Method for potting an FSM rotor and FSM rotor with hybrid rotor potting

Abstract

Method for potting an FSM rotor (100) for an electric machine, comprising a rotor body (110) and a rotor winding (120) applied thereto, wherein a first potting compound (M1) and a second potting compound (M2) are used for the potting process and the first potting compound (M1) has a density at least twice that of the second potting compound (M2), comprising the steps: - Arranging the FSM rotor (100) to be cast in a vertical orientation in a casting mold (200); - Introducing the first potting compound (M1) from below into the potting mold (200) until a certain pre-filling height (H1) is reached, at which the first potting compound (M1) reaches at least to the lower end face (S2) of the rotor winding (120); - Introducing the second potting compound (M2) from above into the potting mold (200), whereby the second potting compound (M2) is poured onto the rotor winding (120) and drawn into the rotor winding (120); - further introduction of the first potting compound (M1) from below into the potting mold (200) until a certain final filling height (H2) is reached; - Curing of the potting compounds (M1, M2).

Description

[0001] The invention relates to a method for encapsulating an FSM rotor for an electrical machine. The invention further relates to a encapsulated FSM rotor.

[0002] A separately excited synchronous machine (SMM) is an electrical machine (E-machine) that can be operated as a motor and / or generator. It has a stator (stator) with several spatially offset stator coils and a rotor (rotor) rotatably arranged within the stator, which is provided with at least one rotor winding that acts as an electromagnet. The rotor winding is typically made of insulated copper wires. A separately excited synchronous machine has good efficiency and good power density.

[0003] The rotor winding can be permanently fixed with a potting compound, e.g. a plastic compound or the like, to prevent the rotor winding or the copper wires from slipping during operation, where high centrifugal forces and strong vibrations sometimes occur.

[0004] WO 2019 / 115043 A1 describes the application of a potting compound by injection molding. For this purpose, the rotor is placed, preferably vertically, into a suitable injection molding tool and, preferably, overmolded with a thermoset. This process involves (very high) injection pressures of 500 bar and more.

[0005] The closest US 2003 / 0 001 440 A1 describes a method for manufacturing a stator for an electric rotary machine. The stator comprises a stack of magnetic metal sheets arranged substantially parallel to a plane perpendicular to the rotational axis of the rotor of the rotary machine, with a plurality of teeth defining longitudinally aligned slots. The method comprises the following steps: - Installing electrically conductive wires in the slots and forming winding heads; - Arranging the assembly on a vertical axis; - impregnating the first winding head in an axially upper position with a composition comprising a thermosetting resin and a large particle size filler; - Turning the assembly over and rearranging it on a vertical axis so that the first winding head becomes the lower winding head; - impregnating the conductive wires in the slots under vacuum with another composition containing a thermosetting resin and another filler with smaller particle size; - impregnating the second winding head with a composition containing a thermosetting resin and a large particle size filler; - Polymerization of the compositions.

[0006] WO 2016 / 050 528 A1 describes a method for producing a rotor or stator for an electrical machine, in which a potting compound surrounding the winding is passed through a groove in the base body and its composition is changed as the potting compound is passed through.

[0007] Regarding the state of the art, reference is also made to GB 920 656 A, US 2 400 891 A, DE 101 33 966 A1 and UA 46328 U.

[0008] The invention is intended to provide a further method for casting an FSM rotor or for applying casting compound to an FSM rotor, with which a mechanically stable rotor structure can be achieved without high pressures.

[0009] This is achieved with the inventive method of patent claim 1. The independent patent claim also extends the invention to a cast FSM rotor. Additional features for both subject matters of the invention are derived analogously from the dependent patent claims, the following description of the invention, and the figures.

[0010] The method according to the invention for casting an FSM rotor with a rotor body, which is preferably constructed from stacked rotor laminations, and a rotor winding applied thereto, which is in particular an orthocyclic rotor winding (which is characterized by particularly small or narrow gaps), comprises at least the following steps, to be carried out in this order: - arranging the FSM rotor to be cast in an upright or (axially) vertical orientation in a casting mold, in particular in a cylindrical casting mold, and if necessary closing the casting mold; - introducing a first (liquid) potting compound from below into the potting mold (pouring or pre-pouring) until a certain pre-filling height or a first filling level is reached in the potting mold, at which the first potting compound reaches at least as far as the lower end face of the rotor winding, preferably exactly as far as the lower end face of the rotor winding, but in particular not as far as the upper end face of the rotor winding; - introducing a second (liquid) potting compound from above into the potting mold, wherein the second potting compound is poured, in particular dripped, onto the rotor winding, in particular onto the upper end face of the rotor winding, and, in particular by a capillary effect, penetrates or is drawn into the rotor winding, in particular until the rotor winding is completely filled or soaked; - further or renewed introduction of the first (liquid) casting compound from below into the casting mould (finish casting) until a certain final filling level or a second filling level is reached in the casting mould, at which in particular the first casting compound reaches at least as far as the upper end face of the rotor winding and in particular lies above it; - Curing of the casting compounds, in particular by a self-reactive curing process or by heat activation (i.e. by introducing heat), and optionally demoulding the cast FSM rotor, wherein optionally a subsequent curing of the cast FSM rotor can take place in an oven or the like.

[0011] In addition, the invention provides that the first potting compound has a density that is at least twice higher than that of the second potting compound.

[0012] The invention therefore provides for sequential potting of the FSM rotor with two potting compounds to secure the rotor winding or to apply potting compound. By casting on (sprueing), the rotor winding of the stationary FSM rotor is first sealed downwards and, if necessary, laterally or radially by the first potting compound, so that the second potting compound, which subsequently penetrates the rotor winding from above, cannot flow downwards and, in particular, cannot flow out of the rotor winding laterally. Once the rotor winding is saturated with the second potting compound or has "absorbed" the second potting compound, the final casting (final potting) of the FSM rotor with the first potting compound can take place.Ideally, the second potting compound is then located only within the rotor winding, in particular without any air pockets, and the first potting compound is located, in particular without air pockets, in other rotor areas, e.g., in the rotor voids, especially in the winding chambers, and / or forms an axial and / or radial rotor shell. The two potting compounds essentially form a hybrid rotor potting (see below). An FSM rotor with such a hybrid rotor potting exhibits a very high fill level and good mechanical stability, or mechanically stable winding fixation.

[0013] Preferably, the first potting compound has a higher viscosity (or lower fluidity) and, according to the invention, also a higher density than the second potting compound. Preferably, both the first potting compound and the second potting compound are made of a resin material, in particular the same resin material, for example, a polyester resin or epoxy resin.

[0014] The second potting compound is preferably an unfilled resin material which, due to its low viscosity and high fluidity, can penetrate and be drawn into the rotor winding very well. The first potting compound is preferably a filled resin material which, among other things, has very good mechanical strength and stability properties. A filled resin material is understood in particular to mean that it is enriched with at least one filler, for example in the form of ceramic beads which, for example, can have a diameter of 20 µm to 200 µm, wherein the filler volume fraction is preferably at least 20 vol.%, particularly preferably at least 40 vol.% and in particular at least 60 vol.%. The second potting compound can also be a resin material with a low or lower filler content, the filler content of which is preferably lower than the filler content of the first potting compound and preferably below 30 vol.-%, in particular below 20 vol.%.

[0015] The different viscosities as well as the different densities of the first and second potting compound according to the invention (according to the invention, the first potting compound has a density at least twice higher than that of the second potting compound) make it difficult or impossible for mixing during potting and furthermore promote the separation of the more liquid and lighter second potting compound upwards (see below).

[0016] The first potting compound and / or the second potting compound can be introduced into the casting mold in a volume- or quantity-controlled manner. The required volume or quantity can be calculated or determined through testing. Preferably, the first potting compound and / or, in particular, the second potting compound are introduced into the casting mold in a visually controlled manner. This allows manufacturing tolerances, particularly in the rotor winding, to be taken into account. The visually controlled introduction can be carried out manually or automatically, e.g., by means of a camera. The casting mold can be designed with a viewing window for this purpose.

[0017] The casting of the FSM rotor can be carried out, at least temporarily, in a vacuum. This specifically means that the casting mold is vacuumed at least in phases, preferably during the initial casting with the first casting compound and during the subsequent introduction of the second casting compound. The final casting with the first casting compound can also be carried out without a vacuum, if necessary, so that the vacuum can be released beforehand.

[0018] Preferably, any excess second potting compound that has been introduced into and / or flowed out of the rotor winding and that deposits or accumulates as the uppermost layer in the potting mold after further introduction of the first potting compound is suctioned off or removed in another suitable manner, e.g. by scraping, before curing (of the potting compound) or possibly even during curing. The potting mold can also be designed with an overflow or the like, through which an uppermost (liquid) second potting compound can be separated. Alternatively, the deposited uppermost layer of second potting compound can be mixed with an underlying layer of first potting compound before curing or possibly even during curing, wherein demixing is no longer possible during the remaining curing time.The top layer of second casting compound can also be removed after curing by mechanical post-processing, e.g. by turning.

[0019] An FSM rotor according to the invention for an electric machine, in particular for a traction motor of a motor vehicle, comprises a rotor body and an orthocyclic rotor winding applied to the rotor body. Furthermore, this FSM rotor comprises a hybrid rotor encapsulation formed from two encapsulating compounds, such that the rotor winding is encapsulated or impregnated with a second encapsulating compound and other rotor regions are encapsulated with a first encapsulating compound, wherein the first encapsulating compound also forms an axial and / or radial rotor shell. This hybrid rotor encapsulation is manufactured or produced using the method according to the invention. The method features of the method according to the invention described herein apply analogously to the FSM rotor according to the invention.

[0020] The invention is explained in more detail below with reference to the figures. Fig. 1 schematically illustrates in several individual representations a first preferred embodiment of the method according to the invention. Fig. 2 illustrates schematically analogous to Fig. 1 a second preferred embodiment of the method according to the invention.

[0021] Fig. Figure 1a shows a schematic axial sectional view of an FSM rotor 100 with a rotor body 110 and a rotor winding 120 applied to the rotor body 110, which may comprise multiple winding sections. The rotor winding 120 is preferably an orthocyclic winding. The rotor body 110 is preferably constructed from stacked rotor laminations. The rotor shaft 130 is already assembled or inserted; depending on the design principle, the rotor shaft can also be assembled after encapsulation.

[0022] The FSM rotor 100 is arranged upright or vertically in a casting mold 200, which is also shown only schematically, in particular such that there is essentially no gap between the outer circumferential surface of the rotor body 110 and the inner wall of the casting mold 200. The rotor winding 120 has a lower end face S2 and an upper end face S1. The axial end regions of the rotor winding 120 are also referred to as winding heads. An axial central region of the rotor winding 120 extends between these end regions or winding heads.

[0023] The casting or impregnation of the FSM rotor 100 takes place in several steps, whereby two different casting compounds M1 and M2 are sequentially introduced into the casting mold 200, as explained below.

[0024] First, a first potting compound M1, which is a filled (liquid) resin material, is introduced into the potting mold 200 from below, for example by injection (so-called pouring), until the rising potting compound M1 has reached a certain pre-filling height or filling height H1, at which it reaches at least as far as the lower end face S2 or as far as the lower winding head of the rotor winding 120. This is Fig. 1a illustrates.

[0025] Subsequently, a second potting compound M2, which is an unfilled (low-viscosity) resin material, is introduced into the potting mold 200 from above. The second potting compound M2 is poured onto the rotor winding 120, preferably similar to a trickling process, and is drawn into the rotor winding 120, in particular supported by a capillary effect. This is shown in Fig. 1b. The first potting compound M1 already present in the potting mold 200 prevents the second potting compound M2 from flowing downward out of the rotor winding 120, i.e., the rotor winding 120 is essentially sealed off from below by the first potting compound M1.

[0026] After the rotor winding 120 is completely filled or saturated with the second potting compound M2, the first potting compound M1 is again introduced from below into the potting mold 200 (so-called final pouring) until the rising first potting compound M1 reaches a certain final filling height or final filling height H2, at which it reaches at least as far as the upper end face S2 of the rotor winding 120 or covers the upper winding head. This is shown in Fig. 1c. Any excess second potting compound M2 that may have been introduced into and / or flowed out of the rotor winding 120 is deposited as an upper layer in the potting mold 200 due to its lower viscosity and density compared to the first potting compound M1, which can then be handled accordingly, as described above.

[0027] The casting compounds M1 and M2 are now cured. After the casting compounds M1 and M2 have cured, the casting mold 200 can be opened and the cast FSM rotor 100 can be removed. Preferably, the casting mold 200 is constructed in several parts.

[0028] At the Fig. 2, a higher filling height or pre-filling height H1' below the upper end face S1 is achieved during casting (see Fig. 2a), without the first potting compound M1 (filled resin material) penetrating into the rotor winding 120 due to its comparatively high viscosity and density. The further steps are carried out analogously to the first embodiment (cf. Fig. 1 and previous explanations), whereby the first casting compound M1 is introduced into the second casting compound M2 (see Fig. 2b) seals the FSM rotor 100 or the rotor winding 120 not only downwards, but also laterally or radially.

Claims

[1] Method for encapsulating an FSM rotor (100) for an electrical machine, which has a rotor body (110) and a rotor winding (120) applied thereto, wherein a first encapsulating compound (M1) and a second encapsulating compound (M2) are used for the encapsulation and the first encapsulating compound (M1) has a density at least twice higher than the second encapsulating compound (M2), comprising the steps: - arranging the FSM rotor (100) to be cast in an upright orientation in a casting mold (200); - introducing the first potting compound (M1) from below into the potting mold (200) until a certain pre-filling height (H1) is reached, at which the first potting compound (M1) reaches at least as far as the lower end face (S2) of the rotor winding (120); - introducing the second potting compound (M2) from above into the potting mold (200), wherein the second potting compound (M2) is poured onto the rotor winding (120) and is drawn into the rotor winding (120); - further introducing the first casting compound (M1) from below into the casting mould (200) until a certain final filling height (H2) is reached; - Curing of the casting compounds (M1, M2). [2] Method according to claim 1, characterized by that the first casting compound (M1) has a higher viscosity than the second casting compound (M2). [3] Method according to claim 1 or 2, characterized by that the first potting compound (M1) is a filled resin material and the second potting compound (M2) is an unfilled or less filled resin material. [4] Method according to one of the preceding claims 1 to 3, characterized by that the first casting compound (M1) and / or the second casting compound (M2) are introduced into the casting mold (200) in a volume-controlled manner. [5] Method according to one of the preceding claims 1 to 3, characterized bythat the first casting compound (M1) and / or the second casting compound (M2) are introduced into the casting mold (200) in a visually controlled manner, wherein this visually controlled introduction is carried out automatically by means of camera detection. [6] Method according to one of the preceding claims, characterized by that the casting of the FSM rotor (100) takes place, at least temporarily, in a vacuum. [7] Method according to one of the preceding claims, characterized by that any excess second potting compound (M2) which has been introduced and / or flowed out of the rotor winding (120) and which separates as the uppermost layer in the potting mold (200) after the further introduction of the first potting compound (M1) is sucked off before curing or is mixed with an underlying layer of first potting compound (M1). [8] FSM rotor (100) for an electrical machine, comprising a rotor body (110) and an orthocyclic rotor winding (120) applied thereto, characterized bythat this FSM rotor (100) has a hybrid rotor potting formed from two potting compounds (M1, M2), which is produced by a method according to one of the preceding claims 1 to 7, wherein only the rotor winding (120) is potted with the second potting compound (M2) and other rotor regions are potted with the first potting compound (M1), which also forms an axial and / or radial rotor shell.

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