WO2023006653A1

WO2023006653A1 - Stator-housing assembly for an electric machine, having improved welding joints

Info

Publication number: WO2023006653A1
Application number: PCT/EP2022/070771
Authority: WO
Inventors: Nico Wolf; Thomas DÖRMER; Christine Fritsch
Original assignee: Valeo Eautomotive Germany Gmbh
Priority date: 2021-07-30
Filing date: 2022-07-25
Publication date: 2023-02-02
Also published as: DE102021208273A1

Abstract

Disclosed is a stator-housing assembly (12a, 12b) for an electric machine (1, 1a), said assembly comprising a laminated stator core (7a, 7b) and a stator housing (11a, 11b) that is welded to the laminated stator core (7a, 7b) at multiple welding points (16). The welding joints are created using a refill friction stir spot welding process. Also disclosed is an electric machine (1, 1a) comprising a stator-housing assembly (12a, 12b) of said kind and a vehicle (21) having an electric machine (1, 1a) of said kind.

Description

Electric Machine Stator Case Assembly With Improved Welding TECHNICAL FIELD

The invention relates to a stator-housing arrangement for an electrical machine, a method for producing such a stator-housing arrangement, an electrical machine with such a stator-housing arrangement, and a vehicle with such an electrical machine.

STATE OF THE ART

Electric machines are increasingly being used in electrically powered vehicles and hybrid vehicles, primarily as electric motors for driving a wheel or an axle of such a vehicle.

Such an electric motor is usually mechanically coupled to a gear for speed adjustment. In addition, the electric motor is usually electrically coupled to an inverter, which generates an AC voltage for the operation of the electric motor, for example a polyphase AC voltage, from a DC voltage supplied by a battery.

It is also possible to operate an electric machine as a generator to recuperate kinetic energy from a vehicle. For this purpose, the

Kinetic energy is first converted into electrical energy and then into chemical energy from a vehicle battery.

In addition to a rotor and a stator, relative to which the rotor can rotate, an electrical machine can be equipped with a stator housing in which the rotor and the stator are accommodated. The stator and the stator housing are connected to one another in a torsionally rigid manner in order to be able to transmit the forces or torques occurring in the stator during operation of the electrical machine to the stator housing. The stator is often welded to the stator housing for this purpose. For example, the friction stir spot welding process can be used for this purpose.

A rotating tool is pressed onto the stator housing, causing the stator housing and the stator core to be melted locally.

The rotation also results in a mixing of the materials of the stator housing and the laminated core of the stator. In the further course, the tool is lifted from the welding point, whereupon the melt solidifies again. Depending on the process, there are more or less large indentations at the welding point. The problem here is that the remaining material thickness of the stator housing can be very small, at least locally. Blowholes cannot be completely ruled out either. The result of this is that a heat transfer medium provided for cooling the electrical machine, which flows past the welding point, can under certain circumstances get inside the electrical machine and damage it.

In order to avoid this risk, the use of the friction stir spot welding process in fluid-cooled electrical machines is usually avoided. This is very disadvantageous insofar as other welding methods for welding the various materials from which the stator housing and the laminated core are usually made are unsuitable or only slightly suitable.

Accordingly, it is often necessary to resort to other, more expensive measures for the torsionally rigid connection of the stator housing and the laminated core of the stator, for example the provision of a press fit between the stator housing and the laminated core of the stator. DISCLOSURE OF THE INVENTION

It is therefore an object of the invention to provide an improved stator-housing arrangement, an improved method for producing such a stator-housing arrangement, an improved electrical machine with such a stator-housing arrangement and an improved vehicle with such an electrical machine to specify. In particular, a possibility for the process-reliable, fluid-tight welding of the stator housing and the laminated core of an electrical machine is to be specified.

The object of the invention is achieved by a stator-housing arrangement for an electrical machine, which comprises a stator core and a stator housing, the stator core and the stator housing being welded to one another at a number of weld points using the fill-up stir friction spot welding method.

In addition, the object of the invention is achieved by a method for producing a stator housing arrangement for an electrical machine, which has the following steps:

Providing a laminated stator core and a stator housing, sliding the laminated stator core into the stator housing and permanently connecting the laminated stator core to the stator housing, with - the permanent connection at several weld points using the filling

Friction stir spot welding process is performed.

Furthermore, the object of the invention is achieved by an electrical machine, comprising - a first bearing plate and a second bearing plate, a stator-housing arrangement of the above-mentioned type arranged between the two end shields, as well as stator windings arranged on the stator laminated core and a rotor arranged in the stator with a rotor shaft rotatably mounted in the two end shields.

Finally, the object is also achieved by a vehicle with a drive train that has an electric machine of the type mentioned above, which is provided for driving the vehicle.

The refill friction stir spot welding process is a special variant of the friction welding process in which a multi-part tool is used that has at least one outer tool part and one inner tool part that can be moved axially. During the welding process, the rotating tool is pressed onto the stator housing, causing the stator housing and the stator core to melt locally.

The rotational movement of the tool also results, in particular, in a mixing of the materials of the laminated core of the stator and of the stator housing. In addition, the melt is forced into a cavity within the male mold that is formed when the male mold is in a retracted position.

In the further course, the tool is lifted from the weld, the inner tool part relative to the outer tool part

Weld point is shifted. This pushes the melt in the cavity back into the weld. In contrast to the normal friction stir spot welding process, there is no dent at the welding point, but the welding point is largely flat.

It is particularly advantageous that the welding point can be designed to be liquid-tight and gas-tight in a process-reliable manner, and thus later Operation of the electric machine penetrate no cooling fluid through local defects in the interior of the electric machine and damage it. Furthermore, it is advantageous that the flow conditions in the cooling channel are not affected or are only slightly affected by the planar weld.

Due to the rotational movement in the fill-up stir friction spot welding process, different materials in particular can be welded together well that cannot be welded or can only be welded with difficulty using other welding processes. For example, the stator laminations of the stator laminations can be made of electrical steel and the stator housing can be made of aluminum.

Instead of several welds, it is also possible for the stator core and the stator housing to be welded together at just one weld using the fill-up friction stir spot welding process.

Further advantageous refinements and developments of the invention result from the dependent claims and from the description in conjunction with the figures. The electrical machine can have an outer casing which radially surrounds the stator housing, with a cooling duct being arranged between the stator housing and the outer casing. The welds are advantageously arranged in this cooling channel. As a result, the welding tool can be easily placed on the stator housing.

In particular, the stator housing can have ribs, with the welds being advantageously arranged between the ribs. In this way, the welding tool can also be easily placed on the stator housing. Ribs can be provided both in electrical machines with an outer casing and in electrical machines without an outer casing. The latter are cooled by the ambient air. It is favorable if the welds are evenly distributed over a circumference and/or a length of the laminated core of the stator. As a result, the forces and torques occurring during operation of the electrical machine can be transmitted well from the stator to the stator housing without excessive local voltage peaks occurring.

It is also favorable if the laminated core of the stator is placed on a support prior to welding, which supports the laminated core of the stator on the inside in a rotor bore of the laminated core of the stator. Because of the high force exerted by the tool on the stator-housing assembly, it can be expedient to place the laminated stator core on a support prior to welding, which protects the laminated stator core from deformation during the welding process. The above configurations and developments of the invention can be combined in any desired manner.

BRIEF DESCRIPTION OF THE FIGURES Exemplary embodiments of the invention are shown in the accompanying schematic figures. Show it:

1 shows an exemplary electric machine, illustrated in half section, with a number of welding points between the laminated stator core and the stator housing;

2 shows an illustration of the processes involved in making a weld;

3 shows a further example of a stator-housing arrangement in an oblique view;

FIG. 4 shows the stator-housing arrangement from FIG. 3 in half section and Figure 5 shows a motor vehicle with an electric machine of the type proposed. DETAILED DESCRIPTION OF THE INVENTION

As an introduction, it is stated that the same parts in the different embodiments are provided with the same reference numbers or the same component designations, optionally with different indices. The disclosure contained in the description of a component can be transferred analogously to another component with the same reference number or the same component designation. The position information selected in the description, such as "top", "bottom", "back", "front", "side" and so on, refers to the figure directly described and shown and, if the position changes, to the new one transfer location.

Fig. 1 shows a half section through a schematically illustrated electrical machine 1a. The electrical machine 1a comprises a shaft 2 with a rotor 3 seated thereon, the shaft 2 being mounted such that it can rotate about an axis of rotation A relative to a stator 5 with the aid of (roller) bearings 4a, 4b. The rotor 3 has in particular rotor laminations, which are not shown individually, arranged one behind the other, as well as rotor magnets or a rotor winding. The stator 5 has a plurality of stator laminations 6 arranged one behind the other, which together form a laminated stator core 7a, and a stator winding 8 arranged on the laminated stator core 7a.

In the example shown in FIG. 1, the first bearing 4a sits in a first (front) end shield 9 and the second bearing 4b in a second (rear) end shield 10. The stator housing 11a is arranged between the first end shield 9 and the second end shield 10 , which the stator 5 surrounds. The stator housing 11a and the stator core 7a are part of a stator-housing arrangement 12a or form this.

In addition, the electrical machine 1a has an optional outer casing 13 which radially surrounds the stator housing 11a. Specifically, the outer jacket 13 is seated on optional ribs 14 of the stator housing 11a, as a result of which a cooling channel 15 is formed between the stator housing 11a and the outer jacket 13. The stator laminated core 7a and the stator housing 11a are welded to one another at a number of weld points 16 using the fill-up stir friction spot welding process. Specifically, the welds 16 are arranged between the ribs 14 or in the cooling channel 15 . In principle, however, the weld points 16 could also be arranged at a different location, in particular if ribs 14 or a cooling channel 15 are missing.

2 now shows schematically the production of the stator-housing arrangement 12a, specifically the welding of the stator housing 11a to the stator core 7a. The welding takes place with a rotating tool 17 which has an outer tool part 18 and an axially displaceable inner tool part 19 . The inner tool part 19 is shown in FIG. 2 in a retracted position, as a result of which a cavity is formed between the outer tool part 18 and the inner tool part 19 . During the welding process, the rotating tool is pressed onto the stator housing 11a, causing it to melt locally. In the further course, the laminated core 7a of the stator is also melted locally. The rotational movement also results in particular in a mixing of the materials of the laminated stator core 7a and the stator housing 11a. In addition, the melt is pressed into the cavity inside the outer tool part 18 . In the further course, the tool 17 is withdrawn (that is to say moved upwards in FIG. 2), with the inner tool part 19 being displaced downwards relative to the outer tool part 18. This forces the melt in the cavity back down into weld 16 . In contrast to the normal friction stir spot welding process, there is no dent at the weld point 16, rather the weld point 16 is flat. It is particularly advantageous that the weld point 16 can be made liquid-tight and gas-tight in a process-reliable manner, so that during later operation of the electrical machine 1a no cooling fluid from the cooling channel 15 penetrates through the gaps arranged between the stator laminations 6 into the interior of the electrical machine 1a and damages it can. Furthermore, it is advantageous that the flow of the cooling fluid in the cooling channel 15 is not impaired by the welding point 16 . The method for producing the stator-housing arrangement 12a for the electrical machine 1a thus comprises the following steps:

Providing the laminated stator core 7a and the stator housing 11a, pushing the laminated stator core 7a into the stator housing 11a and permanently connecting the laminated stator core 7a to the stator housing 11a at a plurality of weld points 16 using the fill-up friction stir spot welding process.

Due to the high force that is exerted with the tool 17 on the stator-housing arrangement 12a, it may be expedient to place the stator core 7a on a support 20 before welding, which the stator core 7a on the inside in a rotor bore of the stator core 7a supported, as shown in FIG. This prevents the laminated core 7a of the stator from being deformed during the welding process.

Due to the rotational movement in the fill-up stir friction spot welding process, different materials in particular can be welded together well that cannot be welded or can only be welded with difficulty using other welding processes. For example, the stator laminations 6 of the stator laminations 7a can be made of electrical steel and the stator housing 11a can be made of aluminum. 3 and 4 show another example of a stator-housing arrangement 12b, FIG. 3 in an oblique view, FIG. 4 in a longitudinal section.

The welds 16 are advantageously distributed evenly over a circumference and/or a length of the laminated core 7a, 7b of the stator. As a result, the forces occurring between the laminated stator core 7a, 7b and the stator housing 11a, 11b during operation of the electrical machine 1a can be transmitted well. In other words, the stator laminated core 7a, 7b is connected to the stator housing 11a, 11b via the welds 16 in a torsionally rigid manner. In the examples shown, the rib 14 or the cooling channel 15 run in a wide circumferential area along circles around the axis of rotation A. The course of the rib 14 or the cooling channel 15 only has an axial component in a narrow circumferential area. However, it would also be conceivable for the rib 14 and the cooling channel 15 to run along a helical line with a constant pitch. Furthermore, a plurality of coolant channels 15 through which the coolant flows in parallel can also be provided, which, for example, emanate from a first collector and open into a second collector. In particular, the ribs 14 and coolant channels 15 can then also run in the axial direction.

In an operational arrangement (for example in a vehicle), the cooling channel 15 is hydraulically integrated into a cooling circuit which can comprise a pump and a cooler, for example. For example, water (especially water mixed with antifreeze) or oil can act as a heat transfer medium in the cooling circuit. However, it would also be conceivable for a gaseous heat carrier to circulate in the cooling circuit. It is also possible that the outer casing 13 is omitted and the electrical machine 1a is air-cooled. In particular, ribs 14 running in the axial direction or in the circumferential direction can also be provided in an air-cooled machine 1a. At this point it is also noted that the electrical machine 1a can not only be cooled with the proposed measures, but can of course also be heated. For example, the electrical machine 1a can be preheated at low outside temperatures. Finally, FIG. 5 shows the electrical system installed in a vehicle 21

Machine 1. The vehicle 21 has two axles, one of which is driven. Specifically, the electric machine 1 is connected to the semi-axles 23 of the rear axle via an optional transmission 22 . Finally, the driven wheels 24 are mounted on the semi-axles 23 . The electric machine 1, the transmission 22 and the semi-axles 23 are part of the drive train of the vehicle 21. The vehicle 21 is driven at least partially or temporarily by the electric machine 1. This means that the electric machine 1 can drive the vehicle alone 21 serve or be provided, for example, in combination with an internal combustion engine (hybrid drive).

Finally, it is stated that the scope of protection is determined by the patent claims. However, the description and drawings should be used to interpret the claims. The features contained in the figures can be arbitrarily exchanged and combined with one another. In particular, it is also stated that in reality the devices shown can also include more or fewer components than shown. In some cases, the devices shown or their components may also not be shown to scale and/or enlarged and/or reduced. Reference List

1, 1a electrical machine

2 wave

3 rotors

4a, 4b (roller) bearings

5 stator

6 stator lamination

7a, 7b stator core

8 stator winding

9 first bearing plate

10 second end shield

11a, 11b stator housing

12a, 12b stator housing arrangement

13 outer jacket

14 rib

15 cooling channel

16 weld

17 tool

18 tool outer part

19 inner part of the tool

20 edition

21 vehicle

22 gears

23 semi-axis

24 wheel

A axis of rotation

Claims

patent claims

1. Stator-housing arrangement (12a, 12b) for an electrical machine (1, 1a), comprising a stator core (7a, 7b) and a stator housing (11a, 11b), characterized in that the stator core (7a, 7b ) and the stator housing (11 a, 11 b) are welded together at a plurality of weld points (16) using the fill-up stir friction spot welding process.

2. Stator housing arrangement (12a, 12b) according to claim 1, characterized in that the stator housing (11a, 11b) has ribs (14) and the welds (16) are arranged between the ribs (14).

3. Stator-housing arrangement (12a, 12b) according to claim 1 or 2, characterized in that the welds (16) are evenly distributed over a circumference and/or a length of the stator core (7a, 7b).

4. Stator-housing arrangement (12a, 12b) according to one of claims 1 to 3, characterized in that the stator laminations (6) of the stator core (7a, 7b) consist of electrical steel and the stator housing (11a, 11b) consists of aluminum.

5. Electrical machine (1, 1a), comprising - a first bearing plate (9) and a second bearing plate (10), between the two bearing plates (9, 10) arranged stator housing assembly (12a, 12b) according to one of Claims 1 to 4 and stator windings (8) arranged on the stator core (7a, 7b) and a rotor (3) arranged in the stator (5) with a rotor shaft (2) rotatably mounted in the two end shields (9, 10).

6. Electrical machine (1, 1a) according to claim 5, characterized by an outer casing (13) which surrounds the stator housing (11a, 11b) radially, wherein between the stator housing (11a, 11b) and the outer casing (13) a cooling channel ( 15) is arranged, in which the welds (16) are arranged.

7. Vehicle (21) with a drive train having an electric machine (1, 1a) according to claim 5 or 6, which is provided for driving the vehicle (21).

8. A method for producing a stator-housing arrangement (12a, 12b) for an electrical machine (1, 1a), comprising the steps

Providing a stator core (7a, 7b) and a stator housing (11a, 11b),

Sliding the stator core (7a, 7b) into the stator housing (11a, 11b) and

Permanent connection of the stator core (7a, 7b) to the stator housing (11a, 11b), characterized in that the permanent connection is carried out at a plurality of welds (16) using the fill-up stir friction spot welding process.

9. The method according to claim 8, characterized in that the stator core (7a, 7b) is placed on a support (20) prior to welding, which supports the stator core (7a, 7b) on the inside in a rotor bore of the stator core (7a, 7b). .