating mode switching device of the electric motor when the deactivation device is in a deactivation state. When the deactivation device is in an activation state, there is preferably no electrical connection between the damping signal input and the operating mode switching device. Advantageously, when the deactivation device is in an activation state, the damping signal received from the damping signal input cannot be transferred to the operating mode switching device due to the lack of electrical connection, and therefore the electric motor cannot be switched to the generator operating mode. As a result, preferably, in the case of a functional road wheel steering actuator, the damping signal does not result in a switch of the operating mode of the electric motor. As a result, the electric motor can be switched to the generator operating mode only if the functionality of the road wheel steering actuator and / or the control device is impaired.

[0012] In the generator operating mode, the electric motor provides resistance that prevents the steering angle of the steerable wheels of the motor vehicle from freely changing in any direction, thereby avoiding safety-critical driving situations.

[0013] In particular, the deactivation device is a relay, which in particular is closed in the deactivated state and is open in the activated state.

[0014] Due to the fact that the road wheel steering actuator is preferably configured to test the functionality of the road wheel steering actuator and / or the control device during the start-up operation of the road wheel steering actuator and / or the steer-by-wire steering system, the functionality of the road wheel steering actuator and / or the control device can be automatically tested, in particular by the road wheel steering actuator, before the start of the journey. In particular, to test the functionality during the start-up operation, test signals are used to test different components of the road wheel steering actuator. Alternatively or additionally, the road wheel steering actuator may preferably be designed to monitor the functionality of the road wheel steering actuator and / or the control device continuously, at periodic time intervals, or at random time intervals, in particular during operation of the road wheel steering actuator and / or the steer-by-wire steering system. In particular, the road wheel steering actuator can test itself. In particular, the steer-by-wire steering system may be designed to test the functionality of the road wheel steering actuator and / or the control device.

[0015] Due to the fact that the control device is preferably configured to send a deactivation control signal, in particular to send a deactivation signal only if the road wheel steering actuator and / or the control device do not fulfill the required functionality, the deactivation device can be switched to a deactivated state only in the event of a malfunction of the road wheel steering actuator and / or the control device. However, if the road wheel steering actuator and / or the control device are functioning, the deactivation control signal is preferably not sent, so that the deactivation device remains in an activated state. As a result, only in the event of insufficient functionality of the road wheel steering actuator and / or the control device can a damping signal be sent to the operating mode switching device of the electric motor, so that the electric motor can be switched to a generator operating mode.

[0016] The functionality of the road wheel steering actuator and / or controller is not fulfilled, in particular if the road wheel steering actuator and / or controller is not able to provide a minimum power range, is not ready for operation, in particular is not activated, etc.

[0017] In particular, the damping signal is a signal originating from a unit external to the road wheel steering actuator, in particular from a vehicle motion controller, and is in particular transmitted to a deactivation device and / or a control device, in particular to the electric motor via the deactivation device in a deactivated state, in order to operate the electric motor preferably in generator mode.

[0018] The above-mentioned problem is also solved by a steer-by-wire steering system for a motor vehicle. The steer-by-wire steering system comprises a steering handle, in particular a steering wheel, capable of issuing steering commands, at least one vehicle motion controller, in particular a steering controller and / or an automatic steering controller, at least one road wheel steering actuator designed according to the present invention, and at least one wheel steering unit, in particular a toothed rack, which interacts with the road wheel steering unit to steer at least one wheel of the motor vehicle. The statement that the vehicle motion controller is included in the steer-by-wire steering system particularly means that the steer-by-wire steering system can be operated by the vehicle motion controller, and in particular that the actuator of the steer-by-wire steering system can be operated by the vehicle motion controller, and the operation can in particular be performed directly or indirectly via the steering controller.

[0019] The steering command of the steering wheel is detected by a vehicle motion controller, more particularly a steering controller, and transmitted to a road wheel steering actuator by a hardwired connection, particularly via a cable harness of the motor vehicle. As a result, the movement of the steering wheel can be converted into the movement of the road wheel steering unit and thus the steerable wheels, so that the motor vehicle can be steered.

[0020] When the road wheel steering actuator and / or control device does not fulfill the required function, the deactivation device is in a deactivated state, and as a result, a damping signal can be sent to the operation mode switching device, and the electric motor can be switched to a generator operation mode. As a result, the electric motor provides resistance that prevents the steering angle of at least one steerable wheel of the motor vehicle from moving freely in any direction. As a result, safety-critical driving situations can be avoided.

[0021] In particular, a damping signal may be sent from the vehicle motion controller to the road wheel steering actuator.

[0022] Preferably, the operating mode switching device is a field effect transistor (FET), in particular a metal oxide semiconductor field effect transistor (MOSFET). As a result, it is preferable that the phases of the electric motor can be connected to each other so that the electric motor can be operated in generator mode.

[0023] The vehicle motion controller is a vehicle motion control system, short for VMC (Vehicle Motion Control), that can receive multiple driving conditions and / or parameters and activate multiple vehicle actuators. In particular, the vehicle motion controller is designed to exchange information with a steering controller. In particular, steering commands can be detected by the steering controller and / or feedback, such as steering resistance torque, can be provided to the driver by a feedback actuator based on driving information, such as speed and / or road unevenness and / or feedback from road wheel steering actuators, to provide a natural steering feel.

[0024] The invention will now be explained in more detail on the basis of exemplary embodiments in connection with the accompanying schematic drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows a schematic diagram of a steer-by-wire steering system for a motor vehicle according to an exemplary embodiment of the present invention; [Figure 2] 2 shows an exemplary block diagram of a vehicle motion controller and a road wheel steering actuator of the steer-by-wire steering system according to FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0026] 1 shows a schematic diagram of an exemplary embodiment for a steer-by-wire steering system 1 for a motor vehicle designed according to the present invention. The steer-by-wire steering system 1 comprises a steering wheel 2 connected to a vehicle motion controller 9. In the following exemplary embodiment, the vehicle motion controller 9 comprises a steering controller, which in particular may be an automatic steering controller. Via the steering wheel 2, a driver can issue steering commands and control the motor vehicle. The steering wheel 2 can be rotated in a known manner to introduce steering commands into the steering system 1, which are detected by the vehicle motion controller 9, in particular by using sensor devices and / or actuator devices of the steering system 1, and converted into steering movements of the motor vehicle.

[0027] The steer-by-wire steering system 1 also comprises a road wheel steering unit 5, in particular a toothed rack, a road wheel steering actuator 4 with a control device 45 (FIG. 2), and a steering pinion 42. The road wheel steering actuator 4 is connected to a vehicle motion controller 9 by a cable 10, in particular a cable harness of a motor vehicle, and comprises an electric motor 41, which may in particular be designed as a three-phase permanent magnet synchronous motor. The steering pinion 42 is preferably arranged on a shaft that can be driven by the electric motor 41, more particularly on the rotating shaft of the electric motor 41. The electric motor 41 can drive the steering pinion 42 to act on the road wheel steering unit 5 and to initiate steering movements of steerable road wheels 7 that are connected to the road wheel steering unit 5 via tie rods 6. The tie rods 6 are themselves connected in a known manner to each steered road wheel 7 via a steering knuckle.

[0028] Steering commands detected by the vehicle motion controller 9 are transmitted to the road wheel steering actuator 4. The road wheel steering actuator 4 generates a control signal based, among other things, on the received detected steering command. The control signal is transmitted to the electric motor 41 for converting the detected steering command into a steering movement of the steerable wheels 7. The electric motor 41 then converts the received control signal into a rotation of the steering pinion 42, which converts this rotation into a corresponding linear movement of the toothed rack, resulting in an adjustment of the steering angle of the steerable wheels 7.

[0029] If the road wheel steering actuator 4 and / or the control device 45 have a defect and therefore no longer fulfill the required function, there is a risk that the motor vehicle can no longer be controlled properly. In such a case, a so-called limp-aside maneuver is performed so that the motor vehicle can enter a safe parking position. It is particularly important that the steering angle of the steerable wheels 7 cannot be changed arbitrarily and freely.

[0030] To avoid this, the electric motor 41 is switched to a generator operating mode (FIG. 2) by the operating mode switching device 46 by correspondingly connecting the phases of the electric motor 41 to one another. As a result, the electric motor 41 provides resistance that prevents the steering angle of the steerable wheels 7 of the motor vehicle from moving freely in any direction. In particular, the electric motor 41 is adapted to change operating mode only if the road wheel steering actuator 4 and / or the control device 45 no longer fulfill the required functionality. This means, for example, that the road wheel steering actuator 4 and / or the control device 45 do not provide a minimum power range or are not ready for operation, e.g., have not been started up.

[0031] FIG. 2 shows a block diagram of the vehicle motion controller 9 and the road wheel steering actuator 4 of the steer-by-wire steering system 1.

[0032] The vehicle motion controller 9 comprises an energy supply source 91, a damping signal output 92, and a control device 93. The control device 93 can activate a switching device 94, which can then transition to a closed state. In the closed state, the vehicle motion controller 9 generates a damping signal, which is sent to the road wheel steering actuator 4 via a cable 10.

[0033] The damping signal is received by a damping signal input 43 of the road wheel steering actuator 4 and forwarded to a readback circuit 44 which forwards the damping signal to a deactivation device 47 and / or a control device 45.

[0034] The deactivation device 47 can be switched between a deactivated state and an activated state. To switch the deactivation device 47 to the deactivated state, it must receive a deactivation control signal. When the deactivation control signal is present, the deactivation device 47 is in the deactivated state and connects the readback circuit 44 to the operating mode switching device 46. The deactivation device 47 is, in particular, a relay that is closed in the deactivated state.

[0035] When the control device 45 and the road wheel steering actuator 4 fulfill the required functions, either the deactivation control signal is not output, or the activation control signal for switching the deactivation device 47 to an activation state is output by the control device 45 and sent to the deactivation device 47. In this case, the deactivation device 47 is in an activation state, i.e., an open state, if the deactivation device 47 is designed as a relay, and therefore cannot send a damping signal to the operation mode switching device 46. As a result, it is possible to effectively prevent, for example, an erroneously sent damping signal from reaching the operation mode switching device 46 and thus switching the electric motor 41 to the generator operation mode.

[0036] The functionality of the road wheel steering actuator 4 and / or the control device 45 is tested automatically and / or by the steer-by-wire steering system 1 during start-up operation of the steering system based on a test signal from the road wheel steering actuator 4. The test signal may be transmitted, in particular, by the read-back circuit 44. Alternatively or additionally, the functionality of the road wheel steering actuator 4 and / or the control device 45 is monitored automatically and / or by the steer-by-wire steering system 1 during operation of the road wheel steering actuator 4.

[0037] If the road wheel steering actuator 4 and / or the control device 45 do not fulfill the required function, either the activation control signal is not sent or the deactivation control signal is sent from the control device 45 to the deactivation device 47. If the activation control signal is not sent or the deactivation control signal is sent to the deactivation device 47, the deactivation device 47 is in a deactivated state, whereby a damping signal can be sent from the vehicle operation controller 9 or the read-back circuit 44 to the operation mode switching device 46. Thus, the electric motor 41 can be switched to a generator operation mode, whereby braking or blocking of the steered wheels 7 is performed.

[0038] The deactivation device 47 therefore contributes to ensuring that a safe actuation of the braking or blocking of the steered wheels 7 is carried out. The motor vehicle is then steered, in particular by the vehicle motion controller 9, by selective actuation of further actuators which influence the direction of travel of the motor vehicle, in particular the drive and brake units of the motor vehicle. [Explanation of symbols]

[0039] 1 Steer-by-wire steering system 2 steering wheels 3 Steering gear 4 Road Wheel Steering Actuator 41 Electric Motor 42 Steering pinion 43 Attenuated signal input 44 Readback circuit 45 Control Device 46 Operation mode switching device 47 Deactivation Device 5 Wheel Steering Unit 6 tie rod 7 Steerable wheels 9 Vehicle Operation Controller 91 Energy Sources 92 Attenuated signal output 93 Control Device 94 Switching Device 10 Cable

Claims

1. A road wheel steering actuator (4) for a steer-by-wire steering system (1) for a motor vehicle, the road wheel steering actuator (4) being designed to receive a control signal from a vehicle motion controller (9) to convert a steering command into a steering movement of at least one steerable wheel (7) of the motor vehicle; the road wheel steering actuator (4) comprises an electric motor (41), a deactivation device (47) and a control device (45); A road wheel steering actuator (4), wherein the deactivation device (47) is switchable between a deactivation state and an activation state, and in the deactivation state of the deactivation device (47), the electric motor (41) is switchable to a generator operation mode by a damping signal, The control device (45) is configured to send a deactivation control signal to the deactivation device (47) to switch the deactivation device (47) to the deactivated state.

2. Road wheel steering actuator (4) according to claim 1, characterized in that the deactivation device (47) is a relay.

3. 3. The road wheel steering actuator (4) according to claim 1 or 2, characterized in that the road wheel steering actuator (4) is configured to test the functioning of the road wheel steering actuator (4) and / or the control device (45) during a start-up operation of the road wheel steering actuator (4) and / or during operation of the road wheel steering actuator (4).

4. 2. The road wheel steering actuator (4) according to claim 1, characterized in that the control device (45) is configured to send the deactivation control signal if the road wheel steering actuator (4) and / or the control device (45) do not fulfil a required function.

5. Road wheel steering actuator (4) according to claim 1, characterized in that the damping signal is an external signal.

6. - a steering wheel (2) that can specify steering commands; at least one vehicle motion controller (9); - at least one road wheel steering actuator (4) according to claim 1 and at least one wheel steering unit (5) or toothed rack; wherein the road wheel steering actuator (4) interacts with the wheel steering unit (5) to steer at least one wheel (7) of the motor vehicle.

7. The steer-by-wire steering system (1) according to claim 6, characterized in that a damping signal is issued from the vehicle motion controller (9) to switch the electric motor (41) into a generator operation mode.

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