WO2014005910A2

WO2014005910A2 - Electric machine having a stator blade stack provided with vortex generators for an integrated cooling arrangement

Info

Publication number: WO2014005910A2
Application number: PCT/EP2013/063462
Authority: WO
Inventors: Daniel Kuehbacher
Original assignee: Robert Bosch Gmbh
Priority date: 2012-07-03
Filing date: 2013-06-27
Publication date: 2014-01-09
Also published as: DE102012211501A1; WO2014005910A3

Abstract

The invention relates to an electric machine (1) and a stator (5) suitable for same, in which a through-flow interspace (16) is provided between the stator (5) and preferably a surrounding housing (7), through which interspace the cooling fluid can flow. The stator (5) in this case consists of a plurality of blades (21), which are stacked next to each other and from which vortex generators (19) project radially outwards into the through-flow interspace (16). Said vortex generators (19) can be formed when the blades (21) are punched and ensure good turbulence in the cooling fluid and thus an improved cooling effect.

Description

Description title

Electric machine with a stator-disk set provided with vortex generators for an integrated cooling arrangement

Field of the invention

The present invention relates to an electric machine with an integrated cooling arrangement and to a stator for such an electric machine.

State of the art

Electric machines such as electric motors or generators are used for a wide variety of applications. For example

Electric machines used in motor vehicles to drive the vehicle as a motor or to recuperate kinetic energy as a generator into electrical energy.

In particular, electric machines with high continuous power density, as used for applications in motor vehicles, must be actively cooled. For this purpose, a cooling fluid can be passed to walls of the electric machine along or through these walls to heat from the

Electric machine to pick up and remove.

In order to be able to guide the cooling fluid, such as a cooling liquid, in a targeted manner through the electric machine in such a way that the most efficient possible cooling takes place, conventionally most of the time in a housing

Electric machine suitable cooling channels provided to guide the cooling fluid. Cooling fluid, which has been passed through such a cooling channel and has thereby absorbed heat, can then release this heat, for example in a heat exchanger to the environment and then be passed back into the cooling channel. In this way, a closed cooling circuit can be formed. In order to improve a heat transfer from the electric machine to the cooling fluid on the one hand and on the other hand to keep a necessary pumping power for conveying the cooling fluid within limits, the cooling channel is often formed helical or meandering in the electric machine housing, wherein the

Cooling fluid should be accelerated on the one hand in its flow, on the other hand, however, high flow resistance should be avoided.

It was observed that the described, partly counter-rotating

Requirements for an electric machine cooling with conventional

Cooling arrangements can often be met only insufficient, since, for example, for cooling advantageous geometric structures in the

Electrical machine housing often only with complex manufacturing processes and thus are expensive to produce, which often prevents an economic application of such cooling arrangements.

Disclosure of the invention

The present invention as defined in the independent claims

is claimed, allows efficient cooling of an electric machine at the same time cost manufacturability of the used for this purpose

Cooling arrangement. Advantageous embodiments of the invention

Electric machines are defined in the dependent claims. According to a first aspect of the invention, an electric machine with an integrated cooling arrangement is proposed, wherein the electric machine has a rotor, a stator enclosing the rotor and preferably a housing enclosing the stator. The stator has a

Disk pack on, or is formed by such a disk set, the disk set is composed of a plurality of juxtaposed slats. The electric machine is characterized in that radially outside the stator, i. For example, between the stator and the housing, a flow space is provided, through which a cooling fluid can flow, wherein of at least some of the fins of the disk set so-called vortex generators in the

Protruding flow gap. These vortex generators are like that are configured to generate turbulence in a fluid flowing through the flow gap.

According to another aspect of the invention, a stator for a

Electric motor proposed, wherein the stator has a disk set, which consists of a plurality of juxtaposed slats

is composed. The stator has vortex generators which protrude radially outward from at least some of the fins of the fin package.

Ideas and findings relating to the electric machine proposed here can be seen inter alia in that it has been recognized that targeted guidance and mixing of cooling fluid through structures provided within a housing of an electric machine are often difficult to achieve. Instead, however, a cooling fluid may be passed through a gap between the stator of the

Electric machine and the stator enclosing this housing is provided. The cooling fluid can come into direct thermal contact with the lamellae of the lamellae packages forming the stator and thus ensure an efficient discharge of the heat released there.

It was observed that the cooling fluid guided along the stator should be mixed as precisely as possible in order to be able to mix cooler outer layers of the cooling fluid with hot layers on the surface to be cooled. In this case, the flow resistance that the cooling fluid experiences should be increased as little as possible.

It has been recognized that such thorough mixing of the cooling fluid can be advantageously effected by so-called vortex generators. The

Vortex generators can be formed by regions of the stator-forming plate pack, the projecting from individual lamellae radially outwardly in the flow space between the stator and the

Protruding housing.

By means of these vortex generators, for example, it is possible to avoid a uniformly layered oil due to a high Reynolds number as a result, for example, of a high viscosity of oil used, for example, as cooling fluid Flow forms along the surface of the stator, which is characterized by a low heat exchange transverse to the flow direction. Such uniformly stratified flow would result in low cooling efficiency because the cooling fluid would heat up directly at the wetted surface of the stator and thus absorb little more heat energy, whereas much colder fluid would be available outside a boundary layer adjacent to the stator surface in sufficient

thermal contact with the stator surface passes.

Integrated into the cooling arrangement with the aid proposed herein

Vortex generators (sometimes referred to as longitudinal vortex generator, LVG,) can be the cooling fluid that flows directly on the outside of the

Statorlamellenpakets is performed, selectively circulated and mixed. In this case, a vortex generator generates turbulences in the direction of flow of the cooling fluid, as a result of which colder external fluid layers are swirled into warmer fluid layers adjoining the stator surface. As a result, a large increase in the heat transfer can be achieved, while the pumping costs increase only slightly. Overall, the cooling efficiency of a provided with such a cooling arrangement electric machine can be significantly improved and thus the possible continuous power of the electric machine can be increased.

Another possible advantage of the proposed in one

Electric machine integrated cooling arrangement can be seen that the necessary for a turbulence of the cooling fluid vortex generators can be generated in a very simple manner that they are integrally formed on the fins of the stator laminations.

The stator of the electric machine typically consists of one or more disk packs arranged one behind the other, wherein each of the disk packs in turn consists of a multiplicity of lamellae stacked next to one another. Each of the slats consists of a metallic thin sheet, which can be brought by simple manufacturing processes such as punching and bending in a desired shape.

Conventionally, the lamellae have an annular geometry, wherein an outer edge is circular and inwardly projecting webs are provided, around which, for example, wire windings for generating electric coils for the electric machine are wound. In a central recess within the annular stator blades, the rotor of the electric machine

be included.

While in stators conventional electric machines all lamellae have a circular outer geometry, so that the stack of lamellae has a cylindrical surface, it is now proposed to provide at least some of the lamellae small areas that protrude beyond the circular outer edge of the lamella to the outside. These areas may serve as vortex generators in the stacked stator when installed in the enclosing housing, as they may protrude into a flow of the cooling fluid along the surface of the stator and locally fluidize that flow.

The projecting areas can be co-produced in a simple manner already during the punching of the slats. For this, the conventional need

Punching tools are only slightly modified. When all of the fins have the projecting portions, e.g. to get along with a single punching tool, to obtain the necessary spaces between the vortex generators, superfluous projecting portions can be removed before or after the assembly of the stator blades.

In general, vortex generators can only project directly radially outward from an associated lamella. However, it has been found that it can be advantageous to the generation of vortex, when the vortex generators project obliquely against a flow direction of the fluid in the flow space between the stator and the housing. In other words, a furthest protruding portion of a vortex generator should oppose the

Be aligned through the flow direction of the fluid. An angle of attack of such an obliquely arranged vortex generator may, for example, in the range of 10 ° to 60 ° relative to the direction of flow of the cooling fluid.

The vortex generators may be tapered in a direction toward the housing surrounding the stator. In other words, the vortex generators may be at a radially inner and at the circular Slat adjacent base wider than in a more radially outward area. For example, the vortex generators may be triangular with a radially outwardly directed tip or partially circular outwardly projecting.

Furthermore, the vortex generators may have a through opening in a region of a base adjacent to an associated fin. In other words, the vortex generators need not be formed over the entire surface, but it may be provided one or more openings through which parts of the cooling fluid can flow closer to the adjacent stator. In this way, on the one hand a good mixing of the

Cooling fluids and on the other hand, a good heat transfer from the stator to the cooling fluid can be achieved with low flow resistance.

Two vortex generators adjacent to one another in the longitudinal direction of the disk pack can have a certain distance from one another, which may be greater than a thickness of a disk and preferably a multiple, for example more than 10 times, more preferably more than 50 times, this disk thickness. In this way, it can be considered that a vortex generator can only fulfill its function of generating turbulence satisfactorily if the fluid impinging on the vortex generator could previously flow over a certain free inflow path.

Accordingly, in a disk set, either a vortical generator should not be formed on each disk of the disk pack or, in the case where a vortical generator is formed on each disk of the disk pack, adjacent disks should be circumferentially staggered to prevent each other outwardly projecting and acting as a vortex generator areas of adjacent lamellae are arranged such that they directly adjacent to each other in the longitudinal direction of the disk set and aligned and thus no distance between these vortex generators remains, which could serve as Anströmstrecke for the cooling fluid.

In a special embodiment, a lamella can have a recess radially inwardly of a vortex generator which is formed integrally on the lamella. This recess may for example have a surface which larger than the area of the vortex generator itself. The recess can be produced by punching out a portion projecting beyond the circular outer circumference and serving as a vortex generator, as in the example described above, during the punching process while punching the blade with a purely circular

Outside periphery is punched out, but in addition a further radially inner region is also punched free, so that a between this free punched area and the circular outer periphery of the lamella remaining portion of the lamella-forming sheet in a

subsequent bending step can be bent outward so that it can serve as outwardly projecting vortex generator.

To a flow rate of the cooling fluid by that of the

The flow gap can be formed meander-shaped along an outer surface of the disk set of the stator to be able to increase flow gap formed cooling arrangement and thus to ensure good heat dissipation by the cooling fluid. In this case, the vortex generators can preferably be arranged in the meander-shaped flow-through gap in regions in which the fluid flows substantially perpendicular to a plane of the laminations. In other words, for example, by

Provide suitable webs between the stator and the housing the

Cooling fluid are guided meandering along the surface of the stator, wherein the meandering form formed by the webs should be designed so that a flow direction of the cooling fluid over long areas in the longitudinal direction of the stator, that is perpendicular to the individual slats, aligned so that the vortex generators projecting outwards from the individual lamellae can provide the most efficient possible turbulence of the fluid flowing through. It should be noted that possible benefits and characteristics of

Embodiments of the invention herein are described in part with reference to FIGS

proposed electric machine, partly with respect to a suitable stator and partly with respect to a manufacturing method for this

Components is described. One skilled in the art will recognize that the features may be suitably combined or exchanged with each other, in order to arrive in this way to further embodiments and, where appropriate, to synergy effects.

Brief description of the drawings

Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings, wherein neither the description nor the drawings are to be construed as limiting the invention. FIG. 1 shows a perspective view of a device according to the invention

Electric machine.

FIG. 2 shows a perspective partial view of a stator according to the invention. FIG. 3 shows in a two-dimensional representation a plan view of a stator according to the invention.

FIG. 4 shows plan views of various embodiments of FIG

Vortex generators on lamellae of a stator according to the invention.

Figures 5 and 6 show plan views of alternative embodiments for vortex generators on lamellae of a stator according to the invention.

The figures are only schematic and not to scale. In the figures, like reference numerals designate like or equivalent features.

Embodiments of the invention

Figure 1 shows an electric machine 1 with a rotor 3, a stator 5 and a housing 7. In the rotor 3 are along a cylindrical

Outside perimeter permanent magnets 9 was added. In the stator 5, which also has a cylindrical outer periphery, recesses are provided inwardly, which are separated by webs 11 in the circumferential direction from each other. In the recesses windings of a coil forming electrical conductor (not shown in Figure 1) may be included, by means of which a time-varying magnetic field can be generated to To exert forces on the received in the rotor 3 permanent magnets 9 and thus to enable the rotor 3 relative to the stator 5 in a rotating movement. Between an outer surface 15 of the stator 5 and the housing 7 surrounding the stator, a flow gap 16 is provided. This flow gap 16 is subdivided into individual regions by walls 17 running in the longitudinal direction of the electric machine 1, so that a gaseous or liquid cooling fluid flowing through the flow gap 16 can be meandered along the surface 15 of the stator by means of the walls 17.

In order in the flowing through the flow space 16 fluid

Turbulences are generated starting from the stator 5

Vortex generators 19 are provided, which protrude into the flow gap 16.

As shown in Figure 2, the stator 5 consists of a plurality of fins 21. Each of the fins 21 consists of a thin metal sheet with

for example, a thickness of 0.3 millimeters. The individual lamellae 21 in this case have substantially the same geometry and are arranged stacked next to one another in alignment with one another, so that they form lamella packages, from which in turn the stator 5 can be assembled. At some or preferably all of the lamellae 21, an outwardly projecting area serving as a vortex generator 19 may be integrally formed. The vortex generator 19 is already formed when punching the fins 21, so that its production brings little additional effort with it.

In order for the vortex generator 19 to ensure the best possible turbulence of the cooling fluid flowing in a flow direction 23, it is arranged obliquely opposite to the flow direction 23. In Figure 3 is a two-dimensional developed view of the cylindrical

Outside surface 15 of the stator 5 is shown schematically. Cooling fluid can in a flow direction 23, for example, first coming from a heat exchanger, for example, flow into a flow gap 16, as shown in Figure 3 top left. Through walls 17, the cooling fluid is guided meander-shaped along the surface of the stator 5, wherein the flow direction 23 extends in many areas perpendicular to the extension planes of the fins 21 of the stator 5. After the cooling fluid could absorb heat from the stator 5, it finally flows out of the flow gap 16, as shown in Figure 3 bottom right.

In order to efficiently fluidize the cooling fluid during flow through the flow gap 16 and thus provide good mixing of already heated with still cool portions of the cooling fluid, a plurality of vortex generators 19 are provided. In the example shown in Figure 3, each of the lamellae 21 has a vortex generator 19, wherein the individual lamellae 21 are arranged offset in their circumferential direction 35 to each other so that between some arranged in the longitudinal direction 37 vortex generators 19 some fins 21 are arranged at in which no projecting region is provided at the corresponding position, so that the fluid flowing through receives a sufficiently long free flow path before it encounters a vortex generator 19. The length "d" of the

Anströmstrecke here, for example, be greater than twice the Abraghöhe the vortex generators 19. While this is shown only schematically in FIG. 3, with lamination stacks of real stators, with a sheet thickness of, for example, 0.3 millimeters, ten to seventy fins can be provided between two vortex generators 19 adjacent in the longitudinal direction, in order to ensure a sufficiently long free inflow path.

As an alternative to offset in the circumferential direction of identically formed lamellae and the vortex generators arranged thereon, the required spacing of adjacent vortex generators 19 can also be achieved by stacking different lamellae 21 into a lamella packet, wherein some of the lamellae have outwardly projecting vortex generators and others therebetween lying slats have no such areas. For example, in the intervening fins, these areas may be removed after the initial punching. In Figure 4 different geometries of vortex generators 19 are shown. As shown in Figures 4 a, c, d, f, the

Whirl generators 19 be formed over its entire surface with a triangular, semicircular or rectangular geometry. In the examples illustrated in FIGS. 4 b, e, a passage opening 25 is provided in the region of a base on which the vortex generator 19 adjoins the associated fin. Through this passage opening 25 cooling fluid can flow in the vicinity of the surface of the stator 5 and cool it well, with the surrounding areas of the vortex generator 19 can provide for efficient turbulence of the cooling fluid.

In Figures 5 and 6 are further embodiments of a with

Vortex generators 19 provided lamella 21. As can be seen in FIGS. 5 b and 6 b, a lamella 21 has a recess 29, 33 radially inside a vortex generator 19, which is formed integrally on the lamella. This recess 29, 33 can, as shown in Figures 5 a, 6 a, arise from the fact that already during punching of the lamella 21 within the circular outer periphery lying region 27, 31 of suitable geometry is punched with, so that a radially outward adjacent thereto area can then be selectively bent outwardly and then act as a vortex generator 19 in the flow gap protruding.

With such an embodiment of the slats 21 can be achieved that all the slats of the stator 5 can be formed punching in the same way, but only in some of the slats then the vortex generator 19 forming areas are bent outwards, so that for a sufficient distance between longitudinally adjacent

Vortex generators 19 and thus can be provided for a sufficient inflow.

Claims

claims

Electric machine (1) with integrated cooling arrangement, wherein the

Electric machine (1) comprising:

a rotor (3);

a stator (5) enclosing the rotor (3); wherein the stator (5) comprises a disk pack, which is composed of a plurality of juxtaposed slats (21), characterized in that

radially outwardly of the stator (5) a flow gap (16) is provided, through which a cooling fluid can flow, and

at least some of the lamellae (21) of the disk pack

Vortex generators (19) protrude into the flow space (16) which generate turbulence in a flowing fluid.

Electric machine according to claim 1, wherein a vortex generator (19) on one of the lamellae (21) is integrally formed.

Electric machine according to claim 1 or 2, wherein the vortex generators (19) obliquely against a flow direction (23) of the fluid in the

In the flow gap (16) protrude.

Electric machine according to one of claims 1 to 3, wherein the

Meandering space (16) along a

Outer surface (15) of the disk set of the stator (5) is formed.

Electric machine according to claim 4, wherein the vortex generators (19) are arranged in the meander-shaped flow-through gap (16) in regions in which the fluid flows substantially perpendicular to a plane of the lamellae (21).

6. Electric machine according to one of claims 1 to 5, wherein the

Vortex generators (19) are tapered in a direction radially outwardly.

7. Electric machine according to one of claims 1 to 6, wherein the

Vortex generators (19) in a region of an attached to an associated blade (21) base having a through hole (25). 8. Electric machine according to one of claims 1 to 7, wherein between two in

Longitudinal direction (37) of the disk pack adjacent vortex generators (19) is a distance (d) of more than one thickness of a blade (21).

9. Electric machine according to one of claims 1 to 8, wherein each lamella (21) of the plate pack has a vortex generator (19) and wherein adjacent lamellae (21) in the circumferential direction (35) are arranged offset to one another.

10. Electric machine according to one of claims 1 to 8, wherein not at each blade (21) of the disk set a vortex generator (19) is formed.

1 1. Electric machine according to one of claims 1 to 10, wherein a lamella (21) has a recess (29, 33) radially inwardly of a lamellae (21) integrally formed vortex generator (19).

12. Electric machine according to claim 1 1, wherein the recess (29, 33) has an area larger than the surface of the vortex generator (19).

13. Electric machine according to one of claims 1 to 12, further comprising a stator (5) enclosing housing (7), wherein the

Flow space (16) between the stator (5) and the housing (7) is formed.

14. Stator (5) for an electric machine (1) according to one of claims 1 to 13, wherein the stator (5) has a disk set, which consists of a Variety of side by side stacked blades (21) is composed,

characterized in that

the stator (5) has vortex generators (19) projecting radially outwardly from at least some of the lamellae (21) of the lamina packet.