Antenna arrangement for inductive energy transmission and use of the antenna arrangement

p0001The invention relates to an antenna arrangement having an open magnetic core and a winding.

p0002The invention is in the field of magnetic field antennas used for inductive energy transmission. In principle, it is possible to transmit energy and information by means of electrical or magnetic dipoles. Depending on the control circuit, electromagnetic waves or even predominantly electric or magnetic fields are generated. It may be desirable not to radiate electromagnetic waves, but to limit the generation of magnetic fields, in order to avoid, for example, exposure to organic tissue in the vicinity of the antenna. In particular, relatively high energies can be transmitted without a galvanic coupling by the emission of magnetic fields or the inductive coupling to a magnetic antenna. The effect of such a coupling is limited to a narrow spatial range smaller than about 1 m. Nevertheless, there are numerous possible applications for such a transmission.

p0003In principle, in addition to conventional soft ferrites, most known soft magnetic powder composite materials can be used as pressed magnetic cores. For example, these may consist of iron powder. With such magnetic cores, effective permeabilities between about 10 and 30 can be achieved. Saturation inductions which can be achieved are approximately 1.0 to 1.4 T. Powder composites made of soft magnetic crystalline iron-aluminum-silicon alloys and iron nickel alloys are also known, with which application frequencies up to over 100 kHz can be achieved.

p0004The disadvantage of such composite materials and ferrites is that the pressing technologies allow only simple geometric shapes and that the magnetic cores that are formed are relatively brittle and break-resistant. In addition, the corresponding magnet properties are strongly temperature-dependent, which makes the use of resonant resonant circuits more difficult.

p0005From the <patcit id="pcit0001" dnum="DE19846781A1"><text>DE 19846781 A1</text></patcit> Magnetic cores are known which are produced by injection molding from an injection-moldable plastic and a nanocrystalline alloy.

p0006Corresponding nanocrystalline alloys are, for example, from the <patcit id="pcit0002" dnum="EP0271657A2"><text>EP 0271657 A2</text></patcit> and the <patcit id="pcit0003" dnum="EP0455113A2"><text>EP 0455113 A2</text></patcit> known. Such alloys are produced, for example, by means of the rapid solidification technology in the form of thin alloy strips which are initially amorphous and which are subjected to a heat treatment to form a nanocrystalline structure. Such alloys can be ground to alloy powders with particle sizes smaller than 2 mm. Preferably, so-called flakes are produced with thicknesses between 0.01 and 0.04 mm and widths or lengths of 0.04 to 1 mm per particle. These flakes can be processed with the aid of synthetic resins into composites in which saturation magnetizations greater than 0.5 Tesla and permeabilities between 10 and 200 can be realized. A manufacturing method for such magnetic cores is, for example, shown in FIG<patcit id="pcit0004" dnum="WO0191141A1"><text>WO 0191141 A1</text></patcit> Respectively.

p0007From the <patcit id="pcit0005" dnum="EP0762535A1"><text>EP 0762535 A1</text></patcit> Antennas are known for transponders which also consist of soft magnetic powder composite materials, for example amorphous alloys. Such antennas are used for exchanging information there.

p0008In this case, the failure-proof functioning of the information exchange in a spatial area of ​​a few meters as well as the low susceptibility to interference to metallic objects in the vicinity of the antenna are important.

p0009In <patcit id="pcit0006" dnum="US20030210106A1"><text>US 2003/0210106 A1</text></patcit> An antenna arrangement for the inductive transmission of electrical power is described. A longitudinally extending magnetic core of a receiver, which is wrapped around a conductor, is arranged parallel to one of two opposing planar surfaces of a magnetic core of a transmitter. A contactless electrical coupling of the transmitter with the receiver in the near field of the transmitter with any positioning of the receiver is possible with the<patcit id="pcit0007" dnum="US20030210106A1"><text>US 2003/0210106 A1</text></patcit> Can not be achieved.

p0010The object of the present invention is, on the other hand, to provide an antenna arrangement for use in the inductive transmission of energy, independently of an exact positioning of the antenna arrangement relative to a receiver.

p0011The present invention aims at the effective energy transmission in the near-field region and the reliable functioning independently of an exact positioning of the antenna arrangement relative to a receiver to which the energy is to be transmitted by inductive means. For this purpose, the adjustment of very specific magnetic properties, in particular a sufficient flux with suitable radiation characteristics, is necessary in the antenna arrangement.

p0012With the aid of an antenna arrangement according to the invention, powers between approximately 1 W and 100 W are to be transmitted from a transmitter to a receiver over a distance between approximately 0.5 and 50 cm. Application examples for this are all devices which must be supplied with energy either temporarily or permanently. Due to the exclusively inductive coupling, a frequency range of 10 khz to 150 khz is particularly suitable because of the availability of this frequency band and the dimensioning boundary conditions. In addition, a magnetic flux of at least 20 Wb in the magnet core is to be realized.

p0013Since such antennas, as used in the present antenna arrangement, are mostly the inductive part of a resonant circuit, a high antenna quality of at least 50, preferably even 100, is desirable in the range of the operating frequency for optimizing the energy radiation. In addition, a temperature-independent permeability is required, which is between 30 and 200 for optimal flow control. At higher permeability, the flux bundling in the core is so good that laterally a too low flux fraction emerges from the core and the field strength along the core, ie in the receiver region, becomes strongly inhomogeneous.

p0014The object underlying the present invention can not be solved satisfactorily with the known magnet arrangements, magnetic cores and materials.

p0015According to the invention, it is achieved by means of an arrangement according to claim 1, a process 1 and an arrangement according to claim 11 are solved. Embodiments and further developments of the inventive idea are the subject of subclaims.

p0016According to the invention, the magnetic core contains as a composite a soft magnetic component of finely divided particles and a plastic component, the magnetic core having an initial permeability between 20 and 200 as well as a saturation induction> 0.6 T.

p0017The soft magnetic component consists advantageously of the abovementioned flakes of a nanocrystalline material. This has a saturation magnetization of approximately 1 to 1.6T and permeabilities> 30,000. By mixing with a plastic component, the magnetic circuit is interrupted by the microscopic gaps between the flakes and lower effective permeabilities of 30 to 100 can be set with high quality and temperature constancy. Nevertheless, the high achievable flux density is greater than 0.6 T, typically also greater than 0.9 T. The soft magnetic component of the magnetic core also advantageously has the property that the particles are each individually electrically insulated by a surface layer. This can be realized, for example, by surface oxidation or plastic coating. The particle size can advantageously be less than 2 mm, the particle thicknesses being less than 0.5 mm. Due to this configuration of the particles, particularly low magnetization losses and thus a particularly high quality of the antenna are achieved. Depending on the type and proportion of the plastic used, the mechanical properties can be adjusted with regard to the fracture toughness and flexibility as well as their temperature dependence.

p0018As a plastic component, it is generally possible to choose all thermoplastics or thermosets, such as polyamide, polyacrylate, polyacetate, polyimide or epoxy resin, which can be processed within the framework of the casting resin technology, depending on the desired mechanical and thermal properties.

p0019In the simplest case, the antenna arrangement has, as a magnetic core, a rod or a plate which is provided with a winding. Certain core cross sections are necessary to make the arrangement useful for the effective transfer of energy. If an average flux of at least 20 μWb is to be achieved in the core, an induction of 400 mT is obtained with a cross-section of 0.5 cm². This corresponds to approximately half of the cross-section, which would be necessary if a soft ferrite was used.

p0020In this case, in order to be able to effectively utilize the magnet core for increasing the flux, the coil length of the winding should be greater than its diameter, preferably large compared to the diameter. An essential property of the material used according to the invention is the mechanical insensitivity to impact or vibrations and the free shaping within the scope of manufacture or a subsequent flexibility. The material used according to the invention also allows a small size because of its magnetic properties, which is desirable in many fields of application for cost, space and design reasons.

p0021In order to realize the desired radiation characteristic or flow guidance of the antenna arrangement, it may be advantageous for a plurality of windings to be arranged on the same magnetic core, the longitudinal axes of the windings being at an angle> 0 °, for example, 90 ° to one another. The windings can be simultaneously, phase-offset, or alternately driven to achieve recipients of the inductive energy transfer in various positions. This makes energy transmission more reliable and less sensitive to the relative positioning of transmitter and receiver. The invention also relates to various operating methods of the antenna arrangement according to the invention with intermittent operation of the different windings or the phase-shifted simultaneous driving of the different windings.

p0022In order to achieve such an increased acceptance in the positioning of transmitter and receiver, it is also conceivable that several windings are provided on various magnetic cores of the type mentioned, wherein the emission characteristic of individual magnetic cores is shaped differently or aligned. Also by means of this measure, the optimum positioning range of a receiver of the energy emitted is increased.

p0023Since the antenna arrangement according to the invention is also designed to be space-saving, it can additionally be useful to provide a recess within a magnetic core in which electronic components, for example the drive circuit of the antenna arrangement, can be accommodated. The flux conduction within the magnetic core is hardly adversely affected by such recesses if they are not too large. In addition, the antenna arrangement can advantageously be prefabricated with the drive circuit and can be simply used as an integral module in a device.

p0024The invention is explained in more detail below with reference to the exemplary embodiments shown in the figures of the drawing. It shows:<dl id="dl0001"><dt>FIG</dt><dd>A plate-shaped rectangular configuration of a magnetic core having a winding,</dd><dt>FIG</dt><dd>A corresponding magnetic core having two windings,</dd><dt>FIG</dt><dd>A rod-shaped magnetic core having a winding,</dd><dt>FIG</dt><dd>A rod-shaped magnetic core with an integrated winding and pole shoes, </dd><dt>FIG</dt><dd>A magnetic core with a recess and</dd><dt>FIG</dt><dd>An application of the antenna array with two magnetic cores.</dd></dl>

p0025<figref idrefs="f0001">FIG</figref> Shows a flat magnetic core 1 with a winding 2, the dimensions of the magnetic core being, for example, 20 × 10 × 0.2 cm. The base area of ​​the core is preferably as large as the target area of ​​a receiver to be covered. By virtue of the configuration of the winding, for example a compression of the windings towards the winding ends, a strong flux density is produced that is as homogeneous as possible over the core surface. For the special design of the river alignment and the radiation characteristics, the<figref idrefs="f0001">FIG</figref> A combination of two mutually perpendicular windings 3, 4 on a magnetic core 5, which is designed almost as a square plate. The two windings can be alternately controlled one after the other or simultaneously phase shifted.

p0026With a suitable choice of the plastic component, the entire arrangement according to FIG <figref idrefs="f0001">1 or 2</figref> To be flexible. In any case, however, it is more susceptible to breakage than, for example, an antenna with a ferrite core or a core made of another conventional material.

p0027Particularly suitable for the transmission of energy to a moving receiver, <figref idrefs="f0001">FIG</figref> , With the direction of movement as well as the antenna of the receiver being directed parallel to the longitudinal axis 6 of the winding 7.

p0028In the <figref idrefs="f0002">FIG</figref> Two different magnetic cores 8, 9 are shown which each have a separate winding and whose longitudinal axes are perpendicular to each other to enable different flux densities and radiation characteristics. This is an alternative embodiment to that in the<figref idrefs="f0001">FIG</figref> Illustrated with several windings on a single magnetic core.

p0029The <figref idrefs="f0001">FIG</figref> Shows an arrangement in which the winding 10 is integrated into a magnetic body 11 insofar as it penetrates the magnetic core 11 itself, so that a lower part of the magnetic core 11 in the magnetic core 11, <figref idrefs="f0001">FIG</figref> A yoke that shorts the magnetic flux on the bottom. As a result, and by the pole shoes 12, 13, a shielding effect in a direction (downwards) is achieved with a good radiation emission upwards.

p0030In order to produce such an arrangement, the embodiment shown in FIG <patcit id="pcit0008" dnum="WO0191141A1"><text>WO 0191141 A1</text></patcit> Is particularly suitable in which the winding can also be cast during the production of the magnetic core.

p0031The <figref idrefs="f0002">FIG</figref> Shows a recess 15 in the magnetic core 14, which recess allows components of an electronic circuit, for example, to drive the winding 16.

p0032The <figref idrefs="f0002">FIG</figref> Shows an application example of the antenna arrangement according to the invention with a mobile communication terminal, for example a mobile telephone or a cordless telephone 17, which has a receiving device (not shown in detail) for inductive coupling with the antenna arrangement 18. The antenna arrangement 18 has in a housing 19 the two magnetic cores 8, 9, which are each provided with a winding and can inductively transmit energy to the receiver in the terminal 17. In the terminal 17, besides the receiver, a capacitor or battery for storing the transmitted energy is provided.

p0033In spite of the specialization of the described antenna arrangement on the energy transmission, the same arrangement can also be used for the retransmission of an information, or a signal, which is either likewise transmitted inductively, whereby it would have to be switched between sending and receiving or by evaluating the energy draw of the receiver.

p0034The application of the invention is also conceivable in the transmission of energy from a mobile device to a stationary device, for example in the railway technology for transmitting signals and / or energy from a device attached to a vehicle to a stationary sensor of a control room / signaling device For traffic monitoring.