Coil unit for inductive energy transmission and motor vehicle with the coil unit

Abstract

Coil unit (4) for inductive energy transmission, comprising at least one coil winding (8) and a ferrite core (9), wherein the at least one coil winding (8) and the ferrite core (9) are surrounded by a structure (11) made of a fiber-reinforced plastic, characterized in that a plurality of sensor coils (10) are additionally embedded in the structure (11) made of the fiber-reinforced plastic, which sensor coils are arranged within the at least one coil winding (8), wherein the plurality of sensor coils (10) are introduced in a plane parallel to the ferrite core (9) and cover the entire area within the coil winding (8).

Description

[0001] The invention relates to a coil unit according to the preamble of patent claim 1.

[0002] Such coil units are used for the contactless charging of a motor vehicle's energy storage device, such as a vehicle battery. To charge the energy storage device, the motor vehicle simply needs to be placed for an extended period of time over a primary coil unit as a charging device, which emits a changing magnetic field. Such charging devices can be provided, for example, in public parking spaces to charge the energy storage device (vehicle battery) while the vehicle is parked. Particularly compared to the refueling process when refueling vehicles with fossil fuels, this offers advantages in that no special gas station needs to be visited to at least partially fill the energy storage device, and that charging of the energy storage device is contactless and can therefore be carried out in a particularly ergonomic manner and without any further action by the driver.Furthermore, in contrast to refueling with fossil fuels, no fuel vapors are released during the refueling process or while charging the energy storage device.

[0003] From the generic document WO 2013 / 142 064 A1, a coil unit for inductive energy transmission is already known, which comprises at least one coil winding and a ferrite core, wherein the at least one coil winding and the ferrite core are surrounded by a structure made of a fiber-reinforced plastic.

[0004] DE 10 2010 020 125 A1 shows a coil winding embedded in plastic. US 2014 / 0 253 278 A1 discloses structures made of a glass fiber-reinforced or carbon fiber-reinforced plastic. JP 2013 - 215 073 A discloses that a sensor coil is also provided.

[0005] Furthermore, DE 10 2013 101 150 A1 discloses a coil unit for the inductive transmission of electrical energy. The coil unit comprises a coil, a flux guide unit, and a stray field shield, which are firmly connected to one another, in particular by encapsulation, compression, or screwing, or a combination thereof.

[0006] Furthermore, a coil unit is known from DE 10 2010 050 935 A1 in which the coil windings and a flat ferrite area are cast into a potting compound.

[0007] The object of the invention is to create a coil unit for inductive energy transmission which has good protection against mechanical damage.

[0008] This object is achieved with a coil unit for inductive energy transmission having the features of patent claim 1.

[0009] According to the invention, a coil unit for inductive energy transmission comprises at least one coil winding and a ferrite core. This at least one coil winding and the ferrite core are surrounded by a structure made of fiber-reinforced plastic. Fiber-reinforced plastics exhibit high rigidity. Accordingly, the structure made of fiber-reinforced plastic reliably protects the at least one coil winding and the ferrite core from damage, particularly when the structure made of fiber-reinforced plastic completely surrounds the at least one coil winding and the ferrite core. Furthermore, with appropriate dimensioning of the structure made of fiber-reinforced plastic, the coil unit can exhibit high inherent rigidity, eliminating the need for additional components to reinforce the coil unit. The ferrite core, in particular, is very brittle and can break even under minimal stress.The rigid structure made of fiber-reinforced plastic reliably protects the ferrite core.

[0010] Every fiber-reinforced plastic contains fibers and a matrix in which the fibers are embedded. The fibers conduct the forces. Due to their high stiffness compared to the matrix, they absorb the load. Since the fibers are more stiff than the matrix, the load is conducted along the fibers. Transverse to the fiber, the matrix and fiber often have similar elastic moduli. In addition, the forces must be conducted across the fiber-matrix interface by adhesive forces. Therefore, there is generally no reinforcing effect transverse to the fiber. Polymer fibers, glass fibers, or carbon fibers are particularly suitable as fibers. When using carbon fibers, however, it must be ensured that the fibers do not form electrically conductive closed loops. This can be achieved, for example, by coating the fibers. Functional separation is also possible by using the carbon fibers outside the induction field.

[0011] The matrix embeds the fibers. "Embedding" means that it spatially fixes the fibers and enables load introduction and transfer. The matrix also supports the fibers, for example, preventing buckling under pressure parallel to the fibers. Load transfer occurs via adhesion between the fiber and matrix. This can occur via normal or shear forces. Composites without fiber-matrix adhesion are only load-bearing in exceptional cases. The matrix also protects the fibers against environmental influences.

[0012] Two processes are particularly suitable for producing a coil unit according to the invention: The at least one coil winding and the ferrite core are surrounded by prepregs, which are then pressed into the desired shape under pressure and temperature, where they harden. Prepregs are fiber mats pre-impregnated with reactive resins. The reactive resins consist of a usually highly viscous, but not yet polymerized, thermosetting plastic matrix. The fibers contained therein can be present as a pure unidirectional layer, as a woven fabric, or as a non-crimp fabric. Alternatively, the fibers are applied in a dry state to the at least one coil winding and the ferrite core, for example as mats, and then surrounded by matrix material. Suitable methods for this include the infusion or RTM process.

[0013] Depending on the design of the structure made of fiber-reinforced plastic and the selection of fibers and matrix, the mechanical properties of the structure can be specifically adjusted so that it has the desired bending and / or torsional stiffness.

[0014] According to the invention, several sensor coils are embedded in the fiber-reinforced plastic structure in a plane parallel to the ferrite core, covering the entire area within the coil winding. Such a sensor coil serves to detect disturbances in the magnetic field and thus the presence of metallic foreign bodies.

[0015] Preferably, the at least one coil winding and the ferrite core are connected to one another via a plastic foam, wherein the at least one coil winding, the ferrite core, and the plastic foam are surrounded by the fiber-reinforced plastic structure. Such a plastic foam is significantly more elastic than the fiber-reinforced plastic structure. It thus protects the brittle ferrite core from mechanical stresses that could lead to damage to the ferrite core. Ideally, the ferrite core is completely surrounded by the plastic foam to provide optimal protection.

[0016] The coil unit advantageously serves as a secondary coil mounted on the underside of a motor vehicle. Due to the fiber-reinforced plastic structure, both the at least one coil winding and the ferrite core are well protected against mechanical damage as well as against contamination and corrosion caused by dirt, dust, splash water, road salt, etc. Furthermore, the structure can be designed so that the coil unit serves as a load-bearing component of the motor vehicle. The structure can be designed to withstand the stresses and strains by appropriately selecting and aligning the fibers and choosing the matrix. Ideally, the fibers of the fiber-reinforced plastic structure are aligned with the main load direction of the coil unit.

[0017] Further advantageous embodiments are the subject of subclaims.

[0018] The drawing illustrates an embodiment of the invention, which will be described in more detail below. The individual figures show schematically: Fig. 1 a side view of a motor vehicle with a secondary coil unit parked over a primary coil unit as a charging device, Fig. 2 a schematic elevational section through the secondary coil unit, Fig. 3 a cross-section through the secondary coil unit, Fig. 4 an enlarged detailed view of the Fig. 3 shown cross-section, Fig. 5 a schematic plan view of a sensor coil braid and Fig. 6 a schematic representation of the magnetic flux at the secondary coil unit.

[0019] In Fig. 1 shows a motor vehicle 2 parked in a garage 1. The motor vehicle 2 has a high-voltage battery 3 that can be inductively charged via a secondary coil unit 4 mounted on the underside of the vehicle. For this purpose, the secondary coil unit 4 is connected to the high-voltage battery 3 via a high-voltage cable 5. Below the secondary coil unit 4 is a primary coil unit 6 that serves as a charging device and is arranged on the floor 7 of the garage 1. An air gap remains between the primary coil unit 6 on the floor 7 of the garage 1 and the secondary coil unit 4 on the underside of the motor vehicle 2. To charge the high-voltage battery 3, the primary coil unit 6 emits a changing magnetic field. By induction, the charging current required to charge the high-voltage storage device 2 is generated in the secondary coil unit 4.The power that can be transferred contactlessly from the primary coil unit 6 to the secondary coil unit 4 is higher, the smaller the air gap between the primary coil unit 6 and the secondary coil unit 4 is, and the more precisely the secondary coil unit 4 is located above the primary coil unit 6 without offset in the vehicle longitudinal or transverse direction.

[0020] In Fig. 2 is a schematic elevation section and in Fig. 4 shows a cross-section through the secondary coil unit 4. The coil unit 4 has a rectangular base and is extremely flat overall in the vehicle height direction z. The coil unit comprises several coil windings 8, a ferrite core 9, and several sensor coils 10, which are embedded in a structure 11 made of fiber-reinforced plastic.

[0021] The coil windings 8 are arranged in a ring around a free center in a plane perpendicular to the vehicle height direction z. The coil windings 8 utilize the rectangular base area as much as possible. The ferrite core 9 extends almost completely over the entire base area of ​​the coil unit 4. It has an annular, upwardly bulging groove 13 in which the coil windings 8 are arranged. The coil windings 8 and the ferrite core are separated from each other by a thin layer of the structure 11 made of fiber-reinforced plastic.

[0022] In Fig. 4 is an enlarged section of area A in Fig. 3. In this enlarged illustration, it is clearly visible that in the vehicle height direction z, below the ferrite core 9 and the coil windings 8 in the structure 11 made of fiber-reinforced plastic, several sensor coils 10 are introduced in a plane parallel to the ferrite core 9, which extend in the area within the coil windings 8. Due to their arrangement relative to one another, the sensor coils 10 systematically cover the entire area within the coil windings 8, as can be seen in the plan view of the sensor coils 10 introduced into the coil unit 4 in Fig. 5 is clearly visible.

[0023] The structure 11 made of fiber-reinforced plastic completely surrounds the coil windings 8, the ferrite core 9, and the sensor coils 10, providing them with excellent protection against dirt, dust, splash water, moisture, etc. The fiber-reinforced plastic is a glass-fiber-reinforced plastic. During production, the sensor coils 10, the coil windings 8, and the ferrite core 9 are inserted between the fiberglass layers. A resin matrix is ​​then injected under pressure into a mold using an RTM process. After the resin cures, the fiberglass layers and the matrix together form the structure 11, into which the sensor coils 10, the coil windings 8, and the ferrite core 9 are embedded.

[0024] The structure, made of glass-fiber-reinforced plastic, exhibits exceptionally high rigidity. Therefore, no additional components are required to ensure the required rigidity of the coil unit 4; the coil unit 4 itself is sufficiently rigid. The rigidity of the coil unit 4 can even be dimensioned so large that the coil unit 4 can be used as a load-bearing component of the body of the motor vehicle 2.

[0025] During inductive charging, electromagnetic radiation or changing magnetic or electric fields during charging can lead to incompatibilities with other electronic components of the motor vehicle or even to their malfunction. Therefore, the coil unit 4 is mounted on the underside of the motor vehicle 2 in such a way that the edge regions of the coil unit 4 overlap with an adjacent floor panel 12 of the motor vehicle. The floor panel is made of a paramagnetic, conductive metal (low permeability). The induced eddy currents create a shielding effect. The overlap is designed such that, viewed from below in the vehicle height direction z, the entire area of ​​the coil unit 4 and its surroundings is always shielded from magnetic radiation, either by the ferrite core 9 or by the floor panel 12. Fig.6 shows how the ferrite core 9 and the adjacent floor plate 12 always shield the magnetic radiation M well, so that the radiation cannot interfere with any electrical components of the motor vehicle 2.

Claims

[1] Coil unit (4) for inductive energy transmission, comprising at least one coil winding (8) and a ferrite core (9), wherein the at least one coil winding (8) and the ferrite core (9) are surrounded by a structure (11) made of a fiber-reinforced plastic, characterized by in that a plurality of sensor coils (10) are additionally embedded in the structure (11) made of the fiber-reinforced plastic, which sensor coils are arranged within the at least one coil winding (8), wherein the plurality of sensor coils (10) are introduced in a plane parallel to the ferrite core (9) and cover the entire area within the coil winding (8). [2] Coil unit according to claim 1, characterized by that the structure (11) made of fiber-reinforced plastic completely surrounds the at least one coil winding (8) and the ferrite core (9). [3] Coil unit according to one of the preceding claims, characterized bythat the at least one coil winding (8) and the ferrite core (9) are connected to one another via a plastic foam, wherein the at least one coil winding (8), the ferrite core (9) and the plastic foam are surrounded by the structure (11) made of the fiber-reinforced plastic. [4] Coil unit according to one of the preceding claims, characterized by that the structure (11) consists of a polymer fiber reinforced, glass fiber reinforced or carbon fiber reinforced plastic. [5] Motor vehicle with a coil unit according to one of the preceding claims, characterized by that the coil unit (4) is mounted as a secondary coil on the underside of the motor vehicle. [6] Motor vehicle according to claim 5, characterized by that the coil unit (4) is designed as a supporting component of the motor vehicle. [7] Motor vehicle according to claim 6, characterized bythat the fibers of the fiber-reinforced plastic structure are aligned according to the main loading direction of the coil unit (4). [8] Motor vehicle according to claim 6 or 7, characterized by that the at least one coil winding (8) is arranged in an annular groove (13) in the ferrite core (9).

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