EP3155624A1

EP3155624A1 - Method for forming a frame core having a center leg for an inductive component and frame core produced accordingly

Info

Publication number: EP3155624A1
Application number: EP15729788.8A
Authority: EP
Inventors: Michael Alfons Baumann; Martin Grübl
Original assignee: Sumida Components and Modules GmbH
Current assignee: Sumida Components and Modules GmbH
Priority date: 2014-06-11
Filing date: 2015-06-10
Publication date: 2017-04-19
Also published as: US20170110245A1; DE102014211116A1; CN106415753A; WO2015189245A1; US10170240B2; JP2017517896A

Abstract

The invention relates to a method for forming a frame core (1) having a center leg (3) for an inductive component and an accordingly formed frame core (1) having a center leg (3) and an air gap (4) in the center leg (3). The frame core (1) is formed integrally with the center leg (3), wherein the air gap (4) is pressed into the center leg (3) during the formation of the frame core (1).

Description

A method of forming a frame core with center legs for an inductive component and a corresponding manufactured frame core

Field of the invention

The invention relates to a method for forming a frame core with center leg for an inductive component and a correspondingly produced frame core with center leg, wherein the frame core is formed integrally with center leg and in the center leg, an air gap is pressed.

background

Magnetic cores according to an E core configuration or an E-I core configuration or a dual E core configuration are often used in reactors and transformers. In this case, at least one winding is usually arranged above the middle limb of these magnetic cores. In the manufacture of a magnetic core according to an E-I core configuration, an E-core is combined with an I-core. In the production of magnetic cores according to a double E core configuration, usually two single E cores are glued together. Alternatively, frame cores are used in conjunction with I-cores, with the I-core inserted as a center leg into the frame core and bonded to two opposite sides of the frame core.

In E cores, air gaps can be set to avoid saturation effects in grinding processes with very low manufacturing tolerances, so that an adjustment of the A _L value of a magnetic core by precise grinding is possible. While the winding process of these magnetic cores is not very complicated because a coreless core coil is used and coupled to the core during assembly, it is significantly disadvantageous to join two E core halves together in a separate bonding process. The disadvantage is on the one hand that the splice results in a significant mechanical weakness in the finished component, and on the other hand, the gluing process in production represents a not inconsiderable cost and time factor. In addition, both E-core halves are pressed separately in a press in the production process and then removed from the press. Subsequently, both E-core halves are individually sintered in two separate sintering processes, which means a complex handling for conventional production processes. Due to the inevitable manufacturing tolerances occurring during sintering can also be no longer ensured for two individually sintered core parts, that of the two core parts composite core is produced with the desired accuracy and in particular the outer limbs of two E-core halves face each other plane-parallel.

The manufacturing tolerances occurring in sintered core halves also result in the assembly of two such E-core halves produced at the transition from one core to the other half an offset. The resulting offset points in the finished core represent magnetic field lines in the final inductive component is a bottleneck of the magnetically active core cross section, wherein at the bottleneck premature saturation of the core takes place, which has a decrease in inductance result. In addition, during operation in the finished inductive component, the field lines emerge from saturation regions and gaps in the ferrite region, resulting in additional losses in the winding.

In contrast, although the frame core has the advantage that the core is made in one piece and therefore requires no subsequent bonding process, which compared to bonded core shapes leads to a significantly better mechanical stability and also means a simple manufacturing process due to the lack of bonding process, but it is much more difficult to efficiently insert air gaps in a frame core. For this reason, frame cores are excluded from many power applications.

From the document DE 10 2004 008 961 B4 a frame core is described with a glued into the frame core center piece.

Document DE 1 193 1 19 describes a frame-shaped core part with a balancing pin which is inserted into a semi-cylindrical recess of the frame-shaped core part.

The document EP 004272 A2 discloses a method for producing magnetic cores from molding compounds with soft magnetic properties by pressing a mixture of soft magnetic material and a synthetic resin as a binder, wherein a mixture of iron powder mixed with a thermosetting resin mixed in liquid form into a heated mold and then is pressed.

The document DE 3909624 A1 describes an E-I core with an air gap, wherein the air gap in the I-part of the core is inserted by pressing.

The document DE 2305958 A discloses a sheared two-part magnetic core, which is sheared gap-free by a solid non-magnetic or low-permeability body and the parts of the magnetic core are partly as directly as possible and partly firmly connected to each other over the shearing body. Summary of the invention

In view of the foregoing problems, it is an object of the present invention to fabricate a mechanically stable magnetic core in a simple manufacturing process, wherein the fabricated magnetic core can be used in a wide range of power applications.

The above-mentioned object is achieved by a method for forming a one-piece frame core according to independent claim 1 and a frame core according to independent claim 13. Advantageous embodiments of the method according to claim 1 are defined in the further dependent claims 2 to 12. Advantageous embodiments of the frame core according to claim 13 are defined in the further dependent claims 14 and 15.

In one illustrative embodiment of the invention, a method is provided in which a one-piece frame core is formed with center legs and an air gap is pressed into the center leg during formation of the frame core. The inventively provided method provides a frame core with center leg and air gap in the middle leg, without core-core bonding and grinding processes are needed for the production of an air gap. It is thus produced at low manufacturing tolerances, a mechanically stable core and generally avoided core offset, whereby the EMC behavior is improved. In addition, a Schleifmaßmaß, as required for double-E cores, according to the invention is not necessary, whereby ferrite material is saved. By saving on ferrite material furnace capacity can also be saved.

In a further advantageous embodiment herein, the frame core is formed in a ceramic injection molding process. Alternatively, the frame core is formed with center leg in a transfer molding process. In both cases results in a simple, fast and inexpensive production.

In a further advantageous embodiment of the method, a frame core is formed, wherein the center leg connects two mutually opposite frame sides along a longitudinal direction of the frame core and the air gap passes through the center leg transversely to the longitudinal direction.

In a further advantageous embodiment herein, the frame core further comprises two side leg portions which close the frame core, wherein the side leg portions extend straight or at least partially curved along the longitudinal direction. In a further advantageous embodiment herein, the center leg of each side leg portion is spaced in a direction transverse to the longitudinal direction by at least one parallelepiped or cylindrical winding window.

In a further advantageous embodiment herein, the air gap is pressed at an angle not equal to 90 ° degrees to the longitudinal direction of the center leg. In this case, an air gap is provided with a larger contact surface to the center leg, so that a smaller length of the air gap along the longitudinal direction can be selected.

In advantageous embodiments herein, the air gap is pressed in as a prism-shaped gap or as a roof-shaped gap. Air gaps, such as as a prism, as a wedge or in the shape of a roof pressed air gaps, give the core a non-linear L-I behavior. A non-linear L-I behavior denotes a pronounced and continuously decreasing non-constant inductance with increasing current.

In an advantageous embodiment, the air gap is pressed by means of an easily removable material. This allows for easy formation of the air gap, wherein the gap is subject to low manufacturing tolerances due to acting as a placeholder easily removable material during the manufacturing process and the core is protected from damage.

In an advantageous embodiment, the frame core comprises at least one further center leg, in which during the formation of the frame core, a further air gap is pressed. As a result, integral one-piece frame cores are provided with more than one center leg, each having a pressed-air gap, without sticking core sections during manufacture.

In a further illustrative embodiment of the invention, a frame core is provided with center leg and an air gap in the middle leg, wherein the frame core is integrally formed integrally with the center leg and the air gap in the middle leg.

In an advantageous embodiment herein, the frame core comprises two frame portions and two side leg portions connecting the frame portions along a longitudinal direction to a closed core, wherein the center leg of each side leg portion is spaced in a direction transverse to the longitudinal direction by at least one parallelepiped or cylindrical winding window.

In a further advantageous embodiment, the frame core comprises at least one further center leg, which is formed integrally with the frame core. Brief description of the figures

Further advantages will become apparent from the description of illustrative embodiments taken in accordance with the accompanying drawings, in which:

Fig. 1 shows schematically a frame core with center leg and air gap in the middle leg according to an illustrative embodiment of the invention;

FIG. 2a schematically illustrates a cross-sectional view of an air gap in the center leg according to some illustrative embodiments of the invention; FIG.

FIG. 2b schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG.

FIG. 2c schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG.

FIG. 2d schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG.

FIG. 2e schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG.

FIG. 2f schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG.

FIG. 2g schematically illustrates a cross-sectional view of an air gap according to further illustrative embodiments of the invention; FIG. and

3a to 3e schematically cross-sectional views of frame cores according to alternative

Embodiments of the invention represent. Detailed description

The invention generally provides a one-piece frame core with center pieces and an air gap formed in the center piece. The frame core is formed according to the invention in one piece in a pressing tool, wherein the air gap is introduced directly into the press tool in the center piece. As a result, on the one hand adhesion processes are avoided, as they are common according to the above statements in known closed core configurations formed of two E cores (so-called double E core configurations) or an E core with an I core (so-called E-I core configurations). By avoiding the additional bonding processes, the time required for production is reduced, and the cost of producing corresponding frame cores is kept low. On the other hand, frame cores according to the invention have a greater mechanical stability due to their one-piece design over composite core configurations, since the splices represent significant mechanical weaknesses on the finished core component. Furthermore, the grinding process is eliminated. For a precise grinding of the Luftspates in the middle jacks and for a precise field guidance, the surface grinding of the core back and the side legs is usually a prerequisite. This process is expensive and often mechanically corrodes the cores in the form of chips and cracks. By eliminating the grinding process, the costs are significantly reduced and the component quality is improved. Furthermore, tolerances in the magnetic properties are minimized by the production according to the invention of frame cores with central limbs and air gap pressed therein, since e.g. no more splices are needed, which represent poorly controllable magnetic resistances in known cores. Thus, according to the invention, it is possible to provide frame cores which comply with predetermined magnetic properties within very narrow limits.

Illustrative embodiments will be described below by way of example with reference to the accompanying drawings. Some illustrative embodiments of the invention will be described in more detail below with reference to FIG. 1.

1 schematically illustrates a perspective view of a frame core 1. The frame core 1 consists of a frame section 2 and a center leg 3 with an air gap 4 formed in the center leg 3. The frame section 2 comprises two with respect to the center leg 3 along a longitudinal direction L of FIG Central leg 3 extending leg leg sections 2c. The side leg portions 2c and the center leg 3 are joined along a width direction B oriented perpendicular to the longitudinal direction L on opposite sides of the side leg portions 2c and the center leg 3 from an upper cross yoke portion 2a and a lower cross yoke portion 2b. A depth dimension on the frame core 1 is indicated schematically in Fig. 1 by a depth direction T, which is oriented perpendicular to the longitudinal direction L and width direction B.

The frame core 1 shown in FIG. 1 is formed of at least one soft magnetic ferrite material according to some illustrative embodiments of the invention. In an illustrative example, the at least one soft magnetic ferrite material is provided by, for example, a nickel-zinc ferrite material or a manganese-zinc ferrite material.

In the frame core 1 shown in FIG. 1, the individual core sections have rectangular cross sections perpendicular to the longitudinal direction L. This is not a limitation of the invention. Alternatively, the center leg 3 and / or at least one of the side leg sections 2c and / or the upper transverse yoke section 2a and / or the lower transverse yoke section 2b may have a round or oval cross section perpendicular to the longitudinal direction L. It is noted that the edges of the center leg 3 and / or of at least one of the side leg sections 2 c and / or the upper transverse yoke section 2 a and / or the lower transverse yoke section 2 b may be rounded.

With regard to FIGS. 2 a to 2 e, different configurations of the air gap 4 shown schematically in FIG. 1 will be described below.

FIG. 2 a schematically illustrates an air gap 4 a according to a first embodiment in a side view. For the sake of simplicity, only a region of a central limb 3 a around the air gap 4 a is shown. The air gap 4 a is arranged transversely to a longitudinal direction of the center leg 3 a (see longitudinal direction L in FIG. 1) in the center leg 3 a. In particular, the air gap 4a according to the first embodiment is oriented perpendicular to the longitudinal direction of the center leg 3a. The middle leg 3a may in this case have a rectangular, rounded, oval or round cross section perpendicular to the longitudinal direction (in particular in a plane along the depth and width directions T, B in FIG. 1). As shown in Fig. 2a, the air gap 4a has a length d1. The illustrated air gap 4a is oriented transversely to the longitudinal direction of the center leg 3a, so that the direction in which the air gap 4a passes through the center leg 3a is arranged perpendicularly (approximately 90 ° with fault tolerance) to the longitudinal direction.

2b shows an air gap 4b according to a second embodiment of the invention in a side view perpendicular to a longitudinal direction in an environment around the air gap 4b in the center leg 3b. The center leg 3b can have a rectangular, rounded, oval or round cross section perpendicular to its longitudinal direction or in a plane oriented parallel to the directions B, T (see longitudinal direction L in FIG. The air gap 4b is according to the second embodiment shown in Fig. 2b is pressed as an inclined plane in the center leg 3b and spaced an upper center leg portion MS1 of a lower center leg portion MS2 by a distance d2. In particular, the air gap 4b is oriented transversely to the longitudinal direction (cf., longitudinal direction L in FIG. 1) of the middle limb 3b. An angle at which the air gap 4b is oriented to the longitudinal direction L (see Fig. 1) is not equal to 90 °. The air gap 4b has compared to the air gap 4a larger contact surfaces to the center leg out. Touch surfaces are to be understood as the pole surfaces exposed through the air gap 4b in the middle leg, through which a magnetic flux density ("B field") present in the center leg 4b enters or exits from the middle leg section MS1 or MS2 into the air gap 4b Touching surfaces, the length d2 of the air gap 4b (measured as the distance d2 of the center leg portions MS1 and MS2 spaced apart by the air gap 4b, as shown in Fig. 2b) compared to the length d1 of the air gap 4a smaller (d2 <d1) are selected. In some specific embodiments, the length d2 of the air gap 4b is related to the size of the contact surface or pole surface in the air gap 4b. For example, the length d2 of the air gap 4b is indirectly proportional to the contact area or pole surface in the air gap 4b, so that the length d2 of the air gap 4b Air gap 4b decreases with increasing contact surface or pole face, ie the angle between contact surfaces or pole surfaces and longitudinal direction decreases (an angle of 90 ° corresponds to the orientation of gap 4a of Fig. 2a).

An air gap 4 c according to a third embodiment of the invention is shown in Fig. 2c in a side view of a portion in the center leg around the air gap 4 c around. An upper middle leg section 3c 'has a prismatic or truncated pyramidal or frustoconical shape. A lower center leg section 3c "is designed such that the union of the two core sections 3c 'and 3c" results in a gapless parallelepiped or cylindrical center leg. In other words, the middle leg section 3c "has a depression which is the negative of the prismatic or truncated pyramidal or truncated conical shape of the middle leg section 3c '.

A fourth embodiment is shown diagrammatically in FIG. 2d by means of an air gap 4d in a side view, wherein the air gap 4d is pressed into the center leg, so that an upper center leg section 3d 'has a wedge-shaped or pyramidal or conical shape. A lower middle leg section 3d "is further designed such that a combination of the upper middle leg section 3d 'and the lower middle leg section 3d" results in a gapless parallelepiped or cylindrical center leg. In other words, the center leg section 3d "has a depression which is the negative of the wedge-shaped or pyramidal or conical shape of the middle leg portion 3d 'is.

A fifth embodiment of an air gap 4e is shown in FIG. 2e. The air gap 4e is in this case wedge-shaped pressed into the middle leg 3e.

In the schematic cross-sectional view shown in FIG. 2f, a further embodiment of the fifth embodiment shown in FIG. 2e is shown. The air gap according to this embodiment is formed as a double wedge-shaped air gap which is provided by two wedge-shaped air gap regions 4f and 4f "formed on opposite sides of the middle leg. As shown in Fig. 2f, the middle leg has an upper middle leg section 3f and a lower middle leg section 3f" The lower center leg section 3f "delimits the double wedge-shaped air gap 4f, 4f" by a contact surface which passes through the center leg transversely to the longitudinal direction (see reference character L in FIG In the illustrated example, the contact surface of the lower middle leg section 3f "is oriented perpendicular to the longitudinal direction. Alternatively, the contact surface may be oriented at an angle deviating from 90 ° to the longitudinal direction (see L in Fig. 1); e.g. For example, the contact surface may be provided by a taper of the lower center leg portion. The upper middle leg section 3f has a roof-shaped or wedge-shaped contact surface forming the double-wedge-shaped air gap 4f, 4f "Alternatively, the contact surface of the upper center leg section 3f is pyramid-shaped or cone-shaped.

An alternative embodiment of a double wedge-shaped air gap 4g ', 4g "is shown schematically in a cross-sectional view in Fig. 2. The middle leg has an upper middle leg section 3g' and a lower middle leg section 3g" in an environment of the double wedge-shaped air gap 4g ', 4g " The upper middle leg section 3g 'and the lower middle leg section 3g "each have a roof or wedge-shaped contact surface. Alternatively, the contact surface of the upper center leg portion 3 f is pyramidal or conical. In an illustrative example, the upper and lower middle leg portions 3g ', 3g "are symmetrical to each other, although this is not a limitation of the invention and also asymmetrically designed center leg portions are conceivable.

By the illustrated in Figures 2a to 2e different embodiments of the pressed-in the center leg air gap a characteristic LI behavior is achieved. By means of the air gap 4a of Fig. 2a, a LI curve is achieved, wherein the inductance L to to a current having a substantially constant behavior (L changes in the range l <by less than 10%, preferably less than 5% or less than 1%) and drastically decreases when exceeding. In the embodiments illustrated with reference to FIGS. 2 b to 2 e, on the other hand, there is a falling L over I behavior, which deviates from that to FIG. 2 a by a substantially non-constant behavior.

Frame cores according to the invention are formed in one piece in a pressing tool, wherein the air gap in the center piece is introduced directly into the core into the pressing tool. Manufacturing methods according to the invention include, in some illustrative embodiments, a pressing process wherein the core material is filled into a cavity of a powder-molding die. The die, upper and lower punches are designed to be suitable for integrally forming the frame core with central leg and air gap formed in the middle leg during a pressing operation. It is expressly pointed out that upper punch and lower punch of the pressing tool can consist of several individual stamps, which are independently movable. During or after the pressing process, sintering can take place through the action of heat. Alternatively, frame cores according to the invention are produced in a ceramic injection molding process. In some specific illustrative embodiments, an air gap is injected by means of a correspondingly formed dividing wall which is placed in the cavity between two middle region forming material areas during filling of material or after filling of the material into the cavity.

Alternatively, the air gap is formed by an easily removable material compared to the material of the magnetic core, which is introduced during filling of the cavity between two material areas. For example, a gap-forming material may be provided by a plastic material that is removed from the compact after the pressing operation, eg, during a baking step or an etching step. For this purpose, for example, the cavity is filled with material of the magnetic core, so that a first material region forms in the cavity. Subsequently, the gap-forming material is filled on the first material area. This may include pre-pressing processing steps to provide the gap-forming material with a desired shape corresponding to the shape of the air gap to be formed. Subsequently, by filling with material of the magnetic core, a second material region is formed on the gap-forming material. In a subsequent pressing operation, a compact is produced in which the gap-forming material is arranged between the first and second material region. By removing the gap-forming material by means of heat and / or by the action of a suitable etchant, the air gap is formed. With regard to FIGS. 3 a to 3 e, schematic cross-sectional views of frame cores according to alternative embodiments of the invention are shown, which deviate from the frame core 1 shown schematically in FIG. 1.

Fig. 3a shows schematically a frame core 10 with a center leg 13a and an air gap 14 in the middle leg 13a. The frame core 10 further includes frame portions 12a and 12b extending along a direction B and connected by two side leg portions 12c arranged at opposite ends of the frame portions 12a and 12b, which extend along a longitudinal direction L. The longitudinal direction L extends transversely to the direction B and is oriented perpendicular thereto in the example shown. The frame core 10 is closed by the frame portions 12a, 12b and the side leg portions 12c. Outer surfaces 16 of the frame portions 12a, 12b extend parallel to the direction B.

The center leg 13 a is spaced in the direction B from the side leg portions 12 c on each side by a winding window 15. In at least one of the winding windows 15, a winding (not shown) may be provided, which is arranged above the center leg 13a and / or at least one of the side leg portions 12c. According to the example shown in Fig. 3a, the winding windows in the sectional view shown are rectangular in shape, that is, the winding windows 15 are cuboid in consideration of a depth perpendicular to the directions L and B. The air gap 14 connects the winding windows 15 with each other.

In contrast to the frame core 1 shown in FIG. 1, the frame core 10 according to FIG. 3 a is shown with side leg sections 12 c, which have rounded outer surfaces 17. In this way, an advantageous guidance of a magnetic field in the side leg sections can be achieved. In addition, 10 corners are avoided in the frame core.

Fig. 3b shows schematically a frame core 20 with a center leg 23a and an air gap 24 in the middle leg 23a. The frame core 20 further includes frame portions 22a and 22b extending along a direction B and connected by two side leg portions 22c arranged at opposite ends of the frame portions 22a and 22b and extending along a longitudinal direction L. The longitudinal direction L extends transversely to the direction B and is oriented perpendicular thereto in the example shown. The frame core 20 is closed by the frame portions 22a, 22b and the side leg portions 22c. Outer surfaces 26 of the frame portions 22a, 22b extend parallel to the direction B. The center leg 23a is spaced in the direction B from the side leg portions 22c on each side by a winding window 25. *** " In at least one of the winding windows 25, a winding (not shown) may be provided, which is arranged above the center leg 23a and / or at least one of the side leg portions 22c. According to the example shown in Fig. 3b, the winding windows in the sectional view shown are circular, ie, the winding windows 25 are cylindrical in the frame core 20, taking into account a depth perpendicular to the directions L and B. The winding windows 25 are connected by the air gap 24.

In contrast to the frame core 1 shown in FIG. 1, the frame core 20 according to FIG. 3 b is illustrated with side leg sections 22 c, which have rounded outer surfaces 27. In this way, an advantageous guidance of a magnetic field in the side leg sections can be achieved. In addition, 20 corners are avoided in the frame core.

3c schematically shows a frame core 30 with a center leg 33a and an air gap 34 in the center leg 33a. The frame core 30 further includes frame portions 32a and 32b arcuately extending along a direction B and connected by two side leg portions 32c arranged at opposite ends of the frame portions 32a and 32b, which arcuately extend along a longitudinal direction L. The longitudinal direction L extends transversely to the direction B and is oriented perpendicular thereto in the example shown. The frame core 30 is closed by the frame portions 32a, 32b and the side leg portions 32c. Outer surfaces of the frame portions 32a, 32b are formed arcuate.

The center leg 33a is spaced in the direction B from the side leg portions 32c on each side by a winding window 35. In at least one of the winding windows 35, a winding (not shown) may be provided which is arranged above the center leg 33a and / or at least one of the side leg sections 32c. According to the example shown in Fig. 3c, the winding windows are circular in the sectional view shown, that is, the winding windows 35 are cylindrical in the frame core 30 in consideration of a depth perpendicular to the directions L and B. The winding windows 35 are connected by the air gap 34.

In contrast to the frame core 1 shown in FIG. 1, the frame core 30 according to FIG. 3c is illustrated with side leg portions 32c which have rounded outer surfaces, thus providing an overall cylindrical core configuration. This can be an advantageous a magnetic field in the side leg sections can be achieved. In addition, 30 corners are avoided in the frame core.

FIG. 3d shows a core configuration similar to FIG. 3b. Herein is schematically illustrated a frame core 40 having two center legs 43a, 43b and air gaps 44a, 44b formed therein, respectively. The frame core 40 further includes frame portions 42a and 42b extending in parallel to a direction B and connected by two side leg portions 42c arranged at opposite ends of the frame portions 42a and 42b, which extend along a longitudinal direction L. The longitudinal direction L extends transversely to the direction B and is oriented perpendicular thereto in the example shown. The frame core 40 is closed by the frame portions 42a, 42b and the side leg portions 42c. Outer surfaces of the frame portions 42a, 42b are rounded.

Each center leg 43a, 43b is spaced in the direction B from the side leg portions 42c on each side by one or more winding windows 45. In at least one of the winding windows 45, a winding (not shown) may be provided, which is arranged over at least one of the center legs 43a, 43b and / or at least one of the side leg portions 42c. According to the example shown in Fig. 3d, the winding windows in the sectional view shown are circular, that is, the winding windows 45 are cylindrical in the frame core 40 considering a depth perpendicular to the directions L and B. The winding windows 45 are interconnected by the air gaps 44a, 44b.

In contrast to the frame core 1 shown in FIG. 1, the frame core 40 according to FIG. 3d is illustrated with side leg sections 42c which have rounded outer surfaces. In this way, an advantageous guidance of a magnetic field in the side leg sections can be achieved. In addition, 40 corners are avoided in the frame core. Furthermore, the frame core 40 differs from the frame core 1 in that more than one center leg, here the center leg 43a, 43b are provided, in each of which an air gap 44a, 44b are formed.

FIG. 3e shows a core configuration similar to FIG. 3a. Herein is schematically illustrated a frame core 50 having two center legs 53a, 53b and air gaps 54a, 54b formed therein, respectively. The frame core 50 further includes frame portions 52a and 52b which extend in parallel to a direction B and are connected by two side leg portions 52c arranged at opposite ends of the frame portions 52a and 52b, which extend along a longitudinal direction L. The longitudinal direction L extends transversely to the direction B and is oriented perpendicular thereto in the example shown. The frame core 50 is through the Frame portions 52a, 52b and the side leg portions 52c closed. Outer surfaces of the frame portions 52a, 52b are rounded.

Each center leg 53a, 53b is spaced in the direction B from the side leg portions 52c on each side by one or more winding windows 55. In at least one of the winding windows 55, a winding (not shown) may be provided, which is arranged over at least one of the center legs 53a, 53b and / or at least one of the side leg portions 52c. According to the example shown in Fig. 3e, the winding windows in the sectional view shown are rectangular, that is, the winding windows 55 are cuboid in the frame core 50 considering a depth perpendicular to the directions L and B. The winding windows 55 are interconnected by the air gaps 54a, 54b.

In contrast to the frame core 1 shown in FIG. 1, the frame core 50 according to FIG. 3e is shown with side leg sections 52c, which have rounded outer surfaces. In this way, an advantageous guidance of a magnetic field in the side leg sections can be achieved. In addition, 50 corners are avoided in the frame core. Furthermore, the frame core 50 differs from the frame core 1 in that more than one center leg, here the center legs 53a, 53b are provided, in each of which an air gap 54a, 54b are formed.

In further illustrative embodiments of the invention, each of the air gaps in FIGS. 3a to 3e may be formed according to one of the air gaps described with reference to FIGS. 2a to 2g.

In summary, the invention provides a method of forming a center core frame core for an inductive device and a correspondingly formed center core center core core and air gap in the center leg. The frame core is integrally formed with the center leg, wherein the air gap is pressed during the formation of the frame core in the center leg.

Claims

claims

1 . A method of forming a frame core (1; 10; 20; 30; 40; 50) with center legs (3;

13a; 23a; 33a; 43a; 53a) for an inductive component, wherein the frame core (1; 10; 20; 30; 40; 50) is integrally formed with the center leg (3; 13a; 23a; 33a; 43a; 53a), characterized in that an air gap ( 4; 14; 24; 34; 44a; 54a) during the formation of the frame core (1; 10; 20; 30; 40; 50) is pressed into the middle leg (3; 13a; 23a; 33a; 43a; 53a).

The method of claim 1, wherein the frame core (1; 10; 20; 30; 40; 50) is formed with center legs (3; 13a; 23a; 33a; 43a; 53a) in a ceramic injection molding process.

The method of claim 1, wherein the frame core (1; 10; 20; 30; 40; 50) is formed with center legs (3; 13a; 23a; 33a; 43a; 53a) in a pressing process.

4. The method according to any one of claims 1 to 3, wherein the center leg (3; 13a, 23a;

33a; 43a; 53a) connects two frame portions (2a, 2b; 12a, 12b; 22a, 22b; 32a, 32b; 42a, 42b; 52a, 52b) along a longitudinal direction (L) and the air gap (4; 14; 24; 34; 44a; 54a) passes through the center leg (3; 13a; 23a; 33a; 43a; 53a) transversely to the longitudinal direction (L).

The method of claim 4, wherein the frame core (1; 10; 20; 30; 40; 50) further comprises two side leg portions (2c; 12c; 22c; 32c; 42c; 52c) forming the frame core (1; 10; 20 ; 30; 40; 50), wherein the side leg portions (2c; 12c; 22c; 32c; 42c; 52c) extend straight or at least partially curved along the longitudinal direction (L).

The method of claim 5, wherein the center leg (3; 13a; 23a; 33a; 43a; 53a) of each side leg portion (2c; 12c; 22c; 32c; 42c; 52c) is laterally separated by at least one parallelepiped or cylindrical winding window (15; 25, 35, 45, 55).

7. The method according to any one of claims 4 to 6, wherein the air gap (4b) is pressed at an angle not equal to 90 ° to the longitudinal direction (L).

8. The method according to any one of claims 1 to 7, wherein the air gap as a prism-shaped air gap (4a; 4b) or as a roof-shaped or pyramidal air gap (4c; 4d) or as a wedge-shaped air gap (4e) or as a double wedge-shaped air gap (4f, 4f "4g ', 4g") is pressed in.

A method according to any one of claims 1 to 8, wherein the frame core (1; 10; 20; 30; 40;

50) is formed from at least one ferrite material.

10. The method according to any one of claims 1 to 9, wherein the air gap (4; 14; 24; 34; 44a;

54a) is pressed by means of a partition corresponding to the air gap.

A method according to any one of claims 1 to 9, wherein the air gap (4; 14; 24; 34; 44a;

54a) is pressed in by means of an easily removable material.

12. The method of claim 1, wherein the frame core comprises at least one further center leg in which during the formation of the frame core a further air gap is formed ) is pressed.

13. Frame core (1; 10; 20; 30; 40; 50) with center leg (3) and an air gap (4; 14; 24;

34; 44a; 54a) in the middle leg (3), wherein the frame core (1; 10; 20; 30; 40; 50) is connected to the middle leg (3; 13a; 23a; 33a; 43a; 53a) and the air gap (4; 14; 24; 34; 44a; 54a) is integrally formed integrally in the middle leg (3; 13a; 23a; 33a; 43a; 53a).

The frame core (1; 10; 20; 30; 40; 50) of claim 13, wherein the frame core (1; 10;

20; 30; 40; 50) has two frame portions (2a, 2b, 12a, 12b, 22a, 22b, 32a, 32b, 42a, 42b, 52a, 52b) and two frame portions (2a, 2b, 12a, 12b, 22a, 22b, 32a, 32b; 42a, 42b; 52a, 52b) includes side leg portions (2c; 12c; 22c; 32c; 42c; 52c) connecting to a closed core along a longitudinal direction (L), and wherein the center leg (3; 13a; 23a; 33a; 43a; 53a) of each side leg portion (2c; 12c; 22c; 32c; 42c; 52c) is spaced laterally by at least one parallelepiped or cylindrical winding window (15; 25; 35; 45; 55).

The frame core (40; 50) of claim 13 or 14, wherein the frame core (40; 50) has at least one further center leg (43b; 53b) with air gap (44b; 54b) integral with the frame core (40; 50) is.