DE102015221587A1 - Charging device for inductively charging an electrical energy storage device of a motor vehicle with a foreign body detection device - Google Patents

Abstract

The invention relates to a charging device (2) for inductively charging an electrical energy store (11) of a motor vehicle (9), comprising a primary coil (3) for providing a magnetic field (7) and a foreign body detection device (13) for detecting the presence of a foreign body the magnetic field (7), wherein the foreign matter detecting means (13) comprises a substrate (14) on which a plurality of coils (15) are arranged, and an evaluation unit (16), the substrate (14) being at a predetermined position in the Magnetic field (7) is arranged and wherein the evaluation unit (16) is adapted to detect the presence of the foreign body from the induced in the plurality of coils (15) electrical voltage, wherein each of the coils (15) has a predetermined number of turns in which the number of turns of each of the coils (15) is determined as a function of a position of the coil (15) in the magnetic field (7).

Description

The present invention relates to a charging device for inductively charging an electric energy storage device of a motor vehicle having a primary coil for providing a magnetic field and a foreign matter detecting means for detecting a presence of a (foreign) foreign metal in the magnetic field, wherein the foreign matter detection device comprises a substrate on which a plurality of coils are arranged, and an evaluation unit, wherein the substrate is arranged at a predetermined position in the magnetic field and wherein the evaluation unit is adapted to detect the presence of the foreign body based on the induced voltage in the plurality of coils.

The interest in this case is directed to charging devices which serve to charge an electrical energy store, for example a battery, of a motor vehicle. Such a charging device has a primary coil which is arranged stationary. This primary coil can be incorporated, for example, in the floor of the carriageway or a parking lot. In the motor vehicle, a secondary coil is arranged, which is electrically connected to the energy storage of the motor vehicle. When the secondary coil of the motor vehicle is aligned with the primary coil, electrical energy can be transmitted from the primary coil to the secondary coil by means of the transformer operation. From the primary coil so a magnetic field, in particular an alternating magnetic field is generated, which induces an AC voltage in the secondary coil. This alternating voltage can then be rectified and transmitted to the electrical energy storage.

When inductive charging of the electrical energy storage, the primary coil and the secondary coil at a predetermined distance from each other, which may be up to 20 cm, for example. If foreign bodies, in particular metallic foreign bodies, are present in the intermediate space between the primary coil and the secondary coil, this can lead to them being heated as a result of the magnetic field. For example, the remagnetization or eddy currents can result in temperatures well in excess of 100 ° C. As a result, there is not only the danger that a person can burn on the heated foreign body, but such a foreign body can also start to burn itself and inflame the vehicle in the worst case.

For this reason, it is provided that a corresponding foreign body detection device is provided, by means of which the presence of a metallic foreign body in the magnetic field can be detected. For this purpose, foreign body detection devices are known from the prior art, which have a plurality of coils which are arranged on a substrate. By means of an evaluation unit, the voltage induced in the respective coils can be detected as a result of the magnetic field of the primary coil. If a metallic foreign object is in the region of a coil of the foreign-matter detecting device, the magnetic field is changed at that location. The result is a change in the induced voltage in the coil, which can be detected by the evaluation unit. Furthermore, foreign object detection devices are known from the prior art, in which the coils are arranged on a corresponding substrate or on a printed circuit board. This substrate can then be placed on the primary coil.

It is an object of the present invention to provide a solution, as a charging device of the type mentioned, which comprises a foreign body detection device, can be operated reliably.

This object is achieved by a charging device having the features of patent claim 1. Advantageous developments of the present invention are the subject of the dependent claims.

A charging device according to the invention for inductively charging an electrical energy store of a motor vehicle comprises a primary coil for spreading a magnetic field. In addition, the charging device includes a foreign matter detecting device for detecting a presence of a foreign matter in the magnetic field. The foreign body detection device in turn comprises a substrate on which a plurality of coils is arranged, and an evaluation unit. In this case, the substrate is arranged at a predetermined position in the magnetic field. In addition, the evaluation unit is designed to detect the presence of the foreign body on the basis of the voltage induced in the plurality of coils. Each of the coils has a predetermined number of turns, the number of turns of each of the coils being determined in response to a position of the coil in the magnetic field.

The charging device is used to charge an electrical energy storage, such as a battery, a motor vehicle. In particular, the charging device is used for charging an electrical energy store of an electric vehicle or a hybrid vehicle. The charging device comprises the primary coil, by means of which a magnetic field, in particular a magnetic alternating field, can be provided. With the help of Foreign body detection device of the charging device can be checked whether a foreign body, in particular a metallic foreign body, is in the magnetic field. The foreign body detection device comprises a substrate, which may be formed for example by a printed circuit board. The substrate may be rigid. It can also be provided that the substrate is designed to be flexible. On the substrate a plurality of coils is arranged. For example, the plurality of coils may be distributed over a surface of the substrate. As a result of the magnetic field or the alternating magnetic field which is generated by the primary coil, an electrical voltage is induced in at least some of the coils. This particular induced voltage can be detected by an evaluation unit. The evaluation unit may comprise, for example, a corresponding analog-to-digital converter, by means of which the induced voltage can be sampled. Furthermore, the evaluation unit can be designed to compare the electrical voltages induced in the respective coils in each case with a desired value. This setpoint can be stored, for example, for each of the coils in the evaluation unit. The setpoint may describe the particular induced voltage if there is no metallic debris in the gap between the primary coil and the secondary coil.

According to the invention, it is now provided that each of the coils has a predetermined number of turns, wherein the number of turns of each of the coils is determined as a function of a position of the coil in the magnetic field. The substrate with the coils can be arranged, for example, substantially parallel to the road surface or the main extension direction of the primary coil. Since the magnetic field strength or the magnetic flux density of the magnetic field along the printed circuit board, on which the plurality of coils are located, is not constant, different induced voltages result in the respective coils. The particular induced voltage in the coil depends on the position of the coil in the magnetic field. The respective number of turns of the coils is determined as a function of the position in the magnetic field. For this purpose, the magnetic field generated by the primary coil can be measured. Subsequently, the spatial distribution of the magnetic field can be taken into account during the manufacture or during the design of the coils. By the number of turns, the voltage induced in the respective coil can be adjusted. If the number of turns is increased, the induced voltage can be increased at the same magnetic flux density. For example, the number of turns of the respective coils can be selected such that substantially the same induced voltage results in each of the coils. Thus, a reliable detection of the foreign body can be independent of the position of the foreign body in the magnetic field.

Preferably, the number of turns of each of the coils is determined in response to a magnetic flux density of the magnetic field at the position of the coil. As already explained, the magnetic flux density of the magnetic field provided by the primary coil can be determined. In particular, the magnetic flux density for the respective positions at which the coils are to be arranged can be determined. Subsequently, then the respective coils can be designed with respect to their number of turns. In principle, it can also be provided that the spatial dimensions and / or the position of the coils are adapted as a function of the distribution of the magnetic flux density. In particular, the respective number of turns of the coils can be adjusted so that substantially the same electrical voltage is induced in each of the coils. The number of turns of the respective coils can also be adapted to induce in each of the coils an electrical voltage which is within a predetermined voltage range. Thus, the foreign body along the entire circuit board or the arrangement of the coils can be detected with the same sensitivity.

In one embodiment, a first of the plurality of coils disposed at a first position having a first magnetic flux density has, compared to a second of the plurality of coils, which at a second position having a second magnetic flux larger than the first magnetic flux density Flux density is arranged, a smaller number of turns on. For example, a measuring coil, which is arranged in a region with a strong magnetic field, have only half or a quarter of the windings, such as a coil, which is arranged in a field weaker region. For example, in the region of the center of the primary coil there is a relatively high magnetic field or a maximum of the magnetic flux density. In the peripheral areas of the primary coil, a relatively weak magnetic field with a low magnetic flux density is usually present. However, it can also be provided that the magnetic field of the primary coil is not formed symmetrically and thus the maximum of the magnetic flux density is arranged outside the center of the coil. In principle, the number of turns of the respective coils should be adapted to the magnetic field or the distribution of the magnetic flux density. Thus, the respective coils can be easily adapted to the magnetic field generated by the primary coil.

In a further embodiment, the plurality of coils is divided into several groups and the coils of a group have the same number of turns. Those coils that are in a region where the magnetic flux density is substantially the same may be assigned to a group. The coils are thus divided into several groups depending on their position on the substrate. Thus, for the respective areas exposed to different magnetic flux densities, the induced voltages can be reliably detected.

It is preferably provided that the groups of coils are arranged substantially concentrically to a center of the substrate and the substrate is arranged in the magnetic field such that the center is in a range of a maximum magnetic flux density of the magnetic field. For example, the primary coil may be substantially round. In this case it can be provided that the substrate is substantially round. In this case, the substrate may be arranged such that the center of the substrate is associated with a maximum magnetic flux density of the magnetic field of the primary coil. For example, the maximum magnetic flux density may be in the range associated with a center of the primary coil. The respective coils may be concentric with this center. For example, the respective coils associated with a group may be arranged along a circular ring which is concentric with the center. The respective groups of coils can therefore be arranged overall in concentric rings. It can be provided that the respective coils have the shape of a circular ring segment. In principle, it can also be provided that the respective coils are rectangular or trapezoidal. It can also be provided that the coils have rounded corners. In the middle of the magnetic field or in the region of the maximum magnetic flux density, two coils can be provided, which are each formed semicircular. Thus, overall a high spatial resolution and thus a reliable detection of the foreign body can be achieved.

In a further embodiment, each of the coils has a first single coil element and at least one second single coil element, which are electrically connected in parallel, and the first single coil element is arranged on a front side and the at least one second single coil element is arranged on a rear side of the substrate. For example, the coils may be provided by metal layers on the substrate that have a relatively small layer thickness. When using coils designed in this way, it has been found that the coils are heated during operation. This is due to the skin effect or the displacement effect, because the penetration depth is greater than the available layer thickness of the coil, depending on the frequency of the magnetic field of the primary coil used. In order to reduce this effect, at least two individual coil elements are provided which are electrically connected in parallel. In this case, the individual coil elements can be arranged, for example, on the front and back of the substrate. Thus, an effect known from strands can be achieved. This can prevent the respective coils from heating up during operation. This guarantees overall reliable operation of the coils and thus the foreign body detection device.

In a further embodiment, each of the coils has at least one third individual coil element, which is arranged in an intermediate layer of the substrate and which is electrically connected in parallel to the first single coil element and the second single coil element. The intermediate layer of the substrate may in particular be arranged parallel to the front side and the rear side of the substrate. The substrate may be, for example, a multilayer printed circuit board. In principle, it can also be provided that a plurality of individual coil elements are provided, which are arranged in parallel intermediate layers of the substrate or the printed circuit board. This can prevent heating of the coils during operation.

Furthermore, it is advantageous if the individual coil elements are of identical design and are arranged in alignment with one another along a normal of the substrate. In other words, the single coil elements have the same spatial dimensions and the same number of turns. The individual coil elements thus have the same coil geometry. The individual coils are arranged so that, if one would look through the substrate, the two individual coil elements are arranged congruent to each other. By virtue of this arrangement of the individual coil elements connected electrically in parallel, therefore, two identical windings result, which are comparable to a multi-core stranded wire. Thus, for example, at frequencies of the magnetic field which are below 150 kHz, with a layer thickness of the respective individual coils, which is for example less than 105 microns, the necessary penetration depth can be achieved, so that overall the efficiency can be improved.

In a further embodiment, each coil is electrically connected to at least one capacitor and / or to at least one resistor for adjusting the induced voltage. In the the respective coils induced electrical voltage is detected with the evaluation unit. It has been found that it makes sense not directly high impedance to measure the induced voltage of the coils, but to bring them in advance by means of at least one additionally introduced capacitor in resonance. In other words, the connection of the respective coil with the at least one capacitor results in a resonant circuit. Thus, with the evaluation unit, an induced voltage can be detected, which has a substantially sinusoidal course. Such sinusoidal signals can be evaluated easily and reliably. In principle, it can also be provided that the respective coils are electrically connected to a plurality of capacitors. The capacitors may be connected in series and / or parallel to the coils. This results in the advantage that the amplitude of the induced voltage can be adjusted. For example, the capacitance of the at least one capacitor can be chosen so that a desired deviation from the ideal resonance of the resonant circuit is achieved. Thus, the amplitude of the induced voltage can be easily adjusted. Alternatively or additionally, it can be provided that each of the coils is connected to a resistor or a damping resistor. If the respective coil is additionally connected to at least one capacitor, heating of the at least one capacitor can be prevented in this case. In addition, can be limited by the resistance of the current flowing in the resonant circuit electrical current, so that a temperature increase of the electronic components is also limited. This makes it possible in particular to realize the at least one capacitor and / or the at least one resistor as SMD components. These can be arranged in a particularly space-saving manner on the substrate. Furthermore, by selecting the at least one resistor, the induced voltage can be adjusted to a predetermined level or to a predetermined value. Overall, the at least one capacitor and / or the at least one resistor for each of the coils can be chosen such that the induced voltages of each of the coils are substantially equal.

In a further embodiment, the evaluation unit is designed to determine a measured value for each of the coils, which describes the voltage induced in the coil, and to weight the measured value. Overall, the goal is to obtain substantially the same evaluation voltage and / or the same evaluation current for each of the coils. Due to tolerances in the electronic components, temperature influences or magnetic tolerances, however, the voltages induced in the coils can vary. For this purpose, it is provided that the evaluation unit detects the respective induced voltages and provides a measured value on the basis of the respective detected induced voltages. In this case, it is provided in particular that an automatic adjustment is performed before the start of operation and / or before delivery. In this case, the induced voltage can be read individually when activated primary coil and without the presence of a foreign body each of the coils. With the aid of the evaluation unit, which may include, for example, a corresponding microprocessor, the respective detected induced voltages or the measured values derived therefrom can be weighted accordingly. For this purpose, the respective measured values can, for example, be assigned or factorized by a factor, so that the same measured value results for each of the coils. Thus, a foreign body can then be reliably detected.

Further features of the invention will become apparent from the claims, the figures and the description of the figures. The features and feature combinations mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respectively specified combination but also in other combinations or in isolation, without the frame to leave the invention.

The invention will now be described with reference to preferred embodiments and with reference to the accompanying drawings. Showing:

1 a schematic representation of an arrangement with a charging device and a motor vehicle, wherein the charging device comprises a foreign body detection device;

2 a substrate of the foreign-matter detection device on which a plurality of coils are arranged; and

3 a fragmentary view of the coil according to 2 in a sectioned side view.

In the figures, identical and functionally identical elements are provided with the same reference numerals.

1 shows a schematic representation of an arrangement 1 , The order 1 includes a charging device 2 , which is arranged stationary. The loading device 2 again comprises a presently shown only schematically primary coil 3 , The primary coil 3 is present in the roadway floor 4 arranged. The primary coil 3 is a present only schematically illustrated electrical energy source 5 supplied with electrical energy. In particular, with the electric power source 5 provided an AC voltage. In addition, a power electronics unit 6 provided by means of which, for example, the frequency of the energy source 5 provided AC voltage can be adjusted. With the primary coil 3 becomes a magnetic field 7 provided, which is shown simplified in the present case. In particular, with the primary coil 3 generates a magnetic alternating field.

As a result of the magnetic field 7 that from the primary coil 3 is sent out, a voltage in a secondary coil 8th of a motor vehicle 9 induced. The car 9 is presently designed as an electric vehicle. The secondary coil 8th of the motor vehicle 9 is via a charging unit 10 with an electrical energy storage 11 connected. The loading unit 10 For example, a rectifier for rectifying the in the secondary coil 8th include induced AC voltage. In the electrical energy storage 11 of the motor vehicle 9 it may in particular be a battery. The electrical energy storage 11 is also with a drive motor 12 electrically connected. Thus, the drive motor, which for driving the motor vehicle 9 serves to be supplied with electrical energy.

The loading device 2 further comprises a foreign object detection device 13 , As explained in more detail below, the foreign body detection device comprises 13 a substrate 14 on which a plurality of coils 15 are arranged. The substrate 14 is present on the primary coil 3 arranged. In the coils 15 is due to the magnetic field 7 each induces an electrical voltage. The each in the coils 15 induced electrical voltage can be detected by means of an evaluation unit 16 be recorded. When in a gap 17 between the primary coil 3 and the secondary coil 8th a foreign body, in particular a metallic foreign body is located, the magnetic field changes 7 and thus in at least one of the coils 15 induced voltage. This can be done using the evaluation unit 16 be recorded.

2 shows an embodiment of the substrate 14 the foreign object detection device 13 , The substrate 14 is presently formed by a printed circuit board. On this substrate 14 is the majority of coils 15 arranged. The spools 15 In the present case, these are formed by printed conductors or structured metal layers which are applied to the substrate 14 are applied. The substrate 14 is round in the embodiment. This is particularly useful when the primary coil 3 is also round and a symmetrical magnetic field 7 provides. Basically, the area should be that of the coils 15 is covered, correspond to the area in which the magnetic field 7 the primary coil 3 spreads.

Present are the coils 15 in several groups 18 . 19 . 20 assigned. The spools 15 in the respective groups 18 . 19 . 20 are each arranged along a ring to each other. Present are the coils 15 of the groups 18 . 19 . 20 arranged in three concentric circular rings. The first group 20 includes the coils 15 that are assigned in the innermost annulus. In addition, the first group includes 20 two coils 15 at a midpoint 21 of the substrate 14 adjoin. These two coils 15 are formed substantially semicircular. The spools 15 the second group 19 surround the coils 15 the first group 20 , In addition, the coils surround 15 the third group 18 the coils of the second group 19 ,

The substrate 14 with the coils 15 in the present case becomes the primary coil 3 positioned that is a midpoint 21 of the substrate 14 located in an area where the magnetic flux density of the magnetic field 7 that from the primary coil 3 is generated is maximum. This area is, for example, a center of the primary coil 3 assigned. Due to the spatial distribution of the magnetic field 7 Different magnetic flux densities result on the individual groups 18 . 19 . 20 the coils 15 act. In the present case, the number of turns of the coils differs 15 , The spools 15 the first group 20 present in the present case every two turns. The spools 15 , the second group 19 are assigned, have three turns on. Furthermore, the coils have 15 , the third group 18 are assigned four turns on.

As a result of the magnetic field 7 arises in the area where the coils 15 order the first group, a relatively large magnetic flux density. In the area where the coils 15 the second group 19 are arranged, results in a lower magnetic flux density than in the area in which the coils 15 the first group 20 are arranged. In the area where the coils 15 the third group 18 are arranged, the lowest magnetic flux density results. The fact that in the areas in which the magnetic flux density is lower, the number of turns is increased, which can in the respective coils 15 induced voltage can be increased. Thus it can be achieved that in each of the coils 15 essentially the same voltage is induced. This voltage can then be used with the evaluation unit 16 be evaluated. On the basis of each in the coils 15 induced voltage can be detected by means of the evaluation unit 16 a reading is provided. This measured value can also be weighted accordingly in order to adapt the respective induced voltages to a common mean value. This can be done a reliable detection of the foreign body.

3 shows a partial view of the substrate 14 according to 2 in a sectioned side view. It can be seen that each of the coils 15 two single coil elements 22 . 23 includes. Here is a first single coil element 22 on a front side 24 of the substrate 14 and a second single coil element 23 on a back 25 of the substrate 14 arranged. The two single coil elements 22 . 23 are by means of a via 26 electrically connected or electrically connected in parallel. The two single coil elements 22 . 23 are structurally identical and arranged in alignment with each other. Thus, an arrangement can be achieved, as it is known from wires with single strands. This can be the heating of the coil 15 be reduced as a result of the skin effect.

On the substrate 14 is also a capacitor 27 arranged. This capacitor 27 forms together with the coil 15 a resonant circuit. There is also a resistance 28 provided, which serves as a damping resistor. Using the capacitor 27 and the resistance 28 can change the amplitude of the coil 15 induced voltage can be adjusted. The capacitor 27 and the resistance 28 can for each of the coils 15 or for the respective coils 15 a group 18 . 19 . 20 be interpreted. The capacitor 27 and the resistance 28 can be dimensioned such that the evaluation unit 16 that with the respective coils 15 is connected, receives substantially the same induced voltage. Based on this induced voltage can then with the evaluation 16 a measured value can be determined. In this case, it can also be provided that the respective measured values are determined by means of the evaluation unit 16 be weighted. Thus, a calibration of the respective measured values can be carried out to a common mean value. This can be done in particular before delivery or before operation. This allows a total reliable detection of a foreign body in the magnetic field 7 ,

LIST OF REFERENCE NUMBERS

1

arrangement

2

loader

3

primary coil

4

roadway floor

5

energy

6

Power electronics unit

7

magnetic field

8th

secondary coil

9

motor vehicle

10

charging unit

11

energy storage

12

drive

13

Foreign body detection device

14

substratum

15

Kitchen sink

16

evaluation

17

gap

18, 19, 20

group

21

Focus

22, 23

Single coil element

24

front

25

back

26

via

27

capacitor

28

resistance

Claims (11)

Loading device ( 2 ) for inductively charging an electrical energy store ( 11 ) of a motor vehicle ( 9 ), with a primary coil ( 3 ) for providing a magnetic field ( 7 ) and with a foreign body detection device ( 13 ) for detecting a presence of a foreign body in the magnetic field ( 7 ), wherein the foreign body detection device ( 13 ) a substrate ( 14 ) on which a plurality of coils ( 15 ), and an evaluation unit ( 16 ), wherein the substrate ( 14 ) at a predetermined position in the magnetic field ( 7 ) and wherein the evaluation unit ( 16 ) is designed to detect the presence of the foreign body in the plurality of coils ( 15 ) to detect induced voltage, characterized in that each of the coils ( 15 ) has a predetermined number of turns, the number of turns of each of the coils ( 15 ) depending on a position of the coil ( 15 ) in the magnetic field ( 7 ) is determined. Loading device ( 2 ) according to claim 1, wherein the number of turns of each of the coils ( 15 ) as a function of a magnetic flux density of the magnetic field ( 7 ) at the position of the coil ( 15 ) is determined. Loading device ( 2 ) according to claim 2, wherein a first of the coils ( 15 ), which is arranged at a first position with a first magnetic flux density, in comparison to a second one of the coils ( 15 ) disposed at a second position with a second magnetic flux density larger than the first magnetic flux density has a small number of turns. Loading device ( 2 ) according to one of the preceding claims, wherein the plurality of coils ( 15 ) into several groups ( 18 . 19 . 20 ) and the coils ( 15 ) of a group ( 18 . 19 . 20 ) have the same number of turns. Loading device ( 2 ) according to claim 4, wherein the groups ( 18 . 19 . 20 ) of coils ( 15 ) substantially concentric with a center ( 21 ) of the substrate ( 14 ) are arranged and the substrate ( 14 ) in the magnetic field ( 7 ) is arranged so that the center ( 21 ) is in a range of a maximum magnetic flux density of the magnetic field. Loading device ( 2 ) according to any one of the preceding claims, wherein each of the coils ( 15 ) a first single coil element ( 22 ) and at least one second single coil element ( 23 ), which are electrically connected in parallel, and wherein the first single coil element ( 22 ) on a front side ( 24 ) and the at least one second single coil element ( 23 ) on a back side ( 25 ) of the substrate ( 14 ) is arranged. Loading device ( 2 ) according to claim 6, wherein each of the coils ( 15 ) has at least a third single coil element, which in an intermediate layer of the substrate ( 14 ) and which to the first single coil element ( 22 ) and the second single coil element ( 23 ) is electrically connected in parallel. Loading device ( 2 ) according to claim 6 or 7, wherein the individual coil elements ( 22 . 23 ) are formed the same and along a normal of the substrate ( 14 ) are arranged in alignment with each other. Loading device ( 2 ) according to one of the preceding claims, wherein the respective spatial dimension of the coils ( 15 ) depending on the position of the coil ( 15 ) in the magnetic field ( 7 ) is determined. Loading device ( 2 ) according to any one of the preceding claims, wherein each of the coils ( 15 ) with at least one capacitor ( 27 ) and / or at least one resistor ( 28 ) is electrically connected to adjust the induced voltage. Loading device ( 2 ) according to one of the preceding claims, wherein the evaluation unit ( 16 ) is designed for each of the coils ( 15 ) to determine a measured value, which in the coil ( 15 ) describes the induced voltage and to weight the measured value.

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