DE102021204522A1 - Steering system for a vehicle with an optimized wireless energy transfer to the steering wheel - Google Patents

Abstract

The invention relates to a steering system (1) for a vehicle. The steering system (1) comprises a steering column module (2) which is designed for a stationary arrangement in the vehicle, a steering wheel shaft (3) which is rotatably mounted in the steering column module (2) and has a steering wheel (4) which is non-rotatably fastened to the steering wheel shaft (3), in in which at least one electrical consumer is integrated, and a transformer (6) designed for the wireless power supply of the at least one electrical consumer. The transformer (6) comprises a primary coil (7) fixed in the steering column module (2), a secondary coil (8) non-rotatably connected to the steering wheel shaft (3) and an integrated iron core (9) made of a soft magnetic material, the iron core (9) being at least is partially formed by the steering wheel shaft (3) and / or at least partially non-rotatably connected to it.

Description

technical field

The invention relates to a steering system for a vehicle, in particular for a motor vehicle. The steering system includes a steering column module typically arranged in the area of an instrument panel of the vehicle, which can be adjusted as a whole in one or more directions for individual adjustment to a driver, but is otherwise immovable with respect to the vehicle. Furthermore, the steering system comprises a steering wheel shaft which is rotatably mounted in the steering column module and has a steering wheel which is fastened thereto in a rotationally fixed manner and in which at least one consumer of electrical energy is integrated. A transformer with a primary side fixed in the steering column module and a secondary side non-rotatably connected to the steering wheel shaft is provided for its wireless power supply.

Technical background

Motor vehicles that are currently available usually have a coil spring that establishes the electrical connection to the rotating steering wheel via the steering column module that is firmly connected to the vehicle body. In this way, the spiral spring enables communication with the multifunction buttons in the steering wheel, their lighting or backlighting, detection of the activation of the signal horn and the electrical energy supply to the steering wheel heating, the airbag detonator built into the steering wheel and a steering wheel that may be constructed as a capacitive sensor for the Hands-off detection.

In current vehicles, the steering wheel is typically mechanically connected to the rack via a steering wheel shaft that is non-rotatably connected to the steering wheel, an intermediate steering shaft connected via a cardan joint, and a pinion, which transmits the steering wheel position to the tie rods of the wheels. The clock spring is protected against over-tightening and tearing by preventing the steering wheel movement at a certain angle by a mechanical end stop on the rack.

In contrast, steer-by-wire (SbW) steering systems, which can be used in large series in future in the automotive sector, have no mechanical connection between the steering wheel and the steering gear or the steered wheels of the vehicle. In SbW steering systems, the manual torque that reflects the feedback from the road or the tires to the steering wheel is generated artificially using an electric drive unit, which is referred to as a force feedback actuator (FFA).

• Beispielsweise wird nach einem dieser Ansätze eine Wickelfeder gar nicht benötigt, wenn diejenigen Teile des Lenkrades, die eine Energieversorgung benötigen und mit dem Rest des Fahrzeuges kommunizieren, fest stehen bleiben. Allerdings muss hierfür eine neuartige Lenkradarchitektur entwickelt und gefertigt werden. Weiterhin gibt es bei diesem Ansatz keine mit dem Lenkrad mitrotierenden Tasten/Steuerelemente. Dadurch verändert sich die Position der Fahrerhand zu den zu bedienenden Steuerelementen mit jeder Lenkbewegung. Mitrotierende Tasten hingegen würden sicherstellen, dass diese sich immer in Griffweite des Daumens befinden.

If a clock spring is used in an SbW system to ensure the power supply and communication to the steering wheel, the steering wheel must also have a non-oversteerable end stop to prevent the clock spring from overturning and tearing because the mechanical end stop in the steering gear is no longer available stands. This end stop could either be mechanical and integrated into the steering column module (which would require additional space) or be generated electromagnetically by the FFA (which in turn would require high additional power and more space as this would require a larger FFA to accommodate the required to set higher torques). In this context, a number of different approaches are known:

• For example, according to one of these approaches, a coil spring is not required at all if those parts of the steering wheel that require an energy supply and communicate with the rest of the vehicle remain stationary. However, a new kind of steering wheel architecture has to be developed and manufactured for this. Furthermore, with this approach there are no buttons/controls rotating with the steering wheel. As a result, the position of the driver's hand in relation to the controls to be operated changes with every steering movement. Rotating keys, on the other hand, would ensure that they are always within reach of the thumb.

Another approach uses a clutch between the steering wheel and the steering gear as a fallback level - if the software end stop is oversteered, the clutch closes and the mechanical end stop of the rack engages. As a result, the software end stop can be oversteered with a lower power requirement. However, the coupling between the FFA and the steering gear is an additional component that must be developed and integrated in accordance with the required standards. This results in costs, effort, a larger space requirement and a greater effort to stow the mechanical coupling elements when lowering the steering column. Furthermore, the solution may be haptically noticeable: If the clutch closes during a dynamic steering maneuver, there may be a mechanically locked asynchrony between the steering wheel position and the position of the steered wheels.

• So beschreibt DE 10 2018 219 167 A1 eine Lenkeinrichtung für ein Kraftfahrzeug, die ein drehbar gelagertes Lenkrad mit einem integrierten Airbag mit zugeordneter Zündeinrichtung sowie eine extern zum Lenkrad angeordnete Steuerungseinrichtung zur Gabe eines die Zündung der Zündeinrichtung auslösenden Zündenergiepulses umfasst. Dabei sind die Zündeinrichtung und die Steuerungseinrichtung über eine drahtlose kapazitive oder induktive Energieübertragungseinrichtung gekoppelt, über die der Zündenergiepuls an die Zündeinrichtung übertragbar ist, wobei ein erstes Übertragungselement (beispielsweise eine erste Spule) am Lenkrad und mit diesem drehbar und ein zweites Übertragungselement (beispielsweise eine zweite Spule) positionsfest und benachbart zum ersten Übertragungselement extern zum Lenkrad angeordnet ist.

Furthermore, approaches for wireless communication and power supply of the steering wheel via air transformers are known, which also allow the omission of the clock spring:

• So describes DE 10 2018 219 167 A1 a steering device for a motor vehicle, which integrates a rotatably mounted steering wheel with a th airbag with an associated ignition device and a control device arranged externally to the steering wheel for delivering an ignition energy pulse that triggers the ignition of the ignition device. The ignition device and the control device are coupled via a wireless capacitive or inductive energy transmission device, via which the ignition energy pulse can be transmitted to the ignition device, with a first transmission element (e.g. a first coil) being rotatable on the steering wheel and with it and a second transmission element (e.g. a second Coil) is fixed in position and arranged adjacent to the first transmission element externally to the steering wheel.

Furthermore shows DE 199 46 934 B4 a steering wheel module that combines contactless energy and information transmission as well as angle sensors in a compact two-part component. DE 102 58 871 A1 proposes to save the cost of a separate transmission device in the form of a clock spring, which is traditionally used to exchange information and to transmit electrical power to devices integrated in the steering wheel, such as an airbag or a radio or cruise control control, by using a Steer -by-wire steering devices existing feedback electric motor is used as such a transmission device.

These solutions have the disadvantage that because air is the transmission medium, the distance between the primary side permanently installed in the vehicle and the rotating secondary side of the transformer must be very small, since air has a very low magnetic permeability (µ~1). On the one hand, this limits the possibilities for spatial arrangement: for example, there is no space between the fixed primary side and the secondary side rotating with the steering wheel for a steering column switch module, as is common in today's vehicles for flashing indicators, operating the windshield wipers and activating the high beam is. On the other hand, the efficiency of the electrical power transmission is also too low to efficiently supply larger electrical consumers, such as a steering wheel heater.

It is an object of the present invention to provide an alternative or improved steering system for a vehicle. The invention is aimed at that part of the infrastructure that is intended to make it possible to dispense with the coil spring. It can also be an object of the invention, in particular, to be able to retain the known steering wheel architecture with rotating steering wheel buttons and a steering column switch module according to today's standard. Furthermore, it can also be an object of the invention to enable an energy-efficient supply of large electrical loads such as a steering wheel heater.

Disclosure of Invention

These objects are achieved by a steering system according to claim 1 and by a vehicle equipped with such a steering system, according to the independent claim. Further developments are specified in the dependent claims. All further features and effects mentioned in the claims and the description for the steering system also apply in relation to the vehicle, and vice versa.

According to a first aspect, a steering system for a vehicle, in particular for a motor vehicle, is provided. The steering system includes a steering column module that is designed to be fixed in the vehicle (typically opposite a driver's seat) and optionally adjustable as a whole in one or more directions for individual adjustment to the driver. For example, the steering column module can be adjustable in the axial direction of the steering wheel shaft to adapt the steering wheel to the driver's seating position in the longitudinal direction of the vehicle and/or it can be adjustable in the vertical direction to adapt to the driver's seat height and size. Said adjustability can be carried out manually by the driver himself and/or electrically by means of suitable actuators.

• - eine Lenkradheizung und/oder einen anderen großen Verbraucher, der einen elektrischen Verbrauch von mindestens etwa 30 W, mindestens etwa 40 W oder mindestens etwa 50 W aufweist;
• - eine oder mehrere Lenkradtasten zur Bedienung des Fahrzeugs (beispielsweise zur Steuerung einer Geschwindigkeitsregelanlage) oder eines darin integrierten Infotainment-Systems (beispielsweise eines Radios oder eines Navigationssystems);
• - einen kapazitiven Hands-Off-Erkennungssensor, der zum Erkennen, ob die Hände des Fahrers nicht am Lenkrad sind, ausgebildet ist;
• - einen Airbag;
• - einen Aktuator, der zum Auf- und Zusammenklappen des Lenkrads zu dessen Verkleinerung ausgebildet ist, um das Verstauen des Lenkrads im Inneren der Instrumententafel bei einem hochautomatisierten Fahrbetrieb, wenn es gerade nicht benötigt wird, zu erleichtern.

The steering system also includes a steering wheel shaft that is rotatably mounted in the steering column module and has a steering wheel that is non-rotatably attached to the steering wheel shaft and in which at least one consumer of electrical energy (hereinafter also simply referred to as a consumer or electrical consumer) is integrated. This may include, but is not limited to, one or more of the following consumers:

• - a steering wheel heater and/or other large consumer that has an electrical consumption of at least about 30 W, at least about 40 W or at least about 50 W;
• - One or more steering wheel buttons for operating the vehicle (e.g. to control a cruise control system) or an infotainment system integrated therein (e.g. a radio or a navigation system);
• - A capacitive hands-off detection sensor, which is designed to detect whether the driver's hands are not on the steering wheel;
• - an air bag;
• - an actuator which is designed to fold and unfold the steering wheel to reduce it, in order to facilitate stowage of the steering wheel inside the instrument panel during highly automated driving when it is not needed.

The steering wheel heater can be designed in particular to primarily heat the surface of the steering wheel and as little as possible of its interior in order to minimize the comparatively high consumption of electrical energy of typically around 50 W for the steering wheel heater.

Furthermore, the steering system includes a transformer designed for the wireless power supply of the consumers integrated in the steering wheel. For this purpose, the transformer comprises a primary coil fixed in the steering column module, a secondary coil non-rotatably connected to the steering wheel shaft and an integrated iron core made of a soft magnetic material. The iron core is formed at least partially by the steering wheel shaft and/or is at least partially non-rotatably connected to the steering wheel shaft. In order to convert an available DC voltage into a transformable AC voltage, an inverter connected upstream of the primary coil can be provided. In order to convert the transported AC voltage into a usable DC voltage, a rectifier can be provided downstream of the secondary coil.

One idea of the invention is to provide a suitable transformer as a replacement for the winding spring mentioned at the beginning in the steering system, which, thanks to an iron core integrated in the steering wheel shaft or connected to it in a rotationally fixed manner, can have a significantly higher efficiency than the solution approaches mentioned at the beginning, in order to also be able to handle large electrical To be able to supply consumers such as the steering wheel heater more energy-efficiently than with an air transformer and, for example, over a distance of at least 10 cm. The energy supply must be ensured in particular for electrical consumers such as steering wheel buttons, steering wheel heating and hands-off detection. Since the steering wheel heating in particular represents a large electrical consumer (~50W), transmission with the highest possible efficiency is required for this. This condition can be met with a transformer of the type presented here with an integrated iron core and a corresponding design.

At the same time, information technology communication can take place between the steering wheel (i.e. the electrical consumers integrated therein, such as buttons, sensors and actuators) and, for example, a control unit arranged in the steering column module via a suitable wireless transmission standard (ZigBee, Bluetooth LE, ...) or as a modulated signal be implemented via the transformer. As also described in detail below, the known steering wheel architecture with rotating steering wheel buttons and a steering column switch module according to today's standard can also be retained.

According to one embodiment, the steering wheel shaft forms the iron core of the transformer. In this embodiment, the primary coil fixed in the steering column module is wound in the form of a hollow cylinder around an axial section of the steering wheel shaft that is mounted in the steering column module, with a minimal radial air gap remaining between the hollow cylinder and the steering wheel shaft, which is only just large enough to minimize stray loss for the steering wheel shaft to move can rotate relative to the hollow cylinder without friction. In this embodiment, the secondary coil is firmly wound onto the steering wheel shaft in its axial section on the steering wheel side, again in order to minimize stray losses. In this way, a very high efficiency of, for example, at least 50%, in particular even more than 60%, can be achieved in the transformer.

In an alternative embodiment, the transformer has a structure in which the iron core surrounds the turns of the static primary coil and the rotating secondary coil and has two relatively rotatable sections for this purpose. (Such a transformer structure is sometimes equated with the common term "rotary transformer", which is therefore also used here for this embodiment.) The iron core comprises (in the axial direction of the steering wheel shaft) a primary-side iron core section fixed in the steering column module and a secondary-side iron core section rotating relative thereto , which is non-rotatably connected to the steering wheel shaft. In order to minimize stray losses, these two iron core sections are only separated from one another by a minimal axial air gap, which is just big enough for the secondary-side iron core section to rotate relative to the primary-side iron core section without friction. The primary-side iron core portion surrounds and/or houses the windings of the primary coil and the secondary-side iron core portion surrounds and/or houses the windings of the secondary coil.

This embodiment is thus characterized by an almost closed iron core with a minimal air gap between the primary and secondary sides of the transformer. Also with this one A very high degree of efficiency of, for example, at least 50%, in particular even more than 60%, can therefore be achieved with this structure. However, such a rotary transformer can be more filigree and therefore more expensive to produce than a simple magnetizable steering wheel shaft.

In particular, the steering system of the type set forth herein may be embodied as a steer-by-wire steering system in which there is no mechanical connection between the steering wheel and the steered vehicle wheels, and manual torque applied by the driver to the steering wheel is suitably electrically applied to the wheels is passed on. In this case, the steering system has an electric feedback motor (also referred to herein as a force feedback actuator, FFA) that is designed to generate a manual torque that reflects feedback from the road or the vehicle wheels to the steering wheel.

According to one embodiment of this steer-by-wire steering system, a rotor of the FFA is connected to the steering wheel shaft via a gearbox (located, for example, in the steering column module). The transmission is designed to reduce the rotor speed with a simultaneous increase in torque. This allows the FFA to be smaller and requires less power to operate, but it must be able to rotate faster.

An alternative embodiment to this is based on the following consideration: Since the force feedback actuator is located on the steering column and its stator has considerable inductance, it could in principle also serve as the primary side of the transformer (cf. 3 ). The secondary side is then on the rotor of the FFA. The rotor of the FFA must be firmly connected to the steering wheel, because the supply line of the secondary coil of the transformer has to rotate with the steering wheel speed in order not to twirl.

In other words, in this embodiment the stator of the FFA simultaneously forms the primary side or primary coil of the transformer of the type set forth herein, while the secondary coil of the transformer is tightly wound, i.e. wound, on a rotor of the FFA. H. is fixed to this. This means that the inductance of the FFA can also be used to transfer energy (transformer function). Since the rotor forms the secondary side of the transformer, the rotor must inevitably rotate at the steering wheel speed. This means that no gear can be used between the FFA and the steering wheel and the FFA must therefore be designed to be disproportionately large and power-intensive in order to achieve the necessary manual torques.

In a specific embodiment, the steering system also includes an accumulator (accumulator) arranged in the steering wheel or connected non-rotatably to the steering wheel shaft as an intermediate electrical store for supplying energy to the at least one electrical consumer. Energy peaks can thus be cushioned better. In this case, the steering system can be set up in particular to automatically charge the rechargeable battery via the secondary-side rectifier of the transformer in a suitable interval operation, which can be defined as a function of its residual charge, for example. For example, a suitable interval operation can be defined in that the battery is only recharged when its remaining charge has fallen below a predetermined threshold value. In this way, the starting of the transformer can be saved in the case of only a small amount of energy consumption, which can arise, for example, from pressing steering wheel buttons every now and then.

In particular, the steering system can further comprise a steering column switch module which is mechanically fixed to the steering column module and is arranged in the vehicle between an instrument panel and the steering wheel. The steering column switch module can include, for example, in a manner known per se, steering column switches such as direction indicators (indicators), low beam/high beam switch, windshield wiper control, and much more.

Forms the steering wheel shaft according to the embodiment mentioned above (cf. 1 ) the iron core of the transformer, the primary coil of which is wound around an axial section of the steering wheel shaft mounted in the steering column module and the secondary coil of which is firmly wound on an axial section of the steering wheel shaft on the steering wheel side, so can
the steering column switch module can be arranged axially between the primary coil and the secondary coil of the transformer. With the iron core as a connecting element, the distance between the primary and secondary coils - in contrast to the known solutions with air transformers - can be increased and the steering column switch module fits between the steering column module and the steering wheel. A more efficient supply of large electrical consumers such as the steering wheel heating is possible despite an increased distance of, for example, about 10 cm or more between the primary and secondary coil.

In particular, the iron core of the transformer can reduce eddy current losses be made of layered electrically insulated electrical steel. To increase the efficiency of the transformer, the material of the iron core can have as high a magnetic permeability as possible, for example at least 10,000, in particular at least 25,000, ideally at least 50,000 or even more. A suitable material for the iron core is, for example, what are known as µ-metals (FeNi compounds), whose magnetic permeability can be up to 140,000 (µ-50,000...140,000) depending on the composition.

According to a further aspect, a vehicle, in particular a motor vehicle, is provided which is equipped with a steering system of the type presented here. If the vehicle has, for example, a driver's seat and an instrument panel arranged in front of it, it can
the steering column module of the steering system be fixed in the instrument panel and be adjustable as a whole in one or more directions for individual adjustment to the driver, in particular in the axial direction of the steering wheel shaft in order to adjust the steering wheel to the driver's seating position in a longitudinal direction of the vehicle, and in vertical direction to adapt to the seat height and size of the driver.

1. 1) Im Stillstand bei abgeschaltetem Fahrzeug kann das Lenkrad unendlich oft frei gedreht werden. Ein mechanischer Endanschlag in der Lenksäule als Wickelfederschutz (vgl. den eingangs beschriebenen Stand der Technik) ist nicht mehr nötig und kann entfallen, was Kosten und Bauraum spart.
2. 2) Das Lenkradschloss kann bei einem Steer-by-Wire-System ebenfalls entfallen, da die Lenkung ohne Einschalten der elektrischen Versorgung des Lenksystems nicht möglich ist.
3. 3) Ein lenkradseitiger Softwareendanschlag kann beliebig weit überlenkt werden, ohne dass es zu Beschädigungen im System kommt. (Damit kann das Haltemomentenniveau im Softwareendanschlag reduziert werden und der Strombedarf des FFAs sinkt.) Sollte der FFA im Fehlerfall nicht das volle Moment stellen können, wird durch das dann mögliche Überlenken keine mechanische Beschädigung hervorgerufen.

In general, the steering system according to the invention, which does not require the clock spring mentioned at the outset, can have the following advantages:

1. 1) When stationary with the vehicle switched off, the steering wheel can be turned freely indefinitely. A mechanical end stop in the steering column as coil spring protection (cf. the prior art described above) is no longer necessary and can be omitted, which saves costs and installation space.
2. 2) The steering wheel lock can also be omitted with a steer-by-wire system, as steering is not possible without switching on the power supply to the steering system.
3. 3) A software limit stop on the steering wheel can be oversteered as far as desired without causing damage to the system. (In this way, the holding torque level in the software end stop can be reduced and the power requirement of the FFA decreases.) If the FFA cannot provide the full torque in the event of a fault, no mechanical damage will be caused by the possible oversteering.

1. 1) Durch den Eisenkern wird die magnetische Permeabilität und damit der Wirkungsgrad der Übertragung vergrößert.
2. 2) Durch den Eisenkern als Verbindungselement kann der Abstand zwischen Primär- und Sekundärspule vergrößert werden und das Lenkstockschaltermodul passt zwischen das Lenksäulenmodul und das Lenkrad.
3. 3) Durch die freie Anordnung der Spulen (um den Eisenkern gewickelt, Querschnitt frei skalierbar) ist der Betrag der zu übertragenden Energie beliebig skalierbar.

The steering system according to the invention also has the following advantages, especially compared to the known approaches mentioned at the outset, which propose air-to-air transformers for the wireless power supply of the steering wheel:

1. 1) The iron core increases the magnetic permeability and thus the efficiency of the transmission.
2. 2) Using the iron core as a connecting element, the distance between the primary and secondary coils can be increased, and the steering column switch module fits between the steering column module and the steering wheel.
3. 3) Due to the free arrangement of the coils (wound around the iron core, freely scalable cross-section), the amount of energy to be transmitted can be scaled as required.

• Lenkradheizung P=50W, U=12V => Strombedarf I=4,17A wird sekundärseitig benötigt. Hieraus resultiert der folgende Strombedarf primärseitig:
  • Angenommener Wirkungsgrad 20% (typisch für Luftübertragung): l=4,17A/0,2=20,85A Angenommener Wirkungsgrad 60% (erreichbar mit Eisenkern, selbst bei einem größeren Abstand zwischen Primär- und Sekundärspule, vgl. 1): l=4,17A/0,6=6,95A
  • Das Ergebnis dieser Beispielrechnung zeigt: Mit einem Eisenkern kann der benötigte primärseitige Strom und damit der Leitungsquerschnitt der Primärspule selbst bei einem für die Unterbringung des Lenkstockschaltermoduls vergrößerten Abstand zwischen der Primär- und Sekundärspule um ein Vielfaches reduziert werden.

This can be illustrated using the following example calculation (in this example, only rectified electrical quantities are considered):

• Steering wheel heating P=50W, U=12V => Current requirement I=4.17A is required on the secondary side. This results in the following power requirement on the primary side:
  • Assumed efficiency 20% (typical for air transmission): l=4.17A/0.2=20.85A Assumed efficiency 60% (achievable with iron core, even with a larger distance between primary and secondary coil, cf. 1 ): l=4.17A/0.6=6.95A
  • The result of this sample calculation shows: With an iron core, the required primary-side current and thus the cable cross-section of the primary coil can be reduced many times over, even with an increased distance between the primary and secondary coils to accommodate the steering column switch module.

character list

• 1a-1c ein Ausführungsbeispiel eines Steer-by-Wire-Lenksystems der hierin dargelegten Art mit einem Eisenkern-Transformator zur Energieversorgung lenkradseitiger Verbraucher und mit einem über ein Getriebe mit der Lenkradwelle verbundenen Force-Feedback-Aktuator, in drei verschiedenen schematischen Ansichten;
• 2a-2c einen seitlichen Längsschnitt (2a) des SbW-Lenksystems der 1a-1c sowie einen jeweils vergrößerten Querschnitt einer Primärseite (2b) und einer Sekundärseite (2c) des Transformators mit Blick in axiale Richtung der Lenkradwelle; und
• 3 ein zu 1a-1c alternatives Ausführungsbeispiel eines Steer-by-Wire-Lenksystems der hierin dargelegten Art mit Nutzung des Stators eines Force-Feedback-Aktuators als Primärseite des Transformators.

The embodiments and design variants described above are explained in more detail below with reference to the examples shown in the accompanying drawings. The drawings are purely schematic; in particular, they are not to be understood as true to scale. Identical or corresponding elements bear the same reference numbers in the drawings. Show it:

• 1a-1c an embodiment of a steer-by-wire steering system of the type set out herein with an iron-core transformer for the energy supply of steering wheel-side consumers and with a force feedback actuator connected to the steering wheel shaft via a transmission, in three different schematic views;
• 2a-2c a lateral longitudinal section ( 2a) of the SbW steering system 1a-1c and an enlarged cross section in each case a primary page ( 2 B) and a secondary side ( 2c ) of the transformer looking in the axial direction of the steering wheel shaft; and
• 3 one to 1a-1c alternative embodiment of a steer-by-wire steering system of the type set forth herein utilizing the stator of a force feedback actuator as the primary side of the transformer.

Description of Embodiments

1a until 1c schematically show three different views of an exemplary embodiment of a steering system 1 of the type presented here for a motor vehicle, which is designed as a steer-by-wire steering system and therefore has a force feedback actuator M mentioned above (also called a feedback motor or simply motor M ) includes. The steering system 1 has a steering column module 2, which is designed for an immovable arrangement in the vehicle opposite a driver's seat (not shown) and, if necessary, can be adjusted as a whole for individual adjustment to the driver in one or more directions (e.g. in the vehicle longitudinal and vertical direction). can. Furthermore, the steering system 1 comprises a steering wheel shaft 3 rotatably mounted in the steering column module 2 with a steering wheel 4 fixed to it in a rotationally fixed manner.

while showing 1a a partial circuit diagram of the steering system 1 in a schematic longitudinal section along the steering wheel shaft 3 viewed from above, ie approximately from a vertical direction of an on-board coordinate system. 1b shows a partial circuit diagram of the steering system 1 in a schematic plan view of the steering wheel 4 from the driver's point of view, ie approximately from a longitudinal direction of the motor vehicle. Finally shows 1c a part of the steering system 1 in a further schematic longitudinal section along the steering wheel shaft 3 viewed from the side, ie approximately from a transverse direction of the motor vehicle.

Some consumers of electrical energy (not shown) are integrated in the steering wheel 4, including in this example a steering wheel heater and/or other large consumers that alone or together have an electrical consumption of at least about 50 W; and one or more steering wheel buttons (multifunction buttons) in a schematically indicated steering wheel area 5 and, if necessary, other consumers (not shown) such as a capacitive hands-off detection sensor, an airbag or an actuator for folding and unfolding the steering wheel 4 to stow it in a highly automated driving operation.

For wireless power supply to the consumers integrated in the steering wheel 4, the steering system 1 includes a specially designed and optimized transformer 6. This has a primary coil 7 fixed in the steering column module 2, a secondary coil 8 non-rotatably connected to the steering wheel shaft 3, and an integrated iron core 9 made of a soft magnetic material , In particular in the form of a layered electrically insulated electrical sheet to avoid eddy current losses. In this example, the steering wheel shaft 3 simultaneously assumes the function of the iron core 9 of the transformer 6 and can consist, for example, of layered μ-metals (FeNi compounds), which typically have a magnetic permeability of μ˜50,000 to 140,000.

An inverter 10 (with associated supply lines 11 to the inverter 10) is provided on the steering column side, which converts the DC voltage available on board the vehicle into a transformable AC voltage. The primary coil 7 of the transformer 6 is fixedly connected to the housing of the steering column module 2 and is arranged inside it. It can be wound up as a hollow cylinder, for example, in order to maximize the surface area that faces the steering wheel shaft 3 that transmits the magnetic field. There can only be a minimal air gap 14 between the primary coil 7 and the steering wheel shaft 3 (cf. 2a-2b) be present so that the steering wheel shaft 3 can be rotated freely.

The secondary coil 8 of the transformer 6 can be pressed firmly onto the steering wheel shaft 3 in order to minimize stray losses, since the secondary coil 8 together with the steering wheel 4 rotates at the same speed as the steering wheel shaft 3. On the secondary side is a rectifier 12 (with the associated supply lines 13 from the rectifier 12 to the consumers) which converts the transported AC voltage into a usable DC voltage. The primary and secondary coils 7, 8 can have the same number of turns since the voltage level remains the same in this example.

According to the 1a-1c In the preferred exemplary embodiment outlined, the shaft W of the force feedback actuator M is connected to the steering wheel 4 via a transmission G to transmit the feedback (ie a manual torque corresponding to the feedback from the road or the wheels) to the steering wheel 4 . The gear G is designed to reduce the speed of the force feedback actuator M and at the same time to increase the torque. This means that the force feedback actuator M can be smaller and requires less power, but it must be able to rotate faster than without such a gear G.

The transformer 6 and the force feedback actuator M are in 1a-1c So trained independently and can thereby - like described collectively herein - each must be optimally designed for its own function in order to maximize its efficiency while minimizing electrical energy consumption on board the vehicle. A rotor position sensor is also inherent in the force feedback actuator M, via which the steering wheel position can be determined. An additional steering wheel position sensor, as in the patent mentioned in the opening paragraph DE 199 46 934 B4 proposed, would therefore be superfluous here.

2a shows the in again 1c illustrated lateral longitudinal section of the steering system 1. Also show 2 B and 2c an enlarged cross section of the primary side ( 2 B) and the secondary side ( 2c ) of the transformer 6 of the steering system 1 looking in the axial direction of the steering wheel shaft 3. As in 2a As can be seen, in this exemplary embodiment a distance A of, for example, about 10-15 cm between the primary coil 7 and the secondary coil 8 of the transformer 6 offers sufficient space for attaching a steering column switch module (not shown) mentioned above to a conventional steering wheel architecture used for turn signals and high beams - and windscreen wiper actuation ergonomically well-suited space between the steering wheel 4 and the steering column module 2.

in the in 2 B shown cross-sectional view of the primary side of the transformer 6 is again the iron core 9 - which also forms the steering wheel shaft 3 - shown from layered electrical steel (to increase the magnetic permeability and reduce eddy current losses). Also shown are the primary coil 7, which is wrapped around a section of the steering wheel shaft 3 that is rotatably mounted in the steering column module 2, an air gap 14 between the primary coil 7 and the steering wheel shaft 3 so that the steering wheel shaft 3 can rotate freely, and the supply lines 11 from the inverter 10.

The cross-sectional view of the secondary side of the transformer 6 in 2c can be understood as a view from the driver's perspective through an airbag pot (imagined to be invisible) onto the secondary coil 8 of the transformer 6 . Here you can see again a section of the iron core 9 (ie the steering wheel shaft 3) lying in the steering wheel 4, a secondary coil 8 wound around it and its supply lines 13 to the rectifier 12. In contrast to the primary coil 7, no air gap is required here and the secondary coil is Fixed directly on the steering wheel shaft 3 to increase efficiency.

3 shows a to 1a-1c alternative embodiment of a steering system 1 of the type presented herein, which is designed as a steer-by-wire steering system. A schematic longitudinal section of the steering system 1 is shown at the bottom left, and an enlarged section of the force feedback actuator M contained therein is shown at the top right.

In contrast to 1a-1c serves in 3 the stator 15 of the force feedback actuator M as the primary side of the transformer 6. The force feedback actuator M is shown as an example in a star connection. The ring, at whose various positions the coil windings of the three phases U, V and W of the stator 15 are arranged, symbolically forms the star point. The rotor 16 of the force feedback actuator M is rotatably mounted in the center of the stator 15 . In this example, the rotor 16 is designed with an embedded (“buried”) permanent magnet 17, inside which the steering wheel shaft 3, which serves as the iron core 9 of the transformer 6, in turn runs. The secondary coil 7 of the transformer 6 is fixed on the rotor 16 on the outside.

In this case, the rotor 16 must be firmly connected to the steering wheel 4 because the supply line 13 of the secondary coil 8 must rotate with the steering wheel speed in order not to twirl. In contrast to 1a-1c is in 3 therefore no use of a gear possible, which means a significant restriction for the dimensioning of the feedback actuator M.

Reference List

1

steering system

2

steering column module

3

steering wheel shaft

4

steering wheel

5

Steering wheel area for steering wheel buttons

6

transformer

7

primary coil

8th

secondary coil

9

iron core

10

inverter

11

supply lines to the inverter

12

rectifier

13

leads from the rectifier

14

air gap

15

Stator of the FFA

16

Rotor of the FFA

17

permanent magnet

M

Force Feedback Actuator, FFA, Feedback Motor

W

Wave for transmission of the feedback

G

transmission

A

axial distance between primary coil and secondary coil

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018219167 A1 [0007]
• DE 19946934 B4 [0008, 0041]
• DE 10258871 A1 [0008]

Claims (10)

Steering system (1) for a vehicle, comprising: - A steering column module (2) which is designed for a fixed arrangement in the vehicle; - A steering wheel shaft (3) which is rotatably mounted in the steering column module (2) and has a steering wheel (4) which is fixed in a rotationally fixed manner on the steering wheel shaft (3) and in which at least one electrical consumer is integrated; and - a transformer (6) designed for the wireless power supply of the at least one electrical consumer, which has a primary coil (7) fixed in the steering column module (2) with an upstream inverter (10), a secondary coil (8) non-rotatably connected to the steering wheel shaft (3). a downstream rectifier (12) and an integrated iron core (9) made of a soft magnetic material, the iron core (9) being at least partially formed by the steering wheel shaft (3) and/or being at least partially non-rotatably connected to it. Steering system (1) according to claim 1 , wherein - the steering wheel shaft (3) forms the iron core (9); - the primary coil (7) is wound in the form of a hollow cylinder around an axial section of the steering wheel shaft (3) mounted in the steering column module (2), with a remaining radial air gap (14) between the hollow cylinder and the steering wheel shaft (3) being just as large, that the steering wheel shaft (3) can rotate relative to the hollow cylinder without friction, and - the secondary coil (8) is firmly wound onto the steering wheel shaft (3) in its steering wheel-side axial section; - So that the transformer (6) preferably has an efficiency of at least 50%. Steering system (1) according to claim 1 , wherein - the transformer (6) is designed as a rotary transformer, the iron core of which comprises, in the axial direction of the steering wheel shaft (3), a primary-side iron core section fixed in the steering column module (2) and a secondary-side iron core section connected in a torque-proof manner to the steering wheel shaft (3), which are mutually separated by are separated by an axial air gap just large enough to allow the secondary-side iron core portion to rotate relative to the primary-side iron core portion without friction; - the primary-side iron core section surrounds and/or houses the windings of the primary coil (7), and - the secondary-side iron core section surrounds and/or houses the windings of the secondary coil (8); - So that the transformer (6) preferably has an efficiency of at least 50%. Steering system (1) according to one of the preceding claims, - This is a steer-by-wire steering system with a force feedback actuator (M) which is designed to generate a manual torque which reflects feedback from the road and the vehicle wheels to the steering wheel (4); - Wherein a rotor of the force feedback actuator (M) is connected to the steering wheel shaft (3) via a gear (G), which is designed to reduce the rotor speed while increasing the torque. Steering system (1) according to one of Claims 1 until 3 - which is a steer-by-wire steering system with a force feedback actuator (M) which is designed to generate a manual torque which reflects feedback from the road and the vehicle wheels to the steering wheel (4); - A stator (15) of the force feedback actuator (M) simultaneously forming the primary coil (7) of the transformer (6), and the secondary coil (8) of the transformer (6) on a rotor (16) of the force feedback -Actuator (M) is tightly wound. Steering system (1) according to any one of the preceding claims, wherein the at least one electrical consumer comprises one or more of the following electrical consumers: - A steering wheel heater and/or another large consumer that has an electrical consumption of at least about 30 W, preferably at least about 40 W, particularly preferably at least about 50 W; - one or more steering wheel buttons for operating the vehicle or an infotainment system integrated into it; - A capacitive hands-off detection sensor, which is designed to detect whether the driver's hands are not on the steering wheel; - an air bag; - An actuator that is designed to open and close the steering wheel. Steering system (1) according to any one of the preceding claims, further comprising: - An accumulator arranged in the steering wheel (3) or connected in a rotationally fixed manner to the steering wheel shaft (3) as an intermediate electrical store for supplying energy to the at least one electrical consumer; - Wherein the steering system (1) is preferably set up to automatically charge the accumulator via the secondary-side rectifier (12) of the transformer (6) in an interval operation, which can be defined in particular as a function of its residual charge. Steering system (1) according to one of the preceding claims, - further comprising a steering column switch module which is mechanically fixed to the steering column module (2); - wherein the steering wheel shaft (3) forms the iron core (9) of the transformer (6), the primary coil (7) of which is wound around an axial section of the steering wheel shaft (3) mounted in the steering column module (2) with a radial air gap (14) in between and whose secondary coil (8) is firmly wound onto an axial section of the steering wheel shaft (3) on the steering wheel side, and - the steering column switch module is arranged axially between the primary coil (7) and the secondary coil (8) of the transformer (6). Steering system (1) according to one of the preceding claims, in which the iron core (9) of the transformer (6) - is made of layered electrically insulated electrical steel; and - whose material preferably has a magnetic permeability of at least 10,000, preferably at least 25,000, particularly preferably at least 50,000. Vehicle, in particular a motor vehicle, comprising: - a driver's seat and an instrument panel arranged in front of it; such as - A steering system (1) according to one of the preceding claims, the steering column module (2) of which is fixed in the area of the instrument panel and, if necessary, can be adjusted as a whole in one or more directions for individual adjustment to a driver, in particular in the axial direction of the steering wheel shaft (3) to adjust the steering wheel (4) to the driver's seating position in a longitudinal direction of the vehicle, and/or in a vertical direction to adapt to the driver's seat height and size.

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