WO2015071089A2

WO2015071089A2 - Electric machine with a potted winding head

Info

Publication number: WO2015071089A2
Application number: PCT/EP2014/073095
Authority: WO
Inventors: Horst Braun; Armin Elser; Thomas Bublat; Martin Kuhn
Original assignee: Robert Bosch Gmbh
Priority date: 2013-11-13
Filing date: 2014-10-28
Publication date: 2015-05-21
Also published as: WO2015071089A3; DE102013223051A1

Abstract

The invention relates to an electric machine (1) with a rotor (3), a stator (5), a housing (7), and two winding heads (17). Each of the winding heads (17) has a potting (19) made of an electrically insulating material such as plastic for example, axial end regions of stator windings (15) on the end faces (6) of the stator (5) being potted into said potting. According to the invention, an insulating paper (21) is arranged between the potting (19) of each winding head (17) and an adjacent region of the housing (7). The insulating paper (21) can preferably be adhered to the potting (19) in a bonded manner but is not bonded to the housing (7) such that the potting (19) can be decoupled from the housing (7). In this manner, mechanical stresses between said components (7, 19) due to different thermal expansion coefficients for example can be prevented from occurring.

Description

description

Electric machine with potted winding head

Field of the invention

The present invention relates to an electrical machine, in particular an asynchronous machine, with a potted winding head.

State of the art

Electric machines can be used as motors or generators in

serve different technical applications. Currently

In particular, powerful electric machines designed for use in hybrid or electric vehicles.

In particular, electrical asynchronous machines are known. In these, by means of electrical conductors, which are arranged as stator windings on a stator of the electric machine, a rotating magnetic field can be generated. In a so-called internal electrical machine, the stator surrounds a rotor. For example, in the rotor

Permanent magnets may be provided. Alternatively, the rotor may be formed with a so-called short-circuit cage in which currents and thus also induced magnetic fields can be generated by alternating external magnetic fields. Ultimately, using the in the stator

provided stator windings and thus causing a rotating magnetic field, a rotation of the rotor can be effected. The stator windings of such an electric machine are often arranged so that they extend between two opposite ends of the stator along the stator in a longitudinal direction and to the

Front ends of the stator are deflected transversely to this longitudinal direction loop-like. The stator can have, for example, a base body in which grooves running parallel to the longitudinal direction of the stator are formed.

Stator windings are inserted into these grooves and protrude beyond the front ends of the main body via this in the longitudinal direction and are deflected there from a groove to an adjacent groove. Such an area in which the stator windings over the stator base body project in the longitudinal direction and are deflected, is commonly referred to as a winding head.

To the stator windings relative to each other and with respect to the

Stator basic body to fix, the components of the stator in the

Surrounded generally with an electrically insulating and flowable curable composition. Such a mass may for example be a plastic, in particular thermoplastic or thermoset. For potting the components of the stator are placed in a suitable form and then

Vergussmassse filled. The first liquid casting compound penetrates into cavities between the stator windings and the stator base body, so that these components after a subsequent curing of the

Potting compound are fixed relative to each other.

In DE 10 2009 055 325 AI an electric machine in the form of an asynchronous motor is described, are arranged in the windings in a disk body of a stator.

Disclosure of the invention

Embodiments of the present invention make possible an electric machine, in particular an asynchronous machine, with improved behavior in the event of temperature fluctuations. In particular, due to such temperature fluctuations occurring mechanical stresses can be reduced within the electrical machine. According to one aspect of the present invention, an electric machine is proposed which comprises a rotor, a stator surrounding the rotor, a cylindrical housing surrounding the stator and two winding heads. The stator has a plurality of stator windings of electrical conductors. Each of the winding heads is received in a potting of an electrically insulating material, in the axial end portions of the stator windings are shed at front ends of the stator. The potting has an annular geometry and is disposed within the housing at one of the two opposite ends of the stator. The electric machine is characterized by the fact that between the encapsulation of the winding heads and a

Inner circumference of the housing, i. an insulating paper is temporarily stored in an adjacent area of the housing.

This aspect of the invention may be considered as being based on the following description:

In conventional asynchronous machines were over a

Statorgrundkörper in the axial direction projecting and deflected areas of stator windings, that is, the winding head, so far usually shed so that a potting material was in direct mechanical contact with the housing. The potting adhered to an inner wall of the housing. Such potting is relatively easy to produce, in particular, because the housing surrounding the potting can serve as an outer boundary forming mold during potting.

However, it has been recognized by the inventors of the present invention that problems can occur in previous encapsulations, especially in the event of severe temperature fluctuations. Mechanical degradation of the encapsulant, for example in the form of microcracks, was observed, presumably due to mechanical stresses that occur between the encapsulation and the housing in the event of temperature fluctuations. Such mechanical stresses can be different thermal

Expansion coefficients of the material of the casting, usually plastic, compared to the material of the housing, usually metal originate. In particular, the potting can especially between external wires of the windings and the housing may be formed only as a thin layer in which mechanical stresses can easily lead to cracks.

It is therefore proposed to mechanically largely decouple the encapsulation enclosing a winding head of an electrical machine from a surrounding housing, by interposing a so-called insulating paper between the encapsulation and an adjacent region of the housing.

In this case, an insulation paper can be understood as a film-like or layer-like structure which, on the one hand, has electrically insulating properties and, on the other hand, behaves mechanically similar to a paper or a film. In particular, the insulation paper may have a two-dimensional form, in the longitudinal and transverse dimensions in the range of several

Millimeters or centimeters can be, but a thickness of the insulation paper is only between 0.1 mm and 1 mm.

Such a thin and electrically insulating insulation paper can

For example, even before the casting of the winding heads to a

Inner wall of the housing are attached, so that it extends after the casting of the winding heads between the potting and the housing.

The insulation paper can advantageously enclose the potting along its entire circumference. Furthermore, the insulating paper can be stored over an entire height of the casting between the casting of the winding heads and an adjacent region of the housing. Thus, the insulating paper can separate the encapsulant from an inner wall of the housing over an entire interface towards the surrounding housing, i. electrically isolate.

Preferably, the insulating paper is materially connected to the potting and not materially connected to the housing. In other words, the insulating paper may be formed such that it adheres strongly to the potting on its surface directed to the potting, in particular is adhesively bonded thereto, but with an opposite

Surface is not strongly adhered to the housing, that is not materially connected to the housing. The fact that the insulating paper adheres on the one hand cohesively to the potting, on the other hand but not or only weakly adheres to its opposite surface on the inner wall of the housing, can be avoided that, for example, due to temperature

Dimensional changes strong forces, especially shear forces, occur between the potting and the housing. Instead, for example, when heated the potting and the housing can expand largely independently of each other. For example, due to the higher thermal expansion coefficient of the metal used for this purpose, the housing can expand more than the encapsulation formed with plastic. Since the potting does not or hardly adheres directly to the housing, there are no or little force transmission between the potting and the housing. In extreme cases, even a gap between the potting and the housing can form, which can close again in a subsequent cooling of the electric machine.

Furthermore, by different expansion coefficients of potting and cast-in copper wires, for example, thermo-mechanical

Tensions arise. These can cause cracks, especially at the casting edge

Cause housing. Cracking can be avoided by interposing insulation paper or the like.

The insulation paper can have multiple layers of material. Each of the material layers can be certain mechanical or electrical

Meet requirements. In this way, the insulating paper can advantageously cause both a mechanical decoupling between the potting and the surrounding housing and an electrical insulation between these components.

For example, one of the layers of material may be sufficiently electrically insulating to prevent electrical contact between a conductor of the stator windings and the housing. This can be achieved, for example, that in the event that individual conductors of the stator windings have locally defective enclosing insulation, to a short circuit between such

Ladders can come over the adjacent metallic housing. Furthermore, at least one of the material layers can be mechanically more stable than the encapsulation. By "mechanically stable" it can be understood here that the material layer in question can also withstand forces undamaged, which can lead to damage in the casting

Material layer provided insulation paper can thus stabilize the potting and protect, for example, from signs of wear.

It should be noted that features of an electric machine according to the invention are described herein with reference to various embodiments. A person skilled in the art recognizes that the various features can be exchanged or combined in a suitable manner in order to arrive at further embodiments of the invention in this way.

Short description of the drawing

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, wherein neither the description nor the drawings are to be construed as limiting the invention.

FIG. 1 shows a sectional view through components of a conventional electrical machine.

FIG. 2 shows a perspective view of a stator of an electrical machine before casting.

FIG. 3 shows a sectional view of an electric machine according to an embodiment of the present invention.

FIG. 4 shows a partially cut away, perspective view of a stator and a housing of an electric machine according to one

Embodiment of the present invention. The figures are only schematic and not to scale. Identical or equivalent features are titled in the figures with the same reference numerals.

Embodiments of the invention

FIG. 1 shows components and features of a conventional electrical machine 1 in cross-section. The figure shows only a right half of the cross section. An entire cross-section results from reflection at the

Symmetry axis S.

The electric machine 1 has a rotor 3, a hollow cylindrical stator 5 surrounding the cylindrical rotor 3, and a hollow cylindrical housing 7 surrounding the stator 5. Together, the components 3, 5, 7 form an internal rotor formed asynchronous machine in which the rotor 3 can rotate about the axis of symmetry S and generated by in the stator 5

Magnetic fields is driven for this purpose. The stator 5 is fixed to the housing 7, which in turn may be attached, for example, to a body of a motor vehicle.

FIG. 2 shows a perspective view of a stator 5 before casting. Here, the plane A - A is indicated, along which the cross-sectional view of Figure 1 is added. The stator 5 has a Statorgrund body 9, which is composed of a plurality of composite into a package stator laminations. In the Statorgrund body 9 grooves 13 are formed. In this groove 13 acting as electrical conductors wires 11 are wrapped and form stator windings 15. The stator windings 15 extend between two opposite ends 6 of the stator 5 along its longitudinal direction. At the front ends 6 itself protrude the stator windings 15 on the

Stator basic body 9 in the longitudinal direction and in this case form so-called winding heads 17. In the region of these winding heads 17, the individual stator windings 15 extend transversely to the longitudinal direction of the stator 5, approximately in its circumferential direction. To the stator windings 15 with each other and with respect to the

Stator basic body 9 to fix, they are usually encapsulated with an electrically insulating plastic. The plastic forms a potting 19. Conventionally, the potting 19 thereby illustrated in Figure 1, in the

Essentially in cross-section rectangular shape and adjacent to its radially outer periphery directly to an inner surface 8 of the housing 7 at.

The potting can be formed, for example, such that a cylindrical cavity in which both the lamella base body 9 and the windings 15 of the winding head 17 are filled with liquid plastic and the plastic is subsequently cured. The cylindrical cavity can in this case be limited to the outside by the housing 7 and inwardly by a preferably also cylindrical female mold. After curing, the plastic forms an ideally in cross-section rectangular encapsulation 19, which extends towards an end face 6 of the stator 5 to the

Slat main body 9 connects and in which the stator windings 15 are embedded.

Since the plastic of the potting 19 during casting in the still liquid state with the inner surface 8 of the housing 7 comes into contact, it can during

Curing the plastic to an adhesive, cohesive bond between the potting 19 and the housing 7 come.

It has now been recognized by the inventors of the present invention that problems may arise in the region of the encapsulation 19 adjacent to the housing 7 if the electrical machine itself is exposed to different temperatures, for example due to changing ambient temperatures or due to heating due to efficiency losses of the machine is. In this case, the metallic housing 7 and the metallic wires 11 of the stator windings 15 usually expand substantially more than the molding compound 19 made of plastic, so that it is at a

cohesive bond between these two components 7, 11, 19 can come to mechanical stresses that can damage the integrity of the electric machine 1 over time. According to one embodiment of the present invention, therefore, as shown in Figure 3, between the potting 19, with which a winding head 17 is encapsulated, and an adjacent portion of the housing 7 a

Interposed insulation paper 21. The insulation paper preferably extends along the entire circumference of the encapsulation 17, so that a

Length of the insulating paper 21 substantially the inner circumference of the

Housing 7 corresponds. In the axial direction, the insulating paper 21 preferably extends over the entire height h of the potting 19. In the radial direction, the insulating paper 21 has a thickness d, which is substantially smaller than the thickness of the housing 7 and in particular substantially smaller than the thickness of

Vergusses 19 and for example in the range of 0.1 mm to 1 mm.

Properties of the insulation paper 21 can be chosen such that on the one hand with the potting 19 a strongly adhering, preferably

cohesive connection can enter, but on the other hand at the

Inner surface 8 of the housing 7 at most easily adheres. For this purpose, for example, an inwardly towards the potting 19 to be addressed surface of the insulation paper 21 have a certain roughness, which is generated by microscopic structures or cavities so that liquid plastic during casting of a winding head 7 in structures of the surface rough insulation paper 21 flow and after curing, can form the desired cohesive connection. On the other hand, the insulating paper 21 may be sufficiently dense so that no liquid plastic passes through the insulating paper 21 to an opposite side during the potting, and thus the opposite surface of the insulating paper 21 can not stick to the inner surface 8 of the housing 7.

In particular, the insulation paper 21 may comprise a plurality of material layers. For example, the insulating paper 21 may each comprise a layer of Nomex fabric on the two opposite outer surfaces, the two Nomex fabric layers being separated by an intermediate polyester layer. Such a composite of three layers may typically have a thickness of about 0.2 to 0.4 mm. In the Nomex fabric liquid plastic of the grout 19 can penetrate superficially and stick with it. The intermediate one Polyester layer prevents on the one hand that liquid plastic can get to the opposite Nomex tissue layer, and on the other hand ensures sufficient electrical insulation of the

Insulation paper 21.

On account of the mechanical decoupling between the encapsulation 19 on the one hand and the housing 7 on the other hand caused by the intermediately stored insulation paper 21, it is possible to avoid building up of mechanical stresses between these components 7, 19. For example, due to high temperatures, a gap between the inner surface 8 of the housing 7 and the outer surface of the insulation paper 21 can form with strong expansion of the housing 7, without causing significant mechanical stresses. In addition, due to its electrically insulating properties, the insulation paper 21 can provide additional protection, for example against short circuits between possibly damaged stator windings 15, for example when the casting 19 is damaged, by preventing electrical contact of these stator windings 19 with the electrically conductive housing 7.

Figure 4 illustrates a stator 5 and a surrounding housing 7 for an electric machine according to the invention in a perspective and partially cut away view. Between the potting 19 and an inner surface 8 of the housing 7 in this case the insulating paper 21 is arranged and surrounds the entire annular potting 19 on the outer surface.

Claims

Claims :

Electric machine (1), comprising:

a rotor (3);

a rotor (3) surrounding the stator (5) with a plurality of stator windings (15) made of electrical conductors;

a cylindrical housing (7) surrounding the stator (5);

two windings (17);

wherein each of the winding heads (17) is received in an annular encapsulation (19) made of an electrically insulating material, in the axial end portions of the stator windings (15) at ends (6) of the stator (5) are shed

characterized in that

between the encapsulation (19) of the winding heads (17) and an inner circumference of the housing (7) is interposed an insulating paper (21).

Electric machine according to claim 1, wherein the insulating paper (21) with the encapsulation (19) is integrally connected and the insulating paper (21) to the housing (7) is not materially connected.

An electric machine according to claim 1 or 2, wherein the insulating paper (21) surrounds the potting (19) along its entire circumference.

Electrical machine according to one of claims 1 to 3, wherein the

Insulation paper (21) over an entire height of the encapsulation (19) between the encapsulation (19) of the winding heads (17) and an adjacent region of the housing (7) is interposed.

5. Electrical machine according to one of claims 1 to 4, wherein the insulating paper (21) has a thickness of between 0.1 mm and 1 mm.

6. Electrical machine according to one of claims 1 to 5, wherein the

Insulation paper (21) has multiple layers of material.

7. Electrical machine according to claim 6, wherein at least one of

Material layers is sufficiently electrically insulating to prevent electrical contact between a conductor of the stator windings (15) and the housing (7).

8. Electrical machine according to claim 6 or 7, wherein at least one of the material layers is mechanically stable than the potting (19).