DE102017220201A1 - Coil unit for an inductive charging system - Google Patents

Abstract

A coil unit (110, 120) for an inductive charging system is described. The coil unit (110, 120) includes a coil winding (210) configured to generate a magnetic field (250) in response to a coil current or configured to generate a coil current in response to a magnetic field (250). The coil winding (210) comprises a conductor (211) extending in a winding direction (331) about a coil axis (332) of the coil winding (210). In addition, the coil unit (110, 120) comprises an electrically conductive screen (300) which at least partially surrounds the coil winding (210). In this case, the screen (300) is designed to prevent a current (311, 312) within the screen (300), which rotates the coil axis (332) along the winding direction (331).

Description

The invention relates to a coil unit, in particular a primary unit and / or a secondary unit, for an inductive charging system.

Electric vehicles typically have a battery (i.e., an electrical energy store) in which electrical energy can be stored to operate an electric drive machine of the vehicle. The battery of the vehicle can be charged with electrical energy from a power grid. For this purpose, the battery is coupled to the power grid to transfer the electrical energy from the power grid into the battery of the vehicle. The coupling can be wired (via a charging cable) and / or wireless (based on an inductive coupling between a charging station and the vehicle).

One approach to automatically, wirelessly, inductively charging the battery of the vehicle is to transmit electrical energy to the battery from the floor to the underbody of the vehicle via magnetic induction via the underbody clearance. This is exemplary in 1 shown. In particular shows 1 a vehicle 100 with an energy storage 103 for electrical energy (eg with a rechargeable battery 103 ). The vehicle 100 includes a secondary coil 121 in the vehicle underbody, with the secondary coil 121 via a rectifier with the memory 103 connected to electrical energy. The rectifier is part of a secondary electronics 123 , The secondary coil 121 and the secondary electronics 123 are typically over at least one (AC) line 122 electrically connected to each other and together form a so-called "Wireless Power Transfer" (WPT) vehicle unit 120 or secondary unit 120 ,

The secondary coil 121 the secondary unit 120 can over a primary coil 111 be positioned, the primary coil 111 eg on the floor of a garage. The primary coil 111 is typically part of a so-called WPT ground unit 110 or primary unit 110 , The primary coil 111 is via an (AC) line 112 with a primary electronics 113 and continue to be connected to a power supply. The primary electronics 113 may include a radio frequency generator that provides alternating current (AC) in the primary coil 111 the WPT ground unit 110 generated, whereby a magnetic field (in particular a magnetic charging field) is induced. The magnetic charging field may have a frequency from a predefined charging field frequency range. The charging field frequency of the electromagnetic charging field can be in the range of 80-90 kHz (in particular at 85 kHz).

With sufficient magnetic coupling between primary coil 111 the primary unit 110 and secondary coil 121 the secondary unit 120 (ie with a sufficiently high coupling factor or degree of coupling) on the underside 130 is due to the magnetic field, a corresponding voltage and thus a current in the secondary coil 121 induced. The induced current in the secondary coil 121 the secondary unit 120 is through the rectifier of the secondary electronics 123 rectified and in energy storage 103 saved. Thus, electrical energy can wirelessly from a power supply to the energy storage 103 of the vehicle 100 be transmitted. The charging process can be in the vehicle 100 by a charging controller of the secondary electronics 123 being controlled. The charging control unit can be set up for this purpose, eg wirelessly (for example via WLAN), with the primary unit 110 to communicate.

The sink 111 . 121 a coil unit 110 . 120 , in particular a primary unit 110 or a secondary unit 120 , is typically exposed to relatively high magnetic flux densities. As a result, typically for a coil 111 . 121 Strands used with relatively thin individual wires, resulting in relatively high costs. Furthermore, by a coil 111 . 121 generates electromagnetic fields that are other components of a vehicle 100 can affect. Furthermore, defects can occur on a coil 111 . 121 typically not reliably detected.

The present document addresses the technical problem of providing a cost effective coil unit for an inductive charging system which has a reduced effect on adjacent (electrical and / or electronic) components and / or which allows reliable detection of defects.

The object is solved by the independent claim. Advantageous embodiments are described, inter alia, in the dependent claims. It should be noted that additional features of a claim dependent on an independent claim without the features of the independent claim or only in combination with a subset of the features of the independent claim may form a separate invention independent of the combination of all features of the independent claim, the subject of an independent claim, a divisional application or a subsequent application. This applies equally to technical teachings described in the specification, which is one of the Characteristics of the independent claims can form independent invention.

In one aspect, a coil unit (e.g., a primary unit or a secondary unit) for an inductive charging system is described. The inductive charging system can be designed to charge the energy store of an at least partially electrically driven vehicle, in particular a road motor vehicle.

The coil unit comprises a coil winding which is adapted to generate a magnetic field (in the case of a primary unit) in response to a coil current, or which is adapted to generate a coil current in response to a magnetic field (in the case of a secondary unit). In this case, the coil winding comprises at least one conductor which extends in a winding direction about a coil axis of the coil winding. The coil winding may e.g. forming a circular coil or a double D coil. The coil axis may extend along a transmission path of energy transfer from the primary coil to the secondary coil of an inductive charging system. The at least one conductor (e.g., a strand of a plurality of individual wires) may be wound several times in the winding direction about the spool axis.

In addition, the coil unit includes an electrically conductive shield (e.g., a metal shield) that at least partially encloses the coil winding. In particular, the shield can almost completely surround the coil winding. In this case, the screen can be arranged on the front side of the coil winding (the front side facing the transmission path of the inductive charging system). Furthermore, the screen can be arranged on the rear side of the coil winding (the rear side facing away from the transmission path of the inductive charging system). Further, the screen may extend laterally between the front and the back, both on the inside and on the outside of the coil winding. Thus, the screen can form a wrap around the coil winding.

In this case, however, the screen is designed to prevent a current and / or a closed current path within the screen, which rotates around the coil axis along the winding direction. In particular, the screen can be designed such that the sum current in the screen, which completely circumscribes the coil axis along the winding direction, is zero. Nevertheless, currents in the winding direction can occur in different areas of the screen. However, these currents in the different areas cancel each other out. In other words, the screen is designed such that no current can flow completely through the screen around the coil axis (and thus the screen itself would form a coil winding). In particular, the screen may comprise at least one electrically insulating break or separation point which interrupts the screen transversely to the winding direction. The at least one interruption may be e.g. are each formed by a gap separating the screen along a plane, e.g. perpendicular to the winding direction, separates. For example, a screen may be constructed of a plurality of electrically conductive wires (e.g., 5, 10, 20, 50, 100, 500, 1000 or more wires) each perpendicular to the winding direction and electrically insulated from each other. The wires can completely circulate the coil winding perpendicular to the winding direction. Thus, a purely electrical shielding can be provided, since no (significant) shielding currents are induced by the magnetic field in a screen composed of wires extending perpendicular to the winding direction. By using a plurality of wires, a particularly energy efficient screen can be provided.

By providing a shield, the maximum magnetic flux density of the magnetic field at the conductor of the coil winding can be reduced without substantially influencing the magnetic field at the respective other coil unit of the inductive charging system. As a result, the requirements for the conductors used for the coil winding can be reduced. In particular, individual wires with larger diameters may possibly be used. Thus, the cost of a coil unit can be reduced. Furthermore, the screen can be used for shielding electric fields, thus reducing requirements for EMC filters of the coil unit. Further, the use of a screen enables detection of a coil winding defect.

The shield typically has a first end on a first side of the break and a second end on a second side of the break. The two ends can be spatially separated by a gap. The gap may e.g. 2%, 1% or less of the Windungsumfangs the coil winding be wide.

The interruption may be such that current can not flow directly across the interruption between the first end and the second end. Further, the interruption may be such that current flowing on the first side of the interruption to the first end reverses its direction of flow at the first end and flows away again on the first side of the interruption from the first end. In a corresponding manner, a reversal of the Flow direction of the current within the screen done. It can thus reliably avoid the coil axis circulating current.

The current flowing to the first end may be reversed in a reverse region at the first end into a current flowing away from the first end. The coil winding may have a certain winding circumference, the winding circumference being e.g. the (possibly middle) length of the conductor corresponds to one turn of the coil winding. The reverse area at one end of the screen may extend over 5% or less of the winding circumference.

The reverse region may include a plurality of electrically isolated reversing conductors in which the flow is deflected from a direction of flow to the first end into a direction of flow away from the first end. The reversing conductors may be e.g. be punched out of the surface or from the sheet of the screen.

In this case, a reversing conductor may comprise an input into which current flowing to the first end flows into the reversing conductor. Furthermore, a reversing conductor may include an output from which current flowing away from the first end flows out of the reversing conductor. A reversing conductor can then change its direction of extension between the input and the output by more than 90 ° (in particular by approximately 180 °). For example, a reversing conductor between the input and the output U- or semicircle-shaped. The current in the screen can thus be redirected by the reversing conductors.

The reversing conductors can be arranged next to one another, with two directly adjacent reversing conductors being electrically insulated from each other by an insulating region. In this case, the plurality of reversing conductors may comprise an inner reversing conductor, which has the shortest length compared to the (especially in comparison to all) other reversing conductors. Furthermore, the plurality of reversing conductors may comprise an outer reversing conductor which has the longest length compared to the other reversing conductors (in particular in comparison to all).

By providing individual reversing conductors, the current flow in the reversing region can be distributed as evenly as possible. In particular, it can thus be avoided that relatively high current densities and relatively high ohmic losses occur at the first end of the screen. The second end of the screen may similarly comprise a plurality of reversing conductors.

Thus, the first end of the screen and the second end of the screen may each comprise a reversal region in which the direction of flow of the stream reverses. In this case, the reversal region of the first end and the reversal region of the second end may lie on one another and be electrically insulated from one another by an insulating layer. In particular, the reversal region of the first end and the reversal region of the second end may lie on one another such that the currents in the reversal regions on both sides of the insulating layer have the same direction of flow. The superposed reversal areas may extend along the coil axis or the superposed reversal areas may be bent, so that the superimposed reversal areas at least partially extend parallel to the coil winding. By stacking the reversal areas, the current densities at the ends of the screen can be further reduced.

The shield may be grounded and / or grounded, in particular to facilitate or enhance electrical shielding and / or fault diagnosis.

The shield may include a plurality of shield layers that are electrically isolated from each other. The shield layers can run substantially parallel to the front side, the inside, the back side and / or the outside of the coil winding. By providing several (relatively thin) shield layers, the shielding losses can be further reduced.

The magnetic field without a shield can have a magnetic field line with a field profile transverse to the winding direction, which extends at least partially around the coil winding. In a corresponding manner, the screen may have a screen course transversely to the winding direction, which runs at least partially around the coil winding. In this case, the screen course represents a cross section of the screen transversely to the winding direction. The screen course can have a smaller curvature above the coil winding or on the front side of the coil winding than the field profile. Thus, a reduction of the maximum flux density can be effected on the coil winding unfortunate.

The magnetic field without a shield may have a first maximum flux density in the immediate vicinity of the coil winding (in particular on the conductor of the coil winding) and a second average flux density at a specific distance from the coil winding (eg at the respective other coil unit of the inductive charging system). The screen may be formed such that the magnetic field in the immediate vicinity of the coil winding opposite the first maximum flux density has reduced maximum flux density, and that the magnetic field in the specific distance has an average flux density which substantially corresponds to the second average flux density. To provide such a screen, one or more parameters of the screen (in particular a shape or a cross-section of the screen, a material of the screen and / or a thickness of the screen) can be adapted within the scope of a simulation.

The coil unit may include electronics (e.g., an inverter or a rectifier) configured to provide the coil current to the coil winding (e.g., by means of an inverter) or to rectify the coil current from the coil winding (e.g., by means of a rectifier). The electronics may include a shield electrically coupled to the shield. Thus, a reliable electrical shielding of the entire coil unit can be effected.

The coil unit may include an isolation monitor configured to acquire information regarding a contact resistance between the coil winding and the screen. Based on the contact resistance, it is then possible to reliably detect a defect of the coil winding (due to, for example, a mechanical action).

The coil unit may comprise a coil core which is arranged on one side (in particular on the rear side) of the coil winding. The shield may then have a different shape on the coil core side (i.e., on the back side of the coil winding) than on the side of the coil winding (i.e. In particular, an adaptation to the course of the field lines of the magnetic field can take place on the two sides of the coil winding. Thus, the maximum magnetic flux density at the conductor of the coil winding can be further reduced.

According to a further aspect, an inductive charging system for charging an energy store is described. The charging system includes a primary unit having a primary coil configured to generate a magnetic field for transmitting energy. In addition, the charging system comprises a secondary unit with a secondary coil, which is set up to generate a current for charging the energy store in dependence on the magnetic field. The primary unit and / or the secondary unit may be constructed according to the coil unit described in this document.

According to a further aspect, a charging device is described (in particular for charging the energy accumulator of a vehicle), which comprises the primary unit described in this document.

In another aspect, a road vehicle (particularly a passenger car or a truck or a bus) is described that includes the secondary unit described in this document.

It should be understood that the methods, devices and systems described herein may be used alone as well as in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the methods, devices, and systems described herein may be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

• 1 beispielhafte Komponenten eines induktiven Ladesystems zum Laden des Energiespeichers eines Fahrzeugs;
• 2a bis 2c beispielhafte Spulen für ein induktives Ladesystem;
• 3a beispielhafte Feldlinien bei einer Spulenwicklung ohne Schirm;
• 3b beispielhafte Feldlinien bei einer Spulenwicklung mit Schirm;
• 3c ein beispielhaftes magnetisches Feld, das von den Wirbelströmen eines Schirms bewirkt wird;
• 4a einen beispielhaften Schirm in einer Draufsicht (von der Übertragungsstrecke) auf eine Spulenwicklung;
• 4b beispielhafte Ströme in dem Schirm einer Spulenwicklung;
• 4c einen beispielhaften Umkehrbereich des Schirms einer Spulenwicklung;
• 4d beispielhafte Umkehrbereiche eines Schirms;
• 5a eine beispielhafte Schirmung einer Spuleneinheit; und
• 5b eine beispielhafte Vorrichtung zur Erkennung eines Spulendefekts

Furthermore, the invention will be described in more detail with reference to exemplary embodiments. Show

• 1 exemplary components of an inductive charging system for charging the energy storage of a vehicle;
• 2a to 2c exemplary coils for an inductive charging system;
• 3a exemplary field lines in a coil winding without screen;
• 3b exemplary field lines in a coil winding with screen;
• 3c an exemplary magnetic field caused by the eddy currents of a screen;
• 4a an exemplary screen in a plan view (of the transmission path) on a coil winding;
• 4b exemplary currents in the screen of a coil winding;
• 4c an exemplary reverse region of the screen of a coil winding;
• 4d exemplary reverse regions of a screen;
• 5a an exemplary shield of a coil unit; and
• 5b an exemplary device for detecting a coil defect

As stated above, the present document is concerned with the provision of a cost effective primary unit 110 and / or secondary unit 120 for an inductive charging system, through the impairment of adjacent (electrical and / or electronic) components of a vehicle 100 can be reduced. In this context shows 2a an exemplary primary coil 111 and an exemplary secondary coil 121 , each one a coil core 200 , in particular a ferrite. The coil cores 200 are each formed flat to minimize the extent of the primary unit 110 or the secondary unit 120 in z-direction (ie along the underbody clearance 130 or along the magnetic transmission path of the inductive charging system). Through the primary coil 111 becomes a magnetic field 250 (also referred to in this document as charging field) causes that in the secondary coil 121 a power to charge an energy storage 103 causes.

2 B shows a coil winding 210 (eg the primary coil 111 or the secondary coil 121 ) in a side view. The coil core 200 is typically in relation to the transmission path of the inductive charging system on the back of the coil winding 210 arranged. The coil winding 210 typically includes a plurality of turns of an electrically conductive conductor 211 on. In this case, the conductor 211 be designed as a strand with a plurality of insulated individual wires. The sink 111 . 121 can be used for underbody clearance 130 or to the transmission line out with a cover 220 be covered. 2c shows a plan view of the coil winding 210 and the spool core 200 from the direction of the transmission line.

Due to the locally occurring, relatively high flux densities of the magnetic field 250 within the conductor 211 the coil winding 210 , be as a leader 211 typically uses RF (Radio Frequency) strands with relatively small, mutually insulated strands to account for the displacement effects such as the skin effect, the internal proximity effect, and the external proximity effect in combination. At a transmission frequency of 85kHz, single wires with diameters in the range between 0.05 and 0.1mm are typically used. These diameters are significantly lower than would be required due to the skin effect with a penetration depth> 0.2 mm (for copper). If only the skin effect caused by the alternating current had to be considered, wire diameters of> 0.4 mm would be possible for the insulated individual wires.

However, due to the relatively high flux densities and the resulting proximity effect, single wires with 10 times smaller diameters are required. To a leader 211 Because of the relatively high flux densities, typically 100 times more single wires are used than would be required due to the skin effect. The cost of the individual wires of an HF strand typically increases with decreasing cross section. In addition, the number of required individual wires for a given cross-section or for a given current density increases. Consequently, the relatively high flux densities lead to relatively high costs for the conductor 211 and the coil winding 210 a coil unit 110 . 120 ,

Furthermore, the coils can 111 . 121 an inductive charging system are typically not shielded and therefore act as an "emission element" for electromagnetic fields. In particular, on the coils 111 . 121 no electrical fields are attenuated via an electrically conductive shielding. Therefore, typically expensive EMC filters in electronics 113 . 123 a coil unit 110 . 120 used to restrain interfering frequencies. Possible sources of interference are electronic circuits in electronics 113 . 123 a coil unit 110 . 120 and / or other faults that occur via the leads to the electronics 113 . 123 be coupled into the inductive charging system.

Further, typically on a coil 111 . 121 , in particular on a coil winding 210 , no defect can be detected, especially since no insulation injury to a (grounded) housing can be detected.

3a shows an exemplary course of the field lines 350 a magnetic field 250 around the ladder 211 a coil winding 210 , How out 3a visible, cross the field lines 350 the different turns of the conductor 211 , Further shows 3b an exemplary, interrupted screen 300 , the coil winding 210 surrounds. The screen 300 can the coil winding 210 enclose almost completely. In particular, the umbrella can 300 a nearly closed shell around the coil winding 210 form. On the other hand, the screen has 300 in at least one place an interruption 301 on, allowing a flow of current within the screen 300 in the winding direction 331 is prevented. The winding direction 331 runs around the coil axis 332 the coil winding 210 around.

Such a screen 300 allows that continues to have a magnetic field 250 outside the screen 300 exists, but that the field lines 350 of the magnetic field 250 in the immediate vicinity of the screen 300 (both on the inside and on the outside of the screen 300 ) parallel to the surface of the screen 300 run. So, depending on the shape of the umbrella 300 causes the field lines 350 of the magnetic field 250 not the leader 211 cross. Furthermore, the maxima of the magnetic flux density can be reduced so that the cost of the conductors 211 can be reduced.

3c illustrates the (vortex) flows 311 . 312 that in the screen 300 be effected. The streams 311 . 312 flow in different places of the screen 300 in different directions. In particular, the electricity 312 on the sides of the front side or the back side of the coil winding 210 in a first direction and the current 311 in a central region of the front side or the rear side of the coil winding 210 to flow in an opposite second direction. The reversal of the flow direction of the flow, 311, 312 is thereby by the interruption 301 of the screen 300 causes. Through the streams 311 . 312 in the screen 300 becomes a compensating magnetic field 351 causes that to interfere with the magnetic field 250 the coil winding 210 superimposed, so that an effective magnetic field with the in 3b illustrated field lines 350 results.

4a shows a coil winding 210 with a screen 300 , The screen 300 encloses the coil winding 210 almost complete. This shows the screen 300 but at least one place a break 301 on, by which a current flow along the winding direction 331 is interrupted. In particular, no electricity 311 . 312 directly from the first page of the interruption 301 on the second page of the interruption 302 flow. By the electrical interruption 301 thus becomes a closed conductor loop along the winding direction 311 avoided. As a result of the interruption 301 takes place at the interruption 301 a reversal of the flow direction of the stream 311 . 312 ,

4b illustrates the "unfolded" or "unfolded" screen 300 with the interruption 301 , As in 3b illustrated, the screen encloses 300 both the front and the back of the coil winding 210 , The screen 300 thus has a front side 302 and a back 303 on that in 4b are shown side by side (the areas of the screen 300 for the inside and the outside of the coil winding 210 were each proportionately the front 302 and the back 303 of the screen 300 assigned). The front 302 of the screen 300 points as in 3c shown, two segments 321 . 322 on. In the same way, also the back 303 of the screen 300 two segments 323 . 324 on. In every segment 321 . 322 . 323 . 324 In each case, a current flow in the first flow direction (shown in FIG 3c by a point) and in the opposite second flow direction (shown in FIG 3c through a cross). The reversal of the flow direction of the stream 311 . 312 within a segment 321 . 322 . 323 . 324 takes place at the interruption 301 of the screen 300 ,

In the reversal area 304 at the break 301 of the screen 300 For example, relatively high current densities can occur, which in turn can lead to relatively high ohmic losses. 4c shows a reversal area 304 the back 303 a screen 300 , The end 307 of the screen 300 before the break 301 is in a single reversal ladder 305 split the electricity 312 . 311 when reversing the flow direction. Here are the reversal ladder 305 nested in such a way that an internal first reversing conductor 305 from a longer second reversing conductor 305 surrounded, in turn, by a longer third reversing conductor 305 handle, etc. until an external reversal conductor 305 all other reversal leaders 305 surrounds. The outer reversal conductor 305 borders on the interruption 301 on. The distance to the interruption 301 rising continuously from the outer reversing conductor 305 to the inner first reversing conductor 305 on. Like from the 4c and 4b Obviously, both have the back 303 as well as the front 302 two such arrangements of reversing conductors 305 on.

As a result of such an arrangement of the reversing conductors 305 there is a split of the electricity 311 . 312 in the reversal area 304 on different reversal conductors 305 , so the maximum current density at the ends 307 of the screen 300 near the break 301 can be reduced.

The two ends 307 of the screen 300 at the break 301 can, as in 4d represented, one above the other and through an insulating layer 308 be electrically isolated from each other. It can be the two ends 307 perpendicular to the coil winding 210 parallel to the coil axis 332 stand (as on the left side of 4d shown). Alternatively, the superimposed, electrically isolated ends 307 to the coil winding 210 bent to the space required by the screen 300 at the break 301 to reduce (as on the right side of 4d shown).

At the end 307 the shield 300 can thus at the separation point or the interruption 301 Stamping be made so that individual reversing conductors or reverse wires 305 arise, which lead the different "current paths" to the corresponding return current path. The reversal ladder 305 can be bent up, leaving the reversal ladder 305 the two ends 307 the shield 300 at the break 301 electrically isolated from each other can be arranged. The screen 300 can thus with an insulation layer 308 be pushed together. The current-carrying reversing conductors 305 the two ends 307 then lie directly, electrically isolated to each other when the reversing conductors 305 the two ends 307 each produced with mirrored symmetry (in particular punched) are.

Because the current flows in opposite reverse conductors 305 the two ends 307 of the screen 300 at the break 301 Opposite and equal, the symmetrical current flow is supported and the associated magnetic fields compensate each other locally. The opposite the shielding 300 standing upside down conductor 305 can be bent on one or in pairs on different sides to a flat construction of the coil winding 210 maintain.

The coil winding 210 a primary coil 111 and / or a secondary coil 121 can thus with a suitably designed, electrically conductive (especially metallic) screen 300 be wrapped, with this umbrella 300 along the winding direction 331 is interrupted at least at one point and thus no closed turn along the winding direction 331 the coil winding 210 formed. The screen 300 can be designed such that there is a reduced and homogeneous magnetic field 250 in the coil winding area 210 results. Furthermore, the umbrella 300 be formed such that in the screen 300 As small as possible current densities occur, which are distributed over the surface to reduce ohmic losses. The shape and / or thickness of the shade 300 and / or the distance of the screen 300 to the coil winding 210 can be adjusted so that the lowest possible current densities and thus losses in the screen 300 occur. This can be achieved, for example, by using the largest possible radii. Furthermore, this can be achieved by having the umbrella 300 as parallel as possible to the original field course of the field lines 350 runs.

The screen 300 can be grounded at least one place, so that the screen 300 can be used as a shield against the emission of electric fields. 5a shows a grounded screen 300 , Further shows 5a a shield 502 for the electronics 113 . 123 a coil unit (eg a primary unit 110 or a secondary unit 120 ) as well as a shielding 501 for a line 112 . 122 between a coil 111 . 121 and the electronics 113 . 123 , It can thus efficiently complete a complete shielding of a coil unit 110 . 120 to be provided.

Through a double or multi-walled screen 300 can the electricity 311 . 312 be distributed to a plurality of shield levels or shield layers to change the field line profile in order to reduce the resulting ohmic screen losses. In particular, a screen 300 a plurality of shielding planes or shield layers or shield layers have, which are electrically isolated from each other. Each of the shield layers can be the coil winding 210 enclose. A screen 300 can thus be made up of several isolated layers or layers in order to reduce the ohmic screen losses.

Furthermore, a screen 300 be used with a relatively low total thickness to reduce screen losses. In particular, the thickness of the umbrella 300 1%, 0.5% or less of the winding amount of the coil winding 210 his.

The separation point or the interruption 301 of the screen (along the winding direction 331 ) can be designed to support "current reversal". In particular, the ends can 307 of the screen 300 at the break 301 into individual reversal conductors 305 be divided to a reversal of the flow direction of the stream 311 . 312 at the break 301 to effect. The ideal current flow in the screen 301 can thus by the separation point or the interruption 301 are only slightly affected.

When using a screen 300 can be an isolation monitor 510 between the coil winding 210 and the surrounding screen 300 used to damage the insulation of the coil winding 210 to detect. This is exemplary in 5b shown. In particular, an insulation monitor 510 the resistance between a coil 111 . 121 and measure ground (eg via series resistors 511 ). An electrically conductive contact between the coil caused by a defect 111 . 121 and the (grounded) screen 300 can then through the insulation guard 510 be detected. In particular, damage, eg by falling rocks on the subsoil or by crossing the primary coil 111 be detected by detecting an insulation fault.

A coil 111 . 121 typically has on one side of the coil winding 210 a coil core 200 on. The shape of the screen 300 can with regard to the unilaterally mounted coil core 200 be optimized. In particular, the bending radius of the screen 300 be reduced in places with relatively high current densities. For multi-walled umbrellas 300 In particular, the shape of the one or more outer shield layers can be adapted.

By the measures described in this document, the maximum magnetic flux density, in particular at the edge of a coil winding 210 be reduced. This makes the proximity effect in these areas of the coil winding 210 reduced. As a consequence, with unchanged losses, a larger cross section of the individual wires or wires in the strand 211 the coil winding 210 be used. Furthermore, the distribution of the individual wires of a stranded wire 211 be simplified because of the measures described the field profile of the field lines 350 in the coil winding area 210 has a higher uniformity. Alternatively, with the same cross section of the individual wires, the losses of a coil unit 110 . 120 be reduced. It can thus be an optimization in terms of cost and energy losses.

If a coil 111 . 121 through a conductive and grounded screen 300 This screen can 300 be used for suppression of electric fields. This is particularly advantageous for damping disturbances of the inductive charging system by other consumers (eg by the drive electronics of a vehicle 100 ). The interference of other consumers can be affected by the secondary electronics 123 through to the secondary coil 121 impress. This can also be an inactive inductive charging system while driving a vehicle 100 respectively. The described sheath of the secondary coil 121 can then replace or at least reduce other measures such as EMC filters and / or defeat devices. Furthermore, by the sheathing of the secondary coil 121 with a conductive, grounded screen 300 the emission of high-frequency electrical interference fields, eg by the rectifier electronics of the secondary unit 120 be generated, reduced.

By using a screen 300 becomes the impedance of the wrapped coil 111 . 121 reduced. In doing so, the umbrella can 300 be formed such that the magnetic flux in the immediate vicinity of the coil winding 210 reduced, but further away (especially at the other coil) 111 . 121 ) remains essentially unchanged. This has the positive effect of increasing the inductance of the considered coil 111 . 121 more reduced than the coupled inductance (coupling factor). Thus, a given power can be transmitted with a reduced primary coil current. This leads to reduced reactive power and thus to reduced demands on the electronics 113 . 123 and to the coils 111 . 121 a coil unit 110 . 120 ,

Furthermore, the described measures make it possible to damage a coil in an efficient and reliable manner 111 . 121 to detect, as in case of damage to the coil 111 . 121 with high probability over the screen 300 a violation of the insulation resistance is effected.

The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended to illustrate only the principle of the proposed methods, apparatus and systems.

Claims (18)

Coil unit (110, 120) for an inductive charging system; the coil unit (110, 120) comprising a coil winding (210) arranged to generate a magnetic field (250) in response to a coil current, or adapted to generate a coil current in response to a magnetic field (250); wherein the coil winding (210) comprises a conductor (211) extending in a winding direction (331) about a coil axis (332) of the coil winding (210); and - An electrically conductive screen (300) which surrounds the coil winding (210) at least partially; wherein the screen (300) is adapted to inhibit a current path within the screen (300) completely circulating the coil axis (332) along the winding direction (331). Coil unit (110, 120) according to Claim 1 in that the screen (300) comprises at least one electrically insulating break (301) which interrupts the screen (300) transversely to the winding direction (331). Coil unit (110, 120) according to Claim 2 wherein: the screen (300) includes a first end (307) on a first side of the interruption (301) and a second end (307) on a second side of the interruption (301); and - the interruption (301) is such that current (311, 312) can not flow directly across the interrupt (301) between the first end (307) and the second end (307); and / or - the interruption (301) is such that on the first side of the interruption (301) stream (312) flowing to the first end (307) at the first end (307) reverses its direction of flow and again on the first side the interruption (301) flows away from the first end (307). Coil unit (110, 120) according to one of Claims 2 to 3 in which - the interruption (301) is designed in such a way that a current (312) flowing to the first end (307) in a reversal region (304) at the first end (307) flows into a current flowing away from the first end (307) ( 311) is reversed; and - said inversion region (304) comprises a plurality of electrically isolated return conductors (305) in which said flow (312, 311) deflects from a flow direction flowing to said first end (307) in a flow direction away from said first end (307) becomes. Coil unit (110, 120) according to Claim 4 in which - a reversing conductor (305) comprises an input into which current (312) flowing to the first end (307) flows into the reversing conductor (305); and - a reversing conductor (305) comprises an output from which current (312) flowing away from the first end (307) flows out of the reversing conductor (305); and - a reversing conductor (305) between the input and the output changes its direction of extension by more than 90 °; and / or - a reversing conductor (305) between the input and the output U- or semi-circular runs. Coil unit (110, 120) according to one of Claims 4 to 5 in which - the reversing conductors (305) are arranged side by side; and / or - the plurality of return conductors (305) comprise an inner reversing conductor (305) having the shortest length compared to the other inverting conductors (305); and / or - the plurality of return conductors (305) comprise an outer return conductor (305) having the longest length compared to the other reverse conductors (305); and / or - two directly adjacent reversing conductors (305) are electrically insulated from each other by an isolation region. Coil unit (110, 120) according to one of Claims 4 to 6 wherein the reversing conductors (305) have been punched out of a face of the screen (300). Coil unit (110, 120) according to one of Claims 3 to 7 wherein: - the first end (307) of the screen (300) and the second end (307) of the screen (300) each comprise a reversal region (304) in which a flow direction of the stream (311, 312) reverses; and - the reversal region (304) of the first end (307) and the reversal region (304) of the second end (307) are superposed and electrically insulated from each other by an insulating layer (308). Coil unit (110, 120) according to Claim 8 wherein the reversal region (304) of the first end (307) and the reversal region (304) of the second end (307) are superimposed such that the streams (311, 312) in the reversal regions (204) on both sides of the insulating layer (308) have the same flow direction. Coil unit (110, 120) according to one of Claims 8 to 9 wherein: - the superposed reverse regions (304) extend along the spool axis (332); or - the mutually opposite turning regions (304) are bent, so that the mutually superposed return regions (304) extend at least partially parallel to the coil winding (210). A coil unit (110, 120) according to any one of the preceding claims, wherein the screen (300) is grounded. A coil unit (110, 120) according to any one of the preceding claims, wherein the screen (300) comprises a plurality of shield layers electrically isolated from each other. Coil unit (110, 120) according to one of the preceding claims, wherein - The magnetic field (250) without screen (300) has a magnetic field line (350) with a field transverse to the winding direction (331) which extends at least partially around the coil winding (210); - The screen (300) has a Schirmverlauf transverse to the winding direction (331) which extends at least partially around the coil winding (210); and - The screen path above the coil winding (210) has a smaller curvature than the field profile. Coil unit (110, 120) according to one of the preceding claims, wherein - The magnetic field (250) without screen (300) in close proximity to the coil winding (210) has a first maximum flux density and at a certain distance from the coil winding (210) has a second average flux density; and - The screen (300) is formed such that the magnetic field (250) in the immediate vicinity of the coil winding (210) has a relation to the first maximum flux density reduced flux density, and that the magnetic field (250) at the predetermined distance has a flux density, which substantially corresponds to the second average flux density. Coil unit (110, 120) according to one of the preceding claims, wherein - the coil unit (110, 120) comprises electronics (113, 123) arranged to provide the coil current for the coil winding (210) or to rectify the coil current (210) from the coil winding (210); and - The electronics (113, 123) comprises a shield (501, 502) which is electrically conductively coupled to the screen (300). Coil unit (110, 120) according to one of the preceding claims, wherein the coil unit (110, 120) comprises an isolation monitor (510) arranged to detect information regarding a contact resistance between the coil winding (210) and the screen (300). Coil unit (110, 120) according to one of the preceding claims, wherein - The coil unit (110, 120) comprises a coil core (200) which is arranged on one side of the coil winding (210); - The screen (300) on the coil core (200) facing side of the coil winding (210) has a different shape than on the side facing the bobbin (200) side of the coil winding (210). Inductive charging system for charging an energy store (103); wherein the charging system comprises, a primary unit (110) having a primary coil (111) arranged to generate a magnetic field (250) for transmitting energy; a secondary unit (120) having a secondary coil (121) arranged to generate a current for charging the energy store (103) in response to the magnetic field (250); wherein the primary unit (110) and / or the secondary unit (120) are constructed in accordance with the coil unit (110, 120) of one of the preceding claims.

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