DE102020128013B4 - Coil arrangement for a sensor device for determining a position of an object along a sensitive axis of the sensor device - Google Patents

Abstract

Coil arrangement (10) for a sensor device (40) for determining a position (P) of an object (O) along a sensitive axis (S) of the sensor device (40), the coil arrangement (10) comprising:
- a flat excitation coil (12) and
- a plurality of receiving coils (14), wherein turns (18) of the plurality of receiving coils (14) are arranged around turns (16) of the excitation coil (12), substantially perpendicular to the turns (16) of the excitation coil (12) and symmetrical with respect to a center line (M) of the excitation coil (12) which runs along the sensitive axis (S) of the sensor device (10), wherein a first receiving coil (14) of the plurality of receiving coils (14) is arranged around a second receiving coil (14) of the plurality of receiving coils (14), wherein a portion (34) of the first receiving coil (14) with a first winding density covers a portion (36) of the second receiving coil (14) with a second, different winding density.

Description

The invention relates to a coil arrangement for a sensor device for determining a position of an object along a sensitive axis of the sensor device, such a sensor device and a method for operating the sensor device.

State of the art

It is known from practice that in inductive position sensors, an alternating magnetic field of an excitation coil acts on an electrically conductive and/or magnetizable object in such a way that electrical eddy currents and an alternating magnetic polarization are generated in the object, which generate a temporally changing magnetic field of the object. This magnetic field in turn acts on one or more receiving coils of the position sensor and induces a voltage in them. The position of the object relative to the sensor device can be determined from the induced voltage(s).

The inductive position sensor device with the product name BIP ED2-B133-03-S75 from Balluff GmbH, Neuhausen a.d.F, is designed as a serial sensor with a planar coil system manufactured using circuit board technology. The coil system has an excitation coil and several structured planar receiving coils. In order to determine the object position with respect to the sensor device, the vertical component of the object's magnetic field acting on the coil plane is used. The amplitude and phase of the induced voltage in each of the receiving coils depends on the object position. The measuring range extends to around 130 millimeters (mm).

Position sensor devices of the type BIP CD2-B014-01-EP02 and BIP LD2-T040-02-S4 from Balluff GmbH, Neuhausen a.d.F., for example, are made with coils wound in a row on a ferrite core. Each coil is successively contacted with an identical capacitor to form a corresponding LC oscillating circuit. Each oscillating circuit is set into oscillation by a common oscillator circuit, and a relative object position is determined from the recorded oscillation amplitudes. A measuring range is approximately 14 to 40 mm and depends on the sensor type.

The position sensor devices based on the technologies described above have a blind zone at both end regions along the receiving coils, which leads to a limited measuring range to sensor size ratio. Miniaturization of such types of sensor devices is therefore difficult to achieve.

Furthermore, it can be difficult to install such types of sensor devices flush into an environment because installing the sensor device into the environment requires providing a metal-free zone around the sensor device.

DE 198 33 276 A1 describes an eddy current-based probe system that is used to check the edges of rolled steel bars in particular. It detects defects in both the transverse and longitudinal directions of such bars. The probe provides a combination of several coils with which magnetic flux differences can be detected. The simultaneous sensitivity of the probe in the transverse and longitudinal directions of the test object is forced by the fact that it performs a rotary movement around its vertical axis. An electric asynchronous motor serves as the drive for the rotary movement. The electrical supply and reception signals of the probe system are coupled in and out without contact via a rotary transformer.

DE 198 55 685 A1 describes an inductive linear encoder having a position sensor and a scale which are movable with respect to each other. The sensor comprises a drive line to which an alternating current is supplied and a group of measuring leads at right angles to the drive line in the same plane. The scale is designed to comprise an elongated substrate having a surface on which a series arrangement of patterns in the form of conductive closed loops is periodically arranged at equal intervals. These conductive closed loops are arranged linearly on the substrate in the direction of relative movement. Each loop consists essentially of a receiving conductor segment and signal transmitting conductor segments formed integrally therewith. The receiving conductor segment is responsible for generating an induced current due to a first variable magnetic field generated by the drive coil. The transmitting conductor segments serve to generate second variable magnetic fields which have an opposite polarity and are perpendicular to the first magnetic field. The generation of such second magnetic fields leads to the flow of an induced current in the measuring line of the sensor, which in turn serves as the position measurement output current.

DE 23 26 391 A describes a test coil arrangement for scanning the surface of a metallic test part moving relative to it for defects, consisting of an excitation coil arrangement through which an alternating current flows, the a homogeneous alternating magnetic field is generated over at least part of the surface, which penetrates the surface perpendicularly and induces eddy currents in it, and a receiver coil arrangement arranged in the region of the alternating magnetic field near the surface, the coil axis of which is oriented perpendicular to the direction of the relative movement and perpendicular to the direction of the alternating magnetic field, the receiver coil arrangement consisting of at least two separate receiver coils with coil axes oriented perpendicular to the direction of the relative movement and perpendicular to the direction of the alternating magnetic field, the signals from two receiver coils being electrically superimposed on one another in opposite directions, and the component of the distance between these two receiver coils falling in the direction of the coil axes corresponds approximately to twice the distance between the locations of the two voltage maxima which would arise in one of the two receiver coils when it moved in the direction of the coil axis over an error running transversely to this direction.

DE 699 36 262 T2 describes an induction sensor head for detecting a ferrous or non-ferrous electrically conductive object embedded in a surrounding medium, comprising a field coil with a small axial length to diameter ratio and a pair of coaxially arranged sensing coils, their common axis being oriented orthogonal to the axis of the field coil, and wherein the sensing coils are arranged equidistant from the center of the field coil and lie within the same magnetic flux direction which emerges from the field coil when excited by an electric current, wherein a coaxially arranged twin pair of field coils is provided with a mutual spacing, and two twin pairs of coaxially arranged sensing coils with a small diameter compared to the diameter of the field coils and a higher inductance than that of the field coils with an orthogonally arranged axis are provided and arranged in a central plane parallel to and at approximately half the distance between the winding planes of the two field coils.

There is therefore a need for a new concept and a new mode of operation of a sensor device which has a small size and at the same time a large measuring range, for example a size of about 15 mm in length and about 10 mm in width with a measuring range of about 10 mm.

Disclosure of the invention

It is an object of the present invention to provide a small sensor device with a large measuring range, for example a size of about 15 mm in length and about 10 mm in width with a measuring range of about 10 mm.

The invention is defined by a coil arrangement according to claim 1, a sensor device according to claim 12 and a method for operating a sensor device according to claim 16. Advantageous embodiments are specified in the subclaims.

According to a first aspect, a coil arrangement is provided for a sensor device for determining a position of an object along a sensitive axis of the sensor device, wherein the coil arrangement has a flat excitation coil and at least one receiving coil, the windings of which are arranged around windings of the excitation coil, substantially perpendicular to the windings of the excitation coil and symmetrically with respect to a center line of the excitation coil that runs along the sensitive axis of the sensor device, wherein the coil arrangement has a plurality of receiving coils, wherein windings of the plurality of receiving coils are arranged around the windings of the excitation coil, substantially perpendicular to the windings of the excitation coil and symmetrically with respect to the center line of the excitation coil, wherein a first receiving coil of the plurality of receiving coils is arranged around a second receiving coil of the plurality of receiving coils, wherein a portion of the first receiving coil with a first winding density covers a portion of the second receiving coil with a second, different winding density.

The coil arrangement can therefore have a coil plane that can be defined by the flat excitation coil. The center line of the excitation coil can run in the coil plane and extend along the sensitive axis. The at least one receiving coil can surround the excitation coil, since the turns of the at least one receiving coil can be arranged around the turns of the excitation coil. The turns of the at least one receiving coil can be arranged around the turns of the excitation coil and can be mechanically supported on them. Alternatively, both coils can be arranged at a distance from one another (for example slightly), so that the excitation coil does not mechanically support the at least one receiving coil, but only one layer of a coil body of the at least one receiving coil. capture coil with respect to the excitation coil. Furthermore, the turns of the at least one receiving coil can run essentially perpendicular to the turns of the excitation coil and thus essentially perpendicular to the center line of the excitation coil. The at least one receiving coil can be arranged symmetrically around the center line of the excitation coil, so that the turns of the at least one receiving coil, viewed in plan view of the at least one receiving coil, can extend the same distance from the center line in the coil plane on both sides of the center line or can be at a maximum distance.

When the sensor device is in operation, the coil arrangement can be arranged in the vicinity of an electrically conductive and/or magnetizable object such that the center line of the excitation coil and thus the sensitive axis can be aligned parallel to the assumed line of movement of the object. The excitation coil can be excited with alternating current, with an oscillating current (for example a sinusoidal current), current pulses or a current with a different temporal profile. Due to this excitation of the excitation coil, the excitation coil can form a magnetic field, which in turn can induce eddy currents and/or magnetic polarization in the object. The object can therefore form a temporally changing magnetic field, which can also have a non-vanishing component in the direction of the center line of the excitation coil and thus the sensitive axis. Since the turns of the at least one receiving coil can be arranged substantially perpendicular to this direction, the voltage that can be induced in the receiving coil can occur in the receiving coil according to the longitudinal component of the object field lines.

Preferably, the excitation coil can be excited during operation with a harmonically oscillating sinusoidal current. The magnetic field that can be induced around the object can be similar to a magnetic dipole, which can oscillate harmonically at the same frequency and have a phase that can be determined primarily by the electrical and magnetic properties of the object. If the object moves into an overlap region of the receiving coil in the case of a receiving coil at a substantially constant distance from the coil plane or from an end face of a housing of the sensor device that accommodates the coil arrangement and faces the object, the sinusoidal amplitude of the induced voltage in this receiving coil can first increase and then, as the object moves toward a center point of the receiving coil, drop to zero. If the object moves further beyond a center point of the receiving coil, the amplitude of the voltage can increase again with the opposite sign or opposite phase. If the object moves further away from the receiving coil, the induced voltage can drop again. By evaluating the induced voltage between the two extreme values of its amplitude, the position of the object relative to the coil arrangement and thus to the sensor device that the coil arrangement can have can be determined. If a length of the partial area of the excitation coil that includes the receiving coil is relatively small in relation to a distance between the two extreme values, the previously described antisymmetrical course of the signed amplitude is called the "single characteristic curve" of the narrow receiving coil. If more than one receiving coil is present, the distance between the object and the front face of the sensor device along the line of movement of the object does not necessarily have to be constant; the distance can vary.

An axial or longitudinal position of the object along the center line of the excitation coil with respect to the sensor device can be determined by means of sensor electronics of the sensor device, for example by using techniques according to EP3 108 211 B1 or CN106104210B , in which a determination of the position from the correctly demodulated induced voltage(s) in the receiving coil(s) is carried out by means of multi-phase quadrature demodulation, and/or techniques according to US 2017/344878 A1 in which a joint evaluation of at least two signals is carried out by means of an artificial neural network.

Due to the simultaneous continuous demodulation of the voltage(s) induced in the receiving coil, the sensor device can have a short response time, which can also be suitable for determining a position of a rotating object (e.g. a spindle) with a rotation speed of, for example, more than 40,000 revolutions per minute (e.g. a rotating spindle).

Furthermore, the sensor device, which can in particular have a shield, can be installed flush in a metallic environment, for example a machine wall, with little or no metal-free zone, while the sensor device can be designed to be particularly small.

The coil arrangement with an excitation coil and one or more receiving coils can also be implemented in a small size and with a favorable measuring range to sensor size ratio. In particular, it may be possible to implement a sensor device with a size of approximately 15 mm in length and approximately 10 mm in width with a measuring range of approximately 10 mm.

In one embodiment, the excitation coil can have an elongated cross-section, in particular a substantially rectangular cross-section, and the center line can run along a longitudinal extension of the excitation coil. In other words, the windings of the excitation coil can run along their longitudinal extension. The line of movement along which the object can move can run along the longitudinal direction and parallel to the center line of the excitation coil.

In one embodiment, the excitation coil can be bent or curved along its longitudinal extension (in particular semicircular or with another monotonic curvature characteristic). The line of movement or the trajectory of the object can then also be bent in order to follow the curved center line of the excitation coil. In such an embodiment, for example, an angular offset of a rotatable object can be detected.

Consequently, the coil arrangement according to the two aforementioned embodiments and thus the sensor device can be used for a variety of different object arrangements.

In one embodiment, a winding density of the at least one receiving coil can be constant in at least a partial area of the at least one receiving coil or in the entire at least one receiving coil, as seen along the center line of the excitation coil. This allows the coil arrangement to be structurally very simple. The length of the partial area or the length of the receiving coil, as seen along the center line of the excitation coil, should in particular be smaller than the distance between the two extreme values of the individual characteristic curve of the receiving coil, so that an exact position determination can be made possible.

In one embodiment, the winding density of the at least one receiving coil can vary or change along the center line of the excitation coil. The variation of the winding density along the center line can, for example, follow a periodic location-dependent function (e.g. a binary function).

In one embodiment, the winding density of the at least one receiving coil, viewed along the center line of the excitation coil, can alternate between a first winding density, in particular a high winding density, and a second, different winding density, in particular a low winding density.

In one embodiment, a winding direction of the at least one receiving coil, seen along the center line of the excitation coil, can be the same in at least a partial area of the at least one receiving coil or in the entire at least one receiving coil. As a result, the coil arrangement can be designed to be very simple in terms of construction,

In one embodiment, the winding direction of the at least one receiving coil can vary or change along the center line of the excitation coil. In other words, the winding direction along the center line can be opposite in different sub-areas of the receiving coil or coil areas. The voltage induced in such a receiving coil can be understood as a sum of the spatially offset individual characteristics of the coil parts, each with a sign according to the winding direction. The induced voltage can therefore have a further characteristic that can be used to determine the position.

The receiving coil can, for example, have periodically alternating sub-areas with turns and sub-areas without turns. It is also possible that the winding direction in the successive wound sub-areas (or coil parts) can be opposite. The characteristic curve of such a receiving coil, i.e. the object position dependency or in other words the location dependency of the correctly signed demodulated voltage induced in the receiving coil, can then be a sum of the spatially offset individual characteristic curves of the coil parts, each with a sign according to the winding direction. For example, a receiving coil with periodically arranged essentially identical coil parts (up to the coil ends) can have an essentially periodic characteristic curve.

The sensor device has a plurality of receiving coils, wherein windings of the plurality of receiving coils are arranged around the windings of the excitation coil, substantially perpendicular to the windings of the excitation coil and symmetrically with respect to the center line of the excitation coil. Each of the plurality of receiving coils can be designed as described above and optionally arranged with respect to the excitation coil and/or the object. As a result, a wide area of the excitation coil along its center line can be covered with a receiving coil and each receiving coil can have a clear individual characteristic curve, so that overall a good position determination over a large area can be possible.

In one embodiment, receiving coils of the plurality of receiving coils can be arranged at a distance from one another along the center line of the excitation coil and can be arranged around different sub-areas of the windings of the excitation coil. If the plurality of receiving coils are arranged with sufficiently overlapping individual characteristics, an approximately equally good position determination for the object can be carried out at reduced construction costs by evaluating the induced voltage of two or more adjacent receiving coils. For example, if the multi-phase quadrature demodulation algorithm, as described in CN106104210B is applied, the individual characteristics can overlap sufficiently if the distance between centers of the adjacent receiving coils can definitely be less than the longitudinal distance between the extreme points of the individual characteristics.

A first receiving coil (or optionally a plurality of first receiving coils) of the plurality of receiving coils is arranged around a second receiving coil (or optionally a plurality of second receiving coils) of the plurality of receiving coils, and a section or optionally a plurality of sections of the first receiving coil(s) is covered with a first winding density, for example a high winding density or a low winding density, or optionally a section or optionally a plurality of sections of the second receiving coil(s) can be covered with a second winding density, for example a low winding density or a high winding density. A coil arrangement with an excitation coil and two similar receiving coils (with or without a change in the winding direction) that are offset by a quarter period along the center line of the excitation coil and have periodic sub-regions as described above can be used to carry out high-resolution incremental position determination.

One or more receiving coils of the plurality of receiving coils can be designed with the same or varying winding density as previously described for the at least one receiving coil. In this case, another or more other receiving coils of the plurality of receiving coils can be designed with the same or varying winding density as previously described for the at least one receiving coil.

Additionally or alternatively, one or more receiving coils of the plurality of receiving coils can have an identical or varying winding direction as previously described for the at least one receiving coil. In this case, another or several other receiving coils of the plurality of receiving coils can have a varying or identical winding direction as previously described for the at least one receiving coil.

It is also possible that all receiving coils of the plurality of receiving coils have the same winding density and/or the same winding direction.

The receiving coils of the plurality of receiving coils can also be arranged in opposite directions along the center line, so that the winding density of the two receiving coils is point-symmetrical with respect to the center of the excitation coil and/or the winding direction of the two receiving coils is opposite when viewed along the center line.

In one embodiment, the excitation coil may be formed as a (wound) wire coil or the excitation coil may be formed in and/or on one or more layers of a circuit board.

In one embodiment, the at least one receiving coil (or the or all receiving coils of the plurality of receiving coils) can be formed as a (wound) wire coil or the at least one receiving coil (or the or all receiving coils of the plurality of receiving coils) can be formed in and/or on several layers of a circuit board.

While a wire coil can enable a particularly high number of turns and thus a large amplitude of the induced voltage, coils manufactured using circuit board technology, which can have a limited maximum number of turns in terms of production technology, can be manufactured particularly cost-effectively. Due to the limited number of turns of the receiving coil manufactured using circuit board technology, this coil can also have a low signal-to-noise ratio.

Using multiple layers of a circuit board for the excitation coil can increase the technically producible number of turns of the excitation coil. One coil half can be in a first layer and another coil half in a directly adjacent second layer. layer. In the case of excitation coils with many turns, these can also be manufactured in three or more layers of the circuit board.

In one embodiment, the excitation coil can be manufactured using circuit board technology (i.e. in or on one or more layers of a circuit board), while the receiving coil or coils can be designed as a wire coil that can be arranged around the circuit board. This hybrid implementation of the coil arrangement can be particularly cost-effective and at the same time enable a large voltage amplitude for position determination.

According to a second aspect, a sensor device is provided for determining a position of an object along a sensitive axis of the sensor device, wherein the sensor device comprises a coil arrangement according to the first aspect.

The sensor device can further comprise sensor electronics with which the position determination can be carried out.

In one embodiment, a separate circuit of the sensor electronics can be available for each separate receiving coil. This can simplify position determination because the signals from the different receiving coils can be recorded.

In one embodiment, the sensor device can have a lateral, electrically conductive shielding element that surrounds the coil arrangement laterally continuously and symmetrically. The coil arrangement can be arranged completely behind the cover surface of the lateral shield. The shielding element can be arranged substantially perpendicular to the front surface of the sensor device. An opening in the shielding element, which can point towards the object during operation of the sensor device, can be arranged parallel to the front surface of the sensor device.

In one embodiment, the sensor device can have a planar, electrically conductive shielding element that is arranged on a side of the coil arrangement that faces away from the object. This shielding element can be designed as a rear shielding plate. The side shielding element and the planar shielding element can be made from one part. The planar shielding element can be arranged substantially parallel to the front surface of the sensor device.

Due to the lateral shielding element and/or the planar shielding element, the coil arrangement can be integrated into a magnetic environment, for example in a machine wall, without a disturbing background signal being able to be induced in the receiving coil by the metallic environment.

According to a third aspect, a method is provided for operating a sensor device for determining a position of an object along a sensitive axis of the sensor device, wherein the sensor device has a coil arrangement which has a flat excitation coil and at least one receiving coil, the windings of which are arranged around windings of the excitation coil, substantially perpendicular to the windings of the excitation coil and symmetrically with respect to a center line of the excitation coil which runs along the sensitive axis of the sensor device, wherein the object is moved at a distance from the sensor device along a line of movement which runs substantially perpendicular to the windings of the at least one receiving coil, wherein the coil arrangement has a plurality of receiving coils, wherein windings of the plurality of receiving coils are arranged around the windings of the excitation coil, substantially perpendicular to the windings of the excitation coil and symmetrically with respect to the center line of the excitation coil, wherein a first receiving coil of the plurality of receiving coils is arranged around a second receiving coil of the plurality of receiving coils, wherein a portion of the first receiving coil with a first winding density surrounds a portion of the second Receiving coil covered with a second, different winding density.

When the excitation coil is excited with an oscillating current, the phase of the oscillation of the magnetic field of the object can define a phase in which the voltage induced in the receiving coil(s) oscillates with the largest amplitude. In a position determination, this phase of the induced voltage can be defined as the "detection phase" and the detected voltage amplitude can be defined as a signed quantity that can have the same amplitude as the amplitude of the induced voltage in the detection phase and a sign according to the polarity of the induced voltage in the detection phase.

Short description of the drawings

• 1 zeigt schematisch eine Spulenanordnung gemäß einem ersten Ausführungsbeispiel für eine Sensorvorrichtung zum Ermitteln einer Position eines Objekts relativ zur Sensorvorrichtung in perspektivischer Ansicht;
• 2 zeigt schematisch eine Spulenanordnung gemäß einem zweiten Ausführungsbeispiel in perspektivischer Ansicht;
• 3 zeigt schematisch eine Spulenanordnung gemäß einem dritten Ausführungsbeispiel in perspektivischer Ansicht;
• 4A, 4B und 4C zeigen schematisch eine Anregungsspule und eine erste und zweite Empfangsspule für eine Spulenanordnung gemäß einem vierten Ausführungsbeispiel in Draufsicht auf verschiedene Leiterplattenschichten und im Querschnitt;
• 5 zeigt schematisch eine Spulenanordnung gemäß einem fünften Ausführungsbeispiel in Draufsicht;
• 6A, 6B, 6C zeigen schematisch eine Spulenanordnung gemäß einem sechsten Ausführungsbeispiel in Draufsicht;
• 7 zeigt schematisch eine alternative Realisierung der Empfangsspule der in 6B, 6C gezeigten Spulenanordnung in Draufsicht;
• 8 zeigt schematisch eine Spulenanordnung gemäß einem siebten Ausführungsbeispiel in Draufsicht;
• 9 zeigt schematisch die Sensorvorrichtung gemäß einem Ausführungsbeispiel mit einer zu 3 ähnlichen Spulenanordnung mit drei Empfangsspulen und einer Sensorelektronik;
• 10 zeigt schematisch ein Abschirmelement und die Spulenanordnung der Sensorvorrichtung in 9;
• 11A, 11B, 11C zeigen schematische Diagramme, die Quadratur-Phase-Amplituden von erfassten Spannungen in Empfangsspulen der Spulenanordnung in 9, die in einer Maschinenwand bzw. alleinstehend ist, in Abhängigkeit einer Objektposition zeigen; und
• 12 zeigt ein schematisches Diagramm, das die ermittelte longitudinale Position des Objekts in Abhängigkeit der reellen Objektposition zeigt.

Embodiments of the invention are shown in the drawings and explained in more detail in the following description. They show:

• 1 schematically shows a coil arrangement according to a first embodiment of a sensor device for determining a position of an object relative to the sensor device in a perspective view;
• 2 shows schematically a coil arrangement according to a second embodiment in a perspective view;
• 3 shows schematically a coil arrangement according to a third embodiment in a perspective view;
• 4A , 4B and 4C schematically show an excitation coil and a first and second receiving coil for a coil arrangement according to a fourth embodiment in plan view of various circuit board layers and in cross section;
• 5 shows schematically a coil arrangement according to a fifth embodiment in plan view;
• 6A , 6B , 6C show schematically a coil arrangement according to a sixth embodiment in plan view;
• 7 shows schematically an alternative realization of the receiving coil of the 6B , 6C shown coil arrangement in plan view;
• 8th shows schematically a coil arrangement according to a seventh embodiment in plan view;
• 9 shows schematically the sensor device according to an embodiment with a 3 similar coil arrangement with three receiving coils and sensor electronics;
• 10 shows schematically a shielding element and the coil arrangement of the sensor device in 9 ;
• 11A , 11B , 11C show schematic diagrams showing quadrature phase amplitudes of detected voltages in receiving coils of the coil arrangement in 9 which is in a machine wall or is freestanding, depending on an object position; and
• 12 shows a schematic diagram showing the determined longitudinal position of the object as a function of the real object position.

Embodiments of the invention

Identical or similar components or elements are provided with the same reference symbols.

One in 1 The coil arrangement shown in FIG. 1 and provided with the reference number 10 according to a first exemplary embodiment of a sensor device for determining a position of an object O relative to the sensor device has a flat excitation coil 12 and a receiving coil 14. The excitation coil 12 is designed as a wound wire coil with a substantially rectangular cross-section viewed in a coil plane along its longitudinal extent. Turns 16 of the excitation coil 12 run in the direction of the longitudinal extent of the excitation coil 12. A center line M of the excitation coil 12 in the coil plane corresponds to a longitudinal axis L of the excitation coil 12 and thus of the coil arrangement 10. The receiving coil 14 also has a substantially rectangular cross-section perpendicular to the coil plane. Turns 18 of the receiving coil 14 designed as a wound wire coil are arranged around the turns 16 of the excitation coil 12 so that the turns 16 run perpendicular to the elongated turns 18 viewed along the center line M. The turns 18 are further arranged symmetrically with respect to the center line M of the excitation coil 12, so that the turns 18 are centered around the center line M when viewed on the coil plane, and short turn end sections provided on both sides of the center line M, at which respective turns bend, are equidistant from the center line. The receiving coil 14 only covers a narrow longitudinal region of the excitation coil 12 when viewed along the center line M. Alternatively, the receiving coil 14 can be wide and cover most or all of the excitation coil when viewed along the center line M. A winding density of the receiving coil 14 is constant when viewed along the center line M. Alternatively, the winding density can vary along the center line M of the excitation coil 12. Furthermore, a winding direction of the turns 18 of the receiving coil 14 is constantly the same when viewed along the center line M. A sensor electronics of the sensor device can be connected to terminals 20a, 20b of the excitation coil 12 or 22a, 22b of the receiving coil 14, which are designed as solder contacts at an end region of the coils 12, 14.

The object O can be arranged at a distance from a plane of the coil arrangement 10 on one side of the coil arrangement at a fixed distance D. It is understood that if the sensor device has a housing in which the coil arrangement 10 is accommodated, the distance D can be dimensioned between an end face of the housing facing the object O and the object. The object O can be moved along a fixed line of movement that runs parallel to the center line M that corresponds to a sensitive axis S of the sensor device. The sensor device is set up to determine an axial position P of the object O along the sensitive axis S, for example starting from the center point MP of the excitation coil 12.

This in 2 The embodiment shown is similar to the embodiment in 1 However, instead of a single narrow receiving coil 14, two narrow receiving coils 14a, 14b are provided, which are arranged at a distance from one another. The receiving coils 14a, 14b are provided in different partial areas 24 of the windings 16 of the excitation coil 12. While partial areas 24a, 24c and 24e are not covered by the receiving coils 14a, 14b, the receiving coils 14a, 14b cover the partial areas 24b, 24d. A winding density of the two receiving coils 14a, 14b is constant in each case along the longitudinal extension.

In the 3 shown coil arrangement 10 according to the third embodiment is similar to the coil arrangement 10 in 1 However, the excitation coil 14 is not designed as a wire coil, but as conductor tracks (shown in dashed lines) in a circuit board 26. The circuit board 26 is designed in one layer, so that the windings 16 are structured in a surface 27 of the circuit board 26, which can be arranged adjacent to the object O. Alternatively or additionally, conductor tracks of the excitation coil 12 can be arranged on the surface 27. Connections 20a, 20b are not designed as solder contacts, but as contact surfaces in and/or on the circuit board 26. Instead of a receiving coil 14, three narrow receiving coils 14a, 14b, 14c spaced apart from one another are provided, which are wound around the circuit board 26. Turns 18a, 18b and 18c of the receiving coils 14a, 14b and 14c are realized in partial areas 24b, 24d, 24f of turns 16 of the excitation coil 12, while partial areas 24a, 24c, 24e, 24g of the turns 16 of the excitation coil 12 are uncovered. A winding density of the three receiving coils 14a-14c is constant in each case as seen along the center line M.

In the 4 The coil arrangement 10 shown is similar to the coil arrangement 10 in 3 The circuit board 26 is formed by means of four superimposed layers 28a-28d. The excitation coil 12 is formed in two parts. One half 12a of the excitation coil 12 (solid lines in 4A) is in the inner circuit board layer 28c and a second half 12b of the excitation coil 12 (dashed lines in 4A) in the inner circuit board layer 28b, which is directly adjacent to the circuit board layer 28c. The two coil halves 12a, 12b are connected to one another via a corresponding through-plating or via 29. In addition to the contact surfaces 20a, 20b, the excitation coil 12 has external connections 30a, 30b at its winding ends, which are designed as cables with associated solder contacts. Furthermore, the coil arrangement 10 has only two receiving coils 14a-14b instead of three receiving coils 14a-14c. Windings 18a, 18b of the first and second receiving coils 14a, 14b extend in the circuit board layer 28a (solid lines in 4B) or in the circuit board layer 28d (dashed lines in 4B) which surround the two circuit board layers 28b, 28c on both sides. The conductor tracks of the receiving coils 14a, 14b also penetrate the layers 28b, 28c by means of through-platings or vias 31a-31d. A winding density of the two receiving coils is constant as seen along the longitudinal axis L. External connections 32a-32d, which are designed as cables with solder contacts at the ends, are connected to the contact surfaces 22a-22d of the receiving coils 14a, 14b.

In the 5 The coil arrangement 10 shown according to the fifth embodiment is similar to the coil arrangement 10 in 2 However, the excitation coil 12 does not have a rectangular cross-section, but rather a semicircularly curved cross-section in the coil plane. Instead of two spaced-apart receiving coils 14a, 14b, three spaced-apart receiving coils 14a-14c with a constant winding density of the receiving coils 14a, 14b, 14c are provided, which can each be connected to a different circuit of a sensor electronics via their respective connections 22a-22f. The object O can be moved at a fixed distance D from the coil plane parallel to the center line M. The object O can also be moved at a variable distance D, since more than one receiving coil 14a-14c is provided.

One in 6 The coil arrangement 10 shown is similar to the coil arrangement 10 in 1 However, the coil arrangement has a first and second receiving coil 14a, 14b. The first receiving coil 14a is wound around the excitation coil 12, while the second receiving coil 14b is wound around the excitation coil 12 and the first receiving coil 14a. Turns 18a, 18b of the two receiving coils 14a, 14b extend along an entire longitudinal extent of an excitation coil 12. A winding density of the first receiving coil 14a alternates between a large winding density and a small winding density as seen along a center line M of the excitation coil 12, so that the winding density in spaced-apart partial regions 34a, 34c, 34e, 34g, 34i, 34k, 34m, 34o, 34q of the first receiving coil 14a is large and the winding density in spaced-apart partial regions 34b, 34d, 34f, 34h, 34j, 34l, 34n, 34p, 34r of the first receiving coil 14a is small. The second receiving coil 14b is wound around the first receiving coil 14a and is designed and arranged similarly to the first receiving coil 14a. However, a winding density of the second receiving coil 14b along the As seen along the center line M, the winding density in spaced-apart sub-regions 36a, 36c, 36e, 36g, 36i, 36k, 36m, 36o, 36q, 36s of the second receiving coil 18b is small and the winding density in spaced-apart sub-regions 36b, 36d, 36f, 36h, 36j, 36I, 36n, 36p, 36r of the second receiving coil 14b is large. The first and second receiving coils 14a, 14b are offset from one another along the center line M by a quarter period, which is determined by the winding density change. A sensor device with such a coil arrangement 10 is particularly advantageous if the period corresponds to approximately twice the distance between the two extreme values of the individual characteristic curve of a densely wound coil part, so that the spatial course of the signed amplitudes from the two receiving coils resembles a sine-cosine function pair, which is common in the technology of high-resolution incremental encoders.

The 7 The section of the coil arrangement 10 shown represents an alternative winding type for realizing the receiving coil 14a and/or 14b of the coil arrangement 10 in 6 The winding density of the receiving coil 14a and/or 14b seen along the center line M follows a binary function. In other words, sub-areas 34b, 34d with high winding density and sub-areas 34a, 34c, 34e with only one winding 18 alternate.

One in 8th shown coil arrangement 10 according to a seventh embodiment is similar to the coil arrangement 10 in 1 formed. The excitation coil 12 is shown schematically. However, the coil arrangement 10 has two receiving coils 14a, 14b, which are arranged in opposite directions as seen along the center line M. Both receiving coils 14a, 14b have a winding density that varies as seen along the center line M, so that an outer partial area 34a or 36a of the first receiving coil 14a or the second receiving coil 14b has a greater winding density than an inner partial area 34b or 36b of the first receiving coil 14a or the second receiving coil 14b. Both receiving coils 18a, 18b additionally have a winding direction that changes as seen along the center line M. In other words, the winding direction is reversed so that the partial region 34a, 36a of the receiving coils 14a, 14b has a winding direction opposite to the partial regions 34b, 36b. In addition, the winding direction of the partial region 34a is opposite to the winding direction of the partial region 36a, and the winding direction of the partial region 34b is opposite to the winding direction of the partial region 36b. The first receiving coil 14a and the second receiving coil 14b are additionally partially inserted into one another, so that a line piece 39a of the first receiving coil runs between the partial areas 34a, 34b through an interior of the partial area 36b of the second receiving coil 14b and a line piece 39b of the second receiving coil 14b runs between the partial areas 36a, 36b through an interior of the partial area 34b of the first receiving coil 14b.

It is understood that the winding direction of at least one or all of the receiving coils 14 of the 1 to 7 shown coil arrangements 10 can change.

One in 9 The sensor device 40 shown has a coil arrangement 10 according to 1 to 8 and the sensor electronics, now provided with the reference number 42, via the connections 20, 22 and 30, 32 are electrically coupled to the respective coils 12, 14. For illustration, the coil arrangement 10 is shown in 3 shown. However, the excitation coil 12 is designed as a wire coil. The excitation coil 12 is connected via its connections 20a, 20b to a circuit 43a of the sensor electronics 42. Each of the receiving coils 14a, 14b and 14c is connected via corresponding connections 22a, 22b, 22c, 22d, 22e, 22f to a separate circuit 43b, 43c, 43d of the sensor electronics 42 for determining the position of the object O. The circuits 43b-43d are designed as demodulators. Alternatively, the three receiving coils 14a-14c can be connected to just one circuit, which is designed as a demodulator and which can be operated in a time-multiplexed manner.

As in 10 As shown, the coil arrangement 10 is optionally arranged in a first electrically conductive shielding element 44 of the sensor device 40, which surrounds the coil arrangement 10 laterally and continuously in such a way that the coil arrangement 10 extends centrally in side walls 46a-46d of the shielding element 44. An open cover surface 48a of the first shielding element 44 faces the object. The sensor device 10 also has a second planar, electrically conductive shielding element 50, which is designed as a shielding plate and covers as completely as possible an opening in a further cover surface 48b of the first shielding element 44, which faces away from the object O. The first and second shielding elements 44, 50 are designed in one piece, but can alternatively also be provided as two components. The first and second shielding elements 44 can be made, for example, from copper or from low-magnetizable stainless steel. In an installation situation, the sensor device 40 is installed in a machine wall 52 of a machine, which is made of copper or steel, for example. The sensor device 40 can be installed as in 10 shown be installed directly in the machine wall 52. It is also possible that the sensor device 40 is accommodated in a sensor housing whose front side faces the object O and is aligned parallel to the cover surface 48a of the first shielding element 44.

When the sensor device 40 is in operation, the object O is arranged at a distance D from the coil plane of the excitation coil 12 on the side of the open cover surface 48a of the shielding element 44 and, if present, the end face of the sensor housing. An axial position P of the object O with respect to the sensor device 40 is determined by means of the sensor electronics 42, for example by using techniques according to EP3 108 211 B1 or CN106104210B , in which a determination of the position P is carried out from a correctly demodulated amplitude of the voltage in the receiving coils 14 by means of multi-phase quadrature demodulation, and/or US 2017/344878 A1 in which a joint evaluation of two signals is carried out using an artificial neural network.

In 11A , 11B is the signed amplitude of the quadrature phase component of the induced voltage in the receiving coils 14a, 14b, 14c of the coil arrangement 10 in 10 depending on the object position P. An x-axis 70 indicates the position P in millimeters and a y-axis 72 indicates the amplitude of the voltage in arbitrary units. Curves 74a1-74a3, 74b1-74b3, 74c1-74c3 in 11A denote the amplitude of the voltages in the three receiving coils 14a-14c for a sensor device 40 without shielding element 44 in a state not integrated in the machine wall 60 (solid line), in a steel machine wall (dashed line) and in a copper machine wall installed state (dotted line). In 11 B Corresponding curves 76a1-76a3, 76b1-76b3, 76c1-76c3 are shown for the sensor device 40 with shielding element in the non-installed state, in a steel and in a copper machine wall 60 installed state. It can be seen that the object-related signal component drops significantly due to the shielding element 44, while apart from a non-significant object signal reduction in the case of the copper machine wall 60, the signal size is no longer influenced by the installation situation. An offset also occurs for the first and third receiving coils 14a, 14c. However, this offset is deterministic and independent of the presence or type of the machine wall 60. After subtracting the offset, which is typical for the non-installed situation without an object for each coil, an object position-dependent and installation situation-independent signal group characterizing only the object position is obtained ( 11C )

12 shows the determined longitudinal position of the object as a function of the real object position P when applying the multiphase quadrature demodulation algorithm from EP3 108 211 B1 An x-axis 76 indicates the object position in millimeters and a y-axis 78 indicates the determined longitudinal position in arbitrary units. Curves 80a-80c show the determined longitudinal position for object distances of 0.25 mm, 0.5 mm and 1 mm measured perpendicularly from the front face of a sensor housing. It can be seen that the measuring range is linear and extends approximately 10 mm centered on a center point of the receiving coils 14. The coil arrangement 10 is arranged behind the front face and parallel to the front face.

Claims (16)

Coil arrangement (10) for a sensor device (40) for determining a position (P) of an object (O) along a sensitive axis (S) of the sensor device (40), the coil arrangement (10) comprising: - a flat excitation coil (12) and - a plurality of receiving coils (14), wherein turns (18) of the plurality of receiving coils (14) are arranged around turns (16) of the excitation coil (12), substantially perpendicular to the turns (16) of the excitation coil (12) and symmetrical with respect to a center line (M) of the excitation coil (12) which runs along the sensitive axis (S) of the sensor device (10), wherein a first receiving coil (14) of the plurality of receiving coils (14) is arranged around a second receiving coil (14) of the plurality of receiving coils (14), wherein a section (34) of the first receiving coil (14) with a first winding density has a section (36) of the second receiving coil (14) is covered with a second, different winding density. Coil arrangement (10) according to Claim 1 , wherein the excitation coil (12) has an elongated cross-section and the center line (M) runs along a longitudinal extension of the excitation coil (12). Coil arrangement (10) according to Claim 2 , wherein the excitation coil (12) is curved when viewed along the center line (M). Coil arrangement (10) according to one of the preceding claims, wherein a winding density of the at least one receiving coil (14) is constant along the center line (M) of the excitation coil (12) in at least a partial region (34) of the at least one receiving coil (14) or along the entire at least one receiving coil (14). Coil arrangement (10) according to one of the Claims 1 until 4 , wherein a winding density of the at least one receiving coil (14) varies along the center line (M) of the excitation coil (12). Coil arrangement (10) according to Claim 5 , wherein the winding density of the at least one receiving coil (14) alternates between a first winding density and a second, different winding density as viewed along the center line (M) of the excitation coil (12). Coil arrangement (10) according to one of the Claims 1 until 6 , wherein a winding direction of the at least one receiving coil (14) along the center line (M) of the excitation coil (12) is the same in at least a partial region (34) of the at least one receiving coil (14) or in the entire at least one receiving coil (14). Coil arrangement (10) according to one of the Claims 1 until 7 , wherein a winding direction of the at least one receiving coil (14) varies along the center line (M) of the excitation coil (12). Coil arrangement (10) according to one of the Claims 1 until 8th , wherein receiving coils (14) of the plurality of receiving coils (14) are arranged spaced apart from one another along the center line (M) of the excitation coil (12) and are arranged around different partial regions (24) of the windings (16) of the excitation coil (12). Coil arrangement (10) according to one of the preceding claims, wherein the excitation coil (12) is designed as a wire coil or wherein the excitation coil (12) is formed in and/or on a layer (28b, 28c) or several layers (28b 28c) of a printed circuit board (26). Coil arrangement (10) according to one of the preceding claims, wherein the at least one receiving coil (14) is designed as a wire coil or wherein the at least one receiving coil (14) is formed in and/or on several layers (28a-28d) of a printed circuit board (26). Sensor device (40) for determining a position (P) of an object (O) along a sensitive axis (S) of the sensor device (40), wherein the sensor device (40) comprises a coil arrangement (10) according to one of the Claims 1 until 11 having. Sensor device (40) according to Claim 12 , wherein the sensor device (40) has a separate circuit (43a, 43b) for each receiving coil (14). Sensor device (40) according to Claim 12 or 13 , wherein the sensor device (40) has a lateral, electrically conductive shielding element (44) which surrounds the coil arrangement (10) laterally continuously and symmetrically. Sensor device (40) according to one of the Claims 12 until 14 , wherein the sensor device (40) comprises a planar, electrically conductive shielding element (50) arranged on a side of the coil arrangement (10) facing away from the object (O). Method for operating a sensor device (40) for determining a position (P) of an object (O) along a sensitive axis (S) of the sensor device (40), wherein the sensor device (40) has a coil arrangement (10) which has a flat excitation coil (12) and a plurality of receiving coils (14), wherein turns (18) of the plurality of receiving coils (14) are arranged around turns (16) of the excitation coil (12), substantially perpendicular to the turns (16) of the excitation coil (12) and symmetrically with respect to a center line (M) of the excitation coil (12) which runs along the sensitive axis (S) of the sensor device (10), wherein the object (O) is moved at a distance from the sensor device along a line of movement along the sensitive axis (S), wherein a first receiving coil (14) of the plurality of receiving coils (14) is arranged around a second receiving coil (14) of the plurality of receiving coils (14) wherein a portion (34) of the first receiving coil (14) having a first winding density covers a portion (36) of the second receiving coil (14) having a second, different winding density.

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