ELECTRIC MACHINE

Abstract

An electric machine includes a conductor structure having at least one metallic conductor element made from at least one of aluminum, copper, and silver having a monocrystalline or columnar crystal structure. The conductor structure may be formed from a plurality of individual flat conductor elements integrally bonded together by welding or soldering to form a winding. The metallic conductor element may be cut from an aluminum, copper, or silver bar having a monocrystalline or columnar crystal structure. A wafer having a plurality of conductor elements may be cut from a bar with the conductor elements separated from the wafer.

Claims

1. An electric machine comprising: a conductor structure having at least one metallic conductor element formed of at least one metal selected from aluminum copper, and silver, the at least one conductor element having a monocrystalline or columnar crystal structure.

2. The electric machine of claim 1 wherein the at least one metallic conductor element comprises a wound wire.

3. The electric machine of claim 1 wherein the at least one metallic conductor element comprises a plurality of individually prefabricated conductor elements integrally bonded together.

4. The electric machine of claim 3 wherein the conductor structure comprises a winding having a plurality of turns and wherein each of the plurality of conductor elements integrally bonded together includes at most one turn.

5. The electric machine of claim 1 wherein the electric machine includes a squirrel-cage rotor and wherein the conductor structure comprises a single conductor element having a monocrystalline crystal structure formed as a rotor cage of the squirrel-cage rotor.

6. The electric machine of claim 1 wherein the at least one metallic conductor element comprises a plurality of conductor elements integrally welded together.

7. The electric machine of claim 1 wherein the monocrystalline or columnar crystal structure is oriented in a longitudinal direction of the conductor element.

8. The electric machine of claim 1 further comprising a stator having a stator core formed from an iron alloy, wherein the conductor structure and the, at least one conductor element comprises copper wire windings wound around at least a port of the stator core, and wherein the monocrystalline or columnar crystal structure is oriented in a longitudinal direction of the copper wire windings.

9. The electric machine of claim 1 wherein the conductor structure comprises a winding formed from individual conductor elements, the winding having a plurality of successive turns each of which includes two turn elements corresponding to two of the individual conductor elements, wherein each turn element is limited to one turn and does not overlap with itself.

10. A method for making a conductor structure of an electric machine, comprising: forming at least one conductor element from at least one metal selected from aluminum, copper, and silver having a monocrystalline or columnar crystal structures; and forming the at least one conductor element into the conductor structure.

11. The method of claim 10 wherein forming the at least one conductor element comprises cutting the at least one conductor element from an aluminum, copper, or silver bar.

12. The method of claim 11 wherein cutting the at least one conductor element comprises cutting a wafer from the aluminum, copper, or silver bar, and separating the at least one conductor element from the wafer.

13. The method of claim 12 wherein separating the at least one conductor element comprises cutting the at least one conductor element from the wafer.

14. The method of claim 11 wherein forming at least one conductor element comprises forming a plurality of conductor elements each having not more than one bend, and bonding the conductor elements together to form a winding.

15. The method of claim 14 wherein bonding the conductor elements comprises welding the conductor elements together.

16. The method of claim 10 wherein forming the at least one conductor element comprises casting the at least one conductor element in a casting mold.

17. An electric machine comprising: a conductor structure having a plurality of conductor elements individually formed from copper having a monocrystalline or columnar crystal structure integrally bonded together.

18. The electric machine of claim 17 wherein the conductor structure comprises a stator winding.

19. The electric machine of claim 18 wherein the conductor elements are welded together.

20. The electric machine of claim 19 wherein each of the conductor elements includes at most one turn.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows a schematic sectional illustration of an electric motor according to the disclosure.

[0030] FIG. 2 shows a perspective illustration of a monocrystalline body.

[0031] FIG. 3 shows a plan view of a wafer cut from a body as shown in FIG. 2.

[0032] FIG. 4 shows a perspective illustration of a winding of a stator according to the disclosure.

[0033] FIG. 5 shows an illustration of part of a stator corresponding to the illustration of FIG. 4.

[0034] FIG. 6 shows a perspective illustration of a squirrel-cage rotor of an electric motor according to the disclosure.

[0035] FIG. 7 shows a perspective illustration of a rotor cage of the squirrel-cage rotor from FIG. 6.

[0036] FIG. 8 shows a schematic illustration of a device for producing a rotor cage according to the disclosure.

DETAILED DESCRIPTION

[0037] As required, detailed embodiments of the claimed subject matter are disclosed herein; however, it is to be understood that the disclosed embodiments are merely representative and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the claimed subject matter.

[0038] Like parts are provided with like reference signs in the different figures, and therefore will also generally only be described once.

[0039] FIG. 1 shows a schematic sectional illustration of a representative electric motor 1 according to this disclosure, more specifically of an asynchronous motor. The electric motor 1 has a stationary housing 2, on which a shaft 3 is rotatably mounted by means of two bearings 4. A rotor or squirrel-cage rotor 10 is connected to the shaft 3. The squirrel-cage rotor has a laminated core 11 and a rotor cage 12, which will be explained in greater detail below with reference to FIGS. 6 and 7. A stationary part or stator 15 is mounted fixedly to the housing 2. The stator 15 has a core 16 formed from an iron alloy, which is surrounded in some sections by a plurality of windings 17.

[0040] Each winding 17 is formed by a wire 19, the course of which (similarly to the other components of the electric motor 1) is shown here only schematically. The wire 19 consists in the present case of copper or has a copper content of more than 98%. The crystal structure of the wire 19 is columnar, i.e. it consists of pillar-like crystals or column-like crystals. These are oriented predominantly in the longitudinal direction of the wire 19, whereby the wire 19 has a lower specific resistance than a corresponding wire with a globular crystal structure. It is therefore possible, in comparison to a conventional wire, to use either a thinner wire or to realize, with the same wire cross section, a lower resistance, which has an advantageous effect on the performance of the electric motor 1. In addition, the wire 19 has a lower tendency to heating on account if its low ohmic resistance. Lastly, the lower ohmic resistance is also accompanied by an increased thermal conductivity, and therefore the heat dissipation from any regions of the wire 19 potentially heated to a greater extent is possible more easily. The resistance of the wire 19 can be further reduced in that a wire made of silver or a silver alloy with high silver content is used. The wire 19 can be produced for example by means of the Ohno Continuous Casting (OCC) method. In some circumstances, the production of a wire 19 with monocrystalline structure is also possible here.

[0041] In the embodiment shown in FIG. 1 each winding 17 is manufactured from a one-piece wire 19, which on account of its flexibility, can be wound around the stator core 16. According to an alternative embodiment which is explained with reference to FIGS. 2-5, the windings 17 of the stator 15 can be joined together from prefabricated conductor elements 22, 23. The starting point of manufacture is a monocrystalline bar 20 shown schematically in FIG. 2, which can also be referred to simply as a bar. This can be manufactured for example in the Czochralski method or by means of the Bridgman-Stockbarger method. For most applications, for example in the automotive field, the bar 20 is manufactured from aluminum or copper, whereas for other applications, for example in aircraft construction, a bar 20 can be manufactured from silver.

[0042] As shown in FIGS. 2 and 3, a plurality of wafers 21 can be cut from the monocrystalline bar 20. The individual wafer 21 has a disc-like structure and a substantially circular cross section. The thickness of the wafer 21 can be selected according to the desired thickness of the conductor elements 22, 23. FIG. 3 shows a plan view of a wafer 21 with the contours of conductor elements 22, 23 which are cut out from said wafer. The geometry and arrangement of the individual conductor elements 22, 23 has been selected here merely by way of example and in practice can also be selected differently. Three turn elements 22 and one end element 23 are shown. Of course, the number and arrangement of the cut-out conductor elements 22, 23 are normally selected so that the material of the wafer 21 is utilized as optimally as possible.

[0043] FIG. 4 shows a winding 17 which has been manufactured from the conductor elements 22, 23. The winding 17 has a plurality of successive turns 18, each of which is composed of two turn elements 22. Here, each turn element 22 is limited to one turn 18, i.e. it does not overlap with itself and therefore can be obtained from the two-dimensional form of the wafer 21 without (significant) shaping. At each end, an end element 23 is connected to a connection element 22. The end elements 23 are used for the electrical connection of the winding 17 within the electric motor 1. The conductor elements 22, 23 can be connected to one another by welding, for example by gas welding, microplasma welding, electron beam welding or laser beam welding. The finished windings 17 can then be inserted into the coil core 16, as shown in FIG. 5.

[0044] FIG. 6 is a perspective illustration of the squirrel-cage rotor 10 and of the shaft 3 and the bearing 4. As already mentioned, the squirrel-cage rotor 10 has a laminated core 11 and also a rotor cage 12, which is shown separately in FIG. 7. In this example, the rotor cage 12 is shaped in one piece from copper with a monocrystalline structure. It has a complex three-dimensional structure with apertures. Specifically, two tangentially circumferential rings 12.1 are formed at the axial end faces and are connected to one another by a plurality of bars 12.2. In this example the bars 12.2 run in a straight line, but at an incline to the axial direction. However, other courses are also possible, for example an axial course or a non-straight, for example curved course.

[0045] FIG. 8 is a schematic sectional illustration of a device for producing the rotor cage 12 from FIG. 7. A casting mold 40 includes a cavity 41 into which copper in liquid form is poured. In the uppermost region, the cavity 41 has a filling portion 41.1, which is adjoined by a mold portion 41.2. The mold portion 41.2 defines the actual shape of the rotor cage 12. A substantially spiraled selector portion 41.3 is formed below the mold portion 41.2. Below this, the casting mold 40 is adjoined by a copper plate 42 having a plurality of cooling channels 43. Whilst the liquid copper is being poured in through the filling portion 41.1, the casting mold 40 can be heated or temperature-controlled to prevent a premature solidification of the copper. The copper plate 42 is cooled in the intended manner by conducting a coolant (for example water) through the cooling channels 43. This leads to an onset of solidification of the copper in the selector portion 41.3, starting from the bottom and progressing upwardly. The spiral shape of the selector portion 41.3 means that, at least in the upper part of said portion, a monocrystalline structure forms, which then also continues in the mold portion 41.2. Once the copper has fully solidified, the casting mold 40 is removed, which, with the geometry of the cavity 41 shown here, is possible only by destroying the casting mold 40. The parts of the copper body which correspond to the selector portion 41.3 and the filling portion 41.1 are then separated, whereby the rotor cage 12 shown in FIG. 7 is obtained. The separated parts can be melted down and re-used. The method described here can be applied also to a rotor cage 12 which is manufactured from silver.

[0046] Although the described representative embodiments relate to an asynchronous motor, similar or other conductor structures with columnar or monocrystalline crystal structure can also be produced for synchronous motors or other electric machines.

[0047] While representative embodiments are described above, it is not intended that these embodiments describe all possible forms of the claimed subject matter. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the claimed subject matter. Additionally, the features of various implementing embodiments may be combined to form further embodiments that may not be explicitly illustrated or described.