Method for manufacturing a capacitor

Abstract

The present invention relates to a method for producing a capacitor, comprising the steps of: winding a dielectric layer and an electrically conductive layer around a rotation axis on a winding core to form a winding, wherein the winding core has a non-circular cross-section, and pressing the winding perpendicular to the rotation axis.

Description

Prior ArtThe present invention relates to a method for producing a capacitor and to a capacitor.Cost reduction is an important issue in product development and plays an important role, especially for automobile suppliers, in obtaining new projects in the dynamic and competitive world electric car industry. The intermediate circuit capacitor is generally the most expensive individual component in the inverter. Here, the inverter, the electric motor and the battery belong to the three most important assemblies of an electric vehicle, so that the reduction in the costs of the intermediate circuit capacitor has a high threshold value. The costs for an intermediate circuit capacitor are essentially formed by the winding, the connections and the housing. There have been few approaches to reduce the cost of the winding. Capacitors having a high capacitance would normally require a plurality of alternating dielectric and electrically conductive layers as the winding resulting in large windings. This presents a problem in the prior art because large coils can dissipate poor heat and are difficult to process. In particular, large windings make it difficult to press the winding.Disclosure of the InventionThe method according to the invention for producing a capacitor having the features of claim 1 and the capacitor having the features of claim 9 have the advantage that a capacitor having a winding is provided, which can be produced reliably and economically with a high capacitance. This is achieved according to the invention in that a dielectric layer and an electrically conductive layer are wound to form a winding around a rotational axis of a winding core. The winding core has a non-round cross section. The winding is then pressed perpendicularly to the axis of rotation. Due to the non-round cross section of the winding core, the winding has to be less shaped during the pressing process, so that the winding can have a higher number of windings with a high process capability. The increased number of windings results in a high-capacitance winding, so that the number of windings in a capacitor can be reduced. The reduced number of windings in the capacitor can reduce the manufacturing costs of the capacitor. The electrically conductive layer is preferably made of a metal. The dielectric layer is preferably made of a plastic.The dependent claims show preferred developments of the invention.Preferably, a maximum width of the winding core is greater than a maximum height of the winding core. Thus, the forming work when pressing the coil can be reduced. The maximum width and the maximum height of the winding core are constant, preferably along the length of the winding core.More preferably, the winding core has an oval cross section. As a result, a relatively uniform winding of the dielectric layer and of the electrical layer can take place. Alternatively, the winding core can also have a rectangular cross section with rounded corners.Alternatively, the winding core preferably has a polygonal cross section. The polygonal cross section is preferably a hexagon. This allows reliable fabrication of large windings. More preferably, two sides of the polygonal cross section are longer than further sides of the polygonal cross section.Particularly preferably, the winding core is rotationally symmetrical with respect to the axis of rotation.Preferably, the winding is pressed perpendicular to a transverse axis of the winding. The transverse axis preferably extends along a maximum width of the winding. The resulting winding has an improved surface area to volume ratio, whereby heat dissipation can be improved.More preferably, an inner surface of the winding is compressed so that the inner surface lies flat against each other. Thus, the winding has a minimized cavity in the interior of the winding, preferably no cavity, whereby the power density of the capacitor can be increased. The inner surface is preferably in contact with the winding core during winding.According to a further preferred embodiment of the invention, the maximum width of the winding core is at least twice as great as the maximum height of the winding core. The resulting winding can thus be reliably pressed, since a low forming work has to be carried out. Furthermore, the resulting winding enabled good heat dissipation.Further preferably, a maximum width of the winding before pressing is at least twice as large as the maximum width of the winding core. Due to the large difference between the maximum width of the winding and the maximum width of the winding core, a high capacity can be made possible at low manufacturing costs.The invention further relates to a capacitor which comprises a housing in which at least one winding of alternating dielectric layers and electrical layers is arranged. The winding is produced according to a method described above. The capacitor is preferably an intermediate circuit capacitor. Furthermore, the capacitor preferably has at least two dielectric layers and at least two electrically conductive layers, which are wound up alternately. Furthermore, the capacitor preferably has a contact-making region, via which the capacitor can be electrically contacted.Preferably, the dielectric layer and / or the electrically conductive layer of the winding is a foil. A thin layer composite with a high capacity can thus be made possible cost-effectively. For example, the dielectric layer is a film that is metallized. Alternatively, the dielectric layer can be a plastic film and the electrically conductive layer can be a metal film.Brief Description of the DrawingsHereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic flow diagram of a method according to a first exemplary embodiment, FIG. 2 shows a schematic illustration of a winding before a second step according to a first exemplary embodiment, FIG. 3 shows a schematic illustration of the winding after a second step according to the first exemplary embodiment, FIG. 4 shows a schematic illustration of a winding before a second step according to a second exemplary embodiment, and FIG. 5 is a schematic diagram of a capacitor having four windings according to the first embodiment.Embodiments of the InventionAll the same components, elements and / or units are preferably provided with the same reference numerals in all the figures.Next, referring to FIGS. 1 to 3 and 5, a method of manufacturing a capacitor 1 and a winding 5 of a capacitor 1 according to a first preferred embodiment of the present invention will be described in detail.FIG. 1 shows a schematic flow diagram of the method for producing the capacitor 1.In a first step S 1, a dielectric layer 2 and an electrically conductive layer 3 are wound onto a winding core 4, so that the winding 5 with a defined number of layers is produced. The winding core 4 has a non-round cross section and rotates about an axis of rotation X-X. The axis of rotation X-X is preferably a central axis of the winding core 4.The dielectric layer 2 and the electrically conductive layer 3 may be two individual layers or a connected layer.In a second step S 2, the winding 5 is pressed perpendicularly to the axis of rotation X-X. When a pressing force P is applied to the coil 5 from one side or from two opposite sides. Before pressing in the second step S 2, the winding core 4 is preferably removed from the winding 5.Preferably, the pressing force P is also directed perpendicular to a transverse axis Y-Y of the winding 5. The transverse axis Y-Y extends along a maximum width L of the winding 5.After the second step S 2, the electrically conductive layers 3 are preferably contacted, for example by schooling. The electrically conductive layer 3 is preferably contacted at the end faces of the winding 5.Furthermore, the winding 5 can subsequently be impregnated and mounted in a housing. In addition, terminals may be attached to the winding.FIG. 2 shows the winding 5 with winding core 4 according to the first exemplary embodiment of the invention between the first step S 1 and the second step S 2.The winding 5 is wound on a rectangular winding core 4 with rounded corners around its axis of rotation X-X. The winding core has an approximately oval shape. A maximum width L of the winding core 4 is twice as large as a maximum height D of the winding core 4, the maximum height D of the winding core 4 being measured perpendicular to the transverse axis Y-Y. The maximum width L of the winding core 4 and a maximum width W of the winding are measured along a transverse axis Y-Y which intersects perpendicularly the axis of rotation X-X.The dielectric layer 2 and / or the electrically conductive layer 3 lies flush against a surface of the winding core 4 and forms an inner surface 6 of the winding. The plurality of windings of the dielectric layer 2 and the electrically conductive layer 3 result in the maximum width W and a maximum height T 1 of the winding 5.The winding 5 preferably has two independent dielectric layers 2 and two independent electrically conductive layers 3, so that different electrical potentials can be applied to the electrically conductive layers 3.The non-round cross section of the winding core 4 enables a large winding 5 which has a high surface area-volume ratio in order to be able to dissipate heat quickly. Furthermore, the winding 5 can be pressed together reliably in terms of process even in the case of a high number of windings due to the reduced height of the winding core 4.FIG. 3 shows the winding 5 according to the first exemplary embodiment after the pressing in the second step S 2.The coil 5 according to the first embodiment was transformed by the pressing force P, which is oriented perpendicular to the axis of rotation X-X and perpendicular to the transverse axis Y-Y. The pressing force P is preferably applied to the winding 5 by a flat upper tool, wherein the winding 5 is arranged on a flat lower tool. Thus, the coil 5 after pressing has two flat parallel surfaces.After pressing, the maximum height T 1 of the winding 5 has decreased, so that the winding 5 now has the maximum height T 2. The maximum height T 2 of the coil 5 after pressing is preferably the difference between the maximum height T 1 of the coil 5 and the maximum height D of the winding core 4. Furthermore, it should be prevented that the winding 5 is compressed too much, as a result of which the dielectric layers 2 or electrically conductive layers 3 can be damaged.FIG. 4 shows the winding 5 according to a second exemplary embodiment.The second embodiment differs from the first embodiment in the cross section of the winding core 4. In this case, the maximum width L of the winding core 4 is also more than twice as large as the maximum height D of the winding core 4 in the second exemplary embodiment.The maximum width L of the winding core 4 is measured at two corners which lie on the transverse axis Y-Y. Furthermore, the cross section has two sides which are arranged parallel to the transverse axis Y-Y. In this case, the two sides which are arranged parallel to the longitudinal axis Y-Y are longer than the further sides of the hexagonal cross section.The winding core 4 is rotationally symmetrical with respect to the axis of rotation X-X. Furthermore, the cross section of the winding core 4 is mirror-symmetrical to the transverse axis Y-Y. This makes it possible to achieve uniform winding of the dielectric and electrically conductive layer 2, 3 onto the winding core 4.FIG. 5 shows a capacitor 1 with a housing 7, in which four windings 5 according to the first exemplary embodiment are arranged. The capacitor 1 is preferably an intermediate circuit capacitor which is configured to be arranged in an inverter of an electric vehicle.The windings 5 are arranged such that the transverse axes Y-Y of the windings 5 are arranged parallel to each other. The use of fewer windings 5 with a high capacitance enables the production of a cost-effective and powerful capacitor 1 in a small housing 7.

Claims

Method for manufacturing a capacitor (1) comprising the steps of: - winding (S1) a dielectric layer (2) and an electrically conductive layer (3) around an axis of rotation (X-X) on a winding core (4) into a winding (5), the winding core (4) having a non-round cross-section, and - pressing (S2) the winding (5) perpendicular to the axis of rotation (X-X).Method according to claim 1, wherein a maximum width (L) of the winding core (4) is greater than a maximum height (D) of the winding core (4).Method according to claim 2, wherein the winding core (4) has an oval cross-section or a rectangular cross-section with rounded corners.Method according to claim 2, wherein the winding core (4) has a polygonal cross section.Method according to one of the preceding claims, wherein the winding (5) is pressed perpendicularly to a transverse axis (Y-Y) of the winding (5).Method according to one of the preceding claims, wherein an inner surface (6) of the winding (5) is compressed so that the inner surface (6) lies flat against one another.Method according to one of claims 2 to 6, wherein the maximum width (L) of the winding core (4) is at least twice as large as the maximum height (D) of the winding core (4).Method according to one of the preceding claims, wherein a maximum width (W) of the winding (5) before the pressing (S2) is at least twice as large as the maximum width (L) of the winding core (4).Capacitor, in particular an intermediate circuit capacitor, comprising a housing (7) in which at least one winding (5) consisting of alternating dielectric layers (2) and electrically conductive layers (3) is arranged, wherein the winding (5) is produced according to a method according to one of Claims 1 to 8.Capacitor according to claim 9, wherein the dielectric layer (2) and / or the electrically conductive layer (3) is a foil.

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