DE102021117890A1 - Inductive linear position sensor and vehicle with an inductive linear position sensor - Google Patents

Abstract

The invention relates to an inductive linear displacement sensor for recording a position of a movable measurement target, with a base body, a transmission coil and at least one first reception coil arranged along the measurement path, the first reception coil having a first reception coil train and a second reception coil train, each of which is separated from one another along the measurement path each have a course arranged essentially according to an elementary trigonometric function and thus span an induction surface or several induction surfaces, and the position of the measurement target relative to the base body by means of an electromagnetic excitation of the measurement target with the transmission coil and an electromagnetic readout of an electromagnetic field dependent on the position of the measurement target The measurement target reacts by means of the first reception coil, the first reception coil train being the first reception coil and/or the second reception coil train of the first receiving coil is or are arranged constricted in relation to the course according to the elementary trigonometric function in a first end area and/or in a second end area of the measurement path in the direction of a central axis, so that the induction surface or one of the induction surfaces between the first receiving coil train and the second receiving coil train for Dampening of the position of the measurement target dependent electromagnetic reaction in the first end of the measurement path and / or in the second end of the measurement path is reduced or are.

Description

The invention relates to an inductive linear displacement sensor for recording a position of a measurement target movable along a measurement path, having a base body, a transmission coil arranged along the measurement path and at least one first reception coil arranged along the measurement path, the first reception coil having a first reception coil train and a second reception coil train and the first receiving coil train and the second receiving coil train each have a course arranged separately from one another along the measurement path, each essentially according to an elementary trigonometric function, and thus span an induction surface or several induction surfaces, and the position of the measurement target relative to the base body by means of electromagnetic excitation of the measurement target with the Transmission coil and an electromagnetic readout of a dependent on the position of the measurement target electromagnetic response of the measurement target by means of the first rec ang coil takes place. Furthermore, the invention relates to a vehicle, or in general a mechatronic system, which is located in a vehicle, for example, with an inductive linear displacement sensor of the type described above.

Known inductive linear displacement sensors of the type described are used, for example, to record a position of a steering system, in particular a front-axle steering system or a rear-axle steering system for a vehicle. The position of a measurement target in relation to the linear displacement sensor is determined and a conclusion about a steering angle is drawn from this.

Such inductive linear displacement sensors are also known, inter alia, in a redundant structure, so that a corresponding safety level for the safe operation of a corresponding steering system can be maintained.

In particular in the case of inductive linear displacement sensors with courses of corresponding receiving coil strands arranged according to an elementary trigonometric function, it can happen in the end area of the sensor that a recorded signal of the measurement target is no longer essentially linear or even extremely non-linear and thus further electronic components, which are required for further processing of the corresponding Signals are used, for example run into saturation or no longer work reliably. This results in particular in a changed signal amplitude and/or in a signal amplitude offset, in particular in the absence and/or excessive displacement of the measurement target.

The object of the invention is to improve the prior art.

The task is solved by an inductive linear position sensor according to claim 1.

The constriction of the corresponding first receiving coil train and/or the corresponding second receiving coil train in the respective end area causes a signal change due to the reduced induction surface to be damped, so that, for example, a measurement signal is straightened or the measurement signal is prevented from escaping from a signal that can be used by other components or downstream electronics area is attenuated.

In particular, this can prevent a downstream circuit from running outside a measurement range or being led to saturation, for example, due to edge effects that occur in corresponding end areas, so that a measurement signal could no longer be recorded without the configuration according to the invention.

The following terms are explained here:

An “inductive linear path sensor” is a measuring element, a sensor or another electrical or electronic element which is suitable for generating corresponding sensor signals in electrical or electronic form, for example in order to record a linear path of a measurement target. Such an inductive linear displacement sensor has coils, for example, by means of which an electromagnetic reaction can be recorded. In addition, such an inductive linear displacement sensor can also include a coil or multiple coils for exciting a measurement target, for example.

A “position along a measurement path” is a location, in particular a relative location, in relation to, for example, a longitudinal axis or a measurement axis of the inductive linear displacement sensor, which can be specified in relative or absolute terms.

A "measurement target" is, for example, a flat piece of metal, in particular steel or aluminum, which is excited by, for example, electromagnetic fields from the transmitting coil and then has an electromagnetic effect, amplifying or shielding, on one or more receiving coils, so that, for example, an electrical or electromagnetic Behavior of one or more receiving coils is changed so that this change can be recorded as a measurement signal of the inductive linear displacement sensor. In this case, for example, a signal that can be measured without the measurement target is masked out at the corresponding point of the respective receiving coil. However, such a measurement target can also be any other arrangement that can record, convert and/or pass on electromagnetic signals.

A "base body" is, for example, a housing, a frame or another supporting arrangement of the inductive linear displacement sensor, which is suitable for holding, supporting and/or accommodating other components. For example, such a base body is an injection-molded component or a circuit board (PCB, printed circuit board) made of plastic, in which in particular corresponding coils can be accommodated, printed on or injected directly.

A "transmitting coil" is, for example, a ring-shaped, oval or other shaped arrangement of in particular concentric conductor tracks, which is suitable for spanning a coil surface, namely an induction surface, so that when a voltage change is applied, in particular an AC voltage with a frequency of, for example, 1 MHz to 100MHz, a corresponding time-varying electromagnetic signal is sent to the transmission coil, which can then be picked up by the measurement target, for example. An arrangement of this transmitter coil "along the measurement path" describes the fact that, for example, the transmitter coil spans an induction surface, which in particular spans at least the entire measurement path of the inductive linear displacement sensor and thus enables the measurement target to be excited along the entire measurement path.

A "receiving coil" describes a corresponding arrangement of a conductor track or several conductor tracks, with the first receiving coil spanning an induction surface, i.e. the receiving coil being arranged geometrically in such a way that a corresponding surface is spanned between the respective conductor tracks. Such a receiving coil has, for example, a first receiving coil train and a second receiving coil train, with a respective receiving coil train describing a conductor track arranged, for example, on a respective side of a central axis or on a respective side of the measurement path. Such a first receiving coil strand and a second receiving coil strand are arranged geometrically separate from one another in such a way that a corresponding induction surface, namely the surface between the respective receiving coil strands, is spanned.

A course of the respective receiving coil strand along the measurement path, in each case essentially along a course arranged according to an elementary trigonometric function, describes that corresponding receiving coil strands can also run separately from one another along the measurement path, but can each be arranged on different sides of the measurement path. Characteristic of an arrangement running “substantially according to an elementary trigonometric function” is the fact that a meandering arrangement is selected, for example roughly according to a trigonometric function, such as a sine function or a cosine function, but also in other types of functions. “Essentially” describes that a mathematically exact trigonometric function does not have to be mapped, but that another, meandering, rounded function, for example, which resembles a trigonometric function in terms of its progression, can also be mapped.

An "induction surface" is a respective geometric surface spanned between the respective receiving coil strands, which, in connection with an electrical excitation of the corresponding receiving coil, enables an inductive interaction of the respective receiving coil with the measurement target. Such an induction surface can also be referred to as a "coil surface".

"Electromagnetic excitation" of the measurement target describes the above-mentioned excitation of the measurement target, for example by means of an alternating voltage, which is applied to the transmitter coil, so that electromagnetic fields are transferred to the measurement target and induce eddy currents in the measurement target due to the electrical conductivity in the measurement target, which in turn induce magnetic field. This induced magnetic field can then take place, for example, by means of an "electromagnetic readout" by the corresponding receiving coil, for example by generating a corresponding electrical signal in the receiving coil or by changing an electrical oscillation behavior of the receiving coil by a correspondingly induced magnetic field of the measurement target. This signal or this change can then be read out by means of an external sensor system or external electronics. This induction of a magnetic field by the measurement target or a shielding of the magnetic field for the respective receiving coil is an example of an "electromagnetic reaction dependent on the position of the measurement target" of the measurement target. Due to the meandering course, which is in particular arranged essentially according to an elementary trigonometric function, it becomes dependent on the position of the measurement target a different electromagnetic reaction is caused compared to the corresponding receiving coil, since the measurement target is moved over or in relation to different induction surface areas and a different reaction can therefore also be read out.

An “end area” describes an area running along the measurement path or a central axis parallel to the measurement path at a respective end of the measurement path. For example, such an end area is arranged on the base body of a longitudinally aligned inductive linear displacement sensor at a respective beginning and a respective end, i.e. at a furthest deflection or a furthest position of the measurement target in one and/or an opposite direction compared to the inductive linear displacement sensor.

A “central axis” describes a longitudinal axis, for example a geometric one, of the inductive linear displacement sensor, which essentially runs along the measurement path. "Essentially" does not describe the course of the central axis that is exactly parallel or arranged exactly with the measuring path, but sensible technical deviations of, for example, +5° to -5° or also a corresponding offset in relation to an axis of the measuring path of, for example, up to 15% a width of the inductive linear displacement sensor.

"Constricted" describes the fact that the corresponding receiving coil strand runs closer to the central axis than would otherwise be the case at this point due to the course according to the elementary trigonometric function in relation to the longitudinal extension, namely in relation to the measuring path, of the inductive linear displacement sensor. By means of such a constriction, the respective induction surface between the first receiving coil train and the second receiving coil train is reduced, so that there is a smaller reduction area compared to a typical course of the respective receiving coil train without the constriction.

This geometric arrangement of the respective receiving coil strand results in a "dampening" of the electromagnetic reaction, which is dependent on the position of the measurement target, in the respective end area of the measurement path, namely a change in the course of a corresponding measurement signal in such a way that, for example, an excessive sensory reaction in relation to a measurement signal generated is mitigated and thus, for example, an overflow of a corresponding readout electronics due to e.g. reaching saturation is prevented. In this case, for example, a deviation from the linearity of a signal amplitude below a value of 10% compared to a linear signal amplitude can be achieved if this is specified, for example, by operating limits of readout electronics.

In order to design the inductive linear displacement sensor in such a way that an absolute determination of the position of the measurement target relative to the base body of the inductive linear displacement sensor is possible, the inductive linear displacement sensor has a second receiving coil, a third receiving coil, a fourth receiving coil and/or a further receiving coil with a respective first receiving coil train and a respective second receiving coil train, wherein the respective first receiving coil train and the respective second receiving coil train are designed in such a way that the respective first receiving coil train and the respective second receiving coil train are arranged separately from one another along the measurement path, each running essentially according to an elementary trigonometric function and thus span an induction surface or several induction surfaces, and determine the position of the measurement target in relation to the base body by means of electromagnetic excitation of the measurement target with the S end coil and an electromagnetic readout of an electromagnetic reaction of the measurement target that is dependent on the position of the measurement target by means of the first reception coil, the second reception coil, the third reception coil, the fourth reception coil and/or the further reception coil, with the respective first reception coil train or the respective second reception coil train of the first receiving coil, the second receiving coil, the third receiving coil, the fourth receiving coil and/or the further receiving coil is or are arranged constricted in relation to the profile of the elementary trigonometric function in a first end area and/or in a second end area of the measuring path in the direction of a central axis , So that the induction surface or one of the induction surfaces between the respective first receiving coil train and the respective second receiving coil train for damping the dependent on the position of the measurement target electromagnetic reaction in is reduced in the first end area of the measurement path and/or in the second end area of the measurement path.

The second receiving coil, the third receiving coil, the fourth receiving coil and/or the further receiving coil can each be configured geometrically analogous to the first receiving coil, but any other geometric configuration is also possible, in particular a different course of the receiving coil strands. Thus, by shifting the corresponding receiving coils relative to one another along the measurement path, for example, a superimposition of ent Speaking signals of the respective receiving coils are used to generate an absolute measurement signal, so that an absolute position of the measurement target relative to the inductive linear displacement sensor can be read. In addition, multiple receiving coils or multiple pairs or groups of receiving coils can create redundancy within an inductive linear displacement sensor, in which the position of the measurement target relative to the base body of the inductive linear displacement sensor is recorded using multiple coils and/or multiple coil groups or coil pairs, so that if one Receiving coil or multiple receiving coils still safely a signal can be picked up. This is particularly necessary when used in safety-critical systems.

A corresponding constriction of the respective receiving coil strand of the respective receiving coil can then take place for exactly the receiving coil or exactly the receiving coils in which, for example, a non-linear effect of a change in position of the measurement target compared to the inductive linear sensor in the respective end area is to be expected. Thus, one receiving coil, several receiving coils or also all receiving coils can be provided with a corresponding constriction, if this is necessary.

In one embodiment, the respective first receiving coil train and the respective second receiving coil train in the first end area of the measurement path and/or in the second end area of the measurement path is/are designed to run convexly in relation to the central axis, so that an exponential damping of the reaction dependent on the position of the measurement target occurs in the first end area of the measurement path and/or in the second end area of the measurement path.

An exponential, namely excessive, damping of a respective signal, namely the reaction dependent on the position of the measurement target, can be generated in the respective end area, so that corresponding negative effects are compensated or overcompensated when the respective end area is reached with the measurement target.

"Convex to the central axis" describes a course of the corresponding receiving coil strand, which is curved in the direction of the central axis, after which there is strong damping initially in the direction of the respective end area and thus also a strong reduction in the induction surface, which is then flatter in the direction of the End area expires.

An “exponential damping” describes damping which, contrary to an otherwise linear or essentially linear course, is initially excessively strong and then tapers off in the direction of the end region.

In order to be able to reliably read out corresponding signals from the inductive linear displacement sensor and thus generate a reliable sensor signal, the respective elementary trigonometric function is essentially a sine function, a cosine function, a trapezoidal function and/or a rounded rectangular function, with the first receiving coil, the second receiving coil in particular , the third receiving coil, the fourth receiving coil and/or the further receiving coil along the measurement path and/or along the central axis are offset from one another, in particular are arranged phase-offset by a fraction of their respective period length, for example by π/2.

If a function designed essentially according to a sine function and/or a cosine function is used as the elementary trigonometric function for the course of the respective receiving coil, a periodic change in the measurement signal can be read out when the measurement target is displaced along the measurement path, which then ideally occurs during the Superposition of several receiving coils leads to a linear measurement signal. "Essentially" describes technical deviations from a geometrically exact course of, for example, up to 5%. Corresponding deviations from a sine function and/or a cosine function can also be displayed technically, for example with regard to space optimization or other boundary conditions, so that the respective elementary trigonometric function can also be changed to a trapezoidal function, a rounded trapezoidal function and/or a rounded rectangular function. A trapezoidal function and/or a rectangular function, each with or without rounding, spans a respective induction surface and can lead to a correspondingly usable signal from the inductive linear displacement sensor.

In particular, corresponding receiving coils are offset from one another along the measuring path and/or along the central axis, in particular by a fraction of their respective period length. If the offset achieved in this way is, for example, exactly π/2 in relation to the course of a sine function, then a respectively offset periodic signal is generated when the measurement target is displaced along the measurement path of the inductive linear displacement sensor. Thus, from a calculation of corresponding sensor signals, an absolute value with regard to the position of the measuring be closed in relation to the base body of the inductive linear displacement sensor.

In a further embodiment, the transmission coil is or are excited electromagnetically by means of an exciter circuit, in particular a respective resonant circuit being electrically connected to the transmission coil with an excitation frequency.

Using such an excitation circuit, the transmission coil can be excited electromagnetically, for example, at a frequency that corresponds to a resonance frequency of the transmission coil or a resonance frequency of the measurement target, and thus generates the best possible reaction signal from the measurement target. A respective receiving coil can also be excited by means of a further excitation circuit in such a way that electromagnetic properties of the measurement target and the respective receiving coil are matched to one another, so that the best possible electromagnetic reaction to a change in the position of the measurement target can be recorded by the respective receiving coil.

For example, an oscillating circuit with a corresponding excitation frequency is electrically connected to the transmitting coil and/or the respective receiving coil.

An “exciter circuit” can be any electrical or electronic circuit that is suitable for causing the transmitting coil and/or a respective receiving coil to oscillate electrically. For example, such an excitation circuit is an “oscillating circuit” which, in the simplest case, consists of a capacitance that is attached in addition to the respective coil, namely, for example, a capacitor, and an electrical resistor. In this case, the respective coil would form the inductance of the oscillating circuit. In this case, the electrical resistance can also be formed by respective conductor tracks of the transmission coil or of the reception coil. The same applies to the transmitter coil.

In order to be able to easily read out the position of the measurement target relative to the inductive linear displacement sensor along the measurement path using electronic means, a reaction voltage at the receiving coil or a respective receiving coil, in particular a reaction voltage induced by the reaction of the measurement target, is to be measured using a measuring unit for measuring an electrical tension measurable.

The task of reading out corresponding sensor signals of the inductive linear displacement sensor is thus reduced to reading out corresponding voltages or voltage changes, as a result of which simple electronic components can subsequently be used to reliably read out the inductive linear displacement sensor.

A “reaction voltage” describes, for example, a change in the periodic AC voltage, which is impressed on the respective receiving coil by a corresponding resonant circuit. Such a reaction voltage can therefore also be a voltage difference or a deviation from an expected voltage at a specific measurement time. In particular, such a reaction voltage is induced in the respective receiving coil by the reaction of the measurement target. Alternatively, such a reaction voltage is the voltage induced in the respective receiving coil or the voltage shielded by the respective receiving coil, which can then be measured as a voltage increase in the first case or as a voltage drop in the second case.

A “measuring unit” for measuring an electrical voltage can be, for example, a microcontroller, an integrated circuit or an oscilloscope arrangement. However, any electronic device can be used for this that is able to determine a voltage with a corresponding time resolution and to convert it into a corresponding output signal.

In a further embodiment, the position, in particular an absolute position, of the measurement target, which can be moved linearly along the measurement path, is recorded by means of a mathematical calculation, in particular a division, in a calculation unit which is assigned to the inductive linear displacement sensor, from a signal of the electromagnetic reaction of the first Receiving coil and a respective signal of one or more of the second, third, fourth and / or further receiving coils.

For example, the calculation unit can be used to determine a linearized signal with regard to the position of the measurement target by dividing the sine signal of a first reception coil and the cosine signal of a second reception coil, in the case of mutually assigned receiving coils that are offset by an amount of π/2, i.e. by forming a cotangent . Other mathematical calculations are possible here, which can each be adapted to the geometric shape of the receiving coils.

If such a calculation is carried out with respect to two receptions assigned to one another coil through for several pairs of receiving coils, a redundant linear signal of the position of the measurement target relative to the base body of the inductive linear displacement sensor can be determined, so that a particularly reliable determination of the position of the measurement target relative to the base body of the inductive linear displacement sensor is made possible.

A "mathematical calculation" describes every possible addition, subtraction, division or multiplication or complex calculation between different signals, for example different voltage changes at different receiving coils.

A "calculation unit" is, for example, a microcontroller, an integrated circuit or an electronic arrangement which is suitable for carrying out corresponding calculations. An arrangement of corresponding resistors, for example a voltage divider, can also be sufficient for this purpose for simple mathematical calculations.

A "signal" of the electromagnetic reaction is, for example, a voltage change, a voltage or a current flow, which is used to transmit the corresponding measured value.

In order to be able to construct the inductive linear displacement sensor in a particularly compact manner, the transmission coil is arranged on an outer region of the base body, in particular around an edge of the base body, with the transmission coil being formed in particular from a plurality of turns and/or a number of levels of respective turns.

The transmission coil thus forms, for example, an outer boundary of the inductive linear displacement sensor, which additionally ensures that a measurement target guided along the measurement path via the inductive linear displacement sensor is brought into electromagnetic engagement with the transmission coil at all times, as a result of which a particularly reliable inductive linear displacement sensor is created.

An “outer area” describes the area of the base body which runs, for example, along a contour of the base body with a width of, for example, 10% of the area of the base body. A corresponding “edge” of the base body runs along the contour of the base body, for example along an elongate extent of the base body.

A "winding" of the transmission coil is a respective closed course of a corresponding conductor track or, for example, of a wire forming the transmission coil, ie a course of the conductor track around a full angle of 360°.

A “plane” made up of respective windings describes a geometric plane in which a corresponding winding is arranged, which is arranged essentially perpendicular to a central axis of the corresponding transmission coil.

In a further embodiment, the first receiving coil and/or the second receiving coil, the third receiving coil, the fourth receiving coil and/or the further receiving coil is or are surrounded by the transmitting coil on the base body, in particular within a base area formed by the transmitting coil.

This structure of the inductive linear displacement sensor ensures a particularly compact design, it also being ensured in particular that a corresponding measurement target is electromagnetically engaged with the respective receiving coil over the entire measurement path of the inductive linear displacement sensor.

In a further aspect, the object is achieved by a vehicle according to claim 10.

Such a vehicle can advantageously use the above-described advantages of a correspondingly reliable, compactly implemented inductive linear displacement sensor. For example, a redundant inductive linear displacement sensor can be created by means of an arrangement of several receiving coils according to the type described above, which, for example, makes a front-axle steering system or a rear-axle steering system of a corresponding vehicle particularly reliable.

• 1 eine schematische Darstellung eines Lenkgetriebes in isometrischer Ansicht,
• 2 eine schematische Darstellung einer Sensoranordnung im Lenkgetriebe der 1,
• 3 eine Übersichtsdarstellung eines induktiven Linearwegsensors, sowie
• 4 eine vergrößerte Detaildarstellung des induktiven Linearwegsensors der 3.

The invention is explained in more detail below using exemplary embodiments. Show it

• 1 a schematic representation of a steering gear in an isometric view,
• 2 a schematic representation of a sensor arrangement in the steering gear 1 ,
• 3 an overview of an inductive linear displacement sensor, and
• 4 an enlarged detailed view of the inductive linear displacement sensor 3 .

A steering gear 101 has a drive 103, the drive 103 including a motor (not shown). A steering linkage 107 with connection heads 109 is guided within a guide tube 105 . At this point, the detailed design of the mechanics of the steering gear 101 is omitted. However, it should be mentioned that the Drive 103 located motor acts by means of a toothed belt on a spindle drive for the steering linkage 107, so that the steering linkage 107 can be moved axially along a linear movement 111 in the steering gear 101. The steering gear 101 is used, for example, for the rear-axle steering of a vehicle (not shown), in which case the corresponding mechanical components of an articulation of the rear-wheel steering, for example tie rods or control arms, are mechanically contacted with the connection heads 109, so that the linear movement 111 of the steering linkage 107 results in a corresponding steering angle Wheels is effected (detailed representation omitted).

Furthermore, a measurement target 303 is arranged inside the drive 103 on the steering linkage 107, which is movable in relation to a linear displacement sensor 301 arranged fixedly opposite the drive 103 and the guide tube 105 with the linear movement 111 of the steering linkage 107 (for a detailed illustration see Fig 2 ).

If the steering linkage 107 is now moved in the guide tube 105 by means of the drive 103, with the steering linkage 107 executing the linear movement 111, the measurement target 303, which is fixedly arranged on the steering linkage 107, is also moved along a linear movement 311 relative to the linear displacement sensor 301. The measurement target 303 sweeps over the linear displacement sensor 301 along a central axis 351, which also runs along the measurement path of the linear displacement sensor 301 at the same time. A position of the measurement target 303 recorded in this way thus also correlates with the respective steering angle caused by the movement of the steering linkage 107 and can thus be used as feedback for the steering angle.

The linear displacement sensor 301 has a base body 315, which is a plastic injection molded part. A transmission coil 321 made of conductor tracks runs along an edge 317 of the base body 315 in several planes (into the plane of the image), which is excited by means of an external resonant circuit (not shown), so that the transmission coil 321 generates a constant, time-varying electromagnetic alternating field in one operating state For example, emits a constant amplitude. Depending on the circumstances, the frequency of this alternating field is matched to the electromagnetic behavior of the components, in particular a measurement target 303, of the linear displacement sensor 301 and can vary. The purpose of the tuning is to be able to generate a signal that is as unambiguous and clear as possible, for example to a resonant frequency or preferred frequency for the formation of eddy currents in the measurement target 303.

A plurality of receiving coils are arranged within the area formed by the transmitting coil 321 . The receiving coil 331 and the receiving coil 335 are arranged symmetrically to an axis of symmetry 353 , ie they run on both sides of this axis of symmetry 353 symmetrically to their respective coil turns lying opposite the axis of symmetry 353 . A reception coil 333 and a reception coil 337 are arranged asymmetrically with respect to the axis of symmetry 353 along the central axis 351 .

The reception coil 331 and the reception coil 335 form a first group of reception coils, the reception coil 333 and the reception coil 337 form a second group of reception coils. A respective group of receiving coils is used to generate a part of a redundant measurement signal for a position of the measurement target 303 in relation to the linear displacement sensor 301, so that a correspondingly determined steering angle also satisfies a desired safety level for a signal correlated with the steering angle.

In this case, the receiving coil 331 and the receiving coil 335 are arranged relative to one another along the central axis 351 by a phase offset 362, which corresponds to an offset of π/2 of their respective period length. The receiving coils 333 and 337 are arranged relative to one another by an offset 361, which also corresponds to an amount of π/2 of the period length. Each receiving coil is designed according to a sine/cosine curve, as a result of which an induction surface is stretched between the corresponding receiving coil strands. A first receiving coil train 338 and a second receiving coil train 339 are described here for the receiving coil 337 as an example. The other receiving coils also have corresponding receiving coil strands, which meander around the central axis 351 according to the sine/cosine function.

The respective receiving coils can also be excited with a respective resonant circuit (not shown), but this is not the case for the present example. If measurement target 303 now slides along central axis 351 over base body 315 of linear displacement sensor 301, measurement target 303 is excited by the electromagnetic field of transmission coil 321 and, due to induction processes located in measurement target 303, shields electromagnetic fields from the reception coils, and their electromagnetic behavior accordingly is changed by locally reducing the voltages induced by the transmitter coil. A resulting change in an electrical voltage measured at the receiving coils can then be used to determine the Position of the measurement target 303 are used in relation to the respective receiving coil. If two mutually phase-shifted receiving coils of a respective group are read out together and their voltage deviations are offset against one another, for example in a calculation unit or a control unit (not shown), for example by division, an absolute position of the measurement target 303 relative to the base body 315 of the linear displacement sensor 301 be read out. Consequently, an absolute steering angle can also be determined. A corresponding reading of a second group of receiving coils can then be used to achieve a safety level by means of redundancy.

A special feature of the receiving coil 337 according to the invention is explained in detail below (cf 4 ):

Compared to a profile 345 of the reception coil 337 following the sine/cosine function, this reception coil 337 is narrowed in an end area 347 and also in an end area 349 symmetrically with respect to the axis of symmetry 353 . For this purpose, the respective receiver coil train 338 and receiver coil train 339 have a constriction 341 and a constriction 340, with the respective receiver coil train being designed with a convex bulge in the direction of the central axis 351, resulting in a reduced induction surface 347 compared to the induction surface spanned by the undisturbed course 345. Viewed from the edge 317 of the base body 315, this course appears concave, i.e. indented in the direction of the central axis 351.

This arrangement of the receiving coil strands in the end area 347 and also in the end area 349 correspondingly exponentially dampens any signal distortion that occurs when the measurement target 303 reaches the respective end area. In this way, non-linearities that sometimes occur in the calculation described above can be mitigated.

A diagram 501 shows the correspondingly recorded voltage signals of the respective receiving coils as an example. Diagram 501 has an abscissa 503 and an ordinate 505, with the position of the measurement target relative to linear displacement sensor 301 being plotted on abscissa 503, for example between −30 mm and +30 mm, ordinate 505 represents a correspondingly measured voltage amplitude in the respective receiving coils of a respective signal. The signal 531 is assigned to the receiving coil 331, the signal 533 to the receiving coil 333, the signal 535 to the receiving coil 335 and the signal 537 to the receiving coil 337. The representation in the diagram 501 corresponds to a completely linearized configuration of the linear displacement sensor 301 by means of the configuration according to the invention.

reference list

101

steering gear

103

drive

105

guide tube

107

steering linkage

109

connection head

111

linear motion

301

linear displacement sensor

303

measurement target

311

linear motion

315

body

317

edge

321

transmitter coil

331

receiving coil

333

receiving coil

335

receiving coil

337

receiving coil

338

receive coil train

339

receive coil train

340

constriction

341

constriction

342

induction surface

345

Course

347

end area

349

end area

351

central axis

353

axis of symmetry

361

offset

362

offset

501

diagram

503

abscissa

505

ordinate

531

signal

533

signal

535

signal

537

signal

Claims (10)

Inductive linear displacement sensor (301) for recording a position (311) of a measurement target (303) movable along a measurement path (351), with a base body (315), a transmission coil (321) arranged along the measurement path (351) and at least one along the measurement path (351) arranged first receiving coil (337), wherein the first receiving coil (337) has a first receiving coil train (338) and a second receiving coil train (339) and the first receiving coil train (338) and the second receiving coil train (339) each along a separate line of the measurement path (351) each have a course arranged essentially according to an elementary trigonometric function and thus span an induction surface or several induction surfaces, and the position of the measurement target (303) relative to the base body (315) by means of electromagnetic excitation of the measurement target (303) with the Transmission coil (321) and an electromagnetic readout from the position (311) of the measurement target (303)-dependent electromagnetic reaction of the measurement target (303) by means of the first receiving coil (337), characterized in that the first receiving coil train (338) of the first receiving coil (337) and/or the second receiving coil train (339) of the first receiving coil (303) compared to the course (345) according to the elementary trigonometric function in a first end area (347) and/or in a second end area (349) of the measurement path (351) in the direction of a central axis (351) constricted (340, 341). is or are, so that the induction surface (342) or one of the induction surfaces (342) between the first receiving coil train (338) and the second receiving coil train (339) for damping the position (311) of the measurement target (303) dependent electromagnetic reaction in the first End area (347) of the measuring path (351) and/or in the second end area (349) of the measuring path (351) is or are reduced. Inductive linear position sensor according to claim 2 , characterized by a second reception coil (331), a third reception coil (333), a fourth reception coil (335) and/or a further reception coil with a respective first reception coil train and a respective second reception coil train, the respective first reception coil train and the respective second reception coil train are designed in such a way that the respective first receiving coil train and the respective second receiving coil train are arranged separately from one another along the measuring path (351), each running essentially according to an elementary trigonometric function and thus each spanning an induction surface or in each case several induction surfaces, and the position (311) of the measurement target (303) relative to the base body (315) by means of electromagnetic excitation of the measurement target (303) with the transmission coil (321) and electromagnetic reading of an electromagnetic reaction dependent on the position (311) of the measurement target (303). of the measurement target (303) by means of the first receiving coil (337), the second receiving coil (331), the third receiving coil (333), the fourth receiving coil (335) and/or the further receiving coil, with the respective first receiving coil strand and/or the respective second receiving coil phase of the first receiving coil (337), the second receiving coil (331), the third receiving coil (333), the fourth receiving coil (335) and/or the further receiving coil compared to the course of the elementary trigonometric function in a first end region (347) and/or in a second end region (349) of the measuring path (311) is or are arranged constricted in the direction of a central axis (351), so that the induction surface or one of the induction surfaces between the respective first receiver coil train and the respective second receiver coil train for damping the Position (311) of the measurement target (303) dependent electromagnetic reaction in the first end (347) of Messwe ges (351) and/or in the second end area (349) of the measuring path (351) is reduced. Inductive linear position sensor according to claim 1 or 2 , characterized in that the respective first receiving coil train and the respective second receiving coil train in the first end region (347) of the measurement path (351) and/or in the second end region (349) of the measurement path (351) is designed to run convexly towards the central axis (351) or are, so that an exponential damping of the position of the measurement target (303)-dependent reaction in the first end area (347) of the measurement path (351) and/or in the second end area (349) of the measurement path (351) is achieved. Inductive linear displacement sensor according to one of the preceding claims, characterized in that the respective elementary trigonometric function is essentially a sine function, a cosine function, a trapezoidal function and/or a rounded rectangular function, with the first receiving coil (337), the second receiving coil (331) in particular , the third receiving coil (333), the fourth receiving coil (335) and/or the further receiving coil along the measuring path (351) and/or along the central axis (351) offset (361, 362) from one another, in particular by a fraction of their respective period length , for example by Pi/2, are arranged out of phase. Inductive linear displacement sensor according to one of the preceding claims, characterized in that the transmitting coil (321) and/or the respective receiving coil (331, 333, 335, 337) is or are being excited electromagnetically by means of an excitation circuit, with in particular a respective resonant circuit having an excitation frequency is electrically connected to the transmitting coil (321) and/or the respective receiving coil (331, 333, 335, 337). Inductive linear displacement sensor according to one of the preceding claims, characterized in that a reaction voltage of a receiving coil (331, 333, 335, 337) or a respective receiving coil (331, 333, 335, 337), in particular one induced by the reaction of the measurement target (303). Response voltage can be measured using a measuring unit for measuring an electrical voltage. Inductive linear displacement sensor according to one of the preceding claims, characterized in that the position (311), in particular an absolute position, of the measurement target (303) movable linearly along the measurement path (351) is recorded by means of a mathematical calculation, in particular a division, in a calculation unit , which is assigned to the inductive linear displacement sensor (301), from a signal of the electromagnetic reaction of the first receiving coil (337) and a respective signal of one or more of the second receiving coil (331), the third receiving coil (333), the fourth receiving coil (335) and/or further receiving coils. Inductive linear displacement sensor according to one of the preceding claims, characterized in that the transmission coil (321) is arranged on an outer region (317) of the base body (315), in particular around an edge of the base body (315), the transmission coil (321) in particular is formed of multiple turns and / or multiple levels of respective turns. Inductive linear displacement sensor according to one of the preceding claims, characterized in that the first receiving coil (337) and/or the second receiving coil (331), the third receiving coil (333), the fourth receiving coil (335) and/or the further receiving coil is different from the transmitting coil (321) is or are surrounded on the base body (315), in particular arranged within a base area formed by the transmission coil (321). Vehicle with an inductive linear displacement sensor (301) according to one of the preceding Claims 1 until 9 , wherein the inductive linear displacement sensor (301) is used in particular for recording a steering angle of a steering system, for example a front-axle steering system or a rear-axle steering system of a vehicle.

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