METHOD FOR PRODUCE A VOLUME-SHAPED METAL BODY

Description

[0001] The invention lies in the field of mechanical engineering and production technology, in particular foundry technology. It can be used to particular advantage in the manufacture of coils, spirals or springs.

[0002] Winded coils are used in electrical machines. These coils only partially fill the available installation space. This results in a lower power and torque density of the electrical machines relative to their weight and size. Cast aluminum and copper coils can compensate for this disadvantage; however, no mass-producible processes for manufacturing cast aluminum and copper coils, or cast coils made of aluminum and copper alloys, in permanent molds with sufficient service life are currently known.

[0003] To increase the power density or torque density of electrical machines, complex, often manually manufactured coils are currently wound to slightly improve the fill factor compared to mass-produced methods. Wire with the same cross-section is used across the entire height of the windings. Furthermore, in conventional electrical machines, the windings of the coil, arranged from the inside out, impair heat dissipation and lead to increased heating of the coils, thus necessitating a limitation of the maximum current density relative to the cross-sectional area of ​​the winding.

[0004] Cast Al and Cu coils or cast coils made of Al and Cu alloys are already known, but so far they are not produced in permanent molds, but in lost molds such as in investment casting or the lost-foam process or by using salt cores that define the contour and prevent direct contact of the melt with the tool.

[0005] For the production of a wide variety of geometries, a contour-defining mold is used according to current technology. For complex geometries, cores are inserted or slides are used in addition to the mold, which has one or more divisions for easy removal of the castings.

[0006] The high casting temperature of copper components, exceeding 1100°C, places increased demands on the tooling and core. The thermal stress, and especially the temperature shock during mold filling, leads to a short tool life and limits component quality, or necessitates extensive post-processing.

[0007] Previous tooling concepts always resulted in geometrically complex permanent molds or the additional use of movable slides or cores (permanent or non-permanent). Such molds could only be used in laboratory settings because they required extensive maintenance and resulted in high reject rates.

[0008] Patent application EP 2 819 276 A2 discloses a geometrically modified model geometry that enables a simply shaped, two-part permanent mold for the casting process. This is achieved by rotating the windings by 180° each, thus significantly reducing the geometric complexity of the coil. However, after casting, a highly complex forming process is required to achieve the coil geometry in its installed state.

[0009] Document DE 10 2012 212637 A1 shows a coil for an electrical device, in particular an electrical machine, for arrangement around at least one first core carrying a magnetic field and having a coil longitudinal axis extending in the direction of the magnetic field, wherein the coil has several turns cast from an electrically conductive coil material and the turns and / or turning sections have cross-sectional areas of different sizes and / or different shapes depending on their position in the coil longitudinal direction.

[0010] Groninger M. et al. describe in "Casting production of coils for electrical machines", ELECTRIC DRIVES PRODUCTION CONFERENCE (EDPC), 2011 1ST INTERNATIONAL, IEEE, September 28, 2011 (2011-09-28), pages 159-161, XP032000385, DOI: 10.1109 / EDPC.2011.6085534; ISBN: 978-1-4577-1371-2, that coils are manufactured using a casting process. In this process, the coils are formed from flat conductors stacked on top of each other. Compared to the final geometry, the positive model of the coil is stretched and has a defined spacing between the individual turns, which is greater than the thickness of the insulating layer. This allows for the casting process and the subsequent insulation of the coils. Afterward, the coil is compressed to achieve its final geometry.

[0011] The German patent application DE 10 2014 222468 A1 relates to a method for manufacturing at least one coil having several turns and at least two legs for an electrical machine, comprising at least the following steps: providing a wire-shaped starting workpiece; winding the wire-shaped starting workpiece into a starting coil, such that several turns and at least two legs are formed; arranging the wound wire-shaped starting workpiece in an annular slot of a first forming tool; forming the wire-shaped starting workpiece in at least one forming step into a workpiece using one of the following methods: i. extrusion or ii. forging; wherein a punch is inserted into the annular slot of the first forming tool and the starting workpiece, as a result of the forming, rests against an inner circumferential surface and an outer circumferential surface of the annular slot.

[0012] Publication JP 2009 153287 A is dedicated to providing a molded coil that reduces the assembly process and the number of parts while exhibiting high heat dissipation. It describes: a plurality of coils arranged along a circular arc; a resin mold section designed to embed and connect the coils; connection terminal sections exposed by the resin mold section; and holes formed inside each coil for inserting cores of magnetic material.

[0013] The publication EP 2 387 135 A2 relates to a method for manufacturing an electrotechnical coil with one or more windings, wherein a negative mold containing a coil geometry, in particular a expendable mold or a permanent mold, is provided or manufactured, wherein a coil material suitable for forming the winding(s), in particular an electrically conductive metal, is poured in liquid form into this negative mold, and wherein this coil material is solidified and / or allowed to solidify under controlled conditions. Furthermore, the invention relates to coils manufactured accordingly.

[0014] The present invention is based on the objective of creating a simple manufacturing method for helical metal bodies that allows for the economical use of casting molds and enables a high fill level of the helix.

[0015] According to the invention, the problem is solved by a method having the features of claim 1, and claims 2 to 6 present embodiments of the method.

[0016] Accordingly, the invention relates to a method for producing a helical metal body, in which a pre-formed, helical metal body is first produced in a mold by a casting process and then compressed by deformation along its longitudinal axis.

[0017] The invention allows the production of a helical body by casting, whereby the mold can be designed with relatively thick walls due to a sufficiently large distance between individual helical turns. The deformation of the metal body after the casting process allows for flexibility in the design of the mold produced by casting. After casting, the target shape of the metal body can then be achieved by deformation, whereby significantly smaller gaps between the individual turns of the helical structure can be achieved in the target shape, gaps that are difficult or impossible to achieve using conventional casting techniques due to the limitations imposed by the mold.

[0018] The process further involves compressing the metal body, at least partially, by plastic deformation along its longitudinal axis after casting.

[0019] Plastic deformation of the metal body ensures that its target shape is stable and maintained without the need for fixing agents.

[0020] The process can be further enhanced by processing the metal body after casting and before compression, in particular by grinding and / or polishing and / or coating.

[0021] Because, for example, the spaces between the spiral flutes and other parts of the metal body are more accessible in the pre-formed state after casting than after reaching the target shape, the aforementioned processing steps can be carried out particularly conveniently before the metal body is deformed / compressed into the target shape.

[0022] The method can be further developed by sliding the helical metal body onto a mandrel with a free end and a first stop shoulder to compress it, and by inserting the free end of the mandrel into a receptacle with a second stop shoulder to such an extent that the metal body is compressed between the stop shoulders.

[0023] Since the metal body, even in the form it assumes during the casting process, is already helical, it can easily be pushed onto a mandrel and compressed there along the longitudinal axis of the helix. A first stop shoulder on the mandrel side serves this purpose. The receptacle, for example, has an opening into which the mandrel, but not the metal body, can be inserted. A second stop shoulder can then be provided at this opening. When the mandrel is inserted into the opening of the receptacle, the helical metal body is compressed longitudinally between the first and second metal shoulders until it reaches the final shape or even beyond.

[0024] The method is characterized in that, during the production of the pre-formed metal body, at least one, in particular at least two, deformation areas are provided or created in each turn of the helix by a narrowing of the material cross-section, which are plastically deformed first when the body is compressed.

[0025] The deformation zones of a coil-shaped helix with a rectangular cross-section can be located on the shorter or longer sides of the individual turns / volumes, or at the corners of the individual turns. The cross-sectional constrictions can be incorporated into the casting mold of the metal body.

[0026] The process can be further developed by fixing the metal body with respect to its length after compression using a fixing agent.

[0027] Fixing can be achieved, for example, by dipping into a coating material or potting, or by attaching an external mechanical clamp / clip that holds the windings of the helix together axially. The clamp / clip must then either be made of a non-conductive material or be electrically insulated from the metal body.

[0028] The process can be further developed by first producing a lost model body, in particular made of a non-metallic material, in the desired target shape of the compressed helical metal body, expanding the model body by pre-deformation along the longitudinal axis, and using the expanded model body as a positive mold for casting the pre-formed metal body, in particular by producing a mold for the casting process using the model body or by using it in a lost-wax casting process.

[0029] The model is thus pre-deformed after its production by expanding the helix in the axial direction. Cross-sectional constrictions can also be incorporated into the model to create weakened deformation zones in the subsequently cast metal body. The metal body is then molded from this pre-deformed model and, if necessary, machined. Finally, the metal body is compressed into its final shape.

[0030] Also described is a device for producing a helical metal body of the type described above, with a mandrel having a free end and a first stop shoulder spaced apart from the free end, dimensioned in such a way as to form a stop for a helical metal body pushed onto the mandrel, and with a receptacle having an opening for inserting the free end of the mandrel and a second stop shoulder surrounding the opening for the metal body.

[0031] The device can be designed such that the mandrel, in the area of ​​the first stop shoulder, has external dimensions that allow for a positive-locking engagement of the pre-formed metal body, and that the mandrel tapers towards its free end in at least one first direction of expansion of its cross-section. The mandrel can advantageously have the shape and size of the central, continuous axial opening in the target shape of the metal body. To facilitate insertion into the metal body before its final deformation, the mandrel has a taper at its free end. The first stop shoulder can be designed as a flange on the mandrel.

[0032] The device can be further designed by forming a longitudinal stop for inserting the mandrel into the receptacle through the shaping of the mandrel and the receptacle, which determines the length of the compressed helical metal body.

[0033] The invention is shown below with reference to exemplary embodiments in figures of a drawing and then explained. Fig. 1 a perspective view of a helical body, Fig. 2 a helical body compressed along the longitudinal axis of the helix in three successive stages, Fig. 3 a helical body compressed along the longitudinal axis of the helix on a mandrel of a machining device between two stop shoulders in three successive stages, Fig. 4 a helical body with deformation areas shown, and Fig. 5 a schematic of the manufacturing process using a model body.

[0034] The following describes the production of lost patterns for use in investment casting using a simple tooling concept. The complexity of the coil geometry for the lost pattern is specifically reduced by plastically deforming the winding head in combination with a twist of the long winding side by <=90°. This enables the use of a simple two-part tooling concept for the production of castings (e.g., die casting, low-pressure casting, permanent mold casting, metal powder injection molding) or pattern plates or lost patterns (e.g., in wax injection molding, sand casting, sand casting with Disamatic, EPS patterns for lost foam). For this purpose, the winding head and the winding (long lamellae) of one pattern body are deformed in such a way that they conform to the geometry described in the following description: Figure 1 take on the depicted form. Figure 1This represents the form of a model body, which can initially have the target shape of the helical metal body and is then pre-deformed by expansion along the longitudinal axis 6 to form the mold for the metal body. However, this shape also corresponds to that of a helical metal body after casting and before compression in the longitudinal direction 6. The connections at the winding head 2 and the individual turns 3, 4, 5 of the helix are shown. For the casting process of the metal body to be produced, the individual turns of the helix have the increased spacing D. This avoids delicate and complex areas in the mold design.

[0035] This results in a robust, maintenance-friendly concept for all types of plug-in coils.

[0036] Pre-deformation at the winding head and twisting in the winding on the pattern enable the mass production of cast coils using permanent mold processes and expendable patterns as well as expendable molds. After the casting process, the casting system for feeding the molten metal for the subsequent process step can remain attached to the casting as a handling aid. This has the particular advantage that the actual casting, which is often made of pure aluminum (R99.7 or similar) or E-copper and exhibits very low strength and high ductility, is protected from further plastic deformation. The cast coil is fixed in the pre-deformed position, which is very advantageous for the subsequent process steps and enables automated processes.In particular, process steps such as deburring, polishing, cleaning, grinding, and coating are significantly simplified by the improved accessibility resulting from the pre-formed coil with increased pitch. Downstream processes can be performed before or after the casting system is removed, or only after further downstream processing steps (grinding, polishing, and coating for electrical insulation). An additional advantage of this geometry variant is the simple forming process after casting, achieved by inserting a guide rod into the core of the coil and directly forming the coils against each other.

[0037] This is achieved by threading a mandrel with a stop shoulder, as in Figure 2 depicted. Figure 2Figure 1 shows three different compression stages of the helical metal body in three successive stages from top to bottom, with an uncompressed form at the top, a partially compressed form in the middle, and a fully compressed form along the longitudinal axis at the bottom. On the left side of the metal body, a mandrel 7 with a free end 7a and a first stop shoulder 7b is shown, while on the right side, a receptacle 8 with a second stop shoulder 8a and an opening 8b for receiving the free end 7a of the mandrel 7 is shown.

[0038] The metal body (1') can either be deformed plastically after compression in the Figure 2The shortened target shape can remain below, or it can be held compressed by fixing means 10. Such fixing means can, for example, consist of a mechanical clamp / clip 10. However, the metal body can also be fixed, for example, by bonding it with an insulating material that simultaneously insulates the turns of the helix from each other.

[0039] Figure 3Figure 1 shows, in three different stages, the insertion of a mandrel 7 into a helical metal body 1 and the progressive compression of the helical metal body along its longitudinal axis 6, which runs parallel to the longitudinal axis of the mandrel 7. Using the mandrel 7 and the receptacle 8, the coil is deformed into its target / installed state. The forming process and calibration can be combined here. The compression can be continued until, after the elastic deformation components have relaxed, the target shape is achieved through the remaining plastic deformation. The mandrel is thin at its free end 7a to simplify threading and becomes thicker towards the first stop shoulder 7b, where its cross-section corresponds to the final contour of the coil's interior. Ideally, the final contour of the coil's interior has at least the same height as the coil / helical metal body in its target shape.

[0040] In the Figure 4 It has been shown that deformation zones 10, 11, 12, 13 are provided at certain locations on the helical metal body. These zones have a reduced cross-sectional area of ​​the material, allowing even slight deformation at these locations to transition from elastic to plastic deformation. This reduces the proportion of elastic deformation during compression of the metal body, enabling better prediction and attainment of the target shape. These deformation zones can be located, for example, at the corners of the coils or on the straight sections of the coils.

[0041] In the Figure 5A schematic representation of a model body 11 manufactured in the target shape is initially shown. This is modified into a longitudinally expanded, pre-deformed model body 11' and then translated into a metal body 13 in a similarly expanded form by means of a molding process. This can then be processed in potential work steps 14, for example by deburring and / or coating, and is subsequently compressed into the metal body 13'.

[0042] The combination of a winding head pre-deformed relative to the target shape and a twist of the winding in the pre-deformed state of less than 90 degrees relative to the target shape yields the following advantages: The combined and variable adjustment of the winding head modification and simultaneous twisting of the coil by an angle of less than 90° allows the tooling concept to be used for any type and size of plug-in coils. No draft angles are required at relevant points on the windings (parallel and non-parallel windings are possible), thus avoiding a manufacturing-related reduction in the slot fill factor. The pre-deformed coil can be formed into its final installation state by simply pushing it together using a mandrel. The mandrel geometry can be designed so that the forming process directly calibrates the coil to its final geometry.A small blasting surface of the tool allows the use of smaller injection molding machines, smaller tools or multiple cavities.

[0043] The invention can be used in the production of cast coils in a wide variety of sizes (e.g., small geometries such as those used in steering motors are required for permanent molds in aluminum die casting or MIM for copper coils; large coils can be produced using lost foam or sand casting).

[0044] A further advantage of the invention is the option of using shell casting instead of ingot casting. This is made possible by pre-deformation.

[0045] Sufficient space is created between the individual coils of the mold to allow for the shell formation during investment casting. This avoids the problem of the mold shells growing together in thin-walled molds or when the spacing between the individual coils is too small.

[0046] Burrs that form on the coiled metal body during casting are easily accessible before final deformation and can, for example, be removed automatically.

[0047] A closed shell / ceramic mold usable according to the invention in investment casting and in lost foam casting processes enables the production of a burr-free casting with an excellent surface finish; only the casting system needs to be removed and post-processed. The individual process steps are particularly suitable for automation in series production.

[0048] The invention makes it possible to mass-produce cast coils with materials such as aluminum and copper or aluminum and copper alloys, thereby significantly increasing productivity, design freedom, and cost-effectiveness in series production. Furthermore, the described method allows other materials suitable for casting to be formed into a helical geometry. Additionally, different coils with varying numbers of turns, turn thicknesses, and turn widths can be produced in a single outer mold with optionally different inner inserts, for example, made of ceramic material, thus enabling a variety of designs. The present invention therefore makes a significant contribution to the cost-effective production of coils, e.g.,This technology is used for applications as coils in electrical machines, and new manufacturing processes for electrical machines with higher power density and efficiency compared to the state of the art are being developed. By employing this innovative concept for manufacturing filaments / coils or coil models or lost-wax coil molds in geometrically simple tools, robust and automatable manufacturing processes for large-scale production are enabled.

[0049] In addition to conventional casting processes such as die casting, low-pressure casting, sand casting, lost foam core pack process, gravity casting, tilting die casting, investment casting and the various derivatives, the geometry can be used to pour the melt into one half of a tool with the described contour, close the tool and thus distribute the melt in the contour analogous to a waffle iron.

[0050] Simple visual inspections of the castings and metallographic analysis provide information about the manufacturing history and production method of the castings. In particular, plastically deformed areas in the winding and the winding head can be detected metallographically.

Claims

1. A method for producing a helical metal body (1'), in which a preformed, helical metal body (1, 13) is first produced in a mold by a casting process and then compressed by deformation along its longitudinal axis (6), wherein at least one, in particular at least two, deformation regions (10, 11, 12, 13) are provided or produced in each turn (3, 4, 5) of the helix during the production of the preformed metal body (1, 13), which regions are first plastically deformed when the metal body is compressed, wherein the at least one deformation region is provided or produced in each turn of the helix by a material cross-sectional constriction.

2. The method according to claim 1, characterized in that the metal body (1, 13) is processed after casting and before compression, in particular by grinding and / or polishing and / or coating.

3. The method according to one of claims 1 or 2, characterized in that, in order to compress the helical metal body (1, 13), it is pushed onto a mandrel (7) having a free end (7a) and a first stop shoulder (7b), and in that the free end (7a) of the mandrel is pushed into a receptacle (8) with a second stop shoulder (8a) until the metal body is compressed between the stop shoulders (7b, 8a).

4. The method according to one of claims 1 to 3, characterized in that at least two deformation regions (10, 11, 12 13) are provided or produced in each turn of the helix.

5. The method according to one of claims 1 to 4, characterised in that after the compression, the metal body (1') is fixed with respect to its length by fixing means (9).

6. The method for the production of a helical metal body (1') according to one of claims 1 to 5, characterised in that firstly a lost model body, for example a foam part for a lost foam method, in particular made of a non-metallic material, is produced in the desired target shape of the compressed coiled metal body (1') in that the model body is expanded by predeformation along the longitudinal axis and in that the expanded model body is used as positive mould for the casting of the predeformed metal body (1), in particular by producing a mould for the casting method with the help of the model body or by use in a melting method.