DE102022129626A1 - stator - Google Patents

Abstract

The invention relates to a stator (1) for an electrical machine (2), in particular within a drive train (3) of a motor vehicle (4), wherein the stator (1) is designed in the shape of a cylindrical ring and has a plurality of stator teeth (5), which in the circumferential direction between adjacent stator teeth (5) each define a stator groove (6) extending in the radial direction and running in the axial direction through the stator (1), with two groove side walls (7) and a groove base (8), into which a current-carrying winding (9) comprising a plurality of conductors (10) is inserted, wherein the conductors (10) emerge from the stator (1) at the end faces (11) of the stator (1), each forming a winding head (12), wherein an impregnation ring (13, 23) is in contact with the two end faces (11, 21) of the stator (1), from which a plurality of teeth (14) extend radially inwards, which Stator slots (6) are each enclosed at least in sections on the slot base (8) and the slot side walls (7), wherein the impregnation ring (13, 23) has a channel system (15) by means of which a flowable electrical insulation medium (16) can be fed from the radial direction to the channel system (15) and in the radial direction and in the circumferential direction through one of the teeth (14) of the impregnation ring (13, 23) to the stator slots (6).

Description

The present invention relates to a stator for an electrical machine, in particular within a drive train of a motor vehicle, wherein the stator is cylindrical in shape and has a plurality of stator teeth, which in the circumferential direction between adjacent stator teeth each define a stator groove extending in the radial direction and running in the axial direction through the stator, with two groove side walls and a groove base, into which a current-carrying winding comprising a plurality of conductors is inserted, wherein the conductors emerge from the stator on the end faces of the stator, each forming a winding head.

Electric motors are increasingly being used to power motor vehicles in order to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the suitability of electric drives for everyday use and to offer users the same driving comfort they are used to.

A detailed description of an electric drive can be found in an article in the magazine ATZ, 63rd year, 05/20 6, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrated and flexible electric drive unit for electric vehicles. This article describes a drive unit for an axle of a vehicle, which includes an electric motor that is arranged concentrically to a bevel gear differential. Such drive units are also referred to as electric axles.

In addition to purely electrically operated drive trains, hybrid drive trains are also known. Such drive trains in a hybrid vehicle usually comprise a combination of an internal combustion engine and an electric motor and enable - for example in urban areas - purely electric operation while at the same time providing sufficient range and availability, especially for cross-country journeys. In certain operating situations, it is also possible to use the internal combustion engine and the electric motor to drive simultaneously.

For the development of electrical machines, in particular electrical machines for the above-mentioned hybrid or fully electric motor vehicles or also for wheel hub drives, basically different winding technologies for a stator of an electrical machine are known.

In electrical machines that have a stator with a hollow cylindrical stator, i.e. are designed as an internal rotor machine, and that are configured for use as a traction drive for a motor vehicle, they often have a stator winding with a rectangular cross-section in order to achieve a high power density. In electrical machines that are intended for driving motor vehicles, the stator windings are therefore typically designed as hairpin windings. In this case, for example, essentially U-shaped wire segments are introduced into the stator slots from one end face of the stator and then formed on an opposite end face of the stator and connected, for example, by welding.

With such hairpin windings, it is also known to electrically insulate them together with the winding head of the hairpin winding by means of a so-called full casting of the stator. However, there is a risk that air and creepage distances may form during the casting process and that local electrical short circuits may occur during operation of the stator, which can have a negative impact on the performance of the electrical machine and is often undesirable.

As an alternative or in addition to a full encapsulation, closed caps for insulating the hairpin ends on a winding head of a hairpin winding are also known from the prior art. An example of this is in the JP2000209802A disclosed.

It is also known to insulate and fix the winding and the slots in a stator by trickle impregnation, immersion impregnation or roll impregnation. In trickle impregnation, resin is poured onto the winding head using one or more nozzles. The resin is sucked into the slots by capillary effects and, if necessary, by tilting the stator in the system. In immersion and roll impregnation, the stator is completely or, if necessary, partially immersed in a resin bath and, if necessary, rotated around its own axis (rolled).

These solutions have a number of disadvantages. For example, process-related contamination can occur at various points on the stator, such as between the slots, on the inner diameter of the stator, on the outer diameter and also on the end faces, which can be a major problem, especially with screwed stators, as the screwing areas are contaminated with resin drops/traces and therefore disrupt secure screwing and sometimes make it impossible. The consequence of this contamination is rework or mas Masking is unsuitable due to the high capillarity of the resin. Furthermore, performance losses can occur due to air inclusions and contamination, resulting in poorer cooling properties, as the resin must be drawn in by capillary effects alone. Filling levels in the region of 70% are usually achieved here.

The processes mentioned also have a comparatively high resin consumption with correspondingly high costs, since the resin can only enter the slots indirectly via the winding heads. In some application scenarios, such as wet-running electrical machines, the winding heads must also be kept free of resin.

It is therefore the object of the invention to minimize or completely eliminate the problems known from the prior art and to provide a stator which allows an accurate and clean introduction of an insulating means into the slots and between the winding of the stator.

This object is achieved by a stator for an electrical machine, in particular within a drive train of a motor vehicle, wherein the stator is designed in the shape of a cylindrical ring and has a plurality of stator teeth, which in the circumferential direction between adjacent stator teeth each define a stator groove extending in the radial direction and running in the axial direction through the stator, with two groove side walls and a groove base, into which a current-carrying winding comprising a plurality of conductors is inserted, wherein the conductors emerge from the stator at the end faces of the stator, forming a winding head, wherein an impregnation ring is in each case located on the two end faces of the stator, from which a plurality of teeth extend radially inwards, which enclose the stator grooves at least in sections on the groove base and the groove side walls, wherein the impregnation ring has a channel system, by means of which a flowable electrical insulation medium can be fed from the radial direction to the channel system and in the radial direction and in the circumferential direction through one of the teeth of the Impregnation ring, which can be fed into the stator slots.

This has the advantage of providing a cost-effective and optimized solution for introducing the insulating agent, such as a resin, into the stator slots of the stator, and the impregnation rings can be used to guarantee defined positioning and clean injection of the insulating agent. In addition, this solution with the impregnation rings offers a high level of flexibility and can be installed in many different stators that differ in the number of slots or windings. Other advantages include reduced insulating agent consumption, as the impregnation rings allow the resin to be introduced into the slot areas in a targeted manner. The targeted introduction of the insulating agent into the slot areas also allows a higher fill factor of the insulating agent to be achieved than with conventional methods. This also allows better bonding of the winding to the stator, which can have a positive influence on the NVH behavior, the susceptibility of the stator to vibration, and the positioning of the winding. Finally, a high fill factor of insulation also leads to optimized cooling behavior, since the heat dissipation from the winding into the stator can be achieved well via the insulation.

The process also means that the inner diameter, the end faces and the outer diameter of the stator do not become contaminated. The channel and the channel system can direct the insulation through the impregnation rings in a targeted manner, preventing it from leaking out of the inner diameter. The end faces are also not further wetted and contaminated by the insulation, as the insulation collects in a targeted manner in the channel system of an impregnation ring. This means that only minimal contamination, if any, can occur due to centrifugal forces when the stator rotates during impregnation.

The teeth of the impregnation ring can also be useful as a bending device when twisting a hairpin winding and/or as a "spacer" between the conductors. This can also protect any insulation paper in the stator slots from being damaged by the winding during twisting.

The stator according to the invention is intended for use in an electrical machine. The electrical machine serves to convert electrical energy into mechanical energy and/or vice versa, and it generally comprises the stationary part referred to as the stator, stand or armature and a part referred to as the rotor or runner and arranged to be movable, in particular rotatable, relative to the stationary part. In particular, the electrical machine is dimensioned such that vehicle speeds of greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. The electric motor particularly preferably has an output of greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is further preferred that the electrical machine has speeds of greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, most preferably greater than 12,500 rpm.

The stator can in particular be supplied with current by power electronics. The power electronics are preferably a combination of different components which control or regulate a current to the stator, preferably including the peripheral components required for this, such as cooling elements or power supplies. In particular, the power electronics contain one or more power electronics components which are set up to control or regulate a current. These are particularly preferably one or more power switches, e.g. power transistors. The power electronics particularly preferably have more than two, particularly preferably three separate phases or current paths, each with at least one of its own power electronics component. The power electronics are preferably designed to control or regulate a power with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W per phase. The power electronics are preferably connected to the stator winding of the stator via an HV terminal (HV = high voltage).

For the purposes of this application, motor vehicles are land vehicles that are moved by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), lorries (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOM) or tractors.

The stator according to the invention can preferably be configured for a radial flux machine. The stator of a radial flux machine is usually cylindrical or cylindrically ring-shaped and generally consists of a stator body which is formed by electrical sheets which are electrically insulated from one another and are layered and packaged to form sheet stacks. This structure keeps the eddy currents in the stator caused by the stator field to a minimum. Stator slots which accommodate the stator winding or parts of the stator winding are distributed over the circumference and arranged parallel to the rotor shaft. Depending on the design towards the surface, the slots can be closed with closure elements such as closure wedges or covers or the like to prevent the stator winding from coming loose.

The stator body is preferably formed in one piece. A one-piece stator body is characterized by the fact that the entire stator body is formed in one piece over its circumference. The stator body is generally formed from a large number of stacked laminated electrical sheets, with each of the electrical sheets being closed to form a circular ring. The individual sheets can be held together in the stator body, for example, by gluing, welding or screwing.

The stator teeth of the stator are preferably formed in the stator body. Stator teeth are components of the stator body that are designed as circumferentially spaced, tooth-like parts of the stator body that are directed radially inwards (inner rotor) or radially outwards (outer rotor), and between their free ends and a rotor body an air gap is formed for the magnetic field and for the rotary movement of the rotor. The air gap is the non-magnetic gap that exists between the rotor and the stator. In a radial flow machine, for example, this is an essentially circular gap with a radial width that corresponds to the distance between the rotor body and the stator body.

A stator winding is embedded in the stator slots of the stator according to the invention. A stator winding comprises electrically conductive conductors whose length is significantly greater than their diameter. The stator winding can basically have any cross-sectional shape. Rectangular cross-sectional shapes are preferred, as these allow high packing and therefore power densities to be achieved. A stator winding is particularly preferably made of copper. The winding is preferably designed as a hairpin winding or wave winding.

According to an advantageous embodiment of the invention, it can be provided that the impregnation rings, each with the corresponding end face, of the stator each define one of the channel systems. The advantage of this embodiment is that the impregnation rings can be manufactured particularly inexpensively, since the channel system in the impregnation rings can be designed to be open towards the end faces, since a closed channel structure is created by placing the impregnation rings on the corresponding end faces.

According to a further preferred development of the invention, it can also be provided that the impregnation rings each have a circumferential groove on their radially outer surface, from which a radial channel of the channel system extends from the outside to the inside through the teeth. This allows a particularly good distribution of the insulation agent to be achieved. Furthermore, the groove protects the winding heads from unwanted wetting. by the insulating material during the casting process.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that, starting from the radial channel, at least one tangential channel extending in the circumferential direction up to a groove side wall is formed in each of the teeth of the impregnation rings, which further promotes a uniform distribution of the insulating agent.

According to a further particularly preferred embodiment of the invention, it can be provided that the at least one tangential channel extends from the radial channel in the circumferential direction to two opposite side walls, which contributes to a further optimization of the distribution of the insulating agent.

Furthermore, the invention can also be further developed in such a way that a plurality of tangential channels are formed at radial distances in each of the teeth of the impregnation rings. The advantage of this design is a further improvement in the distribution of the insulating agent.

In a likewise preferred embodiment variant of the invention, it can also be provided that the tangential channels and/or the radial channels are designed as grooves, which is particularly favorable in terms of manufacturing technology.

It may also be advantageous to further develop the invention in such a way that the first impregnation ring on the first end face of the stator is essentially identical to the second impregnation ring on the second end face of the stator. The advantage that can be achieved in this way is that the manufacturing costs for the impregnation rings can be further reduced by an increased proportion of identical parts.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that the winding heads are not wetted by the insulating agent. This can ensure that the gaps between the electrical conductors of the winding heads remain free and thus passages for coolants from, for example, centrifugal cooling or cooling oil showers are present within the winding head.

Finally, the invention can also be advantageously designed such that the impregnation ring is formed from a plastic, which is particularly preferable in terms of manufacturing technology and cost.

The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

• 1 ein Kraftfahrzeug mit einem elektrischen Antriebstrang in einer schematischen Blockschaltdarstellung,
• 2 einen bewickelten Stator einer elektrischen Maschine in einer perspektivischen Darstellung,
• 3 einen bewickelten Stator einer elektrischen Maschine in einer Seitenansicht,
• 4 einen Stator in einer schematischen Querschnittsansicht,
• 5 ein Imprägnierungsring in einer perspektivischen Ansicht,
• 6 eine Detaildarstellung der Rückseite des Imprägnierungsrings in einer perspektivischen Ansicht,
• 7 eine Querschnittsansicht des Imprägnierungsrings und des Stators,
• 8 eine erste Axialschnittansicht des Stators,
• 9 eine zweite Axialschnittansicht des Stators.

It shows:

• 1 a motor vehicle with an electric drive train in a schematic block diagram,
• 2 a wound stator of an electrical machine in a perspective view,
• 3 a wound stator of an electrical machine in a side view,
• 4 a stator in a schematic cross-sectional view,
• 5 an impregnation ring in a perspective view,
• 6 a detailed view of the back of the impregnation ring in a perspective view,
• 7 a cross-sectional view of the impregnation ring and the stator,
• 8th a first axial sectional view of the stator,
• 9 a second axial section view of the stator.

The 1 shows an electric machine 2 within a drive train 3 of a motor vehicle 4. The drive train 3 comprises the electric machine 2 and a transmission 20 forming a structural unit with the electric machine 2.

As shown by the 2 As can be seen, the stator 1 is designed in the shape of a cylinder ring and has a plurality of stator teeth 5, which in the circumferential direction between adjacent stator teeth 5 each define a stator slot 6 extending in the radial direction and running in the axial direction through the stator 1 with two slot side walls 7 and a slot base 8, in which a current-carrying winding 9 comprising a plurality of conductors 10 is inserted. This can also be clearly seen from the 4 comprehend.

The conductors 10 on the front sides 11 of the stator 1 emerge from the stator 1, forming a winding head 12. As can be seen from the 3 , an impregnation ring 13, 23 is located on the two end faces 11, 21 of the stator 1, from which a plurality of teeth 14 extend radially inwards, which enclose the stator slots 6 at least in sections on the slot base 8 and the slot side walls 7, as is also the case, for example, in the 7 can be seen. The impregnation ring 13,23 has a channel system 15, by means of which a flowable electrical insulation medium 16 can be fed during an impregnation process from the radial direction to the channel system 15 and in the radial direction and in the circumferential direction through one of the teeth 14 of the impregnation ring 13, 23 to the stator slots 6. The first impregnation ring 13 on the first end face 11 of the stator 1 is essentially identical to the second impregnation ring 23 on the second end face 21 of the stator 1. The impregnation rings 13, 23 are formed from a plastic in the embodiment shown. 5 shows an impregnation ring 13,23 in a perspective view.

From the overview of the 7-9 it is evident that the impregnation rings 13, 23 each define one of the channel systems 15 with the corresponding end face 11, 21 of the stator 1. The impregnation rings 13, 23 each have a circumferential groove 17 on their radially outer surface, from which a radial channel 18 of the channel system 15 extends from the outside to the inside through the teeth 14.

Like in the 6 As shown, tangential channels 19, which run parallel in the circumferential direction from the radial channel 18 and extend in the circumferential direction to two opposite side walls 7, are formed in each of the teeth 14 of the impregnation rings 13, 23. Both the tangential channels 19 and the radial channels 18 are designed as grooves in the embodiment shown. The impregnation rings 13, 23 can thus ensure that the winding heads 12 are not wetted by the insulation agent 16 during impregnation.

The impregnation process therefore proceeds as follows. The impregnation rings 13, 23 are attached to the front of the stator 1 and the stator 1 is then wound. The insulation 16, for example a resin, is then poured into the grooves 17 of the impregnation rings 13 and not, as is usual, onto one of the winding heads 12. This keeps the winding heads 12 clean and free of insulation 16. The contour of the groove 17 guides the insulation 16 via the channel system 15 in the desired direction into the stator slots 6 and thus prevents the stator 1 from being contaminated by the insulation 16 on its inner diameter, on the front surfaces or the outer diameter. The channel system 15 formed in the impregnation rings 13, 23 gives the insulation a predefined direction of travel. The channel system 15 with its radial channels 18 and its tangential channels 19 serves to guide the insulating agent 16 directly into the stator slots 6 and to absorb it there. This can in particular also prevent the insulating agent 16 from reaching unwanted places, such as the inner or outer diameter of the stator or its end faces.

The invention is not limited to the embodiments shown in the figures. The above description is therefore not to be regarded as restrictive, but as explanatory. The following patent claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a ranking.

List of reference symbols

1

stator

2

electric machine

3

Drivetrain

4

Motor vehicle

5

Stator teeth

6

Stator slot

7

Groove side walls

8th

Groove base

9

Winding

10

Director

11

Front side

12

Winding head

13

Impregnation ring

14

Teeth

15

Channel system

16

Insulating agents

17

gutter

18

Radial channel

19

Tangential channel

20

transmission

21

Front side

23

Impregnation ring

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed 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 accepts no liability for any errors or omissions.

Cited patent literature

• JP 2000209802 A [0008]

Claims (10)

Stator (1) for an electrical machine (2), in particular within a drive train (3) of a motor vehicle (4), wherein the stator (1) is designed in the shape of a cylindrical ring and has a plurality of stator teeth (5), which in the circumferential direction between adjacent stator teeth (5) each define a stator groove (6) extending in the radial direction and running in the axial direction through the stator (1), with two groove side walls (7) and a groove base (8), into which a current-carrying winding (9) comprising a plurality of conductors (10) is inserted, wherein the conductors (10) emerge from the stator (1) at the end faces (11) of the stator (1), each forming a winding head (12), characterized in that an impregnation ring (13, 23) is in contact with the two end faces (11, 21) of the stator (1), from which a plurality of teeth (14) extend radially inwards, which Stator slots (6) are each enclosed at least in sections on the slot base (8) and the slot side walls (7), wherein the impregnation ring (13, 23) has a channel system (15) by means of which a flowable electrical insulation medium (16) can be fed from the radial direction to the channel system (15) and in the radial direction and in the circumferential direction through one of the teeth (14) of the impregnation ring (13, 23) to the stator slots (6). Stator (1) after Claim 1 , characterized in that the impregnation rings (13, 23) each define one of the channel systems (15) with the corresponding end face (11, 21) of the stator (1). Stator (1) after Claim 1 or 2 , characterized in that the impregnation rings (13,23) each have a circumferential groove (17) on their radially outer surface, from which a radial channel (18) of the channel system (15) extends from the outside to the inside radially through the teeth (14). Stator (1) after Claim 3 , characterized in that starting from the radial channel (18), at least one tangential channel (19) extending in the circumferential direction up to a groove side wall (7) is formed in each case one of the teeth (14) of the impregnation rings (13, 23). Stator (1) after Claim 4 , characterized in that the at least one tangential channel (19) extends from the radial channel (18) in the circumferential direction to two opposite side walls (7). Stator (1) after Claim 4 or 5 , characterized in that a plurality of tangential channels (19) are formed radially spaced in each of the teeth (14) of the impregnation rings (13,23). Stator (1) according to one of the preceding claims, characterized in that the tangential channels (19) and/or the radial channels (18) are designed as grooves. Stator (1) according to one of the preceding claims, characterized in that the first impregnation ring (13) on the first end face (11) of the stator (1) is substantially identical to the second impregnation ring (23) on the second end face (21) of the stator (1). Stator (1) according to one of the preceding claims, characterized in that the winding heads (12) are not wetted by the insulating means (16). Stator (1) according to one of the preceding claims, characterized in that the impregnation ring (13,23) is formed from a plastic.

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