DE102021105812A1 - Stator and method of manufacturing a stator - Google Patents

Abstract

The invention relates to a stator (1) for an electrical machine (2), comprising a stator body (3) with a large number of stator teeth (4) distributed around the circumference and formed between the stator teeth (4) and extending in the axial direction through the stator (1 ) extending stator slots (5), with stator windings (6) arranged radially one above the other being accommodated in the stator slots (7), which are each encased by insulation (8), the insulation (8) being at least partially on a stator slot (7) abuts, the insulation (8) having a lateral surface that is rectangular in cross-section, a first pair of diagonally opposite contact sections (9) and a second pair of diagonally opposite contact sections (10) being formed on the insulation (8), the first pair of contact sections (9) in the circumferential direction and / or in the radial direction from the outer surface (11) of the insulation extend out more than the z wide pair of contact sections (10), so that in the stator slot (7) used assembly state, the first contact sections (9) and the second contact sections (10) on the inside of the stator slot (7).

Description

The present invention relates to a stator for an electrical machine, comprising a stator body with a plurality of circumferentially distributed stator teeth and stator slots formed between the stator teeth and extending in the axial direction through the stator, with stator windings arranged radially one above the other being accommodated in the stator slots are each encased in insulation, with the insulation resting at least in regions on a stator slot. The invention also relates to a method for producing a stator.

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

A detailed description of an electric drive can be found in an article in the ATZ magazine, volume 113, 05/2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrative 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 and coaxially with a bevel gear differential, with a switchable 2-speed planetary gear set being arranged in the power train between the electric motor and the bevel gear differential, which is also is positioned coaxially to the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and allows a good compromise between climbing ability, acceleration and energy consumption due to the switchable 2-speed planetary gear set. Such drive units are also referred to as e-axles or electrically operable drive train.

In addition to purely electrically operated drive trains, hybrid drive trains are also known. Such drive trains of a hybrid vehicle usually include a combination of an internal combustion engine and an electric motor, and allow - for example in urban areas - a purely electric mode of operation with simultaneous sufficient range and availability, especially for cross-country trips. In addition, there is the possibility, in certain operating situations, to be driven simultaneously by the internal combustion engine and the electric motor.

In the development of electric machines intended for e-axles or hybrid modules, there is a continuing need to increase their power densities, so that the cooling of the electric machines required for this is becoming increasingly important. Due to the necessary cooling capacity, hydraulic fluids, such as cooling oils, have prevailed in most concepts for dissipating heat from the thermally stressed areas of an electrical machine.

Jacket cooling and winding overhang cooling are known, for example, from the prior art for cooling electrical machines using hydraulic fluids. While jacket cooling transfers the heat generated on the outer surface of the stator laminations into a cooling circuit, with winding overhang cooling the heat transfer takes place directly on the conductors outside of the stator laminations in the area of the winding overhangs into the fluid.

Further improvements are offered by separate cooling ducts, which can be integrated into the laminated core of the stator (see e.g. EP3157138 A1 ) as well as in the slot in addition to the conductors (see e.g. Markus Schiefer: Indirect winding cooling of highly utilized permanently excited synchronous machines with tooth coil winding, dissertation, Karlsruhe Institute of Technology (KIT), 2017).

As a rule, there is no need for sealing towards the center of the stator in the case of stators, since there is no hydraulic fluid in this area. However, concepts are known in which hydraulic fluid flows directly around the windings in order to increase the power density. Improved cooling with direct contact between the hydraulic fluid and the conductor in the slot is already known in principle from the prior art. For example, describes DE102015013018 A1 a solution for electrical machines with single-tooth winding, where the fluid flows directly around the windings that are wound around the teeth.

Alternating magnetic attraction/repulsion forces act between the current-carrying conductors themselves and the stator slot. A freely (i.e. with play) inserted conductor would be excited to vibrate during operation. On the one hand, this can be associated with annoying noise, on the other hand, repeated impacts on the slot wall of the stator can lead to damage to the insulating coating and thus to short circuits or similar failures. Similar effects can also occur as a result of acceleration when driving (e.g. braking, cornering, potholes).

For efficient cooling of the current-carrying conductors with direct slot cooling, the cooling medium should reach as many sides of the conductor cross-section as possible in order to dissipate the heat generated there. In the case of a package of several adjacent conductors in a slot, it must be ensured in particular that the individual conductors within the package are each spaced apart from one another. In addition, there should be as equal a distance as possible to both flanks of the groove. This requirement can be met if the insulation jacket of the conductors is designed with a profiled cross-section, which forms the cooling channels together with the stator wall. In the case of dry stators, the conductors are fixed in the slot with a casting compound after assembly. This is not a sensible option for the directly cooled stator, as it means that the required cooling channels around the conductors can be closed.

Contrasting with these requirements is the need for the conductor mat in particular to be mountable radially in the stator slots in the case of a wave winding. Both the slot in the stamped and packaged stator and the height and width of the sheathed conductor are subject to tolerances. Both components must be matched so that the widest conductor can still be inserted into the narrowest slot. In the reverse tolerance case, where the narrowest conductor is paired with the widest slot, this inevitably leads to circumferential play and the associated disadvantages described above.

Oversize design and radial pressing of the conductors into the stator is not a sensible option due to the risk of damage.

It is therefore the object of the present invention to provide a stator which at least reduces or completely eliminates the described disadvantages of the prior art. It is also the object of the invention to implement an optimized manufacturing process for a stator.

This object is achieved by a stator for an electrical machine, comprising a stator body with a plurality of circumferentially distributed stator teeth and formed between the stator teeth, extending in the axial direction through the stator stator slots, wherein in the stator slots radially stacked stator windings are accommodated, which which are each encased by an insulation, the insulation at least partially lying against a stator slot, the insulation having a lateral surface with a rectangular cross section, a first pair of diagonally opposite contact sections and a second pair of diagonally opposite contact sections being formed on the insulation are, wherein the first pair of contact sections extend in the circumferential direction and/or in the radial direction more out of the jacket surface of the insulation than the second pair of contact sections, so that in the stator slot set assembly state, the first contact sections and the second contact sections rest on the inside of the stator slot.

The insulation of the stator windings thus serves to space the current-carrying stator windings within the stator slots of directly cooled stators. As a result, a stator with a particularly advantageous geometry of stator slot and stator or insulation cross section can be realized for a directly cooled stator, in which there is no play between the stator windings encased by the insulation and the stator slot wall in any tolerance position.

This can effectively prevent damage and noise during operation of the stator.

Furthermore, due to the geometric design according to the invention, a sufficient cooling channel can be implemented around all sides of a rectangular conductor cross section, so that efficient cooling of the stator winding can be achieved.

By inserting the stator windings, in particular radially, into the stator slot, simple assembly and avoidance of damage during assembly can be achieved.

First, the individual elements of the claimed subject matter of the invention are explained in the order in which they are mentioned in the set of claims, and particularly preferred configurations of the subject matter of the invention are described below.

The stator is designed in particular as a stator for a radial flow machine. The stator of a radial flux machine is usually constructed cylindrically and preferably consists of electrical laminations that are electrically insulated from one another and are constructed in layers and packaged to form laminations. Distributed over the circumference, grooves are let into the electrical sheet running parallel to the rotor shaft and accommodate the stator winding or parts of the stator winding.

The stator can be designed as a stator for an internal rotor or an external rotor. In the case of an internal rotor, the stator teeth extend radially inwards, while in the case of an external rotor they extend radially outwards.

The stator according to the invention is preferably provided for an electric machine, in particular for use within a drive train of a hybrid or all-electric motor vehicle. In particular, the electrical machine is dimensioned in such a way that vehicle speeds of more than 50 km/h, preferably more than 80 km/h and in particular more than 100 km/h can be achieved. The electric motor particularly preferably has an output of more than 30 kW, preferably more than 50 kW and in particular more than 70 kW. Furthermore, it is preferred that the electrical machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, very particularly preferably greater than 12,500 rpm.

Stator teeth are components of the stator body which are designed as circumferentially spaced, tooth-like radially inward or radially outward parts of the stator body and between their free ends and a rotor body an air gap for the magnetic field is formed.

A stator winding is an electrically conductive conductor whose length is significantly greater than its length perpendicular to the length. In principle, the stator winding can have any desired cross-sectional shape. Rectangular cross-sectional shapes are preferred, since they can be used to achieve high packing densities and consequently high power densities. A stator winding made of copper is very particularly preferably formed. According to the invention, a stator winding has insulation. To insulate the stator winding, for example, mica paper, which for mechanical reasons can be reinforced by a glass fabric carrier, can be wound in ribbon form around one or more stator windings, which are impregnated with a hardening resin. In principle, it is also possible to use a hardenable polymer or lacquer layer without mica paper to insulate a stator winding.

According to a preferred embodiment of the invention, it can be advantageous for a coolant to flow through the stator slots, so that the stator can be cooled particularly effectively. The stator slots through which a hydraulic fluid flows during operation are thus sealed radially inwards or outwards towards the rotor by the stator slot sealing means, so that the pressurized hydraulic fluid largely remains completely in the stator space. Furthermore, it can be advantageous for the coolant in the stator slots to have a pressure of 0.1-2 bar.

According to an advantageous embodiment of the invention, it can be provided that the stator windings have a rectangular cross-sectional contour.

According to a further preferred development of the invention, it can also be provided that the insulation in the radial direction between a first contact section and a second contact section in the circumferential direction has a first groove on both sides that is open in the circumferential direction.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the insulation has a second groove open in the radial direction on both sides in the circumferential direction between a first contact section and a second contact section in the radial direction.

1. a) Bereitstellung von Statorwicklungen mit einer Isolierung, die eine im Querschnitt rechteckige Mantelfläche aufweist, wobei ein erstes Paar von sich diagonal gegenüberliegenden Anlageabschnitten sowie ein zweites Paar von sich diagonal gegenüberliegenden Anlageabschnitten an der Isolierung ausgebildet sind, wobei das erste Paar von Anlageabschnitten sich in Umfangsrichtung und/oder in radialer Richtung stärker aus der Mantelfläche der Isolierung herauserstrecken als das zweite Paar von Anlageabschnitten,
2. b) Einsetzen der Statorwicklungen in radialer Richtung in die Statornuten,
3. c) Drehung der Statorwicklungen um ihre jeweilige Axialachse in den Statornuten, so dass die ersten Anlageabschnitte und die zweiten Anlageabschnitte an der Innenseite der Statornut anliegen.

The object of the invention is also achieved by a method for producing a stator for an electrical machine, comprising a stator body with a plurality of stator teeth arranged distributed circumferentially and stator slots formed between the stator teeth and extending through the stator in the axial direction, with radial in the stator slots Stator windings arranged one above the other are accommodated, which are each encased in insulation, the insulation being in contact with a stator slot at least in some areas, comprising the following steps:

1. a) Provision of stator windings with insulation that has a lateral surface that is rectangular in cross section, with a first pair of diagonally opposite contact sections and a second pair of diagonally opposite contact sections being formed on the insulation, with the first pair of contact sections being in the circumferential direction and/or extend more out of the lateral surface of the insulation in the radial direction than the second pair of contact sections,
2. b) inserting the stator windings in the radial direction into the stator slots,
3. c) rotation of the stator windings about their respective axial axis in the stator slots, so that the first contact sections and the second contact sections bear against the inside of the stator slot.

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

• 1 einen Stator mit einer Statornut in einer teilperspektivischen Ansicht,
• 2 eine Statorwicklung mit Isolierung in einer perspektivischen Darstellung und
• 3 in einer Statornut radial gestapelte Statorwicklungen mit Isolierungen in drei verschiedenen Tolleranzsituationen.

Show it:

• 1 a stator with a stator slot in a partial perspective view,
• 2 a stator winding with insulation in a perspective view and
• 3 Stator windings stacked radially in a stator slot with insulation in three different tolerance situations.

the 1 shows a stator 1 for an electrical machine, comprising a stator body 3 with a large number of stator teeth 4 distributed around the circumference and stator slots 5 formed between the stator teeth 4 and extending in the axial direction through the stator 1, with stator windings 6 arranged radially one above the other in the stator slots 7 are included, which are each encased by an insulation 8, and wherein the insulation formed from a plastic 8 at least partially rests on a stator slot 7.

The insulation 8 has a lateral surface that is rectangular in cross section, with a first pair of diagonally opposite contact sections 9 and a second pair of diagonally opposite contact sections 10 being formed on the insulation 8 . The stator windings 6 encased by the insulation 8 also have a rectangular cross-sectional contour. The first pair of contact sections 9 extends further out of the lateral surface 11 of the insulation in the circumferential direction and in the radial direction than the second pair of contact sections 10, so that when installed in the stator slot 7, the first contact sections 9 and the second contact sections 10 abut on the inside of the stator slot 7.

As well as the synopsis of 1 and 2 is easily removable, the insulation 8 in the radial direction between a first contact section 9 and a second contact section 10 in the circumferential direction has a first groove 12 that is open in the circumferential direction on both sides. Also in the circumferential direction between a first contact section 9 and a second contact section 10 in the radial direction, the insulation 8 has a second groove 13 open in the radial direction on both sides, so that a total of four grooves 12,13 are formed on the insulation in the circumferential direction.

1. a) Bereitstellung von Statorwicklungen 6 mit einer Isolierung 8, die eine im Querschnitt rechteckige Mantelfläche aufweist, wobei ein erstes Paar von sich diagonal gegenüberliegenden Anlageabschnitten 9 sowie ein zweites Paar von sich diagonal gegenüberliegenden Anlageabschnitten 10 an der Isolierung 8 ausgebildet sind, wobei das erste Paar von Anlageabschnitten 9 sich in Umfangsrichtung und/oder in radialer Richtung stärker aus der Mantelfläche 11 der Isolierung herauserstrecken als das zweite Paar von Anlageabschnitten 10,
2. b) Einsetzen der Statorwicklungen 6 in radialer Richtung in die Statornuten 7,
3. c) Drehung der Statorwicklungen 6 um ihre jeweilige Axialachse in den Statornuten 7, so dass die ersten Anlageabschnitte 9 und die zweiten Anlageabschnitte 10 an der Innenseite der Statornut 7 anliegen.

Based on 3 a method for producing the stator 1 for an electrical machine is explained, comprising a stator body 3 with a plurality of stator teeth 4 distributed around the circumference and stator slots 5 formed between the stator teeth 4 and extending through the stator 1 in the axial direction, wherein in the stator slots 7 Stator windings 6 arranged radially one above the other are accommodated, which are each encased in insulation 8, the insulation 8 resting at least in regions on a stator slot 7, comprising the following steps:

1. a) Provision of stator windings 6 with insulation 8, which has a lateral surface that is rectangular in cross section, with a first pair of diagonally opposite contact sections 9 and a second pair of diagonally opposite contact sections 10 being formed on the insulation 8, with the first pair of contact sections 9 extend more out of the lateral surface 11 of the insulation in the circumferential direction and/or in the radial direction than the second pair of contact sections 10,
2. b) inserting the stator windings 6 in the radial direction into the stator slots 7,
3. c) rotation of the stator windings 6 about their respective axial axis in the stator slots 7 so that the first contact sections 9 and the second contact sections 10 bear against the inside of the stator slot 7 .

The torsional flexibility of the stator windings 6 encased by the insulation 8 in the axial direction can thus be used to twist them about their longitudinal axis when they are inserted into the stator slot 7 . With the twisting of the rectangular basic cross-section, its width increases relative to the flanks or inner walls of the stator slot 7 depending on the twisting angle, which is shown in illustrations a and c in FIG 3 is shown, in which the stator windings 6 are fixed in the stator slot 7 in a correspondingly twisted manner.

• In der mittleren Darstellung b der 3 ist der Nominalfall der in der Statornut 7 angeordneten Statorwicklungen 6 gezeigt. In einem ersten Toleranzfall, der in der Darstellung a der 3 gezeigt ist, liegen die breiteste Statorwicklung 6 mit der schmalster Statornut 7 vor. In diesem Fall liegt die Hochachse der rechteckigen Statorwicklung 6 parallel zur Statornut-Mittelachse. Die Breiten sind so abgestimmt, dass die Montage ohne Überschneidung möglich ist. Die Statorwicklung 6 ist ohne Spiel in Umfangsrichtung in der Statornut 7 zentriert.

By means of the insulation 8, the stator slot 7 and the stator windings 6 can be matched to one another as follows:

• In the middle representation b the 3 the nominal case of the stator windings 6 arranged in the stator slot 7 is shown. In a first tolerance case, which is shown in the representation a 3 is shown, the widest stator winding 6 with the narrowest stator slot 7 is present. In this case, the vertical axis of the rectangular stator winding 6 is parallel to the central axis of the stator slot. The widths are coordinated in such a way that assembly is possible without overlapping. The stator winding 6 is centered in the stator slot 7 without play in the circumferential direction.

In a second tolerance case, which is shown in the representation c of 3 is shown, the narrowest stator windings 6 with the widest stator slot 7 are present. An assembly of the stator windings 6 in the stator slot 7 is easily possible due to the existing play. After insertion into the stator slot 7, each of the stator windings 6 in the Sta tornut 7 twisted about its longitudinal axis until its flanks rest on both sides of the outer surface of the stator slot 7. Thus, the stator windings 6 are also centered in the circumferential direction in the stator slot 7 without play in the outlined tolerance case.

In order to enable the torsional movement for the second tolerance case, the conductor cross-section must be designed asymmetrically, as is the case, for example, in 2 shown and described accordingly.

The design of the insulation has contact sections 9,10 at the four corners of the rectangular basic cross section of the wave winding 6, which form the cooling channels for direct slot cooling together with the lateral surface of the stator slots 7, which can be seen well from the representations of 1 and 3 reveals. The system sections 9,10 are designed in the same way at two mutually diagonal corners, but differ from the system sections 9,10 in the length and width directions of the rectangular cross section.

Both types of plant sections 9.10 have a shoulder characteristic in the radial direction and in the circumferential direction. However, their distance from the rectangular base body of the stator winding 6 differs; two paragraphs with a small and two paragraphs with a large distance are used.

When the first stator winding 6 is inserted into the stator slot 7 , the high/wide shoulder/contact section 9 on the top side of the conductor first comes into contact with the top side of the stator slot 7 . Depending on the tolerance position of the stator slot 7 and the stator winding 6, this stator winding 6 is either already centered in the circumferential direction or has play in the circumferential direction. In the latter case, it can pivot around the first contact point by radial pressure (e.g. by an assembly tool) until the contact sections 9,10 come into contact with the flank of the stator slot 7 in the circumferential direction and thus center the stator winding 6 in the circumferential direction.

The same behavior occurs for the other stator windings 6, so that all the stator windings 6 assume a position with play-free centering in the circumferential direction.

Depending on the tolerance level and the torsion angle of the individual stator windings, there is a variation in the package height in the radial direction. When designing the groove depth, it should be adjusted so that there is no radial play in critical tolerance cases. The radial overhang in the opposite tolerance case can then be compensated by the radial flexibility of the conductor pack when inserting a slot sealing element by compressing the conductor pack.

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

Reference List

1

stator

3

stator body

4

stator teeth

6

stator windings

7

stator slots

8th

insulation

9

plant sections

10

plant sections

11

lateral surface

12

groove

13

groove

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 3157138 A1 [0007]
• DE 102015013018 A1 [0008]

Claims (5)

Stator (1) for an electrical machine, comprising a stator body (3) with a large number of stator teeth (4) distributed around the circumference and stator slots (7) formed between the stator teeth (4) and extending through the stator (1) in the axial direction, Stator windings (6) arranged radially one above the other are accommodated in the stator slots (7), which are each encased in insulation (8), the insulation (8) resting at least in regions on a stator slot (7), characterized in that the Insulation (8) has a lateral surface that is rectangular in cross-section, a first pair of diagonally opposite contact sections (9) and a second pair of diagonally opposite contact sections (10) being formed on the insulation (8), the first pair of contact sections (9) extend more out of the lateral surface (11) of the insulation in the circumferential direction and/or in the radial direction than the second pair r of contact sections (10), so that when installed in the stator slot (7), the first contact sections (9) and the second contact sections (10) rest against the inside of the stator slot (7). Stator (1) after claim 1 , characterized in that the stator windings (6) have a rectangular cross-sectional contour. Stator (1) after claim 1 or 2 , characterized in that the insulation (8) in the radial direction between a first contact section (9) and a second contact section (10) in the circumferential direction on both sides in each case have a circumferentially open first groove (12). Stator (1) according to one of the preceding claims, characterized in that the insulation (8) has a second groove (13) open in the radial direction on both sides in the circumferential direction between a first contact section (9) and a second contact section (10) in the radial direction . Method for producing a stator (1) for an electrical machine (2), comprising a stator body (3) with a plurality of stator teeth (4) distributed around the circumference and formed between the stator teeth (4) and extending in the axial direction through the stator (1 ) extending stator slots (5), with stator windings (6) arranged radially one above the other being accommodated in the stator slots (7), which are each encased by insulation (8), the insulation (8) being at least partially on a stator slot (7) is present, comprising the following steps: a) Provision of stator windings (6) with insulation (8), which has a lateral surface with a rectangular cross section, with a first pair of diagonally opposite contact sections (9) and a second pair of diagonally opposite contact sections (10) on the insulation (8) are formed, with the first pair of contact sections (9) extending out more in the circumferential direction and/or in the radial direction from the lateral surface (11) of the insulation than the second pair of contact sections (10), b) inserting the stator windings (6) in the radial direction into the stator slots (7), c) rotation of the stator windings (6) about their respective axial axis in the stator slots (7) so that the first contact sections (9) and the second contact sections (10) rest against the inside of the stator slot (7).

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