DE102020104663A1 - ELECTRIC DRIVE MACHINE FOR DRIVING A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to an electric drive machine for driving a motor vehicle, comprising a stator; a rotor; a cooling circuit with a hollow shaft rotatably mounted to the stator, on which the rotor is arranged in a rotationally fixed manner, a conveying device of the cooling circuit being designed to convey a cooling medium for cooling the rotor and / or the stator through the hollow shaft; at least one measure for enlarging a heat transfer area between the hollow shaft and the cooling medium flowing through the hollow shaft and / or for generating turbulence in the cooling medium flowing through the hollow shaft. The invention also relates to a motor vehicle with at least one such electrical drive machine.

Description

The present invention relates to an electrical drive machine for driving a motor vehicle and a motor vehicle with at least one such electrical drive machine.

Effective rotor cooling in electric drive machines is an essential requirement for high continuous power, in particular in current-excited synchronous machines and asynchronous machines, as they are often used in electrically driven motor vehicles. A high continuous output is essential for dynamic driving behavior and when driving uphill or when operating with a trailer.

It is therefore the object of the present invention to provide a solution by means of which particularly effective cooling of an electric drive machine designed for driving a motor vehicle can be ensured.

This object is achieved by an electric drive machine for driving a motor vehicle with the features of claim 1. Further possible embodiments of the invention are given in particular in the dependent claims.

The electric drive machine according to the invention for driving a motor vehicle comprises a stator, a rotor and a cooling circuit with a hollow shaft which is rotatably mounted relative to the stator and on which the rotor is arranged in a rotationally fixed manner. In other words, a channel in the interior of the hollow shaft forms part of the cooling circuit. In addition, a conveying device of the cooling circuit is designed to convey a cooling medium for cooling the rotor and / or the stator through the hollow shaft. The cooling medium can be, for example, oil or, for example, water. Furthermore, the electric drive machine has at least one measure for enlarging a heat transfer area between the hollow shaft and the cooling medium flowing through the hollow shaft and / or for generating turbulence in the cooling medium flowing through the hollow shaft.

The invention is based, in particular, on the knowledge that a heat transfer from the hollow shaft on which the rotor is arranged to the cooling medium flowing through the hollow shaft may not be sufficient with high performance requirements, which can lead to overheating of the rotor or to performance degradation due to reasons for component protection can. In addition, the invention is based on the knowledge that the heat transfer from the hollow shaft to the cooling medium is influenced in particular by the available heat transfer area multiplied by a heat transfer coefficient in a boundary layer of the cooling medium.

In the electric drive machine according to the invention, a particularly high cooling capacity is achieved by providing at least one measure for increasing the heat transfer area between the hollow shaft and the cooling medium flowing through the hollow shaft and / or at least one measure for generating turbulence in the cooling medium flowing through the hollow shaft. The enlargement of the heat transfer surface and the generation of turbulence can - depending on the measure chosen - be implemented by one and the same measure, but need not be.

In the interior of the hollow shaft, specific measures are provided which help to enlarge the heat transfer area between the hollow shaft and the cooling medium flowing through the hollow shaft and / or to increase the heat transfer coefficient, in particular by means of measures that lead to the generation of turbulence in the cooling medium. Measures leading to the enlargement of the heat transfer surface and / or the generation of turbulence can be provided independently of one another, and these can also occur coupled with one another.

As a result, the electric drive machine makes it possible to create a relatively low temperature difference between the cooling medium and the hollow shaft with a constant and high heat flow, or to achieve a particularly high cooling capacity with the same temperature difference compared to a smooth hollow shaft inner surface. Depending on the specific structure of the cooling circuit, it is also possible in the case of the electric drive machine to cool both the stator and the rotor via the cooling circuit. The particularly good heat transfer from the hollow shaft to the cooling medium makes it possible in particular to cool the rotor very efficiently, since it is attached to an outside of the hollow shaft. Heat can thus be conducted from the rotor via the hollow shaft to the cooling medium, which flows through the hollow shaft inside.

One possible embodiment of the invention provides that an inside of the hollow shaft is provided with a surface structure in order to enlarge the heat transfer surface and / or to generate the turbulence. The inside of the hollow shaft is therefore not smooth, but has the surface structure mentioned. Because the inside of the hollow shaft said surface structure has, compared to a smooth inside of the hollow shaft, an enlarged heat transfer surface is provided for dissipating heat to the cooling medium flowing through the hollow shaft. Depending on the design of this surface structure, it can also contribute to generating turbulence in the cooling medium flowing through the hollow shaft and thus increasing the heat transfer coefficient.

According to a further possible embodiment of the invention, it is provided that the surface structure comprises a spiral winding along the inside of the hollow shaft. This spiral can be produced, for example, by turning, milling, reshaping, thread cutting or, for example, by extrusion. Such a spiral for enlarging the heat transfer surface can therefore be produced in a particularly simple manner on the inside of the hollow shaft. A particularly large heat transfer surface with a very good heat transfer effect can be provided via this spiral.

According to a further possible embodiment of the invention, it is provided that the surface structure comprises a further spiral winding along the inside of the hollow shaft, the spirals running in opposite directions. Opposite means that one spiral is designed in the form of a right-hand thread and the other spiral in the form of a left-hand thread. Both spirals running in opposite directions can be produced, for example, by turning, milling, forming or thread cutting, so they can be implemented with very simple production processes. Because the surface structure has the two spirals running in opposite directions, a particularly large heat transfer surface is created between the hollow shaft and the cooling medium flowing through the hollow shaft. In addition, no twist is impressed on the cooling medium when it flows through the hollow shaft, since the two spirals run in opposite directions when viewed in the circumferential direction.

According to a further possible embodiment of the invention, it is provided that the surface structure comprises cooling ribs protruding into the interior of the hollow shaft, for example by circumferential ribs, i.e. in the form of rings, or axial ribs, for example. A correspondingly large increase in the heat transfer surface between the hollow shaft and the cooling medium flowing through the hollow shaft can be created via the cooling ribs. Depending on the shape of the cooling ribs, it is also possible to use these cooling ribs to generate turbulence in the cooling medium flowing through the hollow shaft, thus increasing the heat transfer coefficient accordingly. In principle, the surface structure can have any elements or shapes that ensure a roughness of the surface structure of the inside of the hollow shaft and thus contribute to increasing the heat transfer surface and / or generating turbulence in the cooling medium flowing through the hollow shaft.

Another possible embodiment of the invention provides that an insert part with structures that generate turbulence is arranged in the interior of the hollow shaft in order to generate the turbulence. In particular, the insert can be made of plastic. Above all, if the insert is made of plastic, there can be the advantage that no complex reworking of the hollow shaft or machining of the insert is necessary. The insert can be produced, for example, by injection molding, which can result in particularly large degrees of freedom with regard to the geometric configuration of the insert. The insert with the structures that generate turbulence therefore improves, in particular, the heat transfer through the generation of turbulence. The insert can, for example, have a cylindrical main body from which the turbulence-generating structures can extend in the radial direction. Other shapes of the insert are also possible, in principle all shapes that can contribute to generating locally high flow velocities or turbulence in the coolant.

According to a further possible embodiment of the invention, it is provided that at least one component with at least one element protruding radially into the interior of the hollow shaft is pressed into the hollow shaft to enlarge the heat transfer surface and / or to generate the turbulence. The component can in particular be pressed into the hollow shaft in such a way that it rests flush against the inside of the hollow shaft. The component can, for example, be made from a material with good thermal conductivity, for example from a metallic alloy or the like. The pressed-in component can be produced, for example, by casting, extrusion, milling or turning. In particular, it can be provided that the inside of the hollow shaft itself is not machined at all in order to achieve said enlargement of the heat transfer surface and / or generation of the turbulence. Both can be realized by the pressed-in component. In this case, the component is thermally connected to the hollow shaft. Several such components can also be provided, i.e. multi-part concepts, for example in the form of pressed-in disks, rings, bushings or other flow objects that can serve to enlarge the heat transfer surface and / or to generate said turbulence.

Another possible embodiment of the invention provides that the hollow shaft has a single inlet opening running in the axial direction and at least one outlet opening running in the radial direction for the cooling medium. In other words, the hollow shaft can be designed as a type of blind hole, wherein the cooling medium can be fed into the interior of the hollow shaft via said inlet opening. The inlet opening can be connected, for example, to a coolant inlet nozzle, via which the coolant can be supplied. The cooling medium can flow in particular along the rotor via the at least one outlet opening running in the radial direction, whereby it can also be provided, depending on the coolant flow, that the coolant can also flow along the stator. If the coolant flows both directly along the rotor and along the stator, it is provided in particular that it is an electrically non-conductive coolant. The coolant circuit can in particular also include a coolant sump, via which the coolant, after having flowed along the stator and / or rotor, can reach a coolant reservoir of the cooling circuit. From there, the coolant can be fed to a coolant cooler, for example, before it is fed back to the hollow shaft.

According to a further possible embodiment of the invention, it is provided that the cooling circuit leads from the hollow shaft to the rotor and to the stator. Both the rotor and the stator come into direct contact with the cooling medium, so that excess heat from the stator and the rotor is also dissipated directly to the cooling medium. In addition, excess heat, in particular from the rotor, can also be carried away to the cooling medium via the hollow shaft, since the rotor is attached to the outside of the hollow shaft. Because the cooling circuit leads from the hollow shaft to the rotor and to the stator, particularly effective cooling of the rotor and stator can be achieved. This is because the coolant can come into direct contact with the rotor and stator and thereby dissipate excess heat from these components particularly effectively.

The motor vehicle according to the invention comprises at least one electrical drive machine according to the invention or at least one possible configuration of the electrical drive machine.

Further features of the invention can emerge from the claims, the figures and the description of the figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations shown below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination, but also in other combinations or alone, without the scope of the invention to leave.

• 1 eine schematische Seitenschnittansicht einer teilweise dargestellten ersten Ausführungsform einer elektrischen Antriebsmaschine;
• 2 eine schematische Seitenschnittansicht einer teilweise dargestellten zweiten Ausführungsform der elektrischen Antriebsmaschine;
• 3 eine schematische Seitenschnittansicht einer teilweise dargestellten dritten Ausführungsform der elektrischen Antriebsmaschine;
• 4 eine schematische Seitenschnittansicht einer teilweise dargestellten vierten Ausführungsform der elektrischen Antriebsmaschine;

The drawing shows in:

• 1 a schematic side sectional view of a partially illustrated first embodiment of an electric drive machine;
• 2 a schematic side sectional view of a partially illustrated second embodiment of the electric drive machine;
• 3 a schematic side sectional view of a partially illustrated third embodiment of the electric drive machine;
• 4th a schematic side sectional view of a partially illustrated fourth embodiment of the electric drive machine;

Identical and functionally identical elements are provided with the same reference symbols in the figures.

A first embodiment of an electric drive machine 10 for a motor vehicle is partially in a schematic sectional view in 1 shown. The electric prime mover 10 comprises a stator, not shown here, and a rotor 12th . It also includes the electric drive machine 10 an unspecified cooling circuit with a hollow shaft rotatably mounted to the stator 14th on which the rotor 12th Is rotatably arranged. A conveying device of the cooling circuit, not shown here, is designed to convey a cooling medium indicated schematically by the arrows 16 to cool the rotor 12th and / or the stator, not shown here, through the hollow shaft 14th to transport. The hollow shaft 14th is about respective radial bearings 18th rotatably mounted, for example on a housing, not shown here, of the electric drive machine 10 .

To increase a heat transfer area between the hollow shaft 14th and through the hollow shaft 14th flowing cooling medium 16 is an inside of the hollow shaft 14th with a down along the inside of the hollow shaft 14th winding spiral 20th Mistake. The spiral 20th can be produced, for example, by turning, milling, forming or, for example, by extrusion. The spiral 20th thus forms a surface structure on the inside of the hollow shaft 14th , which increase the heat transfer surface of the inside of the hollow shaft 14th contributes. This enlargement of the heat transfer surface enables particularly good heat transfer from the hollow shaft 14th on the coolant 16 take place.

In 2 is a further possible embodiment of the electric drive machine 10 partially shown in a schematic side sectional view. On the inside of the hollow shaft 14th is another stretching along the inside of the hollow shaft 14th winding spiral 22nd formed, the spirals 20th , 22nd run in opposite directions. In the embodiment shown here, in order to enlarge the heat transfer surface, the hollow shaft has a surface structure on its inside, which has the two counter-rotating spirals 20th , 22nd having. Both spirals 20th , 22nd can be produced, for example, by turning, milling, forming or also by extrusion. By providing the two counter-rotating spirals 20th , 22nd on the inside of the hollow shaft 14th becomes a particularly strong surface enlargement of the heat transfer surface of the hollow shaft 14th created. In addition, the cooling medium 16 when flowing through the hollow shaft 14th no twist imposed because the two spirals 20th , 22nd run in opposite directions.

In 3 is a third possible embodiment of the electric drive machine 10 partially shown in a schematic side sectional view. To generate turbulence when passing through the hollow shaft 14th flowing cooling medium 16 it is in this embodiment of the electric drive machine 10 provided an insert 24 , in particular made of plastic, with structures that generate turbulence 26th to be provided.

The insert made in particular from plastic 24 can, for example, have a type of cylindrical main body, from which the turbulence-generating structures start in the radial direction 26th can extend.

The insert 24 can be produced, for example, by injection molding, so that relatively large degrees of freedom can result with regard to the geometry design. The insert 24 serves in particular to reduce turbulence in the cooling medium 16 when flowing through the hollow shaft 14th to create. The hollow shaft 14th does not have to be processed on the inside at all in this embodiment, so it can remain completely smooth on its inside. In principle, however, it is also possible, in addition, on the inside of the hollow shaft 14th to provide a wide variety of surface structures.

In 4th is finally a fourth possible embodiment of the electric drive machine 10 partially shown in a schematic side sectional view. To enlarge the heat transfer surface and / or to generate the turbulence is in the hollow shaft 14th a component 28 with several in the radial direction into the interior of the hollow shaft 14th protruding elements 30th pressed in. The component 28 can in particular be made of a material that conducts heat well, for example a metallic alloy. The component 28 can be produced, for example, by casting, extrusion, milling or turning. In particular, it can be provided that the hollow shaft 14th the inside is not machined, so it can remain smooth because the pressed-in component 28 with its in the radial direction into the interior of the hollow shaft 14th protruding elements 30th provides for the enlargement of the heat transfer surface and / or for the generation of the turbulence. With the elements 30th it can be, for example, cooling fins, spirals or other elements that are used to enlarge the heat transfer surface and / or to generate the turbulence in the cooling medium 16 suitable. Instead of a single pressed-in component 28 can also have several individual pressed-in components 28 , for example in the form of pressed-in disks, rings, bushings or other flow objects.

All embodiments of the electric drive machine shown here 10 have in common that the hollow shaft 14th a single inlet opening running in the axial direction 32 and two outlet openings running in the radial direction 34 for the cooling medium 16 having. This allows the cooling circuit from the hollow shaft 14th to the rotor 12th and lead to the stator, not shown here. The inlet openings running in the axial direction 32 and the two outlet openings running in the radial direction 34 are therefore components of the already mentioned coolant circuit, which can also have a coolant sump (not shown here), a coolant reservoir and a coolant cooler.

The cooling medium can pass through the coolant sump 16 after flowing along the rotor 12th and flow off again at the stator and are fed to the coolant reservoir. From there, the cooling medium can 16 be conveyed by means of the coolant pump to the coolant cooler, where excess heat is extracted. Then the cooling medium 16 again via the inlet opening 32 the hollow shaft 14th are fed.

Notwithstanding the representations in the figures, it is also possible that in the inlet opening 32 a lance for introducing the cooling medium 16 protrudes to this into the interior of the hollow shaft 14th to feed. In this context, it can be provided that the hollow shaft 14th not the outlet openings running in the radial direction 34 having, the cooling medium 16 the hollow shaft 14th in this case, for example, exclusively through the inlet opening 32 leaves, for example in an annular area surrounding the lance. The rotor 12th and the stator will not be affected by the cooling medium in this case 16 flows around. The heat transfer, especially from the rotor 12th , then takes place via the hollow shaft 14th to the cooling medium flowing in it 16 .

Depending on the boundary conditions and in particular the heat loss occurring on the rotor 12th and / or stator, the variant with the lance and without the outlet openings running in the radial direction can be used 34 be sufficient for cooling. In this case, the flow losses can be lower than in the embodiments shown in the figures, since neither the rotor 12th the cooling medium still has to pass through the stator. The required coolant pump can thus be dimensioned correspondingly smaller.

List of reference symbols

10

electric prime mover

12th

rotor

14th

Hollow shaft

16

Cooling medium

18th

Radial bearing

20th

spiral

22nd

another spiral

24

Insert

26th

Structures of the insert that create turbulence

28

Component pressed into the hollow shaft

30th

Elements of the component projecting into the interior of the hollow shaft in the radial direction

32

inlet opening of the hollow shaft running in the axial direction

34

outlet openings of the hollow shaft that run in the radial direction

Claims (10)

An electric prime mover (10) for propelling a motor vehicle, comprising - a stator; - a rotor (12); - A cooling circuit with a hollow shaft (14) rotatably mounted to the stator, on which the rotor (12) is arranged in a rotationally fixed manner, a conveying device of the cooling circuit being designed to supply a cooling medium (16) for cooling the rotor (12) and / or the Conveying the stator through the hollow shaft (14); - At least one measure to enlarge a heat transfer area between the hollow shaft (14) and the cooling medium (16) flowing through the hollow shaft (14) and / or to generate turbulence in the cooling medium (16) flowing through the hollow shaft (14). Electric drive machine (10) according to Claim 1 , characterized in that an inside of the hollow shaft (14) is provided with a surface structure to enlarge the heat transfer surface and / or to generate the turbulence. Electric drive machine (10) according to Claim 2 , characterized in that the surface structure comprises a spiral (20) winding along the inside of the hollow shaft (14). Electric drive machine (10) according to Claim 2 or 3 , characterized in that the surface structure comprises a further spiral (22) winding along the inside of the hollow shaft (14), the spirals (20, 22) running in opposite directions. Electric drive machine (10) according to one of the Claims 2 until 4th , characterized in that the surface structure comprises cooling ribs protruding into the interior of the hollow shaft (14), in particular in the form of circumferential ring ribs or axial ribs. Electric drive machine (10) according to one of the preceding claims, characterized in that an insert (24), in particular made of plastic, with structures (26) that generate turbulence is arranged in the interior of the hollow shaft (14) to generate the turbulence. Electric drive machine (10) according to one of the preceding claims, characterized in that to enlarge the heat transfer surface and / or to generate the turbulence in the hollow shaft (14) at least one component (28) with at least one in the radial direction into the interior of the hollow shaft (14 ) protruding element (30) is pressed. Electric drive machine (10) according to one of the preceding claims, characterized in that the hollow shaft (14) has a single inlet opening (32) running in the axial direction and at least one outlet opening (34) running in the radial direction for the cooling medium (16). Electric drive machine (10) according to one of the preceding claims, characterized in that the cooling circuit leads from the hollow shaft (14) to the rotor (12) and to the stator. Motor vehicle with at least one electric drive machine (10) according to one of the preceding claims.

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