Device for detecting an object above a primary coil of an arrangement for inductive energy transmission

Abstract

Device for detecting an object (6) above a primary coil (2) of an arrangement for inductive energy transmission with - a base plate (1) having the primary coil (2), and - a coil carrier (3) with magnetic field measuring coils arranged thereon, which is arranged above the primary coil (2), - measuring means (11) designed to detect the current through and / or the voltage at terminals of the measuring coils, wherein the voltage or the current is caused by a magnetic field generated by the primary coil (2), - comparison means (12) which are designed to compare the measured voltages and / or currents in the at least two measuring coils with each other or with reference voltages and / or reference currents, and - evaluation means (13) which are designed to determine the presence of an object (6) above the primary coil (2) from the comparison result, wherein the coil carrier (3) is elastically mounted so that when the object (6) is present, the position of the measuring coils in the magnetic field of the primary coil (2) changes, whereby the current through and / or the voltage at the terminals of the measuring coils changes, from which the presence of the object (6) can be inferred.

Description

[0001] The invention relates to a device for detecting an object above a primary coil of an arrangement for inductive energy transmission with a base plate which has the primary coil and a coil carrier with measuring coils arranged thereon, which is arranged above the primary coil.

[0002] Such a device is known from DE 10 2009 033 237 A1.

[0003] In the known device, a large number of measuring coils are arranged in a matrix and cover almost the entire area occupied by the primary coil. They are used to detect metallic objects located above this area. For this purpose, a current is applied to them at times when the primary coil is not energized, and the impedance of the measuring coils is determined. This impedance has a different value when a metallic object is located in a space above the primary coil than in an open space. Since the impedance of the measuring coils in whose area the object is located changes more significantly, not only the presence of such an object can be detected, but also its position within the space.

[0004] However, such detection can only occur when no magnetic field generated by the primary coil influences the impedance measurement, i.e., when the primary coil is not energized. Furthermore, a complex evaluation device is required, as the measuring coils must be actively energized. Furthermore, a large number of measuring coils must be provided across the entire area to detect foreign objects with sufficient spatial resolution.

[0005] DE 10 2017 106 917 A1 discloses a coil unit comprising a coil, at least one sensor for detecting an object located above or around the coil unit, and a housing for accommodating the coil and the at least one sensor. The housing is provided with a partition plate and at least one pillar for maintaining the interior space for the sensor.

[0006] US 2013 / 0 069 441 A1 discloses a system for wireless energy transmission, which comprises a foreign body detection system and at least one wireless energy transmission source configured to generate an oscillating magnetic field. The foreign bodies can be detected by at least one field gradiometer positioned in the oscillating magnetic field.

[0007] DE 10 2014 207 890 A1 discloses a foreign body detection device comprising a substrate and a plurality of coils. The coils are formed by at least one structured, conductive layer supported by the substrate.

[0008] JP 2014-75899 A discloses a cover for a protective housing for a power transmission coil. The cover has a layered structure formed from a plurality of resin plates. An upper, outward-facing resin plate is made of a weather-resistant synthetic resin material. A lower resin plate, facing the coil body, is made of a flame-retardant synthetic resin material.

[0009] US 2016 / 0 164 333 A1 discloses a position detection coil arranged as a foreign object detector that detects a condition in which a foreign object is present on the upper surface of an installation panel. An alarm unit issues an alarm when a foreign object is detected by the position detection coil.

[0010] DE 11 2013 004 161 T5 discloses a contactless power receiving device including a power receiving coil that receives the supply of electrical power in a contactless manner using electromagnetic induction. The power receiving device further includes foreign matter detection means contained in an installation section arranged at a lower portion of the power receiving coil. The foreign matter detection means detects a foreign matter in the lower portion of the power receiving coil.

[0011] CN 107 707 040 A discloses a wireless charging device comprising a transmitting circuit, a control circuit, and a detecting circuit. The detecting circuit detects whether or not an object is on a tray. The control circuit controls the deactivation of the transmitting circuit when no object is on the tray.

[0012] It is the object of the invention to provide a device for detecting an object above a primary coil during inductive energy transmission, which can be manufactured and operated with little effort and thus cost-effectively.

[0013] The object is achieved by a device according to claim 1. Advantageous further developments are specified in the subclaims.

[0014] Accordingly, a device according to the invention for detecting an object above a primary coil of an arrangement for inductive energy transmission is formed with a base plate having the primary coil and a coil carrier with magnetic field measuring coils arranged thereon, which is arranged above the primary coil, as well as with measuring means designed to detect the current through and / or the voltage at terminals of the measuring coils, wherein the voltage or current is caused by a magnetic field generated by the primary coil. The device further comprises comparison means designed to compare the measured voltages and / or currents in the at least two measuring coils with one another or with reference voltages and / or reference currents, as well as evaluation means designed to determine the presence of an object above the primary coil from the comparison result.The coil carrier is elastically mounted in the manner according to the invention, so that when the object is present, the position of the measuring coils in the magnetic field of the primary coil changes, whereby the current through and / or the voltage at the terminals of the measuring coils changes, from which the presence of the object is inferred.

[0015] The measuring coils are therefore not actively energized to detect non-metallic objects. Instead, the magnetic field of the primary coil induces voltages in the measuring coils, which are influenced by the position of the measuring coils. Since the coil carrier is elastically mounted, the measuring coils tilt when the coil carrier is subjected to asymmetrical loading by an object located on it or are pushed closer to the primary coil. The induced voltages can be used to determine the presence of an object above the primary coil, either lying on the coil carrier or, in the case of a living object such as a cat, sitting on it.

[0016] The induced voltages of the measuring coils change when the position of the measuring coils in the magnetic field of the primary coil changes.

[0017] If the measuring coils are terminated with a resistor, the current flowing in the measuring coils can be determined from the voltage drop across them.

[0018] In an advantageous embodiment of the invention, the coil carrier is mounted on spring elements.

[0019] In an advantageous development of the invention, the measuring coils are planar coils which, in a further development, are printed on a film.

[0020] This allows for a low installation height and, if necessary, simple production, which is a great advantage when inductively charging vehicle batteries.

[0021] The device according to the invention has the advantage that already existing measuring coils, which are used, for example, for vehicle position detection or for the detection of metallic objects, can also be used for the detection of non-metallic, in particular living objects, due to the elastic mounting according to the invention.

[0022] The invention will be explained in more detail below using exemplary embodiments with the aid of figures. Fig. 1 a first schematic representation of a device according to the invention and Fig. 2 a second schematic representation of the device when loaded with an object.

[0023] In the schematic representation of a device according to the invention for detecting an object 6 via a primary coil 2, the primary coil is installed in a housing that lies on a base plate 1. It would be equally possible to install the housing within the base plate 1. Above the primary coil 2, a coil carrier 3 is elastically mounted, wherein in the embodiments of the Fig. 1 and Fig. 2 is arranged above the primary coil 2 by means of spring elements 5.

[0024] A number of measuring coils are to be formed on the coil carrier 3, which is shown in the Fig. 1 and Fig. 2, which can be formed, for example, as planar coils on a foil. An example of such planar coils is given in DE 10 2009 033 237 A1.

[0025] Above the coil carrier 3, a cover 4 is provided to protect the measuring coils on the coil carrier 3. The measuring coils on the coil carrier 3 are connected via a line 15 to a control unit 10, which in turn supplies a control current to the primary coil 2 via lines 14.

[0026] The control unit 10 includes measuring means 11 that detect the voltages at the measuring coils or the currents flowing therein based on a voltage induced in the measuring coils by the magnetic field of the primary coil 2. The control unit 10 also includes comparison means 12 that compares the detected voltages and / or currents with expected voltages or currents, respectively, and finally, evaluation means 13 that interrupts the control current to the primary coil 2 depending on the deviation of the detected voltages and / or currents from the reference values ​​if, based on the signals from the evaluation means 13, an object 6 is assumed to be on the coil carrier 3.

[0027] In the Fig. 2, an object 6 is placed centrally on the coil carrier 3, which, due to its weight, moves the coil carrier 3 against the spring force of the spring elements 5 towards the primary coil 2, so that the magnetic field generated by the primary coil 2, which penetrates the measuring coils on the coil carrier 3, changes and consequently the induced voltages or the currents flowing thereby are changed, which can be detected by the control unit 10. The control unit 10 is shown in the illustration of Fig. 2 is not shown again, but should of course be there.

[0028] If the object 6 is not located centrally on the coil carrier 3, but on an edge area of ​​the coil carrier 3, the coil carrier 3 would tilt slightly, which would also lead to different voltages in the measuring coils, whereby the position of the object 6 could possibly even be determined at least roughly.

[0029] By appropriately designing the spring force of the spring elements 5 and the sensitivity of the measuring 11, comparison 12 and evaluation means 13 in the control unit 10, it can be determined from which weight an object is to be detected and also up to which weight.

Claims

[1] Device for detecting an object (6) above a primary coil (2) of an arrangement for inductive energy transmission with - a base plate (1) having the primary coil (2), and - a coil carrier (3) with magnetic field measuring coils arranged thereon, which is arranged above the primary coil (2), - measuring means (11) designed to detect the current through and / or the voltage at terminals of the measuring coils, wherein the voltage or the current is caused by a magnetic field generated by the primary coil (2), - comparison means (12) which are designed to compare the measured voltages and / or currents in the at least two measuring coils with each other or with reference voltages and / or reference currents, and - evaluation means (13) which are designed to determine the presence of an object (6) above the primary coil (2) from the comparison result, wherein the coil carrier (3) is elastically mounted so that when the object (6) is present, the position of the measuring coils in the magnetic field of the primary coil (2) changes, whereby the current through and / or the voltage at the terminals of the measuring coils changes, from which the presence of the object (6) can be inferred. [2] Device according to claim 1, characterized by that the coil carrier (3) is mounted on spring elements (5). [3] Device according to claim 1 or 2, characterized by that the measuring coils are planar coils. [4] Device according to claim 3, characterized by that the measuring coils are printed on a foil.

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