WO2022073536A1

WO2022073536A1 - Electrical machine

Info

Publication number: WO2022073536A1
Application number: PCT/DE2021/100733
Authority: WO
Inventors: Alexander Keune; Patrick Gramann; Jonas Kniel; Michael Heilmann
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2020-10-07
Filing date: 2021-09-07
Publication date: 2022-04-14
Also published as: DE102020126184A1; DE102020126184B4

Abstract

The invention relates to an electrical machine (1), in particular for a hybrid or fully electric powertrain (2) of a motor vehicle (3), comprising a stator (5) which is arranged in a rotationally fixed manner relative to a machine housing (4), and a rotor (6) which is rotatable relative to the stator (5), the stator (5) having a stator body (7) formed in particular from laminated cores, and the stator body (7) having a plurality of stator grooves (8) which extend through the stator body (7) in the axial direction and are radially open at the edges, for receiving at least one stator winding (9) each, wherein a cooling medium (13) can flow through the stator grooves (8), wherein the stator winding (9) has an in particular rectangular cross-section, and wherein at least one spacer element (10), which has a U-shaped or C-shaped cross-section and fits around the cross-sectional contour of the stator winding (9) at least in some sections, is situated on the stator winding (9).

Description

electrical machine

The present invention relates to an electric machine, in particular for a hybrid or all-electric drive train of a motor vehicle, comprising a stator arranged in a rotationally fixed manner to a machine housing and a rotor which can rotate relative to the stator, the stator having a stator body formed in particular from laminated cores, and the stator body having a plurality of radially open-edged stator slots extending in the axial direction through the stator body for receiving at least one stator winding, wherein a cooling medium can flow through the stator slots.

During operation, electrical machines generate power loss in the form of heat. Active cooling is required when cooling via free convection, thermal conduction to neighboring components or thermal radiation into the environment is no longer sufficient. Such cooling can be effected by a moving fluid which, in the case of an internal rotor, is guided, for example, through a cooling jacket lying around the stator.

With direct cooling, it is possible to dissipate the heat generated at the point of origin. As a result, the general temperature level in electrical machines can be lowered and a more homogeneous temperature distribution can be ensured. This also makes it possible, for example, to use less expensive and lighter materials.

Further improvements in cooling are offered, for example, by separate cooling ducts, which are introduced both into the laminated core of the stator and into the slot in addition to the conductors.

It is the object of the invention to provide an electrical machine which has improved active cooling by a cooling medium. This object is achieved by an electric machine, in particular for a hybrid or all-electric drive train of a motor vehicle, comprising a stator arranged in a rotationally fixed manner with respect to a machine housing and a rotor which can be rotated relative to the stator, the stator having a stator body formed in particular from laminated cores, and the stator body having a has a plurality of stator slots, which extend in the axial direction through the stator body and are radially open at the edges, each for receiving at least one stator winding, with a cooling medium being able to flow through the stator slots, with the stator winding having an in particular rectangular cross section, with at least one on the stator winding having a U-shaped cross section or a C-shaped spacer element is arranged which at least partially encompasses the cross-sectional contour of the stator winding.

As a result, the stator windings located in a stator slot can be spaced apart from one another and from the stator slot in a defined and at the same time flexible manner by arranging spacer elements on one or more stator windings. As a result, cooling channels through which the cooling medium can flow are defined between the stator windings and between the stator windings and the stator slots. The spacer elements can be produced inexpensively and can be arranged flexibly on the stator windings, so that various flow channel configurations can be formed very easily, through which active cooling of the stator winding and/or the stator slots can be carried out in a very controlled manner and individually tailored to an electrical machine by means of a cooling medium can be realized.

A spacer element or the spacer elements therefore ensure that a cooling medium, for example hydraulic oil, can flow through the stator slots under defined and optimized flow conditions, and a defined positioning or holding of the stator winding in the stator slots of the stator can be implemented. The spacer elements allow defined cooling channels to be formed, which in particular have a low pressure loss. Furthermore, high thermal Realize transition rates through the forced convection of the cooling medium between the stator slots and the cooling medium and between the stator winding and the cooling medium.

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.

Electrical machines within the meaning of this invention are used to convert electrical energy into mechanical energy and/or vice versa, and generally include a stationary part referred to as a stator, stand or armature and a part referred to as a rotor or runner and arranged movably relative to the stationary part.

In the case of electrical machines designed as rotary machines, a distinction is made in particular between radial flux machines and axial flux machines. A radial flux machine is characterized in that the magnetic field lines extend in the radial direction in the air gap formed between rotor and stator, while in the case of an axial flux machine the magnetic field lines extend in the axial direction in the air gap formed between rotor and stator. In connection with this invention, the electrical machine is preferably designed as a radial flow machine.

The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics. The motor housing can also be part of a cooling system for the electric machine and can be designed in such a way that cooling fluid can be supplied to the electric machine via the motor housing and/or the heat can be dissipated to the outside via the housing surfaces. In addition, the motor housing protects the electrical machine and any electronics that may be present from external influences. A motor housing can be formed in particular from a metallic material. Advantageously, the motor housing can be formed from a cast metal material, such as gray cast iron or cast steel. In principle, it is also conceivable to form the motor housing entirely or partially from a plastic.

The stator of a radial flow machine is usually constructed cylindrically and generally consists of electrical laminations that are electrically insulated from one another and are constructed in layers and packaged to form laminated cores. This structure keeps the eddy currents in the stator caused by the stator field low. Distributed over the circumference, stator slots or peripherally closed recesses are let into the electrical steel sheet running parallel to the rotor shaft and accommodate the stator winding or parts of the stator winding. Depending on the construction towards the surface, the slots can be closed with locking elements such as locking wedges or covers or the like in order to prevent the stator winding from being detached.

A laminated core or stator laminated core is understood to be a plurality of laminated individual laminations, which are generally produced from electrical steel sheet and are stacked and packaged one on top of the other to form a stack, the so-called laminated core. The individual laminations can then remain held together in the laminated core by gluing, welding or wedging or screwing or the like.

The stator within the meaning of this invention comprises a stator body which can be constructed in one piece or in segments. A one-piece stator body is characterized in that the entire stator body is formed in one piece, viewed circumferentially. The stator body is generally formed from a large number of stacked, laminated electrical laminations, with each of the electrical laminations being closed to form a circular ring.

A segmented stator body is characterized in that it is made up of individual stator segment parts. The stator body can be made up of individual stator teeth or stator tooth groups, with each individual stator tooth or each individual stator tooth group may be formed from a plurality of stacked laminated electrical laminations, each of the electrical laminations being formed as a stator segment lamination part.

A stator winding is an electrically conductive conductor whose length is significantly greater than its diameter. 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. A stator winding preferably 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 lacquer layer without mica paper in order to insulate a stator winding.

According to an advantageous embodiment of the invention, it can be provided that a plurality of individual stator windings run parallel at least in sections in the direction of their longitudinal extension and/or in a common winding plane. The advantage of this configuration is that it allows a high packing density of the stator windings to be achieved, resulting in an improved power density. On the other hand, a simple and defined arrangement of the stator windings relative to one another can be achieved in this way.

According to a further preferred further development of the invention, it can also be provided that a stator winding has a plurality of spacer elements spaced apart from one another along its longitudinal extent. It can hereby be achieved that cooling channels for the cooling medium can be configured very specifically over the longitudinal extent of a stator winding. Furthermore, according to a likewise advantageous embodiment of the invention, provision can be made for parallel stator windings to have groups of spacer elements offset from one another in the longitudinal extension, as a result of which the coolant flow can be controlled even more specifically, so that the heat dissipation can be designed even more efficiently with regard to a given stator construction can.

According to a further particularly preferred embodiment of the invention, it can be provided that the spacer element encompasses at least two stator windings that are in contact with one another. This can be particularly advantageous when there are at least two winding mats that are inserted into the stator slot, in which case the spacer elements can also connect the layers of these winding mats to one another.

Furthermore, the invention can also be further developed such that the spacer elements are of essentially identical design, as a result of which the manufacturing costs of the electrical machine can be kept low by avoiding component complexity.

In a likewise preferred embodiment variant of the invention, it can also be provided that the spacer element has flanks that converge conically, as a result of which the spacer element can exert a certain spring-elastic clamping force on the spacer element and can thus be fixed to a stator winding.

It can also be advantageous to further develop the invention such that the spacer element has at least one flank that deviates from the rectangular shape, in particular a triangular flank. The advantage that can be realized in this way is that the flow resistance of the cooling medium at the flank can be set very precisely, which in turn allows a further improvement in the modeling of the coolant convection. The flank, which is in the flow direction of the cooling medium, can have a shape that results in an elevation of the flow resistance compared to a rectangular flank or to a reduction in the flow resistance compared to a rectangular flank. By increasing the flow resistance, the volume flow of a cooling medium can be reduced locally at the stator winding compared to a rectangular flank, or can be increased locally if the flow resistance is reduced.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that the spacer element is formed from a particularly electrically insulating plastic, in particular by means of an injection molding or extrusion process, which allows the spacer element to be produced particularly cost-effectively.

Finally, the invention can also be implemented in an advantageous manner such that the spacer element is arranged in a materially bonded manner, in particular by means of an adhesive, on the stator winding, so that the spacer element is captively fixed to the stator winding.

Furthermore, it is fundamentally also conceivable that the spacer element is an adhesive strip with an adhesive strip thickness of between 0.1-1.0 mm, preferably 0.25-0.5 mm, as a result of which the spacer element can be formed in a particularly cost-effective manner.

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

FIG. 1 shows a schematic cross-sectional view through an electrical machine according to the prior art,

FIG. 2 shows a schematic cross-sectional view through a first embodiment of an electrical machine according to the invention,

FIG. 3 shows a schematic cross-sectional view through a second embodiment of an electrical machine according to the invention,

FIG. 4 shows a schematic perspective representation of stator windings in a stator slot,

FIG. 5 shows a schematic perspective detailed illustration of stator windings with spacer elements,

FIG. 6 shows a schematic cross-sectional view through an embodiment of a spacer element, and

Figure 7 is a schematic sectional view of various stator windings in spacer elements, and

FIG. 8 shows a schematic block diagram of a motor vehicle with an electric machine.

FIG. 1 shows an electric machine 1, in particular for a hybrid (upper figure, FIG. 8) or all-electric drive train 2 (lower figure, FIG. 8) of a motor vehicle 3, as shown in FIG. 8 by way of example.

Such electrical machines 1 are basically known from the prior art. They include a rotary test arranged on a machine housing 4 Stator 5 and a rotor 6 that is rotatable relative to the stator 5. The stator 5 has a stator body 7 formed from stacks of laminations, which has a plurality of stator slots 8, which extend in the axial direction through the stator body 7 and are radially open at the edges, for receiving at least one stator winding 9 each. In the exemplary embodiment shown in FIG. 1, there are a total of three stator windings 9 in the circumferential direction and three stator windings in the radial direction in a stator slot

8 arranged, wherein the stator windings 9 have a substantially identical rectangular cross-sectional contour.

Based on this prior art, various embodiments are explained in more detail below.

Figure 2 shows a first embodiment of the invention, in which the stator winding

9 has a rectangular cross section and at least one spacer element 10 which is U-shaped in cross section and at least partially encompasses the cross-sectional contour of the stator winding 9 is arranged on the stator winding 9 . As a result, channels are formed between the stator winding 9 and the stator slot 8 so that a cooling medium 13 can flow through the stator slots 8 . It can be seen that, depending on the arrangement of the U-shaped spacer element 10, one or more channels run on a radially running side wall of a stator slot 8 or on a head wall of a stator slot 8 running in the circumferential direction. The spacer elements 10 are arranged offset to one another over the axial longitudinal extension of the stator windings 9, which can be seen by looking at the opposing stator slots 8 or stator windings 9 together. In the embodiments shown in FIG. 2, the spacer elements 10 are in direct contact with the walls of the stator slots 8 . The spacer elements 10 can thus also secure or fix the stator windings 9 in a stator slot 8, for example by means of a corresponding press fit.

Of course, a plurality of stator windings 9 can also be encompassed and held by a spacer element 10 in a stator slot 8, as is shown by way of example in FIG. The electrical machine 1 can also be further developed in such a way that several layers of stator windings 9 are arranged parallel to one another in a stator slot 8 . This is shown as an example in FIG. 4 and is explained in more detail below. It can be seen from FIG. 4 that a plurality of individual stator windings 9 run parallel in the direction of their longitudinal extent and in a common winding plane 11 . In the embodiment shown in FIG. 4, two radial winding planes 11 run parallel to one another. For better understanding, these are shown spaced apart from each other in the stator slot 8, but in an actual embodiment of the invention, these two winding planes 11 are in contact with one another.

In FIG. 4, a stator winding 9 has a plurality of spacer elements 10 spaced apart from one another along its longitudinal extent, with stator windings 9 running parallel having groups of spacer elements 10 arranged offset to one another in the longitudinal extent. This creates a channel-like structure between the stator windings 9 and the stator slot 8 through which the cooling medium 13 can flow. 4 shows how different channel-like structures can be formed by a different arrangement of the spacer elements 10 on the stator windings 9 and how the cooling system can be easily and flexibly adapted to an existing electrical machine 1. FIG. 4 also shows that the spacer elements 10 in the illustrated embodiment each encompass at least two adjacent stator windings 9 and are of essentially identical design.

Of course, it is also possible to design the spacer elements 10 to be different from one another or to form groups of spacer elements 10 that are different from one another and to arrange them on the stator windings 9, which is shown by way of example in FIG.

The front spacer element 10 in the figure is U-shaped in cross section and has three rectangular peripheral sections. This is the illustration behind- The spacer element 10, on the other hand, has a flank 12 that deviates from the rectangular shape, which flank 12 is designed as a triangular flank 12 in the exemplary embodiment shown. The arrow in FIG. 5 indicates the flow direction of the cooling medium 13 along the stator windings 9, which runs essentially in the axial direction when it is inserted in the stator slot 8.

This representation in FIG. 5 clearly shows how the flow resistance can be configured by the geometric shape of the spacer elements 10 . In the direction of flow of the cooling medium 13 shown, the front spacer element 10 causes a greater flow resistance in the flow situation shown due to the rectangular flanks 12 than the triangular flanks 12 of the rear spacer element 10. By specifically arranging spacer elements 10 that are differently configured, in particular with regard to the flow surface The cooling capacity of the cooling medium 13 on the stator windings 9 can thus be controlled and adjusted in a very targeted and defined manner.

Figure 6 shows a cross-sectional view of a spacer element 10 known from Figure 5. This representation clearly shows that the spacer element 10 has flanks 12 conically converging towards one another, as a result of which a certain spring-elastic clamping force of the flanks 12 is applied to the stator winding 9 when it is placed on the latter acts and the spacer element 10 is fixed to the stator winding 9 . Alternatively or additionally, the spacer element 10 can be arranged on the stator winding 9 in a materially bonded manner, in particular by means of an adhesive.

The spacer element 10 is formed from an electrically insulating plastic, in particular by means of an injection molding or extrusion process. However, the spacer element 10 can also be designed as an adhesive strip with an adhesive strip thickness of between 0.1-1.0 mm, preferably 0.25-0.5 mm.

FIG. 7 shows further possible embodiments of the spacer element 10 and the stator winding 9. The stator windings 9 in illustration a have a Fl-shaped cross section and are surrounded by the U-shaped spacer element 10. In the embodiment shown in figure b, the stator windings 9 have a round or elliptical cross-sectional profile. In this embodiment, the spacer element 10 has a C-shaped profile, so that the stator windings 9 are arranged captively in the spacer element.

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 features of the same type, without specifying a ranking.

Reference character list

1 machine

2 power train 3 motor vehicle

4 machine housing

5 stator

6 rotors

7 stator body 8 stator slots

9 stator winding

10 spacer

11 winding level

12 flanks 13 cooling medium

Claims

Claims Electrical machine (1), in particular for a hybrid or fully electric drive train (2) of a motor vehicle (3), comprising a stator (5) arranged in a rotationally fixed manner to a machine housing (4) and a rotor (6) rotatable relative to the stator (5). , wherein the stator (5) has a stator body (7) formed in particular from stacks of laminations, and the stator body (7) has a plurality of stator slots (8) which extend in the axial direction through the stator body (7) and are radially open at the edges for receiving at least one in each case Stator winding (9), wherein a cooling medium (13) can flow through the stator slots (8), characterized in that the stator winding (9) has an in particular rectangular cross section, with at least one U-shaped cross section or - The C-shaped, the cross-sectional contour of the stator winding (9) is arranged at least partially encompassing spacer element (10). Electrical machine (1) according to Claim 1, characterized in that a plurality of individual stator windings (9) run parallel at least in sections in the direction of their longitudinal extension and/or in a common winding plane (11). Electrical machine (1) according to one of the preceding claims, characterized in that a stator winding (9) has a plurality of mutually spaced spacer elements (10) along its longitudinal extent. Electrical machine (1) according to one of the preceding claims, characterized in that parallel running stator windings (9) offset to one another in the longitudinal extent arranged groups of spacer elements (10). Electrical machine (1) according to one of the preceding claims, characterized in that the spacer element (10) encompasses at least two adjacent stator windings (9). Electrical machine (1) according to any one of the preceding claims, characterized in that the spacer elements (10) are substantially identical. Electrical machine (1) according to any one of the preceding claims, characterized in that the spacer element (10) conically converging flanks (12). Electrical machine (1) according to one of the preceding claims, characterized in that the spacer element (10) has at least one flank (12) deviating from the rectangular shape, in particular a triangular flank (12). Electrical machine (1) according to one of the preceding claims, characterized in that the spacer element (10) is formed from a plastic which in particular has an electrically insulating effect, in particular by means of an injection molding or extrusion process. Electrical machine (1) according to one of the preceding claims , characterized in that the spacer element (10) is arranged cohesively, in particular by means of an adhesive, on the stator winding (9). - 16 - Electrical machine (1), according to any one of the preceding claims, characterized in that the spacer element (10) is an adhesive strip with an adhesive strip thickness between 0.1-1 .0 mm, preferably 0.25-0.5 mm.