Secondary coil unit with a service opening

Abstract

Secondary coil unit (210) for a vehicle (100), wherein the secondary coil unit (210) comprises, - a housing (211, 212) with a lid (301) that can be removed from the housing (211, 212); and - a secondary coil (121) arranged in the housing (211, 212) which encloses a core area (221); wherein the cover (301) and the housing (211, 212) are designed such that by removing the cover (301) from the housing (211, 212) an opening is created in the core area (221) through the secondary coil unit (210); wherein the opening is designed such that, in the installed state of the secondary coil unit (210), the opening allows access to one or more components (202) on an area of ​​an underbody of the vehicle (100) covered by the secondary coil unit (210).

Description

[0001] The invention relates to a charging coil for the inductive charging of an electrical energy storage device of a motor vehicle.

[0002] Electric vehicles typically have a battery that stores electrical energy to power the vehicle's electric motor. The vehicle's battery can be recharged using electrical energy from the power grid. For this purpose, the battery is connected to the power grid to transfer electrical energy from the grid to the vehicle's battery. This connection can be wired (via a charging cable) and / or wireless (using inductive coupling between a charging station and the vehicle).

[0003] One approach to automatic, wireless, inductive charging of the vehicle's battery involves transferring electrical energy from the ground to the vehicle's underbody via magnetic induction across the underbody clearance. This is exemplified in Fig. 1 shown. In particular, it shows Fig. 1. A vehicle 100 with an electrical energy storage device 103 (e.g., a rechargeable battery 103). The vehicle 100 includes a secondary coil 121 on the vehicle underbody, the secondary coil 121 being connected to the electrical energy storage device 103 via an impedance matching device (not shown) and a rectifier 101. The secondary coil 121 is typically part of a so-called "Wireless Power Transfer" (WPT) vehicle unit 120.

[0004] The secondary coil 121 of the WPT vehicle unit 120 can be positioned above a primary coil 111, the primary coil 111 being, for example, mounted on the floor of a garage. The primary coil 111 is typically part of a so-called WPT ground unit 110. The primary coil 111 is connected to a power supply 113. The power supply 113 can include a radio frequency generator or inverter that generates an AC (alternating current) current in the primary coil of the WPT ground unit 110, thereby inducing a magnetic field (in particular, an electromagnetic charging field). The electromagnetic charging field can have 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, 85 kHz).

[0005] With sufficient magnetic coupling between the primary coil 111 of the WPT ground unit 110 and the secondary coil 121 of the WPT vehicle unit 120 via the underbody clearance 130, a corresponding voltage and thus also a current is induced in the secondary coil 121 by the magnetic field. The induced current in the secondary coil 121 of the WPT vehicle unit 120 is rectified by the rectifier 101 and stored in the energy storage device 103. In this way, electrical energy can be transferred wirelessly from the power supply 113 to the energy storage device 103 of the vehicle 100. The charging process can be controlled in the vehicle 100 by a charging control unit 105. The charging control unit 105 can be configured for this purpose, e.g., wirelessly, to communicate with the WPT ground unit 110.

[0006] The secondary coil 121 is typically installed in a housing and covers a relatively large area on the underbody of a vehicle 100. The space requirement of a secondary coil 121 typically increases with increasing charging power and / or with increasing underbody clearance 130.

[0007] US 5,264,776 A describes an inductive charging interface for a vehicle. DE 10 2005 029 599 B3 describes a system for contactless energy transfer. EP 2 891 575 A1 describes a transformer element for an inductive energy transfer system.

[0008] This document addresses the technical challenge of efficiently integrating large-area secondary coils 121 into a vehicle 100 (e.g., for high charging capacities). The aim is to provide these large-area secondary coils 121 in such a way as to minimize any impairment of other vehicle functions, and especially access to other vehicle components.

[0009] The problem is solved by the independent claims. Advantageous embodiments are described, among other things, in the dependent claims.

[0010] According to one aspect, a secondary coil unit for a vehicle is described. The secondary coil unit can be used, in particular, to receive electrical energy via a charging field for charging an electrical energy storage device of the vehicle. The secondary coil unit can, for example, be part of the WPT vehicle unit of a vehicle. Specifically, the secondary coil unit can be mounted on the underbody of the vehicle and connected to a rectifier of the WPT vehicle unit via a connecting cable.

[0011] The secondary coil unit comprises a housing with a removable cover. It also includes a secondary coil located within the housing, which encloses a core area. The cover and housing are designed such that removing the cover from the housing creates an opening through the secondary coil unit. This opening, when the secondary coil unit is installed, provides access to one or more components (e.g., an oil pan) in an area of ​​the vehicle's underbody covered by the secondary coil unit.

[0012] The secondary coil unit thus enables efficient access to components on the underbody of a vehicle. The cover typically does not contain any electrical and / or current-carrying elements, as these are usually located outside the core area. This allows for safe access to components on the underbody of a vehicle. Furthermore, providing such an opening within a secondary coil unit enables the use of secondary coils that cover a relatively large area on the underbody of a vehicle. This opening thus allows the use of large-area secondary coils, for example, to increase the charging power of an inductive charging system.

[0013] The cover can include a cover layer made of a coil core material. This core material typically comprises one or more ferromagnetic or ferrimagnetic materials (especially ferrite). The cover layer can thus contribute to the field line guidance of the charging field. This cover layer can extend at least partially into the core area if the cover is attached to the housing. The cover layer can increase the inductance of the secondary coil and the coupling degree with a primary coil, thereby enabling higher charging power.

[0014] The secondary coil assembly can comprise a housing layer made of a coil core material, the coil core material typically comprising one or more ferromagnetic or ferrimagnetic materials. The housing layer is located within the housing of the secondary coil assembly (and not in the cover of the secondary coil assembly). In particular, the housing layer can be fixed to the secondary coil. The housing layer can cover at least one side (in particular the top side, i.e., the side facing away from the primary coil) of the secondary coil, the housing layer having an opening in the core region. The housing layer can extend over a surface perpendicular to a longitudinal axis of the secondary coil. The housing layer can further increase the inductance of the secondary coil.

[0015] The housing layer and the cover layer can be designed such that they partially overlap when the cover is attached to the housing. This overlap can reduce the magnetic resistance between the housing and cover layers, thereby enabling a higher degree of coupling between the secondary and primary coils.

[0016] The casing layer can be divided into a multitude of segments, each separated by a gap. This is advantageous because segmenting the casing layer prevents damage to the casing layer due to mechanical stress. Alternatively, the cover layer can be continuous and not segmented. The magnetic flux in the individual segments of the casing layer can then be combined by the cover layer, which is advantageous with respect to the coupling degree of the secondary coil to the primary coil.

[0017] The housing can include a first protective layer, and the cover can include a second protective layer. These protective layers are located on the side of the secondary coil unit that faces away from the vehicle when the unit is installed. The protective layers thus shield the secondary coil unit from stone chips and / or other mechanical stresses that may originate from the road surface. The protective layers can be made of a composite material or a fiber-reinforced plastic (e.g., a polymer fiber-reinforced, glass fiber-reinforced, or aramid fiber-containing plastic).

[0018] Due to the provision of a separate cover that can be detached from the secondary coil assembly housing, the second protective layer can be made thinner than the first. In particular, a higher probability of damage to the cover can be accepted, since a damaged cover (unlike an entire secondary coil assembly) can be replaced cost-effectively. The use of a relatively thin second protective layer allows a ferromagnetic or ferrimagnetic cover layer to be positioned as close as possible to a primary coil, thus achieving a high degree of coupling.

[0019] The lid and housing may include fastening means by which the lid can be (removably) locked or attached to the housing. These fastening means may include, for example, a screw connection and / or, preferably, a bayonet fitting.

[0020] The secondary coil can, for example, include a circular coil (with one core area) and / or a double-D coil (with two core areas).

[0021] The secondary coil unit typically has a planar extension along a surface that, when the secondary coil unit is installed, runs parallel to the vehicle's underbody (and perpendicular to the longitudinal axis of the secondary coil). Field lines of a magnetic field in the core area can then run perpendicular to this surface (and parallel to the longitudinal axis of the secondary coil).

[0022] According to another aspect, an (inductive) charging device (e.g., a WPT vehicle unit) for a vehicle is described. The charging device includes a secondary coil unit described in this document. Furthermore, the charging device includes a control unit (e.g., a charging control unit) configured to determine whether the cover of the secondary coil unit is attached to the housing. The control unit can, in particular, be configured to determine an indication of the inductance of the secondary coil of the secondary coil unit. It can then be determined, based on this inductance indication, whether the cover of the secondary coil unit is attached to the housing.

[0023] The control unit can also be configured to inform the vehicle user that the secondary coil unit cover is not attached to the housing. This can prevent damage to the secondary coil unit during driving and / or reduced charging performance during charging.

[0024] According to another aspect, a motor vehicle (in particular a road vehicle, e.g. a passenger car, a truck or a motorcycle) is described that includes the secondary coil unit described in this document.

[0025] It should be noted that the devices and systems described in this document can be used both alone and in combination with other devices and systems described in this document. Furthermore, any aspect of the devices and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.

[0026] The invention will now be described in more detail using exemplary embodiments. Fig. 1 exemplary components of an inductive charging system; Fig. 2a an exemplary arrangement of a secondary coil unit on the underbody of a vehicle; Fig. 2b an exemplary secondary coil unit in a side view; Fig. 2c an exemplary secondary coil unit in a top view; Fig. 3a An exemplary secondary coil unit with removable cover in a side view; Fig. 3b an exemplary secondary coil unit with removable cover in a top view; Fig. 3c an exemplary secondary coil unit with a cover having an extended coil core or with an extended cover layer made of coil core material (e.g. ferrite); and Fig. Figure 3d shows an exemplary secondary coil unit with a segmented coil core.

[0027] As stated at the outset, this document deals with the provision of large-area secondary coils 121 for an inductive charging system for charging the energy storage device 103 of a vehicle 100. Fig. Figure 2a shows an exemplary arrangement of a secondary coil unit 210 (with a secondary coil 121) on the underbody of a vehicle 100. The secondary coil unit 210 is typically attached to one or more supports of the vehicle 100 by means of fasteners 203. Furthermore, the secondary coil unit 210 is typically coupled to the rectifier 101 via a connecting cable 204.

[0028] In the illustrated example, the secondary coil unit 210 obscures the drain 202 of an oil pan 201 of the vehicle 100. Such a situation can occur particularly in hybrid vehicles that have both an internal combustion engine and an electric motor to power the vehicle 100. To allow access to the drain 202 (e.g., for an oil change), the secondary coil unit 210 must be removed. This is typically a time-consuming process. Furthermore, the removal process can damage a plug connection between the secondary coil unit 210 and the connecting cable 204. Additionally, due to potential voltages on the connecting cable 204, strict safety precautions must typically be taken during removal.

[0029] A large secondary coil unit 210 thus makes it more difficult to access components 201, 202 of the vehicle 100, which are obscured by the secondary coil unit 210. To limit this problem, the size of the secondary coil unit 210 can be limited, but this will limit the maximum possible charging power of the inductive charging system.

[0030] Fig. Figure 2b shows an exemplary structure of a secondary coil unit 210 in a side view. The secondary coil unit 210 comprises the secondary coil 121, a housing layer 213 made of a ferromagnetic or ferrimagnetic material (e.g., ferrite), and a housing 212, 211 (e.g., with a stabilizing housing back wall 212 and a protective cover or protective layer 211). As shown in Figure 2b, the secondary coil unit 210 comprises the secondary coil 121, a housing layer 213 made of a ferromagnetic or ferrimagnetic material (e.g., ferrite), and a housing 212, 211 (e.g., with a stabilizing housing back wall 212 and a protective cover or protective layer 211). Fig. As can be seen in Figure 2c, a circular or, if applicable, a double-D secondary coil 121 is typically used, which allows for the construction of a relatively flat secondary coil 121. Both coil types enclose at least one core area 221 (two core areas in the case of a double-D secondary coil 121), which is typically filled with a ferromagnetic or ferrimagnetic material to enable the highest possible degree of coupling to the primary coil 111.

[0031] The core area 221 of the secondary coil unit 210, which is enclosed by the (optionally circular) secondary coil 121, can be efficiently used to provide an opening in the secondary coil unit 210. This opening allows access to concealed components 201, 202 of the vehicle 100 without having to disassemble the secondary coil unit 210. Providing such an opening thus makes it possible to use large-area secondary coil units 210 (which enable high charging power) while still ensuring easy access to the concealed components 201, 202 of the vehicle 100.

[0032] Fig. Figure 3a shows an exemplary secondary coil unit 210 with a removable cover 301 in a sectional side view. The removable cover 301 comprises a cover layer 305 with a (ferromagnetic or ferrimagnetic) coil core material to enable the highest possible degree of coupling with the primary coil 111. The cover 301 thus (at least partially) assumes the function of the ferromagnetic or ferrimagnetic housing layer 213 of the secondary coil unit 210. The cover layer 305 of the cover 301 is preferably in contact with the (remaining) housing layer 213 of the secondary coil unit 210. In particular, a transition 302 between the cover layer 305 of the cover 301 and the housing layer 213 of the secondary coil unit 210 has the largest possible overlap and the smallest possible distance, so that the magnetic resistance at the transition 302 is as low as possible.

[0033] The cover 301 can be locked to the housing 211, 212 of the secondary coil unit 210 by means of a suitable fastening 303 (e.g., a bayonet fitting and / or a screw connection). In the closed state, the secondary coil unit 210 with cover 301 exhibits virtually the same properties with regard to inductive charging as a secondary coil unit 210 without cover 301. On the other hand, the cover 301 allows easy access to components 201, 202 of the vehicle 100 that are concealed by the secondary coil unit 210. This is particularly important because Fig. Figure 3b shows a secondary coil unit 210 with cover 301 in a top view.

[0034] The cover 301 can consist largely of a ferromagnetic or ferrimagnetic cover layer 305. Stabilization of the cover 301 can be achieved using relatively thin materials (e.g., composite materials). In other words, the cover 301 can have a relatively thin protective layer 306. Extensive protection of the cover 301 is not required, unlike the rest of the secondary coil unit 210, since a defective cover 301 can be replaced relatively cost-effectively if necessary. This allows (as in Fig. 3c), to bring the ferromagnetic or ferrimagnetic cover layer 305 of the cover 301 closer to the primary coil 111 (compared to a secondary coil unit 210 without cover 301), so that the coupling degree and thus the maximum charging power can be increased.

[0035] Furthermore, the use of a cover 301 enables the segmentation of the ferromagnetic or ferrimagnetic housing layer 213 into separate ferromagnetic or ferrimagnetic segments 313. The magnetic flux in the individual segments 313 can be combined by the (non-segmented) cover 301. By segmenting the ferromagnetic or ferrimagnetic housing layer 213, fractures of the typically brittle ferromagnetic or ferrimagnetic material can be avoided.

[0036] The charging control unit 105 can be configured to determine whether the cover 301 is attached to the secondary coil unit 210 or not. This allows a notification to be displayed to the vehicle 100 user if the secondary coil unit 210 is not closed with the cover 301, and consequently, if there is a risk of damage to the secondary coil unit 210 (during driving) or a reduced coupling degree and / or reduced charging power (during charging). For this purpose, the vehicle 100 can have means by which the inductance of the secondary coil 121 can be measured. For example, a resonant frequency of the resonant circuit of the WPT vehicle unit 120, which includes the secondary coil 121, can be determined. The inductance of the secondary coil 121 can then be determined from the resonant frequency.If the measured inductance is below a predefined inductance threshold, it can be concluded that the cover 301 is not located on the secondary coil unit 210. This measurement can also be performed without the primary coil 111 (e.g., during operation).

[0037] Alternatively, one or more transmission parameters for a charging process can be determined during charging operation (e.g., a charging field frequency that maximizes charging power). Based on these transmission parameters, it can then be determined whether the cover 301 is positioned on the secondary coil unit 210.

[0038] A secondary coil unit 210 with a service opening is described. The service opening is provided in a core area 221 of the secondary coil unit 210, which contains no current-carrying parts. Thus, the service opening can be provided in a cost-effective manner. A cover 301 is provided in the inner part of the secondary coil unit 210 (i.e., in the core area 221 of the secondary coil 121). The cover 301 comprises only one or more ferromagnetic or ferrimagnetic materials (e.g., ferrites) and a housing or protective layer for stabilization. The cover 301 typically does not include any electrical parts of the secondary coil unit 210.

[0039] As already explained, the cover 301 can be fastened 303 by a bayonet fitting and / or a screw connection. To optimize the field flux in the secondary coil unit 201, the ferromagnetic or ferrimagnetic materials of the cover 301 and the housing 211, 212 of the secondary coil unit 210 are provided with the widest possible overlap 302. The ferromagnetic or ferrimagnetic material of the cover 301 can extend into a region below the secondary coil 121, so that the magnetic distance between the secondary coil unit 210 (with cover 301) and a primary coil 111 can be reduced.

[0040] The cover 301 and, if applicable, the secondary coil unit 210 can be laminated in composite materials. This allows for compact stabilization and protection against mechanical impacts.

[0041] A diagnostic function can be provided (e.g., by the charging control unit 104) that uses the inductance values ​​of the coils 111, 121 of the charging system (especially the secondary coil 121) to detect whether the cover 301 is present or not. For this purpose, coil parameters can be monitored. This can also be done on the vehicle side even without a primary coil 111 being present. The cover status can be diagnosed during charging by monitoring the charging parameters or transmission parameters. Alternatively or additionally, a separate sensor can be provided for cover diagnostics that directly detects whether the cover 301 is attached to the housing 211, 212 of the secondary coil unit 210 or not.

[0042] A service opening for a secondary coil unit 210 can be used for different coil types (especially for circular coils and / or for double D coils) that have a sufficiently large core area 221 running parallel to the underbody of the vehicle 100.

[0043] The robustness of the remaining secondary coil unit 210 (without cover 301) can be increased, in particular, by segmenting the ferromagnetic or ferrimagnetic material of the housing layer 213 of the secondary coil unit 210. The cover 301 can then combine the magnetic flux of the individual segments 313.

[0044] A service cover 301 provides easy access to components 201 and 202 of a vehicle 100 located behind the secondary coil unit 210. Removing and reinstalling the cover 301 does not require moving any electrical parts of the secondary coil unit 210, thus eliminating the need for special safety precautions. Furthermore, complex wiring configurations for disassembling the secondary coil unit 210 are avoided. Additionally, the presence of a cover 301 in the secondary coil unit 210 reduces the likelihood of damage to the unit in the event of mechanical impact (e.g., from a stone chip or driving over a curb). In many cases, mechanical impact will only damage the cover 301, which can be replaced cost-effectively. This reduces the operating costs of the vehicle 100.

Claims

[1] Secondary coil unit (210) for a vehicle (100), the secondary coil unit (210) comprising - a housing (211, 212) with a cover (301) which can be removed from the housing (211, 212); and - a secondary coil (121) arranged in the housing (211, 212) and enclosing a core region (221); wherein the cover (301) and the housing (211, 212) are designed such that, by removing the cover (301) from the housing (211, 212), an opening is created in the core region (221) through the secondary coil unit (210); wherein the opening is designed such that, in the installed state of the secondary coil unit (210), the opening allows access to one or more components (202) on a region of an underbody of the vehicle (100) covered by the secondary coil unit (210). [2] Secondary coil unit (210) according to claim 1, wherein - the cover (301) comprises a cover layer (305) made of a coil core material; and - the cover layer (305) extends at least partially into the core region (221) when the cover (301) is arranged on the housing (211, 212). [3] Secondary coil unit (210) according to claim 2, wherein - the secondary coil unit (210) comprises a housing layer (213) made of a coil core material; and - the housing layer (213) and the cover layer (305) are formed such that the housing layer (213) and the cover layer (305) partially overlap when the cover (301) is arranged on the housing (211, 212). [4] Secondary coil unit (210) according to claim 3, wherein the housing layer (213) comprises a plurality of segments (313) each separated from each other by a gap. [5] Secondary coil unit (210) according to one of the preceding claims, wherein - the housing (211, 212) comprises a first protective layer (211) and the cover (301) comprises a second protective layer (306), which are arranged on a side of the secondary coil unit (210) which, in the installed state of the secondary coil unit (210), faces away from the vehicle (100); and - the second protective layer (306) is thinner than the first protective layer (211). [6] Secondary coil unit (210) according to one of the preceding claims, wherein - the cover (301) and the housing (211, 212) comprise fastening means with which the cover (301) can be locked to the housing (211, 212); and - the fastening means comprise in particular a screw connection and / or a bayonet lock. [7] Secondary coil unit (210) according to one of the preceding claims, wherein - the secondary coil (121) comprises a circular coil and / or a double-D coil; and / or - the secondary coil unit (210) has a planar extension along an extension surface which, in the installed state of the secondary coil unit (210), runs parallel to an underbody of the vehicle (100); and - Field lines of a magnetic field in the core area (221) run perpendicular to the expansion surface. [8] Charging device (120, 105) for a vehicle (100), the charging device (120, 105) comprising - a secondary coil unit (210) according to one of the preceding claims; and - a control unit (105) configured to determine whether the cover (301) of the secondary coil unit (210) is arranged on the housing (211, 212). [9] Charging device (120, 105) according to claim 8, wherein the control unit (105) is arranged - to determine an indication of an inductance of the secondary coil (121) of the secondary coil unit (210); and - to determine, on the basis of the inductance index, whether the cover (301) of the secondary coil unit (210) is arranged on the housing (211, 212).

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