DE102019109886A1 - Manual force actuator with a sensor system for torque detection - Google Patents

Abstract

The invention relates to a manual force actuator (10) with a longitudinal axis (L) for a steer-by-wire steering system of a vehicle, having an outer housing arrangement (12), an electric motor (14), the electric motor (14) along the longitudinal axis ( L) at one end of the housing arrangement (12) is arranged non-rotatably on the housing arrangement (12), at least one steering spindle (16) for absorbing a steering torque of a steering wheel (18), the steering spindle (16) being rotatable about the longitudinal axis (L) in the housing arrangement (12) is mounted, and wherein the steering spindle (16) for transmitting a torque (D) is at least indirectly connected to the electric motor (14), at least one bearing (20) for rotatably supporting the steering spindle (16) in the housing arrangement (12), wherein the manual force actuator (10) has a sensor system (22) for torque detection on the steering spindle (16) designed as a sensor carrier.

Description

The invention relates to a manual force actuator with a longitudinal axis for a steer-by-wire steering system of a vehicle according to claim 1.

Steer-by-wire steering systems for motor vehicles receive manual steering commands from the driver, like conventional mechanical steering systems, by turning a steering wheel of an input unit. This causes the rotation of a steering spindle which, however, is not mechanically connected to the wheels to be steered via the steering gear, but rather interacts with angle of rotation or torque sensors that detect the steering command and output a determined electrical control signal to a steering actuator that is an electric actuator sets a corresponding steering angle of the wheels.

With steer-by-wire steering systems, the driver does not receive any direct physical feedback from the steered wheels via the steering line, which in conventional mechanically coupled steering systems is a reaction or restoring torque depending on the condition of the road surface, the vehicle speed, the current steering angle and other operating conditions reported back to the steering wheel. The lack of haptic feedback makes it difficult for the driver to safely grasp current driving situations and to carry out appropriate steering maneuvers, which impairs vehicle steerability and thus driving safety.

In order to generate a realistic driving experience, it is known in the prior art to record parameters such as vehicle speed, steering angle, steering reaction torque and the like from an actual current driving situation or to calculate them in a simulation, and from these with a manual force actuator through a feedback signal to form corresponding torque generated by an electric motor. For this purpose, the manual force actuator comprises an actuating drive serving as a manual torque or steering wheel actuator.

Thus, depending on the feedback signal, a restoring torque or torque corresponding to the real reaction torque is coupled into the steering wheel via the steering spindle. Such systems, also known as “force feedback” systems, give the driver the impression of a real driving situation as with conventional steering, which facilitates an intuitive reaction.

Steer-by-wire steering systems are generally known, for example each with an input unit which has a manual force actuator driven by an electric motor with a housing arrangement. The electric motor can be controlled by an electronic control unit that adjusts the motor current as a function of measured values that characterize the respective driving situation. The motor shaft is coupled directly to the steering spindle, so the motor torque is identical to the manual torque coupled into the steering spindle. The motor unit is flanged axially to the casing unit with respect to the longitudinal axis and the motor shaft is connected to the steering spindle mounted in the casing unit via a coupling.

An essential parameter for controlling the manual force actuator is, in addition to parameters related to the driving situation, a steering torque that is generated by a steering wheel or a driver. The intensity of the steering torque is detected in the steering train and transmitted to control electronics and the electric motor for applying a steering resistance to the steering spindle. In order to generate the most realistic possible steering resistance by means of a torque, it is necessary to detect the steering torque and the torque counteracting by the electric motor as precisely as possible in order to give the driver a balanced steering feel.

The task of the current development is to develop a manual force actuator for a steer-by-wire steering system that has a compact design and enables inexpensive and reliable torque detection of a steering spindle for a realistic steering resistance.

The object is achieved according to the invention by a manual force actuator with a longitudinal axis for a steer-by-wire steering system of a vehicle with the features of claim 1 and a sensor system for a manual force actuator with the features of claim 10. Preferred embodiments of the invention are set out in the dependent claims and the following description, each of which can represent an aspect of the invention individually or in combination. The invention thus relates to a manual force actuator with a longitudinal axis for a steer-by-wire steering system of a vehicle
an outer housing assembly,
an electric motor, wherein the electric motor is arranged non-rotatably on the housing arrangement along the longitudinal axis at one end of the housing arrangement, at least one steering spindle for receiving a steering torque of a steering wheel, wherein the steering spindle is rotatably mounted about the longitudinal axis in the housing arrangement, and the steering spindle for transmission a torque is at least indirectly connected to the electric motor,
at least one bearing for the rotatable mounting of the steering spindle in the housing arrangement,
wherein the manual force actuator has a sensor system for torque detection on the steering spindle designed as a sensor carrier.

The object is thus achieved according to the invention in particular by an advantageously arranged sensor system. It has been found that a sensor system arranged on the steering spindle enables detection values that are as accurate as possible. One of the reasons for this is that the direct arrangement of the sensor system on the steering spindle largely avoids the influence of further disturbance variables. In order to optimize the detection result, it can be provided that different detection methods are combined with one another. Depending on the detection method, a single one can be sufficient for a reliable detection result. In particular, the space required is optimized by using the space around the steering spindle, which is essentially present.

According to a preferred embodiment of the invention it is provided that the sensor system has means for torque detection by means of optical detection. Optical detection has the advantage that it enables contactless and therefore low-wear detection. The individual components of the sensor system therefore do not have to be replaced by new components after a certain period of use due to wear.

According to a preferred embodiment of the invention it is provided that
the means for optical detection comprise a coding arranged on the steering spindle, an optical sensor for detecting the coding and a computing unit. The torque can be detected by a, in particular elastic, deformation of the steering spindle, which takes place as a result of the torsion applied about the longitudinal axis. The computing unit can derive the torque accordingly from the detected rotation or deformation.

According to a preferred embodiment of the invention it is provided that
the coding is a single-track or multi-track coding, the coding extending in particular around the circumference of the longitudinal spindle. A particularly multi-track coding enables the most accurate and therefore reliable measurement results possible.

According to a preferred embodiment of the invention it is provided that claims, characterized in that
the sensor system for detecting the steering torque has at least one, preferably at least two strain gauges, which is or are arranged on an outer surface of the left-hand spindle. A torque on the steering spindle leads to a deformation of the same and thus also of the measuring bridge with the at least one strain gauge. The voltage in the measuring bridge thus changes so that the torque can be detected based on it. Strain gauges have the advantage of being robust and accurate. The assembly is done with a manageable effort and the components are easily available.

According to a preferred embodiment of the invention it is provided that
the sensor system has means for magnetostrictive torque detection. Magnetostrictive torque detection has the advantage that it enables contactless and therefore low-wear detection. The individual components of the sensor system therefore do not have to be replaced by new components after a certain period of use due to wear. This solution is based on the idea of using the principle of inverse magnetostriction for torque detection in such a way that the steering spindle is designed as a sensor carrier and functions as a primary sensor.

As is well known, magnetostriction is the elastic deformation of the molecular structure of ferromagnetic materials. The micromechanical deformation takes place when the magnetization changes. Therefore, the length of a body changes under the influence of an external magnetic field.

The use of means for magnetostrictive torque detection as a sensor system has the advantage that they are robust and durable. They have a simple structure and are non-contact and therefore maintenance-free.

According to a preferred embodiment of the invention it is provided that
the manual power actuator has an annular body that surrounds the steering spindle circumferentially with at least one magnetic track and a hollow cylinder body with at least one magnetic sensor in such a way that the annular body and the hollow cylinder body are designed coaxially to one another that in the event of a torsion of the steering spindle about the longitudinal axis of the at least one magnetic sensor the torque acting on the longitudinal axis is detected via the at least one magnetic track. It has been found that this arrangement enables a compact design and, at the same time, reliable detection of the torque.

The ring body can, for example, have a plurality of magnetic bodies arranged one on top of the other in such a way that the ring body has none emits substantial magnetic field. In this exemplary case, the ring body is considered a closed ring body.

The hollow cylinder body can be a jacket which extends over a substantial length of the steering spindle along the longitudinal axis. The hollow cylinder body can thus serve as a protective jacket and as a holding device for the at least one magnetic track.

According to a preferred embodiment of the invention it is provided that
the ring body has two magnetic tracks with two opposing magnetic fields, and that the hollow cylinder body has two magnetic sensors, the two magnetic tracks and the two magnetic sensors being arranged one after the other along the longitudinal axis in such a way that a magnetic sensor for magnetostrictive torque detection is assigned to a magnetic track. The effect of inverse magnetostriction is thus used for torque detection. The effect is based on two oppositely coded magnetic tracks applied to the steering spindle as primary sensors, whose magnetic field changes are tapped without contact by secondary sensors. The opposing coding of the magnetic tracks enables precise measurement even under the influence of external magnetic fields. The two magnetic fields are coded in opposite directions in order to detect an offset value due to the earth's magnetic field. Thus, if the first magnetic track in the unloaded state of the steering spindle gives a positive value by the assigned magnetic sensor and the second magnetic track in the unloaded state of the steering spindle gives a negative value by the assigned magnetic sensor, the amount of these values being the same, this amount corresponds to the offset value of the earth's magnetic field, which can now be calibrated out.

According to a preferred embodiment of the invention it is provided that
the ring body is directly or indirectly inseparably connected to the steering spindle. Magnetic coding is therefore an integral part of the steering spindle, so that the steering spindle functions as a primary sensor. An existing component, namely the steering spindle, becomes a primary sensor without significant material expenditure and without additional elements. This saves costs and installation space.

The invention also relates to a sensor system for a manual force actuator with at least one of the preceding features, characterized by the features of the sensor system according to at least one of the preceding claims.

• 1: eine schematische Schnittansicht eines Handkraftaktuators gemäß einer beispielhaften Ausgestaltung der Erfindung,
• 2: eine schematische Seitenansicht einer Lenkspindel des Handkraftaktuators nach 1 mit Mitteln zur optischen Drehmomentdetektion als erste Ausführungsform eines Sensorsystems,
• 3: zwei schematische Seitenansichten einer Lenkspindel des Handkraftaktuators nach 1 mit einem Dehnungsmessstreifen zur Drehmomentdetektion, jeweils im entspannten und im belasteten Zustand, als zweite Ausführungsform eines Sensorsystems,
• 4: eine schematische Seitenansicht einer Lenkspindel des Handkraftaktuators nach 1 mit Mitteln zur magnetostriktiven Drehmomentdetektion, als dritte Ausführungsform eines Sensorsystems, und
• 5: zwei schematische Frontansichten auf eine Stirnseite einer Lenkspindel des Handkraftaktuators nach 1 und 4 mit den Mitteln zur magnetostriktiven Drehmomentdetektion, jeweils im entspannten und im belasteten Zustand.

In the following, the invention is explained by way of example with reference to the attached drawings using a preferred exemplary embodiment, the features shown below being able to represent an aspect of the invention both individually and in combination. It shows:

• 1 : a schematic sectional view of a manual force actuator according to an exemplary embodiment of the invention,
• 2 : a schematic side view of a steering spindle of the manual power actuator according to 1 with means for optical torque detection as the first embodiment of a sensor system,
• 3 : two schematic side views of a steering spindle of the manual force actuator according to 1 with a strain gauge for torque detection, in each case in the relaxed and in the loaded state, as a second embodiment of a sensor system,
• 4th : a schematic side view of a steering spindle of the manual power actuator according to 1 with means for magnetostrictive torque detection, as a third embodiment of a sensor system, and
• 5 : two schematic front views of one end face of a steering spindle of the manual force actuator 1 and 4th with the means for magnetostrictive torque detection, in each case in the relaxed and in the loaded state.

The 1 shows a preferred embodiment of a manual force actuator 10 with a longitudinal axis L. for a steer-by-wire steering system of a vehicle, comprising an outer housing arrangement 12 ,
an electric motor 14th , the electric motor 14th along the longitudinal axis L. at one end of the housing assembly 12 non-rotatably on the housing assembly 12 is arranged
at least one steering spindle 16 for receiving a steering torque of a steering wheel 18th , with the steering shaft 16 around the longitudinal axis L. rotatable in the housing assembly 12 is mounted, and wherein the steering shaft 16 for transmitting a torque D. at least indirectly with the electric motor 14th connected is,
at least one warehouse 20th for the rotatable mounting of the steering spindle 16 in the housing arrangement 12 ,
being the hand force actuator 10 a sensor system 22nd for torque detection on the steering spindle designed as a sensor carrier 16 having.

• die beispielsweise modular aufgebaute Gehäuseanordnung 12, umfassend insbesondere folgende Komponenten
• den Elektromotor 14 zum aktiven Stellen eines definierten Lenkwiderstands, beispielsweise von etwa zehn Newtonmeter,
• die mindestens eine Lenkspindel 16 zur Drehmomentaufnahme des Lenkrads 18,
• das Lager 20 zur Lagerung der Lenkspindel 16,
• das Sensorsystem 22, das an der Lenkspindel 16 angeordnet ist,
• ein Winkelsensor 24 zur Rotorlangenermittlung für eine Regelung des Handkraftaktuators 10,
• eine Sperre 26 für Systemausfall und Zusatzfunktionen, die ein aktives Stellmoment als der Lenkwiderstand erfordern,
• ein Reibelement 28 zur Erzeugung einer Grundreibung im System, zur Vermeidung einer synthetischen Haptik.

A more comprehensive, exemplary structure of the manual force actuator 10 thus has for a steering by means of direct drive according to a preferred embodiment of the invention:

• the modular housing arrangement, for example 12 , comprising in particular the following components
• the electric motor 14th for actively setting a defined steering resistance, for example about ten newton meters,
• the at least one steering shaft 16 to absorb the torque of the steering wheel 18th ,
• the warehouse 20th for mounting the steering spindle 16 ,
• the sensor system 22nd that on the steering shaft 16 is arranged
• an angle sensor 24 for determining the rotor length for regulating the manual force actuator 10 ,
• a lock 26th for system failure and additional functions that require an active control torque as the steering resistance,
• a friction element 28 to generate a basic friction in the system, to avoid synthetic haptics.

The housing arrangement shown 12 includes as in 1 two housing modules shown as an example. However, a single housing body can also be sufficient.

2 shows a first embodiment of the sensor system 22nd , the sensor system 22nd Has means for torque detection by means of optical detection.

To 2 it is provided, for example, that the means for optical torque detection are one on the steering spindle 16 arranged coding 30th , an optical sensor 32 for detection of the coding 30th and a computing unit 34 include.

To 2 it is also provided that the coding 30th is a two-lane coding, the coding being 30th especially circumferentially to the longitudinal spindle 16 extends.

3 , divided in 3a and 3b , shows a second embodiment of the sensor system 22nd , the sensor system 22nd has at least one strain gauge for detecting the steering torque, which is located on an outer surface of the left-hand spindle 16 is arranged.

3a shows the strain gauge with a stretch at rest S1 . 3b shows the strain gauge with a strain in the loaded state S2 , so if the steering shaft 16 with a stressful torque D. is applied.

4th shows a third embodiment of the sensor system 22nd , the sensor system 22nd Has means for magnetostrictive torque detection.

To 4th is provided, for example, that the manual force actuator 10 one the steering shaft 16 circumferentially enclosing ring body 40 with at least one magnetic track 36a , 36b and a hollow cylindrical body 42 with at least one magnetic sensor 38a , 38b has such that the ring body 40 and the hollow cylinder body 42 are formed coaxially to one another in such a way that in the event of torsion of the steering spindle 16 around the longitudinal axis L. the at least one magnetic sensor 38a , 38b that on the longitudinal axis L. acting torque D. via the at least one magnetic track 36a , 36b detected.

To 4th it is also provided by way of example that the ring body 40 two magnetic tracks 36a , 36b with two opposing magnetic fields, and that the hollow cylindrical body 42 two magnetic sensors 38a , 38b having,
where the two magnetic tracks 36a , 36b and the two magnetic sensors 38a , 38b such along the longitudinal axis L. are arranged one after the other that each have a magnetic sensor 38a , 38b for magnetostrictive torque detection of a magnetic track 36a , 36b assigned. 4th reveals the magnetic tracks 36a , 36b of the ring body 40 for schematic reasons with clear contours to illustrate the two opposing magnetic fields. In particular, it is provided that the ring body with the two magnetic tracks 36a , 36b is formed in one piece.

To 4th it is also provided by way of example that the ring body 40 indirectly inseparable from the steering shaft 16 connected is. Examples of connection options are shrink-fitting or welding, although the exact selection is not relevant.

5a shows a front view of an end face of the steering shaft 16 at rest. Circumferentially around the steering shaft 16 is a magnetic track 36a as part of the ring body 40 arranged. This magnetic track 36a includes, for example, a large number of elementary magnets. This creates a closed magnetic ring. This means that there is no magnetic field from the magnetic sensor 38a can be detected.

That from the magnetic sensor 38a detectable magnetic field becomes detectable, however, as in 5b shown when the steering shaft 16 with a stressful torque D. is applied. This corresponds to a load condition on the steering shaft 16 . As an example, the application of torque leads to a deformation of the steering spindle 16 , from which the changed position of the elementary magnets and thus a change in the magnetic field results. This magnetic field change is caused by the magnetic sensor 38a detected. The torque can then be determined.

List of reference symbols

10

Manual force actuator

12

Housing arrangement

14th

Electric motor

16

Steering shaft

18th

Steering wheel

20th

warehouse

22nd

Sensor system

24

Angle sensor

26th

Lock

28

Friction element

30th

Coding

32

Optical sensor

34

Arithmetic unit

36a

Magnetic track

36b

Magnetic track

38a

Magnetic sensor

38b

Magnetic sensor

40

Ring body

42

Hollow cylinder body

L.

Longitudinal axis

D.

Torque

S1

Stretching at rest

S2

Elongation under load

Claims (10)

Manual force actuator (10) with a longitudinal axis (L) for a steer-by-wire steering system of a vehicle, comprising - an outer housing arrangement (12), - an electric motor (14), the electric motor (14) along the longitudinal axis (L) at one end of the housing arrangement (12) is arranged non-rotatably on the housing arrangement (12), - at least one steering spindle (16) for absorbing a steering torque of a steering wheel (18), the steering spindle (16) being rotatable about the longitudinal axis (L) in the Housing arrangement (12) is mounted, and wherein the steering spindle (16) for transmitting a torque (D) is at least indirectly connected to the electric motor (14), - at least one bearing (20) for rotatably supporting the steering spindle (16) in the housing arrangement (12), characterized in that the manual force actuator (10) has a sensor system (22) for torque detection on the steering spindle (16) designed as a sensor carrier. Manual force actuator (10) Claim 1 , characterized in that the sensor system (22) has means for torque detection by means of optical detection. Manual force actuator (10) Claim 1 or 2 , characterized in that the means for optical torque detection comprise a coding (30) arranged on the steering spindle (16), an optical sensor (32) for detecting the coding (30) and a computing unit (34). Manual force actuator (10) Claim 2 or 3 , characterized in that the coding (30) is a single-track or multi-track coding, the coding extending in particular around the circumference of the longitudinal spindle (16). Manual force actuator (10) according to at least one of the preceding claims, characterized in that the sensor system (22) for detecting the steering torque has at least one, preferably at least two, strain gauges which is or are arranged on an outer surface of the left-hand spindle (16). Manual force actuator (10) according to at least one of the preceding claims, characterized in that the sensor system (22) has means for magnetostrictive torque detection. Manual force actuator (10) according to the preceding claim, characterized in that the manual force actuator (10) has an annular body (40) which surrounds the steering spindle (16) and has at least one magnetic track (36a, 36b) and a hollow cylinder body (42) with at least one magnetic sensor ( 38a, 38b) in such a way that the ring body (40) and the hollow cylinder body (42) are formed coaxially to one another in such a way that in the event of a torsion of the steering spindle (16) about the longitudinal axis (L) the at least one magnetic sensor (38a, 38b) the torque (D) acting on the longitudinal axis (L) is detected via the at least one magnetic track (36a, 36b). Manual force actuator (10) according to the preceding claim, characterized in that the ring body (40) has two magnetic tracks (36a, 36b) with two opposing magnetic fields, and that the hollow cylinder body (42) has two magnetic sensors (38a, 38b), the two magnetic tracks (36a, 36b) and the two magnetic sensors (38a, 38b) being arranged one after the other along the longitudinal axis (L) in such a way that one magnetic sensor (38a , 38b) for magnetostrictive torque detection is assigned to a magnetic track (36a, 36b). Handkraftaktuator (10), characterized 7 or 8, that the ring body (40) is directly or indirectly connected inseparably to the steering spindle (16) to at least one of the claims. Sensor system (22) for torque detection on a steering spindle (16) designed as a sensor carrier for a manual force actuator (10) according to at least one of the preceding claims, characterized by the features of the sensor system (22) according to at least one of the preceding claims.

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