DE102021126419A1 - Stator of an electrical machine and method for producing a laminated core for an electrical machine - Google Patents

Abstract

The production of a laminated core (2) of a stator (1) of an electrical machine comprises the following steps: - providing a number of electrical laminations (3), each having a waviness, - stacking the electrical laminations (3) to form a laminated core (2) with an uncompressed Thickness (DLo),- Compressing the laminated core (2) while reducing the waviness of the electrical laminations (3) to such an extent that the laminated core (2) reaches a compressed thickness (Dcom) which is no more than 98% of the uncompressed thickness (DLo). .

Description

The invention relates to a method for producing a laminated core of a stator of an electrical machine. Furthermore, the invention relates to a stator of an electrical machine, ie an electric motor or generator.

The EP 2 355 308 A2 discloses an electric motor whose stator includes a plurality of windings. The central axes of the individual windings are aligned in the radial direction of the electric motor, so that the windings are arranged in a star shape overall. The windings arranged in a star shape and distributed around the circumference of the stator are connected to one another by clamp-like connecting elements which are located near the outer circumference of the stator.

The CN 106936271A discloses a device which is provided for assembling flat elements of a stator of an electric motor. The device comprises several pressure plates with which pressure can be exerted on the elements to be assembled.

Laminated cores of stators that are used in electric motors are usually made of electrical steel, with the individual sheets being electrically insulated from one another. In this context, reference is made to the standard DIN EN 10106:2016-03 "Cold-rolled, non-grain-oriented electrical strip and sheet in the final annealed condition".

The stacking factor, among other things, can be used as a measure of the quality of a laminated stator core. The stacking factor, which can also refer to the rotors of electrical machines, describes the density of a package made of electrical steel. Among other things, the maximum torque and the efficiency of an electric motor depend on the stacking factor. Depending on the exact design, achievable values of the stacking factor can be between 94% and 97%, for example. In this context, reference is made to the standard DIN EN 60404-13 "Magnetic materials - test methods for measuring the density, the specific resistance and the stacking factor of electrical sheet and strip".

From the DE 25 36 390 B1 discloses a squirrel-cage rotor for an electrical machine with a squirrel cage injected into the laminated rotor core. The squirrel-cage cage keeps the laminated rotor core pressed together and comprises short-circuit rings on the face side, with at least one of the short-circuit rings being toothed with a rotor hub or rotor shaft in a way that prevents it from twisting and shifting.

The DE 10 2008 032 214 B4 discloses a reluctance motor, the rotor of which has recess areas arranged regularly in the circumferential direction. The rotor is designed as a laminated core, with the recesses being punched out of the sheet metal parts. The individual sheet metal parts can be held together by punching. Optionally, the recesses are injected with plastic.

The DE 10 2016 24 249 A1 describes a method for producing a rotor for a synchronous reluctance machine, which comprises the method steps of stacking a rotor stack and spraying flux barriers within the rotor stack with a plastic material containing magnetic particles. The magnetic particles are also aligned by applying an external magnetic field.

From the DE 10 2017 220 123 A1 a slot wall insulation for a stator of an electric motor is known. The slot wall insulation should be able to be formed directly on a surface of a stator lamination in an injection molding process. Thus, the slot wall insulation is tooth-shaped. Due to the tooth-shaped design, a recess is formed which is suitable for receiving an electrical conductor.

The invention is based on the object of achieving progress in the production of stators for electrical machines, with the aim being to achieve a particularly favorable ratio between production costs and electrical properties of the end product, ie the electric motor or generator.

• - Stapeln der Elektrobleche zu einem Blechpaket mit einer unkomprimierten Dicke, wobei die aufeinander liegenden Elektrobleche in diesem Zustand einen zumindest geringfügig federelastischen Stapel bilden,
• - Komprimieren des Blechpakets gegen die gegebenen Federkräfte unter Reduzierung der Welligkeit der Elektrobleche soweit, dass das Blechpaket eine komprimierte Dicke erreicht, welche nicht mehr als 98 % der unkomprimierten Dicke, beispielsweise lediglich 95 % oder sogar einen geringeren Anteil der unkomprimierten Dicke, beträgt.

This object is achieved according to the invention by a method for producing a laminated core which has the features of claim 1 and is intended for use as part of a stator of an electrical machine. The manufacturing process is based on the provision of a large number of electrical steel sheets with significant waviness, i.e. a deviation from a geometrically ideal, flat shape, and includes the following steps:

• - Stacking the electrical laminations to form a laminated core with an uncompressed thickness, the electrical laminations lying on top of one another forming an at least slightly resilient stack in this state,
• - Compressing the laminated core against the given spring forces while reducing the waviness of the electrical laminations to such an extent that the laminated core reaches a compressed thickness which is no more than 98% of the uncompressed thickness, for example only 95% or even a smaller proportion of the uncompressed thickness.

This method can be used in particular to produce a stator which is designed according to claim 6 and comprises a plurality of compressed laminated cores made of electrical steel sheet stacked on top of one another.

In an advantageous procedure, the laminated core is compressed using a resin located between the electrical laminations, the finished, compressed laminated core being held together at least predominantly by the resin. A laminated core with a high stacking factor, in particular a stacking factor of at least 96%, can thus be produced in an efficient manner, with complex technologies for connecting the electrical laminations being able to be dispensed with.

The stacking factor of the laminated core can be determined in a proven manner, in particular by measuring the masses and dimensions of the laminated core and/or taking them from stored data, with known material properties, in particular the density of materials, also being included in the calculation.

The resin, which connects the electrical laminations to one another and at the same time ensures that the individual laminations are maintained in a geometrically at least approximately ideal, planar form, can be provided as the sole means of electrical insulation between the electrical laminations. In comparison to sheet stacks, which are produced by stamping and stacking without adhesive materials, the connection using resin is not only an efficient, easily reproducible technology, but is also characterized by a comparatively high packing density, since air volumes between the individual sheets are practically completely avoided , i.e. a high stacking factor.

Optionally, the resin can also be used to fix electrical conductors that extend in the axial direction of the laminated core and—if necessary—to be electrically insulated from the electrical laminations. The electrical conductors, which are connected to the stator core formed from electrical laminations as part of the manufacturing process, represent a wave winding overall. In the production of the stator core, methods known in principle, in particular punched packeting, can be used.

Depending on the process variant, the resin can be applied to the electrical steel sheets at different stages of the manufacturing process. For example, the resin is applied, which is also referred to as the impregnation process, after the metal sheets have been separated from a strip-shaped starting material. It is also possible to apply resin at different points of the starting or intermediate products in different stages of the process. In all cases, any spring deflection of the laminated core is almost completely eliminated after its completion.

In order to achieve the desired high stacking factor, the hardening process takes place, in which the electrical steel sheets are permanently connected to one another while the resin hardens, using a prestressing force on the laminated core. The prestressing force, that is to say the compressive force, can be applied by a press of a type which is known in principle. The press is actuated, for example, hydraulically, pneumatically or electromechanically. The additional time required by using the press and the curing time compared to purely mechanical connection methods is accepted.

• 1 einen Stator eines Elektromotors in perspektivischer Ansicht,
• 2 eine zur Herstellung des Stators zu verwendende Anordnung aus gestapelten Elektroblechen in einer Ansicht analog 1,
• 3 eine Anordnung aus aufeinander gestapelten Elektroblechen, wie sie Teil des Stators nach 1 sind,
• 4 lose aufeinander liegende Elektrobleche, wie sie als im Herstellungsverfahren auftretendes Zwischenprodukt in der Anordnung nach 2 vorhanden sind.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. Herein show, partly symbolized:

• 1 a perspective view of a stator of an electric motor,
• 2 an arrangement of stacked electrical laminations to be used for the production of the stator in a view analogous 1 ,
• 3 an arrangement of stacked electrical laminations, as part of the stator 1 are,
• 4 Electrical steel sheets lying loosely on top of each other, as shown in the arrangement as an intermediate product occurring in the manufacturing process 2 available.

A stator 1 of an electric motor, not shown in detail, comprises a multiplicity of individual electrical laminations 3 which are connected to form laminations 2 . Four laminated cores 2 can be seen in the exemplary embodiment. Likewise, only a single laminated core 2 could be provided. Overall, the electric motor comprising the stator 1 is a permanent-magnet synchronous machine. The associated rotor of the electric motor, equipped with permanent magnets, for example rare earth magnets, is not shown.

In the inner peripheral surface of the laminated core 2 numerous stator slots 4 are formed, in which electrical conductors 6 are located in the finished stator 1, which together form a wave winding. Furthermore, in the 1 and 2 several longitudinal grooves 8 in the outer peripheral surface of the stator 1 can be seen.

All of the laminated cores 2 are defined as the stator block 9 . The shape of the stator block 9 changes in the course of the manufacturing process, as in FIGS 3 and 4 is visualized in partly greatly exaggerated representation. It is assumed that each electrical steel sheet 3 has a significant waviness. In this state, there is a thickness D _Lo of the laminated core 2 and a height H _Lo of the entire stator block 9 to be measured in the same direction, ie in the axial direction of the stator 1 . The actual number of electrical laminations 3 per laminated core 2 is far higher than in 4 drawn.

In order to permanently connect the electrical sheets 3 to one another and at the same time to largely eliminate their waviness, a resin 5 is used, which in 4 is only shown as an indication. In fact, the resin 5 covers the entire surface of the electrical steel sheets 3 . Starting from the in 4 illustrated state, the electrical steel sheets 3 including the intermediate layers of resin 5 are compressed by a press, not shown, so that the in 3 outlined state, in which the thickness of the laminated core 2 has decreased to the combined thickness D _com is reached. In this state, the height of the entire stator block 9 is reduced to H _com .

With the method described, on the one hand the stator block 9 is produced in an efficient manner and on the other hand a high stacking factor of the laminated core 2 is achieved. Without using any additional elements, such as tie rods, a stacking factor of each individual laminated core 2 and also of the entire stator block 9 of between 94% and 97% can be achieved. Optionally, the resin 5 is also used to anchor the conductors 6 in the stator slots 4.

reference list

1

stator

2

laminated core

3

electrical steel

4

stator slot

5

resin

6

Director

7

free space

8th

longitudinal groove

9

stator block

DLo

thick, loose

Dcom

thick, compressed

HLo

height, loose

Hcom

height, compressed

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2355308 A2 [0002]
• CN 106936271A [0003]
• DE 2536390 B1 [0006]
• DE 102008032214 B4 [0007]
• DE 10201624249 A1 [0008]
• DE 102017220123 A1 [0009]

Claims (9)

Method for producing a laminated core (2) of a stator (1) of an electrical machine, with the following steps: - providing a number of electrical laminations (3) which each have a waviness, - stacking the electrical laminations (3) to form a laminated core (2). an uncompressed thickness (D _Lo ), - compressing the laminated core (2) while reducing the waviness of the electrical laminations (3) to such an extent that the laminated core (2) achieves a compressed thickness (D _com ) which is no more than 98% of the uncompressed thickness (D _Lo ) is. procedure after claim 1 , characterized in that the compression of the laminated core (2) takes place using a resin (5) located between the electrical laminations (3). procedure after claim 2 , characterized in that the compressed laminated core (2) is held together predominantly or exclusively by the resin (5). procedure after claim 2 or 3 , characterized in that the resin (5) is introduced as the only means of electrical insulation between the electrical steel sheets (3). Procedure according to one of claims 2 until 4 , characterized in that the resin (5) at the same time fixes electrical conductors (6) which extend in the axial direction of the laminated core (2) and in relation to the electrical laminations (3) are electrically insulated. Stator (1) of an electrical machine, comprising several laminated cores (2) constructed from electrical laminations (3). claim 1 . Stator (1) after claim 6 , characterized in that it comprises at least three identical laminated cores (2). Stator (1) after claim 6 or 7 , characterized in that it comprises a number of stator slots (4) which extend in the axial direction of the laminated cores (2). Stator (1) according to one of Claims 6 until 8th , characterized by a stacking factor of at least 96%.

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