Method for assembling a magnetic core for a transformer

Abstract

A method is described for the assembly of a magnetic core for a transformer, with the following steps: Cutting sheet metal blanks from transformer sheet, stacking the sheet metal blanks to form magnetic core segments, placing a permanent magnet at one of the magnetic core segments so that the latter is magnetized by the permanent magnet, formation of the magnetic core by placing the remaining magnetic core segments against the permanent magnet, or against a magnetic core segment already magnetized by the permanent magnet. A magnetic core is also disclosed.

Claims

1. A method of assembling a magnetic core for a transformer, comprising: cutting sheet metal blanks from a transformer sheet; stacking the sheet metal blanks to form a plurality of magnetic core segments, each of the plurality of magnetic core segments being formed by a separate sheet metal stack; placing a permanent magnet at one of the magnetic core segments to thereby magnetize the one of the plurality of magnetic core segments by the permanent magnet; and subsequent to the step of placing the permanent magnet, forming the magnetic core by placing remaining magnetic core segments at the permanent magnet or against another of the plurality of magnetic core segments which is already magnetized by the permanent magnet wherein the magnetic core includes a plurality of legs and each magnetic core segment forms no more than one leg of the magnetic core.

2. The method according to claim 1, wherein the permanent magnet is a ferrite magnet.

3. The method according to claim 1, wherein a first end face of a first longitudinal leg of the magnetic core contacts the permanent magnet, and a second end face of the first longitudinal leg contacts a transverse leg of the magnetic core.

4. The method according to claim 3, wherein a longitudinal side of a second longitudinal leg contacts an end face of the two transverse legs.

5. The method of claim 1 wherein the plurality of legs includes a plurality of transversely extending legs and a plurality of longitudinally extending legs.

6. The method of claim 1 wherein interfaces between adjacent legs of the magnetic core extend either transversely or longitudinally.

7. The method of claim 1 wherein the plurality of legs includes three longitudinally extending legs and two transversely extending legs, each of the longitudinally extending legs being defined by a separate core segment and each of the transversely extending legs being defined by two separate core segments.

8. The method according to claim 7, wherein each of the core segments defining the transverse legs engages a central one of the longitudinal legs and has a rounded corner, each of the rounded corners of the core segments defining the transverse legs defining an edge that terminates at the central one of the longitudinal legs.

9. The method of claim 1 further comprising a step of subjecting the transformer to a temperature which exceeds the Curie temperature of the permanent magnet.

10. A method of assembling a magnetic core for a transformer, comprising: cutting sheet metal blanks from a transformer sheet; stacking the sheet metal blanks to form magnetic core segments; placing a permanent magnet at one of the magnetic core segments to thereby magnetize the one magnetic core segment by the permanent magnet; subsequent to the step of placing the permanent magnet, forming the magnetic core by placing remaining magnetic core segments at the permanent magnet or against another of the magnetic core segments which is already magnetized by the permanent magnet; and subjecting the transformer to a temperature which exceeds the Curie temperature of the permanent magnet.

11. The method according to claim 10, wherein the permanent magnet is a ferrite magnet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 shows an embodiment of an inventive magnetic core;

(3) FIG. 2 shows an embodiment of a transformer with a magnetic core as in FIG. 1;

(4) FIG. 3 shows a cross-sectional view through FIG. 2;

(5) FIG. 4 shows a further embodiment of an inventive magnetic core;

(6) FIG. 5 shows a further embodiment of an inventive magnetic core; and

(7) FIG. 6 shows sheet metal blanks for the legs of this magnetic core.

DESCRIPTION

(8) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(9) FIG. 1 shows a magnetic core for a transformer, for example an ignition coil, which has four separate core segments made of soft iron, namely a first longitudinal leg 1, a second longitudinal leg 2, a first transverse leg 3 and a second transverse leg 4. The legs 1, 2, 3, 4 are formed as stacks of mutually abutting sheet metal blanks. Such stacks are sometimes also referred to as packages.

(10) The magnetic core additionally contains a permanent magnet 5, which is arranged between a first end face of the first longitudinal leg 1 and a longitudinal side of the first transverse leg 3. The first longitudinal leg 1 of the magnetic circuit as shown is located with its first end face on the permanent magnet 5 and with its second end face on the second transverse leg 4.

(11) The first longitudinal leg 1 is widened on its first end face, which abuts against the permanent magnet 5, for example a ferrite magnet. In this manner, a permanent magnet with an enlarged surface area can be used and the coupling of magnetic flux into the first longitudinal leg 1 can be increased. The first longitudinal leg 1, for example, can be designed as an L-shape. In the example embodiment shown, the width of the first longitudinal leg 1 increases continuously into an end section. The first longitudinal leg 1 thus has a wedge-shaped extension in its end section on its longitudinal side facing the second longitudinal leg 2.

(12) The two transverse legs 3, 4 are of the same design, each with one end face facing towards the second longitudinal leg 2 and one longitudinal side facing towards the first longitudinal leg 1. In the embodiment shown the first longitudinal leg 1 is therefore shorter than the second longitudinal leg 2. The transverse legs 3, 4 and the second longitudinal leg 2 can have the same width. The first longitudinal leg 1 can be wider than the second longitudinal leg 2 and the two transverse legs 3, 4. For example, the transverse legs 3, 4 and the second longitudinal leg 2 can everywhere have a width that is less than two thirds of the minimum width of the first longitudinal leg 1; for example, the transverse legs 3, 4 and the second longitudinal leg 2 can have a width that is not more than half the width of a main section of the first longitudinal leg 1.

(13) The interfaces with which the legs 1, 2, 3, 4 abut against each other, or against the permanent magnet 5, extend either in a longitudinal direction or in a transverse direction. In this manner the assembly of the magnetic core and the production of the individual legs 1, 2, 3 and 4 can be facilitated.

(14) FIG. 2 shows in a side view, and FIG. 3 shows schematically in a cross-sectional view, a transformer in the form of an ignition coil, which contains a magnetic core as in FIG. 1. The second longitudinal leg 2 and the two transverse legs 3, 4 of the magnetic core are clearly visible. The first longitudinal leg 1 is surrounded by the primary windings 12 and secondary windings 11 of the transformer. In the embodiment shown, the secondary winding 11 is wound around the primary winding 12 as a chamber winding. However, ignition coils can also be implemented with an external primary winding.

(15) FIG. 4 shows a further embodiment of a magnetic core for a transformer. This magnetic core contains a central longitudinal leg 20, outer longitudinal legs 21, 22 and two transverse legs 23, 24. Between the central longitudinal leg and the transverse leg 24 a permanent magnet 5, for example a ferrite magnet, is arranged. A first end face of the central longitudinal leg 20 thus abuts against the permanent magnet 5 and a second end face abuts against the transverse leg 23. The central longitudinal leg 20 has a widened cross-section in the form of a foot at its end facing towards the permanent magnet 5.

(16) FIG. 5 shows a modified embodiment, which differs from the embodiment shown in FIG. 3 only in the configuration of the transverse legs. Instead of continuous transverse legs, the magnetic core shown in FIG. 5 has divided transverse legs 23a, 23b and 24a, 24b, each of which extends from the central longitudinal leg 20 to one of the outer longitudinal legs 21, 22. In the region of the central longitudinal leg 20, the transverse legs 23, 24, or 23a, 23b, 24a, 24b, can be adapted to the magnetic flux as shown in FIG. 4, so that a rounded recess ensues towards the central longitudinal leg 20. In this manner, a weight saving can be achieved without any negative influence on the magnetic field.

(17) FIG. 6 shows how to cut out transformer blanks economically for the legs 1, 2, 3, 4 from a strip of transformer sheet, that is to say, how to utilize the transformer sheet efficiently and minimise waste. The blanks of transformer sheet are then layered to form a stack that forms one of the legs 1, 2, 3, 4. Transformer sheet is sometimes also referred to as electrical sheet or core lamination. Here these take the form of reinforced soft magnetic iron, for example iron reinforced with silicon.

(18) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SYMBOLS

(19) 1 Longitudinal leg 2 Longitudinal leg 3 Transverse leg 4 Transverse leg 5 Permanent magnet