Coil arrangement with a plurality of coil pairs arranged thereon in one plane and device with such a coil arrangement

Abstract

The invention relates to a coil arrangement with a plurality of coil pairs (1; 10; 20a, 20b) arranged in a plane, the individual coils of which are each designed and connected to one another in such a way that the currents (3, 4; 12, 13) induced in them by a magnetic field are oppositely directed and equal in magnitude, wherein the coil pairs (1; 10; 20a, 20b) are designed with point symmetry and are oriented to one another in such a way that a magnetically effective object (22) located at the symmetry point (14) of a coil pair (1; 10; 20a, 20b) cancels the equality of the currents (3, 4; 12, 13) of at least one adjacent coil pair (1; 10; 20a, 20b).

Description

The invention relates to a coil arrangement having a plurality of coil pairs arranged in a plane, the individual coils of which are each formed and connected to one another in such a way that the currents induced therein by a magnetic field are directed in opposite directions and of the same magnitude. The invention also relates to a device for inductively transmitting energy, having a primary coil and a secondary coil, between which a coil arrangement of this type is arranged.Such a coil arrangement and such a device are known from US 2013 / 0 169 062 A1. In this document, on the one hand, a coil pair of two semicircular individual coils produced from a wire is described, in which the individual coils are rotated relative to one another, so that the currents caused by a magnetic field passing through them are opposite and of the same magnitude, i.e. cancel one another out. Thus, a homogeneous, interference-free magnetic field generated by a primary coil of a device for inductive energy transmission, which penetrates the individual coils, does not generate any voltage at their wire ends.US 2013 / 0 169 062 A1, on the other hand, discloses a circular coil arrangement with coil pairs, which is designed with individual coils formed from circle segments, which are likewise produced with only one wire.US 2014 / 0 111 019 A1 discloses wireless energy transfer apparatus, methods and systems comprising an energy source having at least one resonator, an energy receiver having at least one resonator, a first detector having one or more loops of conductive material configured to generate an electrical signal based on a magnetic field between the energy source and the energy receiver, a second detector having conductive material, and control electronics coupled to the first and second detectors, wherein the control electronics are configured during operation to measure the electrical signal of the first detector and compare the measured electrical signal of the first detector with electrical base information for the first detector to determine information about whether debris is between the energy source and the energy receiver.DE 10 2012 205 283 A1 discloses an apparatus for inductive power transmission, which comprises a primary unit having a primary coil and a secondary unit having a secondary coil, and in which the primary coil induces a magnetic transmission field in a transmission region between the primary unit and the secondary unit, and which has an even number of detector coil elements which are wound in opposite pairs and form a detector pair.The problem with these arrangements of the coil pairs is that there are points of symmetry and lines of symmetry, so that magnetically active objects which disturb the magnetic field and are intended to be detected in principle by the coil arrangement are not detected if they lie on or above these points of symmetry and lines of symmetry, since the disturbance of the magnetic field in the individual coils of the coil pairs likewise has a symmetrical effect and leads to no induced voltage or no current caused thereby.It is therefore the object of the invention to specify a coil arrangement and a device with such a coil arrangement, in which it is possible to detect all magnetically active objects despite partial balances. The object is achieved by a coil arrangement according to claim 1 and a device with such a coil arrangement according to claim 7. Advantageous refinements are specified in the dependent claims.Accordingly, in a coil arrangement having a plurality of coil pairs arranged in a plane, the individual coils of which are each formed and connected to one another in such a way that the currents induced therein by a magnetic field are directed in opposite directions and of the same size, the coil pairs are formed point-symmetrically and are arranged oriented with respect to one another in such a way that a magnetically active object which is located at the point of symmetry of a coil pair cancels the equality of the currents of at least one adjacent coil pair.Even if a coil pair does not experience any change in the current flowing through its conductor, since the change in the magnetic field due to the magnetically active object has the same effect in terms of amount in both individual coils of the coil pair but in the opposite direction, the presence of this object is nevertheless detected in a coil arrangement according to the invention, because an adjacent coil pair is oriented in such a way that different magnetic field changes and thus different currents occur in its individual coils due to the object, which no longer cancel one another out. Whenever an object in such a coil arrangement comes to lie on a point of symmetry of a coil pair, there will always be at least one further adjacent coil pair by means of which the object is detected.The lines of the individual coils of a coil pair are routed in the form of an eight.This means only the basic relationship of the two individual coils of a coil pair to one another and not their shape. Although this can be approximately circular, it preferably has the shape of a square or a diamond or any other shape in which coil pairs can be arranged next to one another in such a way that there are not too many gaps in which a magnetic field is not detected.The axes passing through the loops and the loop connection point of an eight of two adjacent coil pairs whose loop connection points are spaced apart from each other by one of the two eight loops are perpendicular to each other.Thus, the most closely adjacent coil pairs, which are almost touching without overlapping, are always aligned with each other such that their axes are at right angles to each other. The axis concerned is the one which passes through the two eight loops and the loop connection point, that is to say usually the point of symmetry. This axis is usually also an axis of symmetry of a coil pair.This orientation with respect to one another ensures that an object which lies on the point of symmetry or the axis of symmetry of the one coil pair and is therefore not detected by this coil pair is in any case recognized by this closest adjacent coil pair.In the case of a spatially homogeneous magnetic field penetrating the coils of the coil arrangement, it is advantageous if, in one embodiment of the coil arrangement according to the invention, the individual coils all have the same shape and size. This ensures that, in the event that no object is in the region of the coil arrangement, no induced voltage arises at the terminals of the coil pairs.In an advantageous embodiment, the coil arrangement is formed on a coil carrier. This can be, for example, a foil or a printed circuit board.In a development, the coil pair can be printed on the coil carrier.In a device according to the invention for inductively transmitting energy with a primary coil and a secondary coil, a coil arrangement according to the invention is arranged between the primary coil and the secondary coil.A coil arrangement according to the invention can thus be used in an advantageous manner in such a device for inductively transmitting energy for detecting magnetically active objects, for example metals such as coins, since these should lead to a disconnection of the energy transmission due to heating due to eddy currents and thus to an increased risk of fire.The coil arrangement can be arranged on the primary coil in a simple manner.The invention is described in more detail below with reference to exemplary embodiments with the aid of figures. Figure shows FIG. 1 shows a first embodiment of a coil pair according to the prior art, FIG. 2 shows a second advantageous embodiment of a coil pair, FIG. 3 shows a first coil arrangement according to the invention with coil pairs according to FIG. 2 FIG. 4 shows a second coil arrangement according to the invention with coil pairs according to FIG. 2, and FIG. 5 shows a device for inductively transmitting energy, having a primary coil and a secondary coil, between which a coil arrangement according to the invention is arranged.FIG. 1 shows a coil pair 1 which is manufactured from a conductor 2. The conductor 2 can be a wire or a conductor track printed or otherwise applied to a foil or a printed circuit board.A first individual coil is produced by first guiding the conductor 2 straight in a first section a. It is then guided counterclockwise in a second section b in a semicircle, in order subsequently to be guided almost parallel to section a, but crossing it again approximately straight in a third section c. It is then guided in a fourth section d in a semicircle in the clockwise direction. Thus, an approximately elliptical or circular double coil is produced which has two loops a, b and c, d which are wound as an eight and lie next to one another in one plane.If a homogeneous magnetic field is directed into the coil plane of FIG. 1, a voltage is induced in each of the individual coils, which leads to a current flow corresponding to the arrows 3, 4, which therefore flow in the same conductor 2 in opposite directions and cancel one another out due to the symmetry of the individual coils.This has the advantage that in the case of a homogeneous magnetic field without disturbance no voltage is applied to the wire ends and thus no heat-generating currents can flow.Another embodiment of a coil pair having the described characteristics is shown in Fig. 2. The coil pair 10 there is formed with a conductor 11 which is initially guided straight in a first lead section a here in order to then bend downward to the right at an angle of approximately 45° and then to be guided counterclockwise in a square b back to the first bending point and to form a first individual coil. At the break point, the conductor 11 is then guided straight further in order to then be guided clockwise back again in a further square c to the break point and from this to be guided parallel to the first lead section a in a second lead section d.Here too, a planar coil pair 10 is formed, in which currents corresponding to the arrows 12 and 13 form which cancel one another out under a homogeneous magnetic field which penetrates the individual coils. In the embodiment of FIG. 2, many coil pairs 10 can be formed side by side without leaving larger areas not covered by a coil.The coil pair 10 of Figure 2 has a point of symmetry 14 which coincides with the break point of the conductor 11 and there is an axis 15 which passes through the eight loops and the point of symmetry 14 and forms an axis of symmetry.If a magnetically active object comes to lie on the point of symmetry 14 or along the axis 15, the magnetic field in both individual coils is influenced in the same way, for example amplified, as a result of which, however, the currents in both individual coils of the coil pair 10 change in the same way and therefore no voltage or current change can be detected at the coil connections.FIGS. 1 and 2 show symmetrical coil pairs 1, 10, since a homogeneous magnetic field is assumed. However, the coil pairs can be adapted to a non-uniform magnetic field by changing the size of one of the individual coils by making it correspondingly larger in order to achieve the same total flux if the magnetic field in the one individual coil is weaker.Instead of a square shape, as shown in FIG. 2 for a single coil, a diamond can also be selected, whereby good surface coverage can likewise be achieved in a coil arrangement with a plurality of coil pairs.FIG. 3 now shows a coil arrangement according to the invention using the example of coil pairs 20 a, 20 bcorresponding to the shape of FIG. 2, i.e. an eight with square loops. In this case, a plurality of such coil pairs 20 a, 20 bare formed in an interleaved manner, preferably on a coil carrier 21. The coil carrier 21 can be a foil or a printed circuit board, for example. The coil pairs can be fastened as wire coils thereon, e.g. glued or printed, e.g. as a paste.In the coil arrangement of FIG. 3, a first number of coil pairs 20a are arranged on the coil carrier 21 in such a way that their axes are inclined at 45° counterclockwise from the perpendicular and parallel rows are formed with these coil pairs 20a, wherein coil pairs 20a lying in one row adjoin one another with the coil vertices 23, 24 lying on one axis and the coil pairs 20a of the row adjacent thereto are offset by a single coil and adjoin one another with their coil vertices 25, 26 furthest from their axis.This results in a field of individual coils of the first number of coil pairs 20a, between the individual coils of which approximately the surface of an individual coil remains free.These clearances are occupied by individual coils of the coil pairs of the second number of coil pairs 20 b, wherein the axes of these coil pairs 20 bof the second number of coil pairs are inclined by 45° clockwise from the perpendicular, i.e. by 90° with respect to the axes of the coil pairs 20 aof the first number of coil pairs. The axes of the coil pairs 20a are thus perpendicular to the axes of the coil pairs 20b.In addition, a point of symmetry 14 of a coil pair 20 aof the first number of coil pairs is spaced apart from a point of symmetry 14 of a coil pair 20 bof the second number of coil pairs by a single coil and vice versa. Thus, the points of symmetry of the coil pairs 20a of the first number of coil pairs never coincide with those of the coil pairs 20b of the second number of coil pairs.Thus, in a manner according to the invention, an object 22 which lies on a point of symmetry 14 of a coil pair of the one number of coil pairs and therefore cannot be detected by the latter is in any case detected by the directly adjacent coil pair of the other number of coil pairs, since its individual coils have a different distance from the object 22 by this arrangement, whereby different changes in the magnetic field penetrating its individual coils result and therefore a voltage or a current can be detected.FIG. 4 shows a similar arrangement of the coil pairs as in FIG. 3, wherein here all coil pairs are rotated by 45° with respect to the arrangement according to FIG. 3. The coil pairs are not designated in detail, since they correspond to those of FIG. 3.FIG. 5 shows a device for inductively transferring energy with a primary coil 31 on a floor panel 30 and a secondary coil 34 on a vehicle panel 33, in which a coil arrangement according to the invention with coil pairs 20 a, 20 bon a coil carrier 21 is arranged between the primary and the secondary coil 31 m34 according to FIG. 3 or FIG. 4, for example. The coil pairs 20 a, 20 bare penetrated by a magnetic field 35 which is generated, for example, by the primary coil 31. It would also be possible to generate the magnetic field 35 by means of the secondary coil 34 in order to detect magnetically active, in particular metallic, foreign objects.In this device, an object can also be detected when positioned on a point of symmetry or a line of symmetry, although coil pairs are used in which no voltage is detectable at their connections without interference from a foreign object in the case of a homogeneous magnetic field generated by the primary coil.

Claims

Coil arrangement having a plurality of coil pairs (1; 10; 20a, 20b) arranged in a plane, which are formed with in each case only two individual coils, wherein the lines (2) of the individual coils of a coil pair (1; 10; 20a, 20b) are guided in the form of an eight, and wherein the individual coils are in each case formed and connected to one another in such a way that the currents (3, 4; 12, 13) induced therein by a magnetic field are directed in opposite directions and of the same size, wherein the coil pairs (1; 10; 20a, 20b) are formed point-symmetrically and arranged in such a way that a magnetically active object (22) which is located at the point of symmetry (14) of a coil pair (1; 10; 20a, 20b) is arranged in such a way that the currents (3, 4; 12, 13) of at least one adjacent coil pair (1; 10; 20a, 20b), wherein the axes (15) passing through the loops and the loop connection point (14) of the eight loops of two adjacent coil pairs (20a, 20b) whose loop connection points (14) are spaced apart from one another by one of the two eight loops are perpendicular to one another.Coil arrangement according to claim 1, characterised in that the individual coils all have the same shape and size.Coil arrangement according to one of the preceding claims, characterized in that it is formed on a coil carrier (21).Coil arrangement according to claim 3, characterised in that the coil pairs (20a, 20b) are printed on the coil carrier (21).Device for inductively transmitting energy, having a primary coil and a secondary coil, between which a coil arrangement according to one of Claims 1 to 4 is arranged.The apparatus of claim 5, wherein the coil assembly is disposed on the primary coil.

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