DE102023201211A1 - Device for inductively charging a battery of a motor vehicle - Google Patents

Abstract

The invention describes a device (1) for inductively charging a battery of a motor vehicle. The device (1) according to the invention comprises a housing (10) with a carrier plate (11) and a cover plate (12) and a strand carrier (20) arranged in the housing (10), in which a primary coil (22) formed from a strand (21) is arranged in order to inductively transmit energy to a secondary coil of the motor vehicle when the motor vehicle is above the housing (10) and the primary coil (22) and the secondary coil have a predetermined spatial relationship to one another. Furthermore, a ferrite layer (30) arranged in the housing (10) is included, which is formed from a plurality of ferrite tiles (30K) in order to obtain a desired magnetic field guidance and a predetermined range of self-inductance. The ferrite tiles (30K) are arranged in a single layer in a plane.

Description

The invention relates to a device for inductively charging a battery of a motor vehicle.

When a motor vehicle battery is inductively charged using an inductive charging device, also known as a power transformer, energy is transferred over distances of a few centimeters to around 20 centimeters using the transformer principle. Depending on the distance, structure and power, a magnetic field is created between an external floor coil (so-called primary coil) of the power transformer and an underbody coil on the vehicle (so-called secondary coil). The better the two coils are aligned with each other, the lower the magnetic stray field (EMC), the lower the magnetic load for people in the vicinity of the device and/or the more power can be transferred to the vehicle's battery.

The efficiency of inductive energy transfer depends not only on the alignment of the external floor coil and the vehicle-side underbody coil in relation to their horizontal distance and their vertical distance, but also on the electromagnetic properties of the power transformer or transmission system.

The electromagnetic properties to be achieved by the power transformer are defined by the coupling factor and an inductance value related to the power class. Such a definition for a base-side power transformer for inductive charging of a motor vehicle battery with a charging power of less than 11 kW is described, for example, in the international standard ISO/FDIS 19363 Annex B.2. The structural design of the power transformer for inductive charging described in this standard is in 1 shown in an exploded view. 2 shows a cutaway side view of the power transformer from 1 in a schematic representation. A coordinate system defining the position of the power transformer 1 in space with three orthogonally aligned axes x, y and z is above 2 shown.

The power transformer 1 (device for inductive charging) comprises a housing 10 with a carrier plate 11 arranged on the bottom and a cover plate 12 closing the housing at the top. The carrier plate 11 is usually made of a metal, e.g. aluminum. The cover plate 12 is made of a material that has no electrically conductive properties, such as plastic or GRP (glass fiber reinforced plastic).

A strand carrier 20 made of non-conductive material (eg plastic or GRP) is arranged in the housing 10. The strand carrier 20 has a spiral-shaped groove (not visible in the figures) into which a strand 21 wound to form a primary coil 22 is inserted. The strand 21 is thus, as can be seen from the schematic cross-sectional representation of the 2 , is arranged entirely in the strand carrier 20. The strand carrier 20 adjoins the underside of the cover plate 12 facing the housing interior.

A ferrite layer 30 comprising a plurality of ferrite tiles 30K is provided beneath the strand carrier 20. According to the reference design described in the above-mentioned standard, the ferrite tiles 30K are arranged in a step-like manner, with the tiles identified by the reference numeral 31 being arranged in a first plane associated with the strand carrier 20, the ferrite tiles 32 in a second plane below it and the ferrite tiles 33 in a third plane facing the carrier plate 11 ( 2 ). The edges of adjacent ferrite tiles, which are located in different planes, border in the z-direction of the 2 shown spatial coordinate system without overlapping. The stepped arrangement of the 30K ferrite tiles in three different planes enables the desired magnetic field guidance. The gap-free arrangement of the ferrite tiles in plan view along the z-direction prevents field build-up and thus losses. Furthermore, the stepped arrangement of the ferrite tiles makes it possible to achieve a self-inductance required in the reference design, which must lie in a specified reference band.

The ferrite tiles 30K are held by a carrier 25. The carrier holding the ferrite tiles 31, 32, 33 is structurally complex and therefore expensive to manufacture. The carrier material holding the ferrite tiles 30K is made of a plastic or another non-electrically conductive material due to the magnetic conditions. The ferrite tiles 31, 32, 33 located in the three levels have different distances from the carrier plate 11, whereby the distance of the ferrite tiles 33 in the third level from the carrier plate is designated by h _1. The distance of the ferrite tiles 31 and 32 in the first and second levels is correspondingly greater.

The distance h ₁ results from the electromagnetic properties of the power transformer 1. In the reference design of the standard mentioned, this is approximately 15 mm. The distance h ₁ between the carrier plate 11 and the lowest, third The thickness of the ferrite tiles determines the thermal conductivity, which is low due to the size of the distance h _1. As a result, the dissipation of the power loss generated in the primary coil is inadequate.

Since the temperature in the carrier 25 and the other components can become very high, it is advisable to monitor the temperature and, if a maximum permissible temperature is exceeded, to reduce the power of the power transformer 1 accordingly. As a result, the performance of the base-side power transformer is limited by the electrical operating points as well as by the ambient conditions.

Alternatively, the power loss arising in the power transformer 1 can be dissipated using appropriate additional (e.g. liquid) cooling media, whereby heat can be released to the environment elsewhere by means of heat exchange. The additional effort involved increases the manufacturing costs in an undesirable way. Furthermore, complex and cyclical maintenance work may be required during the product's service life.

It is an object of the invention to provide a device for inductively charging a battery of a motor vehicle, which is functionally and/or structurally improved in such a way that a constant power transmission is possible without complex means for heat dissipation.

This object is achieved by a device for inductive charging according to the features of claim 1. Advantageous embodiments emerge from the dependent claims.

A device for inductively charging a battery of a vehicle is proposed. The device represents a power transformer that is positioned on the ground in the parking space of a motor vehicle. The device comprises a housing with a carrier plate and a cover plate. While the carrier plate consists of a metallic material, e.g. aluminum, the cover plate is made of an electrically non-conductive material, e.g. a plastic or a glass fiber reinforced plastic (GRP). A strand carrier is arranged in the housing. A primary coil formed from a strand is arranged in the strand carrier in order to inductively transmit energy to a secondary coil of the motor vehicle when the motor vehicle is above the housing and the primary coil and the secondary coil have a predetermined spatial relationship to one another. A ferrite layer formed from a plurality of ferrite tiles is arranged in the housing. The plurality of ferrite tiles enables a desired magnetic field guidance and compliance with a predetermined range of self-inductance, which in particular lies in a predefined tolerance band. The device is characterized by the fact that the ferrite tiles are arranged in a single layer in a single plane.

With the single-layer arrangement of the ferrite tiles in one plane, the distance between the ferrite layer and the carrier plate can be reduced. This allows the path for thermal heat dissipation to be modified in such a way that it is possible to ensure sufficient dissipation of power losses with purely passive heat dissipation without an additional cooling medium. At the same time, it is ensured that the magnetic properties in terms of coupling factor and self-inductance meet the requirements described in the international standard ISO/FDIS 19363 Annex B.2.

The ferrite tiles used in the ferrite layer have the same thickness and are particularly rectangular in shape. Such ferrite tiles can be manufactured in a few standardized sizes, for example 100 mm × 150 mm, 100 mm × 50 mm and 100 mm × 100 mm. Using ferrite tiles in a few standardized sizes enables simple and cost-effective production.

Because, according to an expedient embodiment, the plane in which the ferrite tiles are arranged in a single layer runs parallel to the carrier plate and the cover plate, a structurally simple structure can be ensured. This is made possible by the fact that a carrier that accommodates the ferrite arrangement, which is preferably manufactured as an injection-molded part, can be manufactured in a structurally much simpler and more cost-effective manner.

It is also useful if opposing edges of two adjacent ferrite tiles are spaced a predetermined distance apart in a direction lying in the plane. By spacing adjacent ferrite tiles apart, manufacturing tolerances of the ferrite tiles can be compensated. Since these are made of a very brittle material and are therefore sensitive to mechanical stress, damage to the edges of the ferrite tiles during production and due to dynamic stress when the vehicle drives over the device can be avoided. This can increase the reliability of the inductive charging device as a whole.

The distance between two opposite edges is preferably about 2 to 3 mm. Basically, the aim is to The distance between two adjacent tiles should be as small as possible to avoid eddy current losses. Tests have shown that a distance in the above range satisfies both mechanical and electromagnetic requirements.

It is also expedient if the ferrite layer projects beyond the primary coil formed from the strand in every direction of extension of the plane. In other words, sections of those ferrite tiles that are arranged at outer positions of the ferrite layer project beyond the edges of the primary coil in a plan view and form a frame around the primary coil. This makes it possible to maintain the required magnetic properties of the inductive charging device as in the reference design.

According to a further practical design, the ferrite tiles leave a central area in the plane of the ferrite layer through which the stranded wire connections of the primary coil are routed. The recess provided in the central area does not influence the magnetic field guidance and the required self-inductance, as has been demonstrated in simulations. The electrical connection of the primary coil can be made easily from the underside of the charging device thanks to this design.

While the ferrite layer is arranged in the housing between the carrier plate and the strand carrier, the ferrite layer borders on the strand carrier, with a gap remaining between the ferrite layer and the primary coil being filled with a potting material made of non-conductive material. The gap has a thickness that is smaller than the thickness of the primary coil. Compared to the reference design described in the international standard, the gap can be made smaller.

It is also useful if the distance between the ferrite layer and the carrier plate is greater or significantly greater than the distance between the ferrite layer and the cover plate. It has been shown that the distance between the ferrite layer and the cover plate can be reduced to about 2 mm, while the distance between the ferrite layer and the carrier plate is 6 mm.

Compared to the reference design described in the international standard, the overall height of the inductive charging device can be significantly reduced. In particular, the comparatively much smaller distance between the ferrite layer and the carrier plate ensures easier dissipation of waste heat that occurs in the primary coil during operation.

• 1 eine perspektivische, auseinandergezogene Darstellung einer aus dem Stand der Technik bekannten Vorrichtung zum induktiven Laden mit einer Leistung von bis zu 11 kW;
• 2 eine schematische Querschnittsdarstellung des Aufbaus der in 1 dargestellten Vorrichtung;
• 3 eine schematische Querschnittsdarstellung einer erfindungsgemäßen Vorrichtung zum induktiven Laden mit elektrischen Eigenschaften, die denen des Referenzdesigns aus 1 und 2 entsprechen; und
• 4 eine Draufsicht auf die Anordnung einer Vielzahl von Ferritkacheln zur Ausbildung einer Ferritschicht in der erfindungsgemäßen Vorrichtung.

The invention is described in more detail below with reference to the figures.

• 1 a perspective, exploded view of a device known from the prior art for inductive charging with a power of up to 11 kW;
• 2 a schematic cross-sectional view of the structure of the 1 device shown;
• 3 a schematic cross-sectional view of a device according to the invention for inductive charging with electrical properties that correspond to those of the reference design from 1 and 2 correspond; and
• 4 a plan view of the arrangement of a plurality of ferrite tiles for forming a ferrite layer in the device according to the invention.

3 shows a schematic cross-sectional view of a device 1 according to the invention for inductively charging a battery of a motor vehicle not shown in the figures. The device 1 represents a power transformer, the construction of which is in principle similar to the construction already used in connection with the 1 and 2 explained.

The device 1 accordingly comprises a housing 10 with a carrier plate 11 and a cover plate 12. The carrier plate 11 is made of a metal, in particular aluminum, for reasons of stability. The cover plate 12 is made of an electrically non-conductive material, such as a plastic or a glass fiber reinforced plastic (GRP). As a result, the device 1, which is positioned in a parking space for the inductive charging of the battery of the motor vehicle, can also be driven over by the motor vehicle without being damaged.

A stranded wire carrier 20 and a ferrite layer 30 are arranged in the housing 10 below the cover plate 12. A spiral-shaped groove is made in the stranded wire carrier 20, in which a primary coil 22 formed from a stranded wire 21 is arranged. The stranded wire 21 is, as can be seen from the schematic cross-sectional view of the 3 , is arranged entirely in the strand carrier 20. By means of the primary coil 22, energy can be inductively transmitted to a secondary coil of the motor vehicle when the motor vehicle is above the housing 10 and the primary coil 22 and the secondary coil have a predetermined spatial relationship to one another.

Above the device 1, a coordinate system is shown, which shows three orthogonal axes x, y and z aligned with one another and defines the position of the device 1 in space. The main surfaces of the housing, ie the support plate 11 and the cover plate 12, are arranged parallel to a plane spanned by the x-axis and y-axis. The z-axis, which is perpendicular to this, shows the vertical axis arranged relative to the floor of the parking space, which points away from the floor on which the device 1 is arranged.

The ferrite layer 30 is arranged on or in a carrier 25 between the strand carrier 20, which accommodates the primary coil 22, and the carrier plate 11. The carrier 25 is designed in particular as an injection-molded component made of a plastic. The ferrite layer 30 is formed in a known manner from a plurality of ferrite tiles 30K. The ferrite tiles 30K are, as can be seen from the cross-sectional view of the 3 As is readily apparent, the strand carrier 20 is arranged in a single layer in a plane which runs parallel to the planes in which the carrier plate 11, the cover plate 12 and the strand carrier 20 run.

The 30K ferrite tiles are arranged in a regular manner with a small distance from each other, as can be seen particularly from the top view of the 4 emerges. 4 shows the top view of the arrangement of a plurality of ferrite tiles 30K for forming the ferrite layer 30 in the device according to 3 .

In this exemplary embodiment, five ferrite tiles are arranged in the x-direction and five ferrite tiles in the y-direction. The ferrite tiles 30K each have a rectangular shape, with 30 ferrite tiles of different, but standardized, sizes being arranged within the ferrite layer. The ferrite tiles 30K in the top and bottom rows (in the x-direction) have a size of 100 mm × 150 mm. The ferrite tiles 30K arranged in the second to fourth rows and in the first, second, fourth and fifth columns (in the y-direction) have a size of 100 mm × 100 mm. The ferrite tiles 30K arranged in the second and fourth rows and in the third column have a size of 100 mm × 50 mm.

The number of ferrite tiles and the determination of their respective sizes are generally determined by the area of the ferrite layer and the magnetic properties to be achieved in order to obtain a magnetic field guide and to be able to realize the self-inductance within a specified tolerance range.

Since the ferrite tiles are made of a brittle material, e.g. N95 from Epcos TDK, they are arranged at a distance from each other. In the embodiment according to 4 The three ferrite tiles 30K arranged at the top right (in the drawing) have their respective side edges marked 30K1, 30K2, 30K3. It is easily apparent that opposite edges 30K1 and 30K2 or 30K2 and 30K3 of two adjacent ferrite tiles 30K have a predetermined distance a ₁ or a _2. The distances a ₁ and a ₂ are preferably approximately the same, but this is not mandatory. The distance is preferably between 2 and 3 mm and takes into account manufacturing tolerances of the ferrite tiles 30K and assembly in order to avoid damage to the ferrite tiles 30K, both during production and when driving over the device 1 with a motor vehicle.

The ferrite tiles 30K are arranged in the ferrite layer 30 in such a way that there is an area without ferrite tiles in a central area. Through this area, stranded wire connections of the primary coil 22 (not shown) can be led in the direction of the carrier plate 11 to connection elements (also not shown).

The single-layer arrangement of the ferrite tiles 30K has the advantage that the distance between the ferrite layer 30 and the carrier plate 11 (distance h ₂ ) can be chosen smaller than in the reference design according to 2 At the same time, the gap 23 formed between the ferrite layer 30 and the strand carrier 20, which is filled with a casting compound 24 and has the width or thickness d ₂ , can be made smaller than the corresponding gap in the reference design according to 2 . As a result, the overall height of the device 1 can be made smaller than is the case with the reference design with the same magnetic properties in terms of magnetic field guidance, coupling factor and self-inductance.

A further advantage is that due to the comparatively lower height h ₂ between the ferrite layer 30 and the carrier plate 11, the primary coil 22 can be cooled or waste heat from the primary coil 22 can be dissipated without active cooling measures in the direction of the metallic carrier plate 11. In contrast, in the reference design according to 2 It is necessary to provide active cooling measures or a temperature sensor which reduces the power of the primary coil 22 in order to avoid damage due to thermal overload.

A further change, which makes it possible to achieve the same magnetic properties in terms of magnetic field guidance, self-inductance and coupling factor with a single-layer structure of the ferrite tiles 30K in one plane, is that the area occupied by the ferrite layer 30 in the outer edge area protrudes beyond the outer edges of the primary coil in the strand carrier 20. This is in 3 characterized by a distance d ₃ which has an overlap or projection of approximately 20 to 40 mm over the primary coil 22.

Although the cross-sectional view of 3 the impression is created that the projection of width d ₃ is only provided in the direction of the x-axis, it should be noted that the projection of corresponding width is also provided in a direction running in the y-direction of the device 1. In other words, the area occupied by the ferrite tiles 30K is increased in the x- and y-direction compared to a primary coil 22, which structurally corresponds to the reference design.

The single-layer arrangement of the ferrite tiles 30K in one plane enables a simplified structure of the carrier 25 with regard to its mechanical construction and mechanical load-bearing capacity with regard to the ability to drive over it. In addition, since the ferrite layer 30 can be formed with ferrite tiles 30K in a standardized size, the number of ferrite tiles required can be reduced. Complex mechanical structures, which must have sufficient thermal conductivity, can be avoided. Overall, the device for inductive charging can therefore be manufactured more easily and cost-effectively.

Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

List of reference symbols

1

Device for inductive charging (power transformer)

10

Housing

11

Carrier plate

12

Cover plate

20

Strand carrier

21

Strand

22

Primary coil

23

Gap/distance

24

Casting material

25

carrier

30

Ferrite layer

30K

Ferrite tiles

30K1, 30K2, 30K3

Edges of the ferrite tile 30K

31

Ferrite tile in first level

32

Ferrite tile in second level

33

Ferrite tile in third level

34

Central area without ferrite tile

h1, h2

Distance between ferrite layer and carrier plate

d1, d2

Distance between ferrite layer and strand carrier

d3

Overhang

Claims (10)

Device (1) for inductively charging a battery of a motor vehicle, comprising: - a housing (10) with a carrier plate (11) and a cover plate (12); - a strand carrier (20) arranged in the housing (10), in which a primary coil (22) formed from a strand (21) is arranged in order to inductively transmit energy to a secondary coil of the motor vehicle when the motor vehicle is above the housing (10) and the primary coil (22) and the secondary coil have a predetermined spatial relationship to one another; and - a ferrite layer (30) arranged in the housing (10), which is formed from a plurality of ferrite tiles (30K) in order to obtain a desired magnetic field guidance and a predetermined range of self-inductance; characterized in that the ferrite tiles (30K) are arranged in a single layer in a plane. Device according to Claim 1 , characterized in that the plane runs parallel to the carrier plate (11) and the cover plate (12). Device according to Claim 1 or 2 , characterized in that opposite edges (31k, 32k, 33k) of two adjacent ferrite tiles (30K) have a predetermined distance from each other in a direction lying in the plane. Device according to Claim 3 , characterized in that the distance between two opposite edges (31k, 32k, 33k) is approximately 2 to 3 mm. Device according to one of the preceding claims, characterized in that the ferrite layer (30) projects beyond the primary coil (22) formed from the strand (21) in each extension direction of the plane. Device according to one of the preceding claims, characterized in that the ferrite tiles (30K) leave out a central region in the plane of the ferrite layer through which stranded wire connections of the primary coil (22) are guided. Device according to one of the preceding claims, characterized in that the ferrite layer (30) is arranged in the housing (10) between the carrier plate (11) and the primary coil (22). Device according to one of the preceding claims, characterized in that the ferrite layer (30) adjoins the stranded wire carrier (20), wherein a gap (23) remaining between the ferrite layer (30) and the stranded wire carrier (20) is filled with a potting material (24) made of non-conductive material. Device according to Claim 8 , characterized in that the gap has a thickness which is smaller than the thickness of the primary coil (22). Device according to one of the preceding claims, characterized in that the distance between the ferrite layer (30) and the carrier plate (11) is greater or substantially greater than the distance between the ferrite layer (30) and the strand carrier (20).

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