Coil unit having an injection-molded casing, and method for producing the coil unit

Abstract

The present invention relates to an integrated coil unit comprising: a magnetic core; a coil which is wound around the magnetic core and is designed to conduct electrical current; and a casing, wherein the casing is an injection-molded plastics component, and wherein the magnetic core and the coil are encapsulated by the casing and in combination enhance the electromagnetic, mechanical, and thermal properties.

Description

[0001] R.415976

[0002] - 1 -

[0003] Description

[0004] title

[0005] Coil unit with injection-molded housing and method for manufacturing the coil unit

[0006] State of the art

[0007] The present invention relates to a coil unit and a method for manufacturing the coil unit.

[0008] Electrical coil assemblies, such as chokes or transformers, are an important component of many electrical assemblies, such as current transformers. To mechanically protect the coil assemblies, electrically insulate them, and dissipate heat, the coils are typically housed in a separate casing and potted with a potting compound. Two-component potting compounds are most commonly used, which are characterized by long curing times, high material costs, limited thermal conductivity, and poor recyclability. A desirable solution would be a coil assembly that offers good mechanical protection, good electrical insulation, and good thermal properties, while being easy, fast, and cost-effective to manufacture.

[0009] Disclosure of the invention

[0010] The coil unit according to the invention, comprising the features of claim 1, and the method for manufacturing the coil unit, comprising the features of claim 9, have the advantage that a housing can be easily, quickly, and cost-effectively integrated into the coil unit, thereby enabling reliable heat dissipation and electrical insulation. According to the invention, this is achieved by the coil unit having a magnetic core and a coil wound around the magnetic core.

[0011] -2 -

[0012] The coil unit is designed to conduct an electric current. Furthermore, the coil unit comprises a housing, which is an injection-molded component, and the magnetic core and coil are overmolded by the housing. Overmolding the magnetic core and coil with the housing eliminates the need for potting compound, thus reducing costs and manufacturing time. Overmolding the magnetic core and coil also allows for direct contact with the housing, improving the electrical insulation, mechanical strength, and thermal properties of the coil unit. Injection-molded plastic components cure faster than two-component potting compounds, further reducing manufacturing time. The housing is preferably made of a thermoplastic. The coil can contribute to heat distribution and dissipation to the outside.to be carried away from the inside of the component, for example to one side towards a cooler.

[0013] The magnetic core is preferably a toroidal core. Depending on the configuration, the coil unit can, for example, form a choke due to its electromagnetic properties.

[0014] The dependent claims describe preferred embodiments of the invention.

[0015] Preferably, at least one mounting element is integrated into the housing to secure the coil unit. This mounting element allows the coil unit to be attached, for example, to another housing, a cooler, or a printed circuit board. Manufacturing the housing from a plastic injection-molded component allows the mounting element to be easily molded or integrated into the housing as an insert.

[0016] The housing preferably features a coil connection for electrically contacting the coil unit. This connection can be, for example, a plug, allowing for quick and easy connection of the coil unit. Integrating the coil unit and the coil connection into the housing results in a compact, integrated design and reduced costs.

[0017] The housing is preferably produced using a multi-component injection molding process from a first plastic and an R.415976.

[0018] - 3 -

[0019] A second plastic is produced. The first and second plastics have different thermal conductivity coefficients and / or dielectric strengths. This allows, for example, the production of a housing that exhibits both high thermal conductivity and high electrical insulation strength. This can be achieved, for instance, by placing a plastic with high thermal conductivity along coils with the same electrical potential and a plastic with high dielectric strength between coils with different electrical potentials. Furthermore, a plastic with high dielectric strength can be placed adjacent to neighboring components of the coil unit, while a plastic with a high thermal conductivity coefficient can be placed adjacent to a cooling structure or cooling element, or between a cooling structure or cooling element and the coils.

[0020] The housing preferably contains a thermally conductive filler. Quartz is preferably used as the thermally conductive filler; for higher thermal conductivity, aluminum oxide or boron nitride can also be used. This improves the thermal conductivity of the housing and ensures reliable cooling of the coil unit.

[0021] The housing preferably contains a magnetically conductive filler to influence the electromagnetic properties of the coil unit. This can be used, for example, for flux guidance and / or shielding.

[0022] Preferably, the housing features a cooling structure, which is formed in particular by means of cooling fins and / or cooling channels. The cooling structure can be easily and cost-effectively integrated into the housing during the injection molding process and can improve the cooling of the coil unit.

[0023] Furthermore, the coil assembly preferably includes a cooling element, wherein the cooling element is arranged on a flat surface of the housing. The cooling element can provide reliable cooling of the coil assembly via its flat surface. Additionally, other electrical components can be cooled using the cooling element. Since the coil can distribute heat well along the coil assembly, the arrangement of the cooling element on R.415976

[0024] - 4 -

[0025] The entire coil assembly is reliably cooled by the flat surface of the housing. The cooling element is preferably in good thermal contact with the coil assembly via a thermal interface material (TIM), which can be added separately or already integrated into the housing. The TIM serves to compensate for unevenness between the two joining partners or is bonded to them.

[0026] Preferably, the coil comprises a primary coil and a secondary coil, wherein the primary and secondary coils are configured to have different electrical potentials. The housing can provide reliable electrical insulation between the primary coil and the secondary coil. The coil unit can be designed as a transformer by means of the primary and secondary coils.

[0027] Preferably, the magnetic core comprises a first magnetic core and a second magnetic core, which are arranged, in particular, coaxially to each other. For example, the first coil and the second coil can be wound around the first magnetic core to form a transformer. Additionally, the first coil can be wound around the second magnetic core to form an inductor.

[0028] Furthermore, the invention relates to a method for manufacturing a previously described coil unit. In the method, a coil is wound around a magnetic core in a first step. In a subsequent step, the coil and the magnetic core are overmolded with a plastic in an injection mold to form a housing. This allows for the rapid and cost-effective production of a coil unit that exhibits good electrical, thermal, and mechanical properties.

[0029] The plastic preferably comprises a thermally conductive filler, with an injection molding direction running substantially parallel to the coil, preferably to maximize thermal conductivity. The filler preferably includes fibrous elements that preferably align themselves in the flow direction of the soft plastic during injection molding. By aligning the injection molding direction parallel to the coil, the thermally conductive filler particles can align themselves parallel to the coil, thereby improving the thermal conductivity parallel to the coil and the electrical insulation properties of the housing perpendicular to the coil.

[0030] -5 -

[0031] The coil can be improved. Essentially parallel to the coil means that the plastic with the heat-conducting filler particles spreads along the coil in the injection mold, but can also move perpendicular to the coil locally due to flow irregularities. Alternatively, the injection direction runs perpendicular to a flat surface of the housing to which a cooling element is attached.

[0032] Brief description of the drawings

[0033] A preferred embodiment of the invention is described in detail below with reference to the accompanying drawings. The drawing shows:

[0034] Figure 1 shows a schematic perspective view of a coil unit according to a preferred embodiment of the invention and

[0035] Figure 2 shows a schematic perspective view of the coil unit according to the preferred embodiment of the invention without a housing.

[0036] Embodiments of the invention

[0037] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0038] Below, with reference to Figures 1 and 2, a coil unit 1 and a method for manufacturing the coil unit 1 are described in detail.

[0039] Figure 1 shows the coil unit 1 according to the preferred embodiment of the invention. The coil unit 1 comprises a magnetic core 2 and a coil 3, the coil 3 being wound around the magnetic core 2. The magnetic core 2 and the coil 3 are enclosed by a housing 10, which is designed as a plastic injection-molded component.

[0040] The magnetic core 2 can be made, for example, from a ferrite core, a powder core, or an electrical steel sheet and is characterized by the fact that it has a R.415976

[0041] - 6 -

[0042] exhibits defined magnetic permeability and a high magnetic saturation flux density

[0043] The coil 3 is wound around the magnetic core 2. Preferably, the coil 3 has a primary coil 5 and a secondary coil 6, which are arranged alternately next to each other and can have different electrical potentials. Preferably, the primary coil 5 is wound around the inner and outer magnetic core 2, and the secondary coil 6 only around the outer magnetic core 2. Preferably, the windings of the primary coil 5 and the secondary coil 6 alternate circumferentially around the magnetic core 2. The exemplary arrangement of the magnetic core 2 and the coil 3 of the coil unit 1 shown can combine the functions of a transformer and an inductor in a single component.

[0044] The housing 10 is a plastic injection-molded component and can be manufactured by overmolding the coil 3 and the magnetic core 2 with a plastic material in an injection mold. Thermally conductive fillers can be integrated into the material of the housing 10 to improve its thermal conductivity. The injection molding direction preferably runs substantially parallel to the coil 3, so that the thermally conductive filler aligns itself parallel to the coil 3.

[0045] The housing 10 incorporates fastening elements 11, which allow the coil unit 1 to be attached to other components. The fastening elements 11 are preferably designed as sleeves that are integrated into the housing 10 as inserts. The sleeves of the fastening elements 11 can be threaded to allow the coil unit 1 to be attached, for example, by means of a screw connection.

[0046] Preferably, the fastening elements are arranged at the edge of the housing. Preferably, the fastening elements 11 are attached to the housing 10 by means of ribs. In addition to transmitting mechanical forces, the ribs can serve as a cooling structure 13 to dissipate heat from the coil unit 1.

[0047] Alternatively, the fastening element 11 can also be secured by means of a central screw, preferably through the opening of the magnetic core or toroidal core, and guide pins for cooler positioning. For more uniform R.415976

[0048] - 7 -

[0049] For force distribution or cooling, the screw assembly can also have a plate or washer.

[0050] Furthermore, two coil terminals 11 are preferably integrated into the housing 10, which can help to electrically contact the primary coil 5 and the secondary coil 6. Preferably, the ends of the coils 3 extend from the coil terminals 12. Thus, the ends are preferably placed at a defined location for easy contact.

[0051] The housing 10 can be manufactured from several plastics using a multi-component injection molding process, with the plastics being optimized for their respective positions and functions on the coil unit 1, for example, to improve the thermal conductivity and dielectric strength of the housing. Furthermore, one of the plastics can contain magnetically conductive particles that influence the electromagnetic properties.

[0052] A cooling element 4, shown schematically, is arranged on the underside of the housing 10. The cooling element 4 is positioned on a flat surface of the housing 10 and thus enables reliable cooling of the coil unit 1.

[0053] Figure 2 shows the magnetic core 2 and the coil 3 from Figure 1. However, in comparison to Figure 1, the housing 10 has been hidden in Figure 2.

[0054] In the process for manufacturing the coil unit 1, the component shown in Figure 2 is first produced by winding the coil 3 around the magnetic core 2. Subsequently, the body consisting of coil 3 and magnetic core 2 can be placed in an injection mold and overmolded with plastic to form the housing 10.

[0055] Thus, by overmolding the magnetic core and the coil, the coil unit 1 can be manufactured quickly and cost-effectively, with the housing providing reliable cooling and electrical insulation while protecting the coil and the magnetic core from environmental influences and enabling easy mounting and contacting of the coil unit 1.

Claims

R.415976 - 8 - Claims 1. Coil unit, comprising a magnetic core (2), a coil (3) wound around the magnetic core (2) and configured to conduct an electric current, and a case (10), wherein the housing (10) is a plastic injection molded component, and wherein the magnetic core (2) and the coil (3) are overmolded by the housing.

2. Coil unit according to one of the preceding claims, wherein at least one fastening element (11) is integrated into the housing (10) to fasten the coil unit (1).

3. Coil unit according to one of the preceding claims, wherein the housing (10) has a coil connection (12) to electrically contact the coil unit (1).

4. Coil unit according to one of the preceding claims, wherein the housing (10) is manufactured in a multi-component injection molding process from a first plastic and a second plastic, wherein the first plastic and the second plastic have different thermal conductivity coefficients and / or dielectric strengths.

5. Coil unit according to one of the preceding claims, wherein the housing (10) comprises a thermally conductive filler.

6. Coil unit according to one of the preceding claims, wherein the housing (10) comprises a magnetically conductive plastic which is configured to influence the electromagnetic properties of the coil unit. R.415976 - 9 - 7. Coil unit according to one of the preceding claims, wherein the housing (10) has a cooling structure (13), in particular cooling fins and / or cooling channels.

8. Coil unit according to one of the preceding claims, comprising a cooling element (4), wherein the cooling element (4) is arranged on a flat surface of the housing (10).

9. Coil unit according to one of the preceding claims, wherein the coil (3) comprises a primary coil (5) and a secondary coil (6), wherein the primary coil (5) and the secondary coil (6) are configured to have different electrical potentials.

10. Method for manufacturing a coil unit according to any of the preceding claims, comprising the steps: Winding a coil (3) around a magnetic core (2) and Overmolding of the coil (3) and the magnetic core (2) with a plastic in an injection mold to form a housing (10).

11. Method according to claim 10, wherein the plastic comprises a thermally conductive filler and wherein an injection molding direction runs substantially parallel to the coil (3).

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