Method for producing a rotor, rotor, and electric machine

Abstract

The invention relates to a method for producing a rotor (1) for an electric machine (2). According to the method, - a laminated core (3) having grooves (6) extending in the axial direction (5) is provided, - the axial length LB of the laminated core (3) is detected, - slot closure wedges (7) with a defined axial length LN are provided, wherein LN ≥ LB, - the slots (6) of the laminated core (3) are lined with a plastic layer (8), - a plastic layer (8) with a defined axial length LK1, LK2 is applied onto both end faces (10) of the laminated core (3) in such a way that (I) applies so that the plastic layer (8) serves as a tolerance compensation layer, - a plurality of rotor windings (9) are wound on the laminated core (3), and - a slot closure wedge (7) with a defined axial length LN is inserted into each slot (6), thus creating a flat end-face sealing surface (12) which extends at least approximately around the end faces of the slot closure wedges (7) and the plastic layer (8).

Description

[0001] Method for producing a rotor, rotor and electrical machine

[0002] The present invention relates to a method for producing a rotor for an electrical machine. The invention also relates to a rotor produced by this method and to an electrical machine comprising such a rotor.

[0003] DE 10 2015 119 235 B4 discloses a device for injection molding and spraying objects, comprising an upper element and a lower element, which enclose a contiguous volume consisting of a filling chamber for receiving the object and casting material, as well as a sprue for receiving casting material. The upper element is arranged to be movable relative to the lower element. A piston, movable relative to the upper element, is integrated within the upper element in such a way that the position of the piston is varied in an axial direction depending on a dimension of the object. The piston also has a shoulder for changing a volume as a fill quantity compensation of the casting material within the supply.Regardless of the object's axial dimensions and a volume that varies with the object's axial dimensions, the total volume for the casting material within the fixture remains constant. This should make it possible to encase laminated cores for rotors despite differing external dimensions in such a way that the same external dimensions are achieved after encasing, thus meeting high dimensional accuracy requirements.

[0004] From EP 3 871 323 B1, a stator / rotor device for electric motors is known with at least one or more stator / rotor stack devices stacked one above the other, each of which is designed as a component that is rotationally symmetrical to a rotational axis.

[0005] DE 10 2019 113 596 A1 discloses an electric machine for driving a motor vehicle with a rotor comprising a central rotor shaft and a laminated core formed from several rotor laminations and fastened to the rotor shaft. The laminated core is contacted on at least one axial side by an end plate that compensates for tolerances, which in turn is supported by a retaining ring pressed onto the rotor shaft. This is intended to create a rotor that is easy to manufacture and has sufficient strength to transmit the highest possible torques.

[0006] In general, the production of rotors for electrical machines often involves the problem that the axial length of a laminated core exhibits an inaccuracy of up to one sheet thickness due to the integer number of individual laminations. With multiple laminated cores, this tolerance accumulates. If a slot-locking wedge is manufactured using a specific tool, a difference remains between the axial length of the laminated core and the length of the slot-locking wedge after its installation. This difference cannot be reliably compensated by a seal of a balancing ring that is attached to prevent coolant from escaping from the interior of the rotor into the machine's air gap.

[0007] The present invention therefore addresses the problem of providing a method by which a cooling fluid-filled rotor for an electric machine can be manufactured more easily and cost-effectively. This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0008] The present invention is based on the general idea of ​​compensating for manufacturing-related differences in the axial length of laminated cores relative to the length of the slot closure wedges by means of a plastic layer sprayed onto the two end faces of the laminated cores. The length always refers to the axial direction of the rotor. This creates a sealing surface that is flat, i.e., stepless, on the end face and in the circumferential direction. This not only simplifies the sealing of cooling channels running in the slot closure wedges, but also allows a previously wet-rotor rotor to be designed as a dry-rotor rotor, thus avoiding the considerable drag losses associated with wet-rotor rotors.In the inventive method for producing a rotor for an electrical machine, in particular for a separately excited synchronous machine, at least one laminated core composed of individual laminations with slots separated from one another in the circumferential direction and extending in the axial direction is initially provided. Of course, depending on the size of the rotor, several laminated cores each composed of individual laminations can be positioned one behind the other in the axial direction. Thereafter, an axial length LB of the at least one laminated core is recorded, i.e., measured. Subsequently, slot closure wedges with a predefined axial length LN are provided, wherein the axial length LN of the slot closure wedges is greater than or equal to the axial length LB of the laminated core.Since the laminated cores are composed of individual laminations, each with an axial thickness of typically between 0.15 and 0.20 mm, the respective laminated cores have a tolerance in their axial length of plus / minus the length of an individual lamination. This can therefore be up to 0.40 mm per laminated core for the previously described length of the individual laminations. If several such laminated cores are arranged one behind the other in the axial direction, for example four laminated cores, the tolerance can be as low as 1.6 mm. Once at least one laminated core has been manufactured, the slots of this laminated core are lined with a layer of plastic for electrical insulation. This eliminates the need for insulating paper previously used in this area and generally simplifies rotor production.The method according to the invention is then divided into two parts, wherein according to a first alternative embodiment of the method according to the invention, a plastic layer is applied to the two end faces of the laminated core and, in the case of several laminated cores, to the two outer end faces simultaneously with the lining of the slots with the plastic layer or thereafter, or the plastic layer is applied with a predefined axial length LKI, LK2 such that the sum of the axial lengths LKI + LK2 + LB corresponds at least substantially to the axial length LN of the slot closure wedge, so that the plastic layer serves as a tolerance compensation layer for at least approximately compensating for an axial difference between the laminated core and later the slot closure wedges to be inserted into the slots.This makes it possible for the plastic layer applied to the end face of the laminated core to serve as a tolerance compensation layer to compensate for an axial difference between the at least one laminated core and the slot closure wedges that will later be inserted into the individual slots to compress the rotor windings. The rotor windings are then wound evenly distributed in the circumferential direction around the pole cores of the pole teeth of the laminated core. Once winding is complete, a slot closure wedge with the previously described predefined axial length LN is inserted into each slot. Together with the plastic layers applied to the end face of the laminated core, this creates an at least virtually flat end face sealing surface that extends around the end faces of the slot closure wedges and the plastic layer.

[0009] According to the second alternative embodiment of the method according to the invention, after the slots of the laminated core have been lined with a plastic layer for electrical insulation, rotor windings are wound on the pole cores of the laminated core, and a slot closure wedge with a predefined axial length LN is inserted into each slot. Subsequently, a plastic layer with a predefined axial length LKI, LK2 is applied to both end faces of the laminated core in such a way that LKI + LK2 + LB = LN or LKI + LK2 + LB = LN, so that the plastic layer serves as a tolerance compensation layer to compensate for an axial difference between the laminated core and the slot closure wedges inserted into the slots, and thereby a flat end-face sealing surface is created that extends at least almost all the way around the end faces of the slot closure wedges and the plastic layer.

[0010] The overall axial length of the rotor is a tool-dependent dimension. The continuous, circumferentially continuous and at least nearly flat end-face sealing surface makes sealing the interior of the rotor significantly easier. This is because a seal arranged in a balancing ring, over which the balancing ring is pushed onto the end faces of the laminated cores or slot closure wedges, no longer has to compensate for axial differences between the laminated cores and adjacent slot closure wedges. This makes it possible to design rotors for separately excited synchronous machines, which are typically designed as wet rotors and therefore have considerable drag losses, as dry rotors with comparative ease. This is because the sealing of the interior of the rotor is comparatively easy using the plastic layer on the end face, which acts as a tolerance compensation layer and provides a flat sealing surface.In an advantageous development of the method according to the invention, the at least one laminated core is mounted on a shaft in a rotationally fixed manner. The rotor includes not only the at least one laminated core, but also the shaft, onto which the at least one laminated core is mounted in a rotationally fixed manner, for example, by means of an adhesive or a form-fitting connection. Such a form-fitting connection can, on the one hand, enable the at least one laminated core to be easily slid onto the shaft, while, on the other, ensuring reliable torque transmission.

[0011] Overmolding of the laminated core to create the frontal tolerance compensation layer as well as any slot insulation is possible without a previously mounted shaft, if, for example, a mandrel takes over the centering of the laminated cores with and without previously mounted winding supports.

[0012] In a further advantageous embodiment of the method according to the invention, a balancing ring with an internal seal is placed on the sealing surface, which seals the coolant-carrying area of ​​the rotor from the air gap. Such a balancing ring serves to compensate for rotor imbalances and, at the same time, through its internally arranged seal, together with the laminated core and the slot closure wedges, tightly seals the rotor interior to prevent coolant from escaping into the air gap. Purely theoretically, it is of course conceivable for the seal in the balancing ring to also close individual cooling channels and leave other cooling channels at least partially open at the front, thereby enabling flow and thus improved cooling of the laminated cores. Preferably, however, the entire coolant-carrying area of ​​the rotor is sealed. The sealing surface expediently runs in a ring shape outside the rotor windings.The circumferential and flat sealing surface, which extends at least annularly outside the rotor windings, is contacted and sealed by the seal of the balancing ring, preventing coolant flowing inside the rotor from escaping. This makes it comparatively easy to convert a rotor typically designed as a wet rotor for a separately excited synchronous machine into a dry rotor, thus significantly reducing drag losses typical of wet rotors.

[0013] The present invention is further based on the general idea of ​​producing a rotor according to the method described in the previous paragraphs, thus transferring the advantages described with regard to the method to the rotor. Specifically, these advantages lie in comparatively simple production and the possibility of designing a wet rotor, previously used for separately excited synchronous machines, as a dry rotor for the first time. This reduces drag losses and significantly increases the performance of a separately excited synchronous machine equipped with such a rotor.

[0014] In an advantageous development of the rotor according to the invention, the slot closure wedges are made of an electrically non-conductive material, in particular plastic. The slot closure wedges serve to compress the rotor windings. Manufacturing the slot closure wedges from plastic, in particular as a plastic injection-molded part, enables not only cost-effective but also high-quality and extremely dimensionally accurate production.

[0015] Advantageously, a cooling channel through which a coolant flows is arranged in at least one slot closure wedge to cool the rotor windings and thus the rotor. Preferably, coolant circulates in a sealed rotor interior, also in direct contact with the rotor windings, which can thus be cooled easily and effectively. This significantly increases the performance of a separately excited synchronous machine equipped with such a rotor.

[0016] The present invention is further based on the general idea of ​​equipping an electrical machine, for example an electric motor, with a rotor described in the previous paragraphs and thereby transferring the advantages described with regard to the rotor to the electrical machine. The advantages here lie in particular in simple and cost-effective production of the rotor and thus indirectly also of the electrical machine, while at the same time the previously required insulating paper for electrical insulation between the laminated cores and the rotor windings can be dispensed with. The lining of the slots and the application of the end-face plastic layer designed as a tolerance compensation layer can preferably be accomplished in a common process step, such as overmolding, which considerably simplifies production.

[0017] In an advantageous development of the electrical machine according to the invention, it is designed as a separately excited synchronous machine. In separately excited synchronous machines, the rotor, in which the magnetic field is generated, runs synchronously with a rotating field of the stator. Such separately excited synchronous machines are used particularly in electric vehicles.

[0018] Further important features and advantages of the invention emerge from the dependent claims, the drawings, and the associated description of the figures with reference to the drawings. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention.

[0019] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0020] They show, schematically

[0021] Figure 1 ad different process steps of a process according to the invention for producing a rotor,

[0022] Figure 2 is a front view of a laminated core according to the invention,

[0023] Figure 3 is a representation as in Figure 2, but with applied

[0024] rotor windings,

[0025] Figure 4 is a representation as in Figure 3, but with slot closure wedges inserted, which merges flush with the surface into the plastic layer, which in this case is ring-shaped and applied to the front side of the laminated core,

[0026] Figure 5 shows a detailed view of the rotor according to the invention to illustrate axial length differences between the laminated core and a slot closure wedge as well as a plastic layer compensating for the axial length difference,

[0027] Figure 6 is a front view of a rotor according to the invention with laminated core, plastic layer and slot closure wedge, but without rotor windings,

[0028] Figure 7 is a diagram illustrating the axial length differences between the laminated core and the slot closure wedge as well as the compensation of this length difference by the plastic layer arranged on the front side of the laminated core.

[0029] According to Figures 1a to 1d, a method according to the invention for producing a rotor 1 for an electrical machine 2 (not described in more detail) is shown. In the method according to the invention, a laminated core 3 is first assembled from individual sheets, wherein the laminated core 3 has slots 6 which are separated from one another in the circumferential direction 4 and run in the axial direction 5 (see also Figures 2 - 6). The axial direction 5 extends parallel to the axis of rotation. Subsequently, an axial length LB of the laminated core 3 is recorded, for example measured. For the method according to the invention, slot closure wedges 7 (see Figures 1b, 1d and 4 - 7) are also provided, wherein these slot closure wedges 7 have a production-related predefined axial length LN. The slot closure wedges 7 are usually made of an electrically non-conductive material, for example plastic, and are used for compression orpressing the rotor windings 9 against the respective pole core 18 of the laminated core 3. The length LN is greater than or equal to the length LB, so that the slot closure wedges 7 project beyond the laminated core 3 in the axial direction 5. Subsequently, the slots 6 of the laminated core 3 are lined with a plastic layer 8 in order to prevent direct and electrically conductive contact between a rotor winding 9 and the laminated core 3, thus preventing a short circuit.

[0030] At this stage, the method according to the invention can be pursued according to a first alternative embodiment or a second alternative embodiment:

[0031] In the first alternative embodiment, a plastic layer 8 with a predefined axial length LKI, LK2 is applied simultaneously or subsequently to each of the end faces 10 in such a way that the sum of the axial lengths LKI + LK2 + LB of the two plastic layers 8 and of the laminated core 3 at least substantially corresponds to the axial length LN of the slot closure wedges 7, as shown in Figure 1d. The plastic layer 8 on the end face 10 of the laminated cores 3 can be formed integrally with the plastic layer 8 in the slots 6 or separately from it. By producing the lining in the slots 6 and the plastic layers 8 at the same time, the cycle time can be reduced and the previously required insulating paper can be saved.

[0032] The plastic layer 8 serves as a tolerance compensation layer to compensate for any axial difference between the laminated core 3 and the slot closure wedges 7 to be inserted (later) into the individual slots 6. The plastic layer 8 can also be designed as a tolerance compensation layer with pre-assembled slot closure wedges 7, and thus with a pre-wound rotor 1. After the plastic layers 8 have been applied, the rotor windings 9 are applied to the laminated core 3, with the rotor windings 9 being wound around individual pole cores 18 of pole teeth 11 of the laminated cores 3. The pole cores 18 define the slots 6 and are delimited on the outside by pole shoes 19, which hold the rotor windings 9 against centrifugal forces.Subsequently, a slot closure wedge 7 with the predefined axial length LN is inserted into each of the slots 6, thereby creating a preferably flat end-face sealing surface 12 that extends over the end faces of the slot closure wedges 7 and the end-face plastic layer 8. By applying the plastic layers 8 to the two end faces 10 of the laminated cores 3, it is thus possible to compensate for production-related axial tolerances, whereby an at least almost flat and continuous sealing surface 12 can be created, which enables the sealing of the rotor interior between the laminated core 3 or the slot closure wedges 7 on the one hand and the balancing ring 15 on the other. This in turn offers the possibility of designing a wet rotor, which has previously been used, for example, in electrical machines 2 designed as separately excited synchronous machines, as a dry rotor, or even of flooding the entire rotor interior with cooling medium.

[0033] In the second alternative embodiment, rotor windings 9 are wound on the pole cores 18 of the laminated core 3, with a slot closure wedge 7 with a predefined axial length LN being inserted into each slot 6. Subsequently, a plastic layer 8 with a predefined axial length LKI, LK2 is applied to both end faces 10 of the laminated core 3 in such a way that LKI + LK2 + LB = LN or LKI + LK2 + LB = LN, so that the plastic layer 8 serves as a tolerance compensation layer to compensate for an axial difference between the laminated core 3 and the slot closure wedges 7 inserted into the slots 6, and thereby an at least almost flat, circumferential end-face sealing surface 12 is created over the end faces of the slot closure wedges 7 and the plastic layer 8.

[0034] The prefabricated assembly consisting of laminated core 3, plastic layers 8, rotor windings 9 and slot closure wedges 7 is now mounted in a rotationally fixed manner on a shaft 14 (see Figure 4), whereby a rotationally fixed connection with the shaft

[0035] 14 This can be achieved, for example, by gluing, soldering, welding, or a form-lock connection. A form-lock connection, in particular, offers the great advantage of allowing easy assembly by simply sliding it on, while still ensuring reliable, high torque transmission.

[0036] Once the rotor 1 has reached this manufacturing stage, a balancing ring 15 with a seal 16 is placed on the sealing surface 12, enabling reliable sealing of the laminated core 3 to the outside. The plastic layer 8 applied to the front side of the laminated cores 3 can extend in a ring shape outside the rotor windings 9, as shown, for example, in Figure 4, thereby forming an annular sealing surface 12.

[0037] Finally, if one looks at Figure 7, one can see that the plastic layer 8 applied to the front side of the laminated core 3 serves to compensate for an axial length difference between the laminated core 3 and the slot closure wedges 7, so that they lie flat in a tool 17 via their sealing surface 12.

[0038] All in all, the method according to the invention can be used to significantly simplify the end-face sealing of the laminated core 3 and the rotor interior or the cooling channels 13, which run in the slot closure wedges 7, since the plastic layers 8 applied to the end face and designed as a tolerance compensation layer create a seal 16 on a balancing ring

[0039] 15, an at least almost, preferably even completely flat and continuously extending sealing surface 12 is created, which enables significantly simplified sealing. The plastic layer 8 applied in the grooves 6 also eliminates the need for insulating paper previously used there, further simplifying the manufacture of the rotor 1 according to the invention.

[0040] If several partial laminated cores are arranged one behind the other in the axial direction 5, the length LB of the laminated core 3 to be used for the method according to the invention is the sum of all individual thicknesses of the individual partial laminated cores.

[0041] Due to the almost flat sealing surface 12, which is designed in particular without sharp edges, it is comparatively easy to create a dry rotor from a wet rotor, which has significantly lower values ​​in terms of drag losses, so that the electric machine 2 with the rotor 1 produced according to the invention has a significantly higher efficiency.

Claims

Claims 1 . Method for producing a rotor (1) for an electrical machine (2), in which - a laminated core (3) composed of individual sheets is provided with grooves (6) separated from one another in the circumferential direction (4) and extending in the axial direction (5), wherein pole cores (18) with pole shoes (19) are arranged between the grooves (6), - an axial length LB of the laminated core (3) is recorded, - slot closure wedges (7) with a predefined axial length LN are provided, where LN > LB, - the grooves (6) of the laminated core (3) are lined with a plastic layer (8) for electrical insulation, in which further - simultaneously or subsequently, a plastic layer (8) is applied to both end faces (10) of the laminated core (3) with a predefined axial length LKI, LK2 such that LKI + LK2 + LB = LN or LKI + LK2 + LB = LN, so that the plastic layer (8) serves as a tolerance compensation layer to compensate for an axial difference between the laminated core (3) and the slot closure wedges (7) to be inserted later into the slots (6), - rotor windings (9) are wound on the pole cores (18) of the laminated core (3), - a slot closure wedge (7) with a predefined axial length LN is inserted into each slot (6), thereby creating a flat, end-face sealing surface (12) that extends at least almost all the way around the end faces of the slot closure wedges (7) and the plastic layer (8), or - rotor windings (9) are wound on the pole cores (18) of the laminated core (3), - a slot closure wedge (7) with a predefined axial length LN is inserted into each slot (6), - a plastic layer (8) is applied to both end faces (10) of the laminated core (3) with a predefined axial length LKI, LK2 such that LKI + LK2 + LB = LN or LKI + LK2 + LB = LN, so that the plastic layer (8) serves as a tolerance compensation layer to compensate for an axial difference between the laminated core (3) and the slot closure wedges (7) inserted into the slots (6), and thereby a flat end-face sealing surface (12) is created which extends at least almost all the way around the end faces of the slot closure wedges (7) and the plastic layer (8).

2. Method according to claim 1, characterized in that the laminated core (3) is mounted on a shaft (14) in a rotationally fixed manner.

3. Method according to claim 1 or 2, characterized in that a balancing ring (15) with a seal (16) is placed on the sealing surface (12), which seals the balancing ring (15) against the laminated core (3).

4. Method according to one of the preceding claims, characterized in that the sealing surface (12) extends in a ring shape outside the rotor windings (9).

5. Rotor (1) for an electrical machine (2), manufactured according to the method according to one of the preceding claims.

6. Rotor (1) according to claim 5, characterized in that the slot closure wedges (7) are made of an electrically non-conductive material, in particular of plastic.

7. Rotor (1) according to claim 5 or 6, characterized in that a cooling channel (13) through which a cooling liquid can flow is arranged in at least one slot closure wedge (7) for cooling the rotor windings (9).

8. Electrical machine (2) with a rotor (1) according to one of claims 5 to 7.

9. Electrical machine (2) according to claim 8, characterized in that the electrical machine (2) is designed as a separately excited synchronous machine.

Images