METHOD AND DEVICE FOR PRODUCE A RING STRIP CORE

Description

[0001] The invention relates to methods and devices for manufacturing a ring core such as is used, for example, for transformers or chokes.

[0002] Chokes are coils or inductors used to limit currents in electrical lines, to temporarily store energy in the form of their magnetic field, for impedance matching, or for filtering. Most chokes have a magnetic core because they then require significantly fewer turns for the same inductance compared to air-core chokes.

[0003] Transformers typically consist of two or more coils, usually wound from insulated copper wire, located on a common magnetic core. They are used, for example, for voltage conversion in power supply systems and technical devices. They are also required for signal transmission and protective isolation.

[0004] Magnetic cores consist of a soft magnetic material with the highest possible magnetic saturation flux density and high magnetic permeability. This allows the magnetic flux generated when current flows through the coil's electrical conductor to be focused and guided with minimal loss, thereby increasing the inductance. High permeability increases the magnetic field of an inductor by up to five orders of magnitude compared to an inductor with an air core, allowing the dimensions of an inductor with a magnetic core to be smaller than those of an air-core inductor.

[0005] To combat eddy current losses, the magnetic cores of transformers and electric motors are not solid, but laminated. These die-cut or cut electrical steel sheets are coated with a heat-resistant and insulating lacquer and stacked into blocks or rolled into rings, oriented parallel to the magnetic field lines. The magnetic flux is thus distributed across individual, separate fluxes within each sheet, resulting in only smaller eddy currents and significantly lower overall power loss than in a solid material. The sheets are typically less than 1 mm thick. The thinner the sheet, the lower the eddy current losses and the higher the permissible operating frequency.

[0006] Laminated magnetic cores are primarily used in the low-frequency range of 16 to 400 Hz. Wound tape cores with tape thicknesses around 20 µm, however, can be used up to 100 kHz. For high-frequency applications, powder cores or ferrite cores are predominantly used for transformers, coils, and chokes.

[0007] Tape cores are wound from a thin, soft magnetic tape with a thickness between (typically and depending on the alloy) 20 µm and 1 mm. The simplest and most cost-effective form to manufacture is a toroidal tape core. Except for the negligible transition between the tape layers, this creates an ideal, closed magnetic circuit with a uniform cross-section. The dynamic properties are largely determined by the alloy used and the tape thickness.

[0008] Ring cores are typically manufactured from a long strip, which usually first needs to be cut to the required width. They are therefore also called cut cores. The strip is wound into a core using a winding machine. After winding, a heat treatment is performed to adjust or achieve the core's magnetic properties, at temperatures between approximately 200°C and 600°C, depending on the alloy. During heat treatment, the material changes not only its magnetic properties but also its mechanical properties. Amorphous and nanocrystalline alloys are quite brittle after heat treatment and can therefore be easily damaged mechanically.

[0009] JP S61 42906 shows a process in which a tape core is wound. This is then cut open to slide on the coils, and subsequently reassembled.

[0010] Improved methods and devices for manufacturing a ring core are proposed below.

[0011] A proposed device for manufacturing a ring core comprises: A winding device with two rotating winding mandrels arranged at a distance from each other for winding the tape, wherein the winding mandrels can be driven either rotating about a first axis of rotation or rotating about a common second axis of rotation, and wherein the winding mandrels can be moved perpendicular to the axes of rotation to adjust their distance, two tape feed devices each with at least one tape reel for providing a soft magnetic tape, an insertion device with at least one manipulator for inserting separating discs into a forming tape winding, and at least one cutting device for stepwise and offset cutting of the tape winding into a plurality of tape sections.

[0012] Other aspects of the proposed device include, that the tape feeding devices each comprise at least two tape reels for providing soft magnetic tape of different widths; that the tape feeding devices each have a multi-reel magazine to which at least two tape reels can be interchangeably attached; that a tape tensioning device is provided for maintaining a predefinable tape tension; that a coating device for applying an insulating layer or bonding layer to the tape may be provided; that a coil feeding device with a manipulator for picking up and placing coils on the tape sections is provided; that a closing device with a manipulator for forming free ends of the tape sections into a closed ring is provided; that the closing device comprises a manipulator for attaching a tensioning band enclosing the entire magnetic core.

[0013] A proposed method for manufacturing a ring core comprises the following steps: Providing a soft magnetic tape on at least two tape reels, unwinding the tape from two tape reels and winding the tape onto two spaced-apart winding mandrels to form a multi-layered first tape roll by rotating the winding mandrels around a first axis of rotation, inserting a separating plate into the forming first tape rolls after several layers, reducing the distance between the winding mandrels until the first tape rolls touch each other, unwinding the tape from two tape reels and winding the tape into a multi-layered second tape roll that wraps around the first tape rolls by rotating the winding mandrels around a common second axis of rotation, inserting a separating plate into the forming second tape roll after several layers, gradually cutting the tape rolls into a plurality of tape sections, picking up at least one reel and fixing the reel onto the tape sections.Shaping the free ends of the strip sections and joining the ends of the strip sections to form a closed ring.

[0014] Other aspects of the proposed device include, that for each winding mandrel, tapes of different widths are provided on at least two tape reels; that an insulating or bonding layer can be applied to the tape between unwinding and winding; that in a final step, a tension band or tensioning structure enclosing the entire magnetic core is attached; that the first tape windings on the winding mandrels are formed from at least two tapes of different widths with increasing width from the inside out, and the second tape winding on the first tape windings is formed analogously from at least two tapes of different widths with decreasing width from the inside out.

[0015] The device and method are explained in more detail below using an exemplary embodiment and the accompanying drawings. These drawings show: Fig. 1a bis 1d the schematic process of winding the tape in a front view, Fig. 2a und 2b the schematic process of winding the tape in a top view, and Fig. 3a bis 3f the schematic process of cutting the tape windings, fixing the spools and joining the tape sections.

[0016] The representations of Fig. 1a bis 1d Figure 1 shows a front view of a device for manufacturing a toroidal core with two tape coils 3 for providing a thin, soft magnetic tape 1 and with two rotatably driven winding mandrels 5 for winding the tape 1 into multilayer tape coils 8, 9, the distance between which is adjustable, and with two nozzles 10 of a coating device for applying an insulating layer or bonding layer to the tape 1. The winding mandrels 5 can be driven separately about a first axis of rotation 6 or together about a second axis of rotation 7, wherein the first axes of rotation 6 and the second axis of rotation 7 are aligned parallel to each other. The winding mandrels 5 have a rectangular cross-section adapted to the transformer to be manufactured, and frame elements 14 of a holding frame may already be inserted into the winding mandrels 5.Whether the belts 1 are used as single belts or as multiple belts is irrelevant for the proposed method. It only affects the productivity of the proposed device.

[0017] As in the Fig. 2a und 2b As shown in a top view, the tape feed device for each winding mandrel 5 not only has a single tape spool 3, but also a multi-spool magazine 4 to which four tape spools 3 with tape 1 of different widths can be interchangeably attached. This allows the first tape windings 8 on the winding mandrels 5 to be formed from up to four tapes of different widths, with the width increasing from the inside out. After a certain number of layers of a tape 1 of a specific width have been wound, the multi-spool magazine 4 is reconfigured so that winding continues with a tape 1 of a greater width. Winding begins with the narrowest tape 1. When the desired thickness of this tape 1 is reached, the winding is interrupted, the tape 1 is cut, and the next wider tape 1 is coupled to the narrower tape 1 (e.g., with double-sided adhesive tape), and then the winding process continues.

[0018] For the subsequent separation process, separating plates 11 are inserted into the first two tape winders 8 after, for example, approximately 5 mm of tape winder thickness, when winding the tape 1 into two tape winders 8. Fig. 3a bis 3c The separating plates 11 are shown. They are intended to prevent the underlying material layer from being cut during a separation cut. The separating plate 11 can be made of various materials, as it is removed after the separation cut. It is irrelevant whether the cut is made directly into the separating plate 11 or whether there is a recess in the separating plate 11 at the separation point. The separating plate 11 can advantageously be made of a permanent magnet, which allows for easy fixation and removal after the separation cut. A recess must be provided for a permanent magnet version.

[0019] Once the desired thickness of the second strip is reached, the third and fourth strips are wound analogously. However, for the last (widest) strip, winding only occurs up to half the desired thickness. The winding of the strip 1 onto the winding mandrels 5 by rotation around the respective first axis of rotation 6 is described in Fig. 1b and Fig. 2a depicted.

[0020] Then the winding device is stopped and the winding mandrels 5 are moved towards each other in a plane perpendicular to the axes of rotation 6, 7 until the first tape coils 8 touch each other (shown in Fig. 1c and Fig. 2b ). Now, the unwinding from both tape feed devices onto the two previously produced first tape winders 8 takes place simultaneously, by rotating the two winding mandrels 5 together around the second rotary axis 7 arranged between them, so that a second tape winder 9 enclosing the two first tape winders 8 is created (shown in Fig. 1d and Fig. 2b ).

[0021] The bandwidth is reduced by one step each time the desired thickness is reached. This results in an overall ovalized core cross-sectional geometry.

[0022] Analogous to what has already been described above, when winding the tape 1 into a second tape winder 9, separating plates 11 are positioned at the desired separation points when the respective desired layer thickness is reached and inserted into the forming second tape winder 9.

[0023] If coating the tape 1 with an insulating or bonding layer is required, this can be applied continuously during the winding process. In this case, however, a multi-layered tape 1 should not be used. After the winding process is complete, a tape coil 8, 9 is present, as shown in Fig. 3a is shown.

[0024] After completion of the winding process, the (upper) part of the core holding device 14 is mounted, as Fig. 3b shows. Afterwards, the core can be removed from the device and the tape winding 8, 9 must be separated in order to position and fix the spools 13. In Fig. 3b Figure 12 shows how the cutting device 12 is cutting through the first winding layers of the outer, second tape winding 9 up to an inserted cutting plate 11. Fig. 3c All winding layers of the outer, second tape winding 9 have been cut and the cutting device is just beginning to cut the first winding layers of one of the two inner, first tape windings 8 up to an inserted cutting plate 11.

[0025] The tape coil 8, 9 is cut by a cutting device 12, for example by means of an abrasive cutting disc. The cutting process is carried out with the smallest possible cutting width (for example approx. 1-2 mm) at the points where the cutting discs 11 have been inserted, in each case from the outside up to the cutting disc 11.

[0026] The cut ends of the strip sections 2 then fall downwards due to gravity, revealing the next cutting point. After all cutting processes are complete and the free ends of the strip sections 2 created by the cutting are hanging down ( Fig. 3d ), spools 13 can be pushed onto the free ends of the tape sections 2, or the spools 13 are positioned ready and the free ends of the tape sections 2 are lowered into the spools 13 ( Fig. 3e ).

[0027] Then the (lower) part of the holding device 14 is positioned and fixed on the core ( Fig. 3e ), then the open legs 2 are closed, starting from the middle ( Fig. 3f The positioning is designed so that the free ends of the band sections 2 meet almost flush; this is made possible by indenting the lower retaining frame 14 by half the cutting width in the direction of the upper retaining frame 14.

[0028] To assist the closing process, a tension band should be placed around the fully wound transformer core, which may already have been fixed in the upper retaining frame 14.

[0029] After closing the core ring, the lower retaining frame 14 is completed ( Fig. 3f ). This completes the basic structure of the transformer, consisting of the core, coil 13 and mounting frame 14.

[0030] If the core is to be delivered to a transformer manufacturer as a partial product, the lower support frame 14 can be mounted before separation. However, the lower support frame 14 must then be disassembled and reassembled for the installation of the coils 13. Bezugszeichenliste

[0031] 1 Soft magnetic tape 2 Tape section 3 Tape reel 4 Multi-spool magazine 5 Winding mandrel 6 First rotary axis 7 Second rotary axis 8 First tape winding 9 Second tape winding 10 Coating nozzles 11 Separating plate 12 Separating device 13 Reel 14 Holding frame elements

Claims

1. An apparatus for producing a tape-wound toroidal core, comprising • a winding device with two rotationally drivable winding mandrels (5) arranged at a distance from each other for winding up the tape (1), wherein the winding mandrels (5) are selectively rotationally drivable about in each case a first axis of rotation (6) or about a common second axis of rotation (7), and wherein the winding mandrels (5) are movable perpendicular to the axes of rotation (6, 7) for adjusting the distance between them, • two tape feeding devices, each having at least one tape coil (3) for providing a soft-magnetic tape (1), • at least one separating device (12) for cutting through the tape roll (8, 9) to form a plurality of tape sections (2), characterized by an insertion device having at least one manipulator for inserting separating plates (11) into a tape roll (8, 9) being formed.

2. The apparatus as claimed in claim 1, in which the tape feeding devices each comprise at least two tape coils (3) for providing soft-magnetic tape (1) of differing width.

3. The apparatus as claimed in claim 2, wherein the tape feeding devices each have a multi-coil magazine (4), to which at least two tape coils (3) are interchangeably attachable.

4. The apparatus as claimed in any one of claims 1 to 3, comprising a tape tensioning device for maintaining a predeterminable tape tension.

5. The apparatus as claimed in any one of claims 1 to 4, comprising a coating device (10) for applying an insulation layer or connecting layer to the tape (1).

6. The apparatus as claimed in any one of claims 1 to 5, comprising a coil feeding device with a manipulator for picking up and depositing coils (13) on the tape sections (2).

7. The apparatus as claimed in any one of claims 1 to 6, comprising a closing device with a manipulator for reshaping free ends of the tape sections (2) into a closed ring.

8. The apparatus as claimed in claim 7, in which the closing device comprises a manipulator for attaching a tensioning tape enclosing the entire magnetic core.

9. A method for producing a tape-wound toroidal core, comprising the steps of: • providing a soft-magnetic tape (1) on at least two tape coils (3), • unwinding the tape (1) from two tape coils (3) and winding up the tape (1) onto two winding mandrels (5) arranged at a distance from each other to form in each case a multi-layer first tape roll (8) by rotating the winding mandrels (5) about a respective first axis of rotation (6), wherein, after in each case a plurality of layers, a separating plate (11) is inserted into the first tape rolls (8) being formed, • reducing the distance between the winding mandrels (5) until the first tape rolls (8) touch each other, • unwinding the tape (1) from two tape coils (3) and winding up the tape (1) to form a multi-layer second tape roll (9) which loops around the first tape rolls (8) by rotating the winding mandrels (5) about a common second axis of rotation (7), wherein, after in each case a plurality of layers, a separating plate (11) is inserted into the second tape roll (9) being formed, • gradually cutting through the tape rolls (8, 9) to form a plurality of tape sections (2), • picking up at least one coil (13) and depositing the coil (13) on the tape sections (2), • reshaping free ends of the tape sections (2) and connecting the ends of the tape sections (2) to form a closed ring.

10. The method as claimed in claim 9, in which, for each winding mandrel (5), tapes (1) of differing width are provided on in each case at least two tape coils (3).

11. The method as claimed in claim 9 or 10, in which, between the unwinding and the winding up of the tape (1), an insulation layer or connecting layer is applied to the tape (1).

12. The method as claimed in any one of claims 9 to 11, in which a tensioning tape enclosing the entire magnetic core is attached.

13. The method as claimed in any one of claims 9 to 12, in which the first tape rolls (8) on the winding mandrels (5) are formed from at least two tapes (1) of differing width with an increasing width from the inside to the outside and the second tape roll (9) is formed on the first tape rolls (8) from at least two tapes (1) of differing width with a decreasing width from the inside to the outside.

14. The method as claimed in claim 13, in which at least four tapes (1) of differing width are used to form a magnetic core with an at least eight-fold stepped cross section.