Meshwork and device for detecting an object in a magnetic field, method for producing the meshwork, and inductive charging unit

A meshwork for detecting an object in a magnetic field is provided. The meshwork includes a plurality of sensor lines. The sensor lines are connected together parallel to one another in a first direction. The sensor lines define multiple meshes in a second direction running transversely to the first direction. The respective meshes of adjacent sensor lines are coupled together such that the sensor lines form the meshwork. A device for detecting an object in a magnetic field, a method for producing the meshwork, and an inductive charging unit are also provided.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a meshwork for object recognition in a magnetic field. Furthermore, the invention relates to a corresponding device for object recognition in a magnetic field, and to a method for producing the meshwork. Finally, the invention relates to a corresponding inductive charging unit.

Foreign bodies are undesirable in a magnetic field of an inductive charging unit; they can reduce the charging efficiency. Stringent requirements are made of devices for foreign body detection and result in complex and cost-intensive production of the charging units.

An objective on which the invention is based is to provide a meshwork and a corresponding device for object recognition in a magnetic field, a method for producing the meshwork and also a corresponding inductive charging unit which contribute to keeping down complexity and costs during the production of the charging unit.

This and other objectives are achieved by way of the features in accordance with embodiment of the invention.

In accordance with a first aspect, the invention relates to a meshwork for object recognition in a magnetic field. The meshwork includes a plurality of sensor lines arranged in a manner strung together parallel to one another in a first direction. The sensor lines span a plurality of meshes in a second direction extending transversely with respect to the first direction. The meshes of adjacent sensor lines are respectively coupled to one another, such that the sensor lines form the meshwork.

The meshwork advantageously enables reliable detection of foreign bodies in the magnetic field. No circuit board is required for this, however, and so a material outlay, weight, structural space volume and costs of a device for object recognition in a magnetic field can be kept low. In particular, the meshwork enables a high flexibility in the adaptation of such a device to the area of an energy transmission coil of an inductive charging unit with regard to standardized printed circuit board manufacture and size. A printed circuit board is advantageously avoided; rather, the meshwork replaces the printed circuit board with coils of conductor tracks. The meshwork can advantageously be produced simply and cost-effectively using established concepts and machines. In this case, in particular, a number of turns and mesh size can easily be adapted to the stated objective.

The sensor lines are arranged substantially parallel in the first direction. The second direction is in particular perpendicular to the first direction. The coupled meshes span a meshwork extending in the first and second directions. The meshes form in particular sensor coils of a device for object recognition in a magnetic field. The sensor line is preferably formed from an enameled wire. Individual sensor coils can be connected in series in this case. In particular, the sensor coils connected in series can be wound in the same sense. Each mesh can in particular comprise or consist of a plurality of wire loops, wherein a wire loop respectively forms a turn of the respective sensor coil.

In one advantageous configuration in accordance with the first aspect, the meshes of adjacent sensor lines respectively intermesh, such that the meshwork is formed in a concatenated fashion.

This advantageously enables a mechanically robust and flexible embodiment of the meshwork.

In a further advantageous configuration in accordance with the first aspect, the meshwork includes coupling elements. The meshes of adjacent sensor lines are respectively coupled to one another by way of a coupling element.

By way of example, holders or clips are considered as coupling elements.

In a further advantageous configuration in accordance with the first aspect, the sensor lines respectively have a first section extending in the second direction and a second section extending counter to the second direction. In this case, each of the meshes is formed from the first and second sections. The sensor line is furthermore formed in such a way that the second section crosses over the first section at a beginning of each mesh in relation to the second direction and/or at an end of each mesh in relation to the second direction.

This advantageously enables a mechanically robust and flexible embodiment of the meshwork. In addition, by way of example, the meshes of adjacent sensor lines can respectively intermesh, thus giving rise to a particularly mechanically robust and flexible meshwork in the manner of a wire meshing.

In a further advantageous configuration in accordance with the first aspect, the meshwork includes coupling elements. The sensor lines respectively have a first section extending in the second direction and a second section extending counter to the second direction. In this case, each mesh is formed from the first and second sections. The second section is furthermore coupled to the first section by way of a coupling element at a beginning of each mesh in relation to the second direction and/or at an end of each mesh in relation to the second direction.

This advantageously enables a flexible shaping of the mashes. In addition, by way of example, the meshes of adjacent sensor lines can respectively be coupled to one another by way of a coupling element, thus enabling a flexible shaping of a pattern of the meshwork.

In a further advantageous configuration in accordance with the first aspect, the meshes respectively enclose an area whose size varies. The size varies here in such a way that a size ratio of the areas with respect to one another is between 0.5 and 2.

Inhomogeneities of the magnetic field can thus advantageously be taken into account. By way of example, in a region with field strength of comparatively high magnitude, jeopardization by foreign bodies is particularly high, and so a more accurate detection is desired there. The size of the meshes arranged there can then be chosen to be smaller, for example, than in regions with field strength of lower magnitude.

In accordance with a second aspect, the invention relates to a device for object recognition in a magnetic field. The device includes a first meshwork in accordance with the first aspect and evaluation electronics for object recognition. The evaluation electronics are coupled to the sensor lines of the first meshwork in terms of signaling.

A device of this type is advantageously free of a circuit board of the evaluation electronics. By virtue of the sensor lines spanning the meshwork, it is possible simultaneously to realize a connection line to the evaluation electronics, such that additional plug connections can be avoided. By way of example, for this purpose, the individual sensor lines are led out over a length to a plug connector that can be led directly to a circuit board of the evaluation electronics.

Advantageously, the device thus has a comparatively small sensitive portion which can be arranged variably on account of the flexible connection by way of the sensor lines.

In one advantageous configuration in accordance with the second aspect, the device includes a further meshwork in accordance with the first aspect. In this case, the further meshwork is arranged at a distance from the first meshwork parallel to the first meshwork in a third direction extending transversely with respect to the first and second directions. The sensor lines of the further meshwork are likewise coupled to the evaluation electronics in terms of signaling.

Advantageously, it is thereby possible to increase a number of turns of the sensor coils formed by the meshes and thus to contribute to a detection sensitivity of the device. Alternatively or additionally, gaps in the first meshwork can be closed by the further meshwork. Alternatively or additionally, inhomogeneities of the magnetic field can furthermore be taken into account by means of the further meshwork.

In a further advantageous configuration in accordance with the second aspect, the meshes of the first meshwork respectively enclose a first area. Furthermore, the meshes of the further meshwork respectively enclose a further area. In this case, a size ratio of the first area to the further area is between 0.5 and 2.

This advantageously makes it possible to take account of inhomogeneities of the magnetic field. In particular, a detection sensitivity and/or degree of detail of the detection can be increased in this case.

In accordance with a third aspect, the invention relates to a method for producing a meshwork for object recognition in a magnetic field. In the method, a plurality of sensor lines are provided. Afterward, the sensor lines are arranged in a manner strung together parallel to one another in a first direction. In this case, the sensor lines are arranged in such a way that they respectively span a plurality of meshes in a second direction extending transversely with respect to the first direction. Here the meshes of adjacent sensor lines are respectively coupled to one another, such that the sensor lines form the meshwork.

Advantageously, the meshwork can be produced particularly simply and cost-effectively. In particular, methods of wire meshing production and/or additional modifications thereof can be used for producing the meshwork. Clipping or further methods like those from textile production can also be used in this case.

In one advantageous configuration in accordance with the third aspect, the method comprises the following steps:a) providing a first sensor line of the plurality of sensor lines, which forms a plurality of first meshes,b) providing a further sensor line of the plurality of sensor lines having a first and a second section,c) arranging the sensor lines in a manner strung together parallel to one another in the first direction in such a way that the sensor lines respectively span a plurality of meshes in the second direction extending transversely with respect to the first direction, and respectively coupling the meshes of adjacent sensor lines to one another, such that the sensor lines form the meshwork, by carrying out the following steps:c1) guiding the further sensor line in the second direction through the first meshes in such a way that the first section of the further sensor line crosses over the first sensor line at a beginning of each first mesh in relation to the second direction and at an end of each first mesh in relation to the second direction,c2) pulling the first section of the further sensor line by way of a first comb respectively between crossover points of the first and further sensor lines in the first direction, such that an area segment is respectively enclosed between the first section of the further sensor line and the first meshes,c3) guiding the second section of the further sensor line counter to the second direction through the area segments, in such a way that the second section of the further sensor line crosses over the first section of the further sensor line at an end of each first mesh in relation to the second direction and at a beginning of each first mesh in relation to the second direction, andc4) pulling the second section of the further sensor line by way of a second comb respectively between crossover points of the first and second sections of the further sensor line in the first direction, such that further meshes are respectively formed by the first and second sections of the further sensor line.

The method described enables particularly simple, cost-effective production of the meshwork.

In a further advantageous configuration in accordance with the third aspect, an end of the second section that is guided out of the meshwork counter to the second direction serves as further sensor line having a respective first and second section. Steps c1) to c4) are carried out once again with the led-out end of the second section as a further sensor line.

Advantageously, this makes it possible to increase the number of turns of the sensor coils formed by the meshes, with the result that it is possible to contribute to a detection sensitivity.

In a further advantageous configuration in accordance with the third aspect, the meshwork is produced by one of either embroidering, weaving or clipping of the sensor lines.

In accordance with a fourth aspect, the invention relates to an inductive charging unit for a vehicle. The charging unit includes a primary coil for inductive coupling to a secondary coil assigned to the vehicle, and a device for object recognition in accordance with the second aspect.

Advantageously, the device can be integrated into a housing of the charging unit in a simple manner on account of the flexible meshwork. By way of example, for this purpose the meshwork is laminated into a glass fiber reinforced plastic of the housing. The evaluation electronics can be arranged in a protected region of the housing in a dedicated manner on account of the flexible connection line. A contribution to a mechanical robustness of the charging unit is advantageously made in this way.

In accordance with a further aspect, the invention relates to an inductive charging unit for a vehicle. The charging unit includes a secondary coil for inductive coupling to a primary coil assigned to a ground unit, and a device for object recognition in accordance with the second aspect. The charging unit in accordance with the fifth aspect can in particular be configured analogously to the charging unit in accordance with the fourth aspect and have similar advantages.

In one advantageous configuration in accordance with the fourth or fifth aspect, the device is arranged in such a way that voltages induced in the meshes by a magnetic field of the primary coil during operation of the charging unit respectively compensate for one another.

Advantageously, the sensor coils formed by the meshes of the meshwork can then be wound in opposite senses or in the same sense. Advantageously, a meshwork in accordance with the first or third aspect can thus be used in the charging unit.

Particularly in the case where the device or the meshwork is arranged symmetrically relative to the respective coil, the voltages induced in the meshes can respectively compensate for one another.

In a further advantageous configuration in accordance with the fourth or fifth aspect, the charging unit includes a housing with holding elements. The meshwork is clamped in a fixing fashion in the housing by way of the holding elements.

Exemplary embodiments of the invention are explained in greater detail below with reference to the schematic drawings. Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

Elements of identical design or function are provided with the same reference signs throughout the figures.

FIG. 1shows a construction of an inductive charging system, including a first charging unit100, which for example is arranged on the ground and can also be referred to as a ground unit, and also a second charging unit200, which for example is assigned to a vehicle and is arranged on the underbody thereof.

The first charging unit100includes a housing101, a primary coil103arranged in the housing101, and also a ferrite105. Analogously thereto, the second charging unit200likewise includes a housing201, a secondary coil203and also a ferrite205.

For the purpose of inductively charging the vehicle, the two charging units100,200are arranged one above another at a predefined distance d. Energy is transferred by way of magnetic coupling of the primary and secondary coils103,203. On account of the large air gap between the charging units100,200, the coils103,203are only loosely coupled.

The second charging unit200can include a capacitor besides the secondary coil203for impedance matching purposes. Moreover, by way of example, a rectifier, vehicle-side control electronics, a WLAN interface and a high-voltage energy store are assigned to the vehicle in this context.

FIG. 2shows for example a construction of the first charging unit100in plan view. The second charging unit200has, in principle, a construction identical to the first charging unit100, but mirrored vertically.

FIG. 3shows the first charging unit100once again in a schematic detailed view with impedance matching and additional functional components. Besides the primary coil103and the ferrite105(not illustrated in more specific detail here), the first charging unit100includes for example a resonance capacitor111, which is coupled to the primary coil103. Furthermore, the first charging unit100includes for example a positioning unit113for guiding and/or positioning the vehicle having the second charging unit200above the first charging unit100, for example including six sensor coils, an FOD unit115, (“Foreign Object Detection”, FOD) for detecting foreign bodies in the magnetic field of the first charging unit100, for example including sixty sensor coils, a temperature sensor117and a control unit119for signal evaluation. In order to protect the two charging units100,200, in the case where the FOD unit115detects a metallic foreign body, the primary coil103can be switched off.

Furthermore, the first charging unit100has a supply input121, for example an RF multiple-stranded wire, via which the first charging unit100is supplied with electrical energy, for example having a frequency of 85 kHz. Furthermore, the first charging unit100has a protective conductor input123and communication inputs125,127and129. By way of example, the communication inputs125are configured for communication by way of a CAN protocol, while a voltage of 12 V is present at the input127and a reference potential is present at the input129. Optionally, part of the electronics or the entire electronics of the first charging unit100can for example also be arranged externally in a wall unit120(so-called “wallbox”) and be coupled to the first charging unit100via the inputs121-129. The wall unit120can have for example a power supply, by way of example with 230 V AC with inverter, power regulation, WLAN interface and internet connection.

FIG. 4shows the charging system once again in a perspective oblique view. The two charging units100,200extend parallel to one another in a first direction X and a second direction Y, at a distance from one another in a third direction Z. A space between the two charging units100,200for energy transfer is “flooded” with magnetic flux density during the operation of said charging units. If metallic or conductive foreign bodies10(FIG. 5) were present there, they would be heated. In order to prevent this in principle or at least to prevent excessive heating, the space is monitored by way of an FOD unit115. In the event of metallic objects10being present, the energy transfer or the magnetic field can be switched off. Optionally, a warning can be communicated to a user.

FIG. 5illustrates a few magnetic field lines B by way of example. In this case, the flux density of the magnetic field during the operation of the two charging units100,200has a high magnitude in the ferrites105,205. Near the turns of the coils103,203, the flux density already has a lower magnitude, and decreases further within the air gap between the two charging units100,200. The flux density has a very low magnitude outside the air gap. The electrically conductive and/or ferromagnetic object10illustrated inFIG. 5is situated in the region of high field strength.

The object10is for example a flat disk such as a coin (FIG. 6). In the object10, according to the law of induction

∮∂A⁡(t)⁢E→·d⁢s→=-∫A⁡(t)⁢∂B→∂t·d⁢A→
a voltage is induced in the circumference of the object10, said voltage corresponding to a change in the magnetic flux through the area of said object. Accordingly, the effect thus becomes smaller if the disk is not perpendicular to the magnetic field lines B (less flux through the disk) and almost completely vanishes if the disk is oriented parallel to the magnetic field lines B.

As illustrated inFIG. 7, this leads to a current flow I at the edge of the object10as far as a penetration depth T on account of the skin effect. A field-free region11remains in the interior of the object10. The current flow I in turn generates an oppositely directed magnetic field that is superposed with the magnetic field lines B, thus giving rise to a field-free region around the object10(seeFIG. 8). Losses arise as a result of ohmic losses at the resistance of the current flow I constricted owing to the skin effect at the circumference of the object10.

In order to detect the object10, it is possible to use sensor coil arrays as FOD unit115, for example, which function in a manner similar to a conventional metal detector, as illustrated with reference toFIGS. 9A-9D. In particular, various measurement methods are contemplated here:

FIG. 9Ashows (from left to right) a sensor coil1151, an excitation coil and an equivalent circuit diagram in the case of pulse measurements; a decay time constant is considered here as a typical characteristic variable.

FIG. 9Bshows (from left to right) two coupled sensor coils1151and an equivalent circuit diagram in the case of measurement by way of AC excitation; induced voltage and phase are considered here as a typical characteristic variable.

FIG. 9Cshows (from left to right) a sensor coil1151and an equivalent circuit diagram in the case of resonance measurement under AC excitation; a resonant frequency is considered here as a typical characteristic variable.

FIG. 9D, finally, shows a plurality of sensor coils1151and a primary coil103(alternatively, a secondary coil203can also be used) in the case of analysis of the magnetic field of the energy transfer; induced voltage and phase are considered here as a typical characteristic variable.

As already illustrated inFIG. 5, the FOD unit115can be arranged in a plane directly above the primary coil103within the housing101. Alternatively or additionally, analogously thereto, an FOD unit215can also be arranged in a plane directly below the secondary coil203within the housing201. A construction of these FOD units115,215can be implemented by way of a printed circuit board, for example, which covers an entire area above and respectively below the coil103,203. Sensor coils1151for detecting the object10by way of the measurement methods described with reference toFIGS. 9A-9Dare realized by means of correspondingly shaped conductor tracks. The region with magnetic flux density of high magnitude is monitored using the large area above and respectively below the coil103,203that is used for energy transfer. At least a two-layered embodiment is demanded for the printed circuit board in order to be able to produce crossovers. Components need not be equipped apart from the contacting.

In order to be able to recognize all relevant foreign bodies10in all possible positions, very many sensor coils1151, for example, can be realized on the printed circuit board. It should be taken into consideration here that although small sensor coils1151are sensitive to small objects10, they are insensitive to objects10that are far away from the sensor coils1151. Furthermore, large sensor coils1151can detect small objects10poorly. Uniform sensor coils1151do not take account of an inhomogeneity of the magnetic field during the operation of the charging units100,200. A large number of coil sizes and shapes of the sensor coils1151in turn requires a high application outlay on account of the different sensitivities. Finally, the objects10in the air gap, depending on position and size, influence a multiplicity of sensor coils1151simultaneously.

FIG. 10shows an exemplary FOD unit115in plan view with thirty-six sensor coils1151, which, in accordance with the number of sensor coils1151, yields thirty-six different measurement values for the characteristic variables indicated inFIGS. 9A-9D.

In order to prevent the number of evaluation circuits and processes from increasing unduly, the sensor coils1151can therefore be connected in series. InFIG. 11, the thirty-six sensor coils1151have been combined to form ten coil series1153. As illustrated schematically on the basis of the arrows, here sensor coils1151respectively wound alternately in opposite senses are combined to form a coil series1153.

FIG. 12shows a coil series1153having sensor coils1151wound in opposite senses. The coil series1153is realized by a sensor line1150, for example, which is coupled by its beginning and end to the control unit119or evaluation electronics. The sensor line1150forms fine meshes21by way of example, wherein that part of the sensor line1150which is illustrated in a dashed manner respectively symbolizes a part of the sensor line1150that extends in the background. Each mesh21has only one turn in the present case. In a departure from this, the meshes21can also have a plurality of turns, that is to say as a generalization n turns (cf.FIG. 12). In this case, each of the coil series1153can be arranged above the respective coil103,203such that the voltages induced by the energy transfer mutually almost completely compensate for one another.

Owing to the size of the region to be monitored, very large printed circuit boards are necessary, or it is even necessary to use a plurality thereof. This leads to high costs, since firstly the area of the printed circuit board(s) causes high costs. In the case of a plurality of printed circuit boards, an additional connection technique is necessary. In addition, on account of the size and standard production dimensions, a high degree of waste has to be taken into account. Furthermore, the printed circuit board has to be secured in the corresponding housing101,201by way of corresponding devices. In particular, in the case of the first charging unit100it is necessary to ensure strength to withstand being driven over and, in the case of the second charging unit200, it is necessary to ensure vehicle underbody requirements such as unproblematic placement on bollards or the like. This leads to an additional mechanical complexity of the charging units100,200.

It is proposed to produce, instead of a circuit board, a meshwork20composed of enameled copper wire (FIGS. 13 to 27) and to integrate said meshwork20into the housing101,201of the respective coil103,203(FIGS. 28 and 29).

This makes use of the following insight, in particular: if a coil series1153covers both directions of the magnetic field during the operation of the charging units100,200, then the induced voltages almost completely compensate for one another even in the case of windings in the same sense. The coil series1153should be arranged for this purpose in such a way that the sum of the area elements of the sensor coils1151of the respective coil series1153multiplied by the flux density perpendicular thereto is approximately zero. This is the case for example for arrangement as illustrated inFIG. 5of the FOD unit115fromFIG. 13with coupling of the sensor coils1151to form coil series1153according toFIG. 14.

FIG. 15shows a coil series1153having sensor coils1151wound in the same sense, analogously toFIG. 12. The coil series1153is once again realized by a sensor line1150, for example, which is coupled by its beginning and end to the control unit119or evaluation electronics. The sensor line1150forms five meshes21by way of example. Each mesh21has only one turn in the present case. In a departure from this, the meshes21can also have a plurality of turns, that is to say as a generalization n turns (cf.FIG. 15). In this case, each of the coil series1153can be arranged above the respective coil103,203such that the voltages induced by the energy transfer mutually almost completely compensate for one another.

FIG. 16shows a first exemplary embodiment of a meshwork20, by way of example consisting of fifty sensor coils1151, combined to form ten coil series1153each having five sensor coils1151. The coil series1153are arranged in a manner strung together parallel to one another in the first direction X and extend in each case in the second direction Y.

In this case, analogously toFIG. 15, each coil series1153has a sensor line1150having sensor coils1151wound in the same sense, said sensor line being formed from enameled copper wire, for example. In contrast toFIG. 15, however, in a first embodiment variant (FIG. 17), the sensor line1150cross itself at a crossover point22in each case at the beginning and respectively end of each mesh21in relation to the second direction Y, thus giving rise to a braiding analogous to a wire mesh fence.

Additionally or alternatively, in a second embodiment variant (FIG. 18), the coil series1153can have a holder or clip26, which holds the meshes21together, in each case at the beginning and respectively end of each mesh21in relation to the second direction Y.

As illustrated with reference toFIG. 19, such a construction of the meshwork20can be supplemented by a spacer27. As a result, further area embodiments can be produced, for example, such as a hexagonal meshwork20in a second exemplary embodiment (FIG. 20).

In a third exemplary embodiment (FIG. 21), the meshwork20can alternatively also be produced by means of knitting or, in a fourth exemplary embodiment (FIG. 22), also in a manner resembling weaving. In the case of production by way of knitting, the shape of the meshes21can for example additionally be maintained by holders or clips26(cf.FIGS. 18 to 20). In the case of production resembling weaving, a warp thread28and weft thread29are used. Unlike in the case of weaving, however, a not very “wide-meshed” product is designed. The weft threads29can be used together with a comb24,25(cf.FIGS. 25A-25E) to the effect that the weft thread29clamps corresponding meshes21.

FIG. 23shows two coil series1153arranged parallel in accordance with the first embodiment variant of the first exemplary embodiment, wherein analogously toFIG. 12once again that part of the sensor line1150which is illustrated in a dashed manner symbolizes in each case a part of the sensor line1150that extends in the background. Analogously to the crossing of the respective sensor line1150between the meshes21of the respective coil series1153, here the sensor lines1150are also concatenated together at a crossover point22at the beginning and respectively end of each mesh21in relation to the first direction X.

In addition, the meshwork20can have fixing points23at the edge, at which fixing points said meshwork can be clamped.

A free space between the two parallel coil series1153can be covered for example by stacking an additional coil series1153of a further meshwork in the third direction Z, said stacking being offset in the first and second directions X, Y.

Alternatively, as illustrated with reference toFIG. 24, in a fifth exemplary embodiment, the meshwork20fromFIG. 23can be completed to form a more complex meshwork20by a further coil series1153being braided into the existing crossover points22.

A method for producing the meshwork20fromFIG. 23is explained below with reference toFIGS. 25A to 25E.

In a first step (FIG. 25A), a sensor line1150is led through existing meshwork20in the second direction Y, existing meshes21being forced apart.

In a subsequent second step (FIG. 25B), a first comb24pulls a led-through section of the sensor line1150in the first direction X.

In a subsequent third step (FIG. 25C), a remaining section of the sensor line1150is threaded back through the meshes21newly clamped as a result of the second step, counter to the second direction Y. As in the first step, these meshes21for this purpose are forced apart perpendicular to the plane of the illustration.

In a subsequent fourth step (FIG. 25D), a second comb25then pulls down in the first direction X that section of the sensor line1150that was threaded in in the third step, with the result that once again new meshes21are clamped.

A subsequent fifth step (FIG. 25E) substantially corresponds to the first step. The first to fourth steps are repeated in order to realize a plurality of turns.

FIG. 26shows a sixth exemplary embodiment of a meshwork20in plan view and sectional view above the primary coil103. In addition to the previous exemplary embodiments, the meshwork20has meshes21of different sizes. In particular, an area in a region12of increased flux density above the windings of the primary coil103is adapted to the flux density.

Alternatively or additionally, as already mentioned in association withFIGS. 23, 24, it is possible moreover for a plurality of meshworks to be arranged one above another. In the seventh exemplary embodiment illustrated inFIG. 27, two meshworks20,30having different mesh sizes are illustrated in a manner placed one above the other and displaced slightly relative to one another. The meshes21of the first meshwork20are approximately double the size of the meshes31of the second meshwork30.

FIG. 28shows one exemplary embodiment of a first inductive charging unit100. The first charging unit100includes a housing101having for example two die-cast shaped parts.

The cover surface of the housing101, which faces a second inductive charging unit upon coupling thereto, is formed in particular from a non-conductive material such as plastic or fiber composite materials. This enables a simple integration of the meshwork20into the housing101. In particular, the meshwork20can be integrated into the housing101by means of lamination into plastic.

By way of example, the meshwork20includes holding elements1155at its corners, said holding elements clamping the meshwork20in the correct position. These can be concomitantly cast in, for example.

As illustrated inFIG. 29, sensor lines1150as a flexible connection1157can be led from the meshwork20in a corresponding length e.g. to a plug connector1191arranged on a circuit board119of the control unit119.

The meshwork20is advantageously free of a carrier circuit board. Furthermore, the sensor coils1151are not merely embroidered onto a support web, rather a support web is produced from coil structures. The latter can be cast directly into plastic. The meshwork20is thus itself the support web.

Individual sensor coils1151can be connected in series in this case. The meshwork20can advantageously be integrated into existing housing component parts in a simple manner. The sensor lines1150clamping the meshwork20can simultaneously serve to form a connection line1157through to the control unit119of the evaluation electronics. Methods of wire meshing production and/or additional notifications thereof can be used for producing the meshwork20. Further methods, such as those from textile production, can also be used in this case. By varying the mesh areas within a meshwork20, it is possible to take account of inhomogeneous requirements within the overall area of an FOD unit115. Furthermore, a simple adaptation of the geometry of the meshes21can be effected by using additional holders and clips26. With the use of a plurality of meshworks20one above another, it is advantageously possible to realize very dense nets having different mesh sizes.

LIST OF REFERENCE SIGNS