WO2020244700A1

WO2020244700A1 - Electric machine having micro-structured rotor and/or stator surface and drivetrain unit

Info

Publication number: WO2020244700A1
Application number: PCT/DE2020/100369
Authority: WO
Inventors: Gerald KÜSTLER
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2019-06-04
Filing date: 2020-05-04
Publication date: 2020-12-10
Also published as: DE102019114958A1

Abstract

The invention relates to an electric machine (1) for a drive of a motor vehicle, having a stator (2) fixed to the housing and a rotor (5), rotatably mounted relative to the stator (2) about a rotation axis (3) and spaced apart from the stator (2) by a radial gap (4), wherein the rotor (5) has, on the surface (6) thereof facing the radial gap (4), and/or the stator has (2), on the surface (7) thereof facing the radial gap (4), a surface structure (8a, 8b), which reduces an aerodynamic resistance. The invention additionally relates to a drivetrain unit (12) having said electric machine (1).

Description

Electric machine with microstructured rotor and / or stator surface and drive train unit

The invention relates to an electrical machine for driving a motor vehicle, such as a car, truck, bus or other commercial vehicle, with a stator fixed to the housing and a stator rotatably mounted relative to the stator about an axis of rotation (preferably arranged radially within the stator), rotor spaced from the stator by a radial gap. The electric machine is designed to drive a purely electrically driven or hybridized motor vehicle.

Generic electrical machines are sufficiently known from the prior art. Efforts are also already known to implement the electrical machines as high-speed as possible. For example, a document with the name “High speed PM machines” from the Technical University of Darmstadt from the Institute for Electrical Energy Conversion, written by Professor A. Binder, is known, in which the focus is on the design of a rotor of the electrical machine.

It has been shown that for the use of electrical machines, preferably for the purely electric drive of a motor vehicle, it is advantageous if the electrical machine can be designed for even higher speeds. With the higher speeds, however, some difficulties arise, such as, for example, providing a permanent storage and increased losses due to corresponding resistances. In particular, it has been found that the aerodynamic losses increase sharply at higher speeds. It is known that these aerodynamic losses (air friction losses) can amount to approx. 350 W at 40,000 rpm and even approx. 800 W at 60,000 rpm.

It is therefore the object of the present invention to avoid the disadvantages known from the prior art and in particular to provide an electrical machine that is suitable for the highest possible speeds and can be operated with the lowest possible efficiency. This is achieved according to the invention in that the rotor on its surface facing the radial gap (preferably a radial outer surface) and / or the stator on its surface facing the radial gap (preferably a radial inner surface) has / has a surface structure that reduces aerodynamic drag. A surface structure is to be understood in particular as a plurality of depressions or elevations which, due to their arrangement to one another / distribution over the surface, form a regular pattern.

This surface structure (s) can reduce the aerodynamic loss in the higher single-digit percentage range (approx. 5% to 8%).

Further advantageous embodiments are claimed with the subclaims and explained in more detail below.

Accordingly, it is furthermore advantageous if the surface structure (as a recess structure) has a plurality of recesses which are arranged distributed in the circumferential direction. The surface structure thus preferably extends continuously along a circumference in the circumferential direction.

It has also proven to be expedient if the several depressions forming the surface structure are implemented as grooves or as spherical segment-shaped depressions (preferably with the formation of a golf ball surface). As a result, structures are created that generate particularly low aerodynamic resistance.

It is also advantageous if the surface structure has a plurality of elevations which are arranged distributed in the circumferential direction. The elevations are then implemented as ribs, for example.

With regard to the attachment of the surface structure, it has been found to be particularly advantageous if the surface structure has a separate coating, preferably a film, more preferably a lacquer, is applied. This keeps the manufacturing effort as low as possible.

In addition, it is advantageous if a first surface structure (the surface structure implemented on the rotor) is preferably formed on a reinforcement sleeve that is attached to the rotor and directly forms the surface of the rotor. The reinforcement sleeve can for example be made of a plastic, more preferably a fiber-reinforced plastic. A total weight is thus kept as low as possible.

It is also advantageous if a second surface structure (the surface structure implemented on the stator) is preferably formed on a reinforcement sleeve that is attached to the stator and directly forms the surface of the stator.

With regard to the production of the surface structure, it is also expedient if this surface structure is produced via a mechanical deformation process, such as embossing (preferably micro-embossing), or more preferably roller burnishing or particularly preferably pressing, of the respective surface. This results in an efficiently producible surface structure.

If the surface structure is created via a chemical etching process of the respective surface, it can be selected as small as desired, especially in the micro range as a microstructure.

If the surface structure is generated by a laser structuring process of the respective surface, the manufacturing effort is further reduced.

The invention also relates to a drive train unit for a motor vehicle with the electrical machine according to the invention according to at least one of the previously described embodiments.

In this context, it is also useful if the electrical machine is dimensioned such that the rotor rotates at a speed of more than 30,000 RPM, more preferably more than 40,000 RPM, particularly preferably up to or more than 50,000 RPM, can be driven. As a result, the electrical machine is designed to put a drive train with a high degree of efficiency.

The electrical machine is preferably implemented as an internal rotor motor; in white direct versions, training as an external rotor motor is preferably implemented.

In other words, according to the invention, a microstructured rotor surface (preferably outer surface) and / or a microstructured stator surface (preferably inner surface) is implemented in a high-speed electrical machine to reduce aerodynamic drag. The rotor surface and / or the stator surface have the microstructured surfaces, for example in the form of grooves / ribs or hollows / dents.

The invention will now be described in more detail below with reference to figures

Show it:

1 shows a longitudinal sectional view of an electrical machine according to the invention according to a first exemplary embodiment, the electrical machine being shown schematically.

Fig. 2 is a perspective view of a surface structure as shown on a

Rotor of the electrical machine according to Fig. 1 is implemented,

3 shows a perspective view of a surface structure according to a second

Embodiment, as well

FIG. 4 shows a schematic view of the integrated in a drive train unit according to FIG. 1. trained electrical machine The figures are only of a schematic nature and are therefore only used to understand the invention. The same elements are provided with the same reference numerals.

In connection with FIGS. 1 and 4 is an electrical machine according to the invention

1 can be recognized in its basic structure. The electrical machine 1 is used as a drive machine of a motor vehicle. In particular, the electric machine 1 is integrated in a purely electrically designed drive train unit 12 of the motor vehicle, the drive train unit 12 being further connected to drive several wheels of the motor vehicle. The drive train unit 12, as can be seen from FIG. 4, is preferably equipped in a typical manner with a transmission 13, via which transmission 13 the electric machine 1 is coupled or can be coupled to two drive axles 14a, 14b coupled to the wheels of the motor vehicle. The electrical machine 1 is implemented as a high-speed electrical machine 1 and is dimensioned such that its rotor 5 can implement a speed of up to 50,000 rpm, more preferably up to 60,000 rpm, when the drive train unit 12 is in operation.

The electrical machine 1, as shown in more detail in FIG. 1, basically has a ring-shaped stator 2 which is firmly received in a housing 15 (FIG. 4). Radially within the stator 2, a rotor 5 is rotatable relative to the stator 2 aufgenom men. In particular, the rotor 5 is mounted in the housing 15 so as to be rotatable about an axis of rotation 3. A radial gap 4 / air gap shown radially in FIG. 1 between the rotor 5 / a radial outer surface 6 (first surface) of the rotor 5 and the stator

2 / an inner surface 7 (second surface) of the stator 2 is shown disproportionately large in Fig. 1 for clarification purposes.

According to the invention, a first surface structure 8a is formed on the outer surface 6 of the rotor 5, which surface structure is designed and dimensioned in such a way that it reduces an aerodynamic resistance of the rotor 5 in relation to a smooth outer surface. A (second) surface structure 8b is also formed on the inner surface 7 and is designed and dimensioned in such a way that it reduces an aerodynamic resistance of the rotor 5 with respect to a smooth inner surface. In In further embodiments, only one of the two surface structures 8a or 8b is implemented, so that either the first surface structure 8a is provided on the rotor 5 or the second surface structure 8b is provided on the stator 2.

An exemplary design of the first surface structure 8a according to the first exemplary embodiment can be clearly seen in FIG. The first surface structure 8a extends in a circumferential direction, i. H. along a circular line running concentrically around the axis of rotation 3, around the entire circumference of the rotor 5. The first surface structure 8a has several depressions 9, which together form a pattern called a microstructure. The first surface structure 8a is realized in this embodiment as a groove structure and thus its individual depressions 9 implemented as grooves. By the implemented as grooves Ver depressions 9 webs / ribs are thus formed that run parallel to each other. The depressions 9 implemented as grooves preferably run axially / along the axis of rotation 3.

According to a second exemplary embodiment, which is illustrated in connection with FIG. 3, the first surface structure 8a can also be implemented in other ways. In FIG. 3, the first surface structure 8a is implemented as a golf ball surface and thus has depressions 9 in the form of spherical segment-shaped depressions / dents. The depressions 9 of FIG. 3 are again arranged continuously in the circumferential direction and distributed in the axial direction (in a plurality of rows). In principle, any other shapes of depressions 9 are also possible, a microstructure always being implemented.

In this context, it should be pointed out that the second surface structure 8b can be formed in the two exemplary embodiments according to the first surface structure 8a. In the first exemplary embodiment according to FIG. 1, the second surface structure 8b is thus also made possible by means of the depressions 9 implemented as grooves, and can alternatively also be designed as spherical segment-shaped depressions. In the second exemplary embodiment according to FIG. 1, the second surface structure 8b is also equipped by means of the depressions 9 implemented as spherical segment-shaped depressions, alternatively can also be designed as grooves. In the production of the surface structures 8a, 8b, it has proven to be particularly expedient if these are formed in a separately applied coating. This coating is realized, for example, as an adhesive film, a lacquer or a sleeve (reinforcement sleeve). In the embodiment as a reinforcement sleeve, this is preferably attached to an outside 10 of the rotor 5 or inside 11 of the stator 2 in order to directly form the outside surface 6 or the inside surface 7.

According to further preferred embodiments, it has also turned out to be advantageous if the respective surface structure 8a, 8b is produced by means of a mechanical shaping process, such as embossing or rolling or pressing, of the inner surface 7 or the outer surface 6. Chemical etching is also implemented in further versions. Furthermore, a laser structuring of the respective surface 6, 7 is implemented in further versions.

In other words, the design according to the invention implements a reduction in the aerodynamic resistance through a (micro) structured rotor and stator surface 6, 7 in a high-speed electrical machine 1. On the one hand, the rotor and stator surfaces 6, 7 can be provided with microstructured structures; so-called riplets (ribs / grooves). The riplets can be implemented, for example, using appropriate varnishes or foils. Processes such as laser structuring, chemical etching or micro-embossing are also conceivable. On the other hand, so-called dimples (depressions) can be embossed / embossed on the surfaces 6, 7 (analogous to golf balls). Forming processes such as embossing, pressing or roller burnishing are also available for production. In some cases, reinforcement sleeves are already used in high-speed machines, which ensure the structural strength of the stator 2 under the high tensile forces. Corresponding structuring of the reinforcement sleeve, which is then attached to the stator 2, is preferably already carried out in production. Based on current literature values, a reduction in aerodynamic resistance in the single-digit percentage range can be expected (5% -8%). With aerodynamic optimization, however, is natural always ensure that the influence on the size of the air gap 4 is kept as small as possible.

List of references for electrical machine

stator

Axis of rotation

Radial gap

rotor

Exterior surface

Inner surface

a first surface structure

b second surface structure

deepening

0 outside

1 inside

2 drive train unit

3 gears

4a first drive axle

4b second drive axle

5 housing

Claims

1. Electrical machine (1) for driving a motor vehicle, with a stator (2) fixed to the housing and a stator (2) rotatably mounted relative to the stator (2) about an axis of rotation (3) via a radial gap (4) ) spaced rotor (5), characterized in that the rotor (5) on its surface (6) facing the radial gap (4) and / or the stator (2) on its surface (7) facing the radial gap (4) has a aerodynamic drag reducing surface structure (8a, 8b) have / has.

2. Electrical machine (1) according to claim 1, characterized in that a plurality of the surface structure (8a, 8b) forming depressions (9) are implemented as grooves or spherical segment-shaped depressions.

3. Electrical machine (1) according to claim 1 or 2, characterized in that the surface structure (8a, 8b) is applied via a separate coating.

4. Electrical machine (1) according to one of claims 1 to 3, characterized in that a first surface structure (8a) attached to a on the Ro gate (5), the surface (6) of the rotor (5) directly form the reinforcing sleeve is trained.

5. Electrical machine (1) according to one of claims 1 to 4, characterized in that a second surface structure (8b) is formed on a surface (7) of the stator (2) attached to the stator (2) directly with the reinforcing sleeve is.

6. Electrical machine (1) according to one of claims 1 to 5, characterized in that the surface structure (8a, 8b) of the respective surface (6, 7) via a mechanical reshaping process, such as embossing or roller burnishing or pressing is generated. 7. Electrical machine (1) according to one of claims 1 to 6, characterized in that the surface structure (8a, 8b) via a chemical etching process of the respective surface (6,

7) is generated.

8. Electrical machine (1) according to one of claims 1 to 7, characterized in that the surface structure (8a, 8b) is generated via a laser structuring process of the respective surface (6, 7).

9. Drive train unit (12) for a motor vehicle, with an electrical Ma machine (1) according to at least one of claims 1 to 8.

10. The drive train unit (12) according to claim 9, characterized in that the electrical machine (1) is dimensioned such that the rotor (5) can be driven at a speed of more than 30,000 rpm.