MAGNETIC CIRCUIT, MAGNETIC COMPONENT AND METHOD FOR MANUFACTURING A MAGNETIC COMPONENT

The present invention rates to a closed magnetic circuit for guiding a magnetic flux having a magnetic core with a first core member and a second core member, wherein the first core member being configured with an opening and a portion of the second core member is accommodated in the opening such that a gap for increasing the reluctance of the closed magnetic circuit is provided and encircles the portion of the core member. The present invention further relates to a magnetic component having the closed magnetic circuit and a carrier for holding the closed magnetic circuit and securing the gap. The present invention also relates to a method for manufacturing a magnetic component.

REFERENCE DATA

The present application claims priority of European patent application EP22164806 of Mar. 28, 2022, the content whereof are entirely incorporated.

TECHNICAL DOMAIN

The present invention concerns a magnetic circuit with improved magnetic stability over a high temperature range, a magnetic component with enhanced mechanical properties and a method for manufacturing the magnetic component.

RELATED ART

Magnetic components are key elements of power electronics and are found in a wide range of applications in all industrial sectors. Inductors are used, among others, in filter, voltage converters, and in power factor compensation.

Besides their electrical characteristics, magnetic components must also fulfil specifications for dimensions, heat dissipation, heat resistance, immunity to vibrations, and many other parameters. In automotive applications, where magnetic components are increasingly common, these specifications are especially stringent. As a result, magnetic components are complex products that are difficult to design and customize to all the possible applications.

A state-of the art magnetic component is the result of a trade-off between the desired nominal inductance value, the size, weight, and footprint dictated by the desired application, the choice of material, layout, and cooling.

Applications to the automotive sector, as well as in other demanding areas, require superior manufacturability, reliability, resistance to mechanical shocks and vibrations in an extended temperature range, together with a precise control of the tolerances and low thermal drifts.

FIG.1shows an example of a magnetic component2well known from the prior art. The magnetic circuit1consists of a first core member10, a second core member20, two spacers3and two coils (not illustrated) carried by the second core member20. The coils can be connected to a device external to the magnetic component2, for example, a power converter for supplying electrical power to a consumer in a vehicle.

Depending on the interconnection of the coils, can the magnetic component provide a common-mode choke, differential-mode choke, line inductor or a transformer.

The first core member10is provided in the form of a solid elongated plate. The second core member20is provided in a U-shape with a solid elongated plate and two limbs in the shape of round cylinders attached to and extending from the solid elongated plate.

The core members10,20are made of a soft magnetic material, whereas the second core member20is an assembly formed by the solid elongated plate and the limbs attached to the plate by an adhesive bond.

The spacers3are provided in the form of two round flat plates. The spacers3are made of an electrically non-conductive, non-magnetic material such as a glass-reinforced epoxy laminate or ceramic material. The two materials as mentioned are just a limited selection of well-known materials. Other materials might be used instead.

Glass-reinforced epoxy laminate materials are inexpensive and can be machined with standard tools and equipment available in most industries nowadays. Ceramic materials, to the contrary, are expensive materials and they need to be machined carefully using special tools and equipment.

The two materials are different in their coefficient of expansion and contraction. Epoxy laminate materials expand/contract more when facing temperature variation than ceramic materials.

The spacers3are placed between the top surface of the first core member10and the distal ends of the limbs of the second core member20. The spacers3are fixated with glue to the first and second core member10,20to form a magnetic circuit assembly1.

The spacers3are providing two gaps between the first and second core member10,20to increase the reluctance of the magnetic circuit1and energy can be stored in said gap. The gap is sometimes referred to as “airgap”, even when it is not filled with air but with a non-conductive, non-magnetic material having magnetic properties comparable with air.

The magnetic circuit assembly1is placed inside housing4. The housing4can be filled with a potting compound to hold the magnetic circuit1and provide a thermally conductive path for cooling between housing4and the magnetic circuit assembly1.

Using spacers3made of the example materials as outlined before has many disadvantages. The spacers3need to be glued or fixated differently to the first and second core member10,20.

This is disadvantageous as the glue needs to harden, before the housing4can be filled with potting compound. It increases the time for manufacturing the magnetic component2drastically, which leads to additional costs, particularly when the magnetic component2is destined for manufacturing in mass production.

On the other hand needs the gap mechanically constant over a high temperature range, so that the reluctance of the magnetic circuit1does not vary. Any mechanical variation of the gap leads to a decrease or increase of the reluctance of the magnetic circuit1.

Thus, glass-reinforced epoxy laminate materials are often unsuitable for this purpose, whereas ceramic materials are too expensive when the magnetic component shall be manufactured in high volumes, even when they provide improved stability over a high temperature range.

Other solutions known from prior art doesn’t provide a satisfactory solution for the technical problems as set-out before either.

US6919788 discloses electrical inductors or transformers with a low profile and suitable to carry high amount of currents. The inductors/transformers includes a ferromagnetic core structure with multiple gaps to reduce stray electromagnetic fields. The ferromagnetic core structure is held in place by using adhesives, whereas the gaps are secured by potting material.

US20150170820 discloses magnetic component assemblies for circuit boards including single, shaped magnetic core pieces formed with a physical gap and conductive windings assembled to the cores via the gaps. The physical gaps in the core are filled with an expandable magnetic material to eliminate minute non-magnetic gaps and enhance magnetic performance. Thus, this disclosure suggests avoiding non-magnetic gaps at all. The magnetic component assemblies may define power inductors.

US20110133874 discloses a method for making a magnetic component. The method comprises providing a core with one or more ridges protruding from one or more surfaces of the core; depositing one or more electrically conductive materials on the core; and removing at least a portion of the one or more ridges to form one or more continuous conductors wound around the core. Each of the one or more continuous conductors defines at least one insulating gap. Further, a magnetic component and methods for making the magnetic component are presented.

SHORT DISCLOSURE OF THE INVENTION

The present invention aims to provide a magnetic circuit that overcomes the shortcomings and limitations of state of the art. The present invention provides a magnetic circuit with stable electrical properties over a high temperature range, in particular with respect to the stability of the reluctance. The stability of reluctance of the magnetic circuit is crucial and often a concern discussed in state of the art.

In addition and closely linked to the first aim, provides the invention a solution that overcomes the shortcomings and limitations of state of the art by the provision of a magnetic component that has stable electrical properties over a high temperature range by waiving the need of loose spacers for providing an axial gap.

The present invention aims to provide a method for manufacturing a magnetic component that is suitable for manufacturing the magnetic circuit and the magnetic components in high volumes by drastically reducing the steps needed for manufacturing. The magnetic circuit and the magnetic component can be manufactured without the need of adhesives to secure the gap between the first and second core member. The bill of material for producing the magnetic component is reduced at the same time.

According to the invention, these aims are attained by the object of the attached claims, and especially by a magnetic circuit for guiding a magnetic flux generated by a coil carrying an electric current.

The magnetic circuit comprises a magnetic core with a first core member and a second core member, wherein the first core member is configured with an opening having a sidewall with a first surface, wherein the opening accommodates only a portion of the second core member, the portion having an outer wall with a second surface, wherein the sidewall and the outer wall are mutually facing each other and the portion of the second core member is configured such that the first and second surface are separated by a gap increasing the reluctance of the magnetic circuit.

The opening might accommodate only a portion of the second core member, meaning that the second core member may not be entirely accommodated in the opening comprised in the first core member. Thus some portions of the second core member might protrude and/or stand out from the opening.

The gap can enclose and/or encircles the portion of the second core member accommodated in the opening and may be configured to extend radially or with radial symmetry relative to the portion of the second core member accommodated in the opening.

The opening of the first core member can be designed as a through-hole and the portion of the second core member accommodated in the trough-hole may extend via the full extension of the through-hole for providing the gap along with the full extension. Alternatively, the opening might be configured as a blind hole.

The outline contour of the portion of the second core member accommodated in the opening being a blind hole or a through-hole can be equal to an inner contour of the opening or through-hole, wherein the outline or inner contour may be circular, elliptic, rectangular, polygonal or triangular.

An electrically non-conductive, non-magnetic element may be arranged in the gap and can be in contact with the first and second surface to define and secure a distance between the first surface and the second surface for mechanically securing the second core element with respect to the first core element.

The said element can be made of an elastic material, such as industrial silicone or may be provided by a plastic material suitable for this kind of application. The material might keep its mechanical properties in a temperature range between -40° C. and +160° C. The shape of the element can correspond to the outline contour and/or the inner contour of the of the opening or through-hole.

The magnetic circuit can comprise a coil for generating an alternating magnetic field. The coil may be wound around the second core member and may comprise an electrical insulation for insulating the coil from the second and first core members.

Alternatively or in addition can the electrically non-conductive, non-magnetic element be configured and used to insulate the coil from the first and/or second core member.

The first and/or the second core member can comprise and may be made of a soft magnetic material, such as soft ferrite, being one or a combination of manganese-zinc or/and nickel-zinc. Alternatively, or in addition, can the core members comprise other soft magnetic materials, such as iron powder.

The first and second core members may comprise an elongated member in the shape of a plate.

The second core member can include a plurality of elongated limbs attached to and extending from one surface of the elongated member of the second core member. The second core member can be configured with a clearance hole extending through at least one elongated limb and the elongated member of the second core member.

The magnetic circuit can be configured with a first core member comprising a plurality of openings in the form of blind holes and/or a plurality of through-holes. Each of the openings and/or through holes may accommodate a portion of an elongated limb of the second core member.

The first and/or second core member can be formed integrally, whereas the shape is obtainable in one manufacturing step using a compression mould.

These aims are further attained by the object of a magnetic component, such as inductor or transformer, comprises a magnetic circuit as disclosed before and a carrier for accommodation the magnetic circuit with a base plate having an upper surface and a lower surface, wherein the lower surface being substantially flat and wherein the upper surface being configured with a plurality of protrusions extending from the upper surface and being configured for holding the magnetic circuit, wherein a first protrusion is elongated with reference to a second protrusion.

The magnetic component can be mounted in a vehicle, such as an automotive, and being part of the vehicle’s electrical power supply. The temperature range in which the magnetic component can be operated reaches from -40° C. to +160° C., or even higher.

The first and second protrusion can be provided by an electrically non-conductive material, non-magnetic material, preferably one or a mixture of a plastic, ceramic, rubber, silicone or composite material.

The carrier can be made of the same material as the first and second protrusion.

The first protrusion and/or the second protrusion can be configured to extend via the through-hole comprised in the first core member of the magnetic circuit as disclosed before, wherein the electrically non-conductive element of the magnetic circuit arranged in the gap may be provided by the first or second protrusion, extending via the through-hole.

The first and/or the second protrusion can be configured to secure the first core member by providing a mechanical connection between a surface of the first core member and the protrusion. The mechanical connection may be established by using a press fit, tight fit and/or snug fit.

The first protrusion can be configured to secure the second core member, wherein the first protrusion may enclose the portion of the second core member and/or may extend through the clearance hole comprised in at least one limb of the second core member.

The first or the second protrusion may further extend into or extend via the gap provided between the first core member accommodating a portion of the second core member in the through-hole of the first core member and may hold the gap mechanically constant.

The first protrusion can be elongated and may has a distal end. The first protrusion can be configured to enter the clearance hole comprised in the second core member at one end and may exit the clearance hole at a second end, such that the distal end can protrude from the second end of the clearance hole to form an excess length.

The magnetic component can be configured with a carrier having a plurality of protrusions similarly configurated as the first and/or the second protrusion disclosed before, wherein each can be provided for securing a first and/or a second core member.

A third protrusion (or a plurality of third protrutions) may extend from the second surface and can be configurated to circumferentially surround the base plate for providing a raised border and thereby enclosing an inner volume.

The magnetic component may be configured with a plurality of lashes extending from the base plate and suitable for fixing the carrier on a surface, preferably a surface of a cooling plate external to the magnetic component.

The shape of the carrier may be formed integrally in one manufacturing step by means of a compression mould.

Another aim is attained by a method for manufacturing a magnetic as disclosed hereinbefore.

The method comprises the steps of providing a carrier, a first and a second core member and securing a position of a portion of the second core member accommodated in an opening of the first core member by means of a protrusion provided on a surface of the carrier.

a method for manufacturing a magnetic as disclosed hereinbefore, the method comprises the steps of providing a carrier, a first and a second core member and securing a position of a portion of the second core member accommodated in an opening of the first core member by means of a protrusion provided on a surface of the carrier.

The method may comprise the step of pushing a second protrusion through a through-hole provided in the first core member and thereby providing a first firm mechanical connection between the second protrusion and the first core member by applying mechanical and/or thermal energy to the second protrusion.

Applying mechanical and/or thermal energy to the second protrusion might lead to forming the second protrusion into a different shape being suitable to hold the first and/or second core member.

The method may include the step of pushing a first protrusion being configured in an elongated shape and having a distal end, through a clearance hole provided in the second core member and thereby providing a second firm mechanical connection between the distal end and the second core member using a machine or means for screwing, riveting, pressing and/or melting.

The method can also comprise the step of filling an inner volume of the carrier with a potting compound and letting the potting compound cure. Alternatively, can the use of potting compounds be omitted. In this situation, might the base plate not be configured with a third protrusion circumferentially surrounding the carrier. This can be advantageous when the magnetic component is cooled by convection.

It needs to be noted that all drawings herein presented are not in scale and might differ in size and/or scale when embodied.

EXAMPLES OF EMBODIMENTS OF THE PRESENT INVENTION

All examples presented herein are axially symmetric, indicated by a dotted line in the figures.

FIGS.2A to2Cillustrate multiple examples of the core members10,20. All core members10,20are made of a soft magnetic material, such as electronic iron, Si-steel, Manganese-zinc or Nickel-zinc ferrite and/or a combination thereof. Amorphous and nanocrystalline alloys might be used alternatively.

In a sectional view illustratesFIG.2Aa first core member10in the shape of an elongated plate12. The elongated first core member10comprises two openings14, each configured as a blind hole, extending into the elongated plated12by approximately ⅔ in thickness. The blind holes14are provided in a circular shape, which might be drilled into the material using a milling head. Each blind hole14comprised an inner sidewall15with a surface and a bottom wall with another surface.

FIG.2Bshows the first core member10ofFIG.2Awith the difference that the openings14are provided by through-holes11, each comprising an inner sidewall15with a surface. The bottom wall is omitted accordingly. The shape of the first core member10can be provided in one manufacturing step by pressing the magnetic material using a compression mould.

All following examples use the first core member10as disclosed before and illustrated inFIGS.2A or2B. The shape of an elongated plate12is synonym for other suitable shapes. Thus, any other shape, with one, two or more openings, might be used instead.

The second core member20, ofFIG.1is also illustrated inFIG.2Cin a sectional view with fewer details.

The second core member20comprises in this example an elongated plate22and two elongated limbs21extending from the elongated plate22of the second core member20. The shape of the elongated limbs21is circular.

In contrast to the example shown inFIG.1, the second core member20inFIG.2Cis integrally formed. The shape of the second core member20can be provided in one manufacturing step by pressing the magnetic material using a compression mould.

The following examples use the second core member20as disclosed before and illustrated inFIG.2C, if not stated differently. The shape of an elongated plate22along with the limbs21is synonym for other suitable shapes. The second core member20might be configured with a different number of limbs21or a different number of other protrutions extending from or being part of the second core member20.

FIG.3illustrates a magnetic circuit1formed by the magnetic core members10,20shown inFIGS.2A and2C. The magnetic circuit1comprises, in this example, a first core member10in the shape of an elongated plate12, with two openings14being configured as blind holes. The second core member20comprises a further elongated plate22and two elongated limbs21extending from the elongated plate22of the second core member20.

The blind holes14and the elongated limbs21are configured in a circular shape. The diameter of the blind holes14is greater than the diameter of the elongated limbs21.

Each blind hole14accommodates a portion24of one elongated limb21. The end faces of the elongated limbs21are in contact with the bottom wall of the blind holes14. Each portion24of an elongated limb21is placed in the corresponding blind hole14, such that the sidewall15of the blind hole14surrounds the portion24accommodated in the blind hole14radial symmetrical. The position of limbs21is secured by the spacer16introduced into the gap13between the sidewall15of the blind hole14and the portion24.

The spacer16for securing the position is made of a non-conductive, non-magnetic material. In this example, a rubber or industrial silicone material provides a tight connection between the inner wall15of the blind hole14and portion24for securing the position. For manufacturing are the spacers16first pushed into the blind holes14and each limb21is inserted into a corresponding opening comprised in the spacer16.

Arranging the gap13radially between the inner wall15of a blind hole14and a portion24of one elongated limb21provides the advantage that magnetic properties, such as the reluctance of the magnetic circuit1, are more stable over an extended temperature range compared to the magnetic circuit1disclosed inFIG.1. Due to its geometry, the mechanical variation of the gap over temperature is more limited than the example discussed inFIG.1.

FIG.4shows an example of a magnetic component2in a sectional view, comprising the core members10,20as illustrated inFIGS.2B and2C. The core members10,20provide a magnetic circuit. The magnetic component2comprises a coil40for generating a magnetic field resulting in a flux guided by the magnetic circuit and formed by the first and second core members10,20. The magnetic circuit and the coil40are supported and mechanically fixated by the carrier30.

The first core member10is provided in the form of an elongated plate, with two through-holes as illustrated inFIG.2B. The second core member20is similarly configured as in the examples shown inFIG.2CorFIG.3, with an elongated plate22and two limbs21extending from the elongated plate20.

The trough-holes and the elongated limbs21are configured in a circular shape. The diameter of the trough-holes is greater than the diameter of the elongated limbs21.

The carrier30is made in this example of plastic material, preferably in the form of a thermosetting polymer with high thermal conductivity. The carrier30comprises a base plate (not referenced) with a lower surface35. The lower surface35can be brought into contact with a cooling plate of an external cooling device for cooling the magnetic component2.

Multiple protrusions31,32extending from the upper surface of the base plate of the carrier30. Each of the most elongated protrusions31extend via a through-hole provided in the first core member10. The most elongated protrusions31are configured to contact the inner wall of the through-holes of the first core member10and provide a snug fit.

Each of the most elongated protrusion31is provided with an inner volume. The elongated limbs21of the second core member20are accommodated in said inner volume and are mechanically secured by most elongated protrusions31.

It can be noticed that the most elongated protrusions32provide multiple functions to the magnetic component2. They mechanically secure and hold the first and second core members10,20in place. The most elongated protrusions32also secure the gap13between the sidewall of the through-hole and the portion of the elongated limbs extending via the through-holes provided in the first core member10. The portion of the elongated limbs extends via the through-hole and the full extension of the trough-hole.

The most elongated protrusion32on the left also provides an insulation barrier between the coil40and the limb21of the second core member20.

Second protrutions32on the outer left and right extendfrom the base plate of the carrier30for securing the first core member10.

FIG.5illustrates a further example of a magnetic component2, comprising a first and a second core member10,20for providing a magnetic circuit1. The carrier30provides the same functionality as the carrier disclosed inFIG.4, namely securing the core members10,20. The carrier comprises a third protrusion33, surrounding the the base plate of the carrier30.

FIG.6illustrates in a more detailed sectional view the carrier30shown inFIG.5.

The carrier30is configured with a base plate having a lower surface35. Multiple protrusions extend from the upper surface of the base plate. Two most elongated protrusions in the form of cylinders are extending from the upper surface. Second protrusion32partly enclose the most elongated protrusions31and a third protrusion33surrounds the base plate to provide a side wall of a housing enclosing an inner volume. The carrier30is made of a plastic material with high thermal conductivity. Laces34with holes on the left and right are provided to fixate the carrier30on an external surface, such as a cooling plate.

FIG.7illustrates in a more detailed sectional view the magnetic circuit1shown inFIG.5. The magnetic circuit1comprises a first core member1in the form of an elongated plate12having two through-holes11. The second core member20has an elongated plate22and two elingated limbs21extending from the elongated plate22. The limbs21are hollow, as a clearance hole extends through the limbs21and the elongated plate22.

Each through-hole11accommodates a portion24of the elongated limbs21. The diameter of the through-holes12is greater than the outer diameter of the portion24of the limbs21accommodated in the trough-holes11. As the trough-holes11and the limbs21are provided in a circular shape, and due to the different diameters, surrounds a gap13the portion24of the elongated limbs21radially.

FIG.8shows the configuration of the gap13in a more detailed top view. It can be noticed that a portion of each hollow limb21is placed in one corresponding through-hole provided in the first core member10. A gap13surrounds each portion radial symmetrically.

When the first core member10and the hollow limbs21are made of a material with a comparable coefficient of expansion and contraction, the first core member10expands/contracts by nearly by the same amount as the hollow limbs21comprised in the through-holes. This leads to a gap13with minimal mechanical variation over temperature and thus to an almost constant reluctance of the magnetic circuit.

FIG.9illustrates an assembly of a magnetic component2in a sectional view. The magnetic component comprises the carrier30as shown inFIG.6and the magnetic circuit as illustrated inFIG.7.

For assembling the first core member10is in a first step placed on the upper surface of the carrier30such that the most elongated protrution31and the second protrusion32extends via the trough-holes provided in the first core member10.

In a subsequent step are the most elongated protrusions31pushed through the clearance holes23provided in the second core member20such that the distal ends36of the most elongated protrusions31projects out of the clearance hole23comprised in the elongated plate22of the second core member20. The most elongated protrusions and the second protrusions31,32secure the second core member32. The first core member is secured by the second protrusion31.

It can be noticed that the gap31between the inner side wall of the trough-hole and the portion of the elongated limbs21extending into the trough hole are filled by the second protrusions32and thereby mechanically fixated. The protrusions31,32and/or the dimensions of the trough-hole and the clearance hole are configured to provide a snug fit for firmly holding the assembly.

A side wall provided by the third protrusion33may surround the magnetic circuit and provide an inner volume that can be filled with a potting compound in a subsequent manufacturing step.

The assembly as illustrated inFIG.9avoids the usage of adhesives to secure the elements of the magnetic circuit because the carrier30provides a stable fixation means by its mechanical construction. The magnetic properties, in particular, the reactance of the magnetic circuit is very stable over a high temperature range due to the radial gap13which is provided and secured by the second protrusions32extending via the trough-holes in the first core member10.

The position of the first and/or second core member10,20accommodated by the carrier30can be secured alternatively or in addition to the snug fit discussed before.

The magnetic component2illustrated inFIG.10is obtainable by a further manufacturing step. In this subsequent manufacuting step are the distal ends36of the most elongated protrutions31, projecting out of the clearance holes melted to provide first and second firm mechanical connection37,38for securing the core members10,20.

For that purporse the carrier30is provided by a different plastic material that can be melted, such as a thermoplastic material. When the carrier is made of a thermosetting polymer, might some parts of the carrier30be designed specifically to be melted. In this case might the carried30be made of a mixture of plastic materials comprising different material properties.

Melting the material provides the advantage over bonding with adhesives that the material is hardened immediately, which provides a much faster and more practical fixation technology.

Any other fixation technology, for instance, screwing, can be used instead of or in addition to melting.